개념 설명 전체 · v6.18.37 / fs/exec.c
1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * linux/fs/exec.c 4 * 5 * Copyright (C) 1991, 1992 Linus Torvalds 6 */ 7 8 /* 9 * #!-checking implemented by tytso. 10 */ 11 /* 12 * Demand-loading implemented 01.12.91 - no need to read anything but 13 * the header into memory. The inode of the executable is put into 14 * "current->executable", and page faults do the actual loading. Clean. 15 * 16 * Once more I can proudly say that linux stood up to being changed: it 17 * was less than 2 hours work to get demand-loading completely implemented. 18 * 19 * Demand loading changed July 1993 by Eric Youngdale. Use mmap instead, 20 * current->executable is only used by the procfs. This allows a dispatch 21 * table to check for several different types of binary formats. We keep 22 * trying until we recognize the file or we run out of supported binary 23 * formats. 24 */ 25 26 #include <linux/kernel_read_file.h> 27 #include <linux/slab.h> 28 #include <linux/file.h> 29 #include <linux/fdtable.h> 30 #include <linux/mm.h> 31 #include <linux/stat.h> 32 #include <linux/fcntl.h> 33 #include <linux/swap.h> 34 #include <linux/string.h> 35 #include <linux/init.h> 36 #include <linux/sched/mm.h> 37 #include <linux/sched/coredump.h> 38 #include <linux/sched/signal.h> 39 #include <linux/sched/numa_balancing.h> 40 #include <linux/sched/task.h> 41 #include <linux/pagemap.h> 42 #include <linux/perf_event.h> 43 #include <linux/highmem.h> 44 #include <linux/spinlock.h> 45 #include <linux/key.h> 46 #include <linux/personality.h> 47 #include <linux/binfmts.h> 48 #include <linux/utsname.h> 49 #include <linux/pid_namespace.h> 50 #include <linux/module.h> 51 #include <linux/namei.h> 52 #include <linux/mount.h> 53 #include <linux/security.h> 54 #include <linux/syscalls.h> 55 #include <linux/tsacct_kern.h> 56 #include <linux/cn_proc.h> 57 #include <linux/audit.h> 58 #include <linux/kmod.h> 59 #include <linux/fsnotify.h> 60 #include <linux/fs_struct.h> 61 #include <linux/oom.h> 62 #include <linux/compat.h> 63 #include <linux/vmalloc.h> 64 #include <linux/io_uring.h> 65 #include <linux/syscall_user_dispatch.h> 66 #include <linux/coredump.h> 67 #include <linux/time_namespace.h> 68 #include <linux/user_events.h> 69 #include <linux/rseq.h> 70 #include <linux/ksm.h> 71 72 #include <linux/uaccess.h> 73 #include <asm/mmu_context.h> 74 #include <asm/tlb.h> 75 76 #include <trace/events/task.h> 77 #include "internal.h" 78 79 #include <trace/events/sched.h> 80 81 /* For vma exec functions. */ 82 #include "../mm/internal.h" 83 84 static int bprm_creds_from_file(struct linux_binprm *bprm); 85 86 int suid_dumpable = 0; 87 88 static LIST_HEAD(formats); 89 static DEFINE_RWLOCK(binfmt_lock); 90 91 void __register_binfmt(struct linux_binfmt * fmt, int insert) 92 { 93 write_lock(&binfmt_lock); 94 insert ? list_add(&fmt->lh, &formats) : 95 list_add_tail(&fmt->lh, &formats); 96 write_unlock(&binfmt_lock); 97 } 98 99 EXPORT_SYMBOL(__register_binfmt); 100 101 void unregister_binfmt(struct linux_binfmt * fmt) 102 { 103 write_lock(&binfmt_lock); 104 list_del(&fmt->lh); 105 write_unlock(&binfmt_lock); 106 } 107 108 EXPORT_SYMBOL(unregister_binfmt); 109 110 static inline void put_binfmt(struct linux_binfmt * fmt) 111 { 112 module_put(fmt->module); 113 } 114 115 bool path_noexec(const struct path *path) 116 { 117 /* If it's an anonymous inode make sure that we catch any shenanigans. */ 118 VFS_WARN_ON_ONCE(IS_ANON_FILE(d_inode(path->dentry)) && 119 !(path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC)); 120 return (path->mnt->mnt_flags & MNT_NOEXEC) || 121 (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC); 122 } 123 124 #ifdef CONFIG_MMU 125 /* 126 * The nascent bprm->mm is not visible until exec_mmap() but it can 127 * use a lot of memory, account these pages in current->mm temporary 128 * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we 129 * change the counter back via acct_arg_size(0). 130 */ 131 static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages) 132 { 133 struct mm_struct *mm = current->mm; 134 long diff = (long)(pages - bprm->vma_pages); 135 136 if (!mm || !diff) 137 return; 138 139 bprm->vma_pages = pages; 140 add_mm_counter(mm, MM_ANONPAGES, diff); 141 } 142 143 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, 144 int write) 145 { 146 struct page *page; 147 struct vm_area_struct *vma = bprm->vma; 148 struct mm_struct *mm = bprm->mm; 149 int ret; 150 151 /* 152 * Avoid relying on expanding the stack down in GUP (which 153 * does not work for STACK_GROWSUP anyway), and just do it 154 * ahead of time. 155 */ 156 if (!mmap_read_lock_maybe_expand(mm, vma, pos, write)) 157 return NULL; 158 159 /* 160 * We are doing an exec(). 'current' is the process 161 * doing the exec and 'mm' is the new process's mm. 162 */ 163 ret = get_user_pages_remote(mm, pos, 1, 164 write ? FOLL_WRITE : 0, 165 &page, NULL); 166 mmap_read_unlock(mm); 167 if (ret <= 0) 168 return NULL; 169 170 if (write) 171 acct_arg_size(bprm, vma_pages(vma)); 172 173 return page; 174 } 175 176 static void put_arg_page(struct page *page) 177 { 178 put_page(page); 179 } 180 181 static void free_arg_pages(struct linux_binprm *bprm) 182 { 183 } 184 185 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, 186 struct page *page) 187 { 188 flush_cache_page(bprm->vma, pos, page_to_pfn(page)); 189 } 190 191 static bool valid_arg_len(struct linux_binprm *bprm, long len) 192 { 193 return len <= MAX_ARG_STRLEN; 194 } 195 196 #else 197 198 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages) 199 { 200 } 201 202 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, 203 int write) 204 { 205 struct page *page; 206 207 page = bprm->page[pos / PAGE_SIZE]; 208 if (!page && write) { 209 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO); 210 if (!page) 211 return NULL; 212 bprm->page[pos / PAGE_SIZE] = page; 213 } 214 215 return page; 216 } 217 218 static void put_arg_page(struct page *page) 219 { 220 } 221 222 static void free_arg_page(struct linux_binprm *bprm, int i) 223 { 224 if (bprm->page[i]) { 225 __free_page(bprm->page[i]); 226 bprm->page[i] = NULL; 227 } 228 } 229 230 static void free_arg_pages(struct linux_binprm *bprm) 231 { 232 int i; 233 234 for (i = 0; i < MAX_ARG_PAGES; i++) 235 free_arg_page(bprm, i); 236 } 237 238 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, 239 struct page *page) 240 { 241 } 242 243 static bool valid_arg_len(struct linux_binprm *bprm, long len) 244 { 245 return len <= bprm->p; 246 } 247 248 #endif /* CONFIG_MMU */ 249 250 /* 251 * Create a new mm_struct and populate it with a temporary stack 252 * vm_area_struct. We don't have enough context at this point to set the stack 253 * flags, permissions, and offset, so we use temporary values. We'll update 254 * them later in setup_arg_pages(). 255 */ 256 static int bprm_mm_init(struct linux_binprm *bprm) 257 { 258 int err; 259 struct mm_struct *mm = NULL; 260 261 bprm->mm = mm = mm_alloc(); 262 err = -ENOMEM; 263 if (!mm) 264 goto err; 265 266 /* Save current stack limit for all calculations made during exec. */ 267 task_lock(current->group_leader); 268 bprm->rlim_stack = current->signal->rlim[RLIMIT_STACK]; 269 task_unlock(current->group_leader); 270 271 #ifndef CONFIG_MMU 272 bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *); 273 #else 274 err = create_init_stack_vma(bprm->mm, &bprm->vma, &bprm->p); 275 if (err) 276 goto err; 277 #endif 278 279 return 0; 280 281 err: 282 if (mm) { 283 bprm->mm = NULL; 284 mmdrop(mm); 285 } 286 287 return err; 288 } 289 290 struct user_arg_ptr { 291 #ifdef CONFIG_COMPAT 292 bool is_compat; 293 #endif 294 union { 295 const char __user *const __user *native; 296 #ifdef CONFIG_COMPAT 297 const compat_uptr_t __user *compat; 298 #endif 299 } ptr; 300 }; 301 302 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr) 303 { 304 const char __user *native; 305 306 #ifdef CONFIG_COMPAT 307 if (unlikely(argv.is_compat)) { 308 compat_uptr_t compat; 309 310 if (get_user(compat, argv.ptr.compat + nr)) 311 return ERR_PTR(-EFAULT); 312 313 return compat_ptr(compat); 314 } 315 #endif 316 317 if (get_user(native, argv.ptr.native + nr)) 318 return ERR_PTR(-EFAULT); 319 320 return native; 321 } 322 323 /* 324 * count() counts the number of strings in array ARGV. 325 */ 326 static int count(struct user_arg_ptr argv, int max) 327 { 328 int i = 0; 329 330 if (argv.ptr.native != NULL) { 331 for (;;) { 332 const char __user *p = get_user_arg_ptr(argv, i); 333 334 if (!p) 335 break; 336 337 if (IS_ERR(p)) 338 return -EFAULT; 339 340 if (i >= max) 341 return -E2BIG; 342 ++i; 343 344 if (fatal_signal_pending(current)) 345 return -ERESTARTNOHAND; 346 cond_resched(); 347 } 348 } 349 return i; 350 } 351 352 static int count_strings_kernel(const char *const *argv) 353 { 354 int i; 355 356 if (!argv) 357 return 0; 358 359 for (i = 0; argv[i]; ++i) { 360 if (i >= MAX_ARG_STRINGS) 361 return -E2BIG; 362 if (fatal_signal_pending(current)) 363 return -ERESTARTNOHAND; 364 cond_resched(); 365 } 366 return i; 367 } 368 369 static inline int bprm_set_stack_limit(struct linux_binprm *bprm, 370 unsigned long limit) 371 { 372 #ifdef CONFIG_MMU 373 /* Avoid a pathological bprm->p. */ 374 if (bprm->p < limit) 375 return -E2BIG; 376 bprm->argmin = bprm->p - limit; 377 #endif 378 return 0; 379 } 380 static inline bool bprm_hit_stack_limit(struct linux_binprm *bprm) 381 { 382 #ifdef CONFIG_MMU 383 return bprm->p < bprm->argmin; 384 #else 385 return false; 386 #endif 387 } 388 389 /* 390 * Calculate bprm->argmin from: 391 * - _STK_LIM 392 * - ARG_MAX 393 * - bprm->rlim_stack.rlim_cur 394 * - bprm->argc 395 * - bprm->envc 396 * - bprm->p 397 */ 398 static int bprm_stack_limits(struct linux_binprm *bprm) 399 { 400 unsigned long limit, ptr_size; 401 402 /* 403 * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM 404 * (whichever is smaller) for the argv+env strings. 405 * This ensures that: 406 * - the remaining binfmt code will not run out of stack space, 407 * - the program will have a reasonable amount of stack left 408 * to work from. 409 */ 410 limit = _STK_LIM / 4 * 3; 411 limit = min(limit, bprm->rlim_stack.rlim_cur / 4); 412 /* 413 * We've historically supported up to 32 pages (ARG_MAX) 414 * of argument strings even with small stacks 415 */ 416 limit = max_t(unsigned long, limit, ARG_MAX); 417 /* Reject totally pathological counts. */ 418 if (bprm->argc < 0 || bprm->envc < 0) 419 return -E2BIG; 420 /* 421 * We must account for the size of all the argv and envp pointers to 422 * the argv and envp strings, since they will also take up space in 423 * the stack. They aren't stored until much later when we can't 424 * signal to the parent that the child has run out of stack space. 425 * Instead, calculate it here so it's possible to fail gracefully. 426 * 427 * In the case of argc = 0, make sure there is space for adding a 428 * empty string (which will bump argc to 1), to ensure confused 429 * userspace programs don't start processing from argv[1], thinking 430 * argc can never be 0, to keep them from walking envp by accident. 431 * See do_execveat_common(). 432 */ 433 if (check_add_overflow(max(bprm->argc, 1), bprm->envc, &ptr_size) || 434 check_mul_overflow(ptr_size, sizeof(void *), &ptr_size)) 435 return -E2BIG; 436 if (limit <= ptr_size) 437 return -E2BIG; 438 limit -= ptr_size; 439 440 return bprm_set_stack_limit(bprm, limit); 441 } 442 443 /* 444 * 'copy_strings()' copies argument/environment strings from the old 445 * processes's memory to the new process's stack. The call to get_user_pages() 446 * ensures the destination page is created and not swapped out. 447 */ 448 static int copy_strings(int argc, struct user_arg_ptr argv, 449 struct linux_binprm *bprm) 450 { 451 struct page *kmapped_page = NULL; 452 char *kaddr = NULL; 453 unsigned long kpos = 0; 454 int ret; 455 456 while (argc-- > 0) { 457 const char __user *str; 458 int len; 459 unsigned long pos; 460 461 ret = -EFAULT; 462 str = get_user_arg_ptr(argv, argc); 463 if (IS_ERR(str)) 464 goto out; 465 466 len = strnlen_user(str, MAX_ARG_STRLEN); 467 if (!len) 468 goto out; 469 470 ret = -E2BIG; 471 if (!valid_arg_len(bprm, len)) 472 goto out; 473 474 /* We're going to work our way backwards. */ 475 pos = bprm->p; 476 str += len; 477 bprm->p -= len; 478 if (bprm_hit_stack_limit(bprm)) 479 goto out; 480 481 while (len > 0) { 482 int offset, bytes_to_copy; 483 484 if (fatal_signal_pending(current)) { 485 ret = -ERESTARTNOHAND; 486 goto out; 487 } 488 cond_resched(); 489 490 offset = pos % PAGE_SIZE; 491 if (offset == 0) 492 offset = PAGE_SIZE; 493 494 bytes_to_copy = offset; 495 if (bytes_to_copy > len) 496 bytes_to_copy = len; 497 498 offset -= bytes_to_copy; 499 pos -= bytes_to_copy; 500 str -= bytes_to_copy; 501 len -= bytes_to_copy; 502 503 if (!kmapped_page || kpos != (pos & PAGE_MASK)) { 504 struct page *page; 505 506 page = get_arg_page(bprm, pos, 1); 507 if (!page) { 508 ret = -E2BIG; 509 goto out; 510 } 511 512 if (kmapped_page) { 513 flush_dcache_page(kmapped_page); 514 kunmap_local(kaddr); 515 put_arg_page(kmapped_page); 516 } 517 kmapped_page = page; 518 kaddr = kmap_local_page(kmapped_page); 519 kpos = pos & PAGE_MASK; 520 flush_arg_page(bprm, kpos, kmapped_page); 521 } 522 if (copy_from_user(kaddr+offset, str, bytes_to_copy)) { 523 ret = -EFAULT; 524 goto out; 525 } 526 } 527 } 528 ret = 0; 529 out: 530 if (kmapped_page) { 531 flush_dcache_page(kmapped_page); 532 kunmap_local(kaddr); 533 put_arg_page(kmapped_page); 534 } 535 return ret; 536 } 537 538 /* 539 * Copy and argument/environment string from the kernel to the processes stack. 540 */ 541 int copy_string_kernel(const char *arg, struct linux_binprm *bprm) 542 { 543 int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */; 544 unsigned long pos = bprm->p; 545 546 if (len == 0) 547 return -EFAULT; 548 if (!valid_arg_len(bprm, len)) 549 return -E2BIG; 550 551 /* We're going to work our way backwards. */ 552 arg += len; 553 bprm->p -= len; 554 if (bprm_hit_stack_limit(bprm)) 555 return -E2BIG; 556 557 while (len > 0) { 558 unsigned int bytes_to_copy = min_t(unsigned int, len, 559 min_not_zero(offset_in_page(pos), PAGE_SIZE)); 560 struct page *page; 561 562 pos -= bytes_to_copy; 563 arg -= bytes_to_copy; 564 len -= bytes_to_copy; 565 566 page = get_arg_page(bprm, pos, 1); 567 if (!page) 568 return -E2BIG; 569 flush_arg_page(bprm, pos & PAGE_MASK, page); 570 memcpy_to_page(page, offset_in_page(pos), arg, bytes_to_copy); 571 put_arg_page(page); 572 } 573 574 return 0; 575 } 576 EXPORT_SYMBOL(copy_string_kernel); 577 578 static int copy_strings_kernel(int argc, const char *const *argv, 579 struct linux_binprm *bprm) 580 { 581 while (argc-- > 0) { 582 int ret = copy_string_kernel(argv[argc], bprm); 583 if (ret < 0) 584 return ret; 585 if (fatal_signal_pending(current)) 586 return -ERESTARTNOHAND; 587 cond_resched(); 588 } 589 return 0; 590 } 591 592 #ifdef CONFIG_MMU 593 594 /* 595 * Finalizes the stack vm_area_struct. The flags and permissions are updated, 596 * the stack is optionally relocated, and some extra space is added. 597 */ 598 int setup_arg_pages(struct linux_binprm *bprm, 599 unsigned long stack_top, 600 int executable_stack) 601 { 602 int ret; 603 unsigned long stack_shift; 604 struct mm_struct *mm = current->mm; 605 struct vm_area_struct *vma = bprm->vma; 606 struct vm_area_struct *prev = NULL; 607 vm_flags_t vm_flags; 608 unsigned long stack_base; 609 unsigned long stack_size; 610 unsigned long stack_expand; 611 unsigned long rlim_stack; 612 struct mmu_gather tlb; 613 struct vma_iterator vmi; 614 615 #ifdef CONFIG_STACK_GROWSUP 616 /* Limit stack size */ 617 stack_base = bprm->rlim_stack.rlim_max; 618 619 stack_base = calc_max_stack_size(stack_base); 620 621 /* Add space for stack randomization. */ 622 if (current->flags & PF_RANDOMIZE) 623 stack_base += (STACK_RND_MASK << PAGE_SHIFT); 624 625 /* Make sure we didn't let the argument array grow too large. */ 626 if (vma->vm_end - vma->vm_start > stack_base) 627 return -ENOMEM; 628 629 stack_base = PAGE_ALIGN(stack_top - stack_base); 630 631 stack_shift = vma->vm_start - stack_base; 632 mm->arg_start = bprm->p - stack_shift; 633 bprm->p = vma->vm_end - stack_shift; 634 #else 635 stack_top = arch_align_stack(stack_top); 636 stack_top = PAGE_ALIGN(stack_top); 637 638 if (unlikely(stack_top < mmap_min_addr) || 639 unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr)) 640 return -ENOMEM; 641 642 stack_shift = vma->vm_end - stack_top; 643 644 bprm->p -= stack_shift; 645 mm->arg_start = bprm->p; 646 #endif 647 648 bprm->exec -= stack_shift; 649 650 if (mmap_write_lock_killable(mm)) 651 return -EINTR; 652 653 vm_flags = VM_STACK_FLAGS; 654 655 /* 656 * Adjust stack execute permissions; explicitly enable for 657 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone 658 * (arch default) otherwise. 659 */ 660 if (unlikely(executable_stack == EXSTACK_ENABLE_X)) 661 vm_flags |= VM_EXEC; 662 else if (executable_stack == EXSTACK_DISABLE_X) 663 vm_flags &= ~VM_EXEC; 664 vm_flags |= mm->def_flags; 665 vm_flags |= VM_STACK_INCOMPLETE_SETUP; 666 667 vma_iter_init(&vmi, mm, vma->vm_start); 668 669 tlb_gather_mmu(&tlb, mm); 670 ret = mprotect_fixup(&vmi, &tlb, vma, &prev, vma->vm_start, vma->vm_end, 671 vm_flags); 672 tlb_finish_mmu(&tlb); 673 674 if (ret) 675 goto out_unlock; 676 BUG_ON(prev != vma); 677 678 if (unlikely(vm_flags & VM_EXEC)) { 679 pr_warn_once("process '%pD4' started with executable stack\n", 680 bprm->file); 681 } 682 683 /* Move stack pages down in memory. */ 684 if (stack_shift) { 685 /* 686 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once 687 * the binfmt code determines where the new stack should reside, we shift it to 688 * its final location. 689 */ 690 ret = relocate_vma_down(vma, stack_shift); 691 if (ret) 692 goto out_unlock; 693 } 694 695 /* mprotect_fixup is overkill to remove the temporary stack flags */ 696 vm_flags_clear(vma, VM_STACK_INCOMPLETE_SETUP); 697 698 stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */ 699 stack_size = vma->vm_end - vma->vm_start; 700 /* 701 * Align this down to a page boundary as expand_stack 702 * will align it up. 703 */ 704 rlim_stack = bprm->rlim_stack.rlim_cur & PAGE_MASK; 705 706 stack_expand = min(rlim_stack, stack_size + stack_expand); 707 708 #ifdef CONFIG_STACK_GROWSUP 709 stack_base = vma->vm_start + stack_expand; 710 #else 711 stack_base = vma->vm_end - stack_expand; 712 #endif 713 current->mm->start_stack = bprm->p; 714 ret = expand_stack_locked(vma, stack_base); 715 if (ret) 716 ret = -EFAULT; 717 718 out_unlock: 719 mmap_write_unlock(mm); 720 return ret; 721 } 722 EXPORT_SYMBOL(setup_arg_pages); 723 724 #else 725 726 /* 727 * Transfer the program arguments and environment from the holding pages 728 * onto the stack. The provided stack pointer is adjusted accordingly. 729 */ 730 int transfer_args_to_stack(struct linux_binprm *bprm, 731 unsigned long *sp_location) 732 { 733 unsigned long index, stop, sp; 734 int ret = 0; 735 736 stop = bprm->p >> PAGE_SHIFT; 737 sp = *sp_location; 738 739 for (index = MAX_ARG_PAGES - 1; index >= stop; index--) { 740 unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0; 741 char *src = kmap_local_page(bprm->page[index]) + offset; 742 sp -= PAGE_SIZE - offset; 743 if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0) 744 ret = -EFAULT; 745 kunmap_local(src); 746 if (ret) 747 goto out; 748 } 749 750 bprm->exec += *sp_location - MAX_ARG_PAGES * PAGE_SIZE; 751 *sp_location = sp; 752 753 out: 754 return ret; 755 } 756 EXPORT_SYMBOL(transfer_args_to_stack); 757 758 #endif /* CONFIG_MMU */ 759 760 /* 761 * On success, caller must call do_close_execat() on the returned 762 * struct file to close it. 763 */ 764 static struct file *do_open_execat(int fd, struct filename *name, int flags) 765 { 766 int err; 767 struct file *file __free(fput) = NULL; 768 struct open_flags open_exec_flags = { 769 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC, 770 .acc_mode = MAY_EXEC, 771 .intent = LOOKUP_OPEN, 772 .lookup_flags = LOOKUP_FOLLOW, 773 }; 774 775 if ((flags & 776 ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH | AT_EXECVE_CHECK)) != 0) 777 return ERR_PTR(-EINVAL); 778 if (flags & AT_SYMLINK_NOFOLLOW) 779 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW; 780 if (flags & AT_EMPTY_PATH) 781 open_exec_flags.lookup_flags |= LOOKUP_EMPTY; 782 783 file = do_filp_open(fd, name, &open_exec_flags); 784 if (IS_ERR(file)) 785 return file; 786 787 if (path_noexec(&file->f_path)) 788 return ERR_PTR(-EACCES); 789 790 /* 791 * In the past the regular type check was here. It moved to may_open() in 792 * 633fb6ac3980 ("exec: move S_ISREG() check earlier"). Since then it is 793 * an invariant that all non-regular files error out before we get here. 794 */ 795 if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode))) 796 return ERR_PTR(-EACCES); 797 798 err = exe_file_deny_write_access(file); 799 if (err) 800 return ERR_PTR(err); 801 802 return no_free_ptr(file); 803 } 804 805 /** 806 * open_exec - Open a path name for execution 807 * 808 * @name: path name to open with the intent of executing it. 809 * 810 * Returns ERR_PTR on failure or allocated struct file on success. 811 * 812 * As this is a wrapper for the internal do_open_execat(), callers 813 * must call exe_file_allow_write_access() before fput() on release. Also see 814 * do_close_execat(). 815 */ 816 struct file *open_exec(const char *name) 817 { 818 struct filename *filename = getname_kernel(name); 819 struct file *f = ERR_CAST(filename); 820 821 if (!IS_ERR(filename)) { 822 f = do_open_execat(AT_FDCWD, filename, 0); 823 putname(filename); 824 } 825 return f; 826 } 827 EXPORT_SYMBOL(open_exec); 828 829 #if defined(CONFIG_BINFMT_FLAT) || defined(CONFIG_BINFMT_ELF_FDPIC) 830 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len) 831 { 832 ssize_t res = vfs_read(file, (void __user *)addr, len, &pos); 833 if (res > 0) 834 flush_icache_user_range(addr, addr + len); 835 return res; 836 } 837 EXPORT_SYMBOL(read_code); 838 #endif 839 840 /* 841 * Maps the mm_struct mm into the current task struct. 842 * On success, this function returns with exec_update_lock 843 * held for writing. 844 */ 845 static int exec_mmap(struct mm_struct *mm) 846 { 847 struct task_struct *tsk; 848 struct mm_struct *old_mm, *active_mm; 849 int ret; 850 851 /* Notify parent that we're no longer interested in the old VM */ 852 tsk = current; 853 old_mm = current->mm; 854 exec_mm_release(tsk, old_mm); 855 856 ret = down_write_killable(&tsk->signal->exec_update_lock); 857 if (ret) 858 return ret; 859 860 if (old_mm) { 861 /* 862 * If there is a pending fatal signal perhaps a signal 863 * whose default action is to create a coredump get 864 * out and die instead of going through with the exec. 865 */ 866 ret = mmap_read_lock_killable(old_mm); 867 if (ret) { 868 up_write(&tsk->signal->exec_update_lock); 869 return ret; 870 } 871 } 872 873 task_lock(tsk); 874 membarrier_exec_mmap(mm); 875 876 local_irq_disable(); 877 active_mm = tsk->active_mm; 878 tsk->active_mm = mm; 879 tsk->mm = mm; 880 mm_init_cid(mm, tsk); 881 /* 882 * This prevents preemption while active_mm is being loaded and 883 * it and mm are being updated, which could cause problems for 884 * lazy tlb mm refcounting when these are updated by context 885 * switches. Not all architectures can handle irqs off over 886 * activate_mm yet. 887 */ 888 if (!IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM)) 889 local_irq_enable(); 890 activate_mm(active_mm, mm); 891 if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM)) 892 local_irq_enable(); 893 lru_gen_add_mm(mm); 894 task_unlock(tsk); 895 lru_gen_use_mm(mm); 896 if (old_mm) { 897 mmap_read_unlock(old_mm); 898 BUG_ON(active_mm != old_mm); 899 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm); 900 mm_update_next_owner(old_mm); 901 mmput(old_mm); 902 return 0; 903 } 904 mmdrop_lazy_tlb(active_mm); 905 return 0; 906 } 907 908 static int de_thread(struct task_struct *tsk) 909 { 910 struct signal_struct *sig = tsk->signal; 911 struct sighand_struct *oldsighand = tsk->sighand; 912 spinlock_t *lock = &oldsighand->siglock; 913 914 if (thread_group_empty(tsk)) 915 goto no_thread_group; 916 917 /* 918 * Kill all other threads in the thread group. 919 */ 920 spin_lock_irq(lock); 921 if ((sig->flags & SIGNAL_GROUP_EXIT) || sig->group_exec_task) { 922 /* 923 * Another group action in progress, just 924 * return so that the signal is processed. 925 */ 926 spin_unlock_irq(lock); 927 return -EAGAIN; 928 } 929 930 sig->group_exec_task = tsk; 931 sig->notify_count = zap_other_threads(tsk); 932 if (!thread_group_leader(tsk)) 933 sig->notify_count--; 934 935 while (sig->notify_count) { 936 __set_current_state(TASK_KILLABLE); 937 spin_unlock_irq(lock); 938 schedule(); 939 if (__fatal_signal_pending(tsk)) 940 goto killed; 941 spin_lock_irq(lock); 942 } 943 spin_unlock_irq(lock); 944 945 /* 946 * At this point all other threads have exited, all we have to 947 * do is to wait for the thread group leader to become inactive, 948 * and to assume its PID: 949 */ 950 if (!thread_group_leader(tsk)) { 951 struct task_struct *leader = tsk->group_leader; 952 953 for (;;) { 954 cgroup_threadgroup_change_begin(tsk); 955 write_lock_irq(&tasklist_lock); 956 /* 957 * Do this under tasklist_lock to ensure that 958 * exit_notify() can't miss ->group_exec_task 959 */ 960 sig->notify_count = -1; 961 if (likely(leader->exit_state)) 962 break; 963 __set_current_state(TASK_KILLABLE); 964 write_unlock_irq(&tasklist_lock); 965 cgroup_threadgroup_change_end(tsk); 966 schedule(); 967 if (__fatal_signal_pending(tsk)) 968 goto killed; 969 } 970 971 /* 972 * The only record we have of the real-time age of a 973 * process, regardless of execs it's done, is start_time. 974 * All the past CPU time is accumulated in signal_struct 975 * from sister threads now dead. But in this non-leader 976 * exec, nothing survives from the original leader thread, 977 * whose birth marks the true age of this process now. 978 * When we take on its identity by switching to its PID, we 979 * also take its birthdate (always earlier than our own). 980 */ 981 tsk->start_time = leader->start_time; 982 tsk->start_boottime = leader->start_boottime; 983 984 BUG_ON(!same_thread_group(leader, tsk)); 985 /* 986 * An exec() starts a new thread group with the 987 * TGID of the previous thread group. Rehash the 988 * two threads with a switched PID, and release 989 * the former thread group leader: 990 */ 991 992 /* Become a process group leader with the old leader's pid. 993 * The old leader becomes a thread of the this thread group. 994 */ 995 exchange_tids(tsk, leader); 996 transfer_pid(leader, tsk, PIDTYPE_TGID); 997 transfer_pid(leader, tsk, PIDTYPE_PGID); 998 transfer_pid(leader, tsk, PIDTYPE_SID); 999 1000 list_replace_rcu(&leader->tasks, &tsk->tasks); 1001 list_replace_init(&leader->sibling, &tsk->sibling); 1002 1003 tsk->group_leader = tsk; 1004 leader->group_leader = tsk; 1005 1006 tsk->exit_signal = SIGCHLD; 1007 leader->exit_signal = -1; 1008 1009 BUG_ON(leader->exit_state != EXIT_ZOMBIE); 1010 leader->exit_state = EXIT_DEAD; 1011 /* 1012 * We are going to release_task()->ptrace_unlink() silently, 1013 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees 1014 * the tracer won't block again waiting for this thread. 1015 */ 1016 if (unlikely(leader->ptrace)) 1017 __wake_up_parent(leader, leader->parent); 1018 write_unlock_irq(&tasklist_lock); 1019 cgroup_threadgroup_change_end(tsk); 1020 1021 release_task(leader); 1022 } 1023 1024 sig->group_exec_task = NULL; 1025 sig->notify_count = 0; 1026 1027 no_thread_group: 1028 /* we have changed execution domain */ 1029 tsk->exit_signal = SIGCHLD; 1030 1031 BUG_ON(!thread_group_leader(tsk)); 1032 return 0; 1033 1034 killed: 1035 /* protects against exit_notify() and __exit_signal() */ 1036 read_lock(&tasklist_lock); 1037 sig->group_exec_task = NULL; 1038 sig->notify_count = 0; 1039 read_unlock(&tasklist_lock); 1040 return -EAGAIN; 1041 } 1042 1043 1044 /* 1045 * This function makes sure the current process has its own signal table, 1046 * so that flush_signal_handlers can later reset the handlers without 1047 * disturbing other processes. (Other processes might share the signal 1048 * table via the CLONE_SIGHAND option to clone().) 1049 */ 1050 static int unshare_sighand(struct task_struct *me) 1051 { 1052 struct sighand_struct *oldsighand = me->sighand; 1053 1054 if (refcount_read(&oldsighand->count) != 1) { 1055 struct sighand_struct *newsighand; 1056 /* 1057 * This ->sighand is shared with the CLONE_SIGHAND 1058 * but not CLONE_THREAD task, switch to the new one. 1059 */ 1060 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1061 if (!newsighand) 1062 return -ENOMEM; 1063 1064 refcount_set(&newsighand->count, 1); 1065 1066 write_lock_irq(&tasklist_lock); 1067 spin_lock(&oldsighand->siglock); 1068 memcpy(newsighand->action, oldsighand->action, 1069 sizeof(newsighand->action)); 1070 rcu_assign_pointer(me->sighand, newsighand); 1071 spin_unlock(&oldsighand->siglock); 1072 write_unlock_irq(&tasklist_lock); 1073 1074 __cleanup_sighand(oldsighand); 1075 } 1076 return 0; 1077 } 1078 1079 /* 1080 * This is unlocked -- the string will always be NUL-terminated, but 1081 * may show overlapping contents if racing concurrent reads. 1082 */ 1083 void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec) 1084 { 1085 size_t len = min(strlen(buf), sizeof(tsk->comm) - 1); 1086 1087 trace_task_rename(tsk, buf); 1088 memcpy(tsk->comm, buf, len); 1089 memset(&tsk->comm[len], 0, sizeof(tsk->comm) - len); 1090 perf_event_comm(tsk, exec); 1091 } 1092 1093 /* 1094 * Calling this is the point of no return. None of the failures will be 1095 * seen by userspace since either the process is already taking a fatal 1096 * signal (via de_thread() or coredump), or will have SEGV raised 1097 * (after exec_mmap()) by search_binary_handler (see below). 1098 */ 1099 int begin_new_exec(struct linux_binprm * bprm) 1100 { 1101 struct task_struct *me = current; 1102 int retval; 1103 1104 /* Once we are committed compute the creds */ 1105 retval = bprm_creds_from_file(bprm); 1106 if (retval) 1107 return retval; 1108 1109 /* 1110 * This tracepoint marks the point before flushing the old exec where 1111 * the current task is still unchanged, but errors are fatal (point of 1112 * no return). The later "sched_process_exec" tracepoint is called after 1113 * the current task has successfully switched to the new exec. 1114 */ 1115 trace_sched_prepare_exec(current, bprm); 1116 1117 /* 1118 * Ensure all future errors are fatal. 1119 */ 1120 bprm->point_of_no_return = true; 1121 1122 /* Make this the only thread in the thread group */ 1123 retval = de_thread(me); 1124 if (retval) 1125 goto out; 1126 /* see the comment in check_unsafe_exec() */ 1127 current->fs->in_exec = 0; 1128 /* 1129 * Cancel any io_uring activity across execve 1130 */ 1131 io_uring_task_cancel(); 1132 1133 /* Ensure the files table is not shared. */ 1134 retval = unshare_files(); 1135 if (retval) 1136 goto out; 1137 1138 /* 1139 * Must be called _before_ exec_mmap() as bprm->mm is 1140 * not visible until then. Doing it here also ensures 1141 * we don't race against replace_mm_exe_file(). 1142 */ 1143 retval = set_mm_exe_file(bprm->mm, bprm->file); 1144 if (retval) 1145 goto out; 1146 1147 /* If the binary is not readable then enforce mm->dumpable=0 */ 1148 would_dump(bprm, bprm->file); 1149 if (bprm->have_execfd) 1150 would_dump(bprm, bprm->executable); 1151 1152 /* 1153 * Release all of the old mmap stuff 1154 */ 1155 acct_arg_size(bprm, 0); 1156 retval = exec_mmap(bprm->mm); 1157 if (retval) 1158 goto out; 1159 1160 bprm->mm = NULL; 1161 1162 retval = exec_task_namespaces(); 1163 if (retval) 1164 goto out_unlock; 1165 1166 #ifdef CONFIG_POSIX_TIMERS 1167 spin_lock_irq(&me->sighand->siglock); 1168 posix_cpu_timers_exit(me); 1169 spin_unlock_irq(&me->sighand->siglock); 1170 exit_itimers(me); 1171 flush_itimer_signals(); 1172 #endif 1173 1174 /* 1175 * Make the signal table private. 1176 */ 1177 retval = unshare_sighand(me); 1178 if (retval) 1179 goto out_unlock; 1180 1181 me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | 1182 PF_NOFREEZE | PF_NO_SETAFFINITY); 1183 flush_thread(); 1184 me->personality &= ~bprm->per_clear; 1185 1186 clear_syscall_work_syscall_user_dispatch(me); 1187 1188 /* 1189 * We have to apply CLOEXEC before we change whether the process is 1190 * dumpable (in setup_new_exec) to avoid a race with a process in userspace 1191 * trying to access the should-be-closed file descriptors of a process 1192 * undergoing exec(2). 1193 */ 1194 do_close_on_exec(me->files); 1195 1196 if (bprm->secureexec) { 1197 /* Make sure parent cannot signal privileged process. */ 1198 me->pdeath_signal = 0; 1199 1200 /* 1201 * For secureexec, reset the stack limit to sane default to 1202 * avoid bad behavior from the prior rlimits. This has to 1203 * happen before arch_pick_mmap_layout(), which examines 1204 * RLIMIT_STACK, but after the point of no return to avoid 1205 * needing to clean up the change on failure. 1206 */ 1207 if (bprm->rlim_stack.rlim_cur > _STK_LIM) 1208 bprm->rlim_stack.rlim_cur = _STK_LIM; 1209 } 1210 1211 me->sas_ss_sp = me->sas_ss_size = 0; 1212 1213 /* 1214 * Figure out dumpability. Note that this checking only of current 1215 * is wrong, but userspace depends on it. This should be testing 1216 * bprm->secureexec instead. 1217 */ 1218 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP || 1219 !(uid_eq(current_euid(), current_uid()) && 1220 gid_eq(current_egid(), current_gid()))) 1221 set_dumpable(current->mm, suid_dumpable); 1222 else 1223 set_dumpable(current->mm, SUID_DUMP_USER); 1224 1225 perf_event_exec(); 1226 1227 /* 1228 * If the original filename was empty, alloc_bprm() made up a path 1229 * that will probably not be useful to admins running ps or similar. 1230 * Let's fix it up to be something reasonable. 1231 */ 1232 if (bprm->comm_from_dentry) { 1233 /* 1234 * Hold RCU lock to keep the name from being freed behind our back. 1235 * Use acquire semantics to make sure the terminating NUL from 1236 * __d_alloc() is seen. 1237 * 1238 * Note, we're deliberately sloppy here. We don't need to care about 1239 * detecting a concurrent rename and just want a terminated name. 1240 */ 1241 rcu_read_lock(); 1242 __set_task_comm(me, smp_load_acquire(&bprm->file->f_path.dentry->d_name.name), 1243 true); 1244 rcu_read_unlock(); 1245 } else { 1246 __set_task_comm(me, kbasename(bprm->filename), true); 1247 } 1248 1249 /* An exec changes our domain. We are no longer part of the thread 1250 group */ 1251 WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1); 1252 flush_signal_handlers(me, 0); 1253 1254 retval = set_cred_ucounts(bprm->cred); 1255 if (retval < 0) 1256 goto out_unlock; 1257 1258 /* 1259 * install the new credentials for this executable 1260 */ 1261 security_bprm_committing_creds(bprm); 1262 1263 commit_creds(bprm->cred); 1264 bprm->cred = NULL; 1265 1266 /* 1267 * Disable monitoring for regular users 1268 * when executing setuid binaries. Must 1269 * wait until new credentials are committed 1270 * by commit_creds() above 1271 */ 1272 if (get_dumpable(me->mm) != SUID_DUMP_USER) 1273 perf_event_exit_task(me); 1274 /* 1275 * cred_guard_mutex must be held at least to this point to prevent 1276 * ptrace_attach() from altering our determination of the task's 1277 * credentials; any time after this it may be unlocked. 1278 */ 1279 security_bprm_committed_creds(bprm); 1280 1281 /* Pass the opened binary to the interpreter. */ 1282 if (bprm->have_execfd) { 1283 retval = get_unused_fd_flags(0); 1284 if (retval < 0) 1285 goto out_unlock; 1286 fd_install(retval, bprm->executable); 1287 bprm->executable = NULL; 1288 bprm->execfd = retval; 1289 } 1290 return 0; 1291 1292 out_unlock: 1293 up_write(&me->signal->exec_update_lock); 1294 if (!bprm->cred) 1295 mutex_unlock(&me->signal->cred_guard_mutex); 1296 1297 out: 1298 return retval; 1299 } 1300 EXPORT_SYMBOL(begin_new_exec); 1301 1302 void would_dump(struct linux_binprm *bprm, struct file *file) 1303 { 1304 struct inode *inode = file_inode(file); 1305 struct mnt_idmap *idmap = file_mnt_idmap(file); 1306 if (inode_permission(idmap, inode, MAY_READ) < 0) { 1307 struct user_namespace *old, *user_ns; 1308 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP; 1309 1310 /* Ensure mm->user_ns contains the executable */ 1311 user_ns = old = bprm->mm->user_ns; 1312 while ((user_ns != &init_user_ns) && 1313 !privileged_wrt_inode_uidgid(user_ns, idmap, inode)) 1314 user_ns = user_ns->parent; 1315 1316 if (old != user_ns) { 1317 bprm->mm->user_ns = get_user_ns(user_ns); 1318 put_user_ns(old); 1319 } 1320 } 1321 } 1322 EXPORT_SYMBOL(would_dump); 1323 1324 void setup_new_exec(struct linux_binprm * bprm) 1325 { 1326 /* Setup things that can depend upon the personality */ 1327 struct task_struct *me = current; 1328 1329 arch_pick_mmap_layout(me->mm, &bprm->rlim_stack); 1330 1331 arch_setup_new_exec(); 1332 1333 /* Set the new mm task size. We have to do that late because it may 1334 * depend on TIF_32BIT which is only updated in flush_thread() on 1335 * some architectures like powerpc 1336 */ 1337 me->mm->task_size = TASK_SIZE; 1338 up_write(&me->signal->exec_update_lock); 1339 mutex_unlock(&me->signal->cred_guard_mutex); 1340 } 1341 EXPORT_SYMBOL(setup_new_exec); 1342 1343 /* Runs immediately before start_thread() takes over. */ 1344 void finalize_exec(struct linux_binprm *bprm) 1345 { 1346 /* Store any stack rlimit changes before starting thread. */ 1347 task_lock(current->group_leader); 1348 current->signal->rlim[RLIMIT_STACK] = bprm->rlim_stack; 1349 task_unlock(current->group_leader); 1350 } 1351 EXPORT_SYMBOL(finalize_exec); 1352 1353 /* 1354 * Prepare credentials and lock ->cred_guard_mutex. 1355 * setup_new_exec() commits the new creds and drops the lock. 1356 * Or, if exec fails before, free_bprm() should release ->cred 1357 * and unlock. 1358 */ 1359 static int prepare_bprm_creds(struct linux_binprm *bprm) 1360 { 1361 if (mutex_lock_interruptible(¤t->signal->cred_guard_mutex)) 1362 return -ERESTARTNOINTR; 1363 1364 bprm->cred = prepare_exec_creds(); 1365 if (likely(bprm->cred)) 1366 return 0; 1367 1368 mutex_unlock(¤t->signal->cred_guard_mutex); 1369 return -ENOMEM; 1370 } 1371 1372 /* Matches do_open_execat() */ 1373 static void do_close_execat(struct file *file) 1374 { 1375 if (!file) 1376 return; 1377 exe_file_allow_write_access(file); 1378 fput(file); 1379 } 1380 1381 static void free_bprm(struct linux_binprm *bprm) 1382 { 1383 if (bprm->mm) { 1384 acct_arg_size(bprm, 0); 1385 mmput(bprm->mm); 1386 } 1387 free_arg_pages(bprm); 1388 if (bprm->cred) { 1389 /* in case exec fails before de_thread() succeeds */ 1390 current->fs->in_exec = 0; 1391 mutex_unlock(¤t->signal->cred_guard_mutex); 1392 abort_creds(bprm->cred); 1393 } 1394 do_close_execat(bprm->file); 1395 if (bprm->executable) 1396 fput(bprm->executable); 1397 /* If a binfmt changed the interp, free it. */ 1398 if (bprm->interp != bprm->filename) 1399 kfree(bprm->interp); 1400 kfree(bprm->fdpath); 1401 kfree(bprm); 1402 } 1403 1404 static struct linux_binprm *alloc_bprm(int fd, struct filename *filename, int flags) 1405 { 1406 struct linux_binprm *bprm; 1407 struct file *file; 1408 int retval = -ENOMEM; 1409 1410 file = do_open_execat(fd, filename, flags); 1411 if (IS_ERR(file)) 1412 return ERR_CAST(file); 1413 1414 bprm = kzalloc(sizeof(*bprm), GFP_KERNEL); 1415 if (!bprm) { 1416 do_close_execat(file); 1417 return ERR_PTR(-ENOMEM); 1418 } 1419 1420 bprm->file = file; 1421 1422 if (fd == AT_FDCWD || filename->name[0] == '/') { 1423 bprm->filename = filename->name; 1424 } else { 1425 if (filename->name[0] == '\0') { 1426 bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd); 1427 bprm->comm_from_dentry = 1; 1428 } else { 1429 bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s", 1430 fd, filename->name); 1431 } 1432 if (!bprm->fdpath) 1433 goto out_free; 1434 1435 /* 1436 * Record that a name derived from an O_CLOEXEC fd will be 1437 * inaccessible after exec. This allows the code in exec to 1438 * choose to fail when the executable is not mmaped into the 1439 * interpreter and an open file descriptor is not passed to 1440 * the interpreter. This makes for a better user experience 1441 * than having the interpreter start and then immediately fail 1442 * when it finds the executable is inaccessible. 1443 */ 1444 if (get_close_on_exec(fd)) 1445 bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE; 1446 1447 bprm->filename = bprm->fdpath; 1448 } 1449 bprm->interp = bprm->filename; 1450 1451 /* 1452 * At this point, security_file_open() has already been called (with 1453 * __FMODE_EXEC) and access control checks for AT_EXECVE_CHECK will 1454 * stop just after the security_bprm_creds_for_exec() call in 1455 * bprm_execve(). Indeed, the kernel should not try to parse the 1456 * content of the file with exec_binprm() nor change the calling 1457 * thread, which means that the following security functions will not 1458 * be called: 1459 * - security_bprm_check() 1460 * - security_bprm_creds_from_file() 1461 * - security_bprm_committing_creds() 1462 * - security_bprm_committed_creds() 1463 */ 1464 bprm->is_check = !!(flags & AT_EXECVE_CHECK); 1465 1466 retval = bprm_mm_init(bprm); 1467 if (!retval) 1468 return bprm; 1469 1470 out_free: 1471 free_bprm(bprm); 1472 return ERR_PTR(retval); 1473 } 1474 1475 int bprm_change_interp(const char *interp, struct linux_binprm *bprm) 1476 { 1477 /* If a binfmt changed the interp, free it first. */ 1478 if (bprm->interp != bprm->filename) 1479 kfree(bprm->interp); 1480 bprm->interp = kstrdup(interp, GFP_KERNEL); 1481 if (!bprm->interp) 1482 return -ENOMEM; 1483 return 0; 1484 } 1485 EXPORT_SYMBOL(bprm_change_interp); 1486 1487 /* 1488 * determine how safe it is to execute the proposed program 1489 * - the caller must hold ->cred_guard_mutex to protect against 1490 * PTRACE_ATTACH or seccomp thread-sync 1491 */ 1492 static void check_unsafe_exec(struct linux_binprm *bprm) 1493 { 1494 struct task_struct *p = current, *t; 1495 unsigned n_fs; 1496 1497 if (p->ptrace) 1498 bprm->unsafe |= LSM_UNSAFE_PTRACE; 1499 1500 /* 1501 * This isn't strictly necessary, but it makes it harder for LSMs to 1502 * mess up. 1503 */ 1504 if (task_no_new_privs(current)) 1505 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS; 1506 1507 /* 1508 * If another task is sharing our fs, we cannot safely 1509 * suid exec because the differently privileged task 1510 * will be able to manipulate the current directory, etc. 1511 * It would be nice to force an unshare instead... 1512 * 1513 * Otherwise we set fs->in_exec = 1 to deny clone(CLONE_FS) 1514 * from another sub-thread until de_thread() succeeds, this 1515 * state is protected by cred_guard_mutex we hold. 1516 */ 1517 n_fs = 1; 1518 read_seqlock_excl(&p->fs->seq); 1519 rcu_read_lock(); 1520 for_other_threads(p, t) { 1521 if (t->fs == p->fs) 1522 n_fs++; 1523 } 1524 rcu_read_unlock(); 1525 1526 /* "users" and "in_exec" locked for copy_fs() */ 1527 if (p->fs->users > n_fs) 1528 bprm->unsafe |= LSM_UNSAFE_SHARE; 1529 else 1530 p->fs->in_exec = 1; 1531 read_sequnlock_excl(&p->fs->seq); 1532 } 1533 1534 static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file) 1535 { 1536 /* Handle suid and sgid on files */ 1537 struct mnt_idmap *idmap; 1538 struct inode *inode = file_inode(file); 1539 unsigned int mode; 1540 vfsuid_t vfsuid; 1541 vfsgid_t vfsgid; 1542 int err; 1543 1544 if (!mnt_may_suid(file->f_path.mnt)) 1545 return; 1546 1547 if (task_no_new_privs(current)) 1548 return; 1549 1550 mode = READ_ONCE(inode->i_mode); 1551 if (!(mode & (S_ISUID|S_ISGID))) 1552 return; 1553 1554 idmap = file_mnt_idmap(file); 1555 1556 /* Be careful if suid/sgid is set */ 1557 inode_lock(inode); 1558 1559 /* Atomically reload and check mode/uid/gid now that lock held. */ 1560 mode = inode->i_mode; 1561 vfsuid = i_uid_into_vfsuid(idmap, inode); 1562 vfsgid = i_gid_into_vfsgid(idmap, inode); 1563 err = inode_permission(idmap, inode, MAY_EXEC); 1564 inode_unlock(inode); 1565 1566 /* Did the exec bit vanish out from under us? Give up. */ 1567 if (err) 1568 return; 1569 1570 /* We ignore suid/sgid if there are no mappings for them in the ns */ 1571 if (!vfsuid_has_mapping(bprm->cred->user_ns, vfsuid) || 1572 !vfsgid_has_mapping(bprm->cred->user_ns, vfsgid)) 1573 return; 1574 1575 if (mode & S_ISUID) { 1576 bprm->per_clear |= PER_CLEAR_ON_SETID; 1577 bprm->cred->euid = vfsuid_into_kuid(vfsuid); 1578 } 1579 1580 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { 1581 bprm->per_clear |= PER_CLEAR_ON_SETID; 1582 bprm->cred->egid = vfsgid_into_kgid(vfsgid); 1583 } 1584 } 1585 1586 /* 1587 * Compute brpm->cred based upon the final binary. 1588 */ 1589 static int bprm_creds_from_file(struct linux_binprm *bprm) 1590 { 1591 /* Compute creds based on which file? */ 1592 struct file *file = bprm->execfd_creds ? bprm->executable : bprm->file; 1593 1594 bprm_fill_uid(bprm, file); 1595 return security_bprm_creds_from_file(bprm, file); 1596 } 1597 1598 /* 1599 * Fill the binprm structure from the inode. 1600 * Read the first BINPRM_BUF_SIZE bytes 1601 * 1602 * This may be called multiple times for binary chains (scripts for example). 1603 */ 1604 static int prepare_binprm(struct linux_binprm *bprm) 1605 { 1606 loff_t pos = 0; 1607 1608 memset(bprm->buf, 0, BINPRM_BUF_SIZE); 1609 return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos); 1610 } 1611 1612 /* 1613 * Arguments are '\0' separated strings found at the location bprm->p 1614 * points to; chop off the first by relocating brpm->p to right after 1615 * the first '\0' encountered. 1616 */ 1617 int remove_arg_zero(struct linux_binprm *bprm) 1618 { 1619 unsigned long offset; 1620 char *kaddr; 1621 struct page *page; 1622 1623 if (!bprm->argc) 1624 return 0; 1625 1626 do { 1627 offset = bprm->p & ~PAGE_MASK; 1628 page = get_arg_page(bprm, bprm->p, 0); 1629 if (!page) 1630 return -EFAULT; 1631 kaddr = kmap_local_page(page); 1632 1633 for (; offset < PAGE_SIZE && kaddr[offset]; 1634 offset++, bprm->p++) 1635 ; 1636 1637 kunmap_local(kaddr); 1638 put_arg_page(page); 1639 } while (offset == PAGE_SIZE); 1640 1641 bprm->p++; 1642 bprm->argc--; 1643 1644 return 0; 1645 } 1646 EXPORT_SYMBOL(remove_arg_zero); 1647 1648 /* 1649 * cycle the list of binary formats handler, until one recognizes the image 1650 */ 1651 static int search_binary_handler(struct linux_binprm *bprm) 1652 { 1653 struct linux_binfmt *fmt; 1654 int retval; 1655 1656 retval = prepare_binprm(bprm); 1657 if (retval < 0) 1658 return retval; 1659 1660 retval = security_bprm_check(bprm); 1661 if (retval) 1662 return retval; 1663 1664 read_lock(&binfmt_lock); 1665 list_for_each_entry(fmt, &formats, lh) { 1666 if (!try_module_get(fmt->module)) 1667 continue; 1668 read_unlock(&binfmt_lock); 1669 1670 retval = fmt->load_binary(bprm); 1671 1672 read_lock(&binfmt_lock); 1673 put_binfmt(fmt); 1674 if (bprm->point_of_no_return || (retval != -ENOEXEC)) { 1675 read_unlock(&binfmt_lock); 1676 return retval; 1677 } 1678 } 1679 read_unlock(&binfmt_lock); 1680 1681 return -ENOEXEC; 1682 } 1683 1684 /* binfmt handlers will call back into begin_new_exec() on success. */ 1685 static int exec_binprm(struct linux_binprm *bprm) 1686 { 1687 pid_t old_pid, old_vpid; 1688 int ret, depth; 1689 1690 /* Need to fetch pid before load_binary changes it */ 1691 old_pid = current->pid; 1692 rcu_read_lock(); 1693 old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent)); 1694 rcu_read_unlock(); 1695 1696 /* This allows 4 levels of binfmt rewrites before failing hard. */ 1697 for (depth = 0;; depth++) { 1698 struct file *exec; 1699 if (depth > 5) 1700 return -ELOOP; 1701 1702 ret = search_binary_handler(bprm); 1703 if (ret < 0) 1704 return ret; 1705 if (!bprm->interpreter) 1706 break; 1707 1708 exec = bprm->file; 1709 bprm->file = bprm->interpreter; 1710 bprm->interpreter = NULL; 1711 1712 exe_file_allow_write_access(exec); 1713 if (unlikely(bprm->have_execfd)) { 1714 if (bprm->executable) { 1715 fput(exec); 1716 return -ENOEXEC; 1717 } 1718 bprm->executable = exec; 1719 } else 1720 fput(exec); 1721 } 1722 1723 audit_bprm(bprm); 1724 trace_sched_process_exec(current, old_pid, bprm); 1725 ptrace_event(PTRACE_EVENT_EXEC, old_vpid); 1726 proc_exec_connector(current); 1727 return 0; 1728 } 1729 1730 static int bprm_execve(struct linux_binprm *bprm) 1731 { 1732 int retval; 1733 1734 retval = prepare_bprm_creds(bprm); 1735 if (retval) 1736 return retval; 1737 1738 /* 1739 * Check for unsafe execution states before exec_binprm(), which 1740 * will call back into begin_new_exec(), into bprm_creds_from_file(), 1741 * where setuid-ness is evaluated. 1742 */ 1743 check_unsafe_exec(bprm); 1744 current->in_execve = 1; 1745 sched_mm_cid_before_execve(current); 1746 1747 sched_exec(); 1748 1749 /* Set the unchanging part of bprm->cred */ 1750 retval = security_bprm_creds_for_exec(bprm); 1751 if (retval || bprm->is_check) 1752 goto out; 1753 1754 retval = exec_binprm(bprm); 1755 if (retval < 0) 1756 goto out; 1757 1758 sched_mm_cid_after_execve(current); 1759 rseq_execve(current); 1760 /* execve succeeded */ 1761 current->in_execve = 0; 1762 user_events_execve(current); 1763 acct_update_integrals(current); 1764 task_numa_free(current, false); 1765 return retval; 1766 1767 out: 1768 /* 1769 * If past the point of no return ensure the code never 1770 * returns to the userspace process. Use an existing fatal 1771 * signal if present otherwise terminate the process with 1772 * SIGSEGV. 1773 */ 1774 if (bprm->point_of_no_return && !fatal_signal_pending(current)) 1775 force_fatal_sig(SIGSEGV); 1776 1777 sched_mm_cid_after_execve(current); 1778 rseq_set_notify_resume(current); 1779 current->in_execve = 0; 1780 1781 return retval; 1782 } 1783 1784 static int do_execveat_common(int fd, struct filename *filename, 1785 struct user_arg_ptr argv, 1786 struct user_arg_ptr envp, 1787 int flags) 1788 { 1789 struct linux_binprm *bprm; 1790 int retval; 1791 1792 if (IS_ERR(filename)) 1793 return PTR_ERR(filename); 1794 1795 /* 1796 * We move the actual failure in case of RLIMIT_NPROC excess from 1797 * set*uid() to execve() because too many poorly written programs 1798 * don't check setuid() return code. Here we additionally recheck 1799 * whether NPROC limit is still exceeded. 1800 */ 1801 if ((current->flags & PF_NPROC_EXCEEDED) && 1802 is_rlimit_overlimit(current_ucounts(), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) { 1803 retval = -EAGAIN; 1804 goto out_ret; 1805 } 1806 1807 /* We're below the limit (still or again), so we don't want to make 1808 * further execve() calls fail. */ 1809 current->flags &= ~PF_NPROC_EXCEEDED; 1810 1811 bprm = alloc_bprm(fd, filename, flags); 1812 if (IS_ERR(bprm)) { 1813 retval = PTR_ERR(bprm); 1814 goto out_ret; 1815 } 1816 1817 retval = count(argv, MAX_ARG_STRINGS); 1818 if (retval < 0) 1819 goto out_free; 1820 bprm->argc = retval; 1821 1822 retval = count(envp, MAX_ARG_STRINGS); 1823 if (retval < 0) 1824 goto out_free; 1825 bprm->envc = retval; 1826 1827 retval = bprm_stack_limits(bprm); 1828 if (retval < 0) 1829 goto out_free; 1830 1831 retval = copy_string_kernel(bprm->filename, bprm); 1832 if (retval < 0) 1833 goto out_free; 1834 bprm->exec = bprm->p; 1835 1836 retval = copy_strings(bprm->envc, envp, bprm); 1837 if (retval < 0) 1838 goto out_free; 1839 1840 retval = copy_strings(bprm->argc, argv, bprm); 1841 if (retval < 0) 1842 goto out_free; 1843 1844 /* 1845 * When argv is empty, add an empty string ("") as argv[0] to 1846 * ensure confused userspace programs that start processing 1847 * from argv[1] won't end up walking envp. See also 1848 * bprm_stack_limits(). 1849 */ 1850 if (bprm->argc == 0) { 1851 retval = copy_string_kernel("", bprm); 1852 if (retval < 0) 1853 goto out_free; 1854 bprm->argc = 1; 1855 1856 pr_warn_once("process '%s' launched '%s' with NULL argv: empty string added\n", 1857 current->comm, bprm->filename); 1858 } 1859 1860 retval = bprm_execve(bprm); 1861 out_free: 1862 free_bprm(bprm); 1863 1864 out_ret: 1865 putname(filename); 1866 return retval; 1867 } 1868 1869 int kernel_execve(const char *kernel_filename, 1870 const char *const *argv, const char *const *envp) 1871 { 1872 struct filename *filename; 1873 struct linux_binprm *bprm; 1874 int fd = AT_FDCWD; 1875 int retval; 1876 1877 /* It is non-sense for kernel threads to call execve */ 1878 if (WARN_ON_ONCE(current->flags & PF_KTHREAD)) 1879 return -EINVAL; 1880 1881 filename = getname_kernel(kernel_filename); 1882 if (IS_ERR(filename)) 1883 return PTR_ERR(filename); 1884 1885 bprm = alloc_bprm(fd, filename, 0); 1886 if (IS_ERR(bprm)) { 1887 retval = PTR_ERR(bprm); 1888 goto out_ret; 1889 } 1890 1891 retval = count_strings_kernel(argv); 1892 if (WARN_ON_ONCE(retval == 0)) 1893 retval = -EINVAL; 1894 if (retval < 0) 1895 goto out_free; 1896 bprm->argc = retval; 1897 1898 retval = count_strings_kernel(envp); 1899 if (retval < 0) 1900 goto out_free; 1901 bprm->envc = retval; 1902 1903 retval = bprm_stack_limits(bprm); 1904 if (retval < 0) 1905 goto out_free; 1906 1907 retval = copy_string_kernel(bprm->filename, bprm); 1908 if (retval < 0) 1909 goto out_free; 1910 bprm->exec = bprm->p; 1911 1912 retval = copy_strings_kernel(bprm->envc, envp, bprm); 1913 if (retval < 0) 1914 goto out_free; 1915 1916 retval = copy_strings_kernel(bprm->argc, argv, bprm); 1917 if (retval < 0) 1918 goto out_free; 1919 1920 retval = bprm_execve(bprm); 1921 out_free: 1922 free_bprm(bprm); 1923 out_ret: 1924 putname(filename); 1925 return retval; 1926 } 1927 1928 static int do_execve(struct filename *filename, 1929 const char __user *const __user *__argv, 1930 const char __user *const __user *__envp) 1931 { 1932 struct user_arg_ptr argv = { .ptr.native = __argv }; 1933 struct user_arg_ptr envp = { .ptr.native = __envp }; 1934 return do_execveat_common(AT_FDCWD, filename, argv, envp, 0); 1935 } 1936 1937 static int do_execveat(int fd, struct filename *filename, 1938 const char __user *const __user *__argv, 1939 const char __user *const __user *__envp, 1940 int flags) 1941 { 1942 struct user_arg_ptr argv = { .ptr.native = __argv }; 1943 struct user_arg_ptr envp = { .ptr.native = __envp }; 1944 1945 return do_execveat_common(fd, filename, argv, envp, flags); 1946 } 1947 1948 #ifdef CONFIG_COMPAT 1949 static int compat_do_execve(struct filename *filename, 1950 const compat_uptr_t __user *__argv, 1951 const compat_uptr_t __user *__envp) 1952 { 1953 struct user_arg_ptr argv = { 1954 .is_compat = true, 1955 .ptr.compat = __argv, 1956 }; 1957 struct user_arg_ptr envp = { 1958 .is_compat = true, 1959 .ptr.compat = __envp, 1960 }; 1961 return do_execveat_common(AT_FDCWD, filename, argv, envp, 0); 1962 } 1963 1964 static int compat_do_execveat(int fd, struct filename *filename, 1965 const compat_uptr_t __user *__argv, 1966 const compat_uptr_t __user *__envp, 1967 int flags) 1968 { 1969 struct user_arg_ptr argv = { 1970 .is_compat = true, 1971 .ptr.compat = __argv, 1972 }; 1973 struct user_arg_ptr envp = { 1974 .is_compat = true, 1975 .ptr.compat = __envp, 1976 }; 1977 return do_execveat_common(fd, filename, argv, envp, flags); 1978 } 1979 #endif 1980 1981 void set_binfmt(struct linux_binfmt *new) 1982 { 1983 struct mm_struct *mm = current->mm; 1984 1985 if (mm->binfmt) 1986 module_put(mm->binfmt->module); 1987 1988 mm->binfmt = new; 1989 if (new) 1990 __module_get(new->module); 1991 } 1992 EXPORT_SYMBOL(set_binfmt); 1993 1994 /* 1995 * set_dumpable stores three-value SUID_DUMP_* into mm->flags. 1996 */ 1997 void set_dumpable(struct mm_struct *mm, int value) 1998 { 1999 if (WARN_ON((unsigned)value > SUID_DUMP_ROOT)) 2000 return; 2001 2002 __mm_flags_set_mask_dumpable(mm, value); 2003 } 2004 2005 SYSCALL_DEFINE3(execve, 2006 const char __user *, filename, 2007 const char __user *const __user *, argv, 2008 const char __user *const __user *, envp) 2009 { 2010 return do_execve(getname(filename), argv, envp); 2011 } 2012 2013 SYSCALL_DEFINE5(execveat, 2014 int, fd, const char __user *, filename, 2015 const char __user *const __user *, argv, 2016 const char __user *const __user *, envp, 2017 int, flags) 2018 { 2019 return do_execveat(fd, 2020 getname_uflags(filename, flags), 2021 argv, envp, flags); 2022 } 2023 2024 #ifdef CONFIG_COMPAT 2025 COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename, 2026 const compat_uptr_t __user *, argv, 2027 const compat_uptr_t __user *, envp) 2028 { 2029 return compat_do_execve(getname(filename), argv, envp); 2030 } 2031 2032 COMPAT_SYSCALL_DEFINE5(execveat, int, fd, 2033 const char __user *, filename, 2034 const compat_uptr_t __user *, argv, 2035 const compat_uptr_t __user *, envp, 2036 int, flags) 2037 { 2038 return compat_do_execveat(fd, 2039 getname_uflags(filename, flags), 2040 argv, envp, flags); 2041 } 2042 #endif 2043 2044 #ifdef CONFIG_SYSCTL 2045 2046 static int proc_dointvec_minmax_coredump(const struct ctl_table *table, int write, 2047 void *buffer, size_t *lenp, loff_t *ppos) 2048 { 2049 int error = proc_dointvec_minmax(table, write, buffer, lenp, ppos); 2050 2051 if (!error && write) 2052 validate_coredump_safety(); 2053 return error; 2054 } 2055 2056 static const struct ctl_table fs_exec_sysctls[] = { 2057 { 2058 .procname = "suid_dumpable", 2059 .data = &suid_dumpable, 2060 .maxlen = sizeof(int), 2061 .mode = 0644, 2062 .proc_handler = proc_dointvec_minmax_coredump, 2063 .extra1 = SYSCTL_ZERO, 2064 .extra2 = SYSCTL_TWO, 2065 }, 2066 }; 2067 2068 static int __init init_fs_exec_sysctls(void) 2069 { 2070 register_sysctl_init("fs", fs_exec_sysctls); 2071 return 0; 2072 } 2073 2074 fs_initcall(init_fs_exec_sysctls); 2075 #endif /* CONFIG_SYSCTL */ 2076 2077 #ifdef CONFIG_EXEC_KUNIT_TEST 2078 #include "tests/exec_kunit.c" 2079 #endif