kernel/fork.c

   1 /*
   2  *  linux/kernel/fork.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  *  'fork.c' contains the help-routines for the 'fork' system call
   9  * (see also entry.S and others).
  10  * Fork is rather simple, once you get the hang of it, but the memory
  11  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
  12  */
  13
  14 #include <linux/slab.h>
  15 #include <linux/init.h>
  16 #include <linux/unistd.h>
  17 #include <linux/module.h>
  18 #include <linux/vmalloc.h>
  19 #include <linux/completion.h>
  20 #include <linux/personality.h>
  21 #include <linux/mempolicy.h>
  22 #include <linux/sem.h>
  23 #include <linux/file.h>
  24 #include <linux/fdtable.h>
  25 #include <linux/iocontext.h>
  26 #include <linux/key.h>
  27 #include <linux/binfmts.h>
  28 #include <linux/mman.h>
  29 #include <linux/mmu_notifier.h>
  30 #include <linux/fs.h>
  31 #include <linux/mm.h>
  32 #include <linux/vmacache.h>
  33 #include <linux/nsproxy.h>
  34 #include <linux/capability.h>
  35 #include <linux/cpu.h>
  36 #include <linux/cgroup.h>
  37 #include <linux/security.h>
  38 #include <linux/hugetlb.h>
  39 #include <linux/seccomp.h>
  40 #include <linux/swap.h>
  41 #include <linux/syscalls.h>
  42 #include <linux/jiffies.h>
  43 #include <linux/futex.h>
  44 #include <linux/compat.h>
  45 #include <linux/kthread.h>
  46 #include <linux/task_io_accounting_ops.h>
  47 #include <linux/rcupdate.h>
  48 #include <linux/ptrace.h>
  49 #include <linux/mount.h>
  50 #include <linux/audit.h>
  51 #include <linux/memcontrol.h>
  52 #include <linux/ftrace.h>
  53 #include <linux/proc_fs.h>
  54 #include <linux/profile.h>
  55 #include <linux/rmap.h>
  56 #include <linux/ksm.h>
  57 #include <linux/acct.h>
  58 #include <linux/tsacct_kern.h>
  59 #include <linux/cn_proc.h>
  60 #include <linux/freezer.h>
  61 #include <linux/delayacct.h>
  62 #include <linux/taskstats_kern.h>
  63 #include <linux/random.h>
  64 #include <linux/tty.h>
  65 #include <linux/blkdev.h>
  66 #include <linux/fs_struct.h>
  67 #include <linux/magic.h>
  68 #include <linux/perf_event.h>
  69 #include <linux/posix-timers.h>
  70 #include <linux/user-return-notifier.h>
  71 #include <linux/oom.h>
  72 #include <linux/khugepaged.h>
  73 #include <linux/signalfd.h>
  74 #include <linux/uprobes.h>
  75 #include <linux/aio.h>
  76 #include <linux/compiler.h>
  77 #include <linux/sysctl.h>
  78 #include <linux/kcov.h>
  79
  80 #include <asm/pgtable.h>
  81 #include <asm/pgalloc.h>
  82 #include <asm/uaccess.h>
  83 #include <asm/mmu_context.h>
  84 #include <asm/cacheflush.h>
  85 #include <asm/tlbflush.h>
  86
  87 #include <trace/events/sched.h>
  88
  89 #define CREATE_TRACE_POINTS
  90 #include <trace/events/task.h>
  91
  92 /*
  93  * Minimum number of threads to boot the kernel
  94  */
  95 #define MIN_THREADS 20
  96
  97 /*
  98  * Maximum number of threads
  99  */
 100 #define MAX_THREADS FUTEX_TID_MASK
 101
 102 /*
 103  * Protected counters by write_lock_irq(&tasklist_lock)
 104  */
 105 unsigned long total_forks;      /* Handle normal Linux uptimes. */
 106 int nr_threads;                 /* The idle threads do not count.. */
 107
 108 int max_threads;                /* tunable limit on nr_threads */
 109
 110 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
 111
 112 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
 113
 114 #ifdef CONFIG_PROVE_RCU
 115 int lockdep_tasklist_lock_is_held(void)
 116 {
 117         return lockdep_is_held(&tasklist_lock);
 118 }
 119 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
 120 #endif /* #ifdef CONFIG_PROVE_RCU */
 121
 122 int nr_processes(void)
 123 {
 124         int cpu;
 125         int total = 0;
 126
 127         for_each_possible_cpu(cpu)
 128                 total += per_cpu(process_counts, cpu);
 129
 130         return total;
 131 }
 132
 133 void __weak arch_release_task_struct(struct task_struct *tsk)
 134 {
 135 }
 136
 137 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 138 static struct kmem_cache *task_struct_cachep;
 139
 140 static inline struct task_struct *alloc_task_struct_node(int node)
 141 {
 142         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
 143 }
 144
 145 static inline void free_task_struct(struct task_struct *tsk)
 146 {
 147         kmem_cache_free(task_struct_cachep, tsk);
 148 }
 149 #endif
 150
 151 void __weak arch_release_thread_stack(unsigned long *stack)
 152 {
 153 }
 154
 155 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
 156
 157 /*
 158  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
 159  * kmemcache based allocator.
 160  */
 161 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
 162
 163 #ifdef CONFIG_VMAP_STACK
 164 /*
 165  * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
 166  * flush.  Try to minimize the number of calls by caching stacks.
 167  */
 168 #define NR_CACHED_STACKS 2
 169 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
 170 #endif
 171
 172 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
 173 {
 174 #ifdef CONFIG_VMAP_STACK
 175         void *stack;
 176         int i;
 177
 178         local_irq_disable();
 179         for (i = 0; i < NR_CACHED_STACKS; i++) {
 180                 struct vm_struct *s = this_cpu_read(cached_stacks[i]);
 181
 182                 if (!s)
 183                         continue;
 184                 this_cpu_write(cached_stacks[i], NULL);
 185
 186                 tsk->stack_vm_area = s;
 187                 local_irq_enable();
 188                 return s->addr;
 189         }
 190         local_irq_enable();
 191
 192         stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE,
 193                                      VMALLOC_START, VMALLOC_END,
 194                                      THREADINFO_GFP | __GFP_HIGHMEM,
 195                                      PAGE_KERNEL,
 196                                      0, node, __builtin_return_address(0));
 197
 198         /*
 199          * We can't call find_vm_area() in interrupt context, and
 200          * free_thread_stack() can be called in interrupt context,
 201          * so cache the vm_struct.
 202          */
 203         if (stack)
 204                 tsk->stack_vm_area = find_vm_area(stack);
 205         return stack;
 206 #else
 207         struct page *page = alloc_pages_node(node, THREADINFO_GFP,
 208                                              THREAD_SIZE_ORDER);
 209
 210         return page ? page_address(page) : NULL;
 211 #endif
 212 }
 213
 214 static inline void free_thread_stack(struct task_struct *tsk)
 215 {
 216 #ifdef CONFIG_VMAP_STACK
 217         if (task_stack_vm_area(tsk)) {
 218                 unsigned long flags;
 219                 int i;
 220
 221                 local_irq_save(flags);
 222                 for (i = 0; i < NR_CACHED_STACKS; i++) {
 223                         if (this_cpu_read(cached_stacks[i]))
 224                                 continue;
 225
 226                         this_cpu_write(cached_stacks[i], tsk->stack_vm_area);
 227                         local_irq_restore(flags);
 228                         return;
 229                 }
 230                 local_irq_restore(flags);
 231
 232                 vfree(tsk->stack);
 233                 return;
 234         }
 235 #endif
 236
 237         __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
 238 }
 239 # else
 240 static struct kmem_cache *thread_stack_cache;
 241
 242 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
 243                                                   int node)
 244 {
 245         return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
 246 }
 247
 248 static void free_thread_stack(struct task_struct *tsk)
 249 {
 250         kmem_cache_free(thread_stack_cache, tsk->stack);
 251 }
 252
 253 void thread_stack_cache_init(void)
 254 {
 255         thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE,
 256                                               THREAD_SIZE, 0, NULL);
 257         BUG_ON(thread_stack_cache == NULL);
 258 }
 259 # endif
 260 #endif
 261
 262 /* SLAB cache for signal_struct structures (tsk->signal) */
 263 static struct kmem_cache *signal_cachep;
 264
 265 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 266 struct kmem_cache *sighand_cachep;
 267
 268 /* SLAB cache for files_struct structures (tsk->files) */
 269 struct kmem_cache *files_cachep;
 270
 271 /* SLAB cache for fs_struct structures (tsk->fs) */
 272 struct kmem_cache *fs_cachep;
 273
 274 /* SLAB cache for vm_area_struct structures */
 275 struct kmem_cache *vm_area_cachep;
 276
 277 /* SLAB cache for mm_struct structures (tsk->mm) */
 278 static struct kmem_cache *mm_cachep;
 279
 280 static void account_kernel_stack(struct task_struct *tsk, int account)
 281 {
 282         void *stack = task_stack_page(tsk);
 283         struct vm_struct *vm = task_stack_vm_area(tsk);
 284
 285         BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
 286
 287         if (vm) {
 288                 int i;
 289
 290                 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
 291
 292                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
 293                         mod_zone_page_state(page_zone(vm->pages[i]),
 294                                             NR_KERNEL_STACK_KB,
 295                                             PAGE_SIZE / 1024 * account);
 296                 }
 297
 298                 /* All stack pages belong to the same memcg. */
 299                 memcg_kmem_update_page_stat(vm->pages[0], MEMCG_KERNEL_STACK_KB,
 300                                             account * (THREAD_SIZE / 1024));
 301         } else {
 302                 /*
 303                  * All stack pages are in the same zone and belong to the
 304                  * same memcg.
 305                  */
 306                 struct page *first_page = virt_to_page(stack);
 307
 308                 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
 309                                     THREAD_SIZE / 1024 * account);
 310
 311                 memcg_kmem_update_page_stat(first_page, MEMCG_KERNEL_STACK_KB,
 312                                             account * (THREAD_SIZE / 1024));
 313         }
 314 }
 315
 316 static void release_task_stack(struct task_struct *tsk)
 317 {
 318         if (WARN_ON(tsk->state != TASK_DEAD))
 319                 return;  /* Better to leak the stack than to free prematurely */
 320
 321         account_kernel_stack(tsk, -1);
 322         arch_release_thread_stack(tsk->stack);
 323         free_thread_stack(tsk);
 324         tsk->stack = NULL;
 325 #ifdef CONFIG_VMAP_STACK
 326         tsk->stack_vm_area = NULL;
 327 #endif
 328 }
 329
 330 #ifdef CONFIG_THREAD_INFO_IN_TASK
 331 void put_task_stack(struct task_struct *tsk)
 332 {
 333         if (atomic_dec_and_test(&tsk->stack_refcount))
 334                 release_task_stack(tsk);
 335 }
 336 #endif
 337
 338 void free_task(struct task_struct *tsk)
 339 {
 340 #ifndef CONFIG_THREAD_INFO_IN_TASK
 341         /*
 342          * The task is finally done with both the stack and thread_info,
 343          * so free both.
 344          */
 345         release_task_stack(tsk);
 346 #else
 347         /*
 348          * If the task had a separate stack allocation, it should be gone
 349          * by now.
 350          */
 351         WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0);
 352 #endif
 353         rt_mutex_debug_task_free(tsk);
 354         ftrace_graph_exit_task(tsk);
 355         put_seccomp_filter(tsk);
 356         arch_release_task_struct(tsk);
 357         if (tsk->flags & PF_KTHREAD)
 358                 free_kthread_struct(tsk);
 359         free_task_struct(tsk);
 360 }
 361 EXPORT_SYMBOL(free_task);
 362
 363 static inline void free_signal_struct(struct signal_struct *sig)
 364 {
 365         taskstats_tgid_free(sig);
 366         sched_autogroup_exit(sig);
 367         /*
 368          * __mmdrop is not safe to call from softirq context on x86 due to
 369          * pgd_dtor so postpone it to the async context
 370          */
 371         if (sig->oom_mm)
 372                 mmdrop_async(sig->oom_mm);
 373         kmem_cache_free(signal_cachep, sig);
 374 }
 375
 376 static inline void put_signal_struct(struct signal_struct *sig)
 377 {
 378         if (atomic_dec_and_test(&sig->sigcnt))
 379                 free_signal_struct(sig);
 380 }
 381
 382 void __put_task_struct(struct task_struct *tsk)
 383 {
 384         WARN_ON(!tsk->exit_state);
 385         WARN_ON(atomic_read(&tsk->usage));
 386         WARN_ON(tsk == current);
 387
 388         cgroup_free(tsk);
 389         task_numa_free(tsk);
 390         security_task_free(tsk);
 391         exit_creds(tsk);
 392         delayacct_tsk_free(tsk);
 393         put_signal_struct(tsk->signal);
 394
 395         if (!profile_handoff_task(tsk))
 396                 free_task(tsk);
 397 }
 398 EXPORT_SYMBOL_GPL(__put_task_struct);
 399
 400 void __init __weak arch_task_cache_init(void) { }
 401
 402 /*
 403  * set_max_threads
 404  */
 405 static void set_max_threads(unsigned int max_threads_suggested)
 406 {
 407         u64 threads;
 408
 409         /*
 410          * The number of threads shall be limited such that the thread
 411          * structures may only consume a small part of the available memory.
 412          */
 413         if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
 414                 threads = MAX_THREADS;
 415         else
 416                 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
 417                                     (u64) THREAD_SIZE * 8UL);
 418
 419         if (threads > max_threads_suggested)
 420                 threads = max_threads_suggested;
 421
 422         max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
 423 }
 424
 425 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
 426 /* Initialized by the architecture: */
 427 int arch_task_struct_size __read_mostly;
 428 #endif
 429
 430 void __init fork_init(void)
 431 {
 432         int i;
 433 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 434 #ifndef ARCH_MIN_TASKALIGN
 435 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 436 #endif
 437         /* create a slab on which task_structs can be allocated */
 438         task_struct_cachep = kmem_cache_create("task_struct",
 439                         arch_task_struct_size, ARCH_MIN_TASKALIGN,
 440                         SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL);
 441 #endif
 442
 443         /* do the arch specific task caches init */
 444         arch_task_cache_init();
 445
 446         set_max_threads(MAX_THREADS);
 447
 448         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 449         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 450         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 451                 init_task.signal->rlim[RLIMIT_NPROC];
 452
 453         for (i = 0; i < UCOUNT_COUNTS; i++) {
 454                 init_user_ns.ucount_max[i] = max_threads/2;
 455         }
 456 }
 457
 458 int __weak arch_dup_task_struct(struct task_struct *dst,
 459                                                struct task_struct *src)
 460 {
 461         *dst = *src;
 462         return 0;
 463 }
 464
 465 void set_task_stack_end_magic(struct task_struct *tsk)
 466 {
 467         unsigned long *stackend;
 468
 469         stackend = end_of_stack(tsk);
 470         *stackend = STACK_END_MAGIC;    /* for overflow detection */
 471 }
 472
 473 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 474 {
 475         struct task_struct *tsk;
 476         unsigned long *stack;
 477         struct vm_struct *stack_vm_area;
 478         int err;
 479
 480         if (node == NUMA_NO_NODE)
 481                 node = tsk_fork_get_node(orig);
 482         tsk = alloc_task_struct_node(node);
 483         if (!tsk)
 484                 return NULL;
 485
 486         stack = alloc_thread_stack_node(tsk, node);
 487         if (!stack)
 488                 goto free_tsk;
 489
 490         stack_vm_area = task_stack_vm_area(tsk);
 491
 492         err = arch_dup_task_struct(tsk, orig);
 493
 494         /*
 495          * arch_dup_task_struct() clobbers the stack-related fields.  Make
 496          * sure they're properly initialized before using any stack-related
 497          * functions again.
 498          */
 499         tsk->stack = stack;
 500 #ifdef CONFIG_VMAP_STACK
 501         tsk->stack_vm_area = stack_vm_area;
 502 #endif
 503 #ifdef CONFIG_THREAD_INFO_IN_TASK
 504         atomic_set(&tsk->stack_refcount, 1);
 505 #endif
 506
 507         if (err)
 508                 goto free_stack;
 509
 510 #ifdef CONFIG_SECCOMP
 511         /*
 512          * We must handle setting up seccomp filters once we're under
 513          * the sighand lock in case orig has changed between now and
 514          * then. Until then, filter must be NULL to avoid messing up
 515          * the usage counts on the error path calling free_task.
 516          */
 517         tsk->seccomp.filter = NULL;
 518 #endif
 519
 520         setup_thread_stack(tsk, orig);
 521         clear_user_return_notifier(tsk);
 522         clear_tsk_need_resched(tsk);
 523         set_task_stack_end_magic(tsk);
 524
 525 #ifdef CONFIG_CC_STACKPROTECTOR
 526         tsk->stack_canary = get_random_int();
 527 #endif
 528
 529         /*
 530          * One for us, one for whoever does the "release_task()" (usually
 531          * parent)
 532          */
 533         atomic_set(&tsk->usage, 2);
 534 #ifdef CONFIG_BLK_DEV_IO_TRACE
 535         tsk->btrace_seq = 0;
 536 #endif
 537         tsk->splice_pipe = NULL;
 538         tsk->task_frag.page = NULL;
 539         tsk->wake_q.next = NULL;
 540
 541         account_kernel_stack(tsk, 1);
 542
 543         kcov_task_init(tsk);
 544
 545         return tsk;
 546
 547 free_stack:
 548         free_thread_stack(tsk);
 549 free_tsk:
 550         free_task_struct(tsk);
 551         return NULL;
 552 }
 553
 554 #ifdef CONFIG_MMU
 555 static __latent_entropy int dup_mmap(struct mm_struct *mm,
 556                                         struct mm_struct *oldmm)
 557 {
 558         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 559         struct rb_node **rb_link, *rb_parent;
 560         int retval;
 561         unsigned long charge;
 562
 563         uprobe_start_dup_mmap();
 564         if (down_write_killable(&oldmm->mmap_sem)) {
 565                 retval = -EINTR;
 566                 goto fail_uprobe_end;
 567         }
 568         flush_cache_dup_mm(oldmm);
 569         uprobe_dup_mmap(oldmm, mm);
 570         /*
 571          * Not linked in yet - no deadlock potential:
 572          */
 573         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 574
 575         /* No ordering required: file already has been exposed. */
 576         RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
 577
 578         mm->total_vm = oldmm->total_vm;
 579         mm->data_vm = oldmm->data_vm;
 580         mm->exec_vm = oldmm->exec_vm;
 581         mm->stack_vm = oldmm->stack_vm;
 582
 583         rb_link = &mm->mm_rb.rb_node;
 584         rb_parent = NULL;
 585         pprev = &mm->mmap;
 586         retval = ksm_fork(mm, oldmm);
 587         if (retval)
 588                 goto out;
 589         retval = khugepaged_fork(mm, oldmm);
 590         if (retval)
 591                 goto out;
 592
 593         prev = NULL;
 594         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 595                 struct file *file;
 596
 597                 if (mpnt->vm_flags & VM_DONTCOPY) {
 598                         vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
 599                         continue;
 600                 }
 601                 charge = 0;
 602                 if (mpnt->vm_flags & VM_ACCOUNT) {
 603                         unsigned long len = vma_pages(mpnt);
 604
 605                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
 606                                 goto fail_nomem;
 607                         charge = len;
 608                 }
 609                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 610                 if (!tmp)
 611                         goto fail_nomem;
 612                 *tmp = *mpnt;
 613                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
 614                 retval = vma_dup_policy(mpnt, tmp);
 615                 if (retval)
 616                         goto fail_nomem_policy;
 617                 tmp->vm_mm = mm;
 618                 if (anon_vma_fork(tmp, mpnt))
 619                         goto fail_nomem_anon_vma_fork;
 620                 tmp->vm_flags &=
 621                         ~(VM_LOCKED|VM_LOCKONFAULT|VM_UFFD_MISSING|VM_UFFD_WP);
 622                 tmp->vm_next = tmp->vm_prev = NULL;
 623                 tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
 624                 file = tmp->vm_file;
 625                 if (file) {
 626                         struct inode *inode = file_inode(file);
 627                         struct address_space *mapping = file->f_mapping;
 628
 629                         get_file(file);
 630                         if (tmp->vm_flags & VM_DENYWRITE)
 631                                 atomic_dec(&inode->i_writecount);
 632                         i_mmap_lock_write(mapping);
 633                         if (tmp->vm_flags & VM_SHARED)
 634                                 atomic_inc(&mapping->i_mmap_writable);
 635                         flush_dcache_mmap_lock(mapping);
 636                         /* insert tmp into the share list, just after mpnt */
 637                         vma_interval_tree_insert_after(tmp, mpnt,
 638                                         &mapping->i_mmap);
 639                         flush_dcache_mmap_unlock(mapping);
 640                         i_mmap_unlock_write(mapping);
 641                 }
 642
 643                 /*
 644                  * Clear hugetlb-related page reserves for children. This only
 645                  * affects MAP_PRIVATE mappings. Faults generated by the child
 646                  * are not guaranteed to succeed, even if read-only
 647                  */
 648                 if (is_vm_hugetlb_page(tmp))
 649                         reset_vma_resv_huge_pages(tmp);
 650
 651                 /*
 652                  * Link in the new vma and copy the page table entries.
 653                  */
 654                 *pprev = tmp;
 655                 pprev = &tmp->vm_next;
 656                 tmp->vm_prev = prev;
 657                 prev = tmp;
 658
 659                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 660                 rb_link = &tmp->vm_rb.rb_right;
 661                 rb_parent = &tmp->vm_rb;
 662
 663                 mm->map_count++;
 664                 retval = copy_page_range(mm, oldmm, mpnt);
 665
 666                 if (tmp->vm_ops && tmp->vm_ops->open)
 667                         tmp->vm_ops->open(tmp);
 668
 669                 if (retval)
 670                         goto out;
 671         }
 672         /* a new mm has just been created */
 673         arch_dup_mmap(oldmm, mm);
 674         retval = 0;
 675 out:
 676         up_write(&mm->mmap_sem);
 677         flush_tlb_mm(oldmm);
 678         up_write(&oldmm->mmap_sem);
 679 fail_uprobe_end:
 680         uprobe_end_dup_mmap();
 681         return retval;
 682 fail_nomem_anon_vma_fork:
 683         mpol_put(vma_policy(tmp));
 684 fail_nomem_policy:
 685         kmem_cache_free(vm_area_cachep, tmp);
 686 fail_nomem:
 687         retval = -ENOMEM;
 688         vm_unacct_memory(charge);
 689         goto out;
 690 }
 691
 692 static inline int mm_alloc_pgd(struct mm_struct *mm)
 693 {
 694         mm->pgd = pgd_alloc(mm);
 695         if (unlikely(!mm->pgd))
 696                 return -ENOMEM;
 697         return 0;
 698 }
 699
 700 static inline void mm_free_pgd(struct mm_struct *mm)
 701 {
 702         pgd_free(mm, mm->pgd);
 703 }
 704 #else
 705 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 706 {
 707         down_write(&oldmm->mmap_sem);
 708         RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
 709         up_write(&oldmm->mmap_sem);
 710         return 0;
 711 }
 712 #define mm_alloc_pgd(mm)        (0)
 713 #define mm_free_pgd(mm)
 714 #endif /* CONFIG_MMU */
 715
 716 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 717
 718 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 719 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 720
 721 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 722
 723 static int __init coredump_filter_setup(char *s)
 724 {
 725         default_dump_filter =
 726                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 727                 MMF_DUMP_FILTER_MASK;
 728         return 1;
 729 }
 730
 731 __setup("coredump_filter=", coredump_filter_setup);
 732
 733 #include <linux/init_task.h>
 734
 735 static void mm_init_aio(struct mm_struct *mm)
 736 {
 737 #ifdef CONFIG_AIO
 738         spin_lock_init(&mm->ioctx_lock);
 739         mm->ioctx_table = NULL;
 740 #endif
 741 }
 742
 743 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 744 {
 745 #ifdef CONFIG_MEMCG
 746         mm->owner = p;
 747 #endif
 748 }
 749
 750 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
 751 {
 752         mm->mmap = NULL;
 753         mm->mm_rb = RB_ROOT;
 754         mm->vmacache_seqnum = 0;
 755         atomic_set(&mm->mm_users, 1);
 756         atomic_set(&mm->mm_count, 1);
 757         init_rwsem(&mm->mmap_sem);
 758         INIT_LIST_HEAD(&mm->mmlist);
 759         mm->core_state = NULL;
 760         atomic_long_set(&mm->nr_ptes, 0);
 761         mm_nr_pmds_init(mm);
 762         mm->map_count = 0;
 763         mm->locked_vm = 0;
 764         mm->pinned_vm = 0;
 765         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 766         spin_lock_init(&mm->page_table_lock);
 767         mm_init_cpumask(mm);
 768         mm_init_aio(mm);
 769         mm_init_owner(mm, p);
 770         mmu_notifier_mm_init(mm);
 771         clear_tlb_flush_pending(mm);
 772 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 773         mm->pmd_huge_pte = NULL;
 774 #endif
 775
 776         if (current->mm) {
 777                 mm->flags = current->mm->flags & MMF_INIT_MASK;
 778                 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
 779         } else {
 780                 mm->flags = default_dump_filter;
 781                 mm->def_flags = 0;
 782         }
 783
 784         if (mm_alloc_pgd(mm))
 785                 goto fail_nopgd;
 786
 787         if (init_new_context(p, mm))
 788                 goto fail_nocontext;
 789
 790         return mm;
 791
 792 fail_nocontext:
 793         mm_free_pgd(mm);
 794 fail_nopgd:
 795         free_mm(mm);
 796         return NULL;
 797 }
 798
 799 static void check_mm(struct mm_struct *mm)
 800 {
 801         int i;
 802
 803         for (i = 0; i < NR_MM_COUNTERS; i++) {
 804                 long x = atomic_long_read(&mm->rss_stat.count[i]);
 805
 806                 if (unlikely(x))
 807                         printk(KERN_ALERT "BUG: Bad rss-counter state "
 808                                           "mm:%p idx:%d val:%ld\n", mm, i, x);
 809         }
 810
 811         if (atomic_long_read(&mm->nr_ptes))
 812                 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n",
 813                                 atomic_long_read(&mm->nr_ptes));
 814         if (mm_nr_pmds(mm))
 815                 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
 816                                 mm_nr_pmds(mm));
 817
 818 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 819         VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
 820 #endif
 821 }
 822
 823 /*
 824  * Allocate and initialize an mm_struct.
 825  */
 826 struct mm_struct *mm_alloc(void)
 827 {
 828         struct mm_struct *mm;
 829
 830         mm = allocate_mm();
 831         if (!mm)
 832                 return NULL;
 833
 834         memset(mm, 0, sizeof(*mm));
 835         return mm_init(mm, current);
 836 }
 837
 838 /*
 839  * Called when the last reference to the mm
 840  * is dropped: either by a lazy thread or by
 841  * mmput. Free the page directory and the mm.
 842  */
 843 void __mmdrop(struct mm_struct *mm)
 844 {
 845         BUG_ON(mm == &init_mm);
 846         mm_free_pgd(mm);
 847         destroy_context(mm);
 848         mmu_notifier_mm_destroy(mm);
 849         check_mm(mm);
 850         free_mm(mm);
 851 }
 852 EXPORT_SYMBOL_GPL(__mmdrop);
 853
 854 static inline void __mmput(struct mm_struct *mm)
 855 {
 856         VM_BUG_ON(atomic_read(&mm->mm_users));
 857
 858         uprobe_clear_state(mm);
 859         exit_aio(mm);
 860         ksm_exit(mm);
 861         khugepaged_exit(mm); /* must run before exit_mmap */
 862         exit_mmap(mm);
 863         mm_put_huge_zero_page(mm);
 864         set_mm_exe_file(mm, NULL);
 865         if (!list_empty(&mm->mmlist)) {
 866                 spin_lock(&mmlist_lock);
 867                 list_del(&mm->mmlist);
 868                 spin_unlock(&mmlist_lock);
 869         }
 870         if (mm->binfmt)
 871                 module_put(mm->binfmt->module);
 872         set_bit(MMF_OOM_SKIP, &mm->flags);
 873         mmdrop(mm);
 874 }
 875
 876 /*
 877  * Decrement the use count and release all resources for an mm.
 878  */
 879 void mmput(struct mm_struct *mm)
 880 {
 881         might_sleep();
 882
 883         if (atomic_dec_and_test(&mm->mm_users))
 884                 __mmput(mm);
 885 }
 886 EXPORT_SYMBOL_GPL(mmput);
 887
 888 #ifdef CONFIG_MMU
 889 static void mmput_async_fn(struct work_struct *work)
 890 {
 891         struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work);
 892         __mmput(mm);
 893 }
 894
 895 void mmput_async(struct mm_struct *mm)
 896 {
 897         if (atomic_dec_and_test(&mm->mm_users)) {
 898                 INIT_WORK(&mm->async_put_work, mmput_async_fn);
 899                 schedule_work(&mm->async_put_work);
 900         }
 901 }
 902 #endif
 903
 904 /**
 905  * set_mm_exe_file - change a reference to the mm's executable file
 906  *
 907  * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
 908  *
 909  * Main users are mmput() and sys_execve(). Callers prevent concurrent
 910  * invocations: in mmput() nobody alive left, in execve task is single
 911  * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
 912  * mm->exe_file, but does so without using set_mm_exe_file() in order
 913  * to do avoid the need for any locks.
 914  */
 915 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 916 {
 917         struct file *old_exe_file;
 918
 919         /*
 920          * It is safe to dereference the exe_file without RCU as
 921          * this function is only called if nobody else can access
 922          * this mm -- see comment above for justification.
 923          */
 924         old_exe_file = rcu_dereference_raw(mm->exe_file);
 925
 926         if (new_exe_file)
 927                 get_file(new_exe_file);
 928         rcu_assign_pointer(mm->exe_file, new_exe_file);
 929         if (old_exe_file)
 930                 fput(old_exe_file);
 931 }
 932
 933 /**
 934  * get_mm_exe_file - acquire a reference to the mm's executable file
 935  *
 936  * Returns %NULL if mm has no associated executable file.
 937  * User must release file via fput().
 938  */
 939 struct file *get_mm_exe_file(struct mm_struct *mm)
 940 {
 941         struct file *exe_file;
 942
 943         rcu_read_lock();
 944         exe_file = rcu_dereference(mm->exe_file);
 945         if (exe_file && !get_file_rcu(exe_file))
 946                 exe_file = NULL;
 947         rcu_read_unlock();
 948         return exe_file;
 949 }
 950 EXPORT_SYMBOL(get_mm_exe_file);
 951
 952 /**
 953  * get_task_exe_file - acquire a reference to the task's executable file
 954  *
 955  * Returns %NULL if task's mm (if any) has no associated executable file or
 956  * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
 957  * User must release file via fput().
 958  */
 959 struct file *get_task_exe_file(struct task_struct *task)
 960 {
 961         struct file *exe_file = NULL;
 962         struct mm_struct *mm;
 963
 964         task_lock(task);
 965         mm = task->mm;
 966         if (mm) {
 967                 if (!(task->flags & PF_KTHREAD))
 968                         exe_file = get_mm_exe_file(mm);
 969         }
 970         task_unlock(task);
 971         return exe_file;
 972 }
 973 EXPORT_SYMBOL(get_task_exe_file);
 974
 975 /**
 976  * get_task_mm - acquire a reference to the task's mm
 977  *
 978  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 979  * this kernel workthread has transiently adopted a user mm with use_mm,
 980  * to do its AIO) is not set and if so returns a reference to it, after
 981  * bumping up the use count.  User must release the mm via mmput()
 982  * after use.  Typically used by /proc and ptrace.
 983  */
 984 struct mm_struct *get_task_mm(struct task_struct *task)
 985 {
 986         struct mm_struct *mm;
 987
 988         task_lock(task);
 989         mm = task->mm;
 990         if (mm) {
 991                 if (task->flags & PF_KTHREAD)
 992                         mm = NULL;
 993                 else
 994                         atomic_inc(&mm->mm_users);
 995         }
 996         task_unlock(task);
 997         return mm;
 998 }
 999 EXPORT_SYMBOL_GPL(get_task_mm);
1000
1001 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1002 {
1003         struct mm_struct *mm;
1004         int err;
1005
1006         err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
1007         if (err)
1008                 return ERR_PTR(err);
1009
1010         mm = get_task_mm(task);
1011         if (mm && mm != current->mm &&
1012                         !ptrace_may_access(task, mode)) {
1013                 mmput(mm);
1014                 mm = ERR_PTR(-EACCES);
1015         }
1016         mutex_unlock(&task->signal->cred_guard_mutex);
1017
1018         return mm;
1019 }
1020
1021 static void complete_vfork_done(struct task_struct *tsk)
1022 {
1023         struct completion *vfork;
1024
1025         task_lock(tsk);
1026         vfork = tsk->vfork_done;
1027         if (likely(vfork)) {
1028                 tsk->vfork_done = NULL;
1029                 complete(vfork);
1030         }
1031         task_unlock(tsk);
1032 }
1033
1034 static int wait_for_vfork_done(struct task_struct *child,
1035                                 struct completion *vfork)
1036 {
1037         int killed;
1038
1039         freezer_do_not_count();
1040         killed = wait_for_completion_killable(vfork);
1041         freezer_count();
1042
1043         if (killed) {
1044                 task_lock(child);
1045                 child->vfork_done = NULL;
1046                 task_unlock(child);
1047         }
1048
1049         put_task_struct(child);
1050         return killed;
1051 }
1052
1053 /* Please note the differences between mmput and mm_release.
1054  * mmput is called whenever we stop holding onto a mm_struct,
1055  * error success whatever.
1056  *
1057  * mm_release is called after a mm_struct has been removed
1058  * from the current process.
1059  *
1060  * This difference is important for error handling, when we
1061  * only half set up a mm_struct for a new process and need to restore
1062  * the old one.  Because we mmput the new mm_struct before
1063  * restoring the old one. . .
1064  * Eric Biederman 10 January 1998
1065  */
1066 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1067 {
1068         /* Get rid of any futexes when releasing the mm */
1069 #ifdef CONFIG_FUTEX
1070         if (unlikely(tsk->robust_list)) {
1071                 exit_robust_list(tsk);
1072                 tsk->robust_list = NULL;
1073         }
1074 #ifdef CONFIG_COMPAT
1075         if (unlikely(tsk->compat_robust_list)) {
1076                 compat_exit_robust_list(tsk);
1077                 tsk->compat_robust_list = NULL;
1078         }
1079 #endif
1080         if (unlikely(!list_empty(&tsk->pi_state_list)))
1081                 exit_pi_state_list(tsk);
1082 #endif
1083
1084         uprobe_free_utask(tsk);
1085
1086         /* Get rid of any cached register state */
1087         deactivate_mm(tsk, mm);
1088
1089         /*
1090          * Signal userspace if we're not exiting with a core dump
1091          * because we want to leave the value intact for debugging
1092          * purposes.
1093          */
1094         if (tsk->clear_child_tid) {
1095                 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1096                     atomic_read(&mm->mm_users) > 1) {
1097                         /*
1098                          * We don't check the error code - if userspace has
1099                          * not set up a proper pointer then tough luck.
1100                          */
1101                         put_user(0, tsk->clear_child_tid);
1102                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
1103                                         1, NULL, NULL, 0);
1104                 }
1105                 tsk->clear_child_tid = NULL;
1106         }
1107
1108         /*
1109          * All done, finally we can wake up parent and return this mm to him.
1110          * Also kthread_stop() uses this completion for synchronization.
1111          */
1112         if (tsk->vfork_done)
1113                 complete_vfork_done(tsk);
1114 }
1115
1116 /*
1117  * Allocate a new mm structure and copy contents from the
1118  * mm structure of the passed in task structure.
1119  */
1120 static struct mm_struct *dup_mm(struct task_struct *tsk)
1121 {
1122         struct mm_struct *mm, *oldmm = current->mm;
1123         int err;
1124
1125         mm = allocate_mm();
1126         if (!mm)
1127                 goto fail_nomem;
1128
1129         memcpy(mm, oldmm, sizeof(*mm));
1130
1131         if (!mm_init(mm, tsk))
1132                 goto fail_nomem;
1133
1134         err = dup_mmap(mm, oldmm);
1135         if (err)
1136                 goto free_pt;
1137
1138         mm->hiwater_rss = get_mm_rss(mm);
1139         mm->hiwater_vm = mm->total_vm;
1140
1141         if (mm->binfmt && !try_module_get(mm->binfmt->module))
1142                 goto free_pt;
1143
1144         return mm;
1145
1146 free_pt:
1147         /* don't put binfmt in mmput, we haven't got module yet */
1148         mm->binfmt = NULL;
1149         mmput(mm);
1150
1151 fail_nomem:
1152         return NULL;
1153 }
1154
1155 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1156 {
1157         struct mm_struct *mm, *oldmm;
1158         int retval;
1159
1160         tsk->min_flt = tsk->maj_flt = 0;
1161         tsk->nvcsw = tsk->nivcsw = 0;
1162 #ifdef CONFIG_DETECT_HUNG_TASK
1163         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1164 #endif
1165
1166         tsk->mm = NULL;
1167         tsk->active_mm = NULL;
1168
1169         /*
1170          * Are we cloning a kernel thread?
1171          *
1172          * We need to steal a active VM for that..
1173          */
1174         oldmm = current->mm;
1175         if (!oldmm)
1176                 return 0;
1177
1178         /* initialize the new vmacache entries */
1179         vmacache_flush(tsk);
1180
1181         if (clone_flags & CLONE_VM) {
1182                 atomic_inc(&oldmm->mm_users);
1183                 mm = oldmm;
1184                 goto good_mm;
1185         }
1186
1187         retval = -ENOMEM;
1188         mm = dup_mm(tsk);
1189         if (!mm)
1190                 goto fail_nomem;
1191
1192 good_mm:
1193         tsk->mm = mm;
1194         tsk->active_mm = mm;
1195         return 0;
1196
1197 fail_nomem:
1198         return retval;
1199 }
1200
1201 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1202 {
1203         struct fs_struct *fs = current->fs;
1204         if (clone_flags & CLONE_FS) {
1205                 /* tsk->fs is already what we want */
1206                 spin_lock(&fs->lock);
1207                 if (fs->in_exec) {
1208                         spin_unlock(&fs->lock);
1209                         return -EAGAIN;
1210                 }
1211                 fs->users++;
1212                 spin_unlock(&fs->lock);
1213                 return 0;
1214         }
1215         tsk->fs = copy_fs_struct(fs);
1216         if (!tsk->fs)
1217                 return -ENOMEM;
1218         return 0;
1219 }
1220
1221 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1222 {
1223         struct files_struct *oldf, *newf;
1224         int error = 0;
1225
1226         /*
1227          * A background process may not have any files ...
1228          */
1229         oldf = current->files;
1230         if (!oldf)
1231                 goto out;
1232
1233         if (clone_flags & CLONE_FILES) {
1234                 atomic_inc(&oldf->count);
1235                 goto out;
1236         }
1237
1238         newf = dup_fd(oldf, &error);
1239         if (!newf)
1240                 goto out;
1241
1242         tsk->files = newf;
1243         error = 0;
1244 out:
1245         return error;
1246 }
1247
1248 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1249 {
1250 #ifdef CONFIG_BLOCK
1251         struct io_context *ioc = current->io_context;
1252         struct io_context *new_ioc;
1253
1254         if (!ioc)
1255                 return 0;
1256         /*
1257          * Share io context with parent, if CLONE_IO is set
1258          */
1259         if (clone_flags & CLONE_IO) {
1260                 ioc_task_link(ioc);
1261                 tsk->io_context = ioc;
1262         } else if (ioprio_valid(ioc->ioprio)) {
1263                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1264                 if (unlikely(!new_ioc))
1265                         return -ENOMEM;
1266
1267                 new_ioc->ioprio = ioc->ioprio;
1268                 put_io_context(new_ioc);
1269         }
1270 #endif
1271         return 0;
1272 }
1273
1274 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1275 {
1276         struct sighand_struct *sig;
1277
1278         if (clone_flags & CLONE_SIGHAND) {
1279                 atomic_inc(&current->sighand->count);
1280                 return 0;
1281         }
1282         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1283         rcu_assign_pointer(tsk->sighand, sig);
1284         if (!sig)
1285                 return -ENOMEM;
1286
1287         atomic_set(&sig->count, 1);
1288         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1289         return 0;
1290 }
1291
1292 void __cleanup_sighand(struct sighand_struct *sighand)
1293 {
1294         if (atomic_dec_and_test(&sighand->count)) {
1295                 signalfd_cleanup(sighand);
1296                 /*
1297                  * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
1298                  * without an RCU grace period, see __lock_task_sighand().
1299                  */
1300                 kmem_cache_free(sighand_cachep, sighand);
1301         }
1302 }
1303
1304 /*
1305  * Initialize POSIX timer handling for a thread group.
1306  */
1307 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1308 {
1309         unsigned long cpu_limit;
1310
1311         cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1312         if (cpu_limit != RLIM_INFINITY) {
1313                 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1314                 sig->cputimer.running = true;
1315         }
1316
1317         /* The timer lists. */
1318         INIT_LIST_HEAD(&sig->cpu_timers[0]);
1319         INIT_LIST_HEAD(&sig->cpu_timers[1]);
1320         INIT_LIST_HEAD(&sig->cpu_timers[2]);
1321 }
1322
1323 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1324 {
1325         struct signal_struct *sig;
1326
1327         if (clone_flags & CLONE_THREAD)
1328                 return 0;
1329
1330         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1331         tsk->signal = sig;
1332         if (!sig)
1333                 return -ENOMEM;
1334
1335         sig->nr_threads = 1;
1336         atomic_set(&sig->live, 1);
1337         atomic_set(&sig->sigcnt, 1);
1338
1339         /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1340         sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1341         tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1342
1343         init_waitqueue_head(&sig->wait_chldexit);
1344         sig->curr_target = tsk;
1345         init_sigpending(&sig->shared_pending);
1346         INIT_LIST_HEAD(&sig->posix_timers);
1347         seqlock_init(&sig->stats_lock);
1348         prev_cputime_init(&sig->prev_cputime);
1349
1350         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1351         sig->real_timer.function = it_real_fn;
1352
1353         task_lock(current->group_leader);
1354         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1355         task_unlock(current->group_leader);
1356
1357         posix_cpu_timers_init_group(sig);
1358
1359         tty_audit_fork(sig);
1360         sched_autogroup_fork(sig);
1361
1362         sig->oom_score_adj = current->signal->oom_score_adj;
1363         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1364
1365         sig->has_child_subreaper = current->signal->has_child_subreaper ||
1366                                    current->signal->is_child_subreaper;
1367
1368         mutex_init(&sig->cred_guard_mutex);
1369
1370         return 0;
1371 }
1372
1373 static void copy_seccomp(struct task_struct *p)
1374 {
1375 #ifdef CONFIG_SECCOMP
1376         /*
1377          * Must be called with sighand->lock held, which is common to
1378          * all threads in the group. Holding cred_guard_mutex is not
1379          * needed because this new task is not yet running and cannot
1380          * be racing exec.
1381          */
1382         assert_spin_locked(&current->sighand->siglock);
1383
1384         /* Ref-count the new filter user, and assign it. */
1385         get_seccomp_filter(current);
1386         p->seccomp = current->seccomp;
1387
1388         /*
1389          * Explicitly enable no_new_privs here in case it got set
1390          * between the task_struct being duplicated and holding the
1391          * sighand lock. The seccomp state and nnp must be in sync.
1392          */
1393         if (task_no_new_privs(current))
1394                 task_set_no_new_privs(p);
1395
1396         /*
1397          * If the parent gained a seccomp mode after copying thread
1398          * flags and between before we held the sighand lock, we have
1399          * to manually enable the seccomp thread flag here.
1400          */
1401         if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1402                 set_tsk_thread_flag(p, TIF_SECCOMP);
1403 #endif
1404 }
1405
1406 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1407 {
1408         current->clear_child_tid = tidptr;
1409
1410         return task_pid_vnr(current);
1411 }
1412
1413 static void rt_mutex_init_task(struct task_struct *p)
1414 {
1415         raw_spin_lock_init(&p->pi_lock);
1416 #ifdef CONFIG_RT_MUTEXES
1417         p->pi_waiters = RB_ROOT;
1418         p->pi_waiters_leftmost = NULL;
1419         p->pi_blocked_on = NULL;
1420 #endif
1421 }
1422
1423 /*
1424  * Initialize POSIX timer handling for a single task.
1425  */
1426 static void posix_cpu_timers_init(struct task_struct *tsk)
1427 {
1428         tsk->cputime_expires.prof_exp = 0;
1429         tsk->cputime_expires.virt_exp = 0;
1430         tsk->cputime_expires.sched_exp = 0;
1431         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1432         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1433         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1434 }
1435
1436 static inline void
1437 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1438 {
1439          task->pids[type].pid = pid;
1440 }
1441
1442 /*
1443  * This creates a new process as a copy of the old one,
1444  * but does not actually start it yet.
1445  *
1446  * It copies the registers, and all the appropriate
1447  * parts of the process environment (as per the clone
1448  * flags). The actual kick-off is left to the caller.
1449  */
1450 static __latent_entropy struct task_struct *copy_process(
1451                                         unsigned long clone_flags,
1452                                         unsigned long stack_start,
1453                                         unsigned long stack_size,
1454                                         int __user *child_tidptr,
1455                                         struct pid *pid,
1456                                         int trace,
1457                                         unsigned long tls,
1458                                         int node)
1459 {
1460         int retval;
1461         struct task_struct *p;
1462
1463         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1464                 return ERR_PTR(-EINVAL);
1465
1466         if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1467                 return ERR_PTR(-EINVAL);
1468
1469         /*
1470          * Thread groups must share signals as well, and detached threads
1471          * can only be started up within the thread group.
1472          */
1473         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1474                 return ERR_PTR(-EINVAL);
1475
1476         /*
1477          * Shared signal handlers imply shared VM. By way of the above,
1478          * thread groups also imply shared VM. Blocking this case allows
1479          * for various simplifications in other code.
1480          */
1481         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1482                 return ERR_PTR(-EINVAL);
1483
1484         /*
1485          * Siblings of global init remain as zombies on exit since they are
1486          * not reaped by their parent (swapper). To solve this and to avoid
1487          * multi-rooted process trees, prevent global and container-inits
1488          * from creating siblings.
1489          */
1490         if ((clone_flags & CLONE_PARENT) &&
1491                                 current->signal->flags & SIGNAL_UNKILLABLE)
1492                 return ERR_PTR(-EINVAL);
1493
1494         /*
1495          * If the new process will be in a different pid or user namespace
1496          * do not allow it to share a thread group with the forking task.
1497          */
1498         if (clone_flags & CLONE_THREAD) {
1499                 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1500                     (task_active_pid_ns(current) !=
1501                                 current->nsproxy->pid_ns_for_children))
1502                         return ERR_PTR(-EINVAL);
1503         }
1504
1505         retval = security_task_create(clone_flags);
1506         if (retval)
1507                 goto fork_out;
1508
1509         retval = -ENOMEM;
1510         p = dup_task_struct(current, node);
1511         if (!p)
1512                 goto fork_out;
1513
1514         ftrace_graph_init_task(p);
1515
1516         rt_mutex_init_task(p);
1517
1518 #ifdef CONFIG_PROVE_LOCKING
1519         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1520         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1521 #endif
1522         retval = -EAGAIN;
1523         if (atomic_read(&p->real_cred->user->processes) >=
1524                         task_rlimit(p, RLIMIT_NPROC)) {
1525                 if (p->real_cred->user != INIT_USER &&
1526                     !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1527                         goto bad_fork_free;
1528         }
1529         current->flags &= ~PF_NPROC_EXCEEDED;
1530
1531         retval = copy_creds(p, clone_flags);
1532         if (retval < 0)
1533                 goto bad_fork_free;
1534
1535         /*
1536          * If multiple threads are within copy_process(), then this check
1537          * triggers too late. This doesn't hurt, the check is only there
1538          * to stop root fork bombs.
1539          */
1540         retval = -EAGAIN;
1541         if (nr_threads >= max_threads)
1542                 goto bad_fork_cleanup_count;
1543
1544         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1545         p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1546         p->flags |= PF_FORKNOEXEC;
1547         INIT_LIST_HEAD(&p->children);
1548         INIT_LIST_HEAD(&p->sibling);
1549         rcu_copy_process(p);
1550         p->vfork_done = NULL;
1551         spin_lock_init(&p->alloc_lock);
1552
1553         init_sigpending(&p->pending);
1554
1555         p->utime = p->stime = p->gtime = 0;
1556 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1557         p->utimescaled = p->stimescaled = 0;
1558 #endif
1559         prev_cputime_init(&p->prev_cputime);
1560
1561 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1562         seqcount_init(&p->vtime_seqcount);
1563         p->vtime_snap = 0;
1564         p->vtime_snap_whence = VTIME_INACTIVE;
1565 #endif
1566
1567 #if defined(SPLIT_RSS_COUNTING)
1568         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1569 #endif
1570
1571         p->default_timer_slack_ns = current->timer_slack_ns;
1572
1573         task_io_accounting_init(&p->ioac);
1574         acct_clear_integrals(p);
1575
1576         posix_cpu_timers_init(p);
1577
1578         p->start_time = ktime_get_ns();
1579         p->real_start_time = ktime_get_boot_ns();
1580         p->io_context = NULL;
1581         p->audit_context = NULL;
1582         cgroup_fork(p);
1583 #ifdef CONFIG_NUMA
1584         p->mempolicy = mpol_dup(p->mempolicy);
1585         if (IS_ERR(p->mempolicy)) {
1586                 retval = PTR_ERR(p->mempolicy);
1587                 p->mempolicy = NULL;
1588                 goto bad_fork_cleanup_threadgroup_lock;
1589         }
1590 #endif
1591 #ifdef CONFIG_CPUSETS
1592         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1593         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1594         seqcount_init(&p->mems_allowed_seq);
1595 #endif
1596 #ifdef CONFIG_TRACE_IRQFLAGS
1597         p->irq_events = 0;
1598         p->hardirqs_enabled = 0;
1599         p->hardirq_enable_ip = 0;
1600         p->hardirq_enable_event = 0;
1601         p->hardirq_disable_ip = _THIS_IP_;
1602         p->hardirq_disable_event = 0;
1603         p->softirqs_enabled = 1;
1604         p->softirq_enable_ip = _THIS_IP_;
1605         p->softirq_enable_event = 0;
1606         p->softirq_disable_ip = 0;
1607         p->softirq_disable_event = 0;
1608         p->hardirq_context = 0;
1609         p->softirq_context = 0;
1610 #endif
1611
1612         p->pagefault_disabled = 0;
1613
1614 #ifdef CONFIG_LOCKDEP
1615         p->lockdep_depth = 0; /* no locks held yet */
1616         p->curr_chain_key = 0;
1617         p->lockdep_recursion = 0;
1618 #endif
1619
1620 #ifdef CONFIG_DEBUG_MUTEXES
1621         p->blocked_on = NULL; /* not blocked yet */
1622 #endif
1623 #ifdef CONFIG_BCACHE
1624         p->sequential_io        = 0;
1625         p->sequential_io_avg    = 0;
1626 #endif
1627
1628         /* Perform scheduler related setup. Assign this task to a CPU. */
1629         retval = sched_fork(clone_flags, p);
1630         if (retval)
1631                 goto bad_fork_cleanup_policy;
1632
1633         retval = perf_event_init_task(p);
1634         if (retval)
1635                 goto bad_fork_cleanup_policy;
1636         retval = audit_alloc(p);
1637         if (retval)
1638                 goto bad_fork_cleanup_perf;
1639         /* copy all the process information */
1640         shm_init_task(p);
1641         retval = copy_semundo(clone_flags, p);
1642         if (retval)
1643                 goto bad_fork_cleanup_audit;
1644         retval = copy_files(clone_flags, p);
1645         if (retval)
1646                 goto bad_fork_cleanup_semundo;
1647         retval = copy_fs(clone_flags, p);
1648         if (retval)
1649                 goto bad_fork_cleanup_files;
1650         retval = copy_sighand(clone_flags, p);
1651         if (retval)
1652                 goto bad_fork_cleanup_fs;
1653         retval = copy_signal(clone_flags, p);
1654         if (retval)
1655                 goto bad_fork_cleanup_sighand;
1656         retval = copy_mm(clone_flags, p);
1657         if (retval)
1658                 goto bad_fork_cleanup_signal;
1659         retval = copy_namespaces(clone_flags, p);
1660         if (retval)
1661                 goto bad_fork_cleanup_mm;
1662         retval = copy_io(clone_flags, p);
1663         if (retval)
1664                 goto bad_fork_cleanup_namespaces;
1665         retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1666         if (retval)
1667                 goto bad_fork_cleanup_io;
1668
1669         if (pid != &init_struct_pid) {
1670                 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1671                 if (IS_ERR(pid)) {
1672                         retval = PTR_ERR(pid);
1673                         goto bad_fork_cleanup_thread;
1674                 }
1675         }
1676
1677         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1678         /*
1679          * Clear TID on mm_release()?
1680          */
1681         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1682 #ifdef CONFIG_BLOCK
1683         p->plug = NULL;
1684 #endif
1685 #ifdef CONFIG_FUTEX
1686         p->robust_list = NULL;
1687 #ifdef CONFIG_COMPAT
1688         p->compat_robust_list = NULL;
1689 #endif
1690         INIT_LIST_HEAD(&p->pi_state_list);
1691         p->pi_state_cache = NULL;
1692 #endif
1693         /*
1694          * sigaltstack should be cleared when sharing the same VM
1695          */
1696         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1697                 sas_ss_reset(p);
1698
1699         /*
1700          * Syscall tracing and stepping should be turned off in the
1701          * child regardless of CLONE_PTRACE.
1702          */
1703         user_disable_single_step(p);
1704         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1705 #ifdef TIF_SYSCALL_EMU
1706         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1707 #endif
1708         clear_all_latency_tracing(p);
1709
1710         /* ok, now we should be set up.. */
1711         p->pid = pid_nr(pid);
1712         if (clone_flags & CLONE_THREAD) {
1713                 p->exit_signal = -1;
1714                 p->group_leader = current->group_leader;
1715                 p->tgid = current->tgid;
1716         } else {
1717                 if (clone_flags & CLONE_PARENT)
1718                         p->exit_signal = current->group_leader->exit_signal;
1719                 else
1720                         p->exit_signal = (clone_flags & CSIGNAL);
1721                 p->group_leader = p;
1722                 p->tgid = p->pid;
1723         }
1724
1725         p->nr_dirtied = 0;
1726         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1727         p->dirty_paused_when = 0;
1728
1729         p->pdeath_signal = 0;
1730         INIT_LIST_HEAD(&p->thread_group);
1731         p->task_works = NULL;
1732
1733         threadgroup_change_begin(current);
1734         /*
1735          * Ensure that the cgroup subsystem policies allow the new process to be
1736          * forked. It should be noted the the new process's css_set can be changed
1737          * between here and cgroup_post_fork() if an organisation operation is in
1738          * progress.
1739          */
1740         retval = cgroup_can_fork(p);
1741         if (retval)
1742                 goto bad_fork_free_pid;
1743
1744         /*
1745          * Make it visible to the rest of the system, but dont wake it up yet.
1746          * Need tasklist lock for parent etc handling!
1747          */
1748         write_lock_irq(&tasklist_lock);
1749
1750         /* CLONE_PARENT re-uses the old parent */
1751         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1752                 p->real_parent = current->real_parent;
1753                 p->parent_exec_id = current->parent_exec_id;
1754         } else {
1755                 p->real_parent = current;
1756                 p->parent_exec_id = current->self_exec_id;
1757         }
1758
1759         spin_lock(&current->sighand->siglock);
1760
1761         /*
1762          * Copy seccomp details explicitly here, in case they were changed
1763          * before holding sighand lock.
1764          */
1765         copy_seccomp(p);
1766
1767         /*
1768          * Process group and session signals need to be delivered to just the
1769          * parent before the fork or both the parent and the child after the
1770          * fork. Restart if a signal comes in before we add the new process to
1771          * it's process group.
1772          * A fatal signal pending means that current will exit, so the new
1773          * thread can't slip out of an OOM kill (or normal SIGKILL).
1774         */
1775         recalc_sigpending();
1776         if (signal_pending(current)) {
1777                 spin_unlock(&current->sighand->siglock);
1778                 write_unlock_irq(&tasklist_lock);
1779                 retval = -ERESTARTNOINTR;
1780                 goto bad_fork_cancel_cgroup;
1781         }
1782
1783         if (likely(p->pid)) {
1784                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1785
1786                 init_task_pid(p, PIDTYPE_PID, pid);
1787                 if (thread_group_leader(p)) {
1788                         init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1789                         init_task_pid(p, PIDTYPE_SID, task_session(current));
1790
1791                         if (is_child_reaper(pid)) {
1792                                 ns_of_pid(pid)->child_reaper = p;
1793                                 p->signal->flags |= SIGNAL_UNKILLABLE;
1794                         }
1795
1796                         p->signal->leader_pid = pid;
1797                         p->signal->tty = tty_kref_get(current->signal->tty);
1798                         list_add_tail(&p->sibling, &p->real_parent->children);
1799                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1800                         attach_pid(p, PIDTYPE_PGID);
1801                         attach_pid(p, PIDTYPE_SID);
1802                         __this_cpu_inc(process_counts);
1803                 } else {
1804                         current->signal->nr_threads++;
1805                         atomic_inc(&current->signal->live);
1806                         atomic_inc(&current->signal->sigcnt);
1807                         list_add_tail_rcu(&p->thread_group,
1808                                           &p->group_leader->thread_group);
1809                         list_add_tail_rcu(&p->thread_node,
1810                                           &p->signal->thread_head);
1811                 }
1812                 attach_pid(p, PIDTYPE_PID);
1813                 nr_threads++;
1814         }
1815
1816         total_forks++;
1817         spin_unlock(&current->sighand->siglock);
1818         syscall_tracepoint_update(p);
1819         write_unlock_irq(&tasklist_lock);
1820
1821         proc_fork_connector(p);
1822         cgroup_post_fork(p);
1823         threadgroup_change_end(current);
1824         perf_event_fork(p);
1825
1826         trace_task_newtask(p, clone_flags);
1827         uprobe_copy_process(p, clone_flags);
1828
1829         return p;
1830
1831 bad_fork_cancel_cgroup:
1832         cgroup_cancel_fork(p);
1833 bad_fork_free_pid:
1834         threadgroup_change_end(current);
1835         if (pid != &init_struct_pid)
1836                 free_pid(pid);
1837 bad_fork_cleanup_thread:
1838         exit_thread(p);
1839 bad_fork_cleanup_io:
1840         if (p->io_context)
1841                 exit_io_context(p);
1842 bad_fork_cleanup_namespaces:
1843         exit_task_namespaces(p);
1844 bad_fork_cleanup_mm:
1845         if (p->mm)
1846                 mmput(p->mm);
1847 bad_fork_cleanup_signal:
1848         if (!(clone_flags & CLONE_THREAD))
1849                 free_signal_struct(p->signal);
1850 bad_fork_cleanup_sighand:
1851         __cleanup_sighand(p->sighand);
1852 bad_fork_cleanup_fs:
1853         exit_fs(p); /* blocking */
1854 bad_fork_cleanup_files:
1855         exit_files(p); /* blocking */
1856 bad_fork_cleanup_semundo:
1857         exit_sem(p);
1858 bad_fork_cleanup_audit:
1859         audit_free(p);
1860 bad_fork_cleanup_perf:
1861         perf_event_free_task(p);
1862 bad_fork_cleanup_policy:
1863 #ifdef CONFIG_NUMA
1864         mpol_put(p->mempolicy);
1865 bad_fork_cleanup_threadgroup_lock:
1866 #endif
1867         delayacct_tsk_free(p);
1868 bad_fork_cleanup_count:
1869         atomic_dec(&p->cred->user->processes);
1870         exit_creds(p);
1871 bad_fork_free:
1872         p->state = TASK_DEAD;
1873         put_task_stack(p);
1874         free_task(p);
1875 fork_out:
1876         return ERR_PTR(retval);
1877 }
1878
1879 static inline void init_idle_pids(struct pid_link *links)
1880 {
1881         enum pid_type type;
1882
1883         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1884                 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1885                 links[type].pid = &init_struct_pid;
1886         }
1887 }
1888
1889 struct task_struct *fork_idle(int cpu)
1890 {
1891         struct task_struct *task;
1892         task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0,
1893                             cpu_to_node(cpu));
1894         if (!IS_ERR(task)) {
1895                 init_idle_pids(task->pids);
1896                 init_idle(task, cpu);
1897         }
1898
1899         return task;
1900 }
1901
1902 /*
1903  *  Ok, this is the main fork-routine.
1904  *
1905  * It copies the process, and if successful kick-starts
1906  * it and waits for it to finish using the VM if required.
1907  */
1908 long _do_fork(unsigned long clone_flags,
1909               unsigned long stack_start,
1910               unsigned long stack_size,
1911               int __user *parent_tidptr,
1912               int __user *child_tidptr,
1913               unsigned long tls)
1914 {
1915         struct task_struct *p;
1916         int trace = 0;
1917         long nr;
1918
1919         /*
1920          * Determine whether and which event to report to ptracer.  When
1921          * called from kernel_thread or CLONE_UNTRACED is explicitly
1922          * requested, no event is reported; otherwise, report if the event
1923          * for the type of forking is enabled.
1924          */
1925         if (!(clone_flags & CLONE_UNTRACED)) {
1926                 if (clone_flags & CLONE_VFORK)
1927                         trace = PTRACE_EVENT_VFORK;
1928                 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1929                         trace = PTRACE_EVENT_CLONE;
1930                 else
1931                         trace = PTRACE_EVENT_FORK;
1932
1933                 if (likely(!ptrace_event_enabled(current, trace)))
1934                         trace = 0;
1935         }
1936
1937         p = copy_process(clone_flags, stack_start, stack_size,
1938                          child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
1939         add_latent_entropy();
1940         /*
1941          * Do this prior waking up the new thread - the thread pointer
1942          * might get invalid after that point, if the thread exits quickly.
1943          */
1944         if (!IS_ERR(p)) {
1945                 struct completion vfork;
1946                 struct pid *pid;
1947
1948                 trace_sched_process_fork(current, p);
1949
1950                 pid = get_task_pid(p, PIDTYPE_PID);
1951                 nr = pid_vnr(pid);
1952
1953                 if (clone_flags & CLONE_PARENT_SETTID)
1954                         put_user(nr, parent_tidptr);
1955
1956                 if (clone_flags & CLONE_VFORK) {
1957                         p->vfork_done = &vfork;
1958                         init_completion(&vfork);
1959                         get_task_struct(p);
1960                 }
1961
1962                 wake_up_new_task(p);
1963
1964                 /* forking complete and child started to run, tell ptracer */
1965                 if (unlikely(trace))
1966                         ptrace_event_pid(trace, pid);
1967
1968                 if (clone_flags & CLONE_VFORK) {
1969                         if (!wait_for_vfork_done(p, &vfork))
1970                                 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
1971                 }
1972
1973                 put_pid(pid);
1974         } else {
1975                 nr = PTR_ERR(p);
1976         }
1977         return nr;
1978 }
1979
1980 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
1981 /* For compatibility with architectures that call do_fork directly rather than
1982  * using the syscall entry points below. */
1983 long do_fork(unsigned long clone_flags,
1984               unsigned long stack_start,
1985               unsigned long stack_size,
1986               int __user *parent_tidptr,
1987               int __user *child_tidptr)
1988 {
1989         return _do_fork(clone_flags, stack_start, stack_size,
1990                         parent_tidptr, child_tidptr, 0);
1991 }
1992 #endif
1993
1994 /*
1995  * Create a kernel thread.
1996  */
1997 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
1998 {
1999         return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
2000                 (unsigned long)arg, NULL, NULL, 0);
2001 }
2002
2003 #ifdef __ARCH_WANT_SYS_FORK
2004 SYSCALL_DEFINE0(fork)
2005 {
2006 #ifdef CONFIG_MMU
2007         return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
2008 #else
2009         /* can not support in nommu mode */
2010         return -EINVAL;
2011 #endif
2012 }
2013 #endif
2014
2015 #ifdef __ARCH_WANT_SYS_VFORK
2016 SYSCALL_DEFINE0(vfork)
2017 {
2018         return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
2019                         0, NULL, NULL, 0);
2020 }
2021 #endif
2022
2023 #ifdef __ARCH_WANT_SYS_CLONE
2024 #ifdef CONFIG_CLONE_BACKWARDS
2025 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2026                  int __user *, parent_tidptr,
2027                  unsigned long, tls,
2028                  int __user *, child_tidptr)
2029 #elif defined(CONFIG_CLONE_BACKWARDS2)
2030 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2031                  int __user *, parent_tidptr,
2032                  int __user *, child_tidptr,
2033                  unsigned long, tls)
2034 #elif defined(CONFIG_CLONE_BACKWARDS3)
2035 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2036                 int, stack_size,
2037                 int __user *, parent_tidptr,
2038                 int __user *, child_tidptr,
2039                 unsigned long, tls)
2040 #else
2041 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2042                  int __user *, parent_tidptr,
2043                  int __user *, child_tidptr,
2044                  unsigned long, tls)
2045 #endif
2046 {
2047         return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
2048 }
2049 #endif
2050
2051 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2052 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2053 #endif
2054
2055 static void sighand_ctor(void *data)
2056 {
2057         struct sighand_struct *sighand = data;
2058
2059         spin_lock_init(&sighand->siglock);
2060         init_waitqueue_head(&sighand->signalfd_wqh);
2061 }
2062
2063 void __init proc_caches_init(void)
2064 {
2065         sighand_cachep = kmem_cache_create("sighand_cache",
2066                         sizeof(struct sighand_struct), 0,
2067                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
2068                         SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor);
2069         signal_cachep = kmem_cache_create("signal_cache",
2070                         sizeof(struct signal_struct), 0,
2071                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2072                         NULL);
2073         files_cachep = kmem_cache_create("files_cache",
2074                         sizeof(struct files_struct), 0,
2075                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2076                         NULL);
2077         fs_cachep = kmem_cache_create("fs_cache",
2078                         sizeof(struct fs_struct), 0,
2079                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2080                         NULL);
2081         /*
2082          * FIXME! The "sizeof(struct mm_struct)" currently includes the
2083          * whole struct cpumask for the OFFSTACK case. We could change
2084          * this to *only* allocate as much of it as required by the
2085          * maximum number of CPU's we can ever have.  The cpumask_allocation
2086          * is at the end of the structure, exactly for that reason.
2087          */
2088         mm_cachep = kmem_cache_create("mm_struct",
2089                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
2090                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2091                         NULL);
2092         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2093         mmap_init();
2094         nsproxy_cache_init();
2095 }
2096
2097 /*
2098  * Check constraints on flags passed to the unshare system call.
2099  */
2100 static int check_unshare_flags(unsigned long unshare_flags)
2101 {
2102         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2103                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2104                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2105                                 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2106                 return -EINVAL;
2107         /*
2108          * Not implemented, but pretend it works if there is nothing
2109          * to unshare.  Note that unsharing the address space or the
2110          * signal handlers also need to unshare the signal queues (aka
2111          * CLONE_THREAD).
2112          */
2113         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2114                 if (!thread_group_empty(current))
2115                         return -EINVAL;
2116         }
2117         if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2118                 if (atomic_read(&current->sighand->count) > 1)
2119                         return -EINVAL;
2120         }
2121         if (unshare_flags & CLONE_VM) {
2122                 if (!current_is_single_threaded())
2123                         return -EINVAL;
2124         }
2125
2126         return 0;
2127 }
2128
2129 /*
2130  * Unshare the filesystem structure if it is being shared
2131  */
2132 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2133 {
2134         struct fs_struct *fs = current->fs;
2135
2136         if (!(unshare_flags & CLONE_FS) || !fs)
2137                 return 0;
2138
2139         /* don't need lock here; in the worst case we'll do useless copy */
2140         if (fs->users == 1)
2141                 return 0;
2142
2143         *new_fsp = copy_fs_struct(fs);
2144         if (!*new_fsp)
2145                 return -ENOMEM;
2146
2147         return 0;
2148 }
2149
2150 /*
2151  * Unshare file descriptor table if it is being shared
2152  */
2153 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2154 {
2155         struct files_struct *fd = current->files;
2156         int error = 0;
2157
2158         if ((unshare_flags & CLONE_FILES) &&
2159             (fd && atomic_read(&fd->count) > 1)) {
2160                 *new_fdp = dup_fd(fd, &error);
2161                 if (!*new_fdp)
2162                         return error;
2163         }
2164
2165         return 0;
2166 }
2167
2168 /*
2169  * unshare allows a process to 'unshare' part of the process
2170  * context which was originally shared using clone.  copy_*
2171  * functions used by do_fork() cannot be used here directly
2172  * because they modify an inactive task_struct that is being
2173  * constructed. Here we are modifying the current, active,
2174  * task_struct.
2175  */
2176 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2177 {
2178         struct fs_struct *fs, *new_fs = NULL;
2179         struct files_struct *fd, *new_fd = NULL;
2180         struct cred *new_cred = NULL;
2181         struct nsproxy *new_nsproxy = NULL;
2182         int do_sysvsem = 0;
2183         int err;
2184
2185         /*
2186          * If unsharing a user namespace must also unshare the thread group
2187          * and unshare the filesystem root and working directories.
2188          */
2189         if (unshare_flags & CLONE_NEWUSER)
2190                 unshare_flags |= CLONE_THREAD | CLONE_FS;
2191         /*
2192          * If unsharing vm, must also unshare signal handlers.
2193          */
2194         if (unshare_flags & CLONE_VM)
2195                 unshare_flags |= CLONE_SIGHAND;
2196         /*
2197          * If unsharing a signal handlers, must also unshare the signal queues.
2198          */
2199         if (unshare_flags & CLONE_SIGHAND)
2200                 unshare_flags |= CLONE_THREAD;
2201         /*
2202          * If unsharing namespace, must also unshare filesystem information.
2203          */
2204         if (unshare_flags & CLONE_NEWNS)
2205                 unshare_flags |= CLONE_FS;
2206
2207         err = check_unshare_flags(unshare_flags);
2208         if (err)
2209                 goto bad_unshare_out;
2210         /*
2211          * CLONE_NEWIPC must also detach from the undolist: after switching
2212          * to a new ipc namespace, the semaphore arrays from the old
2213          * namespace are unreachable.
2214          */
2215         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2216                 do_sysvsem = 1;
2217         err = unshare_fs(unshare_flags, &new_fs);
2218         if (err)
2219                 goto bad_unshare_out;
2220         err = unshare_fd(unshare_flags, &new_fd);
2221         if (err)
2222                 goto bad_unshare_cleanup_fs;
2223         err = unshare_userns(unshare_flags, &new_cred);
2224         if (err)
2225                 goto bad_unshare_cleanup_fd;
2226         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2227                                          new_cred, new_fs);
2228         if (err)
2229                 goto bad_unshare_cleanup_cred;
2230
2231         if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2232                 if (do_sysvsem) {
2233                         /*
2234                          * CLONE_SYSVSEM is equivalent to sys_exit().
2235                          */
2236                         exit_sem(current);
2237                 }
2238                 if (unshare_flags & CLONE_NEWIPC) {
2239                         /* Orphan segments in old ns (see sem above). */
2240                         exit_shm(current);
2241                         shm_init_task(current);
2242                 }
2243
2244                 if (new_nsproxy)
2245                         switch_task_namespaces(current, new_nsproxy);
2246
2247                 task_lock(current);
2248
2249                 if (new_fs) {
2250                         fs = current->fs;
2251                         spin_lock(&fs->lock);
2252                         current->fs = new_fs;
2253                         if (--fs->users)
2254                                 new_fs = NULL;
2255                         else
2256                                 new_fs = fs;
2257                         spin_unlock(&fs->lock);
2258                 }
2259
2260                 if (new_fd) {
2261                         fd = current->files;
2262                         current->files = new_fd;
2263                         new_fd = fd;
2264                 }
2265
2266                 task_unlock(current);
2267
2268                 if (new_cred) {
2269                         /* Install the new user namespace */
2270                         commit_creds(new_cred);
2271                         new_cred = NULL;
2272                 }
2273         }
2274
2275 bad_unshare_cleanup_cred:
2276         if (new_cred)
2277                 put_cred(new_cred);
2278 bad_unshare_cleanup_fd:
2279         if (new_fd)
2280                 put_files_struct(new_fd);
2281
2282 bad_unshare_cleanup_fs:
2283         if (new_fs)
2284                 free_fs_struct(new_fs);
2285
2286 bad_unshare_out:
2287         return err;
2288 }
2289
2290 /*
2291  *      Helper to unshare the files of the current task.
2292  *      We don't want to expose copy_files internals to
2293  *      the exec layer of the kernel.
2294  */
2295
2296 int unshare_files(struct files_struct **displaced)
2297 {
2298         struct task_struct *task = current;
2299         struct files_struct *copy = NULL;
2300         int error;
2301
2302         error = unshare_fd(CLONE_FILES, &copy);
2303         if (error || !copy) {
2304                 *displaced = NULL;
2305                 return error;
2306         }
2307         *displaced = task->files;
2308         task_lock(task);
2309         task->files = copy;
2310         task_unlock(task);
2311         return 0;
2312 }
2313
2314 int sysctl_max_threads(struct ctl_table *table, int write,
2315                        void __user *buffer, size_t *lenp, loff_t *ppos)
2316 {
2317         struct ctl_table t;
2318         int ret;
2319         int threads = max_threads;
2320         int min = MIN_THREADS;
2321         int max = MAX_THREADS;
2322
2323         t = *table;
2324         t.data = &threads;
2325         t.extra1 = &min;
2326         t.extra2 = &max;
2327
2328         ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2329         if (ret || !write)
2330                 return ret;
2331
2332         set_max_threads(threads);
2333
2334         return 0;
2335 }