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; 224 struct rlimit *rlim; 225 226 /* 227 * Since the stack will hold pointers to the strings, we 228 * must account for them as well. 229 * 230 * The size calculation is the entire vma while each arg page is 231 * built, so each time we get here it's calculating how far it 232 * is currently (rather than each call being just the newly 233 * added size from the arg page). As a result, we need to 234 * always add the entire size of the pointers, so that on the 235 * last call to get_arg_page() we'll actually have the entire 236 * correct size. 237 */ 238 ptr_size = (bprm->argc + bprm->envc) * sizeof(void *); 239 if (ptr_size > ULONG_MAX - size) 240 goto fail; 241 size += ptr_size; 242 243 acct_arg_size(bprm, size / PAGE_SIZE); 244 245 /* 246 * We've historically supported up to 32 pages (ARG_MAX) 247 * of argument strings even with small stacks 248 */ 249 if (size <= ARG_MAX) 250 return page; 251 252 /* 253 * Limit to 1/4-th the stack size 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 rlim = current->signal->rlim; 260 if (size > READ_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) 261 goto fail; 262 } 263 264 return page; 265 266 fail: 267 put_page(page); 268 return NULL; 269 } 270 271 static void put_arg_page(struct page *page) 272 { 273 put_page(page); 274 } 275 276 static void free_arg_pages(struct linux_binprm *bprm) 277 { 278 } 279 280 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, 281 struct page *page) 282 { 283 flush_cache_page(bprm->vma, pos, page_to_pfn(page)); 284 } 285 286 static int __bprm_mm_init(struct linux_binprm *bprm) 287 { 288 int err; 289 struct vm_area_struct *vma = NULL; 290 struct mm_struct *mm = bprm->mm; 291 292 bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL); 293 if (!vma) 294 return -ENOMEM; 295 296 if (down_write_killable(&mm->mmap_sem)) { 297 err = -EINTR; 298 goto err_free; 299 } 300 vma->vm_mm = mm; 301 302 /* 303 * Place the stack at the largest stack address the architecture 304 * supports. Later, we'll move this to an appropriate place. We don't 305 * use STACK_TOP because that can depend on attributes which aren't 306 * configured yet. 307 */ 308 BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP); 309 vma->vm_end = STACK_TOP_MAX; 310 vma->vm_start = vma->vm_end - PAGE_SIZE; 311 vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP; 312 vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); 313 INIT_LIST_HEAD(&vma->anon_vma_chain); 314 315 err = insert_vm_struct(mm, vma); 316 if (err) 317 goto err; 318 319 mm->stack_vm = mm->total_vm = 1; 320 arch_bprm_mm_init(mm, vma); 321 up_write(&mm->mmap_sem); 322 bprm->p = vma->vm_end - sizeof(void *); 323 return 0; 324 err: 325 up_write(&mm->mmap_sem); 326 err_free: 327 bprm->vma = NULL; 328 kmem_cache_free(vm_area_cachep, vma); 329 return err; 330 } 331 332 static bool valid_arg_len(struct linux_binprm *bprm, long len) 333 { 334 return len <= MAX_ARG_STRLEN; 335 } 336 337 #else 338 339 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages) 340 { 341 } 342 343 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, 344 int write) 345 { 346 struct page *page; 347 348 page = bprm->page[pos / PAGE_SIZE]; 349 if (!page && write) { 350 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO); 351 if (!page) 352 return NULL; 353 bprm->page[pos / PAGE_SIZE] = page; 354 } 355 356 return page; 357 } 358 359 static void put_arg_page(struct page *page) 360 { 361 } 362 363 static void free_arg_page(struct linux_binprm *bprm, int i) 364 { 365 if (bprm->page[i]) { 366 __free_page(bprm->page[i]); 367 bprm->page[i] = NULL; 368 } 369 } 370 371 static void free_arg_pages(struct linux_binprm *bprm) 372 { 373 int i; 374 375 for (i = 0; i < MAX_ARG_PAGES; i++) 376 free_arg_page(bprm, i); 377 } 378 379 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, 380 struct page *page) 381 { 382 } 383 384 static int __bprm_mm_init(struct linux_binprm *bprm) 385 { 386 bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *); 387 return 0; 388 } 389 390 static bool valid_arg_len(struct linux_binprm *bprm, long len) 391 { 392 return len <= bprm->p; 393 } 394 395 #endif /* CONFIG_MMU */ 396 397 /* 398 * Create a new mm_struct and populate it with a temporary stack 399 * vm_area_struct. We don't have enough context at this point to set the stack 400 * flags, permissions, and offset, so we use temporary values. We'll update 401 * them later in setup_arg_pages(). 402 */ 403 static int bprm_mm_init(struct linux_binprm *bprm) 404 { 405 int err; 406 struct mm_struct *mm = NULL; 407 408 bprm->mm = mm = mm_alloc(); 409 err = -ENOMEM; 410 if (!mm) 411 goto err; 412 413 err = __bprm_mm_init(bprm); 414 if (err) 415 goto err; 416 417 return 0; 418 419 err: 420 if (mm) { 421 bprm->mm = NULL; 422 mmdrop(mm); 423 } 424 425 return err; 426 } 427 428 struct user_arg_ptr { 429 #ifdef CONFIG_COMPAT 430 bool is_compat; 431 #endif 432 union { 433 const char __user *const __user *native; 434 #ifdef CONFIG_COMPAT 435 const compat_uptr_t __user *compat; 436 #endif 437 } ptr; 438 }; 439 440 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr) 441 { 442 const char __user *native; 443 444 #ifdef CONFIG_COMPAT 445 if (unlikely(argv.is_compat)) { 446 compat_uptr_t compat; 447 448 if (get_user(compat, argv.ptr.compat + nr)) 449 return ERR_PTR(-EFAULT); 450 451 return compat_ptr(compat); 452 } 453 #endif 454 455 if (get_user(native, argv.ptr.native + nr)) 456 return ERR_PTR(-EFAULT); 457 458 return native; 459 } 460 461 /* 462 * count() counts the number of strings in array ARGV. 463 */ 464 static int count(struct user_arg_ptr argv, int max) 465 { 466 int i = 0; 467 468 if (argv.ptr.native != NULL) { 469 for (;;) { 470 const char __user *p = get_user_arg_ptr(argv, i); 471 472 if (!p) 473 break; 474 475 if (IS_ERR(p)) 476 return -EFAULT; 477 478 if (i >= max) 479 return -E2BIG; 480 ++i; 481 482 if (fatal_signal_pending(current)) 483 return -ERESTARTNOHAND; 484 cond_resched(); 485 } 486 } 487 return i; 488 } 489 490 /* 491 * 'copy_strings()' copies argument/environment strings from the old 492 * processes's memory to the new process's stack. The call to get_user_pages() 493 * ensures the destination page is created and not swapped out. 494 */ 495 static int copy_strings(int argc, struct user_arg_ptr argv, 496 struct linux_binprm *bprm) 497 { 498 struct page *kmapped_page = NULL; 499 char *kaddr = NULL; 500 unsigned long kpos = 0; 501 int ret; 502 503 while (argc-- > 0) { 504 const char __user *str; 505 int len; 506 unsigned long pos; 507 508 ret = -EFAULT; 509 str = get_user_arg_ptr(argv, argc); 510 if (IS_ERR(str)) 511 goto out; 512 513 len = strnlen_user(str, MAX_ARG_STRLEN); 514 if (!len) 515 goto out; 516 517 ret = -E2BIG; 518 if (!valid_arg_len(bprm, len)) 519 goto out; 520 521 /* We're going to work our way backwords. */ 522 pos = bprm->p; 523 str += len; 524 bprm->p -= len; 525 526 while (len > 0) { 527 int offset, bytes_to_copy; 528 529 if (fatal_signal_pending(current)) { 530 ret = -ERESTARTNOHAND; 531 goto out; 532 } 533 cond_resched(); 534 535 offset = pos % PAGE_SIZE; 536 if (offset == 0) 537 offset = PAGE_SIZE; 538 539 bytes_to_copy = offset; 540 if (bytes_to_copy > len) 541 bytes_to_copy = len; 542 543 offset -= bytes_to_copy; 544 pos -= bytes_to_copy; 545 str -= bytes_to_copy; 546 len -= bytes_to_copy; 547 548 if (!kmapped_page || kpos != (pos & PAGE_MASK)) { 549 struct page *page; 550 551 page = get_arg_page(bprm, pos, 1); 552 if (!page) { 553 ret = -E2BIG; 554 goto out; 555 } 556 557 if (kmapped_page) { 558 flush_kernel_dcache_page(kmapped_page); 559 kunmap(kmapped_page); 560 put_arg_page(kmapped_page); 561 } 562 kmapped_page = page; 563 kaddr = kmap(kmapped_page); 564 kpos = pos & PAGE_MASK; 565 flush_arg_page(bprm, kpos, kmapped_page); 566 } 567 if (copy_from_user(kaddr+offset, str, bytes_to_copy)) { 568 ret = -EFAULT; 569 goto out; 570 } 571 } 572 } 573 ret = 0; 574 out: 575 if (kmapped_page) { 576 flush_kernel_dcache_page(kmapped_page); 577 kunmap(kmapped_page); 578 put_arg_page(kmapped_page); 579 } 580 return ret; 581 } 582 583 /* 584 * Like copy_strings, but get argv and its values from kernel memory. 585 */ 586 int copy_strings_kernel(int argc, const char *const *__argv, 587 struct linux_binprm *bprm) 588 { 589 int r; 590 mm_segment_t oldfs = get_fs(); 591 struct user_arg_ptr argv = { 592 .ptr.native = (const char __user *const __user *)__argv, 593 }; 594 595 set_fs(KERNEL_DS); 596 r = copy_strings(argc, argv, bprm); 597 set_fs(oldfs); 598 599 return r; 600 } 601 EXPORT_SYMBOL(copy_strings_kernel); 602 603 #ifdef CONFIG_MMU 604 605 /* 606 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once 607 * the binfmt code determines where the new stack should reside, we shift it to 608 * its final location. The process proceeds as follows: 609 * 610 * 1) Use shift to calculate the new vma endpoints. 611 * 2) Extend vma to cover both the old and new ranges. This ensures the 612 * arguments passed to subsequent functions are consistent. 613 * 3) Move vma's page tables to the new range. 614 * 4) Free up any cleared pgd range. 615 * 5) Shrink the vma to cover only the new range. 616 */ 617 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift) 618 { 619 struct mm_struct *mm = vma->vm_mm; 620 unsigned long old_start = vma->vm_start; 621 unsigned long old_end = vma->vm_end; 622 unsigned long length = old_end - old_start; 623 unsigned long new_start = old_start - shift; 624 unsigned long new_end = old_end - shift; 625 struct mmu_gather tlb; 626 627 BUG_ON(new_start > new_end); 628 629 /* 630 * ensure there are no vmas between where we want to go 631 * and where we are 632 */ 633 if (vma != find_vma(mm, new_start)) 634 return -EFAULT; 635 636 /* 637 * cover the whole range: [new_start, old_end) 638 */ 639 if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL)) 640 return -ENOMEM; 641 642 /* 643 * move the page tables downwards, on failure we rely on 644 * process cleanup to remove whatever mess we made. 645 */ 646 if (length != move_page_tables(vma, old_start, 647 vma, new_start, length, false)) 648 return -ENOMEM; 649 650 lru_add_drain(); 651 tlb_gather_mmu(&tlb, mm, old_start, old_end); 652 if (new_end > old_start) { 653 /* 654 * when the old and new regions overlap clear from new_end. 655 */ 656 free_pgd_range(&tlb, new_end, old_end, new_end, 657 vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING); 658 } else { 659 /* 660 * otherwise, clean from old_start; this is done to not touch 661 * the address space in [new_end, old_start) some architectures 662 * have constraints on va-space that make this illegal (IA64) - 663 * for the others its just a little faster. 664 */ 665 free_pgd_range(&tlb, old_start, old_end, new_end, 666 vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING); 667 } 668 tlb_finish_mmu(&tlb, old_start, old_end); 669 670 /* 671 * Shrink the vma to just the new range. Always succeeds. 672 */ 673 vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL); 674 675 return 0; 676 } 677 678 /* 679 * Finalizes the stack vm_area_struct. The flags and permissions are updated, 680 * the stack is optionally relocated, and some extra space is added. 681 */ 682 int setup_arg_pages(struct linux_binprm *bprm, 683 unsigned long stack_top, 684 int executable_stack) 685 { 686 unsigned long ret; 687 unsigned long stack_shift; 688 struct mm_struct *mm = current->mm; 689 struct vm_area_struct *vma = bprm->vma; 690 struct vm_area_struct *prev = NULL; 691 unsigned long vm_flags; 692 unsigned long stack_base; 693 unsigned long stack_size; 694 unsigned long stack_expand; 695 unsigned long rlim_stack; 696 697 #ifdef CONFIG_STACK_GROWSUP 698 /* Limit stack size */ 699 stack_base = rlimit_max(RLIMIT_STACK); 700 if (stack_base > STACK_SIZE_MAX) 701 stack_base = STACK_SIZE_MAX; 702 703 /* Add space for stack randomization. */ 704 stack_base += (STACK_RND_MASK << PAGE_SHIFT); 705 706 /* Make sure we didn't let the argument array grow too large. */ 707 if (vma->vm_end - vma->vm_start > stack_base) 708 return -ENOMEM; 709 710 stack_base = PAGE_ALIGN(stack_top - stack_base); 711 712 stack_shift = vma->vm_start - stack_base; 713 mm->arg_start = bprm->p - stack_shift; 714 bprm->p = vma->vm_end - stack_shift; 715 #else 716 stack_top = arch_align_stack(stack_top); 717 stack_top = PAGE_ALIGN(stack_top); 718 719 if (unlikely(stack_top < mmap_min_addr) || 720 unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr)) 721 return -ENOMEM; 722 723 stack_shift = vma->vm_end - stack_top; 724 725 bprm->p -= stack_shift; 726 mm->arg_start = bprm->p; 727 #endif 728 729 if (bprm->loader) 730 bprm->loader -= stack_shift; 731 bprm->exec -= stack_shift; 732 733 if (down_write_killable(&mm->mmap_sem)) 734 return -EINTR; 735 736 vm_flags = VM_STACK_FLAGS; 737 738 /* 739 * Adjust stack execute permissions; explicitly enable for 740 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone 741 * (arch default) otherwise. 742 */ 743 if (unlikely(executable_stack == EXSTACK_ENABLE_X)) 744 vm_flags |= VM_EXEC; 745 else if (executable_stack == EXSTACK_DISABLE_X) 746 vm_flags &= ~VM_EXEC; 747 vm_flags |= mm->def_flags; 748 vm_flags |= VM_STACK_INCOMPLETE_SETUP; 749 750 ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end, 751 vm_flags); 752 if (ret) 753 goto out_unlock; 754 BUG_ON(prev != vma); 755 756 /* Move stack pages down in memory. */ 757 if (stack_shift) { 758 ret = shift_arg_pages(vma, stack_shift); 759 if (ret) 760 goto out_unlock; 761 } 762 763 /* mprotect_fixup is overkill to remove the temporary stack flags */ 764 vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP; 765 766 stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */ 767 stack_size = vma->vm_end - vma->vm_start; 768 /* 769 * Align this down to a page boundary as expand_stack 770 * will align it up. 771 */ 772 rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK; 773 #ifdef CONFIG_STACK_GROWSUP 774 if (stack_size + stack_expand > rlim_stack) 775 stack_base = vma->vm_start + rlim_stack; 776 else 777 stack_base = vma->vm_end + stack_expand; 778 #else 779 if (stack_size + stack_expand > rlim_stack) 780 stack_base = vma->vm_end - rlim_stack; 781 else 782 stack_base = vma->vm_start - stack_expand; 783 #endif 784 current->mm->start_stack = bprm->p; 785 ret = expand_stack(vma, stack_base); 786 if (ret) 787 ret = -EFAULT; 788 789 out_unlock: 790 up_write(&mm->mmap_sem); 791 return ret; 792 } 793 EXPORT_SYMBOL(setup_arg_pages); 794 795 #else 796 797 /* 798 * Transfer the program arguments and environment from the holding pages 799 * onto the stack. The provided stack pointer is adjusted accordingly. 800 */ 801 int transfer_args_to_stack(struct linux_binprm *bprm, 802 unsigned long *sp_location) 803 { 804 unsigned long index, stop, sp; 805 int ret = 0; 806 807 stop = bprm->p >> PAGE_SHIFT; 808 sp = *sp_location; 809 810 for (index = MAX_ARG_PAGES - 1; index >= stop; index--) { 811 unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0; 812 char *src = kmap(bprm->page[index]) + offset; 813 sp -= PAGE_SIZE - offset; 814 if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0) 815 ret = -EFAULT; 816 kunmap(bprm->page[index]); 817 if (ret) 818 goto out; 819 } 820 821 *sp_location = sp; 822 823 out: 824 return ret; 825 } 826 EXPORT_SYMBOL(transfer_args_to_stack); 827 828 #endif /* CONFIG_MMU */ 829 830 static struct file *do_open_execat(int fd, struct filename *name, int flags) 831 { 832 struct file *file; 833 int err; 834 struct open_flags open_exec_flags = { 835 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC, 836 .acc_mode = MAY_EXEC, 837 .intent = LOOKUP_OPEN, 838 .lookup_flags = LOOKUP_FOLLOW, 839 }; 840 841 if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0) 842 return ERR_PTR(-EINVAL); 843 if (flags & AT_SYMLINK_NOFOLLOW) 844 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW; 845 if (flags & AT_EMPTY_PATH) 846 open_exec_flags.lookup_flags |= LOOKUP_EMPTY; 847 848 file = do_filp_open(fd, name, &open_exec_flags); 849 if (IS_ERR(file)) 850 goto out; 851 852 err = -EACCES; 853 if (!S_ISREG(file_inode(file)->i_mode)) 854 goto exit; 855 856 if (path_noexec(&file->f_path)) 857 goto exit; 858 859 err = deny_write_access(file); 860 if (err) 861 goto exit; 862 863 if (name->name[0] != '\0') 864 fsnotify_open(file); 865 866 out: 867 return file; 868 869 exit: 870 fput(file); 871 return ERR_PTR(err); 872 } 873 874 struct file *open_exec(const char *name) 875 { 876 struct filename *filename = getname_kernel(name); 877 struct file *f = ERR_CAST(filename); 878 879 if (!IS_ERR(filename)) { 880 f = do_open_execat(AT_FDCWD, filename, 0); 881 putname(filename); 882 } 883 return f; 884 } 885 EXPORT_SYMBOL(open_exec); 886 887 int kernel_read(struct file *file, loff_t offset, 888 char *addr, unsigned long count) 889 { 890 mm_segment_t old_fs; 891 loff_t pos = offset; 892 int result; 893 894 old_fs = get_fs(); 895 set_fs(get_ds()); 896 /* The cast to a user pointer is valid due to the set_fs() */ 897 result = vfs_read(file, (void __user *)addr, count, &pos); 898 set_fs(old_fs); 899 return result; 900 } 901 902 EXPORT_SYMBOL(kernel_read); 903 904 int kernel_read_file(struct file *file, void **buf, loff_t *size, 905 loff_t max_size, enum kernel_read_file_id id) 906 { 907 loff_t i_size, pos; 908 ssize_t bytes = 0; 909 int ret; 910 911 if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0) 912 return -EINVAL; 913 914 ret = security_kernel_read_file(file, id); 915 if (ret) 916 return ret; 917 918 ret = deny_write_access(file); 919 if (ret) 920 return ret; 921 922 i_size = i_size_read(file_inode(file)); 923 if (max_size > 0 && i_size > max_size) { 924 ret = -EFBIG; 925 goto out; 926 } 927 if (i_size <= 0) { 928 ret = -EINVAL; 929 goto out; 930 } 931 932 if (id != READING_FIRMWARE_PREALLOC_BUFFER) 933 *buf = vmalloc(i_size); 934 if (!*buf) { 935 ret = -ENOMEM; 936 goto out; 937 } 938 939 pos = 0; 940 while (pos < i_size) { 941 bytes = kernel_read(file, pos, (char *)(*buf) + pos, 942 i_size - pos); 943 if (bytes < 0) { 944 ret = bytes; 945 goto out; 946 } 947 948 if (bytes == 0) 949 break; 950 pos += bytes; 951 } 952 953 if (pos != i_size) { 954 ret = -EIO; 955 goto out_free; 956 } 957 958 ret = security_kernel_post_read_file(file, *buf, i_size, id); 959 if (!ret) 960 *size = pos; 961 962 out_free: 963 if (ret < 0) { 964 if (id != READING_FIRMWARE_PREALLOC_BUFFER) { 965 vfree(*buf); 966 *buf = NULL; 967 } 968 } 969 970 out: 971 allow_write_access(file); 972 return ret; 973 } 974 EXPORT_SYMBOL_GPL(kernel_read_file); 975 976 int kernel_read_file_from_path(char *path, void **buf, loff_t *size, 977 loff_t max_size, enum kernel_read_file_id id) 978 { 979 struct file *file; 980 int ret; 981 982 if (!path || !*path) 983 return -EINVAL; 984 985 file = filp_open(path, O_RDONLY, 0); 986 if (IS_ERR(file)) 987 return PTR_ERR(file); 988 989 ret = kernel_read_file(file, buf, size, max_size, id); 990 fput(file); 991 return ret; 992 } 993 EXPORT_SYMBOL_GPL(kernel_read_file_from_path); 994 995 int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size, 996 enum kernel_read_file_id id) 997 { 998 struct fd f = fdget(fd); 999 int ret = -EBADF; 1000 1001 if (!f.file) 1002 goto out; 1003 1004 ret = kernel_read_file(f.file, buf, size, max_size, id); 1005 out: 1006 fdput(f); 1007 return ret; 1008 } 1009 EXPORT_SYMBOL_GPL(kernel_read_file_from_fd); 1010 1011 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len) 1012 { 1013 ssize_t res = vfs_read(file, (void __user *)addr, len, &pos); 1014 if (res > 0) 1015 flush_icache_range(addr, addr + len); 1016 return res; 1017 } 1018 EXPORT_SYMBOL(read_code); 1019 1020 static int exec_mmap(struct mm_struct *mm) 1021 { 1022 struct task_struct *tsk; 1023 struct mm_struct *old_mm, *active_mm; 1024 1025 /* Notify parent that we're no longer interested in the old VM */ 1026 tsk = current; 1027 old_mm = current->mm; 1028 mm_release(tsk, old_mm); 1029 1030 if (old_mm) { 1031 sync_mm_rss(old_mm); 1032 /* 1033 * Make sure that if there is a core dump in progress 1034 * for the old mm, we get out and die instead of going 1035 * through with the exec. We must hold mmap_sem around 1036 * checking core_state and changing tsk->mm. 1037 */ 1038 down_read(&old_mm->mmap_sem); 1039 if (unlikely(old_mm->core_state)) { 1040 up_read(&old_mm->mmap_sem); 1041 return -EINTR; 1042 } 1043 } 1044 task_lock(tsk); 1045 active_mm = tsk->active_mm; 1046 tsk->mm = mm; 1047 tsk->active_mm = mm; 1048 activate_mm(active_mm, mm); 1049 tsk->mm->vmacache_seqnum = 0; 1050 vmacache_flush(tsk); 1051 task_unlock(tsk); 1052 if (old_mm) { 1053 up_read(&old_mm->mmap_sem); 1054 BUG_ON(active_mm != old_mm); 1055 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm); 1056 mm_update_next_owner(old_mm); 1057 mmput(old_mm); 1058 return 0; 1059 } 1060 mmdrop(active_mm); 1061 return 0; 1062 } 1063 1064 /* 1065 * This function makes sure the current process has its own signal table, 1066 * so that flush_signal_handlers can later reset the handlers without 1067 * disturbing other processes. (Other processes might share the signal 1068 * table via the CLONE_SIGHAND option to clone().) 1069 */ 1070 static int de_thread(struct task_struct *tsk) 1071 { 1072 struct signal_struct *sig = tsk->signal; 1073 struct sighand_struct *oldsighand = tsk->sighand; 1074 spinlock_t *lock = &oldsighand->siglock; 1075 1076 if (thread_group_empty(tsk)) 1077 goto no_thread_group; 1078 1079 /* 1080 * Kill all other threads in the thread group. 1081 */ 1082 spin_lock_irq(lock); 1083 if (signal_group_exit(sig)) { 1084 /* 1085 * Another group action in progress, just 1086 * return so that the signal is processed. 1087 */ 1088 spin_unlock_irq(lock); 1089 return -EAGAIN; 1090 } 1091 1092 sig->group_exit_task = tsk; 1093 sig->notify_count = zap_other_threads(tsk); 1094 if (!thread_group_leader(tsk)) 1095 sig->notify_count--; 1096 1097 while (sig->notify_count) { 1098 __set_current_state(TASK_KILLABLE); 1099 spin_unlock_irq(lock); 1100 schedule(); 1101 if (unlikely(__fatal_signal_pending(tsk))) 1102 goto killed; 1103 spin_lock_irq(lock); 1104 } 1105 spin_unlock_irq(lock); 1106 1107 /* 1108 * At this point all other threads have exited, all we have to 1109 * do is to wait for the thread group leader to become inactive, 1110 * and to assume its PID: 1111 */ 1112 if (!thread_group_leader(tsk)) { 1113 struct task_struct *leader = tsk->group_leader; 1114 1115 for (;;) { 1116 cgroup_threadgroup_change_begin(tsk); 1117 write_lock_irq(&tasklist_lock); 1118 /* 1119 * Do this under tasklist_lock to ensure that 1120 * exit_notify() can't miss ->group_exit_task 1121 */ 1122 sig->notify_count = -1; 1123 if (likely(leader->exit_state)) 1124 break; 1125 __set_current_state(TASK_KILLABLE); 1126 write_unlock_irq(&tasklist_lock); 1127 cgroup_threadgroup_change_end(tsk); 1128 schedule(); 1129 if (unlikely(__fatal_signal_pending(tsk))) 1130 goto killed; 1131 } 1132 1133 /* 1134 * The only record we have of the real-time age of a 1135 * process, regardless of execs it's done, is start_time. 1136 * All the past CPU time is accumulated in signal_struct 1137 * from sister threads now dead. But in this non-leader 1138 * exec, nothing survives from the original leader thread, 1139 * whose birth marks the true age of this process now. 1140 * When we take on its identity by switching to its PID, we 1141 * also take its birthdate (always earlier than our own). 1142 */ 1143 tsk->start_time = leader->start_time; 1144 tsk->real_start_time = leader->real_start_time; 1145 1146 BUG_ON(!same_thread_group(leader, tsk)); 1147 BUG_ON(has_group_leader_pid(tsk)); 1148 /* 1149 * An exec() starts a new thread group with the 1150 * TGID of the previous thread group. Rehash the 1151 * two threads with a switched PID, and release 1152 * the former thread group leader: 1153 */ 1154 1155 /* Become a process group leader with the old leader's pid. 1156 * The old leader becomes a thread of the this thread group. 1157 * Note: The old leader also uses this pid until release_task 1158 * is called. Odd but simple and correct. 1159 */ 1160 tsk->pid = leader->pid; 1161 change_pid(tsk, PIDTYPE_PID, task_pid(leader)); 1162 transfer_pid(leader, tsk, PIDTYPE_PGID); 1163 transfer_pid(leader, tsk, PIDTYPE_SID); 1164 1165 list_replace_rcu(&leader->tasks, &tsk->tasks); 1166 list_replace_init(&leader->sibling, &tsk->sibling); 1167 1168 tsk->group_leader = tsk; 1169 leader->group_leader = tsk; 1170 1171 tsk->exit_signal = SIGCHLD; 1172 leader->exit_signal = -1; 1173 1174 BUG_ON(leader->exit_state != EXIT_ZOMBIE); 1175 leader->exit_state = EXIT_DEAD; 1176 1177 /* 1178 * We are going to release_task()->ptrace_unlink() silently, 1179 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees 1180 * the tracer wont't block again waiting for this thread. 1181 */ 1182 if (unlikely(leader->ptrace)) 1183 __wake_up_parent(leader, leader->parent); 1184 write_unlock_irq(&tasklist_lock); 1185 cgroup_threadgroup_change_end(tsk); 1186 1187 release_task(leader); 1188 } 1189 1190 sig->group_exit_task = NULL; 1191 sig->notify_count = 0; 1192 1193 no_thread_group: 1194 /* we have changed execution domain */ 1195 tsk->exit_signal = SIGCHLD; 1196 1197 #ifdef CONFIG_POSIX_TIMERS 1198 exit_itimers(sig); 1199 flush_itimer_signals(); 1200 #endif 1201 1202 if (atomic_read(&oldsighand->count) != 1) { 1203 struct sighand_struct *newsighand; 1204 /* 1205 * This ->sighand is shared with the CLONE_SIGHAND 1206 * but not CLONE_THREAD task, switch to the new one. 1207 */ 1208 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1209 if (!newsighand) 1210 return -ENOMEM; 1211 1212 atomic_set(&newsighand->count, 1); 1213 memcpy(newsighand->action, oldsighand->action, 1214 sizeof(newsighand->action)); 1215 1216 write_lock_irq(&tasklist_lock); 1217 spin_lock(&oldsighand->siglock); 1218 rcu_assign_pointer(tsk->sighand, newsighand); 1219 spin_unlock(&oldsighand->siglock); 1220 write_unlock_irq(&tasklist_lock); 1221 1222 __cleanup_sighand(oldsighand); 1223 } 1224 1225 BUG_ON(!thread_group_leader(tsk)); 1226 return 0; 1227 1228 killed: 1229 /* protects against exit_notify() and __exit_signal() */ 1230 read_lock(&tasklist_lock); 1231 sig->group_exit_task = NULL; 1232 sig->notify_count = 0; 1233 read_unlock(&tasklist_lock); 1234 return -EAGAIN; 1235 } 1236 1237 char *get_task_comm(char *buf, struct task_struct *tsk) 1238 { 1239 /* buf must be at least sizeof(tsk->comm) in size */ 1240 task_lock(tsk); 1241 strncpy(buf, tsk->comm, sizeof(tsk->comm)); 1242 task_unlock(tsk); 1243 return buf; 1244 } 1245 EXPORT_SYMBOL_GPL(get_task_comm); 1246 1247 /* 1248 * These functions flushes out all traces of the currently running executable 1249 * so that a new one can be started 1250 */ 1251 1252 void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec) 1253 { 1254 task_lock(tsk); 1255 trace_task_rename(tsk, buf); 1256 strlcpy(tsk->comm, buf, sizeof(tsk->comm)); 1257 task_unlock(tsk); 1258 perf_event_comm(tsk, exec); 1259 } 1260 1261 int flush_old_exec(struct linux_binprm * bprm) 1262 { 1263 int retval; 1264 1265 /* 1266 * Make sure we have a private signal table and that 1267 * we are unassociated from the previous thread group. 1268 */ 1269 retval = de_thread(current); 1270 if (retval) 1271 goto out; 1272 1273 /* 1274 * Must be called _before_ exec_mmap() as bprm->mm is 1275 * not visibile until then. This also enables the update 1276 * to be lockless. 1277 */ 1278 set_mm_exe_file(bprm->mm, bprm->file); 1279 1280 /* 1281 * Release all of the old mmap stuff 1282 */ 1283 acct_arg_size(bprm, 0); 1284 retval = exec_mmap(bprm->mm); 1285 if (retval) 1286 goto out; 1287 1288 bprm->mm = NULL; /* We're using it now */ 1289 1290 set_fs(USER_DS); 1291 current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD | 1292 PF_NOFREEZE | PF_NO_SETAFFINITY); 1293 flush_thread(); 1294 current->personality &= ~bprm->per_clear; 1295 1296 /* 1297 * We have to apply CLOEXEC before we change whether the process is 1298 * dumpable (in setup_new_exec) to avoid a race with a process in userspace 1299 * trying to access the should-be-closed file descriptors of a process 1300 * undergoing exec(2). 1301 */ 1302 do_close_on_exec(current->files); 1303 return 0; 1304 1305 out: 1306 return retval; 1307 } 1308 EXPORT_SYMBOL(flush_old_exec); 1309 1310 void would_dump(struct linux_binprm *bprm, struct file *file) 1311 { 1312 struct inode *inode = file_inode(file); 1313 if (inode_permission(inode, MAY_READ) < 0) { 1314 struct user_namespace *old, *user_ns; 1315 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP; 1316 1317 /* Ensure mm->user_ns contains the executable */ 1318 user_ns = old = bprm->mm->user_ns; 1319 while ((user_ns != &init_user_ns) && 1320 !privileged_wrt_inode_uidgid(user_ns, inode)) 1321 user_ns = user_ns->parent; 1322 1323 if (old != user_ns) { 1324 bprm->mm->user_ns = get_user_ns(user_ns); 1325 put_user_ns(old); 1326 } 1327 } 1328 } 1329 EXPORT_SYMBOL(would_dump); 1330 1331 void setup_new_exec(struct linux_binprm * bprm) 1332 { 1333 arch_pick_mmap_layout(current->mm); 1334 1335 /* This is the point of no return */ 1336 current->sas_ss_sp = current->sas_ss_size = 0; 1337 1338 if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid())) 1339 set_dumpable(current->mm, SUID_DUMP_USER); 1340 else 1341 set_dumpable(current->mm, suid_dumpable); 1342 1343 arch_setup_new_exec(); 1344 perf_event_exec(); 1345 __set_task_comm(current, kbasename(bprm->filename), true); 1346 1347 /* Set the new mm task size. We have to do that late because it may 1348 * depend on TIF_32BIT which is only updated in flush_thread() on 1349 * some architectures like powerpc 1350 */ 1351 current->mm->task_size = TASK_SIZE; 1352 1353 /* install the new credentials */ 1354 if (!uid_eq(bprm->cred->uid, current_euid()) || 1355 !gid_eq(bprm->cred->gid, current_egid())) { 1356 current->pdeath_signal = 0; 1357 } else { 1358 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) 1359 set_dumpable(current->mm, suid_dumpable); 1360 } 1361 1362 /* An exec changes our domain. We are no longer part of the thread 1363 group */ 1364 current->self_exec_id++; 1365 flush_signal_handlers(current, 0); 1366 } 1367 EXPORT_SYMBOL(setup_new_exec); 1368 1369 /* 1370 * Prepare credentials and lock ->cred_guard_mutex. 1371 * install_exec_creds() commits the new creds and drops the lock. 1372 * Or, if exec fails before, free_bprm() should release ->cred and 1373 * and unlock. 1374 */ 1375 int prepare_bprm_creds(struct linux_binprm *bprm) 1376 { 1377 if (mutex_lock_interruptible(¤t->signal->cred_guard_mutex)) 1378 return -ERESTARTNOINTR; 1379 1380 bprm->cred = prepare_exec_creds(); 1381 if (likely(bprm->cred)) 1382 return 0; 1383 1384 mutex_unlock(¤t->signal->cred_guard_mutex); 1385 return -ENOMEM; 1386 } 1387 1388 static void free_bprm(struct linux_binprm *bprm) 1389 { 1390 free_arg_pages(bprm); 1391 if (bprm->cred) { 1392 mutex_unlock(¤t->signal->cred_guard_mutex); 1393 abort_creds(bprm->cred); 1394 } 1395 if (bprm->file) { 1396 allow_write_access(bprm->file); 1397 fput(bprm->file); 1398 } 1399 /* If a binfmt changed the interp, free it. */ 1400 if (bprm->interp != bprm->filename) 1401 kfree(bprm->interp); 1402 kfree(bprm); 1403 } 1404 1405 int bprm_change_interp(char *interp, struct linux_binprm *bprm) 1406 { 1407 /* If a binfmt changed the interp, free it first. */ 1408 if (bprm->interp != bprm->filename) 1409 kfree(bprm->interp); 1410 bprm->interp = kstrdup(interp, GFP_KERNEL); 1411 if (!bprm->interp) 1412 return -ENOMEM; 1413 return 0; 1414 } 1415 EXPORT_SYMBOL(bprm_change_interp); 1416 1417 /* 1418 * install the new credentials for this executable 1419 */ 1420 void install_exec_creds(struct linux_binprm *bprm) 1421 { 1422 security_bprm_committing_creds(bprm); 1423 1424 commit_creds(bprm->cred); 1425 bprm->cred = NULL; 1426 1427 /* 1428 * Disable monitoring for regular users 1429 * when executing setuid binaries. Must 1430 * wait until new credentials are committed 1431 * by commit_creds() above 1432 */ 1433 if (get_dumpable(current->mm) != SUID_DUMP_USER) 1434 perf_event_exit_task(current); 1435 /* 1436 * cred_guard_mutex must be held at least to this point to prevent 1437 * ptrace_attach() from altering our determination of the task's 1438 * credentials; any time after this it may be unlocked. 1439 */ 1440 security_bprm_committed_creds(bprm); 1441 mutex_unlock(¤t->signal->cred_guard_mutex); 1442 } 1443 EXPORT_SYMBOL(install_exec_creds); 1444 1445 /* 1446 * determine how safe it is to execute the proposed program 1447 * - the caller must hold ->cred_guard_mutex to protect against 1448 * PTRACE_ATTACH or seccomp thread-sync 1449 */ 1450 static void check_unsafe_exec(struct linux_binprm *bprm) 1451 { 1452 struct task_struct *p = current, *t; 1453 unsigned n_fs; 1454 1455 if (p->ptrace) 1456 bprm->unsafe |= LSM_UNSAFE_PTRACE; 1457 1458 /* 1459 * This isn't strictly necessary, but it makes it harder for LSMs to 1460 * mess up. 1461 */ 1462 if (task_no_new_privs(current)) 1463 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS; 1464 1465 t = p; 1466 n_fs = 1; 1467 spin_lock(&p->fs->lock); 1468 rcu_read_lock(); 1469 while_each_thread(p, t) { 1470 if (t->fs == p->fs) 1471 n_fs++; 1472 } 1473 rcu_read_unlock(); 1474 1475 if (p->fs->users > n_fs) 1476 bprm->unsafe |= LSM_UNSAFE_SHARE; 1477 else 1478 p->fs->in_exec = 1; 1479 spin_unlock(&p->fs->lock); 1480 } 1481 1482 static void bprm_fill_uid(struct linux_binprm *bprm) 1483 { 1484 struct inode *inode; 1485 unsigned int mode; 1486 kuid_t uid; 1487 kgid_t gid; 1488 1489 /* 1490 * Since this can be called multiple times (via prepare_binprm), 1491 * we must clear any previous work done when setting set[ug]id 1492 * bits from any earlier bprm->file uses (for example when run 1493 * first for a setuid script then again for its interpreter). 1494 */ 1495 bprm->cred->euid = current_euid(); 1496 bprm->cred->egid = current_egid(); 1497 1498 if (!mnt_may_suid(bprm->file->f_path.mnt)) 1499 return; 1500 1501 if (task_no_new_privs(current)) 1502 return; 1503 1504 inode = bprm->file->f_path.dentry->d_inode; 1505 mode = READ_ONCE(inode->i_mode); 1506 if (!(mode & (S_ISUID|S_ISGID))) 1507 return; 1508 1509 /* Be careful if suid/sgid is set */ 1510 inode_lock(inode); 1511 1512 /* reload atomically mode/uid/gid now that lock held */ 1513 mode = inode->i_mode; 1514 uid = inode->i_uid; 1515 gid = inode->i_gid; 1516 inode_unlock(inode); 1517 1518 /* We ignore suid/sgid if there are no mappings for them in the ns */ 1519 if (!kuid_has_mapping(bprm->cred->user_ns, uid) || 1520 !kgid_has_mapping(bprm->cred->user_ns, gid)) 1521 return; 1522 1523 if (mode & S_ISUID) { 1524 bprm->per_clear |= PER_CLEAR_ON_SETID; 1525 bprm->cred->euid = uid; 1526 } 1527 1528 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { 1529 bprm->per_clear |= PER_CLEAR_ON_SETID; 1530 bprm->cred->egid = gid; 1531 } 1532 } 1533 1534 /* 1535 * Fill the binprm structure from the inode. 1536 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes 1537 * 1538 * This may be called multiple times for binary chains (scripts for example). 1539 */ 1540 int prepare_binprm(struct linux_binprm *bprm) 1541 { 1542 int retval; 1543 1544 bprm_fill_uid(bprm); 1545 1546 /* fill in binprm security blob */ 1547 retval = security_bprm_set_creds(bprm); 1548 if (retval) 1549 return retval; 1550 bprm->cred_prepared = 1; 1551 1552 memset(bprm->buf, 0, BINPRM_BUF_SIZE); 1553 return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE); 1554 } 1555 1556 EXPORT_SYMBOL(prepare_binprm); 1557 1558 /* 1559 * Arguments are '\0' separated strings found at the location bprm->p 1560 * points to; chop off the first by relocating brpm->p to right after 1561 * the first '\0' encountered. 1562 */ 1563 int remove_arg_zero(struct linux_binprm *bprm) 1564 { 1565 int ret = 0; 1566 unsigned long offset; 1567 char *kaddr; 1568 struct page *page; 1569 1570 if (!bprm->argc) 1571 return 0; 1572 1573 do { 1574 offset = bprm->p & ~PAGE_MASK; 1575 page = get_arg_page(bprm, bprm->p, 0); 1576 if (!page) { 1577 ret = -EFAULT; 1578 goto out; 1579 } 1580 kaddr = kmap_atomic(page); 1581 1582 for (; offset < PAGE_SIZE && kaddr[offset]; 1583 offset++, bprm->p++) 1584 ; 1585 1586 kunmap_atomic(kaddr); 1587 put_arg_page(page); 1588 } while (offset == PAGE_SIZE); 1589 1590 bprm->p++; 1591 bprm->argc--; 1592 ret = 0; 1593 1594 out: 1595 return ret; 1596 } 1597 EXPORT_SYMBOL(remove_arg_zero); 1598 1599 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e)) 1600 /* 1601 * cycle the list of binary formats handler, until one recognizes the image 1602 */ 1603 int search_binary_handler(struct linux_binprm *bprm) 1604 { 1605 bool need_retry = IS_ENABLED(CONFIG_MODULES); 1606 struct linux_binfmt *fmt; 1607 int retval; 1608 1609 /* This allows 4 levels of binfmt rewrites before failing hard. */ 1610 if (bprm->recursion_depth > 5) 1611 return -ELOOP; 1612 1613 retval = security_bprm_check(bprm); 1614 if (retval) 1615 return retval; 1616 1617 retval = -ENOENT; 1618 retry: 1619 read_lock(&binfmt_lock); 1620 list_for_each_entry(fmt, &formats, lh) { 1621 if (!try_module_get(fmt->module)) 1622 continue; 1623 read_unlock(&binfmt_lock); 1624 bprm->recursion_depth++; 1625 retval = fmt->load_binary(bprm); 1626 read_lock(&binfmt_lock); 1627 put_binfmt(fmt); 1628 bprm->recursion_depth--; 1629 if (retval < 0 && !bprm->mm) { 1630 /* we got to flush_old_exec() and failed after it */ 1631 read_unlock(&binfmt_lock); 1632 force_sigsegv(SIGSEGV, current); 1633 return retval; 1634 } 1635 if (retval != -ENOEXEC || !bprm->file) { 1636 read_unlock(&binfmt_lock); 1637 return retval; 1638 } 1639 } 1640 read_unlock(&binfmt_lock); 1641 1642 if (need_retry) { 1643 if (printable(bprm->buf[0]) && printable(bprm->buf[1]) && 1644 printable(bprm->buf[2]) && printable(bprm->buf[3])) 1645 return retval; 1646 if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0) 1647 return retval; 1648 need_retry = false; 1649 goto retry; 1650 } 1651 1652 return retval; 1653 } 1654 EXPORT_SYMBOL(search_binary_handler); 1655 1656 static int exec_binprm(struct linux_binprm *bprm) 1657 { 1658 pid_t old_pid, old_vpid; 1659 int ret; 1660 1661 /* Need to fetch pid before load_binary changes it */ 1662 old_pid = current->pid; 1663 rcu_read_lock(); 1664 old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent)); 1665 rcu_read_unlock(); 1666 1667 ret = search_binary_handler(bprm); 1668 if (ret >= 0) { 1669 audit_bprm(bprm); 1670 trace_sched_process_exec(current, old_pid, bprm); 1671 ptrace_event(PTRACE_EVENT_EXEC, old_vpid); 1672 proc_exec_connector(current); 1673 } 1674 1675 return ret; 1676 } 1677 1678 /* 1679 * sys_execve() executes a new program. 1680 */ 1681 static int do_execveat_common(int fd, struct filename *filename, 1682 struct user_arg_ptr argv, 1683 struct user_arg_ptr envp, 1684 int flags) 1685 { 1686 char *pathbuf = NULL; 1687 struct linux_binprm *bprm; 1688 struct file *file; 1689 struct files_struct *displaced; 1690 int retval; 1691 1692 if (IS_ERR(filename)) 1693 return PTR_ERR(filename); 1694 1695 /* 1696 * We move the actual failure in case of RLIMIT_NPROC excess from 1697 * set*uid() to execve() because too many poorly written programs 1698 * don't check setuid() return code. Here we additionally recheck 1699 * whether NPROC limit is still exceeded. 1700 */ 1701 if ((current->flags & PF_NPROC_EXCEEDED) && 1702 atomic_read(¤t_user()->processes) > rlimit(RLIMIT_NPROC)) { 1703 retval = -EAGAIN; 1704 goto out_ret; 1705 } 1706 1707 /* We're below the limit (still or again), so we don't want to make 1708 * further execve() calls fail. */ 1709 current->flags &= ~PF_NPROC_EXCEEDED; 1710 1711 retval = unshare_files(&displaced); 1712 if (retval) 1713 goto out_ret; 1714 1715 retval = -ENOMEM; 1716 bprm = kzalloc(sizeof(*bprm), GFP_KERNEL); 1717 if (!bprm) 1718 goto out_files; 1719 1720 retval = prepare_bprm_creds(bprm); 1721 if (retval) 1722 goto out_free; 1723 1724 check_unsafe_exec(bprm); 1725 current->in_execve = 1; 1726 1727 file = do_open_execat(fd, filename, flags); 1728 retval = PTR_ERR(file); 1729 if (IS_ERR(file)) 1730 goto out_unmark; 1731 1732 sched_exec(); 1733 1734 bprm->file = file; 1735 if (fd == AT_FDCWD || filename->name[0] == '/') { 1736 bprm->filename = filename->name; 1737 } else { 1738 if (filename->name[0] == '\0') 1739 pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d", fd); 1740 else 1741 pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d/%s", 1742 fd, filename->name); 1743 if (!pathbuf) { 1744 retval = -ENOMEM; 1745 goto out_unmark; 1746 } 1747 /* 1748 * Record that a name derived from an O_CLOEXEC fd will be 1749 * inaccessible after exec. Relies on having exclusive access to 1750 * current->files (due to unshare_files above). 1751 */ 1752 if (close_on_exec(fd, rcu_dereference_raw(current->files->fdt))) 1753 bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE; 1754 bprm->filename = pathbuf; 1755 } 1756 bprm->interp = bprm->filename; 1757 1758 retval = bprm_mm_init(bprm); 1759 if (retval) 1760 goto out_unmark; 1761 1762 bprm->argc = count(argv, MAX_ARG_STRINGS); 1763 if ((retval = bprm->argc) < 0) 1764 goto out; 1765 1766 bprm->envc = count(envp, MAX_ARG_STRINGS); 1767 if ((retval = bprm->envc) < 0) 1768 goto out; 1769 1770 retval = prepare_binprm(bprm); 1771 if (retval < 0) 1772 goto out; 1773 1774 retval = copy_strings_kernel(1, &bprm->filename, bprm); 1775 if (retval < 0) 1776 goto out; 1777 1778 bprm->exec = bprm->p; 1779 retval = copy_strings(bprm->envc, envp, bprm); 1780 if (retval < 0) 1781 goto out; 1782 1783 retval = copy_strings(bprm->argc, argv, bprm); 1784 if (retval < 0) 1785 goto out; 1786 1787 would_dump(bprm, bprm->file); 1788 1789 retval = exec_binprm(bprm); 1790 if (retval < 0) 1791 goto out; 1792 1793 /* execve succeeded */ 1794 current->fs->in_exec = 0; 1795 current->in_execve = 0; 1796 acct_update_integrals(current); 1797 task_numa_free(current); 1798 free_bprm(bprm); 1799 kfree(pathbuf); 1800 putname(filename); 1801 if (displaced) 1802 put_files_struct(displaced); 1803 return retval; 1804 1805 out: 1806 if (bprm->mm) { 1807 acct_arg_size(bprm, 0); 1808 mmput(bprm->mm); 1809 } 1810 1811 out_unmark: 1812 current->fs->in_exec = 0; 1813 current->in_execve = 0; 1814 1815 out_free: 1816 free_bprm(bprm); 1817 kfree(pathbuf); 1818 1819 out_files: 1820 if (displaced) 1821 reset_files_struct(displaced); 1822 out_ret: 1823 putname(filename); 1824 return retval; 1825 } 1826 1827 int do_execve(struct filename *filename, 1828 const char __user *const __user *__argv, 1829 const char __user *const __user *__envp) 1830 { 1831 struct user_arg_ptr argv = { .ptr.native = __argv }; 1832 struct user_arg_ptr envp = { .ptr.native = __envp }; 1833 return do_execveat_common(AT_FDCWD, filename, argv, envp, 0); 1834 } 1835 1836 int do_execveat(int fd, struct filename *filename, 1837 const char __user *const __user *__argv, 1838 const char __user *const __user *__envp, 1839 int flags) 1840 { 1841 struct user_arg_ptr argv = { .ptr.native = __argv }; 1842 struct user_arg_ptr envp = { .ptr.native = __envp }; 1843 1844 return do_execveat_common(fd, filename, argv, envp, flags); 1845 } 1846 1847 #ifdef CONFIG_COMPAT 1848 static int compat_do_execve(struct filename *filename, 1849 const compat_uptr_t __user *__argv, 1850 const compat_uptr_t __user *__envp) 1851 { 1852 struct user_arg_ptr argv = { 1853 .is_compat = true, 1854 .ptr.compat = __argv, 1855 }; 1856 struct user_arg_ptr envp = { 1857 .is_compat = true, 1858 .ptr.compat = __envp, 1859 }; 1860 return do_execveat_common(AT_FDCWD, filename, argv, envp, 0); 1861 } 1862 1863 static int compat_do_execveat(int fd, struct filename *filename, 1864 const compat_uptr_t __user *__argv, 1865 const compat_uptr_t __user *__envp, 1866 int flags) 1867 { 1868 struct user_arg_ptr argv = { 1869 .is_compat = true, 1870 .ptr.compat = __argv, 1871 }; 1872 struct user_arg_ptr envp = { 1873 .is_compat = true, 1874 .ptr.compat = __envp, 1875 }; 1876 return do_execveat_common(fd, filename, argv, envp, flags); 1877 } 1878 #endif 1879 1880 void set_binfmt(struct linux_binfmt *new) 1881 { 1882 struct mm_struct *mm = current->mm; 1883 1884 if (mm->binfmt) 1885 module_put(mm->binfmt->module); 1886 1887 mm->binfmt = new; 1888 if (new) 1889 __module_get(new->module); 1890 } 1891 EXPORT_SYMBOL(set_binfmt); 1892 1893 /* 1894 * set_dumpable stores three-value SUID_DUMP_* into mm->flags. 1895 */ 1896 void set_dumpable(struct mm_struct *mm, int value) 1897 { 1898 unsigned long old, new; 1899 1900 if (WARN_ON((unsigned)value > SUID_DUMP_ROOT)) 1901 return; 1902 1903 do { 1904 old = ACCESS_ONCE(mm->flags); 1905 new = (old & ~MMF_DUMPABLE_MASK) | value; 1906 } while (cmpxchg(&mm->flags, old, new) != old); 1907 } 1908 1909 SYSCALL_DEFINE3(execve, 1910 const char __user *, filename, 1911 const char __user *const __user *, argv, 1912 const char __user *const __user *, envp) 1913 { 1914 return do_execve(getname(filename), argv, envp); 1915 } 1916 1917 SYSCALL_DEFINE5(execveat, 1918 int, fd, const char __user *, filename, 1919 const char __user *const __user *, argv, 1920 const char __user *const __user *, envp, 1921 int, flags) 1922 { 1923 int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0; 1924 1925 return do_execveat(fd, 1926 getname_flags(filename, lookup_flags, NULL), 1927 argv, envp, flags); 1928 } 1929 1930 #ifdef CONFIG_COMPAT 1931 COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename, 1932 const compat_uptr_t __user *, argv, 1933 const compat_uptr_t __user *, envp) 1934 { 1935 return compat_do_execve(getname(filename), argv, envp); 1936 } 1937 1938 COMPAT_SYSCALL_DEFINE5(execveat, int, fd, 1939 const char __user *, filename, 1940 const compat_uptr_t __user *, argv, 1941 const compat_uptr_t __user *, envp, 1942 int, flags) 1943 { 1944 int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0; 1945 1946 return compat_do_execveat(fd, 1947 getname_flags(filename, lookup_flags, NULL), 1948 argv, envp, flags); 1949 } 1950 #endif 1951