52bfe7c20ff61d538e2661073428b72cf4d38bd6
[sfrench/cifs-2.6.git] / kernel / fork.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  linux/kernel/fork.c
4  *
5  *  Copyright (C) 1991, 1992  Linus Torvalds
6  */
7
8 /*
9  *  'fork.c' contains the help-routines for the 'fork' system call
10  * (see also entry.S and others).
11  * Fork is rather simple, once you get the hang of it, but the memory
12  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
13  */
14
15 #include <linux/anon_inodes.h>
16 #include <linux/slab.h>
17 #include <linux/sched/autogroup.h>
18 #include <linux/sched/mm.h>
19 #include <linux/sched/coredump.h>
20 #include <linux/sched/user.h>
21 #include <linux/sched/numa_balancing.h>
22 #include <linux/sched/stat.h>
23 #include <linux/sched/task.h>
24 #include <linux/sched/task_stack.h>
25 #include <linux/sched/cputime.h>
26 #include <linux/seq_file.h>
27 #include <linux/rtmutex.h>
28 #include <linux/init.h>
29 #include <linux/unistd.h>
30 #include <linux/module.h>
31 #include <linux/vmalloc.h>
32 #include <linux/completion.h>
33 #include <linux/personality.h>
34 #include <linux/mempolicy.h>
35 #include <linux/sem.h>
36 #include <linux/file.h>
37 #include <linux/fdtable.h>
38 #include <linux/iocontext.h>
39 #include <linux/key.h>
40 #include <linux/binfmts.h>
41 #include <linux/mman.h>
42 #include <linux/mmu_notifier.h>
43 #include <linux/hmm.h>
44 #include <linux/fs.h>
45 #include <linux/mm.h>
46 #include <linux/vmacache.h>
47 #include <linux/nsproxy.h>
48 #include <linux/capability.h>
49 #include <linux/cpu.h>
50 #include <linux/cgroup.h>
51 #include <linux/security.h>
52 #include <linux/hugetlb.h>
53 #include <linux/seccomp.h>
54 #include <linux/swap.h>
55 #include <linux/syscalls.h>
56 #include <linux/jiffies.h>
57 #include <linux/futex.h>
58 #include <linux/compat.h>
59 #include <linux/kthread.h>
60 #include <linux/task_io_accounting_ops.h>
61 #include <linux/rcupdate.h>
62 #include <linux/ptrace.h>
63 #include <linux/mount.h>
64 #include <linux/audit.h>
65 #include <linux/memcontrol.h>
66 #include <linux/ftrace.h>
67 #include <linux/proc_fs.h>
68 #include <linux/profile.h>
69 #include <linux/rmap.h>
70 #include <linux/ksm.h>
71 #include <linux/acct.h>
72 #include <linux/userfaultfd_k.h>
73 #include <linux/tsacct_kern.h>
74 #include <linux/cn_proc.h>
75 #include <linux/freezer.h>
76 #include <linux/delayacct.h>
77 #include <linux/taskstats_kern.h>
78 #include <linux/random.h>
79 #include <linux/tty.h>
80 #include <linux/blkdev.h>
81 #include <linux/fs_struct.h>
82 #include <linux/magic.h>
83 #include <linux/perf_event.h>
84 #include <linux/posix-timers.h>
85 #include <linux/user-return-notifier.h>
86 #include <linux/oom.h>
87 #include <linux/khugepaged.h>
88 #include <linux/signalfd.h>
89 #include <linux/uprobes.h>
90 #include <linux/aio.h>
91 #include <linux/compiler.h>
92 #include <linux/sysctl.h>
93 #include <linux/kcov.h>
94 #include <linux/livepatch.h>
95 #include <linux/thread_info.h>
96 #include <linux/stackleak.h>
97
98 #include <asm/pgtable.h>
99 #include <asm/pgalloc.h>
100 #include <linux/uaccess.h>
101 #include <asm/mmu_context.h>
102 #include <asm/cacheflush.h>
103 #include <asm/tlbflush.h>
104
105 #include <trace/events/sched.h>
106
107 #define CREATE_TRACE_POINTS
108 #include <trace/events/task.h>
109
110 /*
111  * Minimum number of threads to boot the kernel
112  */
113 #define MIN_THREADS 20
114
115 /*
116  * Maximum number of threads
117  */
118 #define MAX_THREADS FUTEX_TID_MASK
119
120 /*
121  * Protected counters by write_lock_irq(&tasklist_lock)
122  */
123 unsigned long total_forks;      /* Handle normal Linux uptimes. */
124 int nr_threads;                 /* The idle threads do not count.. */
125
126 static int max_threads;         /* tunable limit on nr_threads */
127
128 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
129
130 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
131
132 #ifdef CONFIG_PROVE_RCU
133 int lockdep_tasklist_lock_is_held(void)
134 {
135         return lockdep_is_held(&tasklist_lock);
136 }
137 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
138 #endif /* #ifdef CONFIG_PROVE_RCU */
139
140 int nr_processes(void)
141 {
142         int cpu;
143         int total = 0;
144
145         for_each_possible_cpu(cpu)
146                 total += per_cpu(process_counts, cpu);
147
148         return total;
149 }
150
151 void __weak arch_release_task_struct(struct task_struct *tsk)
152 {
153 }
154
155 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
156 static struct kmem_cache *task_struct_cachep;
157
158 static inline struct task_struct *alloc_task_struct_node(int node)
159 {
160         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
161 }
162
163 static inline void free_task_struct(struct task_struct *tsk)
164 {
165         kmem_cache_free(task_struct_cachep, tsk);
166 }
167 #endif
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                 /* Clear stale pointers from reused stack. */
219                 memset(s->addr, 0, THREAD_SIZE);
220
221                 tsk->stack_vm_area = s;
222                 tsk->stack = s->addr;
223                 return s->addr;
224         }
225
226         /*
227          * Allocated stacks are cached and later reused by new threads,
228          * so memcg accounting is performed manually on assigning/releasing
229          * stacks to tasks. Drop __GFP_ACCOUNT.
230          */
231         stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
232                                      VMALLOC_START, VMALLOC_END,
233                                      THREADINFO_GFP & ~__GFP_ACCOUNT,
234                                      PAGE_KERNEL,
235                                      0, node, __builtin_return_address(0));
236
237         /*
238          * We can't call find_vm_area() in interrupt context, and
239          * free_thread_stack() can be called in interrupt context,
240          * so cache the vm_struct.
241          */
242         if (stack) {
243                 tsk->stack_vm_area = find_vm_area(stack);
244                 tsk->stack = stack;
245         }
246         return stack;
247 #else
248         struct page *page = alloc_pages_node(node, THREADINFO_GFP,
249                                              THREAD_SIZE_ORDER);
250
251         if (likely(page)) {
252                 tsk->stack = page_address(page);
253                 return tsk->stack;
254         }
255         return NULL;
256 #endif
257 }
258
259 static inline void free_thread_stack(struct task_struct *tsk)
260 {
261 #ifdef CONFIG_VMAP_STACK
262         struct vm_struct *vm = task_stack_vm_area(tsk);
263
264         if (vm) {
265                 int i;
266
267                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
268                         mod_memcg_page_state(vm->pages[i],
269                                              MEMCG_KERNEL_STACK_KB,
270                                              -(int)(PAGE_SIZE / 1024));
271
272                         memcg_kmem_uncharge(vm->pages[i], 0);
273                 }
274
275                 for (i = 0; i < NR_CACHED_STACKS; i++) {
276                         if (this_cpu_cmpxchg(cached_stacks[i],
277                                         NULL, tsk->stack_vm_area) != NULL)
278                                 continue;
279
280                         return;
281                 }
282
283                 vfree_atomic(tsk->stack);
284                 return;
285         }
286 #endif
287
288         __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
289 }
290 # else
291 static struct kmem_cache *thread_stack_cache;
292
293 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
294                                                   int node)
295 {
296         unsigned long *stack;
297         stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
298         tsk->stack = stack;
299         return stack;
300 }
301
302 static void free_thread_stack(struct task_struct *tsk)
303 {
304         kmem_cache_free(thread_stack_cache, tsk->stack);
305 }
306
307 void thread_stack_cache_init(void)
308 {
309         thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
310                                         THREAD_SIZE, THREAD_SIZE, 0, 0,
311                                         THREAD_SIZE, NULL);
312         BUG_ON(thread_stack_cache == NULL);
313 }
314 # endif
315 #endif
316
317 /* SLAB cache for signal_struct structures (tsk->signal) */
318 static struct kmem_cache *signal_cachep;
319
320 /* SLAB cache for sighand_struct structures (tsk->sighand) */
321 struct kmem_cache *sighand_cachep;
322
323 /* SLAB cache for files_struct structures (tsk->files) */
324 struct kmem_cache *files_cachep;
325
326 /* SLAB cache for fs_struct structures (tsk->fs) */
327 struct kmem_cache *fs_cachep;
328
329 /* SLAB cache for vm_area_struct structures */
330 static struct kmem_cache *vm_area_cachep;
331
332 /* SLAB cache for mm_struct structures (tsk->mm) */
333 static struct kmem_cache *mm_cachep;
334
335 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
336 {
337         struct vm_area_struct *vma;
338
339         vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
340         if (vma)
341                 vma_init(vma, mm);
342         return vma;
343 }
344
345 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
346 {
347         struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
348
349         if (new) {
350                 *new = *orig;
351                 INIT_LIST_HEAD(&new->anon_vma_chain);
352         }
353         return new;
354 }
355
356 void vm_area_free(struct vm_area_struct *vma)
357 {
358         kmem_cache_free(vm_area_cachep, vma);
359 }
360
361 static void account_kernel_stack(struct task_struct *tsk, int account)
362 {
363         void *stack = task_stack_page(tsk);
364         struct vm_struct *vm = task_stack_vm_area(tsk);
365
366         BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
367
368         if (vm) {
369                 int i;
370
371                 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
372
373                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
374                         mod_zone_page_state(page_zone(vm->pages[i]),
375                                             NR_KERNEL_STACK_KB,
376                                             PAGE_SIZE / 1024 * account);
377                 }
378         } else {
379                 /*
380                  * All stack pages are in the same zone and belong to the
381                  * same memcg.
382                  */
383                 struct page *first_page = virt_to_page(stack);
384
385                 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
386                                     THREAD_SIZE / 1024 * account);
387
388                 mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB,
389                                      account * (THREAD_SIZE / 1024));
390         }
391 }
392
393 static int memcg_charge_kernel_stack(struct task_struct *tsk)
394 {
395 #ifdef CONFIG_VMAP_STACK
396         struct vm_struct *vm = task_stack_vm_area(tsk);
397         int ret;
398
399         if (vm) {
400                 int i;
401
402                 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
403                         /*
404                          * If memcg_kmem_charge() fails, page->mem_cgroup
405                          * pointer is NULL, and both memcg_kmem_uncharge()
406                          * and mod_memcg_page_state() in free_thread_stack()
407                          * will ignore this page. So it's safe.
408                          */
409                         ret = memcg_kmem_charge(vm->pages[i], GFP_KERNEL, 0);
410                         if (ret)
411                                 return ret;
412
413                         mod_memcg_page_state(vm->pages[i],
414                                              MEMCG_KERNEL_STACK_KB,
415                                              PAGE_SIZE / 1024);
416                 }
417         }
418 #endif
419         return 0;
420 }
421
422 static void release_task_stack(struct task_struct *tsk)
423 {
424         if (WARN_ON(tsk->state != TASK_DEAD))
425                 return;  /* Better to leak the stack than to free prematurely */
426
427         account_kernel_stack(tsk, -1);
428         free_thread_stack(tsk);
429         tsk->stack = NULL;
430 #ifdef CONFIG_VMAP_STACK
431         tsk->stack_vm_area = NULL;
432 #endif
433 }
434
435 #ifdef CONFIG_THREAD_INFO_IN_TASK
436 void put_task_stack(struct task_struct *tsk)
437 {
438         if (refcount_dec_and_test(&tsk->stack_refcount))
439                 release_task_stack(tsk);
440 }
441 #endif
442
443 void free_task(struct task_struct *tsk)
444 {
445 #ifndef CONFIG_THREAD_INFO_IN_TASK
446         /*
447          * The task is finally done with both the stack and thread_info,
448          * so free both.
449          */
450         release_task_stack(tsk);
451 #else
452         /*
453          * If the task had a separate stack allocation, it should be gone
454          * by now.
455          */
456         WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
457 #endif
458         rt_mutex_debug_task_free(tsk);
459         ftrace_graph_exit_task(tsk);
460         put_seccomp_filter(tsk);
461         arch_release_task_struct(tsk);
462         if (tsk->flags & PF_KTHREAD)
463                 free_kthread_struct(tsk);
464         free_task_struct(tsk);
465 }
466 EXPORT_SYMBOL(free_task);
467
468 #ifdef CONFIG_MMU
469 static __latent_entropy int dup_mmap(struct mm_struct *mm,
470                                         struct mm_struct *oldmm)
471 {
472         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
473         struct rb_node **rb_link, *rb_parent;
474         int retval;
475         unsigned long charge;
476         LIST_HEAD(uf);
477
478         uprobe_start_dup_mmap();
479         if (down_write_killable(&oldmm->mmap_sem)) {
480                 retval = -EINTR;
481                 goto fail_uprobe_end;
482         }
483         flush_cache_dup_mm(oldmm);
484         uprobe_dup_mmap(oldmm, mm);
485         /*
486          * Not linked in yet - no deadlock potential:
487          */
488         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
489
490         /* No ordering required: file already has been exposed. */
491         RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
492
493         mm->total_vm = oldmm->total_vm;
494         mm->data_vm = oldmm->data_vm;
495         mm->exec_vm = oldmm->exec_vm;
496         mm->stack_vm = oldmm->stack_vm;
497
498         rb_link = &mm->mm_rb.rb_node;
499         rb_parent = NULL;
500         pprev = &mm->mmap;
501         retval = ksm_fork(mm, oldmm);
502         if (retval)
503                 goto out;
504         retval = khugepaged_fork(mm, oldmm);
505         if (retval)
506                 goto out;
507
508         prev = NULL;
509         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
510                 struct file *file;
511
512                 if (mpnt->vm_flags & VM_DONTCOPY) {
513                         vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
514                         continue;
515                 }
516                 charge = 0;
517                 /*
518                  * Don't duplicate many vmas if we've been oom-killed (for
519                  * example)
520                  */
521                 if (fatal_signal_pending(current)) {
522                         retval = -EINTR;
523                         goto out;
524                 }
525                 if (mpnt->vm_flags & VM_ACCOUNT) {
526                         unsigned long len = vma_pages(mpnt);
527
528                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
529                                 goto fail_nomem;
530                         charge = len;
531                 }
532                 tmp = vm_area_dup(mpnt);
533                 if (!tmp)
534                         goto fail_nomem;
535                 retval = vma_dup_policy(mpnt, tmp);
536                 if (retval)
537                         goto fail_nomem_policy;
538                 tmp->vm_mm = mm;
539                 retval = dup_userfaultfd(tmp, &uf);
540                 if (retval)
541                         goto fail_nomem_anon_vma_fork;
542                 if (tmp->vm_flags & VM_WIPEONFORK) {
543                         /* VM_WIPEONFORK gets a clean slate in the child. */
544                         tmp->anon_vma = NULL;
545                         if (anon_vma_prepare(tmp))
546                                 goto fail_nomem_anon_vma_fork;
547                 } else if (anon_vma_fork(tmp, mpnt))
548                         goto fail_nomem_anon_vma_fork;
549                 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
550                 tmp->vm_next = tmp->vm_prev = NULL;
551                 file = tmp->vm_file;
552                 if (file) {
553                         struct inode *inode = file_inode(file);
554                         struct address_space *mapping = file->f_mapping;
555
556                         get_file(file);
557                         if (tmp->vm_flags & VM_DENYWRITE)
558                                 atomic_dec(&inode->i_writecount);
559                         i_mmap_lock_write(mapping);
560                         if (tmp->vm_flags & VM_SHARED)
561                                 atomic_inc(&mapping->i_mmap_writable);
562                         flush_dcache_mmap_lock(mapping);
563                         /* insert tmp into the share list, just after mpnt */
564                         vma_interval_tree_insert_after(tmp, mpnt,
565                                         &mapping->i_mmap);
566                         flush_dcache_mmap_unlock(mapping);
567                         i_mmap_unlock_write(mapping);
568                 }
569
570                 /*
571                  * Clear hugetlb-related page reserves for children. This only
572                  * affects MAP_PRIVATE mappings. Faults generated by the child
573                  * are not guaranteed to succeed, even if read-only
574                  */
575                 if (is_vm_hugetlb_page(tmp))
576                         reset_vma_resv_huge_pages(tmp);
577
578                 /*
579                  * Link in the new vma and copy the page table entries.
580                  */
581                 *pprev = tmp;
582                 pprev = &tmp->vm_next;
583                 tmp->vm_prev = prev;
584                 prev = tmp;
585
586                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
587                 rb_link = &tmp->vm_rb.rb_right;
588                 rb_parent = &tmp->vm_rb;
589
590                 mm->map_count++;
591                 if (!(tmp->vm_flags & VM_WIPEONFORK))
592                         retval = copy_page_range(mm, oldmm, mpnt);
593
594                 if (tmp->vm_ops && tmp->vm_ops->open)
595                         tmp->vm_ops->open(tmp);
596
597                 if (retval)
598                         goto out;
599         }
600         /* a new mm has just been created */
601         retval = arch_dup_mmap(oldmm, mm);
602 out:
603         up_write(&mm->mmap_sem);
604         flush_tlb_mm(oldmm);
605         up_write(&oldmm->mmap_sem);
606         dup_userfaultfd_complete(&uf);
607 fail_uprobe_end:
608         uprobe_end_dup_mmap();
609         return retval;
610 fail_nomem_anon_vma_fork:
611         mpol_put(vma_policy(tmp));
612 fail_nomem_policy:
613         vm_area_free(tmp);
614 fail_nomem:
615         retval = -ENOMEM;
616         vm_unacct_memory(charge);
617         goto out;
618 }
619
620 static inline int mm_alloc_pgd(struct mm_struct *mm)
621 {
622         mm->pgd = pgd_alloc(mm);
623         if (unlikely(!mm->pgd))
624                 return -ENOMEM;
625         return 0;
626 }
627
628 static inline void mm_free_pgd(struct mm_struct *mm)
629 {
630         pgd_free(mm, mm->pgd);
631 }
632 #else
633 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
634 {
635         down_write(&oldmm->mmap_sem);
636         RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
637         up_write(&oldmm->mmap_sem);
638         return 0;
639 }
640 #define mm_alloc_pgd(mm)        (0)
641 #define mm_free_pgd(mm)
642 #endif /* CONFIG_MMU */
643
644 static void check_mm(struct mm_struct *mm)
645 {
646         int i;
647
648         for (i = 0; i < NR_MM_COUNTERS; i++) {
649                 long x = atomic_long_read(&mm->rss_stat.count[i]);
650
651                 if (unlikely(x))
652                         printk(KERN_ALERT "BUG: Bad rss-counter state "
653                                           "mm:%p idx:%d val:%ld\n", mm, i, x);
654         }
655
656         if (mm_pgtables_bytes(mm))
657                 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
658                                 mm_pgtables_bytes(mm));
659
660 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
661         VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
662 #endif
663 }
664
665 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
666 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
667
668 /*
669  * Called when the last reference to the mm
670  * is dropped: either by a lazy thread or by
671  * mmput. Free the page directory and the mm.
672  */
673 void __mmdrop(struct mm_struct *mm)
674 {
675         BUG_ON(mm == &init_mm);
676         WARN_ON_ONCE(mm == current->mm);
677         WARN_ON_ONCE(mm == current->active_mm);
678         mm_free_pgd(mm);
679         destroy_context(mm);
680         mmu_notifier_mm_destroy(mm);
681         check_mm(mm);
682         put_user_ns(mm->user_ns);
683         free_mm(mm);
684 }
685 EXPORT_SYMBOL_GPL(__mmdrop);
686
687 static void mmdrop_async_fn(struct work_struct *work)
688 {
689         struct mm_struct *mm;
690
691         mm = container_of(work, struct mm_struct, async_put_work);
692         __mmdrop(mm);
693 }
694
695 static void mmdrop_async(struct mm_struct *mm)
696 {
697         if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
698                 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
699                 schedule_work(&mm->async_put_work);
700         }
701 }
702
703 static inline void free_signal_struct(struct signal_struct *sig)
704 {
705         taskstats_tgid_free(sig);
706         sched_autogroup_exit(sig);
707         /*
708          * __mmdrop is not safe to call from softirq context on x86 due to
709          * pgd_dtor so postpone it to the async context
710          */
711         if (sig->oom_mm)
712                 mmdrop_async(sig->oom_mm);
713         kmem_cache_free(signal_cachep, sig);
714 }
715
716 static inline void put_signal_struct(struct signal_struct *sig)
717 {
718         if (refcount_dec_and_test(&sig->sigcnt))
719                 free_signal_struct(sig);
720 }
721
722 void __put_task_struct(struct task_struct *tsk)
723 {
724         WARN_ON(!tsk->exit_state);
725         WARN_ON(refcount_read(&tsk->usage));
726         WARN_ON(tsk == current);
727
728         cgroup_free(tsk);
729         task_numa_free(tsk);
730         security_task_free(tsk);
731         exit_creds(tsk);
732         delayacct_tsk_free(tsk);
733         put_signal_struct(tsk->signal);
734
735         if (!profile_handoff_task(tsk))
736                 free_task(tsk);
737 }
738 EXPORT_SYMBOL_GPL(__put_task_struct);
739
740 void __init __weak arch_task_cache_init(void) { }
741
742 /*
743  * set_max_threads
744  */
745 static void set_max_threads(unsigned int max_threads_suggested)
746 {
747         u64 threads;
748         unsigned long nr_pages = totalram_pages();
749
750         /*
751          * The number of threads shall be limited such that the thread
752          * structures may only consume a small part of the available memory.
753          */
754         if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
755                 threads = MAX_THREADS;
756         else
757                 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
758                                     (u64) THREAD_SIZE * 8UL);
759
760         if (threads > max_threads_suggested)
761                 threads = max_threads_suggested;
762
763         max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
764 }
765
766 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
767 /* Initialized by the architecture: */
768 int arch_task_struct_size __read_mostly;
769 #endif
770
771 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
772 {
773         /* Fetch thread_struct whitelist for the architecture. */
774         arch_thread_struct_whitelist(offset, size);
775
776         /*
777          * Handle zero-sized whitelist or empty thread_struct, otherwise
778          * adjust offset to position of thread_struct in task_struct.
779          */
780         if (unlikely(*size == 0))
781                 *offset = 0;
782         else
783                 *offset += offsetof(struct task_struct, thread);
784 }
785
786 void __init fork_init(void)
787 {
788         int i;
789 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
790 #ifndef ARCH_MIN_TASKALIGN
791 #define ARCH_MIN_TASKALIGN      0
792 #endif
793         int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
794         unsigned long useroffset, usersize;
795
796         /* create a slab on which task_structs can be allocated */
797         task_struct_whitelist(&useroffset, &usersize);
798         task_struct_cachep = kmem_cache_create_usercopy("task_struct",
799                         arch_task_struct_size, align,
800                         SLAB_PANIC|SLAB_ACCOUNT,
801                         useroffset, usersize, NULL);
802 #endif
803
804         /* do the arch specific task caches init */
805         arch_task_cache_init();
806
807         set_max_threads(MAX_THREADS);
808
809         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
810         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
811         init_task.signal->rlim[RLIMIT_SIGPENDING] =
812                 init_task.signal->rlim[RLIMIT_NPROC];
813
814         for (i = 0; i < UCOUNT_COUNTS; i++) {
815                 init_user_ns.ucount_max[i] = max_threads/2;
816         }
817
818 #ifdef CONFIG_VMAP_STACK
819         cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
820                           NULL, free_vm_stack_cache);
821 #endif
822
823         lockdep_init_task(&init_task);
824         uprobes_init();
825 }
826
827 int __weak arch_dup_task_struct(struct task_struct *dst,
828                                                struct task_struct *src)
829 {
830         *dst = *src;
831         return 0;
832 }
833
834 void set_task_stack_end_magic(struct task_struct *tsk)
835 {
836         unsigned long *stackend;
837
838         stackend = end_of_stack(tsk);
839         *stackend = STACK_END_MAGIC;    /* for overflow detection */
840 }
841
842 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
843 {
844         struct task_struct *tsk;
845         unsigned long *stack;
846         struct vm_struct *stack_vm_area __maybe_unused;
847         int err;
848
849         if (node == NUMA_NO_NODE)
850                 node = tsk_fork_get_node(orig);
851         tsk = alloc_task_struct_node(node);
852         if (!tsk)
853                 return NULL;
854
855         stack = alloc_thread_stack_node(tsk, node);
856         if (!stack)
857                 goto free_tsk;
858
859         if (memcg_charge_kernel_stack(tsk))
860                 goto free_stack;
861
862         stack_vm_area = task_stack_vm_area(tsk);
863
864         err = arch_dup_task_struct(tsk, orig);
865
866         /*
867          * arch_dup_task_struct() clobbers the stack-related fields.  Make
868          * sure they're properly initialized before using any stack-related
869          * functions again.
870          */
871         tsk->stack = stack;
872 #ifdef CONFIG_VMAP_STACK
873         tsk->stack_vm_area = stack_vm_area;
874 #endif
875 #ifdef CONFIG_THREAD_INFO_IN_TASK
876         refcount_set(&tsk->stack_refcount, 1);
877 #endif
878
879         if (err)
880                 goto free_stack;
881
882 #ifdef CONFIG_SECCOMP
883         /*
884          * We must handle setting up seccomp filters once we're under
885          * the sighand lock in case orig has changed between now and
886          * then. Until then, filter must be NULL to avoid messing up
887          * the usage counts on the error path calling free_task.
888          */
889         tsk->seccomp.filter = NULL;
890 #endif
891
892         setup_thread_stack(tsk, orig);
893         clear_user_return_notifier(tsk);
894         clear_tsk_need_resched(tsk);
895         set_task_stack_end_magic(tsk);
896
897 #ifdef CONFIG_STACKPROTECTOR
898         tsk->stack_canary = get_random_canary();
899 #endif
900         if (orig->cpus_ptr == &orig->cpus_mask)
901                 tsk->cpus_ptr = &tsk->cpus_mask;
902
903         /*
904          * One for us, one for whoever does the "release_task()" (usually
905          * parent)
906          */
907         refcount_set(&tsk->usage, 2);
908 #ifdef CONFIG_BLK_DEV_IO_TRACE
909         tsk->btrace_seq = 0;
910 #endif
911         tsk->splice_pipe = NULL;
912         tsk->task_frag.page = NULL;
913         tsk->wake_q.next = NULL;
914
915         account_kernel_stack(tsk, 1);
916
917         kcov_task_init(tsk);
918
919 #ifdef CONFIG_FAULT_INJECTION
920         tsk->fail_nth = 0;
921 #endif
922
923 #ifdef CONFIG_BLK_CGROUP
924         tsk->throttle_queue = NULL;
925         tsk->use_memdelay = 0;
926 #endif
927
928 #ifdef CONFIG_MEMCG
929         tsk->active_memcg = NULL;
930 #endif
931         return tsk;
932
933 free_stack:
934         free_thread_stack(tsk);
935 free_tsk:
936         free_task_struct(tsk);
937         return NULL;
938 }
939
940 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
941
942 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
943
944 static int __init coredump_filter_setup(char *s)
945 {
946         default_dump_filter =
947                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
948                 MMF_DUMP_FILTER_MASK;
949         return 1;
950 }
951
952 __setup("coredump_filter=", coredump_filter_setup);
953
954 #include <linux/init_task.h>
955
956 static void mm_init_aio(struct mm_struct *mm)
957 {
958 #ifdef CONFIG_AIO
959         spin_lock_init(&mm->ioctx_lock);
960         mm->ioctx_table = NULL;
961 #endif
962 }
963
964 static __always_inline void mm_clear_owner(struct mm_struct *mm,
965                                            struct task_struct *p)
966 {
967 #ifdef CONFIG_MEMCG
968         if (mm->owner == p)
969                 WRITE_ONCE(mm->owner, NULL);
970 #endif
971 }
972
973 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
974 {
975 #ifdef CONFIG_MEMCG
976         mm->owner = p;
977 #endif
978 }
979
980 static void mm_init_uprobes_state(struct mm_struct *mm)
981 {
982 #ifdef CONFIG_UPROBES
983         mm->uprobes_state.xol_area = NULL;
984 #endif
985 }
986
987 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
988         struct user_namespace *user_ns)
989 {
990         mm->mmap = NULL;
991         mm->mm_rb = RB_ROOT;
992         mm->vmacache_seqnum = 0;
993         atomic_set(&mm->mm_users, 1);
994         atomic_set(&mm->mm_count, 1);
995         init_rwsem(&mm->mmap_sem);
996         INIT_LIST_HEAD(&mm->mmlist);
997         mm->core_state = NULL;
998         mm_pgtables_bytes_init(mm);
999         mm->map_count = 0;
1000         mm->locked_vm = 0;
1001         atomic64_set(&mm->pinned_vm, 0);
1002         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1003         spin_lock_init(&mm->page_table_lock);
1004         spin_lock_init(&mm->arg_lock);
1005         mm_init_cpumask(mm);
1006         mm_init_aio(mm);
1007         mm_init_owner(mm, p);
1008         RCU_INIT_POINTER(mm->exe_file, NULL);
1009         mmu_notifier_mm_init(mm);
1010         hmm_mm_init(mm);
1011         init_tlb_flush_pending(mm);
1012 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1013         mm->pmd_huge_pte = NULL;
1014 #endif
1015         mm_init_uprobes_state(mm);
1016
1017         if (current->mm) {
1018                 mm->flags = current->mm->flags & MMF_INIT_MASK;
1019                 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1020         } else {
1021                 mm->flags = default_dump_filter;
1022                 mm->def_flags = 0;
1023         }
1024
1025         if (mm_alloc_pgd(mm))
1026                 goto fail_nopgd;
1027
1028         if (init_new_context(p, mm))
1029                 goto fail_nocontext;
1030
1031         mm->user_ns = get_user_ns(user_ns);
1032         return mm;
1033
1034 fail_nocontext:
1035         mm_free_pgd(mm);
1036 fail_nopgd:
1037         free_mm(mm);
1038         return NULL;
1039 }
1040
1041 /*
1042  * Allocate and initialize an mm_struct.
1043  */
1044 struct mm_struct *mm_alloc(void)
1045 {
1046         struct mm_struct *mm;
1047
1048         mm = allocate_mm();
1049         if (!mm)
1050                 return NULL;
1051
1052         memset(mm, 0, sizeof(*mm));
1053         return mm_init(mm, current, current_user_ns());
1054 }
1055
1056 static inline void __mmput(struct mm_struct *mm)
1057 {
1058         VM_BUG_ON(atomic_read(&mm->mm_users));
1059
1060         uprobe_clear_state(mm);
1061         exit_aio(mm);
1062         ksm_exit(mm);
1063         khugepaged_exit(mm); /* must run before exit_mmap */
1064         exit_mmap(mm);
1065         mm_put_huge_zero_page(mm);
1066         set_mm_exe_file(mm, NULL);
1067         if (!list_empty(&mm->mmlist)) {
1068                 spin_lock(&mmlist_lock);
1069                 list_del(&mm->mmlist);
1070                 spin_unlock(&mmlist_lock);
1071         }
1072         if (mm->binfmt)
1073                 module_put(mm->binfmt->module);
1074         mmdrop(mm);
1075 }
1076
1077 /*
1078  * Decrement the use count and release all resources for an mm.
1079  */
1080 void mmput(struct mm_struct *mm)
1081 {
1082         might_sleep();
1083
1084         if (atomic_dec_and_test(&mm->mm_users))
1085                 __mmput(mm);
1086 }
1087 EXPORT_SYMBOL_GPL(mmput);
1088
1089 #ifdef CONFIG_MMU
1090 static void mmput_async_fn(struct work_struct *work)
1091 {
1092         struct mm_struct *mm = container_of(work, struct mm_struct,
1093                                             async_put_work);
1094
1095         __mmput(mm);
1096 }
1097
1098 void mmput_async(struct mm_struct *mm)
1099 {
1100         if (atomic_dec_and_test(&mm->mm_users)) {
1101                 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1102                 schedule_work(&mm->async_put_work);
1103         }
1104 }
1105 #endif
1106
1107 /**
1108  * set_mm_exe_file - change a reference to the mm's executable file
1109  *
1110  * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1111  *
1112  * Main users are mmput() and sys_execve(). Callers prevent concurrent
1113  * invocations: in mmput() nobody alive left, in execve task is single
1114  * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
1115  * mm->exe_file, but does so without using set_mm_exe_file() in order
1116  * to do avoid the need for any locks.
1117  */
1118 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1119 {
1120         struct file *old_exe_file;
1121
1122         /*
1123          * It is safe to dereference the exe_file without RCU as
1124          * this function is only called if nobody else can access
1125          * this mm -- see comment above for justification.
1126          */
1127         old_exe_file = rcu_dereference_raw(mm->exe_file);
1128
1129         if (new_exe_file)
1130                 get_file(new_exe_file);
1131         rcu_assign_pointer(mm->exe_file, new_exe_file);
1132         if (old_exe_file)
1133                 fput(old_exe_file);
1134 }
1135
1136 /**
1137  * get_mm_exe_file - acquire a reference to the mm's executable file
1138  *
1139  * Returns %NULL if mm has no associated executable file.
1140  * User must release file via fput().
1141  */
1142 struct file *get_mm_exe_file(struct mm_struct *mm)
1143 {
1144         struct file *exe_file;
1145
1146         rcu_read_lock();
1147         exe_file = rcu_dereference(mm->exe_file);
1148         if (exe_file && !get_file_rcu(exe_file))
1149                 exe_file = NULL;
1150         rcu_read_unlock();
1151         return exe_file;
1152 }
1153 EXPORT_SYMBOL(get_mm_exe_file);
1154
1155 /**
1156  * get_task_exe_file - acquire a reference to the task's executable file
1157  *
1158  * Returns %NULL if task's mm (if any) has no associated executable file or
1159  * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1160  * User must release file via fput().
1161  */
1162 struct file *get_task_exe_file(struct task_struct *task)
1163 {
1164         struct file *exe_file = NULL;
1165         struct mm_struct *mm;
1166
1167         task_lock(task);
1168         mm = task->mm;
1169         if (mm) {
1170                 if (!(task->flags & PF_KTHREAD))
1171                         exe_file = get_mm_exe_file(mm);
1172         }
1173         task_unlock(task);
1174         return exe_file;
1175 }
1176 EXPORT_SYMBOL(get_task_exe_file);
1177
1178 /**
1179  * get_task_mm - acquire a reference to the task's mm
1180  *
1181  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
1182  * this kernel workthread has transiently adopted a user mm with use_mm,
1183  * to do its AIO) is not set and if so returns a reference to it, after
1184  * bumping up the use count.  User must release the mm via mmput()
1185  * after use.  Typically used by /proc and ptrace.
1186  */
1187 struct mm_struct *get_task_mm(struct task_struct *task)
1188 {
1189         struct mm_struct *mm;
1190
1191         task_lock(task);
1192         mm = task->mm;
1193         if (mm) {
1194                 if (task->flags & PF_KTHREAD)
1195                         mm = NULL;
1196                 else
1197                         mmget(mm);
1198         }
1199         task_unlock(task);
1200         return mm;
1201 }
1202 EXPORT_SYMBOL_GPL(get_task_mm);
1203
1204 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1205 {
1206         struct mm_struct *mm;
1207         int err;
1208
1209         err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
1210         if (err)
1211                 return ERR_PTR(err);
1212
1213         mm = get_task_mm(task);
1214         if (mm && mm != current->mm &&
1215                         !ptrace_may_access(task, mode)) {
1216                 mmput(mm);
1217                 mm = ERR_PTR(-EACCES);
1218         }
1219         mutex_unlock(&task->signal->cred_guard_mutex);
1220
1221         return mm;
1222 }
1223
1224 static void complete_vfork_done(struct task_struct *tsk)
1225 {
1226         struct completion *vfork;
1227
1228         task_lock(tsk);
1229         vfork = tsk->vfork_done;
1230         if (likely(vfork)) {
1231                 tsk->vfork_done = NULL;
1232                 complete(vfork);
1233         }
1234         task_unlock(tsk);
1235 }
1236
1237 static int wait_for_vfork_done(struct task_struct *child,
1238                                 struct completion *vfork)
1239 {
1240         int killed;
1241
1242         freezer_do_not_count();
1243         cgroup_enter_frozen();
1244         killed = wait_for_completion_killable(vfork);
1245         cgroup_leave_frozen(false);
1246         freezer_count();
1247
1248         if (killed) {
1249                 task_lock(child);
1250                 child->vfork_done = NULL;
1251                 task_unlock(child);
1252         }
1253
1254         put_task_struct(child);
1255         return killed;
1256 }
1257
1258 /* Please note the differences between mmput and mm_release.
1259  * mmput is called whenever we stop holding onto a mm_struct,
1260  * error success whatever.
1261  *
1262  * mm_release is called after a mm_struct has been removed
1263  * from the current process.
1264  *
1265  * This difference is important for error handling, when we
1266  * only half set up a mm_struct for a new process and need to restore
1267  * the old one.  Because we mmput the new mm_struct before
1268  * restoring the old one. . .
1269  * Eric Biederman 10 January 1998
1270  */
1271 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1272 {
1273         /* Get rid of any futexes when releasing the mm */
1274 #ifdef CONFIG_FUTEX
1275         if (unlikely(tsk->robust_list)) {
1276                 exit_robust_list(tsk);
1277                 tsk->robust_list = NULL;
1278         }
1279 #ifdef CONFIG_COMPAT
1280         if (unlikely(tsk->compat_robust_list)) {
1281                 compat_exit_robust_list(tsk);
1282                 tsk->compat_robust_list = NULL;
1283         }
1284 #endif
1285         if (unlikely(!list_empty(&tsk->pi_state_list)))
1286                 exit_pi_state_list(tsk);
1287 #endif
1288
1289         uprobe_free_utask(tsk);
1290
1291         /* Get rid of any cached register state */
1292         deactivate_mm(tsk, mm);
1293
1294         /*
1295          * Signal userspace if we're not exiting with a core dump
1296          * because we want to leave the value intact for debugging
1297          * purposes.
1298          */
1299         if (tsk->clear_child_tid) {
1300                 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1301                     atomic_read(&mm->mm_users) > 1) {
1302                         /*
1303                          * We don't check the error code - if userspace has
1304                          * not set up a proper pointer then tough luck.
1305                          */
1306                         put_user(0, tsk->clear_child_tid);
1307                         do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1308                                         1, NULL, NULL, 0, 0);
1309                 }
1310                 tsk->clear_child_tid = NULL;
1311         }
1312
1313         /*
1314          * All done, finally we can wake up parent and return this mm to him.
1315          * Also kthread_stop() uses this completion for synchronization.
1316          */
1317         if (tsk->vfork_done)
1318                 complete_vfork_done(tsk);
1319 }
1320
1321 /**
1322  * dup_mm() - duplicates an existing mm structure
1323  * @tsk: the task_struct with which the new mm will be associated.
1324  * @oldmm: the mm to duplicate.
1325  *
1326  * Allocates a new mm structure and duplicates the provided @oldmm structure
1327  * content into it.
1328  *
1329  * Return: the duplicated mm or NULL on failure.
1330  */
1331 static struct mm_struct *dup_mm(struct task_struct *tsk,
1332                                 struct mm_struct *oldmm)
1333 {
1334         struct mm_struct *mm;
1335         int err;
1336
1337         mm = allocate_mm();
1338         if (!mm)
1339                 goto fail_nomem;
1340
1341         memcpy(mm, oldmm, sizeof(*mm));
1342
1343         if (!mm_init(mm, tsk, mm->user_ns))
1344                 goto fail_nomem;
1345
1346         err = dup_mmap(mm, oldmm);
1347         if (err)
1348                 goto free_pt;
1349
1350         mm->hiwater_rss = get_mm_rss(mm);
1351         mm->hiwater_vm = mm->total_vm;
1352
1353         if (mm->binfmt && !try_module_get(mm->binfmt->module))
1354                 goto free_pt;
1355
1356         return mm;
1357
1358 free_pt:
1359         /* don't put binfmt in mmput, we haven't got module yet */
1360         mm->binfmt = NULL;
1361         mm_init_owner(mm, NULL);
1362         mmput(mm);
1363
1364 fail_nomem:
1365         return NULL;
1366 }
1367
1368 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1369 {
1370         struct mm_struct *mm, *oldmm;
1371         int retval;
1372
1373         tsk->min_flt = tsk->maj_flt = 0;
1374         tsk->nvcsw = tsk->nivcsw = 0;
1375 #ifdef CONFIG_DETECT_HUNG_TASK
1376         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1377         tsk->last_switch_time = 0;
1378 #endif
1379
1380         tsk->mm = NULL;
1381         tsk->active_mm = NULL;
1382
1383         /*
1384          * Are we cloning a kernel thread?
1385          *
1386          * We need to steal a active VM for that..
1387          */
1388         oldmm = current->mm;
1389         if (!oldmm)
1390                 return 0;
1391
1392         /* initialize the new vmacache entries */
1393         vmacache_flush(tsk);
1394
1395         if (clone_flags & CLONE_VM) {
1396                 mmget(oldmm);
1397                 mm = oldmm;
1398                 goto good_mm;
1399         }
1400
1401         retval = -ENOMEM;
1402         mm = dup_mm(tsk, current->mm);
1403         if (!mm)
1404                 goto fail_nomem;
1405
1406 good_mm:
1407         tsk->mm = mm;
1408         tsk->active_mm = mm;
1409         return 0;
1410
1411 fail_nomem:
1412         return retval;
1413 }
1414
1415 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1416 {
1417         struct fs_struct *fs = current->fs;
1418         if (clone_flags & CLONE_FS) {
1419                 /* tsk->fs is already what we want */
1420                 spin_lock(&fs->lock);
1421                 if (fs->in_exec) {
1422                         spin_unlock(&fs->lock);
1423                         return -EAGAIN;
1424                 }
1425                 fs->users++;
1426                 spin_unlock(&fs->lock);
1427                 return 0;
1428         }
1429         tsk->fs = copy_fs_struct(fs);
1430         if (!tsk->fs)
1431                 return -ENOMEM;
1432         return 0;
1433 }
1434
1435 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1436 {
1437         struct files_struct *oldf, *newf;
1438         int error = 0;
1439
1440         /*
1441          * A background process may not have any files ...
1442          */
1443         oldf = current->files;
1444         if (!oldf)
1445                 goto out;
1446
1447         if (clone_flags & CLONE_FILES) {
1448                 atomic_inc(&oldf->count);
1449                 goto out;
1450         }
1451
1452         newf = dup_fd(oldf, &error);
1453         if (!newf)
1454                 goto out;
1455
1456         tsk->files = newf;
1457         error = 0;
1458 out:
1459         return error;
1460 }
1461
1462 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1463 {
1464 #ifdef CONFIG_BLOCK
1465         struct io_context *ioc = current->io_context;
1466         struct io_context *new_ioc;
1467
1468         if (!ioc)
1469                 return 0;
1470         /*
1471          * Share io context with parent, if CLONE_IO is set
1472          */
1473         if (clone_flags & CLONE_IO) {
1474                 ioc_task_link(ioc);
1475                 tsk->io_context = ioc;
1476         } else if (ioprio_valid(ioc->ioprio)) {
1477                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1478                 if (unlikely(!new_ioc))
1479                         return -ENOMEM;
1480
1481                 new_ioc->ioprio = ioc->ioprio;
1482                 put_io_context(new_ioc);
1483         }
1484 #endif
1485         return 0;
1486 }
1487
1488 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1489 {
1490         struct sighand_struct *sig;
1491
1492         if (clone_flags & CLONE_SIGHAND) {
1493                 refcount_inc(&current->sighand->count);
1494                 return 0;
1495         }
1496         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1497         rcu_assign_pointer(tsk->sighand, sig);
1498         if (!sig)
1499                 return -ENOMEM;
1500
1501         refcount_set(&sig->count, 1);
1502         spin_lock_irq(&current->sighand->siglock);
1503         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1504         spin_unlock_irq(&current->sighand->siglock);
1505         return 0;
1506 }
1507
1508 void __cleanup_sighand(struct sighand_struct *sighand)
1509 {
1510         if (refcount_dec_and_test(&sighand->count)) {
1511                 signalfd_cleanup(sighand);
1512                 /*
1513                  * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1514                  * without an RCU grace period, see __lock_task_sighand().
1515                  */
1516                 kmem_cache_free(sighand_cachep, sighand);
1517         }
1518 }
1519
1520 #ifdef CONFIG_POSIX_TIMERS
1521 /*
1522  * Initialize POSIX timer handling for a thread group.
1523  */
1524 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1525 {
1526         struct posix_cputimers *pct = &sig->posix_cputimers;
1527         unsigned long cpu_limit;
1528
1529         cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1530         posix_cputimers_group_init(pct, cpu_limit);
1531         if (cpu_limit != RLIM_INFINITY)
1532                 sig->cputimer.running = true;
1533 }
1534 #else
1535 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { }
1536 #endif
1537
1538 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1539 {
1540         struct signal_struct *sig;
1541
1542         if (clone_flags & CLONE_THREAD)
1543                 return 0;
1544
1545         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1546         tsk->signal = sig;
1547         if (!sig)
1548                 return -ENOMEM;
1549
1550         sig->nr_threads = 1;
1551         atomic_set(&sig->live, 1);
1552         refcount_set(&sig->sigcnt, 1);
1553
1554         /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1555         sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1556         tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1557
1558         init_waitqueue_head(&sig->wait_chldexit);
1559         sig->curr_target = tsk;
1560         init_sigpending(&sig->shared_pending);
1561         INIT_HLIST_HEAD(&sig->multiprocess);
1562         seqlock_init(&sig->stats_lock);
1563         prev_cputime_init(&sig->prev_cputime);
1564
1565 #ifdef CONFIG_POSIX_TIMERS
1566         INIT_LIST_HEAD(&sig->posix_timers);
1567         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1568         sig->real_timer.function = it_real_fn;
1569 #endif
1570
1571         task_lock(current->group_leader);
1572         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1573         task_unlock(current->group_leader);
1574
1575         posix_cpu_timers_init_group(sig);
1576
1577         tty_audit_fork(sig);
1578         sched_autogroup_fork(sig);
1579
1580         sig->oom_score_adj = current->signal->oom_score_adj;
1581         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1582
1583         mutex_init(&sig->cred_guard_mutex);
1584
1585         return 0;
1586 }
1587
1588 static void copy_seccomp(struct task_struct *p)
1589 {
1590 #ifdef CONFIG_SECCOMP
1591         /*
1592          * Must be called with sighand->lock held, which is common to
1593          * all threads in the group. Holding cred_guard_mutex is not
1594          * needed because this new task is not yet running and cannot
1595          * be racing exec.
1596          */
1597         assert_spin_locked(&current->sighand->siglock);
1598
1599         /* Ref-count the new filter user, and assign it. */
1600         get_seccomp_filter(current);
1601         p->seccomp = current->seccomp;
1602
1603         /*
1604          * Explicitly enable no_new_privs here in case it got set
1605          * between the task_struct being duplicated and holding the
1606          * sighand lock. The seccomp state and nnp must be in sync.
1607          */
1608         if (task_no_new_privs(current))
1609                 task_set_no_new_privs(p);
1610
1611         /*
1612          * If the parent gained a seccomp mode after copying thread
1613          * flags and between before we held the sighand lock, we have
1614          * to manually enable the seccomp thread flag here.
1615          */
1616         if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1617                 set_tsk_thread_flag(p, TIF_SECCOMP);
1618 #endif
1619 }
1620
1621 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1622 {
1623         current->clear_child_tid = tidptr;
1624
1625         return task_pid_vnr(current);
1626 }
1627
1628 static void rt_mutex_init_task(struct task_struct *p)
1629 {
1630         raw_spin_lock_init(&p->pi_lock);
1631 #ifdef CONFIG_RT_MUTEXES
1632         p->pi_waiters = RB_ROOT_CACHED;
1633         p->pi_top_task = NULL;
1634         p->pi_blocked_on = NULL;
1635 #endif
1636 }
1637
1638 static inline void init_task_pid_links(struct task_struct *task)
1639 {
1640         enum pid_type type;
1641
1642         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1643                 INIT_HLIST_NODE(&task->pid_links[type]);
1644         }
1645 }
1646
1647 static inline void
1648 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1649 {
1650         if (type == PIDTYPE_PID)
1651                 task->thread_pid = pid;
1652         else
1653                 task->signal->pids[type] = pid;
1654 }
1655
1656 static inline void rcu_copy_process(struct task_struct *p)
1657 {
1658 #ifdef CONFIG_PREEMPT_RCU
1659         p->rcu_read_lock_nesting = 0;
1660         p->rcu_read_unlock_special.s = 0;
1661         p->rcu_blocked_node = NULL;
1662         INIT_LIST_HEAD(&p->rcu_node_entry);
1663 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1664 #ifdef CONFIG_TASKS_RCU
1665         p->rcu_tasks_holdout = false;
1666         INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1667         p->rcu_tasks_idle_cpu = -1;
1668 #endif /* #ifdef CONFIG_TASKS_RCU */
1669 }
1670
1671 static int pidfd_release(struct inode *inode, struct file *file)
1672 {
1673         struct pid *pid = file->private_data;
1674
1675         file->private_data = NULL;
1676         put_pid(pid);
1677         return 0;
1678 }
1679
1680 #ifdef CONFIG_PROC_FS
1681 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1682 {
1683         struct pid_namespace *ns = proc_pid_ns(file_inode(m->file));
1684         struct pid *pid = f->private_data;
1685
1686         seq_put_decimal_ull(m, "Pid:\t", pid_nr_ns(pid, ns));
1687         seq_putc(m, '\n');
1688 }
1689 #endif
1690
1691 /*
1692  * Poll support for process exit notification.
1693  */
1694 static unsigned int pidfd_poll(struct file *file, struct poll_table_struct *pts)
1695 {
1696         struct task_struct *task;
1697         struct pid *pid = file->private_data;
1698         int poll_flags = 0;
1699
1700         poll_wait(file, &pid->wait_pidfd, pts);
1701
1702         rcu_read_lock();
1703         task = pid_task(pid, PIDTYPE_PID);
1704         /*
1705          * Inform pollers only when the whole thread group exits.
1706          * If the thread group leader exits before all other threads in the
1707          * group, then poll(2) should block, similar to the wait(2) family.
1708          */
1709         if (!task || (task->exit_state && thread_group_empty(task)))
1710                 poll_flags = POLLIN | POLLRDNORM;
1711         rcu_read_unlock();
1712
1713         return poll_flags;
1714 }
1715
1716 const struct file_operations pidfd_fops = {
1717         .release = pidfd_release,
1718         .poll = pidfd_poll,
1719 #ifdef CONFIG_PROC_FS
1720         .show_fdinfo = pidfd_show_fdinfo,
1721 #endif
1722 };
1723
1724 static void __delayed_free_task(struct rcu_head *rhp)
1725 {
1726         struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1727
1728         free_task(tsk);
1729 }
1730
1731 static __always_inline void delayed_free_task(struct task_struct *tsk)
1732 {
1733         if (IS_ENABLED(CONFIG_MEMCG))
1734                 call_rcu(&tsk->rcu, __delayed_free_task);
1735         else
1736                 free_task(tsk);
1737 }
1738
1739 /*
1740  * This creates a new process as a copy of the old one,
1741  * but does not actually start it yet.
1742  *
1743  * It copies the registers, and all the appropriate
1744  * parts of the process environment (as per the clone
1745  * flags). The actual kick-off is left to the caller.
1746  */
1747 static __latent_entropy struct task_struct *copy_process(
1748                                         struct pid *pid,
1749                                         int trace,
1750                                         int node,
1751                                         struct kernel_clone_args *args)
1752 {
1753         int pidfd = -1, retval;
1754         struct task_struct *p;
1755         struct multiprocess_signals delayed;
1756         struct file *pidfile = NULL;
1757         u64 clone_flags = args->flags;
1758
1759         /*
1760          * Don't allow sharing the root directory with processes in a different
1761          * namespace
1762          */
1763         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1764                 return ERR_PTR(-EINVAL);
1765
1766         if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1767                 return ERR_PTR(-EINVAL);
1768
1769         /*
1770          * Thread groups must share signals as well, and detached threads
1771          * can only be started up within the thread group.
1772          */
1773         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1774                 return ERR_PTR(-EINVAL);
1775
1776         /*
1777          * Shared signal handlers imply shared VM. By way of the above,
1778          * thread groups also imply shared VM. Blocking this case allows
1779          * for various simplifications in other code.
1780          */
1781         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1782                 return ERR_PTR(-EINVAL);
1783
1784         /*
1785          * Siblings of global init remain as zombies on exit since they are
1786          * not reaped by their parent (swapper). To solve this and to avoid
1787          * multi-rooted process trees, prevent global and container-inits
1788          * from creating siblings.
1789          */
1790         if ((clone_flags & CLONE_PARENT) &&
1791                                 current->signal->flags & SIGNAL_UNKILLABLE)
1792                 return ERR_PTR(-EINVAL);
1793
1794         /*
1795          * If the new process will be in a different pid or user namespace
1796          * do not allow it to share a thread group with the forking task.
1797          */
1798         if (clone_flags & CLONE_THREAD) {
1799                 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1800                     (task_active_pid_ns(current) !=
1801                                 current->nsproxy->pid_ns_for_children))
1802                         return ERR_PTR(-EINVAL);
1803         }
1804
1805         if (clone_flags & CLONE_PIDFD) {
1806                 /*
1807                  * - CLONE_DETACHED is blocked so that we can potentially
1808                  *   reuse it later for CLONE_PIDFD.
1809                  * - CLONE_THREAD is blocked until someone really needs it.
1810                  */
1811                 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
1812                         return ERR_PTR(-EINVAL);
1813         }
1814
1815         /*
1816          * Force any signals received before this point to be delivered
1817          * before the fork happens.  Collect up signals sent to multiple
1818          * processes that happen during the fork and delay them so that
1819          * they appear to happen after the fork.
1820          */
1821         sigemptyset(&delayed.signal);
1822         INIT_HLIST_NODE(&delayed.node);
1823
1824         spin_lock_irq(&current->sighand->siglock);
1825         if (!(clone_flags & CLONE_THREAD))
1826                 hlist_add_head(&delayed.node, &current->signal->multiprocess);
1827         recalc_sigpending();
1828         spin_unlock_irq(&current->sighand->siglock);
1829         retval = -ERESTARTNOINTR;
1830         if (signal_pending(current))
1831                 goto fork_out;
1832
1833         retval = -ENOMEM;
1834         p = dup_task_struct(current, node);
1835         if (!p)
1836                 goto fork_out;
1837
1838         /*
1839          * This _must_ happen before we call free_task(), i.e. before we jump
1840          * to any of the bad_fork_* labels. This is to avoid freeing
1841          * p->set_child_tid which is (ab)used as a kthread's data pointer for
1842          * kernel threads (PF_KTHREAD).
1843          */
1844         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
1845         /*
1846          * Clear TID on mm_release()?
1847          */
1848         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
1849
1850         ftrace_graph_init_task(p);
1851
1852         rt_mutex_init_task(p);
1853
1854 #ifdef CONFIG_PROVE_LOCKING
1855         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1856         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1857 #endif
1858         retval = -EAGAIN;
1859         if (atomic_read(&p->real_cred->user->processes) >=
1860                         task_rlimit(p, RLIMIT_NPROC)) {
1861                 if (p->real_cred->user != INIT_USER &&
1862                     !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1863                         goto bad_fork_free;
1864         }
1865         current->flags &= ~PF_NPROC_EXCEEDED;
1866
1867         retval = copy_creds(p, clone_flags);
1868         if (retval < 0)
1869                 goto bad_fork_free;
1870
1871         /*
1872          * If multiple threads are within copy_process(), then this check
1873          * triggers too late. This doesn't hurt, the check is only there
1874          * to stop root fork bombs.
1875          */
1876         retval = -EAGAIN;
1877         if (nr_threads >= max_threads)
1878                 goto bad_fork_cleanup_count;
1879
1880         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1881         p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1882         p->flags |= PF_FORKNOEXEC;
1883         INIT_LIST_HEAD(&p->children);
1884         INIT_LIST_HEAD(&p->sibling);
1885         rcu_copy_process(p);
1886         p->vfork_done = NULL;
1887         spin_lock_init(&p->alloc_lock);
1888
1889         init_sigpending(&p->pending);
1890
1891         p->utime = p->stime = p->gtime = 0;
1892 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1893         p->utimescaled = p->stimescaled = 0;
1894 #endif
1895         prev_cputime_init(&p->prev_cputime);
1896
1897 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1898         seqcount_init(&p->vtime.seqcount);
1899         p->vtime.starttime = 0;
1900         p->vtime.state = VTIME_INACTIVE;
1901 #endif
1902
1903 #if defined(SPLIT_RSS_COUNTING)
1904         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1905 #endif
1906
1907         p->default_timer_slack_ns = current->timer_slack_ns;
1908
1909 #ifdef CONFIG_PSI
1910         p->psi_flags = 0;
1911 #endif
1912
1913         task_io_accounting_init(&p->ioac);
1914         acct_clear_integrals(p);
1915
1916         posix_cputimers_init(&p->posix_cputimers);
1917
1918         p->io_context = NULL;
1919         audit_set_context(p, NULL);
1920         cgroup_fork(p);
1921 #ifdef CONFIG_NUMA
1922         p->mempolicy = mpol_dup(p->mempolicy);
1923         if (IS_ERR(p->mempolicy)) {
1924                 retval = PTR_ERR(p->mempolicy);
1925                 p->mempolicy = NULL;
1926                 goto bad_fork_cleanup_threadgroup_lock;
1927         }
1928 #endif
1929 #ifdef CONFIG_CPUSETS
1930         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1931         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1932         seqcount_init(&p->mems_allowed_seq);
1933 #endif
1934 #ifdef CONFIG_TRACE_IRQFLAGS
1935         p->irq_events = 0;
1936         p->hardirqs_enabled = 0;
1937         p->hardirq_enable_ip = 0;
1938         p->hardirq_enable_event = 0;
1939         p->hardirq_disable_ip = _THIS_IP_;
1940         p->hardirq_disable_event = 0;
1941         p->softirqs_enabled = 1;
1942         p->softirq_enable_ip = _THIS_IP_;
1943         p->softirq_enable_event = 0;
1944         p->softirq_disable_ip = 0;
1945         p->softirq_disable_event = 0;
1946         p->hardirq_context = 0;
1947         p->softirq_context = 0;
1948 #endif
1949
1950         p->pagefault_disabled = 0;
1951
1952 #ifdef CONFIG_LOCKDEP
1953         lockdep_init_task(p);
1954 #endif
1955
1956 #ifdef CONFIG_DEBUG_MUTEXES
1957         p->blocked_on = NULL; /* not blocked yet */
1958 #endif
1959 #ifdef CONFIG_BCACHE
1960         p->sequential_io        = 0;
1961         p->sequential_io_avg    = 0;
1962 #endif
1963
1964         /* Perform scheduler related setup. Assign this task to a CPU. */
1965         retval = sched_fork(clone_flags, p);
1966         if (retval)
1967                 goto bad_fork_cleanup_policy;
1968
1969         retval = perf_event_init_task(p);
1970         if (retval)
1971                 goto bad_fork_cleanup_policy;
1972         retval = audit_alloc(p);
1973         if (retval)
1974                 goto bad_fork_cleanup_perf;
1975         /* copy all the process information */
1976         shm_init_task(p);
1977         retval = security_task_alloc(p, clone_flags);
1978         if (retval)
1979                 goto bad_fork_cleanup_audit;
1980         retval = copy_semundo(clone_flags, p);
1981         if (retval)
1982                 goto bad_fork_cleanup_security;
1983         retval = copy_files(clone_flags, p);
1984         if (retval)
1985                 goto bad_fork_cleanup_semundo;
1986         retval = copy_fs(clone_flags, p);
1987         if (retval)
1988                 goto bad_fork_cleanup_files;
1989         retval = copy_sighand(clone_flags, p);
1990         if (retval)
1991                 goto bad_fork_cleanup_fs;
1992         retval = copy_signal(clone_flags, p);
1993         if (retval)
1994                 goto bad_fork_cleanup_sighand;
1995         retval = copy_mm(clone_flags, p);
1996         if (retval)
1997                 goto bad_fork_cleanup_signal;
1998         retval = copy_namespaces(clone_flags, p);
1999         if (retval)
2000                 goto bad_fork_cleanup_mm;
2001         retval = copy_io(clone_flags, p);
2002         if (retval)
2003                 goto bad_fork_cleanup_namespaces;
2004         retval = copy_thread_tls(clone_flags, args->stack, args->stack_size, p,
2005                                  args->tls);
2006         if (retval)
2007                 goto bad_fork_cleanup_io;
2008
2009         stackleak_task_init(p);
2010
2011         if (pid != &init_struct_pid) {
2012                 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
2013                 if (IS_ERR(pid)) {
2014                         retval = PTR_ERR(pid);
2015                         goto bad_fork_cleanup_thread;
2016                 }
2017         }
2018
2019         /*
2020          * This has to happen after we've potentially unshared the file
2021          * descriptor table (so that the pidfd doesn't leak into the child
2022          * if the fd table isn't shared).
2023          */
2024         if (clone_flags & CLONE_PIDFD) {
2025                 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2026                 if (retval < 0)
2027                         goto bad_fork_free_pid;
2028
2029                 pidfd = retval;
2030
2031                 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2032                                               O_RDWR | O_CLOEXEC);
2033                 if (IS_ERR(pidfile)) {
2034                         put_unused_fd(pidfd);
2035                         retval = PTR_ERR(pidfile);
2036                         goto bad_fork_free_pid;
2037                 }
2038                 get_pid(pid);   /* held by pidfile now */
2039
2040                 retval = put_user(pidfd, args->pidfd);
2041                 if (retval)
2042                         goto bad_fork_put_pidfd;
2043         }
2044
2045 #ifdef CONFIG_BLOCK
2046         p->plug = NULL;
2047 #endif
2048 #ifdef CONFIG_FUTEX
2049         p->robust_list = NULL;
2050 #ifdef CONFIG_COMPAT
2051         p->compat_robust_list = NULL;
2052 #endif
2053         INIT_LIST_HEAD(&p->pi_state_list);
2054         p->pi_state_cache = NULL;
2055 #endif
2056         /*
2057          * sigaltstack should be cleared when sharing the same VM
2058          */
2059         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2060                 sas_ss_reset(p);
2061
2062         /*
2063          * Syscall tracing and stepping should be turned off in the
2064          * child regardless of CLONE_PTRACE.
2065          */
2066         user_disable_single_step(p);
2067         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
2068 #ifdef TIF_SYSCALL_EMU
2069         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
2070 #endif
2071         clear_tsk_latency_tracing(p);
2072
2073         /* ok, now we should be set up.. */
2074         p->pid = pid_nr(pid);
2075         if (clone_flags & CLONE_THREAD) {
2076                 p->exit_signal = -1;
2077                 p->group_leader = current->group_leader;
2078                 p->tgid = current->tgid;
2079         } else {
2080                 if (clone_flags & CLONE_PARENT)
2081                         p->exit_signal = current->group_leader->exit_signal;
2082                 else
2083                         p->exit_signal = args->exit_signal;
2084                 p->group_leader = p;
2085                 p->tgid = p->pid;
2086         }
2087
2088         p->nr_dirtied = 0;
2089         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2090         p->dirty_paused_when = 0;
2091
2092         p->pdeath_signal = 0;
2093         INIT_LIST_HEAD(&p->thread_group);
2094         p->task_works = NULL;
2095
2096         cgroup_threadgroup_change_begin(current);
2097         /*
2098          * Ensure that the cgroup subsystem policies allow the new process to be
2099          * forked. It should be noted the the new process's css_set can be changed
2100          * between here and cgroup_post_fork() if an organisation operation is in
2101          * progress.
2102          */
2103         retval = cgroup_can_fork(p);
2104         if (retval)
2105                 goto bad_fork_cgroup_threadgroup_change_end;
2106
2107         /*
2108          * From this point on we must avoid any synchronous user-space
2109          * communication until we take the tasklist-lock. In particular, we do
2110          * not want user-space to be able to predict the process start-time by
2111          * stalling fork(2) after we recorded the start_time but before it is
2112          * visible to the system.
2113          */
2114
2115         p->start_time = ktime_get_ns();
2116         p->real_start_time = ktime_get_boottime_ns();
2117
2118         /*
2119          * Make it visible to the rest of the system, but dont wake it up yet.
2120          * Need tasklist lock for parent etc handling!
2121          */
2122         write_lock_irq(&tasklist_lock);
2123
2124         /* CLONE_PARENT re-uses the old parent */
2125         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2126                 p->real_parent = current->real_parent;
2127                 p->parent_exec_id = current->parent_exec_id;
2128         } else {
2129                 p->real_parent = current;
2130                 p->parent_exec_id = current->self_exec_id;
2131         }
2132
2133         klp_copy_process(p);
2134
2135         spin_lock(&current->sighand->siglock);
2136
2137         /*
2138          * Copy seccomp details explicitly here, in case they were changed
2139          * before holding sighand lock.
2140          */
2141         copy_seccomp(p);
2142
2143         rseq_fork(p, clone_flags);
2144
2145         /* Don't start children in a dying pid namespace */
2146         if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2147                 retval = -ENOMEM;
2148                 goto bad_fork_cancel_cgroup;
2149         }
2150
2151         /* Let kill terminate clone/fork in the middle */
2152         if (fatal_signal_pending(current)) {
2153                 retval = -EINTR;
2154                 goto bad_fork_cancel_cgroup;
2155         }
2156
2157         /* past the last point of failure */
2158         if (pidfile)
2159                 fd_install(pidfd, pidfile);
2160
2161         init_task_pid_links(p);
2162         if (likely(p->pid)) {
2163                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2164
2165                 init_task_pid(p, PIDTYPE_PID, pid);
2166                 if (thread_group_leader(p)) {
2167                         init_task_pid(p, PIDTYPE_TGID, pid);
2168                         init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2169                         init_task_pid(p, PIDTYPE_SID, task_session(current));
2170
2171                         if (is_child_reaper(pid)) {
2172                                 ns_of_pid(pid)->child_reaper = p;
2173                                 p->signal->flags |= SIGNAL_UNKILLABLE;
2174                         }
2175                         p->signal->shared_pending.signal = delayed.signal;
2176                         p->signal->tty = tty_kref_get(current->signal->tty);
2177                         /*
2178                          * Inherit has_child_subreaper flag under the same
2179                          * tasklist_lock with adding child to the process tree
2180                          * for propagate_has_child_subreaper optimization.
2181                          */
2182                         p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2183                                                          p->real_parent->signal->is_child_subreaper;
2184                         list_add_tail(&p->sibling, &p->real_parent->children);
2185                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
2186                         attach_pid(p, PIDTYPE_TGID);
2187                         attach_pid(p, PIDTYPE_PGID);
2188                         attach_pid(p, PIDTYPE_SID);
2189                         __this_cpu_inc(process_counts);
2190                 } else {
2191                         current->signal->nr_threads++;
2192                         atomic_inc(&current->signal->live);
2193                         refcount_inc(&current->signal->sigcnt);
2194                         task_join_group_stop(p);
2195                         list_add_tail_rcu(&p->thread_group,
2196                                           &p->group_leader->thread_group);
2197                         list_add_tail_rcu(&p->thread_node,
2198                                           &p->signal->thread_head);
2199                 }
2200                 attach_pid(p, PIDTYPE_PID);
2201                 nr_threads++;
2202         }
2203         total_forks++;
2204         hlist_del_init(&delayed.node);
2205         spin_unlock(&current->sighand->siglock);
2206         syscall_tracepoint_update(p);
2207         write_unlock_irq(&tasklist_lock);
2208
2209         proc_fork_connector(p);
2210         cgroup_post_fork(p);
2211         cgroup_threadgroup_change_end(current);
2212         perf_event_fork(p);
2213
2214         trace_task_newtask(p, clone_flags);
2215         uprobe_copy_process(p, clone_flags);
2216
2217         return p;
2218
2219 bad_fork_cancel_cgroup:
2220         spin_unlock(&current->sighand->siglock);
2221         write_unlock_irq(&tasklist_lock);
2222         cgroup_cancel_fork(p);
2223 bad_fork_cgroup_threadgroup_change_end:
2224         cgroup_threadgroup_change_end(current);
2225 bad_fork_put_pidfd:
2226         if (clone_flags & CLONE_PIDFD) {
2227                 fput(pidfile);
2228                 put_unused_fd(pidfd);
2229         }
2230 bad_fork_free_pid:
2231         if (pid != &init_struct_pid)
2232                 free_pid(pid);
2233 bad_fork_cleanup_thread:
2234         exit_thread(p);
2235 bad_fork_cleanup_io:
2236         if (p->io_context)
2237                 exit_io_context(p);
2238 bad_fork_cleanup_namespaces:
2239         exit_task_namespaces(p);
2240 bad_fork_cleanup_mm:
2241         if (p->mm) {
2242                 mm_clear_owner(p->mm, p);
2243                 mmput(p->mm);
2244         }
2245 bad_fork_cleanup_signal:
2246         if (!(clone_flags & CLONE_THREAD))
2247                 free_signal_struct(p->signal);
2248 bad_fork_cleanup_sighand:
2249         __cleanup_sighand(p->sighand);
2250 bad_fork_cleanup_fs:
2251         exit_fs(p); /* blocking */
2252 bad_fork_cleanup_files:
2253         exit_files(p); /* blocking */
2254 bad_fork_cleanup_semundo:
2255         exit_sem(p);
2256 bad_fork_cleanup_security:
2257         security_task_free(p);
2258 bad_fork_cleanup_audit:
2259         audit_free(p);
2260 bad_fork_cleanup_perf:
2261         perf_event_free_task(p);
2262 bad_fork_cleanup_policy:
2263         lockdep_free_task(p);
2264 #ifdef CONFIG_NUMA
2265         mpol_put(p->mempolicy);
2266 bad_fork_cleanup_threadgroup_lock:
2267 #endif
2268         delayacct_tsk_free(p);
2269 bad_fork_cleanup_count:
2270         atomic_dec(&p->cred->user->processes);
2271         exit_creds(p);
2272 bad_fork_free:
2273         p->state = TASK_DEAD;
2274         put_task_stack(p);
2275         delayed_free_task(p);
2276 fork_out:
2277         spin_lock_irq(&current->sighand->siglock);
2278         hlist_del_init(&delayed.node);
2279         spin_unlock_irq(&current->sighand->siglock);
2280         return ERR_PTR(retval);
2281 }
2282
2283 static inline void init_idle_pids(struct task_struct *idle)
2284 {
2285         enum pid_type type;
2286
2287         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2288                 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2289                 init_task_pid(idle, type, &init_struct_pid);
2290         }
2291 }
2292
2293 struct task_struct *fork_idle(int cpu)
2294 {
2295         struct task_struct *task;
2296         struct kernel_clone_args args = {
2297                 .flags = CLONE_VM,
2298         };
2299
2300         task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2301         if (!IS_ERR(task)) {
2302                 init_idle_pids(task);
2303                 init_idle(task, cpu);
2304         }
2305
2306         return task;
2307 }
2308
2309 struct mm_struct *copy_init_mm(void)
2310 {
2311         return dup_mm(NULL, &init_mm);
2312 }
2313
2314 /*
2315  *  Ok, this is the main fork-routine.
2316  *
2317  * It copies the process, and if successful kick-starts
2318  * it and waits for it to finish using the VM if required.
2319  */
2320 long _do_fork(struct kernel_clone_args *args)
2321 {
2322         u64 clone_flags = args->flags;
2323         struct completion vfork;
2324         struct pid *pid;
2325         struct task_struct *p;
2326         int trace = 0;
2327         long nr;
2328
2329         /*
2330          * Determine whether and which event to report to ptracer.  When
2331          * called from kernel_thread or CLONE_UNTRACED is explicitly
2332          * requested, no event is reported; otherwise, report if the event
2333          * for the type of forking is enabled.
2334          */
2335         if (!(clone_flags & CLONE_UNTRACED)) {
2336                 if (clone_flags & CLONE_VFORK)
2337                         trace = PTRACE_EVENT_VFORK;
2338                 else if (args->exit_signal != SIGCHLD)
2339                         trace = PTRACE_EVENT_CLONE;
2340                 else
2341                         trace = PTRACE_EVENT_FORK;
2342
2343                 if (likely(!ptrace_event_enabled(current, trace)))
2344                         trace = 0;
2345         }
2346
2347         p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2348         add_latent_entropy();
2349
2350         if (IS_ERR(p))
2351                 return PTR_ERR(p);
2352
2353         /*
2354          * Do this prior waking up the new thread - the thread pointer
2355          * might get invalid after that point, if the thread exits quickly.
2356          */
2357         trace_sched_process_fork(current, p);
2358
2359         pid = get_task_pid(p, PIDTYPE_PID);
2360         nr = pid_vnr(pid);
2361
2362         if (clone_flags & CLONE_PARENT_SETTID)
2363                 put_user(nr, args->parent_tid);
2364
2365         if (clone_flags & CLONE_VFORK) {
2366                 p->vfork_done = &vfork;
2367                 init_completion(&vfork);
2368                 get_task_struct(p);
2369         }
2370
2371         wake_up_new_task(p);
2372
2373         /* forking complete and child started to run, tell ptracer */
2374         if (unlikely(trace))
2375                 ptrace_event_pid(trace, pid);
2376
2377         if (clone_flags & CLONE_VFORK) {
2378                 if (!wait_for_vfork_done(p, &vfork))
2379                         ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2380         }
2381
2382         put_pid(pid);
2383         return nr;
2384 }
2385
2386 bool legacy_clone_args_valid(const struct kernel_clone_args *kargs)
2387 {
2388         /* clone(CLONE_PIDFD) uses parent_tidptr to return a pidfd */
2389         if ((kargs->flags & CLONE_PIDFD) &&
2390             (kargs->flags & CLONE_PARENT_SETTID))
2391                 return false;
2392
2393         return true;
2394 }
2395
2396 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
2397 /* For compatibility with architectures that call do_fork directly rather than
2398  * using the syscall entry points below. */
2399 long do_fork(unsigned long clone_flags,
2400               unsigned long stack_start,
2401               unsigned long stack_size,
2402               int __user *parent_tidptr,
2403               int __user *child_tidptr)
2404 {
2405         struct kernel_clone_args args = {
2406                 .flags          = (clone_flags & ~CSIGNAL),
2407                 .pidfd          = parent_tidptr,
2408                 .child_tid      = child_tidptr,
2409                 .parent_tid     = parent_tidptr,
2410                 .exit_signal    = (clone_flags & CSIGNAL),
2411                 .stack          = stack_start,
2412                 .stack_size     = stack_size,
2413         };
2414
2415         if (!legacy_clone_args_valid(&args))
2416                 return -EINVAL;
2417
2418         return _do_fork(&args);
2419 }
2420 #endif
2421
2422 /*
2423  * Create a kernel thread.
2424  */
2425 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2426 {
2427         struct kernel_clone_args args = {
2428                 .flags          = ((flags | CLONE_VM | CLONE_UNTRACED) & ~CSIGNAL),
2429                 .exit_signal    = (flags & CSIGNAL),
2430                 .stack          = (unsigned long)fn,
2431                 .stack_size     = (unsigned long)arg,
2432         };
2433
2434         return _do_fork(&args);
2435 }
2436
2437 #ifdef __ARCH_WANT_SYS_FORK
2438 SYSCALL_DEFINE0(fork)
2439 {
2440 #ifdef CONFIG_MMU
2441         struct kernel_clone_args args = {
2442                 .exit_signal = SIGCHLD,
2443         };
2444
2445         return _do_fork(&args);
2446 #else
2447         /* can not support in nommu mode */
2448         return -EINVAL;
2449 #endif
2450 }
2451 #endif
2452
2453 #ifdef __ARCH_WANT_SYS_VFORK
2454 SYSCALL_DEFINE0(vfork)
2455 {
2456         struct kernel_clone_args args = {
2457                 .flags          = CLONE_VFORK | CLONE_VM,
2458                 .exit_signal    = SIGCHLD,
2459         };
2460
2461         return _do_fork(&args);
2462 }
2463 #endif
2464
2465 #ifdef __ARCH_WANT_SYS_CLONE
2466 #ifdef CONFIG_CLONE_BACKWARDS
2467 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2468                  int __user *, parent_tidptr,
2469                  unsigned long, tls,
2470                  int __user *, child_tidptr)
2471 #elif defined(CONFIG_CLONE_BACKWARDS2)
2472 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2473                  int __user *, parent_tidptr,
2474                  int __user *, child_tidptr,
2475                  unsigned long, tls)
2476 #elif defined(CONFIG_CLONE_BACKWARDS3)
2477 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2478                 int, stack_size,
2479                 int __user *, parent_tidptr,
2480                 int __user *, child_tidptr,
2481                 unsigned long, tls)
2482 #else
2483 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2484                  int __user *, parent_tidptr,
2485                  int __user *, child_tidptr,
2486                  unsigned long, tls)
2487 #endif
2488 {
2489         struct kernel_clone_args args = {
2490                 .flags          = (clone_flags & ~CSIGNAL),
2491                 .pidfd          = parent_tidptr,
2492                 .child_tid      = child_tidptr,
2493                 .parent_tid     = parent_tidptr,
2494                 .exit_signal    = (clone_flags & CSIGNAL),
2495                 .stack          = newsp,
2496                 .tls            = tls,
2497         };
2498
2499         if (!legacy_clone_args_valid(&args))
2500                 return -EINVAL;
2501
2502         return _do_fork(&args);
2503 }
2504 #endif
2505
2506 #ifdef __ARCH_WANT_SYS_CLONE3
2507 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
2508                                               struct clone_args __user *uargs,
2509                                               size_t size)
2510 {
2511         struct clone_args args;
2512
2513         if (unlikely(size > PAGE_SIZE))
2514                 return -E2BIG;
2515
2516         if (unlikely(size < sizeof(struct clone_args)))
2517                 return -EINVAL;
2518
2519         if (unlikely(!access_ok(uargs, size)))
2520                 return -EFAULT;
2521
2522         if (size > sizeof(struct clone_args)) {
2523                 unsigned char __user *addr;
2524                 unsigned char __user *end;
2525                 unsigned char val;
2526
2527                 addr = (void __user *)uargs + sizeof(struct clone_args);
2528                 end = (void __user *)uargs + size;
2529
2530                 for (; addr < end; addr++) {
2531                         if (get_user(val, addr))
2532                                 return -EFAULT;
2533                         if (val)
2534                                 return -E2BIG;
2535                 }
2536
2537                 size = sizeof(struct clone_args);
2538         }
2539
2540         if (copy_from_user(&args, uargs, size))
2541                 return -EFAULT;
2542
2543         *kargs = (struct kernel_clone_args){
2544                 .flags          = args.flags,
2545                 .pidfd          = u64_to_user_ptr(args.pidfd),
2546                 .child_tid      = u64_to_user_ptr(args.child_tid),
2547                 .parent_tid     = u64_to_user_ptr(args.parent_tid),
2548                 .exit_signal    = args.exit_signal,
2549                 .stack          = args.stack,
2550                 .stack_size     = args.stack_size,
2551                 .tls            = args.tls,
2552         };
2553
2554         return 0;
2555 }
2556
2557 static bool clone3_args_valid(const struct kernel_clone_args *kargs)
2558 {
2559         /*
2560          * All lower bits of the flag word are taken.
2561          * Verify that no other unknown flags are passed along.
2562          */
2563         if (kargs->flags & ~CLONE_LEGACY_FLAGS)
2564                 return false;
2565
2566         /*
2567          * - make the CLONE_DETACHED bit reuseable for clone3
2568          * - make the CSIGNAL bits reuseable for clone3
2569          */
2570         if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
2571                 return false;
2572
2573         if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
2574             kargs->exit_signal)
2575                 return false;
2576
2577         return true;
2578 }
2579
2580 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
2581 {
2582         int err;
2583
2584         struct kernel_clone_args kargs;
2585
2586         err = copy_clone_args_from_user(&kargs, uargs, size);
2587         if (err)
2588                 return err;
2589
2590         if (!clone3_args_valid(&kargs))
2591                 return -EINVAL;
2592
2593         return _do_fork(&kargs);
2594 }
2595 #endif
2596
2597 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2598 {
2599         struct task_struct *leader, *parent, *child;
2600         int res;
2601
2602         read_lock(&tasklist_lock);
2603         leader = top = top->group_leader;
2604 down:
2605         for_each_thread(leader, parent) {
2606                 list_for_each_entry(child, &parent->children, sibling) {
2607                         res = visitor(child, data);
2608                         if (res) {
2609                                 if (res < 0)
2610                                         goto out;
2611                                 leader = child;
2612                                 goto down;
2613                         }
2614 up:
2615                         ;
2616                 }
2617         }
2618
2619         if (leader != top) {
2620                 child = leader;
2621                 parent = child->real_parent;
2622                 leader = parent->group_leader;
2623                 goto up;
2624         }
2625 out:
2626         read_unlock(&tasklist_lock);
2627 }
2628
2629 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2630 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2631 #endif
2632
2633 static void sighand_ctor(void *data)
2634 {
2635         struct sighand_struct *sighand = data;
2636
2637         spin_lock_init(&sighand->siglock);
2638         init_waitqueue_head(&sighand->signalfd_wqh);
2639 }
2640
2641 void __init proc_caches_init(void)
2642 {
2643         unsigned int mm_size;
2644
2645         sighand_cachep = kmem_cache_create("sighand_cache",
2646                         sizeof(struct sighand_struct), 0,
2647                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2648                         SLAB_ACCOUNT, sighand_ctor);
2649         signal_cachep = kmem_cache_create("signal_cache",
2650                         sizeof(struct signal_struct), 0,
2651                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2652                         NULL);
2653         files_cachep = kmem_cache_create("files_cache",
2654                         sizeof(struct files_struct), 0,
2655                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2656                         NULL);
2657         fs_cachep = kmem_cache_create("fs_cache",
2658                         sizeof(struct fs_struct), 0,
2659                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2660                         NULL);
2661
2662         /*
2663          * The mm_cpumask is located at the end of mm_struct, and is
2664          * dynamically sized based on the maximum CPU number this system
2665          * can have, taking hotplug into account (nr_cpu_ids).
2666          */
2667         mm_size = sizeof(struct mm_struct) + cpumask_size();
2668
2669         mm_cachep = kmem_cache_create_usercopy("mm_struct",
2670                         mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
2671                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2672                         offsetof(struct mm_struct, saved_auxv),
2673                         sizeof_field(struct mm_struct, saved_auxv),
2674                         NULL);
2675         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2676         mmap_init();
2677         nsproxy_cache_init();
2678 }
2679
2680 /*
2681  * Check constraints on flags passed to the unshare system call.
2682  */
2683 static int check_unshare_flags(unsigned long unshare_flags)
2684 {
2685         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2686                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2687                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2688                                 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2689                 return -EINVAL;
2690         /*
2691          * Not implemented, but pretend it works if there is nothing
2692          * to unshare.  Note that unsharing the address space or the
2693          * signal handlers also need to unshare the signal queues (aka
2694          * CLONE_THREAD).
2695          */
2696         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2697                 if (!thread_group_empty(current))
2698                         return -EINVAL;
2699         }
2700         if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2701                 if (refcount_read(&current->sighand->count) > 1)
2702                         return -EINVAL;
2703         }
2704         if (unshare_flags & CLONE_VM) {
2705                 if (!current_is_single_threaded())
2706                         return -EINVAL;
2707         }
2708
2709         return 0;
2710 }
2711
2712 /*
2713  * Unshare the filesystem structure if it is being shared
2714  */
2715 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2716 {
2717         struct fs_struct *fs = current->fs;
2718
2719         if (!(unshare_flags & CLONE_FS) || !fs)
2720                 return 0;
2721
2722         /* don't need lock here; in the worst case we'll do useless copy */
2723         if (fs->users == 1)
2724                 return 0;
2725
2726         *new_fsp = copy_fs_struct(fs);
2727         if (!*new_fsp)
2728                 return -ENOMEM;
2729
2730         return 0;
2731 }
2732
2733 /*
2734  * Unshare file descriptor table if it is being shared
2735  */
2736 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2737 {
2738         struct files_struct *fd = current->files;
2739         int error = 0;
2740
2741         if ((unshare_flags & CLONE_FILES) &&
2742             (fd && atomic_read(&fd->count) > 1)) {
2743                 *new_fdp = dup_fd(fd, &error);
2744                 if (!*new_fdp)
2745                         return error;
2746         }
2747
2748         return 0;
2749 }
2750
2751 /*
2752  * unshare allows a process to 'unshare' part of the process
2753  * context which was originally shared using clone.  copy_*
2754  * functions used by do_fork() cannot be used here directly
2755  * because they modify an inactive task_struct that is being
2756  * constructed. Here we are modifying the current, active,
2757  * task_struct.
2758  */
2759 int ksys_unshare(unsigned long unshare_flags)
2760 {
2761         struct fs_struct *fs, *new_fs = NULL;
2762         struct files_struct *fd, *new_fd = NULL;
2763         struct cred *new_cred = NULL;
2764         struct nsproxy *new_nsproxy = NULL;
2765         int do_sysvsem = 0;
2766         int err;
2767
2768         /*
2769          * If unsharing a user namespace must also unshare the thread group
2770          * and unshare the filesystem root and working directories.
2771          */
2772         if (unshare_flags & CLONE_NEWUSER)
2773                 unshare_flags |= CLONE_THREAD | CLONE_FS;
2774         /*
2775          * If unsharing vm, must also unshare signal handlers.
2776          */
2777         if (unshare_flags & CLONE_VM)
2778                 unshare_flags |= CLONE_SIGHAND;
2779         /*
2780          * If unsharing a signal handlers, must also unshare the signal queues.
2781          */
2782         if (unshare_flags & CLONE_SIGHAND)
2783                 unshare_flags |= CLONE_THREAD;
2784         /*
2785          * If unsharing namespace, must also unshare filesystem information.
2786          */
2787         if (unshare_flags & CLONE_NEWNS)
2788                 unshare_flags |= CLONE_FS;
2789
2790         err = check_unshare_flags(unshare_flags);
2791         if (err)
2792                 goto bad_unshare_out;
2793         /*
2794          * CLONE_NEWIPC must also detach from the undolist: after switching
2795          * to a new ipc namespace, the semaphore arrays from the old
2796          * namespace are unreachable.
2797          */
2798         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2799                 do_sysvsem = 1;
2800         err = unshare_fs(unshare_flags, &new_fs);
2801         if (err)
2802                 goto bad_unshare_out;
2803         err = unshare_fd(unshare_flags, &new_fd);
2804         if (err)
2805                 goto bad_unshare_cleanup_fs;
2806         err = unshare_userns(unshare_flags, &new_cred);
2807         if (err)
2808                 goto bad_unshare_cleanup_fd;
2809         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2810                                          new_cred, new_fs);
2811         if (err)
2812                 goto bad_unshare_cleanup_cred;
2813
2814         if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2815                 if (do_sysvsem) {
2816                         /*
2817                          * CLONE_SYSVSEM is equivalent to sys_exit().
2818                          */
2819                         exit_sem(current);
2820                 }
2821                 if (unshare_flags & CLONE_NEWIPC) {
2822                         /* Orphan segments in old ns (see sem above). */
2823                         exit_shm(current);
2824                         shm_init_task(current);
2825                 }
2826
2827                 if (new_nsproxy)
2828                         switch_task_namespaces(current, new_nsproxy);
2829
2830                 task_lock(current);
2831
2832                 if (new_fs) {
2833                         fs = current->fs;
2834                         spin_lock(&fs->lock);
2835                         current->fs = new_fs;
2836                         if (--fs->users)
2837                                 new_fs = NULL;
2838                         else
2839                                 new_fs = fs;
2840                         spin_unlock(&fs->lock);
2841                 }
2842
2843                 if (new_fd) {
2844                         fd = current->files;
2845                         current->files = new_fd;
2846                         new_fd = fd;
2847                 }
2848
2849                 task_unlock(current);
2850
2851                 if (new_cred) {
2852                         /* Install the new user namespace */
2853                         commit_creds(new_cred);
2854                         new_cred = NULL;
2855                 }
2856         }
2857
2858         perf_event_namespaces(current);
2859
2860 bad_unshare_cleanup_cred:
2861         if (new_cred)
2862                 put_cred(new_cred);
2863 bad_unshare_cleanup_fd:
2864         if (new_fd)
2865                 put_files_struct(new_fd);
2866
2867 bad_unshare_cleanup_fs:
2868         if (new_fs)
2869                 free_fs_struct(new_fs);
2870
2871 bad_unshare_out:
2872         return err;
2873 }
2874
2875 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2876 {
2877         return ksys_unshare(unshare_flags);
2878 }
2879
2880 /*
2881  *      Helper to unshare the files of the current task.
2882  *      We don't want to expose copy_files internals to
2883  *      the exec layer of the kernel.
2884  */
2885
2886 int unshare_files(struct files_struct **displaced)
2887 {
2888         struct task_struct *task = current;
2889         struct files_struct *copy = NULL;
2890         int error;
2891
2892         error = unshare_fd(CLONE_FILES, &copy);
2893         if (error || !copy) {
2894                 *displaced = NULL;
2895                 return error;
2896         }
2897         *displaced = task->files;
2898         task_lock(task);
2899         task->files = copy;
2900         task_unlock(task);
2901         return 0;
2902 }
2903
2904 int sysctl_max_threads(struct ctl_table *table, int write,
2905                        void __user *buffer, size_t *lenp, loff_t *ppos)
2906 {
2907         struct ctl_table t;
2908         int ret;
2909         int threads = max_threads;
2910         int min = MIN_THREADS;
2911         int max = MAX_THREADS;
2912
2913         t = *table;
2914         t.data = &threads;
2915         t.extra1 = &min;
2916         t.extra2 = &max;
2917
2918         ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2919         if (ret || !write)
2920                 return ret;
2921
2922         set_max_threads(threads);
2923
2924         return 0;
2925 }