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 goto out_unlock; 629 } 630 631 #ifdef CONFIG_STACK_GROWSUP 632 stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE; 633 #else 634 stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE; 635 #endif 636 ret = expand_stack(vma, stack_base); 637 if (ret) 638 ret = -EFAULT; 639 640 out_unlock: 641 up_write(&mm->mmap_sem); 642 return ret; 643 } 644 EXPORT_SYMBOL(setup_arg_pages); 645 646 #endif /* CONFIG_MMU */ 647 648 struct file *open_exec(const char *name) 649 { 650 struct file *file; 651 int err; 652 653 file = do_filp_open(AT_FDCWD, name, 654 O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0, 655 MAY_EXEC | MAY_OPEN); 656 if (IS_ERR(file)) 657 goto out; 658 659 err = -EACCES; 660 if (!S_ISREG(file->f_path.dentry->d_inode->i_mode)) 661 goto exit; 662 663 if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) 664 goto exit; 665 666 fsnotify_open(file->f_path.dentry); 667 668 err = deny_write_access(file); 669 if (err) 670 goto exit; 671 672 out: 673 return file; 674 675 exit: 676 fput(file); 677 return ERR_PTR(err); 678 } 679 EXPORT_SYMBOL(open_exec); 680 681 int kernel_read(struct file *file, loff_t offset, 682 char *addr, unsigned long count) 683 { 684 mm_segment_t old_fs; 685 loff_t pos = offset; 686 int result; 687 688 old_fs = get_fs(); 689 set_fs(get_ds()); 690 /* The cast to a user pointer is valid due to the set_fs() */ 691 result = vfs_read(file, (void __user *)addr, count, &pos); 692 set_fs(old_fs); 693 return result; 694 } 695 696 EXPORT_SYMBOL(kernel_read); 697 698 static int exec_mmap(struct mm_struct *mm) 699 { 700 struct task_struct *tsk; 701 struct mm_struct * old_mm, *active_mm; 702 703 /* Notify parent that we're no longer interested in the old VM */ 704 tsk = current; 705 old_mm = current->mm; 706 mm_release(tsk, old_mm); 707 708 if (old_mm) { 709 /* 710 * Make sure that if there is a core dump in progress 711 * for the old mm, we get out and die instead of going 712 * through with the exec. We must hold mmap_sem around 713 * checking core_state and changing tsk->mm. 714 */ 715 down_read(&old_mm->mmap_sem); 716 if (unlikely(old_mm->core_state)) { 717 up_read(&old_mm->mmap_sem); 718 return -EINTR; 719 } 720 } 721 task_lock(tsk); 722 active_mm = tsk->active_mm; 723 tsk->mm = mm; 724 tsk->active_mm = mm; 725 activate_mm(active_mm, mm); 726 task_unlock(tsk); 727 arch_pick_mmap_layout(mm); 728 if (old_mm) { 729 up_read(&old_mm->mmap_sem); 730 BUG_ON(active_mm != old_mm); 731 mm_update_next_owner(old_mm); 732 mmput(old_mm); 733 return 0; 734 } 735 mmdrop(active_mm); 736 return 0; 737 } 738 739 /* 740 * This function makes sure the current process has its own signal table, 741 * so that flush_signal_handlers can later reset the handlers without 742 * disturbing other processes. (Other processes might share the signal 743 * table via the CLONE_SIGHAND option to clone().) 744 */ 745 static int de_thread(struct task_struct *tsk) 746 { 747 struct signal_struct *sig = tsk->signal; 748 struct sighand_struct *oldsighand = tsk->sighand; 749 spinlock_t *lock = &oldsighand->siglock; 750 int count; 751 752 if (thread_group_empty(tsk)) 753 goto no_thread_group; 754 755 /* 756 * Kill all other threads in the thread group. 757 */ 758 spin_lock_irq(lock); 759 if (signal_group_exit(sig)) { 760 /* 761 * Another group action in progress, just 762 * return so that the signal is processed. 763 */ 764 spin_unlock_irq(lock); 765 return -EAGAIN; 766 } 767 sig->group_exit_task = tsk; 768 zap_other_threads(tsk); 769 770 /* Account for the thread group leader hanging around: */ 771 count = thread_group_leader(tsk) ? 1 : 2; 772 sig->notify_count = count; 773 while (atomic_read(&sig->count) > count) { 774 __set_current_state(TASK_UNINTERRUPTIBLE); 775 spin_unlock_irq(lock); 776 schedule(); 777 spin_lock_irq(lock); 778 } 779 spin_unlock_irq(lock); 780 781 /* 782 * At this point all other threads have exited, all we have to 783 * do is to wait for the thread group leader to become inactive, 784 * and to assume its PID: 785 */ 786 if (!thread_group_leader(tsk)) { 787 struct task_struct *leader = tsk->group_leader; 788 789 sig->notify_count = -1; /* for exit_notify() */ 790 for (;;) { 791 write_lock_irq(&tasklist_lock); 792 if (likely(leader->exit_state)) 793 break; 794 __set_current_state(TASK_UNINTERRUPTIBLE); 795 write_unlock_irq(&tasklist_lock); 796 schedule(); 797 } 798 799 /* 800 * The only record we have of the real-time age of a 801 * process, regardless of execs it's done, is start_time. 802 * All the past CPU time is accumulated in signal_struct 803 * from sister threads now dead. But in this non-leader 804 * exec, nothing survives from the original leader thread, 805 * whose birth marks the true age of this process now. 806 * When we take on its identity by switching to its PID, we 807 * also take its birthdate (always earlier than our own). 808 */ 809 tsk->start_time = leader->start_time; 810 811 BUG_ON(!same_thread_group(leader, tsk)); 812 BUG_ON(has_group_leader_pid(tsk)); 813 /* 814 * An exec() starts a new thread group with the 815 * TGID of the previous thread group. Rehash the 816 * two threads with a switched PID, and release 817 * the former thread group leader: 818 */ 819 820 /* Become a process group leader with the old leader's pid. 821 * The old leader becomes a thread of the this thread group. 822 * Note: The old leader also uses this pid until release_task 823 * is called. Odd but simple and correct. 824 */ 825 detach_pid(tsk, PIDTYPE_PID); 826 tsk->pid = leader->pid; 827 attach_pid(tsk, PIDTYPE_PID, task_pid(leader)); 828 transfer_pid(leader, tsk, PIDTYPE_PGID); 829 transfer_pid(leader, tsk, PIDTYPE_SID); 830 list_replace_rcu(&leader->tasks, &tsk->tasks); 831 832 tsk->group_leader = tsk; 833 leader->group_leader = tsk; 834 835 tsk->exit_signal = SIGCHLD; 836 837 BUG_ON(leader->exit_state != EXIT_ZOMBIE); 838 leader->exit_state = EXIT_DEAD; 839 write_unlock_irq(&tasklist_lock); 840 841 release_task(leader); 842 } 843 844 sig->group_exit_task = NULL; 845 sig->notify_count = 0; 846 847 no_thread_group: 848 if (current->mm) 849 setmax_mm_hiwater_rss(&sig->maxrss, current->mm); 850 851 exit_itimers(sig); 852 flush_itimer_signals(); 853 854 if (atomic_read(&oldsighand->count) != 1) { 855 struct sighand_struct *newsighand; 856 /* 857 * This ->sighand is shared with the CLONE_SIGHAND 858 * but not CLONE_THREAD task, switch to the new one. 859 */ 860 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 861 if (!newsighand) 862 return -ENOMEM; 863 864 atomic_set(&newsighand->count, 1); 865 memcpy(newsighand->action, oldsighand->action, 866 sizeof(newsighand->action)); 867 868 write_lock_irq(&tasklist_lock); 869 spin_lock(&oldsighand->siglock); 870 rcu_assign_pointer(tsk->sighand, newsighand); 871 spin_unlock(&oldsighand->siglock); 872 write_unlock_irq(&tasklist_lock); 873 874 __cleanup_sighand(oldsighand); 875 } 876 877 BUG_ON(!thread_group_leader(tsk)); 878 return 0; 879 } 880 881 /* 882 * These functions flushes out all traces of the currently running executable 883 * so that a new one can be started 884 */ 885 static void flush_old_files(struct files_struct * files) 886 { 887 long j = -1; 888 struct fdtable *fdt; 889 890 spin_lock(&files->file_lock); 891 for (;;) { 892 unsigned long set, i; 893 894 j++; 895 i = j * __NFDBITS; 896 fdt = files_fdtable(files); 897 if (i >= fdt->max_fds) 898 break; 899 set = fdt->close_on_exec->fds_bits[j]; 900 if (!set) 901 continue; 902 fdt->close_on_exec->fds_bits[j] = 0; 903 spin_unlock(&files->file_lock); 904 for ( ; set ; i++,set >>= 1) { 905 if (set & 1) { 906 sys_close(i); 907 } 908 } 909 spin_lock(&files->file_lock); 910 911 } 912 spin_unlock(&files->file_lock); 913 } 914 915 char *get_task_comm(char *buf, struct task_struct *tsk) 916 { 917 /* buf must be at least sizeof(tsk->comm) in size */ 918 task_lock(tsk); 919 strncpy(buf, tsk->comm, sizeof(tsk->comm)); 920 task_unlock(tsk); 921 return buf; 922 } 923 924 void set_task_comm(struct task_struct *tsk, char *buf) 925 { 926 task_lock(tsk); 927 strlcpy(tsk->comm, buf, sizeof(tsk->comm)); 928 task_unlock(tsk); 929 perf_event_comm(tsk); 930 } 931 932 int flush_old_exec(struct linux_binprm * bprm) 933 { 934 char * name; 935 int i, ch, retval; 936 char tcomm[sizeof(current->comm)]; 937 938 /* 939 * Make sure we have a private signal table and that 940 * we are unassociated from the previous thread group. 941 */ 942 retval = de_thread(current); 943 if (retval) 944 goto out; 945 946 set_mm_exe_file(bprm->mm, bprm->file); 947 948 /* 949 * Release all of the old mmap stuff 950 */ 951 retval = exec_mmap(bprm->mm); 952 if (retval) 953 goto out; 954 955 bprm->mm = NULL; /* We're using it now */ 956 957 /* This is the point of no return */ 958 current->sas_ss_sp = current->sas_ss_size = 0; 959 960 if (current_euid() == current_uid() && current_egid() == current_gid()) 961 set_dumpable(current->mm, 1); 962 else 963 set_dumpable(current->mm, suid_dumpable); 964 965 name = bprm->filename; 966 967 /* Copies the binary name from after last slash */ 968 for (i=0; (ch = *(name++)) != '\0';) { 969 if (ch == '/') 970 i = 0; /* overwrite what we wrote */ 971 else 972 if (i < (sizeof(tcomm) - 1)) 973 tcomm[i++] = ch; 974 } 975 tcomm[i] = '\0'; 976 set_task_comm(current, tcomm); 977 978 current->flags &= ~PF_RANDOMIZE; 979 flush_thread(); 980 981 /* Set the new mm task size. We have to do that late because it may 982 * depend on TIF_32BIT which is only updated in flush_thread() on 983 * some architectures like powerpc 984 */ 985 current->mm->task_size = TASK_SIZE; 986 987 /* install the new credentials */ 988 if (bprm->cred->uid != current_euid() || 989 bprm->cred->gid != current_egid()) { 990 current->pdeath_signal = 0; 991 } else if (file_permission(bprm->file, MAY_READ) || 992 bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) { 993 set_dumpable(current->mm, suid_dumpable); 994 } 995 996 current->personality &= ~bprm->per_clear; 997 998 /* 999 * Flush performance counters when crossing a 1000 * security domain: 1001 */ 1002 if (!get_dumpable(current->mm)) 1003 perf_event_exit_task(current); 1004 1005 /* An exec changes our domain. We are no longer part of the thread 1006 group */ 1007 1008 current->self_exec_id++; 1009 1010 flush_signal_handlers(current, 0); 1011 flush_old_files(current->files); 1012 1013 return 0; 1014 1015 out: 1016 return retval; 1017 } 1018 1019 EXPORT_SYMBOL(flush_old_exec); 1020 1021 /* 1022 * Prepare credentials and lock ->cred_guard_mutex. 1023 * install_exec_creds() commits the new creds and drops the lock. 1024 * Or, if exec fails before, free_bprm() should release ->cred and 1025 * and unlock. 1026 */ 1027 int prepare_bprm_creds(struct linux_binprm *bprm) 1028 { 1029 if (mutex_lock_interruptible(¤t->cred_guard_mutex)) 1030 return -ERESTARTNOINTR; 1031 1032 bprm->cred = prepare_exec_creds(); 1033 if (likely(bprm->cred)) 1034 return 0; 1035 1036 mutex_unlock(¤t->cred_guard_mutex); 1037 return -ENOMEM; 1038 } 1039 1040 void free_bprm(struct linux_binprm *bprm) 1041 { 1042 free_arg_pages(bprm); 1043 if (bprm->cred) { 1044 mutex_unlock(¤t->cred_guard_mutex); 1045 abort_creds(bprm->cred); 1046 } 1047 kfree(bprm); 1048 } 1049 1050 /* 1051 * install the new credentials for this executable 1052 */ 1053 void install_exec_creds(struct linux_binprm *bprm) 1054 { 1055 security_bprm_committing_creds(bprm); 1056 1057 commit_creds(bprm->cred); 1058 bprm->cred = NULL; 1059 /* 1060 * cred_guard_mutex must be held at least to this point to prevent 1061 * ptrace_attach() from altering our determination of the task's 1062 * credentials; any time after this it may be unlocked. 1063 */ 1064 security_bprm_committed_creds(bprm); 1065 mutex_unlock(¤t->cred_guard_mutex); 1066 } 1067 EXPORT_SYMBOL(install_exec_creds); 1068 1069 /* 1070 * determine how safe it is to execute the proposed program 1071 * - the caller must hold current->cred_guard_mutex to protect against 1072 * PTRACE_ATTACH 1073 */ 1074 int check_unsafe_exec(struct linux_binprm *bprm) 1075 { 1076 struct task_struct *p = current, *t; 1077 unsigned n_fs; 1078 int res = 0; 1079 1080 bprm->unsafe = tracehook_unsafe_exec(p); 1081 1082 n_fs = 1; 1083 write_lock(&p->fs->lock); 1084 rcu_read_lock(); 1085 for (t = next_thread(p); t != p; t = next_thread(t)) { 1086 if (t->fs == p->fs) 1087 n_fs++; 1088 } 1089 rcu_read_unlock(); 1090 1091 if (p->fs->users > n_fs) { 1092 bprm->unsafe |= LSM_UNSAFE_SHARE; 1093 } else { 1094 res = -EAGAIN; 1095 if (!p->fs->in_exec) { 1096 p->fs->in_exec = 1; 1097 res = 1; 1098 } 1099 } 1100 write_unlock(&p->fs->lock); 1101 1102 return res; 1103 } 1104 1105 /* 1106 * Fill the binprm structure from the inode. 1107 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes 1108 * 1109 * This may be called multiple times for binary chains (scripts for example). 1110 */ 1111 int prepare_binprm(struct linux_binprm *bprm) 1112 { 1113 umode_t mode; 1114 struct inode * inode = bprm->file->f_path.dentry->d_inode; 1115 int retval; 1116 1117 mode = inode->i_mode; 1118 if (bprm->file->f_op == NULL) 1119 return -EACCES; 1120 1121 /* clear any previous set[ug]id data from a previous binary */ 1122 bprm->cred->euid = current_euid(); 1123 bprm->cred->egid = current_egid(); 1124 1125 if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) { 1126 /* Set-uid? */ 1127 if (mode & S_ISUID) { 1128 bprm->per_clear |= PER_CLEAR_ON_SETID; 1129 bprm->cred->euid = inode->i_uid; 1130 } 1131 1132 /* Set-gid? */ 1133 /* 1134 * If setgid is set but no group execute bit then this 1135 * is a candidate for mandatory locking, not a setgid 1136 * executable. 1137 */ 1138 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { 1139 bprm->per_clear |= PER_CLEAR_ON_SETID; 1140 bprm->cred->egid = inode->i_gid; 1141 } 1142 } 1143 1144 /* fill in binprm security blob */ 1145 retval = security_bprm_set_creds(bprm); 1146 if (retval) 1147 return retval; 1148 bprm->cred_prepared = 1; 1149 1150 memset(bprm->buf, 0, BINPRM_BUF_SIZE); 1151 return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE); 1152 } 1153 1154 EXPORT_SYMBOL(prepare_binprm); 1155 1156 /* 1157 * Arguments are '\0' separated strings found at the location bprm->p 1158 * points to; chop off the first by relocating brpm->p to right after 1159 * the first '\0' encountered. 1160 */ 1161 int remove_arg_zero(struct linux_binprm *bprm) 1162 { 1163 int ret = 0; 1164 unsigned long offset; 1165 char *kaddr; 1166 struct page *page; 1167 1168 if (!bprm->argc) 1169 return 0; 1170 1171 do { 1172 offset = bprm->p & ~PAGE_MASK; 1173 page = get_arg_page(bprm, bprm->p, 0); 1174 if (!page) { 1175 ret = -EFAULT; 1176 goto out; 1177 } 1178 kaddr = kmap_atomic(page, KM_USER0); 1179 1180 for (; offset < PAGE_SIZE && kaddr[offset]; 1181 offset++, bprm->p++) 1182 ; 1183 1184 kunmap_atomic(kaddr, KM_USER0); 1185 put_arg_page(page); 1186 1187 if (offset == PAGE_SIZE) 1188 free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1); 1189 } while (offset == PAGE_SIZE); 1190 1191 bprm->p++; 1192 bprm->argc--; 1193 ret = 0; 1194 1195 out: 1196 return ret; 1197 } 1198 EXPORT_SYMBOL(remove_arg_zero); 1199 1200 /* 1201 * cycle the list of binary formats handler, until one recognizes the image 1202 */ 1203 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs) 1204 { 1205 unsigned int depth = bprm->recursion_depth; 1206 int try,retval; 1207 struct linux_binfmt *fmt; 1208 1209 retval = security_bprm_check(bprm); 1210 if (retval) 1211 return retval; 1212 retval = ima_bprm_check(bprm); 1213 if (retval) 1214 return retval; 1215 1216 /* kernel module loader fixup */ 1217 /* so we don't try to load run modprobe in kernel space. */ 1218 set_fs(USER_DS); 1219 1220 retval = audit_bprm(bprm); 1221 if (retval) 1222 return retval; 1223 1224 retval = -ENOENT; 1225 for (try=0; try<2; try++) { 1226 read_lock(&binfmt_lock); 1227 list_for_each_entry(fmt, &formats, lh) { 1228 int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary; 1229 if (!fn) 1230 continue; 1231 if (!try_module_get(fmt->module)) 1232 continue; 1233 read_unlock(&binfmt_lock); 1234 retval = fn(bprm, regs); 1235 /* 1236 * Restore the depth counter to its starting value 1237 * in this call, so we don't have to rely on every 1238 * load_binary function to restore it on return. 1239 */ 1240 bprm->recursion_depth = depth; 1241 if (retval >= 0) { 1242 if (depth == 0) 1243 tracehook_report_exec(fmt, bprm, regs); 1244 put_binfmt(fmt); 1245 allow_write_access(bprm->file); 1246 if (bprm->file) 1247 fput(bprm->file); 1248 bprm->file = NULL; 1249 current->did_exec = 1; 1250 proc_exec_connector(current); 1251 return retval; 1252 } 1253 read_lock(&binfmt_lock); 1254 put_binfmt(fmt); 1255 if (retval != -ENOEXEC || bprm->mm == NULL) 1256 break; 1257 if (!bprm->file) { 1258 read_unlock(&binfmt_lock); 1259 return retval; 1260 } 1261 } 1262 read_unlock(&binfmt_lock); 1263 if (retval != -ENOEXEC || bprm->mm == NULL) { 1264 break; 1265 #ifdef CONFIG_MODULES 1266 } else { 1267 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e)) 1268 if (printable(bprm->buf[0]) && 1269 printable(bprm->buf[1]) && 1270 printable(bprm->buf[2]) && 1271 printable(bprm->buf[3])) 1272 break; /* -ENOEXEC */ 1273 request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2])); 1274 #endif 1275 } 1276 } 1277 return retval; 1278 } 1279 1280 EXPORT_SYMBOL(search_binary_handler); 1281 1282 /* 1283 * sys_execve() executes a new program. 1284 */ 1285 int do_execve(char * filename, 1286 char __user *__user *argv, 1287 char __user *__user *envp, 1288 struct pt_regs * regs) 1289 { 1290 struct linux_binprm *bprm; 1291 struct file *file; 1292 struct files_struct *displaced; 1293 bool clear_in_exec; 1294 int retval; 1295 1296 retval = unshare_files(&displaced); 1297 if (retval) 1298 goto out_ret; 1299 1300 retval = -ENOMEM; 1301 bprm = kzalloc(sizeof(*bprm), GFP_KERNEL); 1302 if (!bprm) 1303 goto out_files; 1304 1305 retval = prepare_bprm_creds(bprm); 1306 if (retval) 1307 goto out_free; 1308 1309 retval = check_unsafe_exec(bprm); 1310 if (retval < 0) 1311 goto out_free; 1312 clear_in_exec = retval; 1313 current->in_execve = 1; 1314 1315 file = open_exec(filename); 1316 retval = PTR_ERR(file); 1317 if (IS_ERR(file)) 1318 goto out_unmark; 1319 1320 sched_exec(); 1321 1322 bprm->file = file; 1323 bprm->filename = filename; 1324 bprm->interp = filename; 1325 1326 retval = bprm_mm_init(bprm); 1327 if (retval) 1328 goto out_file; 1329 1330 bprm->argc = count(argv, MAX_ARG_STRINGS); 1331 if ((retval = bprm->argc) < 0) 1332 goto out; 1333 1334 bprm->envc = count(envp, MAX_ARG_STRINGS); 1335 if ((retval = bprm->envc) < 0) 1336 goto out; 1337 1338 retval = prepare_binprm(bprm); 1339 if (retval < 0) 1340 goto out; 1341 1342 retval = copy_strings_kernel(1, &bprm->filename, bprm); 1343 if (retval < 0) 1344 goto out; 1345 1346 bprm->exec = bprm->p; 1347 retval = copy_strings(bprm->envc, envp, bprm); 1348 if (retval < 0) 1349 goto out; 1350 1351 retval = copy_strings(bprm->argc, argv, bprm); 1352 if (retval < 0) 1353 goto out; 1354 1355 current->flags &= ~PF_KTHREAD; 1356 retval = search_binary_handler(bprm,regs); 1357 if (retval < 0) 1358 goto out; 1359 1360 current->stack_start = current->mm->start_stack; 1361 1362 /* execve succeeded */ 1363 current->fs->in_exec = 0; 1364 current->in_execve = 0; 1365 acct_update_integrals(current); 1366 free_bprm(bprm); 1367 if (displaced) 1368 put_files_struct(displaced); 1369 return retval; 1370 1371 out: 1372 if (bprm->mm) 1373 mmput (bprm->mm); 1374 1375 out_file: 1376 if (bprm->file) { 1377 allow_write_access(bprm->file); 1378 fput(bprm->file); 1379 } 1380 1381 out_unmark: 1382 if (clear_in_exec) 1383 current->fs->in_exec = 0; 1384 current->in_execve = 0; 1385 1386 out_free: 1387 free_bprm(bprm); 1388 1389 out_files: 1390 if (displaced) 1391 reset_files_struct(displaced); 1392 out_ret: 1393 return retval; 1394 } 1395 1396 void set_binfmt(struct linux_binfmt *new) 1397 { 1398 struct mm_struct *mm = current->mm; 1399 1400 if (mm->binfmt) 1401 module_put(mm->binfmt->module); 1402 1403 mm->binfmt = new; 1404 if (new) 1405 __module_get(new->module); 1406 } 1407 1408 EXPORT_SYMBOL(set_binfmt); 1409 1410 /* format_corename will inspect the pattern parameter, and output a 1411 * name into corename, which must have space for at least 1412 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator. 1413 */ 1414 static int format_corename(char *corename, long signr) 1415 { 1416 const struct cred *cred = current_cred(); 1417 const char *pat_ptr = core_pattern; 1418 int ispipe = (*pat_ptr == '|'); 1419 char *out_ptr = corename; 1420 char *const out_end = corename + CORENAME_MAX_SIZE; 1421 int rc; 1422 int pid_in_pattern = 0; 1423 1424 /* Repeat as long as we have more pattern to process and more output 1425 space */ 1426 while (*pat_ptr) { 1427 if (*pat_ptr != '%') { 1428 if (out_ptr == out_end) 1429 goto out; 1430 *out_ptr++ = *pat_ptr++; 1431 } else { 1432 switch (*++pat_ptr) { 1433 case 0: 1434 goto out; 1435 /* Double percent, output one percent */ 1436 case '%': 1437 if (out_ptr == out_end) 1438 goto out; 1439 *out_ptr++ = '%'; 1440 break; 1441 /* pid */ 1442 case 'p': 1443 pid_in_pattern = 1; 1444 rc = snprintf(out_ptr, out_end - out_ptr, 1445 "%d", task_tgid_vnr(current)); 1446 if (rc > out_end - out_ptr) 1447 goto out; 1448 out_ptr += rc; 1449 break; 1450 /* uid */ 1451 case 'u': 1452 rc = snprintf(out_ptr, out_end - out_ptr, 1453 "%d", cred->uid); 1454 if (rc > out_end - out_ptr) 1455 goto out; 1456 out_ptr += rc; 1457 break; 1458 /* gid */ 1459 case 'g': 1460 rc = snprintf(out_ptr, out_end - out_ptr, 1461 "%d", cred->gid); 1462 if (rc > out_end - out_ptr) 1463 goto out; 1464 out_ptr += rc; 1465 break; 1466 /* signal that caused the coredump */ 1467 case 's': 1468 rc = snprintf(out_ptr, out_end - out_ptr, 1469 "%ld", signr); 1470 if (rc > out_end - out_ptr) 1471 goto out; 1472 out_ptr += rc; 1473 break; 1474 /* UNIX time of coredump */ 1475 case 't': { 1476 struct timeval tv; 1477 do_gettimeofday(&tv); 1478 rc = snprintf(out_ptr, out_end - out_ptr, 1479 "%lu", tv.tv_sec); 1480 if (rc > out_end - out_ptr) 1481 goto out; 1482 out_ptr += rc; 1483 break; 1484 } 1485 /* hostname */ 1486 case 'h': 1487 down_read(&uts_sem); 1488 rc = snprintf(out_ptr, out_end - out_ptr, 1489 "%s", utsname()->nodename); 1490 up_read(&uts_sem); 1491 if (rc > out_end - out_ptr) 1492 goto out; 1493 out_ptr += rc; 1494 break; 1495 /* executable */ 1496 case 'e': 1497 rc = snprintf(out_ptr, out_end - out_ptr, 1498 "%s", current->comm); 1499 if (rc > out_end - out_ptr) 1500 goto out; 1501 out_ptr += rc; 1502 break; 1503 /* core limit size */ 1504 case 'c': 1505 rc = snprintf(out_ptr, out_end - out_ptr, 1506 "%lu", current->signal->rlim[RLIMIT_CORE].rlim_cur); 1507 if (rc > out_end - out_ptr) 1508 goto out; 1509 out_ptr += rc; 1510 break; 1511 default: 1512 break; 1513 } 1514 ++pat_ptr; 1515 } 1516 } 1517 /* Backward compatibility with core_uses_pid: 1518 * 1519 * If core_pattern does not include a %p (as is the default) 1520 * and core_uses_pid is set, then .%pid will be appended to 1521 * the filename. Do not do this for piped commands. */ 1522 if (!ispipe && !pid_in_pattern && core_uses_pid) { 1523 rc = snprintf(out_ptr, out_end - out_ptr, 1524 ".%d", task_tgid_vnr(current)); 1525 if (rc > out_end - out_ptr) 1526 goto out; 1527 out_ptr += rc; 1528 } 1529 out: 1530 *out_ptr = 0; 1531 return ispipe; 1532 } 1533 1534 static int zap_process(struct task_struct *start) 1535 { 1536 struct task_struct *t; 1537 int nr = 0; 1538 1539 start->signal->flags = SIGNAL_GROUP_EXIT; 1540 start->signal->group_stop_count = 0; 1541 1542 t = start; 1543 do { 1544 if (t != current && t->mm) { 1545 sigaddset(&t->pending.signal, SIGKILL); 1546 signal_wake_up(t, 1); 1547 nr++; 1548 } 1549 } while_each_thread(start, t); 1550 1551 return nr; 1552 } 1553 1554 static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm, 1555 struct core_state *core_state, int exit_code) 1556 { 1557 struct task_struct *g, *p; 1558 unsigned long flags; 1559 int nr = -EAGAIN; 1560 1561 spin_lock_irq(&tsk->sighand->siglock); 1562 if (!signal_group_exit(tsk->signal)) { 1563 mm->core_state = core_state; 1564 tsk->signal->group_exit_code = exit_code; 1565 nr = zap_process(tsk); 1566 } 1567 spin_unlock_irq(&tsk->sighand->siglock); 1568 if (unlikely(nr < 0)) 1569 return nr; 1570 1571 if (atomic_read(&mm->mm_users) == nr + 1) 1572 goto done; 1573 /* 1574 * We should find and kill all tasks which use this mm, and we should 1575 * count them correctly into ->nr_threads. We don't take tasklist 1576 * lock, but this is safe wrt: 1577 * 1578 * fork: 1579 * None of sub-threads can fork after zap_process(leader). All 1580 * processes which were created before this point should be 1581 * visible to zap_threads() because copy_process() adds the new 1582 * process to the tail of init_task.tasks list, and lock/unlock 1583 * of ->siglock provides a memory barrier. 1584 * 1585 * do_exit: 1586 * The caller holds mm->mmap_sem. This means that the task which 1587 * uses this mm can't pass exit_mm(), so it can't exit or clear 1588 * its ->mm. 1589 * 1590 * de_thread: 1591 * It does list_replace_rcu(&leader->tasks, ¤t->tasks), 1592 * we must see either old or new leader, this does not matter. 1593 * However, it can change p->sighand, so lock_task_sighand(p) 1594 * must be used. Since p->mm != NULL and we hold ->mmap_sem 1595 * it can't fail. 1596 * 1597 * Note also that "g" can be the old leader with ->mm == NULL 1598 * and already unhashed and thus removed from ->thread_group. 1599 * This is OK, __unhash_process()->list_del_rcu() does not 1600 * clear the ->next pointer, we will find the new leader via 1601 * next_thread(). 1602 */ 1603 rcu_read_lock(); 1604 for_each_process(g) { 1605 if (g == tsk->group_leader) 1606 continue; 1607 if (g->flags & PF_KTHREAD) 1608 continue; 1609 p = g; 1610 do { 1611 if (p->mm) { 1612 if (unlikely(p->mm == mm)) { 1613 lock_task_sighand(p, &flags); 1614 nr += zap_process(p); 1615 unlock_task_sighand(p, &flags); 1616 } 1617 break; 1618 } 1619 } while_each_thread(g, p); 1620 } 1621 rcu_read_unlock(); 1622 done: 1623 atomic_set(&core_state->nr_threads, nr); 1624 return nr; 1625 } 1626 1627 static int coredump_wait(int exit_code, struct core_state *core_state) 1628 { 1629 struct task_struct *tsk = current; 1630 struct mm_struct *mm = tsk->mm; 1631 struct completion *vfork_done; 1632 int core_waiters; 1633 1634 init_completion(&core_state->startup); 1635 core_state->dumper.task = tsk; 1636 core_state->dumper.next = NULL; 1637 core_waiters = zap_threads(tsk, mm, core_state, exit_code); 1638 up_write(&mm->mmap_sem); 1639 1640 if (unlikely(core_waiters < 0)) 1641 goto fail; 1642 1643 /* 1644 * Make sure nobody is waiting for us to release the VM, 1645 * otherwise we can deadlock when we wait on each other 1646 */ 1647 vfork_done = tsk->vfork_done; 1648 if (vfork_done) { 1649 tsk->vfork_done = NULL; 1650 complete(vfork_done); 1651 } 1652 1653 if (core_waiters) 1654 wait_for_completion(&core_state->startup); 1655 fail: 1656 return core_waiters; 1657 } 1658 1659 static void coredump_finish(struct mm_struct *mm) 1660 { 1661 struct core_thread *curr, *next; 1662 struct task_struct *task; 1663 1664 next = mm->core_state->dumper.next; 1665 while ((curr = next) != NULL) { 1666 next = curr->next; 1667 task = curr->task; 1668 /* 1669 * see exit_mm(), curr->task must not see 1670 * ->task == NULL before we read ->next. 1671 */ 1672 smp_mb(); 1673 curr->task = NULL; 1674 wake_up_process(task); 1675 } 1676 1677 mm->core_state = NULL; 1678 } 1679 1680 /* 1681 * set_dumpable converts traditional three-value dumpable to two flags and 1682 * stores them into mm->flags. It modifies lower two bits of mm->flags, but 1683 * these bits are not changed atomically. So get_dumpable can observe the 1684 * intermediate state. To avoid doing unexpected behavior, get get_dumpable 1685 * return either old dumpable or new one by paying attention to the order of 1686 * modifying the bits. 1687 * 1688 * dumpable | mm->flags (binary) 1689 * old new | initial interim final 1690 * ---------+----------------------- 1691 * 0 1 | 00 01 01 1692 * 0 2 | 00 10(*) 11 1693 * 1 0 | 01 00 00 1694 * 1 2 | 01 11 11 1695 * 2 0 | 11 10(*) 00 1696 * 2 1 | 11 11 01 1697 * 1698 * (*) get_dumpable regards interim value of 10 as 11. 1699 */ 1700 void set_dumpable(struct mm_struct *mm, int value) 1701 { 1702 switch (value) { 1703 case 0: 1704 clear_bit(MMF_DUMPABLE, &mm->flags); 1705 smp_wmb(); 1706 clear_bit(MMF_DUMP_SECURELY, &mm->flags); 1707 break; 1708 case 1: 1709 set_bit(MMF_DUMPABLE, &mm->flags); 1710 smp_wmb(); 1711 clear_bit(MMF_DUMP_SECURELY, &mm->flags); 1712 break; 1713 case 2: 1714 set_bit(MMF_DUMP_SECURELY, &mm->flags); 1715 smp_wmb(); 1716 set_bit(MMF_DUMPABLE, &mm->flags); 1717 break; 1718 } 1719 } 1720 1721 int get_dumpable(struct mm_struct *mm) 1722 { 1723 int ret; 1724 1725 ret = mm->flags & 0x3; 1726 return (ret >= 2) ? 2 : ret; 1727 } 1728 1729 static void wait_for_dump_helpers(struct file *file) 1730 { 1731 struct pipe_inode_info *pipe; 1732 1733 pipe = file->f_path.dentry->d_inode->i_pipe; 1734 1735 pipe_lock(pipe); 1736 pipe->readers++; 1737 pipe->writers--; 1738 1739 while ((pipe->readers > 1) && (!signal_pending(current))) { 1740 wake_up_interruptible_sync(&pipe->wait); 1741 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 1742 pipe_wait(pipe); 1743 } 1744 1745 pipe->readers--; 1746 pipe->writers++; 1747 pipe_unlock(pipe); 1748 1749 } 1750 1751 1752 void do_coredump(long signr, int exit_code, struct pt_regs *regs) 1753 { 1754 struct core_state core_state; 1755 char corename[CORENAME_MAX_SIZE + 1]; 1756 struct mm_struct *mm = current->mm; 1757 struct linux_binfmt * binfmt; 1758 struct inode * inode; 1759 struct file * file; 1760 const struct cred *old_cred; 1761 struct cred *cred; 1762 int retval = 0; 1763 int flag = 0; 1764 int ispipe = 0; 1765 unsigned long core_limit = current->signal->rlim[RLIMIT_CORE].rlim_cur; 1766 char **helper_argv = NULL; 1767 int helper_argc = 0; 1768 int dump_count = 0; 1769 static atomic_t core_dump_count = ATOMIC_INIT(0); 1770 1771 audit_core_dumps(signr); 1772 1773 binfmt = mm->binfmt; 1774 if (!binfmt || !binfmt->core_dump) 1775 goto fail; 1776 1777 cred = prepare_creds(); 1778 if (!cred) { 1779 retval = -ENOMEM; 1780 goto fail; 1781 } 1782 1783 down_write(&mm->mmap_sem); 1784 /* 1785 * If another thread got here first, or we are not dumpable, bail out. 1786 */ 1787 if (mm->core_state || !get_dumpable(mm)) { 1788 up_write(&mm->mmap_sem); 1789 put_cred(cred); 1790 goto fail; 1791 } 1792 1793 /* 1794 * We cannot trust fsuid as being the "true" uid of the 1795 * process nor do we know its entire history. We only know it 1796 * was tainted so we dump it as root in mode 2. 1797 */ 1798 if (get_dumpable(mm) == 2) { /* Setuid core dump mode */ 1799 flag = O_EXCL; /* Stop rewrite attacks */ 1800 cred->fsuid = 0; /* Dump root private */ 1801 } 1802 1803 retval = coredump_wait(exit_code, &core_state); 1804 if (retval < 0) { 1805 put_cred(cred); 1806 goto fail; 1807 } 1808 1809 old_cred = override_creds(cred); 1810 1811 /* 1812 * Clear any false indication of pending signals that might 1813 * be seen by the filesystem code called to write the core file. 1814 */ 1815 clear_thread_flag(TIF_SIGPENDING); 1816 1817 /* 1818 * lock_kernel() because format_corename() is controlled by sysctl, which 1819 * uses lock_kernel() 1820 */ 1821 lock_kernel(); 1822 ispipe = format_corename(corename, signr); 1823 unlock_kernel(); 1824 1825 if ((!ispipe) && (core_limit < binfmt->min_coredump)) 1826 goto fail_unlock; 1827 1828 if (ispipe) { 1829 if (core_limit == 0) { 1830 /* 1831 * Normally core limits are irrelevant to pipes, since 1832 * we're not writing to the file system, but we use 1833 * core_limit of 0 here as a speacial value. Any 1834 * non-zero limit gets set to RLIM_INFINITY below, but 1835 * a limit of 0 skips the dump. This is a consistent 1836 * way to catch recursive crashes. We can still crash 1837 * if the core_pattern binary sets RLIM_CORE = !0 1838 * but it runs as root, and can do lots of stupid things 1839 * Note that we use task_tgid_vnr here to grab the pid 1840 * of the process group leader. That way we get the 1841 * right pid if a thread in a multi-threaded 1842 * core_pattern process dies. 1843 */ 1844 printk(KERN_WARNING 1845 "Process %d(%s) has RLIMIT_CORE set to 0\n", 1846 task_tgid_vnr(current), current->comm); 1847 printk(KERN_WARNING "Aborting core\n"); 1848 goto fail_unlock; 1849 } 1850 1851 dump_count = atomic_inc_return(&core_dump_count); 1852 if (core_pipe_limit && (core_pipe_limit < dump_count)) { 1853 printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n", 1854 task_tgid_vnr(current), current->comm); 1855 printk(KERN_WARNING "Skipping core dump\n"); 1856 goto fail_dropcount; 1857 } 1858 1859 helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc); 1860 if (!helper_argv) { 1861 printk(KERN_WARNING "%s failed to allocate memory\n", 1862 __func__); 1863 goto fail_dropcount; 1864 } 1865 1866 core_limit = RLIM_INFINITY; 1867 1868 /* SIGPIPE can happen, but it's just never processed */ 1869 if (call_usermodehelper_pipe(helper_argv[0], helper_argv, NULL, 1870 &file)) { 1871 printk(KERN_INFO "Core dump to %s pipe failed\n", 1872 corename); 1873 goto fail_dropcount; 1874 } 1875 } else 1876 file = filp_open(corename, 1877 O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag, 1878 0600); 1879 if (IS_ERR(file)) 1880 goto fail_dropcount; 1881 inode = file->f_path.dentry->d_inode; 1882 if (inode->i_nlink > 1) 1883 goto close_fail; /* multiple links - don't dump */ 1884 if (!ispipe && d_unhashed(file->f_path.dentry)) 1885 goto close_fail; 1886 1887 /* AK: actually i see no reason to not allow this for named pipes etc., 1888 but keep the previous behaviour for now. */ 1889 if (!ispipe && !S_ISREG(inode->i_mode)) 1890 goto close_fail; 1891 /* 1892 * Dont allow local users get cute and trick others to coredump 1893 * into their pre-created files: 1894 */ 1895 if (inode->i_uid != current_fsuid()) 1896 goto close_fail; 1897 if (!file->f_op) 1898 goto close_fail; 1899 if (!file->f_op->write) 1900 goto close_fail; 1901 if (!ispipe && do_truncate(file->f_path.dentry, 0, 0, file) != 0) 1902 goto close_fail; 1903 1904 retval = binfmt->core_dump(signr, regs, file, core_limit); 1905 1906 if (retval) 1907 current->signal->group_exit_code |= 0x80; 1908 close_fail: 1909 if (ispipe && core_pipe_limit) 1910 wait_for_dump_helpers(file); 1911 filp_close(file, NULL); 1912 fail_dropcount: 1913 if (dump_count) 1914 atomic_dec(&core_dump_count); 1915 fail_unlock: 1916 if (helper_argv) 1917 argv_free(helper_argv); 1918 1919 revert_creds(old_cred); 1920 put_cred(cred); 1921 coredump_finish(mm); 1922 fail: 1923 return; 1924 } 1925