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/smp_lock.h> 18 #include <linux/module.h> 19 #include <linux/vmalloc.h> 20 #include <linux/completion.h> 21 #include <linux/namespace.h> 22 #include <linux/personality.h> 23 #include <linux/mempolicy.h> 24 #include <linux/sem.h> 25 #include <linux/file.h> 26 #include <linux/key.h> 27 #include <linux/binfmts.h> 28 #include <linux/mman.h> 29 #include <linux/fs.h> 30 #include <linux/capability.h> 31 #include <linux/cpu.h> 32 #include <linux/cpuset.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/rcupdate.h> 39 #include <linux/ptrace.h> 40 #include <linux/mount.h> 41 #include <linux/audit.h> 42 #include <linux/profile.h> 43 #include <linux/rmap.h> 44 #include <linux/acct.h> 45 #include <linux/cn_proc.h> 46 #include <linux/delayacct.h> 47 #include <linux/taskstats_kern.h> 48 49 #include <asm/pgtable.h> 50 #include <asm/pgalloc.h> 51 #include <asm/uaccess.h> 52 #include <asm/mmu_context.h> 53 #include <asm/cacheflush.h> 54 #include <asm/tlbflush.h> 55 56 /* 57 * Protected counters by write_lock_irq(&tasklist_lock) 58 */ 59 unsigned long total_forks; /* Handle normal Linux uptimes. */ 60 int nr_threads; /* The idle threads do not count.. */ 61 62 int max_threads; /* tunable limit on nr_threads */ 63 64 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 65 66 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 67 68 int nr_processes(void) 69 { 70 int cpu; 71 int total = 0; 72 73 for_each_online_cpu(cpu) 74 total += per_cpu(process_counts, cpu); 75 76 return total; 77 } 78 79 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 80 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 81 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 82 static kmem_cache_t *task_struct_cachep; 83 #endif 84 85 /* SLAB cache for signal_struct structures (tsk->signal) */ 86 static kmem_cache_t *signal_cachep; 87 88 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 89 kmem_cache_t *sighand_cachep; 90 91 /* SLAB cache for files_struct structures (tsk->files) */ 92 kmem_cache_t *files_cachep; 93 94 /* SLAB cache for fs_struct structures (tsk->fs) */ 95 kmem_cache_t *fs_cachep; 96 97 /* SLAB cache for vm_area_struct structures */ 98 kmem_cache_t *vm_area_cachep; 99 100 /* SLAB cache for mm_struct structures (tsk->mm) */ 101 static kmem_cache_t *mm_cachep; 102 103 void free_task(struct task_struct *tsk) 104 { 105 free_thread_info(tsk->thread_info); 106 rt_mutex_debug_task_free(tsk); 107 free_task_struct(tsk); 108 } 109 EXPORT_SYMBOL(free_task); 110 111 void __put_task_struct(struct task_struct *tsk) 112 { 113 WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE))); 114 WARN_ON(atomic_read(&tsk->usage)); 115 WARN_ON(tsk == current); 116 117 security_task_free(tsk); 118 free_uid(tsk->user); 119 put_group_info(tsk->group_info); 120 121 if (!profile_handoff_task(tsk)) 122 free_task(tsk); 123 } 124 125 void __init fork_init(unsigned long mempages) 126 { 127 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 128 #ifndef ARCH_MIN_TASKALIGN 129 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 130 #endif 131 /* create a slab on which task_structs can be allocated */ 132 task_struct_cachep = 133 kmem_cache_create("task_struct", sizeof(struct task_struct), 134 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL); 135 #endif 136 137 /* 138 * The default maximum number of threads is set to a safe 139 * value: the thread structures can take up at most half 140 * of memory. 141 */ 142 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 143 144 /* 145 * we need to allow at least 20 threads to boot a system 146 */ 147 if(max_threads < 20) 148 max_threads = 20; 149 150 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 151 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 152 init_task.signal->rlim[RLIMIT_SIGPENDING] = 153 init_task.signal->rlim[RLIMIT_NPROC]; 154 } 155 156 static struct task_struct *dup_task_struct(struct task_struct *orig) 157 { 158 struct task_struct *tsk; 159 struct thread_info *ti; 160 161 prepare_to_copy(orig); 162 163 tsk = alloc_task_struct(); 164 if (!tsk) 165 return NULL; 166 167 ti = alloc_thread_info(tsk); 168 if (!ti) { 169 free_task_struct(tsk); 170 return NULL; 171 } 172 173 *tsk = *orig; 174 tsk->thread_info = ti; 175 setup_thread_stack(tsk, orig); 176 177 /* One for us, one for whoever does the "release_task()" (usually parent) */ 178 atomic_set(&tsk->usage,2); 179 atomic_set(&tsk->fs_excl, 0); 180 tsk->btrace_seq = 0; 181 tsk->splice_pipe = NULL; 182 return tsk; 183 } 184 185 #ifdef CONFIG_MMU 186 static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 187 { 188 struct vm_area_struct *mpnt, *tmp, **pprev; 189 struct rb_node **rb_link, *rb_parent; 190 int retval; 191 unsigned long charge; 192 struct mempolicy *pol; 193 194 down_write(&oldmm->mmap_sem); 195 flush_cache_mm(oldmm); 196 /* 197 * Not linked in yet - no deadlock potential: 198 */ 199 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 200 201 mm->locked_vm = 0; 202 mm->mmap = NULL; 203 mm->mmap_cache = NULL; 204 mm->free_area_cache = oldmm->mmap_base; 205 mm->cached_hole_size = ~0UL; 206 mm->map_count = 0; 207 cpus_clear(mm->cpu_vm_mask); 208 mm->mm_rb = RB_ROOT; 209 rb_link = &mm->mm_rb.rb_node; 210 rb_parent = NULL; 211 pprev = &mm->mmap; 212 213 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 214 struct file *file; 215 216 if (mpnt->vm_flags & VM_DONTCOPY) { 217 long pages = vma_pages(mpnt); 218 mm->total_vm -= pages; 219 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 220 -pages); 221 continue; 222 } 223 charge = 0; 224 if (mpnt->vm_flags & VM_ACCOUNT) { 225 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 226 if (security_vm_enough_memory(len)) 227 goto fail_nomem; 228 charge = len; 229 } 230 tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL); 231 if (!tmp) 232 goto fail_nomem; 233 *tmp = *mpnt; 234 pol = mpol_copy(vma_policy(mpnt)); 235 retval = PTR_ERR(pol); 236 if (IS_ERR(pol)) 237 goto fail_nomem_policy; 238 vma_set_policy(tmp, pol); 239 tmp->vm_flags &= ~VM_LOCKED; 240 tmp->vm_mm = mm; 241 tmp->vm_next = NULL; 242 anon_vma_link(tmp); 243 file = tmp->vm_file; 244 if (file) { 245 struct inode *inode = file->f_dentry->d_inode; 246 get_file(file); 247 if (tmp->vm_flags & VM_DENYWRITE) 248 atomic_dec(&inode->i_writecount); 249 250 /* insert tmp into the share list, just after mpnt */ 251 spin_lock(&file->f_mapping->i_mmap_lock); 252 tmp->vm_truncate_count = mpnt->vm_truncate_count; 253 flush_dcache_mmap_lock(file->f_mapping); 254 vma_prio_tree_add(tmp, mpnt); 255 flush_dcache_mmap_unlock(file->f_mapping); 256 spin_unlock(&file->f_mapping->i_mmap_lock); 257 } 258 259 /* 260 * Link in the new vma and copy the page table entries. 261 */ 262 *pprev = tmp; 263 pprev = &tmp->vm_next; 264 265 __vma_link_rb(mm, tmp, rb_link, rb_parent); 266 rb_link = &tmp->vm_rb.rb_right; 267 rb_parent = &tmp->vm_rb; 268 269 mm->map_count++; 270 retval = copy_page_range(mm, oldmm, mpnt); 271 272 if (tmp->vm_ops && tmp->vm_ops->open) 273 tmp->vm_ops->open(tmp); 274 275 if (retval) 276 goto out; 277 } 278 retval = 0; 279 out: 280 up_write(&mm->mmap_sem); 281 flush_tlb_mm(oldmm); 282 up_write(&oldmm->mmap_sem); 283 return retval; 284 fail_nomem_policy: 285 kmem_cache_free(vm_area_cachep, tmp); 286 fail_nomem: 287 retval = -ENOMEM; 288 vm_unacct_memory(charge); 289 goto out; 290 } 291 292 static inline int mm_alloc_pgd(struct mm_struct * mm) 293 { 294 mm->pgd = pgd_alloc(mm); 295 if (unlikely(!mm->pgd)) 296 return -ENOMEM; 297 return 0; 298 } 299 300 static inline void mm_free_pgd(struct mm_struct * mm) 301 { 302 pgd_free(mm->pgd); 303 } 304 #else 305 #define dup_mmap(mm, oldmm) (0) 306 #define mm_alloc_pgd(mm) (0) 307 #define mm_free_pgd(mm) 308 #endif /* CONFIG_MMU */ 309 310 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 311 312 #define allocate_mm() (kmem_cache_alloc(mm_cachep, SLAB_KERNEL)) 313 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 314 315 #include <linux/init_task.h> 316 317 static struct mm_struct * mm_init(struct mm_struct * mm) 318 { 319 atomic_set(&mm->mm_users, 1); 320 atomic_set(&mm->mm_count, 1); 321 init_rwsem(&mm->mmap_sem); 322 INIT_LIST_HEAD(&mm->mmlist); 323 mm->core_waiters = 0; 324 mm->nr_ptes = 0; 325 set_mm_counter(mm, file_rss, 0); 326 set_mm_counter(mm, anon_rss, 0); 327 spin_lock_init(&mm->page_table_lock); 328 rwlock_init(&mm->ioctx_list_lock); 329 mm->ioctx_list = NULL; 330 mm->free_area_cache = TASK_UNMAPPED_BASE; 331 mm->cached_hole_size = ~0UL; 332 333 if (likely(!mm_alloc_pgd(mm))) { 334 mm->def_flags = 0; 335 return mm; 336 } 337 free_mm(mm); 338 return NULL; 339 } 340 341 /* 342 * Allocate and initialize an mm_struct. 343 */ 344 struct mm_struct * mm_alloc(void) 345 { 346 struct mm_struct * mm; 347 348 mm = allocate_mm(); 349 if (mm) { 350 memset(mm, 0, sizeof(*mm)); 351 mm = mm_init(mm); 352 } 353 return mm; 354 } 355 356 /* 357 * Called when the last reference to the mm 358 * is dropped: either by a lazy thread or by 359 * mmput. Free the page directory and the mm. 360 */ 361 void fastcall __mmdrop(struct mm_struct *mm) 362 { 363 BUG_ON(mm == &init_mm); 364 mm_free_pgd(mm); 365 destroy_context(mm); 366 free_mm(mm); 367 } 368 369 /* 370 * Decrement the use count and release all resources for an mm. 371 */ 372 void mmput(struct mm_struct *mm) 373 { 374 might_sleep(); 375 376 if (atomic_dec_and_test(&mm->mm_users)) { 377 exit_aio(mm); 378 exit_mmap(mm); 379 if (!list_empty(&mm->mmlist)) { 380 spin_lock(&mmlist_lock); 381 list_del(&mm->mmlist); 382 spin_unlock(&mmlist_lock); 383 } 384 put_swap_token(mm); 385 mmdrop(mm); 386 } 387 } 388 EXPORT_SYMBOL_GPL(mmput); 389 390 /** 391 * get_task_mm - acquire a reference to the task's mm 392 * 393 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning 394 * this kernel workthread has transiently adopted a user mm with use_mm, 395 * to do its AIO) is not set and if so returns a reference to it, after 396 * bumping up the use count. User must release the mm via mmput() 397 * after use. Typically used by /proc and ptrace. 398 */ 399 struct mm_struct *get_task_mm(struct task_struct *task) 400 { 401 struct mm_struct *mm; 402 403 task_lock(task); 404 mm = task->mm; 405 if (mm) { 406 if (task->flags & PF_BORROWED_MM) 407 mm = NULL; 408 else 409 atomic_inc(&mm->mm_users); 410 } 411 task_unlock(task); 412 return mm; 413 } 414 EXPORT_SYMBOL_GPL(get_task_mm); 415 416 /* Please note the differences between mmput and mm_release. 417 * mmput is called whenever we stop holding onto a mm_struct, 418 * error success whatever. 419 * 420 * mm_release is called after a mm_struct has been removed 421 * from the current process. 422 * 423 * This difference is important for error handling, when we 424 * only half set up a mm_struct for a new process and need to restore 425 * the old one. Because we mmput the new mm_struct before 426 * restoring the old one. . . 427 * Eric Biederman 10 January 1998 428 */ 429 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 430 { 431 struct completion *vfork_done = tsk->vfork_done; 432 433 /* Get rid of any cached register state */ 434 deactivate_mm(tsk, mm); 435 436 /* notify parent sleeping on vfork() */ 437 if (vfork_done) { 438 tsk->vfork_done = NULL; 439 complete(vfork_done); 440 } 441 if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) { 442 u32 __user * tidptr = tsk->clear_child_tid; 443 tsk->clear_child_tid = NULL; 444 445 /* 446 * We don't check the error code - if userspace has 447 * not set up a proper pointer then tough luck. 448 */ 449 put_user(0, tidptr); 450 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 451 } 452 } 453 454 /* 455 * Allocate a new mm structure and copy contents from the 456 * mm structure of the passed in task structure. 457 */ 458 static struct mm_struct *dup_mm(struct task_struct *tsk) 459 { 460 struct mm_struct *mm, *oldmm = current->mm; 461 int err; 462 463 if (!oldmm) 464 return NULL; 465 466 mm = allocate_mm(); 467 if (!mm) 468 goto fail_nomem; 469 470 memcpy(mm, oldmm, sizeof(*mm)); 471 472 if (!mm_init(mm)) 473 goto fail_nomem; 474 475 if (init_new_context(tsk, mm)) 476 goto fail_nocontext; 477 478 err = dup_mmap(mm, oldmm); 479 if (err) 480 goto free_pt; 481 482 mm->hiwater_rss = get_mm_rss(mm); 483 mm->hiwater_vm = mm->total_vm; 484 485 return mm; 486 487 free_pt: 488 mmput(mm); 489 490 fail_nomem: 491 return NULL; 492 493 fail_nocontext: 494 /* 495 * If init_new_context() failed, we cannot use mmput() to free the mm 496 * because it calls destroy_context() 497 */ 498 mm_free_pgd(mm); 499 free_mm(mm); 500 return NULL; 501 } 502 503 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 504 { 505 struct mm_struct * mm, *oldmm; 506 int retval; 507 508 tsk->min_flt = tsk->maj_flt = 0; 509 tsk->nvcsw = tsk->nivcsw = 0; 510 511 tsk->mm = NULL; 512 tsk->active_mm = NULL; 513 514 /* 515 * Are we cloning a kernel thread? 516 * 517 * We need to steal a active VM for that.. 518 */ 519 oldmm = current->mm; 520 if (!oldmm) 521 return 0; 522 523 if (clone_flags & CLONE_VM) { 524 atomic_inc(&oldmm->mm_users); 525 mm = oldmm; 526 goto good_mm; 527 } 528 529 retval = -ENOMEM; 530 mm = dup_mm(tsk); 531 if (!mm) 532 goto fail_nomem; 533 534 good_mm: 535 tsk->mm = mm; 536 tsk->active_mm = mm; 537 return 0; 538 539 fail_nomem: 540 return retval; 541 } 542 543 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old) 544 { 545 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 546 /* We don't need to lock fs - think why ;-) */ 547 if (fs) { 548 atomic_set(&fs->count, 1); 549 rwlock_init(&fs->lock); 550 fs->umask = old->umask; 551 read_lock(&old->lock); 552 fs->rootmnt = mntget(old->rootmnt); 553 fs->root = dget(old->root); 554 fs->pwdmnt = mntget(old->pwdmnt); 555 fs->pwd = dget(old->pwd); 556 if (old->altroot) { 557 fs->altrootmnt = mntget(old->altrootmnt); 558 fs->altroot = dget(old->altroot); 559 } else { 560 fs->altrootmnt = NULL; 561 fs->altroot = NULL; 562 } 563 read_unlock(&old->lock); 564 } 565 return fs; 566 } 567 568 struct fs_struct *copy_fs_struct(struct fs_struct *old) 569 { 570 return __copy_fs_struct(old); 571 } 572 573 EXPORT_SYMBOL_GPL(copy_fs_struct); 574 575 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk) 576 { 577 if (clone_flags & CLONE_FS) { 578 atomic_inc(¤t->fs->count); 579 return 0; 580 } 581 tsk->fs = __copy_fs_struct(current->fs); 582 if (!tsk->fs) 583 return -ENOMEM; 584 return 0; 585 } 586 587 static int count_open_files(struct fdtable *fdt) 588 { 589 int size = fdt->max_fdset; 590 int i; 591 592 /* Find the last open fd */ 593 for (i = size/(8*sizeof(long)); i > 0; ) { 594 if (fdt->open_fds->fds_bits[--i]) 595 break; 596 } 597 i = (i+1) * 8 * sizeof(long); 598 return i; 599 } 600 601 static struct files_struct *alloc_files(void) 602 { 603 struct files_struct *newf; 604 struct fdtable *fdt; 605 606 newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL); 607 if (!newf) 608 goto out; 609 610 atomic_set(&newf->count, 1); 611 612 spin_lock_init(&newf->file_lock); 613 newf->next_fd = 0; 614 fdt = &newf->fdtab; 615 fdt->max_fds = NR_OPEN_DEFAULT; 616 fdt->max_fdset = EMBEDDED_FD_SET_SIZE; 617 fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init; 618 fdt->open_fds = (fd_set *)&newf->open_fds_init; 619 fdt->fd = &newf->fd_array[0]; 620 INIT_RCU_HEAD(&fdt->rcu); 621 fdt->free_files = NULL; 622 fdt->next = NULL; 623 rcu_assign_pointer(newf->fdt, fdt); 624 out: 625 return newf; 626 } 627 628 /* 629 * Allocate a new files structure and copy contents from the 630 * passed in files structure. 631 * errorp will be valid only when the returned files_struct is NULL. 632 */ 633 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) 634 { 635 struct files_struct *newf; 636 struct file **old_fds, **new_fds; 637 int open_files, size, i, expand; 638 struct fdtable *old_fdt, *new_fdt; 639 640 *errorp = -ENOMEM; 641 newf = alloc_files(); 642 if (!newf) 643 goto out; 644 645 spin_lock(&oldf->file_lock); 646 old_fdt = files_fdtable(oldf); 647 new_fdt = files_fdtable(newf); 648 size = old_fdt->max_fdset; 649 open_files = count_open_files(old_fdt); 650 expand = 0; 651 652 /* 653 * Check whether we need to allocate a larger fd array or fd set. 654 * Note: we're not a clone task, so the open count won't change. 655 */ 656 if (open_files > new_fdt->max_fdset) { 657 new_fdt->max_fdset = 0; 658 expand = 1; 659 } 660 if (open_files > new_fdt->max_fds) { 661 new_fdt->max_fds = 0; 662 expand = 1; 663 } 664 665 /* if the old fdset gets grown now, we'll only copy up to "size" fds */ 666 if (expand) { 667 spin_unlock(&oldf->file_lock); 668 spin_lock(&newf->file_lock); 669 *errorp = expand_files(newf, open_files-1); 670 spin_unlock(&newf->file_lock); 671 if (*errorp < 0) 672 goto out_release; 673 new_fdt = files_fdtable(newf); 674 /* 675 * Reacquire the oldf lock and a pointer to its fd table 676 * who knows it may have a new bigger fd table. We need 677 * the latest pointer. 678 */ 679 spin_lock(&oldf->file_lock); 680 old_fdt = files_fdtable(oldf); 681 } 682 683 old_fds = old_fdt->fd; 684 new_fds = new_fdt->fd; 685 686 memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8); 687 memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8); 688 689 for (i = open_files; i != 0; i--) { 690 struct file *f = *old_fds++; 691 if (f) { 692 get_file(f); 693 } else { 694 /* 695 * The fd may be claimed in the fd bitmap but not yet 696 * instantiated in the files array if a sibling thread 697 * is partway through open(). So make sure that this 698 * fd is available to the new process. 699 */ 700 FD_CLR(open_files - i, new_fdt->open_fds); 701 } 702 rcu_assign_pointer(*new_fds++, f); 703 } 704 spin_unlock(&oldf->file_lock); 705 706 /* compute the remainder to be cleared */ 707 size = (new_fdt->max_fds - open_files) * sizeof(struct file *); 708 709 /* This is long word aligned thus could use a optimized version */ 710 memset(new_fds, 0, size); 711 712 if (new_fdt->max_fdset > open_files) { 713 int left = (new_fdt->max_fdset-open_files)/8; 714 int start = open_files / (8 * sizeof(unsigned long)); 715 716 memset(&new_fdt->open_fds->fds_bits[start], 0, left); 717 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left); 718 } 719 720 out: 721 return newf; 722 723 out_release: 724 free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset); 725 free_fdset (new_fdt->open_fds, new_fdt->max_fdset); 726 free_fd_array(new_fdt->fd, new_fdt->max_fds); 727 kmem_cache_free(files_cachep, newf); 728 return NULL; 729 } 730 731 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 732 { 733 struct files_struct *oldf, *newf; 734 int error = 0; 735 736 /* 737 * A background process may not have any files ... 738 */ 739 oldf = current->files; 740 if (!oldf) 741 goto out; 742 743 if (clone_flags & CLONE_FILES) { 744 atomic_inc(&oldf->count); 745 goto out; 746 } 747 748 /* 749 * Note: we may be using current for both targets (See exec.c) 750 * This works because we cache current->files (old) as oldf. Don't 751 * break this. 752 */ 753 tsk->files = NULL; 754 newf = dup_fd(oldf, &error); 755 if (!newf) 756 goto out; 757 758 tsk->files = newf; 759 error = 0; 760 out: 761 return error; 762 } 763 764 /* 765 * Helper to unshare the files of the current task. 766 * We don't want to expose copy_files internals to 767 * the exec layer of the kernel. 768 */ 769 770 int unshare_files(void) 771 { 772 struct files_struct *files = current->files; 773 int rc; 774 775 BUG_ON(!files); 776 777 /* This can race but the race causes us to copy when we don't 778 need to and drop the copy */ 779 if(atomic_read(&files->count) == 1) 780 { 781 atomic_inc(&files->count); 782 return 0; 783 } 784 rc = copy_files(0, current); 785 if(rc) 786 current->files = files; 787 return rc; 788 } 789 790 EXPORT_SYMBOL(unshare_files); 791 792 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk) 793 { 794 struct sighand_struct *sig; 795 796 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 797 atomic_inc(¤t->sighand->count); 798 return 0; 799 } 800 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 801 rcu_assign_pointer(tsk->sighand, sig); 802 if (!sig) 803 return -ENOMEM; 804 atomic_set(&sig->count, 1); 805 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 806 return 0; 807 } 808 809 void __cleanup_sighand(struct sighand_struct *sighand) 810 { 811 if (atomic_dec_and_test(&sighand->count)) 812 kmem_cache_free(sighand_cachep, sighand); 813 } 814 815 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk) 816 { 817 struct signal_struct *sig; 818 int ret; 819 820 if (clone_flags & CLONE_THREAD) { 821 atomic_inc(¤t->signal->count); 822 atomic_inc(¤t->signal->live); 823 taskstats_tgid_alloc(current->signal); 824 return 0; 825 } 826 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 827 tsk->signal = sig; 828 if (!sig) 829 return -ENOMEM; 830 831 ret = copy_thread_group_keys(tsk); 832 if (ret < 0) { 833 kmem_cache_free(signal_cachep, sig); 834 return ret; 835 } 836 837 atomic_set(&sig->count, 1); 838 atomic_set(&sig->live, 1); 839 init_waitqueue_head(&sig->wait_chldexit); 840 sig->flags = 0; 841 sig->group_exit_code = 0; 842 sig->group_exit_task = NULL; 843 sig->group_stop_count = 0; 844 sig->curr_target = NULL; 845 init_sigpending(&sig->shared_pending); 846 INIT_LIST_HEAD(&sig->posix_timers); 847 848 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL); 849 sig->it_real_incr.tv64 = 0; 850 sig->real_timer.function = it_real_fn; 851 sig->tsk = tsk; 852 853 sig->it_virt_expires = cputime_zero; 854 sig->it_virt_incr = cputime_zero; 855 sig->it_prof_expires = cputime_zero; 856 sig->it_prof_incr = cputime_zero; 857 858 sig->leader = 0; /* session leadership doesn't inherit */ 859 sig->tty_old_pgrp = 0; 860 861 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 862 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 863 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 864 sig->sched_time = 0; 865 INIT_LIST_HEAD(&sig->cpu_timers[0]); 866 INIT_LIST_HEAD(&sig->cpu_timers[1]); 867 INIT_LIST_HEAD(&sig->cpu_timers[2]); 868 taskstats_tgid_init(sig); 869 870 task_lock(current->group_leader); 871 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 872 task_unlock(current->group_leader); 873 874 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 875 /* 876 * New sole thread in the process gets an expiry time 877 * of the whole CPU time limit. 878 */ 879 tsk->it_prof_expires = 880 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 881 } 882 acct_init_pacct(&sig->pacct); 883 884 return 0; 885 } 886 887 void __cleanup_signal(struct signal_struct *sig) 888 { 889 exit_thread_group_keys(sig); 890 taskstats_tgid_free(sig); 891 kmem_cache_free(signal_cachep, sig); 892 } 893 894 static inline void cleanup_signal(struct task_struct *tsk) 895 { 896 struct signal_struct *sig = tsk->signal; 897 898 atomic_dec(&sig->live); 899 900 if (atomic_dec_and_test(&sig->count)) 901 __cleanup_signal(sig); 902 } 903 904 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p) 905 { 906 unsigned long new_flags = p->flags; 907 908 new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE); 909 new_flags |= PF_FORKNOEXEC; 910 if (!(clone_flags & CLONE_PTRACE)) 911 p->ptrace = 0; 912 p->flags = new_flags; 913 } 914 915 asmlinkage long sys_set_tid_address(int __user *tidptr) 916 { 917 current->clear_child_tid = tidptr; 918 919 return current->pid; 920 } 921 922 static inline void rt_mutex_init_task(struct task_struct *p) 923 { 924 #ifdef CONFIG_RT_MUTEXES 925 spin_lock_init(&p->pi_lock); 926 plist_head_init(&p->pi_waiters, &p->pi_lock); 927 p->pi_blocked_on = NULL; 928 #endif 929 } 930 931 /* 932 * This creates a new process as a copy of the old one, 933 * but does not actually start it yet. 934 * 935 * It copies the registers, and all the appropriate 936 * parts of the process environment (as per the clone 937 * flags). The actual kick-off is left to the caller. 938 */ 939 static struct task_struct *copy_process(unsigned long clone_flags, 940 unsigned long stack_start, 941 struct pt_regs *regs, 942 unsigned long stack_size, 943 int __user *parent_tidptr, 944 int __user *child_tidptr, 945 int pid) 946 { 947 int retval; 948 struct task_struct *p = NULL; 949 950 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 951 return ERR_PTR(-EINVAL); 952 953 /* 954 * Thread groups must share signals as well, and detached threads 955 * can only be started up within the thread group. 956 */ 957 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 958 return ERR_PTR(-EINVAL); 959 960 /* 961 * Shared signal handlers imply shared VM. By way of the above, 962 * thread groups also imply shared VM. Blocking this case allows 963 * for various simplifications in other code. 964 */ 965 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 966 return ERR_PTR(-EINVAL); 967 968 retval = security_task_create(clone_flags); 969 if (retval) 970 goto fork_out; 971 972 retval = -ENOMEM; 973 p = dup_task_struct(current); 974 if (!p) 975 goto fork_out; 976 977 #ifdef CONFIG_TRACE_IRQFLAGS 978 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 979 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 980 #endif 981 retval = -EAGAIN; 982 if (atomic_read(&p->user->processes) >= 983 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 984 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 985 p->user != &root_user) 986 goto bad_fork_free; 987 } 988 989 atomic_inc(&p->user->__count); 990 atomic_inc(&p->user->processes); 991 get_group_info(p->group_info); 992 993 /* 994 * If multiple threads are within copy_process(), then this check 995 * triggers too late. This doesn't hurt, the check is only there 996 * to stop root fork bombs. 997 */ 998 if (nr_threads >= max_threads) 999 goto bad_fork_cleanup_count; 1000 1001 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1002 goto bad_fork_cleanup_count; 1003 1004 if (p->binfmt && !try_module_get(p->binfmt->module)) 1005 goto bad_fork_cleanup_put_domain; 1006 1007 p->did_exec = 0; 1008 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1009 copy_flags(clone_flags, p); 1010 p->pid = pid; 1011 retval = -EFAULT; 1012 if (clone_flags & CLONE_PARENT_SETTID) 1013 if (put_user(p->pid, parent_tidptr)) 1014 goto bad_fork_cleanup; 1015 1016 INIT_LIST_HEAD(&p->children); 1017 INIT_LIST_HEAD(&p->sibling); 1018 p->vfork_done = NULL; 1019 spin_lock_init(&p->alloc_lock); 1020 1021 clear_tsk_thread_flag(p, TIF_SIGPENDING); 1022 init_sigpending(&p->pending); 1023 1024 p->utime = cputime_zero; 1025 p->stime = cputime_zero; 1026 p->sched_time = 0; 1027 p->rchar = 0; /* I/O counter: bytes read */ 1028 p->wchar = 0; /* I/O counter: bytes written */ 1029 p->syscr = 0; /* I/O counter: read syscalls */ 1030 p->syscw = 0; /* I/O counter: write syscalls */ 1031 acct_clear_integrals(p); 1032 1033 p->it_virt_expires = cputime_zero; 1034 p->it_prof_expires = cputime_zero; 1035 p->it_sched_expires = 0; 1036 INIT_LIST_HEAD(&p->cpu_timers[0]); 1037 INIT_LIST_HEAD(&p->cpu_timers[1]); 1038 INIT_LIST_HEAD(&p->cpu_timers[2]); 1039 1040 p->lock_depth = -1; /* -1 = no lock */ 1041 do_posix_clock_monotonic_gettime(&p->start_time); 1042 p->security = NULL; 1043 p->io_context = NULL; 1044 p->io_wait = NULL; 1045 p->audit_context = NULL; 1046 cpuset_fork(p); 1047 #ifdef CONFIG_NUMA 1048 p->mempolicy = mpol_copy(p->mempolicy); 1049 if (IS_ERR(p->mempolicy)) { 1050 retval = PTR_ERR(p->mempolicy); 1051 p->mempolicy = NULL; 1052 goto bad_fork_cleanup_cpuset; 1053 } 1054 mpol_fix_fork_child_flag(p); 1055 #endif 1056 #ifdef CONFIG_TRACE_IRQFLAGS 1057 p->irq_events = 0; 1058 p->hardirqs_enabled = 0; 1059 p->hardirq_enable_ip = 0; 1060 p->hardirq_enable_event = 0; 1061 p->hardirq_disable_ip = _THIS_IP_; 1062 p->hardirq_disable_event = 0; 1063 p->softirqs_enabled = 1; 1064 p->softirq_enable_ip = _THIS_IP_; 1065 p->softirq_enable_event = 0; 1066 p->softirq_disable_ip = 0; 1067 p->softirq_disable_event = 0; 1068 p->hardirq_context = 0; 1069 p->softirq_context = 0; 1070 #endif 1071 #ifdef CONFIG_LOCKDEP 1072 p->lockdep_depth = 0; /* no locks held yet */ 1073 p->curr_chain_key = 0; 1074 p->lockdep_recursion = 0; 1075 #endif 1076 1077 rt_mutex_init_task(p); 1078 1079 #ifdef CONFIG_DEBUG_MUTEXES 1080 p->blocked_on = NULL; /* not blocked yet */ 1081 #endif 1082 1083 p->tgid = p->pid; 1084 if (clone_flags & CLONE_THREAD) 1085 p->tgid = current->tgid; 1086 1087 if ((retval = security_task_alloc(p))) 1088 goto bad_fork_cleanup_policy; 1089 if ((retval = audit_alloc(p))) 1090 goto bad_fork_cleanup_security; 1091 /* copy all the process information */ 1092 if ((retval = copy_semundo(clone_flags, p))) 1093 goto bad_fork_cleanup_audit; 1094 if ((retval = copy_files(clone_flags, p))) 1095 goto bad_fork_cleanup_semundo; 1096 if ((retval = copy_fs(clone_flags, p))) 1097 goto bad_fork_cleanup_files; 1098 if ((retval = copy_sighand(clone_flags, p))) 1099 goto bad_fork_cleanup_fs; 1100 if ((retval = copy_signal(clone_flags, p))) 1101 goto bad_fork_cleanup_sighand; 1102 if ((retval = copy_mm(clone_flags, p))) 1103 goto bad_fork_cleanup_signal; 1104 if ((retval = copy_keys(clone_flags, p))) 1105 goto bad_fork_cleanup_mm; 1106 if ((retval = copy_namespace(clone_flags, p))) 1107 goto bad_fork_cleanup_keys; 1108 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1109 if (retval) 1110 goto bad_fork_cleanup_namespace; 1111 1112 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1113 /* 1114 * Clear TID on mm_release()? 1115 */ 1116 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1117 p->robust_list = NULL; 1118 #ifdef CONFIG_COMPAT 1119 p->compat_robust_list = NULL; 1120 #endif 1121 INIT_LIST_HEAD(&p->pi_state_list); 1122 p->pi_state_cache = NULL; 1123 1124 /* 1125 * sigaltstack should be cleared when sharing the same VM 1126 */ 1127 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1128 p->sas_ss_sp = p->sas_ss_size = 0; 1129 1130 /* 1131 * Syscall tracing should be turned off in the child regardless 1132 * of CLONE_PTRACE. 1133 */ 1134 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1135 #ifdef TIF_SYSCALL_EMU 1136 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1137 #endif 1138 1139 /* Our parent execution domain becomes current domain 1140 These must match for thread signalling to apply */ 1141 1142 p->parent_exec_id = p->self_exec_id; 1143 1144 /* ok, now we should be set up.. */ 1145 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1146 p->pdeath_signal = 0; 1147 p->exit_state = 0; 1148 1149 /* 1150 * Ok, make it visible to the rest of the system. 1151 * We dont wake it up yet. 1152 */ 1153 p->group_leader = p; 1154 INIT_LIST_HEAD(&p->thread_group); 1155 INIT_LIST_HEAD(&p->ptrace_children); 1156 INIT_LIST_HEAD(&p->ptrace_list); 1157 1158 /* Perform scheduler related setup. Assign this task to a CPU. */ 1159 sched_fork(p, clone_flags); 1160 1161 /* Need tasklist lock for parent etc handling! */ 1162 write_lock_irq(&tasklist_lock); 1163 1164 /* 1165 * The task hasn't been attached yet, so its cpus_allowed mask will 1166 * not be changed, nor will its assigned CPU. 1167 * 1168 * The cpus_allowed mask of the parent may have changed after it was 1169 * copied first time - so re-copy it here, then check the child's CPU 1170 * to ensure it is on a valid CPU (and if not, just force it back to 1171 * parent's CPU). This avoids alot of nasty races. 1172 */ 1173 p->cpus_allowed = current->cpus_allowed; 1174 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1175 !cpu_online(task_cpu(p)))) 1176 set_task_cpu(p, smp_processor_id()); 1177 1178 /* CLONE_PARENT re-uses the old parent */ 1179 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1180 p->real_parent = current->real_parent; 1181 else 1182 p->real_parent = current; 1183 p->parent = p->real_parent; 1184 1185 spin_lock(¤t->sighand->siglock); 1186 1187 /* 1188 * Process group and session signals need to be delivered to just the 1189 * parent before the fork or both the parent and the child after the 1190 * fork. Restart if a signal comes in before we add the new process to 1191 * it's process group. 1192 * A fatal signal pending means that current will exit, so the new 1193 * thread can't slip out of an OOM kill (or normal SIGKILL). 1194 */ 1195 recalc_sigpending(); 1196 if (signal_pending(current)) { 1197 spin_unlock(¤t->sighand->siglock); 1198 write_unlock_irq(&tasklist_lock); 1199 retval = -ERESTARTNOINTR; 1200 goto bad_fork_cleanup_namespace; 1201 } 1202 1203 if (clone_flags & CLONE_THREAD) { 1204 p->group_leader = current->group_leader; 1205 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1206 1207 if (!cputime_eq(current->signal->it_virt_expires, 1208 cputime_zero) || 1209 !cputime_eq(current->signal->it_prof_expires, 1210 cputime_zero) || 1211 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1212 !list_empty(¤t->signal->cpu_timers[0]) || 1213 !list_empty(¤t->signal->cpu_timers[1]) || 1214 !list_empty(¤t->signal->cpu_timers[2])) { 1215 /* 1216 * Have child wake up on its first tick to check 1217 * for process CPU timers. 1218 */ 1219 p->it_prof_expires = jiffies_to_cputime(1); 1220 } 1221 } 1222 1223 /* 1224 * inherit ioprio 1225 */ 1226 p->ioprio = current->ioprio; 1227 1228 if (likely(p->pid)) { 1229 add_parent(p); 1230 if (unlikely(p->ptrace & PT_PTRACED)) 1231 __ptrace_link(p, current->parent); 1232 1233 if (thread_group_leader(p)) { 1234 p->signal->tty = current->signal->tty; 1235 p->signal->pgrp = process_group(current); 1236 p->signal->session = current->signal->session; 1237 attach_pid(p, PIDTYPE_PGID, process_group(p)); 1238 attach_pid(p, PIDTYPE_SID, p->signal->session); 1239 1240 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1241 __get_cpu_var(process_counts)++; 1242 } 1243 attach_pid(p, PIDTYPE_PID, p->pid); 1244 nr_threads++; 1245 } 1246 1247 total_forks++; 1248 spin_unlock(¤t->sighand->siglock); 1249 write_unlock_irq(&tasklist_lock); 1250 proc_fork_connector(p); 1251 return p; 1252 1253 bad_fork_cleanup_namespace: 1254 exit_namespace(p); 1255 bad_fork_cleanup_keys: 1256 exit_keys(p); 1257 bad_fork_cleanup_mm: 1258 if (p->mm) 1259 mmput(p->mm); 1260 bad_fork_cleanup_signal: 1261 cleanup_signal(p); 1262 bad_fork_cleanup_sighand: 1263 __cleanup_sighand(p->sighand); 1264 bad_fork_cleanup_fs: 1265 exit_fs(p); /* blocking */ 1266 bad_fork_cleanup_files: 1267 exit_files(p); /* blocking */ 1268 bad_fork_cleanup_semundo: 1269 exit_sem(p); 1270 bad_fork_cleanup_audit: 1271 audit_free(p); 1272 bad_fork_cleanup_security: 1273 security_task_free(p); 1274 bad_fork_cleanup_policy: 1275 #ifdef CONFIG_NUMA 1276 mpol_free(p->mempolicy); 1277 bad_fork_cleanup_cpuset: 1278 #endif 1279 cpuset_exit(p); 1280 bad_fork_cleanup: 1281 if (p->binfmt) 1282 module_put(p->binfmt->module); 1283 bad_fork_cleanup_put_domain: 1284 module_put(task_thread_info(p)->exec_domain->module); 1285 bad_fork_cleanup_count: 1286 put_group_info(p->group_info); 1287 atomic_dec(&p->user->processes); 1288 free_uid(p->user); 1289 bad_fork_free: 1290 free_task(p); 1291 fork_out: 1292 return ERR_PTR(retval); 1293 } 1294 1295 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1296 { 1297 memset(regs, 0, sizeof(struct pt_regs)); 1298 return regs; 1299 } 1300 1301 struct task_struct * __devinit fork_idle(int cpu) 1302 { 1303 struct task_struct *task; 1304 struct pt_regs regs; 1305 1306 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, NULL, 0); 1307 if (!task) 1308 return ERR_PTR(-ENOMEM); 1309 init_idle(task, cpu); 1310 1311 return task; 1312 } 1313 1314 static inline int fork_traceflag (unsigned clone_flags) 1315 { 1316 if (clone_flags & CLONE_UNTRACED) 1317 return 0; 1318 else if (clone_flags & CLONE_VFORK) { 1319 if (current->ptrace & PT_TRACE_VFORK) 1320 return PTRACE_EVENT_VFORK; 1321 } else if ((clone_flags & CSIGNAL) != SIGCHLD) { 1322 if (current->ptrace & PT_TRACE_CLONE) 1323 return PTRACE_EVENT_CLONE; 1324 } else if (current->ptrace & PT_TRACE_FORK) 1325 return PTRACE_EVENT_FORK; 1326 1327 return 0; 1328 } 1329 1330 /* 1331 * Ok, this is the main fork-routine. 1332 * 1333 * It copies the process, and if successful kick-starts 1334 * it and waits for it to finish using the VM if required. 1335 */ 1336 long do_fork(unsigned long clone_flags, 1337 unsigned long stack_start, 1338 struct pt_regs *regs, 1339 unsigned long stack_size, 1340 int __user *parent_tidptr, 1341 int __user *child_tidptr) 1342 { 1343 struct task_struct *p; 1344 int trace = 0; 1345 struct pid *pid = alloc_pid(); 1346 long nr; 1347 1348 if (!pid) 1349 return -EAGAIN; 1350 nr = pid->nr; 1351 if (unlikely(current->ptrace)) { 1352 trace = fork_traceflag (clone_flags); 1353 if (trace) 1354 clone_flags |= CLONE_PTRACE; 1355 } 1356 1357 p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, nr); 1358 /* 1359 * Do this prior waking up the new thread - the thread pointer 1360 * might get invalid after that point, if the thread exits quickly. 1361 */ 1362 if (!IS_ERR(p)) { 1363 struct completion vfork; 1364 1365 if (clone_flags & CLONE_VFORK) { 1366 p->vfork_done = &vfork; 1367 init_completion(&vfork); 1368 } 1369 1370 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) { 1371 /* 1372 * We'll start up with an immediate SIGSTOP. 1373 */ 1374 sigaddset(&p->pending.signal, SIGSTOP); 1375 set_tsk_thread_flag(p, TIF_SIGPENDING); 1376 } 1377 1378 if (!(clone_flags & CLONE_STOPPED)) 1379 wake_up_new_task(p, clone_flags); 1380 else 1381 p->state = TASK_STOPPED; 1382 1383 if (unlikely (trace)) { 1384 current->ptrace_message = nr; 1385 ptrace_notify ((trace << 8) | SIGTRAP); 1386 } 1387 1388 if (clone_flags & CLONE_VFORK) { 1389 wait_for_completion(&vfork); 1390 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) 1391 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); 1392 } 1393 } else { 1394 free_pid(pid); 1395 nr = PTR_ERR(p); 1396 } 1397 return nr; 1398 } 1399 1400 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1401 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1402 #endif 1403 1404 static void sighand_ctor(void *data, kmem_cache_t *cachep, unsigned long flags) 1405 { 1406 struct sighand_struct *sighand = data; 1407 1408 if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) == 1409 SLAB_CTOR_CONSTRUCTOR) 1410 spin_lock_init(&sighand->siglock); 1411 } 1412 1413 void __init proc_caches_init(void) 1414 { 1415 sighand_cachep = kmem_cache_create("sighand_cache", 1416 sizeof(struct sighand_struct), 0, 1417 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU, 1418 sighand_ctor, NULL); 1419 signal_cachep = kmem_cache_create("signal_cache", 1420 sizeof(struct signal_struct), 0, 1421 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1422 files_cachep = kmem_cache_create("files_cache", 1423 sizeof(struct files_struct), 0, 1424 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1425 fs_cachep = kmem_cache_create("fs_cache", 1426 sizeof(struct fs_struct), 0, 1427 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1428 vm_area_cachep = kmem_cache_create("vm_area_struct", 1429 sizeof(struct vm_area_struct), 0, 1430 SLAB_PANIC, NULL, NULL); 1431 mm_cachep = kmem_cache_create("mm_struct", 1432 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1433 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1434 } 1435 1436 1437 /* 1438 * Check constraints on flags passed to the unshare system call and 1439 * force unsharing of additional process context as appropriate. 1440 */ 1441 static inline void check_unshare_flags(unsigned long *flags_ptr) 1442 { 1443 /* 1444 * If unsharing a thread from a thread group, must also 1445 * unshare vm. 1446 */ 1447 if (*flags_ptr & CLONE_THREAD) 1448 *flags_ptr |= CLONE_VM; 1449 1450 /* 1451 * If unsharing vm, must also unshare signal handlers. 1452 */ 1453 if (*flags_ptr & CLONE_VM) 1454 *flags_ptr |= CLONE_SIGHAND; 1455 1456 /* 1457 * If unsharing signal handlers and the task was created 1458 * using CLONE_THREAD, then must unshare the thread 1459 */ 1460 if ((*flags_ptr & CLONE_SIGHAND) && 1461 (atomic_read(¤t->signal->count) > 1)) 1462 *flags_ptr |= CLONE_THREAD; 1463 1464 /* 1465 * If unsharing namespace, must also unshare filesystem information. 1466 */ 1467 if (*flags_ptr & CLONE_NEWNS) 1468 *flags_ptr |= CLONE_FS; 1469 } 1470 1471 /* 1472 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1473 */ 1474 static int unshare_thread(unsigned long unshare_flags) 1475 { 1476 if (unshare_flags & CLONE_THREAD) 1477 return -EINVAL; 1478 1479 return 0; 1480 } 1481 1482 /* 1483 * Unshare the filesystem structure if it is being shared 1484 */ 1485 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1486 { 1487 struct fs_struct *fs = current->fs; 1488 1489 if ((unshare_flags & CLONE_FS) && 1490 (fs && atomic_read(&fs->count) > 1)) { 1491 *new_fsp = __copy_fs_struct(current->fs); 1492 if (!*new_fsp) 1493 return -ENOMEM; 1494 } 1495 1496 return 0; 1497 } 1498 1499 /* 1500 * Unshare the namespace structure if it is being shared 1501 */ 1502 static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs) 1503 { 1504 struct namespace *ns = current->namespace; 1505 1506 if ((unshare_flags & CLONE_NEWNS) && 1507 (ns && atomic_read(&ns->count) > 1)) { 1508 if (!capable(CAP_SYS_ADMIN)) 1509 return -EPERM; 1510 1511 *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs); 1512 if (!*new_nsp) 1513 return -ENOMEM; 1514 } 1515 1516 return 0; 1517 } 1518 1519 /* 1520 * Unsharing of sighand for tasks created with CLONE_SIGHAND is not 1521 * supported yet 1522 */ 1523 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1524 { 1525 struct sighand_struct *sigh = current->sighand; 1526 1527 if ((unshare_flags & CLONE_SIGHAND) && 1528 (sigh && atomic_read(&sigh->count) > 1)) 1529 return -EINVAL; 1530 else 1531 return 0; 1532 } 1533 1534 /* 1535 * Unshare vm if it is being shared 1536 */ 1537 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1538 { 1539 struct mm_struct *mm = current->mm; 1540 1541 if ((unshare_flags & CLONE_VM) && 1542 (mm && atomic_read(&mm->mm_users) > 1)) { 1543 return -EINVAL; 1544 } 1545 1546 return 0; 1547 } 1548 1549 /* 1550 * Unshare file descriptor table if it is being shared 1551 */ 1552 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1553 { 1554 struct files_struct *fd = current->files; 1555 int error = 0; 1556 1557 if ((unshare_flags & CLONE_FILES) && 1558 (fd && atomic_read(&fd->count) > 1)) { 1559 *new_fdp = dup_fd(fd, &error); 1560 if (!*new_fdp) 1561 return error; 1562 } 1563 1564 return 0; 1565 } 1566 1567 /* 1568 * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not 1569 * supported yet 1570 */ 1571 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp) 1572 { 1573 if (unshare_flags & CLONE_SYSVSEM) 1574 return -EINVAL; 1575 1576 return 0; 1577 } 1578 1579 /* 1580 * unshare allows a process to 'unshare' part of the process 1581 * context which was originally shared using clone. copy_* 1582 * functions used by do_fork() cannot be used here directly 1583 * because they modify an inactive task_struct that is being 1584 * constructed. Here we are modifying the current, active, 1585 * task_struct. 1586 */ 1587 asmlinkage long sys_unshare(unsigned long unshare_flags) 1588 { 1589 int err = 0; 1590 struct fs_struct *fs, *new_fs = NULL; 1591 struct namespace *ns, *new_ns = NULL; 1592 struct sighand_struct *sigh, *new_sigh = NULL; 1593 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1594 struct files_struct *fd, *new_fd = NULL; 1595 struct sem_undo_list *new_ulist = NULL; 1596 1597 check_unshare_flags(&unshare_flags); 1598 1599 /* Return -EINVAL for all unsupported flags */ 1600 err = -EINVAL; 1601 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1602 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM)) 1603 goto bad_unshare_out; 1604 1605 if ((err = unshare_thread(unshare_flags))) 1606 goto bad_unshare_out; 1607 if ((err = unshare_fs(unshare_flags, &new_fs))) 1608 goto bad_unshare_cleanup_thread; 1609 if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs))) 1610 goto bad_unshare_cleanup_fs; 1611 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1612 goto bad_unshare_cleanup_ns; 1613 if ((err = unshare_vm(unshare_flags, &new_mm))) 1614 goto bad_unshare_cleanup_sigh; 1615 if ((err = unshare_fd(unshare_flags, &new_fd))) 1616 goto bad_unshare_cleanup_vm; 1617 if ((err = unshare_semundo(unshare_flags, &new_ulist))) 1618 goto bad_unshare_cleanup_fd; 1619 1620 if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) { 1621 1622 task_lock(current); 1623 1624 if (new_fs) { 1625 fs = current->fs; 1626 current->fs = new_fs; 1627 new_fs = fs; 1628 } 1629 1630 if (new_ns) { 1631 ns = current->namespace; 1632 current->namespace = new_ns; 1633 new_ns = ns; 1634 } 1635 1636 if (new_sigh) { 1637 sigh = current->sighand; 1638 rcu_assign_pointer(current->sighand, new_sigh); 1639 new_sigh = sigh; 1640 } 1641 1642 if (new_mm) { 1643 mm = current->mm; 1644 active_mm = current->active_mm; 1645 current->mm = new_mm; 1646 current->active_mm = new_mm; 1647 activate_mm(active_mm, new_mm); 1648 new_mm = mm; 1649 } 1650 1651 if (new_fd) { 1652 fd = current->files; 1653 current->files = new_fd; 1654 new_fd = fd; 1655 } 1656 1657 task_unlock(current); 1658 } 1659 1660 bad_unshare_cleanup_fd: 1661 if (new_fd) 1662 put_files_struct(new_fd); 1663 1664 bad_unshare_cleanup_vm: 1665 if (new_mm) 1666 mmput(new_mm); 1667 1668 bad_unshare_cleanup_sigh: 1669 if (new_sigh) 1670 if (atomic_dec_and_test(&new_sigh->count)) 1671 kmem_cache_free(sighand_cachep, new_sigh); 1672 1673 bad_unshare_cleanup_ns: 1674 if (new_ns) 1675 put_namespace(new_ns); 1676 1677 bad_unshare_cleanup_fs: 1678 if (new_fs) 1679 put_fs_struct(new_fs); 1680 1681 bad_unshare_cleanup_thread: 1682 bad_unshare_out: 1683 return err; 1684 } 1685