Merge tag 'selinux-pr-20170831' of git://git.kernel.org/pub/scm/linux/kernel/git...
[sfrench/cifs-2.6.git] / kernel / fork.c
1 /*
2  *  linux/kernel/fork.c
3  *
4  *  Copyright (C) 1991, 1992  Linus Torvalds
5  */
6
7 /*
8  *  'fork.c' contains the help-routines for the 'fork' system call
9  * (see also entry.S and others).
10  * Fork is rather simple, once you get the hang of it, but the memory
11  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
12  */
13
14 #include <linux/slab.h>
15 #include <linux/sched/autogroup.h>
16 #include <linux/sched/mm.h>
17 #include <linux/sched/coredump.h>
18 #include <linux/sched/user.h>
19 #include <linux/sched/numa_balancing.h>
20 #include <linux/sched/stat.h>
21 #include <linux/sched/task.h>
22 #include <linux/sched/task_stack.h>
23 #include <linux/sched/cputime.h>
24 #include <linux/rtmutex.h>
25 #include <linux/init.h>
26 #include <linux/unistd.h>
27 #include <linux/module.h>
28 #include <linux/vmalloc.h>
29 #include <linux/completion.h>
30 #include <linux/personality.h>
31 #include <linux/mempolicy.h>
32 #include <linux/sem.h>
33 #include <linux/file.h>
34 #include <linux/fdtable.h>
35 #include <linux/iocontext.h>
36 #include <linux/key.h>
37 #include <linux/binfmts.h>
38 #include <linux/mman.h>
39 #include <linux/mmu_notifier.h>
40 #include <linux/hmm.h>
41 #include <linux/fs.h>
42 #include <linux/mm.h>
43 #include <linux/vmacache.h>
44 #include <linux/nsproxy.h>
45 #include <linux/capability.h>
46 #include <linux/cpu.h>
47 #include <linux/cgroup.h>
48 #include <linux/security.h>
49 #include <linux/hugetlb.h>
50 #include <linux/seccomp.h>
51 #include <linux/swap.h>
52 #include <linux/syscalls.h>
53 #include <linux/jiffies.h>
54 #include <linux/futex.h>
55 #include <linux/compat.h>
56 #include <linux/kthread.h>
57 #include <linux/task_io_accounting_ops.h>
58 #include <linux/rcupdate.h>
59 #include <linux/ptrace.h>
60 #include <linux/mount.h>
61 #include <linux/audit.h>
62 #include <linux/memcontrol.h>
63 #include <linux/ftrace.h>
64 #include <linux/proc_fs.h>
65 #include <linux/profile.h>
66 #include <linux/rmap.h>
67 #include <linux/ksm.h>
68 #include <linux/acct.h>
69 #include <linux/userfaultfd_k.h>
70 #include <linux/tsacct_kern.h>
71 #include <linux/cn_proc.h>
72 #include <linux/freezer.h>
73 #include <linux/delayacct.h>
74 #include <linux/taskstats_kern.h>
75 #include <linux/random.h>
76 #include <linux/tty.h>
77 #include <linux/blkdev.h>
78 #include <linux/fs_struct.h>
79 #include <linux/magic.h>
80 #include <linux/perf_event.h>
81 #include <linux/posix-timers.h>
82 #include <linux/user-return-notifier.h>
83 #include <linux/oom.h>
84 #include <linux/khugepaged.h>
85 #include <linux/signalfd.h>
86 #include <linux/uprobes.h>
87 #include <linux/aio.h>
88 #include <linux/compiler.h>
89 #include <linux/sysctl.h>
90 #include <linux/kcov.h>
91 #include <linux/livepatch.h>
92 #include <linux/thread_info.h>
93
94 #include <asm/pgtable.h>
95 #include <asm/pgalloc.h>
96 #include <linux/uaccess.h>
97 #include <asm/mmu_context.h>
98 #include <asm/cacheflush.h>
99 #include <asm/tlbflush.h>
100
101 #include <trace/events/sched.h>
102
103 #define CREATE_TRACE_POINTS
104 #include <trace/events/task.h>
105
106 /*
107  * Minimum number of threads to boot the kernel
108  */
109 #define MIN_THREADS 20
110
111 /*
112  * Maximum number of threads
113  */
114 #define MAX_THREADS FUTEX_TID_MASK
115
116 /*
117  * Protected counters by write_lock_irq(&tasklist_lock)
118  */
119 unsigned long total_forks;      /* Handle normal Linux uptimes. */
120 int nr_threads;                 /* The idle threads do not count.. */
121
122 int max_threads;                /* tunable limit on nr_threads */
123
124 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
125
126 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
127
128 #ifdef CONFIG_PROVE_RCU
129 int lockdep_tasklist_lock_is_held(void)
130 {
131         return lockdep_is_held(&tasklist_lock);
132 }
133 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
134 #endif /* #ifdef CONFIG_PROVE_RCU */
135
136 int nr_processes(void)
137 {
138         int cpu;
139         int total = 0;
140
141         for_each_possible_cpu(cpu)
142                 total += per_cpu(process_counts, cpu);
143
144         return total;
145 }
146
147 void __weak arch_release_task_struct(struct task_struct *tsk)
148 {
149 }
150
151 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
152 static struct kmem_cache *task_struct_cachep;
153
154 static inline struct task_struct *alloc_task_struct_node(int node)
155 {
156         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
157 }
158
159 static inline void free_task_struct(struct task_struct *tsk)
160 {
161         kmem_cache_free(task_struct_cachep, tsk);
162 }
163 #endif
164
165 void __weak arch_release_thread_stack(unsigned long *stack)
166 {
167 }
168
169 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
170
171 /*
172  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
173  * kmemcache based allocator.
174  */
175 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
176
177 #ifdef CONFIG_VMAP_STACK
178 /*
179  * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
180  * flush.  Try to minimize the number of calls by caching stacks.
181  */
182 #define NR_CACHED_STACKS 2
183 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
184
185 static int free_vm_stack_cache(unsigned int cpu)
186 {
187         struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
188         int i;
189
190         for (i = 0; i < NR_CACHED_STACKS; i++) {
191                 struct vm_struct *vm_stack = cached_vm_stacks[i];
192
193                 if (!vm_stack)
194                         continue;
195
196                 vfree(vm_stack->addr);
197                 cached_vm_stacks[i] = NULL;
198         }
199
200         return 0;
201 }
202 #endif
203
204 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
205 {
206 #ifdef CONFIG_VMAP_STACK
207         void *stack;
208         int i;
209
210         for (i = 0; i < NR_CACHED_STACKS; i++) {
211                 struct vm_struct *s;
212
213                 s = this_cpu_xchg(cached_stacks[i], NULL);
214
215                 if (!s)
216                         continue;
217
218                 tsk->stack_vm_area = s;
219                 return s->addr;
220         }
221
222         stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
223                                      VMALLOC_START, VMALLOC_END,
224                                      THREADINFO_GFP,
225                                      PAGE_KERNEL,
226                                      0, node, __builtin_return_address(0));
227
228         /*
229          * We can't call find_vm_area() in interrupt context, and
230          * free_thread_stack() can be called in interrupt context,
231          * so cache the vm_struct.
232          */
233         if (stack)
234                 tsk->stack_vm_area = find_vm_area(stack);
235         return stack;
236 #else
237         struct page *page = alloc_pages_node(node, THREADINFO_GFP,
238                                              THREAD_SIZE_ORDER);
239
240         return page ? page_address(page) : NULL;
241 #endif
242 }
243
244 static inline void free_thread_stack(struct task_struct *tsk)
245 {
246 #ifdef CONFIG_VMAP_STACK
247         if (task_stack_vm_area(tsk)) {
248                 int i;
249
250                 for (i = 0; i < NR_CACHED_STACKS; i++) {
251                         if (this_cpu_cmpxchg(cached_stacks[i],
252                                         NULL, tsk->stack_vm_area) != NULL)
253                                 continue;
254
255                         return;
256                 }
257
258                 vfree_atomic(tsk->stack);
259                 return;
260         }
261 #endif
262
263         __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
264 }
265 # else
266 static struct kmem_cache *thread_stack_cache;
267
268 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
269                                                   int node)
270 {
271         return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
272 }
273
274 static void free_thread_stack(struct task_struct *tsk)
275 {
276         kmem_cache_free(thread_stack_cache, tsk->stack);
277 }
278
279 void thread_stack_cache_init(void)
280 {
281         thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE,
282                                               THREAD_SIZE, 0, NULL);
283         BUG_ON(thread_stack_cache == NULL);
284 }
285 # endif
286 #endif
287
288 /* SLAB cache for signal_struct structures (tsk->signal) */
289 static struct kmem_cache *signal_cachep;
290
291 /* SLAB cache for sighand_struct structures (tsk->sighand) */
292 struct kmem_cache *sighand_cachep;
293
294 /* SLAB cache for files_struct structures (tsk->files) */
295 struct kmem_cache *files_cachep;
296
297 /* SLAB cache for fs_struct structures (tsk->fs) */
298 struct kmem_cache *fs_cachep;
299
300 /* SLAB cache for vm_area_struct structures */
301 struct kmem_cache *vm_area_cachep;
302
303 /* SLAB cache for mm_struct structures (tsk->mm) */
304 static struct kmem_cache *mm_cachep;
305
306 static void account_kernel_stack(struct task_struct *tsk, int account)
307 {
308         void *stack = task_stack_page(tsk);
309         struct vm_struct *vm = task_stack_vm_area(tsk);
310
311         BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
312
313         if (vm) {
314                 int i;
315
316                 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
317
318                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
319                         mod_zone_page_state(page_zone(vm->pages[i]),
320                                             NR_KERNEL_STACK_KB,
321                                             PAGE_SIZE / 1024 * account);
322                 }
323
324                 /* All stack pages belong to the same memcg. */
325                 mod_memcg_page_state(vm->pages[0], MEMCG_KERNEL_STACK_KB,
326                                      account * (THREAD_SIZE / 1024));
327         } else {
328                 /*
329                  * All stack pages are in the same zone and belong to the
330                  * same memcg.
331                  */
332                 struct page *first_page = virt_to_page(stack);
333
334                 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
335                                     THREAD_SIZE / 1024 * account);
336
337                 mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB,
338                                      account * (THREAD_SIZE / 1024));
339         }
340 }
341
342 static void release_task_stack(struct task_struct *tsk)
343 {
344         if (WARN_ON(tsk->state != TASK_DEAD))
345                 return;  /* Better to leak the stack than to free prematurely */
346
347         account_kernel_stack(tsk, -1);
348         arch_release_thread_stack(tsk->stack);
349         free_thread_stack(tsk);
350         tsk->stack = NULL;
351 #ifdef CONFIG_VMAP_STACK
352         tsk->stack_vm_area = NULL;
353 #endif
354 }
355
356 #ifdef CONFIG_THREAD_INFO_IN_TASK
357 void put_task_stack(struct task_struct *tsk)
358 {
359         if (atomic_dec_and_test(&tsk->stack_refcount))
360                 release_task_stack(tsk);
361 }
362 #endif
363
364 void free_task(struct task_struct *tsk)
365 {
366 #ifndef CONFIG_THREAD_INFO_IN_TASK
367         /*
368          * The task is finally done with both the stack and thread_info,
369          * so free both.
370          */
371         release_task_stack(tsk);
372 #else
373         /*
374          * If the task had a separate stack allocation, it should be gone
375          * by now.
376          */
377         WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0);
378 #endif
379         rt_mutex_debug_task_free(tsk);
380         ftrace_graph_exit_task(tsk);
381         put_seccomp_filter(tsk);
382         arch_release_task_struct(tsk);
383         if (tsk->flags & PF_KTHREAD)
384                 free_kthread_struct(tsk);
385         free_task_struct(tsk);
386 }
387 EXPORT_SYMBOL(free_task);
388
389 static inline void free_signal_struct(struct signal_struct *sig)
390 {
391         taskstats_tgid_free(sig);
392         sched_autogroup_exit(sig);
393         /*
394          * __mmdrop is not safe to call from softirq context on x86 due to
395          * pgd_dtor so postpone it to the async context
396          */
397         if (sig->oom_mm)
398                 mmdrop_async(sig->oom_mm);
399         kmem_cache_free(signal_cachep, sig);
400 }
401
402 static inline void put_signal_struct(struct signal_struct *sig)
403 {
404         if (atomic_dec_and_test(&sig->sigcnt))
405                 free_signal_struct(sig);
406 }
407
408 void __put_task_struct(struct task_struct *tsk)
409 {
410         WARN_ON(!tsk->exit_state);
411         WARN_ON(atomic_read(&tsk->usage));
412         WARN_ON(tsk == current);
413
414         cgroup_free(tsk);
415         task_numa_free(tsk);
416         security_task_free(tsk);
417         exit_creds(tsk);
418         delayacct_tsk_free(tsk);
419         put_signal_struct(tsk->signal);
420
421         if (!profile_handoff_task(tsk))
422                 free_task(tsk);
423 }
424 EXPORT_SYMBOL_GPL(__put_task_struct);
425
426 void __init __weak arch_task_cache_init(void) { }
427
428 /*
429  * set_max_threads
430  */
431 static void set_max_threads(unsigned int max_threads_suggested)
432 {
433         u64 threads;
434
435         /*
436          * The number of threads shall be limited such that the thread
437          * structures may only consume a small part of the available memory.
438          */
439         if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
440                 threads = MAX_THREADS;
441         else
442                 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
443                                     (u64) THREAD_SIZE * 8UL);
444
445         if (threads > max_threads_suggested)
446                 threads = max_threads_suggested;
447
448         max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
449 }
450
451 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
452 /* Initialized by the architecture: */
453 int arch_task_struct_size __read_mostly;
454 #endif
455
456 void __init fork_init(void)
457 {
458         int i;
459 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
460 #ifndef ARCH_MIN_TASKALIGN
461 #define ARCH_MIN_TASKALIGN      0
462 #endif
463         int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
464
465         /* create a slab on which task_structs can be allocated */
466         task_struct_cachep = kmem_cache_create("task_struct",
467                         arch_task_struct_size, align,
468                         SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL);
469 #endif
470
471         /* do the arch specific task caches init */
472         arch_task_cache_init();
473
474         set_max_threads(MAX_THREADS);
475
476         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
477         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
478         init_task.signal->rlim[RLIMIT_SIGPENDING] =
479                 init_task.signal->rlim[RLIMIT_NPROC];
480
481         for (i = 0; i < UCOUNT_COUNTS; i++) {
482                 init_user_ns.ucount_max[i] = max_threads/2;
483         }
484
485 #ifdef CONFIG_VMAP_STACK
486         cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
487                           NULL, free_vm_stack_cache);
488 #endif
489
490         lockdep_init_task(&init_task);
491 }
492
493 int __weak arch_dup_task_struct(struct task_struct *dst,
494                                                struct task_struct *src)
495 {
496         *dst = *src;
497         return 0;
498 }
499
500 void set_task_stack_end_magic(struct task_struct *tsk)
501 {
502         unsigned long *stackend;
503
504         stackend = end_of_stack(tsk);
505         *stackend = STACK_END_MAGIC;    /* for overflow detection */
506 }
507
508 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
509 {
510         struct task_struct *tsk;
511         unsigned long *stack;
512         struct vm_struct *stack_vm_area;
513         int err;
514
515         if (node == NUMA_NO_NODE)
516                 node = tsk_fork_get_node(orig);
517         tsk = alloc_task_struct_node(node);
518         if (!tsk)
519                 return NULL;
520
521         stack = alloc_thread_stack_node(tsk, node);
522         if (!stack)
523                 goto free_tsk;
524
525         stack_vm_area = task_stack_vm_area(tsk);
526
527         err = arch_dup_task_struct(tsk, orig);
528
529         /*
530          * arch_dup_task_struct() clobbers the stack-related fields.  Make
531          * sure they're properly initialized before using any stack-related
532          * functions again.
533          */
534         tsk->stack = stack;
535 #ifdef CONFIG_VMAP_STACK
536         tsk->stack_vm_area = stack_vm_area;
537 #endif
538 #ifdef CONFIG_THREAD_INFO_IN_TASK
539         atomic_set(&tsk->stack_refcount, 1);
540 #endif
541
542         if (err)
543                 goto free_stack;
544
545 #ifdef CONFIG_SECCOMP
546         /*
547          * We must handle setting up seccomp filters once we're under
548          * the sighand lock in case orig has changed between now and
549          * then. Until then, filter must be NULL to avoid messing up
550          * the usage counts on the error path calling free_task.
551          */
552         tsk->seccomp.filter = NULL;
553 #endif
554
555         setup_thread_stack(tsk, orig);
556         clear_user_return_notifier(tsk);
557         clear_tsk_need_resched(tsk);
558         set_task_stack_end_magic(tsk);
559
560 #ifdef CONFIG_CC_STACKPROTECTOR
561         tsk->stack_canary = get_random_canary();
562 #endif
563
564         /*
565          * One for us, one for whoever does the "release_task()" (usually
566          * parent)
567          */
568         atomic_set(&tsk->usage, 2);
569 #ifdef CONFIG_BLK_DEV_IO_TRACE
570         tsk->btrace_seq = 0;
571 #endif
572         tsk->splice_pipe = NULL;
573         tsk->task_frag.page = NULL;
574         tsk->wake_q.next = NULL;
575
576         account_kernel_stack(tsk, 1);
577
578         kcov_task_init(tsk);
579
580 #ifdef CONFIG_FAULT_INJECTION
581         tsk->fail_nth = 0;
582 #endif
583
584         return tsk;
585
586 free_stack:
587         free_thread_stack(tsk);
588 free_tsk:
589         free_task_struct(tsk);
590         return NULL;
591 }
592
593 #ifdef CONFIG_MMU
594 static __latent_entropy int dup_mmap(struct mm_struct *mm,
595                                         struct mm_struct *oldmm)
596 {
597         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
598         struct rb_node **rb_link, *rb_parent;
599         int retval;
600         unsigned long charge;
601         LIST_HEAD(uf);
602
603         uprobe_start_dup_mmap();
604         if (down_write_killable(&oldmm->mmap_sem)) {
605                 retval = -EINTR;
606                 goto fail_uprobe_end;
607         }
608         flush_cache_dup_mm(oldmm);
609         uprobe_dup_mmap(oldmm, mm);
610         /*
611          * Not linked in yet - no deadlock potential:
612          */
613         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
614
615         /* No ordering required: file already has been exposed. */
616         RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
617
618         mm->total_vm = oldmm->total_vm;
619         mm->data_vm = oldmm->data_vm;
620         mm->exec_vm = oldmm->exec_vm;
621         mm->stack_vm = oldmm->stack_vm;
622
623         rb_link = &mm->mm_rb.rb_node;
624         rb_parent = NULL;
625         pprev = &mm->mmap;
626         retval = ksm_fork(mm, oldmm);
627         if (retval)
628                 goto out;
629         retval = khugepaged_fork(mm, oldmm);
630         if (retval)
631                 goto out;
632
633         prev = NULL;
634         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
635                 struct file *file;
636
637                 if (mpnt->vm_flags & VM_DONTCOPY) {
638                         vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
639                         continue;
640                 }
641                 charge = 0;
642                 if (mpnt->vm_flags & VM_ACCOUNT) {
643                         unsigned long len = vma_pages(mpnt);
644
645                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
646                                 goto fail_nomem;
647                         charge = len;
648                 }
649                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
650                 if (!tmp)
651                         goto fail_nomem;
652                 *tmp = *mpnt;
653                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
654                 retval = vma_dup_policy(mpnt, tmp);
655                 if (retval)
656                         goto fail_nomem_policy;
657                 tmp->vm_mm = mm;
658                 retval = dup_userfaultfd(tmp, &uf);
659                 if (retval)
660                         goto fail_nomem_anon_vma_fork;
661                 if (tmp->vm_flags & VM_WIPEONFORK) {
662                         /* VM_WIPEONFORK gets a clean slate in the child. */
663                         tmp->anon_vma = NULL;
664                         if (anon_vma_prepare(tmp))
665                                 goto fail_nomem_anon_vma_fork;
666                 } else if (anon_vma_fork(tmp, mpnt))
667                         goto fail_nomem_anon_vma_fork;
668                 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
669                 tmp->vm_next = tmp->vm_prev = NULL;
670                 file = tmp->vm_file;
671                 if (file) {
672                         struct inode *inode = file_inode(file);
673                         struct address_space *mapping = file->f_mapping;
674
675                         get_file(file);
676                         if (tmp->vm_flags & VM_DENYWRITE)
677                                 atomic_dec(&inode->i_writecount);
678                         i_mmap_lock_write(mapping);
679                         if (tmp->vm_flags & VM_SHARED)
680                                 atomic_inc(&mapping->i_mmap_writable);
681                         flush_dcache_mmap_lock(mapping);
682                         /* insert tmp into the share list, just after mpnt */
683                         vma_interval_tree_insert_after(tmp, mpnt,
684                                         &mapping->i_mmap);
685                         flush_dcache_mmap_unlock(mapping);
686                         i_mmap_unlock_write(mapping);
687                 }
688
689                 /*
690                  * Clear hugetlb-related page reserves for children. This only
691                  * affects MAP_PRIVATE mappings. Faults generated by the child
692                  * are not guaranteed to succeed, even if read-only
693                  */
694                 if (is_vm_hugetlb_page(tmp))
695                         reset_vma_resv_huge_pages(tmp);
696
697                 /*
698                  * Link in the new vma and copy the page table entries.
699                  */
700                 *pprev = tmp;
701                 pprev = &tmp->vm_next;
702                 tmp->vm_prev = prev;
703                 prev = tmp;
704
705                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
706                 rb_link = &tmp->vm_rb.rb_right;
707                 rb_parent = &tmp->vm_rb;
708
709                 mm->map_count++;
710                 if (!(tmp->vm_flags & VM_WIPEONFORK))
711                         retval = copy_page_range(mm, oldmm, mpnt);
712
713                 if (tmp->vm_ops && tmp->vm_ops->open)
714                         tmp->vm_ops->open(tmp);
715
716                 if (retval)
717                         goto out;
718         }
719         /* a new mm has just been created */
720         arch_dup_mmap(oldmm, mm);
721         retval = 0;
722 out:
723         up_write(&mm->mmap_sem);
724         flush_tlb_mm(oldmm);
725         up_write(&oldmm->mmap_sem);
726         dup_userfaultfd_complete(&uf);
727 fail_uprobe_end:
728         uprobe_end_dup_mmap();
729         return retval;
730 fail_nomem_anon_vma_fork:
731         mpol_put(vma_policy(tmp));
732 fail_nomem_policy:
733         kmem_cache_free(vm_area_cachep, tmp);
734 fail_nomem:
735         retval = -ENOMEM;
736         vm_unacct_memory(charge);
737         goto out;
738 }
739
740 static inline int mm_alloc_pgd(struct mm_struct *mm)
741 {
742         mm->pgd = pgd_alloc(mm);
743         if (unlikely(!mm->pgd))
744                 return -ENOMEM;
745         return 0;
746 }
747
748 static inline void mm_free_pgd(struct mm_struct *mm)
749 {
750         pgd_free(mm, mm->pgd);
751 }
752 #else
753 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
754 {
755         down_write(&oldmm->mmap_sem);
756         RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
757         up_write(&oldmm->mmap_sem);
758         return 0;
759 }
760 #define mm_alloc_pgd(mm)        (0)
761 #define mm_free_pgd(mm)
762 #endif /* CONFIG_MMU */
763
764 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
765
766 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
767 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
768
769 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
770
771 static int __init coredump_filter_setup(char *s)
772 {
773         default_dump_filter =
774                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
775                 MMF_DUMP_FILTER_MASK;
776         return 1;
777 }
778
779 __setup("coredump_filter=", coredump_filter_setup);
780
781 #include <linux/init_task.h>
782
783 static void mm_init_aio(struct mm_struct *mm)
784 {
785 #ifdef CONFIG_AIO
786         spin_lock_init(&mm->ioctx_lock);
787         mm->ioctx_table = NULL;
788 #endif
789 }
790
791 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
792 {
793 #ifdef CONFIG_MEMCG
794         mm->owner = p;
795 #endif
796 }
797
798 static void mm_init_uprobes_state(struct mm_struct *mm)
799 {
800 #ifdef CONFIG_UPROBES
801         mm->uprobes_state.xol_area = NULL;
802 #endif
803 }
804
805 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
806         struct user_namespace *user_ns)
807 {
808         mm->mmap = NULL;
809         mm->mm_rb = RB_ROOT;
810         mm->vmacache_seqnum = 0;
811         atomic_set(&mm->mm_users, 1);
812         atomic_set(&mm->mm_count, 1);
813         init_rwsem(&mm->mmap_sem);
814         INIT_LIST_HEAD(&mm->mmlist);
815         mm->core_state = NULL;
816         atomic_long_set(&mm->nr_ptes, 0);
817         mm_nr_pmds_init(mm);
818         mm->map_count = 0;
819         mm->locked_vm = 0;
820         mm->pinned_vm = 0;
821         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
822         spin_lock_init(&mm->page_table_lock);
823         mm_init_cpumask(mm);
824         mm_init_aio(mm);
825         mm_init_owner(mm, p);
826         RCU_INIT_POINTER(mm->exe_file, NULL);
827         mmu_notifier_mm_init(mm);
828         hmm_mm_init(mm);
829         init_tlb_flush_pending(mm);
830 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
831         mm->pmd_huge_pte = NULL;
832 #endif
833         mm_init_uprobes_state(mm);
834
835         if (current->mm) {
836                 mm->flags = current->mm->flags & MMF_INIT_MASK;
837                 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
838         } else {
839                 mm->flags = default_dump_filter;
840                 mm->def_flags = 0;
841         }
842
843         if (mm_alloc_pgd(mm))
844                 goto fail_nopgd;
845
846         if (init_new_context(p, mm))
847                 goto fail_nocontext;
848
849         mm->user_ns = get_user_ns(user_ns);
850         return mm;
851
852 fail_nocontext:
853         mm_free_pgd(mm);
854 fail_nopgd:
855         free_mm(mm);
856         return NULL;
857 }
858
859 static void check_mm(struct mm_struct *mm)
860 {
861         int i;
862
863         for (i = 0; i < NR_MM_COUNTERS; i++) {
864                 long x = atomic_long_read(&mm->rss_stat.count[i]);
865
866                 if (unlikely(x))
867                         printk(KERN_ALERT "BUG: Bad rss-counter state "
868                                           "mm:%p idx:%d val:%ld\n", mm, i, x);
869         }
870
871         if (atomic_long_read(&mm->nr_ptes))
872                 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n",
873                                 atomic_long_read(&mm->nr_ptes));
874         if (mm_nr_pmds(mm))
875                 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
876                                 mm_nr_pmds(mm));
877
878 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
879         VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
880 #endif
881 }
882
883 /*
884  * Allocate and initialize an mm_struct.
885  */
886 struct mm_struct *mm_alloc(void)
887 {
888         struct mm_struct *mm;
889
890         mm = allocate_mm();
891         if (!mm)
892                 return NULL;
893
894         memset(mm, 0, sizeof(*mm));
895         return mm_init(mm, current, current_user_ns());
896 }
897
898 /*
899  * Called when the last reference to the mm
900  * is dropped: either by a lazy thread or by
901  * mmput. Free the page directory and the mm.
902  */
903 void __mmdrop(struct mm_struct *mm)
904 {
905         BUG_ON(mm == &init_mm);
906         mm_free_pgd(mm);
907         destroy_context(mm);
908         hmm_mm_destroy(mm);
909         mmu_notifier_mm_destroy(mm);
910         check_mm(mm);
911         put_user_ns(mm->user_ns);
912         free_mm(mm);
913 }
914 EXPORT_SYMBOL_GPL(__mmdrop);
915
916 static inline void __mmput(struct mm_struct *mm)
917 {
918         VM_BUG_ON(atomic_read(&mm->mm_users));
919
920         uprobe_clear_state(mm);
921         exit_aio(mm);
922         ksm_exit(mm);
923         khugepaged_exit(mm); /* must run before exit_mmap */
924         exit_mmap(mm);
925         mm_put_huge_zero_page(mm);
926         set_mm_exe_file(mm, NULL);
927         if (!list_empty(&mm->mmlist)) {
928                 spin_lock(&mmlist_lock);
929                 list_del(&mm->mmlist);
930                 spin_unlock(&mmlist_lock);
931         }
932         if (mm->binfmt)
933                 module_put(mm->binfmt->module);
934         mmdrop(mm);
935 }
936
937 /*
938  * Decrement the use count and release all resources for an mm.
939  */
940 void mmput(struct mm_struct *mm)
941 {
942         might_sleep();
943
944         if (atomic_dec_and_test(&mm->mm_users))
945                 __mmput(mm);
946 }
947 EXPORT_SYMBOL_GPL(mmput);
948
949 /**
950  * set_mm_exe_file - change a reference to the mm's executable file
951  *
952  * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
953  *
954  * Main users are mmput() and sys_execve(). Callers prevent concurrent
955  * invocations: in mmput() nobody alive left, in execve task is single
956  * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
957  * mm->exe_file, but does so without using set_mm_exe_file() in order
958  * to do avoid the need for any locks.
959  */
960 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
961 {
962         struct file *old_exe_file;
963
964         /*
965          * It is safe to dereference the exe_file without RCU as
966          * this function is only called if nobody else can access
967          * this mm -- see comment above for justification.
968          */
969         old_exe_file = rcu_dereference_raw(mm->exe_file);
970
971         if (new_exe_file)
972                 get_file(new_exe_file);
973         rcu_assign_pointer(mm->exe_file, new_exe_file);
974         if (old_exe_file)
975                 fput(old_exe_file);
976 }
977
978 /**
979  * get_mm_exe_file - acquire a reference to the mm's executable file
980  *
981  * Returns %NULL if mm has no associated executable file.
982  * User must release file via fput().
983  */
984 struct file *get_mm_exe_file(struct mm_struct *mm)
985 {
986         struct file *exe_file;
987
988         rcu_read_lock();
989         exe_file = rcu_dereference(mm->exe_file);
990         if (exe_file && !get_file_rcu(exe_file))
991                 exe_file = NULL;
992         rcu_read_unlock();
993         return exe_file;
994 }
995 EXPORT_SYMBOL(get_mm_exe_file);
996
997 /**
998  * get_task_exe_file - acquire a reference to the task's executable file
999  *
1000  * Returns %NULL if task's mm (if any) has no associated executable file or
1001  * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1002  * User must release file via fput().
1003  */
1004 struct file *get_task_exe_file(struct task_struct *task)
1005 {
1006         struct file *exe_file = NULL;
1007         struct mm_struct *mm;
1008
1009         task_lock(task);
1010         mm = task->mm;
1011         if (mm) {
1012                 if (!(task->flags & PF_KTHREAD))
1013                         exe_file = get_mm_exe_file(mm);
1014         }
1015         task_unlock(task);
1016         return exe_file;
1017 }
1018 EXPORT_SYMBOL(get_task_exe_file);
1019
1020 /**
1021  * get_task_mm - acquire a reference to the task's mm
1022  *
1023  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
1024  * this kernel workthread has transiently adopted a user mm with use_mm,
1025  * to do its AIO) is not set and if so returns a reference to it, after
1026  * bumping up the use count.  User must release the mm via mmput()
1027  * after use.  Typically used by /proc and ptrace.
1028  */
1029 struct mm_struct *get_task_mm(struct task_struct *task)
1030 {
1031         struct mm_struct *mm;
1032
1033         task_lock(task);
1034         mm = task->mm;
1035         if (mm) {
1036                 if (task->flags & PF_KTHREAD)
1037                         mm = NULL;
1038                 else
1039                         mmget(mm);
1040         }
1041         task_unlock(task);
1042         return mm;
1043 }
1044 EXPORT_SYMBOL_GPL(get_task_mm);
1045
1046 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1047 {
1048         struct mm_struct *mm;
1049         int err;
1050
1051         err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
1052         if (err)
1053                 return ERR_PTR(err);
1054
1055         mm = get_task_mm(task);
1056         if (mm && mm != current->mm &&
1057                         !ptrace_may_access(task, mode)) {
1058                 mmput(mm);
1059                 mm = ERR_PTR(-EACCES);
1060         }
1061         mutex_unlock(&task->signal->cred_guard_mutex);
1062
1063         return mm;
1064 }
1065
1066 static void complete_vfork_done(struct task_struct *tsk)
1067 {
1068         struct completion *vfork;
1069
1070         task_lock(tsk);
1071         vfork = tsk->vfork_done;
1072         if (likely(vfork)) {
1073                 tsk->vfork_done = NULL;
1074                 complete(vfork);
1075         }
1076         task_unlock(tsk);
1077 }
1078
1079 static int wait_for_vfork_done(struct task_struct *child,
1080                                 struct completion *vfork)
1081 {
1082         int killed;
1083
1084         freezer_do_not_count();
1085         killed = wait_for_completion_killable(vfork);
1086         freezer_count();
1087
1088         if (killed) {
1089                 task_lock(child);
1090                 child->vfork_done = NULL;
1091                 task_unlock(child);
1092         }
1093
1094         put_task_struct(child);
1095         return killed;
1096 }
1097
1098 /* Please note the differences between mmput and mm_release.
1099  * mmput is called whenever we stop holding onto a mm_struct,
1100  * error success whatever.
1101  *
1102  * mm_release is called after a mm_struct has been removed
1103  * from the current process.
1104  *
1105  * This difference is important for error handling, when we
1106  * only half set up a mm_struct for a new process and need to restore
1107  * the old one.  Because we mmput the new mm_struct before
1108  * restoring the old one. . .
1109  * Eric Biederman 10 January 1998
1110  */
1111 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1112 {
1113         /* Get rid of any futexes when releasing the mm */
1114 #ifdef CONFIG_FUTEX
1115         if (unlikely(tsk->robust_list)) {
1116                 exit_robust_list(tsk);
1117                 tsk->robust_list = NULL;
1118         }
1119 #ifdef CONFIG_COMPAT
1120         if (unlikely(tsk->compat_robust_list)) {
1121                 compat_exit_robust_list(tsk);
1122                 tsk->compat_robust_list = NULL;
1123         }
1124 #endif
1125         if (unlikely(!list_empty(&tsk->pi_state_list)))
1126                 exit_pi_state_list(tsk);
1127 #endif
1128
1129         uprobe_free_utask(tsk);
1130
1131         /* Get rid of any cached register state */
1132         deactivate_mm(tsk, mm);
1133
1134         /*
1135          * Signal userspace if we're not exiting with a core dump
1136          * because we want to leave the value intact for debugging
1137          * purposes.
1138          */
1139         if (tsk->clear_child_tid) {
1140                 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1141                     atomic_read(&mm->mm_users) > 1) {
1142                         /*
1143                          * We don't check the error code - if userspace has
1144                          * not set up a proper pointer then tough luck.
1145                          */
1146                         put_user(0, tsk->clear_child_tid);
1147                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
1148                                         1, NULL, NULL, 0);
1149                 }
1150                 tsk->clear_child_tid = NULL;
1151         }
1152
1153         /*
1154          * All done, finally we can wake up parent and return this mm to him.
1155          * Also kthread_stop() uses this completion for synchronization.
1156          */
1157         if (tsk->vfork_done)
1158                 complete_vfork_done(tsk);
1159 }
1160
1161 /*
1162  * Allocate a new mm structure and copy contents from the
1163  * mm structure of the passed in task structure.
1164  */
1165 static struct mm_struct *dup_mm(struct task_struct *tsk)
1166 {
1167         struct mm_struct *mm, *oldmm = current->mm;
1168         int err;
1169
1170         mm = allocate_mm();
1171         if (!mm)
1172                 goto fail_nomem;
1173
1174         memcpy(mm, oldmm, sizeof(*mm));
1175
1176         if (!mm_init(mm, tsk, mm->user_ns))
1177                 goto fail_nomem;
1178
1179         err = dup_mmap(mm, oldmm);
1180         if (err)
1181                 goto free_pt;
1182
1183         mm->hiwater_rss = get_mm_rss(mm);
1184         mm->hiwater_vm = mm->total_vm;
1185
1186         if (mm->binfmt && !try_module_get(mm->binfmt->module))
1187                 goto free_pt;
1188
1189         return mm;
1190
1191 free_pt:
1192         /* don't put binfmt in mmput, we haven't got module yet */
1193         mm->binfmt = NULL;
1194         mmput(mm);
1195
1196 fail_nomem:
1197         return NULL;
1198 }
1199
1200 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1201 {
1202         struct mm_struct *mm, *oldmm;
1203         int retval;
1204
1205         tsk->min_flt = tsk->maj_flt = 0;
1206         tsk->nvcsw = tsk->nivcsw = 0;
1207 #ifdef CONFIG_DETECT_HUNG_TASK
1208         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1209 #endif
1210
1211         tsk->mm = NULL;
1212         tsk->active_mm = NULL;
1213
1214         /*
1215          * Are we cloning a kernel thread?
1216          *
1217          * We need to steal a active VM for that..
1218          */
1219         oldmm = current->mm;
1220         if (!oldmm)
1221                 return 0;
1222
1223         /* initialize the new vmacache entries */
1224         vmacache_flush(tsk);
1225
1226         if (clone_flags & CLONE_VM) {
1227                 mmget(oldmm);
1228                 mm = oldmm;
1229                 goto good_mm;
1230         }
1231
1232         retval = -ENOMEM;
1233         mm = dup_mm(tsk);
1234         if (!mm)
1235                 goto fail_nomem;
1236
1237 good_mm:
1238         tsk->mm = mm;
1239         tsk->active_mm = mm;
1240         return 0;
1241
1242 fail_nomem:
1243         return retval;
1244 }
1245
1246 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1247 {
1248         struct fs_struct *fs = current->fs;
1249         if (clone_flags & CLONE_FS) {
1250                 /* tsk->fs is already what we want */
1251                 spin_lock(&fs->lock);
1252                 if (fs->in_exec) {
1253                         spin_unlock(&fs->lock);
1254                         return -EAGAIN;
1255                 }
1256                 fs->users++;
1257                 spin_unlock(&fs->lock);
1258                 return 0;
1259         }
1260         tsk->fs = copy_fs_struct(fs);
1261         if (!tsk->fs)
1262                 return -ENOMEM;
1263         return 0;
1264 }
1265
1266 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1267 {
1268         struct files_struct *oldf, *newf;
1269         int error = 0;
1270
1271         /*
1272          * A background process may not have any files ...
1273          */
1274         oldf = current->files;
1275         if (!oldf)
1276                 goto out;
1277
1278         if (clone_flags & CLONE_FILES) {
1279                 atomic_inc(&oldf->count);
1280                 goto out;
1281         }
1282
1283         newf = dup_fd(oldf, &error);
1284         if (!newf)
1285                 goto out;
1286
1287         tsk->files = newf;
1288         error = 0;
1289 out:
1290         return error;
1291 }
1292
1293 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1294 {
1295 #ifdef CONFIG_BLOCK
1296         struct io_context *ioc = current->io_context;
1297         struct io_context *new_ioc;
1298
1299         if (!ioc)
1300                 return 0;
1301         /*
1302          * Share io context with parent, if CLONE_IO is set
1303          */
1304         if (clone_flags & CLONE_IO) {
1305                 ioc_task_link(ioc);
1306                 tsk->io_context = ioc;
1307         } else if (ioprio_valid(ioc->ioprio)) {
1308                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1309                 if (unlikely(!new_ioc))
1310                         return -ENOMEM;
1311
1312                 new_ioc->ioprio = ioc->ioprio;
1313                 put_io_context(new_ioc);
1314         }
1315 #endif
1316         return 0;
1317 }
1318
1319 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1320 {
1321         struct sighand_struct *sig;
1322
1323         if (clone_flags & CLONE_SIGHAND) {
1324                 atomic_inc(&current->sighand->count);
1325                 return 0;
1326         }
1327         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1328         rcu_assign_pointer(tsk->sighand, sig);
1329         if (!sig)
1330                 return -ENOMEM;
1331
1332         atomic_set(&sig->count, 1);
1333         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1334         return 0;
1335 }
1336
1337 void __cleanup_sighand(struct sighand_struct *sighand)
1338 {
1339         if (atomic_dec_and_test(&sighand->count)) {
1340                 signalfd_cleanup(sighand);
1341                 /*
1342                  * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1343                  * without an RCU grace period, see __lock_task_sighand().
1344                  */
1345                 kmem_cache_free(sighand_cachep, sighand);
1346         }
1347 }
1348
1349 #ifdef CONFIG_POSIX_TIMERS
1350 /*
1351  * Initialize POSIX timer handling for a thread group.
1352  */
1353 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1354 {
1355         unsigned long cpu_limit;
1356
1357         cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1358         if (cpu_limit != RLIM_INFINITY) {
1359                 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC;
1360                 sig->cputimer.running = true;
1361         }
1362
1363         /* The timer lists. */
1364         INIT_LIST_HEAD(&sig->cpu_timers[0]);
1365         INIT_LIST_HEAD(&sig->cpu_timers[1]);
1366         INIT_LIST_HEAD(&sig->cpu_timers[2]);
1367 }
1368 #else
1369 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { }
1370 #endif
1371
1372 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1373 {
1374         struct signal_struct *sig;
1375
1376         if (clone_flags & CLONE_THREAD)
1377                 return 0;
1378
1379         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1380         tsk->signal = sig;
1381         if (!sig)
1382                 return -ENOMEM;
1383
1384         sig->nr_threads = 1;
1385         atomic_set(&sig->live, 1);
1386         atomic_set(&sig->sigcnt, 1);
1387
1388         /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1389         sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1390         tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1391
1392         init_waitqueue_head(&sig->wait_chldexit);
1393         sig->curr_target = tsk;
1394         init_sigpending(&sig->shared_pending);
1395         seqlock_init(&sig->stats_lock);
1396         prev_cputime_init(&sig->prev_cputime);
1397
1398 #ifdef CONFIG_POSIX_TIMERS
1399         INIT_LIST_HEAD(&sig->posix_timers);
1400         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1401         sig->real_timer.function = it_real_fn;
1402 #endif
1403
1404         task_lock(current->group_leader);
1405         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1406         task_unlock(current->group_leader);
1407
1408         posix_cpu_timers_init_group(sig);
1409
1410         tty_audit_fork(sig);
1411         sched_autogroup_fork(sig);
1412
1413         sig->oom_score_adj = current->signal->oom_score_adj;
1414         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1415
1416         mutex_init(&sig->cred_guard_mutex);
1417
1418         return 0;
1419 }
1420
1421 static void copy_seccomp(struct task_struct *p)
1422 {
1423 #ifdef CONFIG_SECCOMP
1424         /*
1425          * Must be called with sighand->lock held, which is common to
1426          * all threads in the group. Holding cred_guard_mutex is not
1427          * needed because this new task is not yet running and cannot
1428          * be racing exec.
1429          */
1430         assert_spin_locked(&current->sighand->siglock);
1431
1432         /* Ref-count the new filter user, and assign it. */
1433         get_seccomp_filter(current);
1434         p->seccomp = current->seccomp;
1435
1436         /*
1437          * Explicitly enable no_new_privs here in case it got set
1438          * between the task_struct being duplicated and holding the
1439          * sighand lock. The seccomp state and nnp must be in sync.
1440          */
1441         if (task_no_new_privs(current))
1442                 task_set_no_new_privs(p);
1443
1444         /*
1445          * If the parent gained a seccomp mode after copying thread
1446          * flags and between before we held the sighand lock, we have
1447          * to manually enable the seccomp thread flag here.
1448          */
1449         if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1450                 set_tsk_thread_flag(p, TIF_SECCOMP);
1451 #endif
1452 }
1453
1454 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1455 {
1456         current->clear_child_tid = tidptr;
1457
1458         return task_pid_vnr(current);
1459 }
1460
1461 static void rt_mutex_init_task(struct task_struct *p)
1462 {
1463         raw_spin_lock_init(&p->pi_lock);
1464 #ifdef CONFIG_RT_MUTEXES
1465         p->pi_waiters = RB_ROOT_CACHED;
1466         p->pi_top_task = NULL;
1467         p->pi_blocked_on = NULL;
1468 #endif
1469 }
1470
1471 #ifdef CONFIG_POSIX_TIMERS
1472 /*
1473  * Initialize POSIX timer handling for a single task.
1474  */
1475 static void posix_cpu_timers_init(struct task_struct *tsk)
1476 {
1477         tsk->cputime_expires.prof_exp = 0;
1478         tsk->cputime_expires.virt_exp = 0;
1479         tsk->cputime_expires.sched_exp = 0;
1480         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1481         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1482         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1483 }
1484 #else
1485 static inline void posix_cpu_timers_init(struct task_struct *tsk) { }
1486 #endif
1487
1488 static inline void
1489 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1490 {
1491          task->pids[type].pid = pid;
1492 }
1493
1494 static inline void rcu_copy_process(struct task_struct *p)
1495 {
1496 #ifdef CONFIG_PREEMPT_RCU
1497         p->rcu_read_lock_nesting = 0;
1498         p->rcu_read_unlock_special.s = 0;
1499         p->rcu_blocked_node = NULL;
1500         INIT_LIST_HEAD(&p->rcu_node_entry);
1501 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1502 #ifdef CONFIG_TASKS_RCU
1503         p->rcu_tasks_holdout = false;
1504         INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1505         p->rcu_tasks_idle_cpu = -1;
1506 #endif /* #ifdef CONFIG_TASKS_RCU */
1507 }
1508
1509 /*
1510  * This creates a new process as a copy of the old one,
1511  * but does not actually start it yet.
1512  *
1513  * It copies the registers, and all the appropriate
1514  * parts of the process environment (as per the clone
1515  * flags). The actual kick-off is left to the caller.
1516  */
1517 static __latent_entropy struct task_struct *copy_process(
1518                                         unsigned long clone_flags,
1519                                         unsigned long stack_start,
1520                                         unsigned long stack_size,
1521                                         int __user *child_tidptr,
1522                                         struct pid *pid,
1523                                         int trace,
1524                                         unsigned long tls,
1525                                         int node)
1526 {
1527         int retval;
1528         struct task_struct *p;
1529
1530         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1531                 return ERR_PTR(-EINVAL);
1532
1533         if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1534                 return ERR_PTR(-EINVAL);
1535
1536         /*
1537          * Thread groups must share signals as well, and detached threads
1538          * can only be started up within the thread group.
1539          */
1540         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1541                 return ERR_PTR(-EINVAL);
1542
1543         /*
1544          * Shared signal handlers imply shared VM. By way of the above,
1545          * thread groups also imply shared VM. Blocking this case allows
1546          * for various simplifications in other code.
1547          */
1548         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1549                 return ERR_PTR(-EINVAL);
1550
1551         /*
1552          * Siblings of global init remain as zombies on exit since they are
1553          * not reaped by their parent (swapper). To solve this and to avoid
1554          * multi-rooted process trees, prevent global and container-inits
1555          * from creating siblings.
1556          */
1557         if ((clone_flags & CLONE_PARENT) &&
1558                                 current->signal->flags & SIGNAL_UNKILLABLE)
1559                 return ERR_PTR(-EINVAL);
1560
1561         /*
1562          * If the new process will be in a different pid or user namespace
1563          * do not allow it to share a thread group with the forking task.
1564          */
1565         if (clone_flags & CLONE_THREAD) {
1566                 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1567                     (task_active_pid_ns(current) !=
1568                                 current->nsproxy->pid_ns_for_children))
1569                         return ERR_PTR(-EINVAL);
1570         }
1571
1572         retval = -ENOMEM;
1573         p = dup_task_struct(current, node);
1574         if (!p)
1575                 goto fork_out;
1576
1577         /*
1578          * This _must_ happen before we call free_task(), i.e. before we jump
1579          * to any of the bad_fork_* labels. This is to avoid freeing
1580          * p->set_child_tid which is (ab)used as a kthread's data pointer for
1581          * kernel threads (PF_KTHREAD).
1582          */
1583         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1584         /*
1585          * Clear TID on mm_release()?
1586          */
1587         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1588
1589         ftrace_graph_init_task(p);
1590
1591         rt_mutex_init_task(p);
1592
1593 #ifdef CONFIG_PROVE_LOCKING
1594         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1595         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1596 #endif
1597         retval = -EAGAIN;
1598         if (atomic_read(&p->real_cred->user->processes) >=
1599                         task_rlimit(p, RLIMIT_NPROC)) {
1600                 if (p->real_cred->user != INIT_USER &&
1601                     !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1602                         goto bad_fork_free;
1603         }
1604         current->flags &= ~PF_NPROC_EXCEEDED;
1605
1606         retval = copy_creds(p, clone_flags);
1607         if (retval < 0)
1608                 goto bad_fork_free;
1609
1610         /*
1611          * If multiple threads are within copy_process(), then this check
1612          * triggers too late. This doesn't hurt, the check is only there
1613          * to stop root fork bombs.
1614          */
1615         retval = -EAGAIN;
1616         if (nr_threads >= max_threads)
1617                 goto bad_fork_cleanup_count;
1618
1619         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1620         p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1621         p->flags |= PF_FORKNOEXEC;
1622         INIT_LIST_HEAD(&p->children);
1623         INIT_LIST_HEAD(&p->sibling);
1624         rcu_copy_process(p);
1625         p->vfork_done = NULL;
1626         spin_lock_init(&p->alloc_lock);
1627
1628         init_sigpending(&p->pending);
1629
1630         p->utime = p->stime = p->gtime = 0;
1631 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1632         p->utimescaled = p->stimescaled = 0;
1633 #endif
1634         prev_cputime_init(&p->prev_cputime);
1635
1636 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1637         seqcount_init(&p->vtime.seqcount);
1638         p->vtime.starttime = 0;
1639         p->vtime.state = VTIME_INACTIVE;
1640 #endif
1641
1642 #if defined(SPLIT_RSS_COUNTING)
1643         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1644 #endif
1645
1646         p->default_timer_slack_ns = current->timer_slack_ns;
1647
1648         task_io_accounting_init(&p->ioac);
1649         acct_clear_integrals(p);
1650
1651         posix_cpu_timers_init(p);
1652
1653         p->start_time = ktime_get_ns();
1654         p->real_start_time = ktime_get_boot_ns();
1655         p->io_context = NULL;
1656         p->audit_context = NULL;
1657         cgroup_fork(p);
1658 #ifdef CONFIG_NUMA
1659         p->mempolicy = mpol_dup(p->mempolicy);
1660         if (IS_ERR(p->mempolicy)) {
1661                 retval = PTR_ERR(p->mempolicy);
1662                 p->mempolicy = NULL;
1663                 goto bad_fork_cleanup_threadgroup_lock;
1664         }
1665 #endif
1666 #ifdef CONFIG_CPUSETS
1667         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1668         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1669         seqcount_init(&p->mems_allowed_seq);
1670 #endif
1671 #ifdef CONFIG_TRACE_IRQFLAGS
1672         p->irq_events = 0;
1673         p->hardirqs_enabled = 0;
1674         p->hardirq_enable_ip = 0;
1675         p->hardirq_enable_event = 0;
1676         p->hardirq_disable_ip = _THIS_IP_;
1677         p->hardirq_disable_event = 0;
1678         p->softirqs_enabled = 1;
1679         p->softirq_enable_ip = _THIS_IP_;
1680         p->softirq_enable_event = 0;
1681         p->softirq_disable_ip = 0;
1682         p->softirq_disable_event = 0;
1683         p->hardirq_context = 0;
1684         p->softirq_context = 0;
1685 #endif
1686
1687         p->pagefault_disabled = 0;
1688
1689 #ifdef CONFIG_LOCKDEP
1690         p->lockdep_depth = 0; /* no locks held yet */
1691         p->curr_chain_key = 0;
1692         p->lockdep_recursion = 0;
1693         lockdep_init_task(p);
1694 #endif
1695
1696 #ifdef CONFIG_DEBUG_MUTEXES
1697         p->blocked_on = NULL; /* not blocked yet */
1698 #endif
1699 #ifdef CONFIG_BCACHE
1700         p->sequential_io        = 0;
1701         p->sequential_io_avg    = 0;
1702 #endif
1703
1704         /* Perform scheduler related setup. Assign this task to a CPU. */
1705         retval = sched_fork(clone_flags, p);
1706         if (retval)
1707                 goto bad_fork_cleanup_policy;
1708
1709         retval = perf_event_init_task(p);
1710         if (retval)
1711                 goto bad_fork_cleanup_policy;
1712         retval = audit_alloc(p);
1713         if (retval)
1714                 goto bad_fork_cleanup_perf;
1715         /* copy all the process information */
1716         shm_init_task(p);
1717         retval = security_task_alloc(p, clone_flags);
1718         if (retval)
1719                 goto bad_fork_cleanup_audit;
1720         retval = copy_semundo(clone_flags, p);
1721         if (retval)
1722                 goto bad_fork_cleanup_security;
1723         retval = copy_files(clone_flags, p);
1724         if (retval)
1725                 goto bad_fork_cleanup_semundo;
1726         retval = copy_fs(clone_flags, p);
1727         if (retval)
1728                 goto bad_fork_cleanup_files;
1729         retval = copy_sighand(clone_flags, p);
1730         if (retval)
1731                 goto bad_fork_cleanup_fs;
1732         retval = copy_signal(clone_flags, p);
1733         if (retval)
1734                 goto bad_fork_cleanup_sighand;
1735         retval = copy_mm(clone_flags, p);
1736         if (retval)
1737                 goto bad_fork_cleanup_signal;
1738         retval = copy_namespaces(clone_flags, p);
1739         if (retval)
1740                 goto bad_fork_cleanup_mm;
1741         retval = copy_io(clone_flags, p);
1742         if (retval)
1743                 goto bad_fork_cleanup_namespaces;
1744         retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1745         if (retval)
1746                 goto bad_fork_cleanup_io;
1747
1748         if (pid != &init_struct_pid) {
1749                 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1750                 if (IS_ERR(pid)) {
1751                         retval = PTR_ERR(pid);
1752                         goto bad_fork_cleanup_thread;
1753                 }
1754         }
1755
1756 #ifdef CONFIG_BLOCK
1757         p->plug = NULL;
1758 #endif
1759 #ifdef CONFIG_FUTEX
1760         p->robust_list = NULL;
1761 #ifdef CONFIG_COMPAT
1762         p->compat_robust_list = NULL;
1763 #endif
1764         INIT_LIST_HEAD(&p->pi_state_list);
1765         p->pi_state_cache = NULL;
1766 #endif
1767         /*
1768          * sigaltstack should be cleared when sharing the same VM
1769          */
1770         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1771                 sas_ss_reset(p);
1772
1773         /*
1774          * Syscall tracing and stepping should be turned off in the
1775          * child regardless of CLONE_PTRACE.
1776          */
1777         user_disable_single_step(p);
1778         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1779 #ifdef TIF_SYSCALL_EMU
1780         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1781 #endif
1782         clear_all_latency_tracing(p);
1783
1784         /* ok, now we should be set up.. */
1785         p->pid = pid_nr(pid);
1786         if (clone_flags & CLONE_THREAD) {
1787                 p->exit_signal = -1;
1788                 p->group_leader = current->group_leader;
1789                 p->tgid = current->tgid;
1790         } else {
1791                 if (clone_flags & CLONE_PARENT)
1792                         p->exit_signal = current->group_leader->exit_signal;
1793                 else
1794                         p->exit_signal = (clone_flags & CSIGNAL);
1795                 p->group_leader = p;
1796                 p->tgid = p->pid;
1797         }
1798
1799         p->nr_dirtied = 0;
1800         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1801         p->dirty_paused_when = 0;
1802
1803         p->pdeath_signal = 0;
1804         INIT_LIST_HEAD(&p->thread_group);
1805         p->task_works = NULL;
1806
1807         cgroup_threadgroup_change_begin(current);
1808         /*
1809          * Ensure that the cgroup subsystem policies allow the new process to be
1810          * forked. It should be noted the the new process's css_set can be changed
1811          * between here and cgroup_post_fork() if an organisation operation is in
1812          * progress.
1813          */
1814         retval = cgroup_can_fork(p);
1815         if (retval)
1816                 goto bad_fork_free_pid;
1817
1818         /*
1819          * Make it visible to the rest of the system, but dont wake it up yet.
1820          * Need tasklist lock for parent etc handling!
1821          */
1822         write_lock_irq(&tasklist_lock);
1823
1824         /* CLONE_PARENT re-uses the old parent */
1825         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1826                 p->real_parent = current->real_parent;
1827                 p->parent_exec_id = current->parent_exec_id;
1828         } else {
1829                 p->real_parent = current;
1830                 p->parent_exec_id = current->self_exec_id;
1831         }
1832
1833         klp_copy_process(p);
1834
1835         spin_lock(&current->sighand->siglock);
1836
1837         /*
1838          * Copy seccomp details explicitly here, in case they were changed
1839          * before holding sighand lock.
1840          */
1841         copy_seccomp(p);
1842
1843         /*
1844          * Process group and session signals need to be delivered to just the
1845          * parent before the fork or both the parent and the child after the
1846          * fork. Restart if a signal comes in before we add the new process to
1847          * it's process group.
1848          * A fatal signal pending means that current will exit, so the new
1849          * thread can't slip out of an OOM kill (or normal SIGKILL).
1850         */
1851         recalc_sigpending();
1852         if (signal_pending(current)) {
1853                 retval = -ERESTARTNOINTR;
1854                 goto bad_fork_cancel_cgroup;
1855         }
1856         if (unlikely(!(ns_of_pid(pid)->nr_hashed & PIDNS_HASH_ADDING))) {
1857                 retval = -ENOMEM;
1858                 goto bad_fork_cancel_cgroup;
1859         }
1860
1861         if (likely(p->pid)) {
1862                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1863
1864                 init_task_pid(p, PIDTYPE_PID, pid);
1865                 if (thread_group_leader(p)) {
1866                         init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1867                         init_task_pid(p, PIDTYPE_SID, task_session(current));
1868
1869                         if (is_child_reaper(pid)) {
1870                                 ns_of_pid(pid)->child_reaper = p;
1871                                 p->signal->flags |= SIGNAL_UNKILLABLE;
1872                         }
1873
1874                         p->signal->leader_pid = pid;
1875                         p->signal->tty = tty_kref_get(current->signal->tty);
1876                         /*
1877                          * Inherit has_child_subreaper flag under the same
1878                          * tasklist_lock with adding child to the process tree
1879                          * for propagate_has_child_subreaper optimization.
1880                          */
1881                         p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
1882                                                          p->real_parent->signal->is_child_subreaper;
1883                         list_add_tail(&p->sibling, &p->real_parent->children);
1884                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1885                         attach_pid(p, PIDTYPE_PGID);
1886                         attach_pid(p, PIDTYPE_SID);
1887                         __this_cpu_inc(process_counts);
1888                 } else {
1889                         current->signal->nr_threads++;
1890                         atomic_inc(&current->signal->live);
1891                         atomic_inc(&current->signal->sigcnt);
1892                         list_add_tail_rcu(&p->thread_group,
1893                                           &p->group_leader->thread_group);
1894                         list_add_tail_rcu(&p->thread_node,
1895                                           &p->signal->thread_head);
1896                 }
1897                 attach_pid(p, PIDTYPE_PID);
1898                 nr_threads++;
1899         }
1900
1901         total_forks++;
1902         spin_unlock(&current->sighand->siglock);
1903         syscall_tracepoint_update(p);
1904         write_unlock_irq(&tasklist_lock);
1905
1906         proc_fork_connector(p);
1907         cgroup_post_fork(p);
1908         cgroup_threadgroup_change_end(current);
1909         perf_event_fork(p);
1910
1911         trace_task_newtask(p, clone_flags);
1912         uprobe_copy_process(p, clone_flags);
1913
1914         return p;
1915
1916 bad_fork_cancel_cgroup:
1917         spin_unlock(&current->sighand->siglock);
1918         write_unlock_irq(&tasklist_lock);
1919         cgroup_cancel_fork(p);
1920 bad_fork_free_pid:
1921         cgroup_threadgroup_change_end(current);
1922         if (pid != &init_struct_pid)
1923                 free_pid(pid);
1924 bad_fork_cleanup_thread:
1925         exit_thread(p);
1926 bad_fork_cleanup_io:
1927         if (p->io_context)
1928                 exit_io_context(p);
1929 bad_fork_cleanup_namespaces:
1930         exit_task_namespaces(p);
1931 bad_fork_cleanup_mm:
1932         if (p->mm)
1933                 mmput(p->mm);
1934 bad_fork_cleanup_signal:
1935         if (!(clone_flags & CLONE_THREAD))
1936                 free_signal_struct(p->signal);
1937 bad_fork_cleanup_sighand:
1938         __cleanup_sighand(p->sighand);
1939 bad_fork_cleanup_fs:
1940         exit_fs(p); /* blocking */
1941 bad_fork_cleanup_files:
1942         exit_files(p); /* blocking */
1943 bad_fork_cleanup_semundo:
1944         exit_sem(p);
1945 bad_fork_cleanup_security:
1946         security_task_free(p);
1947 bad_fork_cleanup_audit:
1948         audit_free(p);
1949 bad_fork_cleanup_perf:
1950         perf_event_free_task(p);
1951 bad_fork_cleanup_policy:
1952         lockdep_free_task(p);
1953 #ifdef CONFIG_NUMA
1954         mpol_put(p->mempolicy);
1955 bad_fork_cleanup_threadgroup_lock:
1956 #endif
1957         delayacct_tsk_free(p);
1958 bad_fork_cleanup_count:
1959         atomic_dec(&p->cred->user->processes);
1960         exit_creds(p);
1961 bad_fork_free:
1962         p->state = TASK_DEAD;
1963         put_task_stack(p);
1964         free_task(p);
1965 fork_out:
1966         return ERR_PTR(retval);
1967 }
1968
1969 static inline void init_idle_pids(struct pid_link *links)
1970 {
1971         enum pid_type type;
1972
1973         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1974                 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1975                 links[type].pid = &init_struct_pid;
1976         }
1977 }
1978
1979 struct task_struct *fork_idle(int cpu)
1980 {
1981         struct task_struct *task;
1982         task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0,
1983                             cpu_to_node(cpu));
1984         if (!IS_ERR(task)) {
1985                 init_idle_pids(task->pids);
1986                 init_idle(task, cpu);
1987         }
1988
1989         return task;
1990 }
1991
1992 /*
1993  *  Ok, this is the main fork-routine.
1994  *
1995  * It copies the process, and if successful kick-starts
1996  * it and waits for it to finish using the VM if required.
1997  */
1998 long _do_fork(unsigned long clone_flags,
1999               unsigned long stack_start,
2000               unsigned long stack_size,
2001               int __user *parent_tidptr,
2002               int __user *child_tidptr,
2003               unsigned long tls)
2004 {
2005         struct task_struct *p;
2006         int trace = 0;
2007         long nr;
2008
2009         /*
2010          * Determine whether and which event to report to ptracer.  When
2011          * called from kernel_thread or CLONE_UNTRACED is explicitly
2012          * requested, no event is reported; otherwise, report if the event
2013          * for the type of forking is enabled.
2014          */
2015         if (!(clone_flags & CLONE_UNTRACED)) {
2016                 if (clone_flags & CLONE_VFORK)
2017                         trace = PTRACE_EVENT_VFORK;
2018                 else if ((clone_flags & CSIGNAL) != SIGCHLD)
2019                         trace = PTRACE_EVENT_CLONE;
2020                 else
2021                         trace = PTRACE_EVENT_FORK;
2022
2023                 if (likely(!ptrace_event_enabled(current, trace)))
2024                         trace = 0;
2025         }
2026
2027         p = copy_process(clone_flags, stack_start, stack_size,
2028                          child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
2029         add_latent_entropy();
2030         /*
2031          * Do this prior waking up the new thread - the thread pointer
2032          * might get invalid after that point, if the thread exits quickly.
2033          */
2034         if (!IS_ERR(p)) {
2035                 struct completion vfork;
2036                 struct pid *pid;
2037
2038                 trace_sched_process_fork(current, p);
2039
2040                 pid = get_task_pid(p, PIDTYPE_PID);
2041                 nr = pid_vnr(pid);
2042
2043                 if (clone_flags & CLONE_PARENT_SETTID)
2044                         put_user(nr, parent_tidptr);
2045
2046                 if (clone_flags & CLONE_VFORK) {
2047                         p->vfork_done = &vfork;
2048                         init_completion(&vfork);
2049                         get_task_struct(p);
2050                 }
2051
2052                 wake_up_new_task(p);
2053
2054                 /* forking complete and child started to run, tell ptracer */
2055                 if (unlikely(trace))
2056                         ptrace_event_pid(trace, pid);
2057
2058                 if (clone_flags & CLONE_VFORK) {
2059                         if (!wait_for_vfork_done(p, &vfork))
2060                                 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2061                 }
2062
2063                 put_pid(pid);
2064         } else {
2065                 nr = PTR_ERR(p);
2066         }
2067         return nr;
2068 }
2069
2070 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
2071 /* For compatibility with architectures that call do_fork directly rather than
2072  * using the syscall entry points below. */
2073 long do_fork(unsigned long clone_flags,
2074               unsigned long stack_start,
2075               unsigned long stack_size,
2076               int __user *parent_tidptr,
2077               int __user *child_tidptr)
2078 {
2079         return _do_fork(clone_flags, stack_start, stack_size,
2080                         parent_tidptr, child_tidptr, 0);
2081 }
2082 #endif
2083
2084 /*
2085  * Create a kernel thread.
2086  */
2087 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2088 {
2089         return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
2090                 (unsigned long)arg, NULL, NULL, 0);
2091 }
2092
2093 #ifdef __ARCH_WANT_SYS_FORK
2094 SYSCALL_DEFINE0(fork)
2095 {
2096 #ifdef CONFIG_MMU
2097         return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
2098 #else
2099         /* can not support in nommu mode */
2100         return -EINVAL;
2101 #endif
2102 }
2103 #endif
2104
2105 #ifdef __ARCH_WANT_SYS_VFORK
2106 SYSCALL_DEFINE0(vfork)
2107 {
2108         return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
2109                         0, NULL, NULL, 0);
2110 }
2111 #endif
2112
2113 #ifdef __ARCH_WANT_SYS_CLONE
2114 #ifdef CONFIG_CLONE_BACKWARDS
2115 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2116                  int __user *, parent_tidptr,
2117                  unsigned long, tls,
2118                  int __user *, child_tidptr)
2119 #elif defined(CONFIG_CLONE_BACKWARDS2)
2120 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2121                  int __user *, parent_tidptr,
2122                  int __user *, child_tidptr,
2123                  unsigned long, tls)
2124 #elif defined(CONFIG_CLONE_BACKWARDS3)
2125 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2126                 int, stack_size,
2127                 int __user *, parent_tidptr,
2128                 int __user *, child_tidptr,
2129                 unsigned long, tls)
2130 #else
2131 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2132                  int __user *, parent_tidptr,
2133                  int __user *, child_tidptr,
2134                  unsigned long, tls)
2135 #endif
2136 {
2137         return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
2138 }
2139 #endif
2140
2141 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2142 {
2143         struct task_struct *leader, *parent, *child;
2144         int res;
2145
2146         read_lock(&tasklist_lock);
2147         leader = top = top->group_leader;
2148 down:
2149         for_each_thread(leader, parent) {
2150                 list_for_each_entry(child, &parent->children, sibling) {
2151                         res = visitor(child, data);
2152                         if (res) {
2153                                 if (res < 0)
2154                                         goto out;
2155                                 leader = child;
2156                                 goto down;
2157                         }
2158 up:
2159                         ;
2160                 }
2161         }
2162
2163         if (leader != top) {
2164                 child = leader;
2165                 parent = child->real_parent;
2166                 leader = parent->group_leader;
2167                 goto up;
2168         }
2169 out:
2170         read_unlock(&tasklist_lock);
2171 }
2172
2173 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2174 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2175 #endif
2176
2177 static void sighand_ctor(void *data)
2178 {
2179         struct sighand_struct *sighand = data;
2180
2181         spin_lock_init(&sighand->siglock);
2182         init_waitqueue_head(&sighand->signalfd_wqh);
2183 }
2184
2185 void __init proc_caches_init(void)
2186 {
2187         sighand_cachep = kmem_cache_create("sighand_cache",
2188                         sizeof(struct sighand_struct), 0,
2189                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2190                         SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor);
2191         signal_cachep = kmem_cache_create("signal_cache",
2192                         sizeof(struct signal_struct), 0,
2193                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2194                         NULL);
2195         files_cachep = kmem_cache_create("files_cache",
2196                         sizeof(struct files_struct), 0,
2197                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2198                         NULL);
2199         fs_cachep = kmem_cache_create("fs_cache",
2200                         sizeof(struct fs_struct), 0,
2201                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2202                         NULL);
2203         /*
2204          * FIXME! The "sizeof(struct mm_struct)" currently includes the
2205          * whole struct cpumask for the OFFSTACK case. We could change
2206          * this to *only* allocate as much of it as required by the
2207          * maximum number of CPU's we can ever have.  The cpumask_allocation
2208          * is at the end of the structure, exactly for that reason.
2209          */
2210         mm_cachep = kmem_cache_create("mm_struct",
2211                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
2212                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2213                         NULL);
2214         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2215         mmap_init();
2216         nsproxy_cache_init();
2217 }
2218
2219 /*
2220  * Check constraints on flags passed to the unshare system call.
2221  */
2222 static int check_unshare_flags(unsigned long unshare_flags)
2223 {
2224         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2225                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2226                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2227                                 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2228                 return -EINVAL;
2229         /*
2230          * Not implemented, but pretend it works if there is nothing
2231          * to unshare.  Note that unsharing the address space or the
2232          * signal handlers also need to unshare the signal queues (aka
2233          * CLONE_THREAD).
2234          */
2235         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2236                 if (!thread_group_empty(current))
2237                         return -EINVAL;
2238         }
2239         if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2240                 if (atomic_read(&current->sighand->count) > 1)
2241                         return -EINVAL;
2242         }
2243         if (unshare_flags & CLONE_VM) {
2244                 if (!current_is_single_threaded())
2245                         return -EINVAL;
2246         }
2247
2248         return 0;
2249 }
2250
2251 /*
2252  * Unshare the filesystem structure if it is being shared
2253  */
2254 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2255 {
2256         struct fs_struct *fs = current->fs;
2257
2258         if (!(unshare_flags & CLONE_FS) || !fs)
2259                 return 0;
2260
2261         /* don't need lock here; in the worst case we'll do useless copy */
2262         if (fs->users == 1)
2263                 return 0;
2264
2265         *new_fsp = copy_fs_struct(fs);
2266         if (!*new_fsp)
2267                 return -ENOMEM;
2268
2269         return 0;
2270 }
2271
2272 /*
2273  * Unshare file descriptor table if it is being shared
2274  */
2275 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2276 {
2277         struct files_struct *fd = current->files;
2278         int error = 0;
2279
2280         if ((unshare_flags & CLONE_FILES) &&
2281             (fd && atomic_read(&fd->count) > 1)) {
2282                 *new_fdp = dup_fd(fd, &error);
2283                 if (!*new_fdp)
2284                         return error;
2285         }
2286
2287         return 0;
2288 }
2289
2290 /*
2291  * unshare allows a process to 'unshare' part of the process
2292  * context which was originally shared using clone.  copy_*
2293  * functions used by do_fork() cannot be used here directly
2294  * because they modify an inactive task_struct that is being
2295  * constructed. Here we are modifying the current, active,
2296  * task_struct.
2297  */
2298 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2299 {
2300         struct fs_struct *fs, *new_fs = NULL;
2301         struct files_struct *fd, *new_fd = NULL;
2302         struct cred *new_cred = NULL;
2303         struct nsproxy *new_nsproxy = NULL;
2304         int do_sysvsem = 0;
2305         int err;
2306
2307         /*
2308          * If unsharing a user namespace must also unshare the thread group
2309          * and unshare the filesystem root and working directories.
2310          */
2311         if (unshare_flags & CLONE_NEWUSER)
2312                 unshare_flags |= CLONE_THREAD | CLONE_FS;
2313         /*
2314          * If unsharing vm, must also unshare signal handlers.
2315          */
2316         if (unshare_flags & CLONE_VM)
2317                 unshare_flags |= CLONE_SIGHAND;
2318         /*
2319          * If unsharing a signal handlers, must also unshare the signal queues.
2320          */
2321         if (unshare_flags & CLONE_SIGHAND)
2322                 unshare_flags |= CLONE_THREAD;
2323         /*
2324          * If unsharing namespace, must also unshare filesystem information.
2325          */
2326         if (unshare_flags & CLONE_NEWNS)
2327                 unshare_flags |= CLONE_FS;
2328
2329         err = check_unshare_flags(unshare_flags);
2330         if (err)
2331                 goto bad_unshare_out;
2332         /*
2333          * CLONE_NEWIPC must also detach from the undolist: after switching
2334          * to a new ipc namespace, the semaphore arrays from the old
2335          * namespace are unreachable.
2336          */
2337         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2338                 do_sysvsem = 1;
2339         err = unshare_fs(unshare_flags, &new_fs);
2340         if (err)
2341                 goto bad_unshare_out;
2342         err = unshare_fd(unshare_flags, &new_fd);
2343         if (err)
2344                 goto bad_unshare_cleanup_fs;
2345         err = unshare_userns(unshare_flags, &new_cred);
2346         if (err)
2347                 goto bad_unshare_cleanup_fd;
2348         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2349                                          new_cred, new_fs);
2350         if (err)
2351                 goto bad_unshare_cleanup_cred;
2352
2353         if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2354                 if (do_sysvsem) {
2355                         /*
2356                          * CLONE_SYSVSEM is equivalent to sys_exit().
2357                          */
2358                         exit_sem(current);
2359                 }
2360                 if (unshare_flags & CLONE_NEWIPC) {
2361                         /* Orphan segments in old ns (see sem above). */
2362                         exit_shm(current);
2363                         shm_init_task(current);
2364                 }
2365
2366                 if (new_nsproxy)
2367                         switch_task_namespaces(current, new_nsproxy);
2368
2369                 task_lock(current);
2370
2371                 if (new_fs) {
2372                         fs = current->fs;
2373                         spin_lock(&fs->lock);
2374                         current->fs = new_fs;
2375                         if (--fs->users)
2376                                 new_fs = NULL;
2377                         else
2378                                 new_fs = fs;
2379                         spin_unlock(&fs->lock);
2380                 }
2381
2382                 if (new_fd) {
2383                         fd = current->files;
2384                         current->files = new_fd;
2385                         new_fd = fd;
2386                 }
2387
2388                 task_unlock(current);
2389
2390                 if (new_cred) {
2391                         /* Install the new user namespace */
2392                         commit_creds(new_cred);
2393                         new_cred = NULL;
2394                 }
2395         }
2396
2397         perf_event_namespaces(current);
2398
2399 bad_unshare_cleanup_cred:
2400         if (new_cred)
2401                 put_cred(new_cred);
2402 bad_unshare_cleanup_fd:
2403         if (new_fd)
2404                 put_files_struct(new_fd);
2405
2406 bad_unshare_cleanup_fs:
2407         if (new_fs)
2408                 free_fs_struct(new_fs);
2409
2410 bad_unshare_out:
2411         return err;
2412 }
2413
2414 /*
2415  *      Helper to unshare the files of the current task.
2416  *      We don't want to expose copy_files internals to
2417  *      the exec layer of the kernel.
2418  */
2419
2420 int unshare_files(struct files_struct **displaced)
2421 {
2422         struct task_struct *task = current;
2423         struct files_struct *copy = NULL;
2424         int error;
2425
2426         error = unshare_fd(CLONE_FILES, &copy);
2427         if (error || !copy) {
2428                 *displaced = NULL;
2429                 return error;
2430         }
2431         *displaced = task->files;
2432         task_lock(task);
2433         task->files = copy;
2434         task_unlock(task);
2435         return 0;
2436 }
2437
2438 int sysctl_max_threads(struct ctl_table *table, int write,
2439                        void __user *buffer, size_t *lenp, loff_t *ppos)
2440 {
2441         struct ctl_table t;
2442         int ret;
2443         int threads = max_threads;
2444         int min = MIN_THREADS;
2445         int max = MAX_THREADS;
2446
2447         t = *table;
2448         t.data = &threads;
2449         t.extra1 = &min;
2450         t.extra2 = &max;
2451
2452         ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2453         if (ret || !write)
2454                 return ret;
2455
2456         set_max_threads(threads);
2457
2458         return 0;
2459 }