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/pagemap.h> 36 #include <linux/perf_event.h> 37 #include <linux/highmem.h> 38 #include <linux/spinlock.h> 39 #include <linux/key.h> 40 #include <linux/personality.h> 41 #include <linux/binfmts.h> 42 #include <linux/utsname.h> 43 #include <linux/pid_namespace.h> 44 #include <linux/module.h> 45 #include <linux/namei.h> 46 #include <linux/mount.h> 47 #include <linux/security.h> 48 #include <linux/syscalls.h> 49 #include <linux/tsacct_kern.h> 50 #include <linux/cn_proc.h> 51 #include <linux/audit.h> 52 #include <linux/tracehook.h> 53 #include <linux/kmod.h> 54 #include <linux/fsnotify.h> 55 #include <linux/fs_struct.h> 56 #include <linux/pipe_fs_i.h> 57 #include <linux/oom.h> 58 #include <linux/compat.h> 59 #include <linux/vmalloc.h> 60 61 #include <asm/uaccess.h> 62 #include <asm/mmu_context.h> 63 #include <asm/tlb.h> 64 65 #include <trace/events/task.h> 66 #include "internal.h" 67 68 #include <trace/events/sched.h> 69 70 int suid_dumpable = 0; 71 72 static LIST_HEAD(formats); 73 static DEFINE_RWLOCK(binfmt_lock); 74 75 void __register_binfmt(struct linux_binfmt * fmt, int insert) 76 { 77 BUG_ON(!fmt); 78 if (WARN_ON(!fmt->load_binary)) 79 return; 80 write_lock(&binfmt_lock); 81 insert ? list_add(&fmt->lh, &formats) : 82 list_add_tail(&fmt->lh, &formats); 83 write_unlock(&binfmt_lock); 84 } 85 86 EXPORT_SYMBOL(__register_binfmt); 87 88 void unregister_binfmt(struct linux_binfmt * fmt) 89 { 90 write_lock(&binfmt_lock); 91 list_del(&fmt->lh); 92 write_unlock(&binfmt_lock); 93 } 94 95 EXPORT_SYMBOL(unregister_binfmt); 96 97 static inline void put_binfmt(struct linux_binfmt * fmt) 98 { 99 module_put(fmt->module); 100 } 101 102 bool path_noexec(const struct path *path) 103 { 104 return (path->mnt->mnt_flags & MNT_NOEXEC) || 105 (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC); 106 } 107 108 #ifdef CONFIG_USELIB 109 /* 110 * Note that a shared library must be both readable and executable due to 111 * security reasons. 112 * 113 * Also note that we take the address to load from from the file itself. 114 */ 115 SYSCALL_DEFINE1(uselib, const char __user *, library) 116 { 117 struct linux_binfmt *fmt; 118 struct file *file; 119 struct filename *tmp = getname(library); 120 int error = PTR_ERR(tmp); 121 static const struct open_flags uselib_flags = { 122 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC, 123 .acc_mode = MAY_READ | MAY_EXEC, 124 .intent = LOOKUP_OPEN, 125 .lookup_flags = LOOKUP_FOLLOW, 126 }; 127 128 if (IS_ERR(tmp)) 129 goto out; 130 131 file = do_filp_open(AT_FDCWD, tmp, &uselib_flags); 132 putname(tmp); 133 error = PTR_ERR(file); 134 if (IS_ERR(file)) 135 goto out; 136 137 error = -EINVAL; 138 if (!S_ISREG(file_inode(file)->i_mode)) 139 goto exit; 140 141 error = -EACCES; 142 if (path_noexec(&file->f_path)) 143 goto exit; 144 145 fsnotify_open(file); 146 147 error = -ENOEXEC; 148 149 read_lock(&binfmt_lock); 150 list_for_each_entry(fmt, &formats, lh) { 151 if (!fmt->load_shlib) 152 continue; 153 if (!try_module_get(fmt->module)) 154 continue; 155 read_unlock(&binfmt_lock); 156 error = fmt->load_shlib(file); 157 read_lock(&binfmt_lock); 158 put_binfmt(fmt); 159 if (error != -ENOEXEC) 160 break; 161 } 162 read_unlock(&binfmt_lock); 163 exit: 164 fput(file); 165 out: 166 return error; 167 } 168 #endif /* #ifdef CONFIG_USELIB */ 169 170 #ifdef CONFIG_MMU 171 /* 172 * The nascent bprm->mm is not visible until exec_mmap() but it can 173 * use a lot of memory, account these pages in current->mm temporary 174 * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we 175 * change the counter back via acct_arg_size(0). 176 */ 177 static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages) 178 { 179 struct mm_struct *mm = current->mm; 180 long diff = (long)(pages - bprm->vma_pages); 181 182 if (!mm || !diff) 183 return; 184 185 bprm->vma_pages = pages; 186 add_mm_counter(mm, MM_ANONPAGES, diff); 187 } 188 189 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, 190 int write) 191 { 192 struct page *page; 193 int ret; 194 195 #ifdef CONFIG_STACK_GROWSUP 196 if (write) { 197 ret = expand_downwards(bprm->vma, pos); 198 if (ret < 0) 199 return NULL; 200 } 201 #endif 202 /* 203 * We are doing an exec(). 'current' is the process 204 * doing the exec and bprm->mm is the new process's mm. 205 */ 206 ret = get_user_pages_remote(current, bprm->mm, pos, 1, write, 207 1, &page, NULL); 208 if (ret <= 0) 209 return NULL; 210 211 if (write) { 212 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start; 213 struct rlimit *rlim; 214 215 acct_arg_size(bprm, size / PAGE_SIZE); 216 217 /* 218 * We've historically supported up to 32 pages (ARG_MAX) 219 * of argument strings even with small stacks 220 */ 221 if (size <= ARG_MAX) 222 return page; 223 224 /* 225 * Limit to 1/4-th the stack size for the argv+env strings. 226 * This ensures that: 227 * - the remaining binfmt code will not run out of stack space, 228 * - the program will have a reasonable amount of stack left 229 * to work from. 230 */ 231 rlim = current->signal->rlim; 232 if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) { 233 put_page(page); 234 return NULL; 235 } 236 } 237 238 return page; 239 } 240 241 static void put_arg_page(struct page *page) 242 { 243 put_page(page); 244 } 245 246 static void free_arg_page(struct linux_binprm *bprm, int i) 247 { 248 } 249 250 static void free_arg_pages(struct linux_binprm *bprm) 251 { 252 } 253 254 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, 255 struct page *page) 256 { 257 flush_cache_page(bprm->vma, pos, page_to_pfn(page)); 258 } 259 260 static int __bprm_mm_init(struct linux_binprm *bprm) 261 { 262 int err; 263 struct vm_area_struct *vma = NULL; 264 struct mm_struct *mm = bprm->mm; 265 266 bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL); 267 if (!vma) 268 return -ENOMEM; 269 270 down_write(&mm->mmap_sem); 271 vma->vm_mm = mm; 272 273 /* 274 * Place the stack at the largest stack address the architecture 275 * supports. Later, we'll move this to an appropriate place. We don't 276 * use STACK_TOP because that can depend on attributes which aren't 277 * configured yet. 278 */ 279 BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP); 280 vma->vm_end = STACK_TOP_MAX; 281 vma->vm_start = vma->vm_end - PAGE_SIZE; 282 vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP; 283 vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); 284 INIT_LIST_HEAD(&vma->anon_vma_chain); 285 286 err = insert_vm_struct(mm, vma); 287 if (err) 288 goto err; 289 290 mm->stack_vm = mm->total_vm = 1; 291 arch_bprm_mm_init(mm, vma); 292 up_write(&mm->mmap_sem); 293 bprm->p = vma->vm_end - sizeof(void *); 294 return 0; 295 err: 296 up_write(&mm->mmap_sem); 297 bprm->vma = NULL; 298 kmem_cache_free(vm_area_cachep, vma); 299 return err; 300 } 301 302 static bool valid_arg_len(struct linux_binprm *bprm, long len) 303 { 304 return len <= MAX_ARG_STRLEN; 305 } 306 307 #else 308 309 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages) 310 { 311 } 312 313 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, 314 int write) 315 { 316 struct page *page; 317 318 page = bprm->page[pos / PAGE_SIZE]; 319 if (!page && write) { 320 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO); 321 if (!page) 322 return NULL; 323 bprm->page[pos / PAGE_SIZE] = page; 324 } 325 326 return page; 327 } 328 329 static void put_arg_page(struct page *page) 330 { 331 } 332 333 static void free_arg_page(struct linux_binprm *bprm, int i) 334 { 335 if (bprm->page[i]) { 336 __free_page(bprm->page[i]); 337 bprm->page[i] = NULL; 338 } 339 } 340 341 static void free_arg_pages(struct linux_binprm *bprm) 342 { 343 int i; 344 345 for (i = 0; i < MAX_ARG_PAGES; i++) 346 free_arg_page(bprm, i); 347 } 348 349 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, 350 struct page *page) 351 { 352 } 353 354 static int __bprm_mm_init(struct linux_binprm *bprm) 355 { 356 bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *); 357 return 0; 358 } 359 360 static bool valid_arg_len(struct linux_binprm *bprm, long len) 361 { 362 return len <= bprm->p; 363 } 364 365 #endif /* CONFIG_MMU */ 366 367 /* 368 * Create a new mm_struct and populate it with a temporary stack 369 * vm_area_struct. We don't have enough context at this point to set the stack 370 * flags, permissions, and offset, so we use temporary values. We'll update 371 * them later in setup_arg_pages(). 372 */ 373 static int bprm_mm_init(struct linux_binprm *bprm) 374 { 375 int err; 376 struct mm_struct *mm = NULL; 377 378 bprm->mm = mm = mm_alloc(); 379 err = -ENOMEM; 380 if (!mm) 381 goto err; 382 383 err = __bprm_mm_init(bprm); 384 if (err) 385 goto err; 386 387 return 0; 388 389 err: 390 if (mm) { 391 bprm->mm = NULL; 392 mmdrop(mm); 393 } 394 395 return err; 396 } 397 398 struct user_arg_ptr { 399 #ifdef CONFIG_COMPAT 400 bool is_compat; 401 #endif 402 union { 403 const char __user *const __user *native; 404 #ifdef CONFIG_COMPAT 405 const compat_uptr_t __user *compat; 406 #endif 407 } ptr; 408 }; 409 410 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr) 411 { 412 const char __user *native; 413 414 #ifdef CONFIG_COMPAT 415 if (unlikely(argv.is_compat)) { 416 compat_uptr_t compat; 417 418 if (get_user(compat, argv.ptr.compat + nr)) 419 return ERR_PTR(-EFAULT); 420 421 return compat_ptr(compat); 422 } 423 #endif 424 425 if (get_user(native, argv.ptr.native + nr)) 426 return ERR_PTR(-EFAULT); 427 428 return native; 429 } 430 431 /* 432 * count() counts the number of strings in array ARGV. 433 */ 434 static int count(struct user_arg_ptr argv, int max) 435 { 436 int i = 0; 437 438 if (argv.ptr.native != NULL) { 439 for (;;) { 440 const char __user *p = get_user_arg_ptr(argv, i); 441 442 if (!p) 443 break; 444 445 if (IS_ERR(p)) 446 return -EFAULT; 447 448 if (i >= max) 449 return -E2BIG; 450 ++i; 451 452 if (fatal_signal_pending(current)) 453 return -ERESTARTNOHAND; 454 cond_resched(); 455 } 456 } 457 return i; 458 } 459 460 /* 461 * 'copy_strings()' copies argument/environment strings from the old 462 * processes's memory to the new process's stack. The call to get_user_pages() 463 * ensures the destination page is created and not swapped out. 464 */ 465 static int copy_strings(int argc, struct user_arg_ptr argv, 466 struct linux_binprm *bprm) 467 { 468 struct page *kmapped_page = NULL; 469 char *kaddr = NULL; 470 unsigned long kpos = 0; 471 int ret; 472 473 while (argc-- > 0) { 474 const char __user *str; 475 int len; 476 unsigned long pos; 477 478 ret = -EFAULT; 479 str = get_user_arg_ptr(argv, argc); 480 if (IS_ERR(str)) 481 goto out; 482 483 len = strnlen_user(str, MAX_ARG_STRLEN); 484 if (!len) 485 goto out; 486 487 ret = -E2BIG; 488 if (!valid_arg_len(bprm, len)) 489 goto out; 490 491 /* We're going to work our way backwords. */ 492 pos = bprm->p; 493 str += len; 494 bprm->p -= len; 495 496 while (len > 0) { 497 int offset, bytes_to_copy; 498 499 if (fatal_signal_pending(current)) { 500 ret = -ERESTARTNOHAND; 501 goto out; 502 } 503 cond_resched(); 504 505 offset = pos % PAGE_SIZE; 506 if (offset == 0) 507 offset = PAGE_SIZE; 508 509 bytes_to_copy = offset; 510 if (bytes_to_copy > len) 511 bytes_to_copy = len; 512 513 offset -= bytes_to_copy; 514 pos -= bytes_to_copy; 515 str -= bytes_to_copy; 516 len -= bytes_to_copy; 517 518 if (!kmapped_page || kpos != (pos & PAGE_MASK)) { 519 struct page *page; 520 521 page = get_arg_page(bprm, pos, 1); 522 if (!page) { 523 ret = -E2BIG; 524 goto out; 525 } 526 527 if (kmapped_page) { 528 flush_kernel_dcache_page(kmapped_page); 529 kunmap(kmapped_page); 530 put_arg_page(kmapped_page); 531 } 532 kmapped_page = page; 533 kaddr = kmap(kmapped_page); 534 kpos = pos & PAGE_MASK; 535 flush_arg_page(bprm, kpos, kmapped_page); 536 } 537 if (copy_from_user(kaddr+offset, str, bytes_to_copy)) { 538 ret = -EFAULT; 539 goto out; 540 } 541 } 542 } 543 ret = 0; 544 out: 545 if (kmapped_page) { 546 flush_kernel_dcache_page(kmapped_page); 547 kunmap(kmapped_page); 548 put_arg_page(kmapped_page); 549 } 550 return ret; 551 } 552 553 /* 554 * Like copy_strings, but get argv and its values from kernel memory. 555 */ 556 int copy_strings_kernel(int argc, const char *const *__argv, 557 struct linux_binprm *bprm) 558 { 559 int r; 560 mm_segment_t oldfs = get_fs(); 561 struct user_arg_ptr argv = { 562 .ptr.native = (const char __user *const __user *)__argv, 563 }; 564 565 set_fs(KERNEL_DS); 566 r = copy_strings(argc, argv, bprm); 567 set_fs(oldfs); 568 569 return r; 570 } 571 EXPORT_SYMBOL(copy_strings_kernel); 572 573 #ifdef CONFIG_MMU 574 575 /* 576 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once 577 * the binfmt code determines where the new stack should reside, we shift it to 578 * its final location. The process proceeds as follows: 579 * 580 * 1) Use shift to calculate the new vma endpoints. 581 * 2) Extend vma to cover both the old and new ranges. This ensures the 582 * arguments passed to subsequent functions are consistent. 583 * 3) Move vma's page tables to the new range. 584 * 4) Free up any cleared pgd range. 585 * 5) Shrink the vma to cover only the new range. 586 */ 587 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift) 588 { 589 struct mm_struct *mm = vma->vm_mm; 590 unsigned long old_start = vma->vm_start; 591 unsigned long old_end = vma->vm_end; 592 unsigned long length = old_end - old_start; 593 unsigned long new_start = old_start - shift; 594 unsigned long new_end = old_end - shift; 595 struct mmu_gather tlb; 596 597 BUG_ON(new_start > new_end); 598 599 /* 600 * ensure there are no vmas between where we want to go 601 * and where we are 602 */ 603 if (vma != find_vma(mm, new_start)) 604 return -EFAULT; 605 606 /* 607 * cover the whole range: [new_start, old_end) 608 */ 609 if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL)) 610 return -ENOMEM; 611 612 /* 613 * move the page tables downwards, on failure we rely on 614 * process cleanup to remove whatever mess we made. 615 */ 616 if (length != move_page_tables(vma, old_start, 617 vma, new_start, length, false)) 618 return -ENOMEM; 619 620 lru_add_drain(); 621 tlb_gather_mmu(&tlb, mm, old_start, old_end); 622 if (new_end > old_start) { 623 /* 624 * when the old and new regions overlap clear from new_end. 625 */ 626 free_pgd_range(&tlb, new_end, old_end, new_end, 627 vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING); 628 } else { 629 /* 630 * otherwise, clean from old_start; this is done to not touch 631 * the address space in [new_end, old_start) some architectures 632 * have constraints on va-space that make this illegal (IA64) - 633 * for the others its just a little faster. 634 */ 635 free_pgd_range(&tlb, old_start, old_end, new_end, 636 vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING); 637 } 638 tlb_finish_mmu(&tlb, old_start, old_end); 639 640 /* 641 * Shrink the vma to just the new range. Always succeeds. 642 */ 643 vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL); 644 645 return 0; 646 } 647 648 /* 649 * Finalizes the stack vm_area_struct. The flags and permissions are updated, 650 * the stack is optionally relocated, and some extra space is added. 651 */ 652 int setup_arg_pages(struct linux_binprm *bprm, 653 unsigned long stack_top, 654 int executable_stack) 655 { 656 unsigned long ret; 657 unsigned long stack_shift; 658 struct mm_struct *mm = current->mm; 659 struct vm_area_struct *vma = bprm->vma; 660 struct vm_area_struct *prev = NULL; 661 unsigned long vm_flags; 662 unsigned long stack_base; 663 unsigned long stack_size; 664 unsigned long stack_expand; 665 unsigned long rlim_stack; 666 667 #ifdef CONFIG_STACK_GROWSUP 668 /* Limit stack size */ 669 stack_base = rlimit_max(RLIMIT_STACK); 670 if (stack_base > STACK_SIZE_MAX) 671 stack_base = STACK_SIZE_MAX; 672 673 /* Add space for stack randomization. */ 674 stack_base += (STACK_RND_MASK << PAGE_SHIFT); 675 676 /* Make sure we didn't let the argument array grow too large. */ 677 if (vma->vm_end - vma->vm_start > stack_base) 678 return -ENOMEM; 679 680 stack_base = PAGE_ALIGN(stack_top - stack_base); 681 682 stack_shift = vma->vm_start - stack_base; 683 mm->arg_start = bprm->p - stack_shift; 684 bprm->p = vma->vm_end - stack_shift; 685 #else 686 stack_top = arch_align_stack(stack_top); 687 stack_top = PAGE_ALIGN(stack_top); 688 689 if (unlikely(stack_top < mmap_min_addr) || 690 unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr)) 691 return -ENOMEM; 692 693 stack_shift = vma->vm_end - stack_top; 694 695 bprm->p -= stack_shift; 696 mm->arg_start = bprm->p; 697 #endif 698 699 if (bprm->loader) 700 bprm->loader -= stack_shift; 701 bprm->exec -= stack_shift; 702 703 down_write(&mm->mmap_sem); 704 vm_flags = VM_STACK_FLAGS; 705 706 /* 707 * Adjust stack execute permissions; explicitly enable for 708 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone 709 * (arch default) otherwise. 710 */ 711 if (unlikely(executable_stack == EXSTACK_ENABLE_X)) 712 vm_flags |= VM_EXEC; 713 else if (executable_stack == EXSTACK_DISABLE_X) 714 vm_flags &= ~VM_EXEC; 715 vm_flags |= mm->def_flags; 716 vm_flags |= VM_STACK_INCOMPLETE_SETUP; 717 718 ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end, 719 vm_flags); 720 if (ret) 721 goto out_unlock; 722 BUG_ON(prev != vma); 723 724 /* Move stack pages down in memory. */ 725 if (stack_shift) { 726 ret = shift_arg_pages(vma, stack_shift); 727 if (ret) 728 goto out_unlock; 729 } 730 731 /* mprotect_fixup is overkill to remove the temporary stack flags */ 732 vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP; 733 734 stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */ 735 stack_size = vma->vm_end - vma->vm_start; 736 /* 737 * Align this down to a page boundary as expand_stack 738 * will align it up. 739 */ 740 rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK; 741 #ifdef CONFIG_STACK_GROWSUP 742 if (stack_size + stack_expand > rlim_stack) 743 stack_base = vma->vm_start + rlim_stack; 744 else 745 stack_base = vma->vm_end + stack_expand; 746 #else 747 if (stack_size + stack_expand > rlim_stack) 748 stack_base = vma->vm_end - rlim_stack; 749 else 750 stack_base = vma->vm_start - stack_expand; 751 #endif 752 current->mm->start_stack = bprm->p; 753 ret = expand_stack(vma, stack_base); 754 if (ret) 755 ret = -EFAULT; 756 757 out_unlock: 758 up_write(&mm->mmap_sem); 759 return ret; 760 } 761 EXPORT_SYMBOL(setup_arg_pages); 762 763 #endif /* CONFIG_MMU */ 764 765 static struct file *do_open_execat(int fd, struct filename *name, int flags) 766 { 767 struct file *file; 768 int err; 769 struct open_flags open_exec_flags = { 770 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC, 771 .acc_mode = MAY_EXEC, 772 .intent = LOOKUP_OPEN, 773 .lookup_flags = LOOKUP_FOLLOW, 774 }; 775 776 if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0) 777 return ERR_PTR(-EINVAL); 778 if (flags & AT_SYMLINK_NOFOLLOW) 779 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW; 780 if (flags & AT_EMPTY_PATH) 781 open_exec_flags.lookup_flags |= LOOKUP_EMPTY; 782 783 file = do_filp_open(fd, name, &open_exec_flags); 784 if (IS_ERR(file)) 785 goto out; 786 787 err = -EACCES; 788 if (!S_ISREG(file_inode(file)->i_mode)) 789 goto exit; 790 791 if (path_noexec(&file->f_path)) 792 goto exit; 793 794 err = deny_write_access(file); 795 if (err) 796 goto exit; 797 798 if (name->name[0] != '\0') 799 fsnotify_open(file); 800 801 out: 802 return file; 803 804 exit: 805 fput(file); 806 return ERR_PTR(err); 807 } 808 809 struct file *open_exec(const char *name) 810 { 811 struct filename *filename = getname_kernel(name); 812 struct file *f = ERR_CAST(filename); 813 814 if (!IS_ERR(filename)) { 815 f = do_open_execat(AT_FDCWD, filename, 0); 816 putname(filename); 817 } 818 return f; 819 } 820 EXPORT_SYMBOL(open_exec); 821 822 int kernel_read(struct file *file, loff_t offset, 823 char *addr, unsigned long count) 824 { 825 mm_segment_t old_fs; 826 loff_t pos = offset; 827 int result; 828 829 old_fs = get_fs(); 830 set_fs(get_ds()); 831 /* The cast to a user pointer is valid due to the set_fs() */ 832 result = vfs_read(file, (void __user *)addr, count, &pos); 833 set_fs(old_fs); 834 return result; 835 } 836 837 EXPORT_SYMBOL(kernel_read); 838 839 int kernel_read_file(struct file *file, void **buf, loff_t *size, 840 loff_t max_size, enum kernel_read_file_id id) 841 { 842 loff_t i_size, pos; 843 ssize_t bytes = 0; 844 int ret; 845 846 if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0) 847 return -EINVAL; 848 849 ret = security_kernel_read_file(file, id); 850 if (ret) 851 return ret; 852 853 i_size = i_size_read(file_inode(file)); 854 if (max_size > 0 && i_size > max_size) 855 return -EFBIG; 856 if (i_size <= 0) 857 return -EINVAL; 858 859 *buf = vmalloc(i_size); 860 if (!*buf) 861 return -ENOMEM; 862 863 pos = 0; 864 while (pos < i_size) { 865 bytes = kernel_read(file, pos, (char *)(*buf) + pos, 866 i_size - pos); 867 if (bytes < 0) { 868 ret = bytes; 869 goto out; 870 } 871 872 if (bytes == 0) 873 break; 874 pos += bytes; 875 } 876 877 if (pos != i_size) { 878 ret = -EIO; 879 goto out; 880 } 881 882 ret = security_kernel_post_read_file(file, *buf, i_size, id); 883 if (!ret) 884 *size = pos; 885 886 out: 887 if (ret < 0) { 888 vfree(*buf); 889 *buf = NULL; 890 } 891 return ret; 892 } 893 EXPORT_SYMBOL_GPL(kernel_read_file); 894 895 int kernel_read_file_from_path(char *path, void **buf, loff_t *size, 896 loff_t max_size, enum kernel_read_file_id id) 897 { 898 struct file *file; 899 int ret; 900 901 if (!path || !*path) 902 return -EINVAL; 903 904 file = filp_open(path, O_RDONLY, 0); 905 if (IS_ERR(file)) 906 return PTR_ERR(file); 907 908 ret = kernel_read_file(file, buf, size, max_size, id); 909 fput(file); 910 return ret; 911 } 912 EXPORT_SYMBOL_GPL(kernel_read_file_from_path); 913 914 int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size, 915 enum kernel_read_file_id id) 916 { 917 struct fd f = fdget(fd); 918 int ret = -EBADF; 919 920 if (!f.file) 921 goto out; 922 923 ret = kernel_read_file(f.file, buf, size, max_size, id); 924 out: 925 fdput(f); 926 return ret; 927 } 928 EXPORT_SYMBOL_GPL(kernel_read_file_from_fd); 929 930 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len) 931 { 932 ssize_t res = vfs_read(file, (void __user *)addr, len, &pos); 933 if (res > 0) 934 flush_icache_range(addr, addr + len); 935 return res; 936 } 937 EXPORT_SYMBOL(read_code); 938 939 static int exec_mmap(struct mm_struct *mm) 940 { 941 struct task_struct *tsk; 942 struct mm_struct *old_mm, *active_mm; 943 944 /* Notify parent that we're no longer interested in the old VM */ 945 tsk = current; 946 old_mm = current->mm; 947 mm_release(tsk, old_mm); 948 949 if (old_mm) { 950 sync_mm_rss(old_mm); 951 /* 952 * Make sure that if there is a core dump in progress 953 * for the old mm, we get out and die instead of going 954 * through with the exec. We must hold mmap_sem around 955 * checking core_state and changing tsk->mm. 956 */ 957 down_read(&old_mm->mmap_sem); 958 if (unlikely(old_mm->core_state)) { 959 up_read(&old_mm->mmap_sem); 960 return -EINTR; 961 } 962 } 963 task_lock(tsk); 964 active_mm = tsk->active_mm; 965 tsk->mm = mm; 966 tsk->active_mm = mm; 967 activate_mm(active_mm, mm); 968 tsk->mm->vmacache_seqnum = 0; 969 vmacache_flush(tsk); 970 task_unlock(tsk); 971 if (old_mm) { 972 up_read(&old_mm->mmap_sem); 973 BUG_ON(active_mm != old_mm); 974 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm); 975 mm_update_next_owner(old_mm); 976 mmput(old_mm); 977 return 0; 978 } 979 mmdrop(active_mm); 980 return 0; 981 } 982 983 /* 984 * This function makes sure the current process has its own signal table, 985 * so that flush_signal_handlers can later reset the handlers without 986 * disturbing other processes. (Other processes might share the signal 987 * table via the CLONE_SIGHAND option to clone().) 988 */ 989 static int de_thread(struct task_struct *tsk) 990 { 991 struct signal_struct *sig = tsk->signal; 992 struct sighand_struct *oldsighand = tsk->sighand; 993 spinlock_t *lock = &oldsighand->siglock; 994 995 if (thread_group_empty(tsk)) 996 goto no_thread_group; 997 998 /* 999 * Kill all other threads in the thread group. 1000 */ 1001 spin_lock_irq(lock); 1002 if (signal_group_exit(sig)) { 1003 /* 1004 * Another group action in progress, just 1005 * return so that the signal is processed. 1006 */ 1007 spin_unlock_irq(lock); 1008 return -EAGAIN; 1009 } 1010 1011 sig->group_exit_task = tsk; 1012 sig->notify_count = zap_other_threads(tsk); 1013 if (!thread_group_leader(tsk)) 1014 sig->notify_count--; 1015 1016 while (sig->notify_count) { 1017 __set_current_state(TASK_KILLABLE); 1018 spin_unlock_irq(lock); 1019 schedule(); 1020 if (unlikely(__fatal_signal_pending(tsk))) 1021 goto killed; 1022 spin_lock_irq(lock); 1023 } 1024 spin_unlock_irq(lock); 1025 1026 /* 1027 * At this point all other threads have exited, all we have to 1028 * do is to wait for the thread group leader to become inactive, 1029 * and to assume its PID: 1030 */ 1031 if (!thread_group_leader(tsk)) { 1032 struct task_struct *leader = tsk->group_leader; 1033 1034 for (;;) { 1035 threadgroup_change_begin(tsk); 1036 write_lock_irq(&tasklist_lock); 1037 /* 1038 * Do this under tasklist_lock to ensure that 1039 * exit_notify() can't miss ->group_exit_task 1040 */ 1041 sig->notify_count = -1; 1042 if (likely(leader->exit_state)) 1043 break; 1044 __set_current_state(TASK_KILLABLE); 1045 write_unlock_irq(&tasklist_lock); 1046 threadgroup_change_end(tsk); 1047 schedule(); 1048 if (unlikely(__fatal_signal_pending(tsk))) 1049 goto killed; 1050 } 1051 1052 /* 1053 * The only record we have of the real-time age of a 1054 * process, regardless of execs it's done, is start_time. 1055 * All the past CPU time is accumulated in signal_struct 1056 * from sister threads now dead. But in this non-leader 1057 * exec, nothing survives from the original leader thread, 1058 * whose birth marks the true age of this process now. 1059 * When we take on its identity by switching to its PID, we 1060 * also take its birthdate (always earlier than our own). 1061 */ 1062 tsk->start_time = leader->start_time; 1063 tsk->real_start_time = leader->real_start_time; 1064 1065 BUG_ON(!same_thread_group(leader, tsk)); 1066 BUG_ON(has_group_leader_pid(tsk)); 1067 /* 1068 * An exec() starts a new thread group with the 1069 * TGID of the previous thread group. Rehash the 1070 * two threads with a switched PID, and release 1071 * the former thread group leader: 1072 */ 1073 1074 /* Become a process group leader with the old leader's pid. 1075 * The old leader becomes a thread of the this thread group. 1076 * Note: The old leader also uses this pid until release_task 1077 * is called. Odd but simple and correct. 1078 */ 1079 tsk->pid = leader->pid; 1080 change_pid(tsk, PIDTYPE_PID, task_pid(leader)); 1081 transfer_pid(leader, tsk, PIDTYPE_PGID); 1082 transfer_pid(leader, tsk, PIDTYPE_SID); 1083 1084 list_replace_rcu(&leader->tasks, &tsk->tasks); 1085 list_replace_init(&leader->sibling, &tsk->sibling); 1086 1087 tsk->group_leader = tsk; 1088 leader->group_leader = tsk; 1089 1090 tsk->exit_signal = SIGCHLD; 1091 leader->exit_signal = -1; 1092 1093 BUG_ON(leader->exit_state != EXIT_ZOMBIE); 1094 leader->exit_state = EXIT_DEAD; 1095 1096 /* 1097 * We are going to release_task()->ptrace_unlink() silently, 1098 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees 1099 * the tracer wont't block again waiting for this thread. 1100 */ 1101 if (unlikely(leader->ptrace)) 1102 __wake_up_parent(leader, leader->parent); 1103 write_unlock_irq(&tasklist_lock); 1104 threadgroup_change_end(tsk); 1105 1106 release_task(leader); 1107 } 1108 1109 sig->group_exit_task = NULL; 1110 sig->notify_count = 0; 1111 1112 no_thread_group: 1113 /* we have changed execution domain */ 1114 tsk->exit_signal = SIGCHLD; 1115 1116 exit_itimers(sig); 1117 flush_itimer_signals(); 1118 1119 if (atomic_read(&oldsighand->count) != 1) { 1120 struct sighand_struct *newsighand; 1121 /* 1122 * This ->sighand is shared with the CLONE_SIGHAND 1123 * but not CLONE_THREAD task, switch to the new one. 1124 */ 1125 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1126 if (!newsighand) 1127 return -ENOMEM; 1128 1129 atomic_set(&newsighand->count, 1); 1130 memcpy(newsighand->action, oldsighand->action, 1131 sizeof(newsighand->action)); 1132 1133 write_lock_irq(&tasklist_lock); 1134 spin_lock(&oldsighand->siglock); 1135 rcu_assign_pointer(tsk->sighand, newsighand); 1136 spin_unlock(&oldsighand->siglock); 1137 write_unlock_irq(&tasklist_lock); 1138 1139 __cleanup_sighand(oldsighand); 1140 } 1141 1142 BUG_ON(!thread_group_leader(tsk)); 1143 return 0; 1144 1145 killed: 1146 /* protects against exit_notify() and __exit_signal() */ 1147 read_lock(&tasklist_lock); 1148 sig->group_exit_task = NULL; 1149 sig->notify_count = 0; 1150 read_unlock(&tasklist_lock); 1151 return -EAGAIN; 1152 } 1153 1154 char *get_task_comm(char *buf, struct task_struct *tsk) 1155 { 1156 /* buf must be at least sizeof(tsk->comm) in size */ 1157 task_lock(tsk); 1158 strncpy(buf, tsk->comm, sizeof(tsk->comm)); 1159 task_unlock(tsk); 1160 return buf; 1161 } 1162 EXPORT_SYMBOL_GPL(get_task_comm); 1163 1164 /* 1165 * These functions flushes out all traces of the currently running executable 1166 * so that a new one can be started 1167 */ 1168 1169 void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec) 1170 { 1171 task_lock(tsk); 1172 trace_task_rename(tsk, buf); 1173 strlcpy(tsk->comm, buf, sizeof(tsk->comm)); 1174 task_unlock(tsk); 1175 perf_event_comm(tsk, exec); 1176 } 1177 1178 int flush_old_exec(struct linux_binprm * bprm) 1179 { 1180 int retval; 1181 1182 /* 1183 * Make sure we have a private signal table and that 1184 * we are unassociated from the previous thread group. 1185 */ 1186 retval = de_thread(current); 1187 if (retval) 1188 goto out; 1189 1190 /* 1191 * Must be called _before_ exec_mmap() as bprm->mm is 1192 * not visibile until then. This also enables the update 1193 * to be lockless. 1194 */ 1195 set_mm_exe_file(bprm->mm, bprm->file); 1196 1197 /* 1198 * Release all of the old mmap stuff 1199 */ 1200 acct_arg_size(bprm, 0); 1201 retval = exec_mmap(bprm->mm); 1202 if (retval) 1203 goto out; 1204 1205 bprm->mm = NULL; /* We're using it now */ 1206 1207 set_fs(USER_DS); 1208 current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD | 1209 PF_NOFREEZE | PF_NO_SETAFFINITY); 1210 flush_thread(); 1211 current->personality &= ~bprm->per_clear; 1212 1213 return 0; 1214 1215 out: 1216 return retval; 1217 } 1218 EXPORT_SYMBOL(flush_old_exec); 1219 1220 void would_dump(struct linux_binprm *bprm, struct file *file) 1221 { 1222 if (inode_permission(file_inode(file), MAY_READ) < 0) 1223 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP; 1224 } 1225 EXPORT_SYMBOL(would_dump); 1226 1227 void setup_new_exec(struct linux_binprm * bprm) 1228 { 1229 arch_pick_mmap_layout(current->mm); 1230 1231 /* This is the point of no return */ 1232 current->sas_ss_sp = current->sas_ss_size = 0; 1233 1234 if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid())) 1235 set_dumpable(current->mm, SUID_DUMP_USER); 1236 else 1237 set_dumpable(current->mm, suid_dumpable); 1238 1239 perf_event_exec(); 1240 __set_task_comm(current, kbasename(bprm->filename), true); 1241 1242 /* Set the new mm task size. We have to do that late because it may 1243 * depend on TIF_32BIT which is only updated in flush_thread() on 1244 * some architectures like powerpc 1245 */ 1246 current->mm->task_size = TASK_SIZE; 1247 1248 /* install the new credentials */ 1249 if (!uid_eq(bprm->cred->uid, current_euid()) || 1250 !gid_eq(bprm->cred->gid, current_egid())) { 1251 current->pdeath_signal = 0; 1252 } else { 1253 would_dump(bprm, bprm->file); 1254 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) 1255 set_dumpable(current->mm, suid_dumpable); 1256 } 1257 1258 /* An exec changes our domain. We are no longer part of the thread 1259 group */ 1260 current->self_exec_id++; 1261 flush_signal_handlers(current, 0); 1262 do_close_on_exec(current->files); 1263 } 1264 EXPORT_SYMBOL(setup_new_exec); 1265 1266 /* 1267 * Prepare credentials and lock ->cred_guard_mutex. 1268 * install_exec_creds() commits the new creds and drops the lock. 1269 * Or, if exec fails before, free_bprm() should release ->cred and 1270 * and unlock. 1271 */ 1272 int prepare_bprm_creds(struct linux_binprm *bprm) 1273 { 1274 if (mutex_lock_interruptible(¤t->signal->cred_guard_mutex)) 1275 return -ERESTARTNOINTR; 1276 1277 bprm->cred = prepare_exec_creds(); 1278 if (likely(bprm->cred)) 1279 return 0; 1280 1281 mutex_unlock(¤t->signal->cred_guard_mutex); 1282 return -ENOMEM; 1283 } 1284 1285 static void free_bprm(struct linux_binprm *bprm) 1286 { 1287 free_arg_pages(bprm); 1288 if (bprm->cred) { 1289 mutex_unlock(¤t->signal->cred_guard_mutex); 1290 abort_creds(bprm->cred); 1291 } 1292 if (bprm->file) { 1293 allow_write_access(bprm->file); 1294 fput(bprm->file); 1295 } 1296 /* If a binfmt changed the interp, free it. */ 1297 if (bprm->interp != bprm->filename) 1298 kfree(bprm->interp); 1299 kfree(bprm); 1300 } 1301 1302 int bprm_change_interp(char *interp, struct linux_binprm *bprm) 1303 { 1304 /* If a binfmt changed the interp, free it first. */ 1305 if (bprm->interp != bprm->filename) 1306 kfree(bprm->interp); 1307 bprm->interp = kstrdup(interp, GFP_KERNEL); 1308 if (!bprm->interp) 1309 return -ENOMEM; 1310 return 0; 1311 } 1312 EXPORT_SYMBOL(bprm_change_interp); 1313 1314 /* 1315 * install the new credentials for this executable 1316 */ 1317 void install_exec_creds(struct linux_binprm *bprm) 1318 { 1319 security_bprm_committing_creds(bprm); 1320 1321 commit_creds(bprm->cred); 1322 bprm->cred = NULL; 1323 1324 /* 1325 * Disable monitoring for regular users 1326 * when executing setuid binaries. Must 1327 * wait until new credentials are committed 1328 * by commit_creds() above 1329 */ 1330 if (get_dumpable(current->mm) != SUID_DUMP_USER) 1331 perf_event_exit_task(current); 1332 /* 1333 * cred_guard_mutex must be held at least to this point to prevent 1334 * ptrace_attach() from altering our determination of the task's 1335 * credentials; any time after this it may be unlocked. 1336 */ 1337 security_bprm_committed_creds(bprm); 1338 mutex_unlock(¤t->signal->cred_guard_mutex); 1339 } 1340 EXPORT_SYMBOL(install_exec_creds); 1341 1342 /* 1343 * determine how safe it is to execute the proposed program 1344 * - the caller must hold ->cred_guard_mutex to protect against 1345 * PTRACE_ATTACH or seccomp thread-sync 1346 */ 1347 static void check_unsafe_exec(struct linux_binprm *bprm) 1348 { 1349 struct task_struct *p = current, *t; 1350 unsigned n_fs; 1351 1352 if (p->ptrace) { 1353 if (p->ptrace & PT_PTRACE_CAP) 1354 bprm->unsafe |= LSM_UNSAFE_PTRACE_CAP; 1355 else 1356 bprm->unsafe |= LSM_UNSAFE_PTRACE; 1357 } 1358 1359 /* 1360 * This isn't strictly necessary, but it makes it harder for LSMs to 1361 * mess up. 1362 */ 1363 if (task_no_new_privs(current)) 1364 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS; 1365 1366 t = p; 1367 n_fs = 1; 1368 spin_lock(&p->fs->lock); 1369 rcu_read_lock(); 1370 while_each_thread(p, t) { 1371 if (t->fs == p->fs) 1372 n_fs++; 1373 } 1374 rcu_read_unlock(); 1375 1376 if (p->fs->users > n_fs) 1377 bprm->unsafe |= LSM_UNSAFE_SHARE; 1378 else 1379 p->fs->in_exec = 1; 1380 spin_unlock(&p->fs->lock); 1381 } 1382 1383 static void bprm_fill_uid(struct linux_binprm *bprm) 1384 { 1385 struct inode *inode; 1386 unsigned int mode; 1387 kuid_t uid; 1388 kgid_t gid; 1389 1390 /* clear any previous set[ug]id data from a previous binary */ 1391 bprm->cred->euid = current_euid(); 1392 bprm->cred->egid = current_egid(); 1393 1394 if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) 1395 return; 1396 1397 if (task_no_new_privs(current)) 1398 return; 1399 1400 inode = file_inode(bprm->file); 1401 mode = READ_ONCE(inode->i_mode); 1402 if (!(mode & (S_ISUID|S_ISGID))) 1403 return; 1404 1405 /* Be careful if suid/sgid is set */ 1406 inode_lock(inode); 1407 1408 /* reload atomically mode/uid/gid now that lock held */ 1409 mode = inode->i_mode; 1410 uid = inode->i_uid; 1411 gid = inode->i_gid; 1412 inode_unlock(inode); 1413 1414 /* We ignore suid/sgid if there are no mappings for them in the ns */ 1415 if (!kuid_has_mapping(bprm->cred->user_ns, uid) || 1416 !kgid_has_mapping(bprm->cred->user_ns, gid)) 1417 return; 1418 1419 if (mode & S_ISUID) { 1420 bprm->per_clear |= PER_CLEAR_ON_SETID; 1421 bprm->cred->euid = uid; 1422 } 1423 1424 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { 1425 bprm->per_clear |= PER_CLEAR_ON_SETID; 1426 bprm->cred->egid = gid; 1427 } 1428 } 1429 1430 /* 1431 * Fill the binprm structure from the inode. 1432 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes 1433 * 1434 * This may be called multiple times for binary chains (scripts for example). 1435 */ 1436 int prepare_binprm(struct linux_binprm *bprm) 1437 { 1438 int retval; 1439 1440 bprm_fill_uid(bprm); 1441 1442 /* fill in binprm security blob */ 1443 retval = security_bprm_set_creds(bprm); 1444 if (retval) 1445 return retval; 1446 bprm->cred_prepared = 1; 1447 1448 memset(bprm->buf, 0, BINPRM_BUF_SIZE); 1449 return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE); 1450 } 1451 1452 EXPORT_SYMBOL(prepare_binprm); 1453 1454 /* 1455 * Arguments are '\0' separated strings found at the location bprm->p 1456 * points to; chop off the first by relocating brpm->p to right after 1457 * the first '\0' encountered. 1458 */ 1459 int remove_arg_zero(struct linux_binprm *bprm) 1460 { 1461 int ret = 0; 1462 unsigned long offset; 1463 char *kaddr; 1464 struct page *page; 1465 1466 if (!bprm->argc) 1467 return 0; 1468 1469 do { 1470 offset = bprm->p & ~PAGE_MASK; 1471 page = get_arg_page(bprm, bprm->p, 0); 1472 if (!page) { 1473 ret = -EFAULT; 1474 goto out; 1475 } 1476 kaddr = kmap_atomic(page); 1477 1478 for (; offset < PAGE_SIZE && kaddr[offset]; 1479 offset++, bprm->p++) 1480 ; 1481 1482 kunmap_atomic(kaddr); 1483 put_arg_page(page); 1484 1485 if (offset == PAGE_SIZE) 1486 free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1); 1487 } while (offset == PAGE_SIZE); 1488 1489 bprm->p++; 1490 bprm->argc--; 1491 ret = 0; 1492 1493 out: 1494 return ret; 1495 } 1496 EXPORT_SYMBOL(remove_arg_zero); 1497 1498 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e)) 1499 /* 1500 * cycle the list of binary formats handler, until one recognizes the image 1501 */ 1502 int search_binary_handler(struct linux_binprm *bprm) 1503 { 1504 bool need_retry = IS_ENABLED(CONFIG_MODULES); 1505 struct linux_binfmt *fmt; 1506 int retval; 1507 1508 /* This allows 4 levels of binfmt rewrites before failing hard. */ 1509 if (bprm->recursion_depth > 5) 1510 return -ELOOP; 1511 1512 retval = security_bprm_check(bprm); 1513 if (retval) 1514 return retval; 1515 1516 retval = -ENOENT; 1517 retry: 1518 read_lock(&binfmt_lock); 1519 list_for_each_entry(fmt, &formats, lh) { 1520 if (!try_module_get(fmt->module)) 1521 continue; 1522 read_unlock(&binfmt_lock); 1523 bprm->recursion_depth++; 1524 retval = fmt->load_binary(bprm); 1525 read_lock(&binfmt_lock); 1526 put_binfmt(fmt); 1527 bprm->recursion_depth--; 1528 if (retval < 0 && !bprm->mm) { 1529 /* we got to flush_old_exec() and failed after it */ 1530 read_unlock(&binfmt_lock); 1531 force_sigsegv(SIGSEGV, current); 1532 return retval; 1533 } 1534 if (retval != -ENOEXEC || !bprm->file) { 1535 read_unlock(&binfmt_lock); 1536 return retval; 1537 } 1538 } 1539 read_unlock(&binfmt_lock); 1540 1541 if (need_retry) { 1542 if (printable(bprm->buf[0]) && printable(bprm->buf[1]) && 1543 printable(bprm->buf[2]) && printable(bprm->buf[3])) 1544 return retval; 1545 if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0) 1546 return retval; 1547 need_retry = false; 1548 goto retry; 1549 } 1550 1551 return retval; 1552 } 1553 EXPORT_SYMBOL(search_binary_handler); 1554 1555 static int exec_binprm(struct linux_binprm *bprm) 1556 { 1557 pid_t old_pid, old_vpid; 1558 int ret; 1559 1560 /* Need to fetch pid before load_binary changes it */ 1561 old_pid = current->pid; 1562 rcu_read_lock(); 1563 old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent)); 1564 rcu_read_unlock(); 1565 1566 ret = search_binary_handler(bprm); 1567 if (ret >= 0) { 1568 audit_bprm(bprm); 1569 trace_sched_process_exec(current, old_pid, bprm); 1570 ptrace_event(PTRACE_EVENT_EXEC, old_vpid); 1571 proc_exec_connector(current); 1572 } 1573 1574 return ret; 1575 } 1576 1577 /* 1578 * sys_execve() executes a new program. 1579 */ 1580 static int do_execveat_common(int fd, struct filename *filename, 1581 struct user_arg_ptr argv, 1582 struct user_arg_ptr envp, 1583 int flags) 1584 { 1585 char *pathbuf = NULL; 1586 struct linux_binprm *bprm; 1587 struct file *file; 1588 struct files_struct *displaced; 1589 int retval; 1590 1591 if (IS_ERR(filename)) 1592 return PTR_ERR(filename); 1593 1594 /* 1595 * We move the actual failure in case of RLIMIT_NPROC excess from 1596 * set*uid() to execve() because too many poorly written programs 1597 * don't check setuid() return code. Here we additionally recheck 1598 * whether NPROC limit is still exceeded. 1599 */ 1600 if ((current->flags & PF_NPROC_EXCEEDED) && 1601 atomic_read(¤t_user()->processes) > rlimit(RLIMIT_NPROC)) { 1602 retval = -EAGAIN; 1603 goto out_ret; 1604 } 1605 1606 /* We're below the limit (still or again), so we don't want to make 1607 * further execve() calls fail. */ 1608 current->flags &= ~PF_NPROC_EXCEEDED; 1609 1610 retval = unshare_files(&displaced); 1611 if (retval) 1612 goto out_ret; 1613 1614 retval = -ENOMEM; 1615 bprm = kzalloc(sizeof(*bprm), GFP_KERNEL); 1616 if (!bprm) 1617 goto out_files; 1618 1619 retval = prepare_bprm_creds(bprm); 1620 if (retval) 1621 goto out_free; 1622 1623 check_unsafe_exec(bprm); 1624 current->in_execve = 1; 1625 1626 file = do_open_execat(fd, filename, flags); 1627 retval = PTR_ERR(file); 1628 if (IS_ERR(file)) 1629 goto out_unmark; 1630 1631 sched_exec(); 1632 1633 bprm->file = file; 1634 if (fd == AT_FDCWD || filename->name[0] == '/') { 1635 bprm->filename = filename->name; 1636 } else { 1637 if (filename->name[0] == '\0') 1638 pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d", fd); 1639 else 1640 pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d/%s", 1641 fd, filename->name); 1642 if (!pathbuf) { 1643 retval = -ENOMEM; 1644 goto out_unmark; 1645 } 1646 /* 1647 * Record that a name derived from an O_CLOEXEC fd will be 1648 * inaccessible after exec. Relies on having exclusive access to 1649 * current->files (due to unshare_files above). 1650 */ 1651 if (close_on_exec(fd, rcu_dereference_raw(current->files->fdt))) 1652 bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE; 1653 bprm->filename = pathbuf; 1654 } 1655 bprm->interp = bprm->filename; 1656 1657 retval = bprm_mm_init(bprm); 1658 if (retval) 1659 goto out_unmark; 1660 1661 bprm->argc = count(argv, MAX_ARG_STRINGS); 1662 if ((retval = bprm->argc) < 0) 1663 goto out; 1664 1665 bprm->envc = count(envp, MAX_ARG_STRINGS); 1666 if ((retval = bprm->envc) < 0) 1667 goto out; 1668 1669 retval = prepare_binprm(bprm); 1670 if (retval < 0) 1671 goto out; 1672 1673 retval = copy_strings_kernel(1, &bprm->filename, bprm); 1674 if (retval < 0) 1675 goto out; 1676 1677 bprm->exec = bprm->p; 1678 retval = copy_strings(bprm->envc, envp, bprm); 1679 if (retval < 0) 1680 goto out; 1681 1682 retval = copy_strings(bprm->argc, argv, bprm); 1683 if (retval < 0) 1684 goto out; 1685 1686 retval = exec_binprm(bprm); 1687 if (retval < 0) 1688 goto out; 1689 1690 /* execve succeeded */ 1691 current->fs->in_exec = 0; 1692 current->in_execve = 0; 1693 acct_update_integrals(current); 1694 task_numa_free(current); 1695 free_bprm(bprm); 1696 kfree(pathbuf); 1697 putname(filename); 1698 if (displaced) 1699 put_files_struct(displaced); 1700 return retval; 1701 1702 out: 1703 if (bprm->mm) { 1704 acct_arg_size(bprm, 0); 1705 mmput(bprm->mm); 1706 } 1707 1708 out_unmark: 1709 current->fs->in_exec = 0; 1710 current->in_execve = 0; 1711 1712 out_free: 1713 free_bprm(bprm); 1714 kfree(pathbuf); 1715 1716 out_files: 1717 if (displaced) 1718 reset_files_struct(displaced); 1719 out_ret: 1720 putname(filename); 1721 return retval; 1722 } 1723 1724 int do_execve(struct filename *filename, 1725 const char __user *const __user *__argv, 1726 const char __user *const __user *__envp) 1727 { 1728 struct user_arg_ptr argv = { .ptr.native = __argv }; 1729 struct user_arg_ptr envp = { .ptr.native = __envp }; 1730 return do_execveat_common(AT_FDCWD, filename, argv, envp, 0); 1731 } 1732 1733 int do_execveat(int fd, struct filename *filename, 1734 const char __user *const __user *__argv, 1735 const char __user *const __user *__envp, 1736 int flags) 1737 { 1738 struct user_arg_ptr argv = { .ptr.native = __argv }; 1739 struct user_arg_ptr envp = { .ptr.native = __envp }; 1740 1741 return do_execveat_common(fd, filename, argv, envp, flags); 1742 } 1743 1744 #ifdef CONFIG_COMPAT 1745 static int compat_do_execve(struct filename *filename, 1746 const compat_uptr_t __user *__argv, 1747 const compat_uptr_t __user *__envp) 1748 { 1749 struct user_arg_ptr argv = { 1750 .is_compat = true, 1751 .ptr.compat = __argv, 1752 }; 1753 struct user_arg_ptr envp = { 1754 .is_compat = true, 1755 .ptr.compat = __envp, 1756 }; 1757 return do_execveat_common(AT_FDCWD, filename, argv, envp, 0); 1758 } 1759 1760 static int compat_do_execveat(int fd, struct filename *filename, 1761 const compat_uptr_t __user *__argv, 1762 const compat_uptr_t __user *__envp, 1763 int flags) 1764 { 1765 struct user_arg_ptr argv = { 1766 .is_compat = true, 1767 .ptr.compat = __argv, 1768 }; 1769 struct user_arg_ptr envp = { 1770 .is_compat = true, 1771 .ptr.compat = __envp, 1772 }; 1773 return do_execveat_common(fd, filename, argv, envp, flags); 1774 } 1775 #endif 1776 1777 void set_binfmt(struct linux_binfmt *new) 1778 { 1779 struct mm_struct *mm = current->mm; 1780 1781 if (mm->binfmt) 1782 module_put(mm->binfmt->module); 1783 1784 mm->binfmt = new; 1785 if (new) 1786 __module_get(new->module); 1787 } 1788 EXPORT_SYMBOL(set_binfmt); 1789 1790 /* 1791 * set_dumpable stores three-value SUID_DUMP_* into mm->flags. 1792 */ 1793 void set_dumpable(struct mm_struct *mm, int value) 1794 { 1795 unsigned long old, new; 1796 1797 if (WARN_ON((unsigned)value > SUID_DUMP_ROOT)) 1798 return; 1799 1800 do { 1801 old = ACCESS_ONCE(mm->flags); 1802 new = (old & ~MMF_DUMPABLE_MASK) | value; 1803 } while (cmpxchg(&mm->flags, old, new) != old); 1804 } 1805 1806 SYSCALL_DEFINE3(execve, 1807 const char __user *, filename, 1808 const char __user *const __user *, argv, 1809 const char __user *const __user *, envp) 1810 { 1811 return do_execve(getname(filename), argv, envp); 1812 } 1813 1814 SYSCALL_DEFINE5(execveat, 1815 int, fd, const char __user *, filename, 1816 const char __user *const __user *, argv, 1817 const char __user *const __user *, envp, 1818 int, flags) 1819 { 1820 int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0; 1821 1822 return do_execveat(fd, 1823 getname_flags(filename, lookup_flags, NULL), 1824 argv, envp, flags); 1825 } 1826 1827 #ifdef CONFIG_COMPAT 1828 COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename, 1829 const compat_uptr_t __user *, argv, 1830 const compat_uptr_t __user *, envp) 1831 { 1832 return compat_do_execve(getname(filename), argv, envp); 1833 } 1834 1835 COMPAT_SYSCALL_DEFINE5(execveat, int, fd, 1836 const char __user *, filename, 1837 const compat_uptr_t __user *, argv, 1838 const compat_uptr_t __user *, envp, 1839 int, flags) 1840 { 1841 int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0; 1842 1843 return compat_do_execveat(fd, 1844 getname_flags(filename, lookup_flags, NULL), 1845 argv, envp, flags); 1846 } 1847 #endif 1848