xref: /openbmc/linux/kernel/fork.c (revision ccc319dc)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  linux/kernel/fork.c
4  *
5  *  Copyright (C) 1991, 1992  Linus Torvalds
6  */
7 
8 /*
9  *  'fork.c' contains the help-routines for the 'fork' system call
10  * (see also entry.S and others).
11  * Fork is rather simple, once you get the hang of it, but the memory
12  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
13  */
14 
15 #include <linux/anon_inodes.h>
16 #include <linux/slab.h>
17 #include <linux/sched/autogroup.h>
18 #include <linux/sched/mm.h>
19 #include <linux/sched/coredump.h>
20 #include <linux/sched/user.h>
21 #include <linux/sched/numa_balancing.h>
22 #include <linux/sched/stat.h>
23 #include <linux/sched/task.h>
24 #include <linux/sched/task_stack.h>
25 #include <linux/sched/cputime.h>
26 #include <linux/seq_file.h>
27 #include <linux/rtmutex.h>
28 #include <linux/init.h>
29 #include <linux/unistd.h>
30 #include <linux/module.h>
31 #include <linux/vmalloc.h>
32 #include <linux/completion.h>
33 #include <linux/personality.h>
34 #include <linux/mempolicy.h>
35 #include <linux/sem.h>
36 #include <linux/file.h>
37 #include <linux/fdtable.h>
38 #include <linux/iocontext.h>
39 #include <linux/key.h>
40 #include <linux/binfmts.h>
41 #include <linux/mman.h>
42 #include <linux/mmu_notifier.h>
43 #include <linux/fs.h>
44 #include <linux/mm.h>
45 #include <linux/mm_inline.h>
46 #include <linux/vmacache.h>
47 #include <linux/nsproxy.h>
48 #include <linux/capability.h>
49 #include <linux/cpu.h>
50 #include <linux/cgroup.h>
51 #include <linux/security.h>
52 #include <linux/hugetlb.h>
53 #include <linux/seccomp.h>
54 #include <linux/swap.h>
55 #include <linux/syscalls.h>
56 #include <linux/jiffies.h>
57 #include <linux/futex.h>
58 #include <linux/compat.h>
59 #include <linux/kthread.h>
60 #include <linux/task_io_accounting_ops.h>
61 #include <linux/rcupdate.h>
62 #include <linux/ptrace.h>
63 #include <linux/mount.h>
64 #include <linux/audit.h>
65 #include <linux/memcontrol.h>
66 #include <linux/ftrace.h>
67 #include <linux/proc_fs.h>
68 #include <linux/profile.h>
69 #include <linux/rmap.h>
70 #include <linux/ksm.h>
71 #include <linux/acct.h>
72 #include <linux/userfaultfd_k.h>
73 #include <linux/tsacct_kern.h>
74 #include <linux/cn_proc.h>
75 #include <linux/freezer.h>
76 #include <linux/delayacct.h>
77 #include <linux/taskstats_kern.h>
78 #include <linux/random.h>
79 #include <linux/tty.h>
80 #include <linux/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 #include <linux/sched/mm.h>
101 
102 #include <asm/pgalloc.h>
103 #include <linux/uaccess.h>
104 #include <asm/mmu_context.h>
105 #include <asm/cacheflush.h>
106 #include <asm/tlbflush.h>
107 
108 #include <trace/events/sched.h>
109 
110 #define CREATE_TRACE_POINTS
111 #include <trace/events/task.h>
112 
113 /*
114  * Minimum number of threads to boot the kernel
115  */
116 #define MIN_THREADS 20
117 
118 /*
119  * Maximum number of threads
120  */
121 #define MAX_THREADS FUTEX_TID_MASK
122 
123 /*
124  * Protected counters by write_lock_irq(&tasklist_lock)
125  */
126 unsigned long total_forks;	/* Handle normal Linux uptimes. */
127 int nr_threads;			/* The idle threads do not count.. */
128 
129 static int max_threads;		/* tunable limit on nr_threads */
130 
131 #define NAMED_ARRAY_INDEX(x)	[x] = __stringify(x)
132 
133 static const char * const resident_page_types[] = {
134 	NAMED_ARRAY_INDEX(MM_FILEPAGES),
135 	NAMED_ARRAY_INDEX(MM_ANONPAGES),
136 	NAMED_ARRAY_INDEX(MM_SWAPENTS),
137 	NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
138 };
139 
140 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
141 
142 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
143 
144 #ifdef CONFIG_PROVE_RCU
145 int lockdep_tasklist_lock_is_held(void)
146 {
147 	return lockdep_is_held(&tasklist_lock);
148 }
149 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
150 #endif /* #ifdef CONFIG_PROVE_RCU */
151 
152 int nr_processes(void)
153 {
154 	int cpu;
155 	int total = 0;
156 
157 	for_each_possible_cpu(cpu)
158 		total += per_cpu(process_counts, cpu);
159 
160 	return total;
161 }
162 
163 void __weak arch_release_task_struct(struct task_struct *tsk)
164 {
165 }
166 
167 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
168 static struct kmem_cache *task_struct_cachep;
169 
170 static inline struct task_struct *alloc_task_struct_node(int node)
171 {
172 	return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
173 }
174 
175 static inline void free_task_struct(struct task_struct *tsk)
176 {
177 	kmem_cache_free(task_struct_cachep, tsk);
178 }
179 #endif
180 
181 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
182 
183 /*
184  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
185  * kmemcache based allocator.
186  */
187 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
188 
189 #  ifdef CONFIG_VMAP_STACK
190 /*
191  * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
192  * flush.  Try to minimize the number of calls by caching stacks.
193  */
194 #define NR_CACHED_STACKS 2
195 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
196 
197 struct vm_stack {
198 	struct rcu_head rcu;
199 	struct vm_struct *stack_vm_area;
200 };
201 
202 static bool try_release_thread_stack_to_cache(struct vm_struct *vm)
203 {
204 	unsigned int i;
205 
206 	for (i = 0; i < NR_CACHED_STACKS; i++) {
207 		if (this_cpu_cmpxchg(cached_stacks[i], NULL, vm) != NULL)
208 			continue;
209 		return true;
210 	}
211 	return false;
212 }
213 
214 static void thread_stack_free_rcu(struct rcu_head *rh)
215 {
216 	struct vm_stack *vm_stack = container_of(rh, struct vm_stack, rcu);
217 
218 	if (try_release_thread_stack_to_cache(vm_stack->stack_vm_area))
219 		return;
220 
221 	vfree(vm_stack);
222 }
223 
224 static void thread_stack_delayed_free(struct task_struct *tsk)
225 {
226 	struct vm_stack *vm_stack = tsk->stack;
227 
228 	vm_stack->stack_vm_area = tsk->stack_vm_area;
229 	call_rcu(&vm_stack->rcu, thread_stack_free_rcu);
230 }
231 
232 static int free_vm_stack_cache(unsigned int cpu)
233 {
234 	struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
235 	int i;
236 
237 	for (i = 0; i < NR_CACHED_STACKS; i++) {
238 		struct vm_struct *vm_stack = cached_vm_stacks[i];
239 
240 		if (!vm_stack)
241 			continue;
242 
243 		vfree(vm_stack->addr);
244 		cached_vm_stacks[i] = NULL;
245 	}
246 
247 	return 0;
248 }
249 
250 static int memcg_charge_kernel_stack(struct vm_struct *vm)
251 {
252 	int i;
253 	int ret;
254 
255 	BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
256 	BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
257 
258 	for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
259 		ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL, 0);
260 		if (ret)
261 			goto err;
262 	}
263 	return 0;
264 err:
265 	/*
266 	 * If memcg_kmem_charge_page() fails, page's memory cgroup pointer is
267 	 * NULL, and memcg_kmem_uncharge_page() in free_thread_stack() will
268 	 * ignore this page.
269 	 */
270 	for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
271 		memcg_kmem_uncharge_page(vm->pages[i], 0);
272 	return ret;
273 }
274 
275 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
276 {
277 	struct vm_struct *vm;
278 	void *stack;
279 	int i;
280 
281 	for (i = 0; i < NR_CACHED_STACKS; i++) {
282 		struct vm_struct *s;
283 
284 		s = this_cpu_xchg(cached_stacks[i], NULL);
285 
286 		if (!s)
287 			continue;
288 
289 		/* Reset stack metadata. */
290 		kasan_unpoison_range(s->addr, THREAD_SIZE);
291 
292 		stack = kasan_reset_tag(s->addr);
293 
294 		/* Clear stale pointers from reused stack. */
295 		memset(stack, 0, THREAD_SIZE);
296 
297 		if (memcg_charge_kernel_stack(s)) {
298 			vfree(s->addr);
299 			return -ENOMEM;
300 		}
301 
302 		tsk->stack_vm_area = s;
303 		tsk->stack = stack;
304 		return 0;
305 	}
306 
307 	/*
308 	 * Allocated stacks are cached and later reused by new threads,
309 	 * so memcg accounting is performed manually on assigning/releasing
310 	 * stacks to tasks. Drop __GFP_ACCOUNT.
311 	 */
312 	stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
313 				     VMALLOC_START, VMALLOC_END,
314 				     THREADINFO_GFP & ~__GFP_ACCOUNT,
315 				     PAGE_KERNEL,
316 				     0, node, __builtin_return_address(0));
317 	if (!stack)
318 		return -ENOMEM;
319 
320 	vm = find_vm_area(stack);
321 	if (memcg_charge_kernel_stack(vm)) {
322 		vfree(stack);
323 		return -ENOMEM;
324 	}
325 	/*
326 	 * We can't call find_vm_area() in interrupt context, and
327 	 * free_thread_stack() can be called in interrupt context,
328 	 * so cache the vm_struct.
329 	 */
330 	tsk->stack_vm_area = vm;
331 	stack = kasan_reset_tag(stack);
332 	tsk->stack = stack;
333 	return 0;
334 }
335 
336 static void free_thread_stack(struct task_struct *tsk)
337 {
338 	if (!try_release_thread_stack_to_cache(tsk->stack_vm_area))
339 		thread_stack_delayed_free(tsk);
340 
341 	tsk->stack = NULL;
342 	tsk->stack_vm_area = NULL;
343 }
344 
345 #  else /* !CONFIG_VMAP_STACK */
346 
347 static void thread_stack_free_rcu(struct rcu_head *rh)
348 {
349 	__free_pages(virt_to_page(rh), THREAD_SIZE_ORDER);
350 }
351 
352 static void thread_stack_delayed_free(struct task_struct *tsk)
353 {
354 	struct rcu_head *rh = tsk->stack;
355 
356 	call_rcu(rh, thread_stack_free_rcu);
357 }
358 
359 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
360 {
361 	struct page *page = alloc_pages_node(node, THREADINFO_GFP,
362 					     THREAD_SIZE_ORDER);
363 
364 	if (likely(page)) {
365 		tsk->stack = kasan_reset_tag(page_address(page));
366 		return 0;
367 	}
368 	return -ENOMEM;
369 }
370 
371 static void free_thread_stack(struct task_struct *tsk)
372 {
373 	thread_stack_delayed_free(tsk);
374 	tsk->stack = NULL;
375 }
376 
377 #  endif /* CONFIG_VMAP_STACK */
378 # else /* !(THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)) */
379 
380 static struct kmem_cache *thread_stack_cache;
381 
382 static void thread_stack_free_rcu(struct rcu_head *rh)
383 {
384 	kmem_cache_free(thread_stack_cache, rh);
385 }
386 
387 static void thread_stack_delayed_free(struct task_struct *tsk)
388 {
389 	struct rcu_head *rh = tsk->stack;
390 
391 	call_rcu(rh, thread_stack_free_rcu);
392 }
393 
394 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
395 {
396 	unsigned long *stack;
397 	stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
398 	stack = kasan_reset_tag(stack);
399 	tsk->stack = stack;
400 	return stack ? 0 : -ENOMEM;
401 }
402 
403 static void free_thread_stack(struct task_struct *tsk)
404 {
405 	thread_stack_delayed_free(tsk);
406 	tsk->stack = NULL;
407 }
408 
409 void thread_stack_cache_init(void)
410 {
411 	thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
412 					THREAD_SIZE, THREAD_SIZE, 0, 0,
413 					THREAD_SIZE, NULL);
414 	BUG_ON(thread_stack_cache == NULL);
415 }
416 
417 # endif /* THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) */
418 #else /* CONFIG_ARCH_THREAD_STACK_ALLOCATOR */
419 
420 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
421 {
422 	unsigned long *stack;
423 
424 	stack = arch_alloc_thread_stack_node(tsk, node);
425 	tsk->stack = stack;
426 	return stack ? 0 : -ENOMEM;
427 }
428 
429 static void free_thread_stack(struct task_struct *tsk)
430 {
431 	arch_free_thread_stack(tsk);
432 	tsk->stack = NULL;
433 }
434 
435 #endif /* !CONFIG_ARCH_THREAD_STACK_ALLOCATOR */
436 
437 /* SLAB cache for signal_struct structures (tsk->signal) */
438 static struct kmem_cache *signal_cachep;
439 
440 /* SLAB cache for sighand_struct structures (tsk->sighand) */
441 struct kmem_cache *sighand_cachep;
442 
443 /* SLAB cache for files_struct structures (tsk->files) */
444 struct kmem_cache *files_cachep;
445 
446 /* SLAB cache for fs_struct structures (tsk->fs) */
447 struct kmem_cache *fs_cachep;
448 
449 /* SLAB cache for vm_area_struct structures */
450 static struct kmem_cache *vm_area_cachep;
451 
452 /* SLAB cache for mm_struct structures (tsk->mm) */
453 static struct kmem_cache *mm_cachep;
454 
455 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
456 {
457 	struct vm_area_struct *vma;
458 
459 	vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
460 	if (vma)
461 		vma_init(vma, mm);
462 	return vma;
463 }
464 
465 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
466 {
467 	struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
468 
469 	if (new) {
470 		ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
471 		ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
472 		/*
473 		 * orig->shared.rb may be modified concurrently, but the clone
474 		 * will be reinitialized.
475 		 */
476 		*new = data_race(*orig);
477 		INIT_LIST_HEAD(&new->anon_vma_chain);
478 		new->vm_next = new->vm_prev = NULL;
479 		dup_anon_vma_name(orig, new);
480 	}
481 	return new;
482 }
483 
484 void vm_area_free(struct vm_area_struct *vma)
485 {
486 	free_anon_vma_name(vma);
487 	kmem_cache_free(vm_area_cachep, vma);
488 }
489 
490 static void account_kernel_stack(struct task_struct *tsk, int account)
491 {
492 	if (IS_ENABLED(CONFIG_VMAP_STACK)) {
493 		struct vm_struct *vm = task_stack_vm_area(tsk);
494 		int i;
495 
496 		for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
497 			mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB,
498 					      account * (PAGE_SIZE / 1024));
499 	} else {
500 		void *stack = task_stack_page(tsk);
501 
502 		/* All stack pages are in the same node. */
503 		mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB,
504 				      account * (THREAD_SIZE / 1024));
505 	}
506 }
507 
508 void exit_task_stack_account(struct task_struct *tsk)
509 {
510 	account_kernel_stack(tsk, -1);
511 
512 	if (IS_ENABLED(CONFIG_VMAP_STACK)) {
513 		struct vm_struct *vm;
514 		int i;
515 
516 		vm = task_stack_vm_area(tsk);
517 		for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
518 			memcg_kmem_uncharge_page(vm->pages[i], 0);
519 	}
520 }
521 
522 static void release_task_stack(struct task_struct *tsk)
523 {
524 	if (WARN_ON(READ_ONCE(tsk->__state) != TASK_DEAD))
525 		return;  /* Better to leak the stack than to free prematurely */
526 
527 	free_thread_stack(tsk);
528 }
529 
530 #ifdef CONFIG_THREAD_INFO_IN_TASK
531 void put_task_stack(struct task_struct *tsk)
532 {
533 	if (refcount_dec_and_test(&tsk->stack_refcount))
534 		release_task_stack(tsk);
535 }
536 #endif
537 
538 void free_task(struct task_struct *tsk)
539 {
540 	release_user_cpus_ptr(tsk);
541 	scs_release(tsk);
542 
543 #ifndef CONFIG_THREAD_INFO_IN_TASK
544 	/*
545 	 * The task is finally done with both the stack and thread_info,
546 	 * so free both.
547 	 */
548 	release_task_stack(tsk);
549 #else
550 	/*
551 	 * If the task had a separate stack allocation, it should be gone
552 	 * by now.
553 	 */
554 	WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
555 #endif
556 	rt_mutex_debug_task_free(tsk);
557 	ftrace_graph_exit_task(tsk);
558 	arch_release_task_struct(tsk);
559 	if (tsk->flags & PF_KTHREAD)
560 		free_kthread_struct(tsk);
561 	free_task_struct(tsk);
562 }
563 EXPORT_SYMBOL(free_task);
564 
565 static void dup_mm_exe_file(struct mm_struct *mm, struct mm_struct *oldmm)
566 {
567 	struct file *exe_file;
568 
569 	exe_file = get_mm_exe_file(oldmm);
570 	RCU_INIT_POINTER(mm->exe_file, exe_file);
571 	/*
572 	 * We depend on the oldmm having properly denied write access to the
573 	 * exe_file already.
574 	 */
575 	if (exe_file && deny_write_access(exe_file))
576 		pr_warn_once("deny_write_access() failed in %s\n", __func__);
577 }
578 
579 #ifdef CONFIG_MMU
580 static __latent_entropy int dup_mmap(struct mm_struct *mm,
581 					struct mm_struct *oldmm)
582 {
583 	struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
584 	struct rb_node **rb_link, *rb_parent;
585 	int retval;
586 	unsigned long charge;
587 	LIST_HEAD(uf);
588 
589 	uprobe_start_dup_mmap();
590 	if (mmap_write_lock_killable(oldmm)) {
591 		retval = -EINTR;
592 		goto fail_uprobe_end;
593 	}
594 	flush_cache_dup_mm(oldmm);
595 	uprobe_dup_mmap(oldmm, mm);
596 	/*
597 	 * Not linked in yet - no deadlock potential:
598 	 */
599 	mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING);
600 
601 	/* No ordering required: file already has been exposed. */
602 	dup_mm_exe_file(mm, oldmm);
603 
604 	mm->total_vm = oldmm->total_vm;
605 	mm->data_vm = oldmm->data_vm;
606 	mm->exec_vm = oldmm->exec_vm;
607 	mm->stack_vm = oldmm->stack_vm;
608 
609 	rb_link = &mm->mm_rb.rb_node;
610 	rb_parent = NULL;
611 	pprev = &mm->mmap;
612 	retval = ksm_fork(mm, oldmm);
613 	if (retval)
614 		goto out;
615 	khugepaged_fork(mm, oldmm);
616 
617 	prev = NULL;
618 	for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
619 		struct file *file;
620 
621 		if (mpnt->vm_flags & VM_DONTCOPY) {
622 			vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
623 			continue;
624 		}
625 		charge = 0;
626 		/*
627 		 * Don't duplicate many vmas if we've been oom-killed (for
628 		 * example)
629 		 */
630 		if (fatal_signal_pending(current)) {
631 			retval = -EINTR;
632 			goto out;
633 		}
634 		if (mpnt->vm_flags & VM_ACCOUNT) {
635 			unsigned long len = vma_pages(mpnt);
636 
637 			if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
638 				goto fail_nomem;
639 			charge = len;
640 		}
641 		tmp = vm_area_dup(mpnt);
642 		if (!tmp)
643 			goto fail_nomem;
644 		retval = vma_dup_policy(mpnt, tmp);
645 		if (retval)
646 			goto fail_nomem_policy;
647 		tmp->vm_mm = mm;
648 		retval = dup_userfaultfd(tmp, &uf);
649 		if (retval)
650 			goto fail_nomem_anon_vma_fork;
651 		if (tmp->vm_flags & VM_WIPEONFORK) {
652 			/*
653 			 * VM_WIPEONFORK gets a clean slate in the child.
654 			 * Don't prepare anon_vma until fault since we don't
655 			 * copy page for current vma.
656 			 */
657 			tmp->anon_vma = NULL;
658 		} else if (anon_vma_fork(tmp, mpnt))
659 			goto fail_nomem_anon_vma_fork;
660 		tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
661 		file = tmp->vm_file;
662 		if (file) {
663 			struct address_space *mapping = file->f_mapping;
664 
665 			get_file(file);
666 			i_mmap_lock_write(mapping);
667 			if (tmp->vm_flags & VM_SHARED)
668 				mapping_allow_writable(mapping);
669 			flush_dcache_mmap_lock(mapping);
670 			/* insert tmp into the share list, just after mpnt */
671 			vma_interval_tree_insert_after(tmp, mpnt,
672 					&mapping->i_mmap);
673 			flush_dcache_mmap_unlock(mapping);
674 			i_mmap_unlock_write(mapping);
675 		}
676 
677 		/*
678 		 * Clear hugetlb-related page reserves for children. This only
679 		 * affects MAP_PRIVATE mappings. Faults generated by the child
680 		 * are not guaranteed to succeed, even if read-only
681 		 */
682 		if (is_vm_hugetlb_page(tmp))
683 			reset_vma_resv_huge_pages(tmp);
684 
685 		/*
686 		 * Link in the new vma and copy the page table entries.
687 		 */
688 		*pprev = tmp;
689 		pprev = &tmp->vm_next;
690 		tmp->vm_prev = prev;
691 		prev = tmp;
692 
693 		__vma_link_rb(mm, tmp, rb_link, rb_parent);
694 		rb_link = &tmp->vm_rb.rb_right;
695 		rb_parent = &tmp->vm_rb;
696 
697 		mm->map_count++;
698 		if (!(tmp->vm_flags & VM_WIPEONFORK))
699 			retval = copy_page_range(tmp, mpnt);
700 
701 		if (tmp->vm_ops && tmp->vm_ops->open)
702 			tmp->vm_ops->open(tmp);
703 
704 		if (retval)
705 			goto out;
706 	}
707 	/* a new mm has just been created */
708 	retval = arch_dup_mmap(oldmm, mm);
709 out:
710 	mmap_write_unlock(mm);
711 	flush_tlb_mm(oldmm);
712 	mmap_write_unlock(oldmm);
713 	dup_userfaultfd_complete(&uf);
714 fail_uprobe_end:
715 	uprobe_end_dup_mmap();
716 	return retval;
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 out;
725 }
726 
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 
735 static inline void mm_free_pgd(struct mm_struct *mm)
736 {
737 	pgd_free(mm, mm->pgd);
738 }
739 #else
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 
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  */
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 
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 
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 
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 
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 
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 
852 void __init __weak arch_task_cache_init(void) { }
853 
854 /*
855  * set_max_threads
856  */
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
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 
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 < MAX_PER_NAMESPACE_UCOUNTS; i++)
929 		init_user_ns.ucount_max[i] = max_threads/2;
930 
931 	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC,      RLIM_INFINITY);
932 	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE,   RLIM_INFINITY);
933 	set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY);
934 	set_rlimit_ucount_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 
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 
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 
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 	kmap_local_fork(tsk);
1030 
1031 #ifdef CONFIG_FAULT_INJECTION
1032 	tsk->fail_nth = 0;
1033 #endif
1034 
1035 #ifdef CONFIG_BLK_CGROUP
1036 	tsk->throttle_queue = NULL;
1037 	tsk->use_memdelay = 0;
1038 #endif
1039 
1040 #ifdef CONFIG_IOMMU_SVA
1041 	tsk->pasid_activated = 0;
1042 #endif
1043 
1044 #ifdef CONFIG_MEMCG
1045 	tsk->active_memcg = NULL;
1046 #endif
1047 
1048 #ifdef CONFIG_CPU_SUP_INTEL
1049 	tsk->reported_split_lock = 0;
1050 #endif
1051 
1052 	return tsk;
1053 
1054 free_stack:
1055 	exit_task_stack_account(tsk);
1056 	free_thread_stack(tsk);
1057 free_tsk:
1058 	free_task_struct(tsk);
1059 	return NULL;
1060 }
1061 
1062 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
1063 
1064 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
1065 
1066 static int __init coredump_filter_setup(char *s)
1067 {
1068 	default_dump_filter =
1069 		(simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
1070 		MMF_DUMP_FILTER_MASK;
1071 	return 1;
1072 }
1073 
1074 __setup("coredump_filter=", coredump_filter_setup);
1075 
1076 #include <linux/init_task.h>
1077 
1078 static void mm_init_aio(struct mm_struct *mm)
1079 {
1080 #ifdef CONFIG_AIO
1081 	spin_lock_init(&mm->ioctx_lock);
1082 	mm->ioctx_table = NULL;
1083 #endif
1084 }
1085 
1086 static __always_inline void mm_clear_owner(struct mm_struct *mm,
1087 					   struct task_struct *p)
1088 {
1089 #ifdef CONFIG_MEMCG
1090 	if (mm->owner == p)
1091 		WRITE_ONCE(mm->owner, NULL);
1092 #endif
1093 }
1094 
1095 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1096 {
1097 #ifdef CONFIG_MEMCG
1098 	mm->owner = p;
1099 #endif
1100 }
1101 
1102 static void mm_init_uprobes_state(struct mm_struct *mm)
1103 {
1104 #ifdef CONFIG_UPROBES
1105 	mm->uprobes_state.xol_area = NULL;
1106 #endif
1107 }
1108 
1109 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
1110 	struct user_namespace *user_ns)
1111 {
1112 	mm->mmap = NULL;
1113 	mm->mm_rb = RB_ROOT;
1114 	mm->vmacache_seqnum = 0;
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 	return mm;
1156 
1157 fail_nocontext:
1158 	mm_free_pgd(mm);
1159 fail_nopgd:
1160 	free_mm(mm);
1161 	return NULL;
1162 }
1163 
1164 /*
1165  * Allocate and initialize an mm_struct.
1166  */
1167 struct mm_struct *mm_alloc(void)
1168 {
1169 	struct mm_struct *mm;
1170 
1171 	mm = allocate_mm();
1172 	if (!mm)
1173 		return NULL;
1174 
1175 	memset(mm, 0, sizeof(*mm));
1176 	return mm_init(mm, current, current_user_ns());
1177 }
1178 
1179 static inline void __mmput(struct mm_struct *mm)
1180 {
1181 	VM_BUG_ON(atomic_read(&mm->mm_users));
1182 
1183 	uprobe_clear_state(mm);
1184 	exit_aio(mm);
1185 	ksm_exit(mm);
1186 	khugepaged_exit(mm); /* must run before exit_mmap */
1187 	exit_mmap(mm);
1188 	mm_put_huge_zero_page(mm);
1189 	set_mm_exe_file(mm, NULL);
1190 	if (!list_empty(&mm->mmlist)) {
1191 		spin_lock(&mmlist_lock);
1192 		list_del(&mm->mmlist);
1193 		spin_unlock(&mmlist_lock);
1194 	}
1195 	if (mm->binfmt)
1196 		module_put(mm->binfmt->module);
1197 	mmdrop(mm);
1198 }
1199 
1200 /*
1201  * Decrement the use count and release all resources for an mm.
1202  */
1203 void mmput(struct mm_struct *mm)
1204 {
1205 	might_sleep();
1206 
1207 	if (atomic_dec_and_test(&mm->mm_users))
1208 		__mmput(mm);
1209 }
1210 EXPORT_SYMBOL_GPL(mmput);
1211 
1212 #ifdef CONFIG_MMU
1213 static void mmput_async_fn(struct work_struct *work)
1214 {
1215 	struct mm_struct *mm = container_of(work, struct mm_struct,
1216 					    async_put_work);
1217 
1218 	__mmput(mm);
1219 }
1220 
1221 void mmput_async(struct mm_struct *mm)
1222 {
1223 	if (atomic_dec_and_test(&mm->mm_users)) {
1224 		INIT_WORK(&mm->async_put_work, mmput_async_fn);
1225 		schedule_work(&mm->async_put_work);
1226 	}
1227 }
1228 #endif
1229 
1230 /**
1231  * set_mm_exe_file - change a reference to the mm's executable file
1232  *
1233  * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1234  *
1235  * Main users are mmput() and sys_execve(). Callers prevent concurrent
1236  * invocations: in mmput() nobody alive left, in execve task is single
1237  * threaded.
1238  *
1239  * Can only fail if new_exe_file != NULL.
1240  */
1241 int set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1242 {
1243 	struct file *old_exe_file;
1244 
1245 	/*
1246 	 * It is safe to dereference the exe_file without RCU as
1247 	 * this function is only called if nobody else can access
1248 	 * this mm -- see comment above for justification.
1249 	 */
1250 	old_exe_file = rcu_dereference_raw(mm->exe_file);
1251 
1252 	if (new_exe_file) {
1253 		/*
1254 		 * We expect the caller (i.e., sys_execve) to already denied
1255 		 * write access, so this is unlikely to fail.
1256 		 */
1257 		if (unlikely(deny_write_access(new_exe_file)))
1258 			return -EACCES;
1259 		get_file(new_exe_file);
1260 	}
1261 	rcu_assign_pointer(mm->exe_file, new_exe_file);
1262 	if (old_exe_file) {
1263 		allow_write_access(old_exe_file);
1264 		fput(old_exe_file);
1265 	}
1266 	return 0;
1267 }
1268 
1269 /**
1270  * replace_mm_exe_file - replace a reference to the mm's executable file
1271  *
1272  * This changes mm's executable file (shown as symlink /proc/[pid]/exe),
1273  * dealing with concurrent invocation and without grabbing the mmap lock in
1274  * write mode.
1275  *
1276  * Main user is sys_prctl(PR_SET_MM_MAP/EXE_FILE).
1277  */
1278 int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1279 {
1280 	struct vm_area_struct *vma;
1281 	struct file *old_exe_file;
1282 	int ret = 0;
1283 
1284 	/* Forbid mm->exe_file change if old file still mapped. */
1285 	old_exe_file = get_mm_exe_file(mm);
1286 	if (old_exe_file) {
1287 		mmap_read_lock(mm);
1288 		for (vma = mm->mmap; vma && !ret; vma = vma->vm_next) {
1289 			if (!vma->vm_file)
1290 				continue;
1291 			if (path_equal(&vma->vm_file->f_path,
1292 				       &old_exe_file->f_path))
1293 				ret = -EBUSY;
1294 		}
1295 		mmap_read_unlock(mm);
1296 		fput(old_exe_file);
1297 		if (ret)
1298 			return ret;
1299 	}
1300 
1301 	/* set the new file, lockless */
1302 	ret = deny_write_access(new_exe_file);
1303 	if (ret)
1304 		return -EACCES;
1305 	get_file(new_exe_file);
1306 
1307 	old_exe_file = xchg(&mm->exe_file, new_exe_file);
1308 	if (old_exe_file) {
1309 		/*
1310 		 * Don't race with dup_mmap() getting the file and disallowing
1311 		 * write access while someone might open the file writable.
1312 		 */
1313 		mmap_read_lock(mm);
1314 		allow_write_access(old_exe_file);
1315 		fput(old_exe_file);
1316 		mmap_read_unlock(mm);
1317 	}
1318 	return 0;
1319 }
1320 
1321 /**
1322  * get_mm_exe_file - acquire a reference to the mm's executable file
1323  *
1324  * Returns %NULL if mm has no associated executable file.
1325  * User must release file via fput().
1326  */
1327 struct file *get_mm_exe_file(struct mm_struct *mm)
1328 {
1329 	struct file *exe_file;
1330 
1331 	rcu_read_lock();
1332 	exe_file = rcu_dereference(mm->exe_file);
1333 	if (exe_file && !get_file_rcu(exe_file))
1334 		exe_file = NULL;
1335 	rcu_read_unlock();
1336 	return exe_file;
1337 }
1338 
1339 /**
1340  * get_task_exe_file - acquire a reference to the task's executable file
1341  *
1342  * Returns %NULL if task's mm (if any) has no associated executable file or
1343  * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1344  * User must release file via fput().
1345  */
1346 struct file *get_task_exe_file(struct task_struct *task)
1347 {
1348 	struct file *exe_file = NULL;
1349 	struct mm_struct *mm;
1350 
1351 	task_lock(task);
1352 	mm = task->mm;
1353 	if (mm) {
1354 		if (!(task->flags & PF_KTHREAD))
1355 			exe_file = get_mm_exe_file(mm);
1356 	}
1357 	task_unlock(task);
1358 	return exe_file;
1359 }
1360 
1361 /**
1362  * get_task_mm - acquire a reference to the task's mm
1363  *
1364  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
1365  * this kernel workthread has transiently adopted a user mm with use_mm,
1366  * to do its AIO) is not set and if so returns a reference to it, after
1367  * bumping up the use count.  User must release the mm via mmput()
1368  * after use.  Typically used by /proc and ptrace.
1369  */
1370 struct mm_struct *get_task_mm(struct task_struct *task)
1371 {
1372 	struct mm_struct *mm;
1373 
1374 	task_lock(task);
1375 	mm = task->mm;
1376 	if (mm) {
1377 		if (task->flags & PF_KTHREAD)
1378 			mm = NULL;
1379 		else
1380 			mmget(mm);
1381 	}
1382 	task_unlock(task);
1383 	return mm;
1384 }
1385 EXPORT_SYMBOL_GPL(get_task_mm);
1386 
1387 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1388 {
1389 	struct mm_struct *mm;
1390 	int err;
1391 
1392 	err =  down_read_killable(&task->signal->exec_update_lock);
1393 	if (err)
1394 		return ERR_PTR(err);
1395 
1396 	mm = get_task_mm(task);
1397 	if (mm && mm != current->mm &&
1398 			!ptrace_may_access(task, mode)) {
1399 		mmput(mm);
1400 		mm = ERR_PTR(-EACCES);
1401 	}
1402 	up_read(&task->signal->exec_update_lock);
1403 
1404 	return mm;
1405 }
1406 
1407 static void complete_vfork_done(struct task_struct *tsk)
1408 {
1409 	struct completion *vfork;
1410 
1411 	task_lock(tsk);
1412 	vfork = tsk->vfork_done;
1413 	if (likely(vfork)) {
1414 		tsk->vfork_done = NULL;
1415 		complete(vfork);
1416 	}
1417 	task_unlock(tsk);
1418 }
1419 
1420 static int wait_for_vfork_done(struct task_struct *child,
1421 				struct completion *vfork)
1422 {
1423 	int killed;
1424 
1425 	freezer_do_not_count();
1426 	cgroup_enter_frozen();
1427 	killed = wait_for_completion_killable(vfork);
1428 	cgroup_leave_frozen(false);
1429 	freezer_count();
1430 
1431 	if (killed) {
1432 		task_lock(child);
1433 		child->vfork_done = NULL;
1434 		task_unlock(child);
1435 	}
1436 
1437 	put_task_struct(child);
1438 	return killed;
1439 }
1440 
1441 /* Please note the differences between mmput and mm_release.
1442  * mmput is called whenever we stop holding onto a mm_struct,
1443  * error success whatever.
1444  *
1445  * mm_release is called after a mm_struct has been removed
1446  * from the current process.
1447  *
1448  * This difference is important for error handling, when we
1449  * only half set up a mm_struct for a new process and need to restore
1450  * the old one.  Because we mmput the new mm_struct before
1451  * restoring the old one. . .
1452  * Eric Biederman 10 January 1998
1453  */
1454 static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1455 {
1456 	uprobe_free_utask(tsk);
1457 
1458 	/* Get rid of any cached register state */
1459 	deactivate_mm(tsk, mm);
1460 
1461 	/*
1462 	 * Signal userspace if we're not exiting with a core dump
1463 	 * because we want to leave the value intact for debugging
1464 	 * purposes.
1465 	 */
1466 	if (tsk->clear_child_tid) {
1467 		if (atomic_read(&mm->mm_users) > 1) {
1468 			/*
1469 			 * We don't check the error code - if userspace has
1470 			 * not set up a proper pointer then tough luck.
1471 			 */
1472 			put_user(0, tsk->clear_child_tid);
1473 			do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1474 					1, NULL, NULL, 0, 0);
1475 		}
1476 		tsk->clear_child_tid = NULL;
1477 	}
1478 
1479 	/*
1480 	 * All done, finally we can wake up parent and return this mm to him.
1481 	 * Also kthread_stop() uses this completion for synchronization.
1482 	 */
1483 	if (tsk->vfork_done)
1484 		complete_vfork_done(tsk);
1485 }
1486 
1487 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1488 {
1489 	futex_exit_release(tsk);
1490 	mm_release(tsk, mm);
1491 }
1492 
1493 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1494 {
1495 	futex_exec_release(tsk);
1496 	mm_release(tsk, mm);
1497 }
1498 
1499 /**
1500  * dup_mm() - duplicates an existing mm structure
1501  * @tsk: the task_struct with which the new mm will be associated.
1502  * @oldmm: the mm to duplicate.
1503  *
1504  * Allocates a new mm structure and duplicates the provided @oldmm structure
1505  * content into it.
1506  *
1507  * Return: the duplicated mm or NULL on failure.
1508  */
1509 static struct mm_struct *dup_mm(struct task_struct *tsk,
1510 				struct mm_struct *oldmm)
1511 {
1512 	struct mm_struct *mm;
1513 	int err;
1514 
1515 	mm = allocate_mm();
1516 	if (!mm)
1517 		goto fail_nomem;
1518 
1519 	memcpy(mm, oldmm, sizeof(*mm));
1520 
1521 	if (!mm_init(mm, tsk, mm->user_ns))
1522 		goto fail_nomem;
1523 
1524 	err = dup_mmap(mm, oldmm);
1525 	if (err)
1526 		goto free_pt;
1527 
1528 	mm->hiwater_rss = get_mm_rss(mm);
1529 	mm->hiwater_vm = mm->total_vm;
1530 
1531 	if (mm->binfmt && !try_module_get(mm->binfmt->module))
1532 		goto free_pt;
1533 
1534 	return mm;
1535 
1536 free_pt:
1537 	/* don't put binfmt in mmput, we haven't got module yet */
1538 	mm->binfmt = NULL;
1539 	mm_init_owner(mm, NULL);
1540 	mmput(mm);
1541 
1542 fail_nomem:
1543 	return NULL;
1544 }
1545 
1546 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1547 {
1548 	struct mm_struct *mm, *oldmm;
1549 
1550 	tsk->min_flt = tsk->maj_flt = 0;
1551 	tsk->nvcsw = tsk->nivcsw = 0;
1552 #ifdef CONFIG_DETECT_HUNG_TASK
1553 	tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1554 	tsk->last_switch_time = 0;
1555 #endif
1556 
1557 	tsk->mm = NULL;
1558 	tsk->active_mm = NULL;
1559 
1560 	/*
1561 	 * Are we cloning a kernel thread?
1562 	 *
1563 	 * We need to steal a active VM for that..
1564 	 */
1565 	oldmm = current->mm;
1566 	if (!oldmm)
1567 		return 0;
1568 
1569 	/* initialize the new vmacache entries */
1570 	vmacache_flush(tsk);
1571 
1572 	if (clone_flags & CLONE_VM) {
1573 		mmget(oldmm);
1574 		mm = oldmm;
1575 	} else {
1576 		mm = dup_mm(tsk, current->mm);
1577 		if (!mm)
1578 			return -ENOMEM;
1579 	}
1580 
1581 	tsk->mm = mm;
1582 	tsk->active_mm = mm;
1583 	return 0;
1584 }
1585 
1586 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1587 {
1588 	struct fs_struct *fs = current->fs;
1589 	if (clone_flags & CLONE_FS) {
1590 		/* tsk->fs is already what we want */
1591 		spin_lock(&fs->lock);
1592 		if (fs->in_exec) {
1593 			spin_unlock(&fs->lock);
1594 			return -EAGAIN;
1595 		}
1596 		fs->users++;
1597 		spin_unlock(&fs->lock);
1598 		return 0;
1599 	}
1600 	tsk->fs = copy_fs_struct(fs);
1601 	if (!tsk->fs)
1602 		return -ENOMEM;
1603 	return 0;
1604 }
1605 
1606 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1607 {
1608 	struct files_struct *oldf, *newf;
1609 	int error = 0;
1610 
1611 	/*
1612 	 * A background process may not have any files ...
1613 	 */
1614 	oldf = current->files;
1615 	if (!oldf)
1616 		goto out;
1617 
1618 	if (clone_flags & CLONE_FILES) {
1619 		atomic_inc(&oldf->count);
1620 		goto out;
1621 	}
1622 
1623 	newf = dup_fd(oldf, NR_OPEN_MAX, &error);
1624 	if (!newf)
1625 		goto out;
1626 
1627 	tsk->files = newf;
1628 	error = 0;
1629 out:
1630 	return error;
1631 }
1632 
1633 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1634 {
1635 	struct sighand_struct *sig;
1636 
1637 	if (clone_flags & CLONE_SIGHAND) {
1638 		refcount_inc(&current->sighand->count);
1639 		return 0;
1640 	}
1641 	sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1642 	RCU_INIT_POINTER(tsk->sighand, sig);
1643 	if (!sig)
1644 		return -ENOMEM;
1645 
1646 	refcount_set(&sig->count, 1);
1647 	spin_lock_irq(&current->sighand->siglock);
1648 	memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1649 	spin_unlock_irq(&current->sighand->siglock);
1650 
1651 	/* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
1652 	if (clone_flags & CLONE_CLEAR_SIGHAND)
1653 		flush_signal_handlers(tsk, 0);
1654 
1655 	return 0;
1656 }
1657 
1658 void __cleanup_sighand(struct sighand_struct *sighand)
1659 {
1660 	if (refcount_dec_and_test(&sighand->count)) {
1661 		signalfd_cleanup(sighand);
1662 		/*
1663 		 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1664 		 * without an RCU grace period, see __lock_task_sighand().
1665 		 */
1666 		kmem_cache_free(sighand_cachep, sighand);
1667 	}
1668 }
1669 
1670 /*
1671  * Initialize POSIX timer handling for a thread group.
1672  */
1673 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1674 {
1675 	struct posix_cputimers *pct = &sig->posix_cputimers;
1676 	unsigned long cpu_limit;
1677 
1678 	cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1679 	posix_cputimers_group_init(pct, cpu_limit);
1680 }
1681 
1682 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1683 {
1684 	struct signal_struct *sig;
1685 
1686 	if (clone_flags & CLONE_THREAD)
1687 		return 0;
1688 
1689 	sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1690 	tsk->signal = sig;
1691 	if (!sig)
1692 		return -ENOMEM;
1693 
1694 	sig->nr_threads = 1;
1695 	atomic_set(&sig->live, 1);
1696 	refcount_set(&sig->sigcnt, 1);
1697 
1698 	/* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1699 	sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1700 	tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1701 
1702 	init_waitqueue_head(&sig->wait_chldexit);
1703 	sig->curr_target = tsk;
1704 	init_sigpending(&sig->shared_pending);
1705 	INIT_HLIST_HEAD(&sig->multiprocess);
1706 	seqlock_init(&sig->stats_lock);
1707 	prev_cputime_init(&sig->prev_cputime);
1708 
1709 #ifdef CONFIG_POSIX_TIMERS
1710 	INIT_LIST_HEAD(&sig->posix_timers);
1711 	hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1712 	sig->real_timer.function = it_real_fn;
1713 #endif
1714 
1715 	task_lock(current->group_leader);
1716 	memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1717 	task_unlock(current->group_leader);
1718 
1719 	posix_cpu_timers_init_group(sig);
1720 
1721 	tty_audit_fork(sig);
1722 	sched_autogroup_fork(sig);
1723 
1724 	sig->oom_score_adj = current->signal->oom_score_adj;
1725 	sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1726 
1727 	mutex_init(&sig->cred_guard_mutex);
1728 	init_rwsem(&sig->exec_update_lock);
1729 
1730 	return 0;
1731 }
1732 
1733 static void copy_seccomp(struct task_struct *p)
1734 {
1735 #ifdef CONFIG_SECCOMP
1736 	/*
1737 	 * Must be called with sighand->lock held, which is common to
1738 	 * all threads in the group. Holding cred_guard_mutex is not
1739 	 * needed because this new task is not yet running and cannot
1740 	 * be racing exec.
1741 	 */
1742 	assert_spin_locked(&current->sighand->siglock);
1743 
1744 	/* Ref-count the new filter user, and assign it. */
1745 	get_seccomp_filter(current);
1746 	p->seccomp = current->seccomp;
1747 
1748 	/*
1749 	 * Explicitly enable no_new_privs here in case it got set
1750 	 * between the task_struct being duplicated and holding the
1751 	 * sighand lock. The seccomp state and nnp must be in sync.
1752 	 */
1753 	if (task_no_new_privs(current))
1754 		task_set_no_new_privs(p);
1755 
1756 	/*
1757 	 * If the parent gained a seccomp mode after copying thread
1758 	 * flags and between before we held the sighand lock, we have
1759 	 * to manually enable the seccomp thread flag here.
1760 	 */
1761 	if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1762 		set_task_syscall_work(p, SECCOMP);
1763 #endif
1764 }
1765 
1766 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1767 {
1768 	current->clear_child_tid = tidptr;
1769 
1770 	return task_pid_vnr(current);
1771 }
1772 
1773 static void rt_mutex_init_task(struct task_struct *p)
1774 {
1775 	raw_spin_lock_init(&p->pi_lock);
1776 #ifdef CONFIG_RT_MUTEXES
1777 	p->pi_waiters = RB_ROOT_CACHED;
1778 	p->pi_top_task = NULL;
1779 	p->pi_blocked_on = NULL;
1780 #endif
1781 }
1782 
1783 static inline void init_task_pid_links(struct task_struct *task)
1784 {
1785 	enum pid_type type;
1786 
1787 	for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type)
1788 		INIT_HLIST_NODE(&task->pid_links[type]);
1789 }
1790 
1791 static inline void
1792 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1793 {
1794 	if (type == PIDTYPE_PID)
1795 		task->thread_pid = pid;
1796 	else
1797 		task->signal->pids[type] = pid;
1798 }
1799 
1800 static inline void rcu_copy_process(struct task_struct *p)
1801 {
1802 #ifdef CONFIG_PREEMPT_RCU
1803 	p->rcu_read_lock_nesting = 0;
1804 	p->rcu_read_unlock_special.s = 0;
1805 	p->rcu_blocked_node = NULL;
1806 	INIT_LIST_HEAD(&p->rcu_node_entry);
1807 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1808 #ifdef CONFIG_TASKS_RCU
1809 	p->rcu_tasks_holdout = false;
1810 	INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1811 	p->rcu_tasks_idle_cpu = -1;
1812 #endif /* #ifdef CONFIG_TASKS_RCU */
1813 #ifdef CONFIG_TASKS_TRACE_RCU
1814 	p->trc_reader_nesting = 0;
1815 	p->trc_reader_special.s = 0;
1816 	INIT_LIST_HEAD(&p->trc_holdout_list);
1817 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
1818 }
1819 
1820 struct pid *pidfd_pid(const struct file *file)
1821 {
1822 	if (file->f_op == &pidfd_fops)
1823 		return file->private_data;
1824 
1825 	return ERR_PTR(-EBADF);
1826 }
1827 
1828 static int pidfd_release(struct inode *inode, struct file *file)
1829 {
1830 	struct pid *pid = file->private_data;
1831 
1832 	file->private_data = NULL;
1833 	put_pid(pid);
1834 	return 0;
1835 }
1836 
1837 #ifdef CONFIG_PROC_FS
1838 /**
1839  * pidfd_show_fdinfo - print information about a pidfd
1840  * @m: proc fdinfo file
1841  * @f: file referencing a pidfd
1842  *
1843  * Pid:
1844  * This function will print the pid that a given pidfd refers to in the
1845  * pid namespace of the procfs instance.
1846  * If the pid namespace of the process is not a descendant of the pid
1847  * namespace of the procfs instance 0 will be shown as its pid. This is
1848  * similar to calling getppid() on a process whose parent is outside of
1849  * its pid namespace.
1850  *
1851  * NSpid:
1852  * If pid namespaces are supported then this function will also print
1853  * the pid of a given pidfd refers to for all descendant pid namespaces
1854  * starting from the current pid namespace of the instance, i.e. the
1855  * Pid field and the first entry in the NSpid field will be identical.
1856  * If the pid namespace of the process is not a descendant of the pid
1857  * namespace of the procfs instance 0 will be shown as its first NSpid
1858  * entry and no others will be shown.
1859  * Note that this differs from the Pid and NSpid fields in
1860  * /proc/<pid>/status where Pid and NSpid are always shown relative to
1861  * the  pid namespace of the procfs instance. The difference becomes
1862  * obvious when sending around a pidfd between pid namespaces from a
1863  * different branch of the tree, i.e. where no ancestral relation is
1864  * present between the pid namespaces:
1865  * - create two new pid namespaces ns1 and ns2 in the initial pid
1866  *   namespace (also take care to create new mount namespaces in the
1867  *   new pid namespace and mount procfs)
1868  * - create a process with a pidfd in ns1
1869  * - send pidfd from ns1 to ns2
1870  * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
1871  *   have exactly one entry, which is 0
1872  */
1873 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1874 {
1875 	struct pid *pid = f->private_data;
1876 	struct pid_namespace *ns;
1877 	pid_t nr = -1;
1878 
1879 	if (likely(pid_has_task(pid, PIDTYPE_PID))) {
1880 		ns = proc_pid_ns(file_inode(m->file)->i_sb);
1881 		nr = pid_nr_ns(pid, ns);
1882 	}
1883 
1884 	seq_put_decimal_ll(m, "Pid:\t", nr);
1885 
1886 #ifdef CONFIG_PID_NS
1887 	seq_put_decimal_ll(m, "\nNSpid:\t", nr);
1888 	if (nr > 0) {
1889 		int i;
1890 
1891 		/* If nr is non-zero it means that 'pid' is valid and that
1892 		 * ns, i.e. the pid namespace associated with the procfs
1893 		 * instance, is in the pid namespace hierarchy of pid.
1894 		 * Start at one below the already printed level.
1895 		 */
1896 		for (i = ns->level + 1; i <= pid->level; i++)
1897 			seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
1898 	}
1899 #endif
1900 	seq_putc(m, '\n');
1901 }
1902 #endif
1903 
1904 /*
1905  * Poll support for process exit notification.
1906  */
1907 static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
1908 {
1909 	struct pid *pid = file->private_data;
1910 	__poll_t poll_flags = 0;
1911 
1912 	poll_wait(file, &pid->wait_pidfd, pts);
1913 
1914 	/*
1915 	 * Inform pollers only when the whole thread group exits.
1916 	 * If the thread group leader exits before all other threads in the
1917 	 * group, then poll(2) should block, similar to the wait(2) family.
1918 	 */
1919 	if (thread_group_exited(pid))
1920 		poll_flags = EPOLLIN | EPOLLRDNORM;
1921 
1922 	return poll_flags;
1923 }
1924 
1925 const struct file_operations pidfd_fops = {
1926 	.release = pidfd_release,
1927 	.poll = pidfd_poll,
1928 #ifdef CONFIG_PROC_FS
1929 	.show_fdinfo = pidfd_show_fdinfo,
1930 #endif
1931 };
1932 
1933 static void __delayed_free_task(struct rcu_head *rhp)
1934 {
1935 	struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1936 
1937 	free_task(tsk);
1938 }
1939 
1940 static __always_inline void delayed_free_task(struct task_struct *tsk)
1941 {
1942 	if (IS_ENABLED(CONFIG_MEMCG))
1943 		call_rcu(&tsk->rcu, __delayed_free_task);
1944 	else
1945 		free_task(tsk);
1946 }
1947 
1948 static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk)
1949 {
1950 	/* Skip if kernel thread */
1951 	if (!tsk->mm)
1952 		return;
1953 
1954 	/* Skip if spawning a thread or using vfork */
1955 	if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) != CLONE_VM)
1956 		return;
1957 
1958 	/* We need to synchronize with __set_oom_adj */
1959 	mutex_lock(&oom_adj_mutex);
1960 	set_bit(MMF_MULTIPROCESS, &tsk->mm->flags);
1961 	/* Update the values in case they were changed after copy_signal */
1962 	tsk->signal->oom_score_adj = current->signal->oom_score_adj;
1963 	tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min;
1964 	mutex_unlock(&oom_adj_mutex);
1965 }
1966 
1967 #ifdef CONFIG_RV
1968 static void rv_task_fork(struct task_struct *p)
1969 {
1970 	int i;
1971 
1972 	for (i = 0; i < RV_PER_TASK_MONITORS; i++)
1973 		p->rv[i].da_mon.monitoring = false;
1974 }
1975 #else
1976 #define rv_task_fork(p) do {} while (0)
1977 #endif
1978 
1979 /*
1980  * This creates a new process as a copy of the old one,
1981  * but does not actually start it yet.
1982  *
1983  * It copies the registers, and all the appropriate
1984  * parts of the process environment (as per the clone
1985  * flags). The actual kick-off is left to the caller.
1986  */
1987 static __latent_entropy struct task_struct *copy_process(
1988 					struct pid *pid,
1989 					int trace,
1990 					int node,
1991 					struct kernel_clone_args *args)
1992 {
1993 	int pidfd = -1, retval;
1994 	struct task_struct *p;
1995 	struct multiprocess_signals delayed;
1996 	struct file *pidfile = NULL;
1997 	const u64 clone_flags = args->flags;
1998 	struct nsproxy *nsp = current->nsproxy;
1999 
2000 	/*
2001 	 * Don't allow sharing the root directory with processes in a different
2002 	 * namespace
2003 	 */
2004 	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
2005 		return ERR_PTR(-EINVAL);
2006 
2007 	if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
2008 		return ERR_PTR(-EINVAL);
2009 
2010 	/*
2011 	 * Thread groups must share signals as well, and detached threads
2012 	 * can only be started up within the thread group.
2013 	 */
2014 	if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
2015 		return ERR_PTR(-EINVAL);
2016 
2017 	/*
2018 	 * Shared signal handlers imply shared VM. By way of the above,
2019 	 * thread groups also imply shared VM. Blocking this case allows
2020 	 * for various simplifications in other code.
2021 	 */
2022 	if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
2023 		return ERR_PTR(-EINVAL);
2024 
2025 	/*
2026 	 * Siblings of global init remain as zombies on exit since they are
2027 	 * not reaped by their parent (swapper). To solve this and to avoid
2028 	 * multi-rooted process trees, prevent global and container-inits
2029 	 * from creating siblings.
2030 	 */
2031 	if ((clone_flags & CLONE_PARENT) &&
2032 				current->signal->flags & SIGNAL_UNKILLABLE)
2033 		return ERR_PTR(-EINVAL);
2034 
2035 	/*
2036 	 * If the new process will be in a different pid or user namespace
2037 	 * do not allow it to share a thread group with the forking task.
2038 	 */
2039 	if (clone_flags & CLONE_THREAD) {
2040 		if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
2041 		    (task_active_pid_ns(current) != nsp->pid_ns_for_children))
2042 			return ERR_PTR(-EINVAL);
2043 	}
2044 
2045 	/*
2046 	 * If the new process will be in a different time namespace
2047 	 * do not allow it to share VM or a thread group with the forking task.
2048 	 */
2049 	if (clone_flags & (CLONE_THREAD | CLONE_VM)) {
2050 		if (nsp->time_ns != nsp->time_ns_for_children)
2051 			return ERR_PTR(-EINVAL);
2052 	}
2053 
2054 	if (clone_flags & CLONE_PIDFD) {
2055 		/*
2056 		 * - CLONE_DETACHED is blocked so that we can potentially
2057 		 *   reuse it later for CLONE_PIDFD.
2058 		 * - CLONE_THREAD is blocked until someone really needs it.
2059 		 */
2060 		if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
2061 			return ERR_PTR(-EINVAL);
2062 	}
2063 
2064 	/*
2065 	 * Force any signals received before this point to be delivered
2066 	 * before the fork happens.  Collect up signals sent to multiple
2067 	 * processes that happen during the fork and delay them so that
2068 	 * they appear to happen after the fork.
2069 	 */
2070 	sigemptyset(&delayed.signal);
2071 	INIT_HLIST_NODE(&delayed.node);
2072 
2073 	spin_lock_irq(&current->sighand->siglock);
2074 	if (!(clone_flags & CLONE_THREAD))
2075 		hlist_add_head(&delayed.node, &current->signal->multiprocess);
2076 	recalc_sigpending();
2077 	spin_unlock_irq(&current->sighand->siglock);
2078 	retval = -ERESTARTNOINTR;
2079 	if (task_sigpending(current))
2080 		goto fork_out;
2081 
2082 	retval = -ENOMEM;
2083 	p = dup_task_struct(current, node);
2084 	if (!p)
2085 		goto fork_out;
2086 	p->flags &= ~PF_KTHREAD;
2087 	if (args->kthread)
2088 		p->flags |= PF_KTHREAD;
2089 	if (args->io_thread) {
2090 		/*
2091 		 * Mark us an IO worker, and block any signal that isn't
2092 		 * fatal or STOP
2093 		 */
2094 		p->flags |= PF_IO_WORKER;
2095 		siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
2096 	}
2097 
2098 	p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
2099 	/*
2100 	 * Clear TID on mm_release()?
2101 	 */
2102 	p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
2103 
2104 	ftrace_graph_init_task(p);
2105 
2106 	rt_mutex_init_task(p);
2107 
2108 	lockdep_assert_irqs_enabled();
2109 #ifdef CONFIG_PROVE_LOCKING
2110 	DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
2111 #endif
2112 	retval = copy_creds(p, clone_flags);
2113 	if (retval < 0)
2114 		goto bad_fork_free;
2115 
2116 	retval = -EAGAIN;
2117 	if (is_ucounts_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
2118 		if (p->real_cred->user != INIT_USER &&
2119 		    !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
2120 			goto bad_fork_cleanup_count;
2121 	}
2122 	current->flags &= ~PF_NPROC_EXCEEDED;
2123 
2124 	/*
2125 	 * If multiple threads are within copy_process(), then this check
2126 	 * triggers too late. This doesn't hurt, the check is only there
2127 	 * to stop root fork bombs.
2128 	 */
2129 	retval = -EAGAIN;
2130 	if (data_race(nr_threads >= max_threads))
2131 		goto bad_fork_cleanup_count;
2132 
2133 	delayacct_tsk_init(p);	/* Must remain after dup_task_struct() */
2134 	p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE | PF_NO_SETAFFINITY);
2135 	p->flags |= PF_FORKNOEXEC;
2136 	INIT_LIST_HEAD(&p->children);
2137 	INIT_LIST_HEAD(&p->sibling);
2138 	rcu_copy_process(p);
2139 	p->vfork_done = NULL;
2140 	spin_lock_init(&p->alloc_lock);
2141 
2142 	init_sigpending(&p->pending);
2143 
2144 	p->utime = p->stime = p->gtime = 0;
2145 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
2146 	p->utimescaled = p->stimescaled = 0;
2147 #endif
2148 	prev_cputime_init(&p->prev_cputime);
2149 
2150 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
2151 	seqcount_init(&p->vtime.seqcount);
2152 	p->vtime.starttime = 0;
2153 	p->vtime.state = VTIME_INACTIVE;
2154 #endif
2155 
2156 #ifdef CONFIG_IO_URING
2157 	p->io_uring = NULL;
2158 #endif
2159 
2160 #if defined(SPLIT_RSS_COUNTING)
2161 	memset(&p->rss_stat, 0, sizeof(p->rss_stat));
2162 #endif
2163 
2164 	p->default_timer_slack_ns = current->timer_slack_ns;
2165 
2166 #ifdef CONFIG_PSI
2167 	p->psi_flags = 0;
2168 #endif
2169 
2170 	task_io_accounting_init(&p->ioac);
2171 	acct_clear_integrals(p);
2172 
2173 	posix_cputimers_init(&p->posix_cputimers);
2174 
2175 	p->io_context = NULL;
2176 	audit_set_context(p, NULL);
2177 	cgroup_fork(p);
2178 	if (args->kthread) {
2179 		if (!set_kthread_struct(p))
2180 			goto bad_fork_cleanup_delayacct;
2181 	}
2182 #ifdef CONFIG_NUMA
2183 	p->mempolicy = mpol_dup(p->mempolicy);
2184 	if (IS_ERR(p->mempolicy)) {
2185 		retval = PTR_ERR(p->mempolicy);
2186 		p->mempolicy = NULL;
2187 		goto bad_fork_cleanup_delayacct;
2188 	}
2189 #endif
2190 #ifdef CONFIG_CPUSETS
2191 	p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
2192 	p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
2193 	seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock);
2194 #endif
2195 #ifdef CONFIG_TRACE_IRQFLAGS
2196 	memset(&p->irqtrace, 0, sizeof(p->irqtrace));
2197 	p->irqtrace.hardirq_disable_ip	= _THIS_IP_;
2198 	p->irqtrace.softirq_enable_ip	= _THIS_IP_;
2199 	p->softirqs_enabled		= 1;
2200 	p->softirq_context		= 0;
2201 #endif
2202 
2203 	p->pagefault_disabled = 0;
2204 
2205 #ifdef CONFIG_LOCKDEP
2206 	lockdep_init_task(p);
2207 #endif
2208 
2209 #ifdef CONFIG_DEBUG_MUTEXES
2210 	p->blocked_on = NULL; /* not blocked yet */
2211 #endif
2212 #ifdef CONFIG_BCACHE
2213 	p->sequential_io	= 0;
2214 	p->sequential_io_avg	= 0;
2215 #endif
2216 #ifdef CONFIG_BPF_SYSCALL
2217 	RCU_INIT_POINTER(p->bpf_storage, NULL);
2218 	p->bpf_ctx = NULL;
2219 #endif
2220 
2221 	/* Perform scheduler related setup. Assign this task to a CPU. */
2222 	retval = sched_fork(clone_flags, p);
2223 	if (retval)
2224 		goto bad_fork_cleanup_policy;
2225 
2226 	retval = perf_event_init_task(p, clone_flags);
2227 	if (retval)
2228 		goto bad_fork_cleanup_policy;
2229 	retval = audit_alloc(p);
2230 	if (retval)
2231 		goto bad_fork_cleanup_perf;
2232 	/* copy all the process information */
2233 	shm_init_task(p);
2234 	retval = security_task_alloc(p, clone_flags);
2235 	if (retval)
2236 		goto bad_fork_cleanup_audit;
2237 	retval = copy_semundo(clone_flags, p);
2238 	if (retval)
2239 		goto bad_fork_cleanup_security;
2240 	retval = copy_files(clone_flags, p);
2241 	if (retval)
2242 		goto bad_fork_cleanup_semundo;
2243 	retval = copy_fs(clone_flags, p);
2244 	if (retval)
2245 		goto bad_fork_cleanup_files;
2246 	retval = copy_sighand(clone_flags, p);
2247 	if (retval)
2248 		goto bad_fork_cleanup_fs;
2249 	retval = copy_signal(clone_flags, p);
2250 	if (retval)
2251 		goto bad_fork_cleanup_sighand;
2252 	retval = copy_mm(clone_flags, p);
2253 	if (retval)
2254 		goto bad_fork_cleanup_signal;
2255 	retval = copy_namespaces(clone_flags, p);
2256 	if (retval)
2257 		goto bad_fork_cleanup_mm;
2258 	retval = copy_io(clone_flags, p);
2259 	if (retval)
2260 		goto bad_fork_cleanup_namespaces;
2261 	retval = copy_thread(p, args);
2262 	if (retval)
2263 		goto bad_fork_cleanup_io;
2264 
2265 	stackleak_task_init(p);
2266 
2267 	if (pid != &init_struct_pid) {
2268 		pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
2269 				args->set_tid_size);
2270 		if (IS_ERR(pid)) {
2271 			retval = PTR_ERR(pid);
2272 			goto bad_fork_cleanup_thread;
2273 		}
2274 	}
2275 
2276 	/*
2277 	 * This has to happen after we've potentially unshared the file
2278 	 * descriptor table (so that the pidfd doesn't leak into the child
2279 	 * if the fd table isn't shared).
2280 	 */
2281 	if (clone_flags & CLONE_PIDFD) {
2282 		retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2283 		if (retval < 0)
2284 			goto bad_fork_free_pid;
2285 
2286 		pidfd = retval;
2287 
2288 		pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2289 					      O_RDWR | O_CLOEXEC);
2290 		if (IS_ERR(pidfile)) {
2291 			put_unused_fd(pidfd);
2292 			retval = PTR_ERR(pidfile);
2293 			goto bad_fork_free_pid;
2294 		}
2295 		get_pid(pid);	/* held by pidfile now */
2296 
2297 		retval = put_user(pidfd, args->pidfd);
2298 		if (retval)
2299 			goto bad_fork_put_pidfd;
2300 	}
2301 
2302 #ifdef CONFIG_BLOCK
2303 	p->plug = NULL;
2304 #endif
2305 	futex_init_task(p);
2306 
2307 	/*
2308 	 * sigaltstack should be cleared when sharing the same VM
2309 	 */
2310 	if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2311 		sas_ss_reset(p);
2312 
2313 	/*
2314 	 * Syscall tracing and stepping should be turned off in the
2315 	 * child regardless of CLONE_PTRACE.
2316 	 */
2317 	user_disable_single_step(p);
2318 	clear_task_syscall_work(p, SYSCALL_TRACE);
2319 #if defined(CONFIG_GENERIC_ENTRY) || defined(TIF_SYSCALL_EMU)
2320 	clear_task_syscall_work(p, SYSCALL_EMU);
2321 #endif
2322 	clear_tsk_latency_tracing(p);
2323 
2324 	/* ok, now we should be set up.. */
2325 	p->pid = pid_nr(pid);
2326 	if (clone_flags & CLONE_THREAD) {
2327 		p->group_leader = current->group_leader;
2328 		p->tgid = current->tgid;
2329 	} else {
2330 		p->group_leader = p;
2331 		p->tgid = p->pid;
2332 	}
2333 
2334 	p->nr_dirtied = 0;
2335 	p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2336 	p->dirty_paused_when = 0;
2337 
2338 	p->pdeath_signal = 0;
2339 	INIT_LIST_HEAD(&p->thread_group);
2340 	p->task_works = NULL;
2341 	clear_posix_cputimers_work(p);
2342 
2343 #ifdef CONFIG_KRETPROBES
2344 	p->kretprobe_instances.first = NULL;
2345 #endif
2346 #ifdef CONFIG_RETHOOK
2347 	p->rethooks.first = NULL;
2348 #endif
2349 
2350 	/*
2351 	 * Ensure that the cgroup subsystem policies allow the new process to be
2352 	 * forked. It should be noted that the new process's css_set can be changed
2353 	 * between here and cgroup_post_fork() if an organisation operation is in
2354 	 * progress.
2355 	 */
2356 	retval = cgroup_can_fork(p, args);
2357 	if (retval)
2358 		goto bad_fork_put_pidfd;
2359 
2360 	/*
2361 	 * Now that the cgroups are pinned, re-clone the parent cgroup and put
2362 	 * the new task on the correct runqueue. All this *before* the task
2363 	 * becomes visible.
2364 	 *
2365 	 * This isn't part of ->can_fork() because while the re-cloning is
2366 	 * cgroup specific, it unconditionally needs to place the task on a
2367 	 * runqueue.
2368 	 */
2369 	sched_cgroup_fork(p, args);
2370 
2371 	/*
2372 	 * From this point on we must avoid any synchronous user-space
2373 	 * communication until we take the tasklist-lock. In particular, we do
2374 	 * not want user-space to be able to predict the process start-time by
2375 	 * stalling fork(2) after we recorded the start_time but before it is
2376 	 * visible to the system.
2377 	 */
2378 
2379 	p->start_time = ktime_get_ns();
2380 	p->start_boottime = ktime_get_boottime_ns();
2381 
2382 	/*
2383 	 * Make it visible to the rest of the system, but dont wake it up yet.
2384 	 * Need tasklist lock for parent etc handling!
2385 	 */
2386 	write_lock_irq(&tasklist_lock);
2387 
2388 	/* CLONE_PARENT re-uses the old parent */
2389 	if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2390 		p->real_parent = current->real_parent;
2391 		p->parent_exec_id = current->parent_exec_id;
2392 		if (clone_flags & CLONE_THREAD)
2393 			p->exit_signal = -1;
2394 		else
2395 			p->exit_signal = current->group_leader->exit_signal;
2396 	} else {
2397 		p->real_parent = current;
2398 		p->parent_exec_id = current->self_exec_id;
2399 		p->exit_signal = args->exit_signal;
2400 	}
2401 
2402 	klp_copy_process(p);
2403 
2404 	sched_core_fork(p);
2405 
2406 	spin_lock(&current->sighand->siglock);
2407 
2408 	/*
2409 	 * Copy seccomp details explicitly here, in case they were changed
2410 	 * before holding sighand lock.
2411 	 */
2412 	copy_seccomp(p);
2413 
2414 	rv_task_fork(p);
2415 
2416 	rseq_fork(p, clone_flags);
2417 
2418 	/* Don't start children in a dying pid namespace */
2419 	if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2420 		retval = -ENOMEM;
2421 		goto bad_fork_cancel_cgroup;
2422 	}
2423 
2424 	/* Let kill terminate clone/fork in the middle */
2425 	if (fatal_signal_pending(current)) {
2426 		retval = -EINTR;
2427 		goto bad_fork_cancel_cgroup;
2428 	}
2429 
2430 	init_task_pid_links(p);
2431 	if (likely(p->pid)) {
2432 		ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2433 
2434 		init_task_pid(p, PIDTYPE_PID, pid);
2435 		if (thread_group_leader(p)) {
2436 			init_task_pid(p, PIDTYPE_TGID, pid);
2437 			init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2438 			init_task_pid(p, PIDTYPE_SID, task_session(current));
2439 
2440 			if (is_child_reaper(pid)) {
2441 				ns_of_pid(pid)->child_reaper = p;
2442 				p->signal->flags |= SIGNAL_UNKILLABLE;
2443 			}
2444 			p->signal->shared_pending.signal = delayed.signal;
2445 			p->signal->tty = tty_kref_get(current->signal->tty);
2446 			/*
2447 			 * Inherit has_child_subreaper flag under the same
2448 			 * tasklist_lock with adding child to the process tree
2449 			 * for propagate_has_child_subreaper optimization.
2450 			 */
2451 			p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2452 							 p->real_parent->signal->is_child_subreaper;
2453 			list_add_tail(&p->sibling, &p->real_parent->children);
2454 			list_add_tail_rcu(&p->tasks, &init_task.tasks);
2455 			attach_pid(p, PIDTYPE_TGID);
2456 			attach_pid(p, PIDTYPE_PGID);
2457 			attach_pid(p, PIDTYPE_SID);
2458 			__this_cpu_inc(process_counts);
2459 		} else {
2460 			current->signal->nr_threads++;
2461 			atomic_inc(&current->signal->live);
2462 			refcount_inc(&current->signal->sigcnt);
2463 			task_join_group_stop(p);
2464 			list_add_tail_rcu(&p->thread_group,
2465 					  &p->group_leader->thread_group);
2466 			list_add_tail_rcu(&p->thread_node,
2467 					  &p->signal->thread_head);
2468 		}
2469 		attach_pid(p, PIDTYPE_PID);
2470 		nr_threads++;
2471 	}
2472 	total_forks++;
2473 	hlist_del_init(&delayed.node);
2474 	spin_unlock(&current->sighand->siglock);
2475 	syscall_tracepoint_update(p);
2476 	write_unlock_irq(&tasklist_lock);
2477 
2478 	if (pidfile)
2479 		fd_install(pidfd, pidfile);
2480 
2481 	proc_fork_connector(p);
2482 	sched_post_fork(p);
2483 	cgroup_post_fork(p, args);
2484 	perf_event_fork(p);
2485 
2486 	trace_task_newtask(p, clone_flags);
2487 	uprobe_copy_process(p, clone_flags);
2488 
2489 	copy_oom_score_adj(clone_flags, p);
2490 
2491 	return p;
2492 
2493 bad_fork_cancel_cgroup:
2494 	sched_core_free(p);
2495 	spin_unlock(&current->sighand->siglock);
2496 	write_unlock_irq(&tasklist_lock);
2497 	cgroup_cancel_fork(p, args);
2498 bad_fork_put_pidfd:
2499 	if (clone_flags & CLONE_PIDFD) {
2500 		fput(pidfile);
2501 		put_unused_fd(pidfd);
2502 	}
2503 bad_fork_free_pid:
2504 	if (pid != &init_struct_pid)
2505 		free_pid(pid);
2506 bad_fork_cleanup_thread:
2507 	exit_thread(p);
2508 bad_fork_cleanup_io:
2509 	if (p->io_context)
2510 		exit_io_context(p);
2511 bad_fork_cleanup_namespaces:
2512 	exit_task_namespaces(p);
2513 bad_fork_cleanup_mm:
2514 	if (p->mm) {
2515 		mm_clear_owner(p->mm, p);
2516 		mmput(p->mm);
2517 	}
2518 bad_fork_cleanup_signal:
2519 	if (!(clone_flags & CLONE_THREAD))
2520 		free_signal_struct(p->signal);
2521 bad_fork_cleanup_sighand:
2522 	__cleanup_sighand(p->sighand);
2523 bad_fork_cleanup_fs:
2524 	exit_fs(p); /* blocking */
2525 bad_fork_cleanup_files:
2526 	exit_files(p); /* blocking */
2527 bad_fork_cleanup_semundo:
2528 	exit_sem(p);
2529 bad_fork_cleanup_security:
2530 	security_task_free(p);
2531 bad_fork_cleanup_audit:
2532 	audit_free(p);
2533 bad_fork_cleanup_perf:
2534 	perf_event_free_task(p);
2535 bad_fork_cleanup_policy:
2536 	lockdep_free_task(p);
2537 #ifdef CONFIG_NUMA
2538 	mpol_put(p->mempolicy);
2539 #endif
2540 bad_fork_cleanup_delayacct:
2541 	delayacct_tsk_free(p);
2542 bad_fork_cleanup_count:
2543 	dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
2544 	exit_creds(p);
2545 bad_fork_free:
2546 	WRITE_ONCE(p->__state, TASK_DEAD);
2547 	exit_task_stack_account(p);
2548 	put_task_stack(p);
2549 	delayed_free_task(p);
2550 fork_out:
2551 	spin_lock_irq(&current->sighand->siglock);
2552 	hlist_del_init(&delayed.node);
2553 	spin_unlock_irq(&current->sighand->siglock);
2554 	return ERR_PTR(retval);
2555 }
2556 
2557 static inline void init_idle_pids(struct task_struct *idle)
2558 {
2559 	enum pid_type type;
2560 
2561 	for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2562 		INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2563 		init_task_pid(idle, type, &init_struct_pid);
2564 	}
2565 }
2566 
2567 static int idle_dummy(void *dummy)
2568 {
2569 	/* This function is never called */
2570 	return 0;
2571 }
2572 
2573 struct task_struct * __init fork_idle(int cpu)
2574 {
2575 	struct task_struct *task;
2576 	struct kernel_clone_args args = {
2577 		.flags		= CLONE_VM,
2578 		.fn		= &idle_dummy,
2579 		.fn_arg		= NULL,
2580 		.kthread	= 1,
2581 		.idle		= 1,
2582 	};
2583 
2584 	task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2585 	if (!IS_ERR(task)) {
2586 		init_idle_pids(task);
2587 		init_idle(task, cpu);
2588 	}
2589 
2590 	return task;
2591 }
2592 
2593 struct mm_struct *copy_init_mm(void)
2594 {
2595 	return dup_mm(NULL, &init_mm);
2596 }
2597 
2598 /*
2599  * This is like kernel_clone(), but shaved down and tailored to just
2600  * creating io_uring workers. It returns a created task, or an error pointer.
2601  * The returned task is inactive, and the caller must fire it up through
2602  * wake_up_new_task(p). All signals are blocked in the created task.
2603  */
2604 struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
2605 {
2606 	unsigned long flags = CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|
2607 				CLONE_IO;
2608 	struct kernel_clone_args args = {
2609 		.flags		= ((lower_32_bits(flags) | CLONE_VM |
2610 				    CLONE_UNTRACED) & ~CSIGNAL),
2611 		.exit_signal	= (lower_32_bits(flags) & CSIGNAL),
2612 		.fn		= fn,
2613 		.fn_arg		= arg,
2614 		.io_thread	= 1,
2615 	};
2616 
2617 	return copy_process(NULL, 0, node, &args);
2618 }
2619 
2620 /*
2621  *  Ok, this is the main fork-routine.
2622  *
2623  * It copies the process, and if successful kick-starts
2624  * it and waits for it to finish using the VM if required.
2625  *
2626  * args->exit_signal is expected to be checked for sanity by the caller.
2627  */
2628 pid_t kernel_clone(struct kernel_clone_args *args)
2629 {
2630 	u64 clone_flags = args->flags;
2631 	struct completion vfork;
2632 	struct pid *pid;
2633 	struct task_struct *p;
2634 	int trace = 0;
2635 	pid_t nr;
2636 
2637 	/*
2638 	 * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
2639 	 * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
2640 	 * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
2641 	 * field in struct clone_args and it still doesn't make sense to have
2642 	 * them both point at the same memory location. Performing this check
2643 	 * here has the advantage that we don't need to have a separate helper
2644 	 * to check for legacy clone().
2645 	 */
2646 	if ((args->flags & CLONE_PIDFD) &&
2647 	    (args->flags & CLONE_PARENT_SETTID) &&
2648 	    (args->pidfd == args->parent_tid))
2649 		return -EINVAL;
2650 
2651 	/*
2652 	 * Determine whether and which event to report to ptracer.  When
2653 	 * called from kernel_thread or CLONE_UNTRACED is explicitly
2654 	 * requested, no event is reported; otherwise, report if the event
2655 	 * for the type of forking is enabled.
2656 	 */
2657 	if (!(clone_flags & CLONE_UNTRACED)) {
2658 		if (clone_flags & CLONE_VFORK)
2659 			trace = PTRACE_EVENT_VFORK;
2660 		else if (args->exit_signal != SIGCHLD)
2661 			trace = PTRACE_EVENT_CLONE;
2662 		else
2663 			trace = PTRACE_EVENT_FORK;
2664 
2665 		if (likely(!ptrace_event_enabled(current, trace)))
2666 			trace = 0;
2667 	}
2668 
2669 	p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2670 	add_latent_entropy();
2671 
2672 	if (IS_ERR(p))
2673 		return PTR_ERR(p);
2674 
2675 	/*
2676 	 * Do this prior waking up the new thread - the thread pointer
2677 	 * might get invalid after that point, if the thread exits quickly.
2678 	 */
2679 	trace_sched_process_fork(current, p);
2680 
2681 	pid = get_task_pid(p, PIDTYPE_PID);
2682 	nr = pid_vnr(pid);
2683 
2684 	if (clone_flags & CLONE_PARENT_SETTID)
2685 		put_user(nr, args->parent_tid);
2686 
2687 	if (clone_flags & CLONE_VFORK) {
2688 		p->vfork_done = &vfork;
2689 		init_completion(&vfork);
2690 		get_task_struct(p);
2691 	}
2692 
2693 	wake_up_new_task(p);
2694 
2695 	/* forking complete and child started to run, tell ptracer */
2696 	if (unlikely(trace))
2697 		ptrace_event_pid(trace, pid);
2698 
2699 	if (clone_flags & CLONE_VFORK) {
2700 		if (!wait_for_vfork_done(p, &vfork))
2701 			ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2702 	}
2703 
2704 	put_pid(pid);
2705 	return nr;
2706 }
2707 
2708 /*
2709  * Create a kernel thread.
2710  */
2711 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2712 {
2713 	struct kernel_clone_args args = {
2714 		.flags		= ((lower_32_bits(flags) | CLONE_VM |
2715 				    CLONE_UNTRACED) & ~CSIGNAL),
2716 		.exit_signal	= (lower_32_bits(flags) & CSIGNAL),
2717 		.fn		= fn,
2718 		.fn_arg		= arg,
2719 		.kthread	= 1,
2720 	};
2721 
2722 	return kernel_clone(&args);
2723 }
2724 
2725 /*
2726  * Create a user mode thread.
2727  */
2728 pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags)
2729 {
2730 	struct kernel_clone_args args = {
2731 		.flags		= ((lower_32_bits(flags) | CLONE_VM |
2732 				    CLONE_UNTRACED) & ~CSIGNAL),
2733 		.exit_signal	= (lower_32_bits(flags) & CSIGNAL),
2734 		.fn		= fn,
2735 		.fn_arg		= arg,
2736 	};
2737 
2738 	return kernel_clone(&args);
2739 }
2740 
2741 #ifdef __ARCH_WANT_SYS_FORK
2742 SYSCALL_DEFINE0(fork)
2743 {
2744 #ifdef CONFIG_MMU
2745 	struct kernel_clone_args args = {
2746 		.exit_signal = SIGCHLD,
2747 	};
2748 
2749 	return kernel_clone(&args);
2750 #else
2751 	/* can not support in nommu mode */
2752 	return -EINVAL;
2753 #endif
2754 }
2755 #endif
2756 
2757 #ifdef __ARCH_WANT_SYS_VFORK
2758 SYSCALL_DEFINE0(vfork)
2759 {
2760 	struct kernel_clone_args args = {
2761 		.flags		= CLONE_VFORK | CLONE_VM,
2762 		.exit_signal	= SIGCHLD,
2763 	};
2764 
2765 	return kernel_clone(&args);
2766 }
2767 #endif
2768 
2769 #ifdef __ARCH_WANT_SYS_CLONE
2770 #ifdef CONFIG_CLONE_BACKWARDS
2771 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2772 		 int __user *, parent_tidptr,
2773 		 unsigned long, tls,
2774 		 int __user *, child_tidptr)
2775 #elif defined(CONFIG_CLONE_BACKWARDS2)
2776 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2777 		 int __user *, parent_tidptr,
2778 		 int __user *, child_tidptr,
2779 		 unsigned long, tls)
2780 #elif defined(CONFIG_CLONE_BACKWARDS3)
2781 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2782 		int, stack_size,
2783 		int __user *, parent_tidptr,
2784 		int __user *, child_tidptr,
2785 		unsigned long, tls)
2786 #else
2787 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2788 		 int __user *, parent_tidptr,
2789 		 int __user *, child_tidptr,
2790 		 unsigned long, tls)
2791 #endif
2792 {
2793 	struct kernel_clone_args args = {
2794 		.flags		= (lower_32_bits(clone_flags) & ~CSIGNAL),
2795 		.pidfd		= parent_tidptr,
2796 		.child_tid	= child_tidptr,
2797 		.parent_tid	= parent_tidptr,
2798 		.exit_signal	= (lower_32_bits(clone_flags) & CSIGNAL),
2799 		.stack		= newsp,
2800 		.tls		= tls,
2801 	};
2802 
2803 	return kernel_clone(&args);
2804 }
2805 #endif
2806 
2807 #ifdef __ARCH_WANT_SYS_CLONE3
2808 
2809 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
2810 					      struct clone_args __user *uargs,
2811 					      size_t usize)
2812 {
2813 	int err;
2814 	struct clone_args args;
2815 	pid_t *kset_tid = kargs->set_tid;
2816 
2817 	BUILD_BUG_ON(offsetofend(struct clone_args, tls) !=
2818 		     CLONE_ARGS_SIZE_VER0);
2819 	BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) !=
2820 		     CLONE_ARGS_SIZE_VER1);
2821 	BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
2822 		     CLONE_ARGS_SIZE_VER2);
2823 	BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
2824 
2825 	if (unlikely(usize > PAGE_SIZE))
2826 		return -E2BIG;
2827 	if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
2828 		return -EINVAL;
2829 
2830 	err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
2831 	if (err)
2832 		return err;
2833 
2834 	if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
2835 		return -EINVAL;
2836 
2837 	if (unlikely(!args.set_tid && args.set_tid_size > 0))
2838 		return -EINVAL;
2839 
2840 	if (unlikely(args.set_tid && args.set_tid_size == 0))
2841 		return -EINVAL;
2842 
2843 	/*
2844 	 * Verify that higher 32bits of exit_signal are unset and that
2845 	 * it is a valid signal
2846 	 */
2847 	if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
2848 		     !valid_signal(args.exit_signal)))
2849 		return -EINVAL;
2850 
2851 	if ((args.flags & CLONE_INTO_CGROUP) &&
2852 	    (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2))
2853 		return -EINVAL;
2854 
2855 	*kargs = (struct kernel_clone_args){
2856 		.flags		= args.flags,
2857 		.pidfd		= u64_to_user_ptr(args.pidfd),
2858 		.child_tid	= u64_to_user_ptr(args.child_tid),
2859 		.parent_tid	= u64_to_user_ptr(args.parent_tid),
2860 		.exit_signal	= args.exit_signal,
2861 		.stack		= args.stack,
2862 		.stack_size	= args.stack_size,
2863 		.tls		= args.tls,
2864 		.set_tid_size	= args.set_tid_size,
2865 		.cgroup		= args.cgroup,
2866 	};
2867 
2868 	if (args.set_tid &&
2869 		copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
2870 			(kargs->set_tid_size * sizeof(pid_t))))
2871 		return -EFAULT;
2872 
2873 	kargs->set_tid = kset_tid;
2874 
2875 	return 0;
2876 }
2877 
2878 /**
2879  * clone3_stack_valid - check and prepare stack
2880  * @kargs: kernel clone args
2881  *
2882  * Verify that the stack arguments userspace gave us are sane.
2883  * In addition, set the stack direction for userspace since it's easy for us to
2884  * determine.
2885  */
2886 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
2887 {
2888 	if (kargs->stack == 0) {
2889 		if (kargs->stack_size > 0)
2890 			return false;
2891 	} else {
2892 		if (kargs->stack_size == 0)
2893 			return false;
2894 
2895 		if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
2896 			return false;
2897 
2898 #if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
2899 		kargs->stack += kargs->stack_size;
2900 #endif
2901 	}
2902 
2903 	return true;
2904 }
2905 
2906 static bool clone3_args_valid(struct kernel_clone_args *kargs)
2907 {
2908 	/* Verify that no unknown flags are passed along. */
2909 	if (kargs->flags &
2910 	    ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP))
2911 		return false;
2912 
2913 	/*
2914 	 * - make the CLONE_DETACHED bit reusable for clone3
2915 	 * - make the CSIGNAL bits reusable for clone3
2916 	 */
2917 	if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
2918 		return false;
2919 
2920 	if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
2921 	    (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
2922 		return false;
2923 
2924 	if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
2925 	    kargs->exit_signal)
2926 		return false;
2927 
2928 	if (!clone3_stack_valid(kargs))
2929 		return false;
2930 
2931 	return true;
2932 }
2933 
2934 /**
2935  * clone3 - create a new process with specific properties
2936  * @uargs: argument structure
2937  * @size:  size of @uargs
2938  *
2939  * clone3() is the extensible successor to clone()/clone2().
2940  * It takes a struct as argument that is versioned by its size.
2941  *
2942  * Return: On success, a positive PID for the child process.
2943  *         On error, a negative errno number.
2944  */
2945 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
2946 {
2947 	int err;
2948 
2949 	struct kernel_clone_args kargs;
2950 	pid_t set_tid[MAX_PID_NS_LEVEL];
2951 
2952 	kargs.set_tid = set_tid;
2953 
2954 	err = copy_clone_args_from_user(&kargs, uargs, size);
2955 	if (err)
2956 		return err;
2957 
2958 	if (!clone3_args_valid(&kargs))
2959 		return -EINVAL;
2960 
2961 	return kernel_clone(&kargs);
2962 }
2963 #endif
2964 
2965 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2966 {
2967 	struct task_struct *leader, *parent, *child;
2968 	int res;
2969 
2970 	read_lock(&tasklist_lock);
2971 	leader = top = top->group_leader;
2972 down:
2973 	for_each_thread(leader, parent) {
2974 		list_for_each_entry(child, &parent->children, sibling) {
2975 			res = visitor(child, data);
2976 			if (res) {
2977 				if (res < 0)
2978 					goto out;
2979 				leader = child;
2980 				goto down;
2981 			}
2982 up:
2983 			;
2984 		}
2985 	}
2986 
2987 	if (leader != top) {
2988 		child = leader;
2989 		parent = child->real_parent;
2990 		leader = parent->group_leader;
2991 		goto up;
2992 	}
2993 out:
2994 	read_unlock(&tasklist_lock);
2995 }
2996 
2997 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2998 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2999 #endif
3000 
3001 static void sighand_ctor(void *data)
3002 {
3003 	struct sighand_struct *sighand = data;
3004 
3005 	spin_lock_init(&sighand->siglock);
3006 	init_waitqueue_head(&sighand->signalfd_wqh);
3007 }
3008 
3009 void __init proc_caches_init(void)
3010 {
3011 	unsigned int mm_size;
3012 
3013 	sighand_cachep = kmem_cache_create("sighand_cache",
3014 			sizeof(struct sighand_struct), 0,
3015 			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
3016 			SLAB_ACCOUNT, sighand_ctor);
3017 	signal_cachep = kmem_cache_create("signal_cache",
3018 			sizeof(struct signal_struct), 0,
3019 			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3020 			NULL);
3021 	files_cachep = kmem_cache_create("files_cache",
3022 			sizeof(struct files_struct), 0,
3023 			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3024 			NULL);
3025 	fs_cachep = kmem_cache_create("fs_cache",
3026 			sizeof(struct fs_struct), 0,
3027 			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3028 			NULL);
3029 
3030 	/*
3031 	 * The mm_cpumask is located at the end of mm_struct, and is
3032 	 * dynamically sized based on the maximum CPU number this system
3033 	 * can have, taking hotplug into account (nr_cpu_ids).
3034 	 */
3035 	mm_size = sizeof(struct mm_struct) + cpumask_size();
3036 
3037 	mm_cachep = kmem_cache_create_usercopy("mm_struct",
3038 			mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
3039 			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3040 			offsetof(struct mm_struct, saved_auxv),
3041 			sizeof_field(struct mm_struct, saved_auxv),
3042 			NULL);
3043 	vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
3044 	mmap_init();
3045 	nsproxy_cache_init();
3046 }
3047 
3048 /*
3049  * Check constraints on flags passed to the unshare system call.
3050  */
3051 static int check_unshare_flags(unsigned long unshare_flags)
3052 {
3053 	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
3054 				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
3055 				CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
3056 				CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP|
3057 				CLONE_NEWTIME))
3058 		return -EINVAL;
3059 	/*
3060 	 * Not implemented, but pretend it works if there is nothing
3061 	 * to unshare.  Note that unsharing the address space or the
3062 	 * signal handlers also need to unshare the signal queues (aka
3063 	 * CLONE_THREAD).
3064 	 */
3065 	if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
3066 		if (!thread_group_empty(current))
3067 			return -EINVAL;
3068 	}
3069 	if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
3070 		if (refcount_read(&current->sighand->count) > 1)
3071 			return -EINVAL;
3072 	}
3073 	if (unshare_flags & CLONE_VM) {
3074 		if (!current_is_single_threaded())
3075 			return -EINVAL;
3076 	}
3077 
3078 	return 0;
3079 }
3080 
3081 /*
3082  * Unshare the filesystem structure if it is being shared
3083  */
3084 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
3085 {
3086 	struct fs_struct *fs = current->fs;
3087 
3088 	if (!(unshare_flags & CLONE_FS) || !fs)
3089 		return 0;
3090 
3091 	/* don't need lock here; in the worst case we'll do useless copy */
3092 	if (fs->users == 1)
3093 		return 0;
3094 
3095 	*new_fsp = copy_fs_struct(fs);
3096 	if (!*new_fsp)
3097 		return -ENOMEM;
3098 
3099 	return 0;
3100 }
3101 
3102 /*
3103  * Unshare file descriptor table if it is being shared
3104  */
3105 int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
3106 	       struct files_struct **new_fdp)
3107 {
3108 	struct files_struct *fd = current->files;
3109 	int error = 0;
3110 
3111 	if ((unshare_flags & CLONE_FILES) &&
3112 	    (fd && atomic_read(&fd->count) > 1)) {
3113 		*new_fdp = dup_fd(fd, max_fds, &error);
3114 		if (!*new_fdp)
3115 			return error;
3116 	}
3117 
3118 	return 0;
3119 }
3120 
3121 /*
3122  * unshare allows a process to 'unshare' part of the process
3123  * context which was originally shared using clone.  copy_*
3124  * functions used by kernel_clone() cannot be used here directly
3125  * because they modify an inactive task_struct that is being
3126  * constructed. Here we are modifying the current, active,
3127  * task_struct.
3128  */
3129 int ksys_unshare(unsigned long unshare_flags)
3130 {
3131 	struct fs_struct *fs, *new_fs = NULL;
3132 	struct files_struct *new_fd = NULL;
3133 	struct cred *new_cred = NULL;
3134 	struct nsproxy *new_nsproxy = NULL;
3135 	int do_sysvsem = 0;
3136 	int err;
3137 
3138 	/*
3139 	 * If unsharing a user namespace must also unshare the thread group
3140 	 * and unshare the filesystem root and working directories.
3141 	 */
3142 	if (unshare_flags & CLONE_NEWUSER)
3143 		unshare_flags |= CLONE_THREAD | CLONE_FS;
3144 	/*
3145 	 * If unsharing vm, must also unshare signal handlers.
3146 	 */
3147 	if (unshare_flags & CLONE_VM)
3148 		unshare_flags |= CLONE_SIGHAND;
3149 	/*
3150 	 * If unsharing a signal handlers, must also unshare the signal queues.
3151 	 */
3152 	if (unshare_flags & CLONE_SIGHAND)
3153 		unshare_flags |= CLONE_THREAD;
3154 	/*
3155 	 * If unsharing namespace, must also unshare filesystem information.
3156 	 */
3157 	if (unshare_flags & CLONE_NEWNS)
3158 		unshare_flags |= CLONE_FS;
3159 
3160 	err = check_unshare_flags(unshare_flags);
3161 	if (err)
3162 		goto bad_unshare_out;
3163 	/*
3164 	 * CLONE_NEWIPC must also detach from the undolist: after switching
3165 	 * to a new ipc namespace, the semaphore arrays from the old
3166 	 * namespace are unreachable.
3167 	 */
3168 	if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
3169 		do_sysvsem = 1;
3170 	err = unshare_fs(unshare_flags, &new_fs);
3171 	if (err)
3172 		goto bad_unshare_out;
3173 	err = unshare_fd(unshare_flags, NR_OPEN_MAX, &new_fd);
3174 	if (err)
3175 		goto bad_unshare_cleanup_fs;
3176 	err = unshare_userns(unshare_flags, &new_cred);
3177 	if (err)
3178 		goto bad_unshare_cleanup_fd;
3179 	err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
3180 					 new_cred, new_fs);
3181 	if (err)
3182 		goto bad_unshare_cleanup_cred;
3183 
3184 	if (new_cred) {
3185 		err = set_cred_ucounts(new_cred);
3186 		if (err)
3187 			goto bad_unshare_cleanup_cred;
3188 	}
3189 
3190 	if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
3191 		if (do_sysvsem) {
3192 			/*
3193 			 * CLONE_SYSVSEM is equivalent to sys_exit().
3194 			 */
3195 			exit_sem(current);
3196 		}
3197 		if (unshare_flags & CLONE_NEWIPC) {
3198 			/* Orphan segments in old ns (see sem above). */
3199 			exit_shm(current);
3200 			shm_init_task(current);
3201 		}
3202 
3203 		if (new_nsproxy)
3204 			switch_task_namespaces(current, new_nsproxy);
3205 
3206 		task_lock(current);
3207 
3208 		if (new_fs) {
3209 			fs = current->fs;
3210 			spin_lock(&fs->lock);
3211 			current->fs = new_fs;
3212 			if (--fs->users)
3213 				new_fs = NULL;
3214 			else
3215 				new_fs = fs;
3216 			spin_unlock(&fs->lock);
3217 		}
3218 
3219 		if (new_fd)
3220 			swap(current->files, new_fd);
3221 
3222 		task_unlock(current);
3223 
3224 		if (new_cred) {
3225 			/* Install the new user namespace */
3226 			commit_creds(new_cred);
3227 			new_cred = NULL;
3228 		}
3229 	}
3230 
3231 	perf_event_namespaces(current);
3232 
3233 bad_unshare_cleanup_cred:
3234 	if (new_cred)
3235 		put_cred(new_cred);
3236 bad_unshare_cleanup_fd:
3237 	if (new_fd)
3238 		put_files_struct(new_fd);
3239 
3240 bad_unshare_cleanup_fs:
3241 	if (new_fs)
3242 		free_fs_struct(new_fs);
3243 
3244 bad_unshare_out:
3245 	return err;
3246 }
3247 
3248 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
3249 {
3250 	return ksys_unshare(unshare_flags);
3251 }
3252 
3253 /*
3254  *	Helper to unshare the files of the current task.
3255  *	We don't want to expose copy_files internals to
3256  *	the exec layer of the kernel.
3257  */
3258 
3259 int unshare_files(void)
3260 {
3261 	struct task_struct *task = current;
3262 	struct files_struct *old, *copy = NULL;
3263 	int error;
3264 
3265 	error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, &copy);
3266 	if (error || !copy)
3267 		return error;
3268 
3269 	old = task->files;
3270 	task_lock(task);
3271 	task->files = copy;
3272 	task_unlock(task);
3273 	put_files_struct(old);
3274 	return 0;
3275 }
3276 
3277 int sysctl_max_threads(struct ctl_table *table, int write,
3278 		       void *buffer, size_t *lenp, loff_t *ppos)
3279 {
3280 	struct ctl_table t;
3281 	int ret;
3282 	int threads = max_threads;
3283 	int min = 1;
3284 	int max = MAX_THREADS;
3285 
3286 	t = *table;
3287 	t.data = &threads;
3288 	t.extra1 = &min;
3289 	t.extra2 = &max;
3290 
3291 	ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
3292 	if (ret || !write)
3293 		return ret;
3294 
3295 	max_threads = threads;
3296 
3297 	return 0;
3298 }
3299