1 /* 2 * linux/fs/exec.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7 /* 8 * #!-checking implemented by tytso. 9 */ 10 /* 11 * Demand-loading implemented 01.12.91 - no need to read anything but 12 * the header into memory. The inode of the executable is put into 13 * "current->executable", and page faults do the actual loading. Clean. 14 * 15 * Once more I can proudly say that linux stood up to being changed: it 16 * was less than 2 hours work to get demand-loading completely implemented. 17 * 18 * Demand loading changed July 1993 by Eric Youngdale. Use mmap instead, 19 * current->executable is only used by the procfs. This allows a dispatch 20 * table to check for several different types of binary formats. We keep 21 * trying until we recognize the file or we run out of supported binary 22 * formats. 23 */ 24 25 #include <linux/slab.h> 26 #include <linux/file.h> 27 #include <linux/fdtable.h> 28 #include <linux/mm.h> 29 #include <linux/stat.h> 30 #include <linux/fcntl.h> 31 #include <linux/smp_lock.h> 32 #include <linux/swap.h> 33 #include <linux/string.h> 34 #include <linux/init.h> 35 #include <linux/pagemap.h> 36 #include <linux/highmem.h> 37 #include <linux/spinlock.h> 38 #include <linux/key.h> 39 #include <linux/personality.h> 40 #include <linux/binfmts.h> 41 #include <linux/utsname.h> 42 #include <linux/pid_namespace.h> 43 #include <linux/module.h> 44 #include <linux/namei.h> 45 #include <linux/proc_fs.h> 46 #include <linux/mount.h> 47 #include <linux/security.h> 48 #include <linux/syscalls.h> 49 #include <linux/tsacct_kern.h> 50 #include <linux/cn_proc.h> 51 #include <linux/audit.h> 52 #include <linux/tracehook.h> 53 #include <linux/kmod.h> 54 #include <linux/fsnotify.h> 55 56 #include <asm/uaccess.h> 57 #include <asm/mmu_context.h> 58 #include <asm/tlb.h> 59 #include "internal.h" 60 61 int core_uses_pid; 62 char core_pattern[CORENAME_MAX_SIZE] = "core"; 63 int suid_dumpable = 0; 64 65 /* The maximal length of core_pattern is also specified in sysctl.c */ 66 67 static LIST_HEAD(formats); 68 static DEFINE_RWLOCK(binfmt_lock); 69 70 int register_binfmt(struct linux_binfmt * fmt) 71 { 72 if (!fmt) 73 return -EINVAL; 74 write_lock(&binfmt_lock); 75 list_add(&fmt->lh, &formats); 76 write_unlock(&binfmt_lock); 77 return 0; 78 } 79 80 EXPORT_SYMBOL(register_binfmt); 81 82 void unregister_binfmt(struct linux_binfmt * fmt) 83 { 84 write_lock(&binfmt_lock); 85 list_del(&fmt->lh); 86 write_unlock(&binfmt_lock); 87 } 88 89 EXPORT_SYMBOL(unregister_binfmt); 90 91 static inline void put_binfmt(struct linux_binfmt * fmt) 92 { 93 module_put(fmt->module); 94 } 95 96 /* 97 * Note that a shared library must be both readable and executable due to 98 * security reasons. 99 * 100 * Also note that we take the address to load from from the file itself. 101 */ 102 SYSCALL_DEFINE1(uselib, const char __user *, library) 103 { 104 struct file *file; 105 struct nameidata nd; 106 char *tmp = getname(library); 107 int error = PTR_ERR(tmp); 108 109 if (!IS_ERR(tmp)) { 110 error = path_lookup_open(AT_FDCWD, tmp, 111 LOOKUP_FOLLOW, &nd, 112 FMODE_READ|FMODE_EXEC); 113 putname(tmp); 114 } 115 if (error) 116 goto out; 117 118 error = -EINVAL; 119 if (!S_ISREG(nd.path.dentry->d_inode->i_mode)) 120 goto exit; 121 122 error = -EACCES; 123 if (nd.path.mnt->mnt_flags & MNT_NOEXEC) 124 goto exit; 125 126 error = inode_permission(nd.path.dentry->d_inode, 127 MAY_READ | MAY_EXEC | MAY_OPEN); 128 if (error) 129 goto exit; 130 131 file = nameidata_to_filp(&nd, O_RDONLY|O_LARGEFILE); 132 error = PTR_ERR(file); 133 if (IS_ERR(file)) 134 goto out; 135 136 fsnotify_open(file->f_path.dentry); 137 138 error = -ENOEXEC; 139 if(file->f_op) { 140 struct linux_binfmt * fmt; 141 142 read_lock(&binfmt_lock); 143 list_for_each_entry(fmt, &formats, lh) { 144 if (!fmt->load_shlib) 145 continue; 146 if (!try_module_get(fmt->module)) 147 continue; 148 read_unlock(&binfmt_lock); 149 error = fmt->load_shlib(file); 150 read_lock(&binfmt_lock); 151 put_binfmt(fmt); 152 if (error != -ENOEXEC) 153 break; 154 } 155 read_unlock(&binfmt_lock); 156 } 157 fput(file); 158 out: 159 return error; 160 exit: 161 release_open_intent(&nd); 162 path_put(&nd.path); 163 goto out; 164 } 165 166 #ifdef CONFIG_MMU 167 168 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, 169 int write) 170 { 171 struct page *page; 172 int ret; 173 174 #ifdef CONFIG_STACK_GROWSUP 175 if (write) { 176 ret = expand_stack_downwards(bprm->vma, pos); 177 if (ret < 0) 178 return NULL; 179 } 180 #endif 181 ret = get_user_pages(current, bprm->mm, pos, 182 1, write, 1, &page, NULL); 183 if (ret <= 0) 184 return NULL; 185 186 if (write) { 187 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start; 188 struct rlimit *rlim; 189 190 /* 191 * We've historically supported up to 32 pages (ARG_MAX) 192 * of argument strings even with small stacks 193 */ 194 if (size <= ARG_MAX) 195 return page; 196 197 /* 198 * Limit to 1/4-th the stack size for the argv+env strings. 199 * This ensures that: 200 * - the remaining binfmt code will not run out of stack space, 201 * - the program will have a reasonable amount of stack left 202 * to work from. 203 */ 204 rlim = current->signal->rlim; 205 if (size > rlim[RLIMIT_STACK].rlim_cur / 4) { 206 put_page(page); 207 return NULL; 208 } 209 } 210 211 return page; 212 } 213 214 static void put_arg_page(struct page *page) 215 { 216 put_page(page); 217 } 218 219 static void free_arg_page(struct linux_binprm *bprm, int i) 220 { 221 } 222 223 static void free_arg_pages(struct linux_binprm *bprm) 224 { 225 } 226 227 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, 228 struct page *page) 229 { 230 flush_cache_page(bprm->vma, pos, page_to_pfn(page)); 231 } 232 233 static int __bprm_mm_init(struct linux_binprm *bprm) 234 { 235 int err; 236 struct vm_area_struct *vma = NULL; 237 struct mm_struct *mm = bprm->mm; 238 239 bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL); 240 if (!vma) 241 return -ENOMEM; 242 243 down_write(&mm->mmap_sem); 244 vma->vm_mm = mm; 245 246 /* 247 * Place the stack at the largest stack address the architecture 248 * supports. Later, we'll move this to an appropriate place. We don't 249 * use STACK_TOP because that can depend on attributes which aren't 250 * configured yet. 251 */ 252 vma->vm_end = STACK_TOP_MAX; 253 vma->vm_start = vma->vm_end - PAGE_SIZE; 254 vma->vm_flags = VM_STACK_FLAGS; 255 vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); 256 err = insert_vm_struct(mm, vma); 257 if (err) 258 goto err; 259 260 mm->stack_vm = mm->total_vm = 1; 261 up_write(&mm->mmap_sem); 262 bprm->p = vma->vm_end - sizeof(void *); 263 return 0; 264 err: 265 up_write(&mm->mmap_sem); 266 bprm->vma = NULL; 267 kmem_cache_free(vm_area_cachep, vma); 268 return err; 269 } 270 271 static bool valid_arg_len(struct linux_binprm *bprm, long len) 272 { 273 return len <= MAX_ARG_STRLEN; 274 } 275 276 #else 277 278 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, 279 int write) 280 { 281 struct page *page; 282 283 page = bprm->page[pos / PAGE_SIZE]; 284 if (!page && write) { 285 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO); 286 if (!page) 287 return NULL; 288 bprm->page[pos / PAGE_SIZE] = page; 289 } 290 291 return page; 292 } 293 294 static void put_arg_page(struct page *page) 295 { 296 } 297 298 static void free_arg_page(struct linux_binprm *bprm, int i) 299 { 300 if (bprm->page[i]) { 301 __free_page(bprm->page[i]); 302 bprm->page[i] = NULL; 303 } 304 } 305 306 static void free_arg_pages(struct linux_binprm *bprm) 307 { 308 int i; 309 310 for (i = 0; i < MAX_ARG_PAGES; i++) 311 free_arg_page(bprm, i); 312 } 313 314 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, 315 struct page *page) 316 { 317 } 318 319 static int __bprm_mm_init(struct linux_binprm *bprm) 320 { 321 bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *); 322 return 0; 323 } 324 325 static bool valid_arg_len(struct linux_binprm *bprm, long len) 326 { 327 return len <= bprm->p; 328 } 329 330 #endif /* CONFIG_MMU */ 331 332 /* 333 * Create a new mm_struct and populate it with a temporary stack 334 * vm_area_struct. We don't have enough context at this point to set the stack 335 * flags, permissions, and offset, so we use temporary values. We'll update 336 * them later in setup_arg_pages(). 337 */ 338 int bprm_mm_init(struct linux_binprm *bprm) 339 { 340 int err; 341 struct mm_struct *mm = NULL; 342 343 bprm->mm = mm = mm_alloc(); 344 err = -ENOMEM; 345 if (!mm) 346 goto err; 347 348 err = init_new_context(current, mm); 349 if (err) 350 goto err; 351 352 err = __bprm_mm_init(bprm); 353 if (err) 354 goto err; 355 356 return 0; 357 358 err: 359 if (mm) { 360 bprm->mm = NULL; 361 mmdrop(mm); 362 } 363 364 return err; 365 } 366 367 /* 368 * count() counts the number of strings in array ARGV. 369 */ 370 static int count(char __user * __user * argv, int max) 371 { 372 int i = 0; 373 374 if (argv != NULL) { 375 for (;;) { 376 char __user * p; 377 378 if (get_user(p, argv)) 379 return -EFAULT; 380 if (!p) 381 break; 382 argv++; 383 if (i++ >= max) 384 return -E2BIG; 385 cond_resched(); 386 } 387 } 388 return i; 389 } 390 391 /* 392 * 'copy_strings()' copies argument/environment strings from the old 393 * processes's memory to the new process's stack. The call to get_user_pages() 394 * ensures the destination page is created and not swapped out. 395 */ 396 static int copy_strings(int argc, char __user * __user * argv, 397 struct linux_binprm *bprm) 398 { 399 struct page *kmapped_page = NULL; 400 char *kaddr = NULL; 401 unsigned long kpos = 0; 402 int ret; 403 404 while (argc-- > 0) { 405 char __user *str; 406 int len; 407 unsigned long pos; 408 409 if (get_user(str, argv+argc) || 410 !(len = strnlen_user(str, MAX_ARG_STRLEN))) { 411 ret = -EFAULT; 412 goto out; 413 } 414 415 if (!valid_arg_len(bprm, len)) { 416 ret = -E2BIG; 417 goto out; 418 } 419 420 /* We're going to work our way backwords. */ 421 pos = bprm->p; 422 str += len; 423 bprm->p -= len; 424 425 while (len > 0) { 426 int offset, bytes_to_copy; 427 428 offset = pos % PAGE_SIZE; 429 if (offset == 0) 430 offset = PAGE_SIZE; 431 432 bytes_to_copy = offset; 433 if (bytes_to_copy > len) 434 bytes_to_copy = len; 435 436 offset -= bytes_to_copy; 437 pos -= bytes_to_copy; 438 str -= bytes_to_copy; 439 len -= bytes_to_copy; 440 441 if (!kmapped_page || kpos != (pos & PAGE_MASK)) { 442 struct page *page; 443 444 page = get_arg_page(bprm, pos, 1); 445 if (!page) { 446 ret = -E2BIG; 447 goto out; 448 } 449 450 if (kmapped_page) { 451 flush_kernel_dcache_page(kmapped_page); 452 kunmap(kmapped_page); 453 put_arg_page(kmapped_page); 454 } 455 kmapped_page = page; 456 kaddr = kmap(kmapped_page); 457 kpos = pos & PAGE_MASK; 458 flush_arg_page(bprm, kpos, kmapped_page); 459 } 460 if (copy_from_user(kaddr+offset, str, bytes_to_copy)) { 461 ret = -EFAULT; 462 goto out; 463 } 464 } 465 } 466 ret = 0; 467 out: 468 if (kmapped_page) { 469 flush_kernel_dcache_page(kmapped_page); 470 kunmap(kmapped_page); 471 put_arg_page(kmapped_page); 472 } 473 return ret; 474 } 475 476 /* 477 * Like copy_strings, but get argv and its values from kernel memory. 478 */ 479 int copy_strings_kernel(int argc,char ** argv, struct linux_binprm *bprm) 480 { 481 int r; 482 mm_segment_t oldfs = get_fs(); 483 set_fs(KERNEL_DS); 484 r = copy_strings(argc, (char __user * __user *)argv, bprm); 485 set_fs(oldfs); 486 return r; 487 } 488 EXPORT_SYMBOL(copy_strings_kernel); 489 490 #ifdef CONFIG_MMU 491 492 /* 493 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once 494 * the binfmt code determines where the new stack should reside, we shift it to 495 * its final location. The process proceeds as follows: 496 * 497 * 1) Use shift to calculate the new vma endpoints. 498 * 2) Extend vma to cover both the old and new ranges. This ensures the 499 * arguments passed to subsequent functions are consistent. 500 * 3) Move vma's page tables to the new range. 501 * 4) Free up any cleared pgd range. 502 * 5) Shrink the vma to cover only the new range. 503 */ 504 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift) 505 { 506 struct mm_struct *mm = vma->vm_mm; 507 unsigned long old_start = vma->vm_start; 508 unsigned long old_end = vma->vm_end; 509 unsigned long length = old_end - old_start; 510 unsigned long new_start = old_start - shift; 511 unsigned long new_end = old_end - shift; 512 struct mmu_gather *tlb; 513 514 BUG_ON(new_start > new_end); 515 516 /* 517 * ensure there are no vmas between where we want to go 518 * and where we are 519 */ 520 if (vma != find_vma(mm, new_start)) 521 return -EFAULT; 522 523 /* 524 * cover the whole range: [new_start, old_end) 525 */ 526 vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL); 527 528 /* 529 * move the page tables downwards, on failure we rely on 530 * process cleanup to remove whatever mess we made. 531 */ 532 if (length != move_page_tables(vma, old_start, 533 vma, new_start, length)) 534 return -ENOMEM; 535 536 lru_add_drain(); 537 tlb = tlb_gather_mmu(mm, 0); 538 if (new_end > old_start) { 539 /* 540 * when the old and new regions overlap clear from new_end. 541 */ 542 free_pgd_range(tlb, new_end, old_end, new_end, 543 vma->vm_next ? vma->vm_next->vm_start : 0); 544 } else { 545 /* 546 * otherwise, clean from old_start; this is done to not touch 547 * the address space in [new_end, old_start) some architectures 548 * have constraints on va-space that make this illegal (IA64) - 549 * for the others its just a little faster. 550 */ 551 free_pgd_range(tlb, old_start, old_end, new_end, 552 vma->vm_next ? vma->vm_next->vm_start : 0); 553 } 554 tlb_finish_mmu(tlb, new_end, old_end); 555 556 /* 557 * shrink the vma to just the new range. 558 */ 559 vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL); 560 561 return 0; 562 } 563 564 #define EXTRA_STACK_VM_PAGES 20 /* random */ 565 566 /* 567 * Finalizes the stack vm_area_struct. The flags and permissions are updated, 568 * the stack is optionally relocated, and some extra space is added. 569 */ 570 int setup_arg_pages(struct linux_binprm *bprm, 571 unsigned long stack_top, 572 int executable_stack) 573 { 574 unsigned long ret; 575 unsigned long stack_shift; 576 struct mm_struct *mm = current->mm; 577 struct vm_area_struct *vma = bprm->vma; 578 struct vm_area_struct *prev = NULL; 579 unsigned long vm_flags; 580 unsigned long stack_base; 581 582 #ifdef CONFIG_STACK_GROWSUP 583 /* Limit stack size to 1GB */ 584 stack_base = current->signal->rlim[RLIMIT_STACK].rlim_max; 585 if (stack_base > (1 << 30)) 586 stack_base = 1 << 30; 587 588 /* Make sure we didn't let the argument array grow too large. */ 589 if (vma->vm_end - vma->vm_start > stack_base) 590 return -ENOMEM; 591 592 stack_base = PAGE_ALIGN(stack_top - stack_base); 593 594 stack_shift = vma->vm_start - stack_base; 595 mm->arg_start = bprm->p - stack_shift; 596 bprm->p = vma->vm_end - stack_shift; 597 #else 598 stack_top = arch_align_stack(stack_top); 599 stack_top = PAGE_ALIGN(stack_top); 600 stack_shift = vma->vm_end - stack_top; 601 602 bprm->p -= stack_shift; 603 mm->arg_start = bprm->p; 604 #endif 605 606 if (bprm->loader) 607 bprm->loader -= stack_shift; 608 bprm->exec -= stack_shift; 609 610 down_write(&mm->mmap_sem); 611 vm_flags = VM_STACK_FLAGS; 612 613 /* 614 * Adjust stack execute permissions; explicitly enable for 615 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone 616 * (arch default) otherwise. 617 */ 618 if (unlikely(executable_stack == EXSTACK_ENABLE_X)) 619 vm_flags |= VM_EXEC; 620 else if (executable_stack == EXSTACK_DISABLE_X) 621 vm_flags &= ~VM_EXEC; 622 vm_flags |= mm->def_flags; 623 624 ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end, 625 vm_flags); 626 if (ret) 627 goto out_unlock; 628 BUG_ON(prev != vma); 629 630 /* Move stack pages down in memory. */ 631 if (stack_shift) { 632 ret = shift_arg_pages(vma, stack_shift); 633 if (ret) { 634 up_write(&mm->mmap_sem); 635 return ret; 636 } 637 } 638 639 #ifdef CONFIG_STACK_GROWSUP 640 stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE; 641 #else 642 stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE; 643 #endif 644 ret = expand_stack(vma, stack_base); 645 if (ret) 646 ret = -EFAULT; 647 648 out_unlock: 649 up_write(&mm->mmap_sem); 650 return 0; 651 } 652 EXPORT_SYMBOL(setup_arg_pages); 653 654 #endif /* CONFIG_MMU */ 655 656 struct file *open_exec(const char *name) 657 { 658 struct nameidata nd; 659 struct file *file; 660 int err; 661 662 err = path_lookup_open(AT_FDCWD, name, LOOKUP_FOLLOW, &nd, 663 FMODE_READ|FMODE_EXEC); 664 if (err) 665 goto out; 666 667 err = -EACCES; 668 if (!S_ISREG(nd.path.dentry->d_inode->i_mode)) 669 goto out_path_put; 670 671 if (nd.path.mnt->mnt_flags & MNT_NOEXEC) 672 goto out_path_put; 673 674 err = inode_permission(nd.path.dentry->d_inode, MAY_EXEC | MAY_OPEN); 675 if (err) 676 goto out_path_put; 677 678 file = nameidata_to_filp(&nd, O_RDONLY|O_LARGEFILE); 679 if (IS_ERR(file)) 680 return file; 681 682 fsnotify_open(file->f_path.dentry); 683 684 err = deny_write_access(file); 685 if (err) { 686 fput(file); 687 goto out; 688 } 689 690 return file; 691 692 out_path_put: 693 release_open_intent(&nd); 694 path_put(&nd.path); 695 out: 696 return ERR_PTR(err); 697 } 698 EXPORT_SYMBOL(open_exec); 699 700 int kernel_read(struct file *file, unsigned long offset, 701 char *addr, unsigned long count) 702 { 703 mm_segment_t old_fs; 704 loff_t pos = offset; 705 int result; 706 707 old_fs = get_fs(); 708 set_fs(get_ds()); 709 /* The cast to a user pointer is valid due to the set_fs() */ 710 result = vfs_read(file, (void __user *)addr, count, &pos); 711 set_fs(old_fs); 712 return result; 713 } 714 715 EXPORT_SYMBOL(kernel_read); 716 717 static int exec_mmap(struct mm_struct *mm) 718 { 719 struct task_struct *tsk; 720 struct mm_struct * old_mm, *active_mm; 721 722 /* Notify parent that we're no longer interested in the old VM */ 723 tsk = current; 724 old_mm = current->mm; 725 mm_release(tsk, old_mm); 726 727 if (old_mm) { 728 /* 729 * Make sure that if there is a core dump in progress 730 * for the old mm, we get out and die instead of going 731 * through with the exec. We must hold mmap_sem around 732 * checking core_state and changing tsk->mm. 733 */ 734 down_read(&old_mm->mmap_sem); 735 if (unlikely(old_mm->core_state)) { 736 up_read(&old_mm->mmap_sem); 737 return -EINTR; 738 } 739 } 740 task_lock(tsk); 741 active_mm = tsk->active_mm; 742 tsk->mm = mm; 743 tsk->active_mm = mm; 744 activate_mm(active_mm, mm); 745 task_unlock(tsk); 746 arch_pick_mmap_layout(mm); 747 if (old_mm) { 748 up_read(&old_mm->mmap_sem); 749 BUG_ON(active_mm != old_mm); 750 mm_update_next_owner(old_mm); 751 mmput(old_mm); 752 return 0; 753 } 754 mmdrop(active_mm); 755 return 0; 756 } 757 758 /* 759 * This function makes sure the current process has its own signal table, 760 * so that flush_signal_handlers can later reset the handlers without 761 * disturbing other processes. (Other processes might share the signal 762 * table via the CLONE_SIGHAND option to clone().) 763 */ 764 static int de_thread(struct task_struct *tsk) 765 { 766 struct signal_struct *sig = tsk->signal; 767 struct sighand_struct *oldsighand = tsk->sighand; 768 spinlock_t *lock = &oldsighand->siglock; 769 int count; 770 771 if (thread_group_empty(tsk)) 772 goto no_thread_group; 773 774 /* 775 * Kill all other threads in the thread group. 776 */ 777 spin_lock_irq(lock); 778 if (signal_group_exit(sig)) { 779 /* 780 * Another group action in progress, just 781 * return so that the signal is processed. 782 */ 783 spin_unlock_irq(lock); 784 return -EAGAIN; 785 } 786 sig->group_exit_task = tsk; 787 zap_other_threads(tsk); 788 789 /* Account for the thread group leader hanging around: */ 790 count = thread_group_leader(tsk) ? 1 : 2; 791 sig->notify_count = count; 792 while (atomic_read(&sig->count) > count) { 793 __set_current_state(TASK_UNINTERRUPTIBLE); 794 spin_unlock_irq(lock); 795 schedule(); 796 spin_lock_irq(lock); 797 } 798 spin_unlock_irq(lock); 799 800 /* 801 * At this point all other threads have exited, all we have to 802 * do is to wait for the thread group leader to become inactive, 803 * and to assume its PID: 804 */ 805 if (!thread_group_leader(tsk)) { 806 struct task_struct *leader = tsk->group_leader; 807 808 sig->notify_count = -1; /* for exit_notify() */ 809 for (;;) { 810 write_lock_irq(&tasklist_lock); 811 if (likely(leader->exit_state)) 812 break; 813 __set_current_state(TASK_UNINTERRUPTIBLE); 814 write_unlock_irq(&tasklist_lock); 815 schedule(); 816 } 817 818 /* 819 * The only record we have of the real-time age of a 820 * process, regardless of execs it's done, is start_time. 821 * All the past CPU time is accumulated in signal_struct 822 * from sister threads now dead. But in this non-leader 823 * exec, nothing survives from the original leader thread, 824 * whose birth marks the true age of this process now. 825 * When we take on its identity by switching to its PID, we 826 * also take its birthdate (always earlier than our own). 827 */ 828 tsk->start_time = leader->start_time; 829 830 BUG_ON(!same_thread_group(leader, tsk)); 831 BUG_ON(has_group_leader_pid(tsk)); 832 /* 833 * An exec() starts a new thread group with the 834 * TGID of the previous thread group. Rehash the 835 * two threads with a switched PID, and release 836 * the former thread group leader: 837 */ 838 839 /* Become a process group leader with the old leader's pid. 840 * The old leader becomes a thread of the this thread group. 841 * Note: The old leader also uses this pid until release_task 842 * is called. Odd but simple and correct. 843 */ 844 detach_pid(tsk, PIDTYPE_PID); 845 tsk->pid = leader->pid; 846 attach_pid(tsk, PIDTYPE_PID, task_pid(leader)); 847 transfer_pid(leader, tsk, PIDTYPE_PGID); 848 transfer_pid(leader, tsk, PIDTYPE_SID); 849 list_replace_rcu(&leader->tasks, &tsk->tasks); 850 851 tsk->group_leader = tsk; 852 leader->group_leader = tsk; 853 854 tsk->exit_signal = SIGCHLD; 855 856 BUG_ON(leader->exit_state != EXIT_ZOMBIE); 857 leader->exit_state = EXIT_DEAD; 858 write_unlock_irq(&tasklist_lock); 859 860 release_task(leader); 861 } 862 863 sig->group_exit_task = NULL; 864 sig->notify_count = 0; 865 866 no_thread_group: 867 exit_itimers(sig); 868 flush_itimer_signals(); 869 870 if (atomic_read(&oldsighand->count) != 1) { 871 struct sighand_struct *newsighand; 872 /* 873 * This ->sighand is shared with the CLONE_SIGHAND 874 * but not CLONE_THREAD task, switch to the new one. 875 */ 876 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 877 if (!newsighand) 878 return -ENOMEM; 879 880 atomic_set(&newsighand->count, 1); 881 memcpy(newsighand->action, oldsighand->action, 882 sizeof(newsighand->action)); 883 884 write_lock_irq(&tasklist_lock); 885 spin_lock(&oldsighand->siglock); 886 rcu_assign_pointer(tsk->sighand, newsighand); 887 spin_unlock(&oldsighand->siglock); 888 write_unlock_irq(&tasklist_lock); 889 890 __cleanup_sighand(oldsighand); 891 } 892 893 BUG_ON(!thread_group_leader(tsk)); 894 return 0; 895 } 896 897 /* 898 * These functions flushes out all traces of the currently running executable 899 * so that a new one can be started 900 */ 901 static void flush_old_files(struct files_struct * files) 902 { 903 long j = -1; 904 struct fdtable *fdt; 905 906 spin_lock(&files->file_lock); 907 for (;;) { 908 unsigned long set, i; 909 910 j++; 911 i = j * __NFDBITS; 912 fdt = files_fdtable(files); 913 if (i >= fdt->max_fds) 914 break; 915 set = fdt->close_on_exec->fds_bits[j]; 916 if (!set) 917 continue; 918 fdt->close_on_exec->fds_bits[j] = 0; 919 spin_unlock(&files->file_lock); 920 for ( ; set ; i++,set >>= 1) { 921 if (set & 1) { 922 sys_close(i); 923 } 924 } 925 spin_lock(&files->file_lock); 926 927 } 928 spin_unlock(&files->file_lock); 929 } 930 931 char *get_task_comm(char *buf, struct task_struct *tsk) 932 { 933 /* buf must be at least sizeof(tsk->comm) in size */ 934 task_lock(tsk); 935 strncpy(buf, tsk->comm, sizeof(tsk->comm)); 936 task_unlock(tsk); 937 return buf; 938 } 939 940 void set_task_comm(struct task_struct *tsk, char *buf) 941 { 942 task_lock(tsk); 943 strlcpy(tsk->comm, buf, sizeof(tsk->comm)); 944 task_unlock(tsk); 945 } 946 947 int flush_old_exec(struct linux_binprm * bprm) 948 { 949 char * name; 950 int i, ch, retval; 951 char tcomm[sizeof(current->comm)]; 952 953 /* 954 * Make sure we have a private signal table and that 955 * we are unassociated from the previous thread group. 956 */ 957 retval = de_thread(current); 958 if (retval) 959 goto out; 960 961 set_mm_exe_file(bprm->mm, bprm->file); 962 963 /* 964 * Release all of the old mmap stuff 965 */ 966 retval = exec_mmap(bprm->mm); 967 if (retval) 968 goto out; 969 970 bprm->mm = NULL; /* We're using it now */ 971 972 /* This is the point of no return */ 973 current->sas_ss_sp = current->sas_ss_size = 0; 974 975 if (current_euid() == current_uid() && current_egid() == current_gid()) 976 set_dumpable(current->mm, 1); 977 else 978 set_dumpable(current->mm, suid_dumpable); 979 980 name = bprm->filename; 981 982 /* Copies the binary name from after last slash */ 983 for (i=0; (ch = *(name++)) != '\0';) { 984 if (ch == '/') 985 i = 0; /* overwrite what we wrote */ 986 else 987 if (i < (sizeof(tcomm) - 1)) 988 tcomm[i++] = ch; 989 } 990 tcomm[i] = '\0'; 991 set_task_comm(current, tcomm); 992 993 current->flags &= ~PF_RANDOMIZE; 994 flush_thread(); 995 996 /* Set the new mm task size. We have to do that late because it may 997 * depend on TIF_32BIT which is only updated in flush_thread() on 998 * some architectures like powerpc 999 */ 1000 current->mm->task_size = TASK_SIZE; 1001 1002 /* install the new credentials */ 1003 if (bprm->cred->uid != current_euid() || 1004 bprm->cred->gid != current_egid()) { 1005 current->pdeath_signal = 0; 1006 } else if (file_permission(bprm->file, MAY_READ) || 1007 bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) { 1008 set_dumpable(current->mm, suid_dumpable); 1009 } 1010 1011 current->personality &= ~bprm->per_clear; 1012 1013 /* An exec changes our domain. We are no longer part of the thread 1014 group */ 1015 1016 current->self_exec_id++; 1017 1018 flush_signal_handlers(current, 0); 1019 flush_old_files(current->files); 1020 1021 return 0; 1022 1023 out: 1024 return retval; 1025 } 1026 1027 EXPORT_SYMBOL(flush_old_exec); 1028 1029 /* 1030 * install the new credentials for this executable 1031 */ 1032 void install_exec_creds(struct linux_binprm *bprm) 1033 { 1034 security_bprm_committing_creds(bprm); 1035 1036 commit_creds(bprm->cred); 1037 bprm->cred = NULL; 1038 1039 /* cred_exec_mutex must be held at least to this point to prevent 1040 * ptrace_attach() from altering our determination of the task's 1041 * credentials; any time after this it may be unlocked */ 1042 1043 security_bprm_committed_creds(bprm); 1044 } 1045 EXPORT_SYMBOL(install_exec_creds); 1046 1047 /* 1048 * determine how safe it is to execute the proposed program 1049 * - the caller must hold current->cred_exec_mutex to protect against 1050 * PTRACE_ATTACH 1051 */ 1052 void check_unsafe_exec(struct linux_binprm *bprm, struct files_struct *files) 1053 { 1054 struct task_struct *p = current, *t; 1055 unsigned long flags; 1056 unsigned n_fs, n_files, n_sighand; 1057 1058 bprm->unsafe = tracehook_unsafe_exec(p); 1059 1060 n_fs = 1; 1061 n_files = 1; 1062 n_sighand = 1; 1063 lock_task_sighand(p, &flags); 1064 for (t = next_thread(p); t != p; t = next_thread(t)) { 1065 if (t->fs == p->fs) 1066 n_fs++; 1067 if (t->files == files) 1068 n_files++; 1069 n_sighand++; 1070 } 1071 1072 if (atomic_read(&p->fs->count) > n_fs || 1073 atomic_read(&p->files->count) > n_files || 1074 atomic_read(&p->sighand->count) > n_sighand) 1075 bprm->unsafe |= LSM_UNSAFE_SHARE; 1076 1077 unlock_task_sighand(p, &flags); 1078 } 1079 1080 /* 1081 * Fill the binprm structure from the inode. 1082 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes 1083 * 1084 * This may be called multiple times for binary chains (scripts for example). 1085 */ 1086 int prepare_binprm(struct linux_binprm *bprm) 1087 { 1088 umode_t mode; 1089 struct inode * inode = bprm->file->f_path.dentry->d_inode; 1090 int retval; 1091 1092 mode = inode->i_mode; 1093 if (bprm->file->f_op == NULL) 1094 return -EACCES; 1095 1096 /* clear any previous set[ug]id data from a previous binary */ 1097 bprm->cred->euid = current_euid(); 1098 bprm->cred->egid = current_egid(); 1099 1100 if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) { 1101 /* Set-uid? */ 1102 if (mode & S_ISUID) { 1103 bprm->per_clear |= PER_CLEAR_ON_SETID; 1104 bprm->cred->euid = inode->i_uid; 1105 } 1106 1107 /* Set-gid? */ 1108 /* 1109 * If setgid is set but no group execute bit then this 1110 * is a candidate for mandatory locking, not a setgid 1111 * executable. 1112 */ 1113 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { 1114 bprm->per_clear |= PER_CLEAR_ON_SETID; 1115 bprm->cred->egid = inode->i_gid; 1116 } 1117 } 1118 1119 /* fill in binprm security blob */ 1120 retval = security_bprm_set_creds(bprm); 1121 if (retval) 1122 return retval; 1123 bprm->cred_prepared = 1; 1124 1125 memset(bprm->buf, 0, BINPRM_BUF_SIZE); 1126 return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE); 1127 } 1128 1129 EXPORT_SYMBOL(prepare_binprm); 1130 1131 /* 1132 * Arguments are '\0' separated strings found at the location bprm->p 1133 * points to; chop off the first by relocating brpm->p to right after 1134 * the first '\0' encountered. 1135 */ 1136 int remove_arg_zero(struct linux_binprm *bprm) 1137 { 1138 int ret = 0; 1139 unsigned long offset; 1140 char *kaddr; 1141 struct page *page; 1142 1143 if (!bprm->argc) 1144 return 0; 1145 1146 do { 1147 offset = bprm->p & ~PAGE_MASK; 1148 page = get_arg_page(bprm, bprm->p, 0); 1149 if (!page) { 1150 ret = -EFAULT; 1151 goto out; 1152 } 1153 kaddr = kmap_atomic(page, KM_USER0); 1154 1155 for (; offset < PAGE_SIZE && kaddr[offset]; 1156 offset++, bprm->p++) 1157 ; 1158 1159 kunmap_atomic(kaddr, KM_USER0); 1160 put_arg_page(page); 1161 1162 if (offset == PAGE_SIZE) 1163 free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1); 1164 } while (offset == PAGE_SIZE); 1165 1166 bprm->p++; 1167 bprm->argc--; 1168 ret = 0; 1169 1170 out: 1171 return ret; 1172 } 1173 EXPORT_SYMBOL(remove_arg_zero); 1174 1175 /* 1176 * cycle the list of binary formats handler, until one recognizes the image 1177 */ 1178 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs) 1179 { 1180 unsigned int depth = bprm->recursion_depth; 1181 int try,retval; 1182 struct linux_binfmt *fmt; 1183 1184 retval = security_bprm_check(bprm); 1185 if (retval) 1186 return retval; 1187 1188 /* kernel module loader fixup */ 1189 /* so we don't try to load run modprobe in kernel space. */ 1190 set_fs(USER_DS); 1191 1192 retval = audit_bprm(bprm); 1193 if (retval) 1194 return retval; 1195 1196 retval = -ENOENT; 1197 for (try=0; try<2; try++) { 1198 read_lock(&binfmt_lock); 1199 list_for_each_entry(fmt, &formats, lh) { 1200 int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary; 1201 if (!fn) 1202 continue; 1203 if (!try_module_get(fmt->module)) 1204 continue; 1205 read_unlock(&binfmt_lock); 1206 retval = fn(bprm, regs); 1207 /* 1208 * Restore the depth counter to its starting value 1209 * in this call, so we don't have to rely on every 1210 * load_binary function to restore it on return. 1211 */ 1212 bprm->recursion_depth = depth; 1213 if (retval >= 0) { 1214 if (depth == 0) 1215 tracehook_report_exec(fmt, bprm, regs); 1216 put_binfmt(fmt); 1217 allow_write_access(bprm->file); 1218 if (bprm->file) 1219 fput(bprm->file); 1220 bprm->file = NULL; 1221 current->did_exec = 1; 1222 proc_exec_connector(current); 1223 return retval; 1224 } 1225 read_lock(&binfmt_lock); 1226 put_binfmt(fmt); 1227 if (retval != -ENOEXEC || bprm->mm == NULL) 1228 break; 1229 if (!bprm->file) { 1230 read_unlock(&binfmt_lock); 1231 return retval; 1232 } 1233 } 1234 read_unlock(&binfmt_lock); 1235 if (retval != -ENOEXEC || bprm->mm == NULL) { 1236 break; 1237 #ifdef CONFIG_MODULES 1238 } else { 1239 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e)) 1240 if (printable(bprm->buf[0]) && 1241 printable(bprm->buf[1]) && 1242 printable(bprm->buf[2]) && 1243 printable(bprm->buf[3])) 1244 break; /* -ENOEXEC */ 1245 request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2])); 1246 #endif 1247 } 1248 } 1249 return retval; 1250 } 1251 1252 EXPORT_SYMBOL(search_binary_handler); 1253 1254 void free_bprm(struct linux_binprm *bprm) 1255 { 1256 free_arg_pages(bprm); 1257 if (bprm->cred) 1258 abort_creds(bprm->cred); 1259 kfree(bprm); 1260 } 1261 1262 /* 1263 * sys_execve() executes a new program. 1264 */ 1265 int do_execve(char * filename, 1266 char __user *__user *argv, 1267 char __user *__user *envp, 1268 struct pt_regs * regs) 1269 { 1270 struct linux_binprm *bprm; 1271 struct file *file; 1272 struct files_struct *displaced; 1273 int retval; 1274 1275 retval = unshare_files(&displaced); 1276 if (retval) 1277 goto out_ret; 1278 1279 retval = -ENOMEM; 1280 bprm = kzalloc(sizeof(*bprm), GFP_KERNEL); 1281 if (!bprm) 1282 goto out_files; 1283 1284 retval = mutex_lock_interruptible(¤t->cred_exec_mutex); 1285 if (retval < 0) 1286 goto out_free; 1287 1288 retval = -ENOMEM; 1289 bprm->cred = prepare_exec_creds(); 1290 if (!bprm->cred) 1291 goto out_unlock; 1292 check_unsafe_exec(bprm, displaced); 1293 1294 file = open_exec(filename); 1295 retval = PTR_ERR(file); 1296 if (IS_ERR(file)) 1297 goto out_unlock; 1298 1299 sched_exec(); 1300 1301 bprm->file = file; 1302 bprm->filename = filename; 1303 bprm->interp = filename; 1304 1305 retval = bprm_mm_init(bprm); 1306 if (retval) 1307 goto out_file; 1308 1309 bprm->argc = count(argv, MAX_ARG_STRINGS); 1310 if ((retval = bprm->argc) < 0) 1311 goto out; 1312 1313 bprm->envc = count(envp, MAX_ARG_STRINGS); 1314 if ((retval = bprm->envc) < 0) 1315 goto out; 1316 1317 retval = prepare_binprm(bprm); 1318 if (retval < 0) 1319 goto out; 1320 1321 retval = copy_strings_kernel(1, &bprm->filename, bprm); 1322 if (retval < 0) 1323 goto out; 1324 1325 bprm->exec = bprm->p; 1326 retval = copy_strings(bprm->envc, envp, bprm); 1327 if (retval < 0) 1328 goto out; 1329 1330 retval = copy_strings(bprm->argc, argv, bprm); 1331 if (retval < 0) 1332 goto out; 1333 1334 current->flags &= ~PF_KTHREAD; 1335 retval = search_binary_handler(bprm,regs); 1336 if (retval < 0) 1337 goto out; 1338 1339 /* execve succeeded */ 1340 mutex_unlock(¤t->cred_exec_mutex); 1341 acct_update_integrals(current); 1342 free_bprm(bprm); 1343 if (displaced) 1344 put_files_struct(displaced); 1345 return retval; 1346 1347 out: 1348 if (bprm->mm) 1349 mmput (bprm->mm); 1350 1351 out_file: 1352 if (bprm->file) { 1353 allow_write_access(bprm->file); 1354 fput(bprm->file); 1355 } 1356 1357 out_unlock: 1358 mutex_unlock(¤t->cred_exec_mutex); 1359 1360 out_free: 1361 free_bprm(bprm); 1362 1363 out_files: 1364 if (displaced) 1365 reset_files_struct(displaced); 1366 out_ret: 1367 return retval; 1368 } 1369 1370 int set_binfmt(struct linux_binfmt *new) 1371 { 1372 struct linux_binfmt *old = current->binfmt; 1373 1374 if (new) { 1375 if (!try_module_get(new->module)) 1376 return -1; 1377 } 1378 current->binfmt = new; 1379 if (old) 1380 module_put(old->module); 1381 return 0; 1382 } 1383 1384 EXPORT_SYMBOL(set_binfmt); 1385 1386 /* format_corename will inspect the pattern parameter, and output a 1387 * name into corename, which must have space for at least 1388 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator. 1389 */ 1390 static int format_corename(char *corename, long signr) 1391 { 1392 const struct cred *cred = current_cred(); 1393 const char *pat_ptr = core_pattern; 1394 int ispipe = (*pat_ptr == '|'); 1395 char *out_ptr = corename; 1396 char *const out_end = corename + CORENAME_MAX_SIZE; 1397 int rc; 1398 int pid_in_pattern = 0; 1399 1400 /* Repeat as long as we have more pattern to process and more output 1401 space */ 1402 while (*pat_ptr) { 1403 if (*pat_ptr != '%') { 1404 if (out_ptr == out_end) 1405 goto out; 1406 *out_ptr++ = *pat_ptr++; 1407 } else { 1408 switch (*++pat_ptr) { 1409 case 0: 1410 goto out; 1411 /* Double percent, output one percent */ 1412 case '%': 1413 if (out_ptr == out_end) 1414 goto out; 1415 *out_ptr++ = '%'; 1416 break; 1417 /* pid */ 1418 case 'p': 1419 pid_in_pattern = 1; 1420 rc = snprintf(out_ptr, out_end - out_ptr, 1421 "%d", task_tgid_vnr(current)); 1422 if (rc > out_end - out_ptr) 1423 goto out; 1424 out_ptr += rc; 1425 break; 1426 /* uid */ 1427 case 'u': 1428 rc = snprintf(out_ptr, out_end - out_ptr, 1429 "%d", cred->uid); 1430 if (rc > out_end - out_ptr) 1431 goto out; 1432 out_ptr += rc; 1433 break; 1434 /* gid */ 1435 case 'g': 1436 rc = snprintf(out_ptr, out_end - out_ptr, 1437 "%d", cred->gid); 1438 if (rc > out_end - out_ptr) 1439 goto out; 1440 out_ptr += rc; 1441 break; 1442 /* signal that caused the coredump */ 1443 case 's': 1444 rc = snprintf(out_ptr, out_end - out_ptr, 1445 "%ld", signr); 1446 if (rc > out_end - out_ptr) 1447 goto out; 1448 out_ptr += rc; 1449 break; 1450 /* UNIX time of coredump */ 1451 case 't': { 1452 struct timeval tv; 1453 do_gettimeofday(&tv); 1454 rc = snprintf(out_ptr, out_end - out_ptr, 1455 "%lu", tv.tv_sec); 1456 if (rc > out_end - out_ptr) 1457 goto out; 1458 out_ptr += rc; 1459 break; 1460 } 1461 /* hostname */ 1462 case 'h': 1463 down_read(&uts_sem); 1464 rc = snprintf(out_ptr, out_end - out_ptr, 1465 "%s", utsname()->nodename); 1466 up_read(&uts_sem); 1467 if (rc > out_end - out_ptr) 1468 goto out; 1469 out_ptr += rc; 1470 break; 1471 /* executable */ 1472 case 'e': 1473 rc = snprintf(out_ptr, out_end - out_ptr, 1474 "%s", current->comm); 1475 if (rc > out_end - out_ptr) 1476 goto out; 1477 out_ptr += rc; 1478 break; 1479 /* core limit size */ 1480 case 'c': 1481 rc = snprintf(out_ptr, out_end - out_ptr, 1482 "%lu", current->signal->rlim[RLIMIT_CORE].rlim_cur); 1483 if (rc > out_end - out_ptr) 1484 goto out; 1485 out_ptr += rc; 1486 break; 1487 default: 1488 break; 1489 } 1490 ++pat_ptr; 1491 } 1492 } 1493 /* Backward compatibility with core_uses_pid: 1494 * 1495 * If core_pattern does not include a %p (as is the default) 1496 * and core_uses_pid is set, then .%pid will be appended to 1497 * the filename. Do not do this for piped commands. */ 1498 if (!ispipe && !pid_in_pattern && core_uses_pid) { 1499 rc = snprintf(out_ptr, out_end - out_ptr, 1500 ".%d", task_tgid_vnr(current)); 1501 if (rc > out_end - out_ptr) 1502 goto out; 1503 out_ptr += rc; 1504 } 1505 out: 1506 *out_ptr = 0; 1507 return ispipe; 1508 } 1509 1510 static int zap_process(struct task_struct *start) 1511 { 1512 struct task_struct *t; 1513 int nr = 0; 1514 1515 start->signal->flags = SIGNAL_GROUP_EXIT; 1516 start->signal->group_stop_count = 0; 1517 1518 t = start; 1519 do { 1520 if (t != current && t->mm) { 1521 sigaddset(&t->pending.signal, SIGKILL); 1522 signal_wake_up(t, 1); 1523 nr++; 1524 } 1525 } while_each_thread(start, t); 1526 1527 return nr; 1528 } 1529 1530 static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm, 1531 struct core_state *core_state, int exit_code) 1532 { 1533 struct task_struct *g, *p; 1534 unsigned long flags; 1535 int nr = -EAGAIN; 1536 1537 spin_lock_irq(&tsk->sighand->siglock); 1538 if (!signal_group_exit(tsk->signal)) { 1539 mm->core_state = core_state; 1540 tsk->signal->group_exit_code = exit_code; 1541 nr = zap_process(tsk); 1542 } 1543 spin_unlock_irq(&tsk->sighand->siglock); 1544 if (unlikely(nr < 0)) 1545 return nr; 1546 1547 if (atomic_read(&mm->mm_users) == nr + 1) 1548 goto done; 1549 /* 1550 * We should find and kill all tasks which use this mm, and we should 1551 * count them correctly into ->nr_threads. We don't take tasklist 1552 * lock, but this is safe wrt: 1553 * 1554 * fork: 1555 * None of sub-threads can fork after zap_process(leader). All 1556 * processes which were created before this point should be 1557 * visible to zap_threads() because copy_process() adds the new 1558 * process to the tail of init_task.tasks list, and lock/unlock 1559 * of ->siglock provides a memory barrier. 1560 * 1561 * do_exit: 1562 * The caller holds mm->mmap_sem. This means that the task which 1563 * uses this mm can't pass exit_mm(), so it can't exit or clear 1564 * its ->mm. 1565 * 1566 * de_thread: 1567 * It does list_replace_rcu(&leader->tasks, ¤t->tasks), 1568 * we must see either old or new leader, this does not matter. 1569 * However, it can change p->sighand, so lock_task_sighand(p) 1570 * must be used. Since p->mm != NULL and we hold ->mmap_sem 1571 * it can't fail. 1572 * 1573 * Note also that "g" can be the old leader with ->mm == NULL 1574 * and already unhashed and thus removed from ->thread_group. 1575 * This is OK, __unhash_process()->list_del_rcu() does not 1576 * clear the ->next pointer, we will find the new leader via 1577 * next_thread(). 1578 */ 1579 rcu_read_lock(); 1580 for_each_process(g) { 1581 if (g == tsk->group_leader) 1582 continue; 1583 if (g->flags & PF_KTHREAD) 1584 continue; 1585 p = g; 1586 do { 1587 if (p->mm) { 1588 if (unlikely(p->mm == mm)) { 1589 lock_task_sighand(p, &flags); 1590 nr += zap_process(p); 1591 unlock_task_sighand(p, &flags); 1592 } 1593 break; 1594 } 1595 } while_each_thread(g, p); 1596 } 1597 rcu_read_unlock(); 1598 done: 1599 atomic_set(&core_state->nr_threads, nr); 1600 return nr; 1601 } 1602 1603 static int coredump_wait(int exit_code, struct core_state *core_state) 1604 { 1605 struct task_struct *tsk = current; 1606 struct mm_struct *mm = tsk->mm; 1607 struct completion *vfork_done; 1608 int core_waiters; 1609 1610 init_completion(&core_state->startup); 1611 core_state->dumper.task = tsk; 1612 core_state->dumper.next = NULL; 1613 core_waiters = zap_threads(tsk, mm, core_state, exit_code); 1614 up_write(&mm->mmap_sem); 1615 1616 if (unlikely(core_waiters < 0)) 1617 goto fail; 1618 1619 /* 1620 * Make sure nobody is waiting for us to release the VM, 1621 * otherwise we can deadlock when we wait on each other 1622 */ 1623 vfork_done = tsk->vfork_done; 1624 if (vfork_done) { 1625 tsk->vfork_done = NULL; 1626 complete(vfork_done); 1627 } 1628 1629 if (core_waiters) 1630 wait_for_completion(&core_state->startup); 1631 fail: 1632 return core_waiters; 1633 } 1634 1635 static void coredump_finish(struct mm_struct *mm) 1636 { 1637 struct core_thread *curr, *next; 1638 struct task_struct *task; 1639 1640 next = mm->core_state->dumper.next; 1641 while ((curr = next) != NULL) { 1642 next = curr->next; 1643 task = curr->task; 1644 /* 1645 * see exit_mm(), curr->task must not see 1646 * ->task == NULL before we read ->next. 1647 */ 1648 smp_mb(); 1649 curr->task = NULL; 1650 wake_up_process(task); 1651 } 1652 1653 mm->core_state = NULL; 1654 } 1655 1656 /* 1657 * set_dumpable converts traditional three-value dumpable to two flags and 1658 * stores them into mm->flags. It modifies lower two bits of mm->flags, but 1659 * these bits are not changed atomically. So get_dumpable can observe the 1660 * intermediate state. To avoid doing unexpected behavior, get get_dumpable 1661 * return either old dumpable or new one by paying attention to the order of 1662 * modifying the bits. 1663 * 1664 * dumpable | mm->flags (binary) 1665 * old new | initial interim final 1666 * ---------+----------------------- 1667 * 0 1 | 00 01 01 1668 * 0 2 | 00 10(*) 11 1669 * 1 0 | 01 00 00 1670 * 1 2 | 01 11 11 1671 * 2 0 | 11 10(*) 00 1672 * 2 1 | 11 11 01 1673 * 1674 * (*) get_dumpable regards interim value of 10 as 11. 1675 */ 1676 void set_dumpable(struct mm_struct *mm, int value) 1677 { 1678 switch (value) { 1679 case 0: 1680 clear_bit(MMF_DUMPABLE, &mm->flags); 1681 smp_wmb(); 1682 clear_bit(MMF_DUMP_SECURELY, &mm->flags); 1683 break; 1684 case 1: 1685 set_bit(MMF_DUMPABLE, &mm->flags); 1686 smp_wmb(); 1687 clear_bit(MMF_DUMP_SECURELY, &mm->flags); 1688 break; 1689 case 2: 1690 set_bit(MMF_DUMP_SECURELY, &mm->flags); 1691 smp_wmb(); 1692 set_bit(MMF_DUMPABLE, &mm->flags); 1693 break; 1694 } 1695 } 1696 1697 int get_dumpable(struct mm_struct *mm) 1698 { 1699 int ret; 1700 1701 ret = mm->flags & 0x3; 1702 return (ret >= 2) ? 2 : ret; 1703 } 1704 1705 void do_coredump(long signr, int exit_code, struct pt_regs *regs) 1706 { 1707 struct core_state core_state; 1708 char corename[CORENAME_MAX_SIZE + 1]; 1709 struct mm_struct *mm = current->mm; 1710 struct linux_binfmt * binfmt; 1711 struct inode * inode; 1712 struct file * file; 1713 const struct cred *old_cred; 1714 struct cred *cred; 1715 int retval = 0; 1716 int flag = 0; 1717 int ispipe = 0; 1718 unsigned long core_limit = current->signal->rlim[RLIMIT_CORE].rlim_cur; 1719 char **helper_argv = NULL; 1720 int helper_argc = 0; 1721 char *delimit; 1722 1723 audit_core_dumps(signr); 1724 1725 binfmt = current->binfmt; 1726 if (!binfmt || !binfmt->core_dump) 1727 goto fail; 1728 1729 cred = prepare_creds(); 1730 if (!cred) { 1731 retval = -ENOMEM; 1732 goto fail; 1733 } 1734 1735 down_write(&mm->mmap_sem); 1736 /* 1737 * If another thread got here first, or we are not dumpable, bail out. 1738 */ 1739 if (mm->core_state || !get_dumpable(mm)) { 1740 up_write(&mm->mmap_sem); 1741 put_cred(cred); 1742 goto fail; 1743 } 1744 1745 /* 1746 * We cannot trust fsuid as being the "true" uid of the 1747 * process nor do we know its entire history. We only know it 1748 * was tainted so we dump it as root in mode 2. 1749 */ 1750 if (get_dumpable(mm) == 2) { /* Setuid core dump mode */ 1751 flag = O_EXCL; /* Stop rewrite attacks */ 1752 cred->fsuid = 0; /* Dump root private */ 1753 } 1754 1755 retval = coredump_wait(exit_code, &core_state); 1756 if (retval < 0) { 1757 put_cred(cred); 1758 goto fail; 1759 } 1760 1761 old_cred = override_creds(cred); 1762 1763 /* 1764 * Clear any false indication of pending signals that might 1765 * be seen by the filesystem code called to write the core file. 1766 */ 1767 clear_thread_flag(TIF_SIGPENDING); 1768 1769 /* 1770 * lock_kernel() because format_corename() is controlled by sysctl, which 1771 * uses lock_kernel() 1772 */ 1773 lock_kernel(); 1774 ispipe = format_corename(corename, signr); 1775 unlock_kernel(); 1776 /* 1777 * Don't bother to check the RLIMIT_CORE value if core_pattern points 1778 * to a pipe. Since we're not writing directly to the filesystem 1779 * RLIMIT_CORE doesn't really apply, as no actual core file will be 1780 * created unless the pipe reader choses to write out the core file 1781 * at which point file size limits and permissions will be imposed 1782 * as it does with any other process 1783 */ 1784 if ((!ispipe) && (core_limit < binfmt->min_coredump)) 1785 goto fail_unlock; 1786 1787 if (ispipe) { 1788 helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc); 1789 if (!helper_argv) { 1790 printk(KERN_WARNING "%s failed to allocate memory\n", 1791 __func__); 1792 goto fail_unlock; 1793 } 1794 /* Terminate the string before the first option */ 1795 delimit = strchr(corename, ' '); 1796 if (delimit) 1797 *delimit = '\0'; 1798 delimit = strrchr(helper_argv[0], '/'); 1799 if (delimit) 1800 delimit++; 1801 else 1802 delimit = helper_argv[0]; 1803 if (!strcmp(delimit, current->comm)) { 1804 printk(KERN_NOTICE "Recursive core dump detected, " 1805 "aborting\n"); 1806 goto fail_unlock; 1807 } 1808 1809 core_limit = RLIM_INFINITY; 1810 1811 /* SIGPIPE can happen, but it's just never processed */ 1812 if (call_usermodehelper_pipe(corename+1, helper_argv, NULL, 1813 &file)) { 1814 printk(KERN_INFO "Core dump to %s pipe failed\n", 1815 corename); 1816 goto fail_unlock; 1817 } 1818 } else 1819 file = filp_open(corename, 1820 O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag, 1821 0600); 1822 if (IS_ERR(file)) 1823 goto fail_unlock; 1824 inode = file->f_path.dentry->d_inode; 1825 if (inode->i_nlink > 1) 1826 goto close_fail; /* multiple links - don't dump */ 1827 if (!ispipe && d_unhashed(file->f_path.dentry)) 1828 goto close_fail; 1829 1830 /* AK: actually i see no reason to not allow this for named pipes etc., 1831 but keep the previous behaviour for now. */ 1832 if (!ispipe && !S_ISREG(inode->i_mode)) 1833 goto close_fail; 1834 /* 1835 * Dont allow local users get cute and trick others to coredump 1836 * into their pre-created files: 1837 */ 1838 if (inode->i_uid != current_fsuid()) 1839 goto close_fail; 1840 if (!file->f_op) 1841 goto close_fail; 1842 if (!file->f_op->write) 1843 goto close_fail; 1844 if (!ispipe && do_truncate(file->f_path.dentry, 0, 0, file) != 0) 1845 goto close_fail; 1846 1847 retval = binfmt->core_dump(signr, regs, file, core_limit); 1848 1849 if (retval) 1850 current->signal->group_exit_code |= 0x80; 1851 close_fail: 1852 filp_close(file, NULL); 1853 fail_unlock: 1854 if (helper_argv) 1855 argv_free(helper_argv); 1856 1857 revert_creds(old_cred); 1858 put_cred(cred); 1859 coredump_finish(mm); 1860 fail: 1861 return; 1862 } 1863