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