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