개념 설명 전체 · v6.18.37 / kernel/fork.c

    1 // SPDX-License-Identifier: GPL-2.0-only
    2 /*
    3  *  linux/kernel/fork.c
    4  *
    5  *  Copyright (C) 1991, 1992  Linus Torvalds
    6  */
    7 
    8 /*
    9  *  'fork.c' contains the help-routines for the 'fork' system call
   10  * (see also entry.S and others).
   11  * Fork is rather simple, once you get the hang of it, but the memory
   12  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
   13  */
   14 
   15 #include <linux/anon_inodes.h>
   16 #include <linux/slab.h>
   17 #include <linux/sched/autogroup.h>
   18 #include <linux/sched/mm.h>
   19 #include <linux/sched/user.h>
   20 #include <linux/sched/numa_balancing.h>
   21 #include <linux/sched/stat.h>
   22 #include <linux/sched/task.h>
   23 #include <linux/sched/task_stack.h>
   24 #include <linux/sched/cputime.h>
   25 #include <linux/sched/ext.h>
   26 #include <linux/seq_file.h>
   27 #include <linux/rtmutex.h>
   28 #include <linux/init.h>
   29 #include <linux/unistd.h>
   30 #include <linux/module.h>
   31 #include <linux/vmalloc.h>
   32 #include <linux/completion.h>
   33 #include <linux/personality.h>
   34 #include <linux/mempolicy.h>
   35 #include <linux/sem.h>
   36 #include <linux/file.h>
   37 #include <linux/fdtable.h>
   38 #include <linux/iocontext.h>
   39 #include <linux/key.h>
   40 #include <linux/kmsan.h>
   41 #include <linux/binfmts.h>
   42 #include <linux/mman.h>
   43 #include <linux/mmu_notifier.h>
   44 #include <linux/fs.h>
   45 #include <linux/mm.h>
   46 #include <linux/mm_inline.h>
   47 #include <linux/memblock.h>
   48 #include <linux/nsproxy.h>
   49 #include <linux/capability.h>
   50 #include <linux/cpu.h>
   51 #include <linux/cgroup.h>
   52 #include <linux/security.h>
   53 #include <linux/hugetlb.h>
   54 #include <linux/seccomp.h>
   55 #include <linux/swap.h>
   56 #include <linux/syscalls.h>
   57 #include <linux/syscall_user_dispatch.h>
   58 #include <linux/jiffies.h>
   59 #include <linux/futex.h>
   60 #include <linux/compat.h>
   61 #include <linux/kthread.h>
   62 #include <linux/task_io_accounting_ops.h>
   63 #include <linux/rcupdate.h>
   64 #include <linux/ptrace.h>
   65 #include <linux/mount.h>
   66 #include <linux/audit.h>
   67 #include <linux/memcontrol.h>
   68 #include <linux/ftrace.h>
   69 #include <linux/proc_fs.h>
   70 #include <linux/profile.h>
   71 #include <linux/rmap.h>
   72 #include <linux/ksm.h>
   73 #include <linux/acct.h>
   74 #include <linux/userfaultfd_k.h>
   75 #include <linux/tsacct_kern.h>
   76 #include <linux/cn_proc.h>
   77 #include <linux/freezer.h>
   78 #include <linux/delayacct.h>
   79 #include <linux/taskstats_kern.h>
   80 #include <linux/tty.h>
   81 #include <linux/fs_struct.h>
   82 #include <linux/magic.h>
   83 #include <linux/perf_event.h>
   84 #include <linux/posix-timers.h>
   85 #include <linux/user-return-notifier.h>
   86 #include <linux/oom.h>
   87 #include <linux/khugepaged.h>
   88 #include <linux/signalfd.h>
   89 #include <linux/uprobes.h>
   90 #include <linux/aio.h>
   91 #include <linux/compiler.h>
   92 #include <linux/sysctl.h>
   93 #include <linux/kcov.h>
   94 #include <linux/livepatch.h>
   95 #include <linux/thread_info.h>
   96 #include <linux/kstack_erase.h>
   97 #include <linux/kasan.h>
   98 #include <linux/randomize_kstack.h>
   99 #include <linux/scs.h>
  100 #include <linux/io_uring.h>
  101 #include <linux/bpf.h>
  102 #include <linux/stackprotector.h>
  103 #include <linux/user_events.h>
  104 #include <linux/iommu.h>
  105 #include <linux/rseq.h>
  106 #include <uapi/linux/pidfd.h>
  107 #include <linux/pidfs.h>
  108 #include <linux/tick.h>
  109 #include <linux/unwind_deferred.h>
  110 
  111 #include <asm/pgalloc.h>
  112 #include <linux/uaccess.h>
  113 #include <asm/mmu_context.h>
  114 #include <asm/cacheflush.h>
  115 #include <asm/tlbflush.h>
  116 
  117 /* For dup_mmap(). */
  118 #include "../mm/internal.h"
  119 
  120 #include <trace/events/sched.h>
  121 
  122 #define CREATE_TRACE_POINTS
  123 #include <trace/events/task.h>
  124 
  125 #include <kunit/visibility.h>
  126 
  127 /*
  128  * Minimum number of threads to boot the kernel
  129  */
  130 #define MIN_THREADS 20
  131 
  132 /*
  133  * Maximum number of threads
  134  */
  135 #define MAX_THREADS FUTEX_TID_MASK
  136 
  137 /*
  138  * Protected counters by write_lock_irq(&tasklist_lock)
  139  */
  140 unsigned long total_forks;	/* Handle normal Linux uptimes. */
  141 int nr_threads;			/* The idle threads do not count.. */
  142 
  143 static int max_threads;		/* tunable limit on nr_threads */
  144 
  145 #define NAMED_ARRAY_INDEX(x)	[x] = __stringify(x)
  146 
  147 static const char * const resident_page_types[] = {
  148 	NAMED_ARRAY_INDEX(MM_FILEPAGES),
  149 	NAMED_ARRAY_INDEX(MM_ANONPAGES),
  150 	NAMED_ARRAY_INDEX(MM_SWAPENTS),
  151 	NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
  152 };
  153 
  154 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  155 
  156 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  157 
  158 #ifdef CONFIG_PROVE_RCU
  159 int lockdep_tasklist_lock_is_held(void)
  160 {
  161 	return lockdep_is_held(&tasklist_lock);
  162 }
  163 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
  164 #endif /* #ifdef CONFIG_PROVE_RCU */
  165 
  166 int nr_processes(void)
  167 {
  168 	int cpu;
  169 	int total = 0;
  170 
  171 	for_each_possible_cpu(cpu)
  172 		total += per_cpu(process_counts, cpu);
  173 
  174 	return total;
  175 }
  176 
  177 void __weak arch_release_task_struct(struct task_struct *tsk)
  178 {
  179 }
  180 
  181 static struct kmem_cache *task_struct_cachep;
  182 
  183 static inline struct task_struct *alloc_task_struct_node(int node)
  184 {
  185 	return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
  186 }
  187 
  188 static inline void free_task_struct(struct task_struct *tsk)
  189 {
  190 	kmem_cache_free(task_struct_cachep, tsk);
  191 }
  192 
  193 #ifdef CONFIG_VMAP_STACK
  194 /*
  195  * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
  196  * flush.  Try to minimize the number of calls by caching stacks.
  197  */
  198 #define NR_CACHED_STACKS 2
  199 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
  200 /*
  201  * Allocated stacks are cached and later reused by new threads, so memcg
  202  * accounting is performed by the code assigning/releasing stacks to tasks.
  203  * We need a zeroed memory without __GFP_ACCOUNT.
  204  */
  205 #define GFP_VMAP_STACK (GFP_KERNEL | __GFP_ZERO)
  206 
  207 struct vm_stack {
  208 	struct rcu_head rcu;
  209 	struct vm_struct *stack_vm_area;
  210 };
  211 
  212 static bool try_release_thread_stack_to_cache(struct vm_struct *vm_area)
  213 {
  214 	unsigned int i;
  215 
  216 	for (i = 0; i < NR_CACHED_STACKS; i++) {
  217 		struct vm_struct *tmp = NULL;
  218 
  219 		if (this_cpu_try_cmpxchg(cached_stacks[i], &tmp, vm_area))
  220 			return true;
  221 	}
  222 	return false;
  223 }
  224 
  225 static void thread_stack_free_rcu(struct rcu_head *rh)
  226 {
  227 	struct vm_stack *vm_stack = container_of(rh, struct vm_stack, rcu);
  228 	struct vm_struct *vm_area = vm_stack->stack_vm_area;
  229 
  230 	if (try_release_thread_stack_to_cache(vm_stack->stack_vm_area))
  231 		return;
  232 
  233 	vfree(vm_area->addr);
  234 }
  235 
  236 static void thread_stack_delayed_free(struct task_struct *tsk)
  237 {
  238 	struct vm_stack *vm_stack = tsk->stack;
  239 
  240 	vm_stack->stack_vm_area = tsk->stack_vm_area;
  241 	call_rcu(&vm_stack->rcu, thread_stack_free_rcu);
  242 }
  243 
  244 static int free_vm_stack_cache(unsigned int cpu)
  245 {
  246 	struct vm_struct **cached_vm_stack_areas = per_cpu_ptr(cached_stacks, cpu);
  247 	int i;
  248 
  249 	for (i = 0; i < NR_CACHED_STACKS; i++) {
  250 		struct vm_struct *vm_area = cached_vm_stack_areas[i];
  251 
  252 		if (!vm_area)
  253 			continue;
  254 
  255 		vfree(vm_area->addr);
  256 		cached_vm_stack_areas[i] = NULL;
  257 	}
  258 
  259 	return 0;
  260 }
  261 
  262 static int memcg_charge_kernel_stack(struct vm_struct *vm_area)
  263 {
  264 	int i;
  265 	int ret;
  266 	int nr_charged = 0;
  267 
  268 	BUG_ON(vm_area->nr_pages != THREAD_SIZE / PAGE_SIZE);
  269 
  270 	for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
  271 		ret = memcg_kmem_charge_page(vm_area->pages[i], GFP_KERNEL, 0);
  272 		if (ret)
  273 			goto err;
  274 		nr_charged++;
  275 	}
  276 	return 0;
  277 err:
  278 	for (i = 0; i < nr_charged; i++)
  279 		memcg_kmem_uncharge_page(vm_area->pages[i], 0);
  280 	return ret;
  281 }
  282 
  283 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
  284 {
  285 	struct vm_struct *vm_area;
  286 	void *stack;
  287 	int i;
  288 
  289 	for (i = 0; i < NR_CACHED_STACKS; i++) {
  290 		vm_area = this_cpu_xchg(cached_stacks[i], NULL);
  291 		if (!vm_area)
  292 			continue;
  293 
  294 		if (memcg_charge_kernel_stack(vm_area)) {
  295 			vfree(vm_area->addr);
  296 			return -ENOMEM;
  297 		}
  298 
  299 		/* Reset stack metadata. */
  300 		kasan_unpoison_range(vm_area->addr, THREAD_SIZE);
  301 
  302 		stack = kasan_reset_tag(vm_area->addr);
  303 
  304 		/* Clear stale pointers from reused stack. */
  305 		memset(stack, 0, THREAD_SIZE);
  306 
  307 		tsk->stack_vm_area = vm_area;
  308 		tsk->stack = stack;
  309 		return 0;
  310 	}
  311 
  312 	stack = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN,
  313 				     GFP_VMAP_STACK,
  314 				     node, __builtin_return_address(0));
  315 	if (!stack)
  316 		return -ENOMEM;
  317 
  318 	vm_area = find_vm_area(stack);
  319 	if (memcg_charge_kernel_stack(vm_area)) {
  320 		vfree(stack);
  321 		return -ENOMEM;
  322 	}
  323 	/*
  324 	 * We can't call find_vm_area() in interrupt context, and
  325 	 * free_thread_stack() can be called in interrupt context,
  326 	 * so cache the vm_struct.
  327 	 */
  328 	tsk->stack_vm_area = vm_area;
  329 	stack = kasan_reset_tag(stack);
  330 	tsk->stack = stack;
  331 	return 0;
  332 }
  333 
  334 static void free_thread_stack(struct task_struct *tsk)
  335 {
  336 	if (!try_release_thread_stack_to_cache(tsk->stack_vm_area))
  337 		thread_stack_delayed_free(tsk);
  338 
  339 	tsk->stack = NULL;
  340 	tsk->stack_vm_area = NULL;
  341 }
  342 
  343 #else /* !CONFIG_VMAP_STACK */
  344 
  345 /*
  346  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
  347  * kmemcache based allocator.
  348  */
  349 #if THREAD_SIZE >= PAGE_SIZE
  350 
  351 static void thread_stack_free_rcu(struct rcu_head *rh)
  352 {
  353 	__free_pages(virt_to_page(rh), THREAD_SIZE_ORDER);
  354 }
  355 
  356 static void thread_stack_delayed_free(struct task_struct *tsk)
  357 {
  358 	struct rcu_head *rh = tsk->stack;
  359 
  360 	call_rcu(rh, thread_stack_free_rcu);
  361 }
  362 
  363 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
  364 {
  365 	struct page *page = alloc_pages_node(node, THREADINFO_GFP,
  366 					     THREAD_SIZE_ORDER);
  367 
  368 	if (likely(page)) {
  369 		tsk->stack = kasan_reset_tag(page_address(page));
  370 		return 0;
  371 	}
  372 	return -ENOMEM;
  373 }
  374 
  375 static void free_thread_stack(struct task_struct *tsk)
  376 {
  377 	thread_stack_delayed_free(tsk);
  378 	tsk->stack = NULL;
  379 }
  380 
  381 #else /* !(THREAD_SIZE >= PAGE_SIZE) */
  382 
  383 static struct kmem_cache *thread_stack_cache;
  384 
  385 static void thread_stack_free_rcu(struct rcu_head *rh)
  386 {
  387 	kmem_cache_free(thread_stack_cache, rh);
  388 }
  389 
  390 static void thread_stack_delayed_free(struct task_struct *tsk)
  391 {
  392 	struct rcu_head *rh = tsk->stack;
  393 
  394 	call_rcu(rh, thread_stack_free_rcu);
  395 }
  396 
  397 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
  398 {
  399 	unsigned long *stack;
  400 	stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
  401 	stack = kasan_reset_tag(stack);
  402 	tsk->stack = stack;
  403 	return stack ? 0 : -ENOMEM;
  404 }
  405 
  406 static void free_thread_stack(struct task_struct *tsk)
  407 {
  408 	thread_stack_delayed_free(tsk);
  409 	tsk->stack = NULL;
  410 }
  411 
  412 void thread_stack_cache_init(void)
  413 {
  414 	thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
  415 					THREAD_SIZE, THREAD_SIZE, 0, 0,
  416 					THREAD_SIZE, NULL);
  417 	BUG_ON(thread_stack_cache == NULL);
  418 }
  419 
  420 #endif /* THREAD_SIZE >= PAGE_SIZE */
  421 #endif /* CONFIG_VMAP_STACK */
  422 
  423 /* SLAB cache for signal_struct structures (tsk->signal) */
  424 static struct kmem_cache *signal_cachep;
  425 
  426 /* SLAB cache for sighand_struct structures (tsk->sighand) */
  427 struct kmem_cache *sighand_cachep;
  428 
  429 /* SLAB cache for files_struct structures (tsk->files) */
  430 struct kmem_cache *files_cachep;
  431 
  432 /* SLAB cache for fs_struct structures (tsk->fs) */
  433 struct kmem_cache *fs_cachep;
  434 
  435 /* SLAB cache for mm_struct structures (tsk->mm) */
  436 static struct kmem_cache *mm_cachep;
  437 
  438 static void account_kernel_stack(struct task_struct *tsk, int account)
  439 {
  440 	if (IS_ENABLED(CONFIG_VMAP_STACK)) {
  441 		struct vm_struct *vm_area = task_stack_vm_area(tsk);
  442 		int i;
  443 
  444 		for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
  445 			mod_lruvec_page_state(vm_area->pages[i], NR_KERNEL_STACK_KB,
  446 					      account * (PAGE_SIZE / 1024));
  447 	} else {
  448 		void *stack = task_stack_page(tsk);
  449 
  450 		/* All stack pages are in the same node. */
  451 		mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB,
  452 				      account * (THREAD_SIZE / 1024));
  453 	}
  454 }
  455 
  456 void exit_task_stack_account(struct task_struct *tsk)
  457 {
  458 	account_kernel_stack(tsk, -1);
  459 
  460 	if (IS_ENABLED(CONFIG_VMAP_STACK)) {
  461 		struct vm_struct *vm_area;
  462 		int i;
  463 
  464 		vm_area = task_stack_vm_area(tsk);
  465 		for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
  466 			memcg_kmem_uncharge_page(vm_area->pages[i], 0);
  467 	}
  468 }
  469 
  470 static void release_task_stack(struct task_struct *tsk)
  471 {
  472 	if (WARN_ON(READ_ONCE(tsk->__state) != TASK_DEAD))
  473 		return;  /* Better to leak the stack than to free prematurely */
  474 
  475 	free_thread_stack(tsk);
  476 }
  477 
  478 #ifdef CONFIG_THREAD_INFO_IN_TASK
  479 void put_task_stack(struct task_struct *tsk)
  480 {
  481 	if (refcount_dec_and_test(&tsk->stack_refcount))
  482 		release_task_stack(tsk);
  483 }
  484 #endif
  485 
  486 void free_task(struct task_struct *tsk)
  487 {
  488 #ifdef CONFIG_SECCOMP
  489 	WARN_ON_ONCE(tsk->seccomp.filter);
  490 #endif
  491 	release_user_cpus_ptr(tsk);
  492 	scs_release(tsk);
  493 
  494 #ifndef CONFIG_THREAD_INFO_IN_TASK
  495 	/*
  496 	 * The task is finally done with both the stack and thread_info,
  497 	 * so free both.
  498 	 */
  499 	release_task_stack(tsk);
  500 #else
  501 	/*
  502 	 * If the task had a separate stack allocation, it should be gone
  503 	 * by now.
  504 	 */
  505 	WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
  506 #endif
  507 	rt_mutex_debug_task_free(tsk);
  508 	ftrace_graph_exit_task(tsk);
  509 	arch_release_task_struct(tsk);
  510 	if (tsk->flags & PF_KTHREAD)
  511 		free_kthread_struct(tsk);
  512 	bpf_task_storage_free(tsk);
  513 	free_task_struct(tsk);
  514 }
  515 EXPORT_SYMBOL(free_task);
  516 
  517 void dup_mm_exe_file(struct mm_struct *mm, struct mm_struct *oldmm)
  518 {
  519 	struct file *exe_file;
  520 
  521 	exe_file = get_mm_exe_file(oldmm);
  522 	RCU_INIT_POINTER(mm->exe_file, exe_file);
  523 	/*
  524 	 * We depend on the oldmm having properly denied write access to the
  525 	 * exe_file already.
  526 	 */
  527 	if (exe_file && exe_file_deny_write_access(exe_file))
  528 		pr_warn_once("exe_file_deny_write_access() failed in %s\n", __func__);
  529 }
  530 
  531 #ifdef CONFIG_MMU
  532 static inline int mm_alloc_pgd(struct mm_struct *mm)
  533 {
  534 	mm->pgd = pgd_alloc(mm);
  535 	if (unlikely(!mm->pgd))
  536 		return -ENOMEM;
  537 	return 0;
  538 }
  539 
  540 static inline void mm_free_pgd(struct mm_struct *mm)
  541 {
  542 	pgd_free(mm, mm->pgd);
  543 }
  544 #else
  545 #define mm_alloc_pgd(mm)	(0)
  546 #define mm_free_pgd(mm)
  547 #endif /* CONFIG_MMU */
  548 
  549 #ifdef CONFIG_MM_ID
  550 static DEFINE_IDA(mm_ida);
  551 
  552 static inline int mm_alloc_id(struct mm_struct *mm)
  553 {
  554 	int ret;
  555 
  556 	ret = ida_alloc_range(&mm_ida, MM_ID_MIN, MM_ID_MAX, GFP_KERNEL);
  557 	if (ret < 0)
  558 		return ret;
  559 	mm->mm_id = ret;
  560 	return 0;
  561 }
  562 
  563 static inline void mm_free_id(struct mm_struct *mm)
  564 {
  565 	const mm_id_t id = mm->mm_id;
  566 
  567 	mm->mm_id = MM_ID_DUMMY;
  568 	if (id == MM_ID_DUMMY)
  569 		return;
  570 	if (WARN_ON_ONCE(id < MM_ID_MIN || id > MM_ID_MAX))
  571 		return;
  572 	ida_free(&mm_ida, id);
  573 }
  574 #else /* !CONFIG_MM_ID */
  575 static inline int mm_alloc_id(struct mm_struct *mm) { return 0; }
  576 static inline void mm_free_id(struct mm_struct *mm) {}
  577 #endif /* CONFIG_MM_ID */
  578 
  579 static void check_mm(struct mm_struct *mm)
  580 {
  581 	int i;
  582 
  583 	BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
  584 			 "Please make sure 'struct resident_page_types[]' is updated as well");
  585 
  586 	for (i = 0; i < NR_MM_COUNTERS; i++) {
  587 		long x = percpu_counter_sum(&mm->rss_stat[i]);
  588 
  589 		if (unlikely(x)) {
  590 			pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld Comm:%s Pid:%d\n",
  591 				 mm, resident_page_types[i], x,
  592 				 current->comm,
  593 				 task_pid_nr(current));
  594 		}
  595 	}
  596 
  597 	if (mm_pgtables_bytes(mm))
  598 		pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
  599 				mm_pgtables_bytes(mm));
  600 
  601 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !defined(CONFIG_SPLIT_PMD_PTLOCKS)
  602 	VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
  603 #endif
  604 }
  605 
  606 #define allocate_mm()	(kmem_cache_alloc(mm_cachep, GFP_KERNEL))
  607 #define free_mm(mm)	(kmem_cache_free(mm_cachep, (mm)))
  608 
  609 static void do_check_lazy_tlb(void *arg)
  610 {
  611 	struct mm_struct *mm = arg;
  612 
  613 	WARN_ON_ONCE(current->active_mm == mm);
  614 }
  615 
  616 static void do_shoot_lazy_tlb(void *arg)
  617 {
  618 	struct mm_struct *mm = arg;
  619 
  620 	if (current->active_mm == mm) {
  621 		WARN_ON_ONCE(current->mm);
  622 		current->active_mm = &init_mm;
  623 		switch_mm(mm, &init_mm, current);
  624 	}
  625 }
  626 
  627 static void cleanup_lazy_tlbs(struct mm_struct *mm)
  628 {
  629 	if (!IS_ENABLED(CONFIG_MMU_LAZY_TLB_SHOOTDOWN)) {
  630 		/*
  631 		 * In this case, lazy tlb mms are refounted and would not reach
  632 		 * __mmdrop until all CPUs have switched away and mmdrop()ed.
  633 		 */
  634 		return;
  635 	}
  636 
  637 	/*
  638 	 * Lazy mm shootdown does not refcount "lazy tlb mm" usage, rather it
  639 	 * requires lazy mm users to switch to another mm when the refcount
  640 	 * drops to zero, before the mm is freed. This requires IPIs here to
  641 	 * switch kernel threads to init_mm.
  642 	 *
  643 	 * archs that use IPIs to flush TLBs can piggy-back that lazy tlb mm
  644 	 * switch with the final userspace teardown TLB flush which leaves the
  645 	 * mm lazy on this CPU but no others, reducing the need for additional
  646 	 * IPIs here. There are cases where a final IPI is still required here,
  647 	 * such as the final mmdrop being performed on a different CPU than the
  648 	 * one exiting, or kernel threads using the mm when userspace exits.
  649 	 *
  650 	 * IPI overheads have not found to be expensive, but they could be
  651 	 * reduced in a number of possible ways, for example (roughly
  652 	 * increasing order of complexity):
  653 	 * - The last lazy reference created by exit_mm() could instead switch
  654 	 *   to init_mm, however it's probable this will run on the same CPU
  655 	 *   immediately afterwards, so this may not reduce IPIs much.
  656 	 * - A batch of mms requiring IPIs could be gathered and freed at once.
  657 	 * - CPUs store active_mm where it can be remotely checked without a
  658 	 *   lock, to filter out false-positives in the cpumask.
  659 	 * - After mm_users or mm_count reaches zero, switching away from the
  660 	 *   mm could clear mm_cpumask to reduce some IPIs, perhaps together
  661 	 *   with some batching or delaying of the final IPIs.
  662 	 * - A delayed freeing and RCU-like quiescing sequence based on mm
  663 	 *   switching to avoid IPIs completely.
  664 	 */
  665 	on_each_cpu_mask(mm_cpumask(mm), do_shoot_lazy_tlb, (void *)mm, 1);
  666 	if (IS_ENABLED(CONFIG_DEBUG_VM_SHOOT_LAZIES))
  667 		on_each_cpu(do_check_lazy_tlb, (void *)mm, 1);
  668 }
  669 
  670 /*
  671  * Called when the last reference to the mm
  672  * is dropped: either by a lazy thread or by
  673  * mmput. Free the page directory and the mm.
  674  */
  675 void __mmdrop(struct mm_struct *mm)
  676 {
  677 	BUG_ON(mm == &init_mm);
  678 	WARN_ON_ONCE(mm == current->mm);
  679 
  680 	/* Ensure no CPUs are using this as their lazy tlb mm */
  681 	cleanup_lazy_tlbs(mm);
  682 
  683 	WARN_ON_ONCE(mm == current->active_mm);
  684 	mm_free_pgd(mm);
  685 	mm_free_id(mm);
  686 	destroy_context(mm);
  687 	mmu_notifier_subscriptions_destroy(mm);
  688 	check_mm(mm);
  689 	put_user_ns(mm->user_ns);
  690 	mm_pasid_drop(mm);
  691 	mm_destroy_cid(mm);
  692 	percpu_counter_destroy_many(mm->rss_stat, NR_MM_COUNTERS);
  693 
  694 	free_mm(mm);
  695 }
  696 EXPORT_SYMBOL_GPL(__mmdrop);
  697 
  698 static void mmdrop_async_fn(struct work_struct *work)
  699 {
  700 	struct mm_struct *mm;
  701 
  702 	mm = container_of(work, struct mm_struct, async_put_work);
  703 	__mmdrop(mm);
  704 }
  705 
  706 static void mmdrop_async(struct mm_struct *mm)
  707 {
  708 	if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
  709 		INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
  710 		schedule_work(&mm->async_put_work);
  711 	}
  712 }
  713 
  714 static inline void free_signal_struct(struct signal_struct *sig)
  715 {
  716 	taskstats_tgid_free(sig);
  717 	sched_autogroup_exit(sig);
  718 	/*
  719 	 * __mmdrop is not safe to call from softirq context on x86 due to
  720 	 * pgd_dtor so postpone it to the async context
  721 	 */
  722 	if (sig->oom_mm)
  723 		mmdrop_async(sig->oom_mm);
  724 	kmem_cache_free(signal_cachep, sig);
  725 }
  726 
  727 static inline void put_signal_struct(struct signal_struct *sig)
  728 {
  729 	if (refcount_dec_and_test(&sig->sigcnt))
  730 		free_signal_struct(sig);
  731 }
  732 
  733 void __put_task_struct(struct task_struct *tsk)
  734 {
  735 	WARN_ON(!tsk->exit_state);
  736 	WARN_ON(refcount_read(&tsk->usage));
  737 	WARN_ON(tsk == current);
  738 
  739 	unwind_task_free(tsk);
  740 	sched_ext_free(tsk);
  741 	io_uring_free(tsk);
  742 	cgroup_free(tsk);
  743 	task_numa_free(tsk, true);
  744 	security_task_free(tsk);
  745 	exit_creds(tsk);
  746 	delayacct_tsk_free(tsk);
  747 	put_signal_struct(tsk->signal);
  748 	sched_core_free(tsk);
  749 	free_task(tsk);
  750 }
  751 EXPORT_SYMBOL_GPL(__put_task_struct);
  752 
  753 void __put_task_struct_rcu_cb(struct rcu_head *rhp)
  754 {
  755 	struct task_struct *task = container_of(rhp, struct task_struct, rcu);
  756 
  757 	__put_task_struct(task);
  758 }
  759 EXPORT_SYMBOL_GPL(__put_task_struct_rcu_cb);
  760 
  761 void __init __weak arch_task_cache_init(void) { }
  762 
  763 /*
  764  * set_max_threads
  765  */
  766 static void __init set_max_threads(unsigned int max_threads_suggested)
  767 {
  768 	u64 threads;
  769 	unsigned long nr_pages = memblock_estimated_nr_free_pages();
  770 
  771 	/*
  772 	 * The number of threads shall be limited such that the thread
  773 	 * structures may only consume a small part of the available memory.
  774 	 */
  775 	if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
  776 		threads = MAX_THREADS;
  777 	else
  778 		threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
  779 				    (u64) THREAD_SIZE * 8UL);
  780 
  781 	if (threads > max_threads_suggested)
  782 		threads = max_threads_suggested;
  783 
  784 	max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
  785 }
  786 
  787 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
  788 /* Initialized by the architecture: */
  789 int arch_task_struct_size __read_mostly;
  790 #endif
  791 
  792 static void __init task_struct_whitelist(unsigned long *offset, unsigned long *size)
  793 {
  794 	/* Fetch thread_struct whitelist for the architecture. */
  795 	arch_thread_struct_whitelist(offset, size);
  796 
  797 	/*
  798 	 * Handle zero-sized whitelist or empty thread_struct, otherwise
  799 	 * adjust offset to position of thread_struct in task_struct.
  800 	 */
  801 	if (unlikely(*size == 0))
  802 		*offset = 0;
  803 	else
  804 		*offset += offsetof(struct task_struct, thread);
  805 }
  806 
  807 void __init fork_init(void)
  808 {
  809 	int i;
  810 #ifndef ARCH_MIN_TASKALIGN
  811 #define ARCH_MIN_TASKALIGN	0
  812 #endif
  813 	int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
  814 	unsigned long useroffset, usersize;
  815 
  816 	/* create a slab on which task_structs can be allocated */
  817 	task_struct_whitelist(&useroffset, &usersize);
  818 	task_struct_cachep = kmem_cache_create_usercopy("task_struct",
  819 			arch_task_struct_size, align,
  820 			SLAB_PANIC|SLAB_ACCOUNT,
  821 			useroffset, usersize, NULL);
  822 
  823 	/* do the arch specific task caches init */
  824 	arch_task_cache_init();
  825 
  826 	set_max_threads(MAX_THREADS);
  827 
  828 	init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
  829 	init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
  830 	init_task.signal->rlim[RLIMIT_SIGPENDING] =
  831 		init_task.signal->rlim[RLIMIT_NPROC];
  832 
  833 	for (i = 0; i < UCOUNT_COUNTS; i++)
  834 		init_user_ns.ucount_max[i] = max_threads/2;
  835 
  836 	set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_NPROC,      RLIM_INFINITY);
  837 	set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE,   RLIM_INFINITY);
  838 	set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY);
  839 	set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK,    RLIM_INFINITY);
  840 
  841 #ifdef CONFIG_VMAP_STACK
  842 	cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
  843 			  NULL, free_vm_stack_cache);
  844 #endif
  845 
  846 	scs_init();
  847 
  848 	lockdep_init_task(&init_task);
  849 	uprobes_init();
  850 }
  851 
  852 int __weak arch_dup_task_struct(struct task_struct *dst,
  853 					       struct task_struct *src)
  854 {
  855 	*dst = *src;
  856 	return 0;
  857 }
  858 
  859 void set_task_stack_end_magic(struct task_struct *tsk)
  860 {
  861 	unsigned long *stackend;
  862 
  863 	stackend = end_of_stack(tsk);
  864 	*stackend = STACK_END_MAGIC;	/* for overflow detection */
  865 }
  866 
  867 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
  868 {
  869 	struct task_struct *tsk;
  870 	int err;
  871 
  872 	if (node == NUMA_NO_NODE)
  873 		node = tsk_fork_get_node(orig);
  874 	tsk = alloc_task_struct_node(node);
  875 	if (!tsk)
  876 		return NULL;
  877 
  878 	err = arch_dup_task_struct(tsk, orig);
  879 	if (err)
  880 		goto free_tsk;
  881 
  882 	err = alloc_thread_stack_node(tsk, node);
  883 	if (err)
  884 		goto free_tsk;
  885 
  886 #ifdef CONFIG_THREAD_INFO_IN_TASK
  887 	refcount_set(&tsk->stack_refcount, 1);
  888 #endif
  889 	account_kernel_stack(tsk, 1);
  890 
  891 	err = scs_prepare(tsk, node);
  892 	if (err)
  893 		goto free_stack;
  894 
  895 #ifdef CONFIG_SECCOMP
  896 	/*
  897 	 * We must handle setting up seccomp filters once we're under
  898 	 * the sighand lock in case orig has changed between now and
  899 	 * then. Until then, filter must be NULL to avoid messing up
  900 	 * the usage counts on the error path calling free_task.
  901 	 */
  902 	tsk->seccomp.filter = NULL;
  903 #endif
  904 
  905 	setup_thread_stack(tsk, orig);
  906 	clear_user_return_notifier(tsk);
  907 	clear_tsk_need_resched(tsk);
  908 	set_task_stack_end_magic(tsk);
  909 	clear_syscall_work_syscall_user_dispatch(tsk);
  910 
  911 #ifdef CONFIG_STACKPROTECTOR
  912 	tsk->stack_canary = get_random_canary();
  913 #endif
  914 	if (orig->cpus_ptr == &orig->cpus_mask)
  915 		tsk->cpus_ptr = &tsk->cpus_mask;
  916 	dup_user_cpus_ptr(tsk, orig, node);
  917 
  918 	/*
  919 	 * One for the user space visible state that goes away when reaped.
  920 	 * One for the scheduler.
  921 	 */
  922 	refcount_set(&tsk->rcu_users, 2);
  923 	/* One for the rcu users */
  924 	refcount_set(&tsk->usage, 1);
  925 #ifdef CONFIG_BLK_DEV_IO_TRACE
  926 	tsk->btrace_seq = 0;
  927 #endif
  928 	tsk->splice_pipe = NULL;
  929 	tsk->task_frag.page = NULL;
  930 	tsk->wake_q.next = NULL;
  931 	tsk->worker_private = NULL;
  932 
  933 	kcov_task_init(tsk);
  934 	kmsan_task_create(tsk);
  935 	kmap_local_fork(tsk);
  936 
  937 #ifdef CONFIG_FAULT_INJECTION
  938 	tsk->fail_nth = 0;
  939 #endif
  940 
  941 #ifdef CONFIG_BLK_CGROUP
  942 	tsk->throttle_disk = NULL;
  943 	tsk->use_memdelay = 0;
  944 #endif
  945 
  946 #ifdef CONFIG_ARCH_HAS_CPU_PASID
  947 	tsk->pasid_activated = 0;
  948 #endif
  949 
  950 #ifdef CONFIG_MEMCG
  951 	tsk->active_memcg = NULL;
  952 #endif
  953 
  954 #ifdef CONFIG_X86_BUS_LOCK_DETECT
  955 	tsk->reported_split_lock = 0;
  956 #endif
  957 
  958 #ifdef CONFIG_SCHED_MM_CID
  959 	tsk->mm_cid = -1;
  960 	tsk->last_mm_cid = -1;
  961 	tsk->mm_cid_active = 0;
  962 	tsk->migrate_from_cpu = -1;
  963 #endif
  964 	return tsk;
  965 
  966 free_stack:
  967 	exit_task_stack_account(tsk);
  968 	free_thread_stack(tsk);
  969 free_tsk:
  970 	free_task_struct(tsk);
  971 	return NULL;
  972 }
  973 
  974 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
  975 
  976 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
  977 
  978 static int __init coredump_filter_setup(char *s)
  979 {
  980 	default_dump_filter =
  981 		(simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
  982 		MMF_DUMP_FILTER_MASK;
  983 	return 1;
  984 }
  985 
  986 __setup("coredump_filter=", coredump_filter_setup);
  987 
  988 #include <linux/init_task.h>
  989 
  990 static void mm_init_aio(struct mm_struct *mm)
  991 {
  992 #ifdef CONFIG_AIO
  993 	spin_lock_init(&mm->ioctx_lock);
  994 	mm->ioctx_table = NULL;
  995 #endif
  996 }
  997 
  998 static __always_inline void mm_clear_owner(struct mm_struct *mm,
  999 					   struct task_struct *p)
 1000 {
 1001 #ifdef CONFIG_MEMCG
 1002 	if (mm->owner == p)
 1003 		WRITE_ONCE(mm->owner, NULL);
 1004 #endif
 1005 }
 1006 
 1007 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 1008 {
 1009 #ifdef CONFIG_MEMCG
 1010 	mm->owner = p;
 1011 #endif
 1012 }
 1013 
 1014 static void mm_init_uprobes_state(struct mm_struct *mm)
 1015 {
 1016 #ifdef CONFIG_UPROBES
 1017 	mm->uprobes_state.xol_area = NULL;
 1018 	arch_uprobe_init_state(mm);
 1019 #endif
 1020 }
 1021 
 1022 static void mmap_init_lock(struct mm_struct *mm)
 1023 {
 1024 	init_rwsem(&mm->mmap_lock);
 1025 	mm_lock_seqcount_init(mm);
 1026 #ifdef CONFIG_PER_VMA_LOCK
 1027 	rcuwait_init(&mm->vma_writer_wait);
 1028 #endif
 1029 }
 1030 
 1031 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
 1032 	struct user_namespace *user_ns)
 1033 {
 1034 	mt_init_flags(&mm->mm_mt, MM_MT_FLAGS);
 1035 	mt_set_external_lock(&mm->mm_mt, &mm->mmap_lock);
 1036 	atomic_set(&mm->mm_users, 1);
 1037 	atomic_set(&mm->mm_count, 1);
 1038 	seqcount_init(&mm->write_protect_seq);
 1039 	mmap_init_lock(mm);
 1040 	INIT_LIST_HEAD(&mm->mmlist);
 1041 	mm_pgtables_bytes_init(mm);
 1042 	mm->map_count = 0;
 1043 	mm->locked_vm = 0;
 1044 	atomic64_set(&mm->pinned_vm, 0);
 1045 	memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 1046 	spin_lock_init(&mm->page_table_lock);
 1047 	spin_lock_init(&mm->arg_lock);
 1048 	mm_init_cpumask(mm);
 1049 	mm_init_aio(mm);
 1050 	mm_init_owner(mm, p);
 1051 	mm_pasid_init(mm);
 1052 	RCU_INIT_POINTER(mm->exe_file, NULL);
 1053 	mmu_notifier_subscriptions_init(mm);
 1054 	init_tlb_flush_pending(mm);
 1055 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !defined(CONFIG_SPLIT_PMD_PTLOCKS)
 1056 	mm->pmd_huge_pte = NULL;
 1057 #endif
 1058 	mm_init_uprobes_state(mm);
 1059 	hugetlb_count_init(mm);
 1060 
 1061 	mm_flags_clear_all(mm);
 1062 	if (current->mm) {
 1063 		unsigned long flags = __mm_flags_get_word(current->mm);
 1064 
 1065 		__mm_flags_set_word(mm, mmf_init_legacy_flags(flags));
 1066 		mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
 1067 	} else {
 1068 		__mm_flags_set_word(mm, default_dump_filter);
 1069 		mm->def_flags = 0;
 1070 	}
 1071 
 1072 	if (futex_mm_init(mm))
 1073 		goto fail_mm_init;
 1074 
 1075 	if (mm_alloc_pgd(mm))
 1076 		goto fail_nopgd;
 1077 
 1078 	if (mm_alloc_id(mm))
 1079 		goto fail_noid;
 1080 
 1081 	if (init_new_context(p, mm))
 1082 		goto fail_nocontext;
 1083 
 1084 	if (mm_alloc_cid(mm, p))
 1085 		goto fail_cid;
 1086 
 1087 	if (percpu_counter_init_many(mm->rss_stat, 0, GFP_KERNEL_ACCOUNT,
 1088 				     NR_MM_COUNTERS))
 1089 		goto fail_pcpu;
 1090 
 1091 	mm->user_ns = get_user_ns(user_ns);
 1092 	lru_gen_init_mm(mm);
 1093 	return mm;
 1094 
 1095 fail_pcpu:
 1096 	mm_destroy_cid(mm);
 1097 fail_cid:
 1098 	destroy_context(mm);
 1099 fail_nocontext:
 1100 	mm_free_id(mm);
 1101 fail_noid:
 1102 	mm_free_pgd(mm);
 1103 fail_nopgd:
 1104 	futex_hash_free(mm);
 1105 fail_mm_init:
 1106 	free_mm(mm);
 1107 	return NULL;
 1108 }
 1109 
 1110 /*
 1111  * Allocate and initialize an mm_struct.
 1112  */
 1113 struct mm_struct *mm_alloc(void)
 1114 {
 1115 	struct mm_struct *mm;
 1116 
 1117 	mm = allocate_mm();
 1118 	if (!mm)
 1119 		return NULL;
 1120 
 1121 	memset(mm, 0, sizeof(*mm));
 1122 	return mm_init(mm, current, current_user_ns());
 1123 }
 1124 EXPORT_SYMBOL_IF_KUNIT(mm_alloc);
 1125 
 1126 static inline void __mmput(struct mm_struct *mm)
 1127 {
 1128 	VM_BUG_ON(atomic_read(&mm->mm_users));
 1129 
 1130 	uprobe_clear_state(mm);
 1131 	exit_aio(mm);
 1132 	ksm_exit(mm);
 1133 	khugepaged_exit(mm); /* must run before exit_mmap */
 1134 	exit_mmap(mm);
 1135 	mm_put_huge_zero_folio(mm);
 1136 	set_mm_exe_file(mm, NULL);
 1137 	if (!list_empty(&mm->mmlist)) {
 1138 		spin_lock(&mmlist_lock);
 1139 		list_del(&mm->mmlist);
 1140 		spin_unlock(&mmlist_lock);
 1141 	}
 1142 	if (mm->binfmt)
 1143 		module_put(mm->binfmt->module);
 1144 	lru_gen_del_mm(mm);
 1145 	futex_hash_free(mm);
 1146 	mmdrop(mm);
 1147 }
 1148 
 1149 /*
 1150  * Decrement the use count and release all resources for an mm.
 1151  */
 1152 void mmput(struct mm_struct *mm)
 1153 {
 1154 	might_sleep();
 1155 
 1156 	if (atomic_dec_and_test(&mm->mm_users))
 1157 		__mmput(mm);
 1158 }
 1159 EXPORT_SYMBOL_GPL(mmput);
 1160 
 1161 #if defined(CONFIG_MMU) || defined(CONFIG_FUTEX_PRIVATE_HASH)
 1162 static void mmput_async_fn(struct work_struct *work)
 1163 {
 1164 	struct mm_struct *mm = container_of(work, struct mm_struct,
 1165 					    async_put_work);
 1166 
 1167 	__mmput(mm);
 1168 }
 1169 
 1170 void mmput_async(struct mm_struct *mm)
 1171 {
 1172 	if (atomic_dec_and_test(&mm->mm_users)) {
 1173 		INIT_WORK(&mm->async_put_work, mmput_async_fn);
 1174 		schedule_work(&mm->async_put_work);
 1175 	}
 1176 }
 1177 EXPORT_SYMBOL_GPL(mmput_async);
 1178 #endif
 1179 
 1180 /**
 1181  * set_mm_exe_file - change a reference to the mm's executable file
 1182  * @mm: The mm to change.
 1183  * @new_exe_file: The new file to use.
 1184  *
 1185  * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
 1186  *
 1187  * Main users are mmput() and sys_execve(). Callers prevent concurrent
 1188  * invocations: in mmput() nobody alive left, in execve it happens before
 1189  * the new mm is made visible to anyone.
 1190  *
 1191  * Can only fail if new_exe_file != NULL.
 1192  */
 1193 int set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 1194 {
 1195 	struct file *old_exe_file;
 1196 
 1197 	/*
 1198 	 * It is safe to dereference the exe_file without RCU as
 1199 	 * this function is only called if nobody else can access
 1200 	 * this mm -- see comment above for justification.
 1201 	 */
 1202 	old_exe_file = rcu_dereference_raw(mm->exe_file);
 1203 
 1204 	if (new_exe_file) {
 1205 		/*
 1206 		 * We expect the caller (i.e., sys_execve) to already denied
 1207 		 * write access, so this is unlikely to fail.
 1208 		 */
 1209 		if (unlikely(exe_file_deny_write_access(new_exe_file)))
 1210 			return -EACCES;
 1211 		get_file(new_exe_file);
 1212 	}
 1213 	rcu_assign_pointer(mm->exe_file, new_exe_file);
 1214 	if (old_exe_file) {
 1215 		exe_file_allow_write_access(old_exe_file);
 1216 		fput(old_exe_file);
 1217 	}
 1218 	return 0;
 1219 }
 1220 
 1221 /**
 1222  * replace_mm_exe_file - replace a reference to the mm's executable file
 1223  * @mm: The mm to change.
 1224  * @new_exe_file: The new file to use.
 1225  *
 1226  * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
 1227  *
 1228  * Main user is sys_prctl(PR_SET_MM_MAP/EXE_FILE).
 1229  */
 1230 int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 1231 {
 1232 	struct vm_area_struct *vma;
 1233 	struct file *old_exe_file;
 1234 	int ret = 0;
 1235 
 1236 	/* Forbid mm->exe_file change if old file still mapped. */
 1237 	old_exe_file = get_mm_exe_file(mm);
 1238 	if (old_exe_file) {
 1239 		VMA_ITERATOR(vmi, mm, 0);
 1240 		mmap_read_lock(mm);
 1241 		for_each_vma(vmi, vma) {
 1242 			if (!vma->vm_file)
 1243 				continue;
 1244 			if (path_equal(&vma->vm_file->f_path,
 1245 				       &old_exe_file->f_path)) {
 1246 				ret = -EBUSY;
 1247 				break;
 1248 			}
 1249 		}
 1250 		mmap_read_unlock(mm);
 1251 		fput(old_exe_file);
 1252 		if (ret)
 1253 			return ret;
 1254 	}
 1255 
 1256 	ret = exe_file_deny_write_access(new_exe_file);
 1257 	if (ret)
 1258 		return -EACCES;
 1259 	get_file(new_exe_file);
 1260 
 1261 	/* set the new file */
 1262 	mmap_write_lock(mm);
 1263 	old_exe_file = rcu_dereference_raw(mm->exe_file);
 1264 	rcu_assign_pointer(mm->exe_file, new_exe_file);
 1265 	mmap_write_unlock(mm);
 1266 
 1267 	if (old_exe_file) {
 1268 		exe_file_allow_write_access(old_exe_file);
 1269 		fput(old_exe_file);
 1270 	}
 1271 	return 0;
 1272 }
 1273 
 1274 /**
 1275  * get_mm_exe_file - acquire a reference to the mm's executable file
 1276  * @mm: The mm of interest.
 1277  *
 1278  * Returns %NULL if mm has no associated executable file.
 1279  * User must release file via fput().
 1280  */
 1281 struct file *get_mm_exe_file(struct mm_struct *mm)
 1282 {
 1283 	struct file *exe_file;
 1284 
 1285 	rcu_read_lock();
 1286 	exe_file = get_file_rcu(&mm->exe_file);
 1287 	rcu_read_unlock();
 1288 	return exe_file;
 1289 }
 1290 
 1291 /**
 1292  * get_task_exe_file - acquire a reference to the task's executable file
 1293  * @task: The task.
 1294  *
 1295  * Returns %NULL if task's mm (if any) has no associated executable file or
 1296  * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
 1297  * User must release file via fput().
 1298  */
 1299 struct file *get_task_exe_file(struct task_struct *task)
 1300 {
 1301 	struct file *exe_file = NULL;
 1302 	struct mm_struct *mm;
 1303 
 1304 	if (task->flags & PF_KTHREAD)
 1305 		return NULL;
 1306 
 1307 	task_lock(task);
 1308 	mm = task->mm;
 1309 	if (mm)
 1310 		exe_file = get_mm_exe_file(mm);
 1311 	task_unlock(task);
 1312 	return exe_file;
 1313 }
 1314 
 1315 /**
 1316  * get_task_mm - acquire a reference to the task's mm
 1317  * @task: The task.
 1318  *
 1319  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 1320  * this kernel workthread has transiently adopted a user mm with use_mm,
 1321  * to do its AIO) is not set and if so returns a reference to it, after
 1322  * bumping up the use count.  User must release the mm via mmput()
 1323  * after use.  Typically used by /proc and ptrace.
 1324  */
 1325 struct mm_struct *get_task_mm(struct task_struct *task)
 1326 {
 1327 	struct mm_struct *mm;
 1328 
 1329 	if (task->flags & PF_KTHREAD)
 1330 		return NULL;
 1331 
 1332 	task_lock(task);
 1333 	mm = task->mm;
 1334 	if (mm)
 1335 		mmget(mm);
 1336 	task_unlock(task);
 1337 	return mm;
 1338 }
 1339 EXPORT_SYMBOL_GPL(get_task_mm);
 1340 
 1341 static bool may_access_mm(struct mm_struct *mm, struct task_struct *task, unsigned int mode)
 1342 {
 1343 	if (mm == current->mm)
 1344 		return true;
 1345 	if (ptrace_may_access(task, mode))
 1346 		return true;
 1347 	if ((mode & PTRACE_MODE_READ) && perfmon_capable())
 1348 		return true;
 1349 	return false;
 1350 }
 1351 
 1352 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
 1353 {
 1354 	struct mm_struct *mm;
 1355 	int err;
 1356 
 1357 	err =  down_read_killable(&task->signal->exec_update_lock);
 1358 	if (err)
 1359 		return ERR_PTR(err);
 1360 
 1361 	mm = get_task_mm(task);
 1362 	if (!mm) {
 1363 		mm = ERR_PTR(-ESRCH);
 1364 	} else if (!may_access_mm(mm, task, mode)) {
 1365 		mmput(mm);
 1366 		mm = ERR_PTR(-EACCES);
 1367 	}
 1368 	up_read(&task->signal->exec_update_lock);
 1369 
 1370 	return mm;
 1371 }
 1372 
 1373 static void complete_vfork_done(struct task_struct *tsk)
 1374 {
 1375 	struct completion *vfork;
 1376 
 1377 	task_lock(tsk);
 1378 	vfork = tsk->vfork_done;
 1379 	if (likely(vfork)) {
 1380 		tsk->vfork_done = NULL;
 1381 		complete(vfork);
 1382 	}
 1383 	task_unlock(tsk);
 1384 }
 1385 
 1386 static int wait_for_vfork_done(struct task_struct *child,
 1387 				struct completion *vfork)
 1388 {
 1389 	unsigned int state = TASK_KILLABLE|TASK_FREEZABLE;
 1390 	int killed;
 1391 
 1392 	cgroup_enter_frozen();
 1393 	killed = wait_for_completion_state(vfork, state);
 1394 	cgroup_leave_frozen(false);
 1395 
 1396 	if (killed) {
 1397 		task_lock(child);
 1398 		child->vfork_done = NULL;
 1399 		task_unlock(child);
 1400 	}
 1401 
 1402 	put_task_struct(child);
 1403 	return killed;
 1404 }
 1405 
 1406 /* Please note the differences between mmput and mm_release.
 1407  * mmput is called whenever we stop holding onto a mm_struct,
 1408  * error success whatever.
 1409  *
 1410  * mm_release is called after a mm_struct has been removed
 1411  * from the current process.
 1412  *
 1413  * This difference is important for error handling, when we
 1414  * only half set up a mm_struct for a new process and need to restore
 1415  * the old one.  Because we mmput the new mm_struct before
 1416  * restoring the old one. . .
 1417  * Eric Biederman 10 January 1998
 1418  */
 1419 static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 1420 {
 1421 	uprobe_free_utask(tsk);
 1422 
 1423 	/* Get rid of any cached register state */
 1424 	deactivate_mm(tsk, mm);
 1425 
 1426 	/*
 1427 	 * Signal userspace if we're not exiting with a core dump
 1428 	 * because we want to leave the value intact for debugging
 1429 	 * purposes.
 1430 	 */
 1431 	if (tsk->clear_child_tid) {
 1432 		if (atomic_read(&mm->mm_users) > 1) {
 1433 			/*
 1434 			 * We don't check the error code - if userspace has
 1435 			 * not set up a proper pointer then tough luck.
 1436 			 */
 1437 			put_user(0, tsk->clear_child_tid);
 1438 			do_futex(tsk->clear_child_tid, FUTEX_WAKE,
 1439 					1, NULL, NULL, 0, 0);
 1440 		}
 1441 		tsk->clear_child_tid = NULL;
 1442 	}
 1443 
 1444 	/*
 1445 	 * All done, finally we can wake up parent and return this mm to him.
 1446 	 * Also kthread_stop() uses this completion for synchronization.
 1447 	 */
 1448 	if (tsk->vfork_done)
 1449 		complete_vfork_done(tsk);
 1450 }
 1451 
 1452 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
 1453 {
 1454 	futex_exit_release(tsk);
 1455 	mm_release(tsk, mm);
 1456 }
 1457 
 1458 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
 1459 {
 1460 	futex_exec_release(tsk);
 1461 	mm_release(tsk, mm);
 1462 }
 1463 
 1464 /**
 1465  * dup_mm() - duplicates an existing mm structure
 1466  * @tsk: the task_struct with which the new mm will be associated.
 1467  * @oldmm: the mm to duplicate.
 1468  *
 1469  * Allocates a new mm structure and duplicates the provided @oldmm structure
 1470  * content into it.
 1471  *
 1472  * Return: the duplicated mm or NULL on failure.
 1473  */
 1474 static struct mm_struct *dup_mm(struct task_struct *tsk,
 1475 				struct mm_struct *oldmm)
 1476 {
 1477 	struct mm_struct *mm;
 1478 	int err;
 1479 
 1480 	mm = allocate_mm();
 1481 	if (!mm)
 1482 		goto fail_nomem;
 1483 
 1484 	memcpy(mm, oldmm, sizeof(*mm));
 1485 
 1486 	if (!mm_init(mm, tsk, mm->user_ns))
 1487 		goto fail_nomem;
 1488 
 1489 	uprobe_start_dup_mmap();
 1490 	err = dup_mmap(mm, oldmm);
 1491 	if (err)
 1492 		goto free_pt;
 1493 	uprobe_end_dup_mmap();
 1494 
 1495 	mm->hiwater_rss = get_mm_rss(mm);
 1496 	mm->hiwater_vm = mm->total_vm;
 1497 
 1498 	if (mm->binfmt && !try_module_get(mm->binfmt->module))
 1499 		goto free_pt;
 1500 
 1501 	return mm;
 1502 
 1503 free_pt:
 1504 	/* don't put binfmt in mmput, we haven't got module yet */
 1505 	mm->binfmt = NULL;
 1506 	mm_init_owner(mm, NULL);
 1507 	mmput(mm);
 1508 	if (err)
 1509 		uprobe_end_dup_mmap();
 1510 
 1511 fail_nomem:
 1512 	return NULL;
 1513 }
 1514 
 1515 static int copy_mm(u64 clone_flags, struct task_struct *tsk)
 1516 {
 1517 	struct mm_struct *mm, *oldmm;
 1518 
 1519 	tsk->min_flt = tsk->maj_flt = 0;
 1520 	tsk->nvcsw = tsk->nivcsw = 0;
 1521 #ifdef CONFIG_DETECT_HUNG_TASK
 1522 	tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 1523 	tsk->last_switch_time = 0;
 1524 #endif
 1525 
 1526 	tsk->mm = NULL;
 1527 	tsk->active_mm = NULL;
 1528 
 1529 	/*
 1530 	 * Are we cloning a kernel thread?
 1531 	 *
 1532 	 * We need to steal a active VM for that..
 1533 	 */
 1534 	oldmm = current->mm;
 1535 	if (!oldmm)
 1536 		return 0;
 1537 
 1538 	if (clone_flags & CLONE_VM) {
 1539 		mmget(oldmm);
 1540 		mm = oldmm;
 1541 	} else {
 1542 		mm = dup_mm(tsk, current->mm);
 1543 		if (!mm)
 1544 			return -ENOMEM;
 1545 	}
 1546 
 1547 	tsk->mm = mm;
 1548 	tsk->active_mm = mm;
 1549 	sched_mm_cid_fork(tsk);
 1550 	return 0;
 1551 }
 1552 
 1553 static int copy_fs(u64 clone_flags, struct task_struct *tsk)
 1554 {
 1555 	struct fs_struct *fs = current->fs;
 1556 	if (clone_flags & CLONE_FS) {
 1557 		/* tsk->fs is already what we want */
 1558 		read_seqlock_excl(&fs->seq);
 1559 		/* "users" and "in_exec" locked for check_unsafe_exec() */
 1560 		if (fs->in_exec) {
 1561 			read_sequnlock_excl(&fs->seq);
 1562 			return -EAGAIN;
 1563 		}
 1564 		fs->users++;
 1565 		read_sequnlock_excl(&fs->seq);
 1566 		return 0;
 1567 	}
 1568 	tsk->fs = copy_fs_struct(fs);
 1569 	if (!tsk->fs)
 1570 		return -ENOMEM;
 1571 	return 0;
 1572 }
 1573 
 1574 static int copy_files(u64 clone_flags, struct task_struct *tsk,
 1575 		      int no_files)
 1576 {
 1577 	struct files_struct *oldf, *newf;
 1578 
 1579 	/*
 1580 	 * A background process may not have any files ...
 1581 	 */
 1582 	oldf = current->files;
 1583 	if (!oldf)
 1584 		return 0;
 1585 
 1586 	if (no_files) {
 1587 		tsk->files = NULL;
 1588 		return 0;
 1589 	}
 1590 
 1591 	if (clone_flags & CLONE_FILES) {
 1592 		atomic_inc(&oldf->count);
 1593 		return 0;
 1594 	}
 1595 
 1596 	newf = dup_fd(oldf, NULL);
 1597 	if (IS_ERR(newf))
 1598 		return PTR_ERR(newf);
 1599 
 1600 	tsk->files = newf;
 1601 	return 0;
 1602 }
 1603 
 1604 static int copy_sighand(u64 clone_flags, struct task_struct *tsk)
 1605 {
 1606 	struct sighand_struct *sig;
 1607 
 1608 	if (clone_flags & CLONE_SIGHAND) {
 1609 		refcount_inc(&current->sighand->count);
 1610 		return 0;
 1611 	}
 1612 	sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 1613 	RCU_INIT_POINTER(tsk->sighand, sig);
 1614 	if (!sig)
 1615 		return -ENOMEM;
 1616 
 1617 	refcount_set(&sig->count, 1);
 1618 	spin_lock_irq(&current->sighand->siglock);
 1619 	memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 1620 	spin_unlock_irq(&current->sighand->siglock);
 1621 
 1622 	/* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
 1623 	if (clone_flags & CLONE_CLEAR_SIGHAND)
 1624 		flush_signal_handlers(tsk, 0);
 1625 
 1626 	return 0;
 1627 }
 1628 
 1629 void __cleanup_sighand(struct sighand_struct *sighand)
 1630 {
 1631 	if (refcount_dec_and_test(&sighand->count)) {
 1632 		signalfd_cleanup(sighand);
 1633 		/*
 1634 		 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
 1635 		 * without an RCU grace period, see __lock_task_sighand().
 1636 		 */
 1637 		kmem_cache_free(sighand_cachep, sighand);
 1638 	}
 1639 }
 1640 
 1641 /*
 1642  * Initialize POSIX timer handling for a thread group.
 1643  */
 1644 static void posix_cpu_timers_init_group(struct signal_struct *sig)
 1645 {
 1646 	struct posix_cputimers *pct = &sig->posix_cputimers;
 1647 	unsigned long cpu_limit;
 1648 
 1649 	cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
 1650 	posix_cputimers_group_init(pct, cpu_limit);
 1651 }
 1652 
 1653 static int copy_signal(u64 clone_flags, struct task_struct *tsk)
 1654 {
 1655 	struct signal_struct *sig;
 1656 
 1657 	if (clone_flags & CLONE_THREAD)
 1658 		return 0;
 1659 
 1660 	sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
 1661 	tsk->signal = sig;
 1662 	if (!sig)
 1663 		return -ENOMEM;
 1664 
 1665 	sig->nr_threads = 1;
 1666 	sig->quick_threads = 1;
 1667 	atomic_set(&sig->live, 1);
 1668 	refcount_set(&sig->sigcnt, 1);
 1669 
 1670 	/* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
 1671 	sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
 1672 	tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
 1673 
 1674 	init_waitqueue_head(&sig->wait_chldexit);
 1675 	sig->curr_target = tsk;
 1676 	init_sigpending(&sig->shared_pending);
 1677 	INIT_HLIST_HEAD(&sig->multiprocess);
 1678 	seqlock_init(&sig->stats_lock);
 1679 	prev_cputime_init(&sig->prev_cputime);
 1680 
 1681 #ifdef CONFIG_POSIX_TIMERS
 1682 	INIT_HLIST_HEAD(&sig->posix_timers);
 1683 	INIT_HLIST_HEAD(&sig->ignored_posix_timers);
 1684 	hrtimer_setup(&sig->real_timer, it_real_fn, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 1685 #endif
 1686 
 1687 	task_lock(current->group_leader);
 1688 	memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 1689 	task_unlock(current->group_leader);
 1690 
 1691 	posix_cpu_timers_init_group(sig);
 1692 
 1693 	tty_audit_fork(sig);
 1694 	sched_autogroup_fork(sig);
 1695 
 1696 #ifdef CONFIG_CGROUPS
 1697 	init_rwsem(&sig->cgroup_threadgroup_rwsem);
 1698 #endif
 1699 
 1700 	sig->oom_score_adj = current->signal->oom_score_adj;
 1701 	sig->oom_score_adj_min = current->signal->oom_score_adj_min;
 1702 
 1703 	mutex_init(&sig->cred_guard_mutex);
 1704 	init_rwsem(&sig->exec_update_lock);
 1705 
 1706 	return 0;
 1707 }
 1708 
 1709 static void copy_seccomp(struct task_struct *p)
 1710 {
 1711 #ifdef CONFIG_SECCOMP
 1712 	/*
 1713 	 * Must be called with sighand->lock held, which is common to
 1714 	 * all threads in the group. Holding cred_guard_mutex is not
 1715 	 * needed because this new task is not yet running and cannot
 1716 	 * be racing exec.
 1717 	 */
 1718 	assert_spin_locked(&current->sighand->siglock);
 1719 
 1720 	/* Ref-count the new filter user, and assign it. */
 1721 	get_seccomp_filter(current);
 1722 	p->seccomp = current->seccomp;
 1723 
 1724 	/*
 1725 	 * Explicitly enable no_new_privs here in case it got set
 1726 	 * between the task_struct being duplicated and holding the
 1727 	 * sighand lock. The seccomp state and nnp must be in sync.
 1728 	 */
 1729 	if (task_no_new_privs(current))
 1730 		task_set_no_new_privs(p);
 1731 
 1732 	/*
 1733 	 * If the parent gained a seccomp mode after copying thread
 1734 	 * flags and between before we held the sighand lock, we have
 1735 	 * to manually enable the seccomp thread flag here.
 1736 	 */
 1737 	if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
 1738 		set_task_syscall_work(p, SECCOMP);
 1739 #endif
 1740 }
 1741 
 1742 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
 1743 {
 1744 	current->clear_child_tid = tidptr;
 1745 
 1746 	return task_pid_vnr(current);
 1747 }
 1748 
 1749 static void rt_mutex_init_task(struct task_struct *p)
 1750 {
 1751 	raw_spin_lock_init(&p->pi_lock);
 1752 #ifdef CONFIG_RT_MUTEXES
 1753 	p->pi_waiters = RB_ROOT_CACHED;
 1754 	p->pi_top_task = NULL;
 1755 	p->pi_blocked_on = NULL;
 1756 #endif
 1757 }
 1758 
 1759 static inline void init_task_pid_links(struct task_struct *task)
 1760 {
 1761 	enum pid_type type;
 1762 
 1763 	for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type)
 1764 		INIT_HLIST_NODE(&task->pid_links[type]);
 1765 }
 1766 
 1767 static inline void
 1768 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
 1769 {
 1770 	if (type == PIDTYPE_PID)
 1771 		task->thread_pid = pid;
 1772 	else
 1773 		task->signal->pids[type] = pid;
 1774 }
 1775 
 1776 static inline void rcu_copy_process(struct task_struct *p)
 1777 {
 1778 #ifdef CONFIG_PREEMPT_RCU
 1779 	p->rcu_read_lock_nesting = 0;
 1780 	p->rcu_read_unlock_special.s = 0;
 1781 	p->rcu_blocked_node = NULL;
 1782 	INIT_LIST_HEAD(&p->rcu_node_entry);
 1783 #endif /* #ifdef CONFIG_PREEMPT_RCU */
 1784 #ifdef CONFIG_TASKS_RCU
 1785 	p->rcu_tasks_holdout = false;
 1786 	INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
 1787 	p->rcu_tasks_idle_cpu = -1;
 1788 	INIT_LIST_HEAD(&p->rcu_tasks_exit_list);
 1789 #endif /* #ifdef CONFIG_TASKS_RCU */
 1790 #ifdef CONFIG_TASKS_TRACE_RCU
 1791 	p->trc_reader_nesting = 0;
 1792 	p->trc_reader_special.s = 0;
 1793 	INIT_LIST_HEAD(&p->trc_holdout_list);
 1794 	INIT_LIST_HEAD(&p->trc_blkd_node);
 1795 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
 1796 }
 1797 
 1798 /**
 1799  * pidfd_prepare - allocate a new pidfd_file and reserve a pidfd
 1800  * @pid:   the struct pid for which to create a pidfd
 1801  * @flags: flags of the new @pidfd
 1802  * @ret_file: return the new pidfs file
 1803  *
 1804  * Allocate a new file that stashes @pid and reserve a new pidfd number in the
 1805  * caller's file descriptor table. The pidfd is reserved but not installed yet.
 1806  *
 1807  * The helper verifies that @pid is still in use, without PIDFD_THREAD the
 1808  * task identified by @pid must be a thread-group leader.
 1809  *
 1810  * If this function returns successfully the caller is responsible to either
 1811  * call fd_install() passing the returned pidfd and pidfd file as arguments in
 1812  * order to install the pidfd into its file descriptor table or they must use
 1813  * put_unused_fd() and fput() on the returned pidfd and pidfd file
 1814  * respectively.
 1815  *
 1816  * This function is useful when a pidfd must already be reserved but there
 1817  * might still be points of failure afterwards and the caller wants to ensure
 1818  * that no pidfd is leaked into its file descriptor table.
 1819  *
 1820  * Return: On success, a reserved pidfd is returned from the function and a new
 1821  *         pidfd file is returned in the last argument to the function. On
 1822  *         error, a negative error code is returned from the function and the
 1823  *         last argument remains unchanged.
 1824  */
 1825 int pidfd_prepare(struct pid *pid, unsigned int flags, struct file **ret_file)
 1826 {
 1827 	struct file *pidfs_file;
 1828 
 1829 	/*
 1830 	 * PIDFD_STALE is only allowed to be passed if the caller knows
 1831 	 * that @pid is already registered in pidfs and thus
 1832 	 * PIDFD_INFO_EXIT information is guaranteed to be available.
 1833 	 */
 1834 	if (!(flags & PIDFD_STALE)) {
 1835 		/*
 1836 		 * While holding the pidfd waitqueue lock removing the
 1837 		 * task linkage for the thread-group leader pid
 1838 		 * (PIDTYPE_TGID) isn't possible. Thus, if there's still
 1839 		 * task linkage for PIDTYPE_PID not having thread-group
 1840 		 * leader linkage for the pid means it wasn't a
 1841 		 * thread-group leader in the first place.
 1842 		 */
 1843 		guard(spinlock_irq)(&pid->wait_pidfd.lock);
 1844 
 1845 		/* Task has already been reaped. */
 1846 		if (!pid_has_task(pid, PIDTYPE_PID))
 1847 			return -ESRCH;
 1848 		/*
 1849 		 * If this struct pid isn't used as a thread-group
 1850 		 * leader but the caller requested to create a
 1851 		 * thread-group leader pidfd then report ENOENT.
 1852 		 */
 1853 		if (!(flags & PIDFD_THREAD) && !pid_has_task(pid, PIDTYPE_TGID))
 1854 			return -ENOENT;
 1855 	}
 1856 
 1857 	CLASS(get_unused_fd, pidfd)(O_CLOEXEC);
 1858 	if (pidfd < 0)
 1859 		return pidfd;
 1860 
 1861 	pidfs_file = pidfs_alloc_file(pid, flags | O_RDWR);
 1862 	if (IS_ERR(pidfs_file))
 1863 		return PTR_ERR(pidfs_file);
 1864 
 1865 	*ret_file = pidfs_file;
 1866 	return take_fd(pidfd);
 1867 }
 1868 
 1869 static void __delayed_free_task(struct rcu_head *rhp)
 1870 {
 1871 	struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
 1872 
 1873 	free_task(tsk);
 1874 }
 1875 
 1876 static __always_inline void delayed_free_task(struct task_struct *tsk)
 1877 {
 1878 	if (IS_ENABLED(CONFIG_MEMCG))
 1879 		call_rcu(&tsk->rcu, __delayed_free_task);
 1880 	else
 1881 		free_task(tsk);
 1882 }
 1883 
 1884 static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk)
 1885 {
 1886 	/* Skip if kernel thread */
 1887 	if (!tsk->mm)
 1888 		return;
 1889 
 1890 	/* Skip if spawning a thread or using vfork */
 1891 	if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) != CLONE_VM)
 1892 		return;
 1893 
 1894 	/* We need to synchronize with __set_oom_adj */
 1895 	mutex_lock(&oom_adj_mutex);
 1896 	mm_flags_set(MMF_MULTIPROCESS, tsk->mm);
 1897 	/* Update the values in case they were changed after copy_signal */
 1898 	tsk->signal->oom_score_adj = current->signal->oom_score_adj;
 1899 	tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min;
 1900 	mutex_unlock(&oom_adj_mutex);
 1901 }
 1902 
 1903 #ifdef CONFIG_RV
 1904 static void rv_task_fork(struct task_struct *p)
 1905 {
 1906 	memset(&p->rv, 0, sizeof(p->rv));
 1907 }
 1908 #else
 1909 #define rv_task_fork(p) do {} while (0)
 1910 #endif
 1911 
 1912 static bool need_futex_hash_allocate_default(u64 clone_flags)
 1913 {
 1914 	/*
 1915 	 * Allocate a default futex hash for any sibling that will
 1916 	 * share the parent's mm, except vfork.
 1917 	 */
 1918 	return (clone_flags & (CLONE_VM | CLONE_VFORK)) == CLONE_VM;
 1919 }
 1920 
 1921 /*
 1922  * This creates a new process as a copy of the old one,
 1923  * but does not actually start it yet.
 1924  *
 1925  * It copies the registers, and all the appropriate
 1926  * parts of the process environment (as per the clone
 1927  * flags). The actual kick-off is left to the caller.
 1928  */
 1929 __latent_entropy struct task_struct *copy_process(
 1930 					struct pid *pid,
 1931 					int trace,
 1932 					int node,
 1933 					struct kernel_clone_args *args)
 1934 {
 1935 	int pidfd = -1, retval;
 1936 	struct task_struct *p;
 1937 	struct multiprocess_signals delayed;
 1938 	struct file *pidfile = NULL;
 1939 	const u64 clone_flags = args->flags;
 1940 	struct nsproxy *nsp = current->nsproxy;
 1941 
 1942 	/*
 1943 	 * Don't allow sharing the root directory with processes in a different
 1944 	 * namespace
 1945 	 */
 1946 	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 1947 		return ERR_PTR(-EINVAL);
 1948 
 1949 	if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
 1950 		return ERR_PTR(-EINVAL);
 1951 
 1952 	/*
 1953 	 * Thread groups must share signals as well, and detached threads
 1954 	 * can only be started up within the thread group.
 1955 	 */
 1956 	if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 1957 		return ERR_PTR(-EINVAL);
 1958 
 1959 	/*
 1960 	 * Shared signal handlers imply shared VM. By way of the above,
 1961 	 * thread groups also imply shared VM. Blocking this case allows
 1962 	 * for various simplifications in other code.
 1963 	 */
 1964 	if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
 1965 		return ERR_PTR(-EINVAL);
 1966 
 1967 	/*
 1968 	 * Siblings of global init remain as zombies on exit since they are
 1969 	 * not reaped by their parent (swapper). To solve this and to avoid
 1970 	 * multi-rooted process trees, prevent global and container-inits
 1971 	 * from creating siblings.
 1972 	 */
 1973 	if ((clone_flags & CLONE_PARENT) &&
 1974 				current->signal->flags & SIGNAL_UNKILLABLE)
 1975 		return ERR_PTR(-EINVAL);
 1976 
 1977 	/*
 1978 	 * If the new process will be in a different pid or user namespace
 1979 	 * do not allow it to share a thread group with the forking task.
 1980 	 */
 1981 	if (clone_flags & CLONE_THREAD) {
 1982 		if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
 1983 		    (task_active_pid_ns(current) != nsp->pid_ns_for_children))
 1984 			return ERR_PTR(-EINVAL);
 1985 	}
 1986 
 1987 	if (clone_flags & CLONE_PIDFD) {
 1988 		/*
 1989 		 * - CLONE_DETACHED is blocked so that we can potentially
 1990 		 *   reuse it later for CLONE_PIDFD.
 1991 		 */
 1992 		if (clone_flags & CLONE_DETACHED)
 1993 			return ERR_PTR(-EINVAL);
 1994 	}
 1995 
 1996 	/*
 1997 	 * Force any signals received before this point to be delivered
 1998 	 * before the fork happens.  Collect up signals sent to multiple
 1999 	 * processes that happen during the fork and delay them so that
 2000 	 * they appear to happen after the fork.
 2001 	 */
 2002 	sigemptyset(&delayed.signal);
 2003 	INIT_HLIST_NODE(&delayed.node);
 2004 
 2005 	spin_lock_irq(&current->sighand->siglock);
 2006 	if (!(clone_flags & CLONE_THREAD))
 2007 		hlist_add_head(&delayed.node, &current->signal->multiprocess);
 2008 	recalc_sigpending();
 2009 	spin_unlock_irq(&current->sighand->siglock);
 2010 	retval = -ERESTARTNOINTR;
 2011 	if (task_sigpending(current))
 2012 		goto fork_out;
 2013 
 2014 	retval = -ENOMEM;
 2015 	p = dup_task_struct(current, node);
 2016 	if (!p)
 2017 		goto fork_out;
 2018 	p->flags &= ~PF_KTHREAD;
 2019 	if (args->kthread)
 2020 		p->flags |= PF_KTHREAD;
 2021 	if (args->user_worker) {
 2022 		/*
 2023 		 * Mark us a user worker, and block any signal that isn't
 2024 		 * fatal or STOP
 2025 		 */
 2026 		p->flags |= PF_USER_WORKER;
 2027 		siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
 2028 	}
 2029 	if (args->io_thread)
 2030 		p->flags |= PF_IO_WORKER;
 2031 
 2032 	if (args->name)
 2033 		strscpy_pad(p->comm, args->name, sizeof(p->comm));
 2034 
 2035 	p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
 2036 	/*
 2037 	 * Clear TID on mm_release()?
 2038 	 */
 2039 	p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
 2040 
 2041 	ftrace_graph_init_task(p);
 2042 
 2043 	rt_mutex_init_task(p);
 2044 
 2045 	lockdep_assert_irqs_enabled();
 2046 #ifdef CONFIG_PROVE_LOCKING
 2047 	DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
 2048 #endif
 2049 	retval = copy_creds(p, clone_flags);
 2050 	if (retval < 0)
 2051 		goto bad_fork_free;
 2052 
 2053 	retval = -EAGAIN;
 2054 	if (is_rlimit_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
 2055 		if (p->real_cred->user != INIT_USER &&
 2056 		    !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
 2057 			goto bad_fork_cleanup_count;
 2058 	}
 2059 	current->flags &= ~PF_NPROC_EXCEEDED;
 2060 
 2061 	/*
 2062 	 * If multiple threads are within copy_process(), then this check
 2063 	 * triggers too late. This doesn't hurt, the check is only there
 2064 	 * to stop root fork bombs.
 2065 	 */
 2066 	retval = -EAGAIN;
 2067 	if (data_race(nr_threads >= max_threads))
 2068 		goto bad_fork_cleanup_count;
 2069 
 2070 	delayacct_tsk_init(p);	/* Must remain after dup_task_struct() */
 2071 	p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE | PF_NO_SETAFFINITY);
 2072 	p->flags |= PF_FORKNOEXEC;
 2073 	INIT_LIST_HEAD(&p->children);
 2074 	INIT_LIST_HEAD(&p->sibling);
 2075 	rcu_copy_process(p);
 2076 	p->vfork_done = NULL;
 2077 	spin_lock_init(&p->alloc_lock);
 2078 
 2079 	init_sigpending(&p->pending);
 2080 
 2081 	p->utime = p->stime = p->gtime = 0;
 2082 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
 2083 	p->utimescaled = p->stimescaled = 0;
 2084 #endif
 2085 	prev_cputime_init(&p->prev_cputime);
 2086 
 2087 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
 2088 	seqcount_init(&p->vtime.seqcount);
 2089 	p->vtime.starttime = 0;
 2090 	p->vtime.state = VTIME_INACTIVE;
 2091 #endif
 2092 
 2093 #ifdef CONFIG_IO_URING
 2094 	p->io_uring = NULL;
 2095 #endif
 2096 
 2097 	p->default_timer_slack_ns = current->timer_slack_ns;
 2098 
 2099 #ifdef CONFIG_PSI
 2100 	p->psi_flags = 0;
 2101 #endif
 2102 
 2103 	task_io_accounting_init(&p->ioac);
 2104 	acct_clear_integrals(p);
 2105 
 2106 	posix_cputimers_init(&p->posix_cputimers);
 2107 	tick_dep_init_task(p);
 2108 
 2109 	p->io_context = NULL;
 2110 	audit_set_context(p, NULL);
 2111 	cgroup_fork(p);
 2112 	if (args->kthread) {
 2113 		if (!set_kthread_struct(p))
 2114 			goto bad_fork_cleanup_delayacct;
 2115 	}
 2116 #ifdef CONFIG_NUMA
 2117 	p->mempolicy = mpol_dup(p->mempolicy);
 2118 	if (IS_ERR(p->mempolicy)) {
 2119 		retval = PTR_ERR(p->mempolicy);
 2120 		p->mempolicy = NULL;
 2121 		goto bad_fork_cleanup_delayacct;
 2122 	}
 2123 #endif
 2124 #ifdef CONFIG_CPUSETS
 2125 	p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
 2126 	seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock);
 2127 #endif
 2128 #ifdef CONFIG_TRACE_IRQFLAGS
 2129 	memset(&p->irqtrace, 0, sizeof(p->irqtrace));
 2130 	p->irqtrace.hardirq_disable_ip	= _THIS_IP_;
 2131 	p->irqtrace.softirq_enable_ip	= _THIS_IP_;
 2132 	p->softirqs_enabled		= 1;
 2133 	p->softirq_context		= 0;
 2134 #endif
 2135 
 2136 	p->pagefault_disabled = 0;
 2137 
 2138 	lockdep_init_task(p);
 2139 
 2140 	p->blocked_on = NULL; /* not blocked yet */
 2141 
 2142 #ifdef CONFIG_BCACHE
 2143 	p->sequential_io	= 0;
 2144 	p->sequential_io_avg	= 0;
 2145 #endif
 2146 #ifdef CONFIG_BPF_SYSCALL
 2147 	RCU_INIT_POINTER(p->bpf_storage, NULL);
 2148 	p->bpf_ctx = NULL;
 2149 #endif
 2150 
 2151 	unwind_task_init(p);
 2152 
 2153 	/* Perform scheduler related setup. Assign this task to a CPU. */
 2154 	retval = sched_fork(clone_flags, p);
 2155 	if (retval)
 2156 		goto bad_fork_cleanup_policy;
 2157 
 2158 	retval = perf_event_init_task(p, clone_flags);
 2159 	if (retval)
 2160 		goto bad_fork_sched_cancel_fork;
 2161 	retval = audit_alloc(p);
 2162 	if (retval)
 2163 		goto bad_fork_cleanup_perf;
 2164 	/* copy all the process information */
 2165 	shm_init_task(p);
 2166 	retval = security_task_alloc(p, clone_flags);
 2167 	if (retval)
 2168 		goto bad_fork_cleanup_audit;
 2169 	retval = copy_semundo(clone_flags, p);
 2170 	if (retval)
 2171 		goto bad_fork_cleanup_security;
 2172 	retval = copy_files(clone_flags, p, args->no_files);
 2173 	if (retval)
 2174 		goto bad_fork_cleanup_semundo;
 2175 	retval = copy_fs(clone_flags, p);
 2176 	if (retval)
 2177 		goto bad_fork_cleanup_files;
 2178 	retval = copy_sighand(clone_flags, p);
 2179 	if (retval)
 2180 		goto bad_fork_cleanup_fs;
 2181 	retval = copy_signal(clone_flags, p);
 2182 	if (retval)
 2183 		goto bad_fork_cleanup_sighand;
 2184 	retval = copy_mm(clone_flags, p);
 2185 	if (retval)
 2186 		goto bad_fork_cleanup_signal;
 2187 	retval = copy_namespaces(clone_flags, p);
 2188 	if (retval)
 2189 		goto bad_fork_cleanup_mm;
 2190 	retval = copy_io(clone_flags, p);
 2191 	if (retval)
 2192 		goto bad_fork_cleanup_namespaces;
 2193 	retval = copy_thread(p, args);
 2194 	if (retval)
 2195 		goto bad_fork_cleanup_io;
 2196 
 2197 	random_kstack_task_init(p);
 2198 	stackleak_task_init(p);
 2199 
 2200 	if (pid != &init_struct_pid) {
 2201 		pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
 2202 				args->set_tid_size);
 2203 		if (IS_ERR(pid)) {
 2204 			retval = PTR_ERR(pid);
 2205 			goto bad_fork_cleanup_thread;
 2206 		}
 2207 	}
 2208 
 2209 	/*
 2210 	 * This has to happen after we've potentially unshared the file
 2211 	 * descriptor table (so that the pidfd doesn't leak into the child
 2212 	 * if the fd table isn't shared).
 2213 	 */
 2214 	if (clone_flags & CLONE_PIDFD) {
 2215 		int flags = (clone_flags & CLONE_THREAD) ? PIDFD_THREAD : 0;
 2216 
 2217 		/*
 2218 		 * Note that no task has been attached to @pid yet indicate
 2219 		 * that via CLONE_PIDFD.
 2220 		 */
 2221 		retval = pidfd_prepare(pid, flags | PIDFD_STALE, &pidfile);
 2222 		if (retval < 0)
 2223 			goto bad_fork_free_pid;
 2224 		pidfd = retval;
 2225 
 2226 		retval = put_user(pidfd, args->pidfd);
 2227 		if (retval)
 2228 			goto bad_fork_put_pidfd;
 2229 	}
 2230 
 2231 #ifdef CONFIG_BLOCK
 2232 	p->plug = NULL;
 2233 #endif
 2234 	futex_init_task(p);
 2235 
 2236 	/*
 2237 	 * sigaltstack should be cleared when sharing the same VM
 2238 	 */
 2239 	if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
 2240 		sas_ss_reset(p);
 2241 
 2242 	/*
 2243 	 * Syscall tracing and stepping should be turned off in the
 2244 	 * child regardless of CLONE_PTRACE.
 2245 	 */
 2246 	user_disable_single_step(p);
 2247 	clear_task_syscall_work(p, SYSCALL_TRACE);
 2248 #if defined(CONFIG_GENERIC_ENTRY) || defined(TIF_SYSCALL_EMU)
 2249 	clear_task_syscall_work(p, SYSCALL_EMU);
 2250 #endif
 2251 	clear_tsk_latency_tracing(p);
 2252 
 2253 	/* ok, now we should be set up.. */
 2254 	p->pid = pid_nr(pid);
 2255 	if (clone_flags & CLONE_THREAD) {
 2256 		p->group_leader = current->group_leader;
 2257 		p->tgid = current->tgid;
 2258 	} else {
 2259 		p->group_leader = p;
 2260 		p->tgid = p->pid;
 2261 	}
 2262 
 2263 	p->nr_dirtied = 0;
 2264 	p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
 2265 	p->dirty_paused_when = 0;
 2266 
 2267 	p->pdeath_signal = 0;
 2268 	p->task_works = NULL;
 2269 	clear_posix_cputimers_work(p);
 2270 
 2271 #ifdef CONFIG_KRETPROBES
 2272 	p->kretprobe_instances.first = NULL;
 2273 #endif
 2274 #ifdef CONFIG_RETHOOK
 2275 	p->rethooks.first = NULL;
 2276 #endif
 2277 
 2278 	/*
 2279 	 * Ensure that the cgroup subsystem policies allow the new process to be
 2280 	 * forked. It should be noted that the new process's css_set can be changed
 2281 	 * between here and cgroup_post_fork() if an organisation operation is in
 2282 	 * progress.
 2283 	 */
 2284 	retval = cgroup_can_fork(p, args);
 2285 	if (retval)
 2286 		goto bad_fork_put_pidfd;
 2287 
 2288 	/*
 2289 	 * Now that the cgroups are pinned, re-clone the parent cgroup and put
 2290 	 * the new task on the correct runqueue. All this *before* the task
 2291 	 * becomes visible.
 2292 	 *
 2293 	 * This isn't part of ->can_fork() because while the re-cloning is
 2294 	 * cgroup specific, it unconditionally needs to place the task on a
 2295 	 * runqueue.
 2296 	 */
 2297 	retval = sched_cgroup_fork(p, args);
 2298 	if (retval)
 2299 		goto bad_fork_cancel_cgroup;
 2300 
 2301 	if (need_futex_hash_allocate_default(clone_flags)) {
 2302 		retval = futex_hash_allocate_default();
 2303 		if (retval)
 2304 			goto bad_fork_cancel_cgroup;
 2305 		/*
 2306 		 * If we fail beyond this point we don't free the allocated
 2307 		 * futex hash map. We assume that another thread will be created
 2308 		 * and makes use of it. The hash map will be freed once the main
 2309 		 * thread terminates.
 2310 		 */
 2311 	}
 2312 	/*
 2313 	 * From this point on we must avoid any synchronous user-space
 2314 	 * communication until we take the tasklist-lock. In particular, we do
 2315 	 * not want user-space to be able to predict the process start-time by
 2316 	 * stalling fork(2) after we recorded the start_time but before it is
 2317 	 * visible to the system.
 2318 	 */
 2319 
 2320 	p->start_time = ktime_get_ns();
 2321 	p->start_boottime = ktime_get_boottime_ns();
 2322 
 2323 	/*
 2324 	 * Make it visible to the rest of the system, but dont wake it up yet.
 2325 	 * Need tasklist lock for parent etc handling!
 2326 	 */
 2327 	write_lock_irq(&tasklist_lock);
 2328 
 2329 	/* CLONE_PARENT re-uses the old parent */
 2330 	if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
 2331 		p->real_parent = current->real_parent;
 2332 		p->parent_exec_id = current->parent_exec_id;
 2333 		if (clone_flags & CLONE_THREAD)
 2334 			p->exit_signal = -1;
 2335 		else
 2336 			p->exit_signal = current->group_leader->exit_signal;
 2337 	} else {
 2338 		p->real_parent = current;
 2339 		p->parent_exec_id = current->self_exec_id;
 2340 		p->exit_signal = args->exit_signal;
 2341 	}
 2342 
 2343 	klp_copy_process(p);
 2344 
 2345 	sched_core_fork(p);
 2346 
 2347 	spin_lock(&current->sighand->siglock);
 2348 
 2349 	rv_task_fork(p);
 2350 
 2351 	rseq_fork(p, clone_flags);
 2352 
 2353 	/* Don't start children in a dying pid namespace */
 2354 	if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
 2355 		retval = -ENOMEM;
 2356 		goto bad_fork_core_free;
 2357 	}
 2358 
 2359 	/* Let kill terminate clone/fork in the middle */
 2360 	if (fatal_signal_pending(current)) {
 2361 		retval = -EINTR;
 2362 		goto bad_fork_core_free;
 2363 	}
 2364 
 2365 	/* No more failure paths after this point. */
 2366 
 2367 	/*
 2368 	 * Copy seccomp details explicitly here, in case they were changed
 2369 	 * before holding sighand lock.
 2370 	 */
 2371 	copy_seccomp(p);
 2372 
 2373 	init_task_pid_links(p);
 2374 	if (likely(p->pid)) {
 2375 		ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
 2376 
 2377 		init_task_pid(p, PIDTYPE_PID, pid);
 2378 		if (thread_group_leader(p)) {
 2379 			init_task_pid(p, PIDTYPE_TGID, pid);
 2380 			init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
 2381 			init_task_pid(p, PIDTYPE_SID, task_session(current));
 2382 
 2383 			if (is_child_reaper(pid)) {
 2384 				ns_of_pid(pid)->child_reaper = p;
 2385 				p->signal->flags |= SIGNAL_UNKILLABLE;
 2386 			}
 2387 			p->signal->shared_pending.signal = delayed.signal;
 2388 			p->signal->tty = tty_kref_get(current->signal->tty);
 2389 			/*
 2390 			 * Inherit has_child_subreaper flag under the same
 2391 			 * tasklist_lock with adding child to the process tree
 2392 			 * for propagate_has_child_subreaper optimization.
 2393 			 */
 2394 			p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
 2395 							 p->real_parent->signal->is_child_subreaper;
 2396 			list_add_tail(&p->sibling, &p->real_parent->children);
 2397 			list_add_tail_rcu(&p->tasks, &init_task.tasks);
 2398 			attach_pid(p, PIDTYPE_TGID);
 2399 			attach_pid(p, PIDTYPE_PGID);
 2400 			attach_pid(p, PIDTYPE_SID);
 2401 			__this_cpu_inc(process_counts);
 2402 		} else {
 2403 			current->signal->nr_threads++;
 2404 			current->signal->quick_threads++;
 2405 			atomic_inc(&current->signal->live);
 2406 			refcount_inc(&current->signal->sigcnt);
 2407 			task_join_group_stop(p);
 2408 			list_add_tail_rcu(&p->thread_node,
 2409 					  &p->signal->thread_head);
 2410 		}
 2411 		attach_pid(p, PIDTYPE_PID);
 2412 		nr_threads++;
 2413 	}
 2414 	total_forks++;
 2415 	hlist_del_init(&delayed.node);
 2416 	spin_unlock(&current->sighand->siglock);
 2417 	syscall_tracepoint_update(p);
 2418 	write_unlock_irq(&tasklist_lock);
 2419 
 2420 	if (pidfile)
 2421 		fd_install(pidfd, pidfile);
 2422 
 2423 	proc_fork_connector(p);
 2424 	sched_post_fork(p);
 2425 	cgroup_post_fork(p, args);
 2426 	perf_event_fork(p);
 2427 
 2428 	trace_task_newtask(p, clone_flags);
 2429 	uprobe_copy_process(p, clone_flags);
 2430 	user_events_fork(p, clone_flags);
 2431 
 2432 	copy_oom_score_adj(clone_flags, p);
 2433 
 2434 	return p;
 2435 
 2436 bad_fork_core_free:
 2437 	sched_core_free(p);
 2438 	spin_unlock(&current->sighand->siglock);
 2439 	write_unlock_irq(&tasklist_lock);
 2440 bad_fork_cancel_cgroup:
 2441 	cgroup_cancel_fork(p, args);
 2442 bad_fork_put_pidfd:
 2443 	if (clone_flags & CLONE_PIDFD) {
 2444 		fput(pidfile);
 2445 		put_unused_fd(pidfd);
 2446 	}
 2447 bad_fork_free_pid:
 2448 	if (pid != &init_struct_pid)
 2449 		free_pid(pid);
 2450 bad_fork_cleanup_thread:
 2451 	exit_thread(p);
 2452 bad_fork_cleanup_io:
 2453 	if (p->io_context)
 2454 		exit_io_context(p);
 2455 bad_fork_cleanup_namespaces:
 2456 	exit_task_namespaces(p);
 2457 bad_fork_cleanup_mm:
 2458 	if (p->mm) {
 2459 		mm_clear_owner(p->mm, p);
 2460 		mmput(p->mm);
 2461 	}
 2462 bad_fork_cleanup_signal:
 2463 	if (!(clone_flags & CLONE_THREAD))
 2464 		free_signal_struct(p->signal);
 2465 bad_fork_cleanup_sighand:
 2466 	__cleanup_sighand(p->sighand);
 2467 bad_fork_cleanup_fs:
 2468 	exit_fs(p); /* blocking */
 2469 bad_fork_cleanup_files:
 2470 	exit_files(p); /* blocking */
 2471 bad_fork_cleanup_semundo:
 2472 	exit_sem(p);
 2473 bad_fork_cleanup_security:
 2474 	security_task_free(p);
 2475 bad_fork_cleanup_audit:
 2476 	audit_free(p);
 2477 bad_fork_cleanup_perf:
 2478 	perf_event_free_task(p);
 2479 bad_fork_sched_cancel_fork:
 2480 	sched_cancel_fork(p);
 2481 bad_fork_cleanup_policy:
 2482 	lockdep_free_task(p);
 2483 #ifdef CONFIG_NUMA
 2484 	mpol_put(p->mempolicy);
 2485 #endif
 2486 bad_fork_cleanup_delayacct:
 2487 	delayacct_tsk_free(p);
 2488 bad_fork_cleanup_count:
 2489 	dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
 2490 	exit_creds(p);
 2491 bad_fork_free:
 2492 	WRITE_ONCE(p->__state, TASK_DEAD);
 2493 	exit_task_stack_account(p);
 2494 	put_task_stack(p);
 2495 	delayed_free_task(p);
 2496 fork_out:
 2497 	spin_lock_irq(&current->sighand->siglock);
 2498 	hlist_del_init(&delayed.node);
 2499 	spin_unlock_irq(&current->sighand->siglock);
 2500 	return ERR_PTR(retval);
 2501 }
 2502 
 2503 static inline void init_idle_pids(struct task_struct *idle)
 2504 {
 2505 	enum pid_type type;
 2506 
 2507 	for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
 2508 		INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
 2509 		init_task_pid(idle, type, &init_struct_pid);
 2510 	}
 2511 }
 2512 
 2513 static int idle_dummy(void *dummy)
 2514 {
 2515 	/* This function is never called */
 2516 	return 0;
 2517 }
 2518 
 2519 struct task_struct * __init fork_idle(int cpu)
 2520 {
 2521 	struct task_struct *task;
 2522 	struct kernel_clone_args args = {
 2523 		.flags		= CLONE_VM,
 2524 		.fn		= &idle_dummy,
 2525 		.fn_arg		= NULL,
 2526 		.kthread	= 1,
 2527 		.idle		= 1,
 2528 	};
 2529 
 2530 	task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
 2531 	if (!IS_ERR(task)) {
 2532 		init_idle_pids(task);
 2533 		init_idle(task, cpu);
 2534 	}
 2535 
 2536 	return task;
 2537 }
 2538 
 2539 /*
 2540  * This is like kernel_clone(), but shaved down and tailored to just
 2541  * creating io_uring workers. It returns a created task, or an error pointer.
 2542  * The returned task is inactive, and the caller must fire it up through
 2543  * wake_up_new_task(p). All signals are blocked in the created task.
 2544  */
 2545 struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
 2546 {
 2547 	unsigned long flags = CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|
 2548 			      CLONE_IO|CLONE_VM|CLONE_UNTRACED;
 2549 	struct kernel_clone_args args = {
 2550 		.flags		= flags,
 2551 		.fn		= fn,
 2552 		.fn_arg		= arg,
 2553 		.io_thread	= 1,
 2554 		.user_worker	= 1,
 2555 	};
 2556 
 2557 	return copy_process(NULL, 0, node, &args);
 2558 }
 2559 
 2560 /*
 2561  *  Ok, this is the main fork-routine.
 2562  *
 2563  * It copies the process, and if successful kick-starts
 2564  * it and waits for it to finish using the VM if required.
 2565  *
 2566  * args->exit_signal is expected to be checked for sanity by the caller.
 2567  */
 2568 pid_t kernel_clone(struct kernel_clone_args *args)
 2569 {
 2570 	u64 clone_flags = args->flags;
 2571 	struct completion vfork;
 2572 	struct pid *pid;
 2573 	struct task_struct *p;
 2574 	int trace = 0;
 2575 	pid_t nr;
 2576 
 2577 	/*
 2578 	 * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
 2579 	 * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
 2580 	 * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
 2581 	 * field in struct clone_args and it still doesn't make sense to have
 2582 	 * them both point at the same memory location. Performing this check
 2583 	 * here has the advantage that we don't need to have a separate helper
 2584 	 * to check for legacy clone().
 2585 	 */
 2586 	if ((clone_flags & CLONE_PIDFD) &&
 2587 	    (clone_flags & CLONE_PARENT_SETTID) &&
 2588 	    (args->pidfd == args->parent_tid))
 2589 		return -EINVAL;
 2590 
 2591 	/*
 2592 	 * Determine whether and which event to report to ptracer.  When
 2593 	 * called from kernel_thread or CLONE_UNTRACED is explicitly
 2594 	 * requested, no event is reported; otherwise, report if the event
 2595 	 * for the type of forking is enabled.
 2596 	 */
 2597 	if (!(clone_flags & CLONE_UNTRACED)) {
 2598 		if (clone_flags & CLONE_VFORK)
 2599 			trace = PTRACE_EVENT_VFORK;
 2600 		else if (args->exit_signal != SIGCHLD)
 2601 			trace = PTRACE_EVENT_CLONE;
 2602 		else
 2603 			trace = PTRACE_EVENT_FORK;
 2604 
 2605 		if (likely(!ptrace_event_enabled(current, trace)))
 2606 			trace = 0;
 2607 	}
 2608 
 2609 	p = copy_process(NULL, trace, NUMA_NO_NODE, args);
 2610 	add_latent_entropy();
 2611 
 2612 	if (IS_ERR(p))
 2613 		return PTR_ERR(p);
 2614 
 2615 	/*
 2616 	 * Do this prior waking up the new thread - the thread pointer
 2617 	 * might get invalid after that point, if the thread exits quickly.
 2618 	 */
 2619 	trace_sched_process_fork(current, p);
 2620 
 2621 	pid = get_task_pid(p, PIDTYPE_PID);
 2622 	nr = pid_vnr(pid);
 2623 
 2624 	if (clone_flags & CLONE_PARENT_SETTID)
 2625 		put_user(nr, args->parent_tid);
 2626 
 2627 	if (clone_flags & CLONE_VFORK) {
 2628 		p->vfork_done = &vfork;
 2629 		init_completion(&vfork);
 2630 		get_task_struct(p);
 2631 	}
 2632 
 2633 	if (IS_ENABLED(CONFIG_LRU_GEN_WALKS_MMU) && !(clone_flags & CLONE_VM)) {
 2634 		/* lock the task to synchronize with memcg migration */
 2635 		task_lock(p);
 2636 		lru_gen_add_mm(p->mm);
 2637 		task_unlock(p);
 2638 	}
 2639 
 2640 	wake_up_new_task(p);
 2641 
 2642 	/* forking complete and child started to run, tell ptracer */
 2643 	if (unlikely(trace))
 2644 		ptrace_event_pid(trace, pid);
 2645 
 2646 	if (clone_flags & CLONE_VFORK) {
 2647 		if (!wait_for_vfork_done(p, &vfork))
 2648 			ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
 2649 	}
 2650 
 2651 	put_pid(pid);
 2652 	return nr;
 2653 }
 2654 
 2655 /*
 2656  * Create a kernel thread.
 2657  */
 2658 pid_t kernel_thread(int (*fn)(void *), void *arg, const char *name,
 2659 		    unsigned long flags)
 2660 {
 2661 	struct kernel_clone_args args = {
 2662 		.flags		= ((flags | CLONE_VM | CLONE_UNTRACED) & ~CSIGNAL),
 2663 		.exit_signal	= (flags & CSIGNAL),
 2664 		.fn		= fn,
 2665 		.fn_arg		= arg,
 2666 		.name		= name,
 2667 		.kthread	= 1,
 2668 	};
 2669 
 2670 	return kernel_clone(&args);
 2671 }
 2672 
 2673 /*
 2674  * Create a user mode thread.
 2675  */
 2676 pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags)
 2677 {
 2678 	struct kernel_clone_args args = {
 2679 		.flags		= ((flags | CLONE_VM | CLONE_UNTRACED) & ~CSIGNAL),
 2680 		.exit_signal	= (flags & CSIGNAL),
 2681 		.fn		= fn,
 2682 		.fn_arg		= arg,
 2683 	};
 2684 
 2685 	return kernel_clone(&args);
 2686 }
 2687 
 2688 #ifdef __ARCH_WANT_SYS_FORK
 2689 SYSCALL_DEFINE0(fork)
 2690 {
 2691 #ifdef CONFIG_MMU
 2692 	struct kernel_clone_args args = {
 2693 		.exit_signal = SIGCHLD,
 2694 	};
 2695 
 2696 	return kernel_clone(&args);
 2697 #else
 2698 	/* can not support in nommu mode */
 2699 	return -EINVAL;
 2700 #endif
 2701 }
 2702 #endif
 2703 
 2704 #ifdef __ARCH_WANT_SYS_VFORK
 2705 SYSCALL_DEFINE0(vfork)
 2706 {
 2707 	struct kernel_clone_args args = {
 2708 		.flags		= CLONE_VFORK | CLONE_VM,
 2709 		.exit_signal	= SIGCHLD,
 2710 	};
 2711 
 2712 	return kernel_clone(&args);
 2713 }
 2714 #endif
 2715 
 2716 #ifdef __ARCH_WANT_SYS_CLONE
 2717 #ifdef CONFIG_CLONE_BACKWARDS
 2718 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
 2719 		 int __user *, parent_tidptr,
 2720 		 unsigned long, tls,
 2721 		 int __user *, child_tidptr)
 2722 #elif defined(CONFIG_CLONE_BACKWARDS2)
 2723 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
 2724 		 int __user *, parent_tidptr,
 2725 		 int __user *, child_tidptr,
 2726 		 unsigned long, tls)
 2727 #elif defined(CONFIG_CLONE_BACKWARDS3)
 2728 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
 2729 		int, stack_size,
 2730 		int __user *, parent_tidptr,
 2731 		int __user *, child_tidptr,
 2732 		unsigned long, tls)
 2733 #else
 2734 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
 2735 		 int __user *, parent_tidptr,
 2736 		 int __user *, child_tidptr,
 2737 		 unsigned long, tls)
 2738 #endif
 2739 {
 2740 	struct kernel_clone_args args = {
 2741 		.flags		= (lower_32_bits(clone_flags) & ~CSIGNAL),
 2742 		.pidfd		= parent_tidptr,
 2743 		.child_tid	= child_tidptr,
 2744 		.parent_tid	= parent_tidptr,
 2745 		.exit_signal	= (lower_32_bits(clone_flags) & CSIGNAL),
 2746 		.stack		= newsp,
 2747 		.tls		= tls,
 2748 	};
 2749 
 2750 	return kernel_clone(&args);
 2751 }
 2752 #endif
 2753 
 2754 static noinline int copy_clone_args_from_user(struct kernel_clone_args *kargs,
 2755 					      struct clone_args __user *uargs,
 2756 					      size_t usize)
 2757 {
 2758 	int err;
 2759 	struct clone_args args;
 2760 	pid_t *kset_tid = kargs->set_tid;
 2761 
 2762 	BUILD_BUG_ON(offsetofend(struct clone_args, tls) !=
 2763 		     CLONE_ARGS_SIZE_VER0);
 2764 	BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) !=
 2765 		     CLONE_ARGS_SIZE_VER1);
 2766 	BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
 2767 		     CLONE_ARGS_SIZE_VER2);
 2768 	BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
 2769 
 2770 	if (unlikely(usize > PAGE_SIZE))
 2771 		return -E2BIG;
 2772 	if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
 2773 		return -EINVAL;
 2774 
 2775 	err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
 2776 	if (err)
 2777 		return err;
 2778 
 2779 	if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
 2780 		return -EINVAL;
 2781 
 2782 	if (unlikely(!args.set_tid && args.set_tid_size > 0))
 2783 		return -EINVAL;
 2784 
 2785 	if (unlikely(args.set_tid && args.set_tid_size == 0))
 2786 		return -EINVAL;
 2787 
 2788 	/*
 2789 	 * Verify that higher 32bits of exit_signal are unset and that
 2790 	 * it is a valid signal
 2791 	 */
 2792 	if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
 2793 		     !valid_signal(args.exit_signal)))
 2794 		return -EINVAL;
 2795 
 2796 	if ((args.flags & CLONE_INTO_CGROUP) &&
 2797 	    (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2))
 2798 		return -EINVAL;
 2799 
 2800 	*kargs = (struct kernel_clone_args){
 2801 		.flags		= args.flags,
 2802 		.pidfd		= u64_to_user_ptr(args.pidfd),
 2803 		.child_tid	= u64_to_user_ptr(args.child_tid),
 2804 		.parent_tid	= u64_to_user_ptr(args.parent_tid),
 2805 		.exit_signal	= args.exit_signal,
 2806 		.stack		= args.stack,
 2807 		.stack_size	= args.stack_size,
 2808 		.tls		= args.tls,
 2809 		.set_tid_size	= args.set_tid_size,
 2810 		.cgroup		= args.cgroup,
 2811 	};
 2812 
 2813 	if (args.set_tid &&
 2814 		copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
 2815 			(kargs->set_tid_size * sizeof(pid_t))))
 2816 		return -EFAULT;
 2817 
 2818 	kargs->set_tid = kset_tid;
 2819 
 2820 	return 0;
 2821 }
 2822 
 2823 /**
 2824  * clone3_stack_valid - check and prepare stack
 2825  * @kargs: kernel clone args
 2826  *
 2827  * Verify that the stack arguments userspace gave us are sane.
 2828  * In addition, set the stack direction for userspace since it's easy for us to
 2829  * determine.
 2830  */
 2831 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
 2832 {
 2833 	if (kargs->stack == 0) {
 2834 		if (kargs->stack_size > 0)
 2835 			return false;
 2836 	} else {
 2837 		if (kargs->stack_size == 0)
 2838 			return false;
 2839 
 2840 		if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
 2841 			return false;
 2842 
 2843 #if !defined(CONFIG_STACK_GROWSUP)
 2844 		kargs->stack += kargs->stack_size;
 2845 #endif
 2846 	}
 2847 
 2848 	return true;
 2849 }
 2850 
 2851 static bool clone3_args_valid(struct kernel_clone_args *kargs)
 2852 {
 2853 	/* Verify that no unknown flags are passed along. */
 2854 	if (kargs->flags &
 2855 	    ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP))
 2856 		return false;
 2857 
 2858 	/*
 2859 	 * - make the CLONE_DETACHED bit reusable for clone3
 2860 	 * - make the CSIGNAL bits reusable for clone3
 2861 	 */
 2862 	if (kargs->flags & (CLONE_DETACHED | (CSIGNAL & (~CLONE_NEWTIME))))
 2863 		return false;
 2864 
 2865 	if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
 2866 	    (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
 2867 		return false;
 2868 
 2869 	if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
 2870 	    kargs->exit_signal)
 2871 		return false;
 2872 
 2873 	if (!clone3_stack_valid(kargs))
 2874 		return false;
 2875 
 2876 	return true;
 2877 }
 2878 
 2879 /**
 2880  * sys_clone3 - create a new process with specific properties
 2881  * @uargs: argument structure
 2882  * @size:  size of @uargs
 2883  *
 2884  * clone3() is the extensible successor to clone()/clone2().
 2885  * It takes a struct as argument that is versioned by its size.
 2886  *
 2887  * Return: On success, a positive PID for the child process.
 2888  *         On error, a negative errno number.
 2889  */
 2890 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
 2891 {
 2892 	int err;
 2893 
 2894 	struct kernel_clone_args kargs;
 2895 	pid_t set_tid[MAX_PID_NS_LEVEL];
 2896 
 2897 #ifdef __ARCH_BROKEN_SYS_CLONE3
 2898 #warning clone3() entry point is missing, please fix
 2899 	return -ENOSYS;
 2900 #endif
 2901 
 2902 	kargs.set_tid = set_tid;
 2903 
 2904 	err = copy_clone_args_from_user(&kargs, uargs, size);
 2905 	if (err)
 2906 		return err;
 2907 
 2908 	if (!clone3_args_valid(&kargs))
 2909 		return -EINVAL;
 2910 
 2911 	return kernel_clone(&kargs);
 2912 }
 2913 
 2914 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
 2915 {
 2916 	struct task_struct *leader, *parent, *child;
 2917 	int res;
 2918 
 2919 	read_lock(&tasklist_lock);
 2920 	leader = top = top->group_leader;
 2921 down:
 2922 	for_each_thread(leader, parent) {
 2923 		list_for_each_entry(child, &parent->children, sibling) {
 2924 			res = visitor(child, data);
 2925 			if (res) {
 2926 				if (res < 0)
 2927 					goto out;
 2928 				leader = child;
 2929 				goto down;
 2930 			}
 2931 up:
 2932 			;
 2933 		}
 2934 	}
 2935 
 2936 	if (leader != top) {
 2937 		child = leader;
 2938 		parent = child->real_parent;
 2939 		leader = parent->group_leader;
 2940 		goto up;
 2941 	}
 2942 out:
 2943 	read_unlock(&tasklist_lock);
 2944 }
 2945 
 2946 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
 2947 #define ARCH_MIN_MMSTRUCT_ALIGN 0
 2948 #endif
 2949 
 2950 static void sighand_ctor(void *data)
 2951 {
 2952 	struct sighand_struct *sighand = data;
 2953 
 2954 	spin_lock_init(&sighand->siglock);
 2955 	init_waitqueue_head(&sighand->signalfd_wqh);
 2956 }
 2957 
 2958 void __init mm_cache_init(void)
 2959 {
 2960 	unsigned int mm_size;
 2961 
 2962 	/*
 2963 	 * The mm_cpumask is located at the end of mm_struct, and is
 2964 	 * dynamically sized based on the maximum CPU number this system
 2965 	 * can have, taking hotplug into account (nr_cpu_ids).
 2966 	 */
 2967 	mm_size = sizeof(struct mm_struct) + cpumask_size() + mm_cid_size();
 2968 
 2969 	mm_cachep = kmem_cache_create_usercopy("mm_struct",
 2970 			mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
 2971 			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
 2972 			offsetof(struct mm_struct, saved_auxv),
 2973 			sizeof_field(struct mm_struct, saved_auxv),
 2974 			NULL);
 2975 }
 2976 
 2977 void __init proc_caches_init(void)
 2978 {
 2979 	sighand_cachep = kmem_cache_create("sighand_cache",
 2980 			sizeof(struct sighand_struct), 0,
 2981 			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
 2982 			SLAB_ACCOUNT, sighand_ctor);
 2983 	signal_cachep = kmem_cache_create("signal_cache",
 2984 			sizeof(struct signal_struct), 0,
 2985 			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
 2986 			NULL);
 2987 	files_cachep = kmem_cache_create("files_cache",
 2988 			sizeof(struct files_struct), 0,
 2989 			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
 2990 			NULL);
 2991 	fs_cachep = kmem_cache_create("fs_cache",
 2992 			sizeof(struct fs_struct), 0,
 2993 			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
 2994 			NULL);
 2995 	mmap_init();
 2996 	nsproxy_cache_init();
 2997 }
 2998 
 2999 /*
 3000  * Check constraints on flags passed to the unshare system call.
 3001  */
 3002 static int check_unshare_flags(unsigned long unshare_flags)
 3003 {
 3004 	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
 3005 				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
 3006 				CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
 3007 				CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP|
 3008 				CLONE_NEWTIME))
 3009 		return -EINVAL;
 3010 	/*
 3011 	 * Not implemented, but pretend it works if there is nothing
 3012 	 * to unshare.  Note that unsharing the address space or the
 3013 	 * signal handlers also need to unshare the signal queues (aka
 3014 	 * CLONE_THREAD).
 3015 	 */
 3016 	if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
 3017 		if (!thread_group_empty(current))
 3018 			return -EINVAL;
 3019 	}
 3020 	if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
 3021 		if (refcount_read(&current->sighand->count) > 1)
 3022 			return -EINVAL;
 3023 	}
 3024 	if (unshare_flags & CLONE_VM) {
 3025 		if (!current_is_single_threaded())
 3026 			return -EINVAL;
 3027 	}
 3028 
 3029 	return 0;
 3030 }
 3031 
 3032 /*
 3033  * Unshare the filesystem structure if it is being shared
 3034  */
 3035 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
 3036 {
 3037 	struct fs_struct *fs = current->fs;
 3038 
 3039 	if (!(unshare_flags & CLONE_FS) || !fs)
 3040 		return 0;
 3041 
 3042 	/* don't need lock here; in the worst case we'll do useless copy */
 3043 	if (!(unshare_flags & CLONE_NEWNS) && fs->users == 1)
 3044 		return 0;
 3045 
 3046 	*new_fsp = copy_fs_struct(fs);
 3047 	if (!*new_fsp)
 3048 		return -ENOMEM;
 3049 
 3050 	return 0;
 3051 }
 3052 
 3053 /*
 3054  * Unshare file descriptor table if it is being shared
 3055  */
 3056 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
 3057 {
 3058 	struct files_struct *fd = current->files;
 3059 
 3060 	if ((unshare_flags & CLONE_FILES) &&
 3061 	    (fd && atomic_read(&fd->count) > 1)) {
 3062 		fd = dup_fd(fd, NULL);
 3063 		if (IS_ERR(fd))
 3064 			return PTR_ERR(fd);
 3065 		*new_fdp = fd;
 3066 	}
 3067 
 3068 	return 0;
 3069 }
 3070 
 3071 /*
 3072  * unshare allows a process to 'unshare' part of the process
 3073  * context which was originally shared using clone.  copy_*
 3074  * functions used by kernel_clone() cannot be used here directly
 3075  * because they modify an inactive task_struct that is being
 3076  * constructed. Here we are modifying the current, active,
 3077  * task_struct.
 3078  */
 3079 int ksys_unshare(unsigned long unshare_flags)
 3080 {
 3081 	struct fs_struct *fs, *new_fs = NULL;
 3082 	struct files_struct *new_fd = NULL;
 3083 	struct cred *new_cred = NULL;
 3084 	struct nsproxy *new_nsproxy = NULL;
 3085 	int do_sysvsem = 0;
 3086 	int err;
 3087 
 3088 	/*
 3089 	 * If unsharing a user namespace must also unshare the thread group
 3090 	 * and unshare the filesystem root and working directories.
 3091 	 */
 3092 	if (unshare_flags & CLONE_NEWUSER)
 3093 		unshare_flags |= CLONE_THREAD | CLONE_FS;
 3094 	/*
 3095 	 * If unsharing vm, must also unshare signal handlers.
 3096 	 */
 3097 	if (unshare_flags & CLONE_VM)
 3098 		unshare_flags |= CLONE_SIGHAND;
 3099 	/*
 3100 	 * If unsharing a signal handlers, must also unshare the signal queues.
 3101 	 */
 3102 	if (unshare_flags & CLONE_SIGHAND)
 3103 		unshare_flags |= CLONE_THREAD;
 3104 	/*
 3105 	 * If unsharing namespace, must also unshare filesystem information.
 3106 	 */
 3107 	if (unshare_flags & CLONE_NEWNS)
 3108 		unshare_flags |= CLONE_FS;
 3109 
 3110 	err = check_unshare_flags(unshare_flags);
 3111 	if (err)
 3112 		goto bad_unshare_out;
 3113 	/*
 3114 	 * CLONE_NEWIPC must also detach from the undolist: after switching
 3115 	 * to a new ipc namespace, the semaphore arrays from the old
 3116 	 * namespace are unreachable.
 3117 	 */
 3118 	if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
 3119 		do_sysvsem = 1;
 3120 	err = unshare_fs(unshare_flags, &new_fs);
 3121 	if (err)
 3122 		goto bad_unshare_out;
 3123 	err = unshare_fd(unshare_flags, &new_fd);
 3124 	if (err)
 3125 		goto bad_unshare_cleanup_fs;
 3126 	err = unshare_userns(unshare_flags, &new_cred);
 3127 	if (err)
 3128 		goto bad_unshare_cleanup_fd;
 3129 	err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
 3130 					 new_cred, new_fs);
 3131 	if (err)
 3132 		goto bad_unshare_cleanup_cred;
 3133 	if (new_cred) {
 3134 		err = set_cred_ucounts(new_cred);
 3135 		if (err)
 3136 			goto bad_unshare_cleanup_nsproxy;
 3137 	}
 3138 
 3139 	if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
 3140 		if (do_sysvsem) {
 3141 			/*
 3142 			 * CLONE_SYSVSEM is equivalent to sys_exit().
 3143 			 */
 3144 			exit_sem(current);
 3145 		}
 3146 		if (unshare_flags & CLONE_NEWIPC) {
 3147 			/* Orphan segments in old ns (see sem above). */
 3148 			exit_shm(current);
 3149 			shm_init_task(current);
 3150 		}
 3151 
 3152 		if (new_nsproxy) {
 3153 			switch_task_namespaces(current, new_nsproxy);
 3154 			new_nsproxy = NULL;
 3155 		}
 3156 
 3157 		task_lock(current);
 3158 
 3159 		if (new_fs) {
 3160 			fs = current->fs;
 3161 			read_seqlock_excl(&fs->seq);
 3162 			current->fs = new_fs;
 3163 			if (--fs->users)
 3164 				new_fs = NULL;
 3165 			else
 3166 				new_fs = fs;
 3167 			read_sequnlock_excl(&fs->seq);
 3168 		}
 3169 
 3170 		if (new_fd)
 3171 			swap(current->files, new_fd);
 3172 
 3173 		task_unlock(current);
 3174 
 3175 		if (new_cred) {
 3176 			/* Install the new user namespace */
 3177 			commit_creds(new_cred);
 3178 			new_cred = NULL;
 3179 		}
 3180 	}
 3181 
 3182 	perf_event_namespaces(current);
 3183 
 3184 bad_unshare_cleanup_nsproxy:
 3185 	if (new_nsproxy)
 3186 		put_nsproxy(new_nsproxy);
 3187 bad_unshare_cleanup_cred:
 3188 	if (new_cred)
 3189 		put_cred(new_cred);
 3190 bad_unshare_cleanup_fd:
 3191 	if (new_fd)
 3192 		put_files_struct(new_fd);
 3193 bad_unshare_cleanup_fs:
 3194 	if (new_fs)
 3195 		free_fs_struct(new_fs);
 3196 
 3197 bad_unshare_out:
 3198 	return err;
 3199 }
 3200 
 3201 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
 3202 {
 3203 	return ksys_unshare(unshare_flags);
 3204 }
 3205 
 3206 /*
 3207  *	Helper to unshare the files of the current task.
 3208  *	We don't want to expose copy_files internals to
 3209  *	the exec layer of the kernel.
 3210  */
 3211 
 3212 int unshare_files(void)
 3213 {
 3214 	struct task_struct *task = current;
 3215 	struct files_struct *old, *copy = NULL;
 3216 	int error;
 3217 
 3218 	error = unshare_fd(CLONE_FILES, &copy);
 3219 	if (error || !copy)
 3220 		return error;
 3221 
 3222 	old = task->files;
 3223 	task_lock(task);
 3224 	task->files = copy;
 3225 	task_unlock(task);
 3226 	put_files_struct(old);
 3227 	return 0;
 3228 }
 3229 
 3230 static int sysctl_max_threads(const struct ctl_table *table, int write,
 3231 		       void *buffer, size_t *lenp, loff_t *ppos)
 3232 {
 3233 	struct ctl_table t;
 3234 	int ret;
 3235 	int threads = max_threads;
 3236 	int min = 1;
 3237 	int max = MAX_THREADS;
 3238 
 3239 	t = *table;
 3240 	t.data = &threads;
 3241 	t.extra1 = &min;
 3242 	t.extra2 = &max;
 3243 
 3244 	ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
 3245 	if (ret || !write)
 3246 		return ret;
 3247 
 3248 	max_threads = threads;
 3249 
 3250 	return 0;
 3251 }
 3252 
 3253 static const struct ctl_table fork_sysctl_table[] = {
 3254 	{
 3255 		.procname	= "threads-max",
 3256 		.data		= NULL,
 3257 		.maxlen		= sizeof(int),
 3258 		.mode		= 0644,
 3259 		.proc_handler	= sysctl_max_threads,
 3260 	},
 3261 };
 3262 
 3263 static int __init init_fork_sysctl(void)
 3264 {
 3265 	register_sysctl_init("kernel", fork_sysctl_table);
 3266 	return 0;
 3267 }
 3268 
 3269 subsys_initcall(init_fork_sysctl);