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/init.h>
  16#include <linux/unistd.h>
  17#include <linux/module.h>
  18#include <linux/vmalloc.h>
  19#include <linux/completion.h>
  20#include <linux/personality.h>
  21#include <linux/mempolicy.h>
  22#include <linux/sem.h>
  23#include <linux/file.h>
  24#include <linux/fdtable.h>
  25#include <linux/iocontext.h>
  26#include <linux/key.h>
  27#include <linux/binfmts.h>
  28#include <linux/mman.h>
  29#include <linux/mmu_notifier.h>
  30#include <linux/fs.h>
  31#include <linux/mm.h>
  32#include <linux/vmacache.h>
  33#include <linux/nsproxy.h>
  34#include <linux/capability.h>
  35#include <linux/cpu.h>
  36#include <linux/cgroup.h>
  37#include <linux/security.h>
  38#include <linux/hugetlb.h>
  39#include <linux/seccomp.h>
  40#include <linux/swap.h>
  41#include <linux/syscalls.h>
  42#include <linux/jiffies.h>
  43#include <linux/futex.h>
  44#include <linux/compat.h>
  45#include <linux/kthread.h>
  46#include <linux/task_io_accounting_ops.h>
  47#include <linux/rcupdate.h>
  48#include <linux/ptrace.h>
  49#include <linux/mount.h>
  50#include <linux/audit.h>
  51#include <linux/memcontrol.h>
  52#include <linux/ftrace.h>
  53#include <linux/proc_fs.h>
  54#include <linux/profile.h>
  55#include <linux/rmap.h>
  56#include <linux/ksm.h>
  57#include <linux/acct.h>
  58#include <linux/tsacct_kern.h>
  59#include <linux/cn_proc.h>
  60#include <linux/freezer.h>
  61#include <linux/delayacct.h>
  62#include <linux/taskstats_kern.h>
  63#include <linux/random.h>
  64#include <linux/tty.h>
  65#include <linux/blkdev.h>
  66#include <linux/fs_struct.h>
  67#include <linux/magic.h>
  68#include <linux/perf_event.h>
  69#include <linux/posix-timers.h>
  70#include <linux/user-return-notifier.h>
  71#include <linux/oom.h>
  72#include <linux/khugepaged.h>
  73#include <linux/signalfd.h>
  74#include <linux/uprobes.h>
  75#include <linux/aio.h>
  76#include <linux/compiler.h>
  77
  78#include <asm/pgtable.h>
  79#include <asm/pgalloc.h>
  80#include <asm/uaccess.h>
  81#include <asm/mmu_context.h>
  82#include <asm/cacheflush.h>
  83#include <asm/tlbflush.h>
  84
  85#include <trace/events/sched.h>
  86
  87#define CREATE_TRACE_POINTS
  88#include <trace/events/task.h>
  89
  90/*
  91 * Protected counters by write_lock_irq(&tasklist_lock)
  92 */
  93unsigned long total_forks;	/* Handle normal Linux uptimes. */
  94int nr_threads;			/* The idle threads do not count.. */
  95
  96int max_threads;		/* tunable limit on nr_threads */
  97
  98DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  99
 100__cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
 101
 102#ifdef CONFIG_PROVE_RCU
 103int lockdep_tasklist_lock_is_held(void)
 104{
 105	return lockdep_is_held(&tasklist_lock);
 106}
 107EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
 108#endif /* #ifdef CONFIG_PROVE_RCU */
 109
 110int nr_processes(void)
 111{
 112	int cpu;
 113	int total = 0;
 114
 115	for_each_possible_cpu(cpu)
 116		total += per_cpu(process_counts, cpu);
 117
 118	return total;
 119}
 120
 121void __weak arch_release_task_struct(struct task_struct *tsk)
 122{
 123}
 124
 125#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 126static struct kmem_cache *task_struct_cachep;
 127
 128static inline struct task_struct *alloc_task_struct_node(int node)
 129{
 130	return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
 131}
 132
 
 
 133static inline void free_task_struct(struct task_struct *tsk)
 134{
 
 135	kmem_cache_free(task_struct_cachep, tsk);
 136}
 137#endif
 138
 139void __weak arch_release_thread_info(struct thread_info *ti)
 140{
 141}
 142
 143#ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
 
 144
 145/*
 146 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
 147 * kmemcache based allocator.
 148 */
 149# if THREAD_SIZE >= PAGE_SIZE
 150static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
 151						  int node)
 152{
 153	struct page *page = alloc_pages_node(node, THREADINFO_GFP_ACCOUNTED,
 154					     THREAD_SIZE_ORDER);
 155
 156	return page ? page_address(page) : NULL;
 157}
 158
 159static inline void free_thread_info(struct thread_info *ti)
 160{
 161	free_memcg_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 
 162}
 163# else
 164static struct kmem_cache *thread_info_cache;
 165
 166static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
 167						  int node)
 168{
 169	return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
 170}
 171
 172static void free_thread_info(struct thread_info *ti)
 173{
 
 174	kmem_cache_free(thread_info_cache, ti);
 175}
 176
 177void thread_info_cache_init(void)
 178{
 179	thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
 180					      THREAD_SIZE, 0, NULL);
 181	BUG_ON(thread_info_cache == NULL);
 182}
 183# endif
 184#endif
 185
 186/* SLAB cache for signal_struct structures (tsk->signal) */
 187static struct kmem_cache *signal_cachep;
 188
 189/* SLAB cache for sighand_struct structures (tsk->sighand) */
 190struct kmem_cache *sighand_cachep;
 191
 192/* SLAB cache for files_struct structures (tsk->files) */
 193struct kmem_cache *files_cachep;
 194
 195/* SLAB cache for fs_struct structures (tsk->fs) */
 196struct kmem_cache *fs_cachep;
 197
 198/* SLAB cache for vm_area_struct structures */
 199struct kmem_cache *vm_area_cachep;
 200
 201/* SLAB cache for mm_struct structures (tsk->mm) */
 202static struct kmem_cache *mm_cachep;
 203
 204static void account_kernel_stack(struct thread_info *ti, int account)
 205{
 206	struct zone *zone = page_zone(virt_to_page(ti));
 207
 208	mod_zone_page_state(zone, NR_KERNEL_STACK, account);
 209}
 210
 211void free_task(struct task_struct *tsk)
 212{
 213	account_kernel_stack(tsk->stack, -1);
 214	arch_release_thread_info(tsk->stack);
 215	free_thread_info(tsk->stack);
 216	rt_mutex_debug_task_free(tsk);
 217	ftrace_graph_exit_task(tsk);
 218	put_seccomp_filter(tsk);
 219	arch_release_task_struct(tsk);
 220	free_task_struct(tsk);
 221}
 222EXPORT_SYMBOL(free_task);
 223
 224static inline void free_signal_struct(struct signal_struct *sig)
 225{
 226	taskstats_tgid_free(sig);
 227	sched_autogroup_exit(sig);
 228	kmem_cache_free(signal_cachep, sig);
 229}
 230
 231static inline void put_signal_struct(struct signal_struct *sig)
 232{
 233	if (atomic_dec_and_test(&sig->sigcnt))
 234		free_signal_struct(sig);
 235}
 236
 237void __put_task_struct(struct task_struct *tsk)
 238{
 239	WARN_ON(!tsk->exit_state);
 240	WARN_ON(atomic_read(&tsk->usage));
 241	WARN_ON(tsk == current);
 242
 243	task_numa_free(tsk);
 244	security_task_free(tsk);
 245	exit_creds(tsk);
 246	delayacct_tsk_free(tsk);
 247	put_signal_struct(tsk->signal);
 248
 249	if (!profile_handoff_task(tsk))
 250		free_task(tsk);
 251}
 252EXPORT_SYMBOL_GPL(__put_task_struct);
 253
 254void __init __weak arch_task_cache_init(void) { }
 255
 256void __init fork_init(unsigned long mempages)
 257{
 258#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 259#ifndef ARCH_MIN_TASKALIGN
 260#define ARCH_MIN_TASKALIGN	L1_CACHE_BYTES
 261#endif
 262	/* create a slab on which task_structs can be allocated */
 263	task_struct_cachep =
 264		kmem_cache_create("task_struct", sizeof(struct task_struct),
 265			ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
 266#endif
 267
 268	/* do the arch specific task caches init */
 269	arch_task_cache_init();
 270
 271	/*
 272	 * The default maximum number of threads is set to a safe
 273	 * value: the thread structures can take up at most half
 274	 * of memory.
 275	 */
 276	max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 277
 278	/*
 279	 * we need to allow at least 20 threads to boot a system
 280	 */
 281	if (max_threads < 20)
 282		max_threads = 20;
 283
 284	init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 285	init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 286	init_task.signal->rlim[RLIMIT_SIGPENDING] =
 287		init_task.signal->rlim[RLIMIT_NPROC];
 288}
 289
 290int __weak arch_dup_task_struct(struct task_struct *dst,
 291					       struct task_struct *src)
 292{
 293	*dst = *src;
 294	return 0;
 295}
 296
 297static struct task_struct *dup_task_struct(struct task_struct *orig)
 298{
 299	struct task_struct *tsk;
 300	struct thread_info *ti;
 301	unsigned long *stackend;
 302	int node = tsk_fork_get_node(orig);
 303	int err;
 304
 305	tsk = alloc_task_struct_node(node);
 306	if (!tsk)
 307		return NULL;
 308
 309	ti = alloc_thread_info_node(tsk, node);
 310	if (!ti)
 311		goto free_tsk;
 
 
 312
 313	err = arch_dup_task_struct(tsk, orig);
 314	if (err)
 315		goto free_ti;
 316
 
 
 
 
 317	tsk->stack = ti;
 318
 319	setup_thread_stack(tsk, orig);
 
 
 
 
 320	clear_user_return_notifier(tsk);
 321	clear_tsk_need_resched(tsk);
 322	stackend = end_of_stack(tsk);
 323	*stackend = STACK_END_MAGIC;	/* for overflow detection */
 324
 325#ifdef CONFIG_CC_STACKPROTECTOR
 326	tsk->stack_canary = get_random_int();
 327#endif
 328
 329	/*
 330	 * One for us, one for whoever does the "release_task()" (usually
 331	 * parent)
 332	 */
 333	atomic_set(&tsk->usage, 2);
 334#ifdef CONFIG_BLK_DEV_IO_TRACE
 335	tsk->btrace_seq = 0;
 336#endif
 337	tsk->splice_pipe = NULL;
 338	tsk->task_frag.page = NULL;
 339
 340	account_kernel_stack(ti, 1);
 341
 342	return tsk;
 343
 344free_ti:
 345	free_thread_info(ti);
 346free_tsk:
 347	free_task_struct(tsk);
 348	return NULL;
 349}
 350
 351#ifdef CONFIG_MMU
 352static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 353{
 354	struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 355	struct rb_node **rb_link, *rb_parent;
 356	int retval;
 357	unsigned long charge;
 
 358
 359	uprobe_start_dup_mmap();
 360	down_write(&oldmm->mmap_sem);
 361	flush_cache_dup_mm(oldmm);
 362	uprobe_dup_mmap(oldmm, mm);
 363	/*
 364	 * Not linked in yet - no deadlock potential:
 365	 */
 366	down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 367
 368	mm->locked_vm = 0;
 369	mm->mmap = NULL;
 370	mm->vmacache_seqnum = 0;
 
 
 371	mm->map_count = 0;
 372	cpumask_clear(mm_cpumask(mm));
 373	mm->mm_rb = RB_ROOT;
 374	rb_link = &mm->mm_rb.rb_node;
 375	rb_parent = NULL;
 376	pprev = &mm->mmap;
 377	retval = ksm_fork(mm, oldmm);
 378	if (retval)
 379		goto out;
 380	retval = khugepaged_fork(mm, oldmm);
 381	if (retval)
 382		goto out;
 383
 384	prev = NULL;
 385	for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 386		struct file *file;
 387
 388		if (mpnt->vm_flags & VM_DONTCOPY) {
 
 
 389			vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 390							-vma_pages(mpnt));
 391			continue;
 392		}
 393		charge = 0;
 394		if (mpnt->vm_flags & VM_ACCOUNT) {
 395			unsigned long len = vma_pages(mpnt);
 396
 397			if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
 398				goto fail_nomem;
 399			charge = len;
 400		}
 401		tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 402		if (!tmp)
 403			goto fail_nomem;
 404		*tmp = *mpnt;
 405		INIT_LIST_HEAD(&tmp->anon_vma_chain);
 406		retval = vma_dup_policy(mpnt, tmp);
 407		if (retval)
 
 408			goto fail_nomem_policy;
 
 409		tmp->vm_mm = mm;
 410		if (anon_vma_fork(tmp, mpnt))
 411			goto fail_nomem_anon_vma_fork;
 412		tmp->vm_flags &= ~VM_LOCKED;
 413		tmp->vm_next = tmp->vm_prev = NULL;
 414		file = tmp->vm_file;
 415		if (file) {
 416			struct inode *inode = file_inode(file);
 417			struct address_space *mapping = file->f_mapping;
 418
 419			get_file(file);
 420			if (tmp->vm_flags & VM_DENYWRITE)
 421				atomic_dec(&inode->i_writecount);
 422			mutex_lock(&mapping->i_mmap_mutex);
 423			if (tmp->vm_flags & VM_SHARED)
 424				mapping->i_mmap_writable++;
 425			flush_dcache_mmap_lock(mapping);
 426			/* insert tmp into the share list, just after mpnt */
 427			if (unlikely(tmp->vm_flags & VM_NONLINEAR))
 428				vma_nonlinear_insert(tmp,
 429						&mapping->i_mmap_nonlinear);
 430			else
 431				vma_interval_tree_insert_after(tmp, mpnt,
 432							&mapping->i_mmap);
 433			flush_dcache_mmap_unlock(mapping);
 434			mutex_unlock(&mapping->i_mmap_mutex);
 435		}
 436
 437		/*
 438		 * Clear hugetlb-related page reserves for children. This only
 439		 * affects MAP_PRIVATE mappings. Faults generated by the child
 440		 * are not guaranteed to succeed, even if read-only
 441		 */
 442		if (is_vm_hugetlb_page(tmp))
 443			reset_vma_resv_huge_pages(tmp);
 444
 445		/*
 446		 * Link in the new vma and copy the page table entries.
 447		 */
 448		*pprev = tmp;
 449		pprev = &tmp->vm_next;
 450		tmp->vm_prev = prev;
 451		prev = tmp;
 452
 453		__vma_link_rb(mm, tmp, rb_link, rb_parent);
 454		rb_link = &tmp->vm_rb.rb_right;
 455		rb_parent = &tmp->vm_rb;
 456
 457		mm->map_count++;
 458		retval = copy_page_range(mm, oldmm, mpnt);
 459
 460		if (tmp->vm_ops && tmp->vm_ops->open)
 461			tmp->vm_ops->open(tmp);
 462
 463		if (retval)
 464			goto out;
 
 
 
 465	}
 466	/* a new mm has just been created */
 467	arch_dup_mmap(oldmm, mm);
 468	retval = 0;
 469out:
 470	up_write(&mm->mmap_sem);
 471	flush_tlb_mm(oldmm);
 472	up_write(&oldmm->mmap_sem);
 473	uprobe_end_dup_mmap();
 474	return retval;
 475fail_nomem_anon_vma_fork:
 476	mpol_put(vma_policy(tmp));
 477fail_nomem_policy:
 478	kmem_cache_free(vm_area_cachep, tmp);
 479fail_nomem:
 480	retval = -ENOMEM;
 481	vm_unacct_memory(charge);
 482	goto out;
 483}
 484
 485static inline int mm_alloc_pgd(struct mm_struct *mm)
 486{
 487	mm->pgd = pgd_alloc(mm);
 488	if (unlikely(!mm->pgd))
 489		return -ENOMEM;
 490	return 0;
 491}
 492
 493static inline void mm_free_pgd(struct mm_struct *mm)
 494{
 495	pgd_free(mm, mm->pgd);
 496}
 497#else
 498#define dup_mmap(mm, oldmm)	(0)
 499#define mm_alloc_pgd(mm)	(0)
 500#define mm_free_pgd(mm)
 501#endif /* CONFIG_MMU */
 502
 503__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 504
 505#define allocate_mm()	(kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 506#define free_mm(mm)	(kmem_cache_free(mm_cachep, (mm)))
 507
 508static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 509
 510static int __init coredump_filter_setup(char *s)
 511{
 512	default_dump_filter =
 513		(simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 514		MMF_DUMP_FILTER_MASK;
 515	return 1;
 516}
 517
 518__setup("coredump_filter=", coredump_filter_setup);
 519
 520#include <linux/init_task.h>
 521
 522static void mm_init_aio(struct mm_struct *mm)
 523{
 524#ifdef CONFIG_AIO
 525	spin_lock_init(&mm->ioctx_lock);
 526	mm->ioctx_table = NULL;
 527#endif
 528}
 529
 530static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
 531{
 532	atomic_set(&mm->mm_users, 1);
 533	atomic_set(&mm->mm_count, 1);
 534	init_rwsem(&mm->mmap_sem);
 535	INIT_LIST_HEAD(&mm->mmlist);
 
 
 536	mm->core_state = NULL;
 537	atomic_long_set(&mm->nr_ptes, 0);
 538	memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 539	spin_lock_init(&mm->page_table_lock);
 
 
 540	mm_init_aio(mm);
 541	mm_init_owner(mm, p);
 542	clear_tlb_flush_pending(mm);
 543
 544	if (current->mm) {
 545		mm->flags = current->mm->flags & MMF_INIT_MASK;
 546		mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
 547	} else {
 548		mm->flags = default_dump_filter;
 549		mm->def_flags = 0;
 550	}
 551
 552	if (likely(!mm_alloc_pgd(mm))) {
 
 553		mmu_notifier_mm_init(mm);
 554		return mm;
 555	}
 556
 557	free_mm(mm);
 558	return NULL;
 559}
 560
 561static void check_mm(struct mm_struct *mm)
 562{
 563	int i;
 564
 565	for (i = 0; i < NR_MM_COUNTERS; i++) {
 566		long x = atomic_long_read(&mm->rss_stat.count[i]);
 567
 568		if (unlikely(x))
 569			printk(KERN_ALERT "BUG: Bad rss-counter state "
 570					  "mm:%p idx:%d val:%ld\n", mm, i, x);
 571	}
 572
 573#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 574	VM_BUG_ON(mm->pmd_huge_pte);
 575#endif
 576}
 577
 578/*
 579 * Allocate and initialize an mm_struct.
 580 */
 581struct mm_struct *mm_alloc(void)
 582{
 583	struct mm_struct *mm;
 584
 585	mm = allocate_mm();
 586	if (!mm)
 587		return NULL;
 588
 589	memset(mm, 0, sizeof(*mm));
 590	mm_init_cpumask(mm);
 591	return mm_init(mm, current);
 592}
 593
 594/*
 595 * Called when the last reference to the mm
 596 * is dropped: either by a lazy thread or by
 597 * mmput. Free the page directory and the mm.
 598 */
 599void __mmdrop(struct mm_struct *mm)
 600{
 601	BUG_ON(mm == &init_mm);
 602	mm_free_pgd(mm);
 603	destroy_context(mm);
 604	mmu_notifier_mm_destroy(mm);
 605	check_mm(mm);
 606	free_mm(mm);
 607}
 608EXPORT_SYMBOL_GPL(__mmdrop);
 609
 610/*
 611 * Decrement the use count and release all resources for an mm.
 612 */
 613void mmput(struct mm_struct *mm)
 614{
 615	might_sleep();
 616
 617	if (atomic_dec_and_test(&mm->mm_users)) {
 618		uprobe_clear_state(mm);
 619		exit_aio(mm);
 620		ksm_exit(mm);
 621		khugepaged_exit(mm); /* must run before exit_mmap */
 622		exit_mmap(mm);
 623		set_mm_exe_file(mm, NULL);
 624		if (!list_empty(&mm->mmlist)) {
 625			spin_lock(&mmlist_lock);
 626			list_del(&mm->mmlist);
 627			spin_unlock(&mmlist_lock);
 628		}
 629		if (mm->binfmt)
 630			module_put(mm->binfmt->module);
 631		mmdrop(mm);
 632	}
 633}
 634EXPORT_SYMBOL_GPL(mmput);
 635
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 636void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 637{
 638	if (new_exe_file)
 639		get_file(new_exe_file);
 640	if (mm->exe_file)
 641		fput(mm->exe_file);
 642	mm->exe_file = new_exe_file;
 
 643}
 644
 645struct file *get_mm_exe_file(struct mm_struct *mm)
 646{
 647	struct file *exe_file;
 648
 649	/* We need mmap_sem to protect against races with removal of exe_file */
 
 650	down_read(&mm->mmap_sem);
 651	exe_file = mm->exe_file;
 652	if (exe_file)
 653		get_file(exe_file);
 654	up_read(&mm->mmap_sem);
 655	return exe_file;
 656}
 657
 658static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
 659{
 660	/* It's safe to write the exe_file pointer without exe_file_lock because
 661	 * this is called during fork when the task is not yet in /proc */
 662	newmm->exe_file = get_mm_exe_file(oldmm);
 663}
 664
 665/**
 666 * get_task_mm - acquire a reference to the task's mm
 667 *
 668 * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 669 * this kernel workthread has transiently adopted a user mm with use_mm,
 670 * to do its AIO) is not set and if so returns a reference to it, after
 671 * bumping up the use count.  User must release the mm via mmput()
 672 * after use.  Typically used by /proc and ptrace.
 673 */
 674struct mm_struct *get_task_mm(struct task_struct *task)
 675{
 676	struct mm_struct *mm;
 677
 678	task_lock(task);
 679	mm = task->mm;
 680	if (mm) {
 681		if (task->flags & PF_KTHREAD)
 682			mm = NULL;
 683		else
 684			atomic_inc(&mm->mm_users);
 685	}
 686	task_unlock(task);
 687	return mm;
 688}
 689EXPORT_SYMBOL_GPL(get_task_mm);
 690
 691struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
 692{
 693	struct mm_struct *mm;
 694	int err;
 695
 696	err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
 697	if (err)
 698		return ERR_PTR(err);
 699
 700	mm = get_task_mm(task);
 701	if (mm && mm != current->mm &&
 702			!ptrace_may_access(task, mode)) {
 703		mmput(mm);
 704		mm = ERR_PTR(-EACCES);
 705	}
 706	mutex_unlock(&task->signal->cred_guard_mutex);
 707
 708	return mm;
 709}
 710
 711static void complete_vfork_done(struct task_struct *tsk)
 712{
 713	struct completion *vfork;
 714
 715	task_lock(tsk);
 716	vfork = tsk->vfork_done;
 717	if (likely(vfork)) {
 718		tsk->vfork_done = NULL;
 719		complete(vfork);
 720	}
 721	task_unlock(tsk);
 722}
 723
 724static int wait_for_vfork_done(struct task_struct *child,
 725				struct completion *vfork)
 726{
 727	int killed;
 728
 729	freezer_do_not_count();
 730	killed = wait_for_completion_killable(vfork);
 731	freezer_count();
 732
 733	if (killed) {
 734		task_lock(child);
 735		child->vfork_done = NULL;
 736		task_unlock(child);
 737	}
 738
 739	put_task_struct(child);
 740	return killed;
 741}
 742
 743/* Please note the differences between mmput and mm_release.
 744 * mmput is called whenever we stop holding onto a mm_struct,
 745 * error success whatever.
 746 *
 747 * mm_release is called after a mm_struct has been removed
 748 * from the current process.
 749 *
 750 * This difference is important for error handling, when we
 751 * only half set up a mm_struct for a new process and need to restore
 752 * the old one.  Because we mmput the new mm_struct before
 753 * restoring the old one. . .
 754 * Eric Biederman 10 January 1998
 755 */
 756void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 757{
 758	/* Get rid of any futexes when releasing the mm */
 759#ifdef CONFIG_FUTEX
 760	if (unlikely(tsk->robust_list)) {
 761		exit_robust_list(tsk);
 762		tsk->robust_list = NULL;
 763	}
 764#ifdef CONFIG_COMPAT
 765	if (unlikely(tsk->compat_robust_list)) {
 766		compat_exit_robust_list(tsk);
 767		tsk->compat_robust_list = NULL;
 768	}
 769#endif
 770	if (unlikely(!list_empty(&tsk->pi_state_list)))
 771		exit_pi_state_list(tsk);
 772#endif
 773
 774	uprobe_free_utask(tsk);
 775
 776	/* Get rid of any cached register state */
 777	deactivate_mm(tsk, mm);
 778
 779	/*
 780	 * If we're exiting normally, clear a user-space tid field if
 781	 * requested.  We leave this alone when dying by signal, to leave
 782	 * the value intact in a core dump, and to save the unnecessary
 783	 * trouble, say, a killed vfork parent shouldn't touch this mm.
 784	 * Userland only wants this done for a sys_exit.
 785	 */
 786	if (tsk->clear_child_tid) {
 787		if (!(tsk->flags & PF_SIGNALED) &&
 788		    atomic_read(&mm->mm_users) > 1) {
 789			/*
 790			 * We don't check the error code - if userspace has
 791			 * not set up a proper pointer then tough luck.
 792			 */
 793			put_user(0, tsk->clear_child_tid);
 794			sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
 795					1, NULL, NULL, 0);
 796		}
 797		tsk->clear_child_tid = NULL;
 798	}
 799
 800	/*
 801	 * All done, finally we can wake up parent and return this mm to him.
 802	 * Also kthread_stop() uses this completion for synchronization.
 803	 */
 804	if (tsk->vfork_done)
 805		complete_vfork_done(tsk);
 806}
 807
 808/*
 809 * Allocate a new mm structure and copy contents from the
 810 * mm structure of the passed in task structure.
 811 */
 812static struct mm_struct *dup_mm(struct task_struct *tsk)
 813{
 814	struct mm_struct *mm, *oldmm = current->mm;
 815	int err;
 816
 
 
 
 817	mm = allocate_mm();
 818	if (!mm)
 819		goto fail_nomem;
 820
 821	memcpy(mm, oldmm, sizeof(*mm));
 822	mm_init_cpumask(mm);
 823
 824#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 825	mm->pmd_huge_pte = NULL;
 826#endif
 
 
 827	if (!mm_init(mm, tsk))
 828		goto fail_nomem;
 829
 830	if (init_new_context(tsk, mm))
 831		goto fail_nocontext;
 832
 833	dup_mm_exe_file(oldmm, mm);
 834
 835	err = dup_mmap(mm, oldmm);
 836	if (err)
 837		goto free_pt;
 838
 839	mm->hiwater_rss = get_mm_rss(mm);
 840	mm->hiwater_vm = mm->total_vm;
 841
 842	if (mm->binfmt && !try_module_get(mm->binfmt->module))
 843		goto free_pt;
 844
 845	return mm;
 846
 847free_pt:
 848	/* don't put binfmt in mmput, we haven't got module yet */
 849	mm->binfmt = NULL;
 850	mmput(mm);
 851
 852fail_nomem:
 853	return NULL;
 854
 855fail_nocontext:
 856	/*
 857	 * If init_new_context() failed, we cannot use mmput() to free the mm
 858	 * because it calls destroy_context()
 859	 */
 860	mm_free_pgd(mm);
 861	free_mm(mm);
 862	return NULL;
 863}
 864
 865static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
 866{
 867	struct mm_struct *mm, *oldmm;
 868	int retval;
 869
 870	tsk->min_flt = tsk->maj_flt = 0;
 871	tsk->nvcsw = tsk->nivcsw = 0;
 872#ifdef CONFIG_DETECT_HUNG_TASK
 873	tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 874#endif
 875
 876	tsk->mm = NULL;
 877	tsk->active_mm = NULL;
 878
 879	/*
 880	 * Are we cloning a kernel thread?
 881	 *
 882	 * We need to steal a active VM for that..
 883	 */
 884	oldmm = current->mm;
 885	if (!oldmm)
 886		return 0;
 887
 888	/* initialize the new vmacache entries */
 889	vmacache_flush(tsk);
 890
 891	if (clone_flags & CLONE_VM) {
 892		atomic_inc(&oldmm->mm_users);
 893		mm = oldmm;
 894		goto good_mm;
 895	}
 896
 897	retval = -ENOMEM;
 898	mm = dup_mm(tsk);
 899	if (!mm)
 900		goto fail_nomem;
 901
 902good_mm:
 903	tsk->mm = mm;
 904	tsk->active_mm = mm;
 905	return 0;
 906
 907fail_nomem:
 908	return retval;
 909}
 910
 911static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 912{
 913	struct fs_struct *fs = current->fs;
 914	if (clone_flags & CLONE_FS) {
 915		/* tsk->fs is already what we want */
 916		spin_lock(&fs->lock);
 917		if (fs->in_exec) {
 918			spin_unlock(&fs->lock);
 919			return -EAGAIN;
 920		}
 921		fs->users++;
 922		spin_unlock(&fs->lock);
 923		return 0;
 924	}
 925	tsk->fs = copy_fs_struct(fs);
 926	if (!tsk->fs)
 927		return -ENOMEM;
 928	return 0;
 929}
 930
 931static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
 932{
 933	struct files_struct *oldf, *newf;
 934	int error = 0;
 935
 936	/*
 937	 * A background process may not have any files ...
 938	 */
 939	oldf = current->files;
 940	if (!oldf)
 941		goto out;
 942
 943	if (clone_flags & CLONE_FILES) {
 944		atomic_inc(&oldf->count);
 945		goto out;
 946	}
 947
 948	newf = dup_fd(oldf, &error);
 949	if (!newf)
 950		goto out;
 951
 952	tsk->files = newf;
 953	error = 0;
 954out:
 955	return error;
 956}
 957
 958static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 959{
 960#ifdef CONFIG_BLOCK
 961	struct io_context *ioc = current->io_context;
 962	struct io_context *new_ioc;
 963
 964	if (!ioc)
 965		return 0;
 966	/*
 967	 * Share io context with parent, if CLONE_IO is set
 968	 */
 969	if (clone_flags & CLONE_IO) {
 970		ioc_task_link(ioc);
 971		tsk->io_context = ioc;
 972	} else if (ioprio_valid(ioc->ioprio)) {
 973		new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
 974		if (unlikely(!new_ioc))
 975			return -ENOMEM;
 976
 977		new_ioc->ioprio = ioc->ioprio;
 978		put_io_context(new_ioc);
 979	}
 980#endif
 981	return 0;
 982}
 983
 984static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 985{
 986	struct sighand_struct *sig;
 987
 988	if (clone_flags & CLONE_SIGHAND) {
 989		atomic_inc(&current->sighand->count);
 990		return 0;
 991	}
 992	sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 993	rcu_assign_pointer(tsk->sighand, sig);
 994	if (!sig)
 995		return -ENOMEM;
 996	atomic_set(&sig->count, 1);
 997	memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 998	return 0;
 999}
1000
1001void __cleanup_sighand(struct sighand_struct *sighand)
1002{
1003	if (atomic_dec_and_test(&sighand->count)) {
1004		signalfd_cleanup(sighand);
1005		kmem_cache_free(sighand_cachep, sighand);
1006	}
1007}
1008
1009
1010/*
1011 * Initialize POSIX timer handling for a thread group.
1012 */
1013static void posix_cpu_timers_init_group(struct signal_struct *sig)
1014{
1015	unsigned long cpu_limit;
1016
1017	/* Thread group counters. */
1018	thread_group_cputime_init(sig);
1019
1020	cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1021	if (cpu_limit != RLIM_INFINITY) {
1022		sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1023		sig->cputimer.running = 1;
1024	}
1025
1026	/* The timer lists. */
1027	INIT_LIST_HEAD(&sig->cpu_timers[0]);
1028	INIT_LIST_HEAD(&sig->cpu_timers[1]);
1029	INIT_LIST_HEAD(&sig->cpu_timers[2]);
1030}
1031
1032static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1033{
1034	struct signal_struct *sig;
1035
1036	if (clone_flags & CLONE_THREAD)
1037		return 0;
1038
1039	sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1040	tsk->signal = sig;
1041	if (!sig)
1042		return -ENOMEM;
1043
1044	sig->nr_threads = 1;
1045	atomic_set(&sig->live, 1);
1046	atomic_set(&sig->sigcnt, 1);
1047
1048	/* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1049	sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1050	tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1051
1052	init_waitqueue_head(&sig->wait_chldexit);
 
 
1053	sig->curr_target = tsk;
1054	init_sigpending(&sig->shared_pending);
1055	INIT_LIST_HEAD(&sig->posix_timers);
1056
1057	hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1058	sig->real_timer.function = it_real_fn;
1059
1060	task_lock(current->group_leader);
1061	memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1062	task_unlock(current->group_leader);
1063
1064	posix_cpu_timers_init_group(sig);
1065
1066	tty_audit_fork(sig);
1067	sched_autogroup_fork(sig);
1068
1069#ifdef CONFIG_CGROUPS
1070	init_rwsem(&sig->group_rwsem);
1071#endif
1072
 
1073	sig->oom_score_adj = current->signal->oom_score_adj;
1074	sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1075
1076	sig->has_child_subreaper = current->signal->has_child_subreaper ||
1077				   current->signal->is_child_subreaper;
1078
1079	mutex_init(&sig->cred_guard_mutex);
1080
1081	return 0;
1082}
1083
 
 
 
 
 
 
 
 
 
1084SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1085{
1086	current->clear_child_tid = tidptr;
1087
1088	return task_pid_vnr(current);
1089}
1090
1091static void rt_mutex_init_task(struct task_struct *p)
1092{
1093	raw_spin_lock_init(&p->pi_lock);
1094#ifdef CONFIG_RT_MUTEXES
1095	p->pi_waiters = RB_ROOT;
1096	p->pi_waiters_leftmost = NULL;
1097	p->pi_blocked_on = NULL;
1098	p->pi_top_task = NULL;
1099#endif
1100}
1101
1102#ifdef CONFIG_MM_OWNER
1103void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1104{
1105	mm->owner = p;
1106}
1107#endif /* CONFIG_MM_OWNER */
1108
1109/*
1110 * Initialize POSIX timer handling for a single task.
1111 */
1112static void posix_cpu_timers_init(struct task_struct *tsk)
1113{
1114	tsk->cputime_expires.prof_exp = 0;
1115	tsk->cputime_expires.virt_exp = 0;
1116	tsk->cputime_expires.sched_exp = 0;
1117	INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1118	INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1119	INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1120}
1121
1122static inline void
1123init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1124{
1125	 task->pids[type].pid = pid;
1126}
1127
1128/*
1129 * This creates a new process as a copy of the old one,
1130 * but does not actually start it yet.
1131 *
1132 * It copies the registers, and all the appropriate
1133 * parts of the process environment (as per the clone
1134 * flags). The actual kick-off is left to the caller.
1135 */
1136static struct task_struct *copy_process(unsigned long clone_flags,
1137					unsigned long stack_start,
 
1138					unsigned long stack_size,
1139					int __user *child_tidptr,
1140					struct pid *pid,
1141					int trace)
1142{
1143	int retval;
1144	struct task_struct *p;
 
1145
1146	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1147		return ERR_PTR(-EINVAL);
1148
1149	if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1150		return ERR_PTR(-EINVAL);
1151
1152	/*
1153	 * Thread groups must share signals as well, and detached threads
1154	 * can only be started up within the thread group.
1155	 */
1156	if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1157		return ERR_PTR(-EINVAL);
1158
1159	/*
1160	 * Shared signal handlers imply shared VM. By way of the above,
1161	 * thread groups also imply shared VM. Blocking this case allows
1162	 * for various simplifications in other code.
1163	 */
1164	if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1165		return ERR_PTR(-EINVAL);
1166
1167	/*
1168	 * Siblings of global init remain as zombies on exit since they are
1169	 * not reaped by their parent (swapper). To solve this and to avoid
1170	 * multi-rooted process trees, prevent global and container-inits
1171	 * from creating siblings.
1172	 */
1173	if ((clone_flags & CLONE_PARENT) &&
1174				current->signal->flags & SIGNAL_UNKILLABLE)
1175		return ERR_PTR(-EINVAL);
1176
1177	/*
1178	 * If the new process will be in a different pid or user namespace
1179	 * do not allow it to share a thread group or signal handlers or
1180	 * parent with the forking task.
1181	 */
1182	if (clone_flags & CLONE_SIGHAND) {
1183		if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1184		    (task_active_pid_ns(current) !=
1185				current->nsproxy->pid_ns_for_children))
1186			return ERR_PTR(-EINVAL);
1187	}
1188
1189	retval = security_task_create(clone_flags);
1190	if (retval)
1191		goto fork_out;
1192
1193	retval = -ENOMEM;
1194	p = dup_task_struct(current);
1195	if (!p)
1196		goto fork_out;
1197
1198	ftrace_graph_init_task(p);
1199	get_seccomp_filter(p);
1200
1201	rt_mutex_init_task(p);
1202
1203#ifdef CONFIG_PROVE_LOCKING
1204	DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1205	DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1206#endif
1207	retval = -EAGAIN;
1208	if (atomic_read(&p->real_cred->user->processes) >=
1209			task_rlimit(p, RLIMIT_NPROC)) {
1210		if (p->real_cred->user != INIT_USER &&
1211		    !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1212			goto bad_fork_free;
1213	}
1214	current->flags &= ~PF_NPROC_EXCEEDED;
1215
1216	retval = copy_creds(p, clone_flags);
1217	if (retval < 0)
1218		goto bad_fork_free;
1219
1220	/*
1221	 * If multiple threads are within copy_process(), then this check
1222	 * triggers too late. This doesn't hurt, the check is only there
1223	 * to stop root fork bombs.
1224	 */
1225	retval = -EAGAIN;
1226	if (nr_threads >= max_threads)
1227		goto bad_fork_cleanup_count;
1228
1229	if (!try_module_get(task_thread_info(p)->exec_domain->module))
1230		goto bad_fork_cleanup_count;
1231
 
1232	delayacct_tsk_init(p);	/* Must remain after dup_task_struct() */
1233	p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1234	p->flags |= PF_FORKNOEXEC;
1235	INIT_LIST_HEAD(&p->children);
1236	INIT_LIST_HEAD(&p->sibling);
1237	rcu_copy_process(p);
1238	p->vfork_done = NULL;
1239	spin_lock_init(&p->alloc_lock);
1240
1241	init_sigpending(&p->pending);
1242
1243	p->utime = p->stime = p->gtime = 0;
1244	p->utimescaled = p->stimescaled = 0;
1245#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
1246	p->prev_cputime.utime = p->prev_cputime.stime = 0;
1247#endif
1248#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1249	seqlock_init(&p->vtime_seqlock);
1250	p->vtime_snap = 0;
1251	p->vtime_snap_whence = VTIME_SLEEPING;
1252#endif
1253
1254#if defined(SPLIT_RSS_COUNTING)
1255	memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1256#endif
1257
1258	p->default_timer_slack_ns = current->timer_slack_ns;
1259
1260	task_io_accounting_init(&p->ioac);
1261	acct_clear_integrals(p);
1262
1263	posix_cpu_timers_init(p);
1264
1265	do_posix_clock_monotonic_gettime(&p->start_time);
1266	p->real_start_time = p->start_time;
1267	monotonic_to_bootbased(&p->real_start_time);
1268	p->io_context = NULL;
1269	p->audit_context = NULL;
1270	if (clone_flags & CLONE_THREAD)
1271		threadgroup_change_begin(current);
1272	cgroup_fork(p);
1273#ifdef CONFIG_NUMA
1274	p->mempolicy = mpol_dup(p->mempolicy);
1275	if (IS_ERR(p->mempolicy)) {
1276		retval = PTR_ERR(p->mempolicy);
1277		p->mempolicy = NULL;
1278		goto bad_fork_cleanup_threadgroup_lock;
1279	}
 
1280#endif
1281#ifdef CONFIG_CPUSETS
1282	p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1283	p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1284	seqcount_init(&p->mems_allowed_seq);
1285#endif
1286#ifdef CONFIG_TRACE_IRQFLAGS
1287	p->irq_events = 0;
 
 
 
1288	p->hardirqs_enabled = 0;
 
1289	p->hardirq_enable_ip = 0;
1290	p->hardirq_enable_event = 0;
1291	p->hardirq_disable_ip = _THIS_IP_;
1292	p->hardirq_disable_event = 0;
1293	p->softirqs_enabled = 1;
1294	p->softirq_enable_ip = _THIS_IP_;
1295	p->softirq_enable_event = 0;
1296	p->softirq_disable_ip = 0;
1297	p->softirq_disable_event = 0;
1298	p->hardirq_context = 0;
1299	p->softirq_context = 0;
1300#endif
1301#ifdef CONFIG_LOCKDEP
1302	p->lockdep_depth = 0; /* no locks held yet */
1303	p->curr_chain_key = 0;
1304	p->lockdep_recursion = 0;
1305#endif
1306
1307#ifdef CONFIG_DEBUG_MUTEXES
1308	p->blocked_on = NULL; /* not blocked yet */
1309#endif
1310#ifdef CONFIG_MEMCG
1311	p->memcg_batch.do_batch = 0;
1312	p->memcg_batch.memcg = NULL;
1313#endif
1314#ifdef CONFIG_BCACHE
1315	p->sequential_io	= 0;
1316	p->sequential_io_avg	= 0;
1317#endif
1318
1319	/* Perform scheduler related setup. Assign this task to a CPU. */
1320	retval = sched_fork(clone_flags, p);
1321	if (retval)
1322		goto bad_fork_cleanup_policy;
1323
1324	retval = perf_event_init_task(p);
1325	if (retval)
1326		goto bad_fork_cleanup_policy;
1327	retval = audit_alloc(p);
1328	if (retval)
1329		goto bad_fork_cleanup_policy;
1330	/* copy all the process information */
1331	retval = copy_semundo(clone_flags, p);
1332	if (retval)
1333		goto bad_fork_cleanup_audit;
1334	retval = copy_files(clone_flags, p);
1335	if (retval)
1336		goto bad_fork_cleanup_semundo;
1337	retval = copy_fs(clone_flags, p);
1338	if (retval)
1339		goto bad_fork_cleanup_files;
1340	retval = copy_sighand(clone_flags, p);
1341	if (retval)
1342		goto bad_fork_cleanup_fs;
1343	retval = copy_signal(clone_flags, p);
1344	if (retval)
1345		goto bad_fork_cleanup_sighand;
1346	retval = copy_mm(clone_flags, p);
1347	if (retval)
1348		goto bad_fork_cleanup_signal;
1349	retval = copy_namespaces(clone_flags, p);
1350	if (retval)
1351		goto bad_fork_cleanup_mm;
1352	retval = copy_io(clone_flags, p);
1353	if (retval)
1354		goto bad_fork_cleanup_namespaces;
1355	retval = copy_thread(clone_flags, stack_start, stack_size, p);
1356	if (retval)
1357		goto bad_fork_cleanup_io;
1358
1359	if (pid != &init_struct_pid) {
1360		retval = -ENOMEM;
1361		pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1362		if (!pid)
1363			goto bad_fork_cleanup_io;
1364	}
1365
 
 
 
 
 
1366	p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1367	/*
1368	 * Clear TID on mm_release()?
1369	 */
1370	p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1371#ifdef CONFIG_BLOCK
1372	p->plug = NULL;
1373#endif
1374#ifdef CONFIG_FUTEX
1375	p->robust_list = NULL;
1376#ifdef CONFIG_COMPAT
1377	p->compat_robust_list = NULL;
1378#endif
1379	INIT_LIST_HEAD(&p->pi_state_list);
1380	p->pi_state_cache = NULL;
1381#endif
 
1382	/*
1383	 * sigaltstack should be cleared when sharing the same VM
1384	 */
1385	if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1386		p->sas_ss_sp = p->sas_ss_size = 0;
1387
1388	/*
1389	 * Syscall tracing and stepping should be turned off in the
1390	 * child regardless of CLONE_PTRACE.
1391	 */
1392	user_disable_single_step(p);
1393	clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1394#ifdef TIF_SYSCALL_EMU
1395	clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1396#endif
1397	clear_all_latency_tracing(p);
1398
1399	/* ok, now we should be set up.. */
1400	p->pid = pid_nr(pid);
1401	if (clone_flags & CLONE_THREAD) {
1402		p->exit_signal = -1;
1403		p->group_leader = current->group_leader;
1404		p->tgid = current->tgid;
1405	} else {
1406		if (clone_flags & CLONE_PARENT)
1407			p->exit_signal = current->group_leader->exit_signal;
1408		else
1409			p->exit_signal = (clone_flags & CSIGNAL);
1410		p->group_leader = p;
1411		p->tgid = p->pid;
1412	}
1413
1414	p->nr_dirtied = 0;
1415	p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1416	p->dirty_paused_when = 0;
1417
1418	p->pdeath_signal = 0;
1419	INIT_LIST_HEAD(&p->thread_group);
1420	p->task_works = NULL;
1421
1422	/*
1423	 * Make it visible to the rest of the system, but dont wake it up yet.
1424	 * Need tasklist lock for parent etc handling!
1425	 */
 
 
 
 
 
 
 
 
 
 
 
1426	write_lock_irq(&tasklist_lock);
1427
1428	/* CLONE_PARENT re-uses the old parent */
1429	if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1430		p->real_parent = current->real_parent;
1431		p->parent_exec_id = current->parent_exec_id;
1432	} else {
1433		p->real_parent = current;
1434		p->parent_exec_id = current->self_exec_id;
1435	}
1436
1437	spin_lock(&current->sighand->siglock);
1438
1439	/*
1440	 * Process group and session signals need to be delivered to just the
1441	 * parent before the fork or both the parent and the child after the
1442	 * fork. Restart if a signal comes in before we add the new process to
1443	 * it's process group.
1444	 * A fatal signal pending means that current will exit, so the new
1445	 * thread can't slip out of an OOM kill (or normal SIGKILL).
1446	*/
1447	recalc_sigpending();
1448	if (signal_pending(current)) {
1449		spin_unlock(&current->sighand->siglock);
1450		write_unlock_irq(&tasklist_lock);
1451		retval = -ERESTARTNOINTR;
1452		goto bad_fork_free_pid;
1453	}
1454
 
 
 
 
 
 
 
 
1455	if (likely(p->pid)) {
1456		ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1457
1458		init_task_pid(p, PIDTYPE_PID, pid);
1459		if (thread_group_leader(p)) {
1460			init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1461			init_task_pid(p, PIDTYPE_SID, task_session(current));
1462
1463			if (is_child_reaper(pid)) {
1464				ns_of_pid(pid)->child_reaper = p;
1465				p->signal->flags |= SIGNAL_UNKILLABLE;
1466			}
1467
1468			p->signal->leader_pid = pid;
1469			p->signal->tty = tty_kref_get(current->signal->tty);
 
 
1470			list_add_tail(&p->sibling, &p->real_parent->children);
1471			list_add_tail_rcu(&p->tasks, &init_task.tasks);
1472			attach_pid(p, PIDTYPE_PGID);
1473			attach_pid(p, PIDTYPE_SID);
1474			__this_cpu_inc(process_counts);
1475		} else {
1476			current->signal->nr_threads++;
1477			atomic_inc(&current->signal->live);
1478			atomic_inc(&current->signal->sigcnt);
1479			list_add_tail_rcu(&p->thread_group,
1480					  &p->group_leader->thread_group);
1481			list_add_tail_rcu(&p->thread_node,
1482					  &p->signal->thread_head);
1483		}
1484		attach_pid(p, PIDTYPE_PID);
1485		nr_threads++;
1486	}
1487
1488	total_forks++;
1489	spin_unlock(&current->sighand->siglock);
1490	write_unlock_irq(&tasklist_lock);
1491	proc_fork_connector(p);
1492	cgroup_post_fork(p);
1493	if (clone_flags & CLONE_THREAD)
1494		threadgroup_change_end(current);
1495	perf_event_fork(p);
1496
1497	trace_task_newtask(p, clone_flags);
1498	uprobe_copy_process(p, clone_flags);
1499
1500	return p;
1501
1502bad_fork_free_pid:
1503	if (pid != &init_struct_pid)
1504		free_pid(pid);
1505bad_fork_cleanup_io:
1506	if (p->io_context)
1507		exit_io_context(p);
1508bad_fork_cleanup_namespaces:
 
 
1509	exit_task_namespaces(p);
1510bad_fork_cleanup_mm:
1511	if (p->mm)
1512		mmput(p->mm);
1513bad_fork_cleanup_signal:
1514	if (!(clone_flags & CLONE_THREAD))
1515		free_signal_struct(p->signal);
1516bad_fork_cleanup_sighand:
1517	__cleanup_sighand(p->sighand);
1518bad_fork_cleanup_fs:
1519	exit_fs(p); /* blocking */
1520bad_fork_cleanup_files:
1521	exit_files(p); /* blocking */
1522bad_fork_cleanup_semundo:
1523	exit_sem(p);
1524bad_fork_cleanup_audit:
1525	audit_free(p);
1526bad_fork_cleanup_policy:
1527	perf_event_free_task(p);
1528#ifdef CONFIG_NUMA
1529	mpol_put(p->mempolicy);
1530bad_fork_cleanup_threadgroup_lock:
1531#endif
1532	if (clone_flags & CLONE_THREAD)
1533		threadgroup_change_end(current);
 
1534	delayacct_tsk_free(p);
1535	module_put(task_thread_info(p)->exec_domain->module);
1536bad_fork_cleanup_count:
1537	atomic_dec(&p->cred->user->processes);
1538	exit_creds(p);
1539bad_fork_free:
1540	free_task(p);
1541fork_out:
1542	return ERR_PTR(retval);
1543}
1544
 
 
 
 
 
 
1545static inline void init_idle_pids(struct pid_link *links)
1546{
1547	enum pid_type type;
1548
1549	for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1550		INIT_HLIST_NODE(&links[type].node); /* not really needed */
1551		links[type].pid = &init_struct_pid;
1552	}
1553}
1554
1555struct task_struct *fork_idle(int cpu)
1556{
1557	struct task_struct *task;
1558	task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0);
 
 
 
1559	if (!IS_ERR(task)) {
1560		init_idle_pids(task->pids);
1561		init_idle(task, cpu);
1562	}
1563
1564	return task;
1565}
1566
1567/*
1568 *  Ok, this is the main fork-routine.
1569 *
1570 * It copies the process, and if successful kick-starts
1571 * it and waits for it to finish using the VM if required.
1572 */
1573long do_fork(unsigned long clone_flags,
1574	      unsigned long stack_start,
 
1575	      unsigned long stack_size,
1576	      int __user *parent_tidptr,
1577	      int __user *child_tidptr)
1578{
1579	struct task_struct *p;
1580	int trace = 0;
1581	long nr;
1582
1583	/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1584	 * Determine whether and which event to report to ptracer.  When
1585	 * called from kernel_thread or CLONE_UNTRACED is explicitly
1586	 * requested, no event is reported; otherwise, report if the event
1587	 * for the type of forking is enabled.
1588	 */
1589	if (!(clone_flags & CLONE_UNTRACED)) {
1590		if (clone_flags & CLONE_VFORK)
1591			trace = PTRACE_EVENT_VFORK;
1592		else if ((clone_flags & CSIGNAL) != SIGCHLD)
1593			trace = PTRACE_EVENT_CLONE;
1594		else
1595			trace = PTRACE_EVENT_FORK;
1596
1597		if (likely(!ptrace_event_enabled(current, trace)))
1598			trace = 0;
1599	}
1600
1601	p = copy_process(clone_flags, stack_start, stack_size,
1602			 child_tidptr, NULL, trace);
1603	/*
1604	 * Do this prior waking up the new thread - the thread pointer
1605	 * might get invalid after that point, if the thread exits quickly.
1606	 */
1607	if (!IS_ERR(p)) {
1608		struct completion vfork;
1609
1610		trace_sched_process_fork(current, p);
1611
1612		nr = task_pid_vnr(p);
1613
1614		if (clone_flags & CLONE_PARENT_SETTID)
1615			put_user(nr, parent_tidptr);
1616
1617		if (clone_flags & CLONE_VFORK) {
1618			p->vfork_done = &vfork;
1619			init_completion(&vfork);
1620			get_task_struct(p);
1621		}
1622
1623		wake_up_new_task(p);
1624
1625		/* forking complete and child started to run, tell ptracer */
1626		if (unlikely(trace))
1627			ptrace_event(trace, nr);
1628
1629		if (clone_flags & CLONE_VFORK) {
1630			if (!wait_for_vfork_done(p, &vfork))
1631				ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
1632		}
1633	} else {
1634		nr = PTR_ERR(p);
1635	}
1636	return nr;
1637}
1638
1639/*
1640 * Create a kernel thread.
1641 */
1642pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
1643{
1644	return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
1645		(unsigned long)arg, NULL, NULL);
1646}
1647
1648#ifdef __ARCH_WANT_SYS_FORK
1649SYSCALL_DEFINE0(fork)
1650{
1651#ifdef CONFIG_MMU
1652	return do_fork(SIGCHLD, 0, 0, NULL, NULL);
1653#else
1654	/* can not support in nommu mode */
1655	return -EINVAL;
1656#endif
1657}
1658#endif
1659
1660#ifdef __ARCH_WANT_SYS_VFORK
1661SYSCALL_DEFINE0(vfork)
1662{
1663	return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
1664			0, NULL, NULL);
1665}
1666#endif
1667
1668#ifdef __ARCH_WANT_SYS_CLONE
1669#ifdef CONFIG_CLONE_BACKWARDS
1670SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1671		 int __user *, parent_tidptr,
1672		 int, tls_val,
1673		 int __user *, child_tidptr)
1674#elif defined(CONFIG_CLONE_BACKWARDS2)
1675SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
1676		 int __user *, parent_tidptr,
1677		 int __user *, child_tidptr,
1678		 int, tls_val)
1679#elif defined(CONFIG_CLONE_BACKWARDS3)
1680SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
1681		int, stack_size,
1682		int __user *, parent_tidptr,
1683		int __user *, child_tidptr,
1684		int, tls_val)
1685#else
1686SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1687		 int __user *, parent_tidptr,
1688		 int __user *, child_tidptr,
1689		 int, tls_val)
1690#endif
1691{
1692	return do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr);
1693}
1694#endif
1695
1696#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1697#define ARCH_MIN_MMSTRUCT_ALIGN 0
1698#endif
1699
1700static void sighand_ctor(void *data)
1701{
1702	struct sighand_struct *sighand = data;
1703
1704	spin_lock_init(&sighand->siglock);
1705	init_waitqueue_head(&sighand->signalfd_wqh);
1706}
1707
1708void __init proc_caches_init(void)
1709{
1710	sighand_cachep = kmem_cache_create("sighand_cache",
1711			sizeof(struct sighand_struct), 0,
1712			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1713			SLAB_NOTRACK, sighand_ctor);
1714	signal_cachep = kmem_cache_create("signal_cache",
1715			sizeof(struct signal_struct), 0,
1716			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1717	files_cachep = kmem_cache_create("files_cache",
1718			sizeof(struct files_struct), 0,
1719			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1720	fs_cachep = kmem_cache_create("fs_cache",
1721			sizeof(struct fs_struct), 0,
1722			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1723	/*
1724	 * FIXME! The "sizeof(struct mm_struct)" currently includes the
1725	 * whole struct cpumask for the OFFSTACK case. We could change
1726	 * this to *only* allocate as much of it as required by the
1727	 * maximum number of CPU's we can ever have.  The cpumask_allocation
1728	 * is at the end of the structure, exactly for that reason.
1729	 */
1730	mm_cachep = kmem_cache_create("mm_struct",
1731			sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1732			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1733	vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1734	mmap_init();
1735	nsproxy_cache_init();
1736}
1737
1738/*
1739 * Check constraints on flags passed to the unshare system call.
1740 */
1741static int check_unshare_flags(unsigned long unshare_flags)
1742{
1743	if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1744				CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1745				CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
1746				CLONE_NEWUSER|CLONE_NEWPID))
1747		return -EINVAL;
1748	/*
1749	 * Not implemented, but pretend it works if there is nothing to
1750	 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1751	 * needs to unshare vm.
1752	 */
1753	if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1754		/* FIXME: get_task_mm() increments ->mm_users */
1755		if (atomic_read(&current->mm->mm_users) > 1)
1756			return -EINVAL;
1757	}
1758
1759	return 0;
1760}
1761
1762/*
1763 * Unshare the filesystem structure if it is being shared
1764 */
1765static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1766{
1767	struct fs_struct *fs = current->fs;
1768
1769	if (!(unshare_flags & CLONE_FS) || !fs)
1770		return 0;
1771
1772	/* don't need lock here; in the worst case we'll do useless copy */
1773	if (fs->users == 1)
1774		return 0;
1775
1776	*new_fsp = copy_fs_struct(fs);
1777	if (!*new_fsp)
1778		return -ENOMEM;
1779
1780	return 0;
1781}
1782
1783/*
1784 * Unshare file descriptor table if it is being shared
1785 */
1786static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1787{
1788	struct files_struct *fd = current->files;
1789	int error = 0;
1790
1791	if ((unshare_flags & CLONE_FILES) &&
1792	    (fd && atomic_read(&fd->count) > 1)) {
1793		*new_fdp = dup_fd(fd, &error);
1794		if (!*new_fdp)
1795			return error;
1796	}
1797
1798	return 0;
1799}
1800
1801/*
1802 * unshare allows a process to 'unshare' part of the process
1803 * context which was originally shared using clone.  copy_*
1804 * functions used by do_fork() cannot be used here directly
1805 * because they modify an inactive task_struct that is being
1806 * constructed. Here we are modifying the current, active,
1807 * task_struct.
1808 */
1809SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1810{
1811	struct fs_struct *fs, *new_fs = NULL;
1812	struct files_struct *fd, *new_fd = NULL;
1813	struct cred *new_cred = NULL;
1814	struct nsproxy *new_nsproxy = NULL;
1815	int do_sysvsem = 0;
1816	int err;
1817
1818	/*
1819	 * If unsharing a user namespace must also unshare the thread.
1820	 */
1821	if (unshare_flags & CLONE_NEWUSER)
1822		unshare_flags |= CLONE_THREAD | CLONE_FS;
1823	/*
1824	 * If unsharing a thread from a thread group, must also unshare vm.
1825	 */
1826	if (unshare_flags & CLONE_THREAD)
1827		unshare_flags |= CLONE_VM;
1828	/*
1829	 * If unsharing vm, must also unshare signal handlers.
1830	 */
1831	if (unshare_flags & CLONE_VM)
1832		unshare_flags |= CLONE_SIGHAND;
1833	/*
1834	 * If unsharing namespace, must also unshare filesystem information.
1835	 */
1836	if (unshare_flags & CLONE_NEWNS)
1837		unshare_flags |= CLONE_FS;
1838
1839	err = check_unshare_flags(unshare_flags);
1840	if (err)
1841		goto bad_unshare_out;
1842	/*
1843	 * CLONE_NEWIPC must also detach from the undolist: after switching
1844	 * to a new ipc namespace, the semaphore arrays from the old
1845	 * namespace are unreachable.
1846	 */
1847	if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1848		do_sysvsem = 1;
1849	err = unshare_fs(unshare_flags, &new_fs);
1850	if (err)
1851		goto bad_unshare_out;
1852	err = unshare_fd(unshare_flags, &new_fd);
1853	if (err)
1854		goto bad_unshare_cleanup_fs;
1855	err = unshare_userns(unshare_flags, &new_cred);
1856	if (err)
1857		goto bad_unshare_cleanup_fd;
1858	err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1859					 new_cred, new_fs);
1860	if (err)
1861		goto bad_unshare_cleanup_cred;
1862
1863	if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
1864		if (do_sysvsem) {
1865			/*
1866			 * CLONE_SYSVSEM is equivalent to sys_exit().
1867			 */
1868			exit_sem(current);
1869		}
1870
1871		if (new_nsproxy)
1872			switch_task_namespaces(current, new_nsproxy);
 
 
1873
1874		task_lock(current);
1875
1876		if (new_fs) {
1877			fs = current->fs;
1878			spin_lock(&fs->lock);
1879			current->fs = new_fs;
1880			if (--fs->users)
1881				new_fs = NULL;
1882			else
1883				new_fs = fs;
1884			spin_unlock(&fs->lock);
1885		}
1886
1887		if (new_fd) {
1888			fd = current->files;
1889			current->files = new_fd;
1890			new_fd = fd;
1891		}
1892
1893		task_unlock(current);
1894
1895		if (new_cred) {
1896			/* Install the new user namespace */
1897			commit_creds(new_cred);
1898			new_cred = NULL;
1899		}
1900	}
1901
1902bad_unshare_cleanup_cred:
1903	if (new_cred)
1904		put_cred(new_cred);
1905bad_unshare_cleanup_fd:
1906	if (new_fd)
1907		put_files_struct(new_fd);
1908
1909bad_unshare_cleanup_fs:
1910	if (new_fs)
1911		free_fs_struct(new_fs);
1912
1913bad_unshare_out:
1914	return err;
1915}
1916
1917/*
1918 *	Helper to unshare the files of the current task.
1919 *	We don't want to expose copy_files internals to
1920 *	the exec layer of the kernel.
1921 */
1922
1923int unshare_files(struct files_struct **displaced)
1924{
1925	struct task_struct *task = current;
1926	struct files_struct *copy = NULL;
1927	int error;
1928
1929	error = unshare_fd(CLONE_FILES, &copy);
1930	if (error || !copy) {
1931		*displaced = NULL;
1932		return error;
1933	}
1934	*displaced = task->files;
1935	task_lock(task);
1936	task->files = copy;
1937	task_unlock(task);
1938	return 0;
1939}