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