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