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/perf_event.h> 37 #include <linux/highmem.h> 38 #include <linux/spinlock.h> 39 #include <linux/key.h> 40 #include <linux/personality.h> 41 #include <linux/binfmts.h> 42 #include <linux/utsname.h> 43 #include <linux/pid_namespace.h> 44 #include <linux/module.h> 45 #include <linux/namei.h> 46 #include <linux/proc_fs.h> 47 #include <linux/mount.h> 48 #include <linux/security.h> 49 #include <linux/ima.h> 50 #include <linux/syscalls.h> 51 #include <linux/tsacct_kern.h> 52 #include <linux/cn_proc.h> 53 #include <linux/audit.h> 54 #include <linux/tracehook.h> 55 #include <linux/kmod.h> 56 #include <linux/fsnotify.h> 57 #include <linux/fs_struct.h> 58 #include <linux/pipe_fs_i.h> 59 60 #include <asm/uaccess.h> 61 #include <asm/mmu_context.h> 62 #include <asm/tlb.h> 63 #include "internal.h" 64 65 int core_uses_pid; 66 char core_pattern[CORENAME_MAX_SIZE] = "core"; 67 unsigned int core_pipe_limit; 68 int suid_dumpable = 0; 69 70 /* The maximal length of core_pattern is also specified in sysctl.c */ 71 72 static LIST_HEAD(formats); 73 static DEFINE_RWLOCK(binfmt_lock); 74 75 int __register_binfmt(struct linux_binfmt * fmt, int insert) 76 { 77 if (!fmt) 78 return -EINVAL; 79 write_lock(&binfmt_lock); 80 insert ? list_add(&fmt->lh, &formats) : 81 list_add_tail(&fmt->lh, &formats); 82 write_unlock(&binfmt_lock); 83 return 0; 84 } 85 86 EXPORT_SYMBOL(__register_binfmt); 87 88 void unregister_binfmt(struct linux_binfmt * fmt) 89 { 90 write_lock(&binfmt_lock); 91 list_del(&fmt->lh); 92 write_unlock(&binfmt_lock); 93 } 94 95 EXPORT_SYMBOL(unregister_binfmt); 96 97 static inline void put_binfmt(struct linux_binfmt * fmt) 98 { 99 module_put(fmt->module); 100 } 101 102 /* 103 * Note that a shared library must be both readable and executable due to 104 * security reasons. 105 * 106 * Also note that we take the address to load from from the file itself. 107 */ 108 SYSCALL_DEFINE1(uselib, const char __user *, library) 109 { 110 struct file *file; 111 char *tmp = getname(library); 112 int error = PTR_ERR(tmp); 113 114 if (IS_ERR(tmp)) 115 goto out; 116 117 file = do_filp_open(AT_FDCWD, tmp, 118 O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0, 119 MAY_READ | MAY_EXEC | MAY_OPEN); 120 putname(tmp); 121 error = PTR_ERR(file); 122 if (IS_ERR(file)) 123 goto out; 124 125 error = -EINVAL; 126 if (!S_ISREG(file->f_path.dentry->d_inode->i_mode)) 127 goto exit; 128 129 error = -EACCES; 130 if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) 131 goto exit; 132 133 fsnotify_open(file->f_path.dentry); 134 135 error = -ENOEXEC; 136 if(file->f_op) { 137 struct linux_binfmt * fmt; 138 139 read_lock(&binfmt_lock); 140 list_for_each_entry(fmt, &formats, lh) { 141 if (!fmt->load_shlib) 142 continue; 143 if (!try_module_get(fmt->module)) 144 continue; 145 read_unlock(&binfmt_lock); 146 error = fmt->load_shlib(file); 147 read_lock(&binfmt_lock); 148 put_binfmt(fmt); 149 if (error != -ENOEXEC) 150 break; 151 } 152 read_unlock(&binfmt_lock); 153 } 154 exit: 155 fput(file); 156 out: 157 return error; 158 } 159 160 #ifdef CONFIG_MMU 161 162 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, 163 int write) 164 { 165 struct page *page; 166 int ret; 167 168 #ifdef CONFIG_STACK_GROWSUP 169 if (write) { 170 ret = expand_stack_downwards(bprm->vma, pos); 171 if (ret < 0) 172 return NULL; 173 } 174 #endif 175 ret = get_user_pages(current, bprm->mm, pos, 176 1, write, 1, &page, NULL); 177 if (ret <= 0) 178 return NULL; 179 180 if (write) { 181 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start; 182 struct rlimit *rlim; 183 184 /* 185 * We've historically supported up to 32 pages (ARG_MAX) 186 * of argument strings even with small stacks 187 */ 188 if (size <= ARG_MAX) 189 return page; 190 191 /* 192 * Limit to 1/4-th the stack size for the argv+env strings. 193 * This ensures that: 194 * - the remaining binfmt code will not run out of stack space, 195 * - the program will have a reasonable amount of stack left 196 * to work from. 197 */ 198 rlim = current->signal->rlim; 199 if (size > rlim[RLIMIT_STACK].rlim_cur / 4) { 200 put_page(page); 201 return NULL; 202 } 203 } 204 205 return page; 206 } 207 208 static void put_arg_page(struct page *page) 209 { 210 put_page(page); 211 } 212 213 static void free_arg_page(struct linux_binprm *bprm, int i) 214 { 215 } 216 217 static void free_arg_pages(struct linux_binprm *bprm) 218 { 219 } 220 221 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, 222 struct page *page) 223 { 224 flush_cache_page(bprm->vma, pos, page_to_pfn(page)); 225 } 226 227 static int __bprm_mm_init(struct linux_binprm *bprm) 228 { 229 int err; 230 struct vm_area_struct *vma = NULL; 231 struct mm_struct *mm = bprm->mm; 232 233 bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL); 234 if (!vma) 235 return -ENOMEM; 236 237 down_write(&mm->mmap_sem); 238 vma->vm_mm = mm; 239 240 /* 241 * Place the stack at the largest stack address the architecture 242 * supports. Later, we'll move this to an appropriate place. We don't 243 * use STACK_TOP because that can depend on attributes which aren't 244 * configured yet. 245 */ 246 vma->vm_end = STACK_TOP_MAX; 247 vma->vm_start = vma->vm_end - PAGE_SIZE; 248 vma->vm_flags = VM_STACK_FLAGS; 249 vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); 250 err = insert_vm_struct(mm, vma); 251 if (err) 252 goto err; 253 254 mm->stack_vm = mm->total_vm = 1; 255 up_write(&mm->mmap_sem); 256 bprm->p = vma->vm_end - sizeof(void *); 257 return 0; 258 err: 259 up_write(&mm->mmap_sem); 260 bprm->vma = NULL; 261 kmem_cache_free(vm_area_cachep, vma); 262 return err; 263 } 264 265 static bool valid_arg_len(struct linux_binprm *bprm, long len) 266 { 267 return len <= MAX_ARG_STRLEN; 268 } 269 270 #else 271 272 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, 273 int write) 274 { 275 struct page *page; 276 277 page = bprm->page[pos / PAGE_SIZE]; 278 if (!page && write) { 279 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO); 280 if (!page) 281 return NULL; 282 bprm->page[pos / PAGE_SIZE] = page; 283 } 284 285 return page; 286 } 287 288 static void put_arg_page(struct page *page) 289 { 290 } 291 292 static void free_arg_page(struct linux_binprm *bprm, int i) 293 { 294 if (bprm->page[i]) { 295 __free_page(bprm->page[i]); 296 bprm->page[i] = NULL; 297 } 298 } 299 300 static void free_arg_pages(struct linux_binprm *bprm) 301 { 302 int i; 303 304 for (i = 0; i < MAX_ARG_PAGES; i++) 305 free_arg_page(bprm, i); 306 } 307 308 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, 309 struct page *page) 310 { 311 } 312 313 static int __bprm_mm_init(struct linux_binprm *bprm) 314 { 315 bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *); 316 return 0; 317 } 318 319 static bool valid_arg_len(struct linux_binprm *bprm, long len) 320 { 321 return len <= bprm->p; 322 } 323 324 #endif /* CONFIG_MMU */ 325 326 /* 327 * Create a new mm_struct and populate it with a temporary stack 328 * vm_area_struct. We don't have enough context at this point to set the stack 329 * flags, permissions, and offset, so we use temporary values. We'll update 330 * them later in setup_arg_pages(). 331 */ 332 int bprm_mm_init(struct linux_binprm *bprm) 333 { 334 int err; 335 struct mm_struct *mm = NULL; 336 337 bprm->mm = mm = mm_alloc(); 338 err = -ENOMEM; 339 if (!mm) 340 goto err; 341 342 err = init_new_context(current, mm); 343 if (err) 344 goto err; 345 346 err = __bprm_mm_init(bprm); 347 if (err) 348 goto err; 349 350 return 0; 351 352 err: 353 if (mm) { 354 bprm->mm = NULL; 355 mmdrop(mm); 356 } 357 358 return err; 359 } 360 361 /* 362 * count() counts the number of strings in array ARGV. 363 */ 364 static int count(char __user * __user * argv, int max) 365 { 366 int i = 0; 367 368 if (argv != NULL) { 369 for (;;) { 370 char __user * p; 371 372 if (get_user(p, argv)) 373 return -EFAULT; 374 if (!p) 375 break; 376 argv++; 377 if (i++ >= max) 378 return -E2BIG; 379 cond_resched(); 380 } 381 } 382 return i; 383 } 384 385 /* 386 * 'copy_strings()' copies argument/environment strings from the old 387 * processes's memory to the new process's stack. The call to get_user_pages() 388 * ensures the destination page is created and not swapped out. 389 */ 390 static int copy_strings(int argc, char __user * __user * argv, 391 struct linux_binprm *bprm) 392 { 393 struct page *kmapped_page = NULL; 394 char *kaddr = NULL; 395 unsigned long kpos = 0; 396 int ret; 397 398 while (argc-- > 0) { 399 char __user *str; 400 int len; 401 unsigned long pos; 402 403 if (get_user(str, argv+argc) || 404 !(len = strnlen_user(str, MAX_ARG_STRLEN))) { 405 ret = -EFAULT; 406 goto out; 407 } 408 409 if (!valid_arg_len(bprm, len)) { 410 ret = -E2BIG; 411 goto out; 412 } 413 414 /* We're going to work our way backwords. */ 415 pos = bprm->p; 416 str += len; 417 bprm->p -= len; 418 419 while (len > 0) { 420 int offset, bytes_to_copy; 421 422 offset = pos % PAGE_SIZE; 423 if (offset == 0) 424 offset = PAGE_SIZE; 425 426 bytes_to_copy = offset; 427 if (bytes_to_copy > len) 428 bytes_to_copy = len; 429 430 offset -= bytes_to_copy; 431 pos -= bytes_to_copy; 432 str -= bytes_to_copy; 433 len -= bytes_to_copy; 434 435 if (!kmapped_page || kpos != (pos & PAGE_MASK)) { 436 struct page *page; 437 438 page = get_arg_page(bprm, pos, 1); 439 if (!page) { 440 ret = -E2BIG; 441 goto out; 442 } 443 444 if (kmapped_page) { 445 flush_kernel_dcache_page(kmapped_page); 446 kunmap(kmapped_page); 447 put_arg_page(kmapped_page); 448 } 449 kmapped_page = page; 450 kaddr = kmap(kmapped_page); 451 kpos = pos & PAGE_MASK; 452 flush_arg_page(bprm, kpos, kmapped_page); 453 } 454 if (copy_from_user(kaddr+offset, str, bytes_to_copy)) { 455 ret = -EFAULT; 456 goto out; 457 } 458 } 459 } 460 ret = 0; 461 out: 462 if (kmapped_page) { 463 flush_kernel_dcache_page(kmapped_page); 464 kunmap(kmapped_page); 465 put_arg_page(kmapped_page); 466 } 467 return ret; 468 } 469 470 /* 471 * Like copy_strings, but get argv and its values from kernel memory. 472 */ 473 int copy_strings_kernel(int argc,char ** argv, struct linux_binprm *bprm) 474 { 475 int r; 476 mm_segment_t oldfs = get_fs(); 477 set_fs(KERNEL_DS); 478 r = copy_strings(argc, (char __user * __user *)argv, bprm); 479 set_fs(oldfs); 480 return r; 481 } 482 EXPORT_SYMBOL(copy_strings_kernel); 483 484 #ifdef CONFIG_MMU 485 486 /* 487 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once 488 * the binfmt code determines where the new stack should reside, we shift it to 489 * its final location. The process proceeds as follows: 490 * 491 * 1) Use shift to calculate the new vma endpoints. 492 * 2) Extend vma to cover both the old and new ranges. This ensures the 493 * arguments passed to subsequent functions are consistent. 494 * 3) Move vma's page tables to the new range. 495 * 4) Free up any cleared pgd range. 496 * 5) Shrink the vma to cover only the new range. 497 */ 498 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift) 499 { 500 struct mm_struct *mm = vma->vm_mm; 501 unsigned long old_start = vma->vm_start; 502 unsigned long old_end = vma->vm_end; 503 unsigned long length = old_end - old_start; 504 unsigned long new_start = old_start - shift; 505 unsigned long new_end = old_end - shift; 506 struct mmu_gather *tlb; 507 508 BUG_ON(new_start > new_end); 509 510 /* 511 * ensure there are no vmas between where we want to go 512 * and where we are 513 */ 514 if (vma != find_vma(mm, new_start)) 515 return -EFAULT; 516 517 /* 518 * cover the whole range: [new_start, old_end) 519 */ 520 vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL); 521 522 /* 523 * move the page tables downwards, on failure we rely on 524 * process cleanup to remove whatever mess we made. 525 */ 526 if (length != move_page_tables(vma, old_start, 527 vma, new_start, length)) 528 return -ENOMEM; 529 530 lru_add_drain(); 531 tlb = tlb_gather_mmu(mm, 0); 532 if (new_end > old_start) { 533 /* 534 * when the old and new regions overlap clear from new_end. 535 */ 536 free_pgd_range(tlb, new_end, old_end, new_end, 537 vma->vm_next ? vma->vm_next->vm_start : 0); 538 } else { 539 /* 540 * otherwise, clean from old_start; this is done to not touch 541 * the address space in [new_end, old_start) some architectures 542 * have constraints on va-space that make this illegal (IA64) - 543 * for the others its just a little faster. 544 */ 545 free_pgd_range(tlb, old_start, old_end, new_end, 546 vma->vm_next ? vma->vm_next->vm_start : 0); 547 } 548 tlb_finish_mmu(tlb, new_end, old_end); 549 550 /* 551 * shrink the vma to just the new range. 552 */ 553 vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL); 554 555 return 0; 556 } 557 558 #define EXTRA_STACK_VM_PAGES 20 /* random */ 559 560 /* 561 * Finalizes the stack vm_area_struct. The flags and permissions are updated, 562 * the stack is optionally relocated, and some extra space is added. 563 */ 564 int setup_arg_pages(struct linux_binprm *bprm, 565 unsigned long stack_top, 566 int executable_stack) 567 { 568 unsigned long ret; 569 unsigned long stack_shift; 570 struct mm_struct *mm = current->mm; 571 struct vm_area_struct *vma = bprm->vma; 572 struct vm_area_struct *prev = NULL; 573 unsigned long vm_flags; 574 unsigned long stack_base; 575 576 #ifdef CONFIG_STACK_GROWSUP 577 /* Limit stack size to 1GB */ 578 stack_base = current->signal->rlim[RLIMIT_STACK].rlim_max; 579 if (stack_base > (1 << 30)) 580 stack_base = 1 << 30; 581 582 /* Make sure we didn't let the argument array grow too large. */ 583 if (vma->vm_end - vma->vm_start > stack_base) 584 return -ENOMEM; 585 586 stack_base = PAGE_ALIGN(stack_top - stack_base); 587 588 stack_shift = vma->vm_start - stack_base; 589 mm->arg_start = bprm->p - stack_shift; 590 bprm->p = vma->vm_end - stack_shift; 591 #else 592 stack_top = arch_align_stack(stack_top); 593 stack_top = PAGE_ALIGN(stack_top); 594 stack_shift = vma->vm_end - stack_top; 595 596 bprm->p -= stack_shift; 597 mm->arg_start = bprm->p; 598 #endif 599 600 if (bprm->loader) 601 bprm->loader -= stack_shift; 602 bprm->exec -= stack_shift; 603 604 down_write(&mm->mmap_sem); 605 vm_flags = VM_STACK_FLAGS; 606 607 /* 608 * Adjust stack execute permissions; explicitly enable for 609 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone 610 * (arch default) otherwise. 611 */ 612 if (unlikely(executable_stack == EXSTACK_ENABLE_X)) 613 vm_flags |= VM_EXEC; 614 else if (executable_stack == EXSTACK_DISABLE_X) 615 vm_flags &= ~VM_EXEC; 616 vm_flags |= mm->def_flags; 617 618 ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end, 619 vm_flags); 620 if (ret) 621 goto out_unlock; 622 BUG_ON(prev != vma); 623 624 /* Move stack pages down in memory. */ 625 if (stack_shift) { 626 ret = shift_arg_pages(vma, stack_shift); 627 if (ret) { 628 up_write(&mm->mmap_sem); 629 return ret; 630 } 631 } 632 633 #ifdef CONFIG_STACK_GROWSUP 634 stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE; 635 #else 636 stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE; 637 #endif 638 ret = expand_stack(vma, stack_base); 639 if (ret) 640 ret = -EFAULT; 641 642 out_unlock: 643 up_write(&mm->mmap_sem); 644 return 0; 645 } 646 EXPORT_SYMBOL(setup_arg_pages); 647 648 #endif /* CONFIG_MMU */ 649 650 struct file *open_exec(const char *name) 651 { 652 struct file *file; 653 int err; 654 655 file = do_filp_open(AT_FDCWD, name, 656 O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0, 657 MAY_EXEC | MAY_OPEN); 658 if (IS_ERR(file)) 659 goto out; 660 661 err = -EACCES; 662 if (!S_ISREG(file->f_path.dentry->d_inode->i_mode)) 663 goto exit; 664 665 if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) 666 goto exit; 667 668 fsnotify_open(file->f_path.dentry); 669 670 err = deny_write_access(file); 671 if (err) 672 goto exit; 673 674 out: 675 return file; 676 677 exit: 678 fput(file); 679 return ERR_PTR(err); 680 } 681 EXPORT_SYMBOL(open_exec); 682 683 int kernel_read(struct file *file, loff_t offset, 684 char *addr, unsigned long count) 685 { 686 mm_segment_t old_fs; 687 loff_t pos = offset; 688 int result; 689 690 old_fs = get_fs(); 691 set_fs(get_ds()); 692 /* The cast to a user pointer is valid due to the set_fs() */ 693 result = vfs_read(file, (void __user *)addr, count, &pos); 694 set_fs(old_fs); 695 return result; 696 } 697 698 EXPORT_SYMBOL(kernel_read); 699 700 static int exec_mmap(struct mm_struct *mm) 701 { 702 struct task_struct *tsk; 703 struct mm_struct * old_mm, *active_mm; 704 705 /* Notify parent that we're no longer interested in the old VM */ 706 tsk = current; 707 old_mm = current->mm; 708 mm_release(tsk, old_mm); 709 710 if (old_mm) { 711 /* 712 * Make sure that if there is a core dump in progress 713 * for the old mm, we get out and die instead of going 714 * through with the exec. We must hold mmap_sem around 715 * checking core_state and changing tsk->mm. 716 */ 717 down_read(&old_mm->mmap_sem); 718 if (unlikely(old_mm->core_state)) { 719 up_read(&old_mm->mmap_sem); 720 return -EINTR; 721 } 722 } 723 task_lock(tsk); 724 active_mm = tsk->active_mm; 725 tsk->mm = mm; 726 tsk->active_mm = mm; 727 activate_mm(active_mm, mm); 728 task_unlock(tsk); 729 arch_pick_mmap_layout(mm); 730 if (old_mm) { 731 up_read(&old_mm->mmap_sem); 732 BUG_ON(active_mm != old_mm); 733 mm_update_next_owner(old_mm); 734 mmput(old_mm); 735 return 0; 736 } 737 mmdrop(active_mm); 738 return 0; 739 } 740 741 /* 742 * This function makes sure the current process has its own signal table, 743 * so that flush_signal_handlers can later reset the handlers without 744 * disturbing other processes. (Other processes might share the signal 745 * table via the CLONE_SIGHAND option to clone().) 746 */ 747 static int de_thread(struct task_struct *tsk) 748 { 749 struct signal_struct *sig = tsk->signal; 750 struct sighand_struct *oldsighand = tsk->sighand; 751 spinlock_t *lock = &oldsighand->siglock; 752 int count; 753 754 if (thread_group_empty(tsk)) 755 goto no_thread_group; 756 757 /* 758 * Kill all other threads in the thread group. 759 */ 760 spin_lock_irq(lock); 761 if (signal_group_exit(sig)) { 762 /* 763 * Another group action in progress, just 764 * return so that the signal is processed. 765 */ 766 spin_unlock_irq(lock); 767 return -EAGAIN; 768 } 769 sig->group_exit_task = tsk; 770 zap_other_threads(tsk); 771 772 /* Account for the thread group leader hanging around: */ 773 count = thread_group_leader(tsk) ? 1 : 2; 774 sig->notify_count = count; 775 while (atomic_read(&sig->count) > count) { 776 __set_current_state(TASK_UNINTERRUPTIBLE); 777 spin_unlock_irq(lock); 778 schedule(); 779 spin_lock_irq(lock); 780 } 781 spin_unlock_irq(lock); 782 783 /* 784 * At this point all other threads have exited, all we have to 785 * do is to wait for the thread group leader to become inactive, 786 * and to assume its PID: 787 */ 788 if (!thread_group_leader(tsk)) { 789 struct task_struct *leader = tsk->group_leader; 790 791 sig->notify_count = -1; /* for exit_notify() */ 792 for (;;) { 793 write_lock_irq(&tasklist_lock); 794 if (likely(leader->exit_state)) 795 break; 796 __set_current_state(TASK_UNINTERRUPTIBLE); 797 write_unlock_irq(&tasklist_lock); 798 schedule(); 799 } 800 801 /* 802 * The only record we have of the real-time age of a 803 * process, regardless of execs it's done, is start_time. 804 * All the past CPU time is accumulated in signal_struct 805 * from sister threads now dead. But in this non-leader 806 * exec, nothing survives from the original leader thread, 807 * whose birth marks the true age of this process now. 808 * When we take on its identity by switching to its PID, we 809 * also take its birthdate (always earlier than our own). 810 */ 811 tsk->start_time = leader->start_time; 812 813 BUG_ON(!same_thread_group(leader, tsk)); 814 BUG_ON(has_group_leader_pid(tsk)); 815 /* 816 * An exec() starts a new thread group with the 817 * TGID of the previous thread group. Rehash the 818 * two threads with a switched PID, and release 819 * the former thread group leader: 820 */ 821 822 /* Become a process group leader with the old leader's pid. 823 * The old leader becomes a thread of the this thread group. 824 * Note: The old leader also uses this pid until release_task 825 * is called. Odd but simple and correct. 826 */ 827 detach_pid(tsk, PIDTYPE_PID); 828 tsk->pid = leader->pid; 829 attach_pid(tsk, PIDTYPE_PID, task_pid(leader)); 830 transfer_pid(leader, tsk, PIDTYPE_PGID); 831 transfer_pid(leader, tsk, PIDTYPE_SID); 832 list_replace_rcu(&leader->tasks, &tsk->tasks); 833 834 tsk->group_leader = tsk; 835 leader->group_leader = tsk; 836 837 tsk->exit_signal = SIGCHLD; 838 839 BUG_ON(leader->exit_state != EXIT_ZOMBIE); 840 leader->exit_state = EXIT_DEAD; 841 write_unlock_irq(&tasklist_lock); 842 843 release_task(leader); 844 } 845 846 sig->group_exit_task = NULL; 847 sig->notify_count = 0; 848 849 no_thread_group: 850 if (current->mm) 851 setmax_mm_hiwater_rss(&sig->maxrss, current->mm); 852 853 exit_itimers(sig); 854 flush_itimer_signals(); 855 856 if (atomic_read(&oldsighand->count) != 1) { 857 struct sighand_struct *newsighand; 858 /* 859 * This ->sighand is shared with the CLONE_SIGHAND 860 * but not CLONE_THREAD task, switch to the new one. 861 */ 862 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 863 if (!newsighand) 864 return -ENOMEM; 865 866 atomic_set(&newsighand->count, 1); 867 memcpy(newsighand->action, oldsighand->action, 868 sizeof(newsighand->action)); 869 870 write_lock_irq(&tasklist_lock); 871 spin_lock(&oldsighand->siglock); 872 rcu_assign_pointer(tsk->sighand, newsighand); 873 spin_unlock(&oldsighand->siglock); 874 write_unlock_irq(&tasklist_lock); 875 876 __cleanup_sighand(oldsighand); 877 } 878 879 BUG_ON(!thread_group_leader(tsk)); 880 return 0; 881 } 882 883 /* 884 * These functions flushes out all traces of the currently running executable 885 * so that a new one can be started 886 */ 887 static void flush_old_files(struct files_struct * files) 888 { 889 long j = -1; 890 struct fdtable *fdt; 891 892 spin_lock(&files->file_lock); 893 for (;;) { 894 unsigned long set, i; 895 896 j++; 897 i = j * __NFDBITS; 898 fdt = files_fdtable(files); 899 if (i >= fdt->max_fds) 900 break; 901 set = fdt->close_on_exec->fds_bits[j]; 902 if (!set) 903 continue; 904 fdt->close_on_exec->fds_bits[j] = 0; 905 spin_unlock(&files->file_lock); 906 for ( ; set ; i++,set >>= 1) { 907 if (set & 1) { 908 sys_close(i); 909 } 910 } 911 spin_lock(&files->file_lock); 912 913 } 914 spin_unlock(&files->file_lock); 915 } 916 917 char *get_task_comm(char *buf, struct task_struct *tsk) 918 { 919 /* buf must be at least sizeof(tsk->comm) in size */ 920 task_lock(tsk); 921 strncpy(buf, tsk->comm, sizeof(tsk->comm)); 922 task_unlock(tsk); 923 return buf; 924 } 925 926 void set_task_comm(struct task_struct *tsk, char *buf) 927 { 928 task_lock(tsk); 929 strlcpy(tsk->comm, buf, sizeof(tsk->comm)); 930 task_unlock(tsk); 931 perf_event_comm(tsk); 932 } 933 934 int flush_old_exec(struct linux_binprm * bprm) 935 { 936 char * name; 937 int i, ch, retval; 938 char tcomm[sizeof(current->comm)]; 939 940 /* 941 * Make sure we have a private signal table and that 942 * we are unassociated from the previous thread group. 943 */ 944 retval = de_thread(current); 945 if (retval) 946 goto out; 947 948 set_mm_exe_file(bprm->mm, bprm->file); 949 950 /* 951 * Release all of the old mmap stuff 952 */ 953 retval = exec_mmap(bprm->mm); 954 if (retval) 955 goto out; 956 957 bprm->mm = NULL; /* We're using it now */ 958 959 /* This is the point of no return */ 960 current->sas_ss_sp = current->sas_ss_size = 0; 961 962 if (current_euid() == current_uid() && current_egid() == current_gid()) 963 set_dumpable(current->mm, 1); 964 else 965 set_dumpable(current->mm, suid_dumpable); 966 967 name = bprm->filename; 968 969 /* Copies the binary name from after last slash */ 970 for (i=0; (ch = *(name++)) != '\0';) { 971 if (ch == '/') 972 i = 0; /* overwrite what we wrote */ 973 else 974 if (i < (sizeof(tcomm) - 1)) 975 tcomm[i++] = ch; 976 } 977 tcomm[i] = '\0'; 978 set_task_comm(current, tcomm); 979 980 current->flags &= ~PF_RANDOMIZE; 981 flush_thread(); 982 983 /* Set the new mm task size. We have to do that late because it may 984 * depend on TIF_32BIT which is only updated in flush_thread() on 985 * some architectures like powerpc 986 */ 987 current->mm->task_size = TASK_SIZE; 988 989 /* install the new credentials */ 990 if (bprm->cred->uid != current_euid() || 991 bprm->cred->gid != current_egid()) { 992 current->pdeath_signal = 0; 993 } else if (file_permission(bprm->file, MAY_READ) || 994 bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) { 995 set_dumpable(current->mm, suid_dumpable); 996 } 997 998 current->personality &= ~bprm->per_clear; 999 1000 /* 1001 * Flush performance counters when crossing a 1002 * security domain: 1003 */ 1004 if (!get_dumpable(current->mm)) 1005 perf_event_exit_task(current); 1006 1007 /* An exec changes our domain. We are no longer part of the thread 1008 group */ 1009 1010 current->self_exec_id++; 1011 1012 flush_signal_handlers(current, 0); 1013 flush_old_files(current->files); 1014 1015 return 0; 1016 1017 out: 1018 return retval; 1019 } 1020 1021 EXPORT_SYMBOL(flush_old_exec); 1022 1023 /* 1024 * Prepare credentials and lock ->cred_guard_mutex. 1025 * install_exec_creds() commits the new creds and drops the lock. 1026 * Or, if exec fails before, free_bprm() should release ->cred and 1027 * and unlock. 1028 */ 1029 int prepare_bprm_creds(struct linux_binprm *bprm) 1030 { 1031 if (mutex_lock_interruptible(¤t->cred_guard_mutex)) 1032 return -ERESTARTNOINTR; 1033 1034 bprm->cred = prepare_exec_creds(); 1035 if (likely(bprm->cred)) 1036 return 0; 1037 1038 mutex_unlock(¤t->cred_guard_mutex); 1039 return -ENOMEM; 1040 } 1041 1042 void free_bprm(struct linux_binprm *bprm) 1043 { 1044 free_arg_pages(bprm); 1045 if (bprm->cred) { 1046 mutex_unlock(¤t->cred_guard_mutex); 1047 abort_creds(bprm->cred); 1048 } 1049 kfree(bprm); 1050 } 1051 1052 /* 1053 * install the new credentials for this executable 1054 */ 1055 void install_exec_creds(struct linux_binprm *bprm) 1056 { 1057 security_bprm_committing_creds(bprm); 1058 1059 commit_creds(bprm->cred); 1060 bprm->cred = NULL; 1061 /* 1062 * cred_guard_mutex must be held at least to this point to prevent 1063 * ptrace_attach() from altering our determination of the task's 1064 * credentials; any time after this it may be unlocked. 1065 */ 1066 security_bprm_committed_creds(bprm); 1067 mutex_unlock(¤t->cred_guard_mutex); 1068 } 1069 EXPORT_SYMBOL(install_exec_creds); 1070 1071 /* 1072 * determine how safe it is to execute the proposed program 1073 * - the caller must hold current->cred_guard_mutex to protect against 1074 * PTRACE_ATTACH 1075 */ 1076 int check_unsafe_exec(struct linux_binprm *bprm) 1077 { 1078 struct task_struct *p = current, *t; 1079 unsigned n_fs; 1080 int res = 0; 1081 1082 bprm->unsafe = tracehook_unsafe_exec(p); 1083 1084 n_fs = 1; 1085 write_lock(&p->fs->lock); 1086 rcu_read_lock(); 1087 for (t = next_thread(p); t != p; t = next_thread(t)) { 1088 if (t->fs == p->fs) 1089 n_fs++; 1090 } 1091 rcu_read_unlock(); 1092 1093 if (p->fs->users > n_fs) { 1094 bprm->unsafe |= LSM_UNSAFE_SHARE; 1095 } else { 1096 res = -EAGAIN; 1097 if (!p->fs->in_exec) { 1098 p->fs->in_exec = 1; 1099 res = 1; 1100 } 1101 } 1102 write_unlock(&p->fs->lock); 1103 1104 return res; 1105 } 1106 1107 /* 1108 * Fill the binprm structure from the inode. 1109 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes 1110 * 1111 * This may be called multiple times for binary chains (scripts for example). 1112 */ 1113 int prepare_binprm(struct linux_binprm *bprm) 1114 { 1115 umode_t mode; 1116 struct inode * inode = bprm->file->f_path.dentry->d_inode; 1117 int retval; 1118 1119 mode = inode->i_mode; 1120 if (bprm->file->f_op == NULL) 1121 return -EACCES; 1122 1123 /* clear any previous set[ug]id data from a previous binary */ 1124 bprm->cred->euid = current_euid(); 1125 bprm->cred->egid = current_egid(); 1126 1127 if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) { 1128 /* Set-uid? */ 1129 if (mode & S_ISUID) { 1130 bprm->per_clear |= PER_CLEAR_ON_SETID; 1131 bprm->cred->euid = inode->i_uid; 1132 } 1133 1134 /* Set-gid? */ 1135 /* 1136 * If setgid is set but no group execute bit then this 1137 * is a candidate for mandatory locking, not a setgid 1138 * executable. 1139 */ 1140 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { 1141 bprm->per_clear |= PER_CLEAR_ON_SETID; 1142 bprm->cred->egid = inode->i_gid; 1143 } 1144 } 1145 1146 /* fill in binprm security blob */ 1147 retval = security_bprm_set_creds(bprm); 1148 if (retval) 1149 return retval; 1150 bprm->cred_prepared = 1; 1151 1152 memset(bprm->buf, 0, BINPRM_BUF_SIZE); 1153 return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE); 1154 } 1155 1156 EXPORT_SYMBOL(prepare_binprm); 1157 1158 /* 1159 * Arguments are '\0' separated strings found at the location bprm->p 1160 * points to; chop off the first by relocating brpm->p to right after 1161 * the first '\0' encountered. 1162 */ 1163 int remove_arg_zero(struct linux_binprm *bprm) 1164 { 1165 int ret = 0; 1166 unsigned long offset; 1167 char *kaddr; 1168 struct page *page; 1169 1170 if (!bprm->argc) 1171 return 0; 1172 1173 do { 1174 offset = bprm->p & ~PAGE_MASK; 1175 page = get_arg_page(bprm, bprm->p, 0); 1176 if (!page) { 1177 ret = -EFAULT; 1178 goto out; 1179 } 1180 kaddr = kmap_atomic(page, KM_USER0); 1181 1182 for (; offset < PAGE_SIZE && kaddr[offset]; 1183 offset++, bprm->p++) 1184 ; 1185 1186 kunmap_atomic(kaddr, KM_USER0); 1187 put_arg_page(page); 1188 1189 if (offset == PAGE_SIZE) 1190 free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1); 1191 } while (offset == PAGE_SIZE); 1192 1193 bprm->p++; 1194 bprm->argc--; 1195 ret = 0; 1196 1197 out: 1198 return ret; 1199 } 1200 EXPORT_SYMBOL(remove_arg_zero); 1201 1202 /* 1203 * cycle the list of binary formats handler, until one recognizes the image 1204 */ 1205 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs) 1206 { 1207 unsigned int depth = bprm->recursion_depth; 1208 int try,retval; 1209 struct linux_binfmt *fmt; 1210 1211 retval = security_bprm_check(bprm); 1212 if (retval) 1213 return retval; 1214 retval = ima_bprm_check(bprm); 1215 if (retval) 1216 return retval; 1217 1218 /* kernel module loader fixup */ 1219 /* so we don't try to load run modprobe in kernel space. */ 1220 set_fs(USER_DS); 1221 1222 retval = audit_bprm(bprm); 1223 if (retval) 1224 return retval; 1225 1226 retval = -ENOENT; 1227 for (try=0; try<2; try++) { 1228 read_lock(&binfmt_lock); 1229 list_for_each_entry(fmt, &formats, lh) { 1230 int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary; 1231 if (!fn) 1232 continue; 1233 if (!try_module_get(fmt->module)) 1234 continue; 1235 read_unlock(&binfmt_lock); 1236 retval = fn(bprm, regs); 1237 /* 1238 * Restore the depth counter to its starting value 1239 * in this call, so we don't have to rely on every 1240 * load_binary function to restore it on return. 1241 */ 1242 bprm->recursion_depth = depth; 1243 if (retval >= 0) { 1244 if (depth == 0) 1245 tracehook_report_exec(fmt, bprm, regs); 1246 put_binfmt(fmt); 1247 allow_write_access(bprm->file); 1248 if (bprm->file) 1249 fput(bprm->file); 1250 bprm->file = NULL; 1251 current->did_exec = 1; 1252 proc_exec_connector(current); 1253 return retval; 1254 } 1255 read_lock(&binfmt_lock); 1256 put_binfmt(fmt); 1257 if (retval != -ENOEXEC || bprm->mm == NULL) 1258 break; 1259 if (!bprm->file) { 1260 read_unlock(&binfmt_lock); 1261 return retval; 1262 } 1263 } 1264 read_unlock(&binfmt_lock); 1265 if (retval != -ENOEXEC || bprm->mm == NULL) { 1266 break; 1267 #ifdef CONFIG_MODULES 1268 } else { 1269 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e)) 1270 if (printable(bprm->buf[0]) && 1271 printable(bprm->buf[1]) && 1272 printable(bprm->buf[2]) && 1273 printable(bprm->buf[3])) 1274 break; /* -ENOEXEC */ 1275 request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2])); 1276 #endif 1277 } 1278 } 1279 return retval; 1280 } 1281 1282 EXPORT_SYMBOL(search_binary_handler); 1283 1284 /* 1285 * sys_execve() executes a new program. 1286 */ 1287 int do_execve(char * filename, 1288 char __user *__user *argv, 1289 char __user *__user *envp, 1290 struct pt_regs * regs) 1291 { 1292 struct linux_binprm *bprm; 1293 struct file *file; 1294 struct files_struct *displaced; 1295 bool clear_in_exec; 1296 int retval; 1297 1298 retval = unshare_files(&displaced); 1299 if (retval) 1300 goto out_ret; 1301 1302 retval = -ENOMEM; 1303 bprm = kzalloc(sizeof(*bprm), GFP_KERNEL); 1304 if (!bprm) 1305 goto out_files; 1306 1307 retval = prepare_bprm_creds(bprm); 1308 if (retval) 1309 goto out_free; 1310 1311 retval = check_unsafe_exec(bprm); 1312 if (retval < 0) 1313 goto out_free; 1314 clear_in_exec = retval; 1315 current->in_execve = 1; 1316 1317 file = open_exec(filename); 1318 retval = PTR_ERR(file); 1319 if (IS_ERR(file)) 1320 goto out_unmark; 1321 1322 sched_exec(); 1323 1324 bprm->file = file; 1325 bprm->filename = filename; 1326 bprm->interp = filename; 1327 1328 retval = bprm_mm_init(bprm); 1329 if (retval) 1330 goto out_file; 1331 1332 bprm->argc = count(argv, MAX_ARG_STRINGS); 1333 if ((retval = bprm->argc) < 0) 1334 goto out; 1335 1336 bprm->envc = count(envp, MAX_ARG_STRINGS); 1337 if ((retval = bprm->envc) < 0) 1338 goto out; 1339 1340 retval = prepare_binprm(bprm); 1341 if (retval < 0) 1342 goto out; 1343 1344 retval = copy_strings_kernel(1, &bprm->filename, bprm); 1345 if (retval < 0) 1346 goto out; 1347 1348 bprm->exec = bprm->p; 1349 retval = copy_strings(bprm->envc, envp, bprm); 1350 if (retval < 0) 1351 goto out; 1352 1353 retval = copy_strings(bprm->argc, argv, bprm); 1354 if (retval < 0) 1355 goto out; 1356 1357 current->flags &= ~PF_KTHREAD; 1358 retval = search_binary_handler(bprm,regs); 1359 if (retval < 0) 1360 goto out; 1361 1362 current->stack_start = current->mm->start_stack; 1363 1364 /* execve succeeded */ 1365 current->fs->in_exec = 0; 1366 current->in_execve = 0; 1367 acct_update_integrals(current); 1368 free_bprm(bprm); 1369 if (displaced) 1370 put_files_struct(displaced); 1371 return retval; 1372 1373 out: 1374 if (bprm->mm) 1375 mmput (bprm->mm); 1376 1377 out_file: 1378 if (bprm->file) { 1379 allow_write_access(bprm->file); 1380 fput(bprm->file); 1381 } 1382 1383 out_unmark: 1384 if (clear_in_exec) 1385 current->fs->in_exec = 0; 1386 current->in_execve = 0; 1387 1388 out_free: 1389 free_bprm(bprm); 1390 1391 out_files: 1392 if (displaced) 1393 reset_files_struct(displaced); 1394 out_ret: 1395 return retval; 1396 } 1397 1398 void set_binfmt(struct linux_binfmt *new) 1399 { 1400 struct mm_struct *mm = current->mm; 1401 1402 if (mm->binfmt) 1403 module_put(mm->binfmt->module); 1404 1405 mm->binfmt = new; 1406 if (new) 1407 __module_get(new->module); 1408 } 1409 1410 EXPORT_SYMBOL(set_binfmt); 1411 1412 /* format_corename will inspect the pattern parameter, and output a 1413 * name into corename, which must have space for at least 1414 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator. 1415 */ 1416 static int format_corename(char *corename, long signr) 1417 { 1418 const struct cred *cred = current_cred(); 1419 const char *pat_ptr = core_pattern; 1420 int ispipe = (*pat_ptr == '|'); 1421 char *out_ptr = corename; 1422 char *const out_end = corename + CORENAME_MAX_SIZE; 1423 int rc; 1424 int pid_in_pattern = 0; 1425 1426 /* Repeat as long as we have more pattern to process and more output 1427 space */ 1428 while (*pat_ptr) { 1429 if (*pat_ptr != '%') { 1430 if (out_ptr == out_end) 1431 goto out; 1432 *out_ptr++ = *pat_ptr++; 1433 } else { 1434 switch (*++pat_ptr) { 1435 case 0: 1436 goto out; 1437 /* Double percent, output one percent */ 1438 case '%': 1439 if (out_ptr == out_end) 1440 goto out; 1441 *out_ptr++ = '%'; 1442 break; 1443 /* pid */ 1444 case 'p': 1445 pid_in_pattern = 1; 1446 rc = snprintf(out_ptr, out_end - out_ptr, 1447 "%d", task_tgid_vnr(current)); 1448 if (rc > out_end - out_ptr) 1449 goto out; 1450 out_ptr += rc; 1451 break; 1452 /* uid */ 1453 case 'u': 1454 rc = snprintf(out_ptr, out_end - out_ptr, 1455 "%d", cred->uid); 1456 if (rc > out_end - out_ptr) 1457 goto out; 1458 out_ptr += rc; 1459 break; 1460 /* gid */ 1461 case 'g': 1462 rc = snprintf(out_ptr, out_end - out_ptr, 1463 "%d", cred->gid); 1464 if (rc > out_end - out_ptr) 1465 goto out; 1466 out_ptr += rc; 1467 break; 1468 /* signal that caused the coredump */ 1469 case 's': 1470 rc = snprintf(out_ptr, out_end - out_ptr, 1471 "%ld", signr); 1472 if (rc > out_end - out_ptr) 1473 goto out; 1474 out_ptr += rc; 1475 break; 1476 /* UNIX time of coredump */ 1477 case 't': { 1478 struct timeval tv; 1479 do_gettimeofday(&tv); 1480 rc = snprintf(out_ptr, out_end - out_ptr, 1481 "%lu", tv.tv_sec); 1482 if (rc > out_end - out_ptr) 1483 goto out; 1484 out_ptr += rc; 1485 break; 1486 } 1487 /* hostname */ 1488 case 'h': 1489 down_read(&uts_sem); 1490 rc = snprintf(out_ptr, out_end - out_ptr, 1491 "%s", utsname()->nodename); 1492 up_read(&uts_sem); 1493 if (rc > out_end - out_ptr) 1494 goto out; 1495 out_ptr += rc; 1496 break; 1497 /* executable */ 1498 case 'e': 1499 rc = snprintf(out_ptr, out_end - out_ptr, 1500 "%s", current->comm); 1501 if (rc > out_end - out_ptr) 1502 goto out; 1503 out_ptr += rc; 1504 break; 1505 /* core limit size */ 1506 case 'c': 1507 rc = snprintf(out_ptr, out_end - out_ptr, 1508 "%lu", current->signal->rlim[RLIMIT_CORE].rlim_cur); 1509 if (rc > out_end - out_ptr) 1510 goto out; 1511 out_ptr += rc; 1512 break; 1513 default: 1514 break; 1515 } 1516 ++pat_ptr; 1517 } 1518 } 1519 /* Backward compatibility with core_uses_pid: 1520 * 1521 * If core_pattern does not include a %p (as is the default) 1522 * and core_uses_pid is set, then .%pid will be appended to 1523 * the filename. Do not do this for piped commands. */ 1524 if (!ispipe && !pid_in_pattern && core_uses_pid) { 1525 rc = snprintf(out_ptr, out_end - out_ptr, 1526 ".%d", task_tgid_vnr(current)); 1527 if (rc > out_end - out_ptr) 1528 goto out; 1529 out_ptr += rc; 1530 } 1531 out: 1532 *out_ptr = 0; 1533 return ispipe; 1534 } 1535 1536 static int zap_process(struct task_struct *start) 1537 { 1538 struct task_struct *t; 1539 int nr = 0; 1540 1541 start->signal->flags = SIGNAL_GROUP_EXIT; 1542 start->signal->group_stop_count = 0; 1543 1544 t = start; 1545 do { 1546 if (t != current && t->mm) { 1547 sigaddset(&t->pending.signal, SIGKILL); 1548 signal_wake_up(t, 1); 1549 nr++; 1550 } 1551 } while_each_thread(start, t); 1552 1553 return nr; 1554 } 1555 1556 static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm, 1557 struct core_state *core_state, int exit_code) 1558 { 1559 struct task_struct *g, *p; 1560 unsigned long flags; 1561 int nr = -EAGAIN; 1562 1563 spin_lock_irq(&tsk->sighand->siglock); 1564 if (!signal_group_exit(tsk->signal)) { 1565 mm->core_state = core_state; 1566 tsk->signal->group_exit_code = exit_code; 1567 nr = zap_process(tsk); 1568 } 1569 spin_unlock_irq(&tsk->sighand->siglock); 1570 if (unlikely(nr < 0)) 1571 return nr; 1572 1573 if (atomic_read(&mm->mm_users) == nr + 1) 1574 goto done; 1575 /* 1576 * We should find and kill all tasks which use this mm, and we should 1577 * count them correctly into ->nr_threads. We don't take tasklist 1578 * lock, but this is safe wrt: 1579 * 1580 * fork: 1581 * None of sub-threads can fork after zap_process(leader). All 1582 * processes which were created before this point should be 1583 * visible to zap_threads() because copy_process() adds the new 1584 * process to the tail of init_task.tasks list, and lock/unlock 1585 * of ->siglock provides a memory barrier. 1586 * 1587 * do_exit: 1588 * The caller holds mm->mmap_sem. This means that the task which 1589 * uses this mm can't pass exit_mm(), so it can't exit or clear 1590 * its ->mm. 1591 * 1592 * de_thread: 1593 * It does list_replace_rcu(&leader->tasks, ¤t->tasks), 1594 * we must see either old or new leader, this does not matter. 1595 * However, it can change p->sighand, so lock_task_sighand(p) 1596 * must be used. Since p->mm != NULL and we hold ->mmap_sem 1597 * it can't fail. 1598 * 1599 * Note also that "g" can be the old leader with ->mm == NULL 1600 * and already unhashed and thus removed from ->thread_group. 1601 * This is OK, __unhash_process()->list_del_rcu() does not 1602 * clear the ->next pointer, we will find the new leader via 1603 * next_thread(). 1604 */ 1605 rcu_read_lock(); 1606 for_each_process(g) { 1607 if (g == tsk->group_leader) 1608 continue; 1609 if (g->flags & PF_KTHREAD) 1610 continue; 1611 p = g; 1612 do { 1613 if (p->mm) { 1614 if (unlikely(p->mm == mm)) { 1615 lock_task_sighand(p, &flags); 1616 nr += zap_process(p); 1617 unlock_task_sighand(p, &flags); 1618 } 1619 break; 1620 } 1621 } while_each_thread(g, p); 1622 } 1623 rcu_read_unlock(); 1624 done: 1625 atomic_set(&core_state->nr_threads, nr); 1626 return nr; 1627 } 1628 1629 static int coredump_wait(int exit_code, struct core_state *core_state) 1630 { 1631 struct task_struct *tsk = current; 1632 struct mm_struct *mm = tsk->mm; 1633 struct completion *vfork_done; 1634 int core_waiters; 1635 1636 init_completion(&core_state->startup); 1637 core_state->dumper.task = tsk; 1638 core_state->dumper.next = NULL; 1639 core_waiters = zap_threads(tsk, mm, core_state, exit_code); 1640 up_write(&mm->mmap_sem); 1641 1642 if (unlikely(core_waiters < 0)) 1643 goto fail; 1644 1645 /* 1646 * Make sure nobody is waiting for us to release the VM, 1647 * otherwise we can deadlock when we wait on each other 1648 */ 1649 vfork_done = tsk->vfork_done; 1650 if (vfork_done) { 1651 tsk->vfork_done = NULL; 1652 complete(vfork_done); 1653 } 1654 1655 if (core_waiters) 1656 wait_for_completion(&core_state->startup); 1657 fail: 1658 return core_waiters; 1659 } 1660 1661 static void coredump_finish(struct mm_struct *mm) 1662 { 1663 struct core_thread *curr, *next; 1664 struct task_struct *task; 1665 1666 next = mm->core_state->dumper.next; 1667 while ((curr = next) != NULL) { 1668 next = curr->next; 1669 task = curr->task; 1670 /* 1671 * see exit_mm(), curr->task must not see 1672 * ->task == NULL before we read ->next. 1673 */ 1674 smp_mb(); 1675 curr->task = NULL; 1676 wake_up_process(task); 1677 } 1678 1679 mm->core_state = NULL; 1680 } 1681 1682 /* 1683 * set_dumpable converts traditional three-value dumpable to two flags and 1684 * stores them into mm->flags. It modifies lower two bits of mm->flags, but 1685 * these bits are not changed atomically. So get_dumpable can observe the 1686 * intermediate state. To avoid doing unexpected behavior, get get_dumpable 1687 * return either old dumpable or new one by paying attention to the order of 1688 * modifying the bits. 1689 * 1690 * dumpable | mm->flags (binary) 1691 * old new | initial interim final 1692 * ---------+----------------------- 1693 * 0 1 | 00 01 01 1694 * 0 2 | 00 10(*) 11 1695 * 1 0 | 01 00 00 1696 * 1 2 | 01 11 11 1697 * 2 0 | 11 10(*) 00 1698 * 2 1 | 11 11 01 1699 * 1700 * (*) get_dumpable regards interim value of 10 as 11. 1701 */ 1702 void set_dumpable(struct mm_struct *mm, int value) 1703 { 1704 switch (value) { 1705 case 0: 1706 clear_bit(MMF_DUMPABLE, &mm->flags); 1707 smp_wmb(); 1708 clear_bit(MMF_DUMP_SECURELY, &mm->flags); 1709 break; 1710 case 1: 1711 set_bit(MMF_DUMPABLE, &mm->flags); 1712 smp_wmb(); 1713 clear_bit(MMF_DUMP_SECURELY, &mm->flags); 1714 break; 1715 case 2: 1716 set_bit(MMF_DUMP_SECURELY, &mm->flags); 1717 smp_wmb(); 1718 set_bit(MMF_DUMPABLE, &mm->flags); 1719 break; 1720 } 1721 } 1722 1723 int get_dumpable(struct mm_struct *mm) 1724 { 1725 int ret; 1726 1727 ret = mm->flags & 0x3; 1728 return (ret >= 2) ? 2 : ret; 1729 } 1730 1731 static void wait_for_dump_helpers(struct file *file) 1732 { 1733 struct pipe_inode_info *pipe; 1734 1735 pipe = file->f_path.dentry->d_inode->i_pipe; 1736 1737 pipe_lock(pipe); 1738 pipe->readers++; 1739 pipe->writers--; 1740 1741 while ((pipe->readers > 1) && (!signal_pending(current))) { 1742 wake_up_interruptible_sync(&pipe->wait); 1743 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 1744 pipe_wait(pipe); 1745 } 1746 1747 pipe->readers--; 1748 pipe->writers++; 1749 pipe_unlock(pipe); 1750 1751 } 1752 1753 1754 void do_coredump(long signr, int exit_code, struct pt_regs *regs) 1755 { 1756 struct core_state core_state; 1757 char corename[CORENAME_MAX_SIZE + 1]; 1758 struct mm_struct *mm = current->mm; 1759 struct linux_binfmt * binfmt; 1760 struct inode * inode; 1761 struct file * file; 1762 const struct cred *old_cred; 1763 struct cred *cred; 1764 int retval = 0; 1765 int flag = 0; 1766 int ispipe = 0; 1767 unsigned long core_limit = current->signal->rlim[RLIMIT_CORE].rlim_cur; 1768 char **helper_argv = NULL; 1769 int helper_argc = 0; 1770 int dump_count = 0; 1771 static atomic_t core_dump_count = ATOMIC_INIT(0); 1772 1773 audit_core_dumps(signr); 1774 1775 binfmt = mm->binfmt; 1776 if (!binfmt || !binfmt->core_dump) 1777 goto fail; 1778 1779 cred = prepare_creds(); 1780 if (!cred) { 1781 retval = -ENOMEM; 1782 goto fail; 1783 } 1784 1785 down_write(&mm->mmap_sem); 1786 /* 1787 * If another thread got here first, or we are not dumpable, bail out. 1788 */ 1789 if (mm->core_state || !get_dumpable(mm)) { 1790 up_write(&mm->mmap_sem); 1791 put_cred(cred); 1792 goto fail; 1793 } 1794 1795 /* 1796 * We cannot trust fsuid as being the "true" uid of the 1797 * process nor do we know its entire history. We only know it 1798 * was tainted so we dump it as root in mode 2. 1799 */ 1800 if (get_dumpable(mm) == 2) { /* Setuid core dump mode */ 1801 flag = O_EXCL; /* Stop rewrite attacks */ 1802 cred->fsuid = 0; /* Dump root private */ 1803 } 1804 1805 retval = coredump_wait(exit_code, &core_state); 1806 if (retval < 0) { 1807 put_cred(cred); 1808 goto fail; 1809 } 1810 1811 old_cred = override_creds(cred); 1812 1813 /* 1814 * Clear any false indication of pending signals that might 1815 * be seen by the filesystem code called to write the core file. 1816 */ 1817 clear_thread_flag(TIF_SIGPENDING); 1818 1819 /* 1820 * lock_kernel() because format_corename() is controlled by sysctl, which 1821 * uses lock_kernel() 1822 */ 1823 lock_kernel(); 1824 ispipe = format_corename(corename, signr); 1825 unlock_kernel(); 1826 1827 if ((!ispipe) && (core_limit < binfmt->min_coredump)) 1828 goto fail_unlock; 1829 1830 if (ispipe) { 1831 if (core_limit == 0) { 1832 /* 1833 * Normally core limits are irrelevant to pipes, since 1834 * we're not writing to the file system, but we use 1835 * core_limit of 0 here as a speacial value. Any 1836 * non-zero limit gets set to RLIM_INFINITY below, but 1837 * a limit of 0 skips the dump. This is a consistent 1838 * way to catch recursive crashes. We can still crash 1839 * if the core_pattern binary sets RLIM_CORE = !0 1840 * but it runs as root, and can do lots of stupid things 1841 * Note that we use task_tgid_vnr here to grab the pid 1842 * of the process group leader. That way we get the 1843 * right pid if a thread in a multi-threaded 1844 * core_pattern process dies. 1845 */ 1846 printk(KERN_WARNING 1847 "Process %d(%s) has RLIMIT_CORE set to 0\n", 1848 task_tgid_vnr(current), current->comm); 1849 printk(KERN_WARNING "Aborting core\n"); 1850 goto fail_unlock; 1851 } 1852 1853 dump_count = atomic_inc_return(&core_dump_count); 1854 if (core_pipe_limit && (core_pipe_limit < dump_count)) { 1855 printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n", 1856 task_tgid_vnr(current), current->comm); 1857 printk(KERN_WARNING "Skipping core dump\n"); 1858 goto fail_dropcount; 1859 } 1860 1861 helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc); 1862 if (!helper_argv) { 1863 printk(KERN_WARNING "%s failed to allocate memory\n", 1864 __func__); 1865 goto fail_dropcount; 1866 } 1867 1868 core_limit = RLIM_INFINITY; 1869 1870 /* SIGPIPE can happen, but it's just never processed */ 1871 if (call_usermodehelper_pipe(helper_argv[0], helper_argv, NULL, 1872 &file)) { 1873 printk(KERN_INFO "Core dump to %s pipe failed\n", 1874 corename); 1875 goto fail_dropcount; 1876 } 1877 } else 1878 file = filp_open(corename, 1879 O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag, 1880 0600); 1881 if (IS_ERR(file)) 1882 goto fail_dropcount; 1883 inode = file->f_path.dentry->d_inode; 1884 if (inode->i_nlink > 1) 1885 goto close_fail; /* multiple links - don't dump */ 1886 if (!ispipe && d_unhashed(file->f_path.dentry)) 1887 goto close_fail; 1888 1889 /* AK: actually i see no reason to not allow this for named pipes etc., 1890 but keep the previous behaviour for now. */ 1891 if (!ispipe && !S_ISREG(inode->i_mode)) 1892 goto close_fail; 1893 /* 1894 * Dont allow local users get cute and trick others to coredump 1895 * into their pre-created files: 1896 */ 1897 if (inode->i_uid != current_fsuid()) 1898 goto close_fail; 1899 if (!file->f_op) 1900 goto close_fail; 1901 if (!file->f_op->write) 1902 goto close_fail; 1903 if (!ispipe && do_truncate(file->f_path.dentry, 0, 0, file) != 0) 1904 goto close_fail; 1905 1906 retval = binfmt->core_dump(signr, regs, file, core_limit); 1907 1908 if (retval) 1909 current->signal->group_exit_code |= 0x80; 1910 close_fail: 1911 if (ispipe && core_pipe_limit) 1912 wait_for_dump_helpers(file); 1913 filp_close(file, NULL); 1914 fail_dropcount: 1915 if (dump_count) 1916 atomic_dec(&core_dump_count); 1917 fail_unlock: 1918 if (helper_argv) 1919 argv_free(helper_argv); 1920 1921 revert_creds(old_cred); 1922 put_cred(cred); 1923 coredump_finish(mm); 1924 fail: 1925 return; 1926 } 1927