kernel/fork.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  linux/kernel/fork.c
   4  *
   5  *  Copyright (C) 1991, 1992  Linus Torvalds
   6  */
   7
   8 /*
   9  *  'fork.c' contains the help-routines for the 'fork' system call
  10  * (see also entry.S and others).
  11  * Fork is rather simple, once you get the hang of it, but the memory
  12  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
  13  */
  14
  15 #include <linux/anon_inodes.h>
  16 #include <linux/slab.h>
  17 #include <linux/sched/autogroup.h>
  18 #include <linux/sched/mm.h>
  19 #include <linux/sched/coredump.h>
  20 #include <linux/sched/user.h>
  21 #include <linux/sched/numa_balancing.h>
  22 #include <linux/sched/stat.h>
  23 #include <linux/sched/task.h>
  24 #include <linux/sched/task_stack.h>
  25 #include <linux/sched/cputime.h>
  26 #include <linux/seq_file.h>
  27 #include <linux/rtmutex.h>
  28 #include <linux/init.h>
  29 #include <linux/unistd.h>
  30 #include <linux/module.h>
  31 #include <linux/vmalloc.h>
  32 #include <linux/completion.h>
  33 #include <linux/personality.h>
  34 #include <linux/mempolicy.h>
  35 #include <linux/sem.h>
  36 #include <linux/file.h>
  37 #include <linux/fdtable.h>
  38 #include <linux/iocontext.h>
  39 #include <linux/key.h>
  40 #include <linux/kmsan.h>
  41 #include <linux/binfmts.h>
  42 #include <linux/mman.h>
  43 #include <linux/mmu_notifier.h>
  44 #include <linux/fs.h>
  45 #include <linux/mm.h>
  46 #include <linux/mm_inline.h>
  47 #include <linux/nsproxy.h>
  48 #include <linux/capability.h>
  49 #include <linux/cpu.h>
  50 #include <linux/cgroup.h>
  51 #include <linux/security.h>
  52 #include <linux/hugetlb.h>
  53 #include <linux/seccomp.h>
  54 #include <linux/swap.h>
  55 #include <linux/syscalls.h>
  56 #include <linux/jiffies.h>
  57 #include <linux/futex.h>
  58 #include <linux/compat.h>
  59 #include <linux/kthread.h>
  60 #include <linux/task_io_accounting_ops.h>
  61 #include <linux/rcupdate.h>
  62 #include <linux/ptrace.h>
  63 #include <linux/mount.h>
  64 #include <linux/audit.h>
  65 #include <linux/memcontrol.h>
  66 #include <linux/ftrace.h>
  67 #include <linux/proc_fs.h>
  68 #include <linux/profile.h>
  69 #include <linux/rmap.h>
  70 #include <linux/ksm.h>
  71 #include <linux/acct.h>
  72 #include <linux/userfaultfd_k.h>
  73 #include <linux/tsacct_kern.h>
  74 #include <linux/cn_proc.h>
  75 #include <linux/freezer.h>
  76 #include <linux/delayacct.h>
  77 #include <linux/taskstats_kern.h>
  78 #include <linux/tty.h>
  79 #include <linux/fs_struct.h>
  80 #include <linux/magic.h>
  81 #include <linux/perf_event.h>
  82 #include <linux/posix-timers.h>
  83 #include <linux/user-return-notifier.h>
  84 #include <linux/oom.h>
  85 #include <linux/khugepaged.h>
  86 #include <linux/signalfd.h>
  87 #include <linux/uprobes.h>
  88 #include <linux/aio.h>
  89 #include <linux/compiler.h>
  90 #include <linux/sysctl.h>
  91 #include <linux/kcov.h>
  92 #include <linux/livepatch.h>
  93 #include <linux/thread_info.h>
  94 #include <linux/stackleak.h>
  95 #include <linux/kasan.h>
  96 #include <linux/scs.h>
  97 #include <linux/io_uring.h>
  98 #include <linux/bpf.h>
  99 #include <linux/stackprotector.h>
 100
 101 #include <asm/pgalloc.h>
 102 #include <linux/uaccess.h>
 103 #include <asm/mmu_context.h>
 104 #include <asm/cacheflush.h>
 105 #include <asm/tlbflush.h>
 106
 107 #include <trace/events/sched.h>
 108
 109 #define CREATE_TRACE_POINTS
 110 #include <trace/events/task.h>
 111
 112 /*
 113  * Minimum number of threads to boot the kernel
 114  */
 115 #define MIN_THREADS 20
 116
 117 /*
 118  * Maximum number of threads
 119  */
 120 #define MAX_THREADS FUTEX_TID_MASK
 121
 122 /*
 123  * Protected counters by write_lock_irq(&tasklist_lock)
 124  */
 125 unsigned long total_forks;      /* Handle normal Linux uptimes. */
 126 int nr_threads;                 /* The idle threads do not count.. */
 127
 128 static int max_threads;         /* tunable limit on nr_threads */
 129
 130 #define NAMED_ARRAY_INDEX(x)    [x] = __stringify(x)
 131
 132 static const char * const resident_page_types[] = {
 133         NAMED_ARRAY_INDEX(MM_FILEPAGES),
 134         NAMED_ARRAY_INDEX(MM_ANONPAGES),
 135         NAMED_ARRAY_INDEX(MM_SWAPENTS),
 136         NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
 137 };
 138
 139 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
 140
 141 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
 142
 143 #ifdef CONFIG_PROVE_RCU
 144 int lockdep_tasklist_lock_is_held(void)
 145 {
 146         return lockdep_is_held(&tasklist_lock);
 147 }
 148 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
 149 #endif /* #ifdef CONFIG_PROVE_RCU */
 150
 151 int nr_processes(void)
 152 {
 153         int cpu;
 154         int total = 0;
 155
 156         for_each_possible_cpu(cpu)
 157                 total += per_cpu(process_counts, cpu);
 158
 159         return total;
 160 }
 161
 162 void __weak arch_release_task_struct(struct task_struct *tsk)
 163 {
 164 }
 165
 166 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 167 static struct kmem_cache *task_struct_cachep;
 168
 169 static inline struct task_struct *alloc_task_struct_node(int node)
 170 {
 171         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
 172 }
 173
 174 static inline void free_task_struct(struct task_struct *tsk)
 175 {
 176         kmem_cache_free(task_struct_cachep, tsk);
 177 }
 178 #endif
 179
 180 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
 181
 182 /*
 183  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
 184  * kmemcache based allocator.
 185  */
 186 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
 187
 188 #  ifdef CONFIG_VMAP_STACK
 189 /*
 190  * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
 191  * flush.  Try to minimize the number of calls by caching stacks.
 192  */
 193 #define NR_CACHED_STACKS 2
 194 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
 195
 196 struct vm_stack {
 197         struct rcu_head rcu;
 198         struct vm_struct *stack_vm_area;
 199 };
 200
 201 static bool try_release_thread_stack_to_cache(struct vm_struct *vm)
 202 {
 203         unsigned int i;
 204
 205         for (i = 0; i < NR_CACHED_STACKS; i++) {
 206                 if (this_cpu_cmpxchg(cached_stacks[i], NULL, vm) != NULL)
 207                         continue;
 208                 return true;
 209         }
 210         return false;
 211 }
 212
 213 static void thread_stack_free_rcu(struct rcu_head *rh)
 214 {
 215         struct vm_stack *vm_stack = container_of(rh, struct vm_stack, rcu);
 216
 217         if (try_release_thread_stack_to_cache(vm_stack->stack_vm_area))
 218                 return;
 219
 220         vfree(vm_stack);
 221 }
 222
 223 static void thread_stack_delayed_free(struct task_struct *tsk)
 224 {
 225         struct vm_stack *vm_stack = tsk->stack;
 226
 227         vm_stack->stack_vm_area = tsk->stack_vm_area;
 228         call_rcu(&vm_stack->rcu, thread_stack_free_rcu);
 229 }
 230
 231 static int free_vm_stack_cache(unsigned int cpu)
 232 {
 233         struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
 234         int i;
 235
 236         for (i = 0; i < NR_CACHED_STACKS; i++) {
 237                 struct vm_struct *vm_stack = cached_vm_stacks[i];
 238
 239                 if (!vm_stack)
 240                         continue;
 241
 242                 vfree(vm_stack->addr);
 243                 cached_vm_stacks[i] = NULL;
 244         }
 245
 246         return 0;
 247 }
 248
 249 static int memcg_charge_kernel_stack(struct vm_struct *vm)
 250 {
 251         int i;
 252         int ret;
 253
 254         BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
 255         BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
 256
 257         for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
 258                 ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL, 0);
 259                 if (ret)
 260                         goto err;
 261         }
 262         return 0;
 263 err:
 264         /*
 265          * If memcg_kmem_charge_page() fails, page's memory cgroup pointer is
 266          * NULL, and memcg_kmem_uncharge_page() in free_thread_stack() will
 267          * ignore this page.
 268          */
 269         for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
 270                 memcg_kmem_uncharge_page(vm->pages[i], 0);
 271         return ret;
 272 }
 273
 274 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
 275 {
 276         struct vm_struct *vm;
 277         void *stack;
 278         int i;
 279
 280         for (i = 0; i < NR_CACHED_STACKS; i++) {
 281                 struct vm_struct *s;
 282
 283                 s = this_cpu_xchg(cached_stacks[i], NULL);
 284
 285                 if (!s)
 286                         continue;
 287
 288                 /* Reset stack metadata. */
 289                 kasan_unpoison_range(s->addr, THREAD_SIZE);
 290
 291                 stack = kasan_reset_tag(s->addr);
 292
 293                 /* Clear stale pointers from reused stack. */
 294                 memset(stack, 0, THREAD_SIZE);
 295
 296                 if (memcg_charge_kernel_stack(s)) {
 297                         vfree(s->addr);
 298                         return -ENOMEM;
 299                 }
 300
 301                 tsk->stack_vm_area = s;
 302                 tsk->stack = stack;
 303                 return 0;
 304         }
 305
 306         /*
 307          * Allocated stacks are cached and later reused by new threads,
 308          * so memcg accounting is performed manually on assigning/releasing
 309          * stacks to tasks. Drop __GFP_ACCOUNT.
 310          */
 311         stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
 312                                      VMALLOC_START, VMALLOC_END,
 313                                      THREADINFO_GFP & ~__GFP_ACCOUNT,
 314                                      PAGE_KERNEL,
 315                                      0, node, __builtin_return_address(0));
 316         if (!stack)
 317                 return -ENOMEM;
 318
 319         vm = find_vm_area(stack);
 320         if (memcg_charge_kernel_stack(vm)) {
 321                 vfree(stack);
 322                 return -ENOMEM;
 323         }
 324         /*
 325          * We can't call find_vm_area() in interrupt context, and
 326          * free_thread_stack() can be called in interrupt context,
 327          * so cache the vm_struct.
 328          */
 329         tsk->stack_vm_area = vm;
 330         stack = kasan_reset_tag(stack);
 331         tsk->stack = stack;
 332         return 0;
 333 }
 334
 335 static void free_thread_stack(struct task_struct *tsk)
 336 {
 337         if (!try_release_thread_stack_to_cache(tsk->stack_vm_area))
 338                 thread_stack_delayed_free(tsk);
 339
 340         tsk->stack = NULL;
 341         tsk->stack_vm_area = NULL;
 342 }
 343
 344 #  else /* !CONFIG_VMAP_STACK */
 345
 346 static void thread_stack_free_rcu(struct rcu_head *rh)
 347 {
 348         __free_pages(virt_to_page(rh), THREAD_SIZE_ORDER);
 349 }
 350
 351 static void thread_stack_delayed_free(struct task_struct *tsk)
 352 {
 353         struct rcu_head *rh = tsk->stack;
 354
 355         call_rcu(rh, thread_stack_free_rcu);
 356 }
 357
 358 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
 359 {
 360         struct page *page = alloc_pages_node(node, THREADINFO_GFP,
 361                                              THREAD_SIZE_ORDER);
 362
 363         if (likely(page)) {
 364                 tsk->stack = kasan_reset_tag(page_address(page));
 365                 return 0;
 366         }
 367         return -ENOMEM;
 368 }
 369
 370 static void free_thread_stack(struct task_struct *tsk)
 371 {
 372         thread_stack_delayed_free(tsk);
 373         tsk->stack = NULL;
 374 }
 375
 376 #  endif /* CONFIG_VMAP_STACK */
 377 # else /* !(THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)) */
 378
 379 static struct kmem_cache *thread_stack_cache;
 380
 381 static void thread_stack_free_rcu(struct rcu_head *rh)
 382 {
 383         kmem_cache_free(thread_stack_cache, rh);
 384 }
 385
 386 static void thread_stack_delayed_free(struct task_struct *tsk)
 387 {
 388         struct rcu_head *rh = tsk->stack;
 389
 390         call_rcu(rh, thread_stack_free_rcu);
 391 }
 392
 393 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
 394 {
 395         unsigned long *stack;
 396         stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
 397         stack = kasan_reset_tag(stack);
 398         tsk->stack = stack;
 399         return stack ? 0 : -ENOMEM;
 400 }
 401
 402 static void free_thread_stack(struct task_struct *tsk)
 403 {
 404         thread_stack_delayed_free(tsk);
 405         tsk->stack = NULL;
 406 }
 407
 408 void thread_stack_cache_init(void)
 409 {
 410         thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
 411                                         THREAD_SIZE, THREAD_SIZE, 0, 0,
 412                                         THREAD_SIZE, NULL);
 413         BUG_ON(thread_stack_cache == NULL);
 414 }
 415
 416 # endif /* THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) */
 417 #else /* CONFIG_ARCH_THREAD_STACK_ALLOCATOR */
 418
 419 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
 420 {
 421         unsigned long *stack;
 422
 423         stack = arch_alloc_thread_stack_node(tsk, node);
 424         tsk->stack = stack;
 425         return stack ? 0 : -ENOMEM;
 426 }
 427
 428 static void free_thread_stack(struct task_struct *tsk)
 429 {
 430         arch_free_thread_stack(tsk);
 431         tsk->stack = NULL;
 432 }
 433
 434 #endif /* !CONFIG_ARCH_THREAD_STACK_ALLOCATOR */
 435
 436 /* SLAB cache for signal_struct structures (tsk->signal) */
 437 static struct kmem_cache *signal_cachep;
 438
 439 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 440 struct kmem_cache *sighand_cachep;
 441
 442 /* SLAB cache for files_struct structures (tsk->files) */
 443 struct kmem_cache *files_cachep;
 444
 445 /* SLAB cache for fs_struct structures (tsk->fs) */
 446 struct kmem_cache *fs_cachep;
 447
 448 /* SLAB cache for vm_area_struct structures */
 449 static struct kmem_cache *vm_area_cachep;
 450
 451 /* SLAB cache for mm_struct structures (tsk->mm) */
 452 static struct kmem_cache *mm_cachep;
 453
 454 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
 455 {
 456         struct vm_area_struct *vma;
 457
 458         vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 459         if (vma)
 460                 vma_init(vma, mm);
 461         return vma;
 462 }
 463
 464 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
 465 {
 466         struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 467
 468         if (new) {
 469                 ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
 470                 ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
 471                 /*
 472                  * orig->shared.rb may be modified concurrently, but the clone
 473                  * will be reinitialized.
 474                  */
 475                 data_race(memcpy(new, orig, sizeof(*new)));
 476                 INIT_LIST_HEAD(&new->anon_vma_chain);
 477                 dup_anon_vma_name(orig, new);
 478         }
 479         return new;
 480 }
 481
 482 void vm_area_free(struct vm_area_struct *vma)
 483 {
 484         free_anon_vma_name(vma);
 485         kmem_cache_free(vm_area_cachep, vma);
 486 }
 487
 488 static void account_kernel_stack(struct task_struct *tsk, int account)
 489 {
 490         if (IS_ENABLED(CONFIG_VMAP_STACK)) {
 491                 struct vm_struct *vm = task_stack_vm_area(tsk);
 492                 int i;
 493
 494                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
 495                         mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB,
 496                                               account * (PAGE_SIZE / 1024));
 497         } else {
 498                 void *stack = task_stack_page(tsk);
 499
 500                 /* All stack pages are in the same node. */
 501                 mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB,
 502                                       account * (THREAD_SIZE / 1024));
 503         }
 504 }
 505
 506 void exit_task_stack_account(struct task_struct *tsk)
 507 {
 508         account_kernel_stack(tsk, -1);
 509
 510         if (IS_ENABLED(CONFIG_VMAP_STACK)) {
 511                 struct vm_struct *vm;
 512                 int i;
 513
 514                 vm = task_stack_vm_area(tsk);
 515                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
 516                         memcg_kmem_uncharge_page(vm->pages[i], 0);
 517         }
 518 }
 519
 520 static void release_task_stack(struct task_struct *tsk)
 521 {
 522         if (WARN_ON(READ_ONCE(tsk->__state) != TASK_DEAD))
 523                 return;  /* Better to leak the stack than to free prematurely */
 524
 525         free_thread_stack(tsk);
 526 }
 527
 528 #ifdef CONFIG_THREAD_INFO_IN_TASK
 529 void put_task_stack(struct task_struct *tsk)
 530 {
 531         if (refcount_dec_and_test(&tsk->stack_refcount))
 532                 release_task_stack(tsk);
 533 }
 534 #endif
 535
 536 void free_task(struct task_struct *tsk)
 537 {
 538 #ifdef CONFIG_SECCOMP
 539         WARN_ON_ONCE(tsk->seccomp.filter);
 540 #endif
 541         release_user_cpus_ptr(tsk);
 542         scs_release(tsk);
 543
 544 #ifndef CONFIG_THREAD_INFO_IN_TASK
 545         /*
 546          * The task is finally done with both the stack and thread_info,
 547          * so free both.
 548          */
 549         release_task_stack(tsk);
 550 #else
 551         /*
 552          * If the task had a separate stack allocation, it should be gone
 553          * by now.
 554          */
 555         WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
 556 #endif
 557         rt_mutex_debug_task_free(tsk);
 558         ftrace_graph_exit_task(tsk);
 559         arch_release_task_struct(tsk);
 560         if (tsk->flags & PF_KTHREAD)
 561                 free_kthread_struct(tsk);
 562         free_task_struct(tsk);
 563 }
 564 EXPORT_SYMBOL(free_task);
 565
 566 static void dup_mm_exe_file(struct mm_struct *mm, struct mm_struct *oldmm)
 567 {
 568         struct file *exe_file;
 569
 570         exe_file = get_mm_exe_file(oldmm);
 571         RCU_INIT_POINTER(mm->exe_file, exe_file);
 572         /*
 573          * We depend on the oldmm having properly denied write access to the
 574          * exe_file already.
 575          */
 576         if (exe_file && deny_write_access(exe_file))
 577                 pr_warn_once("deny_write_access() failed in %s\n", __func__);
 578 }
 579
 580 #ifdef CONFIG_MMU
 581 static __latent_entropy int dup_mmap(struct mm_struct *mm,
 582                                         struct mm_struct *oldmm)
 583 {
 584         struct vm_area_struct *mpnt, *tmp;
 585         int retval;
 586         unsigned long charge = 0;
 587         LIST_HEAD(uf);
 588         VMA_ITERATOR(old_vmi, oldmm, 0);
 589         VMA_ITERATOR(vmi, mm, 0);
 590
 591         uprobe_start_dup_mmap();
 592         if (mmap_write_lock_killable(oldmm)) {
 593                 retval = -EINTR;
 594                 goto fail_uprobe_end;
 595         }
 596         flush_cache_dup_mm(oldmm);
 597         uprobe_dup_mmap(oldmm, mm);
 598         /*
 599          * Not linked in yet - no deadlock potential:
 600          */
 601         mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING);
 602
 603         /* No ordering required: file already has been exposed. */
 604         dup_mm_exe_file(mm, oldmm);
 605
 606         mm->total_vm = oldmm->total_vm;
 607         mm->data_vm = oldmm->data_vm;
 608         mm->exec_vm = oldmm->exec_vm;
 609         mm->stack_vm = oldmm->stack_vm;
 610
 611         retval = ksm_fork(mm, oldmm);
 612         if (retval)
 613                 goto out;
 614         khugepaged_fork(mm, oldmm);
 615
 616         retval = vma_iter_bulk_alloc(&vmi, oldmm->map_count);
 617         if (retval)
 618                 goto out;
 619
 620         for_each_vma(old_vmi, mpnt) {
 621                 struct file *file;
 622
 623                 if (mpnt->vm_flags & VM_DONTCOPY) {
 624                         vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
 625                         continue;
 626                 }
 627                 charge = 0;
 628                 /*
 629                  * Don't duplicate many vmas if we've been oom-killed (for
 630                  * example)
 631                  */
 632                 if (fatal_signal_pending(current)) {
 633                         retval = -EINTR;
 634                         goto loop_out;
 635                 }
 636                 if (mpnt->vm_flags & VM_ACCOUNT) {
 637                         unsigned long len = vma_pages(mpnt);
 638
 639                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
 640                                 goto fail_nomem;
 641                         charge = len;
 642                 }
 643                 tmp = vm_area_dup(mpnt);
 644                 if (!tmp)
 645                         goto fail_nomem;
 646                 retval = vma_dup_policy(mpnt, tmp);
 647                 if (retval)
 648                         goto fail_nomem_policy;
 649                 tmp->vm_mm = mm;
 650                 retval = dup_userfaultfd(tmp, &uf);
 651                 if (retval)
 652                         goto fail_nomem_anon_vma_fork;
 653                 if (tmp->vm_flags & VM_WIPEONFORK) {
 654                         /*
 655                          * VM_WIPEONFORK gets a clean slate in the child.
 656                          * Don't prepare anon_vma until fault since we don't
 657                          * copy page for current vma.
 658                          */
 659                         tmp->anon_vma = NULL;
 660                 } else if (anon_vma_fork(tmp, mpnt))
 661                         goto fail_nomem_anon_vma_fork;
 662                 vm_flags_clear(tmp, VM_LOCKED_MASK);
 663                 file = tmp->vm_file;
 664                 if (file) {
 665                         struct address_space *mapping = file->f_mapping;
 666
 667                         get_file(file);
 668                         i_mmap_lock_write(mapping);
 669                         if (tmp->vm_flags & VM_SHARED)
 670                                 mapping_allow_writable(mapping);
 671                         flush_dcache_mmap_lock(mapping);
 672                         /* insert tmp into the share list, just after mpnt */
 673                         vma_interval_tree_insert_after(tmp, mpnt,
 674                                         &mapping->i_mmap);
 675                         flush_dcache_mmap_unlock(mapping);
 676                         i_mmap_unlock_write(mapping);
 677                 }
 678
 679                 /*
 680                  * Copy/update hugetlb private vma information.
 681                  */
 682                 if (is_vm_hugetlb_page(tmp))
 683                         hugetlb_dup_vma_private(tmp);
 684
 685                 /* Link the vma into the MT */
 686                 if (vma_iter_bulk_store(&vmi, tmp))
 687                         goto fail_nomem_vmi_store;
 688
 689                 mm->map_count++;
 690                 if (!(tmp->vm_flags & VM_WIPEONFORK))
 691                         retval = copy_page_range(tmp, mpnt);
 692
 693                 if (tmp->vm_ops && tmp->vm_ops->open)
 694                         tmp->vm_ops->open(tmp);
 695
 696                 if (retval)
 697                         goto loop_out;
 698         }
 699         /* a new mm has just been created */
 700         retval = arch_dup_mmap(oldmm, mm);
 701 loop_out:
 702         vma_iter_free(&vmi);
 703 out:
 704         mmap_write_unlock(mm);
 705         flush_tlb_mm(oldmm);
 706         mmap_write_unlock(oldmm);
 707         dup_userfaultfd_complete(&uf);
 708 fail_uprobe_end:
 709         uprobe_end_dup_mmap();
 710         return retval;
 711
 712 fail_nomem_vmi_store:
 713         unlink_anon_vmas(tmp);
 714 fail_nomem_anon_vma_fork:
 715         mpol_put(vma_policy(tmp));
 716 fail_nomem_policy:
 717         vm_area_free(tmp);
 718 fail_nomem:
 719         retval = -ENOMEM;
 720         vm_unacct_memory(charge);
 721         goto loop_out;
 722 }
 723
 724 static inline int mm_alloc_pgd(struct mm_struct *mm)
 725 {
 726         mm->pgd = pgd_alloc(mm);
 727         if (unlikely(!mm->pgd))
 728                 return -ENOMEM;
 729         return 0;
 730 }
 731
 732 static inline void mm_free_pgd(struct mm_struct *mm)
 733 {
 734         pgd_free(mm, mm->pgd);
 735 }
 736 #else
 737 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 738 {
 739         mmap_write_lock(oldmm);
 740         dup_mm_exe_file(mm, oldmm);
 741         mmap_write_unlock(oldmm);
 742         return 0;
 743 }
 744 #define mm_alloc_pgd(mm)        (0)
 745 #define mm_free_pgd(mm)
 746 #endif /* CONFIG_MMU */
 747
 748 static void check_mm(struct mm_struct *mm)
 749 {
 750         int i;
 751
 752         BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
 753                          "Please make sure 'struct resident_page_types[]' is updated as well");
 754
 755         for (i = 0; i < NR_MM_COUNTERS; i++) {
 756                 long x = percpu_counter_sum(&mm->rss_stat[i]);
 757
 758                 if (likely(!x))
 759                         continue;
 760
 761                 /* Making sure this is not due to race with CPU offlining. */
 762                 x = percpu_counter_sum_all(&mm->rss_stat[i]);
 763                 if (unlikely(x))
 764                         pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
 765                                  mm, resident_page_types[i], x);
 766         }
 767
 768         if (mm_pgtables_bytes(mm))
 769                 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
 770                                 mm_pgtables_bytes(mm));
 771
 772 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 773         VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
 774 #endif
 775 }
 776
 777 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 778 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 779
 780 /*
 781  * Called when the last reference to the mm
 782  * is dropped: either by a lazy thread or by
 783  * mmput. Free the page directory and the mm.
 784  */
 785 void __mmdrop(struct mm_struct *mm)
 786 {
 787         int i;
 788
 789         BUG_ON(mm == &init_mm);
 790         WARN_ON_ONCE(mm == current->mm);
 791         WARN_ON_ONCE(mm == current->active_mm);
 792         mm_free_pgd(mm);
 793         destroy_context(mm);
 794         mmu_notifier_subscriptions_destroy(mm);
 795         check_mm(mm);
 796         put_user_ns(mm->user_ns);
 797         mm_pasid_drop(mm);
 798
 799         for (i = 0; i < NR_MM_COUNTERS; i++)
 800                 percpu_counter_destroy(&mm->rss_stat[i]);
 801         free_mm(mm);
 802 }
 803 EXPORT_SYMBOL_GPL(__mmdrop);
 804
 805 static void mmdrop_async_fn(struct work_struct *work)
 806 {
 807         struct mm_struct *mm;
 808
 809         mm = container_of(work, struct mm_struct, async_put_work);
 810         __mmdrop(mm);
 811 }
 812
 813 static void mmdrop_async(struct mm_struct *mm)
 814 {
 815         if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
 816                 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
 817                 schedule_work(&mm->async_put_work);
 818         }
 819 }
 820
 821 static inline void free_signal_struct(struct signal_struct *sig)
 822 {
 823         taskstats_tgid_free(sig);
 824         sched_autogroup_exit(sig);
 825         /*
 826          * __mmdrop is not safe to call from softirq context on x86 due to
 827          * pgd_dtor so postpone it to the async context
 828          */
 829         if (sig->oom_mm)
 830                 mmdrop_async(sig->oom_mm);
 831         kmem_cache_free(signal_cachep, sig);
 832 }
 833
 834 static inline void put_signal_struct(struct signal_struct *sig)
 835 {
 836         if (refcount_dec_and_test(&sig->sigcnt))
 837                 free_signal_struct(sig);
 838 }
 839
 840 void __put_task_struct(struct task_struct *tsk)
 841 {
 842         WARN_ON(!tsk->exit_state);
 843         WARN_ON(refcount_read(&tsk->usage));
 844         WARN_ON(tsk == current);
 845
 846         io_uring_free(tsk);
 847         cgroup_free(tsk);
 848         task_numa_free(tsk, true);
 849         security_task_free(tsk);
 850         bpf_task_storage_free(tsk);
 851         exit_creds(tsk);
 852         delayacct_tsk_free(tsk);
 853         put_signal_struct(tsk->signal);
 854         sched_core_free(tsk);
 855         free_task(tsk);
 856 }
 857 EXPORT_SYMBOL_GPL(__put_task_struct);
 858
 859 void __init __weak arch_task_cache_init(void) { }
 860
 861 /*
 862  * set_max_threads
 863  */
 864 static void set_max_threads(unsigned int max_threads_suggested)
 865 {
 866         u64 threads;
 867         unsigned long nr_pages = totalram_pages();
 868
 869         /*
 870          * The number of threads shall be limited such that the thread
 871          * structures may only consume a small part of the available memory.
 872          */
 873         if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
 874                 threads = MAX_THREADS;
 875         else
 876                 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
 877                                     (u64) THREAD_SIZE * 8UL);
 878
 879         if (threads > max_threads_suggested)
 880                 threads = max_threads_suggested;
 881
 882         max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
 883 }
 884
 885 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
 886 /* Initialized by the architecture: */
 887 int arch_task_struct_size __read_mostly;
 888 #endif
 889
 890 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 891 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
 892 {
 893         /* Fetch thread_struct whitelist for the architecture. */
 894         arch_thread_struct_whitelist(offset, size);
 895
 896         /*
 897          * Handle zero-sized whitelist or empty thread_struct, otherwise
 898          * adjust offset to position of thread_struct in task_struct.
 899          */
 900         if (unlikely(*size == 0))
 901                 *offset = 0;
 902         else
 903                 *offset += offsetof(struct task_struct, thread);
 904 }
 905 #endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
 906
 907 void __init fork_init(void)
 908 {
 909         int i;
 910 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 911 #ifndef ARCH_MIN_TASKALIGN
 912 #define ARCH_MIN_TASKALIGN      0
 913 #endif
 914         int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
 915         unsigned long useroffset, usersize;
 916
 917         /* create a slab on which task_structs can be allocated */
 918         task_struct_whitelist(&useroffset, &usersize);
 919         task_struct_cachep = kmem_cache_create_usercopy("task_struct",
 920                         arch_task_struct_size, align,
 921                         SLAB_PANIC|SLAB_ACCOUNT,
 922                         useroffset, usersize, NULL);
 923 #endif
 924
 925         /* do the arch specific task caches init */
 926         arch_task_cache_init();
 927
 928         set_max_threads(MAX_THREADS);
 929
 930         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 931         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 932         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 933                 init_task.signal->rlim[RLIMIT_NPROC];
 934
 935         for (i = 0; i < UCOUNT_COUNTS; i++)
 936                 init_user_ns.ucount_max[i] = max_threads/2;
 937
 938         set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_NPROC,      RLIM_INFINITY);
 939         set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE,   RLIM_INFINITY);
 940         set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY);
 941         set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK,    RLIM_INFINITY);
 942
 943 #ifdef CONFIG_VMAP_STACK
 944         cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
 945                           NULL, free_vm_stack_cache);
 946 #endif
 947
 948         scs_init();
 949
 950         lockdep_init_task(&init_task);
 951         uprobes_init();
 952 }
 953
 954 int __weak arch_dup_task_struct(struct task_struct *dst,
 955                                                struct task_struct *src)
 956 {
 957         *dst = *src;
 958         return 0;
 959 }
 960
 961 void set_task_stack_end_magic(struct task_struct *tsk)
 962 {
 963         unsigned long *stackend;
 964
 965         stackend = end_of_stack(tsk);
 966         *stackend = STACK_END_MAGIC;    /* for overflow detection */
 967 }
 968
 969 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 970 {
 971         struct task_struct *tsk;
 972         int err;
 973
 974         if (node == NUMA_NO_NODE)
 975                 node = tsk_fork_get_node(orig);
 976         tsk = alloc_task_struct_node(node);
 977         if (!tsk)
 978                 return NULL;
 979
 980         err = arch_dup_task_struct(tsk, orig);
 981         if (err)
 982                 goto free_tsk;
 983
 984         err = alloc_thread_stack_node(tsk, node);
 985         if (err)
 986                 goto free_tsk;
 987
 988 #ifdef CONFIG_THREAD_INFO_IN_TASK
 989         refcount_set(&tsk->stack_refcount, 1);
 990 #endif
 991         account_kernel_stack(tsk, 1);
 992
 993         err = scs_prepare(tsk, node);
 994         if (err)
 995                 goto free_stack;
 996
 997 #ifdef CONFIG_SECCOMP
 998         /*
 999          * We must handle setting up seccomp filters once we're under
1000          * the sighand lock in case orig has changed between now and
1001          * then. Until then, filter must be NULL to avoid messing up
1002          * the usage counts on the error path calling free_task.
1003          */
1004         tsk->seccomp.filter = NULL;
1005 #endif
1006
1007         setup_thread_stack(tsk, orig);
1008         clear_user_return_notifier(tsk);
1009         clear_tsk_need_resched(tsk);
1010         set_task_stack_end_magic(tsk);
1011         clear_syscall_work_syscall_user_dispatch(tsk);
1012
1013 #ifdef CONFIG_STACKPROTECTOR
1014         tsk->stack_canary = get_random_canary();
1015 #endif
1016         if (orig->cpus_ptr == &orig->cpus_mask)
1017                 tsk->cpus_ptr = &tsk->cpus_mask;
1018         dup_user_cpus_ptr(tsk, orig, node);
1019
1020         /*
1021          * One for the user space visible state that goes away when reaped.
1022          * One for the scheduler.
1023          */
1024         refcount_set(&tsk->rcu_users, 2);
1025         /* One for the rcu users */
1026         refcount_set(&tsk->usage, 1);
1027 #ifdef CONFIG_BLK_DEV_IO_TRACE
1028         tsk->btrace_seq = 0;
1029 #endif
1030         tsk->splice_pipe = NULL;
1031         tsk->task_frag.page = NULL;
1032         tsk->wake_q.next = NULL;
1033         tsk->worker_private = NULL;
1034
1035         kcov_task_init(tsk);
1036         kmsan_task_create(tsk);
1037         kmap_local_fork(tsk);
1038
1039 #ifdef CONFIG_FAULT_INJECTION
1040         tsk->fail_nth = 0;
1041 #endif
1042
1043 #ifdef CONFIG_BLK_CGROUP
1044         tsk->throttle_disk = NULL;
1045         tsk->use_memdelay = 0;
1046 #endif
1047
1048 #ifdef CONFIG_IOMMU_SVA
1049         tsk->pasid_activated = 0;
1050 #endif
1051
1052 #ifdef CONFIG_MEMCG
1053         tsk->active_memcg = NULL;
1054 #endif
1055
1056 #ifdef CONFIG_CPU_SUP_INTEL
1057         tsk->reported_split_lock = 0;
1058 #endif
1059
1060 #ifdef CONFIG_SCHED_MM_CID
1061         tsk->mm_cid = -1;
1062         tsk->mm_cid_active = 0;
1063 #endif
1064         return tsk;
1065
1066 free_stack:
1067         exit_task_stack_account(tsk);
1068         free_thread_stack(tsk);
1069 free_tsk:
1070         free_task_struct(tsk);
1071         return NULL;
1072 }
1073
1074 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
1075
1076 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
1077
1078 static int __init coredump_filter_setup(char *s)
1079 {
1080         default_dump_filter =
1081                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
1082                 MMF_DUMP_FILTER_MASK;
1083         return 1;
1084 }
1085
1086 __setup("coredump_filter=", coredump_filter_setup);
1087
1088 #include <linux/init_task.h>
1089
1090 static void mm_init_aio(struct mm_struct *mm)
1091 {
1092 #ifdef CONFIG_AIO
1093         spin_lock_init(&mm->ioctx_lock);
1094         mm->ioctx_table = NULL;
1095 #endif
1096 }
1097
1098 static __always_inline void mm_clear_owner(struct mm_struct *mm,
1099                                            struct task_struct *p)
1100 {
1101 #ifdef CONFIG_MEMCG
1102         if (mm->owner == p)
1103                 WRITE_ONCE(mm->owner, NULL);
1104 #endif
1105 }
1106
1107 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1108 {
1109 #ifdef CONFIG_MEMCG
1110         mm->owner = p;
1111 #endif
1112 }
1113
1114 static void mm_init_uprobes_state(struct mm_struct *mm)
1115 {
1116 #ifdef CONFIG_UPROBES
1117         mm->uprobes_state.xol_area = NULL;
1118 #endif
1119 }
1120
1121 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
1122         struct user_namespace *user_ns)
1123 {
1124         int i;
1125
1126         mt_init_flags(&mm->mm_mt, MM_MT_FLAGS);
1127         mt_set_external_lock(&mm->mm_mt, &mm->mmap_lock);
1128         atomic_set(&mm->mm_users, 1);
1129         atomic_set(&mm->mm_count, 1);
1130         seqcount_init(&mm->write_protect_seq);
1131         mmap_init_lock(mm);
1132         INIT_LIST_HEAD(&mm->mmlist);
1133         mm_pgtables_bytes_init(mm);
1134         mm->map_count = 0;
1135         mm->locked_vm = 0;
1136         atomic64_set(&mm->pinned_vm, 0);
1137         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1138         spin_lock_init(&mm->page_table_lock);
1139         spin_lock_init(&mm->arg_lock);
1140         mm_init_cpumask(mm);
1141         mm_init_aio(mm);
1142         mm_init_owner(mm, p);
1143         mm_pasid_init(mm);
1144         RCU_INIT_POINTER(mm->exe_file, NULL);
1145         mmu_notifier_subscriptions_init(mm);
1146         init_tlb_flush_pending(mm);
1147 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1148         mm->pmd_huge_pte = NULL;
1149 #endif
1150         mm_init_uprobes_state(mm);
1151         hugetlb_count_init(mm);
1152
1153         if (current->mm) {
1154                 mm->flags = current->mm->flags & MMF_INIT_MASK;
1155                 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1156         } else {
1157                 mm->flags = default_dump_filter;
1158                 mm->def_flags = 0;
1159         }
1160
1161         if (mm_alloc_pgd(mm))
1162                 goto fail_nopgd;
1163
1164         if (init_new_context(p, mm))
1165                 goto fail_nocontext;
1166
1167         for (i = 0; i < NR_MM_COUNTERS; i++)
1168                 if (percpu_counter_init(&mm->rss_stat[i], 0, GFP_KERNEL_ACCOUNT))
1169                         goto fail_pcpu;
1170
1171         mm->user_ns = get_user_ns(user_ns);
1172         lru_gen_init_mm(mm);
1173         mm_init_cid(mm);
1174         return mm;
1175
1176 fail_pcpu:
1177         while (i > 0)
1178                 percpu_counter_destroy(&mm->rss_stat[--i]);
1179 fail_nocontext:
1180         mm_free_pgd(mm);
1181 fail_nopgd:
1182         free_mm(mm);
1183         return NULL;
1184 }
1185
1186 /*
1187  * Allocate and initialize an mm_struct.
1188  */
1189 struct mm_struct *mm_alloc(void)
1190 {
1191         struct mm_struct *mm;
1192
1193         mm = allocate_mm();
1194         if (!mm)
1195                 return NULL;
1196
1197         memset(mm, 0, sizeof(*mm));
1198         return mm_init(mm, current, current_user_ns());
1199 }
1200
1201 static inline void __mmput(struct mm_struct *mm)
1202 {
1203         VM_BUG_ON(atomic_read(&mm->mm_users));
1204
1205         uprobe_clear_state(mm);
1206         exit_aio(mm);
1207         ksm_exit(mm);
1208         khugepaged_exit(mm); /* must run before exit_mmap */
1209         exit_mmap(mm);
1210         mm_put_huge_zero_page(mm);
1211         set_mm_exe_file(mm, NULL);
1212         if (!list_empty(&mm->mmlist)) {
1213                 spin_lock(&mmlist_lock);
1214                 list_del(&mm->mmlist);
1215                 spin_unlock(&mmlist_lock);
1216         }
1217         if (mm->binfmt)
1218                 module_put(mm->binfmt->module);
1219         lru_gen_del_mm(mm);
1220         mmdrop(mm);
1221 }
1222
1223 /*
1224  * Decrement the use count and release all resources for an mm.
1225  */
1226 void mmput(struct mm_struct *mm)
1227 {
1228         might_sleep();
1229
1230         if (atomic_dec_and_test(&mm->mm_users))
1231                 __mmput(mm);
1232 }
1233 EXPORT_SYMBOL_GPL(mmput);
1234
1235 #ifdef CONFIG_MMU
1236 static void mmput_async_fn(struct work_struct *work)
1237 {
1238         struct mm_struct *mm = container_of(work, struct mm_struct,
1239                                             async_put_work);
1240
1241         __mmput(mm);
1242 }
1243
1244 void mmput_async(struct mm_struct *mm)
1245 {
1246         if (atomic_dec_and_test(&mm->mm_users)) {
1247                 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1248                 schedule_work(&mm->async_put_work);
1249         }
1250 }
1251 EXPORT_SYMBOL_GPL(mmput_async);
1252 #endif
1253
1254 /**
1255  * set_mm_exe_file - change a reference to the mm's executable file
1256  *
1257  * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1258  *
1259  * Main users are mmput() and sys_execve(). Callers prevent concurrent
1260  * invocations: in mmput() nobody alive left, in execve task is single
1261  * threaded.
1262  *
1263  * Can only fail if new_exe_file != NULL.
1264  */
1265 int set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1266 {
1267         struct file *old_exe_file;
1268
1269         /*
1270          * It is safe to dereference the exe_file without RCU as
1271          * this function is only called if nobody else can access
1272          * this mm -- see comment above for justification.
1273          */
1274         old_exe_file = rcu_dereference_raw(mm->exe_file);
1275
1276         if (new_exe_file) {
1277                 /*
1278                  * We expect the caller (i.e., sys_execve) to already denied
1279                  * write access, so this is unlikely to fail.
1280                  */
1281                 if (unlikely(deny_write_access(new_exe_file)))
1282                         return -EACCES;
1283                 get_file(new_exe_file);
1284         }
1285         rcu_assign_pointer(mm->exe_file, new_exe_file);
1286         if (old_exe_file) {
1287                 allow_write_access(old_exe_file);
1288                 fput(old_exe_file);
1289         }
1290         return 0;
1291 }
1292
1293 /**
1294  * replace_mm_exe_file - replace a reference to the mm's executable file
1295  *
1296  * This changes mm's executable file (shown as symlink /proc/[pid]/exe),
1297  * dealing with concurrent invocation and without grabbing the mmap lock in
1298  * write mode.
1299  *
1300  * Main user is sys_prctl(PR_SET_MM_MAP/EXE_FILE).
1301  */
1302 int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1303 {
1304         struct vm_area_struct *vma;
1305         struct file *old_exe_file;
1306         int ret = 0;
1307
1308         /* Forbid mm->exe_file change if old file still mapped. */
1309         old_exe_file = get_mm_exe_file(mm);
1310         if (old_exe_file) {
1311                 VMA_ITERATOR(vmi, mm, 0);
1312                 mmap_read_lock(mm);
1313                 for_each_vma(vmi, vma) {
1314                         if (!vma->vm_file)
1315                                 continue;
1316                         if (path_equal(&vma->vm_file->f_path,
1317                                        &old_exe_file->f_path)) {
1318                                 ret = -EBUSY;
1319                                 break;
1320                         }
1321                 }
1322                 mmap_read_unlock(mm);
1323                 fput(old_exe_file);
1324                 if (ret)
1325                         return ret;
1326         }
1327
1328         /* set the new file, lockless */
1329         ret = deny_write_access(new_exe_file);
1330         if (ret)
1331                 return -EACCES;
1332         get_file(new_exe_file);
1333
1334         old_exe_file = xchg(&mm->exe_file, new_exe_file);
1335         if (old_exe_file) {
1336                 /*
1337                  * Don't race with dup_mmap() getting the file and disallowing
1338                  * write access while someone might open the file writable.
1339                  */
1340                 mmap_read_lock(mm);
1341                 allow_write_access(old_exe_file);
1342                 fput(old_exe_file);
1343                 mmap_read_unlock(mm);
1344         }
1345         return 0;
1346 }
1347
1348 /**
1349  * get_mm_exe_file - acquire a reference to the mm's executable file
1350  *
1351  * Returns %NULL if mm has no associated executable file.
1352  * User must release file via fput().
1353  */
1354 struct file *get_mm_exe_file(struct mm_struct *mm)
1355 {
1356         struct file *exe_file;
1357
1358         rcu_read_lock();
1359         exe_file = rcu_dereference(mm->exe_file);
1360         if (exe_file && !get_file_rcu(exe_file))
1361                 exe_file = NULL;
1362         rcu_read_unlock();
1363         return exe_file;
1364 }
1365
1366 /**
1367  * get_task_exe_file - acquire a reference to the task's executable file
1368  *
1369  * Returns %NULL if task's mm (if any) has no associated executable file or
1370  * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1371  * User must release file via fput().
1372  */
1373 struct file *get_task_exe_file(struct task_struct *task)
1374 {
1375         struct file *exe_file = NULL;
1376         struct mm_struct *mm;
1377
1378         task_lock(task);
1379         mm = task->mm;
1380         if (mm) {
1381                 if (!(task->flags & PF_KTHREAD))
1382                         exe_file = get_mm_exe_file(mm);
1383         }
1384         task_unlock(task);
1385         return exe_file;
1386 }
1387
1388 /**
1389  * get_task_mm - acquire a reference to the task's mm
1390  *
1391  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
1392  * this kernel workthread has transiently adopted a user mm with use_mm,
1393  * to do its AIO) is not set and if so returns a reference to it, after
1394  * bumping up the use count.  User must release the mm via mmput()
1395  * after use.  Typically used by /proc and ptrace.
1396  */
1397 struct mm_struct *get_task_mm(struct task_struct *task)
1398 {
1399         struct mm_struct *mm;
1400
1401         task_lock(task);
1402         mm = task->mm;
1403         if (mm) {
1404                 if (task->flags & PF_KTHREAD)
1405                         mm = NULL;
1406                 else
1407                         mmget(mm);
1408         }
1409         task_unlock(task);
1410         return mm;
1411 }
1412 EXPORT_SYMBOL_GPL(get_task_mm);
1413
1414 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1415 {
1416         struct mm_struct *mm;
1417         int err;
1418
1419         err =  down_read_killable(&task->signal->exec_update_lock);
1420         if (err)
1421                 return ERR_PTR(err);
1422
1423         mm = get_task_mm(task);
1424         if (mm && mm != current->mm &&
1425                         !ptrace_may_access(task, mode)) {
1426                 mmput(mm);
1427                 mm = ERR_PTR(-EACCES);
1428         }
1429         up_read(&task->signal->exec_update_lock);
1430
1431         return mm;
1432 }
1433
1434 static void complete_vfork_done(struct task_struct *tsk)
1435 {
1436         struct completion *vfork;
1437
1438         task_lock(tsk);
1439         vfork = tsk->vfork_done;
1440         if (likely(vfork)) {
1441                 tsk->vfork_done = NULL;
1442                 complete(vfork);
1443         }
1444         task_unlock(tsk);
1445 }
1446
1447 static int wait_for_vfork_done(struct task_struct *child,
1448                                 struct completion *vfork)
1449 {
1450         unsigned int state = TASK_UNINTERRUPTIBLE|TASK_KILLABLE|TASK_FREEZABLE;
1451         int killed;
1452
1453         cgroup_enter_frozen();
1454         killed = wait_for_completion_state(vfork, state);
1455         cgroup_leave_frozen(false);
1456
1457         if (killed) {
1458                 task_lock(child);
1459                 child->vfork_done = NULL;
1460                 task_unlock(child);
1461         }
1462
1463         put_task_struct(child);
1464         return killed;
1465 }
1466
1467 /* Please note the differences between mmput and mm_release.
1468  * mmput is called whenever we stop holding onto a mm_struct,
1469  * error success whatever.
1470  *
1471  * mm_release is called after a mm_struct has been removed
1472  * from the current process.
1473  *
1474  * This difference is important for error handling, when we
1475  * only half set up a mm_struct for a new process and need to restore
1476  * the old one.  Because we mmput the new mm_struct before
1477  * restoring the old one. . .
1478  * Eric Biederman 10 January 1998
1479  */
1480 static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1481 {
1482         uprobe_free_utask(tsk);
1483
1484         /* Get rid of any cached register state */
1485         deactivate_mm(tsk, mm);
1486
1487         /*
1488          * Signal userspace if we're not exiting with a core dump
1489          * because we want to leave the value intact for debugging
1490          * purposes.
1491          */
1492         if (tsk->clear_child_tid) {
1493                 if (atomic_read(&mm->mm_users) > 1) {
1494                         /*
1495                          * We don't check the error code - if userspace has
1496                          * not set up a proper pointer then tough luck.
1497                          */
1498                         put_user(0, tsk->clear_child_tid);
1499                         do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1500                                         1, NULL, NULL, 0, 0);
1501                 }
1502                 tsk->clear_child_tid = NULL;
1503         }
1504
1505         /*
1506          * All done, finally we can wake up parent and return this mm to him.
1507          * Also kthread_stop() uses this completion for synchronization.
1508          */
1509         if (tsk->vfork_done)
1510                 complete_vfork_done(tsk);
1511 }
1512
1513 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1514 {
1515         futex_exit_release(tsk);
1516         mm_release(tsk, mm);
1517 }
1518
1519 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1520 {
1521         futex_exec_release(tsk);
1522         mm_release(tsk, mm);
1523 }
1524
1525 /**
1526  * dup_mm() - duplicates an existing mm structure
1527  * @tsk: the task_struct with which the new mm will be associated.
1528  * @oldmm: the mm to duplicate.
1529  *
1530  * Allocates a new mm structure and duplicates the provided @oldmm structure
1531  * content into it.
1532  *
1533  * Return: the duplicated mm or NULL on failure.
1534  */
1535 static struct mm_struct *dup_mm(struct task_struct *tsk,
1536                                 struct mm_struct *oldmm)
1537 {
1538         struct mm_struct *mm;
1539         int err;
1540
1541         mm = allocate_mm();
1542         if (!mm)
1543                 goto fail_nomem;
1544
1545         memcpy(mm, oldmm, sizeof(*mm));
1546
1547         if (!mm_init(mm, tsk, mm->user_ns))
1548                 goto fail_nomem;
1549
1550         err = dup_mmap(mm, oldmm);
1551         if (err)
1552                 goto free_pt;
1553
1554         mm->hiwater_rss = get_mm_rss(mm);
1555         mm->hiwater_vm = mm->total_vm;
1556
1557         if (mm->binfmt && !try_module_get(mm->binfmt->module))
1558                 goto free_pt;
1559
1560         return mm;
1561
1562 free_pt:
1563         /* don't put binfmt in mmput, we haven't got module yet */
1564         mm->binfmt = NULL;
1565         mm_init_owner(mm, NULL);
1566         mmput(mm);
1567
1568 fail_nomem:
1569         return NULL;
1570 }
1571
1572 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1573 {
1574         struct mm_struct *mm, *oldmm;
1575
1576         tsk->min_flt = tsk->maj_flt = 0;
1577         tsk->nvcsw = tsk->nivcsw = 0;
1578 #ifdef CONFIG_DETECT_HUNG_TASK
1579         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1580         tsk->last_switch_time = 0;
1581 #endif
1582
1583         tsk->mm = NULL;
1584         tsk->active_mm = NULL;
1585
1586         /*
1587          * Are we cloning a kernel thread?
1588          *
1589          * We need to steal a active VM for that..
1590          */
1591         oldmm = current->mm;
1592         if (!oldmm)
1593                 return 0;
1594
1595         if (clone_flags & CLONE_VM) {
1596                 mmget(oldmm);
1597                 mm = oldmm;
1598         } else {
1599                 mm = dup_mm(tsk, current->mm);
1600                 if (!mm)
1601                         return -ENOMEM;
1602         }
1603
1604         tsk->mm = mm;
1605         tsk->active_mm = mm;
1606         sched_mm_cid_fork(tsk);
1607         return 0;
1608 }
1609
1610 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1611 {
1612         struct fs_struct *fs = current->fs;
1613         if (clone_flags & CLONE_FS) {
1614                 /* tsk->fs is already what we want */
1615                 spin_lock(&fs->lock);
1616                 if (fs->in_exec) {
1617                         spin_unlock(&fs->lock);
1618                         return -EAGAIN;
1619                 }
1620                 fs->users++;
1621                 spin_unlock(&fs->lock);
1622                 return 0;
1623         }
1624         tsk->fs = copy_fs_struct(fs);
1625         if (!tsk->fs)
1626                 return -ENOMEM;
1627         return 0;
1628 }
1629
1630 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1631 {
1632         struct files_struct *oldf, *newf;
1633         int error = 0;
1634
1635         /*
1636          * A background process may not have any files ...
1637          */
1638         oldf = current->files;
1639         if (!oldf)
1640                 goto out;
1641
1642         if (clone_flags & CLONE_FILES) {
1643                 atomic_inc(&oldf->count);
1644                 goto out;
1645         }
1646
1647         newf = dup_fd(oldf, NR_OPEN_MAX, &error);
1648         if (!newf)
1649                 goto out;
1650
1651         tsk->files = newf;
1652         error = 0;
1653 out:
1654         return error;
1655 }
1656
1657 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1658 {
1659         struct sighand_struct *sig;
1660
1661         if (clone_flags & CLONE_SIGHAND) {
1662                 refcount_inc(&current->sighand->count);
1663                 return 0;
1664         }
1665         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1666         RCU_INIT_POINTER(tsk->sighand, sig);
1667         if (!sig)
1668                 return -ENOMEM;
1669
1670         refcount_set(&sig->count, 1);
1671         spin_lock_irq(&current->sighand->siglock);
1672         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1673         spin_unlock_irq(&current->sighand->siglock);
1674
1675         /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
1676         if (clone_flags & CLONE_CLEAR_SIGHAND)
1677                 flush_signal_handlers(tsk, 0);
1678
1679         return 0;
1680 }
1681
1682 void __cleanup_sighand(struct sighand_struct *sighand)
1683 {
1684         if (refcount_dec_and_test(&sighand->count)) {
1685                 signalfd_cleanup(sighand);
1686                 /*
1687                  * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1688                  * without an RCU grace period, see __lock_task_sighand().
1689                  */
1690                 kmem_cache_free(sighand_cachep, sighand);
1691         }
1692 }
1693
1694 /*
1695  * Initialize POSIX timer handling for a thread group.
1696  */
1697 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1698 {
1699         struct posix_cputimers *pct = &sig->posix_cputimers;
1700         unsigned long cpu_limit;
1701
1702         cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1703         posix_cputimers_group_init(pct, cpu_limit);
1704 }
1705
1706 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1707 {
1708         struct signal_struct *sig;
1709
1710         if (clone_flags & CLONE_THREAD)
1711                 return 0;
1712
1713         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1714         tsk->signal = sig;
1715         if (!sig)
1716                 return -ENOMEM;
1717
1718         sig->nr_threads = 1;
1719         sig->quick_threads = 1;
1720         atomic_set(&sig->live, 1);
1721         refcount_set(&sig->sigcnt, 1);
1722
1723         /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1724         sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1725         tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1726
1727         init_waitqueue_head(&sig->wait_chldexit);
1728         sig->curr_target = tsk;
1729         init_sigpending(&sig->shared_pending);
1730         INIT_HLIST_HEAD(&sig->multiprocess);
1731         seqlock_init(&sig->stats_lock);
1732         prev_cputime_init(&sig->prev_cputime);
1733
1734 #ifdef CONFIG_POSIX_TIMERS
1735         INIT_LIST_HEAD(&sig->posix_timers);
1736         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1737         sig->real_timer.function = it_real_fn;
1738 #endif
1739
1740         task_lock(current->group_leader);
1741         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1742         task_unlock(current->group_leader);
1743
1744         posix_cpu_timers_init_group(sig);
1745
1746         tty_audit_fork(sig);
1747         sched_autogroup_fork(sig);
1748
1749         sig->oom_score_adj = current->signal->oom_score_adj;
1750         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1751
1752         mutex_init(&sig->cred_guard_mutex);
1753         init_rwsem(&sig->exec_update_lock);
1754
1755         return 0;
1756 }
1757
1758 static void copy_seccomp(struct task_struct *p)
1759 {
1760 #ifdef CONFIG_SECCOMP
1761         /*
1762          * Must be called with sighand->lock held, which is common to
1763          * all threads in the group. Holding cred_guard_mutex is not
1764          * needed because this new task is not yet running and cannot
1765          * be racing exec.
1766          */
1767         assert_spin_locked(&current->sighand->siglock);
1768
1769         /* Ref-count the new filter user, and assign it. */
1770         get_seccomp_filter(current);
1771         p->seccomp = current->seccomp;
1772
1773         /*
1774          * Explicitly enable no_new_privs here in case it got set
1775          * between the task_struct being duplicated and holding the
1776          * sighand lock. The seccomp state and nnp must be in sync.
1777          */
1778         if (task_no_new_privs(current))
1779                 task_set_no_new_privs(p);
1780
1781         /*
1782          * If the parent gained a seccomp mode after copying thread
1783          * flags and between before we held the sighand lock, we have
1784          * to manually enable the seccomp thread flag here.
1785          */
1786         if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1787                 set_task_syscall_work(p, SECCOMP);
1788 #endif
1789 }
1790
1791 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1792 {
1793         current->clear_child_tid = tidptr;
1794
1795         return task_pid_vnr(current);
1796 }
1797
1798 static void rt_mutex_init_task(struct task_struct *p)
1799 {
1800         raw_spin_lock_init(&p->pi_lock);
1801 #ifdef CONFIG_RT_MUTEXES
1802         p->pi_waiters = RB_ROOT_CACHED;
1803         p->pi_top_task = NULL;
1804         p->pi_blocked_on = NULL;
1805 #endif
1806 }
1807
1808 static inline void init_task_pid_links(struct task_struct *task)
1809 {
1810         enum pid_type type;
1811
1812         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type)
1813                 INIT_HLIST_NODE(&task->pid_links[type]);
1814 }
1815
1816 static inline void
1817 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1818 {
1819         if (type == PIDTYPE_PID)
1820                 task->thread_pid = pid;
1821         else
1822                 task->signal->pids[type] = pid;
1823 }
1824
1825 static inline void rcu_copy_process(struct task_struct *p)
1826 {
1827 #ifdef CONFIG_PREEMPT_RCU
1828         p->rcu_read_lock_nesting = 0;
1829         p->rcu_read_unlock_special.s = 0;
1830         p->rcu_blocked_node = NULL;
1831         INIT_LIST_HEAD(&p->rcu_node_entry);
1832 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1833 #ifdef CONFIG_TASKS_RCU
1834         p->rcu_tasks_holdout = false;
1835         INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1836         p->rcu_tasks_idle_cpu = -1;
1837 #endif /* #ifdef CONFIG_TASKS_RCU */
1838 #ifdef CONFIG_TASKS_TRACE_RCU
1839         p->trc_reader_nesting = 0;
1840         p->trc_reader_special.s = 0;
1841         INIT_LIST_HEAD(&p->trc_holdout_list);
1842         INIT_LIST_HEAD(&p->trc_blkd_node);
1843 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
1844 }
1845
1846 struct pid *pidfd_pid(const struct file *file)
1847 {
1848         if (file->f_op == &pidfd_fops)
1849                 return file->private_data;
1850
1851         return ERR_PTR(-EBADF);
1852 }
1853
1854 static int pidfd_release(struct inode *inode, struct file *file)
1855 {
1856         struct pid *pid = file->private_data;
1857
1858         file->private_data = NULL;
1859         put_pid(pid);
1860         return 0;
1861 }
1862
1863 #ifdef CONFIG_PROC_FS
1864 /**
1865  * pidfd_show_fdinfo - print information about a pidfd
1866  * @m: proc fdinfo file
1867  * @f: file referencing a pidfd
1868  *
1869  * Pid:
1870  * This function will print the pid that a given pidfd refers to in the
1871  * pid namespace of the procfs instance.
1872  * If the pid namespace of the process is not a descendant of the pid
1873  * namespace of the procfs instance 0 will be shown as its pid. This is
1874  * similar to calling getppid() on a process whose parent is outside of
1875  * its pid namespace.
1876  *
1877  * NSpid:
1878  * If pid namespaces are supported then this function will also print
1879  * the pid of a given pidfd refers to for all descendant pid namespaces
1880  * starting from the current pid namespace of the instance, i.e. the
1881  * Pid field and the first entry in the NSpid field will be identical.
1882  * If the pid namespace of the process is not a descendant of the pid
1883  * namespace of the procfs instance 0 will be shown as its first NSpid
1884  * entry and no others will be shown.
1885  * Note that this differs from the Pid and NSpid fields in
1886  * /proc/<pid>/status where Pid and NSpid are always shown relative to
1887  * the  pid namespace of the procfs instance. The difference becomes
1888  * obvious when sending around a pidfd between pid namespaces from a
1889  * different branch of the tree, i.e. where no ancestral relation is
1890  * present between the pid namespaces:
1891  * - create two new pid namespaces ns1 and ns2 in the initial pid
1892  *   namespace (also take care to create new mount namespaces in the
1893  *   new pid namespace and mount procfs)
1894  * - create a process with a pidfd in ns1
1895  * - send pidfd from ns1 to ns2
1896  * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
1897  *   have exactly one entry, which is 0
1898  */
1899 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1900 {
1901         struct pid *pid = f->private_data;
1902         struct pid_namespace *ns;
1903         pid_t nr = -1;
1904
1905         if (likely(pid_has_task(pid, PIDTYPE_PID))) {
1906                 ns = proc_pid_ns(file_inode(m->file)->i_sb);
1907                 nr = pid_nr_ns(pid, ns);
1908         }
1909
1910         seq_put_decimal_ll(m, "Pid:\t", nr);
1911
1912 #ifdef CONFIG_PID_NS
1913         seq_put_decimal_ll(m, "\nNSpid:\t", nr);
1914         if (nr > 0) {
1915                 int i;
1916
1917                 /* If nr is non-zero it means that 'pid' is valid and that
1918                  * ns, i.e. the pid namespace associated with the procfs
1919                  * instance, is in the pid namespace hierarchy of pid.
1920                  * Start at one below the already printed level.
1921                  */
1922                 for (i = ns->level + 1; i <= pid->level; i++)
1923                         seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
1924         }
1925 #endif
1926         seq_putc(m, '\n');
1927 }
1928 #endif
1929
1930 /*
1931  * Poll support for process exit notification.
1932  */
1933 static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
1934 {
1935         struct pid *pid = file->private_data;
1936         __poll_t poll_flags = 0;
1937
1938         poll_wait(file, &pid->wait_pidfd, pts);
1939
1940         /*
1941          * Inform pollers only when the whole thread group exits.
1942          * If the thread group leader exits before all other threads in the
1943          * group, then poll(2) should block, similar to the wait(2) family.
1944          */
1945         if (thread_group_exited(pid))
1946                 poll_flags = EPOLLIN | EPOLLRDNORM;
1947
1948         return poll_flags;
1949 }
1950
1951 const struct file_operations pidfd_fops = {
1952         .release = pidfd_release,
1953         .poll = pidfd_poll,
1954 #ifdef CONFIG_PROC_FS
1955         .show_fdinfo = pidfd_show_fdinfo,
1956 #endif
1957 };
1958
1959 static void __delayed_free_task(struct rcu_head *rhp)
1960 {
1961         struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1962
1963         free_task(tsk);
1964 }
1965
1966 static __always_inline void delayed_free_task(struct task_struct *tsk)
1967 {
1968         if (IS_ENABLED(CONFIG_MEMCG))
1969                 call_rcu(&tsk->rcu, __delayed_free_task);
1970         else
1971                 free_task(tsk);
1972 }
1973
1974 static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk)
1975 {
1976         /* Skip if kernel thread */
1977         if (!tsk->mm)
1978                 return;
1979
1980         /* Skip if spawning a thread or using vfork */
1981         if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) != CLONE_VM)
1982                 return;
1983
1984         /* We need to synchronize with __set_oom_adj */
1985         mutex_lock(&oom_adj_mutex);
1986         set_bit(MMF_MULTIPROCESS, &tsk->mm->flags);
1987         /* Update the values in case they were changed after copy_signal */
1988         tsk->signal->oom_score_adj = current->signal->oom_score_adj;
1989         tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min;
1990         mutex_unlock(&oom_adj_mutex);
1991 }
1992
1993 #ifdef CONFIG_RV
1994 static void rv_task_fork(struct task_struct *p)
1995 {
1996         int i;
1997
1998         for (i = 0; i < RV_PER_TASK_MONITORS; i++)
1999                 p->rv[i].da_mon.monitoring = false;
2000 }
2001 #else
2002 #define rv_task_fork(p) do {} while (0)
2003 #endif
2004
2005 /*
2006  * This creates a new process as a copy of the old one,
2007  * but does not actually start it yet.
2008  *
2009  * It copies the registers, and all the appropriate
2010  * parts of the process environment (as per the clone
2011  * flags). The actual kick-off is left to the caller.
2012  */
2013 static __latent_entropy struct task_struct *copy_process(
2014                                         struct pid *pid,
2015                                         int trace,
2016                                         int node,
2017                                         struct kernel_clone_args *args)
2018 {
2019         int pidfd = -1, retval;
2020         struct task_struct *p;
2021         struct multiprocess_signals delayed;
2022         struct file *pidfile = NULL;
2023         const u64 clone_flags = args->flags;
2024         struct nsproxy *nsp = current->nsproxy;
2025
2026         /*
2027          * Don't allow sharing the root directory with processes in a different
2028          * namespace
2029          */
2030         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
2031                 return ERR_PTR(-EINVAL);
2032
2033         if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
2034                 return ERR_PTR(-EINVAL);
2035
2036         /*
2037          * Thread groups must share signals as well, and detached threads
2038          * can only be started up within the thread group.
2039          */
2040         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
2041                 return ERR_PTR(-EINVAL);
2042
2043         /*
2044          * Shared signal handlers imply shared VM. By way of the above,
2045          * thread groups also imply shared VM. Blocking this case allows
2046          * for various simplifications in other code.
2047          */
2048         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
2049                 return ERR_PTR(-EINVAL);
2050
2051         /*
2052          * Siblings of global init remain as zombies on exit since they are
2053          * not reaped by their parent (swapper). To solve this and to avoid
2054          * multi-rooted process trees, prevent global and container-inits
2055          * from creating siblings.
2056          */
2057         if ((clone_flags & CLONE_PARENT) &&
2058                                 current->signal->flags & SIGNAL_UNKILLABLE)
2059                 return ERR_PTR(-EINVAL);
2060
2061         /*
2062          * If the new process will be in a different pid or user namespace
2063          * do not allow it to share a thread group with the forking task.
2064          */
2065         if (clone_flags & CLONE_THREAD) {
2066                 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
2067                     (task_active_pid_ns(current) != nsp->pid_ns_for_children))
2068                         return ERR_PTR(-EINVAL);
2069         }
2070
2071         if (clone_flags & CLONE_PIDFD) {
2072                 /*
2073                  * - CLONE_DETACHED is blocked so that we can potentially
2074                  *   reuse it later for CLONE_PIDFD.
2075                  * - CLONE_THREAD is blocked until someone really needs it.
2076                  */
2077                 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
2078                         return ERR_PTR(-EINVAL);
2079         }
2080
2081         /*
2082          * Force any signals received before this point to be delivered
2083          * before the fork happens.  Collect up signals sent to multiple
2084          * processes that happen during the fork and delay them so that
2085          * they appear to happen after the fork.
2086          */
2087         sigemptyset(&delayed.signal);
2088         INIT_HLIST_NODE(&delayed.node);
2089
2090         spin_lock_irq(&current->sighand->siglock);
2091         if (!(clone_flags & CLONE_THREAD))
2092                 hlist_add_head(&delayed.node, &current->signal->multiprocess);
2093         recalc_sigpending();
2094         spin_unlock_irq(&current->sighand->siglock);
2095         retval = -ERESTARTNOINTR;
2096         if (task_sigpending(current))
2097                 goto fork_out;
2098
2099         retval = -ENOMEM;
2100         p = dup_task_struct(current, node);
2101         if (!p)
2102                 goto fork_out;
2103         p->flags &= ~PF_KTHREAD;
2104         if (args->kthread)
2105                 p->flags |= PF_KTHREAD;
2106         if (args->io_thread) {
2107                 /*
2108                  * Mark us an IO worker, and block any signal that isn't
2109                  * fatal or STOP
2110                  */
2111                 p->flags |= PF_IO_WORKER;
2112                 siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
2113         }
2114
2115         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
2116         /*
2117          * Clear TID on mm_release()?
2118          */
2119         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
2120
2121         ftrace_graph_init_task(p);
2122
2123         rt_mutex_init_task(p);
2124
2125         lockdep_assert_irqs_enabled();
2126 #ifdef CONFIG_PROVE_LOCKING
2127         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
2128 #endif
2129         retval = copy_creds(p, clone_flags);
2130         if (retval < 0)
2131                 goto bad_fork_free;
2132
2133         retval = -EAGAIN;
2134         if (is_rlimit_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
2135                 if (p->real_cred->user != INIT_USER &&
2136                     !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
2137                         goto bad_fork_cleanup_count;
2138         }
2139         current->flags &= ~PF_NPROC_EXCEEDED;
2140
2141         /*
2142          * If multiple threads are within copy_process(), then this check
2143          * triggers too late. This doesn't hurt, the check is only there
2144          * to stop root fork bombs.
2145          */
2146         retval = -EAGAIN;
2147         if (data_race(nr_threads >= max_threads))
2148                 goto bad_fork_cleanup_count;
2149
2150         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
2151         p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE | PF_NO_SETAFFINITY);
2152         p->flags |= PF_FORKNOEXEC;
2153         INIT_LIST_HEAD(&p->children);
2154         INIT_LIST_HEAD(&p->sibling);
2155         rcu_copy_process(p);
2156         p->vfork_done = NULL;
2157         spin_lock_init(&p->alloc_lock);
2158
2159         init_sigpending(&p->pending);
2160
2161         p->utime = p->stime = p->gtime = 0;
2162 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
2163         p->utimescaled = p->stimescaled = 0;
2164 #endif
2165         prev_cputime_init(&p->prev_cputime);
2166
2167 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
2168         seqcount_init(&p->vtime.seqcount);
2169         p->vtime.starttime = 0;
2170         p->vtime.state = VTIME_INACTIVE;
2171 #endif
2172
2173 #ifdef CONFIG_IO_URING
2174         p->io_uring = NULL;
2175 #endif
2176
2177 #if defined(SPLIT_RSS_COUNTING)
2178         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
2179 #endif
2180
2181         p->default_timer_slack_ns = current->timer_slack_ns;
2182
2183 #ifdef CONFIG_PSI
2184         p->psi_flags = 0;
2185 #endif
2186
2187         task_io_accounting_init(&p->ioac);
2188         acct_clear_integrals(p);
2189
2190         posix_cputimers_init(&p->posix_cputimers);
2191
2192         p->io_context = NULL;
2193         audit_set_context(p, NULL);
2194         cgroup_fork(p);
2195         if (args->kthread) {
2196                 if (!set_kthread_struct(p))
2197                         goto bad_fork_cleanup_delayacct;
2198         }
2199 #ifdef CONFIG_NUMA
2200         p->mempolicy = mpol_dup(p->mempolicy);
2201         if (IS_ERR(p->mempolicy)) {
2202                 retval = PTR_ERR(p->mempolicy);
2203                 p->mempolicy = NULL;
2204                 goto bad_fork_cleanup_delayacct;
2205         }
2206 #endif
2207 #ifdef CONFIG_CPUSETS
2208         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
2209         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
2210         seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock);
2211 #endif
2212 #ifdef CONFIG_TRACE_IRQFLAGS
2213         memset(&p->irqtrace, 0, sizeof(p->irqtrace));
2214         p->irqtrace.hardirq_disable_ip  = _THIS_IP_;
2215         p->irqtrace.softirq_enable_ip   = _THIS_IP_;
2216         p->softirqs_enabled             = 1;
2217         p->softirq_context              = 0;
2218 #endif
2219
2220         p->pagefault_disabled = 0;
2221
2222 #ifdef CONFIG_LOCKDEP
2223         lockdep_init_task(p);
2224 #endif
2225
2226 #ifdef CONFIG_DEBUG_MUTEXES
2227         p->blocked_on = NULL; /* not blocked yet */
2228 #endif
2229 #ifdef CONFIG_BCACHE
2230         p->sequential_io        = 0;
2231         p->sequential_io_avg    = 0;
2232 #endif
2233 #ifdef CONFIG_BPF_SYSCALL
2234         RCU_INIT_POINTER(p->bpf_storage, NULL);
2235         p->bpf_ctx = NULL;
2236 #endif
2237
2238         /* Perform scheduler related setup. Assign this task to a CPU. */
2239         retval = sched_fork(clone_flags, p);
2240         if (retval)
2241                 goto bad_fork_cleanup_policy;
2242
2243         retval = perf_event_init_task(p, clone_flags);
2244         if (retval)
2245                 goto bad_fork_cleanup_policy;
2246         retval = audit_alloc(p);
2247         if (retval)
2248                 goto bad_fork_cleanup_perf;
2249         /* copy all the process information */
2250         shm_init_task(p);
2251         retval = security_task_alloc(p, clone_flags);
2252         if (retval)
2253                 goto bad_fork_cleanup_audit;
2254         retval = copy_semundo(clone_flags, p);
2255         if (retval)
2256                 goto bad_fork_cleanup_security;
2257         retval = copy_files(clone_flags, p);
2258         if (retval)
2259                 goto bad_fork_cleanup_semundo;
2260         retval = copy_fs(clone_flags, p);
2261         if (retval)
2262                 goto bad_fork_cleanup_files;
2263         retval = copy_sighand(clone_flags, p);
2264         if (retval)
2265                 goto bad_fork_cleanup_fs;
2266         retval = copy_signal(clone_flags, p);
2267         if (retval)
2268                 goto bad_fork_cleanup_sighand;
2269         retval = copy_mm(clone_flags, p);
2270         if (retval)
2271                 goto bad_fork_cleanup_signal;
2272         retval = copy_namespaces(clone_flags, p);
2273         if (retval)
2274                 goto bad_fork_cleanup_mm;
2275         retval = copy_io(clone_flags, p);
2276         if (retval)
2277                 goto bad_fork_cleanup_namespaces;
2278         retval = copy_thread(p, args);
2279         if (retval)
2280                 goto bad_fork_cleanup_io;
2281
2282         stackleak_task_init(p);
2283
2284         if (pid != &init_struct_pid) {
2285                 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
2286                                 args->set_tid_size);
2287                 if (IS_ERR(pid)) {
2288                         retval = PTR_ERR(pid);
2289                         goto bad_fork_cleanup_thread;
2290                 }
2291         }
2292
2293         /*
2294          * This has to happen after we've potentially unshared the file
2295          * descriptor table (so that the pidfd doesn't leak into the child
2296          * if the fd table isn't shared).
2297          */
2298         if (clone_flags & CLONE_PIDFD) {
2299                 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2300                 if (retval < 0)
2301                         goto bad_fork_free_pid;
2302
2303                 pidfd = retval;
2304
2305                 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2306                                               O_RDWR | O_CLOEXEC);
2307                 if (IS_ERR(pidfile)) {
2308                         put_unused_fd(pidfd);
2309                         retval = PTR_ERR(pidfile);
2310                         goto bad_fork_free_pid;
2311                 }
2312                 get_pid(pid);   /* held by pidfile now */
2313
2314                 retval = put_user(pidfd, args->pidfd);
2315                 if (retval)
2316                         goto bad_fork_put_pidfd;
2317         }
2318
2319 #ifdef CONFIG_BLOCK
2320         p->plug = NULL;
2321 #endif
2322         futex_init_task(p);
2323
2324         /*
2325          * sigaltstack should be cleared when sharing the same VM
2326          */
2327         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2328                 sas_ss_reset(p);
2329
2330         /*
2331          * Syscall tracing and stepping should be turned off in the
2332          * child regardless of CLONE_PTRACE.
2333          */
2334         user_disable_single_step(p);
2335         clear_task_syscall_work(p, SYSCALL_TRACE);
2336 #if defined(CONFIG_GENERIC_ENTRY) || defined(TIF_SYSCALL_EMU)
2337         clear_task_syscall_work(p, SYSCALL_EMU);
2338 #endif
2339         clear_tsk_latency_tracing(p);
2340
2341         /* ok, now we should be set up.. */
2342         p->pid = pid_nr(pid);
2343         if (clone_flags & CLONE_THREAD) {
2344                 p->group_leader = current->group_leader;
2345                 p->tgid = current->tgid;
2346         } else {
2347                 p->group_leader = p;
2348                 p->tgid = p->pid;
2349         }
2350
2351         p->nr_dirtied = 0;
2352         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2353         p->dirty_paused_when = 0;
2354
2355         p->pdeath_signal = 0;
2356         INIT_LIST_HEAD(&p->thread_group);
2357         p->task_works = NULL;
2358         clear_posix_cputimers_work(p);
2359
2360 #ifdef CONFIG_KRETPROBES
2361         p->kretprobe_instances.first = NULL;
2362 #endif
2363 #ifdef CONFIG_RETHOOK
2364         p->rethooks.first = NULL;
2365 #endif
2366
2367         /*
2368          * Ensure that the cgroup subsystem policies allow the new process to be
2369          * forked. It should be noted that the new process's css_set can be changed
2370          * between here and cgroup_post_fork() if an organisation operation is in
2371          * progress.
2372          */
2373         retval = cgroup_can_fork(p, args);
2374         if (retval)
2375                 goto bad_fork_put_pidfd;
2376
2377         /*
2378          * Now that the cgroups are pinned, re-clone the parent cgroup and put
2379          * the new task on the correct runqueue. All this *before* the task
2380          * becomes visible.
2381          *
2382          * This isn't part of ->can_fork() because while the re-cloning is
2383          * cgroup specific, it unconditionally needs to place the task on a
2384          * runqueue.
2385          */
2386         sched_cgroup_fork(p, args);
2387
2388         /*
2389          * From this point on we must avoid any synchronous user-space
2390          * communication until we take the tasklist-lock. In particular, we do
2391          * not want user-space to be able to predict the process start-time by
2392          * stalling fork(2) after we recorded the start_time but before it is
2393          * visible to the system.
2394          */
2395
2396         p->start_time = ktime_get_ns();
2397         p->start_boottime = ktime_get_boottime_ns();
2398
2399         /*
2400          * Make it visible to the rest of the system, but dont wake it up yet.
2401          * Need tasklist lock for parent etc handling!
2402          */
2403         write_lock_irq(&tasklist_lock);
2404
2405         /* CLONE_PARENT re-uses the old parent */
2406         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2407                 p->real_parent = current->real_parent;
2408                 p->parent_exec_id = current->parent_exec_id;
2409                 if (clone_flags & CLONE_THREAD)
2410                         p->exit_signal = -1;
2411                 else
2412                         p->exit_signal = current->group_leader->exit_signal;
2413         } else {
2414                 p->real_parent = current;
2415                 p->parent_exec_id = current->self_exec_id;
2416                 p->exit_signal = args->exit_signal;
2417         }
2418
2419         klp_copy_process(p);
2420
2421         sched_core_fork(p);
2422
2423         spin_lock(&current->sighand->siglock);
2424
2425         rv_task_fork(p);
2426
2427         rseq_fork(p, clone_flags);
2428
2429         /* Don't start children in a dying pid namespace */
2430         if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2431                 retval = -ENOMEM;
2432                 goto bad_fork_cancel_cgroup;
2433         }
2434
2435         /* Let kill terminate clone/fork in the middle */
2436         if (fatal_signal_pending(current)) {
2437                 retval = -EINTR;
2438                 goto bad_fork_cancel_cgroup;
2439         }
2440
2441         /* No more failure paths after this point. */
2442
2443         /*
2444          * Copy seccomp details explicitly here, in case they were changed
2445          * before holding sighand lock.
2446          */
2447         copy_seccomp(p);
2448
2449         init_task_pid_links(p);
2450         if (likely(p->pid)) {
2451                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2452
2453                 init_task_pid(p, PIDTYPE_PID, pid);
2454                 if (thread_group_leader(p)) {
2455                         init_task_pid(p, PIDTYPE_TGID, pid);
2456                         init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2457                         init_task_pid(p, PIDTYPE_SID, task_session(current));
2458
2459                         if (is_child_reaper(pid)) {
2460                                 ns_of_pid(pid)->child_reaper = p;
2461                                 p->signal->flags |= SIGNAL_UNKILLABLE;
2462                         }
2463                         p->signal->shared_pending.signal = delayed.signal;
2464                         p->signal->tty = tty_kref_get(current->signal->tty);
2465                         /*
2466                          * Inherit has_child_subreaper flag under the same
2467                          * tasklist_lock with adding child to the process tree
2468                          * for propagate_has_child_subreaper optimization.
2469                          */
2470                         p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2471                                                          p->real_parent->signal->is_child_subreaper;
2472                         list_add_tail(&p->sibling, &p->real_parent->children);
2473                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
2474                         attach_pid(p, PIDTYPE_TGID);
2475                         attach_pid(p, PIDTYPE_PGID);
2476                         attach_pid(p, PIDTYPE_SID);
2477                         __this_cpu_inc(process_counts);
2478                 } else {
2479                         current->signal->nr_threads++;
2480                         current->signal->quick_threads++;
2481                         atomic_inc(&current->signal->live);
2482                         refcount_inc(&current->signal->sigcnt);
2483                         task_join_group_stop(p);
2484                         list_add_tail_rcu(&p->thread_group,
2485                                           &p->group_leader->thread_group);
2486                         list_add_tail_rcu(&p->thread_node,
2487                                           &p->signal->thread_head);
2488                 }
2489                 attach_pid(p, PIDTYPE_PID);
2490                 nr_threads++;
2491         }
2492         total_forks++;
2493         hlist_del_init(&delayed.node);
2494         spin_unlock(&current->sighand->siglock);
2495         syscall_tracepoint_update(p);
2496         write_unlock_irq(&tasklist_lock);
2497
2498         if (pidfile)
2499                 fd_install(pidfd, pidfile);
2500
2501         proc_fork_connector(p);
2502         sched_post_fork(p);
2503         cgroup_post_fork(p, args);
2504         perf_event_fork(p);
2505
2506         trace_task_newtask(p, clone_flags);
2507         uprobe_copy_process(p, clone_flags);
2508
2509         copy_oom_score_adj(clone_flags, p);
2510
2511         return p;
2512
2513 bad_fork_cancel_cgroup:
2514         sched_core_free(p);
2515         spin_unlock(&current->sighand->siglock);
2516         write_unlock_irq(&tasklist_lock);
2517         cgroup_cancel_fork(p, args);
2518 bad_fork_put_pidfd:
2519         if (clone_flags & CLONE_PIDFD) {
2520                 fput(pidfile);
2521                 put_unused_fd(pidfd);
2522         }
2523 bad_fork_free_pid:
2524         if (pid != &init_struct_pid)
2525                 free_pid(pid);
2526 bad_fork_cleanup_thread:
2527         exit_thread(p);
2528 bad_fork_cleanup_io:
2529         if (p->io_context)
2530                 exit_io_context(p);
2531 bad_fork_cleanup_namespaces:
2532         exit_task_namespaces(p);
2533 bad_fork_cleanup_mm:
2534         if (p->mm) {
2535                 mm_clear_owner(p->mm, p);
2536                 mmput(p->mm);
2537         }
2538 bad_fork_cleanup_signal:
2539         if (!(clone_flags & CLONE_THREAD))
2540                 free_signal_struct(p->signal);
2541 bad_fork_cleanup_sighand:
2542         __cleanup_sighand(p->sighand);
2543 bad_fork_cleanup_fs:
2544         exit_fs(p); /* blocking */
2545 bad_fork_cleanup_files:
2546         exit_files(p); /* blocking */
2547 bad_fork_cleanup_semundo:
2548         exit_sem(p);
2549 bad_fork_cleanup_security:
2550         security_task_free(p);
2551 bad_fork_cleanup_audit:
2552         audit_free(p);
2553 bad_fork_cleanup_perf:
2554         perf_event_free_task(p);
2555 bad_fork_cleanup_policy:
2556         lockdep_free_task(p);
2557 #ifdef CONFIG_NUMA
2558         mpol_put(p->mempolicy);
2559 #endif
2560 bad_fork_cleanup_delayacct:
2561         delayacct_tsk_free(p);
2562 bad_fork_cleanup_count:
2563         dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
2564         exit_creds(p);
2565 bad_fork_free:
2566         WRITE_ONCE(p->__state, TASK_DEAD);
2567         exit_task_stack_account(p);
2568         put_task_stack(p);
2569         delayed_free_task(p);
2570 fork_out:
2571         spin_lock_irq(&current->sighand->siglock);
2572         hlist_del_init(&delayed.node);
2573         spin_unlock_irq(&current->sighand->siglock);
2574         return ERR_PTR(retval);
2575 }
2576
2577 static inline void init_idle_pids(struct task_struct *idle)
2578 {
2579         enum pid_type type;
2580
2581         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2582                 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2583                 init_task_pid(idle, type, &init_struct_pid);
2584         }
2585 }
2586
2587 static int idle_dummy(void *dummy)
2588 {
2589         /* This function is never called */
2590         return 0;
2591 }
2592
2593 struct task_struct * __init fork_idle(int cpu)
2594 {
2595         struct task_struct *task;
2596         struct kernel_clone_args args = {
2597                 .flags          = CLONE_VM,
2598                 .fn             = &idle_dummy,
2599                 .fn_arg         = NULL,
2600                 .kthread        = 1,
2601                 .idle           = 1,
2602         };
2603
2604         task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2605         if (!IS_ERR(task)) {
2606                 init_idle_pids(task);
2607                 init_idle(task, cpu);
2608         }
2609
2610         return task;
2611 }
2612
2613 /*
2614  * This is like kernel_clone(), but shaved down and tailored to just
2615  * creating io_uring workers. It returns a created task, or an error pointer.
2616  * The returned task is inactive, and the caller must fire it up through
2617  * wake_up_new_task(p). All signals are blocked in the created task.
2618  */
2619 struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
2620 {
2621         unsigned long flags = CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|
2622                                 CLONE_IO;
2623         struct kernel_clone_args args = {
2624                 .flags          = ((lower_32_bits(flags) | CLONE_VM |
2625                                     CLONE_UNTRACED) & ~CSIGNAL),
2626                 .exit_signal    = (lower_32_bits(flags) & CSIGNAL),
2627                 .fn             = fn,
2628                 .fn_arg         = arg,
2629                 .io_thread      = 1,
2630         };
2631
2632         return copy_process(NULL, 0, node, &args);
2633 }
2634
2635 /*
2636  *  Ok, this is the main fork-routine.
2637  *
2638  * It copies the process, and if successful kick-starts
2639  * it and waits for it to finish using the VM if required.
2640  *
2641  * args->exit_signal is expected to be checked for sanity by the caller.
2642  */
2643 pid_t kernel_clone(struct kernel_clone_args *args)
2644 {
2645         u64 clone_flags = args->flags;
2646         struct completion vfork;
2647         struct pid *pid;
2648         struct task_struct *p;
2649         int trace = 0;
2650         pid_t nr;
2651
2652         /*
2653          * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
2654          * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
2655          * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
2656          * field in struct clone_args and it still doesn't make sense to have
2657          * them both point at the same memory location. Performing this check
2658          * here has the advantage that we don't need to have a separate helper
2659          * to check for legacy clone().
2660          */
2661         if ((args->flags & CLONE_PIDFD) &&
2662             (args->flags & CLONE_PARENT_SETTID) &&
2663             (args->pidfd == args->parent_tid))
2664                 return -EINVAL;
2665
2666         /*
2667          * Determine whether and which event to report to ptracer.  When
2668          * called from kernel_thread or CLONE_UNTRACED is explicitly
2669          * requested, no event is reported; otherwise, report if the event
2670          * for the type of forking is enabled.
2671          */
2672         if (!(clone_flags & CLONE_UNTRACED)) {
2673                 if (clone_flags & CLONE_VFORK)
2674                         trace = PTRACE_EVENT_VFORK;
2675                 else if (args->exit_signal != SIGCHLD)
2676                         trace = PTRACE_EVENT_CLONE;
2677                 else
2678                         trace = PTRACE_EVENT_FORK;
2679
2680                 if (likely(!ptrace_event_enabled(current, trace)))
2681                         trace = 0;
2682         }
2683
2684         p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2685         add_latent_entropy();
2686
2687         if (IS_ERR(p))
2688                 return PTR_ERR(p);
2689
2690         /*
2691          * Do this prior waking up the new thread - the thread pointer
2692          * might get invalid after that point, if the thread exits quickly.
2693          */
2694         trace_sched_process_fork(current, p);
2695
2696         pid = get_task_pid(p, PIDTYPE_PID);
2697         nr = pid_vnr(pid);
2698
2699         if (clone_flags & CLONE_PARENT_SETTID)
2700                 put_user(nr, args->parent_tid);
2701
2702         if (clone_flags & CLONE_VFORK) {
2703                 p->vfork_done = &vfork;
2704                 init_completion(&vfork);
2705                 get_task_struct(p);
2706         }
2707
2708         if (IS_ENABLED(CONFIG_LRU_GEN) && !(clone_flags & CLONE_VM)) {
2709                 /* lock the task to synchronize with memcg migration */
2710                 task_lock(p);
2711                 lru_gen_add_mm(p->mm);
2712                 task_unlock(p);
2713         }
2714
2715         wake_up_new_task(p);
2716
2717         /* forking complete and child started to run, tell ptracer */
2718         if (unlikely(trace))
2719                 ptrace_event_pid(trace, pid);
2720
2721         if (clone_flags & CLONE_VFORK) {
2722                 if (!wait_for_vfork_done(p, &vfork))
2723                         ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2724         }
2725
2726         put_pid(pid);
2727         return nr;
2728 }
2729
2730 /*
2731  * Create a kernel thread.
2732  */
2733 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2734 {
2735         struct kernel_clone_args args = {
2736                 .flags          = ((lower_32_bits(flags) | CLONE_VM |
2737                                     CLONE_UNTRACED) & ~CSIGNAL),
2738                 .exit_signal    = (lower_32_bits(flags) & CSIGNAL),
2739                 .fn             = fn,
2740                 .fn_arg         = arg,
2741                 .kthread        = 1,
2742         };
2743
2744         return kernel_clone(&args);
2745 }
2746
2747 /*
2748  * Create a user mode thread.
2749  */
2750 pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags)
2751 {
2752         struct kernel_clone_args args = {
2753                 .flags          = ((lower_32_bits(flags) | CLONE_VM |
2754                                     CLONE_UNTRACED) & ~CSIGNAL),
2755                 .exit_signal    = (lower_32_bits(flags) & CSIGNAL),
2756                 .fn             = fn,
2757                 .fn_arg         = arg,
2758         };
2759
2760         return kernel_clone(&args);
2761 }
2762
2763 #ifdef __ARCH_WANT_SYS_FORK
2764 SYSCALL_DEFINE0(fork)
2765 {
2766 #ifdef CONFIG_MMU
2767         struct kernel_clone_args args = {
2768                 .exit_signal = SIGCHLD,
2769         };
2770
2771         return kernel_clone(&args);
2772 #else
2773         /* can not support in nommu mode */
2774         return -EINVAL;
2775 #endif
2776 }
2777 #endif
2778
2779 #ifdef __ARCH_WANT_SYS_VFORK
2780 SYSCALL_DEFINE0(vfork)
2781 {
2782         struct kernel_clone_args args = {
2783                 .flags          = CLONE_VFORK | CLONE_VM,
2784                 .exit_signal    = SIGCHLD,
2785         };
2786
2787         return kernel_clone(&args);
2788 }
2789 #endif
2790
2791 #ifdef __ARCH_WANT_SYS_CLONE
2792 #ifdef CONFIG_CLONE_BACKWARDS
2793 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2794                  int __user *, parent_tidptr,
2795                  unsigned long, tls,
2796                  int __user *, child_tidptr)
2797 #elif defined(CONFIG_CLONE_BACKWARDS2)
2798 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2799                  int __user *, parent_tidptr,
2800                  int __user *, child_tidptr,
2801                  unsigned long, tls)
2802 #elif defined(CONFIG_CLONE_BACKWARDS3)
2803 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2804                 int, stack_size,
2805                 int __user *, parent_tidptr,
2806                 int __user *, child_tidptr,
2807                 unsigned long, tls)
2808 #else
2809 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2810                  int __user *, parent_tidptr,
2811                  int __user *, child_tidptr,
2812                  unsigned long, tls)
2813 #endif
2814 {
2815         struct kernel_clone_args args = {
2816                 .flags          = (lower_32_bits(clone_flags) & ~CSIGNAL),
2817                 .pidfd          = parent_tidptr,
2818                 .child_tid      = child_tidptr,
2819                 .parent_tid     = parent_tidptr,
2820                 .exit_signal    = (lower_32_bits(clone_flags) & CSIGNAL),
2821                 .stack          = newsp,
2822                 .tls            = tls,
2823         };
2824
2825         return kernel_clone(&args);
2826 }
2827 #endif
2828
2829 #ifdef __ARCH_WANT_SYS_CLONE3
2830
2831 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
2832                                               struct clone_args __user *uargs,
2833                                               size_t usize)
2834 {
2835         int err;
2836         struct clone_args args;
2837         pid_t *kset_tid = kargs->set_tid;
2838
2839         BUILD_BUG_ON(offsetofend(struct clone_args, tls) !=
2840                      CLONE_ARGS_SIZE_VER0);
2841         BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) !=
2842                      CLONE_ARGS_SIZE_VER1);
2843         BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
2844                      CLONE_ARGS_SIZE_VER2);
2845         BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
2846
2847         if (unlikely(usize > PAGE_SIZE))
2848                 return -E2BIG;
2849         if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
2850                 return -EINVAL;
2851
2852         err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
2853         if (err)
2854                 return err;
2855
2856         if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
2857                 return -EINVAL;
2858
2859         if (unlikely(!args.set_tid && args.set_tid_size > 0))
2860                 return -EINVAL;
2861
2862         if (unlikely(args.set_tid && args.set_tid_size == 0))
2863                 return -EINVAL;
2864
2865         /*
2866          * Verify that higher 32bits of exit_signal are unset and that
2867          * it is a valid signal
2868          */
2869         if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
2870                      !valid_signal(args.exit_signal)))
2871                 return -EINVAL;
2872
2873         if ((args.flags & CLONE_INTO_CGROUP) &&
2874             (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2))
2875                 return -EINVAL;
2876
2877         *kargs = (struct kernel_clone_args){
2878                 .flags          = args.flags,
2879                 .pidfd          = u64_to_user_ptr(args.pidfd),
2880                 .child_tid      = u64_to_user_ptr(args.child_tid),
2881                 .parent_tid     = u64_to_user_ptr(args.parent_tid),
2882                 .exit_signal    = args.exit_signal,
2883                 .stack          = args.stack,
2884                 .stack_size     = args.stack_size,
2885                 .tls            = args.tls,
2886                 .set_tid_size   = args.set_tid_size,
2887                 .cgroup         = args.cgroup,
2888         };
2889
2890         if (args.set_tid &&
2891                 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
2892                         (kargs->set_tid_size * sizeof(pid_t))))
2893                 return -EFAULT;
2894
2895         kargs->set_tid = kset_tid;
2896
2897         return 0;
2898 }
2899
2900 /**
2901  * clone3_stack_valid - check and prepare stack
2902  * @kargs: kernel clone args
2903  *
2904  * Verify that the stack arguments userspace gave us are sane.
2905  * In addition, set the stack direction for userspace since it's easy for us to
2906  * determine.
2907  */
2908 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
2909 {
2910         if (kargs->stack == 0) {
2911                 if (kargs->stack_size > 0)
2912                         return false;
2913         } else {
2914                 if (kargs->stack_size == 0)
2915                         return false;
2916
2917                 if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
2918                         return false;
2919
2920 #if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
2921                 kargs->stack += kargs->stack_size;
2922 #endif
2923         }
2924
2925         return true;
2926 }
2927
2928 static bool clone3_args_valid(struct kernel_clone_args *kargs)
2929 {
2930         /* Verify that no unknown flags are passed along. */
2931         if (kargs->flags &
2932             ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP))
2933                 return false;
2934
2935         /*
2936          * - make the CLONE_DETACHED bit reusable for clone3
2937          * - make the CSIGNAL bits reusable for clone3
2938          */
2939         if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
2940                 return false;
2941
2942         if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
2943             (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
2944                 return false;
2945
2946         if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
2947             kargs->exit_signal)
2948                 return false;
2949
2950         if (!clone3_stack_valid(kargs))
2951                 return false;
2952
2953         return true;
2954 }
2955
2956 /**
2957  * clone3 - create a new process with specific properties
2958  * @uargs: argument structure
2959  * @size:  size of @uargs
2960  *
2961  * clone3() is the extensible successor to clone()/clone2().
2962  * It takes a struct as argument that is versioned by its size.
2963  *
2964  * Return: On success, a positive PID for the child process.
2965  *         On error, a negative errno number.
2966  */
2967 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
2968 {
2969         int err;
2970
2971         struct kernel_clone_args kargs;
2972         pid_t set_tid[MAX_PID_NS_LEVEL];
2973
2974         kargs.set_tid = set_tid;
2975
2976         err = copy_clone_args_from_user(&kargs, uargs, size);
2977         if (err)
2978                 return err;
2979
2980         if (!clone3_args_valid(&kargs))
2981                 return -EINVAL;
2982
2983         return kernel_clone(&kargs);
2984 }
2985 #endif
2986
2987 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2988 {
2989         struct task_struct *leader, *parent, *child;
2990         int res;
2991
2992         read_lock(&tasklist_lock);
2993         leader = top = top->group_leader;
2994 down:
2995         for_each_thread(leader, parent) {
2996                 list_for_each_entry(child, &parent->children, sibling) {
2997                         res = visitor(child, data);
2998                         if (res) {
2999                                 if (res < 0)
3000                                         goto out;
3001                                 leader = child;
3002                                 goto down;
3003                         }
3004 up:
3005                         ;
3006                 }
3007         }
3008
3009         if (leader != top) {
3010                 child = leader;
3011                 parent = child->real_parent;
3012                 leader = parent->group_leader;
3013                 goto up;
3014         }
3015 out:
3016         read_unlock(&tasklist_lock);
3017 }
3018
3019 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
3020 #define ARCH_MIN_MMSTRUCT_ALIGN 0
3021 #endif
3022
3023 static void sighand_ctor(void *data)
3024 {
3025         struct sighand_struct *sighand = data;
3026
3027         spin_lock_init(&sighand->siglock);
3028         init_waitqueue_head(&sighand->signalfd_wqh);
3029 }
3030
3031 void __init mm_cache_init(void)
3032 {
3033         unsigned int mm_size;
3034
3035         /*
3036          * The mm_cpumask is located at the end of mm_struct, and is
3037          * dynamically sized based on the maximum CPU number this system
3038          * can have, taking hotplug into account (nr_cpu_ids).
3039          */
3040         mm_size = sizeof(struct mm_struct) + cpumask_size() + mm_cid_size();
3041
3042         mm_cachep = kmem_cache_create_usercopy("mm_struct",
3043                         mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
3044                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3045                         offsetof(struct mm_struct, saved_auxv),
3046                         sizeof_field(struct mm_struct, saved_auxv),
3047                         NULL);
3048 }
3049
3050 void __init proc_caches_init(void)
3051 {
3052         sighand_cachep = kmem_cache_create("sighand_cache",
3053                         sizeof(struct sighand_struct), 0,
3054                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
3055                         SLAB_ACCOUNT, sighand_ctor);
3056         signal_cachep = kmem_cache_create("signal_cache",
3057                         sizeof(struct signal_struct), 0,
3058                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3059                         NULL);
3060         files_cachep = kmem_cache_create("files_cache",
3061                         sizeof(struct files_struct), 0,
3062                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3063                         NULL);
3064         fs_cachep = kmem_cache_create("fs_cache",
3065                         sizeof(struct fs_struct), 0,
3066                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3067                         NULL);
3068
3069         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
3070         mmap_init();
3071         nsproxy_cache_init();
3072 }
3073
3074 /*
3075  * Check constraints on flags passed to the unshare system call.
3076  */
3077 static int check_unshare_flags(unsigned long unshare_flags)
3078 {
3079         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
3080                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
3081                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
3082                                 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP|
3083                                 CLONE_NEWTIME))
3084                 return -EINVAL;
3085         /*
3086          * Not implemented, but pretend it works if there is nothing
3087          * to unshare.  Note that unsharing the address space or the
3088          * signal handlers also need to unshare the signal queues (aka
3089          * CLONE_THREAD).
3090          */
3091         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
3092                 if (!thread_group_empty(current))
3093                         return -EINVAL;
3094         }
3095         if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
3096                 if (refcount_read(&current->sighand->count) > 1)
3097                         return -EINVAL;
3098         }
3099         if (unshare_flags & CLONE_VM) {
3100                 if (!current_is_single_threaded())
3101                         return -EINVAL;
3102         }
3103
3104         return 0;
3105 }
3106
3107 /*
3108  * Unshare the filesystem structure if it is being shared
3109  */
3110 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
3111 {
3112         struct fs_struct *fs = current->fs;
3113
3114         if (!(unshare_flags & CLONE_FS) || !fs)
3115                 return 0;
3116
3117         /* don't need lock here; in the worst case we'll do useless copy */
3118         if (fs->users == 1)
3119                 return 0;
3120
3121         *new_fsp = copy_fs_struct(fs);
3122         if (!*new_fsp)
3123                 return -ENOMEM;
3124
3125         return 0;
3126 }
3127
3128 /*
3129  * Unshare file descriptor table if it is being shared
3130  */
3131 int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
3132                struct files_struct **new_fdp)
3133 {
3134         struct files_struct *fd = current->files;
3135         int error = 0;
3136
3137         if ((unshare_flags & CLONE_FILES) &&
3138             (fd && atomic_read(&fd->count) > 1)) {
3139                 *new_fdp = dup_fd(fd, max_fds, &error);
3140                 if (!*new_fdp)
3141                         return error;
3142         }
3143
3144         return 0;
3145 }
3146
3147 /*
3148  * unshare allows a process to 'unshare' part of the process
3149  * context which was originally shared using clone.  copy_*
3150  * functions used by kernel_clone() cannot be used here directly
3151  * because they modify an inactive task_struct that is being
3152  * constructed. Here we are modifying the current, active,
3153  * task_struct.
3154  */
3155 int ksys_unshare(unsigned long unshare_flags)
3156 {
3157         struct fs_struct *fs, *new_fs = NULL;
3158         struct files_struct *new_fd = NULL;
3159         struct cred *new_cred = NULL;
3160         struct nsproxy *new_nsproxy = NULL;
3161         int do_sysvsem = 0;
3162         int err;
3163
3164         /*
3165          * If unsharing a user namespace must also unshare the thread group
3166          * and unshare the filesystem root and working directories.
3167          */
3168         if (unshare_flags & CLONE_NEWUSER)
3169                 unshare_flags |= CLONE_THREAD | CLONE_FS;
3170         /*
3171          * If unsharing vm, must also unshare signal handlers.
3172          */
3173         if (unshare_flags & CLONE_VM)
3174                 unshare_flags |= CLONE_SIGHAND;
3175         /*
3176          * If unsharing a signal handlers, must also unshare the signal queues.
3177          */
3178         if (unshare_flags & CLONE_SIGHAND)
3179                 unshare_flags |= CLONE_THREAD;
3180         /*
3181          * If unsharing namespace, must also unshare filesystem information.
3182          */
3183         if (unshare_flags & CLONE_NEWNS)
3184                 unshare_flags |= CLONE_FS;
3185
3186         err = check_unshare_flags(unshare_flags);
3187         if (err)
3188                 goto bad_unshare_out;
3189         /*
3190          * CLONE_NEWIPC must also detach from the undolist: after switching
3191          * to a new ipc namespace, the semaphore arrays from the old
3192          * namespace are unreachable.
3193          */
3194         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
3195                 do_sysvsem = 1;
3196         err = unshare_fs(unshare_flags, &new_fs);
3197         if (err)
3198                 goto bad_unshare_out;
3199         err = unshare_fd(unshare_flags, NR_OPEN_MAX, &new_fd);
3200         if (err)
3201                 goto bad_unshare_cleanup_fs;
3202         err = unshare_userns(unshare_flags, &new_cred);
3203         if (err)
3204                 goto bad_unshare_cleanup_fd;
3205         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
3206                                          new_cred, new_fs);
3207         if (err)
3208                 goto bad_unshare_cleanup_cred;
3209
3210         if (new_cred) {
3211                 err = set_cred_ucounts(new_cred);
3212                 if (err)
3213                         goto bad_unshare_cleanup_cred;
3214         }
3215
3216         if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
3217                 if (do_sysvsem) {
3218                         /*
3219                          * CLONE_SYSVSEM is equivalent to sys_exit().
3220                          */
3221                         exit_sem(current);
3222                 }
3223                 if (unshare_flags & CLONE_NEWIPC) {
3224                         /* Orphan segments in old ns (see sem above). */
3225                         exit_shm(current);
3226                         shm_init_task(current);
3227                 }
3228
3229                 if (new_nsproxy)
3230                         switch_task_namespaces(current, new_nsproxy);
3231
3232                 task_lock(current);
3233
3234                 if (new_fs) {
3235                         fs = current->fs;
3236                         spin_lock(&fs->lock);
3237                         current->fs = new_fs;
3238                         if (--fs->users)
3239                                 new_fs = NULL;
3240                         else
3241                                 new_fs = fs;
3242                         spin_unlock(&fs->lock);
3243                 }
3244
3245                 if (new_fd)
3246                         swap(current->files, new_fd);
3247
3248                 task_unlock(current);
3249
3250                 if (new_cred) {
3251                         /* Install the new user namespace */
3252                         commit_creds(new_cred);
3253                         new_cred = NULL;
3254                 }
3255         }
3256
3257         perf_event_namespaces(current);
3258
3259 bad_unshare_cleanup_cred:
3260         if (new_cred)
3261                 put_cred(new_cred);
3262 bad_unshare_cleanup_fd:
3263         if (new_fd)
3264                 put_files_struct(new_fd);
3265
3266 bad_unshare_cleanup_fs:
3267         if (new_fs)
3268                 free_fs_struct(new_fs);
3269
3270 bad_unshare_out:
3271         return err;
3272 }
3273
3274 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
3275 {
3276         return ksys_unshare(unshare_flags);
3277 }
3278
3279 /*
3280  *      Helper to unshare the files of the current task.
3281  *      We don't want to expose copy_files internals to
3282  *      the exec layer of the kernel.
3283  */
3284
3285 int unshare_files(void)
3286 {
3287         struct task_struct *task = current;
3288         struct files_struct *old, *copy = NULL;
3289         int error;
3290
3291         error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, &copy);
3292         if (error || !copy)
3293                 return error;
3294
3295         old = task->files;
3296         task_lock(task);
3297         task->files = copy;
3298         task_unlock(task);
3299         put_files_struct(old);
3300         return 0;
3301 }
3302
3303 int sysctl_max_threads(struct ctl_table *table, int write,
3304                        void *buffer, size_t *lenp, loff_t *ppos)
3305 {
3306         struct ctl_table t;
3307         int ret;
3308         int threads = max_threads;
3309         int min = 1;
3310         int max = MAX_THREADS;
3311
3312         t = *table;
3313         t.data = &threads;
3314         t.extra1 = &min;
3315         t.extra2 = &max;
3316
3317         ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
3318         if (ret || !write)
3319                 return ret;
3320
3321         max_threads = threads;
3322
3323         return 0;
3324 }