linux/kernel/fork.c
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   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/nsproxy.h>
  32#include <linux/capability.h>
  33#include <linux/cpu.h>
  34#include <linux/cgroup.h>
  35#include <linux/security.h>
  36#include <linux/hugetlb.h>
  37#include <linux/swap.h>
  38#include <linux/syscalls.h>
  39#include <linux/jiffies.h>
  40#include <linux/futex.h>
  41#include <linux/compat.h>
  42#include <linux/kthread.h>
  43#include <linux/task_io_accounting_ops.h>
  44#include <linux/rcupdate.h>
  45#include <linux/ptrace.h>
  46#include <linux/mount.h>
  47#include <linux/audit.h>
  48#include <linux/memcontrol.h>
  49#include <linux/ftrace.h>
  50#include <linux/profile.h>
  51#include <linux/rmap.h>
  52#include <linux/ksm.h>
  53#include <linux/acct.h>
  54#include <linux/tsacct_kern.h>
  55#include <linux/cn_proc.h>
  56#include <linux/freezer.h>
  57#include <linux/delayacct.h>
  58#include <linux/taskstats_kern.h>
  59#include <linux/random.h>
  60#include <linux/tty.h>
  61#include <linux/blkdev.h>
  62#include <linux/fs_struct.h>
  63#include <linux/magic.h>
  64#include <linux/perf_event.h>
  65#include <linux/posix-timers.h>
  66#include <linux/user-return-notifier.h>
  67#include <linux/oom.h>
  68#include <linux/khugepaged.h>
  69#include <linux/signalfd.h>
  70
  71#include <asm/pgtable.h>
  72#include <asm/pgalloc.h>
  73#include <asm/uaccess.h>
  74#include <asm/mmu_context.h>
  75#include <asm/cacheflush.h>
  76#include <asm/tlbflush.h>
  77
  78#include <trace/events/sched.h>
  79
  80/*
  81 * Protected counters by write_lock_irq(&tasklist_lock)
  82 */
  83unsigned long total_forks;      /* Handle normal Linux uptimes. */
  84int nr_threads;                 /* The idle threads do not count.. */
  85
  86int max_threads;                /* tunable limit on nr_threads */
  87
  88DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  89
  90__cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  91
  92#ifdef CONFIG_PROVE_RCU
  93int lockdep_tasklist_lock_is_held(void)
  94{
  95        return lockdep_is_held(&tasklist_lock);
  96}
  97EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
  98#endif /* #ifdef CONFIG_PROVE_RCU */
  99
 100int nr_processes(void)
 101{
 102        int cpu;
 103        int total = 0;
 104
 105        for_each_possible_cpu(cpu)
 106                total += per_cpu(process_counts, cpu);
 107
 108        return total;
 109}
 110
 111#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 112# define alloc_task_struct_node(node)           \
 113                kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node)
 114# define free_task_struct(tsk)                  \
 115                kmem_cache_free(task_struct_cachep, (tsk))
 116static struct kmem_cache *task_struct_cachep;
 117#endif
 118
 119#ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
 120static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
 121                                                  int node)
 122{
 123#ifdef CONFIG_DEBUG_STACK_USAGE
 124        gfp_t mask = GFP_KERNEL | __GFP_ZERO;
 125#else
 126        gfp_t mask = GFP_KERNEL;
 127#endif
 128        struct page *page = alloc_pages_node(node, mask, THREAD_SIZE_ORDER);
 129
 130        return page ? page_address(page) : NULL;
 131}
 132
 133static inline void free_thread_info(struct thread_info *ti)
 134{
 135        free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 136}
 137#endif
 138
 139/* SLAB cache for signal_struct structures (tsk->signal) */
 140static struct kmem_cache *signal_cachep;
 141
 142/* SLAB cache for sighand_struct structures (tsk->sighand) */
 143struct kmem_cache *sighand_cachep;
 144
 145/* SLAB cache for files_struct structures (tsk->files) */
 146struct kmem_cache *files_cachep;
 147
 148/* SLAB cache for fs_struct structures (tsk->fs) */
 149struct kmem_cache *fs_cachep;
 150
 151/* SLAB cache for vm_area_struct structures */
 152struct kmem_cache *vm_area_cachep;
 153
 154/* SLAB cache for mm_struct structures (tsk->mm) */
 155static struct kmem_cache *mm_cachep;
 156
 157static void account_kernel_stack(struct thread_info *ti, int account)
 158{
 159        struct zone *zone = page_zone(virt_to_page(ti));
 160
 161        mod_zone_page_state(zone, NR_KERNEL_STACK, account);
 162}
 163
 164void free_task(struct task_struct *tsk)
 165{
 166        account_kernel_stack(tsk->stack, -1);
 167        free_thread_info(tsk->stack);
 168        rt_mutex_debug_task_free(tsk);
 169        ftrace_graph_exit_task(tsk);
 170        free_task_struct(tsk);
 171}
 172EXPORT_SYMBOL(free_task);
 173
 174static inline void free_signal_struct(struct signal_struct *sig)
 175{
 176        taskstats_tgid_free(sig);
 177        sched_autogroup_exit(sig);
 178        kmem_cache_free(signal_cachep, sig);
 179}
 180
 181static inline void put_signal_struct(struct signal_struct *sig)
 182{
 183        if (atomic_dec_and_test(&sig->sigcnt))
 184                free_signal_struct(sig);
 185}
 186
 187void __put_task_struct(struct task_struct *tsk)
 188{
 189        WARN_ON(!tsk->exit_state);
 190        WARN_ON(atomic_read(&tsk->usage));
 191        WARN_ON(tsk == current);
 192
 193        exit_creds(tsk);
 194        delayacct_tsk_free(tsk);
 195        put_signal_struct(tsk->signal);
 196
 197        if (!profile_handoff_task(tsk))
 198                free_task(tsk);
 199}
 200EXPORT_SYMBOL_GPL(__put_task_struct);
 201
 202/*
 203 * macro override instead of weak attribute alias, to workaround
 204 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
 205 */
 206#ifndef arch_task_cache_init
 207#define arch_task_cache_init()
 208#endif
 209
 210void __init fork_init(unsigned long mempages)
 211{
 212#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 213#ifndef ARCH_MIN_TASKALIGN
 214#define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 215#endif
 216        /* create a slab on which task_structs can be allocated */
 217        task_struct_cachep =
 218                kmem_cache_create("task_struct", sizeof(struct task_struct),
 219                        ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
 220#endif
 221
 222        /* do the arch specific task caches init */
 223        arch_task_cache_init();
 224
 225        /*
 226         * The default maximum number of threads is set to a safe
 227         * value: the thread structures can take up at most half
 228         * of memory.
 229         */
 230        max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 231
 232        /*
 233         * we need to allow at least 20 threads to boot a system
 234         */
 235        if (max_threads < 20)
 236                max_threads = 20;
 237
 238        init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 239        init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 240        init_task.signal->rlim[RLIMIT_SIGPENDING] =
 241                init_task.signal->rlim[RLIMIT_NPROC];
 242}
 243
 244int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 245                                               struct task_struct *src)
 246{
 247        *dst = *src;
 248        return 0;
 249}
 250
 251static struct task_struct *dup_task_struct(struct task_struct *orig)
 252{
 253        struct task_struct *tsk;
 254        struct thread_info *ti;
 255        unsigned long *stackend;
 256        int node = tsk_fork_get_node(orig);
 257        int err;
 258
 259        prepare_to_copy(orig);
 260
 261        tsk = alloc_task_struct_node(node);
 262        if (!tsk)
 263                return NULL;
 264
 265        ti = alloc_thread_info_node(tsk, node);
 266        if (!ti) {
 267                free_task_struct(tsk);
 268                return NULL;
 269        }
 270
 271        err = arch_dup_task_struct(tsk, orig);
 272        if (err)
 273                goto out;
 274
 275        tsk->stack = ti;
 276
 277        setup_thread_stack(tsk, orig);
 278        clear_user_return_notifier(tsk);
 279        clear_tsk_need_resched(tsk);
 280        stackend = end_of_stack(tsk);
 281        *stackend = STACK_END_MAGIC;    /* for overflow detection */
 282
 283#ifdef CONFIG_CC_STACKPROTECTOR
 284        tsk->stack_canary = get_random_int();
 285#endif
 286
 287        /*
 288         * One for us, one for whoever does the "release_task()" (usually
 289         * parent)
 290         */
 291        atomic_set(&tsk->usage, 2);
 292#ifdef CONFIG_BLK_DEV_IO_TRACE
 293        tsk->btrace_seq = 0;
 294#endif
 295        tsk->splice_pipe = NULL;
 296
 297        account_kernel_stack(ti, 1);
 298
 299        return tsk;
 300
 301out:
 302        free_thread_info(ti);
 303        free_task_struct(tsk);
 304        return NULL;
 305}
 306
 307#ifdef CONFIG_MMU
 308static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 309{
 310        struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 311        struct rb_node **rb_link, *rb_parent;
 312        int retval;
 313        unsigned long charge;
 314        struct mempolicy *pol;
 315
 316        down_write(&oldmm->mmap_sem);
 317        flush_cache_dup_mm(oldmm);
 318        /*
 319         * Not linked in yet - no deadlock potential:
 320         */
 321        down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 322
 323        mm->locked_vm = 0;
 324        mm->mmap = NULL;
 325        mm->mmap_cache = NULL;
 326        mm->free_area_cache = oldmm->mmap_base;
 327        mm->cached_hole_size = ~0UL;
 328        mm->map_count = 0;
 329        cpumask_clear(mm_cpumask(mm));
 330        mm->mm_rb = RB_ROOT;
 331        rb_link = &mm->mm_rb.rb_node;
 332        rb_parent = NULL;
 333        pprev = &mm->mmap;
 334        retval = ksm_fork(mm, oldmm);
 335        if (retval)
 336                goto out;
 337        retval = khugepaged_fork(mm, oldmm);
 338        if (retval)
 339                goto out;
 340
 341        prev = NULL;
 342        for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 343                struct file *file;
 344
 345                if (mpnt->vm_flags & VM_DONTCOPY) {
 346                        long pages = vma_pages(mpnt);
 347                        mm->total_vm -= pages;
 348                        vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 349                                                                -pages);
 350                        continue;
 351                }
 352                charge = 0;
 353                if (mpnt->vm_flags & VM_ACCOUNT) {
 354                        unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 355                        if (security_vm_enough_memory(len))
 356                                goto fail_nomem;
 357                        charge = len;
 358                }
 359                tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 360                if (!tmp)
 361                        goto fail_nomem;
 362                *tmp = *mpnt;
 363                INIT_LIST_HEAD(&tmp->anon_vma_chain);
 364                pol = mpol_dup(vma_policy(mpnt));
 365                retval = PTR_ERR(pol);
 366                if (IS_ERR(pol))
 367                        goto fail_nomem_policy;
 368                vma_set_policy(tmp, pol);
 369                tmp->vm_mm = mm;
 370                if (anon_vma_fork(tmp, mpnt))
 371                        goto fail_nomem_anon_vma_fork;
 372                tmp->vm_flags &= ~VM_LOCKED;
 373                tmp->vm_next = tmp->vm_prev = NULL;
 374                file = tmp->vm_file;
 375                if (file) {
 376                        struct inode *inode = file->f_path.dentry->d_inode;
 377                        struct address_space *mapping = file->f_mapping;
 378
 379                        get_file(file);
 380                        if (tmp->vm_flags & VM_DENYWRITE)
 381                                atomic_dec(&inode->i_writecount);
 382                        mutex_lock(&mapping->i_mmap_mutex);
 383                        if (tmp->vm_flags & VM_SHARED)
 384                                mapping->i_mmap_writable++;
 385                        flush_dcache_mmap_lock(mapping);
 386                        /* insert tmp into the share list, just after mpnt */
 387                        vma_prio_tree_add(tmp, mpnt);
 388                        flush_dcache_mmap_unlock(mapping);
 389                        mutex_unlock(&mapping->i_mmap_mutex);
 390                }
 391
 392                /*
 393                 * Clear hugetlb-related page reserves for children. This only
 394                 * affects MAP_PRIVATE mappings. Faults generated by the child
 395                 * are not guaranteed to succeed, even if read-only
 396                 */
 397                if (is_vm_hugetlb_page(tmp))
 398                        reset_vma_resv_huge_pages(tmp);
 399
 400                /*
 401                 * Link in the new vma and copy the page table entries.
 402                 */
 403                *pprev = tmp;
 404                pprev = &tmp->vm_next;
 405                tmp->vm_prev = prev;
 406                prev = tmp;
 407
 408                __vma_link_rb(mm, tmp, rb_link, rb_parent);
 409                rb_link = &tmp->vm_rb.rb_right;
 410                rb_parent = &tmp->vm_rb;
 411
 412                mm->map_count++;
 413                retval = copy_page_range(mm, oldmm, mpnt);
 414
 415                if (tmp->vm_ops && tmp->vm_ops->open)
 416                        tmp->vm_ops->open(tmp);
 417
 418                if (retval)
 419                        goto out;
 420        }
 421        /* a new mm has just been created */
 422        arch_dup_mmap(oldmm, mm);
 423        retval = 0;
 424out:
 425        up_write(&mm->mmap_sem);
 426        flush_tlb_mm(oldmm);
 427        up_write(&oldmm->mmap_sem);
 428        return retval;
 429fail_nomem_anon_vma_fork:
 430        mpol_put(pol);
 431fail_nomem_policy:
 432        kmem_cache_free(vm_area_cachep, tmp);
 433fail_nomem:
 434        retval = -ENOMEM;
 435        vm_unacct_memory(charge);
 436        goto out;
 437}
 438
 439static inline int mm_alloc_pgd(struct mm_struct *mm)
 440{
 441        mm->pgd = pgd_alloc(mm);
 442        if (unlikely(!mm->pgd))
 443                return -ENOMEM;
 444        return 0;
 445}
 446
 447static inline void mm_free_pgd(struct mm_struct *mm)
 448{
 449        pgd_free(mm, mm->pgd);
 450}
 451#else
 452#define dup_mmap(mm, oldmm)     (0)
 453#define mm_alloc_pgd(mm)        (0)
 454#define mm_free_pgd(mm)
 455#endif /* CONFIG_MMU */
 456
 457__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 458
 459#define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 460#define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 461
 462static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 463
 464static int __init coredump_filter_setup(char *s)
 465{
 466        default_dump_filter =
 467                (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 468                MMF_DUMP_FILTER_MASK;
 469        return 1;
 470}
 471
 472__setup("coredump_filter=", coredump_filter_setup);
 473
 474#include <linux/init_task.h>
 475
 476static void mm_init_aio(struct mm_struct *mm)
 477{
 478#ifdef CONFIG_AIO
 479        spin_lock_init(&mm->ioctx_lock);
 480        INIT_HLIST_HEAD(&mm->ioctx_list);
 481#endif
 482}
 483
 484static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
 485{
 486        atomic_set(&mm->mm_users, 1);
 487        atomic_set(&mm->mm_count, 1);
 488        init_rwsem(&mm->mmap_sem);
 489        INIT_LIST_HEAD(&mm->mmlist);
 490        mm->flags = (current->mm) ?
 491                (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
 492        mm->core_state = NULL;
 493        mm->nr_ptes = 0;
 494        memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 495        spin_lock_init(&mm->page_table_lock);
 496        mm->free_area_cache = TASK_UNMAPPED_BASE;
 497        mm->cached_hole_size = ~0UL;
 498        mm_init_aio(mm);
 499        mm_init_owner(mm, p);
 500
 501        if (likely(!mm_alloc_pgd(mm))) {
 502                mm->def_flags = 0;
 503                mmu_notifier_mm_init(mm);
 504                return mm;
 505        }
 506
 507        free_mm(mm);
 508        return NULL;
 509}
 510
 511/*
 512 * Allocate and initialize an mm_struct.
 513 */
 514struct mm_struct *mm_alloc(void)
 515{
 516        struct mm_struct *mm;
 517
 518        mm = allocate_mm();
 519        if (!mm)
 520                return NULL;
 521
 522        memset(mm, 0, sizeof(*mm));
 523        mm_init_cpumask(mm);
 524        return mm_init(mm, current);
 525}
 526
 527/*
 528 * Called when the last reference to the mm
 529 * is dropped: either by a lazy thread or by
 530 * mmput. Free the page directory and the mm.
 531 */
 532void __mmdrop(struct mm_struct *mm)
 533{
 534        BUG_ON(mm == &init_mm);
 535        mm_free_pgd(mm);
 536        destroy_context(mm);
 537        mmu_notifier_mm_destroy(mm);
 538#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 539        VM_BUG_ON(mm->pmd_huge_pte);
 540#endif
 541        free_mm(mm);
 542}
 543EXPORT_SYMBOL_GPL(__mmdrop);
 544
 545/*
 546 * Decrement the use count and release all resources for an mm.
 547 */
 548void mmput(struct mm_struct *mm)
 549{
 550        might_sleep();
 551
 552        if (atomic_dec_and_test(&mm->mm_users)) {
 553                exit_aio(mm);
 554                ksm_exit(mm);
 555                khugepaged_exit(mm); /* must run before exit_mmap */
 556                exit_mmap(mm);
 557                set_mm_exe_file(mm, NULL);
 558                if (!list_empty(&mm->mmlist)) {
 559                        spin_lock(&mmlist_lock);
 560                        list_del(&mm->mmlist);
 561                        spin_unlock(&mmlist_lock);
 562                }
 563                put_swap_token(mm);
 564                if (mm->binfmt)
 565                        module_put(mm->binfmt->module);
 566                mmdrop(mm);
 567        }
 568}
 569EXPORT_SYMBOL_GPL(mmput);
 570
 571/*
 572 * We added or removed a vma mapping the executable. The vmas are only mapped
 573 * during exec and are not mapped with the mmap system call.
 574 * Callers must hold down_write() on the mm's mmap_sem for these
 575 */
 576void added_exe_file_vma(struct mm_struct *mm)
 577{
 578        mm->num_exe_file_vmas++;
 579}
 580
 581void removed_exe_file_vma(struct mm_struct *mm)
 582{
 583        mm->num_exe_file_vmas--;
 584        if ((mm->num_exe_file_vmas == 0) && mm->exe_file) {
 585                fput(mm->exe_file);
 586                mm->exe_file = NULL;
 587        }
 588
 589}
 590
 591void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 592{
 593        if (new_exe_file)
 594                get_file(new_exe_file);
 595        if (mm->exe_file)
 596                fput(mm->exe_file);
 597        mm->exe_file = new_exe_file;
 598        mm->num_exe_file_vmas = 0;
 599}
 600
 601struct file *get_mm_exe_file(struct mm_struct *mm)
 602{
 603        struct file *exe_file;
 604
 605        /* We need mmap_sem to protect against races with removal of
 606         * VM_EXECUTABLE vmas */
 607        down_read(&mm->mmap_sem);
 608        exe_file = mm->exe_file;
 609        if (exe_file)
 610                get_file(exe_file);
 611        up_read(&mm->mmap_sem);
 612        return exe_file;
 613}
 614
 615static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
 616{
 617        /* It's safe to write the exe_file pointer without exe_file_lock because
 618         * this is called during fork when the task is not yet in /proc */
 619        newmm->exe_file = get_mm_exe_file(oldmm);
 620}
 621
 622/**
 623 * get_task_mm - acquire a reference to the task's mm
 624 *
 625 * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 626 * this kernel workthread has transiently adopted a user mm with use_mm,
 627 * to do its AIO) is not set and if so returns a reference to it, after
 628 * bumping up the use count.  User must release the mm via mmput()
 629 * after use.  Typically used by /proc and ptrace.
 630 */
 631struct mm_struct *get_task_mm(struct task_struct *task)
 632{
 633        struct mm_struct *mm;
 634
 635        task_lock(task);
 636        mm = task->mm;
 637        if (mm) {
 638                if (task->flags & PF_KTHREAD)
 639                        mm = NULL;
 640                else
 641                        atomic_inc(&mm->mm_users);
 642        }
 643        task_unlock(task);
 644        return mm;
 645}
 646EXPORT_SYMBOL_GPL(get_task_mm);
 647
 648/* Please note the differences between mmput and mm_release.
 649 * mmput is called whenever we stop holding onto a mm_struct,
 650 * error success whatever.
 651 *
 652 * mm_release is called after a mm_struct has been removed
 653 * from the current process.
 654 *
 655 * This difference is important for error handling, when we
 656 * only half set up a mm_struct for a new process and need to restore
 657 * the old one.  Because we mmput the new mm_struct before
 658 * restoring the old one. . .
 659 * Eric Biederman 10 January 1998
 660 */
 661void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 662{
 663        struct completion *vfork_done = tsk->vfork_done;
 664
 665        /* Get rid of any futexes when releasing the mm */
 666#ifdef CONFIG_FUTEX
 667        if (unlikely(tsk->robust_list)) {
 668                exit_robust_list(tsk);
 669                tsk->robust_list = NULL;
 670        }
 671#ifdef CONFIG_COMPAT
 672        if (unlikely(tsk->compat_robust_list)) {
 673                compat_exit_robust_list(tsk);
 674                tsk->compat_robust_list = NULL;
 675        }
 676#endif
 677        if (unlikely(!list_empty(&tsk->pi_state_list)))
 678                exit_pi_state_list(tsk);
 679#endif
 680
 681        /* Get rid of any cached register state */
 682        deactivate_mm(tsk, mm);
 683
 684        /* notify parent sleeping on vfork() */
 685        if (vfork_done) {
 686                tsk->vfork_done = NULL;
 687                complete(vfork_done);
 688        }
 689
 690        /*
 691         * If we're exiting normally, clear a user-space tid field if
 692         * requested.  We leave this alone when dying by signal, to leave
 693         * the value intact in a core dump, and to save the unnecessary
 694         * trouble otherwise.  Userland only wants this done for a sys_exit.
 695         */
 696        if (tsk->clear_child_tid) {
 697                if (!(tsk->flags & PF_SIGNALED) &&
 698                    atomic_read(&mm->mm_users) > 1) {
 699                        /*
 700                         * We don't check the error code - if userspace has
 701                         * not set up a proper pointer then tough luck.
 702                         */
 703                        put_user(0, tsk->clear_child_tid);
 704                        sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
 705                                        1, NULL, NULL, 0);
 706                }
 707                tsk->clear_child_tid = NULL;
 708        }
 709}
 710
 711/*
 712 * Allocate a new mm structure and copy contents from the
 713 * mm structure of the passed in task structure.
 714 */
 715struct mm_struct *dup_mm(struct task_struct *tsk)
 716{
 717        struct mm_struct *mm, *oldmm = current->mm;
 718        int err;
 719
 720        if (!oldmm)
 721                return NULL;
 722
 723        mm = allocate_mm();
 724        if (!mm)
 725                goto fail_nomem;
 726
 727        memcpy(mm, oldmm, sizeof(*mm));
 728        mm_init_cpumask(mm);
 729
 730        /* Initializing for Swap token stuff */
 731        mm->token_priority = 0;
 732        mm->last_interval = 0;
 733
 734#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 735        mm->pmd_huge_pte = NULL;
 736#endif
 737
 738        if (!mm_init(mm, tsk))
 739                goto fail_nomem;
 740
 741        if (init_new_context(tsk, mm))
 742                goto fail_nocontext;
 743
 744        dup_mm_exe_file(oldmm, mm);
 745
 746        err = dup_mmap(mm, oldmm);
 747        if (err)
 748                goto free_pt;
 749
 750        mm->hiwater_rss = get_mm_rss(mm);
 751        mm->hiwater_vm = mm->total_vm;
 752
 753        if (mm->binfmt && !try_module_get(mm->binfmt->module))
 754                goto free_pt;
 755
 756        return mm;
 757
 758free_pt:
 759        /* don't put binfmt in mmput, we haven't got module yet */
 760        mm->binfmt = NULL;
 761        mmput(mm);
 762
 763fail_nomem:
 764        return NULL;
 765
 766fail_nocontext:
 767        /*
 768         * If init_new_context() failed, we cannot use mmput() to free the mm
 769         * because it calls destroy_context()
 770         */
 771        mm_free_pgd(mm);
 772        free_mm(mm);
 773        return NULL;
 774}
 775
 776static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
 777{
 778        struct mm_struct *mm, *oldmm;
 779        int retval;
 780
 781        tsk->min_flt = tsk->maj_flt = 0;
 782        tsk->nvcsw = tsk->nivcsw = 0;
 783#ifdef CONFIG_DETECT_HUNG_TASK
 784        tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 785#endif
 786
 787        tsk->mm = NULL;
 788        tsk->active_mm = NULL;
 789
 790        /*
 791         * Are we cloning a kernel thread?
 792         *
 793         * We need to steal a active VM for that..
 794         */
 795        oldmm = current->mm;
 796        if (!oldmm)
 797                return 0;
 798
 799        if (clone_flags & CLONE_VM) {
 800                atomic_inc(&oldmm->mm_users);
 801                mm = oldmm;
 802                goto good_mm;
 803        }
 804
 805        retval = -ENOMEM;
 806        mm = dup_mm(tsk);
 807        if (!mm)
 808                goto fail_nomem;
 809
 810good_mm:
 811        /* Initializing for Swap token stuff */
 812        mm->token_priority = 0;
 813        mm->last_interval = 0;
 814
 815        tsk->mm = mm;
 816        tsk->active_mm = mm;
 817        return 0;
 818
 819fail_nomem:
 820        return retval;
 821}
 822
 823static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 824{
 825        struct fs_struct *fs = current->fs;
 826        if (clone_flags & CLONE_FS) {
 827                /* tsk->fs is already what we want */
 828                spin_lock(&fs->lock);
 829                if (fs->in_exec) {
 830                        spin_unlock(&fs->lock);
 831                        return -EAGAIN;
 832                }
 833                fs->users++;
 834                spin_unlock(&fs->lock);
 835                return 0;
 836        }
 837        tsk->fs = copy_fs_struct(fs);
 838        if (!tsk->fs)
 839                return -ENOMEM;
 840        return 0;
 841}
 842
 843static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
 844{
 845        struct files_struct *oldf, *newf;
 846        int error = 0;
 847
 848        /*
 849         * A background process may not have any files ...
 850         */
 851        oldf = current->files;
 852        if (!oldf)
 853                goto out;
 854
 855        if (clone_flags & CLONE_FILES) {
 856                atomic_inc(&oldf->count);
 857                goto out;
 858        }
 859
 860        newf = dup_fd(oldf, &error);
 861        if (!newf)
 862                goto out;
 863
 864        tsk->files = newf;
 865        error = 0;
 866out:
 867        return error;
 868}
 869
 870static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 871{
 872#ifdef CONFIG_BLOCK
 873        struct io_context *ioc = current->io_context;
 874
 875        if (!ioc)
 876                return 0;
 877        /*
 878         * Share io context with parent, if CLONE_IO is set
 879         */
 880        if (clone_flags & CLONE_IO) {
 881                tsk->io_context = ioc_task_link(ioc);
 882                if (unlikely(!tsk->io_context))
 883                        return -ENOMEM;
 884        } else if (ioprio_valid(ioc->ioprio)) {
 885                tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
 886                if (unlikely(!tsk->io_context))
 887                        return -ENOMEM;
 888
 889                tsk->io_context->ioprio = ioc->ioprio;
 890        }
 891#endif
 892        return 0;
 893}
 894
 895static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 896{
 897        struct sighand_struct *sig;
 898
 899        if (clone_flags & CLONE_SIGHAND) {
 900                atomic_inc(&current->sighand->count);
 901                return 0;
 902        }
 903        sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 904        rcu_assign_pointer(tsk->sighand, sig);
 905        if (!sig)
 906                return -ENOMEM;
 907        atomic_set(&sig->count, 1);
 908        memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 909        return 0;
 910}
 911
 912void __cleanup_sighand(struct sighand_struct *sighand)
 913{
 914        if (atomic_dec_and_test(&sighand->count)) {
 915                signalfd_cleanup(sighand);
 916                kmem_cache_free(sighand_cachep, sighand);
 917        }
 918}
 919
 920
 921/*
 922 * Initialize POSIX timer handling for a thread group.
 923 */
 924static void posix_cpu_timers_init_group(struct signal_struct *sig)
 925{
 926        unsigned long cpu_limit;
 927
 928        /* Thread group counters. */
 929        thread_group_cputime_init(sig);
 930
 931        cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
 932        if (cpu_limit != RLIM_INFINITY) {
 933                sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
 934                sig->cputimer.running = 1;
 935        }
 936
 937        /* The timer lists. */
 938        INIT_LIST_HEAD(&sig->cpu_timers[0]);
 939        INIT_LIST_HEAD(&sig->cpu_timers[1]);
 940        INIT_LIST_HEAD(&sig->cpu_timers[2]);
 941}
 942
 943static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 944{
 945        struct signal_struct *sig;
 946
 947        if (clone_flags & CLONE_THREAD)
 948                return 0;
 949
 950        sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
 951        tsk->signal = sig;
 952        if (!sig)
 953                return -ENOMEM;
 954
 955        sig->nr_threads = 1;
 956        atomic_set(&sig->live, 1);
 957        atomic_set(&sig->sigcnt, 1);
 958        init_waitqueue_head(&sig->wait_chldexit);
 959        if (clone_flags & CLONE_NEWPID)
 960                sig->flags |= SIGNAL_UNKILLABLE;
 961        sig->curr_target = tsk;
 962        init_sigpending(&sig->shared_pending);
 963        INIT_LIST_HEAD(&sig->posix_timers);
 964
 965        hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 966        sig->real_timer.function = it_real_fn;
 967
 968        task_lock(current->group_leader);
 969        memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 970        task_unlock(current->group_leader);
 971
 972        posix_cpu_timers_init_group(sig);
 973
 974        tty_audit_fork(sig);
 975        sched_autogroup_fork(sig);
 976
 977#ifdef CONFIG_CGROUPS
 978        init_rwsem(&sig->threadgroup_fork_lock);
 979#endif
 980
 981        sig->oom_adj = current->signal->oom_adj;
 982        sig->oom_score_adj = current->signal->oom_score_adj;
 983        sig->oom_score_adj_min = current->signal->oom_score_adj_min;
 984
 985        mutex_init(&sig->cred_guard_mutex);
 986
 987        return 0;
 988}
 989
 990static void copy_flags(unsigned long clone_flags, struct task_struct *p)
 991{
 992        unsigned long new_flags = p->flags;
 993
 994        new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
 995        new_flags |= PF_FORKNOEXEC;
 996        new_flags |= PF_STARTING;
 997        p->flags = new_flags;
 998        clear_freeze_flag(p);
 999}
1000
1001SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1002{
1003        current->clear_child_tid = tidptr;
1004
1005        return task_pid_vnr(current);
1006}
1007
1008static void rt_mutex_init_task(struct task_struct *p)
1009{
1010        raw_spin_lock_init(&p->pi_lock);
1011#ifdef CONFIG_RT_MUTEXES
1012        plist_head_init(&p->pi_waiters);
1013        p->pi_blocked_on = NULL;
1014#endif
1015}
1016
1017#ifdef CONFIG_MM_OWNER
1018void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1019{
1020        mm->owner = p;
1021}
1022#endif /* CONFIG_MM_OWNER */
1023
1024/*
1025 * Initialize POSIX timer handling for a single task.
1026 */
1027static void posix_cpu_timers_init(struct task_struct *tsk)
1028{
1029        tsk->cputime_expires.prof_exp = cputime_zero;
1030        tsk->cputime_expires.virt_exp = cputime_zero;
1031        tsk->cputime_expires.sched_exp = 0;
1032        INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1033        INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1034        INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1035}
1036
1037/*
1038 * This creates a new process as a copy of the old one,
1039 * but does not actually start it yet.
1040 *
1041 * It copies the registers, and all the appropriate
1042 * parts of the process environment (as per the clone
1043 * flags). The actual kick-off is left to the caller.
1044 */
1045static struct task_struct *copy_process(unsigned long clone_flags,
1046                                        unsigned long stack_start,
1047                                        struct pt_regs *regs,
1048                                        unsigned long stack_size,
1049                                        int __user *child_tidptr,
1050                                        struct pid *pid,
1051                                        int trace)
1052{
1053        int retval;
1054        struct task_struct *p;
1055        int cgroup_callbacks_done = 0;
1056
1057        if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1058                return ERR_PTR(-EINVAL);
1059
1060        /*
1061         * Thread groups must share signals as well, and detached threads
1062         * can only be started up within the thread group.
1063         */
1064        if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1065                return ERR_PTR(-EINVAL);
1066
1067        /*
1068         * Shared signal handlers imply shared VM. By way of the above,
1069         * thread groups also imply shared VM. Blocking this case allows
1070         * for various simplifications in other code.
1071         */
1072        if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1073                return ERR_PTR(-EINVAL);
1074
1075        /*
1076         * Siblings of global init remain as zombies on exit since they are
1077         * not reaped by their parent (swapper). To solve this and to avoid
1078         * multi-rooted process trees, prevent global and container-inits
1079         * from creating siblings.
1080         */
1081        if ((clone_flags & CLONE_PARENT) &&
1082                                current->signal->flags & SIGNAL_UNKILLABLE)
1083                return ERR_PTR(-EINVAL);
1084
1085        retval = security_task_create(clone_flags);
1086        if (retval)
1087                goto fork_out;
1088
1089        retval = -ENOMEM;
1090        p = dup_task_struct(current);
1091        if (!p)
1092                goto fork_out;
1093
1094        ftrace_graph_init_task(p);
1095
1096        rt_mutex_init_task(p);
1097
1098#ifdef CONFIG_PROVE_LOCKING
1099        DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1100        DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1101#endif
1102        retval = -EAGAIN;
1103        if (atomic_read(&p->real_cred->user->processes) >=
1104                        task_rlimit(p, RLIMIT_NPROC)) {
1105                if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1106                    p->real_cred->user != INIT_USER)
1107                        goto bad_fork_free;
1108        }
1109        current->flags &= ~PF_NPROC_EXCEEDED;
1110
1111        retval = copy_creds(p, clone_flags);
1112        if (retval < 0)
1113                goto bad_fork_free;
1114
1115        /*
1116         * If multiple threads are within copy_process(), then this check
1117         * triggers too late. This doesn't hurt, the check is only there
1118         * to stop root fork bombs.
1119         */
1120        retval = -EAGAIN;
1121        if (nr_threads >= max_threads)
1122                goto bad_fork_cleanup_count;
1123
1124        if (!try_module_get(task_thread_info(p)->exec_domain->module))
1125                goto bad_fork_cleanup_count;
1126
1127        p->did_exec = 0;
1128        delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1129        copy_flags(clone_flags, p);
1130        INIT_LIST_HEAD(&p->children);
1131        INIT_LIST_HEAD(&p->sibling);
1132        rcu_copy_process(p);
1133        p->vfork_done = NULL;
1134        spin_lock_init(&p->alloc_lock);
1135
1136        init_sigpending(&p->pending);
1137
1138        p->utime = cputime_zero;
1139        p->stime = cputime_zero;
1140        p->gtime = cputime_zero;
1141        p->utimescaled = cputime_zero;
1142        p->stimescaled = cputime_zero;
1143#ifndef CONFIG_VIRT_CPU_ACCOUNTING
1144        p->prev_utime = cputime_zero;
1145        p->prev_stime = cputime_zero;
1146#endif
1147#if defined(SPLIT_RSS_COUNTING)
1148        memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1149#endif
1150
1151        p->default_timer_slack_ns = current->timer_slack_ns;
1152
1153        task_io_accounting_init(&p->ioac);
1154        acct_clear_integrals(p);
1155
1156        posix_cpu_timers_init(p);
1157
1158        do_posix_clock_monotonic_gettime(&p->start_time);
1159        p->real_start_time = p->start_time;
1160        monotonic_to_bootbased(&p->real_start_time);
1161        p->io_context = NULL;
1162        p->audit_context = NULL;
1163        if (clone_flags & CLONE_THREAD)
1164                threadgroup_fork_read_lock(current);
1165        cgroup_fork(p);
1166#ifdef CONFIG_NUMA
1167        p->mempolicy = mpol_dup(p->mempolicy);
1168        if (IS_ERR(p->mempolicy)) {
1169                retval = PTR_ERR(p->mempolicy);
1170                p->mempolicy = NULL;
1171                goto bad_fork_cleanup_cgroup;
1172        }
1173        mpol_fix_fork_child_flag(p);
1174#endif
1175#ifdef CONFIG_CPUSETS
1176        p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1177        p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1178#endif
1179#ifdef CONFIG_TRACE_IRQFLAGS
1180        p->irq_events = 0;
1181#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1182        p->hardirqs_enabled = 1;
1183#else
1184        p->hardirqs_enabled = 0;
1185#endif
1186        p->hardirq_enable_ip = 0;
1187        p->hardirq_enable_event = 0;
1188        p->hardirq_disable_ip = _THIS_IP_;
1189        p->hardirq_disable_event = 0;
1190        p->softirqs_enabled = 1;
1191        p->softirq_enable_ip = _THIS_IP_;
1192        p->softirq_enable_event = 0;
1193        p->softirq_disable_ip = 0;
1194        p->softirq_disable_event = 0;
1195        p->hardirq_context = 0;
1196        p->softirq_context = 0;
1197#endif
1198#ifdef CONFIG_LOCKDEP
1199        p->lockdep_depth = 0; /* no locks held yet */
1200        p->curr_chain_key = 0;
1201        p->lockdep_recursion = 0;
1202#endif
1203
1204#ifdef CONFIG_DEBUG_MUTEXES
1205        p->blocked_on = NULL; /* not blocked yet */
1206#endif
1207#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1208        p->memcg_batch.do_batch = 0;
1209        p->memcg_batch.memcg = NULL;
1210#endif
1211
1212        /* Perform scheduler related setup. Assign this task to a CPU. */
1213        sched_fork(p);
1214
1215        retval = perf_event_init_task(p);
1216        if (retval)
1217                goto bad_fork_cleanup_policy;
1218        retval = audit_alloc(p);
1219        if (retval)
1220                goto bad_fork_cleanup_policy;
1221        /* copy all the process information */
1222        retval = copy_semundo(clone_flags, p);
1223        if (retval)
1224                goto bad_fork_cleanup_audit;
1225        retval = copy_files(clone_flags, p);
1226        if (retval)
1227                goto bad_fork_cleanup_semundo;
1228        retval = copy_fs(clone_flags, p);
1229        if (retval)
1230                goto bad_fork_cleanup_files;
1231        retval = copy_sighand(clone_flags, p);
1232        if (retval)
1233                goto bad_fork_cleanup_fs;
1234        retval = copy_signal(clone_flags, p);
1235        if (retval)
1236                goto bad_fork_cleanup_sighand;
1237        retval = copy_mm(clone_flags, p);
1238        if (retval)
1239                goto bad_fork_cleanup_signal;
1240        retval = copy_namespaces(clone_flags, p);
1241        if (retval)
1242                goto bad_fork_cleanup_mm;
1243        retval = copy_io(clone_flags, p);
1244        if (retval)
1245                goto bad_fork_cleanup_namespaces;
1246        retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1247        if (retval)
1248                goto bad_fork_cleanup_io;
1249
1250        if (pid != &init_struct_pid) {
1251                retval = -ENOMEM;
1252                pid = alloc_pid(p->nsproxy->pid_ns);
1253                if (!pid)
1254                        goto bad_fork_cleanup_io;
1255        }
1256
1257        p->pid = pid_nr(pid);
1258        p->tgid = p->pid;
1259        if (clone_flags & CLONE_THREAD)
1260                p->tgid = current->tgid;
1261
1262        p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1263        /*
1264         * Clear TID on mm_release()?
1265         */
1266        p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1267#ifdef CONFIG_BLOCK
1268        p->plug = NULL;
1269#endif
1270#ifdef CONFIG_FUTEX
1271        p->robust_list = NULL;
1272#ifdef CONFIG_COMPAT
1273        p->compat_robust_list = NULL;
1274#endif
1275        INIT_LIST_HEAD(&p->pi_state_list);
1276        p->pi_state_cache = NULL;
1277#endif
1278        /*
1279         * sigaltstack should be cleared when sharing the same VM
1280         */
1281        if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1282                p->sas_ss_sp = p->sas_ss_size = 0;
1283
1284        /*
1285         * Syscall tracing and stepping should be turned off in the
1286         * child regardless of CLONE_PTRACE.
1287         */
1288        user_disable_single_step(p);
1289        clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1290#ifdef TIF_SYSCALL_EMU
1291        clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1292#endif
1293        clear_all_latency_tracing(p);
1294
1295        /* ok, now we should be set up.. */
1296        p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1297        p->pdeath_signal = 0;
1298        p->exit_state = 0;
1299
1300        p->nr_dirtied = 0;
1301        p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1302
1303        /*
1304         * Ok, make it visible to the rest of the system.
1305         * We dont wake it up yet.
1306         */
1307        p->group_leader = p;
1308        INIT_LIST_HEAD(&p->thread_group);
1309
1310        /* Now that the task is set up, run cgroup callbacks if
1311         * necessary. We need to run them before the task is visible
1312         * on the tasklist. */
1313        cgroup_fork_callbacks(p);
1314        cgroup_callbacks_done = 1;
1315
1316        /* Need tasklist lock for parent etc handling! */
1317        write_lock_irq(&tasklist_lock);
1318
1319        /* CLONE_PARENT re-uses the old parent */
1320        if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1321                p->real_parent = current->real_parent;
1322                p->parent_exec_id = current->parent_exec_id;
1323        } else {
1324                p->real_parent = current;
1325                p->parent_exec_id = current->self_exec_id;
1326        }
1327
1328        spin_lock(&current->sighand->siglock);
1329
1330        /*
1331         * Process group and session signals need to be delivered to just the
1332         * parent before the fork or both the parent and the child after the
1333         * fork. Restart if a signal comes in before we add the new process to
1334         * it's process group.
1335         * A fatal signal pending means that current will exit, so the new
1336         * thread can't slip out of an OOM kill (or normal SIGKILL).
1337        */
1338        recalc_sigpending();
1339        if (signal_pending(current)) {
1340                spin_unlock(&current->sighand->siglock);
1341                write_unlock_irq(&tasklist_lock);
1342                retval = -ERESTARTNOINTR;
1343                goto bad_fork_free_pid;
1344        }
1345
1346        if (clone_flags & CLONE_THREAD) {
1347                current->signal->nr_threads++;
1348                atomic_inc(&current->signal->live);
1349                atomic_inc(&current->signal->sigcnt);
1350                p->group_leader = current->group_leader;
1351                list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1352        }
1353
1354        if (likely(p->pid)) {
1355                ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1356
1357                if (thread_group_leader(p)) {
1358                        if (is_child_reaper(pid))
1359                                p->nsproxy->pid_ns->child_reaper = p;
1360
1361                        p->signal->leader_pid = pid;
1362                        p->signal->tty = tty_kref_get(current->signal->tty);
1363                        attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1364                        attach_pid(p, PIDTYPE_SID, task_session(current));
1365                        list_add_tail(&p->sibling, &p->real_parent->children);
1366                        list_add_tail_rcu(&p->tasks, &init_task.tasks);
1367                        __this_cpu_inc(process_counts);
1368                }
1369                attach_pid(p, PIDTYPE_PID, pid);
1370                nr_threads++;
1371        }
1372
1373        total_forks++;
1374        spin_unlock(&current->sighand->siglock);
1375        write_unlock_irq(&tasklist_lock);
1376        proc_fork_connector(p);
1377        cgroup_post_fork(p);
1378        if (clone_flags & CLONE_THREAD)
1379                threadgroup_fork_read_unlock(current);
1380        perf_event_fork(p);
1381        return p;
1382
1383bad_fork_free_pid:
1384        if (pid != &init_struct_pid)
1385                free_pid(pid);
1386bad_fork_cleanup_io:
1387        if (p->io_context)
1388                exit_io_context(p);
1389bad_fork_cleanup_namespaces:
1390        exit_task_namespaces(p);
1391bad_fork_cleanup_mm:
1392        if (p->mm)
1393                mmput(p->mm);
1394bad_fork_cleanup_signal:
1395        if (!(clone_flags & CLONE_THREAD))
1396                free_signal_struct(p->signal);
1397bad_fork_cleanup_sighand:
1398        __cleanup_sighand(p->sighand);
1399bad_fork_cleanup_fs:
1400        exit_fs(p); /* blocking */
1401bad_fork_cleanup_files:
1402        exit_files(p); /* blocking */
1403bad_fork_cleanup_semundo:
1404        exit_sem(p);
1405bad_fork_cleanup_audit:
1406        audit_free(p);
1407bad_fork_cleanup_policy:
1408        perf_event_free_task(p);
1409#ifdef CONFIG_NUMA
1410        mpol_put(p->mempolicy);
1411bad_fork_cleanup_cgroup:
1412#endif
1413        if (clone_flags & CLONE_THREAD)
1414                threadgroup_fork_read_unlock(current);
1415        cgroup_exit(p, cgroup_callbacks_done);
1416        delayacct_tsk_free(p);
1417        module_put(task_thread_info(p)->exec_domain->module);
1418bad_fork_cleanup_count:
1419        atomic_dec(&p->cred->user->processes);
1420        exit_creds(p);
1421bad_fork_free:
1422        free_task(p);
1423fork_out:
1424        return ERR_PTR(retval);
1425}
1426
1427noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1428{
1429        memset(regs, 0, sizeof(struct pt_regs));
1430        return regs;
1431}
1432
1433static inline void init_idle_pids(struct pid_link *links)
1434{
1435        enum pid_type type;
1436
1437        for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1438                INIT_HLIST_NODE(&links[type].node); /* not really needed */
1439                links[type].pid = &init_struct_pid;
1440        }
1441}
1442
1443struct task_struct * __cpuinit fork_idle(int cpu)
1444{
1445        struct task_struct *task;
1446        struct pt_regs regs;
1447
1448        task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1449                            &init_struct_pid, 0);
1450        if (!IS_ERR(task)) {
1451                init_idle_pids(task->pids);
1452                init_idle(task, cpu);
1453        }
1454
1455        return task;
1456}
1457
1458/*
1459 *  Ok, this is the main fork-routine.
1460 *
1461 * It copies the process, and if successful kick-starts
1462 * it and waits for it to finish using the VM if required.
1463 */
1464long do_fork(unsigned long clone_flags,
1465              unsigned long stack_start,
1466              struct pt_regs *regs,
1467              unsigned long stack_size,
1468              int __user *parent_tidptr,
1469              int __user *child_tidptr)
1470{
1471        struct task_struct *p;
1472        int trace = 0;
1473        long nr;
1474
1475        /*
1476         * Do some preliminary argument and permissions checking before we
1477         * actually start allocating stuff
1478         */
1479        if (clone_flags & CLONE_NEWUSER) {
1480                if (clone_flags & CLONE_THREAD)
1481                        return -EINVAL;
1482                /* hopefully this check will go away when userns support is
1483                 * complete
1484                 */
1485                if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1486                                !capable(CAP_SETGID))
1487                        return -EPERM;
1488        }
1489
1490        /*
1491         * Determine whether and which event to report to ptracer.  When
1492         * called from kernel_thread or CLONE_UNTRACED is explicitly
1493         * requested, no event is reported; otherwise, report if the event
1494         * for the type of forking is enabled.
1495         */
1496        if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) {
1497                if (clone_flags & CLONE_VFORK)
1498                        trace = PTRACE_EVENT_VFORK;
1499                else if ((clone_flags & CSIGNAL) != SIGCHLD)
1500                        trace = PTRACE_EVENT_CLONE;
1501                else
1502                        trace = PTRACE_EVENT_FORK;
1503
1504                if (likely(!ptrace_event_enabled(current, trace)))
1505                        trace = 0;
1506        }
1507
1508        p = copy_process(clone_flags, stack_start, regs, stack_size,
1509                         child_tidptr, NULL, trace);
1510        /*
1511         * Do this prior waking up the new thread - the thread pointer
1512         * might get invalid after that point, if the thread exits quickly.
1513         */
1514        if (!IS_ERR(p)) {
1515                struct completion vfork;
1516
1517                trace_sched_process_fork(current, p);
1518
1519                nr = task_pid_vnr(p);
1520
1521                if (clone_flags & CLONE_PARENT_SETTID)
1522                        put_user(nr, parent_tidptr);
1523
1524                if (clone_flags & CLONE_VFORK) {
1525                        p->vfork_done = &vfork;
1526                        init_completion(&vfork);
1527                }
1528
1529                audit_finish_fork(p);
1530
1531                /*
1532                 * We set PF_STARTING at creation in case tracing wants to
1533                 * use this to distinguish a fully live task from one that
1534                 * hasn't finished SIGSTOP raising yet.  Now we clear it
1535                 * and set the child going.
1536                 */
1537                p->flags &= ~PF_STARTING;
1538
1539                wake_up_new_task(p);
1540
1541                /* forking complete and child started to run, tell ptracer */
1542                if (unlikely(trace))
1543                        ptrace_event(trace, nr);
1544
1545                if (clone_flags & CLONE_VFORK) {
1546                        freezer_do_not_count();
1547                        wait_for_completion(&vfork);
1548                        freezer_count();
1549                        ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
1550                }
1551        } else {
1552                nr = PTR_ERR(p);
1553        }
1554        return nr;
1555}
1556
1557#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1558#define ARCH_MIN_MMSTRUCT_ALIGN 0
1559#endif
1560
1561static void sighand_ctor(void *data)
1562{
1563        struct sighand_struct *sighand = data;
1564
1565        spin_lock_init(&sighand->siglock);
1566        init_waitqueue_head(&sighand->signalfd_wqh);
1567}
1568
1569void __init proc_caches_init(void)
1570{
1571        sighand_cachep = kmem_cache_create("sighand_cache",
1572                        sizeof(struct sighand_struct), 0,
1573                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1574                        SLAB_NOTRACK, sighand_ctor);
1575        signal_cachep = kmem_cache_create("signal_cache",
1576                        sizeof(struct signal_struct), 0,
1577                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1578        files_cachep = kmem_cache_create("files_cache",
1579                        sizeof(struct files_struct), 0,
1580                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1581        fs_cachep = kmem_cache_create("fs_cache",
1582                        sizeof(struct fs_struct), 0,
1583                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1584        /*
1585         * FIXME! The "sizeof(struct mm_struct)" currently includes the
1586         * whole struct cpumask for the OFFSTACK case. We could change
1587         * this to *only* allocate as much of it as required by the
1588         * maximum number of CPU's we can ever have.  The cpumask_allocation
1589         * is at the end of the structure, exactly for that reason.
1590         */
1591        mm_cachep = kmem_cache_create("mm_struct",
1592                        sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1593                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1594        vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1595        mmap_init();
1596        nsproxy_cache_init();
1597}
1598
1599/*
1600 * Check constraints on flags passed to the unshare system call.
1601 */
1602static int check_unshare_flags(unsigned long unshare_flags)
1603{
1604        if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1605                                CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1606                                CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1607                return -EINVAL;
1608        /*
1609         * Not implemented, but pretend it works if there is nothing to
1610         * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1611         * needs to unshare vm.
1612         */
1613        if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1614                /* FIXME: get_task_mm() increments ->mm_users */
1615                if (atomic_read(&current->mm->mm_users) > 1)
1616                        return -EINVAL;
1617        }
1618
1619        return 0;
1620}
1621
1622/*
1623 * Unshare the filesystem structure if it is being shared
1624 */
1625static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1626{
1627        struct fs_struct *fs = current->fs;
1628
1629        if (!(unshare_flags & CLONE_FS) || !fs)
1630                return 0;
1631
1632        /* don't need lock here; in the worst case we'll do useless copy */
1633        if (fs->users == 1)
1634                return 0;
1635
1636        *new_fsp = copy_fs_struct(fs);
1637        if (!*new_fsp)
1638                return -ENOMEM;
1639
1640        return 0;
1641}
1642
1643/*
1644 * Unshare file descriptor table if it is being shared
1645 */
1646static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1647{
1648        struct files_struct *fd = current->files;
1649        int error = 0;
1650
1651        if ((unshare_flags & CLONE_FILES) &&
1652            (fd && atomic_read(&fd->count) > 1)) {
1653                *new_fdp = dup_fd(fd, &error);
1654                if (!*new_fdp)
1655                        return error;
1656        }
1657
1658        return 0;
1659}
1660
1661/*
1662 * unshare allows a process to 'unshare' part of the process
1663 * context which was originally shared using clone.  copy_*
1664 * functions used by do_fork() cannot be used here directly
1665 * because they modify an inactive task_struct that is being
1666 * constructed. Here we are modifying the current, active,
1667 * task_struct.
1668 */
1669SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1670{
1671        struct fs_struct *fs, *new_fs = NULL;
1672        struct files_struct *fd, *new_fd = NULL;
1673        struct nsproxy *new_nsproxy = NULL;
1674        int do_sysvsem = 0;
1675        int err;
1676
1677        err = check_unshare_flags(unshare_flags);
1678        if (err)
1679                goto bad_unshare_out;
1680
1681        /*
1682         * If unsharing namespace, must also unshare filesystem information.
1683         */
1684        if (unshare_flags & CLONE_NEWNS)
1685                unshare_flags |= CLONE_FS;
1686        /*
1687         * CLONE_NEWIPC must also detach from the undolist: after switching
1688         * to a new ipc namespace, the semaphore arrays from the old
1689         * namespace are unreachable.
1690         */
1691        if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1692                do_sysvsem = 1;
1693        err = unshare_fs(unshare_flags, &new_fs);
1694        if (err)
1695                goto bad_unshare_out;
1696        err = unshare_fd(unshare_flags, &new_fd);
1697        if (err)
1698                goto bad_unshare_cleanup_fs;
1699        err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs);
1700        if (err)
1701                goto bad_unshare_cleanup_fd;
1702
1703        if (new_fs || new_fd || do_sysvsem || new_nsproxy) {
1704                if (do_sysvsem) {
1705                        /*
1706                         * CLONE_SYSVSEM is equivalent to sys_exit().
1707                         */
1708                        exit_sem(current);
1709                }
1710
1711                if (new_nsproxy) {
1712                        switch_task_namespaces(current, new_nsproxy);
1713                        new_nsproxy = NULL;
1714                }
1715
1716                task_lock(current);
1717
1718                if (new_fs) {
1719                        fs = current->fs;
1720                        spin_lock(&fs->lock);
1721                        current->fs = new_fs;
1722                        if (--fs->users)
1723                                new_fs = NULL;
1724                        else
1725                                new_fs = fs;
1726                        spin_unlock(&fs->lock);
1727                }
1728
1729                if (new_fd) {
1730                        fd = current->files;
1731                        current->files = new_fd;
1732                        new_fd = fd;
1733                }
1734
1735                task_unlock(current);
1736        }
1737
1738        if (new_nsproxy)
1739                put_nsproxy(new_nsproxy);
1740
1741bad_unshare_cleanup_fd:
1742        if (new_fd)
1743                put_files_struct(new_fd);
1744
1745bad_unshare_cleanup_fs:
1746        if (new_fs)
1747                free_fs_struct(new_fs);
1748
1749bad_unshare_out:
1750        return err;
1751}
1752
1753/*
1754 *      Helper to unshare the files of the current task.
1755 *      We don't want to expose copy_files internals to
1756 *      the exec layer of the kernel.
1757 */
1758
1759int unshare_files(struct files_struct **displaced)
1760{
1761        struct task_struct *task = current;
1762        struct files_struct *copy = NULL;
1763        int error;
1764
1765        error = unshare_fd(CLONE_FILES, &copy);
1766        if (error || !copy) {
1767                *displaced = NULL;
1768                return error;
1769        }
1770        *displaced = task->files;
1771        task_lock(task);
1772        task->files = copy;
1773        task_unlock(task);
1774        return 0;
1775}
1776
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