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