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 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 free_task_struct(tsk); 108 } 109 EXPORT_SYMBOL(free_task); 110 111 void __put_task_struct_cb(struct rcu_head *rhp) 112 { 113 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu); 114 115 WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE))); 116 WARN_ON(atomic_read(&tsk->usage)); 117 WARN_ON(tsk == current); 118 119 if (unlikely(tsk->audit_context)) 120 audit_free(tsk); 121 security_task_free(tsk); 122 free_uid(tsk->user); 123 put_group_info(tsk->group_info); 124 125 if (!profile_handoff_task(tsk)) 126 free_task(tsk); 127 } 128 129 void __init fork_init(unsigned long mempages) 130 { 131 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 132 #ifndef ARCH_MIN_TASKALIGN 133 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 134 #endif 135 /* create a slab on which task_structs can be allocated */ 136 task_struct_cachep = 137 kmem_cache_create("task_struct", sizeof(struct task_struct), 138 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL); 139 #endif 140 141 /* 142 * The default maximum number of threads is set to a safe 143 * value: the thread structures can take up at most half 144 * of memory. 145 */ 146 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 147 148 /* 149 * we need to allow at least 20 threads to boot a system 150 */ 151 if(max_threads < 20) 152 max_threads = 20; 153 154 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 155 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 156 init_task.signal->rlim[RLIMIT_SIGPENDING] = 157 init_task.signal->rlim[RLIMIT_NPROC]; 158 } 159 160 static struct task_struct *dup_task_struct(struct task_struct *orig) 161 { 162 struct task_struct *tsk; 163 struct thread_info *ti; 164 165 prepare_to_copy(orig); 166 167 tsk = alloc_task_struct(); 168 if (!tsk) 169 return NULL; 170 171 ti = alloc_thread_info(tsk); 172 if (!ti) { 173 free_task_struct(tsk); 174 return NULL; 175 } 176 177 *tsk = *orig; 178 tsk->thread_info = ti; 179 setup_thread_stack(tsk, orig); 180 181 /* One for us, one for whoever does the "release_task()" (usually parent) */ 182 atomic_set(&tsk->usage,2); 183 atomic_set(&tsk->fs_excl, 0); 184 tsk->btrace_seq = 0; 185 return tsk; 186 } 187 188 #ifdef CONFIG_MMU 189 static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 190 { 191 struct vm_area_struct *mpnt, *tmp, **pprev; 192 struct rb_node **rb_link, *rb_parent; 193 int retval; 194 unsigned long charge; 195 struct mempolicy *pol; 196 197 down_write(&oldmm->mmap_sem); 198 flush_cache_mm(oldmm); 199 down_write(&mm->mmap_sem); 200 201 mm->locked_vm = 0; 202 mm->mmap = NULL; 203 mm->mmap_cache = NULL; 204 mm->free_area_cache = oldmm->mmap_base; 205 mm->cached_hole_size = ~0UL; 206 mm->map_count = 0; 207 cpus_clear(mm->cpu_vm_mask); 208 mm->mm_rb = RB_ROOT; 209 rb_link = &mm->mm_rb.rb_node; 210 rb_parent = NULL; 211 pprev = &mm->mmap; 212 213 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 214 struct file *file; 215 216 if (mpnt->vm_flags & VM_DONTCOPY) { 217 long pages = vma_pages(mpnt); 218 mm->total_vm -= pages; 219 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 220 -pages); 221 continue; 222 } 223 charge = 0; 224 if (mpnt->vm_flags & VM_ACCOUNT) { 225 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 226 if (security_vm_enough_memory(len)) 227 goto fail_nomem; 228 charge = len; 229 } 230 tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL); 231 if (!tmp) 232 goto fail_nomem; 233 *tmp = *mpnt; 234 pol = mpol_copy(vma_policy(mpnt)); 235 retval = PTR_ERR(pol); 236 if (IS_ERR(pol)) 237 goto fail_nomem_policy; 238 vma_set_policy(tmp, pol); 239 tmp->vm_flags &= ~VM_LOCKED; 240 tmp->vm_mm = mm; 241 tmp->vm_next = NULL; 242 anon_vma_link(tmp); 243 file = tmp->vm_file; 244 if (file) { 245 struct inode *inode = file->f_dentry->d_inode; 246 get_file(file); 247 if (tmp->vm_flags & VM_DENYWRITE) 248 atomic_dec(&inode->i_writecount); 249 250 /* insert tmp into the share list, just after mpnt */ 251 spin_lock(&file->f_mapping->i_mmap_lock); 252 tmp->vm_truncate_count = mpnt->vm_truncate_count; 253 flush_dcache_mmap_lock(file->f_mapping); 254 vma_prio_tree_add(tmp, mpnt); 255 flush_dcache_mmap_unlock(file->f_mapping); 256 spin_unlock(&file->f_mapping->i_mmap_lock); 257 } 258 259 /* 260 * Link in the new vma and copy the page table entries. 261 */ 262 *pprev = tmp; 263 pprev = &tmp->vm_next; 264 265 __vma_link_rb(mm, tmp, rb_link, rb_parent); 266 rb_link = &tmp->vm_rb.rb_right; 267 rb_parent = &tmp->vm_rb; 268 269 mm->map_count++; 270 retval = copy_page_range(mm, oldmm, mpnt); 271 272 if (tmp->vm_ops && tmp->vm_ops->open) 273 tmp->vm_ops->open(tmp); 274 275 if (retval) 276 goto out; 277 } 278 retval = 0; 279 out: 280 up_write(&mm->mmap_sem); 281 flush_tlb_mm(oldmm); 282 up_write(&oldmm->mmap_sem); 283 return retval; 284 fail_nomem_policy: 285 kmem_cache_free(vm_area_cachep, tmp); 286 fail_nomem: 287 retval = -ENOMEM; 288 vm_unacct_memory(charge); 289 goto out; 290 } 291 292 static inline int mm_alloc_pgd(struct mm_struct * mm) 293 { 294 mm->pgd = pgd_alloc(mm); 295 if (unlikely(!mm->pgd)) 296 return -ENOMEM; 297 return 0; 298 } 299 300 static inline void mm_free_pgd(struct mm_struct * mm) 301 { 302 pgd_free(mm->pgd); 303 } 304 #else 305 #define dup_mmap(mm, oldmm) (0) 306 #define mm_alloc_pgd(mm) (0) 307 #define mm_free_pgd(mm) 308 #endif /* CONFIG_MMU */ 309 310 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 311 312 #define allocate_mm() (kmem_cache_alloc(mm_cachep, SLAB_KERNEL)) 313 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 314 315 #include <linux/init_task.h> 316 317 static struct mm_struct * mm_init(struct mm_struct * mm) 318 { 319 atomic_set(&mm->mm_users, 1); 320 atomic_set(&mm->mm_count, 1); 321 init_rwsem(&mm->mmap_sem); 322 INIT_LIST_HEAD(&mm->mmlist); 323 mm->core_waiters = 0; 324 mm->nr_ptes = 0; 325 set_mm_counter(mm, file_rss, 0); 326 set_mm_counter(mm, anon_rss, 0); 327 spin_lock_init(&mm->page_table_lock); 328 rwlock_init(&mm->ioctx_list_lock); 329 mm->ioctx_list = NULL; 330 mm->free_area_cache = TASK_UNMAPPED_BASE; 331 mm->cached_hole_size = ~0UL; 332 333 if (likely(!mm_alloc_pgd(mm))) { 334 mm->def_flags = 0; 335 return mm; 336 } 337 free_mm(mm); 338 return NULL; 339 } 340 341 /* 342 * Allocate and initialize an mm_struct. 343 */ 344 struct mm_struct * mm_alloc(void) 345 { 346 struct mm_struct * mm; 347 348 mm = allocate_mm(); 349 if (mm) { 350 memset(mm, 0, sizeof(*mm)); 351 mm = mm_init(mm); 352 } 353 return mm; 354 } 355 356 /* 357 * Called when the last reference to the mm 358 * is dropped: either by a lazy thread or by 359 * mmput. Free the page directory and the mm. 360 */ 361 void fastcall __mmdrop(struct mm_struct *mm) 362 { 363 BUG_ON(mm == &init_mm); 364 mm_free_pgd(mm); 365 destroy_context(mm); 366 free_mm(mm); 367 } 368 369 /* 370 * Decrement the use count and release all resources for an mm. 371 */ 372 void mmput(struct mm_struct *mm) 373 { 374 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 */ 630 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) 631 { 632 struct files_struct *newf; 633 struct file **old_fds, **new_fds; 634 int open_files, size, i, expand; 635 struct fdtable *old_fdt, *new_fdt; 636 637 newf = alloc_files(); 638 if (!newf) 639 goto out; 640 641 spin_lock(&oldf->file_lock); 642 old_fdt = files_fdtable(oldf); 643 new_fdt = files_fdtable(newf); 644 size = old_fdt->max_fdset; 645 open_files = count_open_files(old_fdt); 646 expand = 0; 647 648 /* 649 * Check whether we need to allocate a larger fd array or fd set. 650 * Note: we're not a clone task, so the open count won't change. 651 */ 652 if (open_files > new_fdt->max_fdset) { 653 new_fdt->max_fdset = 0; 654 expand = 1; 655 } 656 if (open_files > new_fdt->max_fds) { 657 new_fdt->max_fds = 0; 658 expand = 1; 659 } 660 661 /* if the old fdset gets grown now, we'll only copy up to "size" fds */ 662 if (expand) { 663 spin_unlock(&oldf->file_lock); 664 spin_lock(&newf->file_lock); 665 *errorp = expand_files(newf, open_files-1); 666 spin_unlock(&newf->file_lock); 667 if (*errorp < 0) 668 goto out_release; 669 new_fdt = files_fdtable(newf); 670 /* 671 * Reacquire the oldf lock and a pointer to its fd table 672 * who knows it may have a new bigger fd table. We need 673 * the latest pointer. 674 */ 675 spin_lock(&oldf->file_lock); 676 old_fdt = files_fdtable(oldf); 677 } 678 679 old_fds = old_fdt->fd; 680 new_fds = new_fdt->fd; 681 682 memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8); 683 memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8); 684 685 for (i = open_files; i != 0; i--) { 686 struct file *f = *old_fds++; 687 if (f) { 688 get_file(f); 689 } else { 690 /* 691 * The fd may be claimed in the fd bitmap but not yet 692 * instantiated in the files array if a sibling thread 693 * is partway through open(). So make sure that this 694 * fd is available to the new process. 695 */ 696 FD_CLR(open_files - i, new_fdt->open_fds); 697 } 698 rcu_assign_pointer(*new_fds++, f); 699 } 700 spin_unlock(&oldf->file_lock); 701 702 /* compute the remainder to be cleared */ 703 size = (new_fdt->max_fds - open_files) * sizeof(struct file *); 704 705 /* This is long word aligned thus could use a optimized version */ 706 memset(new_fds, 0, size); 707 708 if (new_fdt->max_fdset > open_files) { 709 int left = (new_fdt->max_fdset-open_files)/8; 710 int start = open_files / (8 * sizeof(unsigned long)); 711 712 memset(&new_fdt->open_fds->fds_bits[start], 0, left); 713 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left); 714 } 715 716 out: 717 return newf; 718 719 out_release: 720 free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset); 721 free_fdset (new_fdt->open_fds, new_fdt->max_fdset); 722 free_fd_array(new_fdt->fd, new_fdt->max_fds); 723 kmem_cache_free(files_cachep, newf); 724 goto out; 725 } 726 727 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 728 { 729 struct files_struct *oldf, *newf; 730 int error = 0; 731 732 /* 733 * A background process may not have any files ... 734 */ 735 oldf = current->files; 736 if (!oldf) 737 goto out; 738 739 if (clone_flags & CLONE_FILES) { 740 atomic_inc(&oldf->count); 741 goto out; 742 } 743 744 /* 745 * Note: we may be using current for both targets (See exec.c) 746 * This works because we cache current->files (old) as oldf. Don't 747 * break this. 748 */ 749 tsk->files = NULL; 750 error = -ENOMEM; 751 newf = dup_fd(oldf, &error); 752 if (!newf) 753 goto out; 754 755 tsk->files = newf; 756 error = 0; 757 out: 758 return error; 759 } 760 761 /* 762 * Helper to unshare the files of the current task. 763 * We don't want to expose copy_files internals to 764 * the exec layer of the kernel. 765 */ 766 767 int unshare_files(void) 768 { 769 struct files_struct *files = current->files; 770 int rc; 771 772 if(!files) 773 BUG(); 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 void sighand_free_cb(struct rcu_head *rhp) 791 { 792 struct sighand_struct *sp; 793 794 sp = container_of(rhp, struct sighand_struct, rcu); 795 kmem_cache_free(sighand_cachep, sp); 796 } 797 798 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk) 799 { 800 struct sighand_struct *sig; 801 802 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 803 atomic_inc(¤t->sighand->count); 804 return 0; 805 } 806 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 807 rcu_assign_pointer(tsk->sighand, sig); 808 if (!sig) 809 return -ENOMEM; 810 spin_lock_init(&sig->siglock); 811 atomic_set(&sig->count, 1); 812 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 813 return 0; 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 return 0; 825 } 826 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 827 tsk->signal = sig; 828 if (!sig) 829 return -ENOMEM; 830 831 ret = copy_thread_group_keys(tsk); 832 if (ret < 0) { 833 kmem_cache_free(signal_cachep, sig); 834 return ret; 835 } 836 837 atomic_set(&sig->count, 1); 838 atomic_set(&sig->live, 1); 839 init_waitqueue_head(&sig->wait_chldexit); 840 sig->flags = 0; 841 sig->group_exit_code = 0; 842 sig->group_exit_task = NULL; 843 sig->group_stop_count = 0; 844 sig->curr_target = NULL; 845 init_sigpending(&sig->shared_pending); 846 INIT_LIST_HEAD(&sig->posix_timers); 847 848 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL); 849 sig->it_real_incr.tv64 = 0; 850 sig->real_timer.function = it_real_fn; 851 sig->real_timer.data = tsk; 852 853 sig->it_virt_expires = cputime_zero; 854 sig->it_virt_incr = cputime_zero; 855 sig->it_prof_expires = cputime_zero; 856 sig->it_prof_incr = cputime_zero; 857 858 sig->leader = 0; /* session leadership doesn't inherit */ 859 sig->tty_old_pgrp = 0; 860 861 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 862 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 863 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 864 sig->sched_time = 0; 865 INIT_LIST_HEAD(&sig->cpu_timers[0]); 866 INIT_LIST_HEAD(&sig->cpu_timers[1]); 867 INIT_LIST_HEAD(&sig->cpu_timers[2]); 868 869 task_lock(current->group_leader); 870 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 871 task_unlock(current->group_leader); 872 873 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 874 /* 875 * New sole thread in the process gets an expiry time 876 * of the whole CPU time limit. 877 */ 878 tsk->it_prof_expires = 879 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 880 } 881 882 return 0; 883 } 884 885 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p) 886 { 887 unsigned long new_flags = p->flags; 888 889 new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE); 890 new_flags |= PF_FORKNOEXEC; 891 if (!(clone_flags & CLONE_PTRACE)) 892 p->ptrace = 0; 893 p->flags = new_flags; 894 } 895 896 asmlinkage long sys_set_tid_address(int __user *tidptr) 897 { 898 current->clear_child_tid = tidptr; 899 900 return current->pid; 901 } 902 903 /* 904 * This creates a new process as a copy of the old one, 905 * but does not actually start it yet. 906 * 907 * It copies the registers, and all the appropriate 908 * parts of the process environment (as per the clone 909 * flags). The actual kick-off is left to the caller. 910 */ 911 static task_t *copy_process(unsigned long clone_flags, 912 unsigned long stack_start, 913 struct pt_regs *regs, 914 unsigned long stack_size, 915 int __user *parent_tidptr, 916 int __user *child_tidptr, 917 int pid) 918 { 919 int retval; 920 struct task_struct *p = NULL; 921 922 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 923 return ERR_PTR(-EINVAL); 924 925 /* 926 * Thread groups must share signals as well, and detached threads 927 * can only be started up within the thread group. 928 */ 929 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 930 return ERR_PTR(-EINVAL); 931 932 /* 933 * Shared signal handlers imply shared VM. By way of the above, 934 * thread groups also imply shared VM. Blocking this case allows 935 * for various simplifications in other code. 936 */ 937 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 938 return ERR_PTR(-EINVAL); 939 940 retval = security_task_create(clone_flags); 941 if (retval) 942 goto fork_out; 943 944 retval = -ENOMEM; 945 p = dup_task_struct(current); 946 if (!p) 947 goto fork_out; 948 949 retval = -EAGAIN; 950 if (atomic_read(&p->user->processes) >= 951 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 952 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 953 p->user != &root_user) 954 goto bad_fork_free; 955 } 956 957 atomic_inc(&p->user->__count); 958 atomic_inc(&p->user->processes); 959 get_group_info(p->group_info); 960 961 /* 962 * If multiple threads are within copy_process(), then this check 963 * triggers too late. This doesn't hurt, the check is only there 964 * to stop root fork bombs. 965 */ 966 if (nr_threads >= max_threads) 967 goto bad_fork_cleanup_count; 968 969 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 970 goto bad_fork_cleanup_count; 971 972 if (p->binfmt && !try_module_get(p->binfmt->module)) 973 goto bad_fork_cleanup_put_domain; 974 975 p->did_exec = 0; 976 copy_flags(clone_flags, p); 977 p->pid = pid; 978 retval = -EFAULT; 979 if (clone_flags & CLONE_PARENT_SETTID) 980 if (put_user(p->pid, parent_tidptr)) 981 goto bad_fork_cleanup; 982 983 p->proc_dentry = NULL; 984 985 INIT_LIST_HEAD(&p->children); 986 INIT_LIST_HEAD(&p->sibling); 987 p->vfork_done = NULL; 988 spin_lock_init(&p->alloc_lock); 989 spin_lock_init(&p->proc_lock); 990 991 clear_tsk_thread_flag(p, TIF_SIGPENDING); 992 init_sigpending(&p->pending); 993 994 p->utime = cputime_zero; 995 p->stime = cputime_zero; 996 p->sched_time = 0; 997 p->rchar = 0; /* I/O counter: bytes read */ 998 p->wchar = 0; /* I/O counter: bytes written */ 999 p->syscr = 0; /* I/O counter: read syscalls */ 1000 p->syscw = 0; /* I/O counter: write syscalls */ 1001 acct_clear_integrals(p); 1002 1003 p->it_virt_expires = cputime_zero; 1004 p->it_prof_expires = cputime_zero; 1005 p->it_sched_expires = 0; 1006 INIT_LIST_HEAD(&p->cpu_timers[0]); 1007 INIT_LIST_HEAD(&p->cpu_timers[1]); 1008 INIT_LIST_HEAD(&p->cpu_timers[2]); 1009 1010 p->lock_depth = -1; /* -1 = no lock */ 1011 do_posix_clock_monotonic_gettime(&p->start_time); 1012 p->security = NULL; 1013 p->io_context = NULL; 1014 p->io_wait = NULL; 1015 p->audit_context = NULL; 1016 cpuset_fork(p); 1017 #ifdef CONFIG_NUMA 1018 p->mempolicy = mpol_copy(p->mempolicy); 1019 if (IS_ERR(p->mempolicy)) { 1020 retval = PTR_ERR(p->mempolicy); 1021 p->mempolicy = NULL; 1022 goto bad_fork_cleanup_cpuset; 1023 } 1024 mpol_fix_fork_child_flag(p); 1025 #endif 1026 1027 #ifdef CONFIG_DEBUG_MUTEXES 1028 p->blocked_on = NULL; /* not blocked yet */ 1029 #endif 1030 1031 p->tgid = p->pid; 1032 if (clone_flags & CLONE_THREAD) 1033 p->tgid = current->tgid; 1034 1035 if ((retval = security_task_alloc(p))) 1036 goto bad_fork_cleanup_policy; 1037 if ((retval = audit_alloc(p))) 1038 goto bad_fork_cleanup_security; 1039 /* copy all the process information */ 1040 if ((retval = copy_semundo(clone_flags, p))) 1041 goto bad_fork_cleanup_audit; 1042 if ((retval = copy_files(clone_flags, p))) 1043 goto bad_fork_cleanup_semundo; 1044 if ((retval = copy_fs(clone_flags, p))) 1045 goto bad_fork_cleanup_files; 1046 if ((retval = copy_sighand(clone_flags, p))) 1047 goto bad_fork_cleanup_fs; 1048 if ((retval = copy_signal(clone_flags, p))) 1049 goto bad_fork_cleanup_sighand; 1050 if ((retval = copy_mm(clone_flags, p))) 1051 goto bad_fork_cleanup_signal; 1052 if ((retval = copy_keys(clone_flags, p))) 1053 goto bad_fork_cleanup_mm; 1054 if ((retval = copy_namespace(clone_flags, p))) 1055 goto bad_fork_cleanup_keys; 1056 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1057 if (retval) 1058 goto bad_fork_cleanup_namespace; 1059 1060 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1061 /* 1062 * Clear TID on mm_release()? 1063 */ 1064 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1065 1066 /* 1067 * sigaltstack should be cleared when sharing the same VM 1068 */ 1069 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1070 p->sas_ss_sp = p->sas_ss_size = 0; 1071 1072 /* 1073 * Syscall tracing should be turned off in the child regardless 1074 * of CLONE_PTRACE. 1075 */ 1076 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1077 #ifdef TIF_SYSCALL_EMU 1078 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1079 #endif 1080 1081 /* Our parent execution domain becomes current domain 1082 These must match for thread signalling to apply */ 1083 1084 p->parent_exec_id = p->self_exec_id; 1085 1086 /* ok, now we should be set up.. */ 1087 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1088 p->pdeath_signal = 0; 1089 p->exit_state = 0; 1090 1091 /* 1092 * Ok, make it visible to the rest of the system. 1093 * We dont wake it up yet. 1094 */ 1095 p->group_leader = p; 1096 INIT_LIST_HEAD(&p->ptrace_children); 1097 INIT_LIST_HEAD(&p->ptrace_list); 1098 1099 /* Perform scheduler related setup. Assign this task to a CPU. */ 1100 sched_fork(p, clone_flags); 1101 1102 /* Need tasklist lock for parent etc handling! */ 1103 write_lock_irq(&tasklist_lock); 1104 1105 /* 1106 * The task hasn't been attached yet, so its cpus_allowed mask will 1107 * not be changed, nor will its assigned CPU. 1108 * 1109 * The cpus_allowed mask of the parent may have changed after it was 1110 * copied first time - so re-copy it here, then check the child's CPU 1111 * to ensure it is on a valid CPU (and if not, just force it back to 1112 * parent's CPU). This avoids alot of nasty races. 1113 */ 1114 p->cpus_allowed = current->cpus_allowed; 1115 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1116 !cpu_online(task_cpu(p)))) 1117 set_task_cpu(p, smp_processor_id()); 1118 1119 /* 1120 * Check for pending SIGKILL! The new thread should not be allowed 1121 * to slip out of an OOM kill. (or normal SIGKILL.) 1122 */ 1123 if (sigismember(¤t->pending.signal, SIGKILL)) { 1124 write_unlock_irq(&tasklist_lock); 1125 retval = -EINTR; 1126 goto bad_fork_cleanup_namespace; 1127 } 1128 1129 /* CLONE_PARENT re-uses the old parent */ 1130 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1131 p->real_parent = current->real_parent; 1132 else 1133 p->real_parent = current; 1134 p->parent = p->real_parent; 1135 1136 spin_lock(¤t->sighand->siglock); 1137 if (clone_flags & CLONE_THREAD) { 1138 /* 1139 * Important: if an exit-all has been started then 1140 * do not create this new thread - the whole thread 1141 * group is supposed to exit anyway. 1142 */ 1143 if (current->signal->flags & SIGNAL_GROUP_EXIT) { 1144 spin_unlock(¤t->sighand->siglock); 1145 write_unlock_irq(&tasklist_lock); 1146 retval = -EAGAIN; 1147 goto bad_fork_cleanup_namespace; 1148 } 1149 p->group_leader = current->group_leader; 1150 1151 if (current->signal->group_stop_count > 0) { 1152 /* 1153 * There is an all-stop in progress for the group. 1154 * We ourselves will stop as soon as we check signals. 1155 * Make the new thread part of that group stop too. 1156 */ 1157 current->signal->group_stop_count++; 1158 set_tsk_thread_flag(p, TIF_SIGPENDING); 1159 } 1160 1161 if (!cputime_eq(current->signal->it_virt_expires, 1162 cputime_zero) || 1163 !cputime_eq(current->signal->it_prof_expires, 1164 cputime_zero) || 1165 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1166 !list_empty(¤t->signal->cpu_timers[0]) || 1167 !list_empty(¤t->signal->cpu_timers[1]) || 1168 !list_empty(¤t->signal->cpu_timers[2])) { 1169 /* 1170 * Have child wake up on its first tick to check 1171 * for process CPU timers. 1172 */ 1173 p->it_prof_expires = jiffies_to_cputime(1); 1174 } 1175 } 1176 1177 /* 1178 * inherit ioprio 1179 */ 1180 p->ioprio = current->ioprio; 1181 1182 SET_LINKS(p); 1183 if (unlikely(p->ptrace & PT_PTRACED)) 1184 __ptrace_link(p, current->parent); 1185 1186 if (thread_group_leader(p)) { 1187 p->signal->tty = current->signal->tty; 1188 p->signal->pgrp = process_group(current); 1189 p->signal->session = current->signal->session; 1190 attach_pid(p, PIDTYPE_PGID, process_group(p)); 1191 attach_pid(p, PIDTYPE_SID, p->signal->session); 1192 if (p->pid) 1193 __get_cpu_var(process_counts)++; 1194 } 1195 attach_pid(p, PIDTYPE_TGID, p->tgid); 1196 attach_pid(p, PIDTYPE_PID, p->pid); 1197 1198 nr_threads++; 1199 total_forks++; 1200 spin_unlock(¤t->sighand->siglock); 1201 write_unlock_irq(&tasklist_lock); 1202 proc_fork_connector(p); 1203 return p; 1204 1205 bad_fork_cleanup_namespace: 1206 exit_namespace(p); 1207 bad_fork_cleanup_keys: 1208 exit_keys(p); 1209 bad_fork_cleanup_mm: 1210 if (p->mm) 1211 mmput(p->mm); 1212 bad_fork_cleanup_signal: 1213 exit_signal(p); 1214 bad_fork_cleanup_sighand: 1215 exit_sighand(p); 1216 bad_fork_cleanup_fs: 1217 exit_fs(p); /* blocking */ 1218 bad_fork_cleanup_files: 1219 exit_files(p); /* blocking */ 1220 bad_fork_cleanup_semundo: 1221 exit_sem(p); 1222 bad_fork_cleanup_audit: 1223 audit_free(p); 1224 bad_fork_cleanup_security: 1225 security_task_free(p); 1226 bad_fork_cleanup_policy: 1227 #ifdef CONFIG_NUMA 1228 mpol_free(p->mempolicy); 1229 bad_fork_cleanup_cpuset: 1230 #endif 1231 cpuset_exit(p); 1232 bad_fork_cleanup: 1233 if (p->binfmt) 1234 module_put(p->binfmt->module); 1235 bad_fork_cleanup_put_domain: 1236 module_put(task_thread_info(p)->exec_domain->module); 1237 bad_fork_cleanup_count: 1238 put_group_info(p->group_info); 1239 atomic_dec(&p->user->processes); 1240 free_uid(p->user); 1241 bad_fork_free: 1242 free_task(p); 1243 fork_out: 1244 return ERR_PTR(retval); 1245 } 1246 1247 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1248 { 1249 memset(regs, 0, sizeof(struct pt_regs)); 1250 return regs; 1251 } 1252 1253 task_t * __devinit fork_idle(int cpu) 1254 { 1255 task_t *task; 1256 struct pt_regs regs; 1257 1258 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, NULL, 0); 1259 if (!task) 1260 return ERR_PTR(-ENOMEM); 1261 init_idle(task, cpu); 1262 unhash_process(task); 1263 return task; 1264 } 1265 1266 static inline int fork_traceflag (unsigned clone_flags) 1267 { 1268 if (clone_flags & CLONE_UNTRACED) 1269 return 0; 1270 else if (clone_flags & CLONE_VFORK) { 1271 if (current->ptrace & PT_TRACE_VFORK) 1272 return PTRACE_EVENT_VFORK; 1273 } else if ((clone_flags & CSIGNAL) != SIGCHLD) { 1274 if (current->ptrace & PT_TRACE_CLONE) 1275 return PTRACE_EVENT_CLONE; 1276 } else if (current->ptrace & PT_TRACE_FORK) 1277 return PTRACE_EVENT_FORK; 1278 1279 return 0; 1280 } 1281 1282 /* 1283 * Ok, this is the main fork-routine. 1284 * 1285 * It copies the process, and if successful kick-starts 1286 * it and waits for it to finish using the VM if required. 1287 */ 1288 long do_fork(unsigned long clone_flags, 1289 unsigned long stack_start, 1290 struct pt_regs *regs, 1291 unsigned long stack_size, 1292 int __user *parent_tidptr, 1293 int __user *child_tidptr) 1294 { 1295 struct task_struct *p; 1296 int trace = 0; 1297 long pid = alloc_pidmap(); 1298 1299 if (pid < 0) 1300 return -EAGAIN; 1301 if (unlikely(current->ptrace)) { 1302 trace = fork_traceflag (clone_flags); 1303 if (trace) 1304 clone_flags |= CLONE_PTRACE; 1305 } 1306 1307 p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, pid); 1308 /* 1309 * Do this prior waking up the new thread - the thread pointer 1310 * might get invalid after that point, if the thread exits quickly. 1311 */ 1312 if (!IS_ERR(p)) { 1313 struct completion vfork; 1314 1315 if (clone_flags & CLONE_VFORK) { 1316 p->vfork_done = &vfork; 1317 init_completion(&vfork); 1318 } 1319 1320 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) { 1321 /* 1322 * We'll start up with an immediate SIGSTOP. 1323 */ 1324 sigaddset(&p->pending.signal, SIGSTOP); 1325 set_tsk_thread_flag(p, TIF_SIGPENDING); 1326 } 1327 1328 if (!(clone_flags & CLONE_STOPPED)) 1329 wake_up_new_task(p, clone_flags); 1330 else 1331 p->state = TASK_STOPPED; 1332 1333 if (unlikely (trace)) { 1334 current->ptrace_message = pid; 1335 ptrace_notify ((trace << 8) | SIGTRAP); 1336 } 1337 1338 if (clone_flags & CLONE_VFORK) { 1339 wait_for_completion(&vfork); 1340 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) 1341 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); 1342 } 1343 } else { 1344 free_pidmap(pid); 1345 pid = PTR_ERR(p); 1346 } 1347 return pid; 1348 } 1349 1350 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1351 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1352 #endif 1353 1354 void __init proc_caches_init(void) 1355 { 1356 sighand_cachep = kmem_cache_create("sighand_cache", 1357 sizeof(struct sighand_struct), 0, 1358 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1359 signal_cachep = kmem_cache_create("signal_cache", 1360 sizeof(struct signal_struct), 0, 1361 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1362 files_cachep = kmem_cache_create("files_cache", 1363 sizeof(struct files_struct), 0, 1364 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1365 fs_cachep = kmem_cache_create("fs_cache", 1366 sizeof(struct fs_struct), 0, 1367 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1368 vm_area_cachep = kmem_cache_create("vm_area_struct", 1369 sizeof(struct vm_area_struct), 0, 1370 SLAB_PANIC, NULL, NULL); 1371 mm_cachep = kmem_cache_create("mm_struct", 1372 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1373 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1374 } 1375 1376 1377 /* 1378 * Check constraints on flags passed to the unshare system call and 1379 * force unsharing of additional process context as appropriate. 1380 */ 1381 static inline void check_unshare_flags(unsigned long *flags_ptr) 1382 { 1383 /* 1384 * If unsharing a thread from a thread group, must also 1385 * unshare vm. 1386 */ 1387 if (*flags_ptr & CLONE_THREAD) 1388 *flags_ptr |= CLONE_VM; 1389 1390 /* 1391 * If unsharing vm, must also unshare signal handlers. 1392 */ 1393 if (*flags_ptr & CLONE_VM) 1394 *flags_ptr |= CLONE_SIGHAND; 1395 1396 /* 1397 * If unsharing signal handlers and the task was created 1398 * using CLONE_THREAD, then must unshare the thread 1399 */ 1400 if ((*flags_ptr & CLONE_SIGHAND) && 1401 (atomic_read(¤t->signal->count) > 1)) 1402 *flags_ptr |= CLONE_THREAD; 1403 1404 /* 1405 * If unsharing namespace, must also unshare filesystem information. 1406 */ 1407 if (*flags_ptr & CLONE_NEWNS) 1408 *flags_ptr |= CLONE_FS; 1409 } 1410 1411 /* 1412 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1413 */ 1414 static int unshare_thread(unsigned long unshare_flags) 1415 { 1416 if (unshare_flags & CLONE_THREAD) 1417 return -EINVAL; 1418 1419 return 0; 1420 } 1421 1422 /* 1423 * Unshare the filesystem structure if it is being shared 1424 */ 1425 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1426 { 1427 struct fs_struct *fs = current->fs; 1428 1429 if ((unshare_flags & CLONE_FS) && 1430 (fs && atomic_read(&fs->count) > 1)) { 1431 *new_fsp = __copy_fs_struct(current->fs); 1432 if (!*new_fsp) 1433 return -ENOMEM; 1434 } 1435 1436 return 0; 1437 } 1438 1439 /* 1440 * Unshare the namespace structure if it is being shared 1441 */ 1442 static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs) 1443 { 1444 struct namespace *ns = current->namespace; 1445 1446 if ((unshare_flags & CLONE_NEWNS) && 1447 (ns && atomic_read(&ns->count) > 1)) { 1448 if (!capable(CAP_SYS_ADMIN)) 1449 return -EPERM; 1450 1451 *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs); 1452 if (!*new_nsp) 1453 return -ENOMEM; 1454 } 1455 1456 return 0; 1457 } 1458 1459 /* 1460 * Unsharing of sighand for tasks created with CLONE_SIGHAND is not 1461 * supported yet 1462 */ 1463 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1464 { 1465 struct sighand_struct *sigh = current->sighand; 1466 1467 if ((unshare_flags & CLONE_SIGHAND) && 1468 (sigh && atomic_read(&sigh->count) > 1)) 1469 return -EINVAL; 1470 else 1471 return 0; 1472 } 1473 1474 /* 1475 * Unshare vm if it is being shared 1476 */ 1477 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1478 { 1479 struct mm_struct *mm = current->mm; 1480 1481 if ((unshare_flags & CLONE_VM) && 1482 (mm && atomic_read(&mm->mm_users) > 1)) { 1483 return -EINVAL; 1484 } 1485 1486 return 0; 1487 } 1488 1489 /* 1490 * Unshare file descriptor table if it is being shared 1491 */ 1492 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1493 { 1494 struct files_struct *fd = current->files; 1495 int error = 0; 1496 1497 if ((unshare_flags & CLONE_FILES) && 1498 (fd && atomic_read(&fd->count) > 1)) { 1499 *new_fdp = dup_fd(fd, &error); 1500 if (!*new_fdp) 1501 return error; 1502 } 1503 1504 return 0; 1505 } 1506 1507 /* 1508 * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not 1509 * supported yet 1510 */ 1511 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp) 1512 { 1513 if (unshare_flags & CLONE_SYSVSEM) 1514 return -EINVAL; 1515 1516 return 0; 1517 } 1518 1519 /* 1520 * unshare allows a process to 'unshare' part of the process 1521 * context which was originally shared using clone. copy_* 1522 * functions used by do_fork() cannot be used here directly 1523 * because they modify an inactive task_struct that is being 1524 * constructed. Here we are modifying the current, active, 1525 * task_struct. 1526 */ 1527 asmlinkage long sys_unshare(unsigned long unshare_flags) 1528 { 1529 int err = 0; 1530 struct fs_struct *fs, *new_fs = NULL; 1531 struct namespace *ns, *new_ns = NULL; 1532 struct sighand_struct *sigh, *new_sigh = NULL; 1533 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1534 struct files_struct *fd, *new_fd = NULL; 1535 struct sem_undo_list *new_ulist = NULL; 1536 1537 check_unshare_flags(&unshare_flags); 1538 1539 /* Return -EINVAL for all unsupported flags */ 1540 err = -EINVAL; 1541 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1542 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM)) 1543 goto bad_unshare_out; 1544 1545 if ((err = unshare_thread(unshare_flags))) 1546 goto bad_unshare_out; 1547 if ((err = unshare_fs(unshare_flags, &new_fs))) 1548 goto bad_unshare_cleanup_thread; 1549 if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs))) 1550 goto bad_unshare_cleanup_fs; 1551 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1552 goto bad_unshare_cleanup_ns; 1553 if ((err = unshare_vm(unshare_flags, &new_mm))) 1554 goto bad_unshare_cleanup_sigh; 1555 if ((err = unshare_fd(unshare_flags, &new_fd))) 1556 goto bad_unshare_cleanup_vm; 1557 if ((err = unshare_semundo(unshare_flags, &new_ulist))) 1558 goto bad_unshare_cleanup_fd; 1559 1560 if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) { 1561 1562 task_lock(current); 1563 1564 if (new_fs) { 1565 fs = current->fs; 1566 current->fs = new_fs; 1567 new_fs = fs; 1568 } 1569 1570 if (new_ns) { 1571 ns = current->namespace; 1572 current->namespace = new_ns; 1573 new_ns = ns; 1574 } 1575 1576 if (new_sigh) { 1577 sigh = current->sighand; 1578 rcu_assign_pointer(current->sighand, new_sigh); 1579 new_sigh = sigh; 1580 } 1581 1582 if (new_mm) { 1583 mm = current->mm; 1584 active_mm = current->active_mm; 1585 current->mm = new_mm; 1586 current->active_mm = new_mm; 1587 activate_mm(active_mm, new_mm); 1588 new_mm = mm; 1589 } 1590 1591 if (new_fd) { 1592 fd = current->files; 1593 current->files = new_fd; 1594 new_fd = fd; 1595 } 1596 1597 task_unlock(current); 1598 } 1599 1600 bad_unshare_cleanup_fd: 1601 if (new_fd) 1602 put_files_struct(new_fd); 1603 1604 bad_unshare_cleanup_vm: 1605 if (new_mm) 1606 mmput(new_mm); 1607 1608 bad_unshare_cleanup_sigh: 1609 if (new_sigh) 1610 if (atomic_dec_and_test(&new_sigh->count)) 1611 kmem_cache_free(sighand_cachep, new_sigh); 1612 1613 bad_unshare_cleanup_ns: 1614 if (new_ns) 1615 put_namespace(new_ns); 1616 1617 bad_unshare_cleanup_fs: 1618 if (new_fs) 1619 put_fs_struct(new_fs); 1620 1621 bad_unshare_cleanup_thread: 1622 bad_unshare_out: 1623 return err; 1624 } 1625