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/kmsan.h>
41 #include <linux/binfmts.h>
42 #include <linux/mman.h>
43 #include <linux/mmu_notifier.h>
44 #include <linux/fs.h>
45 #include <linux/mm.h>
46 #include <linux/mm_inline.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/fs_struct.h>
81 #include <linux/magic.h>
82 #include <linux/perf_event.h>
83 #include <linux/posix-timers.h>
84 #include <linux/user-return-notifier.h>
85 #include <linux/oom.h>
86 #include <linux/khugepaged.h>
87 #include <linux/signalfd.h>
88 #include <linux/uprobes.h>
89 #include <linux/aio.h>
90 #include <linux/compiler.h>
91 #include <linux/sysctl.h>
92 #include <linux/kcov.h>
93 #include <linux/livepatch.h>
94 #include <linux/thread_info.h>
95 #include <linux/stackleak.h>
96 #include <linux/kasan.h>
97 #include <linux/scs.h>
98 #include <linux/io_uring.h>
99 #include <linux/bpf.h>
100
101 #include <asm/pgalloc.h>
102 #include <linux/uaccess.h>
103 #include <asm/mmu_context.h>
104 #include <asm/cacheflush.h>
105 #include <asm/tlbflush.h>
106
107 #include <trace/events/sched.h>
108
109 #define CREATE_TRACE_POINTS
110 #include <trace/events/task.h>
111
112 /*
113 * Minimum number of threads to boot the kernel
114 */
115 #define MIN_THREADS 20
116
117 /*
118 * Maximum number of threads
119 */
120 #define MAX_THREADS FUTEX_TID_MASK
121
122 /*
123 * Protected counters by write_lock_irq(&tasklist_lock)
124 */
125 unsigned long total_forks; /* Handle normal Linux uptimes. */
126 int nr_threads; /* The idle threads do not count.. */
127
128 static int max_threads; /* tunable limit on nr_threads */
129
130 #define NAMED_ARRAY_INDEX(x) [x] = __stringify(x)
131
132 static const char * const resident_page_types[] = {
133 NAMED_ARRAY_INDEX(MM_FILEPAGES),
134 NAMED_ARRAY_INDEX(MM_ANONPAGES),
135 NAMED_ARRAY_INDEX(MM_SWAPENTS),
136 NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
137 };
138
139 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
140
141 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
142
143 #ifdef CONFIG_PROVE_RCU
lockdep_tasklist_lock_is_held(void)144 int lockdep_tasklist_lock_is_held(void)
145 {
146 return lockdep_is_held(&tasklist_lock);
147 }
148 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
149 #endif /* #ifdef CONFIG_PROVE_RCU */
150
nr_processes(void)151 int nr_processes(void)
152 {
153 int cpu;
154 int total = 0;
155
156 for_each_possible_cpu(cpu)
157 total += per_cpu(process_counts, cpu);
158
159 return total;
160 }
161
arch_release_task_struct(struct task_struct * tsk)162 void __weak arch_release_task_struct(struct task_struct *tsk)
163 {
164 }
165
166 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
167 static struct kmem_cache *task_struct_cachep;
168
alloc_task_struct_node(int node)169 static inline struct task_struct *alloc_task_struct_node(int node)
170 {
171 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
172 }
173
free_task_struct(struct task_struct * tsk)174 static inline void free_task_struct(struct task_struct *tsk)
175 {
176 kmem_cache_free(task_struct_cachep, tsk);
177 }
178 #endif
179
180 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
181
182 /*
183 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
184 * kmemcache based allocator.
185 */
186 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
187
188 # ifdef CONFIG_VMAP_STACK
189 /*
190 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
191 * flush. Try to minimize the number of calls by caching stacks.
192 */
193 #define NR_CACHED_STACKS 2
194 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
195
196 struct vm_stack {
197 struct rcu_head rcu;
198 struct vm_struct *stack_vm_area;
199 };
200
try_release_thread_stack_to_cache(struct vm_struct * vm)201 static bool try_release_thread_stack_to_cache(struct vm_struct *vm)
202 {
203 unsigned int i;
204
205 for (i = 0; i < NR_CACHED_STACKS; i++) {
206 if (this_cpu_cmpxchg(cached_stacks[i], NULL, vm) != NULL)
207 continue;
208 return true;
209 }
210 return false;
211 }
212
thread_stack_free_rcu(struct rcu_head * rh)213 static void thread_stack_free_rcu(struct rcu_head *rh)
214 {
215 struct vm_stack *vm_stack = container_of(rh, struct vm_stack, rcu);
216
217 if (try_release_thread_stack_to_cache(vm_stack->stack_vm_area))
218 return;
219
220 vfree(vm_stack);
221 }
222
thread_stack_delayed_free(struct task_struct * tsk)223 static void thread_stack_delayed_free(struct task_struct *tsk)
224 {
225 struct vm_stack *vm_stack = tsk->stack;
226
227 vm_stack->stack_vm_area = tsk->stack_vm_area;
228 call_rcu(&vm_stack->rcu, thread_stack_free_rcu);
229 }
230
free_vm_stack_cache(unsigned int cpu)231 static int free_vm_stack_cache(unsigned int cpu)
232 {
233 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
234 int i;
235
236 for (i = 0; i < NR_CACHED_STACKS; i++) {
237 struct vm_struct *vm_stack = cached_vm_stacks[i];
238
239 if (!vm_stack)
240 continue;
241
242 vfree(vm_stack->addr);
243 cached_vm_stacks[i] = NULL;
244 }
245
246 return 0;
247 }
248
memcg_charge_kernel_stack(struct vm_struct * vm)249 static int memcg_charge_kernel_stack(struct vm_struct *vm)
250 {
251 int i;
252 int ret;
253
254 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
255 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
256
257 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
258 ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL, 0);
259 if (ret)
260 goto err;
261 }
262 return 0;
263 err:
264 /*
265 * If memcg_kmem_charge_page() fails, page's memory cgroup pointer is
266 * NULL, and memcg_kmem_uncharge_page() in free_thread_stack() will
267 * ignore this page.
268 */
269 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
270 memcg_kmem_uncharge_page(vm->pages[i], 0);
271 return ret;
272 }
273
alloc_thread_stack_node(struct task_struct * tsk,int node)274 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
275 {
276 struct vm_struct *vm;
277 void *stack;
278 int i;
279
280 for (i = 0; i < NR_CACHED_STACKS; i++) {
281 struct vm_struct *s;
282
283 s = this_cpu_xchg(cached_stacks[i], NULL);
284
285 if (!s)
286 continue;
287
288 /* Reset stack metadata. */
289 kasan_unpoison_range(s->addr, THREAD_SIZE);
290
291 stack = kasan_reset_tag(s->addr);
292
293 /* Clear stale pointers from reused stack. */
294 memset(stack, 0, THREAD_SIZE);
295
296 if (memcg_charge_kernel_stack(s)) {
297 vfree(s->addr);
298 return -ENOMEM;
299 }
300
301 tsk->stack_vm_area = s;
302 tsk->stack = stack;
303 return 0;
304 }
305
306 /*
307 * Allocated stacks are cached and later reused by new threads,
308 * so memcg accounting is performed manually on assigning/releasing
309 * stacks to tasks. Drop __GFP_ACCOUNT.
310 */
311 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
312 VMALLOC_START, VMALLOC_END,
313 THREADINFO_GFP & ~__GFP_ACCOUNT,
314 PAGE_KERNEL,
315 0, node, __builtin_return_address(0));
316 if (!stack)
317 return -ENOMEM;
318
319 vm = find_vm_area(stack);
320 if (memcg_charge_kernel_stack(vm)) {
321 vfree(stack);
322 return -ENOMEM;
323 }
324 /*
325 * We can't call find_vm_area() in interrupt context, and
326 * free_thread_stack() can be called in interrupt context,
327 * so cache the vm_struct.
328 */
329 tsk->stack_vm_area = vm;
330 stack = kasan_reset_tag(stack);
331 tsk->stack = stack;
332 return 0;
333 }
334
free_thread_stack(struct task_struct * tsk)335 static void free_thread_stack(struct task_struct *tsk)
336 {
337 if (!try_release_thread_stack_to_cache(tsk->stack_vm_area))
338 thread_stack_delayed_free(tsk);
339
340 tsk->stack = NULL;
341 tsk->stack_vm_area = NULL;
342 }
343
344 # else /* !CONFIG_VMAP_STACK */
345
thread_stack_free_rcu(struct rcu_head * rh)346 static void thread_stack_free_rcu(struct rcu_head *rh)
347 {
348 __free_pages(virt_to_page(rh), THREAD_SIZE_ORDER);
349 }
350
thread_stack_delayed_free(struct task_struct * tsk)351 static void thread_stack_delayed_free(struct task_struct *tsk)
352 {
353 struct rcu_head *rh = tsk->stack;
354
355 call_rcu(rh, thread_stack_free_rcu);
356 }
357
alloc_thread_stack_node(struct task_struct * tsk,int node)358 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
359 {
360 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
361 THREAD_SIZE_ORDER);
362
363 if (likely(page)) {
364 tsk->stack = kasan_reset_tag(page_address(page));
365 return 0;
366 }
367 return -ENOMEM;
368 }
369
free_thread_stack(struct task_struct * tsk)370 static void free_thread_stack(struct task_struct *tsk)
371 {
372 thread_stack_delayed_free(tsk);
373 tsk->stack = NULL;
374 }
375
376 # endif /* CONFIG_VMAP_STACK */
377 # else /* !(THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)) */
378
379 static struct kmem_cache *thread_stack_cache;
380
thread_stack_free_rcu(struct rcu_head * rh)381 static void thread_stack_free_rcu(struct rcu_head *rh)
382 {
383 kmem_cache_free(thread_stack_cache, rh);
384 }
385
thread_stack_delayed_free(struct task_struct * tsk)386 static void thread_stack_delayed_free(struct task_struct *tsk)
387 {
388 struct rcu_head *rh = tsk->stack;
389
390 call_rcu(rh, thread_stack_free_rcu);
391 }
392
alloc_thread_stack_node(struct task_struct * tsk,int node)393 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
394 {
395 unsigned long *stack;
396 stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
397 stack = kasan_reset_tag(stack);
398 tsk->stack = stack;
399 return stack ? 0 : -ENOMEM;
400 }
401
free_thread_stack(struct task_struct * tsk)402 static void free_thread_stack(struct task_struct *tsk)
403 {
404 thread_stack_delayed_free(tsk);
405 tsk->stack = NULL;
406 }
407
thread_stack_cache_init(void)408 void thread_stack_cache_init(void)
409 {
410 thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
411 THREAD_SIZE, THREAD_SIZE, 0, 0,
412 THREAD_SIZE, NULL);
413 BUG_ON(thread_stack_cache == NULL);
414 }
415
416 # endif /* THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) */
417 #else /* CONFIG_ARCH_THREAD_STACK_ALLOCATOR */
418
alloc_thread_stack_node(struct task_struct * tsk,int node)419 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
420 {
421 unsigned long *stack;
422
423 stack = arch_alloc_thread_stack_node(tsk, node);
424 tsk->stack = stack;
425 return stack ? 0 : -ENOMEM;
426 }
427
free_thread_stack(struct task_struct * tsk)428 static void free_thread_stack(struct task_struct *tsk)
429 {
430 arch_free_thread_stack(tsk);
431 tsk->stack = NULL;
432 }
433
434 #endif /* !CONFIG_ARCH_THREAD_STACK_ALLOCATOR */
435
436 /* SLAB cache for signal_struct structures (tsk->signal) */
437 static struct kmem_cache *signal_cachep;
438
439 /* SLAB cache for sighand_struct structures (tsk->sighand) */
440 struct kmem_cache *sighand_cachep;
441
442 /* SLAB cache for files_struct structures (tsk->files) */
443 struct kmem_cache *files_cachep;
444
445 /* SLAB cache for fs_struct structures (tsk->fs) */
446 struct kmem_cache *fs_cachep;
447
448 /* SLAB cache for vm_area_struct structures */
449 static struct kmem_cache *vm_area_cachep;
450
451 /* SLAB cache for mm_struct structures (tsk->mm) */
452 static struct kmem_cache *mm_cachep;
453
vm_area_alloc(struct mm_struct * mm)454 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
455 {
456 struct vm_area_struct *vma;
457
458 vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
459 if (vma)
460 vma_init(vma, mm);
461 return vma;
462 }
463
vm_area_dup(struct vm_area_struct * orig)464 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
465 {
466 struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
467
468 if (new) {
469 ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
470 ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
471 /*
472 * orig->shared.rb may be modified concurrently, but the clone
473 * will be reinitialized.
474 */
475 *new = data_race(*orig);
476 INIT_LIST_HEAD(&new->anon_vma_chain);
477 dup_anon_vma_name(orig, new);
478 }
479 return new;
480 }
481
vm_area_free(struct vm_area_struct * vma)482 void vm_area_free(struct vm_area_struct *vma)
483 {
484 free_anon_vma_name(vma);
485 kmem_cache_free(vm_area_cachep, vma);
486 }
487
account_kernel_stack(struct task_struct * tsk,int account)488 static void account_kernel_stack(struct task_struct *tsk, int account)
489 {
490 if (IS_ENABLED(CONFIG_VMAP_STACK)) {
491 struct vm_struct *vm = task_stack_vm_area(tsk);
492 int i;
493
494 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
495 mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB,
496 account * (PAGE_SIZE / 1024));
497 } else {
498 void *stack = task_stack_page(tsk);
499
500 /* All stack pages are in the same node. */
501 mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB,
502 account * (THREAD_SIZE / 1024));
503 }
504 }
505
exit_task_stack_account(struct task_struct * tsk)506 void exit_task_stack_account(struct task_struct *tsk)
507 {
508 account_kernel_stack(tsk, -1);
509
510 if (IS_ENABLED(CONFIG_VMAP_STACK)) {
511 struct vm_struct *vm;
512 int i;
513
514 vm = task_stack_vm_area(tsk);
515 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
516 memcg_kmem_uncharge_page(vm->pages[i], 0);
517 }
518 }
519
release_task_stack(struct task_struct * tsk)520 static void release_task_stack(struct task_struct *tsk)
521 {
522 if (WARN_ON(READ_ONCE(tsk->__state) != TASK_DEAD))
523 return; /* Better to leak the stack than to free prematurely */
524
525 free_thread_stack(tsk);
526 }
527
528 #ifdef CONFIG_THREAD_INFO_IN_TASK
put_task_stack(struct task_struct * tsk)529 void put_task_stack(struct task_struct *tsk)
530 {
531 if (refcount_dec_and_test(&tsk->stack_refcount))
532 release_task_stack(tsk);
533 }
534 #endif
535
free_task(struct task_struct * tsk)536 void free_task(struct task_struct *tsk)
537 {
538 #ifdef CONFIG_SECCOMP
539 WARN_ON_ONCE(tsk->seccomp.filter);
540 #endif
541 release_user_cpus_ptr(tsk);
542 scs_release(tsk);
543
544 #ifndef CONFIG_THREAD_INFO_IN_TASK
545 /*
546 * The task is finally done with both the stack and thread_info,
547 * so free both.
548 */
549 release_task_stack(tsk);
550 #else
551 /*
552 * If the task had a separate stack allocation, it should be gone
553 * by now.
554 */
555 WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
556 #endif
557 rt_mutex_debug_task_free(tsk);
558 ftrace_graph_exit_task(tsk);
559 arch_release_task_struct(tsk);
560 if (tsk->flags & PF_KTHREAD)
561 free_kthread_struct(tsk);
562 free_task_struct(tsk);
563 }
564 EXPORT_SYMBOL(free_task);
565
dup_mm_exe_file(struct mm_struct * mm,struct mm_struct * oldmm)566 static void dup_mm_exe_file(struct mm_struct *mm, struct mm_struct *oldmm)
567 {
568 struct file *exe_file;
569
570 exe_file = get_mm_exe_file(oldmm);
571 RCU_INIT_POINTER(mm->exe_file, exe_file);
572 /*
573 * We depend on the oldmm having properly denied write access to the
574 * exe_file already.
575 */
576 if (exe_file && deny_write_access(exe_file))
577 pr_warn_once("deny_write_access() failed in %s\n", __func__);
578 }
579
580 #ifdef CONFIG_MMU
dup_mmap(struct mm_struct * mm,struct mm_struct * oldmm)581 static __latent_entropy int dup_mmap(struct mm_struct *mm,
582 struct mm_struct *oldmm)
583 {
584 struct vm_area_struct *mpnt, *tmp;
585 int retval;
586 unsigned long charge = 0;
587 LIST_HEAD(uf);
588 MA_STATE(old_mas, &oldmm->mm_mt, 0, 0);
589 MA_STATE(mas, &mm->mm_mt, 0, 0);
590
591 uprobe_start_dup_mmap();
592 if (mmap_write_lock_killable(oldmm)) {
593 retval = -EINTR;
594 goto fail_uprobe_end;
595 }
596 flush_cache_dup_mm(oldmm);
597 uprobe_dup_mmap(oldmm, mm);
598 /*
599 * Not linked in yet - no deadlock potential:
600 */
601 mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING);
602
603 /* No ordering required: file already has been exposed. */
604 dup_mm_exe_file(mm, oldmm);
605
606 mm->total_vm = oldmm->total_vm;
607 mm->data_vm = oldmm->data_vm;
608 mm->exec_vm = oldmm->exec_vm;
609 mm->stack_vm = oldmm->stack_vm;
610
611 retval = ksm_fork(mm, oldmm);
612 if (retval)
613 goto out;
614 khugepaged_fork(mm, oldmm);
615
616 retval = mas_expected_entries(&mas, oldmm->map_count);
617 if (retval)
618 goto out;
619
620 mas_for_each(&old_mas, mpnt, ULONG_MAX) {
621 struct file *file;
622
623 if (mpnt->vm_flags & VM_DONTCOPY) {
624 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
625 continue;
626 }
627 charge = 0;
628 /*
629 * Don't duplicate many vmas if we've been oom-killed (for
630 * example)
631 */
632 if (fatal_signal_pending(current)) {
633 retval = -EINTR;
634 goto loop_out;
635 }
636 if (mpnt->vm_flags & VM_ACCOUNT) {
637 unsigned long len = vma_pages(mpnt);
638
639 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
640 goto fail_nomem;
641 charge = len;
642 }
643 tmp = vm_area_dup(mpnt);
644 if (!tmp)
645 goto fail_nomem;
646 retval = vma_dup_policy(mpnt, tmp);
647 if (retval)
648 goto fail_nomem_policy;
649 tmp->vm_mm = mm;
650 retval = dup_userfaultfd(tmp, &uf);
651 if (retval)
652 goto fail_nomem_anon_vma_fork;
653 if (tmp->vm_flags & VM_WIPEONFORK) {
654 /*
655 * VM_WIPEONFORK gets a clean slate in the child.
656 * Don't prepare anon_vma until fault since we don't
657 * copy page for current vma.
658 */
659 tmp->anon_vma = NULL;
660 } else if (anon_vma_fork(tmp, mpnt))
661 goto fail_nomem_anon_vma_fork;
662 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
663 file = tmp->vm_file;
664 if (file) {
665 struct address_space *mapping = file->f_mapping;
666
667 get_file(file);
668 i_mmap_lock_write(mapping);
669 if (tmp->vm_flags & VM_SHARED)
670 mapping_allow_writable(mapping);
671 flush_dcache_mmap_lock(mapping);
672 /* insert tmp into the share list, just after mpnt */
673 vma_interval_tree_insert_after(tmp, mpnt,
674 &mapping->i_mmap);
675 flush_dcache_mmap_unlock(mapping);
676 i_mmap_unlock_write(mapping);
677 }
678
679 /*
680 * Copy/update hugetlb private vma information.
681 */
682 if (is_vm_hugetlb_page(tmp))
683 hugetlb_dup_vma_private(tmp);
684
685 /* Link the vma into the MT */
686 mas.index = tmp->vm_start;
687 mas.last = tmp->vm_end - 1;
688 mas_store(&mas, tmp);
689 if (mas_is_err(&mas))
690 goto fail_nomem_mas_store;
691
692 mm->map_count++;
693 if (!(tmp->vm_flags & VM_WIPEONFORK))
694 retval = copy_page_range(tmp, mpnt);
695
696 if (tmp->vm_ops && tmp->vm_ops->open)
697 tmp->vm_ops->open(tmp);
698
699 if (retval)
700 goto loop_out;
701 }
702 /* a new mm has just been created */
703 retval = arch_dup_mmap(oldmm, mm);
704 loop_out:
705 mas_destroy(&mas);
706 out:
707 mmap_write_unlock(mm);
708 flush_tlb_mm(oldmm);
709 mmap_write_unlock(oldmm);
710 dup_userfaultfd_complete(&uf);
711 fail_uprobe_end:
712 uprobe_end_dup_mmap();
713 return retval;
714
715 fail_nomem_mas_store:
716 unlink_anon_vmas(tmp);
717 fail_nomem_anon_vma_fork:
718 mpol_put(vma_policy(tmp));
719 fail_nomem_policy:
720 vm_area_free(tmp);
721 fail_nomem:
722 retval = -ENOMEM;
723 vm_unacct_memory(charge);
724 goto loop_out;
725 }
726
mm_alloc_pgd(struct mm_struct * mm)727 static inline int mm_alloc_pgd(struct mm_struct *mm)
728 {
729 mm->pgd = pgd_alloc(mm);
730 if (unlikely(!mm->pgd))
731 return -ENOMEM;
732 return 0;
733 }
734
mm_free_pgd(struct mm_struct * mm)735 static inline void mm_free_pgd(struct mm_struct *mm)
736 {
737 pgd_free(mm, mm->pgd);
738 }
739 #else
dup_mmap(struct mm_struct * mm,struct mm_struct * oldmm)740 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
741 {
742 mmap_write_lock(oldmm);
743 dup_mm_exe_file(mm, oldmm);
744 mmap_write_unlock(oldmm);
745 return 0;
746 }
747 #define mm_alloc_pgd(mm) (0)
748 #define mm_free_pgd(mm)
749 #endif /* CONFIG_MMU */
750
check_mm(struct mm_struct * mm)751 static void check_mm(struct mm_struct *mm)
752 {
753 int i;
754
755 BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
756 "Please make sure 'struct resident_page_types[]' is updated as well");
757
758 for (i = 0; i < NR_MM_COUNTERS; i++) {
759 long x = atomic_long_read(&mm->rss_stat.count[i]);
760
761 if (unlikely(x))
762 pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
763 mm, resident_page_types[i], x);
764 }
765
766 if (mm_pgtables_bytes(mm))
767 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
768 mm_pgtables_bytes(mm));
769
770 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
771 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
772 #endif
773 }
774
775 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
776 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
777
778 /*
779 * Called when the last reference to the mm
780 * is dropped: either by a lazy thread or by
781 * mmput. Free the page directory and the mm.
782 */
__mmdrop(struct mm_struct * mm)783 void __mmdrop(struct mm_struct *mm)
784 {
785 BUG_ON(mm == &init_mm);
786 WARN_ON_ONCE(mm == current->mm);
787 WARN_ON_ONCE(mm == current->active_mm);
788 mm_free_pgd(mm);
789 destroy_context(mm);
790 mmu_notifier_subscriptions_destroy(mm);
791 check_mm(mm);
792 put_user_ns(mm->user_ns);
793 mm_pasid_drop(mm);
794 free_mm(mm);
795 }
796 EXPORT_SYMBOL_GPL(__mmdrop);
797
mmdrop_async_fn(struct work_struct * work)798 static void mmdrop_async_fn(struct work_struct *work)
799 {
800 struct mm_struct *mm;
801
802 mm = container_of(work, struct mm_struct, async_put_work);
803 __mmdrop(mm);
804 }
805
mmdrop_async(struct mm_struct * mm)806 static void mmdrop_async(struct mm_struct *mm)
807 {
808 if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
809 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
810 schedule_work(&mm->async_put_work);
811 }
812 }
813
free_signal_struct(struct signal_struct * sig)814 static inline void free_signal_struct(struct signal_struct *sig)
815 {
816 taskstats_tgid_free(sig);
817 sched_autogroup_exit(sig);
818 /*
819 * __mmdrop is not safe to call from softirq context on x86 due to
820 * pgd_dtor so postpone it to the async context
821 */
822 if (sig->oom_mm)
823 mmdrop_async(sig->oom_mm);
824 kmem_cache_free(signal_cachep, sig);
825 }
826
put_signal_struct(struct signal_struct * sig)827 static inline void put_signal_struct(struct signal_struct *sig)
828 {
829 if (refcount_dec_and_test(&sig->sigcnt))
830 free_signal_struct(sig);
831 }
832
__put_task_struct(struct task_struct * tsk)833 void __put_task_struct(struct task_struct *tsk)
834 {
835 WARN_ON(!tsk->exit_state);
836 WARN_ON(refcount_read(&tsk->usage));
837 WARN_ON(tsk == current);
838
839 io_uring_free(tsk);
840 cgroup_free(tsk);
841 task_numa_free(tsk, true);
842 security_task_free(tsk);
843 bpf_task_storage_free(tsk);
844 exit_creds(tsk);
845 delayacct_tsk_free(tsk);
846 put_signal_struct(tsk->signal);
847 sched_core_free(tsk);
848 free_task(tsk);
849 }
850 EXPORT_SYMBOL_GPL(__put_task_struct);
851
arch_task_cache_init(void)852 void __init __weak arch_task_cache_init(void) { }
853
854 /*
855 * set_max_threads
856 */
set_max_threads(unsigned int max_threads_suggested)857 static void set_max_threads(unsigned int max_threads_suggested)
858 {
859 u64 threads;
860 unsigned long nr_pages = totalram_pages();
861
862 /*
863 * The number of threads shall be limited such that the thread
864 * structures may only consume a small part of the available memory.
865 */
866 if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
867 threads = MAX_THREADS;
868 else
869 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
870 (u64) THREAD_SIZE * 8UL);
871
872 if (threads > max_threads_suggested)
873 threads = max_threads_suggested;
874
875 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
876 }
877
878 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
879 /* Initialized by the architecture: */
880 int arch_task_struct_size __read_mostly;
881 #endif
882
883 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
task_struct_whitelist(unsigned long * offset,unsigned long * size)884 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
885 {
886 /* Fetch thread_struct whitelist for the architecture. */
887 arch_thread_struct_whitelist(offset, size);
888
889 /*
890 * Handle zero-sized whitelist or empty thread_struct, otherwise
891 * adjust offset to position of thread_struct in task_struct.
892 */
893 if (unlikely(*size == 0))
894 *offset = 0;
895 else
896 *offset += offsetof(struct task_struct, thread);
897 }
898 #endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
899
fork_init(void)900 void __init fork_init(void)
901 {
902 int i;
903 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
904 #ifndef ARCH_MIN_TASKALIGN
905 #define ARCH_MIN_TASKALIGN 0
906 #endif
907 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
908 unsigned long useroffset, usersize;
909
910 /* create a slab on which task_structs can be allocated */
911 task_struct_whitelist(&useroffset, &usersize);
912 task_struct_cachep = kmem_cache_create_usercopy("task_struct",
913 arch_task_struct_size, align,
914 SLAB_PANIC|SLAB_ACCOUNT,
915 useroffset, usersize, NULL);
916 #endif
917
918 /* do the arch specific task caches init */
919 arch_task_cache_init();
920
921 set_max_threads(MAX_THREADS);
922
923 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
924 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
925 init_task.signal->rlim[RLIMIT_SIGPENDING] =
926 init_task.signal->rlim[RLIMIT_NPROC];
927
928 for (i = 0; i < UCOUNT_COUNTS; i++)
929 init_user_ns.ucount_max[i] = max_threads/2;
930
931 set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_NPROC, RLIM_INFINITY);
932 set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, RLIM_INFINITY);
933 set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY);
934 set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK, RLIM_INFINITY);
935
936 #ifdef CONFIG_VMAP_STACK
937 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
938 NULL, free_vm_stack_cache);
939 #endif
940
941 scs_init();
942
943 lockdep_init_task(&init_task);
944 uprobes_init();
945 }
946
arch_dup_task_struct(struct task_struct * dst,struct task_struct * src)947 int __weak arch_dup_task_struct(struct task_struct *dst,
948 struct task_struct *src)
949 {
950 *dst = *src;
951 return 0;
952 }
953
set_task_stack_end_magic(struct task_struct * tsk)954 void set_task_stack_end_magic(struct task_struct *tsk)
955 {
956 unsigned long *stackend;
957
958 stackend = end_of_stack(tsk);
959 *stackend = STACK_END_MAGIC; /* for overflow detection */
960 }
961
dup_task_struct(struct task_struct * orig,int node)962 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
963 {
964 struct task_struct *tsk;
965 int err;
966
967 if (node == NUMA_NO_NODE)
968 node = tsk_fork_get_node(orig);
969 tsk = alloc_task_struct_node(node);
970 if (!tsk)
971 return NULL;
972
973 err = arch_dup_task_struct(tsk, orig);
974 if (err)
975 goto free_tsk;
976
977 err = alloc_thread_stack_node(tsk, node);
978 if (err)
979 goto free_tsk;
980
981 #ifdef CONFIG_THREAD_INFO_IN_TASK
982 refcount_set(&tsk->stack_refcount, 1);
983 #endif
984 account_kernel_stack(tsk, 1);
985
986 err = scs_prepare(tsk, node);
987 if (err)
988 goto free_stack;
989
990 #ifdef CONFIG_SECCOMP
991 /*
992 * We must handle setting up seccomp filters once we're under
993 * the sighand lock in case orig has changed between now and
994 * then. Until then, filter must be NULL to avoid messing up
995 * the usage counts on the error path calling free_task.
996 */
997 tsk->seccomp.filter = NULL;
998 #endif
999
1000 setup_thread_stack(tsk, orig);
1001 clear_user_return_notifier(tsk);
1002 clear_tsk_need_resched(tsk);
1003 set_task_stack_end_magic(tsk);
1004 clear_syscall_work_syscall_user_dispatch(tsk);
1005
1006 #ifdef CONFIG_STACKPROTECTOR
1007 tsk->stack_canary = get_random_canary();
1008 #endif
1009 if (orig->cpus_ptr == &orig->cpus_mask)
1010 tsk->cpus_ptr = &tsk->cpus_mask;
1011 dup_user_cpus_ptr(tsk, orig, node);
1012
1013 /*
1014 * One for the user space visible state that goes away when reaped.
1015 * One for the scheduler.
1016 */
1017 refcount_set(&tsk->rcu_users, 2);
1018 /* One for the rcu users */
1019 refcount_set(&tsk->usage, 1);
1020 #ifdef CONFIG_BLK_DEV_IO_TRACE
1021 tsk->btrace_seq = 0;
1022 #endif
1023 tsk->splice_pipe = NULL;
1024 tsk->task_frag.page = NULL;
1025 tsk->wake_q.next = NULL;
1026 tsk->worker_private = NULL;
1027
1028 kcov_task_init(tsk);
1029 kmsan_task_create(tsk);
1030 kmap_local_fork(tsk);
1031
1032 #ifdef CONFIG_FAULT_INJECTION
1033 tsk->fail_nth = 0;
1034 #endif
1035
1036 #ifdef CONFIG_BLK_CGROUP
1037 tsk->throttle_queue = NULL;
1038 tsk->use_memdelay = 0;
1039 #endif
1040
1041 #ifdef CONFIG_IOMMU_SVA
1042 tsk->pasid_activated = 0;
1043 #endif
1044
1045 #ifdef CONFIG_MEMCG
1046 tsk->active_memcg = NULL;
1047 #endif
1048
1049 #ifdef CONFIG_CPU_SUP_INTEL
1050 tsk->reported_split_lock = 0;
1051 #endif
1052
1053 return tsk;
1054
1055 free_stack:
1056 exit_task_stack_account(tsk);
1057 free_thread_stack(tsk);
1058 free_tsk:
1059 free_task_struct(tsk);
1060 return NULL;
1061 }
1062
1063 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
1064
1065 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
1066
coredump_filter_setup(char * s)1067 static int __init coredump_filter_setup(char *s)
1068 {
1069 default_dump_filter =
1070 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
1071 MMF_DUMP_FILTER_MASK;
1072 return 1;
1073 }
1074
1075 __setup("coredump_filter=", coredump_filter_setup);
1076
1077 #include <linux/init_task.h>
1078
mm_init_aio(struct mm_struct * mm)1079 static void mm_init_aio(struct mm_struct *mm)
1080 {
1081 #ifdef CONFIG_AIO
1082 spin_lock_init(&mm->ioctx_lock);
1083 mm->ioctx_table = NULL;
1084 #endif
1085 }
1086
mm_clear_owner(struct mm_struct * mm,struct task_struct * p)1087 static __always_inline void mm_clear_owner(struct mm_struct *mm,
1088 struct task_struct *p)
1089 {
1090 #ifdef CONFIG_MEMCG
1091 if (mm->owner == p)
1092 WRITE_ONCE(mm->owner, NULL);
1093 #endif
1094 }
1095
mm_init_owner(struct mm_struct * mm,struct task_struct * p)1096 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1097 {
1098 #ifdef CONFIG_MEMCG
1099 mm->owner = p;
1100 #endif
1101 }
1102
mm_init_uprobes_state(struct mm_struct * mm)1103 static void mm_init_uprobes_state(struct mm_struct *mm)
1104 {
1105 #ifdef CONFIG_UPROBES
1106 mm->uprobes_state.xol_area = NULL;
1107 #endif
1108 }
1109
mm_init(struct mm_struct * mm,struct task_struct * p,struct user_namespace * user_ns)1110 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
1111 struct user_namespace *user_ns)
1112 {
1113 mt_init_flags(&mm->mm_mt, MM_MT_FLAGS);
1114 mt_set_external_lock(&mm->mm_mt, &mm->mmap_lock);
1115 atomic_set(&mm->mm_users, 1);
1116 atomic_set(&mm->mm_count, 1);
1117 seqcount_init(&mm->write_protect_seq);
1118 mmap_init_lock(mm);
1119 INIT_LIST_HEAD(&mm->mmlist);
1120 mm_pgtables_bytes_init(mm);
1121 mm->map_count = 0;
1122 mm->locked_vm = 0;
1123 atomic64_set(&mm->pinned_vm, 0);
1124 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1125 spin_lock_init(&mm->page_table_lock);
1126 spin_lock_init(&mm->arg_lock);
1127 mm_init_cpumask(mm);
1128 mm_init_aio(mm);
1129 mm_init_owner(mm, p);
1130 mm_pasid_init(mm);
1131 RCU_INIT_POINTER(mm->exe_file, NULL);
1132 mmu_notifier_subscriptions_init(mm);
1133 init_tlb_flush_pending(mm);
1134 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1135 mm->pmd_huge_pte = NULL;
1136 #endif
1137 mm_init_uprobes_state(mm);
1138 hugetlb_count_init(mm);
1139
1140 if (current->mm) {
1141 mm->flags = current->mm->flags & MMF_INIT_MASK;
1142 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1143 } else {
1144 mm->flags = default_dump_filter;
1145 mm->def_flags = 0;
1146 }
1147
1148 if (mm_alloc_pgd(mm))
1149 goto fail_nopgd;
1150
1151 if (init_new_context(p, mm))
1152 goto fail_nocontext;
1153
1154 mm->user_ns = get_user_ns(user_ns);
1155 lru_gen_init_mm(mm);
1156 return mm;
1157
1158 fail_nocontext:
1159 mm_free_pgd(mm);
1160 fail_nopgd:
1161 free_mm(mm);
1162 return NULL;
1163 }
1164
1165 /*
1166 * Allocate and initialize an mm_struct.
1167 */
mm_alloc(void)1168 struct mm_struct *mm_alloc(void)
1169 {
1170 struct mm_struct *mm;
1171
1172 mm = allocate_mm();
1173 if (!mm)
1174 return NULL;
1175
1176 memset(mm, 0, sizeof(*mm));
1177 return mm_init(mm, current, current_user_ns());
1178 }
1179
__mmput(struct mm_struct * mm)1180 static inline void __mmput(struct mm_struct *mm)
1181 {
1182 VM_BUG_ON(atomic_read(&mm->mm_users));
1183
1184 uprobe_clear_state(mm);
1185 exit_aio(mm);
1186 ksm_exit(mm);
1187 khugepaged_exit(mm); /* must run before exit_mmap */
1188 exit_mmap(mm);
1189 mm_put_huge_zero_page(mm);
1190 set_mm_exe_file(mm, NULL);
1191 if (!list_empty(&mm->mmlist)) {
1192 spin_lock(&mmlist_lock);
1193 list_del(&mm->mmlist);
1194 spin_unlock(&mmlist_lock);
1195 }
1196 if (mm->binfmt)
1197 module_put(mm->binfmt->module);
1198 lru_gen_del_mm(mm);
1199 mmdrop(mm);
1200 }
1201
1202 /*
1203 * Decrement the use count and release all resources for an mm.
1204 */
mmput(struct mm_struct * mm)1205 void mmput(struct mm_struct *mm)
1206 {
1207 might_sleep();
1208
1209 if (atomic_dec_and_test(&mm->mm_users))
1210 __mmput(mm);
1211 }
1212 EXPORT_SYMBOL_GPL(mmput);
1213
1214 #ifdef CONFIG_MMU
mmput_async_fn(struct work_struct * work)1215 static void mmput_async_fn(struct work_struct *work)
1216 {
1217 struct mm_struct *mm = container_of(work, struct mm_struct,
1218 async_put_work);
1219
1220 __mmput(mm);
1221 }
1222
mmput_async(struct mm_struct * mm)1223 void mmput_async(struct mm_struct *mm)
1224 {
1225 if (atomic_dec_and_test(&mm->mm_users)) {
1226 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1227 schedule_work(&mm->async_put_work);
1228 }
1229 }
1230 EXPORT_SYMBOL_GPL(mmput_async);
1231 #endif
1232
1233 /**
1234 * set_mm_exe_file - change a reference to the mm's executable file
1235 *
1236 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1237 *
1238 * Main users are mmput() and sys_execve(). Callers prevent concurrent
1239 * invocations: in mmput() nobody alive left, in execve task is single
1240 * threaded.
1241 *
1242 * Can only fail if new_exe_file != NULL.
1243 */
set_mm_exe_file(struct mm_struct * mm,struct file * new_exe_file)1244 int set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1245 {
1246 struct file *old_exe_file;
1247
1248 /*
1249 * It is safe to dereference the exe_file without RCU as
1250 * this function is only called if nobody else can access
1251 * this mm -- see comment above for justification.
1252 */
1253 old_exe_file = rcu_dereference_raw(mm->exe_file);
1254
1255 if (new_exe_file) {
1256 /*
1257 * We expect the caller (i.e., sys_execve) to already denied
1258 * write access, so this is unlikely to fail.
1259 */
1260 if (unlikely(deny_write_access(new_exe_file)))
1261 return -EACCES;
1262 get_file(new_exe_file);
1263 }
1264 rcu_assign_pointer(mm->exe_file, new_exe_file);
1265 if (old_exe_file) {
1266 allow_write_access(old_exe_file);
1267 fput(old_exe_file);
1268 }
1269 return 0;
1270 }
1271
1272 /**
1273 * replace_mm_exe_file - replace a reference to the mm's executable file
1274 *
1275 * This changes mm's executable file (shown as symlink /proc/[pid]/exe),
1276 * dealing with concurrent invocation and without grabbing the mmap lock in
1277 * write mode.
1278 *
1279 * Main user is sys_prctl(PR_SET_MM_MAP/EXE_FILE).
1280 */
replace_mm_exe_file(struct mm_struct * mm,struct file * new_exe_file)1281 int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1282 {
1283 struct vm_area_struct *vma;
1284 struct file *old_exe_file;
1285 int ret = 0;
1286
1287 /* Forbid mm->exe_file change if old file still mapped. */
1288 old_exe_file = get_mm_exe_file(mm);
1289 if (old_exe_file) {
1290 VMA_ITERATOR(vmi, mm, 0);
1291 mmap_read_lock(mm);
1292 for_each_vma(vmi, vma) {
1293 if (!vma->vm_file)
1294 continue;
1295 if (path_equal(&vma->vm_file->f_path,
1296 &old_exe_file->f_path)) {
1297 ret = -EBUSY;
1298 break;
1299 }
1300 }
1301 mmap_read_unlock(mm);
1302 fput(old_exe_file);
1303 if (ret)
1304 return ret;
1305 }
1306
1307 /* set the new file, lockless */
1308 ret = deny_write_access(new_exe_file);
1309 if (ret)
1310 return -EACCES;
1311 get_file(new_exe_file);
1312
1313 old_exe_file = xchg(&mm->exe_file, new_exe_file);
1314 if (old_exe_file) {
1315 /*
1316 * Don't race with dup_mmap() getting the file and disallowing
1317 * write access while someone might open the file writable.
1318 */
1319 mmap_read_lock(mm);
1320 allow_write_access(old_exe_file);
1321 fput(old_exe_file);
1322 mmap_read_unlock(mm);
1323 }
1324 return 0;
1325 }
1326
1327 /**
1328 * get_mm_exe_file - acquire a reference to the mm's executable file
1329 *
1330 * Returns %NULL if mm has no associated executable file.
1331 * User must release file via fput().
1332 */
get_mm_exe_file(struct mm_struct * mm)1333 struct file *get_mm_exe_file(struct mm_struct *mm)
1334 {
1335 struct file *exe_file;
1336
1337 rcu_read_lock();
1338 exe_file = rcu_dereference(mm->exe_file);
1339 if (exe_file && !get_file_rcu(exe_file))
1340 exe_file = NULL;
1341 rcu_read_unlock();
1342 return exe_file;
1343 }
1344
1345 /**
1346 * get_task_exe_file - acquire a reference to the task's executable file
1347 *
1348 * Returns %NULL if task's mm (if any) has no associated executable file or
1349 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1350 * User must release file via fput().
1351 */
get_task_exe_file(struct task_struct * task)1352 struct file *get_task_exe_file(struct task_struct *task)
1353 {
1354 struct file *exe_file = NULL;
1355 struct mm_struct *mm;
1356
1357 task_lock(task);
1358 mm = task->mm;
1359 if (mm) {
1360 if (!(task->flags & PF_KTHREAD))
1361 exe_file = get_mm_exe_file(mm);
1362 }
1363 task_unlock(task);
1364 return exe_file;
1365 }
1366
1367 /**
1368 * get_task_mm - acquire a reference to the task's mm
1369 *
1370 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
1371 * this kernel workthread has transiently adopted a user mm with use_mm,
1372 * to do its AIO) is not set and if so returns a reference to it, after
1373 * bumping up the use count. User must release the mm via mmput()
1374 * after use. Typically used by /proc and ptrace.
1375 */
get_task_mm(struct task_struct * task)1376 struct mm_struct *get_task_mm(struct task_struct *task)
1377 {
1378 struct mm_struct *mm;
1379
1380 task_lock(task);
1381 mm = task->mm;
1382 if (mm) {
1383 if (task->flags & PF_KTHREAD)
1384 mm = NULL;
1385 else
1386 mmget(mm);
1387 }
1388 task_unlock(task);
1389 return mm;
1390 }
1391 EXPORT_SYMBOL_GPL(get_task_mm);
1392
mm_access(struct task_struct * task,unsigned int mode)1393 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1394 {
1395 struct mm_struct *mm;
1396 int err;
1397
1398 err = down_read_killable(&task->signal->exec_update_lock);
1399 if (err)
1400 return ERR_PTR(err);
1401
1402 mm = get_task_mm(task);
1403 if (mm && mm != current->mm &&
1404 !ptrace_may_access(task, mode)) {
1405 mmput(mm);
1406 mm = ERR_PTR(-EACCES);
1407 }
1408 up_read(&task->signal->exec_update_lock);
1409
1410 return mm;
1411 }
1412
complete_vfork_done(struct task_struct * tsk)1413 static void complete_vfork_done(struct task_struct *tsk)
1414 {
1415 struct completion *vfork;
1416
1417 task_lock(tsk);
1418 vfork = tsk->vfork_done;
1419 if (likely(vfork)) {
1420 tsk->vfork_done = NULL;
1421 complete(vfork);
1422 }
1423 task_unlock(tsk);
1424 }
1425
wait_for_vfork_done(struct task_struct * child,struct completion * vfork)1426 static int wait_for_vfork_done(struct task_struct *child,
1427 struct completion *vfork)
1428 {
1429 unsigned int state = TASK_UNINTERRUPTIBLE|TASK_KILLABLE|TASK_FREEZABLE;
1430 int killed;
1431
1432 cgroup_enter_frozen();
1433 killed = wait_for_completion_state(vfork, state);
1434 cgroup_leave_frozen(false);
1435
1436 if (killed) {
1437 task_lock(child);
1438 child->vfork_done = NULL;
1439 task_unlock(child);
1440 }
1441
1442 put_task_struct(child);
1443 return killed;
1444 }
1445
1446 /* Please note the differences between mmput and mm_release.
1447 * mmput is called whenever we stop holding onto a mm_struct,
1448 * error success whatever.
1449 *
1450 * mm_release is called after a mm_struct has been removed
1451 * from the current process.
1452 *
1453 * This difference is important for error handling, when we
1454 * only half set up a mm_struct for a new process and need to restore
1455 * the old one. Because we mmput the new mm_struct before
1456 * restoring the old one. . .
1457 * Eric Biederman 10 January 1998
1458 */
mm_release(struct task_struct * tsk,struct mm_struct * mm)1459 static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1460 {
1461 uprobe_free_utask(tsk);
1462
1463 /* Get rid of any cached register state */
1464 deactivate_mm(tsk, mm);
1465
1466 /*
1467 * Signal userspace if we're not exiting with a core dump
1468 * because we want to leave the value intact for debugging
1469 * purposes.
1470 */
1471 if (tsk->clear_child_tid) {
1472 if (atomic_read(&mm->mm_users) > 1) {
1473 /*
1474 * We don't check the error code - if userspace has
1475 * not set up a proper pointer then tough luck.
1476 */
1477 put_user(0, tsk->clear_child_tid);
1478 do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1479 1, NULL, NULL, 0, 0);
1480 }
1481 tsk->clear_child_tid = NULL;
1482 }
1483
1484 /*
1485 * All done, finally we can wake up parent and return this mm to him.
1486 * Also kthread_stop() uses this completion for synchronization.
1487 */
1488 if (tsk->vfork_done)
1489 complete_vfork_done(tsk);
1490 }
1491
exit_mm_release(struct task_struct * tsk,struct mm_struct * mm)1492 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1493 {
1494 futex_exit_release(tsk);
1495 mm_release(tsk, mm);
1496 }
1497
exec_mm_release(struct task_struct * tsk,struct mm_struct * mm)1498 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1499 {
1500 futex_exec_release(tsk);
1501 mm_release(tsk, mm);
1502 }
1503
1504 /**
1505 * dup_mm() - duplicates an existing mm structure
1506 * @tsk: the task_struct with which the new mm will be associated.
1507 * @oldmm: the mm to duplicate.
1508 *
1509 * Allocates a new mm structure and duplicates the provided @oldmm structure
1510 * content into it.
1511 *
1512 * Return: the duplicated mm or NULL on failure.
1513 */
dup_mm(struct task_struct * tsk,struct mm_struct * oldmm)1514 static struct mm_struct *dup_mm(struct task_struct *tsk,
1515 struct mm_struct *oldmm)
1516 {
1517 struct mm_struct *mm;
1518 int err;
1519
1520 mm = allocate_mm();
1521 if (!mm)
1522 goto fail_nomem;
1523
1524 memcpy(mm, oldmm, sizeof(*mm));
1525
1526 if (!mm_init(mm, tsk, mm->user_ns))
1527 goto fail_nomem;
1528
1529 err = dup_mmap(mm, oldmm);
1530 if (err)
1531 goto free_pt;
1532
1533 mm->hiwater_rss = get_mm_rss(mm);
1534 mm->hiwater_vm = mm->total_vm;
1535
1536 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1537 goto free_pt;
1538
1539 return mm;
1540
1541 free_pt:
1542 /* don't put binfmt in mmput, we haven't got module yet */
1543 mm->binfmt = NULL;
1544 mm_init_owner(mm, NULL);
1545 mmput(mm);
1546
1547 fail_nomem:
1548 return NULL;
1549 }
1550
copy_mm(unsigned long clone_flags,struct task_struct * tsk)1551 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1552 {
1553 struct mm_struct *mm, *oldmm;
1554
1555 tsk->min_flt = tsk->maj_flt = 0;
1556 tsk->nvcsw = tsk->nivcsw = 0;
1557 #ifdef CONFIG_DETECT_HUNG_TASK
1558 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1559 tsk->last_switch_time = 0;
1560 #endif
1561
1562 tsk->mm = NULL;
1563 tsk->active_mm = NULL;
1564
1565 /*
1566 * Are we cloning a kernel thread?
1567 *
1568 * We need to steal a active VM for that..
1569 */
1570 oldmm = current->mm;
1571 if (!oldmm)
1572 return 0;
1573
1574 if (clone_flags & CLONE_VM) {
1575 mmget(oldmm);
1576 mm = oldmm;
1577 } else {
1578 mm = dup_mm(tsk, current->mm);
1579 if (!mm)
1580 return -ENOMEM;
1581 }
1582
1583 tsk->mm = mm;
1584 tsk->active_mm = mm;
1585 return 0;
1586 }
1587
copy_fs(unsigned long clone_flags,struct task_struct * tsk)1588 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1589 {
1590 struct fs_struct *fs = current->fs;
1591 if (clone_flags & CLONE_FS) {
1592 /* tsk->fs is already what we want */
1593 spin_lock(&fs->lock);
1594 if (fs->in_exec) {
1595 spin_unlock(&fs->lock);
1596 return -EAGAIN;
1597 }
1598 fs->users++;
1599 spin_unlock(&fs->lock);
1600 return 0;
1601 }
1602 tsk->fs = copy_fs_struct(fs);
1603 if (!tsk->fs)
1604 return -ENOMEM;
1605 return 0;
1606 }
1607
copy_files(unsigned long clone_flags,struct task_struct * tsk)1608 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1609 {
1610 struct files_struct *oldf, *newf;
1611 int error = 0;
1612
1613 /*
1614 * A background process may not have any files ...
1615 */
1616 oldf = current->files;
1617 if (!oldf)
1618 goto out;
1619
1620 if (clone_flags & CLONE_FILES) {
1621 atomic_inc(&oldf->count);
1622 goto out;
1623 }
1624
1625 newf = dup_fd(oldf, NR_OPEN_MAX, &error);
1626 if (!newf)
1627 goto out;
1628
1629 tsk->files = newf;
1630 error = 0;
1631 out:
1632 return error;
1633 }
1634
copy_sighand(unsigned long clone_flags,struct task_struct * tsk)1635 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1636 {
1637 struct sighand_struct *sig;
1638
1639 if (clone_flags & CLONE_SIGHAND) {
1640 refcount_inc(¤t->sighand->count);
1641 return 0;
1642 }
1643 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1644 RCU_INIT_POINTER(tsk->sighand, sig);
1645 if (!sig)
1646 return -ENOMEM;
1647
1648 refcount_set(&sig->count, 1);
1649 spin_lock_irq(¤t->sighand->siglock);
1650 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1651 spin_unlock_irq(¤t->sighand->siglock);
1652
1653 /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
1654 if (clone_flags & CLONE_CLEAR_SIGHAND)
1655 flush_signal_handlers(tsk, 0);
1656
1657 return 0;
1658 }
1659
__cleanup_sighand(struct sighand_struct * sighand)1660 void __cleanup_sighand(struct sighand_struct *sighand)
1661 {
1662 if (refcount_dec_and_test(&sighand->count)) {
1663 signalfd_cleanup(sighand);
1664 /*
1665 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1666 * without an RCU grace period, see __lock_task_sighand().
1667 */
1668 kmem_cache_free(sighand_cachep, sighand);
1669 }
1670 }
1671
1672 /*
1673 * Initialize POSIX timer handling for a thread group.
1674 */
posix_cpu_timers_init_group(struct signal_struct * sig)1675 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1676 {
1677 struct posix_cputimers *pct = &sig->posix_cputimers;
1678 unsigned long cpu_limit;
1679
1680 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1681 posix_cputimers_group_init(pct, cpu_limit);
1682 }
1683
copy_signal(unsigned long clone_flags,struct task_struct * tsk)1684 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1685 {
1686 struct signal_struct *sig;
1687
1688 if (clone_flags & CLONE_THREAD)
1689 return 0;
1690
1691 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1692 tsk->signal = sig;
1693 if (!sig)
1694 return -ENOMEM;
1695
1696 sig->nr_threads = 1;
1697 sig->quick_threads = 1;
1698 atomic_set(&sig->live, 1);
1699 refcount_set(&sig->sigcnt, 1);
1700
1701 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1702 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1703 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1704
1705 init_waitqueue_head(&sig->wait_chldexit);
1706 sig->curr_target = tsk;
1707 init_sigpending(&sig->shared_pending);
1708 INIT_HLIST_HEAD(&sig->multiprocess);
1709 seqlock_init(&sig->stats_lock);
1710 prev_cputime_init(&sig->prev_cputime);
1711
1712 #ifdef CONFIG_POSIX_TIMERS
1713 INIT_LIST_HEAD(&sig->posix_timers);
1714 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1715 sig->real_timer.function = it_real_fn;
1716 #endif
1717
1718 task_lock(current->group_leader);
1719 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1720 task_unlock(current->group_leader);
1721
1722 posix_cpu_timers_init_group(sig);
1723
1724 tty_audit_fork(sig);
1725 sched_autogroup_fork(sig);
1726
1727 sig->oom_score_adj = current->signal->oom_score_adj;
1728 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1729
1730 mutex_init(&sig->cred_guard_mutex);
1731 init_rwsem(&sig->exec_update_lock);
1732
1733 return 0;
1734 }
1735
copy_seccomp(struct task_struct * p)1736 static void copy_seccomp(struct task_struct *p)
1737 {
1738 #ifdef CONFIG_SECCOMP
1739 /*
1740 * Must be called with sighand->lock held, which is common to
1741 * all threads in the group. Holding cred_guard_mutex is not
1742 * needed because this new task is not yet running and cannot
1743 * be racing exec.
1744 */
1745 assert_spin_locked(¤t->sighand->siglock);
1746
1747 /* Ref-count the new filter user, and assign it. */
1748 get_seccomp_filter(current);
1749 p->seccomp = current->seccomp;
1750
1751 /*
1752 * Explicitly enable no_new_privs here in case it got set
1753 * between the task_struct being duplicated and holding the
1754 * sighand lock. The seccomp state and nnp must be in sync.
1755 */
1756 if (task_no_new_privs(current))
1757 task_set_no_new_privs(p);
1758
1759 /*
1760 * If the parent gained a seccomp mode after copying thread
1761 * flags and between before we held the sighand lock, we have
1762 * to manually enable the seccomp thread flag here.
1763 */
1764 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1765 set_task_syscall_work(p, SECCOMP);
1766 #endif
1767 }
1768
SYSCALL_DEFINE1(set_tid_address,int __user *,tidptr)1769 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1770 {
1771 current->clear_child_tid = tidptr;
1772
1773 return task_pid_vnr(current);
1774 }
1775
rt_mutex_init_task(struct task_struct * p)1776 static void rt_mutex_init_task(struct task_struct *p)
1777 {
1778 raw_spin_lock_init(&p->pi_lock);
1779 #ifdef CONFIG_RT_MUTEXES
1780 p->pi_waiters = RB_ROOT_CACHED;
1781 p->pi_top_task = NULL;
1782 p->pi_blocked_on = NULL;
1783 #endif
1784 }
1785
init_task_pid_links(struct task_struct * task)1786 static inline void init_task_pid_links(struct task_struct *task)
1787 {
1788 enum pid_type type;
1789
1790 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type)
1791 INIT_HLIST_NODE(&task->pid_links[type]);
1792 }
1793
1794 static inline void
init_task_pid(struct task_struct * task,enum pid_type type,struct pid * pid)1795 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1796 {
1797 if (type == PIDTYPE_PID)
1798 task->thread_pid = pid;
1799 else
1800 task->signal->pids[type] = pid;
1801 }
1802
rcu_copy_process(struct task_struct * p)1803 static inline void rcu_copy_process(struct task_struct *p)
1804 {
1805 #ifdef CONFIG_PREEMPT_RCU
1806 p->rcu_read_lock_nesting = 0;
1807 p->rcu_read_unlock_special.s = 0;
1808 p->rcu_blocked_node = NULL;
1809 INIT_LIST_HEAD(&p->rcu_node_entry);
1810 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1811 #ifdef CONFIG_TASKS_RCU
1812 p->rcu_tasks_holdout = false;
1813 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1814 p->rcu_tasks_idle_cpu = -1;
1815 #endif /* #ifdef CONFIG_TASKS_RCU */
1816 #ifdef CONFIG_TASKS_TRACE_RCU
1817 p->trc_reader_nesting = 0;
1818 p->trc_reader_special.s = 0;
1819 INIT_LIST_HEAD(&p->trc_holdout_list);
1820 INIT_LIST_HEAD(&p->trc_blkd_node);
1821 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
1822 }
1823
pidfd_pid(const struct file * file)1824 struct pid *pidfd_pid(const struct file *file)
1825 {
1826 if (file->f_op == &pidfd_fops)
1827 return file->private_data;
1828
1829 return ERR_PTR(-EBADF);
1830 }
1831
pidfd_release(struct inode * inode,struct file * file)1832 static int pidfd_release(struct inode *inode, struct file *file)
1833 {
1834 struct pid *pid = file->private_data;
1835
1836 file->private_data = NULL;
1837 put_pid(pid);
1838 return 0;
1839 }
1840
1841 #ifdef CONFIG_PROC_FS
1842 /**
1843 * pidfd_show_fdinfo - print information about a pidfd
1844 * @m: proc fdinfo file
1845 * @f: file referencing a pidfd
1846 *
1847 * Pid:
1848 * This function will print the pid that a given pidfd refers to in the
1849 * pid namespace of the procfs instance.
1850 * If the pid namespace of the process is not a descendant of the pid
1851 * namespace of the procfs instance 0 will be shown as its pid. This is
1852 * similar to calling getppid() on a process whose parent is outside of
1853 * its pid namespace.
1854 *
1855 * NSpid:
1856 * If pid namespaces are supported then this function will also print
1857 * the pid of a given pidfd refers to for all descendant pid namespaces
1858 * starting from the current pid namespace of the instance, i.e. the
1859 * Pid field and the first entry in the NSpid field will be identical.
1860 * If the pid namespace of the process is not a descendant of the pid
1861 * namespace of the procfs instance 0 will be shown as its first NSpid
1862 * entry and no others will be shown.
1863 * Note that this differs from the Pid and NSpid fields in
1864 * /proc/<pid>/status where Pid and NSpid are always shown relative to
1865 * the pid namespace of the procfs instance. The difference becomes
1866 * obvious when sending around a pidfd between pid namespaces from a
1867 * different branch of the tree, i.e. where no ancestral relation is
1868 * present between the pid namespaces:
1869 * - create two new pid namespaces ns1 and ns2 in the initial pid
1870 * namespace (also take care to create new mount namespaces in the
1871 * new pid namespace and mount procfs)
1872 * - create a process with a pidfd in ns1
1873 * - send pidfd from ns1 to ns2
1874 * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
1875 * have exactly one entry, which is 0
1876 */
pidfd_show_fdinfo(struct seq_file * m,struct file * f)1877 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1878 {
1879 struct pid *pid = f->private_data;
1880 struct pid_namespace *ns;
1881 pid_t nr = -1;
1882
1883 if (likely(pid_has_task(pid, PIDTYPE_PID))) {
1884 ns = proc_pid_ns(file_inode(m->file)->i_sb);
1885 nr = pid_nr_ns(pid, ns);
1886 }
1887
1888 seq_put_decimal_ll(m, "Pid:\t", nr);
1889
1890 #ifdef CONFIG_PID_NS
1891 seq_put_decimal_ll(m, "\nNSpid:\t", nr);
1892 if (nr > 0) {
1893 int i;
1894
1895 /* If nr is non-zero it means that 'pid' is valid and that
1896 * ns, i.e. the pid namespace associated with the procfs
1897 * instance, is in the pid namespace hierarchy of pid.
1898 * Start at one below the already printed level.
1899 */
1900 for (i = ns->level + 1; i <= pid->level; i++)
1901 seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
1902 }
1903 #endif
1904 seq_putc(m, '\n');
1905 }
1906 #endif
1907
1908 /*
1909 * Poll support for process exit notification.
1910 */
pidfd_poll(struct file * file,struct poll_table_struct * pts)1911 static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
1912 {
1913 struct pid *pid = file->private_data;
1914 __poll_t poll_flags = 0;
1915
1916 poll_wait(file, &pid->wait_pidfd, pts);
1917
1918 /*
1919 * Inform pollers only when the whole thread group exits.
1920 * If the thread group leader exits before all other threads in the
1921 * group, then poll(2) should block, similar to the wait(2) family.
1922 */
1923 if (thread_group_exited(pid))
1924 poll_flags = EPOLLIN | EPOLLRDNORM;
1925
1926 return poll_flags;
1927 }
1928
1929 const struct file_operations pidfd_fops = {
1930 .release = pidfd_release,
1931 .poll = pidfd_poll,
1932 #ifdef CONFIG_PROC_FS
1933 .show_fdinfo = pidfd_show_fdinfo,
1934 #endif
1935 };
1936
__delayed_free_task(struct rcu_head * rhp)1937 static void __delayed_free_task(struct rcu_head *rhp)
1938 {
1939 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1940
1941 free_task(tsk);
1942 }
1943
delayed_free_task(struct task_struct * tsk)1944 static __always_inline void delayed_free_task(struct task_struct *tsk)
1945 {
1946 if (IS_ENABLED(CONFIG_MEMCG))
1947 call_rcu(&tsk->rcu, __delayed_free_task);
1948 else
1949 free_task(tsk);
1950 }
1951
copy_oom_score_adj(u64 clone_flags,struct task_struct * tsk)1952 static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk)
1953 {
1954 /* Skip if kernel thread */
1955 if (!tsk->mm)
1956 return;
1957
1958 /* Skip if spawning a thread or using vfork */
1959 if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) != CLONE_VM)
1960 return;
1961
1962 /* We need to synchronize with __set_oom_adj */
1963 mutex_lock(&oom_adj_mutex);
1964 set_bit(MMF_MULTIPROCESS, &tsk->mm->flags);
1965 /* Update the values in case they were changed after copy_signal */
1966 tsk->signal->oom_score_adj = current->signal->oom_score_adj;
1967 tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min;
1968 mutex_unlock(&oom_adj_mutex);
1969 }
1970
1971 #ifdef CONFIG_RV
rv_task_fork(struct task_struct * p)1972 static void rv_task_fork(struct task_struct *p)
1973 {
1974 int i;
1975
1976 for (i = 0; i < RV_PER_TASK_MONITORS; i++)
1977 p->rv[i].da_mon.monitoring = false;
1978 }
1979 #else
1980 #define rv_task_fork(p) do {} while (0)
1981 #endif
1982
1983 /*
1984 * This creates a new process as a copy of the old one,
1985 * but does not actually start it yet.
1986 *
1987 * It copies the registers, and all the appropriate
1988 * parts of the process environment (as per the clone
1989 * flags). The actual kick-off is left to the caller.
1990 */
copy_process(struct pid * pid,int trace,int node,struct kernel_clone_args * args)1991 static __latent_entropy struct task_struct *copy_process(
1992 struct pid *pid,
1993 int trace,
1994 int node,
1995 struct kernel_clone_args *args)
1996 {
1997 int pidfd = -1, retval;
1998 struct task_struct *p;
1999 struct multiprocess_signals delayed;
2000 struct file *pidfile = NULL;
2001 const u64 clone_flags = args->flags;
2002 struct nsproxy *nsp = current->nsproxy;
2003
2004 /*
2005 * Don't allow sharing the root directory with processes in a different
2006 * namespace
2007 */
2008 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
2009 return ERR_PTR(-EINVAL);
2010
2011 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
2012 return ERR_PTR(-EINVAL);
2013
2014 /*
2015 * Thread groups must share signals as well, and detached threads
2016 * can only be started up within the thread group.
2017 */
2018 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
2019 return ERR_PTR(-EINVAL);
2020
2021 /*
2022 * Shared signal handlers imply shared VM. By way of the above,
2023 * thread groups also imply shared VM. Blocking this case allows
2024 * for various simplifications in other code.
2025 */
2026 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
2027 return ERR_PTR(-EINVAL);
2028
2029 /*
2030 * Siblings of global init remain as zombies on exit since they are
2031 * not reaped by their parent (swapper). To solve this and to avoid
2032 * multi-rooted process trees, prevent global and container-inits
2033 * from creating siblings.
2034 */
2035 if ((clone_flags & CLONE_PARENT) &&
2036 current->signal->flags & SIGNAL_UNKILLABLE)
2037 return ERR_PTR(-EINVAL);
2038
2039 /*
2040 * If the new process will be in a different pid or user namespace
2041 * do not allow it to share a thread group with the forking task.
2042 */
2043 if (clone_flags & CLONE_THREAD) {
2044 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
2045 (task_active_pid_ns(current) != nsp->pid_ns_for_children))
2046 return ERR_PTR(-EINVAL);
2047 }
2048
2049 /*
2050 * If the new process will be in a different time namespace
2051 * do not allow it to share VM or a thread group with the forking task.
2052 */
2053 if (clone_flags & (CLONE_THREAD | CLONE_VM)) {
2054 if (nsp->time_ns != nsp->time_ns_for_children)
2055 return ERR_PTR(-EINVAL);
2056 }
2057
2058 if (clone_flags & CLONE_PIDFD) {
2059 /*
2060 * - CLONE_DETACHED is blocked so that we can potentially
2061 * reuse it later for CLONE_PIDFD.
2062 * - CLONE_THREAD is blocked until someone really needs it.
2063 */
2064 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
2065 return ERR_PTR(-EINVAL);
2066 }
2067
2068 /*
2069 * Force any signals received before this point to be delivered
2070 * before the fork happens. Collect up signals sent to multiple
2071 * processes that happen during the fork and delay them so that
2072 * they appear to happen after the fork.
2073 */
2074 sigemptyset(&delayed.signal);
2075 INIT_HLIST_NODE(&delayed.node);
2076
2077 spin_lock_irq(¤t->sighand->siglock);
2078 if (!(clone_flags & CLONE_THREAD))
2079 hlist_add_head(&delayed.node, ¤t->signal->multiprocess);
2080 recalc_sigpending();
2081 spin_unlock_irq(¤t->sighand->siglock);
2082 retval = -ERESTARTNOINTR;
2083 if (task_sigpending(current))
2084 goto fork_out;
2085
2086 retval = -ENOMEM;
2087 p = dup_task_struct(current, node);
2088 if (!p)
2089 goto fork_out;
2090 p->flags &= ~PF_KTHREAD;
2091 if (args->kthread)
2092 p->flags |= PF_KTHREAD;
2093 if (args->io_thread) {
2094 /*
2095 * Mark us an IO worker, and block any signal that isn't
2096 * fatal or STOP
2097 */
2098 p->flags |= PF_IO_WORKER;
2099 siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
2100 }
2101
2102 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
2103 /*
2104 * Clear TID on mm_release()?
2105 */
2106 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
2107
2108 ftrace_graph_init_task(p);
2109
2110 rt_mutex_init_task(p);
2111
2112 lockdep_assert_irqs_enabled();
2113 #ifdef CONFIG_PROVE_LOCKING
2114 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
2115 #endif
2116 retval = copy_creds(p, clone_flags);
2117 if (retval < 0)
2118 goto bad_fork_free;
2119
2120 retval = -EAGAIN;
2121 if (is_rlimit_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
2122 if (p->real_cred->user != INIT_USER &&
2123 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
2124 goto bad_fork_cleanup_count;
2125 }
2126 current->flags &= ~PF_NPROC_EXCEEDED;
2127
2128 /*
2129 * If multiple threads are within copy_process(), then this check
2130 * triggers too late. This doesn't hurt, the check is only there
2131 * to stop root fork bombs.
2132 */
2133 retval = -EAGAIN;
2134 if (data_race(nr_threads >= max_threads))
2135 goto bad_fork_cleanup_count;
2136
2137 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
2138 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE | PF_NO_SETAFFINITY);
2139 p->flags |= PF_FORKNOEXEC;
2140 INIT_LIST_HEAD(&p->children);
2141 INIT_LIST_HEAD(&p->sibling);
2142 rcu_copy_process(p);
2143 p->vfork_done = NULL;
2144 spin_lock_init(&p->alloc_lock);
2145
2146 init_sigpending(&p->pending);
2147
2148 p->utime = p->stime = p->gtime = 0;
2149 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
2150 p->utimescaled = p->stimescaled = 0;
2151 #endif
2152 prev_cputime_init(&p->prev_cputime);
2153
2154 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
2155 seqcount_init(&p->vtime.seqcount);
2156 p->vtime.starttime = 0;
2157 p->vtime.state = VTIME_INACTIVE;
2158 #endif
2159
2160 #ifdef CONFIG_IO_URING
2161 p->io_uring = NULL;
2162 #endif
2163
2164 #if defined(SPLIT_RSS_COUNTING)
2165 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
2166 #endif
2167
2168 p->default_timer_slack_ns = current->timer_slack_ns;
2169
2170 #ifdef CONFIG_PSI
2171 p->psi_flags = 0;
2172 #endif
2173
2174 task_io_accounting_init(&p->ioac);
2175 acct_clear_integrals(p);
2176
2177 posix_cputimers_init(&p->posix_cputimers);
2178
2179 p->io_context = NULL;
2180 audit_set_context(p, NULL);
2181 cgroup_fork(p);
2182 if (args->kthread) {
2183 if (!set_kthread_struct(p))
2184 goto bad_fork_cleanup_delayacct;
2185 }
2186 #ifdef CONFIG_NUMA
2187 p->mempolicy = mpol_dup(p->mempolicy);
2188 if (IS_ERR(p->mempolicy)) {
2189 retval = PTR_ERR(p->mempolicy);
2190 p->mempolicy = NULL;
2191 goto bad_fork_cleanup_delayacct;
2192 }
2193 #endif
2194 #ifdef CONFIG_CPUSETS
2195 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
2196 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
2197 seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock);
2198 #endif
2199 #ifdef CONFIG_TRACE_IRQFLAGS
2200 memset(&p->irqtrace, 0, sizeof(p->irqtrace));
2201 p->irqtrace.hardirq_disable_ip = _THIS_IP_;
2202 p->irqtrace.softirq_enable_ip = _THIS_IP_;
2203 p->softirqs_enabled = 1;
2204 p->softirq_context = 0;
2205 #endif
2206
2207 p->pagefault_disabled = 0;
2208
2209 #ifdef CONFIG_LOCKDEP
2210 lockdep_init_task(p);
2211 #endif
2212
2213 #ifdef CONFIG_DEBUG_MUTEXES
2214 p->blocked_on = NULL; /* not blocked yet */
2215 #endif
2216 #ifdef CONFIG_BCACHE
2217 p->sequential_io = 0;
2218 p->sequential_io_avg = 0;
2219 #endif
2220 #ifdef CONFIG_BPF_SYSCALL
2221 RCU_INIT_POINTER(p->bpf_storage, NULL);
2222 p->bpf_ctx = NULL;
2223 #endif
2224
2225 /* Perform scheduler related setup. Assign this task to a CPU. */
2226 retval = sched_fork(clone_flags, p);
2227 if (retval)
2228 goto bad_fork_cleanup_policy;
2229
2230 retval = perf_event_init_task(p, clone_flags);
2231 if (retval)
2232 goto bad_fork_cleanup_policy;
2233 retval = audit_alloc(p);
2234 if (retval)
2235 goto bad_fork_cleanup_perf;
2236 /* copy all the process information */
2237 shm_init_task(p);
2238 retval = security_task_alloc(p, clone_flags);
2239 if (retval)
2240 goto bad_fork_cleanup_audit;
2241 retval = copy_semundo(clone_flags, p);
2242 if (retval)
2243 goto bad_fork_cleanup_security;
2244 retval = copy_files(clone_flags, p);
2245 if (retval)
2246 goto bad_fork_cleanup_semundo;
2247 retval = copy_fs(clone_flags, p);
2248 if (retval)
2249 goto bad_fork_cleanup_files;
2250 retval = copy_sighand(clone_flags, p);
2251 if (retval)
2252 goto bad_fork_cleanup_fs;
2253 retval = copy_signal(clone_flags, p);
2254 if (retval)
2255 goto bad_fork_cleanup_sighand;
2256 retval = copy_mm(clone_flags, p);
2257 if (retval)
2258 goto bad_fork_cleanup_signal;
2259 retval = copy_namespaces(clone_flags, p);
2260 if (retval)
2261 goto bad_fork_cleanup_mm;
2262 retval = copy_io(clone_flags, p);
2263 if (retval)
2264 goto bad_fork_cleanup_namespaces;
2265 retval = copy_thread(p, args);
2266 if (retval)
2267 goto bad_fork_cleanup_io;
2268
2269 stackleak_task_init(p);
2270
2271 if (pid != &init_struct_pid) {
2272 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
2273 args->set_tid_size);
2274 if (IS_ERR(pid)) {
2275 retval = PTR_ERR(pid);
2276 goto bad_fork_cleanup_thread;
2277 }
2278 }
2279
2280 /*
2281 * This has to happen after we've potentially unshared the file
2282 * descriptor table (so that the pidfd doesn't leak into the child
2283 * if the fd table isn't shared).
2284 */
2285 if (clone_flags & CLONE_PIDFD) {
2286 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2287 if (retval < 0)
2288 goto bad_fork_free_pid;
2289
2290 pidfd = retval;
2291
2292 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2293 O_RDWR | O_CLOEXEC);
2294 if (IS_ERR(pidfile)) {
2295 put_unused_fd(pidfd);
2296 retval = PTR_ERR(pidfile);
2297 goto bad_fork_free_pid;
2298 }
2299 get_pid(pid); /* held by pidfile now */
2300
2301 retval = put_user(pidfd, args->pidfd);
2302 if (retval)
2303 goto bad_fork_put_pidfd;
2304 }
2305
2306 #ifdef CONFIG_BLOCK
2307 p->plug = NULL;
2308 #endif
2309 futex_init_task(p);
2310
2311 /*
2312 * sigaltstack should be cleared when sharing the same VM
2313 */
2314 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2315 sas_ss_reset(p);
2316
2317 /*
2318 * Syscall tracing and stepping should be turned off in the
2319 * child regardless of CLONE_PTRACE.
2320 */
2321 user_disable_single_step(p);
2322 clear_task_syscall_work(p, SYSCALL_TRACE);
2323 #if defined(CONFIG_GENERIC_ENTRY) || defined(TIF_SYSCALL_EMU)
2324 clear_task_syscall_work(p, SYSCALL_EMU);
2325 #endif
2326 clear_tsk_latency_tracing(p);
2327
2328 /* ok, now we should be set up.. */
2329 p->pid = pid_nr(pid);
2330 if (clone_flags & CLONE_THREAD) {
2331 p->group_leader = current->group_leader;
2332 p->tgid = current->tgid;
2333 } else {
2334 p->group_leader = p;
2335 p->tgid = p->pid;
2336 }
2337
2338 p->nr_dirtied = 0;
2339 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2340 p->dirty_paused_when = 0;
2341
2342 p->pdeath_signal = 0;
2343 INIT_LIST_HEAD(&p->thread_group);
2344 p->task_works = NULL;
2345 clear_posix_cputimers_work(p);
2346
2347 #ifdef CONFIG_KRETPROBES
2348 p->kretprobe_instances.first = NULL;
2349 #endif
2350 #ifdef CONFIG_RETHOOK
2351 p->rethooks.first = NULL;
2352 #endif
2353
2354 /*
2355 * Ensure that the cgroup subsystem policies allow the new process to be
2356 * forked. It should be noted that the new process's css_set can be changed
2357 * between here and cgroup_post_fork() if an organisation operation is in
2358 * progress.
2359 */
2360 retval = cgroup_can_fork(p, args);
2361 if (retval)
2362 goto bad_fork_put_pidfd;
2363
2364 /*
2365 * Now that the cgroups are pinned, re-clone the parent cgroup and put
2366 * the new task on the correct runqueue. All this *before* the task
2367 * becomes visible.
2368 *
2369 * This isn't part of ->can_fork() because while the re-cloning is
2370 * cgroup specific, it unconditionally needs to place the task on a
2371 * runqueue.
2372 */
2373 sched_cgroup_fork(p, args);
2374
2375 /*
2376 * From this point on we must avoid any synchronous user-space
2377 * communication until we take the tasklist-lock. In particular, we do
2378 * not want user-space to be able to predict the process start-time by
2379 * stalling fork(2) after we recorded the start_time but before it is
2380 * visible to the system.
2381 */
2382
2383 p->start_time = ktime_get_ns();
2384 p->start_boottime = ktime_get_boottime_ns();
2385
2386 /*
2387 * Make it visible to the rest of the system, but dont wake it up yet.
2388 * Need tasklist lock for parent etc handling!
2389 */
2390 write_lock_irq(&tasklist_lock);
2391
2392 /* CLONE_PARENT re-uses the old parent */
2393 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2394 p->real_parent = current->real_parent;
2395 p->parent_exec_id = current->parent_exec_id;
2396 if (clone_flags & CLONE_THREAD)
2397 p->exit_signal = -1;
2398 else
2399 p->exit_signal = current->group_leader->exit_signal;
2400 } else {
2401 p->real_parent = current;
2402 p->parent_exec_id = current->self_exec_id;
2403 p->exit_signal = args->exit_signal;
2404 }
2405
2406 klp_copy_process(p);
2407
2408 sched_core_fork(p);
2409
2410 spin_lock(¤t->sighand->siglock);
2411
2412 rv_task_fork(p);
2413
2414 rseq_fork(p, clone_flags);
2415
2416 /* Don't start children in a dying pid namespace */
2417 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2418 retval = -ENOMEM;
2419 goto bad_fork_cancel_cgroup;
2420 }
2421
2422 /* Let kill terminate clone/fork in the middle */
2423 if (fatal_signal_pending(current)) {
2424 retval = -EINTR;
2425 goto bad_fork_cancel_cgroup;
2426 }
2427
2428 /* No more failure paths after this point. */
2429
2430 /*
2431 * Copy seccomp details explicitly here, in case they were changed
2432 * before holding sighand lock.
2433 */
2434 copy_seccomp(p);
2435
2436 init_task_pid_links(p);
2437 if (likely(p->pid)) {
2438 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2439
2440 init_task_pid(p, PIDTYPE_PID, pid);
2441 if (thread_group_leader(p)) {
2442 init_task_pid(p, PIDTYPE_TGID, pid);
2443 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2444 init_task_pid(p, PIDTYPE_SID, task_session(current));
2445
2446 if (is_child_reaper(pid)) {
2447 ns_of_pid(pid)->child_reaper = p;
2448 p->signal->flags |= SIGNAL_UNKILLABLE;
2449 }
2450 p->signal->shared_pending.signal = delayed.signal;
2451 p->signal->tty = tty_kref_get(current->signal->tty);
2452 /*
2453 * Inherit has_child_subreaper flag under the same
2454 * tasklist_lock with adding child to the process tree
2455 * for propagate_has_child_subreaper optimization.
2456 */
2457 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2458 p->real_parent->signal->is_child_subreaper;
2459 list_add_tail(&p->sibling, &p->real_parent->children);
2460 list_add_tail_rcu(&p->tasks, &init_task.tasks);
2461 attach_pid(p, PIDTYPE_TGID);
2462 attach_pid(p, PIDTYPE_PGID);
2463 attach_pid(p, PIDTYPE_SID);
2464 __this_cpu_inc(process_counts);
2465 } else {
2466 current->signal->nr_threads++;
2467 current->signal->quick_threads++;
2468 atomic_inc(¤t->signal->live);
2469 refcount_inc(¤t->signal->sigcnt);
2470 task_join_group_stop(p);
2471 list_add_tail_rcu(&p->thread_group,
2472 &p->group_leader->thread_group);
2473 list_add_tail_rcu(&p->thread_node,
2474 &p->signal->thread_head);
2475 }
2476 attach_pid(p, PIDTYPE_PID);
2477 nr_threads++;
2478 }
2479 total_forks++;
2480 hlist_del_init(&delayed.node);
2481 spin_unlock(¤t->sighand->siglock);
2482 syscall_tracepoint_update(p);
2483 write_unlock_irq(&tasklist_lock);
2484
2485 if (pidfile)
2486 fd_install(pidfd, pidfile);
2487
2488 proc_fork_connector(p);
2489 sched_post_fork(p);
2490 cgroup_post_fork(p, args);
2491 perf_event_fork(p);
2492
2493 trace_task_newtask(p, clone_flags);
2494 uprobe_copy_process(p, clone_flags);
2495
2496 copy_oom_score_adj(clone_flags, p);
2497
2498 return p;
2499
2500 bad_fork_cancel_cgroup:
2501 sched_core_free(p);
2502 spin_unlock(¤t->sighand->siglock);
2503 write_unlock_irq(&tasklist_lock);
2504 cgroup_cancel_fork(p, args);
2505 bad_fork_put_pidfd:
2506 if (clone_flags & CLONE_PIDFD) {
2507 fput(pidfile);
2508 put_unused_fd(pidfd);
2509 }
2510 bad_fork_free_pid:
2511 if (pid != &init_struct_pid)
2512 free_pid(pid);
2513 bad_fork_cleanup_thread:
2514 exit_thread(p);
2515 bad_fork_cleanup_io:
2516 if (p->io_context)
2517 exit_io_context(p);
2518 bad_fork_cleanup_namespaces:
2519 exit_task_namespaces(p);
2520 bad_fork_cleanup_mm:
2521 if (p->mm) {
2522 mm_clear_owner(p->mm, p);
2523 mmput(p->mm);
2524 }
2525 bad_fork_cleanup_signal:
2526 if (!(clone_flags & CLONE_THREAD))
2527 free_signal_struct(p->signal);
2528 bad_fork_cleanup_sighand:
2529 __cleanup_sighand(p->sighand);
2530 bad_fork_cleanup_fs:
2531 exit_fs(p); /* blocking */
2532 bad_fork_cleanup_files:
2533 exit_files(p); /* blocking */
2534 bad_fork_cleanup_semundo:
2535 exit_sem(p);
2536 bad_fork_cleanup_security:
2537 security_task_free(p);
2538 bad_fork_cleanup_audit:
2539 audit_free(p);
2540 bad_fork_cleanup_perf:
2541 perf_event_free_task(p);
2542 bad_fork_cleanup_policy:
2543 lockdep_free_task(p);
2544 #ifdef CONFIG_NUMA
2545 mpol_put(p->mempolicy);
2546 #endif
2547 bad_fork_cleanup_delayacct:
2548 delayacct_tsk_free(p);
2549 bad_fork_cleanup_count:
2550 dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
2551 exit_creds(p);
2552 bad_fork_free:
2553 WRITE_ONCE(p->__state, TASK_DEAD);
2554 exit_task_stack_account(p);
2555 put_task_stack(p);
2556 delayed_free_task(p);
2557 fork_out:
2558 spin_lock_irq(¤t->sighand->siglock);
2559 hlist_del_init(&delayed.node);
2560 spin_unlock_irq(¤t->sighand->siglock);
2561 return ERR_PTR(retval);
2562 }
2563
init_idle_pids(struct task_struct * idle)2564 static inline void init_idle_pids(struct task_struct *idle)
2565 {
2566 enum pid_type type;
2567
2568 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2569 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2570 init_task_pid(idle, type, &init_struct_pid);
2571 }
2572 }
2573
idle_dummy(void * dummy)2574 static int idle_dummy(void *dummy)
2575 {
2576 /* This function is never called */
2577 return 0;
2578 }
2579
fork_idle(int cpu)2580 struct task_struct * __init fork_idle(int cpu)
2581 {
2582 struct task_struct *task;
2583 struct kernel_clone_args args = {
2584 .flags = CLONE_VM,
2585 .fn = &idle_dummy,
2586 .fn_arg = NULL,
2587 .kthread = 1,
2588 .idle = 1,
2589 };
2590
2591 task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2592 if (!IS_ERR(task)) {
2593 init_idle_pids(task);
2594 init_idle(task, cpu);
2595 }
2596
2597 return task;
2598 }
2599
copy_init_mm(void)2600 struct mm_struct *copy_init_mm(void)
2601 {
2602 return dup_mm(NULL, &init_mm);
2603 }
2604
2605 /*
2606 * This is like kernel_clone(), but shaved down and tailored to just
2607 * creating io_uring workers. It returns a created task, or an error pointer.
2608 * The returned task is inactive, and the caller must fire it up through
2609 * wake_up_new_task(p). All signals are blocked in the created task.
2610 */
create_io_thread(int (* fn)(void *),void * arg,int node)2611 struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
2612 {
2613 unsigned long flags = CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|
2614 CLONE_IO;
2615 struct kernel_clone_args args = {
2616 .flags = ((lower_32_bits(flags) | CLONE_VM |
2617 CLONE_UNTRACED) & ~CSIGNAL),
2618 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2619 .fn = fn,
2620 .fn_arg = arg,
2621 .io_thread = 1,
2622 };
2623
2624 return copy_process(NULL, 0, node, &args);
2625 }
2626
2627 /*
2628 * Ok, this is the main fork-routine.
2629 *
2630 * It copies the process, and if successful kick-starts
2631 * it and waits for it to finish using the VM if required.
2632 *
2633 * args->exit_signal is expected to be checked for sanity by the caller.
2634 */
kernel_clone(struct kernel_clone_args * args)2635 pid_t kernel_clone(struct kernel_clone_args *args)
2636 {
2637 u64 clone_flags = args->flags;
2638 struct completion vfork;
2639 struct pid *pid;
2640 struct task_struct *p;
2641 int trace = 0;
2642 pid_t nr;
2643
2644 /*
2645 * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
2646 * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
2647 * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
2648 * field in struct clone_args and it still doesn't make sense to have
2649 * them both point at the same memory location. Performing this check
2650 * here has the advantage that we don't need to have a separate helper
2651 * to check for legacy clone().
2652 */
2653 if ((args->flags & CLONE_PIDFD) &&
2654 (args->flags & CLONE_PARENT_SETTID) &&
2655 (args->pidfd == args->parent_tid))
2656 return -EINVAL;
2657
2658 /*
2659 * Determine whether and which event to report to ptracer. When
2660 * called from kernel_thread or CLONE_UNTRACED is explicitly
2661 * requested, no event is reported; otherwise, report if the event
2662 * for the type of forking is enabled.
2663 */
2664 if (!(clone_flags & CLONE_UNTRACED)) {
2665 if (clone_flags & CLONE_VFORK)
2666 trace = PTRACE_EVENT_VFORK;
2667 else if (args->exit_signal != SIGCHLD)
2668 trace = PTRACE_EVENT_CLONE;
2669 else
2670 trace = PTRACE_EVENT_FORK;
2671
2672 if (likely(!ptrace_event_enabled(current, trace)))
2673 trace = 0;
2674 }
2675
2676 p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2677 add_latent_entropy();
2678
2679 if (IS_ERR(p))
2680 return PTR_ERR(p);
2681
2682 /*
2683 * Do this prior waking up the new thread - the thread pointer
2684 * might get invalid after that point, if the thread exits quickly.
2685 */
2686 trace_sched_process_fork(current, p);
2687
2688 pid = get_task_pid(p, PIDTYPE_PID);
2689 nr = pid_vnr(pid);
2690
2691 if (clone_flags & CLONE_PARENT_SETTID)
2692 put_user(nr, args->parent_tid);
2693
2694 if (clone_flags & CLONE_VFORK) {
2695 p->vfork_done = &vfork;
2696 init_completion(&vfork);
2697 get_task_struct(p);
2698 }
2699
2700 if (IS_ENABLED(CONFIG_LRU_GEN) && !(clone_flags & CLONE_VM)) {
2701 /* lock the task to synchronize with memcg migration */
2702 task_lock(p);
2703 lru_gen_add_mm(p->mm);
2704 task_unlock(p);
2705 }
2706
2707 wake_up_new_task(p);
2708
2709 /* forking complete and child started to run, tell ptracer */
2710 if (unlikely(trace))
2711 ptrace_event_pid(trace, pid);
2712
2713 if (clone_flags & CLONE_VFORK) {
2714 if (!wait_for_vfork_done(p, &vfork))
2715 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2716 }
2717
2718 put_pid(pid);
2719 return nr;
2720 }
2721
2722 /*
2723 * Create a kernel thread.
2724 */
kernel_thread(int (* fn)(void *),void * arg,unsigned long flags)2725 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2726 {
2727 struct kernel_clone_args args = {
2728 .flags = ((lower_32_bits(flags) | CLONE_VM |
2729 CLONE_UNTRACED) & ~CSIGNAL),
2730 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2731 .fn = fn,
2732 .fn_arg = arg,
2733 .kthread = 1,
2734 };
2735
2736 return kernel_clone(&args);
2737 }
2738
2739 /*
2740 * Create a user mode thread.
2741 */
user_mode_thread(int (* fn)(void *),void * arg,unsigned long flags)2742 pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags)
2743 {
2744 struct kernel_clone_args args = {
2745 .flags = ((lower_32_bits(flags) | CLONE_VM |
2746 CLONE_UNTRACED) & ~CSIGNAL),
2747 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2748 .fn = fn,
2749 .fn_arg = arg,
2750 };
2751
2752 return kernel_clone(&args);
2753 }
2754
2755 #ifdef __ARCH_WANT_SYS_FORK
SYSCALL_DEFINE0(fork)2756 SYSCALL_DEFINE0(fork)
2757 {
2758 #ifdef CONFIG_MMU
2759 struct kernel_clone_args args = {
2760 .exit_signal = SIGCHLD,
2761 };
2762
2763 return kernel_clone(&args);
2764 #else
2765 /* can not support in nommu mode */
2766 return -EINVAL;
2767 #endif
2768 }
2769 #endif
2770
2771 #ifdef __ARCH_WANT_SYS_VFORK
SYSCALL_DEFINE0(vfork)2772 SYSCALL_DEFINE0(vfork)
2773 {
2774 struct kernel_clone_args args = {
2775 .flags = CLONE_VFORK | CLONE_VM,
2776 .exit_signal = SIGCHLD,
2777 };
2778
2779 return kernel_clone(&args);
2780 }
2781 #endif
2782
2783 #ifdef __ARCH_WANT_SYS_CLONE
2784 #ifdef CONFIG_CLONE_BACKWARDS
SYSCALL_DEFINE5(clone,unsigned long,clone_flags,unsigned long,newsp,int __user *,parent_tidptr,unsigned long,tls,int __user *,child_tidptr)2785 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2786 int __user *, parent_tidptr,
2787 unsigned long, tls,
2788 int __user *, child_tidptr)
2789 #elif defined(CONFIG_CLONE_BACKWARDS2)
2790 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2791 int __user *, parent_tidptr,
2792 int __user *, child_tidptr,
2793 unsigned long, tls)
2794 #elif defined(CONFIG_CLONE_BACKWARDS3)
2795 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2796 int, stack_size,
2797 int __user *, parent_tidptr,
2798 int __user *, child_tidptr,
2799 unsigned long, tls)
2800 #else
2801 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2802 int __user *, parent_tidptr,
2803 int __user *, child_tidptr,
2804 unsigned long, tls)
2805 #endif
2806 {
2807 struct kernel_clone_args args = {
2808 .flags = (lower_32_bits(clone_flags) & ~CSIGNAL),
2809 .pidfd = parent_tidptr,
2810 .child_tid = child_tidptr,
2811 .parent_tid = parent_tidptr,
2812 .exit_signal = (lower_32_bits(clone_flags) & CSIGNAL),
2813 .stack = newsp,
2814 .tls = tls,
2815 };
2816
2817 return kernel_clone(&args);
2818 }
2819 #endif
2820
2821 #ifdef __ARCH_WANT_SYS_CLONE3
2822
copy_clone_args_from_user(struct kernel_clone_args * kargs,struct clone_args __user * uargs,size_t usize)2823 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
2824 struct clone_args __user *uargs,
2825 size_t usize)
2826 {
2827 int err;
2828 struct clone_args args;
2829 pid_t *kset_tid = kargs->set_tid;
2830
2831 BUILD_BUG_ON(offsetofend(struct clone_args, tls) !=
2832 CLONE_ARGS_SIZE_VER0);
2833 BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) !=
2834 CLONE_ARGS_SIZE_VER1);
2835 BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
2836 CLONE_ARGS_SIZE_VER2);
2837 BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
2838
2839 if (unlikely(usize > PAGE_SIZE))
2840 return -E2BIG;
2841 if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
2842 return -EINVAL;
2843
2844 err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
2845 if (err)
2846 return err;
2847
2848 if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
2849 return -EINVAL;
2850
2851 if (unlikely(!args.set_tid && args.set_tid_size > 0))
2852 return -EINVAL;
2853
2854 if (unlikely(args.set_tid && args.set_tid_size == 0))
2855 return -EINVAL;
2856
2857 /*
2858 * Verify that higher 32bits of exit_signal are unset and that
2859 * it is a valid signal
2860 */
2861 if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
2862 !valid_signal(args.exit_signal)))
2863 return -EINVAL;
2864
2865 if ((args.flags & CLONE_INTO_CGROUP) &&
2866 (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2))
2867 return -EINVAL;
2868
2869 *kargs = (struct kernel_clone_args){
2870 .flags = args.flags,
2871 .pidfd = u64_to_user_ptr(args.pidfd),
2872 .child_tid = u64_to_user_ptr(args.child_tid),
2873 .parent_tid = u64_to_user_ptr(args.parent_tid),
2874 .exit_signal = args.exit_signal,
2875 .stack = args.stack,
2876 .stack_size = args.stack_size,
2877 .tls = args.tls,
2878 .set_tid_size = args.set_tid_size,
2879 .cgroup = args.cgroup,
2880 };
2881
2882 if (args.set_tid &&
2883 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
2884 (kargs->set_tid_size * sizeof(pid_t))))
2885 return -EFAULT;
2886
2887 kargs->set_tid = kset_tid;
2888
2889 return 0;
2890 }
2891
2892 /**
2893 * clone3_stack_valid - check and prepare stack
2894 * @kargs: kernel clone args
2895 *
2896 * Verify that the stack arguments userspace gave us are sane.
2897 * In addition, set the stack direction for userspace since it's easy for us to
2898 * determine.
2899 */
clone3_stack_valid(struct kernel_clone_args * kargs)2900 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
2901 {
2902 if (kargs->stack == 0) {
2903 if (kargs->stack_size > 0)
2904 return false;
2905 } else {
2906 if (kargs->stack_size == 0)
2907 return false;
2908
2909 if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
2910 return false;
2911
2912 #if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
2913 kargs->stack += kargs->stack_size;
2914 #endif
2915 }
2916
2917 return true;
2918 }
2919
clone3_args_valid(struct kernel_clone_args * kargs)2920 static bool clone3_args_valid(struct kernel_clone_args *kargs)
2921 {
2922 /* Verify that no unknown flags are passed along. */
2923 if (kargs->flags &
2924 ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP))
2925 return false;
2926
2927 /*
2928 * - make the CLONE_DETACHED bit reusable for clone3
2929 * - make the CSIGNAL bits reusable for clone3
2930 */
2931 if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
2932 return false;
2933
2934 if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
2935 (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
2936 return false;
2937
2938 if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
2939 kargs->exit_signal)
2940 return false;
2941
2942 if (!clone3_stack_valid(kargs))
2943 return false;
2944
2945 return true;
2946 }
2947
2948 /**
2949 * clone3 - create a new process with specific properties
2950 * @uargs: argument structure
2951 * @size: size of @uargs
2952 *
2953 * clone3() is the extensible successor to clone()/clone2().
2954 * It takes a struct as argument that is versioned by its size.
2955 *
2956 * Return: On success, a positive PID for the child process.
2957 * On error, a negative errno number.
2958 */
SYSCALL_DEFINE2(clone3,struct clone_args __user *,uargs,size_t,size)2959 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
2960 {
2961 int err;
2962
2963 struct kernel_clone_args kargs;
2964 pid_t set_tid[MAX_PID_NS_LEVEL];
2965
2966 kargs.set_tid = set_tid;
2967
2968 err = copy_clone_args_from_user(&kargs, uargs, size);
2969 if (err)
2970 return err;
2971
2972 if (!clone3_args_valid(&kargs))
2973 return -EINVAL;
2974
2975 return kernel_clone(&kargs);
2976 }
2977 #endif
2978
walk_process_tree(struct task_struct * top,proc_visitor visitor,void * data)2979 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2980 {
2981 struct task_struct *leader, *parent, *child;
2982 int res;
2983
2984 read_lock(&tasklist_lock);
2985 leader = top = top->group_leader;
2986 down:
2987 for_each_thread(leader, parent) {
2988 list_for_each_entry(child, &parent->children, sibling) {
2989 res = visitor(child, data);
2990 if (res) {
2991 if (res < 0)
2992 goto out;
2993 leader = child;
2994 goto down;
2995 }
2996 up:
2997 ;
2998 }
2999 }
3000
3001 if (leader != top) {
3002 child = leader;
3003 parent = child->real_parent;
3004 leader = parent->group_leader;
3005 goto up;
3006 }
3007 out:
3008 read_unlock(&tasklist_lock);
3009 }
3010
3011 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
3012 #define ARCH_MIN_MMSTRUCT_ALIGN 0
3013 #endif
3014
sighand_ctor(void * data)3015 static void sighand_ctor(void *data)
3016 {
3017 struct sighand_struct *sighand = data;
3018
3019 spin_lock_init(&sighand->siglock);
3020 init_waitqueue_head(&sighand->signalfd_wqh);
3021 }
3022
proc_caches_init(void)3023 void __init proc_caches_init(void)
3024 {
3025 unsigned int mm_size;
3026
3027 sighand_cachep = kmem_cache_create("sighand_cache",
3028 sizeof(struct sighand_struct), 0,
3029 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
3030 SLAB_ACCOUNT, sighand_ctor);
3031 signal_cachep = kmem_cache_create("signal_cache",
3032 sizeof(struct signal_struct), 0,
3033 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3034 NULL);
3035 files_cachep = kmem_cache_create("files_cache",
3036 sizeof(struct files_struct), 0,
3037 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3038 NULL);
3039 fs_cachep = kmem_cache_create("fs_cache",
3040 sizeof(struct fs_struct), 0,
3041 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3042 NULL);
3043
3044 /*
3045 * The mm_cpumask is located at the end of mm_struct, and is
3046 * dynamically sized based on the maximum CPU number this system
3047 * can have, taking hotplug into account (nr_cpu_ids).
3048 */
3049 mm_size = sizeof(struct mm_struct) + cpumask_size();
3050
3051 mm_cachep = kmem_cache_create_usercopy("mm_struct",
3052 mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
3053 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3054 offsetof(struct mm_struct, saved_auxv),
3055 sizeof_field(struct mm_struct, saved_auxv),
3056 NULL);
3057 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
3058 mmap_init();
3059 nsproxy_cache_init();
3060 }
3061
3062 /*
3063 * Check constraints on flags passed to the unshare system call.
3064 */
check_unshare_flags(unsigned long unshare_flags)3065 static int check_unshare_flags(unsigned long unshare_flags)
3066 {
3067 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
3068 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
3069 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
3070 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP|
3071 CLONE_NEWTIME))
3072 return -EINVAL;
3073 /*
3074 * Not implemented, but pretend it works if there is nothing
3075 * to unshare. Note that unsharing the address space or the
3076 * signal handlers also need to unshare the signal queues (aka
3077 * CLONE_THREAD).
3078 */
3079 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
3080 if (!thread_group_empty(current))
3081 return -EINVAL;
3082 }
3083 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
3084 if (refcount_read(¤t->sighand->count) > 1)
3085 return -EINVAL;
3086 }
3087 if (unshare_flags & CLONE_VM) {
3088 if (!current_is_single_threaded())
3089 return -EINVAL;
3090 }
3091
3092 return 0;
3093 }
3094
3095 /*
3096 * Unshare the filesystem structure if it is being shared
3097 */
unshare_fs(unsigned long unshare_flags,struct fs_struct ** new_fsp)3098 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
3099 {
3100 struct fs_struct *fs = current->fs;
3101
3102 if (!(unshare_flags & CLONE_FS) || !fs)
3103 return 0;
3104
3105 /* don't need lock here; in the worst case we'll do useless copy */
3106 if (fs->users == 1)
3107 return 0;
3108
3109 *new_fsp = copy_fs_struct(fs);
3110 if (!*new_fsp)
3111 return -ENOMEM;
3112
3113 return 0;
3114 }
3115
3116 /*
3117 * Unshare file descriptor table if it is being shared
3118 */
unshare_fd(unsigned long unshare_flags,unsigned int max_fds,struct files_struct ** new_fdp)3119 int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
3120 struct files_struct **new_fdp)
3121 {
3122 struct files_struct *fd = current->files;
3123 int error = 0;
3124
3125 if ((unshare_flags & CLONE_FILES) &&
3126 (fd && atomic_read(&fd->count) > 1)) {
3127 *new_fdp = dup_fd(fd, max_fds, &error);
3128 if (!*new_fdp)
3129 return error;
3130 }
3131
3132 return 0;
3133 }
3134
3135 /*
3136 * unshare allows a process to 'unshare' part of the process
3137 * context which was originally shared using clone. copy_*
3138 * functions used by kernel_clone() cannot be used here directly
3139 * because they modify an inactive task_struct that is being
3140 * constructed. Here we are modifying the current, active,
3141 * task_struct.
3142 */
ksys_unshare(unsigned long unshare_flags)3143 int ksys_unshare(unsigned long unshare_flags)
3144 {
3145 struct fs_struct *fs, *new_fs = NULL;
3146 struct files_struct *new_fd = NULL;
3147 struct cred *new_cred = NULL;
3148 struct nsproxy *new_nsproxy = NULL;
3149 int do_sysvsem = 0;
3150 int err;
3151
3152 /*
3153 * If unsharing a user namespace must also unshare the thread group
3154 * and unshare the filesystem root and working directories.
3155 */
3156 if (unshare_flags & CLONE_NEWUSER)
3157 unshare_flags |= CLONE_THREAD | CLONE_FS;
3158 /*
3159 * If unsharing vm, must also unshare signal handlers.
3160 */
3161 if (unshare_flags & CLONE_VM)
3162 unshare_flags |= CLONE_SIGHAND;
3163 /*
3164 * If unsharing a signal handlers, must also unshare the signal queues.
3165 */
3166 if (unshare_flags & CLONE_SIGHAND)
3167 unshare_flags |= CLONE_THREAD;
3168 /*
3169 * If unsharing namespace, must also unshare filesystem information.
3170 */
3171 if (unshare_flags & CLONE_NEWNS)
3172 unshare_flags |= CLONE_FS;
3173
3174 err = check_unshare_flags(unshare_flags);
3175 if (err)
3176 goto bad_unshare_out;
3177 /*
3178 * CLONE_NEWIPC must also detach from the undolist: after switching
3179 * to a new ipc namespace, the semaphore arrays from the old
3180 * namespace are unreachable.
3181 */
3182 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
3183 do_sysvsem = 1;
3184 err = unshare_fs(unshare_flags, &new_fs);
3185 if (err)
3186 goto bad_unshare_out;
3187 err = unshare_fd(unshare_flags, NR_OPEN_MAX, &new_fd);
3188 if (err)
3189 goto bad_unshare_cleanup_fs;
3190 err = unshare_userns(unshare_flags, &new_cred);
3191 if (err)
3192 goto bad_unshare_cleanup_fd;
3193 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
3194 new_cred, new_fs);
3195 if (err)
3196 goto bad_unshare_cleanup_cred;
3197
3198 if (new_cred) {
3199 err = set_cred_ucounts(new_cred);
3200 if (err)
3201 goto bad_unshare_cleanup_cred;
3202 }
3203
3204 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
3205 if (do_sysvsem) {
3206 /*
3207 * CLONE_SYSVSEM is equivalent to sys_exit().
3208 */
3209 exit_sem(current);
3210 }
3211 if (unshare_flags & CLONE_NEWIPC) {
3212 /* Orphan segments in old ns (see sem above). */
3213 exit_shm(current);
3214 shm_init_task(current);
3215 }
3216
3217 if (new_nsproxy)
3218 switch_task_namespaces(current, new_nsproxy);
3219
3220 task_lock(current);
3221
3222 if (new_fs) {
3223 fs = current->fs;
3224 spin_lock(&fs->lock);
3225 current->fs = new_fs;
3226 if (--fs->users)
3227 new_fs = NULL;
3228 else
3229 new_fs = fs;
3230 spin_unlock(&fs->lock);
3231 }
3232
3233 if (new_fd)
3234 swap(current->files, new_fd);
3235
3236 task_unlock(current);
3237
3238 if (new_cred) {
3239 /* Install the new user namespace */
3240 commit_creds(new_cred);
3241 new_cred = NULL;
3242 }
3243 }
3244
3245 perf_event_namespaces(current);
3246
3247 bad_unshare_cleanup_cred:
3248 if (new_cred)
3249 put_cred(new_cred);
3250 bad_unshare_cleanup_fd:
3251 if (new_fd)
3252 put_files_struct(new_fd);
3253
3254 bad_unshare_cleanup_fs:
3255 if (new_fs)
3256 free_fs_struct(new_fs);
3257
3258 bad_unshare_out:
3259 return err;
3260 }
3261
SYSCALL_DEFINE1(unshare,unsigned long,unshare_flags)3262 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
3263 {
3264 return ksys_unshare(unshare_flags);
3265 }
3266
3267 /*
3268 * Helper to unshare the files of the current task.
3269 * We don't want to expose copy_files internals to
3270 * the exec layer of the kernel.
3271 */
3272
unshare_files(void)3273 int unshare_files(void)
3274 {
3275 struct task_struct *task = current;
3276 struct files_struct *old, *copy = NULL;
3277 int error;
3278
3279 error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, ©);
3280 if (error || !copy)
3281 return error;
3282
3283 old = task->files;
3284 task_lock(task);
3285 task->files = copy;
3286 task_unlock(task);
3287 put_files_struct(old);
3288 return 0;
3289 }
3290
sysctl_max_threads(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)3291 int sysctl_max_threads(struct ctl_table *table, int write,
3292 void *buffer, size_t *lenp, loff_t *ppos)
3293 {
3294 struct ctl_table t;
3295 int ret;
3296 int threads = max_threads;
3297 int min = 1;
3298 int max = MAX_THREADS;
3299
3300 t = *table;
3301 t.data = &threads;
3302 t.extra1 = &min;
3303 t.extra2 = &max;
3304
3305 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
3306 if (ret || !write)
3307 return ret;
3308
3309 max_threads = threads;
3310
3311 return 0;
3312 }
3313