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 BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP); 246 vma->vm_end = STACK_TOP_MAX; 247 vma->vm_start = vma->vm_end - PAGE_SIZE; 248 vma->vm_flags = VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP; 249 vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); 250 INIT_LIST_HEAD(&vma->anon_vma_chain); 251 err = insert_vm_struct(mm, vma); 252 if (err) 253 goto err; 254 255 mm->stack_vm = mm->total_vm = 1; 256 up_write(&mm->mmap_sem); 257 bprm->p = vma->vm_end - sizeof(void *); 258 return 0; 259 err: 260 up_write(&mm->mmap_sem); 261 bprm->vma = NULL; 262 kmem_cache_free(vm_area_cachep, vma); 263 return err; 264 } 265 266 static bool valid_arg_len(struct linux_binprm *bprm, long len) 267 { 268 return len <= MAX_ARG_STRLEN; 269 } 270 271 #else 272 273 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, 274 int write) 275 { 276 struct page *page; 277 278 page = bprm->page[pos / PAGE_SIZE]; 279 if (!page && write) { 280 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO); 281 if (!page) 282 return NULL; 283 bprm->page[pos / PAGE_SIZE] = page; 284 } 285 286 return page; 287 } 288 289 static void put_arg_page(struct page *page) 290 { 291 } 292 293 static void free_arg_page(struct linux_binprm *bprm, int i) 294 { 295 if (bprm->page[i]) { 296 __free_page(bprm->page[i]); 297 bprm->page[i] = NULL; 298 } 299 } 300 301 static void free_arg_pages(struct linux_binprm *bprm) 302 { 303 int i; 304 305 for (i = 0; i < MAX_ARG_PAGES; i++) 306 free_arg_page(bprm, i); 307 } 308 309 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, 310 struct page *page) 311 { 312 } 313 314 static int __bprm_mm_init(struct linux_binprm *bprm) 315 { 316 bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *); 317 return 0; 318 } 319 320 static bool valid_arg_len(struct linux_binprm *bprm, long len) 321 { 322 return len <= bprm->p; 323 } 324 325 #endif /* CONFIG_MMU */ 326 327 /* 328 * Create a new mm_struct and populate it with a temporary stack 329 * vm_area_struct. We don't have enough context at this point to set the stack 330 * flags, permissions, and offset, so we use temporary values. We'll update 331 * them later in setup_arg_pages(). 332 */ 333 int bprm_mm_init(struct linux_binprm *bprm) 334 { 335 int err; 336 struct mm_struct *mm = NULL; 337 338 bprm->mm = mm = mm_alloc(); 339 err = -ENOMEM; 340 if (!mm) 341 goto err; 342 343 err = init_new_context(current, mm); 344 if (err) 345 goto err; 346 347 err = __bprm_mm_init(bprm); 348 if (err) 349 goto err; 350 351 return 0; 352 353 err: 354 if (mm) { 355 bprm->mm = NULL; 356 mmdrop(mm); 357 } 358 359 return err; 360 } 361 362 /* 363 * count() counts the number of strings in array ARGV. 364 */ 365 static int count(char __user * __user * argv, int max) 366 { 367 int i = 0; 368 369 if (argv != NULL) { 370 for (;;) { 371 char __user * p; 372 373 if (get_user(p, argv)) 374 return -EFAULT; 375 if (!p) 376 break; 377 argv++; 378 if (i++ >= max) 379 return -E2BIG; 380 cond_resched(); 381 } 382 } 383 return i; 384 } 385 386 /* 387 * 'copy_strings()' copies argument/environment strings from the old 388 * processes's memory to the new process's stack. The call to get_user_pages() 389 * ensures the destination page is created and not swapped out. 390 */ 391 static int copy_strings(int argc, char __user * __user * argv, 392 struct linux_binprm *bprm) 393 { 394 struct page *kmapped_page = NULL; 395 char *kaddr = NULL; 396 unsigned long kpos = 0; 397 int ret; 398 399 while (argc-- > 0) { 400 char __user *str; 401 int len; 402 unsigned long pos; 403 404 if (get_user(str, argv+argc) || 405 !(len = strnlen_user(str, MAX_ARG_STRLEN))) { 406 ret = -EFAULT; 407 goto out; 408 } 409 410 if (!valid_arg_len(bprm, len)) { 411 ret = -E2BIG; 412 goto out; 413 } 414 415 /* We're going to work our way backwords. */ 416 pos = bprm->p; 417 str += len; 418 bprm->p -= len; 419 420 while (len > 0) { 421 int offset, bytes_to_copy; 422 423 offset = pos % PAGE_SIZE; 424 if (offset == 0) 425 offset = PAGE_SIZE; 426 427 bytes_to_copy = offset; 428 if (bytes_to_copy > len) 429 bytes_to_copy = len; 430 431 offset -= bytes_to_copy; 432 pos -= bytes_to_copy; 433 str -= bytes_to_copy; 434 len -= bytes_to_copy; 435 436 if (!kmapped_page || kpos != (pos & PAGE_MASK)) { 437 struct page *page; 438 439 page = get_arg_page(bprm, pos, 1); 440 if (!page) { 441 ret = -E2BIG; 442 goto out; 443 } 444 445 if (kmapped_page) { 446 flush_kernel_dcache_page(kmapped_page); 447 kunmap(kmapped_page); 448 put_arg_page(kmapped_page); 449 } 450 kmapped_page = page; 451 kaddr = kmap(kmapped_page); 452 kpos = pos & PAGE_MASK; 453 flush_arg_page(bprm, kpos, kmapped_page); 454 } 455 if (copy_from_user(kaddr+offset, str, bytes_to_copy)) { 456 ret = -EFAULT; 457 goto out; 458 } 459 } 460 } 461 ret = 0; 462 out: 463 if (kmapped_page) { 464 flush_kernel_dcache_page(kmapped_page); 465 kunmap(kmapped_page); 466 put_arg_page(kmapped_page); 467 } 468 return ret; 469 } 470 471 /* 472 * Like copy_strings, but get argv and its values from kernel memory. 473 */ 474 int copy_strings_kernel(int argc,char ** argv, struct linux_binprm *bprm) 475 { 476 int r; 477 mm_segment_t oldfs = get_fs(); 478 set_fs(KERNEL_DS); 479 r = copy_strings(argc, (char __user * __user *)argv, bprm); 480 set_fs(oldfs); 481 return r; 482 } 483 EXPORT_SYMBOL(copy_strings_kernel); 484 485 #ifdef CONFIG_MMU 486 487 /* 488 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once 489 * the binfmt code determines where the new stack should reside, we shift it to 490 * its final location. The process proceeds as follows: 491 * 492 * 1) Use shift to calculate the new vma endpoints. 493 * 2) Extend vma to cover both the old and new ranges. This ensures the 494 * arguments passed to subsequent functions are consistent. 495 * 3) Move vma's page tables to the new range. 496 * 4) Free up any cleared pgd range. 497 * 5) Shrink the vma to cover only the new range. 498 */ 499 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift) 500 { 501 struct mm_struct *mm = vma->vm_mm; 502 unsigned long old_start = vma->vm_start; 503 unsigned long old_end = vma->vm_end; 504 unsigned long length = old_end - old_start; 505 unsigned long new_start = old_start - shift; 506 unsigned long new_end = old_end - shift; 507 struct mmu_gather *tlb; 508 509 BUG_ON(new_start > new_end); 510 511 /* 512 * ensure there are no vmas between where we want to go 513 * and where we are 514 */ 515 if (vma != find_vma(mm, new_start)) 516 return -EFAULT; 517 518 /* 519 * cover the whole range: [new_start, old_end) 520 */ 521 if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL)) 522 return -ENOMEM; 523 524 /* 525 * move the page tables downwards, on failure we rely on 526 * process cleanup to remove whatever mess we made. 527 */ 528 if (length != move_page_tables(vma, old_start, 529 vma, new_start, length)) 530 return -ENOMEM; 531 532 lru_add_drain(); 533 tlb = tlb_gather_mmu(mm, 0); 534 if (new_end > old_start) { 535 /* 536 * when the old and new regions overlap clear from new_end. 537 */ 538 free_pgd_range(tlb, new_end, old_end, new_end, 539 vma->vm_next ? vma->vm_next->vm_start : 0); 540 } else { 541 /* 542 * otherwise, clean from old_start; this is done to not touch 543 * the address space in [new_end, old_start) some architectures 544 * have constraints on va-space that make this illegal (IA64) - 545 * for the others its just a little faster. 546 */ 547 free_pgd_range(tlb, old_start, old_end, new_end, 548 vma->vm_next ? vma->vm_next->vm_start : 0); 549 } 550 tlb_finish_mmu(tlb, new_end, old_end); 551 552 /* 553 * Shrink the vma to just the new range. Always succeeds. 554 */ 555 vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL); 556 557 return 0; 558 } 559 560 /* 561 * Finalizes the stack vm_area_struct. The flags and permissions are updated, 562 * the stack is optionally relocated, and some extra space is added. 563 */ 564 int setup_arg_pages(struct linux_binprm *bprm, 565 unsigned long stack_top, 566 int executable_stack) 567 { 568 unsigned long ret; 569 unsigned long stack_shift; 570 struct mm_struct *mm = current->mm; 571 struct vm_area_struct *vma = bprm->vma; 572 struct vm_area_struct *prev = NULL; 573 unsigned long vm_flags; 574 unsigned long stack_base; 575 unsigned long stack_size; 576 unsigned long stack_expand; 577 unsigned long rlim_stack; 578 579 #ifdef CONFIG_STACK_GROWSUP 580 /* Limit stack size to 1GB */ 581 stack_base = rlimit_max(RLIMIT_STACK); 582 if (stack_base > (1 << 30)) 583 stack_base = 1 << 30; 584 585 /* Make sure we didn't let the argument array grow too large. */ 586 if (vma->vm_end - vma->vm_start > stack_base) 587 return -ENOMEM; 588 589 stack_base = PAGE_ALIGN(stack_top - stack_base); 590 591 stack_shift = vma->vm_start - stack_base; 592 mm->arg_start = bprm->p - stack_shift; 593 bprm->p = vma->vm_end - stack_shift; 594 #else 595 stack_top = arch_align_stack(stack_top); 596 stack_top = PAGE_ALIGN(stack_top); 597 stack_shift = vma->vm_end - stack_top; 598 599 bprm->p -= stack_shift; 600 mm->arg_start = bprm->p; 601 #endif 602 603 if (bprm->loader) 604 bprm->loader -= stack_shift; 605 bprm->exec -= stack_shift; 606 607 down_write(&mm->mmap_sem); 608 vm_flags = VM_STACK_FLAGS; 609 610 /* 611 * Adjust stack execute permissions; explicitly enable for 612 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone 613 * (arch default) otherwise. 614 */ 615 if (unlikely(executable_stack == EXSTACK_ENABLE_X)) 616 vm_flags |= VM_EXEC; 617 else if (executable_stack == EXSTACK_DISABLE_X) 618 vm_flags &= ~VM_EXEC; 619 vm_flags |= mm->def_flags; 620 vm_flags |= VM_STACK_INCOMPLETE_SETUP; 621 622 ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end, 623 vm_flags); 624 if (ret) 625 goto out_unlock; 626 BUG_ON(prev != vma); 627 628 /* Move stack pages down in memory. */ 629 if (stack_shift) { 630 ret = shift_arg_pages(vma, stack_shift); 631 if (ret) 632 goto out_unlock; 633 } 634 635 /* mprotect_fixup is overkill to remove the temporary stack flags */ 636 vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP; 637 638 stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */ 639 stack_size = vma->vm_end - vma->vm_start; 640 /* 641 * Align this down to a page boundary as expand_stack 642 * will align it up. 643 */ 644 rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK; 645 #ifdef CONFIG_STACK_GROWSUP 646 if (stack_size + stack_expand > rlim_stack) 647 stack_base = vma->vm_start + rlim_stack; 648 else 649 stack_base = vma->vm_end + stack_expand; 650 #else 651 if (stack_size + stack_expand > rlim_stack) 652 stack_base = vma->vm_end - rlim_stack; 653 else 654 stack_base = vma->vm_start - stack_expand; 655 #endif 656 ret = expand_stack(vma, stack_base); 657 if (ret) 658 ret = -EFAULT; 659 660 out_unlock: 661 up_write(&mm->mmap_sem); 662 return ret; 663 } 664 EXPORT_SYMBOL(setup_arg_pages); 665 666 #endif /* CONFIG_MMU */ 667 668 struct file *open_exec(const char *name) 669 { 670 struct file *file; 671 int err; 672 673 file = do_filp_open(AT_FDCWD, name, 674 O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0, 675 MAY_EXEC | MAY_OPEN); 676 if (IS_ERR(file)) 677 goto out; 678 679 err = -EACCES; 680 if (!S_ISREG(file->f_path.dentry->d_inode->i_mode)) 681 goto exit; 682 683 if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) 684 goto exit; 685 686 fsnotify_open(file->f_path.dentry); 687 688 err = deny_write_access(file); 689 if (err) 690 goto exit; 691 692 out: 693 return file; 694 695 exit: 696 fput(file); 697 return ERR_PTR(err); 698 } 699 EXPORT_SYMBOL(open_exec); 700 701 int kernel_read(struct file *file, loff_t offset, 702 char *addr, unsigned long count) 703 { 704 mm_segment_t old_fs; 705 loff_t pos = offset; 706 int result; 707 708 old_fs = get_fs(); 709 set_fs(get_ds()); 710 /* The cast to a user pointer is valid due to the set_fs() */ 711 result = vfs_read(file, (void __user *)addr, count, &pos); 712 set_fs(old_fs); 713 return result; 714 } 715 716 EXPORT_SYMBOL(kernel_read); 717 718 static int exec_mmap(struct mm_struct *mm) 719 { 720 struct task_struct *tsk; 721 struct mm_struct * old_mm, *active_mm; 722 723 /* Notify parent that we're no longer interested in the old VM */ 724 tsk = current; 725 old_mm = current->mm; 726 sync_mm_rss(tsk, old_mm); 727 mm_release(tsk, old_mm); 728 729 if (old_mm) { 730 /* 731 * Make sure that if there is a core dump in progress 732 * for the old mm, we get out and die instead of going 733 * through with the exec. We must hold mmap_sem around 734 * checking core_state and changing tsk->mm. 735 */ 736 down_read(&old_mm->mmap_sem); 737 if (unlikely(old_mm->core_state)) { 738 up_read(&old_mm->mmap_sem); 739 return -EINTR; 740 } 741 } 742 task_lock(tsk); 743 active_mm = tsk->active_mm; 744 tsk->mm = mm; 745 tsk->active_mm = mm; 746 activate_mm(active_mm, mm); 747 task_unlock(tsk); 748 arch_pick_mmap_layout(mm); 749 if (old_mm) { 750 up_read(&old_mm->mmap_sem); 751 BUG_ON(active_mm != old_mm); 752 mm_update_next_owner(old_mm); 753 mmput(old_mm); 754 return 0; 755 } 756 mmdrop(active_mm); 757 return 0; 758 } 759 760 /* 761 * This function makes sure the current process has its own signal table, 762 * so that flush_signal_handlers can later reset the handlers without 763 * disturbing other processes. (Other processes might share the signal 764 * table via the CLONE_SIGHAND option to clone().) 765 */ 766 static int de_thread(struct task_struct *tsk) 767 { 768 struct signal_struct *sig = tsk->signal; 769 struct sighand_struct *oldsighand = tsk->sighand; 770 spinlock_t *lock = &oldsighand->siglock; 771 772 if (thread_group_empty(tsk)) 773 goto no_thread_group; 774 775 /* 776 * Kill all other threads in the thread group. 777 */ 778 spin_lock_irq(lock); 779 if (signal_group_exit(sig)) { 780 /* 781 * Another group action in progress, just 782 * return so that the signal is processed. 783 */ 784 spin_unlock_irq(lock); 785 return -EAGAIN; 786 } 787 788 sig->group_exit_task = tsk; 789 sig->notify_count = zap_other_threads(tsk); 790 if (!thread_group_leader(tsk)) 791 sig->notify_count--; 792 793 while (sig->notify_count) { 794 __set_current_state(TASK_UNINTERRUPTIBLE); 795 spin_unlock_irq(lock); 796 schedule(); 797 spin_lock_irq(lock); 798 } 799 spin_unlock_irq(lock); 800 801 /* 802 * At this point all other threads have exited, all we have to 803 * do is to wait for the thread group leader to become inactive, 804 * and to assume its PID: 805 */ 806 if (!thread_group_leader(tsk)) { 807 struct task_struct *leader = tsk->group_leader; 808 809 sig->notify_count = -1; /* for exit_notify() */ 810 for (;;) { 811 write_lock_irq(&tasklist_lock); 812 if (likely(leader->exit_state)) 813 break; 814 __set_current_state(TASK_UNINTERRUPTIBLE); 815 write_unlock_irq(&tasklist_lock); 816 schedule(); 817 } 818 819 /* 820 * The only record we have of the real-time age of a 821 * process, regardless of execs it's done, is start_time. 822 * All the past CPU time is accumulated in signal_struct 823 * from sister threads now dead. But in this non-leader 824 * exec, nothing survives from the original leader thread, 825 * whose birth marks the true age of this process now. 826 * When we take on its identity by switching to its PID, we 827 * also take its birthdate (always earlier than our own). 828 */ 829 tsk->start_time = leader->start_time; 830 831 BUG_ON(!same_thread_group(leader, tsk)); 832 BUG_ON(has_group_leader_pid(tsk)); 833 /* 834 * An exec() starts a new thread group with the 835 * TGID of the previous thread group. Rehash the 836 * two threads with a switched PID, and release 837 * the former thread group leader: 838 */ 839 840 /* Become a process group leader with the old leader's pid. 841 * The old leader becomes a thread of the this thread group. 842 * Note: The old leader also uses this pid until release_task 843 * is called. Odd but simple and correct. 844 */ 845 detach_pid(tsk, PIDTYPE_PID); 846 tsk->pid = leader->pid; 847 attach_pid(tsk, PIDTYPE_PID, task_pid(leader)); 848 transfer_pid(leader, tsk, PIDTYPE_PGID); 849 transfer_pid(leader, tsk, PIDTYPE_SID); 850 851 list_replace_rcu(&leader->tasks, &tsk->tasks); 852 list_replace_init(&leader->sibling, &tsk->sibling); 853 854 tsk->group_leader = tsk; 855 leader->group_leader = tsk; 856 857 tsk->exit_signal = SIGCHLD; 858 859 BUG_ON(leader->exit_state != EXIT_ZOMBIE); 860 leader->exit_state = EXIT_DEAD; 861 write_unlock_irq(&tasklist_lock); 862 863 release_task(leader); 864 } 865 866 sig->group_exit_task = NULL; 867 sig->notify_count = 0; 868 869 no_thread_group: 870 if (current->mm) 871 setmax_mm_hiwater_rss(&sig->maxrss, current->mm); 872 873 exit_itimers(sig); 874 flush_itimer_signals(); 875 876 if (atomic_read(&oldsighand->count) != 1) { 877 struct sighand_struct *newsighand; 878 /* 879 * This ->sighand is shared with the CLONE_SIGHAND 880 * but not CLONE_THREAD task, switch to the new one. 881 */ 882 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 883 if (!newsighand) 884 return -ENOMEM; 885 886 atomic_set(&newsighand->count, 1); 887 memcpy(newsighand->action, oldsighand->action, 888 sizeof(newsighand->action)); 889 890 write_lock_irq(&tasklist_lock); 891 spin_lock(&oldsighand->siglock); 892 rcu_assign_pointer(tsk->sighand, newsighand); 893 spin_unlock(&oldsighand->siglock); 894 write_unlock_irq(&tasklist_lock); 895 896 __cleanup_sighand(oldsighand); 897 } 898 899 BUG_ON(!thread_group_leader(tsk)); 900 return 0; 901 } 902 903 /* 904 * These functions flushes out all traces of the currently running executable 905 * so that a new one can be started 906 */ 907 static void flush_old_files(struct files_struct * files) 908 { 909 long j = -1; 910 struct fdtable *fdt; 911 912 spin_lock(&files->file_lock); 913 for (;;) { 914 unsigned long set, i; 915 916 j++; 917 i = j * __NFDBITS; 918 fdt = files_fdtable(files); 919 if (i >= fdt->max_fds) 920 break; 921 set = fdt->close_on_exec->fds_bits[j]; 922 if (!set) 923 continue; 924 fdt->close_on_exec->fds_bits[j] = 0; 925 spin_unlock(&files->file_lock); 926 for ( ; set ; i++,set >>= 1) { 927 if (set & 1) { 928 sys_close(i); 929 } 930 } 931 spin_lock(&files->file_lock); 932 933 } 934 spin_unlock(&files->file_lock); 935 } 936 937 char *get_task_comm(char *buf, struct task_struct *tsk) 938 { 939 /* buf must be at least sizeof(tsk->comm) in size */ 940 task_lock(tsk); 941 strncpy(buf, tsk->comm, sizeof(tsk->comm)); 942 task_unlock(tsk); 943 return buf; 944 } 945 946 void set_task_comm(struct task_struct *tsk, char *buf) 947 { 948 task_lock(tsk); 949 950 /* 951 * Threads may access current->comm without holding 952 * the task lock, so write the string carefully. 953 * Readers without a lock may see incomplete new 954 * names but are safe from non-terminating string reads. 955 */ 956 memset(tsk->comm, 0, TASK_COMM_LEN); 957 wmb(); 958 strlcpy(tsk->comm, buf, sizeof(tsk->comm)); 959 task_unlock(tsk); 960 perf_event_comm(tsk); 961 } 962 963 int flush_old_exec(struct linux_binprm * bprm) 964 { 965 int retval; 966 967 /* 968 * Make sure we have a private signal table and that 969 * we are unassociated from the previous thread group. 970 */ 971 retval = de_thread(current); 972 if (retval) 973 goto out; 974 975 set_mm_exe_file(bprm->mm, bprm->file); 976 977 /* 978 * Release all of the old mmap stuff 979 */ 980 retval = exec_mmap(bprm->mm); 981 if (retval) 982 goto out; 983 984 bprm->mm = NULL; /* We're using it now */ 985 986 current->flags &= ~PF_RANDOMIZE; 987 flush_thread(); 988 current->personality &= ~bprm->per_clear; 989 990 return 0; 991 992 out: 993 return retval; 994 } 995 EXPORT_SYMBOL(flush_old_exec); 996 997 void setup_new_exec(struct linux_binprm * bprm) 998 { 999 int i, ch; 1000 char * name; 1001 char tcomm[sizeof(current->comm)]; 1002 1003 arch_pick_mmap_layout(current->mm); 1004 1005 /* This is the point of no return */ 1006 current->sas_ss_sp = current->sas_ss_size = 0; 1007 1008 if (current_euid() == current_uid() && current_egid() == current_gid()) 1009 set_dumpable(current->mm, 1); 1010 else 1011 set_dumpable(current->mm, suid_dumpable); 1012 1013 name = bprm->filename; 1014 1015 /* Copies the binary name from after last slash */ 1016 for (i=0; (ch = *(name++)) != '\0';) { 1017 if (ch == '/') 1018 i = 0; /* overwrite what we wrote */ 1019 else 1020 if (i < (sizeof(tcomm) - 1)) 1021 tcomm[i++] = ch; 1022 } 1023 tcomm[i] = '\0'; 1024 set_task_comm(current, tcomm); 1025 1026 /* Set the new mm task size. We have to do that late because it may 1027 * depend on TIF_32BIT which is only updated in flush_thread() on 1028 * some architectures like powerpc 1029 */ 1030 current->mm->task_size = TASK_SIZE; 1031 1032 /* install the new credentials */ 1033 if (bprm->cred->uid != current_euid() || 1034 bprm->cred->gid != current_egid()) { 1035 current->pdeath_signal = 0; 1036 } else if (file_permission(bprm->file, MAY_READ) || 1037 bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) { 1038 set_dumpable(current->mm, suid_dumpable); 1039 } 1040 1041 /* 1042 * Flush performance counters when crossing a 1043 * security domain: 1044 */ 1045 if (!get_dumpable(current->mm)) 1046 perf_event_exit_task(current); 1047 1048 /* An exec changes our domain. We are no longer part of the thread 1049 group */ 1050 1051 current->self_exec_id++; 1052 1053 flush_signal_handlers(current, 0); 1054 flush_old_files(current->files); 1055 } 1056 EXPORT_SYMBOL(setup_new_exec); 1057 1058 /* 1059 * Prepare credentials and lock ->cred_guard_mutex. 1060 * install_exec_creds() commits the new creds and drops the lock. 1061 * Or, if exec fails before, free_bprm() should release ->cred and 1062 * and unlock. 1063 */ 1064 int prepare_bprm_creds(struct linux_binprm *bprm) 1065 { 1066 if (mutex_lock_interruptible(¤t->cred_guard_mutex)) 1067 return -ERESTARTNOINTR; 1068 1069 bprm->cred = prepare_exec_creds(); 1070 if (likely(bprm->cred)) 1071 return 0; 1072 1073 mutex_unlock(¤t->cred_guard_mutex); 1074 return -ENOMEM; 1075 } 1076 1077 void free_bprm(struct linux_binprm *bprm) 1078 { 1079 free_arg_pages(bprm); 1080 if (bprm->cred) { 1081 mutex_unlock(¤t->cred_guard_mutex); 1082 abort_creds(bprm->cred); 1083 } 1084 kfree(bprm); 1085 } 1086 1087 /* 1088 * install the new credentials for this executable 1089 */ 1090 void install_exec_creds(struct linux_binprm *bprm) 1091 { 1092 security_bprm_committing_creds(bprm); 1093 1094 commit_creds(bprm->cred); 1095 bprm->cred = NULL; 1096 /* 1097 * cred_guard_mutex must be held at least to this point to prevent 1098 * ptrace_attach() from altering our determination of the task's 1099 * credentials; any time after this it may be unlocked. 1100 */ 1101 security_bprm_committed_creds(bprm); 1102 mutex_unlock(¤t->cred_guard_mutex); 1103 } 1104 EXPORT_SYMBOL(install_exec_creds); 1105 1106 /* 1107 * determine how safe it is to execute the proposed program 1108 * - the caller must hold current->cred_guard_mutex to protect against 1109 * PTRACE_ATTACH 1110 */ 1111 int check_unsafe_exec(struct linux_binprm *bprm) 1112 { 1113 struct task_struct *p = current, *t; 1114 unsigned n_fs; 1115 int res = 0; 1116 1117 bprm->unsafe = tracehook_unsafe_exec(p); 1118 1119 n_fs = 1; 1120 write_lock(&p->fs->lock); 1121 rcu_read_lock(); 1122 for (t = next_thread(p); t != p; t = next_thread(t)) { 1123 if (t->fs == p->fs) 1124 n_fs++; 1125 } 1126 rcu_read_unlock(); 1127 1128 if (p->fs->users > n_fs) { 1129 bprm->unsafe |= LSM_UNSAFE_SHARE; 1130 } else { 1131 res = -EAGAIN; 1132 if (!p->fs->in_exec) { 1133 p->fs->in_exec = 1; 1134 res = 1; 1135 } 1136 } 1137 write_unlock(&p->fs->lock); 1138 1139 return res; 1140 } 1141 1142 /* 1143 * Fill the binprm structure from the inode. 1144 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes 1145 * 1146 * This may be called multiple times for binary chains (scripts for example). 1147 */ 1148 int prepare_binprm(struct linux_binprm *bprm) 1149 { 1150 umode_t mode; 1151 struct inode * inode = bprm->file->f_path.dentry->d_inode; 1152 int retval; 1153 1154 mode = inode->i_mode; 1155 if (bprm->file->f_op == NULL) 1156 return -EACCES; 1157 1158 /* clear any previous set[ug]id data from a previous binary */ 1159 bprm->cred->euid = current_euid(); 1160 bprm->cred->egid = current_egid(); 1161 1162 if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) { 1163 /* Set-uid? */ 1164 if (mode & S_ISUID) { 1165 bprm->per_clear |= PER_CLEAR_ON_SETID; 1166 bprm->cred->euid = inode->i_uid; 1167 } 1168 1169 /* Set-gid? */ 1170 /* 1171 * If setgid is set but no group execute bit then this 1172 * is a candidate for mandatory locking, not a setgid 1173 * executable. 1174 */ 1175 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { 1176 bprm->per_clear |= PER_CLEAR_ON_SETID; 1177 bprm->cred->egid = inode->i_gid; 1178 } 1179 } 1180 1181 /* fill in binprm security blob */ 1182 retval = security_bprm_set_creds(bprm); 1183 if (retval) 1184 return retval; 1185 bprm->cred_prepared = 1; 1186 1187 memset(bprm->buf, 0, BINPRM_BUF_SIZE); 1188 return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE); 1189 } 1190 1191 EXPORT_SYMBOL(prepare_binprm); 1192 1193 /* 1194 * Arguments are '\0' separated strings found at the location bprm->p 1195 * points to; chop off the first by relocating brpm->p to right after 1196 * the first '\0' encountered. 1197 */ 1198 int remove_arg_zero(struct linux_binprm *bprm) 1199 { 1200 int ret = 0; 1201 unsigned long offset; 1202 char *kaddr; 1203 struct page *page; 1204 1205 if (!bprm->argc) 1206 return 0; 1207 1208 do { 1209 offset = bprm->p & ~PAGE_MASK; 1210 page = get_arg_page(bprm, bprm->p, 0); 1211 if (!page) { 1212 ret = -EFAULT; 1213 goto out; 1214 } 1215 kaddr = kmap_atomic(page, KM_USER0); 1216 1217 for (; offset < PAGE_SIZE && kaddr[offset]; 1218 offset++, bprm->p++) 1219 ; 1220 1221 kunmap_atomic(kaddr, KM_USER0); 1222 put_arg_page(page); 1223 1224 if (offset == PAGE_SIZE) 1225 free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1); 1226 } while (offset == PAGE_SIZE); 1227 1228 bprm->p++; 1229 bprm->argc--; 1230 ret = 0; 1231 1232 out: 1233 return ret; 1234 } 1235 EXPORT_SYMBOL(remove_arg_zero); 1236 1237 /* 1238 * cycle the list of binary formats handler, until one recognizes the image 1239 */ 1240 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs) 1241 { 1242 unsigned int depth = bprm->recursion_depth; 1243 int try,retval; 1244 struct linux_binfmt *fmt; 1245 1246 retval = security_bprm_check(bprm); 1247 if (retval) 1248 return retval; 1249 1250 /* kernel module loader fixup */ 1251 /* so we don't try to load run modprobe in kernel space. */ 1252 set_fs(USER_DS); 1253 1254 retval = audit_bprm(bprm); 1255 if (retval) 1256 return retval; 1257 1258 retval = -ENOENT; 1259 for (try=0; try<2; try++) { 1260 read_lock(&binfmt_lock); 1261 list_for_each_entry(fmt, &formats, lh) { 1262 int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary; 1263 if (!fn) 1264 continue; 1265 if (!try_module_get(fmt->module)) 1266 continue; 1267 read_unlock(&binfmt_lock); 1268 retval = fn(bprm, regs); 1269 /* 1270 * Restore the depth counter to its starting value 1271 * in this call, so we don't have to rely on every 1272 * load_binary function to restore it on return. 1273 */ 1274 bprm->recursion_depth = depth; 1275 if (retval >= 0) { 1276 if (depth == 0) 1277 tracehook_report_exec(fmt, bprm, regs); 1278 put_binfmt(fmt); 1279 allow_write_access(bprm->file); 1280 if (bprm->file) 1281 fput(bprm->file); 1282 bprm->file = NULL; 1283 current->did_exec = 1; 1284 proc_exec_connector(current); 1285 return retval; 1286 } 1287 read_lock(&binfmt_lock); 1288 put_binfmt(fmt); 1289 if (retval != -ENOEXEC || bprm->mm == NULL) 1290 break; 1291 if (!bprm->file) { 1292 read_unlock(&binfmt_lock); 1293 return retval; 1294 } 1295 } 1296 read_unlock(&binfmt_lock); 1297 if (retval != -ENOEXEC || bprm->mm == NULL) { 1298 break; 1299 #ifdef CONFIG_MODULES 1300 } else { 1301 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e)) 1302 if (printable(bprm->buf[0]) && 1303 printable(bprm->buf[1]) && 1304 printable(bprm->buf[2]) && 1305 printable(bprm->buf[3])) 1306 break; /* -ENOEXEC */ 1307 request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2])); 1308 #endif 1309 } 1310 } 1311 return retval; 1312 } 1313 1314 EXPORT_SYMBOL(search_binary_handler); 1315 1316 /* 1317 * sys_execve() executes a new program. 1318 */ 1319 int do_execve(char * filename, 1320 char __user *__user *argv, 1321 char __user *__user *envp, 1322 struct pt_regs * regs) 1323 { 1324 struct linux_binprm *bprm; 1325 struct file *file; 1326 struct files_struct *displaced; 1327 bool clear_in_exec; 1328 int retval; 1329 1330 retval = unshare_files(&displaced); 1331 if (retval) 1332 goto out_ret; 1333 1334 retval = -ENOMEM; 1335 bprm = kzalloc(sizeof(*bprm), GFP_KERNEL); 1336 if (!bprm) 1337 goto out_files; 1338 1339 retval = prepare_bprm_creds(bprm); 1340 if (retval) 1341 goto out_free; 1342 1343 retval = check_unsafe_exec(bprm); 1344 if (retval < 0) 1345 goto out_free; 1346 clear_in_exec = retval; 1347 current->in_execve = 1; 1348 1349 file = open_exec(filename); 1350 retval = PTR_ERR(file); 1351 if (IS_ERR(file)) 1352 goto out_unmark; 1353 1354 sched_exec(); 1355 1356 bprm->file = file; 1357 bprm->filename = filename; 1358 bprm->interp = filename; 1359 1360 retval = bprm_mm_init(bprm); 1361 if (retval) 1362 goto out_file; 1363 1364 bprm->argc = count(argv, MAX_ARG_STRINGS); 1365 if ((retval = bprm->argc) < 0) 1366 goto out; 1367 1368 bprm->envc = count(envp, MAX_ARG_STRINGS); 1369 if ((retval = bprm->envc) < 0) 1370 goto out; 1371 1372 retval = prepare_binprm(bprm); 1373 if (retval < 0) 1374 goto out; 1375 1376 retval = copy_strings_kernel(1, &bprm->filename, bprm); 1377 if (retval < 0) 1378 goto out; 1379 1380 bprm->exec = bprm->p; 1381 retval = copy_strings(bprm->envc, envp, bprm); 1382 if (retval < 0) 1383 goto out; 1384 1385 retval = copy_strings(bprm->argc, argv, bprm); 1386 if (retval < 0) 1387 goto out; 1388 1389 current->flags &= ~PF_KTHREAD; 1390 retval = search_binary_handler(bprm,regs); 1391 if (retval < 0) 1392 goto out; 1393 1394 /* execve succeeded */ 1395 current->fs->in_exec = 0; 1396 current->in_execve = 0; 1397 acct_update_integrals(current); 1398 free_bprm(bprm); 1399 if (displaced) 1400 put_files_struct(displaced); 1401 return retval; 1402 1403 out: 1404 if (bprm->mm) 1405 mmput (bprm->mm); 1406 1407 out_file: 1408 if (bprm->file) { 1409 allow_write_access(bprm->file); 1410 fput(bprm->file); 1411 } 1412 1413 out_unmark: 1414 if (clear_in_exec) 1415 current->fs->in_exec = 0; 1416 current->in_execve = 0; 1417 1418 out_free: 1419 free_bprm(bprm); 1420 1421 out_files: 1422 if (displaced) 1423 reset_files_struct(displaced); 1424 out_ret: 1425 return retval; 1426 } 1427 1428 void set_binfmt(struct linux_binfmt *new) 1429 { 1430 struct mm_struct *mm = current->mm; 1431 1432 if (mm->binfmt) 1433 module_put(mm->binfmt->module); 1434 1435 mm->binfmt = new; 1436 if (new) 1437 __module_get(new->module); 1438 } 1439 1440 EXPORT_SYMBOL(set_binfmt); 1441 1442 /* format_corename will inspect the pattern parameter, and output a 1443 * name into corename, which must have space for at least 1444 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator. 1445 */ 1446 static int format_corename(char *corename, long signr) 1447 { 1448 const struct cred *cred = current_cred(); 1449 const char *pat_ptr = core_pattern; 1450 int ispipe = (*pat_ptr == '|'); 1451 char *out_ptr = corename; 1452 char *const out_end = corename + CORENAME_MAX_SIZE; 1453 int rc; 1454 int pid_in_pattern = 0; 1455 1456 /* Repeat as long as we have more pattern to process and more output 1457 space */ 1458 while (*pat_ptr) { 1459 if (*pat_ptr != '%') { 1460 if (out_ptr == out_end) 1461 goto out; 1462 *out_ptr++ = *pat_ptr++; 1463 } else { 1464 switch (*++pat_ptr) { 1465 case 0: 1466 goto out; 1467 /* Double percent, output one percent */ 1468 case '%': 1469 if (out_ptr == out_end) 1470 goto out; 1471 *out_ptr++ = '%'; 1472 break; 1473 /* pid */ 1474 case 'p': 1475 pid_in_pattern = 1; 1476 rc = snprintf(out_ptr, out_end - out_ptr, 1477 "%d", task_tgid_vnr(current)); 1478 if (rc > out_end - out_ptr) 1479 goto out; 1480 out_ptr += rc; 1481 break; 1482 /* uid */ 1483 case 'u': 1484 rc = snprintf(out_ptr, out_end - out_ptr, 1485 "%d", cred->uid); 1486 if (rc > out_end - out_ptr) 1487 goto out; 1488 out_ptr += rc; 1489 break; 1490 /* gid */ 1491 case 'g': 1492 rc = snprintf(out_ptr, out_end - out_ptr, 1493 "%d", cred->gid); 1494 if (rc > out_end - out_ptr) 1495 goto out; 1496 out_ptr += rc; 1497 break; 1498 /* signal that caused the coredump */ 1499 case 's': 1500 rc = snprintf(out_ptr, out_end - out_ptr, 1501 "%ld", signr); 1502 if (rc > out_end - out_ptr) 1503 goto out; 1504 out_ptr += rc; 1505 break; 1506 /* UNIX time of coredump */ 1507 case 't': { 1508 struct timeval tv; 1509 do_gettimeofday(&tv); 1510 rc = snprintf(out_ptr, out_end - out_ptr, 1511 "%lu", tv.tv_sec); 1512 if (rc > out_end - out_ptr) 1513 goto out; 1514 out_ptr += rc; 1515 break; 1516 } 1517 /* hostname */ 1518 case 'h': 1519 down_read(&uts_sem); 1520 rc = snprintf(out_ptr, out_end - out_ptr, 1521 "%s", utsname()->nodename); 1522 up_read(&uts_sem); 1523 if (rc > out_end - out_ptr) 1524 goto out; 1525 out_ptr += rc; 1526 break; 1527 /* executable */ 1528 case 'e': 1529 rc = snprintf(out_ptr, out_end - out_ptr, 1530 "%s", current->comm); 1531 if (rc > out_end - out_ptr) 1532 goto out; 1533 out_ptr += rc; 1534 break; 1535 /* core limit size */ 1536 case 'c': 1537 rc = snprintf(out_ptr, out_end - out_ptr, 1538 "%lu", rlimit(RLIMIT_CORE)); 1539 if (rc > out_end - out_ptr) 1540 goto out; 1541 out_ptr += rc; 1542 break; 1543 default: 1544 break; 1545 } 1546 ++pat_ptr; 1547 } 1548 } 1549 /* Backward compatibility with core_uses_pid: 1550 * 1551 * If core_pattern does not include a %p (as is the default) 1552 * and core_uses_pid is set, then .%pid will be appended to 1553 * the filename. Do not do this for piped commands. */ 1554 if (!ispipe && !pid_in_pattern && core_uses_pid) { 1555 rc = snprintf(out_ptr, out_end - out_ptr, 1556 ".%d", task_tgid_vnr(current)); 1557 if (rc > out_end - out_ptr) 1558 goto out; 1559 out_ptr += rc; 1560 } 1561 out: 1562 *out_ptr = 0; 1563 return ispipe; 1564 } 1565 1566 static int zap_process(struct task_struct *start, int exit_code) 1567 { 1568 struct task_struct *t; 1569 int nr = 0; 1570 1571 start->signal->flags = SIGNAL_GROUP_EXIT; 1572 start->signal->group_exit_code = exit_code; 1573 start->signal->group_stop_count = 0; 1574 1575 t = start; 1576 do { 1577 if (t != current && t->mm) { 1578 sigaddset(&t->pending.signal, SIGKILL); 1579 signal_wake_up(t, 1); 1580 nr++; 1581 } 1582 } while_each_thread(start, t); 1583 1584 return nr; 1585 } 1586 1587 static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm, 1588 struct core_state *core_state, int exit_code) 1589 { 1590 struct task_struct *g, *p; 1591 unsigned long flags; 1592 int nr = -EAGAIN; 1593 1594 spin_lock_irq(&tsk->sighand->siglock); 1595 if (!signal_group_exit(tsk->signal)) { 1596 mm->core_state = core_state; 1597 nr = zap_process(tsk, exit_code); 1598 } 1599 spin_unlock_irq(&tsk->sighand->siglock); 1600 if (unlikely(nr < 0)) 1601 return nr; 1602 1603 if (atomic_read(&mm->mm_users) == nr + 1) 1604 goto done; 1605 /* 1606 * We should find and kill all tasks which use this mm, and we should 1607 * count them correctly into ->nr_threads. We don't take tasklist 1608 * lock, but this is safe wrt: 1609 * 1610 * fork: 1611 * None of sub-threads can fork after zap_process(leader). All 1612 * processes which were created before this point should be 1613 * visible to zap_threads() because copy_process() adds the new 1614 * process to the tail of init_task.tasks list, and lock/unlock 1615 * of ->siglock provides a memory barrier. 1616 * 1617 * do_exit: 1618 * The caller holds mm->mmap_sem. This means that the task which 1619 * uses this mm can't pass exit_mm(), so it can't exit or clear 1620 * its ->mm. 1621 * 1622 * de_thread: 1623 * It does list_replace_rcu(&leader->tasks, ¤t->tasks), 1624 * we must see either old or new leader, this does not matter. 1625 * However, it can change p->sighand, so lock_task_sighand(p) 1626 * must be used. Since p->mm != NULL and we hold ->mmap_sem 1627 * it can't fail. 1628 * 1629 * Note also that "g" can be the old leader with ->mm == NULL 1630 * and already unhashed and thus removed from ->thread_group. 1631 * This is OK, __unhash_process()->list_del_rcu() does not 1632 * clear the ->next pointer, we will find the new leader via 1633 * next_thread(). 1634 */ 1635 rcu_read_lock(); 1636 for_each_process(g) { 1637 if (g == tsk->group_leader) 1638 continue; 1639 if (g->flags & PF_KTHREAD) 1640 continue; 1641 p = g; 1642 do { 1643 if (p->mm) { 1644 if (unlikely(p->mm == mm)) { 1645 lock_task_sighand(p, &flags); 1646 nr += zap_process(p, exit_code); 1647 unlock_task_sighand(p, &flags); 1648 } 1649 break; 1650 } 1651 } while_each_thread(g, p); 1652 } 1653 rcu_read_unlock(); 1654 done: 1655 atomic_set(&core_state->nr_threads, nr); 1656 return nr; 1657 } 1658 1659 static int coredump_wait(int exit_code, struct core_state *core_state) 1660 { 1661 struct task_struct *tsk = current; 1662 struct mm_struct *mm = tsk->mm; 1663 struct completion *vfork_done; 1664 int core_waiters = -EBUSY; 1665 1666 init_completion(&core_state->startup); 1667 core_state->dumper.task = tsk; 1668 core_state->dumper.next = NULL; 1669 1670 down_write(&mm->mmap_sem); 1671 if (!mm->core_state) 1672 core_waiters = zap_threads(tsk, mm, core_state, exit_code); 1673 up_write(&mm->mmap_sem); 1674 1675 if (unlikely(core_waiters < 0)) 1676 goto fail; 1677 1678 /* 1679 * Make sure nobody is waiting for us to release the VM, 1680 * otherwise we can deadlock when we wait on each other 1681 */ 1682 vfork_done = tsk->vfork_done; 1683 if (vfork_done) { 1684 tsk->vfork_done = NULL; 1685 complete(vfork_done); 1686 } 1687 1688 if (core_waiters) 1689 wait_for_completion(&core_state->startup); 1690 fail: 1691 return core_waiters; 1692 } 1693 1694 static void coredump_finish(struct mm_struct *mm) 1695 { 1696 struct core_thread *curr, *next; 1697 struct task_struct *task; 1698 1699 next = mm->core_state->dumper.next; 1700 while ((curr = next) != NULL) { 1701 next = curr->next; 1702 task = curr->task; 1703 /* 1704 * see exit_mm(), curr->task must not see 1705 * ->task == NULL before we read ->next. 1706 */ 1707 smp_mb(); 1708 curr->task = NULL; 1709 wake_up_process(task); 1710 } 1711 1712 mm->core_state = NULL; 1713 } 1714 1715 /* 1716 * set_dumpable converts traditional three-value dumpable to two flags and 1717 * stores them into mm->flags. It modifies lower two bits of mm->flags, but 1718 * these bits are not changed atomically. So get_dumpable can observe the 1719 * intermediate state. To avoid doing unexpected behavior, get get_dumpable 1720 * return either old dumpable or new one by paying attention to the order of 1721 * modifying the bits. 1722 * 1723 * dumpable | mm->flags (binary) 1724 * old new | initial interim final 1725 * ---------+----------------------- 1726 * 0 1 | 00 01 01 1727 * 0 2 | 00 10(*) 11 1728 * 1 0 | 01 00 00 1729 * 1 2 | 01 11 11 1730 * 2 0 | 11 10(*) 00 1731 * 2 1 | 11 11 01 1732 * 1733 * (*) get_dumpable regards interim value of 10 as 11. 1734 */ 1735 void set_dumpable(struct mm_struct *mm, int value) 1736 { 1737 switch (value) { 1738 case 0: 1739 clear_bit(MMF_DUMPABLE, &mm->flags); 1740 smp_wmb(); 1741 clear_bit(MMF_DUMP_SECURELY, &mm->flags); 1742 break; 1743 case 1: 1744 set_bit(MMF_DUMPABLE, &mm->flags); 1745 smp_wmb(); 1746 clear_bit(MMF_DUMP_SECURELY, &mm->flags); 1747 break; 1748 case 2: 1749 set_bit(MMF_DUMP_SECURELY, &mm->flags); 1750 smp_wmb(); 1751 set_bit(MMF_DUMPABLE, &mm->flags); 1752 break; 1753 } 1754 } 1755 1756 static int __get_dumpable(unsigned long mm_flags) 1757 { 1758 int ret; 1759 1760 ret = mm_flags & MMF_DUMPABLE_MASK; 1761 return (ret >= 2) ? 2 : ret; 1762 } 1763 1764 int get_dumpable(struct mm_struct *mm) 1765 { 1766 return __get_dumpable(mm->flags); 1767 } 1768 1769 static void wait_for_dump_helpers(struct file *file) 1770 { 1771 struct pipe_inode_info *pipe; 1772 1773 pipe = file->f_path.dentry->d_inode->i_pipe; 1774 1775 pipe_lock(pipe); 1776 pipe->readers++; 1777 pipe->writers--; 1778 1779 while ((pipe->readers > 1) && (!signal_pending(current))) { 1780 wake_up_interruptible_sync(&pipe->wait); 1781 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); 1782 pipe_wait(pipe); 1783 } 1784 1785 pipe->readers--; 1786 pipe->writers++; 1787 pipe_unlock(pipe); 1788 1789 } 1790 1791 1792 /* 1793 * uhm_pipe_setup 1794 * helper function to customize the process used 1795 * to collect the core in userspace. Specifically 1796 * it sets up a pipe and installs it as fd 0 (stdin) 1797 * for the process. Returns 0 on success, or 1798 * PTR_ERR on failure. 1799 * Note that it also sets the core limit to 1. This 1800 * is a special value that we use to trap recursive 1801 * core dumps 1802 */ 1803 static int umh_pipe_setup(struct subprocess_info *info) 1804 { 1805 struct file *rp, *wp; 1806 struct fdtable *fdt; 1807 struct coredump_params *cp = (struct coredump_params *)info->data; 1808 struct files_struct *cf = current->files; 1809 1810 wp = create_write_pipe(0); 1811 if (IS_ERR(wp)) 1812 return PTR_ERR(wp); 1813 1814 rp = create_read_pipe(wp, 0); 1815 if (IS_ERR(rp)) { 1816 free_write_pipe(wp); 1817 return PTR_ERR(rp); 1818 } 1819 1820 cp->file = wp; 1821 1822 sys_close(0); 1823 fd_install(0, rp); 1824 spin_lock(&cf->file_lock); 1825 fdt = files_fdtable(cf); 1826 FD_SET(0, fdt->open_fds); 1827 FD_CLR(0, fdt->close_on_exec); 1828 spin_unlock(&cf->file_lock); 1829 1830 /* and disallow core files too */ 1831 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1}; 1832 1833 return 0; 1834 } 1835 1836 void do_coredump(long signr, int exit_code, struct pt_regs *regs) 1837 { 1838 struct core_state core_state; 1839 char corename[CORENAME_MAX_SIZE + 1]; 1840 struct mm_struct *mm = current->mm; 1841 struct linux_binfmt * binfmt; 1842 const struct cred *old_cred; 1843 struct cred *cred; 1844 int retval = 0; 1845 int flag = 0; 1846 int ispipe; 1847 static atomic_t core_dump_count = ATOMIC_INIT(0); 1848 struct coredump_params cprm = { 1849 .signr = signr, 1850 .regs = regs, 1851 .limit = rlimit(RLIMIT_CORE), 1852 /* 1853 * We must use the same mm->flags while dumping core to avoid 1854 * inconsistency of bit flags, since this flag is not protected 1855 * by any locks. 1856 */ 1857 .mm_flags = mm->flags, 1858 }; 1859 1860 audit_core_dumps(signr); 1861 1862 binfmt = mm->binfmt; 1863 if (!binfmt || !binfmt->core_dump) 1864 goto fail; 1865 if (!__get_dumpable(cprm.mm_flags)) 1866 goto fail; 1867 1868 cred = prepare_creds(); 1869 if (!cred) 1870 goto fail; 1871 /* 1872 * We cannot trust fsuid as being the "true" uid of the 1873 * process nor do we know its entire history. We only know it 1874 * was tainted so we dump it as root in mode 2. 1875 */ 1876 if (__get_dumpable(cprm.mm_flags) == 2) { 1877 /* Setuid core dump mode */ 1878 flag = O_EXCL; /* Stop rewrite attacks */ 1879 cred->fsuid = 0; /* Dump root private */ 1880 } 1881 1882 retval = coredump_wait(exit_code, &core_state); 1883 if (retval < 0) 1884 goto fail_creds; 1885 1886 old_cred = override_creds(cred); 1887 1888 /* 1889 * Clear any false indication of pending signals that might 1890 * be seen by the filesystem code called to write the core file. 1891 */ 1892 clear_thread_flag(TIF_SIGPENDING); 1893 1894 /* 1895 * lock_kernel() because format_corename() is controlled by sysctl, which 1896 * uses lock_kernel() 1897 */ 1898 lock_kernel(); 1899 ispipe = format_corename(corename, signr); 1900 unlock_kernel(); 1901 1902 if (ispipe) { 1903 int dump_count; 1904 char **helper_argv; 1905 1906 if (cprm.limit == 1) { 1907 /* 1908 * Normally core limits are irrelevant to pipes, since 1909 * we're not writing to the file system, but we use 1910 * cprm.limit of 1 here as a speacial value. Any 1911 * non-1 limit gets set to RLIM_INFINITY below, but 1912 * a limit of 0 skips the dump. This is a consistent 1913 * way to catch recursive crashes. We can still crash 1914 * if the core_pattern binary sets RLIM_CORE = !1 1915 * but it runs as root, and can do lots of stupid things 1916 * Note that we use task_tgid_vnr here to grab the pid 1917 * of the process group leader. That way we get the 1918 * right pid if a thread in a multi-threaded 1919 * core_pattern process dies. 1920 */ 1921 printk(KERN_WARNING 1922 "Process %d(%s) has RLIMIT_CORE set to 1\n", 1923 task_tgid_vnr(current), current->comm); 1924 printk(KERN_WARNING "Aborting core\n"); 1925 goto fail_unlock; 1926 } 1927 cprm.limit = RLIM_INFINITY; 1928 1929 dump_count = atomic_inc_return(&core_dump_count); 1930 if (core_pipe_limit && (core_pipe_limit < dump_count)) { 1931 printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n", 1932 task_tgid_vnr(current), current->comm); 1933 printk(KERN_WARNING "Skipping core dump\n"); 1934 goto fail_dropcount; 1935 } 1936 1937 helper_argv = argv_split(GFP_KERNEL, corename+1, NULL); 1938 if (!helper_argv) { 1939 printk(KERN_WARNING "%s failed to allocate memory\n", 1940 __func__); 1941 goto fail_dropcount; 1942 } 1943 1944 retval = call_usermodehelper_fns(helper_argv[0], helper_argv, 1945 NULL, UMH_WAIT_EXEC, umh_pipe_setup, 1946 NULL, &cprm); 1947 argv_free(helper_argv); 1948 if (retval) { 1949 printk(KERN_INFO "Core dump to %s pipe failed\n", 1950 corename); 1951 goto close_fail; 1952 } 1953 } else { 1954 struct inode *inode; 1955 1956 if (cprm.limit < binfmt->min_coredump) 1957 goto fail_unlock; 1958 1959 cprm.file = filp_open(corename, 1960 O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag, 1961 0600); 1962 if (IS_ERR(cprm.file)) 1963 goto fail_unlock; 1964 1965 inode = cprm.file->f_path.dentry->d_inode; 1966 if (inode->i_nlink > 1) 1967 goto close_fail; 1968 if (d_unhashed(cprm.file->f_path.dentry)) 1969 goto close_fail; 1970 /* 1971 * AK: actually i see no reason to not allow this for named 1972 * pipes etc, but keep the previous behaviour for now. 1973 */ 1974 if (!S_ISREG(inode->i_mode)) 1975 goto close_fail; 1976 /* 1977 * Dont allow local users get cute and trick others to coredump 1978 * into their pre-created files. 1979 */ 1980 if (inode->i_uid != current_fsuid()) 1981 goto close_fail; 1982 if (!cprm.file->f_op || !cprm.file->f_op->write) 1983 goto close_fail; 1984 if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file)) 1985 goto close_fail; 1986 } 1987 1988 retval = binfmt->core_dump(&cprm); 1989 if (retval) 1990 current->signal->group_exit_code |= 0x80; 1991 1992 if (ispipe && core_pipe_limit) 1993 wait_for_dump_helpers(cprm.file); 1994 close_fail: 1995 if (cprm.file) 1996 filp_close(cprm.file, NULL); 1997 fail_dropcount: 1998 if (ispipe) 1999 atomic_dec(&core_dump_count); 2000 fail_unlock: 2001 coredump_finish(mm); 2002 revert_creds(old_cred); 2003 fail_creds: 2004 put_cred(cred); 2005 fail: 2006 return; 2007 } 2008