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/config.h> 15 #include <linux/slab.h> 16 #include <linux/init.h> 17 #include <linux/unistd.h> 18 #include <linux/smp_lock.h> 19 #include <linux/module.h> 20 #include <linux/vmalloc.h> 21 #include <linux/completion.h> 22 #include <linux/namespace.h> 23 #include <linux/personality.h> 24 #include <linux/mempolicy.h> 25 #include <linux/sem.h> 26 #include <linux/file.h> 27 #include <linux/key.h> 28 #include <linux/binfmts.h> 29 #include <linux/mman.h> 30 #include <linux/fs.h> 31 #include <linux/capability.h> 32 #include <linux/cpu.h> 33 #include <linux/cpuset.h> 34 #include <linux/security.h> 35 #include <linux/swap.h> 36 #include <linux/syscalls.h> 37 #include <linux/jiffies.h> 38 #include <linux/futex.h> 39 #include <linux/rcupdate.h> 40 #include <linux/ptrace.h> 41 #include <linux/mount.h> 42 #include <linux/audit.h> 43 #include <linux/profile.h> 44 #include <linux/rmap.h> 45 #include <linux/acct.h> 46 #include <linux/cn_proc.h> 47 48 #include <asm/pgtable.h> 49 #include <asm/pgalloc.h> 50 #include <asm/uaccess.h> 51 #include <asm/mmu_context.h> 52 #include <asm/cacheflush.h> 53 #include <asm/tlbflush.h> 54 55 /* 56 * Protected counters by write_lock_irq(&tasklist_lock) 57 */ 58 unsigned long total_forks; /* Handle normal Linux uptimes. */ 59 int nr_threads; /* The idle threads do not count.. */ 60 61 int max_threads; /* tunable limit on nr_threads */ 62 63 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 64 65 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 66 67 EXPORT_SYMBOL(tasklist_lock); 68 69 int nr_processes(void) 70 { 71 int cpu; 72 int total = 0; 73 74 for_each_online_cpu(cpu) 75 total += per_cpu(process_counts, cpu); 76 77 return total; 78 } 79 80 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 81 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 82 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 83 static kmem_cache_t *task_struct_cachep; 84 #endif 85 86 /* SLAB cache for signal_struct structures (tsk->signal) */ 87 static kmem_cache_t *signal_cachep; 88 89 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 90 kmem_cache_t *sighand_cachep; 91 92 /* SLAB cache for files_struct structures (tsk->files) */ 93 kmem_cache_t *files_cachep; 94 95 /* SLAB cache for fs_struct structures (tsk->fs) */ 96 kmem_cache_t *fs_cachep; 97 98 /* SLAB cache for vm_area_struct structures */ 99 kmem_cache_t *vm_area_cachep; 100 101 /* SLAB cache for mm_struct structures (tsk->mm) */ 102 static kmem_cache_t *mm_cachep; 103 104 void free_task(struct task_struct *tsk) 105 { 106 free_thread_info(tsk->thread_info); 107 rt_mutex_debug_task_free(tsk); 108 free_task_struct(tsk); 109 } 110 EXPORT_SYMBOL(free_task); 111 112 void __put_task_struct(struct task_struct *tsk) 113 { 114 WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE))); 115 WARN_ON(atomic_read(&tsk->usage)); 116 WARN_ON(tsk == current); 117 118 security_task_free(tsk); 119 free_uid(tsk->user); 120 put_group_info(tsk->group_info); 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 down_write(&mm->mmap_sem); 198 199 mm->locked_vm = 0; 200 mm->mmap = NULL; 201 mm->mmap_cache = NULL; 202 mm->free_area_cache = oldmm->mmap_base; 203 mm->cached_hole_size = ~0UL; 204 mm->map_count = 0; 205 cpus_clear(mm->cpu_vm_mask); 206 mm->mm_rb = RB_ROOT; 207 rb_link = &mm->mm_rb.rb_node; 208 rb_parent = NULL; 209 pprev = &mm->mmap; 210 211 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 212 struct file *file; 213 214 if (mpnt->vm_flags & VM_DONTCOPY) { 215 long pages = vma_pages(mpnt); 216 mm->total_vm -= pages; 217 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 218 -pages); 219 continue; 220 } 221 charge = 0; 222 if (mpnt->vm_flags & VM_ACCOUNT) { 223 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 224 if (security_vm_enough_memory(len)) 225 goto fail_nomem; 226 charge = len; 227 } 228 tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL); 229 if (!tmp) 230 goto fail_nomem; 231 *tmp = *mpnt; 232 pol = mpol_copy(vma_policy(mpnt)); 233 retval = PTR_ERR(pol); 234 if (IS_ERR(pol)) 235 goto fail_nomem_policy; 236 vma_set_policy(tmp, pol); 237 tmp->vm_flags &= ~VM_LOCKED; 238 tmp->vm_mm = mm; 239 tmp->vm_next = NULL; 240 anon_vma_link(tmp); 241 file = tmp->vm_file; 242 if (file) { 243 struct inode *inode = file->f_dentry->d_inode; 244 get_file(file); 245 if (tmp->vm_flags & VM_DENYWRITE) 246 atomic_dec(&inode->i_writecount); 247 248 /* insert tmp into the share list, just after mpnt */ 249 spin_lock(&file->f_mapping->i_mmap_lock); 250 tmp->vm_truncate_count = mpnt->vm_truncate_count; 251 flush_dcache_mmap_lock(file->f_mapping); 252 vma_prio_tree_add(tmp, mpnt); 253 flush_dcache_mmap_unlock(file->f_mapping); 254 spin_unlock(&file->f_mapping->i_mmap_lock); 255 } 256 257 /* 258 * Link in the new vma and copy the page table entries. 259 */ 260 *pprev = tmp; 261 pprev = &tmp->vm_next; 262 263 __vma_link_rb(mm, tmp, rb_link, rb_parent); 264 rb_link = &tmp->vm_rb.rb_right; 265 rb_parent = &tmp->vm_rb; 266 267 mm->map_count++; 268 retval = copy_page_range(mm, oldmm, mpnt); 269 270 if (tmp->vm_ops && tmp->vm_ops->open) 271 tmp->vm_ops->open(tmp); 272 273 if (retval) 274 goto out; 275 } 276 retval = 0; 277 out: 278 up_write(&mm->mmap_sem); 279 flush_tlb_mm(oldmm); 280 up_write(&oldmm->mmap_sem); 281 return retval; 282 fail_nomem_policy: 283 kmem_cache_free(vm_area_cachep, tmp); 284 fail_nomem: 285 retval = -ENOMEM; 286 vm_unacct_memory(charge); 287 goto out; 288 } 289 290 static inline int mm_alloc_pgd(struct mm_struct * mm) 291 { 292 mm->pgd = pgd_alloc(mm); 293 if (unlikely(!mm->pgd)) 294 return -ENOMEM; 295 return 0; 296 } 297 298 static inline void mm_free_pgd(struct mm_struct * mm) 299 { 300 pgd_free(mm->pgd); 301 } 302 #else 303 #define dup_mmap(mm, oldmm) (0) 304 #define mm_alloc_pgd(mm) (0) 305 #define mm_free_pgd(mm) 306 #endif /* CONFIG_MMU */ 307 308 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 309 310 #define allocate_mm() (kmem_cache_alloc(mm_cachep, SLAB_KERNEL)) 311 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 312 313 #include <linux/init_task.h> 314 315 static struct mm_struct * mm_init(struct mm_struct * mm) 316 { 317 atomic_set(&mm->mm_users, 1); 318 atomic_set(&mm->mm_count, 1); 319 init_rwsem(&mm->mmap_sem); 320 INIT_LIST_HEAD(&mm->mmlist); 321 mm->core_waiters = 0; 322 mm->nr_ptes = 0; 323 set_mm_counter(mm, file_rss, 0); 324 set_mm_counter(mm, anon_rss, 0); 325 spin_lock_init(&mm->page_table_lock); 326 rwlock_init(&mm->ioctx_list_lock); 327 mm->ioctx_list = NULL; 328 mm->free_area_cache = TASK_UNMAPPED_BASE; 329 mm->cached_hole_size = ~0UL; 330 331 if (likely(!mm_alloc_pgd(mm))) { 332 mm->def_flags = 0; 333 return mm; 334 } 335 free_mm(mm); 336 return NULL; 337 } 338 339 /* 340 * Allocate and initialize an mm_struct. 341 */ 342 struct mm_struct * mm_alloc(void) 343 { 344 struct mm_struct * mm; 345 346 mm = allocate_mm(); 347 if (mm) { 348 memset(mm, 0, sizeof(*mm)); 349 mm = mm_init(mm); 350 } 351 return mm; 352 } 353 354 /* 355 * Called when the last reference to the mm 356 * is dropped: either by a lazy thread or by 357 * mmput. Free the page directory and the mm. 358 */ 359 void fastcall __mmdrop(struct mm_struct *mm) 360 { 361 BUG_ON(mm == &init_mm); 362 mm_free_pgd(mm); 363 destroy_context(mm); 364 free_mm(mm); 365 } 366 367 /* 368 * Decrement the use count and release all resources for an mm. 369 */ 370 void mmput(struct mm_struct *mm) 371 { 372 might_sleep(); 373 374 if (atomic_dec_and_test(&mm->mm_users)) { 375 exit_aio(mm); 376 exit_mmap(mm); 377 if (!list_empty(&mm->mmlist)) { 378 spin_lock(&mmlist_lock); 379 list_del(&mm->mmlist); 380 spin_unlock(&mmlist_lock); 381 } 382 put_swap_token(mm); 383 mmdrop(mm); 384 } 385 } 386 EXPORT_SYMBOL_GPL(mmput); 387 388 /** 389 * get_task_mm - acquire a reference to the task's mm 390 * 391 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning 392 * this kernel workthread has transiently adopted a user mm with use_mm, 393 * to do its AIO) is not set and if so returns a reference to it, after 394 * bumping up the use count. User must release the mm via mmput() 395 * after use. Typically used by /proc and ptrace. 396 */ 397 struct mm_struct *get_task_mm(struct task_struct *task) 398 { 399 struct mm_struct *mm; 400 401 task_lock(task); 402 mm = task->mm; 403 if (mm) { 404 if (task->flags & PF_BORROWED_MM) 405 mm = NULL; 406 else 407 atomic_inc(&mm->mm_users); 408 } 409 task_unlock(task); 410 return mm; 411 } 412 EXPORT_SYMBOL_GPL(get_task_mm); 413 414 /* Please note the differences between mmput and mm_release. 415 * mmput is called whenever we stop holding onto a mm_struct, 416 * error success whatever. 417 * 418 * mm_release is called after a mm_struct has been removed 419 * from the current process. 420 * 421 * This difference is important for error handling, when we 422 * only half set up a mm_struct for a new process and need to restore 423 * the old one. Because we mmput the new mm_struct before 424 * restoring the old one. . . 425 * Eric Biederman 10 January 1998 426 */ 427 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 428 { 429 struct completion *vfork_done = tsk->vfork_done; 430 431 /* Get rid of any cached register state */ 432 deactivate_mm(tsk, mm); 433 434 /* notify parent sleeping on vfork() */ 435 if (vfork_done) { 436 tsk->vfork_done = NULL; 437 complete(vfork_done); 438 } 439 if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) { 440 u32 __user * tidptr = tsk->clear_child_tid; 441 tsk->clear_child_tid = NULL; 442 443 /* 444 * We don't check the error code - if userspace has 445 * not set up a proper pointer then tough luck. 446 */ 447 put_user(0, tidptr); 448 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 449 } 450 } 451 452 /* 453 * Allocate a new mm structure and copy contents from the 454 * mm structure of the passed in task structure. 455 */ 456 static struct mm_struct *dup_mm(struct task_struct *tsk) 457 { 458 struct mm_struct *mm, *oldmm = current->mm; 459 int err; 460 461 if (!oldmm) 462 return NULL; 463 464 mm = allocate_mm(); 465 if (!mm) 466 goto fail_nomem; 467 468 memcpy(mm, oldmm, sizeof(*mm)); 469 470 if (!mm_init(mm)) 471 goto fail_nomem; 472 473 if (init_new_context(tsk, mm)) 474 goto fail_nocontext; 475 476 err = dup_mmap(mm, oldmm); 477 if (err) 478 goto free_pt; 479 480 mm->hiwater_rss = get_mm_rss(mm); 481 mm->hiwater_vm = mm->total_vm; 482 483 return mm; 484 485 free_pt: 486 mmput(mm); 487 488 fail_nomem: 489 return NULL; 490 491 fail_nocontext: 492 /* 493 * If init_new_context() failed, we cannot use mmput() to free the mm 494 * because it calls destroy_context() 495 */ 496 mm_free_pgd(mm); 497 free_mm(mm); 498 return NULL; 499 } 500 501 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 502 { 503 struct mm_struct * mm, *oldmm; 504 int retval; 505 506 tsk->min_flt = tsk->maj_flt = 0; 507 tsk->nvcsw = tsk->nivcsw = 0; 508 509 tsk->mm = NULL; 510 tsk->active_mm = NULL; 511 512 /* 513 * Are we cloning a kernel thread? 514 * 515 * We need to steal a active VM for that.. 516 */ 517 oldmm = current->mm; 518 if (!oldmm) 519 return 0; 520 521 if (clone_flags & CLONE_VM) { 522 atomic_inc(&oldmm->mm_users); 523 mm = oldmm; 524 goto good_mm; 525 } 526 527 retval = -ENOMEM; 528 mm = dup_mm(tsk); 529 if (!mm) 530 goto fail_nomem; 531 532 good_mm: 533 tsk->mm = mm; 534 tsk->active_mm = mm; 535 return 0; 536 537 fail_nomem: 538 return retval; 539 } 540 541 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old) 542 { 543 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 544 /* We don't need to lock fs - think why ;-) */ 545 if (fs) { 546 atomic_set(&fs->count, 1); 547 rwlock_init(&fs->lock); 548 fs->umask = old->umask; 549 read_lock(&old->lock); 550 fs->rootmnt = mntget(old->rootmnt); 551 fs->root = dget(old->root); 552 fs->pwdmnt = mntget(old->pwdmnt); 553 fs->pwd = dget(old->pwd); 554 if (old->altroot) { 555 fs->altrootmnt = mntget(old->altrootmnt); 556 fs->altroot = dget(old->altroot); 557 } else { 558 fs->altrootmnt = NULL; 559 fs->altroot = NULL; 560 } 561 read_unlock(&old->lock); 562 } 563 return fs; 564 } 565 566 struct fs_struct *copy_fs_struct(struct fs_struct *old) 567 { 568 return __copy_fs_struct(old); 569 } 570 571 EXPORT_SYMBOL_GPL(copy_fs_struct); 572 573 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk) 574 { 575 if (clone_flags & CLONE_FS) { 576 atomic_inc(¤t->fs->count); 577 return 0; 578 } 579 tsk->fs = __copy_fs_struct(current->fs); 580 if (!tsk->fs) 581 return -ENOMEM; 582 return 0; 583 } 584 585 static int count_open_files(struct fdtable *fdt) 586 { 587 int size = fdt->max_fdset; 588 int i; 589 590 /* Find the last open fd */ 591 for (i = size/(8*sizeof(long)); i > 0; ) { 592 if (fdt->open_fds->fds_bits[--i]) 593 break; 594 } 595 i = (i+1) * 8 * sizeof(long); 596 return i; 597 } 598 599 static struct files_struct *alloc_files(void) 600 { 601 struct files_struct *newf; 602 struct fdtable *fdt; 603 604 newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL); 605 if (!newf) 606 goto out; 607 608 atomic_set(&newf->count, 1); 609 610 spin_lock_init(&newf->file_lock); 611 newf->next_fd = 0; 612 fdt = &newf->fdtab; 613 fdt->max_fds = NR_OPEN_DEFAULT; 614 fdt->max_fdset = EMBEDDED_FD_SET_SIZE; 615 fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init; 616 fdt->open_fds = (fd_set *)&newf->open_fds_init; 617 fdt->fd = &newf->fd_array[0]; 618 INIT_RCU_HEAD(&fdt->rcu); 619 fdt->free_files = NULL; 620 fdt->next = NULL; 621 rcu_assign_pointer(newf->fdt, fdt); 622 out: 623 return newf; 624 } 625 626 /* 627 * Allocate a new files structure and copy contents from the 628 * passed in files structure. 629 * errorp will be valid only when the returned files_struct is NULL. 630 */ 631 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) 632 { 633 struct files_struct *newf; 634 struct file **old_fds, **new_fds; 635 int open_files, size, i, expand; 636 struct fdtable *old_fdt, *new_fdt; 637 638 *errorp = -ENOMEM; 639 newf = alloc_files(); 640 if (!newf) 641 goto out; 642 643 spin_lock(&oldf->file_lock); 644 old_fdt = files_fdtable(oldf); 645 new_fdt = files_fdtable(newf); 646 size = old_fdt->max_fdset; 647 open_files = count_open_files(old_fdt); 648 expand = 0; 649 650 /* 651 * Check whether we need to allocate a larger fd array or fd set. 652 * Note: we're not a clone task, so the open count won't change. 653 */ 654 if (open_files > new_fdt->max_fdset) { 655 new_fdt->max_fdset = 0; 656 expand = 1; 657 } 658 if (open_files > new_fdt->max_fds) { 659 new_fdt->max_fds = 0; 660 expand = 1; 661 } 662 663 /* if the old fdset gets grown now, we'll only copy up to "size" fds */ 664 if (expand) { 665 spin_unlock(&oldf->file_lock); 666 spin_lock(&newf->file_lock); 667 *errorp = expand_files(newf, open_files-1); 668 spin_unlock(&newf->file_lock); 669 if (*errorp < 0) 670 goto out_release; 671 new_fdt = files_fdtable(newf); 672 /* 673 * Reacquire the oldf lock and a pointer to its fd table 674 * who knows it may have a new bigger fd table. We need 675 * the latest pointer. 676 */ 677 spin_lock(&oldf->file_lock); 678 old_fdt = files_fdtable(oldf); 679 } 680 681 old_fds = old_fdt->fd; 682 new_fds = new_fdt->fd; 683 684 memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8); 685 memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8); 686 687 for (i = open_files; i != 0; i--) { 688 struct file *f = *old_fds++; 689 if (f) { 690 get_file(f); 691 } else { 692 /* 693 * The fd may be claimed in the fd bitmap but not yet 694 * instantiated in the files array if a sibling thread 695 * is partway through open(). So make sure that this 696 * fd is available to the new process. 697 */ 698 FD_CLR(open_files - i, new_fdt->open_fds); 699 } 700 rcu_assign_pointer(*new_fds++, f); 701 } 702 spin_unlock(&oldf->file_lock); 703 704 /* compute the remainder to be cleared */ 705 size = (new_fdt->max_fds - open_files) * sizeof(struct file *); 706 707 /* This is long word aligned thus could use a optimized version */ 708 memset(new_fds, 0, size); 709 710 if (new_fdt->max_fdset > open_files) { 711 int left = (new_fdt->max_fdset-open_files)/8; 712 int start = open_files / (8 * sizeof(unsigned long)); 713 714 memset(&new_fdt->open_fds->fds_bits[start], 0, left); 715 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left); 716 } 717 718 out: 719 return newf; 720 721 out_release: 722 free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset); 723 free_fdset (new_fdt->open_fds, new_fdt->max_fdset); 724 free_fd_array(new_fdt->fd, new_fdt->max_fds); 725 kmem_cache_free(files_cachep, newf); 726 return NULL; 727 } 728 729 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 730 { 731 struct files_struct *oldf, *newf; 732 int error = 0; 733 734 /* 735 * A background process may not have any files ... 736 */ 737 oldf = current->files; 738 if (!oldf) 739 goto out; 740 741 if (clone_flags & CLONE_FILES) { 742 atomic_inc(&oldf->count); 743 goto out; 744 } 745 746 /* 747 * Note: we may be using current for both targets (See exec.c) 748 * This works because we cache current->files (old) as oldf. Don't 749 * break this. 750 */ 751 tsk->files = NULL; 752 newf = dup_fd(oldf, &error); 753 if (!newf) 754 goto out; 755 756 tsk->files = newf; 757 error = 0; 758 out: 759 return error; 760 } 761 762 /* 763 * Helper to unshare the files of the current task. 764 * We don't want to expose copy_files internals to 765 * the exec layer of the kernel. 766 */ 767 768 int unshare_files(void) 769 { 770 struct files_struct *files = current->files; 771 int rc; 772 773 BUG_ON(!files); 774 775 /* This can race but the race causes us to copy when we don't 776 need to and drop the copy */ 777 if(atomic_read(&files->count) == 1) 778 { 779 atomic_inc(&files->count); 780 return 0; 781 } 782 rc = copy_files(0, current); 783 if(rc) 784 current->files = files; 785 return rc; 786 } 787 788 EXPORT_SYMBOL(unshare_files); 789 790 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk) 791 { 792 struct sighand_struct *sig; 793 794 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 795 atomic_inc(¤t->sighand->count); 796 return 0; 797 } 798 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 799 rcu_assign_pointer(tsk->sighand, sig); 800 if (!sig) 801 return -ENOMEM; 802 atomic_set(&sig->count, 1); 803 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 804 return 0; 805 } 806 807 void __cleanup_sighand(struct sighand_struct *sighand) 808 { 809 if (atomic_dec_and_test(&sighand->count)) 810 kmem_cache_free(sighand_cachep, sighand); 811 } 812 813 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk) 814 { 815 struct signal_struct *sig; 816 int ret; 817 818 if (clone_flags & CLONE_THREAD) { 819 atomic_inc(¤t->signal->count); 820 atomic_inc(¤t->signal->live); 821 return 0; 822 } 823 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 824 tsk->signal = sig; 825 if (!sig) 826 return -ENOMEM; 827 828 ret = copy_thread_group_keys(tsk); 829 if (ret < 0) { 830 kmem_cache_free(signal_cachep, sig); 831 return ret; 832 } 833 834 atomic_set(&sig->count, 1); 835 atomic_set(&sig->live, 1); 836 init_waitqueue_head(&sig->wait_chldexit); 837 sig->flags = 0; 838 sig->group_exit_code = 0; 839 sig->group_exit_task = NULL; 840 sig->group_stop_count = 0; 841 sig->curr_target = NULL; 842 init_sigpending(&sig->shared_pending); 843 INIT_LIST_HEAD(&sig->posix_timers); 844 845 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL); 846 sig->it_real_incr.tv64 = 0; 847 sig->real_timer.function = it_real_fn; 848 sig->tsk = tsk; 849 850 sig->it_virt_expires = cputime_zero; 851 sig->it_virt_incr = cputime_zero; 852 sig->it_prof_expires = cputime_zero; 853 sig->it_prof_incr = cputime_zero; 854 855 sig->leader = 0; /* session leadership doesn't inherit */ 856 sig->tty_old_pgrp = 0; 857 858 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 859 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 860 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 861 sig->sched_time = 0; 862 INIT_LIST_HEAD(&sig->cpu_timers[0]); 863 INIT_LIST_HEAD(&sig->cpu_timers[1]); 864 INIT_LIST_HEAD(&sig->cpu_timers[2]); 865 866 task_lock(current->group_leader); 867 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 868 task_unlock(current->group_leader); 869 870 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 871 /* 872 * New sole thread in the process gets an expiry time 873 * of the whole CPU time limit. 874 */ 875 tsk->it_prof_expires = 876 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 877 } 878 acct_init_pacct(&sig->pacct); 879 880 return 0; 881 } 882 883 void __cleanup_signal(struct signal_struct *sig) 884 { 885 exit_thread_group_keys(sig); 886 kmem_cache_free(signal_cachep, sig); 887 } 888 889 static inline void cleanup_signal(struct task_struct *tsk) 890 { 891 struct signal_struct *sig = tsk->signal; 892 893 atomic_dec(&sig->live); 894 895 if (atomic_dec_and_test(&sig->count)) 896 __cleanup_signal(sig); 897 } 898 899 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p) 900 { 901 unsigned long new_flags = p->flags; 902 903 new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE); 904 new_flags |= PF_FORKNOEXEC; 905 if (!(clone_flags & CLONE_PTRACE)) 906 p->ptrace = 0; 907 p->flags = new_flags; 908 } 909 910 asmlinkage long sys_set_tid_address(int __user *tidptr) 911 { 912 current->clear_child_tid = tidptr; 913 914 return current->pid; 915 } 916 917 static inline void rt_mutex_init_task(struct task_struct *p) 918 { 919 #ifdef CONFIG_RT_MUTEXES 920 spin_lock_init(&p->pi_lock); 921 plist_head_init(&p->pi_waiters, &p->pi_lock); 922 p->pi_blocked_on = NULL; 923 # ifdef CONFIG_DEBUG_RT_MUTEXES 924 spin_lock_init(&p->held_list_lock); 925 INIT_LIST_HEAD(&p->held_list_head); 926 # endif 927 #endif 928 } 929 930 /* 931 * This creates a new process as a copy of the old one, 932 * but does not actually start it yet. 933 * 934 * It copies the registers, and all the appropriate 935 * parts of the process environment (as per the clone 936 * flags). The actual kick-off is left to the caller. 937 */ 938 static task_t *copy_process(unsigned long clone_flags, 939 unsigned long stack_start, 940 struct pt_regs *regs, 941 unsigned long stack_size, 942 int __user *parent_tidptr, 943 int __user *child_tidptr, 944 int pid) 945 { 946 int retval; 947 struct task_struct *p = NULL; 948 949 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 950 return ERR_PTR(-EINVAL); 951 952 /* 953 * Thread groups must share signals as well, and detached threads 954 * can only be started up within the thread group. 955 */ 956 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 957 return ERR_PTR(-EINVAL); 958 959 /* 960 * Shared signal handlers imply shared VM. By way of the above, 961 * thread groups also imply shared VM. Blocking this case allows 962 * for various simplifications in other code. 963 */ 964 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 965 return ERR_PTR(-EINVAL); 966 967 retval = security_task_create(clone_flags); 968 if (retval) 969 goto fork_out; 970 971 retval = -ENOMEM; 972 p = dup_task_struct(current); 973 if (!p) 974 goto fork_out; 975 976 retval = -EAGAIN; 977 if (atomic_read(&p->user->processes) >= 978 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 979 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 980 p->user != &root_user) 981 goto bad_fork_free; 982 } 983 984 atomic_inc(&p->user->__count); 985 atomic_inc(&p->user->processes); 986 get_group_info(p->group_info); 987 988 /* 989 * If multiple threads are within copy_process(), then this check 990 * triggers too late. This doesn't hurt, the check is only there 991 * to stop root fork bombs. 992 */ 993 if (nr_threads >= max_threads) 994 goto bad_fork_cleanup_count; 995 996 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 997 goto bad_fork_cleanup_count; 998 999 if (p->binfmt && !try_module_get(p->binfmt->module)) 1000 goto bad_fork_cleanup_put_domain; 1001 1002 p->did_exec = 0; 1003 copy_flags(clone_flags, p); 1004 p->pid = pid; 1005 retval = -EFAULT; 1006 if (clone_flags & CLONE_PARENT_SETTID) 1007 if (put_user(p->pid, parent_tidptr)) 1008 goto bad_fork_cleanup; 1009 1010 INIT_LIST_HEAD(&p->children); 1011 INIT_LIST_HEAD(&p->sibling); 1012 p->vfork_done = NULL; 1013 spin_lock_init(&p->alloc_lock); 1014 1015 clear_tsk_thread_flag(p, TIF_SIGPENDING); 1016 init_sigpending(&p->pending); 1017 1018 p->utime = cputime_zero; 1019 p->stime = cputime_zero; 1020 p->sched_time = 0; 1021 p->rchar = 0; /* I/O counter: bytes read */ 1022 p->wchar = 0; /* I/O counter: bytes written */ 1023 p->syscr = 0; /* I/O counter: read syscalls */ 1024 p->syscw = 0; /* I/O counter: write syscalls */ 1025 acct_clear_integrals(p); 1026 1027 p->it_virt_expires = cputime_zero; 1028 p->it_prof_expires = cputime_zero; 1029 p->it_sched_expires = 0; 1030 INIT_LIST_HEAD(&p->cpu_timers[0]); 1031 INIT_LIST_HEAD(&p->cpu_timers[1]); 1032 INIT_LIST_HEAD(&p->cpu_timers[2]); 1033 1034 p->lock_depth = -1; /* -1 = no lock */ 1035 do_posix_clock_monotonic_gettime(&p->start_time); 1036 p->security = NULL; 1037 p->io_context = NULL; 1038 p->io_wait = NULL; 1039 p->audit_context = NULL; 1040 cpuset_fork(p); 1041 #ifdef CONFIG_NUMA 1042 p->mempolicy = mpol_copy(p->mempolicy); 1043 if (IS_ERR(p->mempolicy)) { 1044 retval = PTR_ERR(p->mempolicy); 1045 p->mempolicy = NULL; 1046 goto bad_fork_cleanup_cpuset; 1047 } 1048 mpol_fix_fork_child_flag(p); 1049 #endif 1050 1051 rt_mutex_init_task(p); 1052 1053 #ifdef CONFIG_DEBUG_MUTEXES 1054 p->blocked_on = NULL; /* not blocked yet */ 1055 #endif 1056 1057 p->tgid = p->pid; 1058 if (clone_flags & CLONE_THREAD) 1059 p->tgid = current->tgid; 1060 1061 if ((retval = security_task_alloc(p))) 1062 goto bad_fork_cleanup_policy; 1063 if ((retval = audit_alloc(p))) 1064 goto bad_fork_cleanup_security; 1065 /* copy all the process information */ 1066 if ((retval = copy_semundo(clone_flags, p))) 1067 goto bad_fork_cleanup_audit; 1068 if ((retval = copy_files(clone_flags, p))) 1069 goto bad_fork_cleanup_semundo; 1070 if ((retval = copy_fs(clone_flags, p))) 1071 goto bad_fork_cleanup_files; 1072 if ((retval = copy_sighand(clone_flags, p))) 1073 goto bad_fork_cleanup_fs; 1074 if ((retval = copy_signal(clone_flags, p))) 1075 goto bad_fork_cleanup_sighand; 1076 if ((retval = copy_mm(clone_flags, p))) 1077 goto bad_fork_cleanup_signal; 1078 if ((retval = copy_keys(clone_flags, p))) 1079 goto bad_fork_cleanup_mm; 1080 if ((retval = copy_namespace(clone_flags, p))) 1081 goto bad_fork_cleanup_keys; 1082 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1083 if (retval) 1084 goto bad_fork_cleanup_namespace; 1085 1086 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1087 /* 1088 * Clear TID on mm_release()? 1089 */ 1090 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1091 p->robust_list = NULL; 1092 #ifdef CONFIG_COMPAT 1093 p->compat_robust_list = NULL; 1094 #endif 1095 INIT_LIST_HEAD(&p->pi_state_list); 1096 p->pi_state_cache = NULL; 1097 1098 /* 1099 * sigaltstack should be cleared when sharing the same VM 1100 */ 1101 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1102 p->sas_ss_sp = p->sas_ss_size = 0; 1103 1104 /* 1105 * Syscall tracing should be turned off in the child regardless 1106 * of CLONE_PTRACE. 1107 */ 1108 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1109 #ifdef TIF_SYSCALL_EMU 1110 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1111 #endif 1112 1113 /* Our parent execution domain becomes current domain 1114 These must match for thread signalling to apply */ 1115 1116 p->parent_exec_id = p->self_exec_id; 1117 1118 /* ok, now we should be set up.. */ 1119 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1120 p->pdeath_signal = 0; 1121 p->exit_state = 0; 1122 1123 /* 1124 * Ok, make it visible to the rest of the system. 1125 * We dont wake it up yet. 1126 */ 1127 p->group_leader = p; 1128 INIT_LIST_HEAD(&p->thread_group); 1129 INIT_LIST_HEAD(&p->ptrace_children); 1130 INIT_LIST_HEAD(&p->ptrace_list); 1131 1132 /* Perform scheduler related setup. Assign this task to a CPU. */ 1133 sched_fork(p, clone_flags); 1134 1135 /* Need tasklist lock for parent etc handling! */ 1136 write_lock_irq(&tasklist_lock); 1137 1138 /* 1139 * The task hasn't been attached yet, so its cpus_allowed mask will 1140 * not be changed, nor will its assigned CPU. 1141 * 1142 * The cpus_allowed mask of the parent may have changed after it was 1143 * copied first time - so re-copy it here, then check the child's CPU 1144 * to ensure it is on a valid CPU (and if not, just force it back to 1145 * parent's CPU). This avoids alot of nasty races. 1146 */ 1147 p->cpus_allowed = current->cpus_allowed; 1148 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1149 !cpu_online(task_cpu(p)))) 1150 set_task_cpu(p, smp_processor_id()); 1151 1152 /* CLONE_PARENT re-uses the old parent */ 1153 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1154 p->real_parent = current->real_parent; 1155 else 1156 p->real_parent = current; 1157 p->parent = p->real_parent; 1158 1159 spin_lock(¤t->sighand->siglock); 1160 1161 /* 1162 * Process group and session signals need to be delivered to just the 1163 * parent before the fork or both the parent and the child after the 1164 * fork. Restart if a signal comes in before we add the new process to 1165 * it's process group. 1166 * A fatal signal pending means that current will exit, so the new 1167 * thread can't slip out of an OOM kill (or normal SIGKILL). 1168 */ 1169 recalc_sigpending(); 1170 if (signal_pending(current)) { 1171 spin_unlock(¤t->sighand->siglock); 1172 write_unlock_irq(&tasklist_lock); 1173 retval = -ERESTARTNOINTR; 1174 goto bad_fork_cleanup_namespace; 1175 } 1176 1177 if (clone_flags & CLONE_THREAD) { 1178 p->group_leader = current->group_leader; 1179 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1180 1181 if (!cputime_eq(current->signal->it_virt_expires, 1182 cputime_zero) || 1183 !cputime_eq(current->signal->it_prof_expires, 1184 cputime_zero) || 1185 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1186 !list_empty(¤t->signal->cpu_timers[0]) || 1187 !list_empty(¤t->signal->cpu_timers[1]) || 1188 !list_empty(¤t->signal->cpu_timers[2])) { 1189 /* 1190 * Have child wake up on its first tick to check 1191 * for process CPU timers. 1192 */ 1193 p->it_prof_expires = jiffies_to_cputime(1); 1194 } 1195 } 1196 1197 /* 1198 * inherit ioprio 1199 */ 1200 p->ioprio = current->ioprio; 1201 1202 if (likely(p->pid)) { 1203 add_parent(p); 1204 if (unlikely(p->ptrace & PT_PTRACED)) 1205 __ptrace_link(p, current->parent); 1206 1207 if (thread_group_leader(p)) { 1208 p->signal->tty = current->signal->tty; 1209 p->signal->pgrp = process_group(current); 1210 p->signal->session = current->signal->session; 1211 attach_pid(p, PIDTYPE_PGID, process_group(p)); 1212 attach_pid(p, PIDTYPE_SID, p->signal->session); 1213 1214 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1215 __get_cpu_var(process_counts)++; 1216 } 1217 attach_pid(p, PIDTYPE_PID, p->pid); 1218 nr_threads++; 1219 } 1220 1221 total_forks++; 1222 spin_unlock(¤t->sighand->siglock); 1223 write_unlock_irq(&tasklist_lock); 1224 proc_fork_connector(p); 1225 return p; 1226 1227 bad_fork_cleanup_namespace: 1228 exit_namespace(p); 1229 bad_fork_cleanup_keys: 1230 exit_keys(p); 1231 bad_fork_cleanup_mm: 1232 if (p->mm) 1233 mmput(p->mm); 1234 bad_fork_cleanup_signal: 1235 cleanup_signal(p); 1236 bad_fork_cleanup_sighand: 1237 __cleanup_sighand(p->sighand); 1238 bad_fork_cleanup_fs: 1239 exit_fs(p); /* blocking */ 1240 bad_fork_cleanup_files: 1241 exit_files(p); /* blocking */ 1242 bad_fork_cleanup_semundo: 1243 exit_sem(p); 1244 bad_fork_cleanup_audit: 1245 audit_free(p); 1246 bad_fork_cleanup_security: 1247 security_task_free(p); 1248 bad_fork_cleanup_policy: 1249 #ifdef CONFIG_NUMA 1250 mpol_free(p->mempolicy); 1251 bad_fork_cleanup_cpuset: 1252 #endif 1253 cpuset_exit(p); 1254 bad_fork_cleanup: 1255 if (p->binfmt) 1256 module_put(p->binfmt->module); 1257 bad_fork_cleanup_put_domain: 1258 module_put(task_thread_info(p)->exec_domain->module); 1259 bad_fork_cleanup_count: 1260 put_group_info(p->group_info); 1261 atomic_dec(&p->user->processes); 1262 free_uid(p->user); 1263 bad_fork_free: 1264 free_task(p); 1265 fork_out: 1266 return ERR_PTR(retval); 1267 } 1268 1269 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1270 { 1271 memset(regs, 0, sizeof(struct pt_regs)); 1272 return regs; 1273 } 1274 1275 task_t * __devinit fork_idle(int cpu) 1276 { 1277 task_t *task; 1278 struct pt_regs regs; 1279 1280 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, NULL, 0); 1281 if (!task) 1282 return ERR_PTR(-ENOMEM); 1283 init_idle(task, cpu); 1284 1285 return task; 1286 } 1287 1288 static inline int fork_traceflag (unsigned clone_flags) 1289 { 1290 if (clone_flags & CLONE_UNTRACED) 1291 return 0; 1292 else if (clone_flags & CLONE_VFORK) { 1293 if (current->ptrace & PT_TRACE_VFORK) 1294 return PTRACE_EVENT_VFORK; 1295 } else if ((clone_flags & CSIGNAL) != SIGCHLD) { 1296 if (current->ptrace & PT_TRACE_CLONE) 1297 return PTRACE_EVENT_CLONE; 1298 } else if (current->ptrace & PT_TRACE_FORK) 1299 return PTRACE_EVENT_FORK; 1300 1301 return 0; 1302 } 1303 1304 /* 1305 * Ok, this is the main fork-routine. 1306 * 1307 * It copies the process, and if successful kick-starts 1308 * it and waits for it to finish using the VM if required. 1309 */ 1310 long do_fork(unsigned long clone_flags, 1311 unsigned long stack_start, 1312 struct pt_regs *regs, 1313 unsigned long stack_size, 1314 int __user *parent_tidptr, 1315 int __user *child_tidptr) 1316 { 1317 struct task_struct *p; 1318 int trace = 0; 1319 struct pid *pid = alloc_pid(); 1320 long nr; 1321 1322 if (!pid) 1323 return -EAGAIN; 1324 nr = pid->nr; 1325 if (unlikely(current->ptrace)) { 1326 trace = fork_traceflag (clone_flags); 1327 if (trace) 1328 clone_flags |= CLONE_PTRACE; 1329 } 1330 1331 p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, nr); 1332 /* 1333 * Do this prior waking up the new thread - the thread pointer 1334 * might get invalid after that point, if the thread exits quickly. 1335 */ 1336 if (!IS_ERR(p)) { 1337 struct completion vfork; 1338 1339 if (clone_flags & CLONE_VFORK) { 1340 p->vfork_done = &vfork; 1341 init_completion(&vfork); 1342 } 1343 1344 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) { 1345 /* 1346 * We'll start up with an immediate SIGSTOP. 1347 */ 1348 sigaddset(&p->pending.signal, SIGSTOP); 1349 set_tsk_thread_flag(p, TIF_SIGPENDING); 1350 } 1351 1352 if (!(clone_flags & CLONE_STOPPED)) 1353 wake_up_new_task(p, clone_flags); 1354 else 1355 p->state = TASK_STOPPED; 1356 1357 if (unlikely (trace)) { 1358 current->ptrace_message = nr; 1359 ptrace_notify ((trace << 8) | SIGTRAP); 1360 } 1361 1362 if (clone_flags & CLONE_VFORK) { 1363 wait_for_completion(&vfork); 1364 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) 1365 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); 1366 } 1367 } else { 1368 free_pid(pid); 1369 nr = PTR_ERR(p); 1370 } 1371 return nr; 1372 } 1373 1374 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1375 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1376 #endif 1377 1378 static void sighand_ctor(void *data, kmem_cache_t *cachep, unsigned long flags) 1379 { 1380 struct sighand_struct *sighand = data; 1381 1382 if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) == 1383 SLAB_CTOR_CONSTRUCTOR) 1384 spin_lock_init(&sighand->siglock); 1385 } 1386 1387 void __init proc_caches_init(void) 1388 { 1389 sighand_cachep = kmem_cache_create("sighand_cache", 1390 sizeof(struct sighand_struct), 0, 1391 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU, 1392 sighand_ctor, NULL); 1393 signal_cachep = kmem_cache_create("signal_cache", 1394 sizeof(struct signal_struct), 0, 1395 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1396 files_cachep = kmem_cache_create("files_cache", 1397 sizeof(struct files_struct), 0, 1398 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1399 fs_cachep = kmem_cache_create("fs_cache", 1400 sizeof(struct fs_struct), 0, 1401 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1402 vm_area_cachep = kmem_cache_create("vm_area_struct", 1403 sizeof(struct vm_area_struct), 0, 1404 SLAB_PANIC, NULL, NULL); 1405 mm_cachep = kmem_cache_create("mm_struct", 1406 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1407 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1408 } 1409 1410 1411 /* 1412 * Check constraints on flags passed to the unshare system call and 1413 * force unsharing of additional process context as appropriate. 1414 */ 1415 static inline void check_unshare_flags(unsigned long *flags_ptr) 1416 { 1417 /* 1418 * If unsharing a thread from a thread group, must also 1419 * unshare vm. 1420 */ 1421 if (*flags_ptr & CLONE_THREAD) 1422 *flags_ptr |= CLONE_VM; 1423 1424 /* 1425 * If unsharing vm, must also unshare signal handlers. 1426 */ 1427 if (*flags_ptr & CLONE_VM) 1428 *flags_ptr |= CLONE_SIGHAND; 1429 1430 /* 1431 * If unsharing signal handlers and the task was created 1432 * using CLONE_THREAD, then must unshare the thread 1433 */ 1434 if ((*flags_ptr & CLONE_SIGHAND) && 1435 (atomic_read(¤t->signal->count) > 1)) 1436 *flags_ptr |= CLONE_THREAD; 1437 1438 /* 1439 * If unsharing namespace, must also unshare filesystem information. 1440 */ 1441 if (*flags_ptr & CLONE_NEWNS) 1442 *flags_ptr |= CLONE_FS; 1443 } 1444 1445 /* 1446 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1447 */ 1448 static int unshare_thread(unsigned long unshare_flags) 1449 { 1450 if (unshare_flags & CLONE_THREAD) 1451 return -EINVAL; 1452 1453 return 0; 1454 } 1455 1456 /* 1457 * Unshare the filesystem structure if it is being shared 1458 */ 1459 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1460 { 1461 struct fs_struct *fs = current->fs; 1462 1463 if ((unshare_flags & CLONE_FS) && 1464 (fs && atomic_read(&fs->count) > 1)) { 1465 *new_fsp = __copy_fs_struct(current->fs); 1466 if (!*new_fsp) 1467 return -ENOMEM; 1468 } 1469 1470 return 0; 1471 } 1472 1473 /* 1474 * Unshare the namespace structure if it is being shared 1475 */ 1476 static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs) 1477 { 1478 struct namespace *ns = current->namespace; 1479 1480 if ((unshare_flags & CLONE_NEWNS) && 1481 (ns && atomic_read(&ns->count) > 1)) { 1482 if (!capable(CAP_SYS_ADMIN)) 1483 return -EPERM; 1484 1485 *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs); 1486 if (!*new_nsp) 1487 return -ENOMEM; 1488 } 1489 1490 return 0; 1491 } 1492 1493 /* 1494 * Unsharing of sighand for tasks created with CLONE_SIGHAND is not 1495 * supported yet 1496 */ 1497 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1498 { 1499 struct sighand_struct *sigh = current->sighand; 1500 1501 if ((unshare_flags & CLONE_SIGHAND) && 1502 (sigh && atomic_read(&sigh->count) > 1)) 1503 return -EINVAL; 1504 else 1505 return 0; 1506 } 1507 1508 /* 1509 * Unshare vm if it is being shared 1510 */ 1511 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1512 { 1513 struct mm_struct *mm = current->mm; 1514 1515 if ((unshare_flags & CLONE_VM) && 1516 (mm && atomic_read(&mm->mm_users) > 1)) { 1517 return -EINVAL; 1518 } 1519 1520 return 0; 1521 } 1522 1523 /* 1524 * Unshare file descriptor table if it is being shared 1525 */ 1526 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1527 { 1528 struct files_struct *fd = current->files; 1529 int error = 0; 1530 1531 if ((unshare_flags & CLONE_FILES) && 1532 (fd && atomic_read(&fd->count) > 1)) { 1533 *new_fdp = dup_fd(fd, &error); 1534 if (!*new_fdp) 1535 return error; 1536 } 1537 1538 return 0; 1539 } 1540 1541 /* 1542 * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not 1543 * supported yet 1544 */ 1545 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp) 1546 { 1547 if (unshare_flags & CLONE_SYSVSEM) 1548 return -EINVAL; 1549 1550 return 0; 1551 } 1552 1553 /* 1554 * unshare allows a process to 'unshare' part of the process 1555 * context which was originally shared using clone. copy_* 1556 * functions used by do_fork() cannot be used here directly 1557 * because they modify an inactive task_struct that is being 1558 * constructed. Here we are modifying the current, active, 1559 * task_struct. 1560 */ 1561 asmlinkage long sys_unshare(unsigned long unshare_flags) 1562 { 1563 int err = 0; 1564 struct fs_struct *fs, *new_fs = NULL; 1565 struct namespace *ns, *new_ns = NULL; 1566 struct sighand_struct *sigh, *new_sigh = NULL; 1567 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1568 struct files_struct *fd, *new_fd = NULL; 1569 struct sem_undo_list *new_ulist = NULL; 1570 1571 check_unshare_flags(&unshare_flags); 1572 1573 /* Return -EINVAL for all unsupported flags */ 1574 err = -EINVAL; 1575 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1576 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM)) 1577 goto bad_unshare_out; 1578 1579 if ((err = unshare_thread(unshare_flags))) 1580 goto bad_unshare_out; 1581 if ((err = unshare_fs(unshare_flags, &new_fs))) 1582 goto bad_unshare_cleanup_thread; 1583 if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs))) 1584 goto bad_unshare_cleanup_fs; 1585 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1586 goto bad_unshare_cleanup_ns; 1587 if ((err = unshare_vm(unshare_flags, &new_mm))) 1588 goto bad_unshare_cleanup_sigh; 1589 if ((err = unshare_fd(unshare_flags, &new_fd))) 1590 goto bad_unshare_cleanup_vm; 1591 if ((err = unshare_semundo(unshare_flags, &new_ulist))) 1592 goto bad_unshare_cleanup_fd; 1593 1594 if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) { 1595 1596 task_lock(current); 1597 1598 if (new_fs) { 1599 fs = current->fs; 1600 current->fs = new_fs; 1601 new_fs = fs; 1602 } 1603 1604 if (new_ns) { 1605 ns = current->namespace; 1606 current->namespace = new_ns; 1607 new_ns = ns; 1608 } 1609 1610 if (new_sigh) { 1611 sigh = current->sighand; 1612 rcu_assign_pointer(current->sighand, new_sigh); 1613 new_sigh = sigh; 1614 } 1615 1616 if (new_mm) { 1617 mm = current->mm; 1618 active_mm = current->active_mm; 1619 current->mm = new_mm; 1620 current->active_mm = new_mm; 1621 activate_mm(active_mm, new_mm); 1622 new_mm = mm; 1623 } 1624 1625 if (new_fd) { 1626 fd = current->files; 1627 current->files = new_fd; 1628 new_fd = fd; 1629 } 1630 1631 task_unlock(current); 1632 } 1633 1634 bad_unshare_cleanup_fd: 1635 if (new_fd) 1636 put_files_struct(new_fd); 1637 1638 bad_unshare_cleanup_vm: 1639 if (new_mm) 1640 mmput(new_mm); 1641 1642 bad_unshare_cleanup_sigh: 1643 if (new_sigh) 1644 if (atomic_dec_and_test(&new_sigh->count)) 1645 kmem_cache_free(sighand_cachep, new_sigh); 1646 1647 bad_unshare_cleanup_ns: 1648 if (new_ns) 1649 put_namespace(new_ns); 1650 1651 bad_unshare_cleanup_fs: 1652 if (new_fs) 1653 put_fs_struct(new_fs); 1654 1655 bad_unshare_cleanup_thread: 1656 bad_unshare_out: 1657 return err; 1658 } 1659