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