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