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/vmacache.h> 30 #include <linux/stat.h> 31 #include <linux/fcntl.h> 32 #include <linux/swap.h> 33 #include <linux/string.h> 34 #include <linux/init.h> 35 #include <linux/sched/mm.h> 36 #include <linux/sched/coredump.h> 37 #include <linux/sched/signal.h> 38 #include <linux/sched/numa_balancing.h> 39 #include <linux/sched/task.h> 40 #include <linux/pagemap.h> 41 #include <linux/perf_event.h> 42 #include <linux/highmem.h> 43 #include <linux/spinlock.h> 44 #include <linux/key.h> 45 #include <linux/personality.h> 46 #include <linux/binfmts.h> 47 #include <linux/utsname.h> 48 #include <linux/pid_namespace.h> 49 #include <linux/module.h> 50 #include <linux/namei.h> 51 #include <linux/mount.h> 52 #include <linux/security.h> 53 #include <linux/syscalls.h> 54 #include <linux/tsacct_kern.h> 55 #include <linux/cn_proc.h> 56 #include <linux/audit.h> 57 #include <linux/tracehook.h> 58 #include <linux/kmod.h> 59 #include <linux/fsnotify.h> 60 #include <linux/fs_struct.h> 61 #include <linux/pipe_fs_i.h> 62 #include <linux/oom.h> 63 #include <linux/compat.h> 64 #include <linux/vmalloc.h> 65 66 #include <linux/uaccess.h> 67 #include <asm/mmu_context.h> 68 #include <asm/tlb.h> 69 70 #include <trace/events/task.h> 71 #include "internal.h" 72 73 #include <trace/events/sched.h> 74 75 int suid_dumpable = 0; 76 77 static LIST_HEAD(formats); 78 static DEFINE_RWLOCK(binfmt_lock); 79 80 void __register_binfmt(struct linux_binfmt * fmt, int insert) 81 { 82 BUG_ON(!fmt); 83 if (WARN_ON(!fmt->load_binary)) 84 return; 85 write_lock(&binfmt_lock); 86 insert ? list_add(&fmt->lh, &formats) : 87 list_add_tail(&fmt->lh, &formats); 88 write_unlock(&binfmt_lock); 89 } 90 91 EXPORT_SYMBOL(__register_binfmt); 92 93 void unregister_binfmt(struct linux_binfmt * fmt) 94 { 95 write_lock(&binfmt_lock); 96 list_del(&fmt->lh); 97 write_unlock(&binfmt_lock); 98 } 99 100 EXPORT_SYMBOL(unregister_binfmt); 101 102 static inline void put_binfmt(struct linux_binfmt * fmt) 103 { 104 module_put(fmt->module); 105 } 106 107 bool path_noexec(const struct path *path) 108 { 109 return (path->mnt->mnt_flags & MNT_NOEXEC) || 110 (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC); 111 } 112 113 #ifdef CONFIG_USELIB 114 /* 115 * Note that a shared library must be both readable and executable due to 116 * security reasons. 117 * 118 * Also note that we take the address to load from from the file itself. 119 */ 120 SYSCALL_DEFINE1(uselib, const char __user *, library) 121 { 122 struct linux_binfmt *fmt; 123 struct file *file; 124 struct filename *tmp = getname(library); 125 int error = PTR_ERR(tmp); 126 static const struct open_flags uselib_flags = { 127 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC, 128 .acc_mode = MAY_READ | MAY_EXEC, 129 .intent = LOOKUP_OPEN, 130 .lookup_flags = LOOKUP_FOLLOW, 131 }; 132 133 if (IS_ERR(tmp)) 134 goto out; 135 136 file = do_filp_open(AT_FDCWD, tmp, &uselib_flags); 137 putname(tmp); 138 error = PTR_ERR(file); 139 if (IS_ERR(file)) 140 goto out; 141 142 error = -EINVAL; 143 if (!S_ISREG(file_inode(file)->i_mode)) 144 goto exit; 145 146 error = -EACCES; 147 if (path_noexec(&file->f_path)) 148 goto exit; 149 150 fsnotify_open(file); 151 152 error = -ENOEXEC; 153 154 read_lock(&binfmt_lock); 155 list_for_each_entry(fmt, &formats, lh) { 156 if (!fmt->load_shlib) 157 continue; 158 if (!try_module_get(fmt->module)) 159 continue; 160 read_unlock(&binfmt_lock); 161 error = fmt->load_shlib(file); 162 read_lock(&binfmt_lock); 163 put_binfmt(fmt); 164 if (error != -ENOEXEC) 165 break; 166 } 167 read_unlock(&binfmt_lock); 168 exit: 169 fput(file); 170 out: 171 return error; 172 } 173 #endif /* #ifdef CONFIG_USELIB */ 174 175 #ifdef CONFIG_MMU 176 /* 177 * The nascent bprm->mm is not visible until exec_mmap() but it can 178 * use a lot of memory, account these pages in current->mm temporary 179 * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we 180 * change the counter back via acct_arg_size(0). 181 */ 182 static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages) 183 { 184 struct mm_struct *mm = current->mm; 185 long diff = (long)(pages - bprm->vma_pages); 186 187 if (!mm || !diff) 188 return; 189 190 bprm->vma_pages = pages; 191 add_mm_counter(mm, MM_ANONPAGES, diff); 192 } 193 194 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, 195 int write) 196 { 197 struct page *page; 198 int ret; 199 unsigned int gup_flags = FOLL_FORCE; 200 201 #ifdef CONFIG_STACK_GROWSUP 202 if (write) { 203 ret = expand_downwards(bprm->vma, pos); 204 if (ret < 0) 205 return NULL; 206 } 207 #endif 208 209 if (write) 210 gup_flags |= FOLL_WRITE; 211 212 /* 213 * We are doing an exec(). 'current' is the process 214 * doing the exec and bprm->mm is the new process's mm. 215 */ 216 ret = get_user_pages_remote(current, bprm->mm, pos, 1, gup_flags, 217 &page, NULL, NULL); 218 if (ret <= 0) 219 return NULL; 220 221 if (write) { 222 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start; 223 unsigned long ptr_size, limit; 224 225 /* 226 * Since the stack will hold pointers to the strings, we 227 * must account for them as well. 228 * 229 * The size calculation is the entire vma while each arg page is 230 * built, so each time we get here it's calculating how far it 231 * is currently (rather than each call being just the newly 232 * added size from the arg page). As a result, we need to 233 * always add the entire size of the pointers, so that on the 234 * last call to get_arg_page() we'll actually have the entire 235 * correct size. 236 */ 237 ptr_size = (bprm->argc + bprm->envc) * sizeof(void *); 238 if (ptr_size > ULONG_MAX - size) 239 goto fail; 240 size += ptr_size; 241 242 acct_arg_size(bprm, size / PAGE_SIZE); 243 244 /* 245 * We've historically supported up to 32 pages (ARG_MAX) 246 * of argument strings even with small stacks 247 */ 248 if (size <= ARG_MAX) 249 return page; 250 251 /* 252 * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM 253 * (whichever is smaller) for the argv+env strings. 254 * This ensures that: 255 * - the remaining binfmt code will not run out of stack space, 256 * - the program will have a reasonable amount of stack left 257 * to work from. 258 */ 259 limit = _STK_LIM / 4 * 3; 260 limit = min(limit, rlimit(RLIMIT_STACK) / 4); 261 if (size > limit) 262 goto fail; 263 } 264 265 return page; 266 267 fail: 268 put_page(page); 269 return NULL; 270 } 271 272 static void put_arg_page(struct page *page) 273 { 274 put_page(page); 275 } 276 277 static void free_arg_pages(struct linux_binprm *bprm) 278 { 279 } 280 281 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, 282 struct page *page) 283 { 284 flush_cache_page(bprm->vma, pos, page_to_pfn(page)); 285 } 286 287 static int __bprm_mm_init(struct linux_binprm *bprm) 288 { 289 int err; 290 struct vm_area_struct *vma = NULL; 291 struct mm_struct *mm = bprm->mm; 292 293 bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL); 294 if (!vma) 295 return -ENOMEM; 296 297 if (down_write_killable(&mm->mmap_sem)) { 298 err = -EINTR; 299 goto err_free; 300 } 301 vma->vm_mm = mm; 302 303 /* 304 * Place the stack at the largest stack address the architecture 305 * supports. Later, we'll move this to an appropriate place. We don't 306 * use STACK_TOP because that can depend on attributes which aren't 307 * configured yet. 308 */ 309 BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP); 310 vma->vm_end = STACK_TOP_MAX; 311 vma->vm_start = vma->vm_end - PAGE_SIZE; 312 vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP; 313 vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); 314 INIT_LIST_HEAD(&vma->anon_vma_chain); 315 316 err = insert_vm_struct(mm, vma); 317 if (err) 318 goto err; 319 320 mm->stack_vm = mm->total_vm = 1; 321 arch_bprm_mm_init(mm, vma); 322 up_write(&mm->mmap_sem); 323 bprm->p = vma->vm_end - sizeof(void *); 324 return 0; 325 err: 326 up_write(&mm->mmap_sem); 327 err_free: 328 bprm->vma = NULL; 329 kmem_cache_free(vm_area_cachep, vma); 330 return err; 331 } 332 333 static bool valid_arg_len(struct linux_binprm *bprm, long len) 334 { 335 return len <= MAX_ARG_STRLEN; 336 } 337 338 #else 339 340 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages) 341 { 342 } 343 344 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, 345 int write) 346 { 347 struct page *page; 348 349 page = bprm->page[pos / PAGE_SIZE]; 350 if (!page && write) { 351 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO); 352 if (!page) 353 return NULL; 354 bprm->page[pos / PAGE_SIZE] = page; 355 } 356 357 return page; 358 } 359 360 static void put_arg_page(struct page *page) 361 { 362 } 363 364 static void free_arg_page(struct linux_binprm *bprm, int i) 365 { 366 if (bprm->page[i]) { 367 __free_page(bprm->page[i]); 368 bprm->page[i] = NULL; 369 } 370 } 371 372 static void free_arg_pages(struct linux_binprm *bprm) 373 { 374 int i; 375 376 for (i = 0; i < MAX_ARG_PAGES; i++) 377 free_arg_page(bprm, i); 378 } 379 380 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, 381 struct page *page) 382 { 383 } 384 385 static int __bprm_mm_init(struct linux_binprm *bprm) 386 { 387 bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *); 388 return 0; 389 } 390 391 static bool valid_arg_len(struct linux_binprm *bprm, long len) 392 { 393 return len <= bprm->p; 394 } 395 396 #endif /* CONFIG_MMU */ 397 398 /* 399 * Create a new mm_struct and populate it with a temporary stack 400 * vm_area_struct. We don't have enough context at this point to set the stack 401 * flags, permissions, and offset, so we use temporary values. We'll update 402 * them later in setup_arg_pages(). 403 */ 404 static int bprm_mm_init(struct linux_binprm *bprm) 405 { 406 int err; 407 struct mm_struct *mm = NULL; 408 409 bprm->mm = mm = mm_alloc(); 410 err = -ENOMEM; 411 if (!mm) 412 goto err; 413 414 err = __bprm_mm_init(bprm); 415 if (err) 416 goto err; 417 418 return 0; 419 420 err: 421 if (mm) { 422 bprm->mm = NULL; 423 mmdrop(mm); 424 } 425 426 return err; 427 } 428 429 struct user_arg_ptr { 430 #ifdef CONFIG_COMPAT 431 bool is_compat; 432 #endif 433 union { 434 const char __user *const __user *native; 435 #ifdef CONFIG_COMPAT 436 const compat_uptr_t __user *compat; 437 #endif 438 } ptr; 439 }; 440 441 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr) 442 { 443 const char __user *native; 444 445 #ifdef CONFIG_COMPAT 446 if (unlikely(argv.is_compat)) { 447 compat_uptr_t compat; 448 449 if (get_user(compat, argv.ptr.compat + nr)) 450 return ERR_PTR(-EFAULT); 451 452 return compat_ptr(compat); 453 } 454 #endif 455 456 if (get_user(native, argv.ptr.native + nr)) 457 return ERR_PTR(-EFAULT); 458 459 return native; 460 } 461 462 /* 463 * count() counts the number of strings in array ARGV. 464 */ 465 static int count(struct user_arg_ptr argv, int max) 466 { 467 int i = 0; 468 469 if (argv.ptr.native != NULL) { 470 for (;;) { 471 const char __user *p = get_user_arg_ptr(argv, i); 472 473 if (!p) 474 break; 475 476 if (IS_ERR(p)) 477 return -EFAULT; 478 479 if (i >= max) 480 return -E2BIG; 481 ++i; 482 483 if (fatal_signal_pending(current)) 484 return -ERESTARTNOHAND; 485 cond_resched(); 486 } 487 } 488 return i; 489 } 490 491 /* 492 * 'copy_strings()' copies argument/environment strings from the old 493 * processes's memory to the new process's stack. The call to get_user_pages() 494 * ensures the destination page is created and not swapped out. 495 */ 496 static int copy_strings(int argc, struct user_arg_ptr argv, 497 struct linux_binprm *bprm) 498 { 499 struct page *kmapped_page = NULL; 500 char *kaddr = NULL; 501 unsigned long kpos = 0; 502 int ret; 503 504 while (argc-- > 0) { 505 const char __user *str; 506 int len; 507 unsigned long pos; 508 509 ret = -EFAULT; 510 str = get_user_arg_ptr(argv, argc); 511 if (IS_ERR(str)) 512 goto out; 513 514 len = strnlen_user(str, MAX_ARG_STRLEN); 515 if (!len) 516 goto out; 517 518 ret = -E2BIG; 519 if (!valid_arg_len(bprm, len)) 520 goto out; 521 522 /* We're going to work our way backwords. */ 523 pos = bprm->p; 524 str += len; 525 bprm->p -= len; 526 527 while (len > 0) { 528 int offset, bytes_to_copy; 529 530 if (fatal_signal_pending(current)) { 531 ret = -ERESTARTNOHAND; 532 goto out; 533 } 534 cond_resched(); 535 536 offset = pos % PAGE_SIZE; 537 if (offset == 0) 538 offset = PAGE_SIZE; 539 540 bytes_to_copy = offset; 541 if (bytes_to_copy > len) 542 bytes_to_copy = len; 543 544 offset -= bytes_to_copy; 545 pos -= bytes_to_copy; 546 str -= bytes_to_copy; 547 len -= bytes_to_copy; 548 549 if (!kmapped_page || kpos != (pos & PAGE_MASK)) { 550 struct page *page; 551 552 page = get_arg_page(bprm, pos, 1); 553 if (!page) { 554 ret = -E2BIG; 555 goto out; 556 } 557 558 if (kmapped_page) { 559 flush_kernel_dcache_page(kmapped_page); 560 kunmap(kmapped_page); 561 put_arg_page(kmapped_page); 562 } 563 kmapped_page = page; 564 kaddr = kmap(kmapped_page); 565 kpos = pos & PAGE_MASK; 566 flush_arg_page(bprm, kpos, kmapped_page); 567 } 568 if (copy_from_user(kaddr+offset, str, bytes_to_copy)) { 569 ret = -EFAULT; 570 goto out; 571 } 572 } 573 } 574 ret = 0; 575 out: 576 if (kmapped_page) { 577 flush_kernel_dcache_page(kmapped_page); 578 kunmap(kmapped_page); 579 put_arg_page(kmapped_page); 580 } 581 return ret; 582 } 583 584 /* 585 * Like copy_strings, but get argv and its values from kernel memory. 586 */ 587 int copy_strings_kernel(int argc, const char *const *__argv, 588 struct linux_binprm *bprm) 589 { 590 int r; 591 mm_segment_t oldfs = get_fs(); 592 struct user_arg_ptr argv = { 593 .ptr.native = (const char __user *const __user *)__argv, 594 }; 595 596 set_fs(KERNEL_DS); 597 r = copy_strings(argc, argv, bprm); 598 set_fs(oldfs); 599 600 return r; 601 } 602 EXPORT_SYMBOL(copy_strings_kernel); 603 604 #ifdef CONFIG_MMU 605 606 /* 607 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once 608 * the binfmt code determines where the new stack should reside, we shift it to 609 * its final location. The process proceeds as follows: 610 * 611 * 1) Use shift to calculate the new vma endpoints. 612 * 2) Extend vma to cover both the old and new ranges. This ensures the 613 * arguments passed to subsequent functions are consistent. 614 * 3) Move vma's page tables to the new range. 615 * 4) Free up any cleared pgd range. 616 * 5) Shrink the vma to cover only the new range. 617 */ 618 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift) 619 { 620 struct mm_struct *mm = vma->vm_mm; 621 unsigned long old_start = vma->vm_start; 622 unsigned long old_end = vma->vm_end; 623 unsigned long length = old_end - old_start; 624 unsigned long new_start = old_start - shift; 625 unsigned long new_end = old_end - shift; 626 struct mmu_gather tlb; 627 628 BUG_ON(new_start > new_end); 629 630 /* 631 * ensure there are no vmas between where we want to go 632 * and where we are 633 */ 634 if (vma != find_vma(mm, new_start)) 635 return -EFAULT; 636 637 /* 638 * cover the whole range: [new_start, old_end) 639 */ 640 if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL)) 641 return -ENOMEM; 642 643 /* 644 * move the page tables downwards, on failure we rely on 645 * process cleanup to remove whatever mess we made. 646 */ 647 if (length != move_page_tables(vma, old_start, 648 vma, new_start, length, false)) 649 return -ENOMEM; 650 651 lru_add_drain(); 652 tlb_gather_mmu(&tlb, mm, old_start, old_end); 653 if (new_end > old_start) { 654 /* 655 * when the old and new regions overlap clear from new_end. 656 */ 657 free_pgd_range(&tlb, new_end, old_end, new_end, 658 vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING); 659 } else { 660 /* 661 * otherwise, clean from old_start; this is done to not touch 662 * the address space in [new_end, old_start) some architectures 663 * have constraints on va-space that make this illegal (IA64) - 664 * for the others its just a little faster. 665 */ 666 free_pgd_range(&tlb, old_start, old_end, new_end, 667 vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING); 668 } 669 tlb_finish_mmu(&tlb, old_start, old_end); 670 671 /* 672 * Shrink the vma to just the new range. Always succeeds. 673 */ 674 vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL); 675 676 return 0; 677 } 678 679 /* 680 * Finalizes the stack vm_area_struct. The flags and permissions are updated, 681 * the stack is optionally relocated, and some extra space is added. 682 */ 683 int setup_arg_pages(struct linux_binprm *bprm, 684 unsigned long stack_top, 685 int executable_stack) 686 { 687 unsigned long ret; 688 unsigned long stack_shift; 689 struct mm_struct *mm = current->mm; 690 struct vm_area_struct *vma = bprm->vma; 691 struct vm_area_struct *prev = NULL; 692 unsigned long vm_flags; 693 unsigned long stack_base; 694 unsigned long stack_size; 695 unsigned long stack_expand; 696 unsigned long rlim_stack; 697 698 #ifdef CONFIG_STACK_GROWSUP 699 /* Limit stack size */ 700 stack_base = rlimit_max(RLIMIT_STACK); 701 if (stack_base > STACK_SIZE_MAX) 702 stack_base = STACK_SIZE_MAX; 703 704 /* Add space for stack randomization. */ 705 stack_base += (STACK_RND_MASK << PAGE_SHIFT); 706 707 /* Make sure we didn't let the argument array grow too large. */ 708 if (vma->vm_end - vma->vm_start > stack_base) 709 return -ENOMEM; 710 711 stack_base = PAGE_ALIGN(stack_top - stack_base); 712 713 stack_shift = vma->vm_start - stack_base; 714 mm->arg_start = bprm->p - stack_shift; 715 bprm->p = vma->vm_end - stack_shift; 716 #else 717 stack_top = arch_align_stack(stack_top); 718 stack_top = PAGE_ALIGN(stack_top); 719 720 if (unlikely(stack_top < mmap_min_addr) || 721 unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr)) 722 return -ENOMEM; 723 724 stack_shift = vma->vm_end - stack_top; 725 726 bprm->p -= stack_shift; 727 mm->arg_start = bprm->p; 728 #endif 729 730 if (bprm->loader) 731 bprm->loader -= stack_shift; 732 bprm->exec -= stack_shift; 733 734 if (down_write_killable(&mm->mmap_sem)) 735 return -EINTR; 736 737 vm_flags = VM_STACK_FLAGS; 738 739 /* 740 * Adjust stack execute permissions; explicitly enable for 741 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone 742 * (arch default) otherwise. 743 */ 744 if (unlikely(executable_stack == EXSTACK_ENABLE_X)) 745 vm_flags |= VM_EXEC; 746 else if (executable_stack == EXSTACK_DISABLE_X) 747 vm_flags &= ~VM_EXEC; 748 vm_flags |= mm->def_flags; 749 vm_flags |= VM_STACK_INCOMPLETE_SETUP; 750 751 ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end, 752 vm_flags); 753 if (ret) 754 goto out_unlock; 755 BUG_ON(prev != vma); 756 757 /* Move stack pages down in memory. */ 758 if (stack_shift) { 759 ret = shift_arg_pages(vma, stack_shift); 760 if (ret) 761 goto out_unlock; 762 } 763 764 /* mprotect_fixup is overkill to remove the temporary stack flags */ 765 vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP; 766 767 stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */ 768 stack_size = vma->vm_end - vma->vm_start; 769 /* 770 * Align this down to a page boundary as expand_stack 771 * will align it up. 772 */ 773 rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK; 774 #ifdef CONFIG_STACK_GROWSUP 775 if (stack_size + stack_expand > rlim_stack) 776 stack_base = vma->vm_start + rlim_stack; 777 else 778 stack_base = vma->vm_end + stack_expand; 779 #else 780 if (stack_size + stack_expand > rlim_stack) 781 stack_base = vma->vm_end - rlim_stack; 782 else 783 stack_base = vma->vm_start - stack_expand; 784 #endif 785 current->mm->start_stack = bprm->p; 786 ret = expand_stack(vma, stack_base); 787 if (ret) 788 ret = -EFAULT; 789 790 out_unlock: 791 up_write(&mm->mmap_sem); 792 return ret; 793 } 794 EXPORT_SYMBOL(setup_arg_pages); 795 796 #else 797 798 /* 799 * Transfer the program arguments and environment from the holding pages 800 * onto the stack. The provided stack pointer is adjusted accordingly. 801 */ 802 int transfer_args_to_stack(struct linux_binprm *bprm, 803 unsigned long *sp_location) 804 { 805 unsigned long index, stop, sp; 806 int ret = 0; 807 808 stop = bprm->p >> PAGE_SHIFT; 809 sp = *sp_location; 810 811 for (index = MAX_ARG_PAGES - 1; index >= stop; index--) { 812 unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0; 813 char *src = kmap(bprm->page[index]) + offset; 814 sp -= PAGE_SIZE - offset; 815 if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0) 816 ret = -EFAULT; 817 kunmap(bprm->page[index]); 818 if (ret) 819 goto out; 820 } 821 822 *sp_location = sp; 823 824 out: 825 return ret; 826 } 827 EXPORT_SYMBOL(transfer_args_to_stack); 828 829 #endif /* CONFIG_MMU */ 830 831 static struct file *do_open_execat(int fd, struct filename *name, int flags) 832 { 833 struct file *file; 834 int err; 835 struct open_flags open_exec_flags = { 836 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC, 837 .acc_mode = MAY_EXEC, 838 .intent = LOOKUP_OPEN, 839 .lookup_flags = LOOKUP_FOLLOW, 840 }; 841 842 if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0) 843 return ERR_PTR(-EINVAL); 844 if (flags & AT_SYMLINK_NOFOLLOW) 845 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW; 846 if (flags & AT_EMPTY_PATH) 847 open_exec_flags.lookup_flags |= LOOKUP_EMPTY; 848 849 file = do_filp_open(fd, name, &open_exec_flags); 850 if (IS_ERR(file)) 851 goto out; 852 853 err = -EACCES; 854 if (!S_ISREG(file_inode(file)->i_mode)) 855 goto exit; 856 857 if (path_noexec(&file->f_path)) 858 goto exit; 859 860 err = deny_write_access(file); 861 if (err) 862 goto exit; 863 864 if (name->name[0] != '\0') 865 fsnotify_open(file); 866 867 out: 868 return file; 869 870 exit: 871 fput(file); 872 return ERR_PTR(err); 873 } 874 875 struct file *open_exec(const char *name) 876 { 877 struct filename *filename = getname_kernel(name); 878 struct file *f = ERR_CAST(filename); 879 880 if (!IS_ERR(filename)) { 881 f = do_open_execat(AT_FDCWD, filename, 0); 882 putname(filename); 883 } 884 return f; 885 } 886 EXPORT_SYMBOL(open_exec); 887 888 int kernel_read_file(struct file *file, void **buf, loff_t *size, 889 loff_t max_size, enum kernel_read_file_id id) 890 { 891 loff_t i_size, pos; 892 ssize_t bytes = 0; 893 int ret; 894 895 if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0) 896 return -EINVAL; 897 898 ret = security_kernel_read_file(file, id); 899 if (ret) 900 return ret; 901 902 ret = deny_write_access(file); 903 if (ret) 904 return ret; 905 906 i_size = i_size_read(file_inode(file)); 907 if (max_size > 0 && i_size > max_size) { 908 ret = -EFBIG; 909 goto out; 910 } 911 if (i_size <= 0) { 912 ret = -EINVAL; 913 goto out; 914 } 915 916 if (id != READING_FIRMWARE_PREALLOC_BUFFER) 917 *buf = vmalloc(i_size); 918 if (!*buf) { 919 ret = -ENOMEM; 920 goto out; 921 } 922 923 pos = 0; 924 while (pos < i_size) { 925 bytes = kernel_read(file, *buf + pos, i_size - pos, &pos); 926 if (bytes < 0) { 927 ret = bytes; 928 goto out; 929 } 930 931 if (bytes == 0) 932 break; 933 } 934 935 if (pos != i_size) { 936 ret = -EIO; 937 goto out_free; 938 } 939 940 ret = security_kernel_post_read_file(file, *buf, i_size, id); 941 if (!ret) 942 *size = pos; 943 944 out_free: 945 if (ret < 0) { 946 if (id != READING_FIRMWARE_PREALLOC_BUFFER) { 947 vfree(*buf); 948 *buf = NULL; 949 } 950 } 951 952 out: 953 allow_write_access(file); 954 return ret; 955 } 956 EXPORT_SYMBOL_GPL(kernel_read_file); 957 958 int kernel_read_file_from_path(const char *path, void **buf, loff_t *size, 959 loff_t max_size, enum kernel_read_file_id id) 960 { 961 struct file *file; 962 int ret; 963 964 if (!path || !*path) 965 return -EINVAL; 966 967 file = filp_open(path, O_RDONLY, 0); 968 if (IS_ERR(file)) 969 return PTR_ERR(file); 970 971 ret = kernel_read_file(file, buf, size, max_size, id); 972 fput(file); 973 return ret; 974 } 975 EXPORT_SYMBOL_GPL(kernel_read_file_from_path); 976 977 int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size, 978 enum kernel_read_file_id id) 979 { 980 struct fd f = fdget(fd); 981 int ret = -EBADF; 982 983 if (!f.file) 984 goto out; 985 986 ret = kernel_read_file(f.file, buf, size, max_size, id); 987 out: 988 fdput(f); 989 return ret; 990 } 991 EXPORT_SYMBOL_GPL(kernel_read_file_from_fd); 992 993 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len) 994 { 995 ssize_t res = vfs_read(file, (void __user *)addr, len, &pos); 996 if (res > 0) 997 flush_icache_range(addr, addr + len); 998 return res; 999 } 1000 EXPORT_SYMBOL(read_code); 1001 1002 static int exec_mmap(struct mm_struct *mm) 1003 { 1004 struct task_struct *tsk; 1005 struct mm_struct *old_mm, *active_mm; 1006 1007 /* Notify parent that we're no longer interested in the old VM */ 1008 tsk = current; 1009 old_mm = current->mm; 1010 mm_release(tsk, old_mm); 1011 1012 if (old_mm) { 1013 sync_mm_rss(old_mm); 1014 /* 1015 * Make sure that if there is a core dump in progress 1016 * for the old mm, we get out and die instead of going 1017 * through with the exec. We must hold mmap_sem around 1018 * checking core_state and changing tsk->mm. 1019 */ 1020 down_read(&old_mm->mmap_sem); 1021 if (unlikely(old_mm->core_state)) { 1022 up_read(&old_mm->mmap_sem); 1023 return -EINTR; 1024 } 1025 } 1026 task_lock(tsk); 1027 active_mm = tsk->active_mm; 1028 tsk->mm = mm; 1029 tsk->active_mm = mm; 1030 activate_mm(active_mm, mm); 1031 tsk->mm->vmacache_seqnum = 0; 1032 vmacache_flush(tsk); 1033 task_unlock(tsk); 1034 if (old_mm) { 1035 up_read(&old_mm->mmap_sem); 1036 BUG_ON(active_mm != old_mm); 1037 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm); 1038 mm_update_next_owner(old_mm); 1039 mmput(old_mm); 1040 return 0; 1041 } 1042 mmdrop(active_mm); 1043 return 0; 1044 } 1045 1046 /* 1047 * This function makes sure the current process has its own signal table, 1048 * so that flush_signal_handlers can later reset the handlers without 1049 * disturbing other processes. (Other processes might share the signal 1050 * table via the CLONE_SIGHAND option to clone().) 1051 */ 1052 static int de_thread(struct task_struct *tsk) 1053 { 1054 struct signal_struct *sig = tsk->signal; 1055 struct sighand_struct *oldsighand = tsk->sighand; 1056 spinlock_t *lock = &oldsighand->siglock; 1057 1058 if (thread_group_empty(tsk)) 1059 goto no_thread_group; 1060 1061 /* 1062 * Kill all other threads in the thread group. 1063 */ 1064 spin_lock_irq(lock); 1065 if (signal_group_exit(sig)) { 1066 /* 1067 * Another group action in progress, just 1068 * return so that the signal is processed. 1069 */ 1070 spin_unlock_irq(lock); 1071 return -EAGAIN; 1072 } 1073 1074 sig->group_exit_task = tsk; 1075 sig->notify_count = zap_other_threads(tsk); 1076 if (!thread_group_leader(tsk)) 1077 sig->notify_count--; 1078 1079 while (sig->notify_count) { 1080 __set_current_state(TASK_KILLABLE); 1081 spin_unlock_irq(lock); 1082 schedule(); 1083 if (unlikely(__fatal_signal_pending(tsk))) 1084 goto killed; 1085 spin_lock_irq(lock); 1086 } 1087 spin_unlock_irq(lock); 1088 1089 /* 1090 * At this point all other threads have exited, all we have to 1091 * do is to wait for the thread group leader to become inactive, 1092 * and to assume its PID: 1093 */ 1094 if (!thread_group_leader(tsk)) { 1095 struct task_struct *leader = tsk->group_leader; 1096 1097 for (;;) { 1098 cgroup_threadgroup_change_begin(tsk); 1099 write_lock_irq(&tasklist_lock); 1100 /* 1101 * Do this under tasklist_lock to ensure that 1102 * exit_notify() can't miss ->group_exit_task 1103 */ 1104 sig->notify_count = -1; 1105 if (likely(leader->exit_state)) 1106 break; 1107 __set_current_state(TASK_KILLABLE); 1108 write_unlock_irq(&tasklist_lock); 1109 cgroup_threadgroup_change_end(tsk); 1110 schedule(); 1111 if (unlikely(__fatal_signal_pending(tsk))) 1112 goto killed; 1113 } 1114 1115 /* 1116 * The only record we have of the real-time age of a 1117 * process, regardless of execs it's done, is start_time. 1118 * All the past CPU time is accumulated in signal_struct 1119 * from sister threads now dead. But in this non-leader 1120 * exec, nothing survives from the original leader thread, 1121 * whose birth marks the true age of this process now. 1122 * When we take on its identity by switching to its PID, we 1123 * also take its birthdate (always earlier than our own). 1124 */ 1125 tsk->start_time = leader->start_time; 1126 tsk->real_start_time = leader->real_start_time; 1127 1128 BUG_ON(!same_thread_group(leader, tsk)); 1129 BUG_ON(has_group_leader_pid(tsk)); 1130 /* 1131 * An exec() starts a new thread group with the 1132 * TGID of the previous thread group. Rehash the 1133 * two threads with a switched PID, and release 1134 * the former thread group leader: 1135 */ 1136 1137 /* Become a process group leader with the old leader's pid. 1138 * The old leader becomes a thread of the this thread group. 1139 * Note: The old leader also uses this pid until release_task 1140 * is called. Odd but simple and correct. 1141 */ 1142 tsk->pid = leader->pid; 1143 change_pid(tsk, PIDTYPE_PID, task_pid(leader)); 1144 transfer_pid(leader, tsk, PIDTYPE_PGID); 1145 transfer_pid(leader, tsk, PIDTYPE_SID); 1146 1147 list_replace_rcu(&leader->tasks, &tsk->tasks); 1148 list_replace_init(&leader->sibling, &tsk->sibling); 1149 1150 tsk->group_leader = tsk; 1151 leader->group_leader = tsk; 1152 1153 tsk->exit_signal = SIGCHLD; 1154 leader->exit_signal = -1; 1155 1156 BUG_ON(leader->exit_state != EXIT_ZOMBIE); 1157 leader->exit_state = EXIT_DEAD; 1158 1159 /* 1160 * We are going to release_task()->ptrace_unlink() silently, 1161 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees 1162 * the tracer wont't block again waiting for this thread. 1163 */ 1164 if (unlikely(leader->ptrace)) 1165 __wake_up_parent(leader, leader->parent); 1166 write_unlock_irq(&tasklist_lock); 1167 cgroup_threadgroup_change_end(tsk); 1168 1169 release_task(leader); 1170 } 1171 1172 sig->group_exit_task = NULL; 1173 sig->notify_count = 0; 1174 1175 no_thread_group: 1176 /* we have changed execution domain */ 1177 tsk->exit_signal = SIGCHLD; 1178 1179 #ifdef CONFIG_POSIX_TIMERS 1180 exit_itimers(sig); 1181 flush_itimer_signals(); 1182 #endif 1183 1184 if (atomic_read(&oldsighand->count) != 1) { 1185 struct sighand_struct *newsighand; 1186 /* 1187 * This ->sighand is shared with the CLONE_SIGHAND 1188 * but not CLONE_THREAD task, switch to the new one. 1189 */ 1190 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1191 if (!newsighand) 1192 return -ENOMEM; 1193 1194 atomic_set(&newsighand->count, 1); 1195 memcpy(newsighand->action, oldsighand->action, 1196 sizeof(newsighand->action)); 1197 1198 write_lock_irq(&tasklist_lock); 1199 spin_lock(&oldsighand->siglock); 1200 rcu_assign_pointer(tsk->sighand, newsighand); 1201 spin_unlock(&oldsighand->siglock); 1202 write_unlock_irq(&tasklist_lock); 1203 1204 __cleanup_sighand(oldsighand); 1205 } 1206 1207 BUG_ON(!thread_group_leader(tsk)); 1208 return 0; 1209 1210 killed: 1211 /* protects against exit_notify() and __exit_signal() */ 1212 read_lock(&tasklist_lock); 1213 sig->group_exit_task = NULL; 1214 sig->notify_count = 0; 1215 read_unlock(&tasklist_lock); 1216 return -EAGAIN; 1217 } 1218 1219 char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk) 1220 { 1221 task_lock(tsk); 1222 strncpy(buf, tsk->comm, buf_size); 1223 task_unlock(tsk); 1224 return buf; 1225 } 1226 EXPORT_SYMBOL_GPL(__get_task_comm); 1227 1228 /* 1229 * These functions flushes out all traces of the currently running executable 1230 * so that a new one can be started 1231 */ 1232 1233 void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec) 1234 { 1235 task_lock(tsk); 1236 trace_task_rename(tsk, buf); 1237 strlcpy(tsk->comm, buf, sizeof(tsk->comm)); 1238 task_unlock(tsk); 1239 perf_event_comm(tsk, exec); 1240 } 1241 1242 /* 1243 * Calling this is the point of no return. None of the failures will be 1244 * seen by userspace since either the process is already taking a fatal 1245 * signal (via de_thread() or coredump), or will have SEGV raised 1246 * (after exec_mmap()) by search_binary_handlers (see below). 1247 */ 1248 int flush_old_exec(struct linux_binprm * bprm) 1249 { 1250 int retval; 1251 1252 /* 1253 * Make sure we have a private signal table and that 1254 * we are unassociated from the previous thread group. 1255 */ 1256 retval = de_thread(current); 1257 if (retval) 1258 goto out; 1259 1260 /* 1261 * Must be called _before_ exec_mmap() as bprm->mm is 1262 * not visibile until then. This also enables the update 1263 * to be lockless. 1264 */ 1265 set_mm_exe_file(bprm->mm, bprm->file); 1266 1267 /* 1268 * Release all of the old mmap stuff 1269 */ 1270 acct_arg_size(bprm, 0); 1271 retval = exec_mmap(bprm->mm); 1272 if (retval) 1273 goto out; 1274 1275 /* 1276 * After clearing bprm->mm (to mark that current is using the 1277 * prepared mm now), we have nothing left of the original 1278 * process. If anything from here on returns an error, the check 1279 * in search_binary_handler() will SEGV current. 1280 */ 1281 bprm->mm = NULL; 1282 1283 set_fs(USER_DS); 1284 current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD | 1285 PF_NOFREEZE | PF_NO_SETAFFINITY); 1286 flush_thread(); 1287 current->personality &= ~bprm->per_clear; 1288 1289 /* 1290 * We have to apply CLOEXEC before we change whether the process is 1291 * dumpable (in setup_new_exec) to avoid a race with a process in userspace 1292 * trying to access the should-be-closed file descriptors of a process 1293 * undergoing exec(2). 1294 */ 1295 do_close_on_exec(current->files); 1296 return 0; 1297 1298 out: 1299 return retval; 1300 } 1301 EXPORT_SYMBOL(flush_old_exec); 1302 1303 void would_dump(struct linux_binprm *bprm, struct file *file) 1304 { 1305 struct inode *inode = file_inode(file); 1306 if (inode_permission(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, 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 /* 1327 * Once here, prepare_binrpm() will not be called any more, so 1328 * the final state of setuid/setgid/fscaps can be merged into the 1329 * secureexec flag. 1330 */ 1331 bprm->secureexec |= bprm->cap_elevated; 1332 1333 if (bprm->secureexec) { 1334 /* Make sure parent cannot signal privileged process. */ 1335 current->pdeath_signal = 0; 1336 1337 /* 1338 * For secureexec, reset the stack limit to sane default to 1339 * avoid bad behavior from the prior rlimits. This has to 1340 * happen before arch_pick_mmap_layout(), which examines 1341 * RLIMIT_STACK, but after the point of no return to avoid 1342 * needing to clean up the change on failure. 1343 */ 1344 if (current->signal->rlim[RLIMIT_STACK].rlim_cur > _STK_LIM) 1345 current->signal->rlim[RLIMIT_STACK].rlim_cur = _STK_LIM; 1346 } 1347 1348 arch_pick_mmap_layout(current->mm); 1349 1350 current->sas_ss_sp = current->sas_ss_size = 0; 1351 1352 /* Figure out dumpability. */ 1353 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP || 1354 bprm->secureexec) 1355 set_dumpable(current->mm, suid_dumpable); 1356 else 1357 set_dumpable(current->mm, SUID_DUMP_USER); 1358 1359 arch_setup_new_exec(); 1360 perf_event_exec(); 1361 __set_task_comm(current, kbasename(bprm->filename), true); 1362 1363 /* Set the new mm task size. We have to do that late because it may 1364 * depend on TIF_32BIT which is only updated in flush_thread() on 1365 * some architectures like powerpc 1366 */ 1367 current->mm->task_size = TASK_SIZE; 1368 1369 /* An exec changes our domain. We are no longer part of the thread 1370 group */ 1371 current->self_exec_id++; 1372 flush_signal_handlers(current, 0); 1373 } 1374 EXPORT_SYMBOL(setup_new_exec); 1375 1376 /* 1377 * Prepare credentials and lock ->cred_guard_mutex. 1378 * install_exec_creds() commits the new creds and drops the lock. 1379 * Or, if exec fails before, free_bprm() should release ->cred and 1380 * and unlock. 1381 */ 1382 int prepare_bprm_creds(struct linux_binprm *bprm) 1383 { 1384 if (mutex_lock_interruptible(¤t->signal->cred_guard_mutex)) 1385 return -ERESTARTNOINTR; 1386 1387 bprm->cred = prepare_exec_creds(); 1388 if (likely(bprm->cred)) 1389 return 0; 1390 1391 mutex_unlock(¤t->signal->cred_guard_mutex); 1392 return -ENOMEM; 1393 } 1394 1395 static void free_bprm(struct linux_binprm *bprm) 1396 { 1397 free_arg_pages(bprm); 1398 if (bprm->cred) { 1399 mutex_unlock(¤t->signal->cred_guard_mutex); 1400 abort_creds(bprm->cred); 1401 } 1402 if (bprm->file) { 1403 allow_write_access(bprm->file); 1404 fput(bprm->file); 1405 } 1406 /* If a binfmt changed the interp, free it. */ 1407 if (bprm->interp != bprm->filename) 1408 kfree(bprm->interp); 1409 kfree(bprm); 1410 } 1411 1412 int bprm_change_interp(const char *interp, struct linux_binprm *bprm) 1413 { 1414 /* If a binfmt changed the interp, free it first. */ 1415 if (bprm->interp != bprm->filename) 1416 kfree(bprm->interp); 1417 bprm->interp = kstrdup(interp, GFP_KERNEL); 1418 if (!bprm->interp) 1419 return -ENOMEM; 1420 return 0; 1421 } 1422 EXPORT_SYMBOL(bprm_change_interp); 1423 1424 /* 1425 * install the new credentials for this executable 1426 */ 1427 void install_exec_creds(struct linux_binprm *bprm) 1428 { 1429 security_bprm_committing_creds(bprm); 1430 1431 commit_creds(bprm->cred); 1432 bprm->cred = NULL; 1433 1434 /* 1435 * Disable monitoring for regular users 1436 * when executing setuid binaries. Must 1437 * wait until new credentials are committed 1438 * by commit_creds() above 1439 */ 1440 if (get_dumpable(current->mm) != SUID_DUMP_USER) 1441 perf_event_exit_task(current); 1442 /* 1443 * cred_guard_mutex must be held at least to this point to prevent 1444 * ptrace_attach() from altering our determination of the task's 1445 * credentials; any time after this it may be unlocked. 1446 */ 1447 security_bprm_committed_creds(bprm); 1448 mutex_unlock(¤t->signal->cred_guard_mutex); 1449 } 1450 EXPORT_SYMBOL(install_exec_creds); 1451 1452 /* 1453 * determine how safe it is to execute the proposed program 1454 * - the caller must hold ->cred_guard_mutex to protect against 1455 * PTRACE_ATTACH or seccomp thread-sync 1456 */ 1457 static void check_unsafe_exec(struct linux_binprm *bprm) 1458 { 1459 struct task_struct *p = current, *t; 1460 unsigned n_fs; 1461 1462 if (p->ptrace) 1463 bprm->unsafe |= LSM_UNSAFE_PTRACE; 1464 1465 /* 1466 * This isn't strictly necessary, but it makes it harder for LSMs to 1467 * mess up. 1468 */ 1469 if (task_no_new_privs(current)) 1470 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS; 1471 1472 t = p; 1473 n_fs = 1; 1474 spin_lock(&p->fs->lock); 1475 rcu_read_lock(); 1476 while_each_thread(p, t) { 1477 if (t->fs == p->fs) 1478 n_fs++; 1479 } 1480 rcu_read_unlock(); 1481 1482 if (p->fs->users > n_fs) 1483 bprm->unsafe |= LSM_UNSAFE_SHARE; 1484 else 1485 p->fs->in_exec = 1; 1486 spin_unlock(&p->fs->lock); 1487 } 1488 1489 static void bprm_fill_uid(struct linux_binprm *bprm) 1490 { 1491 struct inode *inode; 1492 unsigned int mode; 1493 kuid_t uid; 1494 kgid_t gid; 1495 1496 /* 1497 * Since this can be called multiple times (via prepare_binprm), 1498 * we must clear any previous work done when setting set[ug]id 1499 * bits from any earlier bprm->file uses (for example when run 1500 * first for a setuid script then again for its interpreter). 1501 */ 1502 bprm->cred->euid = current_euid(); 1503 bprm->cred->egid = current_egid(); 1504 1505 if (!mnt_may_suid(bprm->file->f_path.mnt)) 1506 return; 1507 1508 if (task_no_new_privs(current)) 1509 return; 1510 1511 inode = bprm->file->f_path.dentry->d_inode; 1512 mode = READ_ONCE(inode->i_mode); 1513 if (!(mode & (S_ISUID|S_ISGID))) 1514 return; 1515 1516 /* Be careful if suid/sgid is set */ 1517 inode_lock(inode); 1518 1519 /* reload atomically mode/uid/gid now that lock held */ 1520 mode = inode->i_mode; 1521 uid = inode->i_uid; 1522 gid = inode->i_gid; 1523 inode_unlock(inode); 1524 1525 /* We ignore suid/sgid if there are no mappings for them in the ns */ 1526 if (!kuid_has_mapping(bprm->cred->user_ns, uid) || 1527 !kgid_has_mapping(bprm->cred->user_ns, gid)) 1528 return; 1529 1530 if (mode & S_ISUID) { 1531 bprm->per_clear |= PER_CLEAR_ON_SETID; 1532 bprm->cred->euid = uid; 1533 } 1534 1535 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { 1536 bprm->per_clear |= PER_CLEAR_ON_SETID; 1537 bprm->cred->egid = gid; 1538 } 1539 } 1540 1541 /* 1542 * Fill the binprm structure from the inode. 1543 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes 1544 * 1545 * This may be called multiple times for binary chains (scripts for example). 1546 */ 1547 int prepare_binprm(struct linux_binprm *bprm) 1548 { 1549 int retval; 1550 loff_t pos = 0; 1551 1552 bprm_fill_uid(bprm); 1553 1554 /* fill in binprm security blob */ 1555 retval = security_bprm_set_creds(bprm); 1556 if (retval) 1557 return retval; 1558 bprm->called_set_creds = 1; 1559 1560 memset(bprm->buf, 0, BINPRM_BUF_SIZE); 1561 return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos); 1562 } 1563 1564 EXPORT_SYMBOL(prepare_binprm); 1565 1566 /* 1567 * Arguments are '\0' separated strings found at the location bprm->p 1568 * points to; chop off the first by relocating brpm->p to right after 1569 * the first '\0' encountered. 1570 */ 1571 int remove_arg_zero(struct linux_binprm *bprm) 1572 { 1573 int ret = 0; 1574 unsigned long offset; 1575 char *kaddr; 1576 struct page *page; 1577 1578 if (!bprm->argc) 1579 return 0; 1580 1581 do { 1582 offset = bprm->p & ~PAGE_MASK; 1583 page = get_arg_page(bprm, bprm->p, 0); 1584 if (!page) { 1585 ret = -EFAULT; 1586 goto out; 1587 } 1588 kaddr = kmap_atomic(page); 1589 1590 for (; offset < PAGE_SIZE && kaddr[offset]; 1591 offset++, bprm->p++) 1592 ; 1593 1594 kunmap_atomic(kaddr); 1595 put_arg_page(page); 1596 } while (offset == PAGE_SIZE); 1597 1598 bprm->p++; 1599 bprm->argc--; 1600 ret = 0; 1601 1602 out: 1603 return ret; 1604 } 1605 EXPORT_SYMBOL(remove_arg_zero); 1606 1607 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e)) 1608 /* 1609 * cycle the list of binary formats handler, until one recognizes the image 1610 */ 1611 int search_binary_handler(struct linux_binprm *bprm) 1612 { 1613 bool need_retry = IS_ENABLED(CONFIG_MODULES); 1614 struct linux_binfmt *fmt; 1615 int retval; 1616 1617 /* This allows 4 levels of binfmt rewrites before failing hard. */ 1618 if (bprm->recursion_depth > 5) 1619 return -ELOOP; 1620 1621 retval = security_bprm_check(bprm); 1622 if (retval) 1623 return retval; 1624 1625 retval = -ENOENT; 1626 retry: 1627 read_lock(&binfmt_lock); 1628 list_for_each_entry(fmt, &formats, lh) { 1629 if (!try_module_get(fmt->module)) 1630 continue; 1631 read_unlock(&binfmt_lock); 1632 bprm->recursion_depth++; 1633 retval = fmt->load_binary(bprm); 1634 read_lock(&binfmt_lock); 1635 put_binfmt(fmt); 1636 bprm->recursion_depth--; 1637 if (retval < 0 && !bprm->mm) { 1638 /* we got to flush_old_exec() and failed after it */ 1639 read_unlock(&binfmt_lock); 1640 force_sigsegv(SIGSEGV, current); 1641 return retval; 1642 } 1643 if (retval != -ENOEXEC || !bprm->file) { 1644 read_unlock(&binfmt_lock); 1645 return retval; 1646 } 1647 } 1648 read_unlock(&binfmt_lock); 1649 1650 if (need_retry) { 1651 if (printable(bprm->buf[0]) && printable(bprm->buf[1]) && 1652 printable(bprm->buf[2]) && printable(bprm->buf[3])) 1653 return retval; 1654 if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0) 1655 return retval; 1656 need_retry = false; 1657 goto retry; 1658 } 1659 1660 return retval; 1661 } 1662 EXPORT_SYMBOL(search_binary_handler); 1663 1664 static int exec_binprm(struct linux_binprm *bprm) 1665 { 1666 pid_t old_pid, old_vpid; 1667 int ret; 1668 1669 /* Need to fetch pid before load_binary changes it */ 1670 old_pid = current->pid; 1671 rcu_read_lock(); 1672 old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent)); 1673 rcu_read_unlock(); 1674 1675 ret = search_binary_handler(bprm); 1676 if (ret >= 0) { 1677 audit_bprm(bprm); 1678 trace_sched_process_exec(current, old_pid, bprm); 1679 ptrace_event(PTRACE_EVENT_EXEC, old_vpid); 1680 proc_exec_connector(current); 1681 } 1682 1683 return ret; 1684 } 1685 1686 /* 1687 * sys_execve() executes a new program. 1688 */ 1689 static int do_execveat_common(int fd, struct filename *filename, 1690 struct user_arg_ptr argv, 1691 struct user_arg_ptr envp, 1692 int flags) 1693 { 1694 char *pathbuf = NULL; 1695 struct linux_binprm *bprm; 1696 struct file *file; 1697 struct files_struct *displaced; 1698 int retval; 1699 1700 if (IS_ERR(filename)) 1701 return PTR_ERR(filename); 1702 1703 /* 1704 * We move the actual failure in case of RLIMIT_NPROC excess from 1705 * set*uid() to execve() because too many poorly written programs 1706 * don't check setuid() return code. Here we additionally recheck 1707 * whether NPROC limit is still exceeded. 1708 */ 1709 if ((current->flags & PF_NPROC_EXCEEDED) && 1710 atomic_read(¤t_user()->processes) > rlimit(RLIMIT_NPROC)) { 1711 retval = -EAGAIN; 1712 goto out_ret; 1713 } 1714 1715 /* We're below the limit (still or again), so we don't want to make 1716 * further execve() calls fail. */ 1717 current->flags &= ~PF_NPROC_EXCEEDED; 1718 1719 retval = unshare_files(&displaced); 1720 if (retval) 1721 goto out_ret; 1722 1723 retval = -ENOMEM; 1724 bprm = kzalloc(sizeof(*bprm), GFP_KERNEL); 1725 if (!bprm) 1726 goto out_files; 1727 1728 retval = prepare_bprm_creds(bprm); 1729 if (retval) 1730 goto out_free; 1731 1732 check_unsafe_exec(bprm); 1733 current->in_execve = 1; 1734 1735 file = do_open_execat(fd, filename, flags); 1736 retval = PTR_ERR(file); 1737 if (IS_ERR(file)) 1738 goto out_unmark; 1739 1740 sched_exec(); 1741 1742 bprm->file = file; 1743 if (fd == AT_FDCWD || filename->name[0] == '/') { 1744 bprm->filename = filename->name; 1745 } else { 1746 if (filename->name[0] == '\0') 1747 pathbuf = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd); 1748 else 1749 pathbuf = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s", 1750 fd, filename->name); 1751 if (!pathbuf) { 1752 retval = -ENOMEM; 1753 goto out_unmark; 1754 } 1755 /* 1756 * Record that a name derived from an O_CLOEXEC fd will be 1757 * inaccessible after exec. Relies on having exclusive access to 1758 * current->files (due to unshare_files above). 1759 */ 1760 if (close_on_exec(fd, rcu_dereference_raw(current->files->fdt))) 1761 bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE; 1762 bprm->filename = pathbuf; 1763 } 1764 bprm->interp = bprm->filename; 1765 1766 retval = bprm_mm_init(bprm); 1767 if (retval) 1768 goto out_unmark; 1769 1770 bprm->argc = count(argv, MAX_ARG_STRINGS); 1771 if ((retval = bprm->argc) < 0) 1772 goto out; 1773 1774 bprm->envc = count(envp, MAX_ARG_STRINGS); 1775 if ((retval = bprm->envc) < 0) 1776 goto out; 1777 1778 retval = prepare_binprm(bprm); 1779 if (retval < 0) 1780 goto out; 1781 1782 retval = copy_strings_kernel(1, &bprm->filename, bprm); 1783 if (retval < 0) 1784 goto out; 1785 1786 bprm->exec = bprm->p; 1787 retval = copy_strings(bprm->envc, envp, bprm); 1788 if (retval < 0) 1789 goto out; 1790 1791 retval = copy_strings(bprm->argc, argv, bprm); 1792 if (retval < 0) 1793 goto out; 1794 1795 would_dump(bprm, bprm->file); 1796 1797 retval = exec_binprm(bprm); 1798 if (retval < 0) 1799 goto out; 1800 1801 /* execve succeeded */ 1802 current->fs->in_exec = 0; 1803 current->in_execve = 0; 1804 membarrier_execve(current); 1805 acct_update_integrals(current); 1806 task_numa_free(current); 1807 free_bprm(bprm); 1808 kfree(pathbuf); 1809 putname(filename); 1810 if (displaced) 1811 put_files_struct(displaced); 1812 return retval; 1813 1814 out: 1815 if (bprm->mm) { 1816 acct_arg_size(bprm, 0); 1817 mmput(bprm->mm); 1818 } 1819 1820 out_unmark: 1821 current->fs->in_exec = 0; 1822 current->in_execve = 0; 1823 1824 out_free: 1825 free_bprm(bprm); 1826 kfree(pathbuf); 1827 1828 out_files: 1829 if (displaced) 1830 reset_files_struct(displaced); 1831 out_ret: 1832 putname(filename); 1833 return retval; 1834 } 1835 1836 int do_execve(struct filename *filename, 1837 const char __user *const __user *__argv, 1838 const char __user *const __user *__envp) 1839 { 1840 struct user_arg_ptr argv = { .ptr.native = __argv }; 1841 struct user_arg_ptr envp = { .ptr.native = __envp }; 1842 return do_execveat_common(AT_FDCWD, filename, argv, envp, 0); 1843 } 1844 1845 int do_execveat(int fd, struct filename *filename, 1846 const char __user *const __user *__argv, 1847 const char __user *const __user *__envp, 1848 int flags) 1849 { 1850 struct user_arg_ptr argv = { .ptr.native = __argv }; 1851 struct user_arg_ptr envp = { .ptr.native = __envp }; 1852 1853 return do_execveat_common(fd, filename, argv, envp, flags); 1854 } 1855 1856 #ifdef CONFIG_COMPAT 1857 static int compat_do_execve(struct filename *filename, 1858 const compat_uptr_t __user *__argv, 1859 const compat_uptr_t __user *__envp) 1860 { 1861 struct user_arg_ptr argv = { 1862 .is_compat = true, 1863 .ptr.compat = __argv, 1864 }; 1865 struct user_arg_ptr envp = { 1866 .is_compat = true, 1867 .ptr.compat = __envp, 1868 }; 1869 return do_execveat_common(AT_FDCWD, filename, argv, envp, 0); 1870 } 1871 1872 static int compat_do_execveat(int fd, struct filename *filename, 1873 const compat_uptr_t __user *__argv, 1874 const compat_uptr_t __user *__envp, 1875 int flags) 1876 { 1877 struct user_arg_ptr argv = { 1878 .is_compat = true, 1879 .ptr.compat = __argv, 1880 }; 1881 struct user_arg_ptr envp = { 1882 .is_compat = true, 1883 .ptr.compat = __envp, 1884 }; 1885 return do_execveat_common(fd, filename, argv, envp, flags); 1886 } 1887 #endif 1888 1889 void set_binfmt(struct linux_binfmt *new) 1890 { 1891 struct mm_struct *mm = current->mm; 1892 1893 if (mm->binfmt) 1894 module_put(mm->binfmt->module); 1895 1896 mm->binfmt = new; 1897 if (new) 1898 __module_get(new->module); 1899 } 1900 EXPORT_SYMBOL(set_binfmt); 1901 1902 /* 1903 * set_dumpable stores three-value SUID_DUMP_* into mm->flags. 1904 */ 1905 void set_dumpable(struct mm_struct *mm, int value) 1906 { 1907 unsigned long old, new; 1908 1909 if (WARN_ON((unsigned)value > SUID_DUMP_ROOT)) 1910 return; 1911 1912 do { 1913 old = READ_ONCE(mm->flags); 1914 new = (old & ~MMF_DUMPABLE_MASK) | value; 1915 } while (cmpxchg(&mm->flags, old, new) != old); 1916 } 1917 1918 SYSCALL_DEFINE3(execve, 1919 const char __user *, filename, 1920 const char __user *const __user *, argv, 1921 const char __user *const __user *, envp) 1922 { 1923 return do_execve(getname(filename), argv, envp); 1924 } 1925 1926 SYSCALL_DEFINE5(execveat, 1927 int, fd, const char __user *, filename, 1928 const char __user *const __user *, argv, 1929 const char __user *const __user *, envp, 1930 int, flags) 1931 { 1932 int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0; 1933 1934 return do_execveat(fd, 1935 getname_flags(filename, lookup_flags, NULL), 1936 argv, envp, flags); 1937 } 1938 1939 #ifdef CONFIG_COMPAT 1940 COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename, 1941 const compat_uptr_t __user *, argv, 1942 const compat_uptr_t __user *, envp) 1943 { 1944 return compat_do_execve(getname(filename), argv, envp); 1945 } 1946 1947 COMPAT_SYSCALL_DEFINE5(execveat, int, fd, 1948 const char __user *, filename, 1949 const compat_uptr_t __user *, argv, 1950 const compat_uptr_t __user *, envp, 1951 int, flags) 1952 { 1953 int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0; 1954 1955 return compat_do_execveat(fd, 1956 getname_flags(filename, lookup_flags, NULL), 1957 argv, envp, flags); 1958 } 1959 #endif 1960