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