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/syscalls.h> 50 #include <linux/tsacct_kern.h> 51 #include <linux/cn_proc.h> 52 #include <linux/audit.h> 53 #include <linux/tracehook.h> 54 #include <linux/kmod.h> 55 #include <linux/fsnotify.h> 56 #include <linux/fs_struct.h> 57 #include <linux/pipe_fs_i.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 unsigned int core_pipe_limit; 67 int suid_dumpable = 0; 68 69 /* The maximal length of core_pattern is also specified in sysctl.c */ 70 71 static LIST_HEAD(formats); 72 static DEFINE_RWLOCK(binfmt_lock); 73 74 int __register_binfmt(struct linux_binfmt * fmt, int insert) 75 { 76 if (!fmt) 77 return -EINVAL; 78 write_lock(&binfmt_lock); 79 insert ? list_add(&fmt->lh, &formats) : 80 list_add_tail(&fmt->lh, &formats); 81 write_unlock(&binfmt_lock); 82 return 0; 83 } 84 85 EXPORT_SYMBOL(__register_binfmt); 86 87 void unregister_binfmt(struct linux_binfmt * fmt) 88 { 89 write_lock(&binfmt_lock); 90 list_del(&fmt->lh); 91 write_unlock(&binfmt_lock); 92 } 93 94 EXPORT_SYMBOL(unregister_binfmt); 95 96 static inline void put_binfmt(struct linux_binfmt * fmt) 97 { 98 module_put(fmt->module); 99 } 100 101 /* 102 * Note that a shared library must be both readable and executable due to 103 * security reasons. 104 * 105 * Also note that we take the address to load from from the file itself. 106 */ 107 SYSCALL_DEFINE1(uselib, const char __user *, library) 108 { 109 struct file *file; 110 char *tmp = getname(library); 111 int error = PTR_ERR(tmp); 112 113 if (IS_ERR(tmp)) 114 goto out; 115 116 file = do_filp_open(AT_FDCWD, tmp, 117 O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0, 118 MAY_READ | MAY_EXEC | MAY_OPEN); 119 putname(tmp); 120 error = PTR_ERR(file); 121 if (IS_ERR(file)) 122 goto out; 123 124 error = -EINVAL; 125 if (!S_ISREG(file->f_path.dentry->d_inode->i_mode)) 126 goto exit; 127 128 error = -EACCES; 129 if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) 130 goto exit; 131 132 fsnotify_open(file->f_path.dentry); 133 134 error = -ENOEXEC; 135 if(file->f_op) { 136 struct linux_binfmt * fmt; 137 138 read_lock(&binfmt_lock); 139 list_for_each_entry(fmt, &formats, lh) { 140 if (!fmt->load_shlib) 141 continue; 142 if (!try_module_get(fmt->module)) 143 continue; 144 read_unlock(&binfmt_lock); 145 error = fmt->load_shlib(file); 146 read_lock(&binfmt_lock); 147 put_binfmt(fmt); 148 if (error != -ENOEXEC) 149 break; 150 } 151 read_unlock(&binfmt_lock); 152 } 153 exit: 154 fput(file); 155 out: 156 return error; 157 } 158 159 #ifdef CONFIG_MMU 160 161 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, 162 int write) 163 { 164 struct page *page; 165 int ret; 166 167 #ifdef CONFIG_STACK_GROWSUP 168 if (write) { 169 ret = expand_stack_downwards(bprm->vma, pos); 170 if (ret < 0) 171 return NULL; 172 } 173 #endif 174 ret = get_user_pages(current, bprm->mm, pos, 175 1, write, 1, &page, NULL); 176 if (ret <= 0) 177 return NULL; 178 179 if (write) { 180 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start; 181 struct rlimit *rlim; 182 183 /* 184 * We've historically supported up to 32 pages (ARG_MAX) 185 * of argument strings even with small stacks 186 */ 187 if (size <= ARG_MAX) 188 return page; 189 190 /* 191 * Limit to 1/4-th the stack size for the argv+env strings. 192 * This ensures that: 193 * - the remaining binfmt code will not run out of stack space, 194 * - the program will have a reasonable amount of stack left 195 * to work from. 196 */ 197 rlim = current->signal->rlim; 198 if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) { 199 put_page(page); 200 return NULL; 201 } 202 } 203 204 return page; 205 } 206 207 static void put_arg_page(struct page *page) 208 { 209 put_page(page); 210 } 211 212 static void free_arg_page(struct linux_binprm *bprm, int i) 213 { 214 } 215 216 static void free_arg_pages(struct linux_binprm *bprm) 217 { 218 } 219 220 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, 221 struct page *page) 222 { 223 flush_cache_page(bprm->vma, pos, page_to_pfn(page)); 224 } 225 226 static int __bprm_mm_init(struct linux_binprm *bprm) 227 { 228 int err; 229 struct vm_area_struct *vma = NULL; 230 struct mm_struct *mm = bprm->mm; 231 232 bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL); 233 if (!vma) 234 return -ENOMEM; 235 236 down_write(&mm->mmap_sem); 237 vma->vm_mm = mm; 238 239 /* 240 * Place the stack at the largest stack address the architecture 241 * supports. Later, we'll move this to an appropriate place. We don't 242 * use STACK_TOP because that can depend on attributes which aren't 243 * configured yet. 244 */ 245 vma->vm_end = STACK_TOP_MAX; 246 vma->vm_start = vma->vm_end - PAGE_SIZE; 247 vma->vm_flags = VM_STACK_FLAGS; 248 vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); 249 INIT_LIST_HEAD(&vma->anon_vma_chain); 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 if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL)) 521 return -ENOMEM; 522 523 /* 524 * move the page tables downwards, on failure we rely on 525 * process cleanup to remove whatever mess we made. 526 */ 527 if (length != move_page_tables(vma, old_start, 528 vma, new_start, length)) 529 return -ENOMEM; 530 531 lru_add_drain(); 532 tlb = tlb_gather_mmu(mm, 0); 533 if (new_end > old_start) { 534 /* 535 * when the old and new regions overlap clear from new_end. 536 */ 537 free_pgd_range(tlb, new_end, old_end, new_end, 538 vma->vm_next ? vma->vm_next->vm_start : 0); 539 } else { 540 /* 541 * otherwise, clean from old_start; this is done to not touch 542 * the address space in [new_end, old_start) some architectures 543 * have constraints on va-space that make this illegal (IA64) - 544 * for the others its just a little faster. 545 */ 546 free_pgd_range(tlb, old_start, old_end, new_end, 547 vma->vm_next ? vma->vm_next->vm_start : 0); 548 } 549 tlb_finish_mmu(tlb, new_end, old_end); 550 551 /* 552 * Shrink the vma to just the new range. Always succeeds. 553 */ 554 vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL); 555 556 return 0; 557 } 558 559 /* 560 * Finalizes the stack vm_area_struct. The flags and permissions are updated, 561 * the stack is optionally relocated, and some extra space is added. 562 */ 563 int setup_arg_pages(struct linux_binprm *bprm, 564 unsigned long stack_top, 565 int executable_stack) 566 { 567 unsigned long ret; 568 unsigned long stack_shift; 569 struct mm_struct *mm = current->mm; 570 struct vm_area_struct *vma = bprm->vma; 571 struct vm_area_struct *prev = NULL; 572 unsigned long vm_flags; 573 unsigned long stack_base; 574 unsigned long stack_size; 575 unsigned long stack_expand; 576 unsigned long rlim_stack; 577 578 #ifdef CONFIG_STACK_GROWSUP 579 /* Limit stack size to 1GB */ 580 stack_base = rlimit_max(RLIMIT_STACK); 581 if (stack_base > (1 << 30)) 582 stack_base = 1 << 30; 583 584 /* Make sure we didn't let the argument array grow too large. */ 585 if (vma->vm_end - vma->vm_start > stack_base) 586 return -ENOMEM; 587 588 stack_base = PAGE_ALIGN(stack_top - stack_base); 589 590 stack_shift = vma->vm_start - stack_base; 591 mm->arg_start = bprm->p - stack_shift; 592 bprm->p = vma->vm_end - stack_shift; 593 #else 594 stack_top = arch_align_stack(stack_top); 595 stack_top = PAGE_ALIGN(stack_top); 596 stack_shift = vma->vm_end - stack_top; 597 598 bprm->p -= stack_shift; 599 mm->arg_start = bprm->p; 600 #endif 601 602 if (bprm->loader) 603 bprm->loader -= stack_shift; 604 bprm->exec -= stack_shift; 605 606 down_write(&mm->mmap_sem); 607 vm_flags = VM_STACK_FLAGS; 608 609 /* 610 * Adjust stack execute permissions; explicitly enable for 611 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone 612 * (arch default) otherwise. 613 */ 614 if (unlikely(executable_stack == EXSTACK_ENABLE_X)) 615 vm_flags |= VM_EXEC; 616 else if (executable_stack == EXSTACK_DISABLE_X) 617 vm_flags &= ~VM_EXEC; 618 vm_flags |= mm->def_flags; 619 620 ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end, 621 vm_flags); 622 if (ret) 623 goto out_unlock; 624 BUG_ON(prev != vma); 625 626 /* Move stack pages down in memory. */ 627 if (stack_shift) { 628 ret = shift_arg_pages(vma, stack_shift); 629 if (ret) 630 goto out_unlock; 631 } 632 633 stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */ 634 stack_size = vma->vm_end - vma->vm_start; 635 /* 636 * Align this down to a page boundary as expand_stack 637 * will align it up. 638 */ 639 rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK; 640 #ifdef CONFIG_STACK_GROWSUP 641 if (stack_size + stack_expand > rlim_stack) 642 stack_base = vma->vm_start + rlim_stack; 643 else 644 stack_base = vma->vm_end + stack_expand; 645 #else 646 if (stack_size + stack_expand > rlim_stack) 647 stack_base = vma->vm_end - rlim_stack; 648 else 649 stack_base = vma->vm_start - stack_expand; 650 #endif 651 ret = expand_stack(vma, stack_base); 652 if (ret) 653 ret = -EFAULT; 654 655 out_unlock: 656 up_write(&mm->mmap_sem); 657 return ret; 658 } 659 EXPORT_SYMBOL(setup_arg_pages); 660 661 #endif /* CONFIG_MMU */ 662 663 struct file *open_exec(const char *name) 664 { 665 struct file *file; 666 int err; 667 668 file = do_filp_open(AT_FDCWD, name, 669 O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0, 670 MAY_EXEC | MAY_OPEN); 671 if (IS_ERR(file)) 672 goto out; 673 674 err = -EACCES; 675 if (!S_ISREG(file->f_path.dentry->d_inode->i_mode)) 676 goto exit; 677 678 if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) 679 goto exit; 680 681 fsnotify_open(file->f_path.dentry); 682 683 err = deny_write_access(file); 684 if (err) 685 goto exit; 686 687 out: 688 return file; 689 690 exit: 691 fput(file); 692 return ERR_PTR(err); 693 } 694 EXPORT_SYMBOL(open_exec); 695 696 int kernel_read(struct file *file, loff_t offset, 697 char *addr, unsigned long count) 698 { 699 mm_segment_t old_fs; 700 loff_t pos = offset; 701 int result; 702 703 old_fs = get_fs(); 704 set_fs(get_ds()); 705 /* The cast to a user pointer is valid due to the set_fs() */ 706 result = vfs_read(file, (void __user *)addr, count, &pos); 707 set_fs(old_fs); 708 return result; 709 } 710 711 EXPORT_SYMBOL(kernel_read); 712 713 static int exec_mmap(struct mm_struct *mm) 714 { 715 struct task_struct *tsk; 716 struct mm_struct * old_mm, *active_mm; 717 718 /* Notify parent that we're no longer interested in the old VM */ 719 tsk = current; 720 old_mm = current->mm; 721 sync_mm_rss(tsk, old_mm); 722 mm_release(tsk, old_mm); 723 724 if (old_mm) { 725 /* 726 * Make sure that if there is a core dump in progress 727 * for the old mm, we get out and die instead of going 728 * through with the exec. We must hold mmap_sem around 729 * checking core_state and changing tsk->mm. 730 */ 731 down_read(&old_mm->mmap_sem); 732 if (unlikely(old_mm->core_state)) { 733 up_read(&old_mm->mmap_sem); 734 return -EINTR; 735 } 736 } 737 task_lock(tsk); 738 active_mm = tsk->active_mm; 739 tsk->mm = mm; 740 tsk->active_mm = mm; 741 activate_mm(active_mm, mm); 742 task_unlock(tsk); 743 arch_pick_mmap_layout(mm); 744 if (old_mm) { 745 up_read(&old_mm->mmap_sem); 746 BUG_ON(active_mm != old_mm); 747 mm_update_next_owner(old_mm); 748 mmput(old_mm); 749 return 0; 750 } 751 mmdrop(active_mm); 752 return 0; 753 } 754 755 /* 756 * This function makes sure the current process has its own signal table, 757 * so that flush_signal_handlers can later reset the handlers without 758 * disturbing other processes. (Other processes might share the signal 759 * table via the CLONE_SIGHAND option to clone().) 760 */ 761 static int de_thread(struct task_struct *tsk) 762 { 763 struct signal_struct *sig = tsk->signal; 764 struct sighand_struct *oldsighand = tsk->sighand; 765 spinlock_t *lock = &oldsighand->siglock; 766 int count; 767 768 if (thread_group_empty(tsk)) 769 goto no_thread_group; 770 771 /* 772 * Kill all other threads in the thread group. 773 */ 774 spin_lock_irq(lock); 775 if (signal_group_exit(sig)) { 776 /* 777 * Another group action in progress, just 778 * return so that the signal is processed. 779 */ 780 spin_unlock_irq(lock); 781 return -EAGAIN; 782 } 783 sig->group_exit_task = tsk; 784 zap_other_threads(tsk); 785 786 /* Account for the thread group leader hanging around: */ 787 count = thread_group_leader(tsk) ? 1 : 2; 788 sig->notify_count = count; 789 while (atomic_read(&sig->count) > count) { 790 __set_current_state(TASK_UNINTERRUPTIBLE); 791 spin_unlock_irq(lock); 792 schedule(); 793 spin_lock_irq(lock); 794 } 795 spin_unlock_irq(lock); 796 797 /* 798 * At this point all other threads have exited, all we have to 799 * do is to wait for the thread group leader to become inactive, 800 * and to assume its PID: 801 */ 802 if (!thread_group_leader(tsk)) { 803 struct task_struct *leader = tsk->group_leader; 804 805 sig->notify_count = -1; /* for exit_notify() */ 806 for (;;) { 807 write_lock_irq(&tasklist_lock); 808 if (likely(leader->exit_state)) 809 break; 810 __set_current_state(TASK_UNINTERRUPTIBLE); 811 write_unlock_irq(&tasklist_lock); 812 schedule(); 813 } 814 815 /* 816 * The only record we have of the real-time age of a 817 * process, regardless of execs it's done, is start_time. 818 * All the past CPU time is accumulated in signal_struct 819 * from sister threads now dead. But in this non-leader 820 * exec, nothing survives from the original leader thread, 821 * whose birth marks the true age of this process now. 822 * When we take on its identity by switching to its PID, we 823 * also take its birthdate (always earlier than our own). 824 */ 825 tsk->start_time = leader->start_time; 826 827 BUG_ON(!same_thread_group(leader, tsk)); 828 BUG_ON(has_group_leader_pid(tsk)); 829 /* 830 * An exec() starts a new thread group with the 831 * TGID of the previous thread group. Rehash the 832 * two threads with a switched PID, and release 833 * the former thread group leader: 834 */ 835 836 /* Become a process group leader with the old leader's pid. 837 * The old leader becomes a thread of the this thread group. 838 * Note: The old leader also uses this pid until release_task 839 * is called. Odd but simple and correct. 840 */ 841 detach_pid(tsk, PIDTYPE_PID); 842 tsk->pid = leader->pid; 843 attach_pid(tsk, PIDTYPE_PID, task_pid(leader)); 844 transfer_pid(leader, tsk, PIDTYPE_PGID); 845 transfer_pid(leader, tsk, PIDTYPE_SID); 846 847 list_replace_rcu(&leader->tasks, &tsk->tasks); 848 list_replace_init(&leader->sibling, &tsk->sibling); 849 850 tsk->group_leader = tsk; 851 leader->group_leader = tsk; 852 853 tsk->exit_signal = SIGCHLD; 854 855 BUG_ON(leader->exit_state != EXIT_ZOMBIE); 856 leader->exit_state = EXIT_DEAD; 857 write_unlock_irq(&tasklist_lock); 858 859 release_task(leader); 860 } 861 862 sig->group_exit_task = NULL; 863 sig->notify_count = 0; 864 865 no_thread_group: 866 if (current->mm) 867 setmax_mm_hiwater_rss(&sig->maxrss, current->mm); 868 869 exit_itimers(sig); 870 flush_itimer_signals(); 871 872 if (atomic_read(&oldsighand->count) != 1) { 873 struct sighand_struct *newsighand; 874 /* 875 * This ->sighand is shared with the CLONE_SIGHAND 876 * but not CLONE_THREAD task, switch to the new one. 877 */ 878 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 879 if (!newsighand) 880 return -ENOMEM; 881 882 atomic_set(&newsighand->count, 1); 883 memcpy(newsighand->action, oldsighand->action, 884 sizeof(newsighand->action)); 885 886 write_lock_irq(&tasklist_lock); 887 spin_lock(&oldsighand->siglock); 888 rcu_assign_pointer(tsk->sighand, newsighand); 889 spin_unlock(&oldsighand->siglock); 890 write_unlock_irq(&tasklist_lock); 891 892 __cleanup_sighand(oldsighand); 893 } 894 895 BUG_ON(!thread_group_leader(tsk)); 896 return 0; 897 } 898 899 /* 900 * These functions flushes out all traces of the currently running executable 901 * so that a new one can be started 902 */ 903 static void flush_old_files(struct files_struct * files) 904 { 905 long j = -1; 906 struct fdtable *fdt; 907 908 spin_lock(&files->file_lock); 909 for (;;) { 910 unsigned long set, i; 911 912 j++; 913 i = j * __NFDBITS; 914 fdt = files_fdtable(files); 915 if (i >= fdt->max_fds) 916 break; 917 set = fdt->close_on_exec->fds_bits[j]; 918 if (!set) 919 continue; 920 fdt->close_on_exec->fds_bits[j] = 0; 921 spin_unlock(&files->file_lock); 922 for ( ; set ; i++,set >>= 1) { 923 if (set & 1) { 924 sys_close(i); 925 } 926 } 927 spin_lock(&files->file_lock); 928 929 } 930 spin_unlock(&files->file_lock); 931 } 932 933 char *get_task_comm(char *buf, struct task_struct *tsk) 934 { 935 /* buf must be at least sizeof(tsk->comm) in size */ 936 task_lock(tsk); 937 strncpy(buf, tsk->comm, sizeof(tsk->comm)); 938 task_unlock(tsk); 939 return buf; 940 } 941 942 void set_task_comm(struct task_struct *tsk, char *buf) 943 { 944 task_lock(tsk); 945 946 /* 947 * Threads may access current->comm without holding 948 * the task lock, so write the string carefully. 949 * Readers without a lock may see incomplete new 950 * names but are safe from non-terminating string reads. 951 */ 952 memset(tsk->comm, 0, TASK_COMM_LEN); 953 wmb(); 954 strlcpy(tsk->comm, buf, sizeof(tsk->comm)); 955 task_unlock(tsk); 956 perf_event_comm(tsk); 957 } 958 959 int flush_old_exec(struct linux_binprm * bprm) 960 { 961 int retval; 962 963 /* 964 * Make sure we have a private signal table and that 965 * we are unassociated from the previous thread group. 966 */ 967 retval = de_thread(current); 968 if (retval) 969 goto out; 970 971 set_mm_exe_file(bprm->mm, bprm->file); 972 973 /* 974 * Release all of the old mmap stuff 975 */ 976 retval = exec_mmap(bprm->mm); 977 if (retval) 978 goto out; 979 980 bprm->mm = NULL; /* We're using it now */ 981 982 current->flags &= ~PF_RANDOMIZE; 983 flush_thread(); 984 current->personality &= ~bprm->per_clear; 985 986 return 0; 987 988 out: 989 return retval; 990 } 991 EXPORT_SYMBOL(flush_old_exec); 992 993 void setup_new_exec(struct linux_binprm * bprm) 994 { 995 int i, ch; 996 char * name; 997 char tcomm[sizeof(current->comm)]; 998 999 arch_pick_mmap_layout(current->mm); 1000 1001 /* This is the point of no return */ 1002 current->sas_ss_sp = current->sas_ss_size = 0; 1003 1004 if (current_euid() == current_uid() && current_egid() == current_gid()) 1005 set_dumpable(current->mm, 1); 1006 else 1007 set_dumpable(current->mm, suid_dumpable); 1008 1009 name = bprm->filename; 1010 1011 /* Copies the binary name from after last slash */ 1012 for (i=0; (ch = *(name++)) != '\0';) { 1013 if (ch == '/') 1014 i = 0; /* overwrite what we wrote */ 1015 else 1016 if (i < (sizeof(tcomm) - 1)) 1017 tcomm[i++] = ch; 1018 } 1019 tcomm[i] = '\0'; 1020 set_task_comm(current, tcomm); 1021 1022 /* Set the new mm task size. We have to do that late because it may 1023 * depend on TIF_32BIT which is only updated in flush_thread() on 1024 * some architectures like powerpc 1025 */ 1026 current->mm->task_size = TASK_SIZE; 1027 1028 /* install the new credentials */ 1029 if (bprm->cred->uid != current_euid() || 1030 bprm->cred->gid != current_egid()) { 1031 current->pdeath_signal = 0; 1032 } else if (file_permission(bprm->file, MAY_READ) || 1033 bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) { 1034 set_dumpable(current->mm, suid_dumpable); 1035 } 1036 1037 /* 1038 * Flush performance counters when crossing a 1039 * security domain: 1040 */ 1041 if (!get_dumpable(current->mm)) 1042 perf_event_exit_task(current); 1043 1044 /* An exec changes our domain. We are no longer part of the thread 1045 group */ 1046 1047 current->self_exec_id++; 1048 1049 flush_signal_handlers(current, 0); 1050 flush_old_files(current->files); 1051 } 1052 EXPORT_SYMBOL(setup_new_exec); 1053 1054 /* 1055 * Prepare credentials and lock ->cred_guard_mutex. 1056 * install_exec_creds() commits the new creds and drops the lock. 1057 * Or, if exec fails before, free_bprm() should release ->cred and 1058 * and unlock. 1059 */ 1060 int prepare_bprm_creds(struct linux_binprm *bprm) 1061 { 1062 if (mutex_lock_interruptible(¤t->cred_guard_mutex)) 1063 return -ERESTARTNOINTR; 1064 1065 bprm->cred = prepare_exec_creds(); 1066 if (likely(bprm->cred)) 1067 return 0; 1068 1069 mutex_unlock(¤t->cred_guard_mutex); 1070 return -ENOMEM; 1071 } 1072 1073 void free_bprm(struct linux_binprm *bprm) 1074 { 1075 free_arg_pages(bprm); 1076 if (bprm->cred) { 1077 mutex_unlock(¤t->cred_guard_mutex); 1078 abort_creds(bprm->cred); 1079 } 1080 kfree(bprm); 1081 } 1082 1083 /* 1084 * install the new credentials for this executable 1085 */ 1086 void install_exec_creds(struct linux_binprm *bprm) 1087 { 1088 security_bprm_committing_creds(bprm); 1089 1090 commit_creds(bprm->cred); 1091 bprm->cred = NULL; 1092 /* 1093 * cred_guard_mutex must be held at least to this point to prevent 1094 * ptrace_attach() from altering our determination of the task's 1095 * credentials; any time after this it may be unlocked. 1096 */ 1097 security_bprm_committed_creds(bprm); 1098 mutex_unlock(¤t->cred_guard_mutex); 1099 } 1100 EXPORT_SYMBOL(install_exec_creds); 1101 1102 /* 1103 * determine how safe it is to execute the proposed program 1104 * - the caller must hold current->cred_guard_mutex to protect against 1105 * PTRACE_ATTACH 1106 */ 1107 int check_unsafe_exec(struct linux_binprm *bprm) 1108 { 1109 struct task_struct *p = current, *t; 1110 unsigned n_fs; 1111 int res = 0; 1112 1113 bprm->unsafe = tracehook_unsafe_exec(p); 1114 1115 n_fs = 1; 1116 write_lock(&p->fs->lock); 1117 rcu_read_lock(); 1118 for (t = next_thread(p); t != p; t = next_thread(t)) { 1119 if (t->fs == p->fs) 1120 n_fs++; 1121 } 1122 rcu_read_unlock(); 1123 1124 if (p->fs->users > n_fs) { 1125 bprm->unsafe |= LSM_UNSAFE_SHARE; 1126 } else { 1127 res = -EAGAIN; 1128 if (!p->fs->in_exec) { 1129 p->fs->in_exec = 1; 1130 res = 1; 1131 } 1132 } 1133 write_unlock(&p->fs->lock); 1134 1135 return res; 1136 } 1137 1138 /* 1139 * Fill the binprm structure from the inode. 1140 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes 1141 * 1142 * This may be called multiple times for binary chains (scripts for example). 1143 */ 1144 int prepare_binprm(struct linux_binprm *bprm) 1145 { 1146 umode_t mode; 1147 struct inode * inode = bprm->file->f_path.dentry->d_inode; 1148 int retval; 1149 1150 mode = inode->i_mode; 1151 if (bprm->file->f_op == NULL) 1152 return -EACCES; 1153 1154 /* clear any previous set[ug]id data from a previous binary */ 1155 bprm->cred->euid = current_euid(); 1156 bprm->cred->egid = current_egid(); 1157 1158 if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) { 1159 /* Set-uid? */ 1160 if (mode & S_ISUID) { 1161 bprm->per_clear |= PER_CLEAR_ON_SETID; 1162 bprm->cred->euid = inode->i_uid; 1163 } 1164 1165 /* Set-gid? */ 1166 /* 1167 * If setgid is set but no group execute bit then this 1168 * is a candidate for mandatory locking, not a setgid 1169 * executable. 1170 */ 1171 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { 1172 bprm->per_clear |= PER_CLEAR_ON_SETID; 1173 bprm->cred->egid = inode->i_gid; 1174 } 1175 } 1176 1177 /* fill in binprm security blob */ 1178 retval = security_bprm_set_creds(bprm); 1179 if (retval) 1180 return retval; 1181 bprm->cred_prepared = 1; 1182 1183 memset(bprm->buf, 0, BINPRM_BUF_SIZE); 1184 return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE); 1185 } 1186 1187 EXPORT_SYMBOL(prepare_binprm); 1188 1189 /* 1190 * Arguments are '\0' separated strings found at the location bprm->p 1191 * points to; chop off the first by relocating brpm->p to right after 1192 * the first '\0' encountered. 1193 */ 1194 int remove_arg_zero(struct linux_binprm *bprm) 1195 { 1196 int ret = 0; 1197 unsigned long offset; 1198 char *kaddr; 1199 struct page *page; 1200 1201 if (!bprm->argc) 1202 return 0; 1203 1204 do { 1205 offset = bprm->p & ~PAGE_MASK; 1206 page = get_arg_page(bprm, bprm->p, 0); 1207 if (!page) { 1208 ret = -EFAULT; 1209 goto out; 1210 } 1211 kaddr = kmap_atomic(page, KM_USER0); 1212 1213 for (; offset < PAGE_SIZE && kaddr[offset]; 1214 offset++, bprm->p++) 1215 ; 1216 1217 kunmap_atomic(kaddr, KM_USER0); 1218 put_arg_page(page); 1219 1220 if (offset == PAGE_SIZE) 1221 free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1); 1222 } while (offset == PAGE_SIZE); 1223 1224 bprm->p++; 1225 bprm->argc--; 1226 ret = 0; 1227 1228 out: 1229 return ret; 1230 } 1231 EXPORT_SYMBOL(remove_arg_zero); 1232 1233 /* 1234 * cycle the list of binary formats handler, until one recognizes the image 1235 */ 1236 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs) 1237 { 1238 unsigned int depth = bprm->recursion_depth; 1239 int try,retval; 1240 struct linux_binfmt *fmt; 1241 1242 retval = security_bprm_check(bprm); 1243 if (retval) 1244 return retval; 1245 1246 /* kernel module loader fixup */ 1247 /* so we don't try to load run modprobe in kernel space. */ 1248 set_fs(USER_DS); 1249 1250 retval = audit_bprm(bprm); 1251 if (retval) 1252 return retval; 1253 1254 retval = -ENOENT; 1255 for (try=0; try<2; try++) { 1256 read_lock(&binfmt_lock); 1257 list_for_each_entry(fmt, &formats, lh) { 1258 int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary; 1259 if (!fn) 1260 continue; 1261 if (!try_module_get(fmt->module)) 1262 continue; 1263 read_unlock(&binfmt_lock); 1264 retval = fn(bprm, regs); 1265 /* 1266 * Restore the depth counter to its starting value 1267 * in this call, so we don't have to rely on every 1268 * load_binary function to restore it on return. 1269 */ 1270 bprm->recursion_depth = depth; 1271 if (retval >= 0) { 1272 if (depth == 0) 1273 tracehook_report_exec(fmt, bprm, regs); 1274 put_binfmt(fmt); 1275 allow_write_access(bprm->file); 1276 if (bprm->file) 1277 fput(bprm->file); 1278 bprm->file = NULL; 1279 current->did_exec = 1; 1280 proc_exec_connector(current); 1281 return retval; 1282 } 1283 read_lock(&binfmt_lock); 1284 put_binfmt(fmt); 1285 if (retval != -ENOEXEC || bprm->mm == NULL) 1286 break; 1287 if (!bprm->file) { 1288 read_unlock(&binfmt_lock); 1289 return retval; 1290 } 1291 } 1292 read_unlock(&binfmt_lock); 1293 if (retval != -ENOEXEC || bprm->mm == NULL) { 1294 break; 1295 #ifdef CONFIG_MODULES 1296 } else { 1297 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e)) 1298 if (printable(bprm->buf[0]) && 1299 printable(bprm->buf[1]) && 1300 printable(bprm->buf[2]) && 1301 printable(bprm->buf[3])) 1302 break; /* -ENOEXEC */ 1303 request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2])); 1304 #endif 1305 } 1306 } 1307 return retval; 1308 } 1309 1310 EXPORT_SYMBOL(search_binary_handler); 1311 1312 /* 1313 * sys_execve() executes a new program. 1314 */ 1315 int do_execve(char * filename, 1316 char __user *__user *argv, 1317 char __user *__user *envp, 1318 struct pt_regs * regs) 1319 { 1320 struct linux_binprm *bprm; 1321 struct file *file; 1322 struct files_struct *displaced; 1323 bool clear_in_exec; 1324 int retval; 1325 1326 retval = unshare_files(&displaced); 1327 if (retval) 1328 goto out_ret; 1329 1330 retval = -ENOMEM; 1331 bprm = kzalloc(sizeof(*bprm), GFP_KERNEL); 1332 if (!bprm) 1333 goto out_files; 1334 1335 retval = prepare_bprm_creds(bprm); 1336 if (retval) 1337 goto out_free; 1338 1339 retval = check_unsafe_exec(bprm); 1340 if (retval < 0) 1341 goto out_free; 1342 clear_in_exec = retval; 1343 current->in_execve = 1; 1344 1345 file = open_exec(filename); 1346 retval = PTR_ERR(file); 1347 if (IS_ERR(file)) 1348 goto out_unmark; 1349 1350 sched_exec(); 1351 1352 bprm->file = file; 1353 bprm->filename = filename; 1354 bprm->interp = filename; 1355 1356 retval = bprm_mm_init(bprm); 1357 if (retval) 1358 goto out_file; 1359 1360 bprm->argc = count(argv, MAX_ARG_STRINGS); 1361 if ((retval = bprm->argc) < 0) 1362 goto out; 1363 1364 bprm->envc = count(envp, MAX_ARG_STRINGS); 1365 if ((retval = bprm->envc) < 0) 1366 goto out; 1367 1368 retval = prepare_binprm(bprm); 1369 if (retval < 0) 1370 goto out; 1371 1372 retval = copy_strings_kernel(1, &bprm->filename, bprm); 1373 if (retval < 0) 1374 goto out; 1375 1376 bprm->exec = bprm->p; 1377 retval = copy_strings(bprm->envc, envp, bprm); 1378 if (retval < 0) 1379 goto out; 1380 1381 retval = copy_strings(bprm->argc, argv, bprm); 1382 if (retval < 0) 1383 goto out; 1384 1385 current->flags &= ~PF_KTHREAD; 1386 retval = search_binary_handler(bprm,regs); 1387 if (retval < 0) 1388 goto out; 1389 1390 current->stack_start = current->mm->start_stack; 1391 1392 /* execve succeeded */ 1393 current->fs->in_exec = 0; 1394 current->in_execve = 0; 1395 acct_update_integrals(current); 1396 free_bprm(bprm); 1397 if (displaced) 1398 put_files_struct(displaced); 1399 return retval; 1400 1401 out: 1402 if (bprm->mm) 1403 mmput (bprm->mm); 1404 1405 out_file: 1406 if (bprm->file) { 1407 allow_write_access(bprm->file); 1408 fput(bprm->file); 1409 } 1410 1411 out_unmark: 1412 if (clear_in_exec) 1413 current->fs->in_exec = 0; 1414 current->in_execve = 0; 1415 1416 out_free: 1417 free_bprm(bprm); 1418 1419 out_files: 1420 if (displaced) 1421 reset_files_struct(displaced); 1422 out_ret: 1423 return retval; 1424 } 1425 1426 void set_binfmt(struct linux_binfmt *new) 1427 { 1428 struct mm_struct *mm = current->mm; 1429 1430 if (mm->binfmt) 1431 module_put(mm->binfmt->module); 1432 1433 mm->binfmt = new; 1434 if (new) 1435 __module_get(new->module); 1436 } 1437 1438 EXPORT_SYMBOL(set_binfmt); 1439 1440 /* format_corename will inspect the pattern parameter, and output a 1441 * name into corename, which must have space for at least 1442 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator. 1443 */ 1444 static int format_corename(char *corename, long signr) 1445 { 1446 const struct cred *cred = current_cred(); 1447 const char *pat_ptr = core_pattern; 1448 int ispipe = (*pat_ptr == '|'); 1449 char *out_ptr = corename; 1450 char *const out_end = corename + CORENAME_MAX_SIZE; 1451 int rc; 1452 int pid_in_pattern = 0; 1453 1454 /* Repeat as long as we have more pattern to process and more output 1455 space */ 1456 while (*pat_ptr) { 1457 if (*pat_ptr != '%') { 1458 if (out_ptr == out_end) 1459 goto out; 1460 *out_ptr++ = *pat_ptr++; 1461 } else { 1462 switch (*++pat_ptr) { 1463 case 0: 1464 goto out; 1465 /* Double percent, output one percent */ 1466 case '%': 1467 if (out_ptr == out_end) 1468 goto out; 1469 *out_ptr++ = '%'; 1470 break; 1471 /* pid */ 1472 case 'p': 1473 pid_in_pattern = 1; 1474 rc = snprintf(out_ptr, out_end - out_ptr, 1475 "%d", task_tgid_vnr(current)); 1476 if (rc > out_end - out_ptr) 1477 goto out; 1478 out_ptr += rc; 1479 break; 1480 /* uid */ 1481 case 'u': 1482 rc = snprintf(out_ptr, out_end - out_ptr, 1483 "%d", cred->uid); 1484 if (rc > out_end - out_ptr) 1485 goto out; 1486 out_ptr += rc; 1487 break; 1488 /* gid */ 1489 case 'g': 1490 rc = snprintf(out_ptr, out_end - out_ptr, 1491 "%d", cred->gid); 1492 if (rc > out_end - out_ptr) 1493 goto out; 1494 out_ptr += rc; 1495 break; 1496 /* signal that caused the coredump */ 1497 case 's': 1498 rc = snprintf(out_ptr, out_end - out_ptr, 1499 "%ld", signr); 1500 if (rc > out_end - out_ptr) 1501 goto out; 1502 out_ptr += rc; 1503 break; 1504 /* UNIX time of coredump */ 1505 case 't': { 1506 struct timeval tv; 1507 do_gettimeofday(&tv); 1508 rc = snprintf(out_ptr, out_end - out_ptr, 1509 "%lu", tv.tv_sec); 1510 if (rc > out_end - out_ptr) 1511 goto out; 1512 out_ptr += rc; 1513 break; 1514 } 1515 /* hostname */ 1516 case 'h': 1517 down_read(&uts_sem); 1518 rc = snprintf(out_ptr, out_end - out_ptr, 1519 "%s", utsname()->nodename); 1520 up_read(&uts_sem); 1521 if (rc > out_end - out_ptr) 1522 goto out; 1523 out_ptr += rc; 1524 break; 1525 /* executable */ 1526 case 'e': 1527 rc = snprintf(out_ptr, out_end - out_ptr, 1528 "%s", current->comm); 1529 if (rc > out_end - out_ptr) 1530 goto out; 1531 out_ptr += rc; 1532 break; 1533 /* core limit size */ 1534 case 'c': 1535 rc = snprintf(out_ptr, out_end - out_ptr, 1536 "%lu", rlimit(RLIMIT_CORE)); 1537 if (rc > out_end - out_ptr) 1538 goto out; 1539 out_ptr += rc; 1540 break; 1541 default: 1542 break; 1543 } 1544 ++pat_ptr; 1545 } 1546 } 1547 /* Backward compatibility with core_uses_pid: 1548 * 1549 * If core_pattern does not include a %p (as is the default) 1550 * and core_uses_pid is set, then .%pid will be appended to 1551 * the filename. Do not do this for piped commands. */ 1552 if (!ispipe && !pid_in_pattern && core_uses_pid) { 1553 rc = snprintf(out_ptr, out_end - out_ptr, 1554 ".%d", task_tgid_vnr(current)); 1555 if (rc > out_end - out_ptr) 1556 goto out; 1557 out_ptr += rc; 1558 } 1559 out: 1560 *out_ptr = 0; 1561 return ispipe; 1562 } 1563 1564 static int zap_process(struct task_struct *start, int exit_code) 1565 { 1566 struct task_struct *t; 1567 int nr = 0; 1568 1569 start->signal->flags = SIGNAL_GROUP_EXIT; 1570 start->signal->group_exit_code = exit_code; 1571 start->signal->group_stop_count = 0; 1572 1573 t = start; 1574 do { 1575 if (t != current && t->mm) { 1576 sigaddset(&t->pending.signal, SIGKILL); 1577 signal_wake_up(t, 1); 1578 nr++; 1579 } 1580 } while_each_thread(start, t); 1581 1582 return nr; 1583 } 1584 1585 static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm, 1586 struct core_state *core_state, int exit_code) 1587 { 1588 struct task_struct *g, *p; 1589 unsigned long flags; 1590 int nr = -EAGAIN; 1591 1592 spin_lock_irq(&tsk->sighand->siglock); 1593 if (!signal_group_exit(tsk->signal)) { 1594 mm->core_state = core_state; 1595 nr = zap_process(tsk, exit_code); 1596 } 1597 spin_unlock_irq(&tsk->sighand->siglock); 1598 if (unlikely(nr < 0)) 1599 return nr; 1600 1601 if (atomic_read(&mm->mm_users) == nr + 1) 1602 goto done; 1603 /* 1604 * We should find and kill all tasks which use this mm, and we should 1605 * count them correctly into ->nr_threads. We don't take tasklist 1606 * lock, but this is safe wrt: 1607 * 1608 * fork: 1609 * None of sub-threads can fork after zap_process(leader). All 1610 * processes which were created before this point should be 1611 * visible to zap_threads() because copy_process() adds the new 1612 * process to the tail of init_task.tasks list, and lock/unlock 1613 * of ->siglock provides a memory barrier. 1614 * 1615 * do_exit: 1616 * The caller holds mm->mmap_sem. This means that the task which 1617 * uses this mm can't pass exit_mm(), so it can't exit or clear 1618 * its ->mm. 1619 * 1620 * de_thread: 1621 * It does list_replace_rcu(&leader->tasks, ¤t->tasks), 1622 * we must see either old or new leader, this does not matter. 1623 * However, it can change p->sighand, so lock_task_sighand(p) 1624 * must be used. Since p->mm != NULL and we hold ->mmap_sem 1625 * it can't fail. 1626 * 1627 * Note also that "g" can be the old leader with ->mm == NULL 1628 * and already unhashed and thus removed from ->thread_group. 1629 * This is OK, __unhash_process()->list_del_rcu() does not 1630 * clear the ->next pointer, we will find the new leader via 1631 * next_thread(). 1632 */ 1633 rcu_read_lock(); 1634 for_each_process(g) { 1635 if (g == tsk->group_leader) 1636 continue; 1637 if (g->flags & PF_KTHREAD) 1638 continue; 1639 p = g; 1640 do { 1641 if (p->mm) { 1642 if (unlikely(p->mm == mm)) { 1643 lock_task_sighand(p, &flags); 1644 nr += zap_process(p, exit_code); 1645 unlock_task_sighand(p, &flags); 1646 } 1647 break; 1648 } 1649 } while_each_thread(g, p); 1650 } 1651 rcu_read_unlock(); 1652 done: 1653 atomic_set(&core_state->nr_threads, nr); 1654 return nr; 1655 } 1656 1657 static int coredump_wait(int exit_code, struct core_state *core_state) 1658 { 1659 struct task_struct *tsk = current; 1660 struct mm_struct *mm = tsk->mm; 1661 struct completion *vfork_done; 1662 int core_waiters; 1663 1664 init_completion(&core_state->startup); 1665 core_state->dumper.task = tsk; 1666 core_state->dumper.next = NULL; 1667 core_waiters = zap_threads(tsk, mm, core_state, exit_code); 1668 up_write(&mm->mmap_sem); 1669 1670 if (unlikely(core_waiters < 0)) 1671 goto fail; 1672 1673 /* 1674 * Make sure nobody is waiting for us to release the VM, 1675 * otherwise we can deadlock when we wait on each other 1676 */ 1677 vfork_done = tsk->vfork_done; 1678 if (vfork_done) { 1679 tsk->vfork_done = NULL; 1680 complete(vfork_done); 1681 } 1682 1683 if (core_waiters) 1684 wait_for_completion(&core_state->startup); 1685 fail: 1686 return core_waiters; 1687 } 1688 1689 static void coredump_finish(struct mm_struct *mm) 1690 { 1691 struct core_thread *curr, *next; 1692 struct task_struct *task; 1693 1694 next = mm->core_state->dumper.next; 1695 while ((curr = next) != NULL) { 1696 next = curr->next; 1697 task = curr->task; 1698 /* 1699 * see exit_mm(), curr->task must not see 1700 * ->task == NULL before we read ->next. 1701 */ 1702 smp_mb(); 1703 curr->task = NULL; 1704 wake_up_process(task); 1705 } 1706 1707 mm->core_state = NULL; 1708 } 1709 1710 /* 1711 * set_dumpable converts traditional three-value dumpable to two flags and 1712 * stores them into mm->flags. It modifies lower two bits of mm->flags, but 1713 * these bits are not changed atomically. So get_dumpable can observe the 1714 * intermediate state. To avoid doing unexpected behavior, get get_dumpable 1715 * return either old dumpable or new one by paying attention to the order of 1716 * modifying the bits. 1717 * 1718 * dumpable | mm->flags (binary) 1719 * old new | initial interim final 1720 * ---------+----------------------- 1721 * 0 1 | 00 01 01 1722 * 0 2 | 00 10(*) 11 1723 * 1 0 | 01 00 00 1724 * 1 2 | 01 11 11 1725 * 2 0 | 11 10(*) 00 1726 * 2 1 | 11 11 01 1727 * 1728 * (*) get_dumpable regards interim value of 10 as 11. 1729 */ 1730 void set_dumpable(struct mm_struct *mm, int value) 1731 { 1732 switch (value) { 1733 case 0: 1734 clear_bit(MMF_DUMPABLE, &mm->flags); 1735 smp_wmb(); 1736 clear_bit(MMF_DUMP_SECURELY, &mm->flags); 1737 break; 1738 case 1: 1739 set_bit(MMF_DUMPABLE, &mm->flags); 1740 smp_wmb(); 1741 clear_bit(MMF_DUMP_SECURELY, &mm->flags); 1742 break; 1743 case 2: 1744 set_bit(MMF_DUMP_SECURELY, &mm->flags); 1745 smp_wmb(); 1746 set_bit(MMF_DUMPABLE, &mm->flags); 1747 break; 1748 } 1749 } 1750 1751 static int __get_dumpable(unsigned long mm_flags) 1752 { 1753 int ret; 1754 1755 ret = mm_flags & MMF_DUMPABLE_MASK; 1756 return (ret >= 2) ? 2 : ret; 1757 } 1758 1759 int get_dumpable(struct mm_struct *mm) 1760 { 1761 return __get_dumpable(mm->flags); 1762 } 1763 1764 static void wait_for_dump_helpers(struct file *file) 1765 { 1766 struct pipe_inode_info *pipe; 1767 1768 pipe = file->f_path.dentry->d_inode->i_pipe; 1769 1770 pipe_lock(pipe); 1771 pipe->readers++; 1772 pipe->writers--; 1773 1774 while ((pipe->readers > 1) && (!signal_pending(current))) { 1775 wake_up_interruptible_sync(&pipe->wait); 1776 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 1777 pipe_wait(pipe); 1778 } 1779 1780 pipe->readers--; 1781 pipe->writers++; 1782 pipe_unlock(pipe); 1783 1784 } 1785 1786 1787 void do_coredump(long signr, int exit_code, struct pt_regs *regs) 1788 { 1789 struct core_state core_state; 1790 char corename[CORENAME_MAX_SIZE + 1]; 1791 struct mm_struct *mm = current->mm; 1792 struct linux_binfmt * binfmt; 1793 struct inode * inode; 1794 const struct cred *old_cred; 1795 struct cred *cred; 1796 int retval = 0; 1797 int flag = 0; 1798 int ispipe = 0; 1799 char **helper_argv = NULL; 1800 int helper_argc = 0; 1801 int dump_count = 0; 1802 static atomic_t core_dump_count = ATOMIC_INIT(0); 1803 struct coredump_params cprm = { 1804 .signr = signr, 1805 .regs = regs, 1806 .limit = rlimit(RLIMIT_CORE), 1807 /* 1808 * We must use the same mm->flags while dumping core to avoid 1809 * inconsistency of bit flags, since this flag is not protected 1810 * by any locks. 1811 */ 1812 .mm_flags = mm->flags, 1813 }; 1814 1815 audit_core_dumps(signr); 1816 1817 binfmt = mm->binfmt; 1818 if (!binfmt || !binfmt->core_dump) 1819 goto fail; 1820 1821 cred = prepare_creds(); 1822 if (!cred) { 1823 retval = -ENOMEM; 1824 goto fail; 1825 } 1826 1827 down_write(&mm->mmap_sem); 1828 /* 1829 * If another thread got here first, or we are not dumpable, bail out. 1830 */ 1831 if (mm->core_state || !__get_dumpable(cprm.mm_flags)) { 1832 up_write(&mm->mmap_sem); 1833 put_cred(cred); 1834 goto fail; 1835 } 1836 1837 /* 1838 * We cannot trust fsuid as being the "true" uid of the 1839 * process nor do we know its entire history. We only know it 1840 * was tainted so we dump it as root in mode 2. 1841 */ 1842 if (__get_dumpable(cprm.mm_flags) == 2) { 1843 /* Setuid core dump mode */ 1844 flag = O_EXCL; /* Stop rewrite attacks */ 1845 cred->fsuid = 0; /* Dump root private */ 1846 } 1847 1848 retval = coredump_wait(exit_code, &core_state); 1849 if (retval < 0) { 1850 put_cred(cred); 1851 goto fail; 1852 } 1853 1854 old_cred = override_creds(cred); 1855 1856 /* 1857 * Clear any false indication of pending signals that might 1858 * be seen by the filesystem code called to write the core file. 1859 */ 1860 clear_thread_flag(TIF_SIGPENDING); 1861 1862 /* 1863 * lock_kernel() because format_corename() is controlled by sysctl, which 1864 * uses lock_kernel() 1865 */ 1866 lock_kernel(); 1867 ispipe = format_corename(corename, signr); 1868 unlock_kernel(); 1869 1870 if ((!ispipe) && (cprm.limit < binfmt->min_coredump)) 1871 goto fail_unlock; 1872 1873 if (ispipe) { 1874 if (cprm.limit == 0) { 1875 /* 1876 * Normally core limits are irrelevant to pipes, since 1877 * we're not writing to the file system, but we use 1878 * cprm.limit of 0 here as a speacial value. Any 1879 * non-zero limit gets set to RLIM_INFINITY below, but 1880 * a limit of 0 skips the dump. This is a consistent 1881 * way to catch recursive crashes. We can still crash 1882 * if the core_pattern binary sets RLIM_CORE = !0 1883 * but it runs as root, and can do lots of stupid things 1884 * Note that we use task_tgid_vnr here to grab the pid 1885 * of the process group leader. That way we get the 1886 * right pid if a thread in a multi-threaded 1887 * core_pattern process dies. 1888 */ 1889 printk(KERN_WARNING 1890 "Process %d(%s) has RLIMIT_CORE set to 0\n", 1891 task_tgid_vnr(current), current->comm); 1892 printk(KERN_WARNING "Aborting core\n"); 1893 goto fail_unlock; 1894 } 1895 1896 dump_count = atomic_inc_return(&core_dump_count); 1897 if (core_pipe_limit && (core_pipe_limit < dump_count)) { 1898 printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n", 1899 task_tgid_vnr(current), current->comm); 1900 printk(KERN_WARNING "Skipping core dump\n"); 1901 goto fail_dropcount; 1902 } 1903 1904 helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc); 1905 if (!helper_argv) { 1906 printk(KERN_WARNING "%s failed to allocate memory\n", 1907 __func__); 1908 goto fail_dropcount; 1909 } 1910 1911 cprm.limit = RLIM_INFINITY; 1912 1913 /* SIGPIPE can happen, but it's just never processed */ 1914 if (call_usermodehelper_pipe(helper_argv[0], helper_argv, NULL, 1915 &cprm.file)) { 1916 printk(KERN_INFO "Core dump to %s pipe failed\n", 1917 corename); 1918 goto fail_dropcount; 1919 } 1920 } else 1921 cprm.file = filp_open(corename, 1922 O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag, 1923 0600); 1924 if (IS_ERR(cprm.file)) 1925 goto fail_dropcount; 1926 inode = cprm.file->f_path.dentry->d_inode; 1927 if (inode->i_nlink > 1) 1928 goto close_fail; /* multiple links - don't dump */ 1929 if (!ispipe && d_unhashed(cprm.file->f_path.dentry)) 1930 goto close_fail; 1931 1932 /* AK: actually i see no reason to not allow this for named pipes etc., 1933 but keep the previous behaviour for now. */ 1934 if (!ispipe && !S_ISREG(inode->i_mode)) 1935 goto close_fail; 1936 /* 1937 * Dont allow local users get cute and trick others to coredump 1938 * into their pre-created files: 1939 * Note, this is not relevant for pipes 1940 */ 1941 if (!ispipe && (inode->i_uid != current_fsuid())) 1942 goto close_fail; 1943 if (!cprm.file->f_op) 1944 goto close_fail; 1945 if (!cprm.file->f_op->write) 1946 goto close_fail; 1947 if (!ispipe && 1948 do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file) != 0) 1949 goto close_fail; 1950 1951 retval = binfmt->core_dump(&cprm); 1952 1953 if (retval) 1954 current->signal->group_exit_code |= 0x80; 1955 close_fail: 1956 if (ispipe && core_pipe_limit) 1957 wait_for_dump_helpers(cprm.file); 1958 filp_close(cprm.file, NULL); 1959 fail_dropcount: 1960 if (dump_count) 1961 atomic_dec(&core_dump_count); 1962 fail_unlock: 1963 if (helper_argv) 1964 argv_free(helper_argv); 1965 1966 revert_creds(old_cred); 1967 put_cred(cred); 1968 coredump_finish(mm); 1969 fail: 1970 return; 1971 } 1972