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/tracehook.h>
  41#include <linux/futex.h>
  42#include <linux/compat.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/proc_fs.h>
  62#include <linux/blkdev.h>
  63#include <linux/fs_struct.h>
  64#include <linux/magic.h>
  65#include <linux/perf_event.h>
  66#include <linux/posix-timers.h>
  67#include <linux/user-return-notifier.h>
  68#include <linux/oom.h>
  69
  70#include <asm/pgtable.h>
  71#include <asm/pgalloc.h>
  72#include <asm/uaccess.h>
  73#include <asm/mmu_context.h>
  74#include <asm/cacheflush.h>
  75#include <asm/tlbflush.h>
  76
  77#include <trace/events/sched.h>
  78
  79/*
  80 * Protected counters by write_lock_irq(&tasklist_lock)
  81 */
  82unsigned long total_forks;      /* Handle normal Linux uptimes. */
  83int nr_threads;                 /* The idle threads do not count.. */
  84
  85int max_threads;                /* tunable limit on nr_threads */
  86
  87DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  88
  89__cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  90
  91#ifdef CONFIG_PROVE_RCU
  92int lockdep_tasklist_lock_is_held(void)
  93{
  94        return lockdep_is_held(&tasklist_lock);
  95}
  96EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
  97#endif /* #ifdef CONFIG_PROVE_RCU */
  98
  99int nr_processes(void)
 100{
 101        int cpu;
 102        int total = 0;
 103
 104        for_each_possible_cpu(cpu)
 105                total += per_cpu(process_counts, cpu);
 106
 107        return total;
 108}
 109
 110#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 111# define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
 112# define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
 113static struct kmem_cache *task_struct_cachep;
 114#endif
 115
 116#ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
 117static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
 118{
 119#ifdef CONFIG_DEBUG_STACK_USAGE
 120        gfp_t mask = GFP_KERNEL | __GFP_ZERO;
 121#else
 122        gfp_t mask = GFP_KERNEL;
 123#endif
 124        return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
 125}
 126
 127static inline void free_thread_info(struct thread_info *ti)
 128{
 129        free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 130}
 131#endif
 132
 133/* SLAB cache for signal_struct structures (tsk->signal) */
 134static struct kmem_cache *signal_cachep;
 135
 136/* SLAB cache for sighand_struct structures (tsk->sighand) */
 137struct kmem_cache *sighand_cachep;
 138
 139/* SLAB cache for files_struct structures (tsk->files) */
 140struct kmem_cache *files_cachep;
 141
 142/* SLAB cache for fs_struct structures (tsk->fs) */
 143struct kmem_cache *fs_cachep;
 144
 145/* SLAB cache for vm_area_struct structures */
 146struct kmem_cache *vm_area_cachep;
 147
 148/* SLAB cache for mm_struct structures (tsk->mm) */
 149static struct kmem_cache *mm_cachep;
 150
 151static void account_kernel_stack(struct thread_info *ti, int account)
 152{
 153        struct zone *zone = page_zone(virt_to_page(ti));
 154
 155        mod_zone_page_state(zone, NR_KERNEL_STACK, account);
 156}
 157
 158void free_task(struct task_struct *tsk)
 159{
 160        prop_local_destroy_single(&tsk->dirties);
 161        account_kernel_stack(tsk->stack, -1);
 162        free_thread_info(tsk->stack);
 163        rt_mutex_debug_task_free(tsk);
 164        ftrace_graph_exit_task(tsk);
 165        free_task_struct(tsk);
 166}
 167EXPORT_SYMBOL(free_task);
 168
 169static inline void free_signal_struct(struct signal_struct *sig)
 170{
 171        taskstats_tgid_free(sig);
 172        kmem_cache_free(signal_cachep, sig);
 173}
 174
 175static inline void put_signal_struct(struct signal_struct *sig)
 176{
 177        if (atomic_dec_and_test(&sig->sigcnt))
 178                free_signal_struct(sig);
 179}
 180
 181void __put_task_struct(struct task_struct *tsk)
 182{
 183        WARN_ON(!tsk->exit_state);
 184        WARN_ON(atomic_read(&tsk->usage));
 185        WARN_ON(tsk == current);
 186
 187        exit_creds(tsk);
 188        delayacct_tsk_free(tsk);
 189        put_signal_struct(tsk->signal);
 190
 191        if (!profile_handoff_task(tsk))
 192                free_task(tsk);
 193}
 194
 195/*
 196 * macro override instead of weak attribute alias, to workaround
 197 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
 198 */
 199#ifndef arch_task_cache_init
 200#define arch_task_cache_init()
 201#endif
 202
 203void __init fork_init(unsigned long mempages)
 204{
 205#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 206#ifndef ARCH_MIN_TASKALIGN
 207#define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 208#endif
 209        /* create a slab on which task_structs can be allocated */
 210        task_struct_cachep =
 211                kmem_cache_create("task_struct", sizeof(struct task_struct),
 212                        ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
 213#endif
 214
 215        /* do the arch specific task caches init */
 216        arch_task_cache_init();
 217
 218        /*
 219         * The default maximum number of threads is set to a safe
 220         * value: the thread structures can take up at most half
 221         * of memory.
 222         */
 223        max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 224
 225        /*
 226         * we need to allow at least 20 threads to boot a system
 227         */
 228        if(max_threads < 20)
 229                max_threads = 20;
 230
 231        init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 232        init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 233        init_task.signal->rlim[RLIMIT_SIGPENDING] =
 234                init_task.signal->rlim[RLIMIT_NPROC];
 235}
 236
 237int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 238                                               struct task_struct *src)
 239{
 240        *dst = *src;
 241        return 0;
 242}
 243
 244static struct task_struct *dup_task_struct(struct task_struct *orig)
 245{
 246        struct task_struct *tsk;
 247        struct thread_info *ti;
 248        unsigned long *stackend;
 249
 250        int err;
 251
 252        prepare_to_copy(orig);
 253
 254        tsk = alloc_task_struct();
 255        if (!tsk)
 256                return NULL;
 257
 258        ti = alloc_thread_info(tsk);
 259        if (!ti) {
 260                free_task_struct(tsk);
 261                return NULL;
 262        }
 263
 264        err = arch_dup_task_struct(tsk, orig);
 265        if (err)
 266                goto out;
 267
 268        tsk->stack = ti;
 269
 270        err = prop_local_init_single(&tsk->dirties);
 271        if (err)
 272                goto out;
 273
 274        setup_thread_stack(tsk, orig);
 275        clear_user_return_notifier(tsk);
 276        clear_tsk_need_resched(tsk);
 277        stackend = end_of_stack(tsk);
 278        *stackend = STACK_END_MAGIC;    /* for overflow detection */
 279
 280#ifdef CONFIG_CC_STACKPROTECTOR
 281        tsk->stack_canary = get_random_int();
 282#endif
 283
 284        /* One for us, one for whoever does the "release_task()" (usually parent) */
 285        atomic_set(&tsk->usage,2);
 286        atomic_set(&tsk->fs_excl, 0);
 287#ifdef CONFIG_BLK_DEV_IO_TRACE
 288        tsk->btrace_seq = 0;
 289#endif
 290        tsk->splice_pipe = NULL;
 291
 292        account_kernel_stack(ti, 1);
 293
 294        return tsk;
 295
 296out:
 297        free_thread_info(ti);
 298        free_task_struct(tsk);
 299        return NULL;
 300}
 301
 302#ifdef CONFIG_MMU
 303static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 304{
 305        struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 306        struct rb_node **rb_link, *rb_parent;
 307        int retval;
 308        unsigned long charge;
 309        struct mempolicy *pol;
 310
 311        down_write(&oldmm->mmap_sem);
 312        flush_cache_dup_mm(oldmm);
 313        /*
 314         * Not linked in yet - no deadlock potential:
 315         */
 316        down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 317
 318        mm->locked_vm = 0;
 319        mm->mmap = NULL;
 320        mm->mmap_cache = NULL;
 321        mm->free_area_cache = oldmm->mmap_base;
 322        mm->cached_hole_size = ~0UL;
 323        mm->map_count = 0;
 324        cpumask_clear(mm_cpumask(mm));
 325        mm->mm_rb = RB_ROOT;
 326        rb_link = &mm->mm_rb.rb_node;
 327        rb_parent = NULL;
 328        pprev = &mm->mmap;
 329        retval = ksm_fork(mm, oldmm);
 330        if (retval)
 331                goto out;
 332
 333        prev = NULL;
 334        for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 335                struct file *file;
 336
 337                if (mpnt->vm_flags & VM_DONTCOPY) {
 338                        long pages = vma_pages(mpnt);
 339                        mm->total_vm -= pages;
 340                        vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 341                                                                -pages);
 342                        continue;
 343                }
 344                charge = 0;
 345                if (mpnt->vm_flags & VM_ACCOUNT) {
 346                        unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 347                        if (security_vm_enough_memory(len))
 348                                goto fail_nomem;
 349                        charge = len;
 350                }
 351                tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 352                if (!tmp)
 353                        goto fail_nomem;
 354                *tmp = *mpnt;
 355                INIT_LIST_HEAD(&tmp->anon_vma_chain);
 356                pol = mpol_dup(vma_policy(mpnt));
 357                retval = PTR_ERR(pol);
 358                if (IS_ERR(pol))
 359                        goto fail_nomem_policy;
 360                vma_set_policy(tmp, pol);
 361                tmp->vm_mm = mm;
 362                if (anon_vma_fork(tmp, mpnt))
 363                        goto fail_nomem_anon_vma_fork;
 364                tmp->vm_flags &= ~VM_LOCKED;
 365                tmp->vm_next = tmp->vm_prev = NULL;
 366                file = tmp->vm_file;
 367                if (file) {
 368                        struct inode *inode = file->f_path.dentry->d_inode;
 369                        struct address_space *mapping = file->f_mapping;
 370
 371                        get_file(file);
 372                        if (tmp->vm_flags & VM_DENYWRITE)
 373                                atomic_dec(&inode->i_writecount);
 374                        spin_lock(&mapping->i_mmap_lock);
 375                        if (tmp->vm_flags & VM_SHARED)
 376                                mapping->i_mmap_writable++;
 377                        tmp->vm_truncate_count = mpnt->vm_truncate_count;
 378                        flush_dcache_mmap_lock(mapping);
 379                        /* insert tmp into the share list, just after mpnt */
 380                        vma_prio_tree_add(tmp, mpnt);
 381                        flush_dcache_mmap_unlock(mapping);
 382                        spin_unlock(&mapping->i_mmap_lock);
 383                }
 384
 385                /*
 386                 * Clear hugetlb-related page reserves for children. This only
 387                 * affects MAP_PRIVATE mappings. Faults generated by the child
 388                 * are not guaranteed to succeed, even if read-only
 389                 */
 390                if (is_vm_hugetlb_page(tmp))
 391                        reset_vma_resv_huge_pages(tmp);
 392
 393                /*
 394                 * Link in the new vma and copy the page table entries.
 395                 */
 396                *pprev = tmp;
 397                pprev = &tmp->vm_next;
 398                tmp->vm_prev = prev;
 399                prev = tmp;
 400
 401                __vma_link_rb(mm, tmp, rb_link, rb_parent);
 402                rb_link = &tmp->vm_rb.rb_right;
 403                rb_parent = &tmp->vm_rb;
 404
 405                mm->map_count++;
 406                retval = copy_page_range(mm, oldmm, mpnt);
 407
 408                if (tmp->vm_ops && tmp->vm_ops->open)
 409                        tmp->vm_ops->open(tmp);
 410
 411                if (retval)
 412                        goto out;
 413        }
 414        /* a new mm has just been created */
 415        arch_dup_mmap(oldmm, mm);
 416        retval = 0;
 417out:
 418        up_write(&mm->mmap_sem);
 419        flush_tlb_mm(oldmm);
 420        up_write(&oldmm->mmap_sem);
 421        return retval;
 422fail_nomem_anon_vma_fork:
 423        mpol_put(pol);
 424fail_nomem_policy:
 425        kmem_cache_free(vm_area_cachep, tmp);
 426fail_nomem:
 427        retval = -ENOMEM;
 428        vm_unacct_memory(charge);
 429        goto out;
 430}
 431
 432static inline int mm_alloc_pgd(struct mm_struct * mm)
 433{
 434        mm->pgd = pgd_alloc(mm);
 435        if (unlikely(!mm->pgd))
 436                return -ENOMEM;
 437        return 0;
 438}
 439
 440static inline void mm_free_pgd(struct mm_struct * mm)
 441{
 442        pgd_free(mm, mm->pgd);
 443}
 444#else
 445#define dup_mmap(mm, oldmm)     (0)
 446#define mm_alloc_pgd(mm)        (0)
 447#define mm_free_pgd(mm)
 448#endif /* CONFIG_MMU */
 449
 450__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 451
 452#define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 453#define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 454
 455static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 456
 457static int __init coredump_filter_setup(char *s)
 458{
 459        default_dump_filter =
 460                (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 461                MMF_DUMP_FILTER_MASK;
 462        return 1;
 463}
 464
 465__setup("coredump_filter=", coredump_filter_setup);
 466
 467#include <linux/init_task.h>
 468
 469static void mm_init_aio(struct mm_struct *mm)
 470{
 471#ifdef CONFIG_AIO
 472        spin_lock_init(&mm->ioctx_lock);
 473        INIT_HLIST_HEAD(&mm->ioctx_list);
 474#endif
 475}
 476
 477static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
 478{
 479        atomic_set(&mm->mm_users, 1);
 480        atomic_set(&mm->mm_count, 1);
 481        init_rwsem(&mm->mmap_sem);
 482        INIT_LIST_HEAD(&mm->mmlist);
 483        mm->flags = (current->mm) ?
 484                (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
 485        mm->core_state = NULL;
 486        mm->nr_ptes = 0;
 487        memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 488        spin_lock_init(&mm->page_table_lock);
 489        mm->free_area_cache = TASK_UNMAPPED_BASE;
 490        mm->cached_hole_size = ~0UL;
 491        mm_init_aio(mm);
 492        mm_init_owner(mm, p);
 493        atomic_set(&mm->oom_disable_count, 0);
 494
 495        if (likely(!mm_alloc_pgd(mm))) {
 496                mm->def_flags = 0;
 497                mmu_notifier_mm_init(mm);
 498                return mm;
 499        }
 500
 501        free_mm(mm);
 502        return NULL;
 503}
 504
 505/*
 506 * Allocate and initialize an mm_struct.
 507 */
 508struct mm_struct * mm_alloc(void)
 509{
 510        struct mm_struct * mm;
 511
 512        mm = allocate_mm();
 513        if (mm) {
 514                memset(mm, 0, sizeof(*mm));
 515                mm = mm_init(mm, current);
 516        }
 517        return mm;
 518}
 519
 520/*
 521 * Called when the last reference to the mm
 522 * is dropped: either by a lazy thread or by
 523 * mmput. Free the page directory and the mm.
 524 */
 525void __mmdrop(struct mm_struct *mm)
 526{
 527        BUG_ON(mm == &init_mm);
 528        mm_free_pgd(mm);
 529        destroy_context(mm);
 530        mmu_notifier_mm_destroy(mm);
 531        free_mm(mm);
 532}
 533EXPORT_SYMBOL_GPL(__mmdrop);
 534
 535/*
 536 * Decrement the use count and release all resources for an mm.
 537 */
 538void mmput(struct mm_struct *mm)
 539{
 540        might_sleep();
 541
 542        if (atomic_dec_and_test(&mm->mm_users)) {
 543                exit_aio(mm);
 544                ksm_exit(mm);
 545                exit_mmap(mm);
 546                set_mm_exe_file(mm, NULL);
 547                if (!list_empty(&mm->mmlist)) {
 548                        spin_lock(&mmlist_lock);
 549                        list_del(&mm->mmlist);
 550                        spin_unlock(&mmlist_lock);
 551                }
 552                put_swap_token(mm);
 553                if (mm->binfmt)
 554                        module_put(mm->binfmt->module);
 555                mmdrop(mm);
 556        }
 557}
 558EXPORT_SYMBOL_GPL(mmput);
 559
 560/**
 561 * get_task_mm - acquire a reference to the task's mm
 562 *
 563 * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 564 * this kernel workthread has transiently adopted a user mm with use_mm,
 565 * to do its AIO) is not set and if so returns a reference to it, after
 566 * bumping up the use count.  User must release the mm via mmput()
 567 * after use.  Typically used by /proc and ptrace.
 568 */
 569struct mm_struct *get_task_mm(struct task_struct *task)
 570{
 571        struct mm_struct *mm;
 572
 573        task_lock(task);
 574        mm = task->mm;
 575        if (mm) {
 576                if (task->flags & PF_KTHREAD)
 577                        mm = NULL;
 578                else
 579                        atomic_inc(&mm->mm_users);
 580        }
 581        task_unlock(task);
 582        return mm;
 583}
 584EXPORT_SYMBOL_GPL(get_task_mm);
 585
 586/* Please note the differences between mmput and mm_release.
 587 * mmput is called whenever we stop holding onto a mm_struct,
 588 * error success whatever.
 589 *
 590 * mm_release is called after a mm_struct has been removed
 591 * from the current process.
 592 *
 593 * This difference is important for error handling, when we
 594 * only half set up a mm_struct for a new process and need to restore
 595 * the old one.  Because we mmput the new mm_struct before
 596 * restoring the old one. . .
 597 * Eric Biederman 10 January 1998
 598 */
 599void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 600{
 601        struct completion *vfork_done = tsk->vfork_done;
 602
 603        /* Get rid of any futexes when releasing the mm */
 604#ifdef CONFIG_FUTEX
 605        if (unlikely(tsk->robust_list)) {
 606                exit_robust_list(tsk);
 607                tsk->robust_list = NULL;
 608        }
 609#ifdef CONFIG_COMPAT
 610        if (unlikely(tsk->compat_robust_list)) {
 611                compat_exit_robust_list(tsk);
 612                tsk->compat_robust_list = NULL;
 613        }
 614#endif
 615        if (unlikely(!list_empty(&tsk->pi_state_list)))
 616                exit_pi_state_list(tsk);
 617#endif
 618
 619        /* Get rid of any cached register state */
 620        deactivate_mm(tsk, mm);
 621
 622        /* notify parent sleeping on vfork() */
 623        if (vfork_done) {
 624                tsk->vfork_done = NULL;
 625                complete(vfork_done);
 626        }
 627
 628        /*
 629         * If we're exiting normally, clear a user-space tid field if
 630         * requested.  We leave this alone when dying by signal, to leave
 631         * the value intact in a core dump, and to save the unnecessary
 632         * trouble otherwise.  Userland only wants this done for a sys_exit.
 633         */
 634        if (tsk->clear_child_tid) {
 635                if (!(tsk->flags & PF_SIGNALED) &&
 636                    atomic_read(&mm->mm_users) > 1) {
 637                        /*
 638                         * We don't check the error code - if userspace has
 639                         * not set up a proper pointer then tough luck.
 640                         */
 641                        put_user(0, tsk->clear_child_tid);
 642                        sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
 643                                        1, NULL, NULL, 0);
 644                }
 645                tsk->clear_child_tid = NULL;
 646        }
 647}
 648
 649/*
 650 * Allocate a new mm structure and copy contents from the
 651 * mm structure of the passed in task structure.
 652 */
 653struct mm_struct *dup_mm(struct task_struct *tsk)
 654{
 655        struct mm_struct *mm, *oldmm = current->mm;
 656        int err;
 657
 658        if (!oldmm)
 659                return NULL;
 660
 661        mm = allocate_mm();
 662        if (!mm)
 663                goto fail_nomem;
 664
 665        memcpy(mm, oldmm, sizeof(*mm));
 666
 667        /* Initializing for Swap token stuff */
 668        mm->token_priority = 0;
 669        mm->last_interval = 0;
 670
 671        if (!mm_init(mm, tsk))
 672                goto fail_nomem;
 673
 674        if (init_new_context(tsk, mm))
 675                goto fail_nocontext;
 676
 677        dup_mm_exe_file(oldmm, mm);
 678
 679        err = dup_mmap(mm, oldmm);
 680        if (err)
 681                goto free_pt;
 682
 683        mm->hiwater_rss = get_mm_rss(mm);
 684        mm->hiwater_vm = mm->total_vm;
 685
 686        if (mm->binfmt && !try_module_get(mm->binfmt->module))
 687                goto free_pt;
 688
 689        return mm;
 690
 691free_pt:
 692        /* don't put binfmt in mmput, we haven't got module yet */
 693        mm->binfmt = NULL;
 694        mmput(mm);
 695
 696fail_nomem:
 697        return NULL;
 698
 699fail_nocontext:
 700        /*
 701         * If init_new_context() failed, we cannot use mmput() to free the mm
 702         * because it calls destroy_context()
 703         */
 704        mm_free_pgd(mm);
 705        free_mm(mm);
 706        return NULL;
 707}
 708
 709static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 710{
 711        struct mm_struct * mm, *oldmm;
 712        int retval;
 713
 714        tsk->min_flt = tsk->maj_flt = 0;
 715        tsk->nvcsw = tsk->nivcsw = 0;
 716#ifdef CONFIG_DETECT_HUNG_TASK
 717        tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 718#endif
 719
 720        tsk->mm = NULL;
 721        tsk->active_mm = NULL;
 722
 723        /*
 724         * Are we cloning a kernel thread?
 725         *
 726         * We need to steal a active VM for that..
 727         */
 728        oldmm = current->mm;
 729        if (!oldmm)
 730                return 0;
 731
 732        if (clone_flags & CLONE_VM) {
 733                atomic_inc(&oldmm->mm_users);
 734                mm = oldmm;
 735                goto good_mm;
 736        }
 737
 738        retval = -ENOMEM;
 739        mm = dup_mm(tsk);
 740        if (!mm)
 741                goto fail_nomem;
 742
 743good_mm:
 744        /* Initializing for Swap token stuff */
 745        mm->token_priority = 0;
 746        mm->last_interval = 0;
 747        if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
 748                atomic_inc(&mm->oom_disable_count);
 749
 750        tsk->mm = mm;
 751        tsk->active_mm = mm;
 752        return 0;
 753
 754fail_nomem:
 755        return retval;
 756}
 757
 758static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 759{
 760        struct fs_struct *fs = current->fs;
 761        if (clone_flags & CLONE_FS) {
 762                /* tsk->fs is already what we want */
 763                spin_lock(&fs->lock);
 764                if (fs->in_exec) {
 765                        spin_unlock(&fs->lock);
 766                        return -EAGAIN;
 767                }
 768                fs->users++;
 769                spin_unlock(&fs->lock);
 770                return 0;
 771        }
 772        tsk->fs = copy_fs_struct(fs);
 773        if (!tsk->fs)
 774                return -ENOMEM;
 775        return 0;
 776}
 777
 778static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 779{
 780        struct files_struct *oldf, *newf;
 781        int error = 0;
 782
 783        /*
 784         * A background process may not have any files ...
 785         */
 786        oldf = current->files;
 787        if (!oldf)
 788                goto out;
 789
 790        if (clone_flags & CLONE_FILES) {
 791                atomic_inc(&oldf->count);
 792                goto out;
 793        }
 794
 795        newf = dup_fd(oldf, &error);
 796        if (!newf)
 797                goto out;
 798
 799        tsk->files = newf;
 800        error = 0;
 801out:
 802        return error;
 803}
 804
 805static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 806{
 807#ifdef CONFIG_BLOCK
 808        struct io_context *ioc = current->io_context;
 809
 810        if (!ioc)
 811                return 0;
 812        /*
 813         * Share io context with parent, if CLONE_IO is set
 814         */
 815        if (clone_flags & CLONE_IO) {
 816                tsk->io_context = ioc_task_link(ioc);
 817                if (unlikely(!tsk->io_context))
 818                        return -ENOMEM;
 819        } else if (ioprio_valid(ioc->ioprio)) {
 820                tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
 821                if (unlikely(!tsk->io_context))
 822                        return -ENOMEM;
 823
 824                tsk->io_context->ioprio = ioc->ioprio;
 825        }
 826#endif
 827        return 0;
 828}
 829
 830static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 831{
 832        struct sighand_struct *sig;
 833
 834        if (clone_flags & CLONE_SIGHAND) {
 835                atomic_inc(&current->sighand->count);
 836                return 0;
 837        }
 838        sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 839        rcu_assign_pointer(tsk->sighand, sig);
 840        if (!sig)
 841                return -ENOMEM;
 842        atomic_set(&sig->count, 1);
 843        memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 844        return 0;
 845}
 846
 847void __cleanup_sighand(struct sighand_struct *sighand)
 848{
 849        if (atomic_dec_and_test(&sighand->count))
 850                kmem_cache_free(sighand_cachep, sighand);
 851}
 852
 853
 854/*
 855 * Initialize POSIX timer handling for a thread group.
 856 */
 857static void posix_cpu_timers_init_group(struct signal_struct *sig)
 858{
 859        unsigned long cpu_limit;
 860
 861        /* Thread group counters. */
 862        thread_group_cputime_init(sig);
 863
 864        cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
 865        if (cpu_limit != RLIM_INFINITY) {
 866                sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
 867                sig->cputimer.running = 1;
 868        }
 869
 870        /* The timer lists. */
 871        INIT_LIST_HEAD(&sig->cpu_timers[0]);
 872        INIT_LIST_HEAD(&sig->cpu_timers[1]);
 873        INIT_LIST_HEAD(&sig->cpu_timers[2]);
 874}
 875
 876static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 877{
 878        struct signal_struct *sig;
 879
 880        if (clone_flags & CLONE_THREAD)
 881                return 0;
 882
 883        sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
 884        tsk->signal = sig;
 885        if (!sig)
 886                return -ENOMEM;
 887
 888        sig->nr_threads = 1;
 889        atomic_set(&sig->live, 1);
 890        atomic_set(&sig->sigcnt, 1);
 891        init_waitqueue_head(&sig->wait_chldexit);
 892        if (clone_flags & CLONE_NEWPID)
 893                sig->flags |= SIGNAL_UNKILLABLE;
 894        sig->curr_target = tsk;
 895        init_sigpending(&sig->shared_pending);
 896        INIT_LIST_HEAD(&sig->posix_timers);
 897
 898        hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 899        sig->real_timer.function = it_real_fn;
 900
 901        task_lock(current->group_leader);
 902        memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 903        task_unlock(current->group_leader);
 904
 905        posix_cpu_timers_init_group(sig);
 906
 907        tty_audit_fork(sig);
 908
 909        sig->oom_adj = current->signal->oom_adj;
 910        sig->oom_score_adj = current->signal->oom_score_adj;
 911
 912        mutex_init(&sig->cred_guard_mutex);
 913
 914        return 0;
 915}
 916
 917static void copy_flags(unsigned long clone_flags, struct task_struct *p)
 918{
 919        unsigned long new_flags = p->flags;
 920
 921        new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
 922        new_flags |= PF_FORKNOEXEC;
 923        new_flags |= PF_STARTING;
 924        p->flags = new_flags;
 925        clear_freeze_flag(p);
 926}
 927
 928SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
 929{
 930        current->clear_child_tid = tidptr;
 931
 932        return task_pid_vnr(current);
 933}
 934
 935static void rt_mutex_init_task(struct task_struct *p)
 936{
 937        raw_spin_lock_init(&p->pi_lock);
 938#ifdef CONFIG_RT_MUTEXES
 939        plist_head_init_raw(&p->pi_waiters, &p->pi_lock);
 940        p->pi_blocked_on = NULL;
 941#endif
 942}
 943
 944#ifdef CONFIG_MM_OWNER
 945void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 946{
 947        mm->owner = p;
 948}
 949#endif /* CONFIG_MM_OWNER */
 950
 951/*
 952 * Initialize POSIX timer handling for a single task.
 953 */
 954static void posix_cpu_timers_init(struct task_struct *tsk)
 955{
 956        tsk->cputime_expires.prof_exp = cputime_zero;
 957        tsk->cputime_expires.virt_exp = cputime_zero;
 958        tsk->cputime_expires.sched_exp = 0;
 959        INIT_LIST_HEAD(&tsk->cpu_timers[0]);
 960        INIT_LIST_HEAD(&tsk->cpu_timers[1]);
 961        INIT_LIST_HEAD(&tsk->cpu_timers[2]);
 962}
 963
 964/*
 965 * This creates a new process as a copy of the old one,
 966 * but does not actually start it yet.
 967 *
 968 * It copies the registers, and all the appropriate
 969 * parts of the process environment (as per the clone
 970 * flags). The actual kick-off is left to the caller.
 971 */
 972static struct task_struct *copy_process(unsigned long clone_flags,
 973                                        unsigned long stack_start,
 974                                        struct pt_regs *regs,
 975                                        unsigned long stack_size,
 976                                        int __user *child_tidptr,
 977                                        struct pid *pid,
 978                                        int trace)
 979{
 980        int retval;
 981        struct task_struct *p;
 982        int cgroup_callbacks_done = 0;
 983
 984        if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 985                return ERR_PTR(-EINVAL);
 986
 987        /*
 988         * Thread groups must share signals as well, and detached threads
 989         * can only be started up within the thread group.
 990         */
 991        if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 992                return ERR_PTR(-EINVAL);
 993
 994        /*
 995         * Shared signal handlers imply shared VM. By way of the above,
 996         * thread groups also imply shared VM. Blocking this case allows
 997         * for various simplifications in other code.
 998         */
 999        if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1000                return ERR_PTR(-EINVAL);
1001
1002        /*
1003         * Siblings of global init remain as zombies on exit since they are
1004         * not reaped by their parent (swapper). To solve this and to avoid
1005         * multi-rooted process trees, prevent global and container-inits
1006         * from creating siblings.
1007         */
1008        if ((clone_flags & CLONE_PARENT) &&
1009                                current->signal->flags & SIGNAL_UNKILLABLE)
1010                return ERR_PTR(-EINVAL);
1011
1012        retval = security_task_create(clone_flags);
1013        if (retval)
1014                goto fork_out;
1015
1016        retval = -ENOMEM;
1017        p = dup_task_struct(current);
1018        if (!p)
1019                goto fork_out;
1020
1021        ftrace_graph_init_task(p);
1022
1023        rt_mutex_init_task(p);
1024
1025#ifdef CONFIG_PROVE_LOCKING
1026        DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1027        DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1028#endif
1029        retval = -EAGAIN;
1030        if (atomic_read(&p->real_cred->user->processes) >=
1031                        task_rlimit(p, RLIMIT_NPROC)) {
1032                if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1033                    p->real_cred->user != INIT_USER)
1034                        goto bad_fork_free;
1035        }
1036
1037        retval = copy_creds(p, clone_flags);
1038        if (retval < 0)
1039                goto bad_fork_free;
1040
1041        /*
1042         * If multiple threads are within copy_process(), then this check
1043         * triggers too late. This doesn't hurt, the check is only there
1044         * to stop root fork bombs.
1045         */
1046        retval = -EAGAIN;
1047        if (nr_threads >= max_threads)
1048                goto bad_fork_cleanup_count;
1049
1050        if (!try_module_get(task_thread_info(p)->exec_domain->module))
1051                goto bad_fork_cleanup_count;
1052
1053        p->did_exec = 0;
1054        delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1055        copy_flags(clone_flags, p);
1056        INIT_LIST_HEAD(&p->children);
1057        INIT_LIST_HEAD(&p->sibling);
1058        rcu_copy_process(p);
1059        p->vfork_done = NULL;
1060        spin_lock_init(&p->alloc_lock);
1061
1062        init_sigpending(&p->pending);
1063
1064        p->utime = cputime_zero;
1065        p->stime = cputime_zero;
1066        p->gtime = cputime_zero;
1067        p->utimescaled = cputime_zero;
1068        p->stimescaled = cputime_zero;
1069#ifndef CONFIG_VIRT_CPU_ACCOUNTING
1070        p->prev_utime = cputime_zero;
1071        p->prev_stime = cputime_zero;
1072#endif
1073#if defined(SPLIT_RSS_COUNTING)
1074        memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1075#endif
1076
1077        p->default_timer_slack_ns = current->timer_slack_ns;
1078
1079        task_io_accounting_init(&p->ioac);
1080        acct_clear_integrals(p);
1081
1082        posix_cpu_timers_init(p);
1083
1084        p->lock_depth = -1;             /* -1 = no lock */
1085        do_posix_clock_monotonic_gettime(&p->start_time);
1086        p->real_start_time = p->start_time;
1087        monotonic_to_bootbased(&p->real_start_time);
1088        p->io_context = NULL;
1089        p->audit_context = NULL;
1090        cgroup_fork(p);
1091#ifdef CONFIG_NUMA
1092        p->mempolicy = mpol_dup(p->mempolicy);
1093        if (IS_ERR(p->mempolicy)) {
1094                retval = PTR_ERR(p->mempolicy);
1095                p->mempolicy = NULL;
1096                goto bad_fork_cleanup_cgroup;
1097        }
1098        mpol_fix_fork_child_flag(p);
1099#endif
1100#ifdef CONFIG_TRACE_IRQFLAGS
1101        p->irq_events = 0;
1102#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1103        p->hardirqs_enabled = 1;
1104#else
1105        p->hardirqs_enabled = 0;
1106#endif
1107        p->hardirq_enable_ip = 0;
1108        p->hardirq_enable_event = 0;
1109        p->hardirq_disable_ip = _THIS_IP_;
1110        p->hardirq_disable_event = 0;
1111        p->softirqs_enabled = 1;
1112        p->softirq_enable_ip = _THIS_IP_;
1113        p->softirq_enable_event = 0;
1114        p->softirq_disable_ip = 0;
1115        p->softirq_disable_event = 0;
1116        p->hardirq_context = 0;
1117        p->softirq_context = 0;
1118#endif
1119#ifdef CONFIG_LOCKDEP
1120        p->lockdep_depth = 0; /* no locks held yet */
1121        p->curr_chain_key = 0;
1122        p->lockdep_recursion = 0;
1123#endif
1124
1125#ifdef CONFIG_DEBUG_MUTEXES
1126        p->blocked_on = NULL; /* not blocked yet */
1127#endif
1128#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1129        p->memcg_batch.do_batch = 0;
1130        p->memcg_batch.memcg = NULL;
1131#endif
1132
1133        /* Perform scheduler related setup. Assign this task to a CPU. */
1134        sched_fork(p, clone_flags);
1135
1136        retval = perf_event_init_task(p);
1137        if (retval)
1138                goto bad_fork_cleanup_policy;
1139
1140        if ((retval = audit_alloc(p)))
1141                goto bad_fork_cleanup_policy;
1142        /* copy all the process information */
1143        if ((retval = copy_semundo(clone_flags, p)))
1144                goto bad_fork_cleanup_audit;
1145        if ((retval = copy_files(clone_flags, p)))
1146                goto bad_fork_cleanup_semundo;
1147        if ((retval = copy_fs(clone_flags, p)))
1148                goto bad_fork_cleanup_files;
1149        if ((retval = copy_sighand(clone_flags, p)))
1150                goto bad_fork_cleanup_fs;
1151        if ((retval = copy_signal(clone_flags, p)))
1152                goto bad_fork_cleanup_sighand;
1153        if ((retval = copy_mm(clone_flags, p)))
1154                goto bad_fork_cleanup_signal;
1155        if ((retval = copy_namespaces(clone_flags, p)))
1156                goto bad_fork_cleanup_mm;
1157        if ((retval = copy_io(clone_flags, p)))
1158                goto bad_fork_cleanup_namespaces;
1159        retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1160        if (retval)
1161                goto bad_fork_cleanup_io;
1162
1163        if (pid != &init_struct_pid) {
1164                retval = -ENOMEM;
1165                pid = alloc_pid(p->nsproxy->pid_ns);
1166                if (!pid)
1167                        goto bad_fork_cleanup_io;
1168
1169                if (clone_flags & CLONE_NEWPID) {
1170                        retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1171                        if (retval < 0)
1172                                goto bad_fork_free_pid;
1173                }
1174        }
1175
1176        p->pid = pid_nr(pid);
1177        p->tgid = p->pid;
1178        if (clone_flags & CLONE_THREAD)
1179                p->tgid = current->tgid;
1180
1181        if (current->nsproxy != p->nsproxy) {
1182                retval = ns_cgroup_clone(p, pid);
1183                if (retval)
1184                        goto bad_fork_free_pid;
1185        }
1186
1187        p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1188        /*
1189         * Clear TID on mm_release()?
1190         */
1191        p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1192#ifdef CONFIG_FUTEX
1193        p->robust_list = NULL;
1194#ifdef CONFIG_COMPAT
1195        p->compat_robust_list = NULL;
1196#endif
1197        INIT_LIST_HEAD(&p->pi_state_list);
1198        p->pi_state_cache = NULL;
1199#endif
1200        /*
1201         * sigaltstack should be cleared when sharing the same VM
1202         */
1203        if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1204                p->sas_ss_sp = p->sas_ss_size = 0;
1205
1206        /*
1207         * Syscall tracing and stepping should be turned off in the
1208         * child regardless of CLONE_PTRACE.
1209         */
1210        user_disable_single_step(p);
1211        clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1212#ifdef TIF_SYSCALL_EMU
1213        clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1214#endif
1215        clear_all_latency_tracing(p);
1216
1217        /* ok, now we should be set up.. */
1218        p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1219        p->pdeath_signal = 0;
1220        p->exit_state = 0;
1221
1222        /*
1223         * Ok, make it visible to the rest of the system.
1224         * We dont wake it up yet.
1225         */
1226        p->group_leader = p;
1227        INIT_LIST_HEAD(&p->thread_group);
1228
1229        /* Now that the task is set up, run cgroup callbacks if
1230         * necessary. We need to run them before the task is visible
1231         * on the tasklist. */
1232        cgroup_fork_callbacks(p);
1233        cgroup_callbacks_done = 1;
1234
1235        /* Need tasklist lock for parent etc handling! */
1236        write_lock_irq(&tasklist_lock);
1237
1238        /* CLONE_PARENT re-uses the old parent */
1239        if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1240                p->real_parent = current->real_parent;
1241                p->parent_exec_id = current->parent_exec_id;
1242        } else {
1243                p->real_parent = current;
1244                p->parent_exec_id = current->self_exec_id;
1245        }
1246
1247        spin_lock(&current->sighand->siglock);
1248
1249        /*
1250         * Process group and session signals need to be delivered to just the
1251         * parent before the fork or both the parent and the child after the
1252         * fork. Restart if a signal comes in before we add the new process to
1253         * it's process group.
1254         * A fatal signal pending means that current will exit, so the new
1255         * thread can't slip out of an OOM kill (or normal SIGKILL).
1256         */
1257        recalc_sigpending();
1258        if (signal_pending(current)) {
1259                spin_unlock(&current->sighand->siglock);
1260                write_unlock_irq(&tasklist_lock);
1261                retval = -ERESTARTNOINTR;
1262                goto bad_fork_free_pid;
1263        }
1264
1265        if (clone_flags & CLONE_THREAD) {
1266                current->signal->nr_threads++;
1267                atomic_inc(&current->signal->live);
1268                atomic_inc(&current->signal->sigcnt);
1269                p->group_leader = current->group_leader;
1270                list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1271        }
1272
1273        if (likely(p->pid)) {
1274                tracehook_finish_clone(p, clone_flags, trace);
1275
1276                if (thread_group_leader(p)) {
1277                        if (clone_flags & CLONE_NEWPID)
1278                                p->nsproxy->pid_ns->child_reaper = p;
1279
1280                        p->signal->leader_pid = pid;
1281                        p->signal->tty = tty_kref_get(current->signal->tty);
1282                        attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1283                        attach_pid(p, PIDTYPE_SID, task_session(current));
1284                        list_add_tail(&p->sibling, &p->real_parent->children);
1285                        list_add_tail_rcu(&p->tasks, &init_task.tasks);
1286                        __get_cpu_var(process_counts)++;
1287                }
1288                attach_pid(p, PIDTYPE_PID, pid);
1289                nr_threads++;
1290        }
1291
1292        total_forks++;
1293        spin_unlock(&current->sighand->siglock);
1294        write_unlock_irq(&tasklist_lock);
1295        proc_fork_connector(p);
1296        cgroup_post_fork(p);
1297        perf_event_fork(p);
1298        return p;
1299
1300bad_fork_free_pid:
1301        if (pid != &init_struct_pid)
1302                free_pid(pid);
1303bad_fork_cleanup_io:
1304        if (p->io_context)
1305                exit_io_context(p);
1306bad_fork_cleanup_namespaces:
1307        exit_task_namespaces(p);
1308bad_fork_cleanup_mm:
1309        if (p->mm) {
1310                task_lock(p);
1311                if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
1312                        atomic_dec(&p->mm->oom_disable_count);
1313                task_unlock(p);
1314                mmput(p->mm);
1315        }
1316bad_fork_cleanup_signal:
1317        if (!(clone_flags & CLONE_THREAD))
1318                free_signal_struct(p->signal);
1319bad_fork_cleanup_sighand:
1320        __cleanup_sighand(p->sighand);
1321bad_fork_cleanup_fs:
1322        exit_fs(p); /* blocking */
1323bad_fork_cleanup_files:
1324        exit_files(p); /* blocking */
1325bad_fork_cleanup_semundo:
1326        exit_sem(p);
1327bad_fork_cleanup_audit:
1328        audit_free(p);
1329bad_fork_cleanup_policy:
1330        perf_event_free_task(p);
1331#ifdef CONFIG_NUMA
1332        mpol_put(p->mempolicy);
1333bad_fork_cleanup_cgroup:
1334#endif
1335        cgroup_exit(p, cgroup_callbacks_done);
1336        delayacct_tsk_free(p);
1337        module_put(task_thread_info(p)->exec_domain->module);
1338bad_fork_cleanup_count:
1339        atomic_dec(&p->cred->user->processes);
1340        exit_creds(p);
1341bad_fork_free:
1342        free_task(p);
1343fork_out:
1344        return ERR_PTR(retval);
1345}
1346
1347noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1348{
1349        memset(regs, 0, sizeof(struct pt_regs));
1350        return regs;
1351}
1352
1353static inline void init_idle_pids(struct pid_link *links)
1354{
1355        enum pid_type type;
1356
1357        for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1358                INIT_HLIST_NODE(&links[type].node); /* not really needed */
1359                links[type].pid = &init_struct_pid;
1360        }
1361}
1362
1363struct task_struct * __cpuinit fork_idle(int cpu)
1364{
1365        struct task_struct *task;
1366        struct pt_regs regs;
1367
1368        task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1369                            &init_struct_pid, 0);
1370        if (!IS_ERR(task)) {
1371                init_idle_pids(task->pids);
1372                init_idle(task, cpu);
1373        }
1374
1375        return task;
1376}
1377
1378/*
1379 *  Ok, this is the main fork-routine.
1380 *
1381 * It copies the process, and if successful kick-starts
1382 * it and waits for it to finish using the VM if required.
1383 */
1384long do_fork(unsigned long clone_flags,
1385              unsigned long stack_start,
1386              struct pt_regs *regs,
1387              unsigned long stack_size,
1388              int __user *parent_tidptr,
1389              int __user *child_tidptr)
1390{
1391        struct task_struct *p;
1392        int trace = 0;
1393        long nr;
1394
1395        /*
1396         * Do some preliminary argument and permissions checking before we
1397         * actually start allocating stuff
1398         */
1399        if (clone_flags & CLONE_NEWUSER) {
1400                if (clone_flags & CLONE_THREAD)
1401                        return -EINVAL;
1402                /* hopefully this check will go away when userns support is
1403                 * complete
1404                 */
1405                if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1406                                !capable(CAP_SETGID))
1407                        return -EPERM;
1408        }
1409
1410        /*
1411         * We hope to recycle these flags after 2.6.26
1412         */
1413        if (unlikely(clone_flags & CLONE_STOPPED)) {
1414                static int __read_mostly count = 100;
1415
1416                if (count > 0 && printk_ratelimit()) {
1417                        char comm[TASK_COMM_LEN];
1418
1419                        count--;
1420                        printk(KERN_INFO "fork(): process `%s' used deprecated "
1421                                        "clone flags 0x%lx\n",
1422                                get_task_comm(comm, current),
1423                                clone_flags & CLONE_STOPPED);
1424                }
1425        }
1426
1427        /*
1428         * When called from kernel_thread, don't do user tracing stuff.
1429         */
1430        if (likely(user_mode(regs)))
1431                trace = tracehook_prepare_clone(clone_flags);
1432
1433        p = copy_process(clone_flags, stack_start, regs, stack_size,
1434                         child_tidptr, NULL, trace);
1435        /*
1436         * Do this prior waking up the new thread - the thread pointer
1437         * might get invalid after that point, if the thread exits quickly.
1438         */
1439        if (!IS_ERR(p)) {
1440                struct completion vfork;
1441
1442                trace_sched_process_fork(current, p);
1443
1444                nr = task_pid_vnr(p);
1445
1446                if (clone_flags & CLONE_PARENT_SETTID)
1447                        put_user(nr, parent_tidptr);
1448
1449                if (clone_flags & CLONE_VFORK) {
1450                        p->vfork_done = &vfork;
1451                        init_completion(&vfork);
1452                }
1453
1454                audit_finish_fork(p);
1455                tracehook_report_clone(regs, clone_flags, nr, p);
1456
1457                /*
1458                 * We set PF_STARTING at creation in case tracing wants to
1459                 * use this to distinguish a fully live task from one that
1460                 * hasn't gotten to tracehook_report_clone() yet.  Now we
1461                 * clear it and set the child going.
1462                 */
1463                p->flags &= ~PF_STARTING;
1464
1465                if (unlikely(clone_flags & CLONE_STOPPED)) {
1466                        /*
1467                         * We'll start up with an immediate SIGSTOP.
1468                         */
1469                        sigaddset(&p->pending.signal, SIGSTOP);
1470                        set_tsk_thread_flag(p, TIF_SIGPENDING);
1471                        __set_task_state(p, TASK_STOPPED);
1472                } else {
1473                        wake_up_new_task(p, clone_flags);
1474                }
1475
1476                tracehook_report_clone_complete(trace, regs,
1477                                                clone_flags, nr, p);
1478
1479                if (clone_flags & CLONE_VFORK) {
1480                        freezer_do_not_count();
1481                        wait_for_completion(&vfork);
1482                        freezer_count();
1483                        tracehook_report_vfork_done(p, nr);
1484                }
1485        } else {
1486                nr = PTR_ERR(p);
1487        }
1488        return nr;
1489}
1490
1491#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1492#define ARCH_MIN_MMSTRUCT_ALIGN 0
1493#endif
1494
1495static void sighand_ctor(void *data)
1496{
1497        struct sighand_struct *sighand = data;
1498
1499        spin_lock_init(&sighand->siglock);
1500        init_waitqueue_head(&sighand->signalfd_wqh);
1501}
1502
1503void __init proc_caches_init(void)
1504{
1505        sighand_cachep = kmem_cache_create("sighand_cache",
1506                        sizeof(struct sighand_struct), 0,
1507                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1508                        SLAB_NOTRACK, sighand_ctor);
1509        signal_cachep = kmem_cache_create("signal_cache",
1510                        sizeof(struct signal_struct), 0,
1511                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1512        files_cachep = kmem_cache_create("files_cache",
1513                        sizeof(struct files_struct), 0,
1514                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1515        fs_cachep = kmem_cache_create("fs_cache",
1516                        sizeof(struct fs_struct), 0,
1517                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1518        mm_cachep = kmem_cache_create("mm_struct",
1519                        sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1520                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1521        vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1522        mmap_init();
1523}
1524
1525/*
1526 * Check constraints on flags passed to the unshare system call and
1527 * force unsharing of additional process context as appropriate.
1528 */
1529static void check_unshare_flags(unsigned long *flags_ptr)
1530{
1531        /*
1532         * If unsharing a thread from a thread group, must also
1533         * unshare vm.
1534         */
1535        if (*flags_ptr & CLONE_THREAD)
1536                *flags_ptr |= CLONE_VM;
1537
1538        /*
1539         * If unsharing vm, must also unshare signal handlers.
1540         */
1541        if (*flags_ptr & CLONE_VM)
1542                *flags_ptr |= CLONE_SIGHAND;
1543
1544        /*
1545         * If unsharing namespace, must also unshare filesystem information.
1546         */
1547        if (*flags_ptr & CLONE_NEWNS)
1548                *flags_ptr |= CLONE_FS;
1549}
1550
1551/*
1552 * Unsharing of tasks created with CLONE_THREAD is not supported yet
1553 */
1554static int unshare_thread(unsigned long unshare_flags)
1555{
1556        if (unshare_flags & CLONE_THREAD)
1557                return -EINVAL;
1558
1559        return 0;
1560}
1561
1562/*
1563 * Unshare the filesystem structure if it is being shared
1564 */
1565static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1566{
1567        struct fs_struct *fs = current->fs;
1568
1569        if (!(unshare_flags & CLONE_FS) || !fs)
1570                return 0;
1571
1572        /* don't need lock here; in the worst case we'll do useless copy */
1573        if (fs->users == 1)
1574                return 0;
1575
1576        *new_fsp = copy_fs_struct(fs);
1577        if (!*new_fsp)
1578                return -ENOMEM;
1579
1580        return 0;
1581}
1582
1583/*
1584 * Unsharing of sighand is not supported yet
1585 */
1586static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1587{
1588        struct sighand_struct *sigh = current->sighand;
1589
1590        if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1591                return -EINVAL;
1592        else
1593                return 0;
1594}
1595
1596/*
1597 * Unshare vm if it is being shared
1598 */
1599static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1600{
1601        struct mm_struct *mm = current->mm;
1602
1603        if ((unshare_flags & CLONE_VM) &&
1604            (mm && atomic_read(&mm->mm_users) > 1)) {
1605                return -EINVAL;
1606        }
1607
1608        return 0;
1609}
1610
1611/*
1612 * Unshare file descriptor table if it is being shared
1613 */
1614static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1615{
1616        struct files_struct *fd = current->files;
1617        int error = 0;
1618
1619        if ((unshare_flags & CLONE_FILES) &&
1620            (fd && atomic_read(&fd->count) > 1)) {
1621                *new_fdp = dup_fd(fd, &error);
1622                if (!*new_fdp)
1623                        return error;
1624        }
1625
1626        return 0;
1627}
1628
1629/*
1630 * unshare allows a process to 'unshare' part of the process
1631 * context which was originally shared using clone.  copy_*
1632 * functions used by do_fork() cannot be used here directly
1633 * because they modify an inactive task_struct that is being
1634 * constructed. Here we are modifying the current, active,
1635 * task_struct.
1636 */
1637SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1638{
1639        int err = 0;
1640        struct fs_struct *fs, *new_fs = NULL;
1641        struct sighand_struct *new_sigh = NULL;
1642        struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1643        struct files_struct *fd, *new_fd = NULL;
1644        struct nsproxy *new_nsproxy = NULL;
1645        int do_sysvsem = 0;
1646
1647        check_unshare_flags(&unshare_flags);
1648
1649        /* Return -EINVAL for all unsupported flags */
1650        err = -EINVAL;
1651        if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1652                                CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1653                                CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1654                goto bad_unshare_out;
1655
1656        /*
1657         * CLONE_NEWIPC must also detach from the undolist: after switching
1658         * to a new ipc namespace, the semaphore arrays from the old
1659         * namespace are unreachable.
1660         */
1661        if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1662                do_sysvsem = 1;
1663        if ((err = unshare_thread(unshare_flags)))
1664                goto bad_unshare_out;
1665        if ((err = unshare_fs(unshare_flags, &new_fs)))
1666                goto bad_unshare_cleanup_thread;
1667        if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1668                goto bad_unshare_cleanup_fs;
1669        if ((err = unshare_vm(unshare_flags, &new_mm)))
1670                goto bad_unshare_cleanup_sigh;
1671        if ((err = unshare_fd(unshare_flags, &new_fd)))
1672                goto bad_unshare_cleanup_vm;
1673        if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1674                        new_fs)))
1675                goto bad_unshare_cleanup_fd;
1676
1677        if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1678                if (do_sysvsem) {
1679                        /*
1680                         * CLONE_SYSVSEM is equivalent to sys_exit().
1681                         */
1682                        exit_sem(current);
1683                }
1684
1685                if (new_nsproxy) {
1686                        switch_task_namespaces(current, new_nsproxy);
1687                        new_nsproxy = NULL;
1688                }
1689
1690                task_lock(current);
1691
1692                if (new_fs) {
1693                        fs = current->fs;
1694                        spin_lock(&fs->lock);
1695                        current->fs = new_fs;
1696                        if (--fs->users)
1697                                new_fs = NULL;
1698                        else
1699                                new_fs = fs;
1700                        spin_unlock(&fs->lock);
1701                }
1702
1703                if (new_mm) {
1704                        mm = current->mm;
1705                        active_mm = current->active_mm;
1706                        current->mm = new_mm;
1707                        current->active_mm = new_mm;
1708                        if (current->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) {
1709                                atomic_dec(&mm->oom_disable_count);
1710                                atomic_inc(&new_mm->oom_disable_count);
1711                        }
1712                        activate_mm(active_mm, new_mm);
1713                        new_mm = mm;
1714                }
1715
1716                if (new_fd) {
1717                        fd = current->files;
1718                        current->files = new_fd;
1719                        new_fd = fd;
1720                }
1721
1722                task_unlock(current);
1723        }
1724
1725        if (new_nsproxy)
1726                put_nsproxy(new_nsproxy);
1727
1728bad_unshare_cleanup_fd:
1729        if (new_fd)
1730                put_files_struct(new_fd);
1731
1732bad_unshare_cleanup_vm:
1733        if (new_mm)
1734                mmput(new_mm);
1735
1736bad_unshare_cleanup_sigh:
1737        if (new_sigh)
1738                if (atomic_dec_and_test(&new_sigh->count))
1739                        kmem_cache_free(sighand_cachep, new_sigh);
1740
1741bad_unshare_cleanup_fs:
1742        if (new_fs)
1743                free_fs_struct(new_fs);
1744
1745bad_unshare_cleanup_thread:
1746bad_unshare_out:
1747        return err;
1748}
1749
1750/*
1751 *      Helper to unshare the files of the current task.
1752 *      We don't want to expose copy_files internals to
1753 *      the exec layer of the kernel.
1754 */
1755
1756int unshare_files(struct files_struct **displaced)
1757{
1758        struct task_struct *task = current;
1759        struct files_struct *copy = NULL;
1760        int error;
1761
1762        error = unshare_fd(CLONE_FILES, &copy);
1763        if (error || !copy) {
1764                *displaced = NULL;
1765                return error;
1766        }
1767        *displaced = task->files;
1768        task_lock(task);
1769        task->files = copy;
1770        task_unlock(task);
1771        return 0;
1772}
1773
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