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