projects/linux·blob v4.18-rc2 · refs

2535 lines · 60.4 KiB

1/*
2 * linux/kernel/fork.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7/*
8 * 'fork.c' contains the help-routines for the 'fork' system call
9 * (see also entry.S and others).
10 * Fork is rather simple, once you get the hang of it, but the memory
11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
12 */
13
14#include <linux/slab.h>
15#include <linux/sched/autogroup.h>
16#include <linux/sched/mm.h>
17#include <linux/sched/coredump.h>
18#include <linux/sched/user.h>
19#include <linux/sched/numa_balancing.h>
20#include <linux/sched/stat.h>
21#include <linux/sched/task.h>
22#include <linux/sched/task_stack.h>
23#include <linux/sched/cputime.h>
24#include <linux/rtmutex.h>
25#include <linux/init.h>
26#include <linux/unistd.h>
27#include <linux/module.h>
28#include <linux/vmalloc.h>
29#include <linux/completion.h>
30#include <linux/personality.h>
31#include <linux/mempolicy.h>
32#include <linux/sem.h>
33#include <linux/file.h>
34#include <linux/fdtable.h>
35#include <linux/iocontext.h>
36#include <linux/key.h>
37#include <linux/binfmts.h>
38#include <linux/mman.h>
39#include <linux/mmu_notifier.h>
40#include <linux/hmm.h>
41#include <linux/fs.h>
42#include <linux/mm.h>
43#include <linux/vmacache.h>
44#include <linux/nsproxy.h>
45#include <linux/capability.h>
46#include <linux/cpu.h>
47#include <linux/cgroup.h>
48#include <linux/security.h>
49#include <linux/hugetlb.h>
50#include <linux/seccomp.h>
51#include <linux/swap.h>
52#include <linux/syscalls.h>
53#include <linux/jiffies.h>
54#include <linux/futex.h>
55#include <linux/compat.h>
56#include <linux/kthread.h>
57#include <linux/task_io_accounting_ops.h>
58#include <linux/rcupdate.h>
59#include <linux/ptrace.h>
60#include <linux/mount.h>
61#include <linux/audit.h>
62#include <linux/memcontrol.h>
63#include <linux/ftrace.h>
64#include <linux/proc_fs.h>
65#include <linux/profile.h>
66#include <linux/rmap.h>
67#include <linux/ksm.h>
68#include <linux/acct.h>
69#include <linux/userfaultfd_k.h>
70#include <linux/tsacct_kern.h>
71#include <linux/cn_proc.h>
72#include <linux/freezer.h>
73#include <linux/delayacct.h>
74#include <linux/taskstats_kern.h>
75#include <linux/random.h>
76#include <linux/tty.h>
77#include <linux/blkdev.h>
78#include <linux/fs_struct.h>
79#include <linux/magic.h>
80#include <linux/sched/mm.h>
81#include <linux/perf_event.h>
82#include <linux/posix-timers.h>
83#include <linux/user-return-notifier.h>
84#include <linux/oom.h>
85#include <linux/khugepaged.h>
86#include <linux/signalfd.h>
87#include <linux/uprobes.h>
88#include <linux/aio.h>
89#include <linux/compiler.h>
90#include <linux/sysctl.h>
91#include <linux/kcov.h>
92#include <linux/livepatch.h>
93#include <linux/thread_info.h>
94
95#include <asm/pgtable.h>
96#include <asm/pgalloc.h>
97#include <linux/uaccess.h>
98#include <asm/mmu_context.h>
99#include <asm/cacheflush.h>
100#include <asm/tlbflush.h>
101
102#include <trace/events/sched.h>
103
104#define CREATE_TRACE_POINTS
105#include <trace/events/task.h>
106
107/*
108 * Minimum number of threads to boot the kernel
109 */
110#define MIN_THREADS 20
111
112/*
113 * Maximum number of threads
114 */
115#define MAX_THREADS FUTEX_TID_MASK
116
117/*
118 * Protected counters by write_lock_irq(&tasklist_lock)
119 */
120unsigned long total_forks; /* Handle normal Linux uptimes. */
121int nr_threads; /* The idle threads do not count.. */
122
123int max_threads; /* tunable limit on nr_threads */
124
125DEFINE_PER_CPU(unsigned long, process_counts) = 0;
126
127__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
128
129#ifdef CONFIG_PROVE_RCU
130int lockdep_tasklist_lock_is_held(void)
131{
132 return lockdep_is_held(&tasklist_lock);
133}
134EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
135#endif /* #ifdef CONFIG_PROVE_RCU */
136
137int nr_processes(void)
138{
139 int cpu;
140 int total = 0;
141
142 for_each_possible_cpu(cpu)
143 total += per_cpu(process_counts, cpu);
144
145 return total;
146}
147
148void __weak arch_release_task_struct(struct task_struct *tsk)
149{
150}
151
152#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
153static struct kmem_cache *task_struct_cachep;
154
155static inline struct task_struct *alloc_task_struct_node(int node)
156{
157 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
158}
159
160static inline void free_task_struct(struct task_struct *tsk)
161{
162 kmem_cache_free(task_struct_cachep, tsk);
163}
164#endif
165
166void __weak arch_release_thread_stack(unsigned long *stack)
167{
168}
169
170#ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
171
172/*
173 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
174 * kmemcache based allocator.
175 */
176# if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
177
178#ifdef CONFIG_VMAP_STACK
179/*
180 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
181 * flush. Try to minimize the number of calls by caching stacks.
182 */
183#define NR_CACHED_STACKS 2
184static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
185
186static int free_vm_stack_cache(unsigned int cpu)
187{
188 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
189 int i;
190
191 for (i = 0; i < NR_CACHED_STACKS; i++) {
192 struct vm_struct *vm_stack = cached_vm_stacks[i];
193
194 if (!vm_stack)
195 continue;
196
197 vfree(vm_stack->addr);
198 cached_vm_stacks[i] = NULL;
199 }
200
201 return 0;
202}
203#endif
204
205static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
206{
207#ifdef CONFIG_VMAP_STACK
208 void *stack;
209 int i;
210
211 for (i = 0; i < NR_CACHED_STACKS; i++) {
212 struct vm_struct *s;
213
214 s = this_cpu_xchg(cached_stacks[i], NULL);
215
216 if (!s)
217 continue;
218
219 /* Clear stale pointers from reused stack. */
220 memset(s->addr, 0, THREAD_SIZE);
221
222 tsk->stack_vm_area = s;
223 return s->addr;
224 }
225
226 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
227 VMALLOC_START, VMALLOC_END,
228 THREADINFO_GFP,
229 PAGE_KERNEL,
230 0, node, __builtin_return_address(0));
231
232 /*
233 * We can't call find_vm_area() in interrupt context, and
234 * free_thread_stack() can be called in interrupt context,
235 * so cache the vm_struct.
236 */
237 if (stack)
238 tsk->stack_vm_area = find_vm_area(stack);
239 return stack;
240#else
241 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
242 THREAD_SIZE_ORDER);
243
244 return page ? page_address(page) : NULL;
245#endif
246}
247
248static inline void free_thread_stack(struct task_struct *tsk)
249{
250#ifdef CONFIG_VMAP_STACK
251 if (task_stack_vm_area(tsk)) {
252 int i;
253
254 for (i = 0; i < NR_CACHED_STACKS; i++) {
255 if (this_cpu_cmpxchg(cached_stacks[i],
256 NULL, tsk->stack_vm_area) != NULL)
257 continue;
258
259 return;
260 }
261
262 vfree_atomic(tsk->stack);
263 return;
264 }
265#endif
266
267 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
268}
269# else
270static struct kmem_cache *thread_stack_cache;
271
272static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
273 int node)
274{
275 return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
276}
277
278static void free_thread_stack(struct task_struct *tsk)
279{
280 kmem_cache_free(thread_stack_cache, tsk->stack);
281}
282
283void thread_stack_cache_init(void)
284{
285 thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
286 THREAD_SIZE, THREAD_SIZE, 0, 0,
287 THREAD_SIZE, NULL);
288 BUG_ON(thread_stack_cache == NULL);
289}
290# endif
291#endif
292
293/* SLAB cache for signal_struct structures (tsk->signal) */
294static struct kmem_cache *signal_cachep;
295
296/* SLAB cache for sighand_struct structures (tsk->sighand) */
297struct kmem_cache *sighand_cachep;
298
299/* SLAB cache for files_struct structures (tsk->files) */
300struct kmem_cache *files_cachep;
301
302/* SLAB cache for fs_struct structures (tsk->fs) */
303struct kmem_cache *fs_cachep;
304
305/* SLAB cache for vm_area_struct structures */
306struct kmem_cache *vm_area_cachep;
307
308/* SLAB cache for mm_struct structures (tsk->mm) */
309static struct kmem_cache *mm_cachep;
310
311static void account_kernel_stack(struct task_struct *tsk, int account)
312{
313 void *stack = task_stack_page(tsk);
314 struct vm_struct *vm = task_stack_vm_area(tsk);
315
316 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
317
318 if (vm) {
319 int i;
320
321 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
322
323 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
324 mod_zone_page_state(page_zone(vm->pages[i]),
325 NR_KERNEL_STACK_KB,
326 PAGE_SIZE / 1024 * account);
327 }
328
329 /* All stack pages belong to the same memcg. */
330 mod_memcg_page_state(vm->pages[0], MEMCG_KERNEL_STACK_KB,
331 account * (THREAD_SIZE / 1024));
332 } else {
333 /*
334 * All stack pages are in the same zone and belong to the
335 * same memcg.
336 */
337 struct page *first_page = virt_to_page(stack);
338
339 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
340 THREAD_SIZE / 1024 * account);
341
342 mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB,
343 account * (THREAD_SIZE / 1024));
344 }
345}
346
347static void release_task_stack(struct task_struct *tsk)
348{
349 if (WARN_ON(tsk->state != TASK_DEAD))
350 return; /* Better to leak the stack than to free prematurely */
351
352 account_kernel_stack(tsk, -1);
353 arch_release_thread_stack(tsk->stack);
354 free_thread_stack(tsk);
355 tsk->stack = NULL;
356#ifdef CONFIG_VMAP_STACK
357 tsk->stack_vm_area = NULL;
358#endif
359}
360
361#ifdef CONFIG_THREAD_INFO_IN_TASK
362void put_task_stack(struct task_struct *tsk)
363{
364 if (atomic_dec_and_test(&tsk->stack_refcount))
365 release_task_stack(tsk);
366}
367#endif
368
369void free_task(struct task_struct *tsk)
370{
371#ifndef CONFIG_THREAD_INFO_IN_TASK
372 /*
373 * The task is finally done with both the stack and thread_info,
374 * so free both.
375 */
376 release_task_stack(tsk);
377#else
378 /*
379 * If the task had a separate stack allocation, it should be gone
380 * by now.
381 */
382 WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0);
383#endif
384 rt_mutex_debug_task_free(tsk);
385 ftrace_graph_exit_task(tsk);
386 put_seccomp_filter(tsk);
387 arch_release_task_struct(tsk);
388 if (tsk->flags & PF_KTHREAD)
389 free_kthread_struct(tsk);
390 free_task_struct(tsk);
391}
392EXPORT_SYMBOL(free_task);
393
394#ifdef CONFIG_MMU
395static __latent_entropy int dup_mmap(struct mm_struct *mm,
396 struct mm_struct *oldmm)
397{
398 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
399 struct rb_node **rb_link, *rb_parent;
400 int retval;
401 unsigned long charge;
402 LIST_HEAD(uf);
403
404 uprobe_start_dup_mmap();
405 if (down_write_killable(&oldmm->mmap_sem)) {
406 retval = -EINTR;
407 goto fail_uprobe_end;
408 }
409 flush_cache_dup_mm(oldmm);
410 uprobe_dup_mmap(oldmm, mm);
411 /*
412 * Not linked in yet - no deadlock potential:
413 */
414 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
415
416 /* No ordering required: file already has been exposed. */
417 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
418
419 mm->total_vm = oldmm->total_vm;
420 mm->data_vm = oldmm->data_vm;
421 mm->exec_vm = oldmm->exec_vm;
422 mm->stack_vm = oldmm->stack_vm;
423
424 rb_link = &mm->mm_rb.rb_node;
425 rb_parent = NULL;
426 pprev = &mm->mmap;
427 retval = ksm_fork(mm, oldmm);
428 if (retval)
429 goto out;
430 retval = khugepaged_fork(mm, oldmm);
431 if (retval)
432 goto out;
433
434 prev = NULL;
435 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
436 struct file *file;
437
438 if (mpnt->vm_flags & VM_DONTCOPY) {
439 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
440 continue;
441 }
442 charge = 0;
443 /*
444 * Don't duplicate many vmas if we've been oom-killed (for
445 * example)
446 */
447 if (fatal_signal_pending(current)) {
448 retval = -EINTR;
449 goto out;
450 }
451 if (mpnt->vm_flags & VM_ACCOUNT) {
452 unsigned long len = vma_pages(mpnt);
453
454 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
455 goto fail_nomem;
456 charge = len;
457 }
458 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
459 if (!tmp)
460 goto fail_nomem;
461 *tmp = *mpnt;
462 INIT_LIST_HEAD(&tmp->anon_vma_chain);
463 retval = vma_dup_policy(mpnt, tmp);
464 if (retval)
465 goto fail_nomem_policy;
466 tmp->vm_mm = mm;
467 retval = dup_userfaultfd(tmp, &uf);
468 if (retval)
469 goto fail_nomem_anon_vma_fork;
470 if (tmp->vm_flags & VM_WIPEONFORK) {
471 /* VM_WIPEONFORK gets a clean slate in the child. */
472 tmp->anon_vma = NULL;
473 if (anon_vma_prepare(tmp))
474 goto fail_nomem_anon_vma_fork;
475 } else if (anon_vma_fork(tmp, mpnt))
476 goto fail_nomem_anon_vma_fork;
477 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
478 tmp->vm_next = tmp->vm_prev = NULL;
479 file = tmp->vm_file;
480 if (file) {
481 struct inode *inode = file_inode(file);
482 struct address_space *mapping = file->f_mapping;
483
484 get_file(file);
485 if (tmp->vm_flags & VM_DENYWRITE)
486 atomic_dec(&inode->i_writecount);
487 i_mmap_lock_write(mapping);
488 if (tmp->vm_flags & VM_SHARED)
489 atomic_inc(&mapping->i_mmap_writable);
490 flush_dcache_mmap_lock(mapping);
491 /* insert tmp into the share list, just after mpnt */
492 vma_interval_tree_insert_after(tmp, mpnt,
493 &mapping->i_mmap);
494 flush_dcache_mmap_unlock(mapping);
495 i_mmap_unlock_write(mapping);
496 }
497
498 /*
499 * Clear hugetlb-related page reserves for children. This only
500 * affects MAP_PRIVATE mappings. Faults generated by the child
501 * are not guaranteed to succeed, even if read-only
502 */
503 if (is_vm_hugetlb_page(tmp))
504 reset_vma_resv_huge_pages(tmp);
505
506 /*
507 * Link in the new vma and copy the page table entries.
508 */
509 *pprev = tmp;
510 pprev = &tmp->vm_next;
511 tmp->vm_prev = prev;
512 prev = tmp;
513
514 __vma_link_rb(mm, tmp, rb_link, rb_parent);
515 rb_link = &tmp->vm_rb.rb_right;
516 rb_parent = &tmp->vm_rb;
517
518 mm->map_count++;
519 if (!(tmp->vm_flags & VM_WIPEONFORK))
520 retval = copy_page_range(mm, oldmm, mpnt);
521
522 if (tmp->vm_ops && tmp->vm_ops->open)
523 tmp->vm_ops->open(tmp);
524
525 if (retval)
526 goto out;
527 }
528 /* a new mm has just been created */
529 arch_dup_mmap(oldmm, mm);
530 retval = 0;
531out:
532 up_write(&mm->mmap_sem);
533 flush_tlb_mm(oldmm);
534 up_write(&oldmm->mmap_sem);
535 dup_userfaultfd_complete(&uf);
536fail_uprobe_end:
537 uprobe_end_dup_mmap();
538 return retval;
539fail_nomem_anon_vma_fork:
540 mpol_put(vma_policy(tmp));
541fail_nomem_policy:
542 kmem_cache_free(vm_area_cachep, tmp);
543fail_nomem:
544 retval = -ENOMEM;
545 vm_unacct_memory(charge);
546 goto out;
547}
548
549static inline int mm_alloc_pgd(struct mm_struct *mm)
550{
551 mm->pgd = pgd_alloc(mm);
552 if (unlikely(!mm->pgd))
553 return -ENOMEM;
554 return 0;
555}
556
557static inline void mm_free_pgd(struct mm_struct *mm)
558{
559 pgd_free(mm, mm->pgd);
560}
561#else
562static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
563{
564 down_write(&oldmm->mmap_sem);
565 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
566 up_write(&oldmm->mmap_sem);
567 return 0;
568}
569#define mm_alloc_pgd(mm) (0)
570#define mm_free_pgd(mm)
571#endif /* CONFIG_MMU */
572
573static void check_mm(struct mm_struct *mm)
574{
575 int i;
576
577 for (i = 0; i < NR_MM_COUNTERS; i++) {
578 long x = atomic_long_read(&mm->rss_stat.count[i]);
579
580 if (unlikely(x))
581 printk(KERN_ALERT "BUG: Bad rss-counter state "
582 "mm:%p idx:%d val:%ld\n", mm, i, x);
583 }
584
585 if (mm_pgtables_bytes(mm))
586 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
587 mm_pgtables_bytes(mm));
588
589#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
590 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
591#endif
592}
593
594#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
595#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
596
597/*
598 * Called when the last reference to the mm
599 * is dropped: either by a lazy thread or by
600 * mmput. Free the page directory and the mm.
601 */
602void __mmdrop(struct mm_struct *mm)
603{
604 BUG_ON(mm == &init_mm);
605 WARN_ON_ONCE(mm == current->mm);
606 WARN_ON_ONCE(mm == current->active_mm);
607 mm_free_pgd(mm);
608 destroy_context(mm);
609 hmm_mm_destroy(mm);
610 mmu_notifier_mm_destroy(mm);
611 check_mm(mm);
612 put_user_ns(mm->user_ns);
613 free_mm(mm);
614}
615EXPORT_SYMBOL_GPL(__mmdrop);
616
617static void mmdrop_async_fn(struct work_struct *work)
618{
619 struct mm_struct *mm;
620
621 mm = container_of(work, struct mm_struct, async_put_work);
622 __mmdrop(mm);
623}
624
625static void mmdrop_async(struct mm_struct *mm)
626{
627 if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
628 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
629 schedule_work(&mm->async_put_work);
630 }
631}
632
633static inline void free_signal_struct(struct signal_struct *sig)
634{
635 taskstats_tgid_free(sig);
636 sched_autogroup_exit(sig);
637 /*
638 * __mmdrop is not safe to call from softirq context on x86 due to
639 * pgd_dtor so postpone it to the async context
640 */
641 if (sig->oom_mm)
642 mmdrop_async(sig->oom_mm);
643 kmem_cache_free(signal_cachep, sig);
644}
645
646static inline void put_signal_struct(struct signal_struct *sig)
647{
648 if (atomic_dec_and_test(&sig->sigcnt))
649 free_signal_struct(sig);
650}
651
652void __put_task_struct(struct task_struct *tsk)
653{
654 WARN_ON(!tsk->exit_state);
655 WARN_ON(atomic_read(&tsk->usage));
656 WARN_ON(tsk == current);
657
658 cgroup_free(tsk);
659 task_numa_free(tsk);
660 security_task_free(tsk);
661 exit_creds(tsk);
662 delayacct_tsk_free(tsk);
663 put_signal_struct(tsk->signal);
664
665 if (!profile_handoff_task(tsk))
666 free_task(tsk);
667}
668EXPORT_SYMBOL_GPL(__put_task_struct);
669
670void __init __weak arch_task_cache_init(void) { }
671
672/*
673 * set_max_threads
674 */
675static void set_max_threads(unsigned int max_threads_suggested)
676{
677 u64 threads;
678
679 /*
680 * The number of threads shall be limited such that the thread
681 * structures may only consume a small part of the available memory.
682 */
683 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
684 threads = MAX_THREADS;
685 else
686 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
687 (u64) THREAD_SIZE * 8UL);
688
689 if (threads > max_threads_suggested)
690 threads = max_threads_suggested;
691
692 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
693}
694
695#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
696/* Initialized by the architecture: */
697int arch_task_struct_size __read_mostly;
698#endif
699
700static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
701{
702 /* Fetch thread_struct whitelist for the architecture. */
703 arch_thread_struct_whitelist(offset, size);
704
705 /*
706 * Handle zero-sized whitelist or empty thread_struct, otherwise
707 * adjust offset to position of thread_struct in task_struct.
708 */
709 if (unlikely(*size == 0))
710 *offset = 0;
711 else
712 *offset += offsetof(struct task_struct, thread);
713}
714
715void __init fork_init(void)
716{
717 int i;
718#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
719#ifndef ARCH_MIN_TASKALIGN
720#define ARCH_MIN_TASKALIGN 0
721#endif
722 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
723 unsigned long useroffset, usersize;
724
725 /* create a slab on which task_structs can be allocated */
726 task_struct_whitelist(&useroffset, &usersize);
727 task_struct_cachep = kmem_cache_create_usercopy("task_struct",
728 arch_task_struct_size, align,
729 SLAB_PANIC|SLAB_ACCOUNT,
730 useroffset, usersize, NULL);
731#endif
732
733 /* do the arch specific task caches init */
734 arch_task_cache_init();
735
736 set_max_threads(MAX_THREADS);
737
738 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
739 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
740 init_task.signal->rlim[RLIMIT_SIGPENDING] =
741 init_task.signal->rlim[RLIMIT_NPROC];
742
743 for (i = 0; i < UCOUNT_COUNTS; i++) {
744 init_user_ns.ucount_max[i] = max_threads/2;
745 }
746
747#ifdef CONFIG_VMAP_STACK
748 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
749 NULL, free_vm_stack_cache);
750#endif
751
752 lockdep_init_task(&init_task);
753}
754
755int __weak arch_dup_task_struct(struct task_struct *dst,
756 struct task_struct *src)
757{
758 *dst = *src;
759 return 0;
760}
761
762void set_task_stack_end_magic(struct task_struct *tsk)
763{
764 unsigned long *stackend;
765
766 stackend = end_of_stack(tsk);
767 *stackend = STACK_END_MAGIC; /* for overflow detection */
768}
769
770static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
771{
772 struct task_struct *tsk;
773 unsigned long *stack;
774 struct vm_struct *stack_vm_area;
775 int err;
776
777 if (node == NUMA_NO_NODE)
778 node = tsk_fork_get_node(orig);
779 tsk = alloc_task_struct_node(node);
780 if (!tsk)
781 return NULL;
782
783 stack = alloc_thread_stack_node(tsk, node);
784 if (!stack)
785 goto free_tsk;
786
787 stack_vm_area = task_stack_vm_area(tsk);
788
789 err = arch_dup_task_struct(tsk, orig);
790
791 /*
792 * arch_dup_task_struct() clobbers the stack-related fields. Make
793 * sure they're properly initialized before using any stack-related
794 * functions again.
795 */
796 tsk->stack = stack;
797#ifdef CONFIG_VMAP_STACK
798 tsk->stack_vm_area = stack_vm_area;
799#endif
800#ifdef CONFIG_THREAD_INFO_IN_TASK
801 atomic_set(&tsk->stack_refcount, 1);
802#endif
803
804 if (err)
805 goto free_stack;
806
807#ifdef CONFIG_SECCOMP
808 /*
809 * We must handle setting up seccomp filters once we're under
810 * the sighand lock in case orig has changed between now and
811 * then. Until then, filter must be NULL to avoid messing up
812 * the usage counts on the error path calling free_task.
813 */
814 tsk->seccomp.filter = NULL;
815#endif
816
817 setup_thread_stack(tsk, orig);
818 clear_user_return_notifier(tsk);
819 clear_tsk_need_resched(tsk);
820 set_task_stack_end_magic(tsk);
821
822#ifdef CONFIG_STACKPROTECTOR
823 tsk->stack_canary = get_random_canary();
824#endif
825
826 /*
827 * One for us, one for whoever does the "release_task()" (usually
828 * parent)
829 */
830 atomic_set(&tsk->usage, 2);
831#ifdef CONFIG_BLK_DEV_IO_TRACE
832 tsk->btrace_seq = 0;
833#endif
834 tsk->splice_pipe = NULL;
835 tsk->task_frag.page = NULL;
836 tsk->wake_q.next = NULL;
837
838 account_kernel_stack(tsk, 1);
839
840 kcov_task_init(tsk);
841
842#ifdef CONFIG_FAULT_INJECTION
843 tsk->fail_nth = 0;
844#endif
845
846 return tsk;
847
848free_stack:
849 free_thread_stack(tsk);
850free_tsk:
851 free_task_struct(tsk);
852 return NULL;
853}
854
855__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
856
857static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
858
859static int __init coredump_filter_setup(char *s)
860{
861 default_dump_filter =
862 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
863 MMF_DUMP_FILTER_MASK;
864 return 1;
865}
866
867__setup("coredump_filter=", coredump_filter_setup);
868
869#include <linux/init_task.h>
870
871static void mm_init_aio(struct mm_struct *mm)
872{
873#ifdef CONFIG_AIO
874 spin_lock_init(&mm->ioctx_lock);
875 mm->ioctx_table = NULL;
876#endif
877}
878
879static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
880{
881#ifdef CONFIG_MEMCG
882 mm->owner = p;
883#endif
884}
885
886static void mm_init_uprobes_state(struct mm_struct *mm)
887{
888#ifdef CONFIG_UPROBES
889 mm->uprobes_state.xol_area = NULL;
890#endif
891}
892
893static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
894 struct user_namespace *user_ns)
895{
896 mm->mmap = NULL;
897 mm->mm_rb = RB_ROOT;
898 mm->vmacache_seqnum = 0;
899 atomic_set(&mm->mm_users, 1);
900 atomic_set(&mm->mm_count, 1);
901 init_rwsem(&mm->mmap_sem);
902 INIT_LIST_HEAD(&mm->mmlist);
903 mm->core_state = NULL;
904 mm_pgtables_bytes_init(mm);
905 mm->map_count = 0;
906 mm->locked_vm = 0;
907 mm->pinned_vm = 0;
908 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
909 spin_lock_init(&mm->page_table_lock);
910 spin_lock_init(&mm->arg_lock);
911 mm_init_cpumask(mm);
912 mm_init_aio(mm);
913 mm_init_owner(mm, p);
914 RCU_INIT_POINTER(mm->exe_file, NULL);
915 mmu_notifier_mm_init(mm);
916 hmm_mm_init(mm);
917 init_tlb_flush_pending(mm);
918#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
919 mm->pmd_huge_pte = NULL;
920#endif
921 mm_init_uprobes_state(mm);
922
923 if (current->mm) {
924 mm->flags = current->mm->flags & MMF_INIT_MASK;
925 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
926 } else {
927 mm->flags = default_dump_filter;
928 mm->def_flags = 0;
929 }
930
931 if (mm_alloc_pgd(mm))
932 goto fail_nopgd;
933
934 if (init_new_context(p, mm))
935 goto fail_nocontext;
936
937 mm->user_ns = get_user_ns(user_ns);
938 return mm;
939
940fail_nocontext:
941 mm_free_pgd(mm);
942fail_nopgd:
943 free_mm(mm);
944 return NULL;
945}
946
947/*
948 * Allocate and initialize an mm_struct.
949 */
950struct mm_struct *mm_alloc(void)
951{
952 struct mm_struct *mm;
953
954 mm = allocate_mm();
955 if (!mm)
956 return NULL;
957
958 memset(mm, 0, sizeof(*mm));
959 return mm_init(mm, current, current_user_ns());
960}
961
962static inline void __mmput(struct mm_struct *mm)
963{
964 VM_BUG_ON(atomic_read(&mm->mm_users));
965
966 uprobe_clear_state(mm);
967 exit_aio(mm);
968 ksm_exit(mm);
969 khugepaged_exit(mm); /* must run before exit_mmap */
970 exit_mmap(mm);
971 mm_put_huge_zero_page(mm);
972 set_mm_exe_file(mm, NULL);
973 if (!list_empty(&mm->mmlist)) {
974 spin_lock(&mmlist_lock);
975 list_del(&mm->mmlist);
976 spin_unlock(&mmlist_lock);
977 }
978 if (mm->binfmt)
979 module_put(mm->binfmt->module);
980 mmdrop(mm);
981}
982
983/*
984 * Decrement the use count and release all resources for an mm.
985 */
986void mmput(struct mm_struct *mm)
987{
988 might_sleep();
989
990 if (atomic_dec_and_test(&mm->mm_users))
991 __mmput(mm);
992}
993EXPORT_SYMBOL_GPL(mmput);
994
995#ifdef CONFIG_MMU
996static void mmput_async_fn(struct work_struct *work)
997{
998 struct mm_struct *mm = container_of(work, struct mm_struct,
999 async_put_work);
1000
1001 __mmput(mm);
1002}
1003
1004void mmput_async(struct mm_struct *mm)
1005{
1006 if (atomic_dec_and_test(&mm->mm_users)) {
1007 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1008 schedule_work(&mm->async_put_work);
1009 }
1010}
1011#endif
1012
1013/**
1014 * set_mm_exe_file - change a reference to the mm's executable file
1015 *
1016 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1017 *
1018 * Main users are mmput() and sys_execve(). Callers prevent concurrent
1019 * invocations: in mmput() nobody alive left, in execve task is single
1020 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
1021 * mm->exe_file, but does so without using set_mm_exe_file() in order
1022 * to do avoid the need for any locks.
1023 */
1024void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1025{
1026 struct file *old_exe_file;
1027
1028 /*
1029 * It is safe to dereference the exe_file without RCU as
1030 * this function is only called if nobody else can access
1031 * this mm -- see comment above for justification.
1032 */
1033 old_exe_file = rcu_dereference_raw(mm->exe_file);
1034
1035 if (new_exe_file)
1036 get_file(new_exe_file);
1037 rcu_assign_pointer(mm->exe_file, new_exe_file);
1038 if (old_exe_file)
1039 fput(old_exe_file);
1040}
1041
1042/**
1043 * get_mm_exe_file - acquire a reference to the mm's executable file
1044 *
1045 * Returns %NULL if mm has no associated executable file.
1046 * User must release file via fput().
1047 */
1048struct file *get_mm_exe_file(struct mm_struct *mm)
1049{
1050 struct file *exe_file;
1051
1052 rcu_read_lock();
1053 exe_file = rcu_dereference(mm->exe_file);
1054 if (exe_file && !get_file_rcu(exe_file))
1055 exe_file = NULL;
1056 rcu_read_unlock();
1057 return exe_file;
1058}
1059EXPORT_SYMBOL(get_mm_exe_file);
1060
1061/**
1062 * get_task_exe_file - acquire a reference to the task's executable file
1063 *
1064 * Returns %NULL if task's mm (if any) has no associated executable file or
1065 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1066 * User must release file via fput().
1067 */
1068struct file *get_task_exe_file(struct task_struct *task)
1069{
1070 struct file *exe_file = NULL;
1071 struct mm_struct *mm;
1072
1073 task_lock(task);
1074 mm = task->mm;
1075 if (mm) {
1076 if (!(task->flags & PF_KTHREAD))
1077 exe_file = get_mm_exe_file(mm);
1078 }
1079 task_unlock(task);
1080 return exe_file;
1081}
1082EXPORT_SYMBOL(get_task_exe_file);
1083
1084/**
1085 * get_task_mm - acquire a reference to the task's mm
1086 *
1087 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
1088 * this kernel workthread has transiently adopted a user mm with use_mm,
1089 * to do its AIO) is not set and if so returns a reference to it, after
1090 * bumping up the use count. User must release the mm via mmput()
1091 * after use. Typically used by /proc and ptrace.
1092 */
1093struct mm_struct *get_task_mm(struct task_struct *task)
1094{
1095 struct mm_struct *mm;
1096
1097 task_lock(task);
1098 mm = task->mm;
1099 if (mm) {
1100 if (task->flags & PF_KTHREAD)
1101 mm = NULL;
1102 else
1103 mmget(mm);
1104 }
1105 task_unlock(task);
1106 return mm;
1107}
1108EXPORT_SYMBOL_GPL(get_task_mm);
1109
1110struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1111{
1112 struct mm_struct *mm;
1113 int err;
1114
1115 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
1116 if (err)
1117 return ERR_PTR(err);
1118
1119 mm = get_task_mm(task);
1120 if (mm && mm != current->mm &&
1121 !ptrace_may_access(task, mode)) {
1122 mmput(mm);
1123 mm = ERR_PTR(-EACCES);
1124 }
1125 mutex_unlock(&task->signal->cred_guard_mutex);
1126
1127 return mm;
1128}
1129
1130static void complete_vfork_done(struct task_struct *tsk)
1131{
1132 struct completion *vfork;
1133
1134 task_lock(tsk);
1135 vfork = tsk->vfork_done;
1136 if (likely(vfork)) {
1137 tsk->vfork_done = NULL;
1138 complete(vfork);
1139 }
1140 task_unlock(tsk);
1141}
1142
1143static int wait_for_vfork_done(struct task_struct *child,
1144 struct completion *vfork)
1145{
1146 int killed;
1147
1148 freezer_do_not_count();
1149 killed = wait_for_completion_killable(vfork);
1150 freezer_count();
1151
1152 if (killed) {
1153 task_lock(child);
1154 child->vfork_done = NULL;
1155 task_unlock(child);
1156 }
1157
1158 put_task_struct(child);
1159 return killed;
1160}
1161
1162/* Please note the differences between mmput and mm_release.
1163 * mmput is called whenever we stop holding onto a mm_struct,
1164 * error success whatever.
1165 *
1166 * mm_release is called after a mm_struct has been removed
1167 * from the current process.
1168 *
1169 * This difference is important for error handling, when we
1170 * only half set up a mm_struct for a new process and need to restore
1171 * the old one. Because we mmput the new mm_struct before
1172 * restoring the old one. . .
1173 * Eric Biederman 10 January 1998
1174 */
1175void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1176{
1177 /* Get rid of any futexes when releasing the mm */
1178#ifdef CONFIG_FUTEX
1179 if (unlikely(tsk->robust_list)) {
1180 exit_robust_list(tsk);
1181 tsk->robust_list = NULL;
1182 }
1183#ifdef CONFIG_COMPAT
1184 if (unlikely(tsk->compat_robust_list)) {
1185 compat_exit_robust_list(tsk);
1186 tsk->compat_robust_list = NULL;
1187 }
1188#endif
1189 if (unlikely(!list_empty(&tsk->pi_state_list)))
1190 exit_pi_state_list(tsk);
1191#endif
1192
1193 uprobe_free_utask(tsk);
1194
1195 /* Get rid of any cached register state */
1196 deactivate_mm(tsk, mm);
1197
1198 /*
1199 * Signal userspace if we're not exiting with a core dump
1200 * because we want to leave the value intact for debugging
1201 * purposes.
1202 */
1203 if (tsk->clear_child_tid) {
1204 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1205 atomic_read(&mm->mm_users) > 1) {
1206 /*
1207 * We don't check the error code - if userspace has
1208 * not set up a proper pointer then tough luck.
1209 */
1210 put_user(0, tsk->clear_child_tid);
1211 do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1212 1, NULL, NULL, 0, 0);
1213 }
1214 tsk->clear_child_tid = NULL;
1215 }
1216
1217 /*
1218 * All done, finally we can wake up parent and return this mm to him.
1219 * Also kthread_stop() uses this completion for synchronization.
1220 */
1221 if (tsk->vfork_done)
1222 complete_vfork_done(tsk);
1223}
1224
1225/*
1226 * Allocate a new mm structure and copy contents from the
1227 * mm structure of the passed in task structure.
1228 */
1229static struct mm_struct *dup_mm(struct task_struct *tsk)
1230{
1231 struct mm_struct *mm, *oldmm = current->mm;
1232 int err;
1233
1234 mm = allocate_mm();
1235 if (!mm)
1236 goto fail_nomem;
1237
1238 memcpy(mm, oldmm, sizeof(*mm));
1239
1240 if (!mm_init(mm, tsk, mm->user_ns))
1241 goto fail_nomem;
1242
1243 err = dup_mmap(mm, oldmm);
1244 if (err)
1245 goto free_pt;
1246
1247 mm->hiwater_rss = get_mm_rss(mm);
1248 mm->hiwater_vm = mm->total_vm;
1249
1250 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1251 goto free_pt;
1252
1253 return mm;
1254
1255free_pt:
1256 /* don't put binfmt in mmput, we haven't got module yet */
1257 mm->binfmt = NULL;
1258 mmput(mm);
1259
1260fail_nomem:
1261 return NULL;
1262}
1263
1264static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1265{
1266 struct mm_struct *mm, *oldmm;
1267 int retval;
1268
1269 tsk->min_flt = tsk->maj_flt = 0;
1270 tsk->nvcsw = tsk->nivcsw = 0;
1271#ifdef CONFIG_DETECT_HUNG_TASK
1272 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1273#endif
1274
1275 tsk->mm = NULL;
1276 tsk->active_mm = NULL;
1277
1278 /*
1279 * Are we cloning a kernel thread?
1280 *
1281 * We need to steal a active VM for that..
1282 */
1283 oldmm = current->mm;
1284 if (!oldmm)
1285 return 0;
1286
1287 /* initialize the new vmacache entries */
1288 vmacache_flush(tsk);
1289
1290 if (clone_flags & CLONE_VM) {
1291 mmget(oldmm);
1292 mm = oldmm;
1293 goto good_mm;
1294 }
1295
1296 retval = -ENOMEM;
1297 mm = dup_mm(tsk);
1298 if (!mm)
1299 goto fail_nomem;
1300
1301good_mm:
1302 tsk->mm = mm;
1303 tsk->active_mm = mm;
1304 return 0;
1305
1306fail_nomem:
1307 return retval;
1308}
1309
1310static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1311{
1312 struct fs_struct *fs = current->fs;
1313 if (clone_flags & CLONE_FS) {
1314 /* tsk->fs is already what we want */
1315 spin_lock(&fs->lock);
1316 if (fs->in_exec) {
1317 spin_unlock(&fs->lock);
1318 return -EAGAIN;
1319 }
1320 fs->users++;
1321 spin_unlock(&fs->lock);
1322 return 0;
1323 }
1324 tsk->fs = copy_fs_struct(fs);
1325 if (!tsk->fs)
1326 return -ENOMEM;
1327 return 0;
1328}
1329
1330static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1331{
1332 struct files_struct *oldf, *newf;
1333 int error = 0;
1334
1335 /*
1336 * A background process may not have any files ...
1337 */
1338 oldf = current->files;
1339 if (!oldf)
1340 goto out;
1341
1342 if (clone_flags & CLONE_FILES) {
1343 atomic_inc(&oldf->count);
1344 goto out;
1345 }
1346
1347 newf = dup_fd(oldf, &error);
1348 if (!newf)
1349 goto out;
1350
1351 tsk->files = newf;
1352 error = 0;
1353out:
1354 return error;
1355}
1356
1357static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1358{
1359#ifdef CONFIG_BLOCK
1360 struct io_context *ioc = current->io_context;
1361 struct io_context *new_ioc;
1362
1363 if (!ioc)
1364 return 0;
1365 /*
1366 * Share io context with parent, if CLONE_IO is set
1367 */
1368 if (clone_flags & CLONE_IO) {
1369 ioc_task_link(ioc);
1370 tsk->io_context = ioc;
1371 } else if (ioprio_valid(ioc->ioprio)) {
1372 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1373 if (unlikely(!new_ioc))
1374 return -ENOMEM;
1375
1376 new_ioc->ioprio = ioc->ioprio;
1377 put_io_context(new_ioc);
1378 }
1379#endif
1380 return 0;
1381}
1382
1383static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1384{
1385 struct sighand_struct *sig;
1386
1387 if (clone_flags & CLONE_SIGHAND) {
1388 atomic_inc(&current->sighand->count);
1389 return 0;
1390 }
1391 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1392 rcu_assign_pointer(tsk->sighand, sig);
1393 if (!sig)
1394 return -ENOMEM;
1395
1396 atomic_set(&sig->count, 1);
1397 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1398 return 0;
1399}
1400
1401void __cleanup_sighand(struct sighand_struct *sighand)
1402{
1403 if (atomic_dec_and_test(&sighand->count)) {
1404 signalfd_cleanup(sighand);
1405 /*
1406 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1407 * without an RCU grace period, see __lock_task_sighand().
1408 */
1409 kmem_cache_free(sighand_cachep, sighand);
1410 }
1411}
1412
1413#ifdef CONFIG_POSIX_TIMERS
1414/*
1415 * Initialize POSIX timer handling for a thread group.
1416 */
1417static void posix_cpu_timers_init_group(struct signal_struct *sig)
1418{
1419 unsigned long cpu_limit;
1420
1421 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1422 if (cpu_limit != RLIM_INFINITY) {
1423 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC;
1424 sig->cputimer.running = true;
1425 }
1426
1427 /* The timer lists. */
1428 INIT_LIST_HEAD(&sig->cpu_timers[0]);
1429 INIT_LIST_HEAD(&sig->cpu_timers[1]);
1430 INIT_LIST_HEAD(&sig->cpu_timers[2]);
1431}
1432#else
1433static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { }
1434#endif
1435
1436static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1437{
1438 struct signal_struct *sig;
1439
1440 if (clone_flags & CLONE_THREAD)
1441 return 0;
1442
1443 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1444 tsk->signal = sig;
1445 if (!sig)
1446 return -ENOMEM;
1447
1448 sig->nr_threads = 1;
1449 atomic_set(&sig->live, 1);
1450 atomic_set(&sig->sigcnt, 1);
1451
1452 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1453 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1454 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1455
1456 init_waitqueue_head(&sig->wait_chldexit);
1457 sig->curr_target = tsk;
1458 init_sigpending(&sig->shared_pending);
1459 seqlock_init(&sig->stats_lock);
1460 prev_cputime_init(&sig->prev_cputime);
1461
1462#ifdef CONFIG_POSIX_TIMERS
1463 INIT_LIST_HEAD(&sig->posix_timers);
1464 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1465 sig->real_timer.function = it_real_fn;
1466#endif
1467
1468 task_lock(current->group_leader);
1469 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1470 task_unlock(current->group_leader);
1471
1472 posix_cpu_timers_init_group(sig);
1473
1474 tty_audit_fork(sig);
1475 sched_autogroup_fork(sig);
1476
1477 sig->oom_score_adj = current->signal->oom_score_adj;
1478 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1479
1480 mutex_init(&sig->cred_guard_mutex);
1481
1482 return 0;
1483}
1484
1485static void copy_seccomp(struct task_struct *p)
1486{
1487#ifdef CONFIG_SECCOMP
1488 /*
1489 * Must be called with sighand->lock held, which is common to
1490 * all threads in the group. Holding cred_guard_mutex is not
1491 * needed because this new task is not yet running and cannot
1492 * be racing exec.
1493 */
1494 assert_spin_locked(&current->sighand->siglock);
1495
1496 /* Ref-count the new filter user, and assign it. */
1497 get_seccomp_filter(current);
1498 p->seccomp = current->seccomp;
1499
1500 /*
1501 * Explicitly enable no_new_privs here in case it got set
1502 * between the task_struct being duplicated and holding the
1503 * sighand lock. The seccomp state and nnp must be in sync.
1504 */
1505 if (task_no_new_privs(current))
1506 task_set_no_new_privs(p);
1507
1508 /*
1509 * If the parent gained a seccomp mode after copying thread
1510 * flags and between before we held the sighand lock, we have
1511 * to manually enable the seccomp thread flag here.
1512 */
1513 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1514 set_tsk_thread_flag(p, TIF_SECCOMP);
1515#endif
1516}
1517
1518SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1519{
1520 current->clear_child_tid = tidptr;
1521
1522 return task_pid_vnr(current);
1523}
1524
1525static void rt_mutex_init_task(struct task_struct *p)
1526{
1527 raw_spin_lock_init(&p->pi_lock);
1528#ifdef CONFIG_RT_MUTEXES
1529 p->pi_waiters = RB_ROOT_CACHED;
1530 p->pi_top_task = NULL;
1531 p->pi_blocked_on = NULL;
1532#endif
1533}
1534
1535#ifdef CONFIG_POSIX_TIMERS
1536/*
1537 * Initialize POSIX timer handling for a single task.
1538 */
1539static void posix_cpu_timers_init(struct task_struct *tsk)
1540{
1541 tsk->cputime_expires.prof_exp = 0;
1542 tsk->cputime_expires.virt_exp = 0;
1543 tsk->cputime_expires.sched_exp = 0;
1544 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1545 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1546 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1547}
1548#else
1549static inline void posix_cpu_timers_init(struct task_struct *tsk) { }
1550#endif
1551
1552static inline void
1553init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1554{
1555 task->pids[type].pid = pid;
1556}
1557
1558static inline void rcu_copy_process(struct task_struct *p)
1559{
1560#ifdef CONFIG_PREEMPT_RCU
1561 p->rcu_read_lock_nesting = 0;
1562 p->rcu_read_unlock_special.s = 0;
1563 p->rcu_blocked_node = NULL;
1564 INIT_LIST_HEAD(&p->rcu_node_entry);
1565#endif /* #ifdef CONFIG_PREEMPT_RCU */
1566#ifdef CONFIG_TASKS_RCU
1567 p->rcu_tasks_holdout = false;
1568 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1569 p->rcu_tasks_idle_cpu = -1;
1570#endif /* #ifdef CONFIG_TASKS_RCU */
1571}
1572
1573/*
1574 * This creates a new process as a copy of the old one,
1575 * but does not actually start it yet.
1576 *
1577 * It copies the registers, and all the appropriate
1578 * parts of the process environment (as per the clone
1579 * flags). The actual kick-off is left to the caller.
1580 */
1581static __latent_entropy struct task_struct *copy_process(
1582 unsigned long clone_flags,
1583 unsigned long stack_start,
1584 unsigned long stack_size,
1585 int __user *child_tidptr,
1586 struct pid *pid,
1587 int trace,
1588 unsigned long tls,
1589 int node)
1590{
1591 int retval;
1592 struct task_struct *p;
1593
1594 /*
1595 * Don't allow sharing the root directory with processes in a different
1596 * namespace
1597 */
1598 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1599 return ERR_PTR(-EINVAL);
1600
1601 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1602 return ERR_PTR(-EINVAL);
1603
1604 /*
1605 * Thread groups must share signals as well, and detached threads
1606 * can only be started up within the thread group.
1607 */
1608 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1609 return ERR_PTR(-EINVAL);
1610
1611 /*
1612 * Shared signal handlers imply shared VM. By way of the above,
1613 * thread groups also imply shared VM. Blocking this case allows
1614 * for various simplifications in other code.
1615 */
1616 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1617 return ERR_PTR(-EINVAL);
1618
1619 /*
1620 * Siblings of global init remain as zombies on exit since they are
1621 * not reaped by their parent (swapper). To solve this and to avoid
1622 * multi-rooted process trees, prevent global and container-inits
1623 * from creating siblings.
1624 */
1625 if ((clone_flags & CLONE_PARENT) &&
1626 current->signal->flags & SIGNAL_UNKILLABLE)
1627 return ERR_PTR(-EINVAL);
1628
1629 /*
1630 * If the new process will be in a different pid or user namespace
1631 * do not allow it to share a thread group with the forking task.
1632 */
1633 if (clone_flags & CLONE_THREAD) {
1634 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1635 (task_active_pid_ns(current) !=
1636 current->nsproxy->pid_ns_for_children))
1637 return ERR_PTR(-EINVAL);
1638 }
1639
1640 retval = -ENOMEM;
1641 p = dup_task_struct(current, node);
1642 if (!p)
1643 goto fork_out;
1644
1645 /*
1646 * This _must_ happen before we call free_task(), i.e. before we jump
1647 * to any of the bad_fork_* labels. This is to avoid freeing
1648 * p->set_child_tid which is (ab)used as a kthread's data pointer for
1649 * kernel threads (PF_KTHREAD).
1650 */
1651 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1652 /*
1653 * Clear TID on mm_release()?
1654 */
1655 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1656
1657 ftrace_graph_init_task(p);
1658
1659 rt_mutex_init_task(p);
1660
1661#ifdef CONFIG_PROVE_LOCKING
1662 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1663 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1664#endif
1665 retval = -EAGAIN;
1666 if (atomic_read(&p->real_cred->user->processes) >=
1667 task_rlimit(p, RLIMIT_NPROC)) {
1668 if (p->real_cred->user != INIT_USER &&
1669 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1670 goto bad_fork_free;
1671 }
1672 current->flags &= ~PF_NPROC_EXCEEDED;
1673
1674 retval = copy_creds(p, clone_flags);
1675 if (retval < 0)
1676 goto bad_fork_free;
1677
1678 /*
1679 * If multiple threads are within copy_process(), then this check
1680 * triggers too late. This doesn't hurt, the check is only there
1681 * to stop root fork bombs.
1682 */
1683 retval = -EAGAIN;
1684 if (nr_threads >= max_threads)
1685 goto bad_fork_cleanup_count;
1686
1687 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1688 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1689 p->flags |= PF_FORKNOEXEC;
1690 INIT_LIST_HEAD(&p->children);
1691 INIT_LIST_HEAD(&p->sibling);
1692 rcu_copy_process(p);
1693 p->vfork_done = NULL;
1694 spin_lock_init(&p->alloc_lock);
1695
1696 init_sigpending(&p->pending);
1697
1698 p->utime = p->stime = p->gtime = 0;
1699#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1700 p->utimescaled = p->stimescaled = 0;
1701#endif
1702 prev_cputime_init(&p->prev_cputime);
1703
1704#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1705 seqcount_init(&p->vtime.seqcount);
1706 p->vtime.starttime = 0;
1707 p->vtime.state = VTIME_INACTIVE;
1708#endif
1709
1710#if defined(SPLIT_RSS_COUNTING)
1711 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1712#endif
1713
1714 p->default_timer_slack_ns = current->timer_slack_ns;
1715
1716 task_io_accounting_init(&p->ioac);
1717 acct_clear_integrals(p);
1718
1719 posix_cpu_timers_init(p);
1720
1721 p->start_time = ktime_get_ns();
1722 p->real_start_time = ktime_get_boot_ns();
1723 p->io_context = NULL;
1724 audit_set_context(p, NULL);
1725 cgroup_fork(p);
1726#ifdef CONFIG_NUMA
1727 p->mempolicy = mpol_dup(p->mempolicy);
1728 if (IS_ERR(p->mempolicy)) {
1729 retval = PTR_ERR(p->mempolicy);
1730 p->mempolicy = NULL;
1731 goto bad_fork_cleanup_threadgroup_lock;
1732 }
1733#endif
1734#ifdef CONFIG_CPUSETS
1735 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1736 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1737 seqcount_init(&p->mems_allowed_seq);
1738#endif
1739#ifdef CONFIG_TRACE_IRQFLAGS
1740 p->irq_events = 0;
1741 p->hardirqs_enabled = 0;
1742 p->hardirq_enable_ip = 0;
1743 p->hardirq_enable_event = 0;
1744 p->hardirq_disable_ip = _THIS_IP_;
1745 p->hardirq_disable_event = 0;
1746 p->softirqs_enabled = 1;
1747 p->softirq_enable_ip = _THIS_IP_;
1748 p->softirq_enable_event = 0;
1749 p->softirq_disable_ip = 0;
1750 p->softirq_disable_event = 0;
1751 p->hardirq_context = 0;
1752 p->softirq_context = 0;
1753#endif
1754
1755 p->pagefault_disabled = 0;
1756
1757#ifdef CONFIG_LOCKDEP
1758 p->lockdep_depth = 0; /* no locks held yet */
1759 p->curr_chain_key = 0;
1760 p->lockdep_recursion = 0;
1761 lockdep_init_task(p);
1762#endif
1763
1764#ifdef CONFIG_DEBUG_MUTEXES
1765 p->blocked_on = NULL; /* not blocked yet */
1766#endif
1767#ifdef CONFIG_BCACHE
1768 p->sequential_io = 0;
1769 p->sequential_io_avg = 0;
1770#endif
1771
1772 /* Perform scheduler related setup. Assign this task to a CPU. */
1773 retval = sched_fork(clone_flags, p);
1774 if (retval)
1775 goto bad_fork_cleanup_policy;
1776
1777 retval = perf_event_init_task(p);
1778 if (retval)
1779 goto bad_fork_cleanup_policy;
1780 retval = audit_alloc(p);
1781 if (retval)
1782 goto bad_fork_cleanup_perf;
1783 /* copy all the process information */
1784 shm_init_task(p);
1785 retval = security_task_alloc(p, clone_flags);
1786 if (retval)
1787 goto bad_fork_cleanup_audit;
1788 retval = copy_semundo(clone_flags, p);
1789 if (retval)
1790 goto bad_fork_cleanup_security;
1791 retval = copy_files(clone_flags, p);
1792 if (retval)
1793 goto bad_fork_cleanup_semundo;
1794 retval = copy_fs(clone_flags, p);
1795 if (retval)
1796 goto bad_fork_cleanup_files;
1797 retval = copy_sighand(clone_flags, p);
1798 if (retval)
1799 goto bad_fork_cleanup_fs;
1800 retval = copy_signal(clone_flags, p);
1801 if (retval)
1802 goto bad_fork_cleanup_sighand;
1803 retval = copy_mm(clone_flags, p);
1804 if (retval)
1805 goto bad_fork_cleanup_signal;
1806 retval = copy_namespaces(clone_flags, p);
1807 if (retval)
1808 goto bad_fork_cleanup_mm;
1809 retval = copy_io(clone_flags, p);
1810 if (retval)
1811 goto bad_fork_cleanup_namespaces;
1812 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1813 if (retval)
1814 goto bad_fork_cleanup_io;
1815
1816 if (pid != &init_struct_pid) {
1817 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1818 if (IS_ERR(pid)) {
1819 retval = PTR_ERR(pid);
1820 goto bad_fork_cleanup_thread;
1821 }
1822 }
1823
1824#ifdef CONFIG_BLOCK
1825 p->plug = NULL;
1826#endif
1827#ifdef CONFIG_FUTEX
1828 p->robust_list = NULL;
1829#ifdef CONFIG_COMPAT
1830 p->compat_robust_list = NULL;
1831#endif
1832 INIT_LIST_HEAD(&p->pi_state_list);
1833 p->pi_state_cache = NULL;
1834#endif
1835 /*
1836 * sigaltstack should be cleared when sharing the same VM
1837 */
1838 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1839 sas_ss_reset(p);
1840
1841 /*
1842 * Syscall tracing and stepping should be turned off in the
1843 * child regardless of CLONE_PTRACE.
1844 */
1845 user_disable_single_step(p);
1846 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1847#ifdef TIF_SYSCALL_EMU
1848 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1849#endif
1850 clear_all_latency_tracing(p);
1851
1852 /* ok, now we should be set up.. */
1853 p->pid = pid_nr(pid);
1854 if (clone_flags & CLONE_THREAD) {
1855 p->exit_signal = -1;
1856 p->group_leader = current->group_leader;
1857 p->tgid = current->tgid;
1858 } else {
1859 if (clone_flags & CLONE_PARENT)
1860 p->exit_signal = current->group_leader->exit_signal;
1861 else
1862 p->exit_signal = (clone_flags & CSIGNAL);
1863 p->group_leader = p;
1864 p->tgid = p->pid;
1865 }
1866
1867 p->nr_dirtied = 0;
1868 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1869 p->dirty_paused_when = 0;
1870
1871 p->pdeath_signal = 0;
1872 INIT_LIST_HEAD(&p->thread_group);
1873 p->task_works = NULL;
1874
1875 cgroup_threadgroup_change_begin(current);
1876 /*
1877 * Ensure that the cgroup subsystem policies allow the new process to be
1878 * forked. It should be noted the the new process's css_set can be changed
1879 * between here and cgroup_post_fork() if an organisation operation is in
1880 * progress.
1881 */
1882 retval = cgroup_can_fork(p);
1883 if (retval)
1884 goto bad_fork_free_pid;
1885
1886 /*
1887 * Make it visible to the rest of the system, but dont wake it up yet.
1888 * Need tasklist lock for parent etc handling!
1889 */
1890 write_lock_irq(&tasklist_lock);
1891
1892 /* CLONE_PARENT re-uses the old parent */
1893 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1894 p->real_parent = current->real_parent;
1895 p->parent_exec_id = current->parent_exec_id;
1896 } else {
1897 p->real_parent = current;
1898 p->parent_exec_id = current->self_exec_id;
1899 }
1900
1901 klp_copy_process(p);
1902
1903 spin_lock(&current->sighand->siglock);
1904
1905 /*
1906 * Copy seccomp details explicitly here, in case they were changed
1907 * before holding sighand lock.
1908 */
1909 copy_seccomp(p);
1910
1911 rseq_fork(p, clone_flags);
1912
1913 /*
1914 * Process group and session signals need to be delivered to just the
1915 * parent before the fork or both the parent and the child after the
1916 * fork. Restart if a signal comes in before we add the new process to
1917 * it's process group.
1918 * A fatal signal pending means that current will exit, so the new
1919 * thread can't slip out of an OOM kill (or normal SIGKILL).
1920 */
1921 recalc_sigpending();
1922 if (signal_pending(current)) {
1923 retval = -ERESTARTNOINTR;
1924 goto bad_fork_cancel_cgroup;
1925 }
1926 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
1927 retval = -ENOMEM;
1928 goto bad_fork_cancel_cgroup;
1929 }
1930
1931 if (likely(p->pid)) {
1932 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1933
1934 init_task_pid(p, PIDTYPE_PID, pid);
1935 if (thread_group_leader(p)) {
1936 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1937 init_task_pid(p, PIDTYPE_SID, task_session(current));
1938
1939 if (is_child_reaper(pid)) {
1940 ns_of_pid(pid)->child_reaper = p;
1941 p->signal->flags |= SIGNAL_UNKILLABLE;
1942 }
1943
1944 p->signal->leader_pid = pid;
1945 p->signal->tty = tty_kref_get(current->signal->tty);
1946 /*
1947 * Inherit has_child_subreaper flag under the same
1948 * tasklist_lock with adding child to the process tree
1949 * for propagate_has_child_subreaper optimization.
1950 */
1951 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
1952 p->real_parent->signal->is_child_subreaper;
1953 list_add_tail(&p->sibling, &p->real_parent->children);
1954 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1955 attach_pid(p, PIDTYPE_PGID);
1956 attach_pid(p, PIDTYPE_SID);
1957 __this_cpu_inc(process_counts);
1958 } else {
1959 current->signal->nr_threads++;
1960 atomic_inc(&current->signal->live);
1961 atomic_inc(&current->signal->sigcnt);
1962 list_add_tail_rcu(&p->thread_group,
1963 &p->group_leader->thread_group);
1964 list_add_tail_rcu(&p->thread_node,
1965 &p->signal->thread_head);
1966 }
1967 attach_pid(p, PIDTYPE_PID);
1968 nr_threads++;
1969 }
1970
1971 total_forks++;
1972 spin_unlock(&current->sighand->siglock);
1973 syscall_tracepoint_update(p);
1974 write_unlock_irq(&tasklist_lock);
1975
1976 proc_fork_connector(p);
1977 cgroup_post_fork(p);
1978 cgroup_threadgroup_change_end(current);
1979 perf_event_fork(p);
1980
1981 trace_task_newtask(p, clone_flags);
1982 uprobe_copy_process(p, clone_flags);
1983
1984 return p;
1985
1986bad_fork_cancel_cgroup:
1987 spin_unlock(&current->sighand->siglock);
1988 write_unlock_irq(&tasklist_lock);
1989 cgroup_cancel_fork(p);
1990bad_fork_free_pid:
1991 cgroup_threadgroup_change_end(current);
1992 if (pid != &init_struct_pid)
1993 free_pid(pid);
1994bad_fork_cleanup_thread:
1995 exit_thread(p);
1996bad_fork_cleanup_io:
1997 if (p->io_context)
1998 exit_io_context(p);
1999bad_fork_cleanup_namespaces:
2000 exit_task_namespaces(p);
2001bad_fork_cleanup_mm:
2002 if (p->mm)
2003 mmput(p->mm);
2004bad_fork_cleanup_signal:
2005 if (!(clone_flags & CLONE_THREAD))
2006 free_signal_struct(p->signal);
2007bad_fork_cleanup_sighand:
2008 __cleanup_sighand(p->sighand);
2009bad_fork_cleanup_fs:
2010 exit_fs(p); /* blocking */
2011bad_fork_cleanup_files:
2012 exit_files(p); /* blocking */
2013bad_fork_cleanup_semundo:
2014 exit_sem(p);
2015bad_fork_cleanup_security:
2016 security_task_free(p);
2017bad_fork_cleanup_audit:
2018 audit_free(p);
2019bad_fork_cleanup_perf:
2020 perf_event_free_task(p);
2021bad_fork_cleanup_policy:
2022 lockdep_free_task(p);
2023#ifdef CONFIG_NUMA
2024 mpol_put(p->mempolicy);
2025bad_fork_cleanup_threadgroup_lock:
2026#endif
2027 delayacct_tsk_free(p);
2028bad_fork_cleanup_count:
2029 atomic_dec(&p->cred->user->processes);
2030 exit_creds(p);
2031bad_fork_free:
2032 p->state = TASK_DEAD;
2033 put_task_stack(p);
2034 free_task(p);
2035fork_out:
2036 return ERR_PTR(retval);
2037}
2038
2039static inline void init_idle_pids(struct pid_link *links)
2040{
2041 enum pid_type type;
2042
2043 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2044 INIT_HLIST_NODE(&links[type].node); /* not really needed */
2045 links[type].pid = &init_struct_pid;
2046 }
2047}
2048
2049struct task_struct *fork_idle(int cpu)
2050{
2051 struct task_struct *task;
2052 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0,
2053 cpu_to_node(cpu));
2054 if (!IS_ERR(task)) {
2055 init_idle_pids(task->pids);
2056 init_idle(task, cpu);
2057 }
2058
2059 return task;
2060}
2061
2062/*
2063 * Ok, this is the main fork-routine.
2064 *
2065 * It copies the process, and if successful kick-starts
2066 * it and waits for it to finish using the VM if required.
2067 */
2068long _do_fork(unsigned long clone_flags,
2069 unsigned long stack_start,
2070 unsigned long stack_size,
2071 int __user *parent_tidptr,
2072 int __user *child_tidptr,
2073 unsigned long tls)
2074{
2075 struct completion vfork;
2076 struct pid *pid;
2077 struct task_struct *p;
2078 int trace = 0;
2079 long nr;
2080
2081 /*
2082 * Determine whether and which event to report to ptracer. When
2083 * called from kernel_thread or CLONE_UNTRACED is explicitly
2084 * requested, no event is reported; otherwise, report if the event
2085 * for the type of forking is enabled.
2086 */
2087 if (!(clone_flags & CLONE_UNTRACED)) {
2088 if (clone_flags & CLONE_VFORK)
2089 trace = PTRACE_EVENT_VFORK;
2090 else if ((clone_flags & CSIGNAL) != SIGCHLD)
2091 trace = PTRACE_EVENT_CLONE;
2092 else
2093 trace = PTRACE_EVENT_FORK;
2094
2095 if (likely(!ptrace_event_enabled(current, trace)))
2096 trace = 0;
2097 }
2098
2099 p = copy_process(clone_flags, stack_start, stack_size,
2100 child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
2101 add_latent_entropy();
2102
2103 if (IS_ERR(p))
2104 return PTR_ERR(p);
2105
2106 /*
2107 * Do this prior waking up the new thread - the thread pointer
2108 * might get invalid after that point, if the thread exits quickly.
2109 */
2110 trace_sched_process_fork(current, p);
2111
2112 pid = get_task_pid(p, PIDTYPE_PID);
2113 nr = pid_vnr(pid);
2114
2115 if (clone_flags & CLONE_PARENT_SETTID)
2116 put_user(nr, parent_tidptr);
2117
2118 if (clone_flags & CLONE_VFORK) {
2119 p->vfork_done = &vfork;
2120 init_completion(&vfork);
2121 get_task_struct(p);
2122 }
2123
2124 wake_up_new_task(p);
2125
2126 /* forking complete and child started to run, tell ptracer */
2127 if (unlikely(trace))
2128 ptrace_event_pid(trace, pid);
2129
2130 if (clone_flags & CLONE_VFORK) {
2131 if (!wait_for_vfork_done(p, &vfork))
2132 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2133 }
2134
2135 put_pid(pid);
2136 return nr;
2137}
2138
2139#ifndef CONFIG_HAVE_COPY_THREAD_TLS
2140/* For compatibility with architectures that call do_fork directly rather than
2141 * using the syscall entry points below. */
2142long do_fork(unsigned long clone_flags,
2143 unsigned long stack_start,
2144 unsigned long stack_size,
2145 int __user *parent_tidptr,
2146 int __user *child_tidptr)
2147{
2148 return _do_fork(clone_flags, stack_start, stack_size,
2149 parent_tidptr, child_tidptr, 0);
2150}
2151#endif
2152
2153/*
2154 * Create a kernel thread.
2155 */
2156pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2157{
2158 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
2159 (unsigned long)arg, NULL, NULL, 0);
2160}
2161
2162#ifdef __ARCH_WANT_SYS_FORK
2163SYSCALL_DEFINE0(fork)
2164{
2165#ifdef CONFIG_MMU
2166 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
2167#else
2168 /* can not support in nommu mode */
2169 return -EINVAL;
2170#endif
2171}
2172#endif
2173
2174#ifdef __ARCH_WANT_SYS_VFORK
2175SYSCALL_DEFINE0(vfork)
2176{
2177 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
2178 0, NULL, NULL, 0);
2179}
2180#endif
2181
2182#ifdef __ARCH_WANT_SYS_CLONE
2183#ifdef CONFIG_CLONE_BACKWARDS
2184SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2185 int __user *, parent_tidptr,
2186 unsigned long, tls,
2187 int __user *, child_tidptr)
2188#elif defined(CONFIG_CLONE_BACKWARDS2)
2189SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2190 int __user *, parent_tidptr,
2191 int __user *, child_tidptr,
2192 unsigned long, tls)
2193#elif defined(CONFIG_CLONE_BACKWARDS3)
2194SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2195 int, stack_size,
2196 int __user *, parent_tidptr,
2197 int __user *, child_tidptr,
2198 unsigned long, tls)
2199#else
2200SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2201 int __user *, parent_tidptr,
2202 int __user *, child_tidptr,
2203 unsigned long, tls)
2204#endif
2205{
2206 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
2207}
2208#endif
2209
2210void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2211{
2212 struct task_struct *leader, *parent, *child;
2213 int res;
2214
2215 read_lock(&tasklist_lock);
2216 leader = top = top->group_leader;
2217down:
2218 for_each_thread(leader, parent) {
2219 list_for_each_entry(child, &parent->children, sibling) {
2220 res = visitor(child, data);
2221 if (res) {
2222 if (res < 0)
2223 goto out;
2224 leader = child;
2225 goto down;
2226 }
2227up:
2228 ;
2229 }
2230 }
2231
2232 if (leader != top) {
2233 child = leader;
2234 parent = child->real_parent;
2235 leader = parent->group_leader;
2236 goto up;
2237 }
2238out:
2239 read_unlock(&tasklist_lock);
2240}
2241
2242#ifndef ARCH_MIN_MMSTRUCT_ALIGN
2243#define ARCH_MIN_MMSTRUCT_ALIGN 0
2244#endif
2245
2246static void sighand_ctor(void *data)
2247{
2248 struct sighand_struct *sighand = data;
2249
2250 spin_lock_init(&sighand->siglock);
2251 init_waitqueue_head(&sighand->signalfd_wqh);
2252}
2253
2254void __init proc_caches_init(void)
2255{
2256 sighand_cachep = kmem_cache_create("sighand_cache",
2257 sizeof(struct sighand_struct), 0,
2258 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2259 SLAB_ACCOUNT, sighand_ctor);
2260 signal_cachep = kmem_cache_create("signal_cache",
2261 sizeof(struct signal_struct), 0,
2262 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2263 NULL);
2264 files_cachep = kmem_cache_create("files_cache",
2265 sizeof(struct files_struct), 0,
2266 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2267 NULL);
2268 fs_cachep = kmem_cache_create("fs_cache",
2269 sizeof(struct fs_struct), 0,
2270 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2271 NULL);
2272 /*
2273 * FIXME! The "sizeof(struct mm_struct)" currently includes the
2274 * whole struct cpumask for the OFFSTACK case. We could change
2275 * this to *only* allocate as much of it as required by the
2276 * maximum number of CPU's we can ever have. The cpumask_allocation
2277 * is at the end of the structure, exactly for that reason.
2278 */
2279 mm_cachep = kmem_cache_create_usercopy("mm_struct",
2280 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
2281 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2282 offsetof(struct mm_struct, saved_auxv),
2283 sizeof_field(struct mm_struct, saved_auxv),
2284 NULL);
2285 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2286 mmap_init();
2287 nsproxy_cache_init();
2288}
2289
2290/*
2291 * Check constraints on flags passed to the unshare system call.
2292 */
2293static int check_unshare_flags(unsigned long unshare_flags)
2294{
2295 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2296 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2297 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2298 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2299 return -EINVAL;
2300 /*
2301 * Not implemented, but pretend it works if there is nothing
2302 * to unshare. Note that unsharing the address space or the
2303 * signal handlers also need to unshare the signal queues (aka
2304 * CLONE_THREAD).
2305 */
2306 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2307 if (!thread_group_empty(current))
2308 return -EINVAL;
2309 }
2310 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2311 if (atomic_read(&current->sighand->count) > 1)
2312 return -EINVAL;
2313 }
2314 if (unshare_flags & CLONE_VM) {
2315 if (!current_is_single_threaded())
2316 return -EINVAL;
2317 }
2318
2319 return 0;
2320}
2321
2322/*
2323 * Unshare the filesystem structure if it is being shared
2324 */
2325static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2326{
2327 struct fs_struct *fs = current->fs;
2328
2329 if (!(unshare_flags & CLONE_FS) || !fs)
2330 return 0;
2331
2332 /* don't need lock here; in the worst case we'll do useless copy */
2333 if (fs->users == 1)
2334 return 0;
2335
2336 *new_fsp = copy_fs_struct(fs);
2337 if (!*new_fsp)
2338 return -ENOMEM;
2339
2340 return 0;
2341}
2342
2343/*
2344 * Unshare file descriptor table if it is being shared
2345 */
2346static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2347{
2348 struct files_struct *fd = current->files;
2349 int error = 0;
2350
2351 if ((unshare_flags & CLONE_FILES) &&
2352 (fd && atomic_read(&fd->count) > 1)) {
2353 *new_fdp = dup_fd(fd, &error);
2354 if (!*new_fdp)
2355 return error;
2356 }
2357
2358 return 0;
2359}
2360
2361/*
2362 * unshare allows a process to 'unshare' part of the process
2363 * context which was originally shared using clone. copy_*
2364 * functions used by do_fork() cannot be used here directly
2365 * because they modify an inactive task_struct that is being
2366 * constructed. Here we are modifying the current, active,
2367 * task_struct.
2368 */
2369int ksys_unshare(unsigned long unshare_flags)
2370{
2371 struct fs_struct *fs, *new_fs = NULL;
2372 struct files_struct *fd, *new_fd = NULL;
2373 struct cred *new_cred = NULL;
2374 struct nsproxy *new_nsproxy = NULL;
2375 int do_sysvsem = 0;
2376 int err;
2377
2378 /*
2379 * If unsharing a user namespace must also unshare the thread group
2380 * and unshare the filesystem root and working directories.
2381 */
2382 if (unshare_flags & CLONE_NEWUSER)
2383 unshare_flags |= CLONE_THREAD | CLONE_FS;
2384 /*
2385 * If unsharing vm, must also unshare signal handlers.
2386 */
2387 if (unshare_flags & CLONE_VM)
2388 unshare_flags |= CLONE_SIGHAND;
2389 /*
2390 * If unsharing a signal handlers, must also unshare the signal queues.
2391 */
2392 if (unshare_flags & CLONE_SIGHAND)
2393 unshare_flags |= CLONE_THREAD;
2394 /*
2395 * If unsharing namespace, must also unshare filesystem information.
2396 */
2397 if (unshare_flags & CLONE_NEWNS)
2398 unshare_flags |= CLONE_FS;
2399
2400 err = check_unshare_flags(unshare_flags);
2401 if (err)
2402 goto bad_unshare_out;
2403 /*
2404 * CLONE_NEWIPC must also detach from the undolist: after switching
2405 * to a new ipc namespace, the semaphore arrays from the old
2406 * namespace are unreachable.
2407 */
2408 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2409 do_sysvsem = 1;
2410 err = unshare_fs(unshare_flags, &new_fs);
2411 if (err)
2412 goto bad_unshare_out;
2413 err = unshare_fd(unshare_flags, &new_fd);
2414 if (err)
2415 goto bad_unshare_cleanup_fs;
2416 err = unshare_userns(unshare_flags, &new_cred);
2417 if (err)
2418 goto bad_unshare_cleanup_fd;
2419 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2420 new_cred, new_fs);
2421 if (err)
2422 goto bad_unshare_cleanup_cred;
2423
2424 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2425 if (do_sysvsem) {
2426 /*
2427 * CLONE_SYSVSEM is equivalent to sys_exit().
2428 */
2429 exit_sem(current);
2430 }
2431 if (unshare_flags & CLONE_NEWIPC) {
2432 /* Orphan segments in old ns (see sem above). */
2433 exit_shm(current);
2434 shm_init_task(current);
2435 }
2436
2437 if (new_nsproxy)
2438 switch_task_namespaces(current, new_nsproxy);
2439
2440 task_lock(current);
2441
2442 if (new_fs) {
2443 fs = current->fs;
2444 spin_lock(&fs->lock);
2445 current->fs = new_fs;
2446 if (--fs->users)
2447 new_fs = NULL;
2448 else
2449 new_fs = fs;
2450 spin_unlock(&fs->lock);
2451 }
2452
2453 if (new_fd) {
2454 fd = current->files;
2455 current->files = new_fd;
2456 new_fd = fd;
2457 }
2458
2459 task_unlock(current);
2460
2461 if (new_cred) {
2462 /* Install the new user namespace */
2463 commit_creds(new_cred);
2464 new_cred = NULL;
2465 }
2466 }
2467
2468 perf_event_namespaces(current);
2469
2470bad_unshare_cleanup_cred:
2471 if (new_cred)
2472 put_cred(new_cred);
2473bad_unshare_cleanup_fd:
2474 if (new_fd)
2475 put_files_struct(new_fd);
2476
2477bad_unshare_cleanup_fs:
2478 if (new_fs)
2479 free_fs_struct(new_fs);
2480
2481bad_unshare_out:
2482 return err;
2483}
2484
2485SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2486{
2487 return ksys_unshare(unshare_flags);
2488}
2489
2490/*
2491 * Helper to unshare the files of the current task.
2492 * We don't want to expose copy_files internals to
2493 * the exec layer of the kernel.
2494 */
2495
2496int unshare_files(struct files_struct **displaced)
2497{
2498 struct task_struct *task = current;
2499 struct files_struct *copy = NULL;
2500 int error;
2501
2502 error = unshare_fd(CLONE_FILES, &copy);
2503 if (error || !copy) {
2504 *displaced = NULL;
2505 return error;
2506 }
2507 *displaced = task->files;
2508 task_lock(task);
2509 task->files = copy;
2510 task_unlock(task);
2511 return 0;
2512}
2513
2514int sysctl_max_threads(struct ctl_table *table, int write,
2515 void __user *buffer, size_t *lenp, loff_t *ppos)
2516{
2517 struct ctl_table t;
2518 int ret;
2519 int threads = max_threads;
2520 int min = MIN_THREADS;
2521 int max = MAX_THREADS;
2522
2523 t = *table;
2524 t.data = &threads;
2525 t.extra1 = &min;
2526 t.extra2 = &max;
2527
2528 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2529 if (ret || !write)
2530 return ret;
2531
2532 set_max_threads(threads);
2533
2534 return 0;
2535}