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/mnt_namespace.h> 21 #include <linux/personality.h> 22 #include <linux/mempolicy.h> 23 #include <linux/sem.h> 24 #include <linux/file.h> 25 #include <linux/key.h> 26 #include <linux/binfmts.h> 27 #include <linux/mman.h> 28 #include <linux/fs.h> 29 #include <linux/nsproxy.h> 30 #include <linux/capability.h> 31 #include <linux/cpu.h> 32 #include <linux/cgroup.h> 33 #include <linux/security.h> 34 #include <linux/swap.h> 35 #include <linux/syscalls.h> 36 #include <linux/jiffies.h> 37 #include <linux/futex.h> 38 #include <linux/task_io_accounting_ops.h> 39 #include <linux/rcupdate.h> 40 #include <linux/ptrace.h> 41 #include <linux/mount.h> 42 #include <linux/audit.h> 43 #include <linux/profile.h> 44 #include <linux/rmap.h> 45 #include <linux/acct.h> 46 #include <linux/tsacct_kern.h> 47 #include <linux/cn_proc.h> 48 #include <linux/freezer.h> 49 #include <linux/delayacct.h> 50 #include <linux/taskstats_kern.h> 51 #include <linux/random.h> 52 #include <linux/tty.h> 53 #include <linux/proc_fs.h> 54 55 #include <asm/pgtable.h> 56 #include <asm/pgalloc.h> 57 #include <asm/uaccess.h> 58 #include <asm/mmu_context.h> 59 #include <asm/cacheflush.h> 60 #include <asm/tlbflush.h> 61 62 /* 63 * Protected counters by write_lock_irq(&tasklist_lock) 64 */ 65 unsigned long total_forks; /* Handle normal Linux uptimes. */ 66 int nr_threads; /* The idle threads do not count.. */ 67 68 int max_threads; /* tunable limit on nr_threads */ 69 70 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 71 72 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 73 74 int nr_processes(void) 75 { 76 int cpu; 77 int total = 0; 78 79 for_each_online_cpu(cpu) 80 total += per_cpu(process_counts, cpu); 81 82 return total; 83 } 84 85 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 86 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 87 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 88 static struct kmem_cache *task_struct_cachep; 89 #endif 90 91 /* SLAB cache for signal_struct structures (tsk->signal) */ 92 static struct kmem_cache *signal_cachep; 93 94 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 95 struct kmem_cache *sighand_cachep; 96 97 /* SLAB cache for files_struct structures (tsk->files) */ 98 struct kmem_cache *files_cachep; 99 100 /* SLAB cache for fs_struct structures (tsk->fs) */ 101 struct kmem_cache *fs_cachep; 102 103 /* SLAB cache for vm_area_struct structures */ 104 struct kmem_cache *vm_area_cachep; 105 106 /* SLAB cache for mm_struct structures (tsk->mm) */ 107 static struct kmem_cache *mm_cachep; 108 109 void free_task(struct task_struct *tsk) 110 { 111 prop_local_destroy_single(&tsk->dirties); 112 free_thread_info(tsk->stack); 113 rt_mutex_debug_task_free(tsk); 114 free_task_struct(tsk); 115 } 116 EXPORT_SYMBOL(free_task); 117 118 void __put_task_struct(struct task_struct *tsk) 119 { 120 WARN_ON(!tsk->exit_state); 121 WARN_ON(atomic_read(&tsk->usage)); 122 WARN_ON(tsk == current); 123 124 security_task_free(tsk); 125 free_uid(tsk->user); 126 put_group_info(tsk->group_info); 127 delayacct_tsk_free(tsk); 128 129 if (!profile_handoff_task(tsk)) 130 free_task(tsk); 131 } 132 133 void __init fork_init(unsigned long mempages) 134 { 135 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 136 #ifndef ARCH_MIN_TASKALIGN 137 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 138 #endif 139 /* create a slab on which task_structs can be allocated */ 140 task_struct_cachep = 141 kmem_cache_create("task_struct", sizeof(struct task_struct), 142 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL); 143 #endif 144 145 /* 146 * The default maximum number of threads is set to a safe 147 * value: the thread structures can take up at most half 148 * of memory. 149 */ 150 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 151 152 /* 153 * we need to allow at least 20 threads to boot a system 154 */ 155 if(max_threads < 20) 156 max_threads = 20; 157 158 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 159 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 160 init_task.signal->rlim[RLIMIT_SIGPENDING] = 161 init_task.signal->rlim[RLIMIT_NPROC]; 162 } 163 164 static struct task_struct *dup_task_struct(struct task_struct *orig) 165 { 166 struct task_struct *tsk; 167 struct thread_info *ti; 168 int err; 169 170 prepare_to_copy(orig); 171 172 tsk = alloc_task_struct(); 173 if (!tsk) 174 return NULL; 175 176 ti = alloc_thread_info(tsk); 177 if (!ti) { 178 free_task_struct(tsk); 179 return NULL; 180 } 181 182 *tsk = *orig; 183 tsk->stack = ti; 184 185 err = prop_local_init_single(&tsk->dirties); 186 if (err) { 187 free_thread_info(ti); 188 free_task_struct(tsk); 189 return NULL; 190 } 191 192 setup_thread_stack(tsk, orig); 193 194 #ifdef CONFIG_CC_STACKPROTECTOR 195 tsk->stack_canary = get_random_int(); 196 #endif 197 198 /* One for us, one for whoever does the "release_task()" (usually parent) */ 199 atomic_set(&tsk->usage,2); 200 atomic_set(&tsk->fs_excl, 0); 201 #ifdef CONFIG_BLK_DEV_IO_TRACE 202 tsk->btrace_seq = 0; 203 #endif 204 tsk->splice_pipe = NULL; 205 return tsk; 206 } 207 208 #ifdef CONFIG_MMU 209 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 210 { 211 struct vm_area_struct *mpnt, *tmp, **pprev; 212 struct rb_node **rb_link, *rb_parent; 213 int retval; 214 unsigned long charge; 215 struct mempolicy *pol; 216 217 down_write(&oldmm->mmap_sem); 218 flush_cache_dup_mm(oldmm); 219 /* 220 * Not linked in yet - no deadlock potential: 221 */ 222 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 223 224 mm->locked_vm = 0; 225 mm->mmap = NULL; 226 mm->mmap_cache = NULL; 227 mm->free_area_cache = oldmm->mmap_base; 228 mm->cached_hole_size = ~0UL; 229 mm->map_count = 0; 230 cpus_clear(mm->cpu_vm_mask); 231 mm->mm_rb = RB_ROOT; 232 rb_link = &mm->mm_rb.rb_node; 233 rb_parent = NULL; 234 pprev = &mm->mmap; 235 236 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 237 struct file *file; 238 239 if (mpnt->vm_flags & VM_DONTCOPY) { 240 long pages = vma_pages(mpnt); 241 mm->total_vm -= pages; 242 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 243 -pages); 244 continue; 245 } 246 charge = 0; 247 if (mpnt->vm_flags & VM_ACCOUNT) { 248 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 249 if (security_vm_enough_memory(len)) 250 goto fail_nomem; 251 charge = len; 252 } 253 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 254 if (!tmp) 255 goto fail_nomem; 256 *tmp = *mpnt; 257 pol = mpol_copy(vma_policy(mpnt)); 258 retval = PTR_ERR(pol); 259 if (IS_ERR(pol)) 260 goto fail_nomem_policy; 261 vma_set_policy(tmp, pol); 262 tmp->vm_flags &= ~VM_LOCKED; 263 tmp->vm_mm = mm; 264 tmp->vm_next = NULL; 265 anon_vma_link(tmp); 266 file = tmp->vm_file; 267 if (file) { 268 struct inode *inode = file->f_path.dentry->d_inode; 269 get_file(file); 270 if (tmp->vm_flags & VM_DENYWRITE) 271 atomic_dec(&inode->i_writecount); 272 273 /* insert tmp into the share list, just after mpnt */ 274 spin_lock(&file->f_mapping->i_mmap_lock); 275 tmp->vm_truncate_count = mpnt->vm_truncate_count; 276 flush_dcache_mmap_lock(file->f_mapping); 277 vma_prio_tree_add(tmp, mpnt); 278 flush_dcache_mmap_unlock(file->f_mapping); 279 spin_unlock(&file->f_mapping->i_mmap_lock); 280 } 281 282 /* 283 * Link in the new vma and copy the page table entries. 284 */ 285 *pprev = tmp; 286 pprev = &tmp->vm_next; 287 288 __vma_link_rb(mm, tmp, rb_link, rb_parent); 289 rb_link = &tmp->vm_rb.rb_right; 290 rb_parent = &tmp->vm_rb; 291 292 mm->map_count++; 293 retval = copy_page_range(mm, oldmm, mpnt); 294 295 if (tmp->vm_ops && tmp->vm_ops->open) 296 tmp->vm_ops->open(tmp); 297 298 if (retval) 299 goto out; 300 } 301 /* a new mm has just been created */ 302 arch_dup_mmap(oldmm, mm); 303 retval = 0; 304 out: 305 up_write(&mm->mmap_sem); 306 flush_tlb_mm(oldmm); 307 up_write(&oldmm->mmap_sem); 308 return retval; 309 fail_nomem_policy: 310 kmem_cache_free(vm_area_cachep, tmp); 311 fail_nomem: 312 retval = -ENOMEM; 313 vm_unacct_memory(charge); 314 goto out; 315 } 316 317 static inline int mm_alloc_pgd(struct mm_struct * mm) 318 { 319 mm->pgd = pgd_alloc(mm); 320 if (unlikely(!mm->pgd)) 321 return -ENOMEM; 322 return 0; 323 } 324 325 static inline void mm_free_pgd(struct mm_struct * mm) 326 { 327 pgd_free(mm->pgd); 328 } 329 #else 330 #define dup_mmap(mm, oldmm) (0) 331 #define mm_alloc_pgd(mm) (0) 332 #define mm_free_pgd(mm) 333 #endif /* CONFIG_MMU */ 334 335 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 336 337 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 338 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 339 340 #include <linux/init_task.h> 341 342 static struct mm_struct * mm_init(struct mm_struct * mm) 343 { 344 atomic_set(&mm->mm_users, 1); 345 atomic_set(&mm->mm_count, 1); 346 init_rwsem(&mm->mmap_sem); 347 INIT_LIST_HEAD(&mm->mmlist); 348 mm->flags = (current->mm) ? current->mm->flags 349 : MMF_DUMP_FILTER_DEFAULT; 350 mm->core_waiters = 0; 351 mm->nr_ptes = 0; 352 set_mm_counter(mm, file_rss, 0); 353 set_mm_counter(mm, anon_rss, 0); 354 spin_lock_init(&mm->page_table_lock); 355 rwlock_init(&mm->ioctx_list_lock); 356 mm->ioctx_list = NULL; 357 mm->free_area_cache = TASK_UNMAPPED_BASE; 358 mm->cached_hole_size = ~0UL; 359 360 if (likely(!mm_alloc_pgd(mm))) { 361 mm->def_flags = 0; 362 return mm; 363 } 364 free_mm(mm); 365 return NULL; 366 } 367 368 /* 369 * Allocate and initialize an mm_struct. 370 */ 371 struct mm_struct * mm_alloc(void) 372 { 373 struct mm_struct * mm; 374 375 mm = allocate_mm(); 376 if (mm) { 377 memset(mm, 0, sizeof(*mm)); 378 mm = mm_init(mm); 379 } 380 return mm; 381 } 382 383 /* 384 * Called when the last reference to the mm 385 * is dropped: either by a lazy thread or by 386 * mmput. Free the page directory and the mm. 387 */ 388 void fastcall __mmdrop(struct mm_struct *mm) 389 { 390 BUG_ON(mm == &init_mm); 391 mm_free_pgd(mm); 392 destroy_context(mm); 393 free_mm(mm); 394 } 395 396 /* 397 * Decrement the use count and release all resources for an mm. 398 */ 399 void mmput(struct mm_struct *mm) 400 { 401 might_sleep(); 402 403 if (atomic_dec_and_test(&mm->mm_users)) { 404 exit_aio(mm); 405 exit_mmap(mm); 406 if (!list_empty(&mm->mmlist)) { 407 spin_lock(&mmlist_lock); 408 list_del(&mm->mmlist); 409 spin_unlock(&mmlist_lock); 410 } 411 put_swap_token(mm); 412 mmdrop(mm); 413 } 414 } 415 EXPORT_SYMBOL_GPL(mmput); 416 417 /** 418 * get_task_mm - acquire a reference to the task's mm 419 * 420 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning 421 * this kernel workthread has transiently adopted a user mm with use_mm, 422 * to do its AIO) is not set and if so returns a reference to it, after 423 * bumping up the use count. User must release the mm via mmput() 424 * after use. Typically used by /proc and ptrace. 425 */ 426 struct mm_struct *get_task_mm(struct task_struct *task) 427 { 428 struct mm_struct *mm; 429 430 task_lock(task); 431 mm = task->mm; 432 if (mm) { 433 if (task->flags & PF_BORROWED_MM) 434 mm = NULL; 435 else 436 atomic_inc(&mm->mm_users); 437 } 438 task_unlock(task); 439 return mm; 440 } 441 EXPORT_SYMBOL_GPL(get_task_mm); 442 443 /* Please note the differences between mmput and mm_release. 444 * mmput is called whenever we stop holding onto a mm_struct, 445 * error success whatever. 446 * 447 * mm_release is called after a mm_struct has been removed 448 * from the current process. 449 * 450 * This difference is important for error handling, when we 451 * only half set up a mm_struct for a new process and need to restore 452 * the old one. Because we mmput the new mm_struct before 453 * restoring the old one. . . 454 * Eric Biederman 10 January 1998 455 */ 456 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 457 { 458 struct completion *vfork_done = tsk->vfork_done; 459 460 /* Get rid of any cached register state */ 461 deactivate_mm(tsk, mm); 462 463 /* notify parent sleeping on vfork() */ 464 if (vfork_done) { 465 tsk->vfork_done = NULL; 466 complete(vfork_done); 467 } 468 469 /* 470 * If we're exiting normally, clear a user-space tid field if 471 * requested. We leave this alone when dying by signal, to leave 472 * the value intact in a core dump, and to save the unnecessary 473 * trouble otherwise. Userland only wants this done for a sys_exit. 474 */ 475 if (tsk->clear_child_tid 476 && !(tsk->flags & PF_SIGNALED) 477 && atomic_read(&mm->mm_users) > 1) { 478 u32 __user * tidptr = tsk->clear_child_tid; 479 tsk->clear_child_tid = NULL; 480 481 /* 482 * We don't check the error code - if userspace has 483 * not set up a proper pointer then tough luck. 484 */ 485 put_user(0, tidptr); 486 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 487 } 488 } 489 490 /* 491 * Allocate a new mm structure and copy contents from the 492 * mm structure of the passed in task structure. 493 */ 494 static struct mm_struct *dup_mm(struct task_struct *tsk) 495 { 496 struct mm_struct *mm, *oldmm = current->mm; 497 int err; 498 499 if (!oldmm) 500 return NULL; 501 502 mm = allocate_mm(); 503 if (!mm) 504 goto fail_nomem; 505 506 memcpy(mm, oldmm, sizeof(*mm)); 507 508 /* Initializing for Swap token stuff */ 509 mm->token_priority = 0; 510 mm->last_interval = 0; 511 512 if (!mm_init(mm)) 513 goto fail_nomem; 514 515 if (init_new_context(tsk, mm)) 516 goto fail_nocontext; 517 518 err = dup_mmap(mm, oldmm); 519 if (err) 520 goto free_pt; 521 522 mm->hiwater_rss = get_mm_rss(mm); 523 mm->hiwater_vm = mm->total_vm; 524 525 return mm; 526 527 free_pt: 528 mmput(mm); 529 530 fail_nomem: 531 return NULL; 532 533 fail_nocontext: 534 /* 535 * If init_new_context() failed, we cannot use mmput() to free the mm 536 * because it calls destroy_context() 537 */ 538 mm_free_pgd(mm); 539 free_mm(mm); 540 return NULL; 541 } 542 543 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 544 { 545 struct mm_struct * mm, *oldmm; 546 int retval; 547 548 tsk->min_flt = tsk->maj_flt = 0; 549 tsk->nvcsw = tsk->nivcsw = 0; 550 551 tsk->mm = NULL; 552 tsk->active_mm = NULL; 553 554 /* 555 * Are we cloning a kernel thread? 556 * 557 * We need to steal a active VM for that.. 558 */ 559 oldmm = current->mm; 560 if (!oldmm) 561 return 0; 562 563 if (clone_flags & CLONE_VM) { 564 atomic_inc(&oldmm->mm_users); 565 mm = oldmm; 566 goto good_mm; 567 } 568 569 retval = -ENOMEM; 570 mm = dup_mm(tsk); 571 if (!mm) 572 goto fail_nomem; 573 574 good_mm: 575 /* Initializing for Swap token stuff */ 576 mm->token_priority = 0; 577 mm->last_interval = 0; 578 579 tsk->mm = mm; 580 tsk->active_mm = mm; 581 return 0; 582 583 fail_nomem: 584 return retval; 585 } 586 587 static struct fs_struct *__copy_fs_struct(struct fs_struct *old) 588 { 589 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 590 /* We don't need to lock fs - think why ;-) */ 591 if (fs) { 592 atomic_set(&fs->count, 1); 593 rwlock_init(&fs->lock); 594 fs->umask = old->umask; 595 read_lock(&old->lock); 596 fs->rootmnt = mntget(old->rootmnt); 597 fs->root = dget(old->root); 598 fs->pwdmnt = mntget(old->pwdmnt); 599 fs->pwd = dget(old->pwd); 600 if (old->altroot) { 601 fs->altrootmnt = mntget(old->altrootmnt); 602 fs->altroot = dget(old->altroot); 603 } else { 604 fs->altrootmnt = NULL; 605 fs->altroot = NULL; 606 } 607 read_unlock(&old->lock); 608 } 609 return fs; 610 } 611 612 struct fs_struct *copy_fs_struct(struct fs_struct *old) 613 { 614 return __copy_fs_struct(old); 615 } 616 617 EXPORT_SYMBOL_GPL(copy_fs_struct); 618 619 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 620 { 621 if (clone_flags & CLONE_FS) { 622 atomic_inc(¤t->fs->count); 623 return 0; 624 } 625 tsk->fs = __copy_fs_struct(current->fs); 626 if (!tsk->fs) 627 return -ENOMEM; 628 return 0; 629 } 630 631 static int count_open_files(struct fdtable *fdt) 632 { 633 int size = fdt->max_fds; 634 int i; 635 636 /* Find the last open fd */ 637 for (i = size/(8*sizeof(long)); i > 0; ) { 638 if (fdt->open_fds->fds_bits[--i]) 639 break; 640 } 641 i = (i+1) * 8 * sizeof(long); 642 return i; 643 } 644 645 static struct files_struct *alloc_files(void) 646 { 647 struct files_struct *newf; 648 struct fdtable *fdt; 649 650 newf = kmem_cache_alloc(files_cachep, GFP_KERNEL); 651 if (!newf) 652 goto out; 653 654 atomic_set(&newf->count, 1); 655 656 spin_lock_init(&newf->file_lock); 657 newf->next_fd = 0; 658 fdt = &newf->fdtab; 659 fdt->max_fds = NR_OPEN_DEFAULT; 660 fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init; 661 fdt->open_fds = (fd_set *)&newf->open_fds_init; 662 fdt->fd = &newf->fd_array[0]; 663 INIT_RCU_HEAD(&fdt->rcu); 664 fdt->next = NULL; 665 rcu_assign_pointer(newf->fdt, fdt); 666 out: 667 return newf; 668 } 669 670 /* 671 * Allocate a new files structure and copy contents from the 672 * passed in files structure. 673 * errorp will be valid only when the returned files_struct is NULL. 674 */ 675 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) 676 { 677 struct files_struct *newf; 678 struct file **old_fds, **new_fds; 679 int open_files, size, i; 680 struct fdtable *old_fdt, *new_fdt; 681 682 *errorp = -ENOMEM; 683 newf = alloc_files(); 684 if (!newf) 685 goto out; 686 687 spin_lock(&oldf->file_lock); 688 old_fdt = files_fdtable(oldf); 689 new_fdt = files_fdtable(newf); 690 open_files = count_open_files(old_fdt); 691 692 /* 693 * Check whether we need to allocate a larger fd array and fd set. 694 * Note: we're not a clone task, so the open count won't change. 695 */ 696 if (open_files > new_fdt->max_fds) { 697 new_fdt->max_fds = 0; 698 spin_unlock(&oldf->file_lock); 699 spin_lock(&newf->file_lock); 700 *errorp = expand_files(newf, open_files-1); 701 spin_unlock(&newf->file_lock); 702 if (*errorp < 0) 703 goto out_release; 704 new_fdt = files_fdtable(newf); 705 /* 706 * Reacquire the oldf lock and a pointer to its fd table 707 * who knows it may have a new bigger fd table. We need 708 * the latest pointer. 709 */ 710 spin_lock(&oldf->file_lock); 711 old_fdt = files_fdtable(oldf); 712 } 713 714 old_fds = old_fdt->fd; 715 new_fds = new_fdt->fd; 716 717 memcpy(new_fdt->open_fds->fds_bits, 718 old_fdt->open_fds->fds_bits, open_files/8); 719 memcpy(new_fdt->close_on_exec->fds_bits, 720 old_fdt->close_on_exec->fds_bits, open_files/8); 721 722 for (i = open_files; i != 0; i--) { 723 struct file *f = *old_fds++; 724 if (f) { 725 get_file(f); 726 } else { 727 /* 728 * The fd may be claimed in the fd bitmap but not yet 729 * instantiated in the files array if a sibling thread 730 * is partway through open(). So make sure that this 731 * fd is available to the new process. 732 */ 733 FD_CLR(open_files - i, new_fdt->open_fds); 734 } 735 rcu_assign_pointer(*new_fds++, f); 736 } 737 spin_unlock(&oldf->file_lock); 738 739 /* compute the remainder to be cleared */ 740 size = (new_fdt->max_fds - open_files) * sizeof(struct file *); 741 742 /* This is long word aligned thus could use a optimized version */ 743 memset(new_fds, 0, size); 744 745 if (new_fdt->max_fds > open_files) { 746 int left = (new_fdt->max_fds-open_files)/8; 747 int start = open_files / (8 * sizeof(unsigned long)); 748 749 memset(&new_fdt->open_fds->fds_bits[start], 0, left); 750 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left); 751 } 752 753 return newf; 754 755 out_release: 756 kmem_cache_free(files_cachep, newf); 757 out: 758 return NULL; 759 } 760 761 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 762 { 763 struct files_struct *oldf, *newf; 764 int error = 0; 765 766 /* 767 * A background process may not have any files ... 768 */ 769 oldf = current->files; 770 if (!oldf) 771 goto out; 772 773 if (clone_flags & CLONE_FILES) { 774 atomic_inc(&oldf->count); 775 goto out; 776 } 777 778 /* 779 * Note: we may be using current for both targets (See exec.c) 780 * This works because we cache current->files (old) as oldf. Don't 781 * break this. 782 */ 783 tsk->files = NULL; 784 newf = dup_fd(oldf, &error); 785 if (!newf) 786 goto out; 787 788 tsk->files = newf; 789 error = 0; 790 out: 791 return error; 792 } 793 794 /* 795 * Helper to unshare the files of the current task. 796 * We don't want to expose copy_files internals to 797 * the exec layer of the kernel. 798 */ 799 800 int unshare_files(void) 801 { 802 struct files_struct *files = current->files; 803 int rc; 804 805 BUG_ON(!files); 806 807 /* This can race but the race causes us to copy when we don't 808 need to and drop the copy */ 809 if(atomic_read(&files->count) == 1) 810 { 811 atomic_inc(&files->count); 812 return 0; 813 } 814 rc = copy_files(0, current); 815 if(rc) 816 current->files = files; 817 return rc; 818 } 819 820 EXPORT_SYMBOL(unshare_files); 821 822 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 823 { 824 struct sighand_struct *sig; 825 826 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 827 atomic_inc(¤t->sighand->count); 828 return 0; 829 } 830 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 831 rcu_assign_pointer(tsk->sighand, sig); 832 if (!sig) 833 return -ENOMEM; 834 atomic_set(&sig->count, 1); 835 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 836 return 0; 837 } 838 839 void __cleanup_sighand(struct sighand_struct *sighand) 840 { 841 if (atomic_dec_and_test(&sighand->count)) 842 kmem_cache_free(sighand_cachep, sighand); 843 } 844 845 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 846 { 847 struct signal_struct *sig; 848 int ret; 849 850 if (clone_flags & CLONE_THREAD) { 851 atomic_inc(¤t->signal->count); 852 atomic_inc(¤t->signal->live); 853 return 0; 854 } 855 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 856 tsk->signal = sig; 857 if (!sig) 858 return -ENOMEM; 859 860 ret = copy_thread_group_keys(tsk); 861 if (ret < 0) { 862 kmem_cache_free(signal_cachep, sig); 863 return ret; 864 } 865 866 atomic_set(&sig->count, 1); 867 atomic_set(&sig->live, 1); 868 init_waitqueue_head(&sig->wait_chldexit); 869 sig->flags = 0; 870 sig->group_exit_code = 0; 871 sig->group_exit_task = NULL; 872 sig->group_stop_count = 0; 873 sig->curr_target = NULL; 874 init_sigpending(&sig->shared_pending); 875 INIT_LIST_HEAD(&sig->posix_timers); 876 877 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 878 sig->it_real_incr.tv64 = 0; 879 sig->real_timer.function = it_real_fn; 880 sig->tsk = tsk; 881 882 sig->it_virt_expires = cputime_zero; 883 sig->it_virt_incr = cputime_zero; 884 sig->it_prof_expires = cputime_zero; 885 sig->it_prof_incr = cputime_zero; 886 887 sig->leader = 0; /* session leadership doesn't inherit */ 888 sig->tty_old_pgrp = NULL; 889 890 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 891 sig->gtime = cputime_zero; 892 sig->cgtime = cputime_zero; 893 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 894 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 895 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 896 sig->sum_sched_runtime = 0; 897 INIT_LIST_HEAD(&sig->cpu_timers[0]); 898 INIT_LIST_HEAD(&sig->cpu_timers[1]); 899 INIT_LIST_HEAD(&sig->cpu_timers[2]); 900 taskstats_tgid_init(sig); 901 902 task_lock(current->group_leader); 903 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 904 task_unlock(current->group_leader); 905 906 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 907 /* 908 * New sole thread in the process gets an expiry time 909 * of the whole CPU time limit. 910 */ 911 tsk->it_prof_expires = 912 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 913 } 914 acct_init_pacct(&sig->pacct); 915 916 tty_audit_fork(sig); 917 918 return 0; 919 } 920 921 void __cleanup_signal(struct signal_struct *sig) 922 { 923 exit_thread_group_keys(sig); 924 kmem_cache_free(signal_cachep, sig); 925 } 926 927 static void cleanup_signal(struct task_struct *tsk) 928 { 929 struct signal_struct *sig = tsk->signal; 930 931 atomic_dec(&sig->live); 932 933 if (atomic_dec_and_test(&sig->count)) 934 __cleanup_signal(sig); 935 } 936 937 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 938 { 939 unsigned long new_flags = p->flags; 940 941 new_flags &= ~PF_SUPERPRIV; 942 new_flags |= PF_FORKNOEXEC; 943 if (!(clone_flags & CLONE_PTRACE)) 944 p->ptrace = 0; 945 p->flags = new_flags; 946 clear_freeze_flag(p); 947 } 948 949 asmlinkage long sys_set_tid_address(int __user *tidptr) 950 { 951 current->clear_child_tid = tidptr; 952 953 return task_pid_vnr(current); 954 } 955 956 static void rt_mutex_init_task(struct task_struct *p) 957 { 958 spin_lock_init(&p->pi_lock); 959 #ifdef CONFIG_RT_MUTEXES 960 plist_head_init(&p->pi_waiters, &p->pi_lock); 961 p->pi_blocked_on = NULL; 962 #endif 963 } 964 965 /* 966 * This creates a new process as a copy of the old one, 967 * but does not actually start it yet. 968 * 969 * It copies the registers, and all the appropriate 970 * parts of the process environment (as per the clone 971 * flags). The actual kick-off is left to the caller. 972 */ 973 static struct task_struct *copy_process(unsigned long clone_flags, 974 unsigned long stack_start, 975 struct pt_regs *regs, 976 unsigned long stack_size, 977 int __user *child_tidptr, 978 struct pid *pid) 979 { 980 int retval; 981 struct task_struct *p; 982 int cgroup_callbacks_done = 0; 983 984 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 985 return ERR_PTR(-EINVAL); 986 987 /* 988 * Thread groups must share signals as well, and detached threads 989 * can only be started up within the thread group. 990 */ 991 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 992 return ERR_PTR(-EINVAL); 993 994 /* 995 * Shared signal handlers imply shared VM. By way of the above, 996 * thread groups also imply shared VM. Blocking this case allows 997 * for various simplifications in other code. 998 */ 999 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1000 return ERR_PTR(-EINVAL); 1001 1002 retval = security_task_create(clone_flags); 1003 if (retval) 1004 goto fork_out; 1005 1006 retval = -ENOMEM; 1007 p = dup_task_struct(current); 1008 if (!p) 1009 goto fork_out; 1010 1011 rt_mutex_init_task(p); 1012 1013 #ifdef CONFIG_TRACE_IRQFLAGS 1014 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1015 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1016 #endif 1017 retval = -EAGAIN; 1018 if (atomic_read(&p->user->processes) >= 1019 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 1020 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1021 p->user != current->nsproxy->user_ns->root_user) 1022 goto bad_fork_free; 1023 } 1024 1025 atomic_inc(&p->user->__count); 1026 atomic_inc(&p->user->processes); 1027 get_group_info(p->group_info); 1028 1029 /* 1030 * If multiple threads are within copy_process(), then this check 1031 * triggers too late. This doesn't hurt, the check is only there 1032 * to stop root fork bombs. 1033 */ 1034 if (nr_threads >= max_threads) 1035 goto bad_fork_cleanup_count; 1036 1037 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1038 goto bad_fork_cleanup_count; 1039 1040 if (p->binfmt && !try_module_get(p->binfmt->module)) 1041 goto bad_fork_cleanup_put_domain; 1042 1043 p->did_exec = 0; 1044 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1045 copy_flags(clone_flags, p); 1046 INIT_LIST_HEAD(&p->children); 1047 INIT_LIST_HEAD(&p->sibling); 1048 p->vfork_done = NULL; 1049 spin_lock_init(&p->alloc_lock); 1050 1051 clear_tsk_thread_flag(p, TIF_SIGPENDING); 1052 init_sigpending(&p->pending); 1053 1054 p->utime = cputime_zero; 1055 p->stime = cputime_zero; 1056 p->gtime = cputime_zero; 1057 p->utimescaled = cputime_zero; 1058 p->stimescaled = cputime_zero; 1059 p->prev_utime = cputime_zero; 1060 p->prev_stime = cputime_zero; 1061 1062 #ifdef CONFIG_TASK_XACCT 1063 p->rchar = 0; /* I/O counter: bytes read */ 1064 p->wchar = 0; /* I/O counter: bytes written */ 1065 p->syscr = 0; /* I/O counter: read syscalls */ 1066 p->syscw = 0; /* I/O counter: write syscalls */ 1067 #endif 1068 task_io_accounting_init(p); 1069 acct_clear_integrals(p); 1070 1071 p->it_virt_expires = cputime_zero; 1072 p->it_prof_expires = cputime_zero; 1073 p->it_sched_expires = 0; 1074 INIT_LIST_HEAD(&p->cpu_timers[0]); 1075 INIT_LIST_HEAD(&p->cpu_timers[1]); 1076 INIT_LIST_HEAD(&p->cpu_timers[2]); 1077 1078 p->lock_depth = -1; /* -1 = no lock */ 1079 do_posix_clock_monotonic_gettime(&p->start_time); 1080 p->real_start_time = p->start_time; 1081 monotonic_to_bootbased(&p->real_start_time); 1082 #ifdef CONFIG_SECURITY 1083 p->security = NULL; 1084 #endif 1085 p->io_context = NULL; 1086 p->audit_context = NULL; 1087 cgroup_fork(p); 1088 #ifdef CONFIG_NUMA 1089 p->mempolicy = mpol_copy(p->mempolicy); 1090 if (IS_ERR(p->mempolicy)) { 1091 retval = PTR_ERR(p->mempolicy); 1092 p->mempolicy = NULL; 1093 goto bad_fork_cleanup_cgroup; 1094 } 1095 mpol_fix_fork_child_flag(p); 1096 #endif 1097 #ifdef CONFIG_TRACE_IRQFLAGS 1098 p->irq_events = 0; 1099 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1100 p->hardirqs_enabled = 1; 1101 #else 1102 p->hardirqs_enabled = 0; 1103 #endif 1104 p->hardirq_enable_ip = 0; 1105 p->hardirq_enable_event = 0; 1106 p->hardirq_disable_ip = _THIS_IP_; 1107 p->hardirq_disable_event = 0; 1108 p->softirqs_enabled = 1; 1109 p->softirq_enable_ip = _THIS_IP_; 1110 p->softirq_enable_event = 0; 1111 p->softirq_disable_ip = 0; 1112 p->softirq_disable_event = 0; 1113 p->hardirq_context = 0; 1114 p->softirq_context = 0; 1115 #endif 1116 #ifdef CONFIG_LOCKDEP 1117 p->lockdep_depth = 0; /* no locks held yet */ 1118 p->curr_chain_key = 0; 1119 p->lockdep_recursion = 0; 1120 #endif 1121 1122 #ifdef CONFIG_DEBUG_MUTEXES 1123 p->blocked_on = NULL; /* not blocked yet */ 1124 #endif 1125 1126 /* Perform scheduler related setup. Assign this task to a CPU. */ 1127 sched_fork(p, clone_flags); 1128 1129 if ((retval = security_task_alloc(p))) 1130 goto bad_fork_cleanup_policy; 1131 if ((retval = audit_alloc(p))) 1132 goto bad_fork_cleanup_security; 1133 /* copy all the process information */ 1134 if ((retval = copy_semundo(clone_flags, p))) 1135 goto bad_fork_cleanup_audit; 1136 if ((retval = copy_files(clone_flags, p))) 1137 goto bad_fork_cleanup_semundo; 1138 if ((retval = copy_fs(clone_flags, p))) 1139 goto bad_fork_cleanup_files; 1140 if ((retval = copy_sighand(clone_flags, p))) 1141 goto bad_fork_cleanup_fs; 1142 if ((retval = copy_signal(clone_flags, p))) 1143 goto bad_fork_cleanup_sighand; 1144 if ((retval = copy_mm(clone_flags, p))) 1145 goto bad_fork_cleanup_signal; 1146 if ((retval = copy_keys(clone_flags, p))) 1147 goto bad_fork_cleanup_mm; 1148 if ((retval = copy_namespaces(clone_flags, p))) 1149 goto bad_fork_cleanup_keys; 1150 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1151 if (retval) 1152 goto bad_fork_cleanup_namespaces; 1153 1154 if (pid != &init_struct_pid) { 1155 retval = -ENOMEM; 1156 pid = alloc_pid(task_active_pid_ns(p)); 1157 if (!pid) 1158 goto bad_fork_cleanup_namespaces; 1159 1160 if (clone_flags & CLONE_NEWPID) { 1161 retval = pid_ns_prepare_proc(task_active_pid_ns(p)); 1162 if (retval < 0) 1163 goto bad_fork_free_pid; 1164 } 1165 } 1166 1167 p->pid = pid_nr(pid); 1168 p->tgid = p->pid; 1169 if (clone_flags & CLONE_THREAD) 1170 p->tgid = current->tgid; 1171 1172 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1173 /* 1174 * Clear TID on mm_release()? 1175 */ 1176 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1177 #ifdef CONFIG_FUTEX 1178 p->robust_list = NULL; 1179 #ifdef CONFIG_COMPAT 1180 p->compat_robust_list = NULL; 1181 #endif 1182 INIT_LIST_HEAD(&p->pi_state_list); 1183 p->pi_state_cache = NULL; 1184 #endif 1185 /* 1186 * sigaltstack should be cleared when sharing the same VM 1187 */ 1188 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1189 p->sas_ss_sp = p->sas_ss_size = 0; 1190 1191 /* 1192 * Syscall tracing should be turned off in the child regardless 1193 * of CLONE_PTRACE. 1194 */ 1195 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1196 #ifdef TIF_SYSCALL_EMU 1197 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1198 #endif 1199 1200 /* Our parent execution domain becomes current domain 1201 These must match for thread signalling to apply */ 1202 p->parent_exec_id = p->self_exec_id; 1203 1204 /* ok, now we should be set up.. */ 1205 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1206 p->pdeath_signal = 0; 1207 p->exit_state = 0; 1208 1209 /* 1210 * Ok, make it visible to the rest of the system. 1211 * We dont wake it up yet. 1212 */ 1213 p->group_leader = p; 1214 INIT_LIST_HEAD(&p->thread_group); 1215 INIT_LIST_HEAD(&p->ptrace_children); 1216 INIT_LIST_HEAD(&p->ptrace_list); 1217 1218 /* Now that the task is set up, run cgroup callbacks if 1219 * necessary. We need to run them before the task is visible 1220 * on the tasklist. */ 1221 cgroup_fork_callbacks(p); 1222 cgroup_callbacks_done = 1; 1223 1224 /* Need tasklist lock for parent etc handling! */ 1225 write_lock_irq(&tasklist_lock); 1226 1227 /* for sys_ioprio_set(IOPRIO_WHO_PGRP) */ 1228 p->ioprio = current->ioprio; 1229 1230 /* 1231 * The task hasn't been attached yet, so its cpus_allowed mask will 1232 * not be changed, nor will its assigned CPU. 1233 * 1234 * The cpus_allowed mask of the parent may have changed after it was 1235 * copied first time - so re-copy it here, then check the child's CPU 1236 * to ensure it is on a valid CPU (and if not, just force it back to 1237 * parent's CPU). This avoids alot of nasty races. 1238 */ 1239 p->cpus_allowed = current->cpus_allowed; 1240 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1241 !cpu_online(task_cpu(p)))) 1242 set_task_cpu(p, smp_processor_id()); 1243 1244 /* CLONE_PARENT re-uses the old parent */ 1245 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1246 p->real_parent = current->real_parent; 1247 else 1248 p->real_parent = current; 1249 p->parent = p->real_parent; 1250 1251 spin_lock(¤t->sighand->siglock); 1252 1253 /* 1254 * Process group and session signals need to be delivered to just the 1255 * parent before the fork or both the parent and the child after the 1256 * fork. Restart if a signal comes in before we add the new process to 1257 * it's process group. 1258 * A fatal signal pending means that current will exit, so the new 1259 * thread can't slip out of an OOM kill (or normal SIGKILL). 1260 */ 1261 recalc_sigpending(); 1262 if (signal_pending(current)) { 1263 spin_unlock(¤t->sighand->siglock); 1264 write_unlock_irq(&tasklist_lock); 1265 retval = -ERESTARTNOINTR; 1266 goto bad_fork_free_pid; 1267 } 1268 1269 if (clone_flags & CLONE_THREAD) { 1270 p->group_leader = current->group_leader; 1271 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1272 1273 if (!cputime_eq(current->signal->it_virt_expires, 1274 cputime_zero) || 1275 !cputime_eq(current->signal->it_prof_expires, 1276 cputime_zero) || 1277 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1278 !list_empty(¤t->signal->cpu_timers[0]) || 1279 !list_empty(¤t->signal->cpu_timers[1]) || 1280 !list_empty(¤t->signal->cpu_timers[2])) { 1281 /* 1282 * Have child wake up on its first tick to check 1283 * for process CPU timers. 1284 */ 1285 p->it_prof_expires = jiffies_to_cputime(1); 1286 } 1287 } 1288 1289 if (likely(p->pid)) { 1290 add_parent(p); 1291 if (unlikely(p->ptrace & PT_PTRACED)) 1292 __ptrace_link(p, current->parent); 1293 1294 if (thread_group_leader(p)) { 1295 if (clone_flags & CLONE_NEWPID) 1296 p->nsproxy->pid_ns->child_reaper = p; 1297 1298 p->signal->tty = current->signal->tty; 1299 set_task_pgrp(p, task_pgrp_nr(current)); 1300 set_task_session(p, task_session_nr(current)); 1301 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1302 attach_pid(p, PIDTYPE_SID, task_session(current)); 1303 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1304 __get_cpu_var(process_counts)++; 1305 } 1306 attach_pid(p, PIDTYPE_PID, pid); 1307 nr_threads++; 1308 } 1309 1310 total_forks++; 1311 spin_unlock(¤t->sighand->siglock); 1312 write_unlock_irq(&tasklist_lock); 1313 proc_fork_connector(p); 1314 cgroup_post_fork(p); 1315 return p; 1316 1317 bad_fork_free_pid: 1318 if (pid != &init_struct_pid) 1319 free_pid(pid); 1320 bad_fork_cleanup_namespaces: 1321 exit_task_namespaces(p); 1322 bad_fork_cleanup_keys: 1323 exit_keys(p); 1324 bad_fork_cleanup_mm: 1325 if (p->mm) 1326 mmput(p->mm); 1327 bad_fork_cleanup_signal: 1328 cleanup_signal(p); 1329 bad_fork_cleanup_sighand: 1330 __cleanup_sighand(p->sighand); 1331 bad_fork_cleanup_fs: 1332 exit_fs(p); /* blocking */ 1333 bad_fork_cleanup_files: 1334 exit_files(p); /* blocking */ 1335 bad_fork_cleanup_semundo: 1336 exit_sem(p); 1337 bad_fork_cleanup_audit: 1338 audit_free(p); 1339 bad_fork_cleanup_security: 1340 security_task_free(p); 1341 bad_fork_cleanup_policy: 1342 #ifdef CONFIG_NUMA 1343 mpol_free(p->mempolicy); 1344 bad_fork_cleanup_cgroup: 1345 #endif 1346 cgroup_exit(p, cgroup_callbacks_done); 1347 delayacct_tsk_free(p); 1348 if (p->binfmt) 1349 module_put(p->binfmt->module); 1350 bad_fork_cleanup_put_domain: 1351 module_put(task_thread_info(p)->exec_domain->module); 1352 bad_fork_cleanup_count: 1353 put_group_info(p->group_info); 1354 atomic_dec(&p->user->processes); 1355 free_uid(p->user); 1356 bad_fork_free: 1357 free_task(p); 1358 fork_out: 1359 return ERR_PTR(retval); 1360 } 1361 1362 noinline struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1363 { 1364 memset(regs, 0, sizeof(struct pt_regs)); 1365 return regs; 1366 } 1367 1368 struct task_struct * __cpuinit fork_idle(int cpu) 1369 { 1370 struct task_struct *task; 1371 struct pt_regs regs; 1372 1373 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1374 &init_struct_pid); 1375 if (!IS_ERR(task)) 1376 init_idle(task, cpu); 1377 1378 return task; 1379 } 1380 1381 static int fork_traceflag(unsigned clone_flags) 1382 { 1383 if (clone_flags & CLONE_UNTRACED) 1384 return 0; 1385 else if (clone_flags & CLONE_VFORK) { 1386 if (current->ptrace & PT_TRACE_VFORK) 1387 return PTRACE_EVENT_VFORK; 1388 } else if ((clone_flags & CSIGNAL) != SIGCHLD) { 1389 if (current->ptrace & PT_TRACE_CLONE) 1390 return PTRACE_EVENT_CLONE; 1391 } else if (current->ptrace & PT_TRACE_FORK) 1392 return PTRACE_EVENT_FORK; 1393 1394 return 0; 1395 } 1396 1397 /* 1398 * Ok, this is the main fork-routine. 1399 * 1400 * It copies the process, and if successful kick-starts 1401 * it and waits for it to finish using the VM if required. 1402 */ 1403 long do_fork(unsigned long clone_flags, 1404 unsigned long stack_start, 1405 struct pt_regs *regs, 1406 unsigned long stack_size, 1407 int __user *parent_tidptr, 1408 int __user *child_tidptr) 1409 { 1410 struct task_struct *p; 1411 int trace = 0; 1412 long nr; 1413 1414 if (unlikely(current->ptrace)) { 1415 trace = fork_traceflag (clone_flags); 1416 if (trace) 1417 clone_flags |= CLONE_PTRACE; 1418 } 1419 1420 p = copy_process(clone_flags, stack_start, regs, stack_size, 1421 child_tidptr, NULL); 1422 /* 1423 * Do this prior waking up the new thread - the thread pointer 1424 * might get invalid after that point, if the thread exits quickly. 1425 */ 1426 if (!IS_ERR(p)) { 1427 struct completion vfork; 1428 1429 /* 1430 * this is enough to call pid_nr_ns here, but this if 1431 * improves optimisation of regular fork() 1432 */ 1433 nr = (clone_flags & CLONE_NEWPID) ? 1434 task_pid_nr_ns(p, current->nsproxy->pid_ns) : 1435 task_pid_vnr(p); 1436 1437 if (clone_flags & CLONE_PARENT_SETTID) 1438 put_user(nr, parent_tidptr); 1439 1440 if (clone_flags & CLONE_VFORK) { 1441 p->vfork_done = &vfork; 1442 init_completion(&vfork); 1443 } 1444 1445 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) { 1446 /* 1447 * We'll start up with an immediate SIGSTOP. 1448 */ 1449 sigaddset(&p->pending.signal, SIGSTOP); 1450 set_tsk_thread_flag(p, TIF_SIGPENDING); 1451 } 1452 1453 if (!(clone_flags & CLONE_STOPPED)) 1454 wake_up_new_task(p, clone_flags); 1455 else 1456 p->state = TASK_STOPPED; 1457 1458 if (unlikely (trace)) { 1459 current->ptrace_message = nr; 1460 ptrace_notify ((trace << 8) | SIGTRAP); 1461 } 1462 1463 if (clone_flags & CLONE_VFORK) { 1464 freezer_do_not_count(); 1465 wait_for_completion(&vfork); 1466 freezer_count(); 1467 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) { 1468 current->ptrace_message = nr; 1469 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); 1470 } 1471 } 1472 } else { 1473 nr = PTR_ERR(p); 1474 } 1475 return nr; 1476 } 1477 1478 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1479 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1480 #endif 1481 1482 static void sighand_ctor(struct kmem_cache *cachep, void *data) 1483 { 1484 struct sighand_struct *sighand = data; 1485 1486 spin_lock_init(&sighand->siglock); 1487 init_waitqueue_head(&sighand->signalfd_wqh); 1488 } 1489 1490 void __init proc_caches_init(void) 1491 { 1492 sighand_cachep = kmem_cache_create("sighand_cache", 1493 sizeof(struct sighand_struct), 0, 1494 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU, 1495 sighand_ctor); 1496 signal_cachep = kmem_cache_create("signal_cache", 1497 sizeof(struct signal_struct), 0, 1498 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1499 files_cachep = kmem_cache_create("files_cache", 1500 sizeof(struct files_struct), 0, 1501 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1502 fs_cachep = kmem_cache_create("fs_cache", 1503 sizeof(struct fs_struct), 0, 1504 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1505 vm_area_cachep = kmem_cache_create("vm_area_struct", 1506 sizeof(struct vm_area_struct), 0, 1507 SLAB_PANIC, NULL); 1508 mm_cachep = kmem_cache_create("mm_struct", 1509 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1510 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1511 } 1512 1513 /* 1514 * Check constraints on flags passed to the unshare system call and 1515 * force unsharing of additional process context as appropriate. 1516 */ 1517 static void check_unshare_flags(unsigned long *flags_ptr) 1518 { 1519 /* 1520 * If unsharing a thread from a thread group, must also 1521 * unshare vm. 1522 */ 1523 if (*flags_ptr & CLONE_THREAD) 1524 *flags_ptr |= CLONE_VM; 1525 1526 /* 1527 * If unsharing vm, must also unshare signal handlers. 1528 */ 1529 if (*flags_ptr & CLONE_VM) 1530 *flags_ptr |= CLONE_SIGHAND; 1531 1532 /* 1533 * If unsharing signal handlers and the task was created 1534 * using CLONE_THREAD, then must unshare the thread 1535 */ 1536 if ((*flags_ptr & CLONE_SIGHAND) && 1537 (atomic_read(¤t->signal->count) > 1)) 1538 *flags_ptr |= CLONE_THREAD; 1539 1540 /* 1541 * If unsharing namespace, must also unshare filesystem information. 1542 */ 1543 if (*flags_ptr & CLONE_NEWNS) 1544 *flags_ptr |= CLONE_FS; 1545 } 1546 1547 /* 1548 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1549 */ 1550 static int unshare_thread(unsigned long unshare_flags) 1551 { 1552 if (unshare_flags & CLONE_THREAD) 1553 return -EINVAL; 1554 1555 return 0; 1556 } 1557 1558 /* 1559 * Unshare the filesystem structure if it is being shared 1560 */ 1561 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1562 { 1563 struct fs_struct *fs = current->fs; 1564 1565 if ((unshare_flags & CLONE_FS) && 1566 (fs && atomic_read(&fs->count) > 1)) { 1567 *new_fsp = __copy_fs_struct(current->fs); 1568 if (!*new_fsp) 1569 return -ENOMEM; 1570 } 1571 1572 return 0; 1573 } 1574 1575 /* 1576 * Unsharing of sighand is not supported yet 1577 */ 1578 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1579 { 1580 struct sighand_struct *sigh = current->sighand; 1581 1582 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1583 return -EINVAL; 1584 else 1585 return 0; 1586 } 1587 1588 /* 1589 * Unshare vm if it is being shared 1590 */ 1591 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1592 { 1593 struct mm_struct *mm = current->mm; 1594 1595 if ((unshare_flags & CLONE_VM) && 1596 (mm && atomic_read(&mm->mm_users) > 1)) { 1597 return -EINVAL; 1598 } 1599 1600 return 0; 1601 } 1602 1603 /* 1604 * Unshare file descriptor table if it is being shared 1605 */ 1606 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1607 { 1608 struct files_struct *fd = current->files; 1609 int error = 0; 1610 1611 if ((unshare_flags & CLONE_FILES) && 1612 (fd && atomic_read(&fd->count) > 1)) { 1613 *new_fdp = dup_fd(fd, &error); 1614 if (!*new_fdp) 1615 return error; 1616 } 1617 1618 return 0; 1619 } 1620 1621 /* 1622 * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not 1623 * supported yet 1624 */ 1625 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp) 1626 { 1627 if (unshare_flags & CLONE_SYSVSEM) 1628 return -EINVAL; 1629 1630 return 0; 1631 } 1632 1633 /* 1634 * unshare allows a process to 'unshare' part of the process 1635 * context which was originally shared using clone. copy_* 1636 * functions used by do_fork() cannot be used here directly 1637 * because they modify an inactive task_struct that is being 1638 * constructed. Here we are modifying the current, active, 1639 * task_struct. 1640 */ 1641 asmlinkage long sys_unshare(unsigned long unshare_flags) 1642 { 1643 int err = 0; 1644 struct fs_struct *fs, *new_fs = NULL; 1645 struct sighand_struct *new_sigh = NULL; 1646 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1647 struct files_struct *fd, *new_fd = NULL; 1648 struct sem_undo_list *new_ulist = NULL; 1649 struct nsproxy *new_nsproxy = NULL; 1650 1651 check_unshare_flags(&unshare_flags); 1652 1653 /* Return -EINVAL for all unsupported flags */ 1654 err = -EINVAL; 1655 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1656 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1657 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER| 1658 CLONE_NEWNET)) 1659 goto bad_unshare_out; 1660 1661 if ((err = unshare_thread(unshare_flags))) 1662 goto bad_unshare_out; 1663 if ((err = unshare_fs(unshare_flags, &new_fs))) 1664 goto bad_unshare_cleanup_thread; 1665 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1666 goto bad_unshare_cleanup_fs; 1667 if ((err = unshare_vm(unshare_flags, &new_mm))) 1668 goto bad_unshare_cleanup_sigh; 1669 if ((err = unshare_fd(unshare_flags, &new_fd))) 1670 goto bad_unshare_cleanup_vm; 1671 if ((err = unshare_semundo(unshare_flags, &new_ulist))) 1672 goto bad_unshare_cleanup_fd; 1673 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1674 new_fs))) 1675 goto bad_unshare_cleanup_semundo; 1676 1677 if (new_fs || new_mm || new_fd || new_ulist || new_nsproxy) { 1678 1679 if (new_nsproxy) { 1680 switch_task_namespaces(current, new_nsproxy); 1681 new_nsproxy = NULL; 1682 } 1683 1684 task_lock(current); 1685 1686 if (new_fs) { 1687 fs = current->fs; 1688 current->fs = new_fs; 1689 new_fs = fs; 1690 } 1691 1692 if (new_mm) { 1693 mm = current->mm; 1694 active_mm = current->active_mm; 1695 current->mm = new_mm; 1696 current->active_mm = new_mm; 1697 activate_mm(active_mm, new_mm); 1698 new_mm = mm; 1699 } 1700 1701 if (new_fd) { 1702 fd = current->files; 1703 current->files = new_fd; 1704 new_fd = fd; 1705 } 1706 1707 task_unlock(current); 1708 } 1709 1710 if (new_nsproxy) 1711 put_nsproxy(new_nsproxy); 1712 1713 bad_unshare_cleanup_semundo: 1714 bad_unshare_cleanup_fd: 1715 if (new_fd) 1716 put_files_struct(new_fd); 1717 1718 bad_unshare_cleanup_vm: 1719 if (new_mm) 1720 mmput(new_mm); 1721 1722 bad_unshare_cleanup_sigh: 1723 if (new_sigh) 1724 if (atomic_dec_and_test(&new_sigh->count)) 1725 kmem_cache_free(sighand_cachep, new_sigh); 1726 1727 bad_unshare_cleanup_fs: 1728 if (new_fs) 1729 put_fs_struct(new_fs); 1730 1731 bad_unshare_cleanup_thread: 1732 bad_unshare_out: 1733 return err; 1734 } 1735