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