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_pages(struct linux_binprm *bprm) 247 { 248 } 249 250 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, 251 struct page *page) 252 { 253 flush_cache_page(bprm->vma, pos, page_to_pfn(page)); 254 } 255 256 static int __bprm_mm_init(struct linux_binprm *bprm) 257 { 258 int err; 259 struct vm_area_struct *vma = NULL; 260 struct mm_struct *mm = bprm->mm; 261 262 bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL); 263 if (!vma) 264 return -ENOMEM; 265 266 if (down_write_killable(&mm->mmap_sem)) { 267 err = -EINTR; 268 goto err_free; 269 } 270 vma->vm_mm = mm; 271 272 /* 273 * Place the stack at the largest stack address the architecture 274 * supports. Later, we'll move this to an appropriate place. We don't 275 * use STACK_TOP because that can depend on attributes which aren't 276 * configured yet. 277 */ 278 BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP); 279 vma->vm_end = STACK_TOP_MAX; 280 vma->vm_start = vma->vm_end - PAGE_SIZE; 281 vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP; 282 vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); 283 INIT_LIST_HEAD(&vma->anon_vma_chain); 284 285 err = insert_vm_struct(mm, vma); 286 if (err) 287 goto err; 288 289 mm->stack_vm = mm->total_vm = 1; 290 arch_bprm_mm_init(mm, vma); 291 up_write(&mm->mmap_sem); 292 bprm->p = vma->vm_end - sizeof(void *); 293 return 0; 294 err: 295 up_write(&mm->mmap_sem); 296 err_free: 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 if (down_write_killable(&mm->mmap_sem)) 704 return -EINTR; 705 706 vm_flags = VM_STACK_FLAGS; 707 708 /* 709 * Adjust stack execute permissions; explicitly enable for 710 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone 711 * (arch default) otherwise. 712 */ 713 if (unlikely(executable_stack == EXSTACK_ENABLE_X)) 714 vm_flags |= VM_EXEC; 715 else if (executable_stack == EXSTACK_DISABLE_X) 716 vm_flags &= ~VM_EXEC; 717 vm_flags |= mm->def_flags; 718 vm_flags |= VM_STACK_INCOMPLETE_SETUP; 719 720 ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end, 721 vm_flags); 722 if (ret) 723 goto out_unlock; 724 BUG_ON(prev != vma); 725 726 /* Move stack pages down in memory. */ 727 if (stack_shift) { 728 ret = shift_arg_pages(vma, stack_shift); 729 if (ret) 730 goto out_unlock; 731 } 732 733 /* mprotect_fixup is overkill to remove the temporary stack flags */ 734 vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP; 735 736 stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */ 737 stack_size = vma->vm_end - vma->vm_start; 738 /* 739 * Align this down to a page boundary as expand_stack 740 * will align it up. 741 */ 742 rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK; 743 #ifdef CONFIG_STACK_GROWSUP 744 if (stack_size + stack_expand > rlim_stack) 745 stack_base = vma->vm_start + rlim_stack; 746 else 747 stack_base = vma->vm_end + stack_expand; 748 #else 749 if (stack_size + stack_expand > rlim_stack) 750 stack_base = vma->vm_end - rlim_stack; 751 else 752 stack_base = vma->vm_start - stack_expand; 753 #endif 754 current->mm->start_stack = bprm->p; 755 ret = expand_stack(vma, stack_base); 756 if (ret) 757 ret = -EFAULT; 758 759 out_unlock: 760 up_write(&mm->mmap_sem); 761 return ret; 762 } 763 EXPORT_SYMBOL(setup_arg_pages); 764 765 #endif /* CONFIG_MMU */ 766 767 static struct file *do_open_execat(int fd, struct filename *name, int flags) 768 { 769 struct file *file; 770 int err; 771 struct open_flags open_exec_flags = { 772 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC, 773 .acc_mode = MAY_EXEC, 774 .intent = LOOKUP_OPEN, 775 .lookup_flags = LOOKUP_FOLLOW, 776 }; 777 778 if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0) 779 return ERR_PTR(-EINVAL); 780 if (flags & AT_SYMLINK_NOFOLLOW) 781 open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW; 782 if (flags & AT_EMPTY_PATH) 783 open_exec_flags.lookup_flags |= LOOKUP_EMPTY; 784 785 file = do_filp_open(fd, name, &open_exec_flags); 786 if (IS_ERR(file)) 787 goto out; 788 789 err = -EACCES; 790 if (!S_ISREG(file_inode(file)->i_mode)) 791 goto exit; 792 793 if (path_noexec(&file->f_path)) 794 goto exit; 795 796 err = deny_write_access(file); 797 if (err) 798 goto exit; 799 800 if (name->name[0] != '\0') 801 fsnotify_open(file); 802 803 out: 804 return file; 805 806 exit: 807 fput(file); 808 return ERR_PTR(err); 809 } 810 811 struct file *open_exec(const char *name) 812 { 813 struct filename *filename = getname_kernel(name); 814 struct file *f = ERR_CAST(filename); 815 816 if (!IS_ERR(filename)) { 817 f = do_open_execat(AT_FDCWD, filename, 0); 818 putname(filename); 819 } 820 return f; 821 } 822 EXPORT_SYMBOL(open_exec); 823 824 int kernel_read(struct file *file, loff_t offset, 825 char *addr, unsigned long count) 826 { 827 mm_segment_t old_fs; 828 loff_t pos = offset; 829 int result; 830 831 old_fs = get_fs(); 832 set_fs(get_ds()); 833 /* The cast to a user pointer is valid due to the set_fs() */ 834 result = vfs_read(file, (void __user *)addr, count, &pos); 835 set_fs(old_fs); 836 return result; 837 } 838 839 EXPORT_SYMBOL(kernel_read); 840 841 int kernel_read_file(struct file *file, void **buf, loff_t *size, 842 loff_t max_size, enum kernel_read_file_id id) 843 { 844 loff_t i_size, pos; 845 ssize_t bytes = 0; 846 int ret; 847 848 if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0) 849 return -EINVAL; 850 851 ret = security_kernel_read_file(file, id); 852 if (ret) 853 return ret; 854 855 ret = deny_write_access(file); 856 if (ret) 857 return ret; 858 859 i_size = i_size_read(file_inode(file)); 860 if (max_size > 0 && i_size > max_size) { 861 ret = -EFBIG; 862 goto out; 863 } 864 if (i_size <= 0) { 865 ret = -EINVAL; 866 goto out; 867 } 868 869 if (id != READING_FIRMWARE_PREALLOC_BUFFER) 870 *buf = vmalloc(i_size); 871 if (!*buf) { 872 ret = -ENOMEM; 873 goto out; 874 } 875 876 pos = 0; 877 while (pos < i_size) { 878 bytes = kernel_read(file, pos, (char *)(*buf) + pos, 879 i_size - pos); 880 if (bytes < 0) { 881 ret = bytes; 882 goto out; 883 } 884 885 if (bytes == 0) 886 break; 887 pos += bytes; 888 } 889 890 if (pos != i_size) { 891 ret = -EIO; 892 goto out_free; 893 } 894 895 ret = security_kernel_post_read_file(file, *buf, i_size, id); 896 if (!ret) 897 *size = pos; 898 899 out_free: 900 if (ret < 0) { 901 if (id != READING_FIRMWARE_PREALLOC_BUFFER) { 902 vfree(*buf); 903 *buf = NULL; 904 } 905 } 906 907 out: 908 allow_write_access(file); 909 return ret; 910 } 911 EXPORT_SYMBOL_GPL(kernel_read_file); 912 913 int kernel_read_file_from_path(char *path, void **buf, loff_t *size, 914 loff_t max_size, enum kernel_read_file_id id) 915 { 916 struct file *file; 917 int ret; 918 919 if (!path || !*path) 920 return -EINVAL; 921 922 file = filp_open(path, O_RDONLY, 0); 923 if (IS_ERR(file)) 924 return PTR_ERR(file); 925 926 ret = kernel_read_file(file, buf, size, max_size, id); 927 fput(file); 928 return ret; 929 } 930 EXPORT_SYMBOL_GPL(kernel_read_file_from_path); 931 932 int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size, 933 enum kernel_read_file_id id) 934 { 935 struct fd f = fdget(fd); 936 int ret = -EBADF; 937 938 if (!f.file) 939 goto out; 940 941 ret = kernel_read_file(f.file, buf, size, max_size, id); 942 out: 943 fdput(f); 944 return ret; 945 } 946 EXPORT_SYMBOL_GPL(kernel_read_file_from_fd); 947 948 ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len) 949 { 950 ssize_t res = vfs_read(file, (void __user *)addr, len, &pos); 951 if (res > 0) 952 flush_icache_range(addr, addr + len); 953 return res; 954 } 955 EXPORT_SYMBOL(read_code); 956 957 static int exec_mmap(struct mm_struct *mm) 958 { 959 struct task_struct *tsk; 960 struct mm_struct *old_mm, *active_mm; 961 962 /* Notify parent that we're no longer interested in the old VM */ 963 tsk = current; 964 old_mm = current->mm; 965 mm_release(tsk, old_mm); 966 967 if (old_mm) { 968 sync_mm_rss(old_mm); 969 /* 970 * Make sure that if there is a core dump in progress 971 * for the old mm, we get out and die instead of going 972 * through with the exec. We must hold mmap_sem around 973 * checking core_state and changing tsk->mm. 974 */ 975 down_read(&old_mm->mmap_sem); 976 if (unlikely(old_mm->core_state)) { 977 up_read(&old_mm->mmap_sem); 978 return -EINTR; 979 } 980 } 981 task_lock(tsk); 982 active_mm = tsk->active_mm; 983 tsk->mm = mm; 984 tsk->active_mm = mm; 985 activate_mm(active_mm, mm); 986 tsk->mm->vmacache_seqnum = 0; 987 vmacache_flush(tsk); 988 task_unlock(tsk); 989 if (old_mm) { 990 up_read(&old_mm->mmap_sem); 991 BUG_ON(active_mm != old_mm); 992 setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm); 993 mm_update_next_owner(old_mm); 994 mmput(old_mm); 995 return 0; 996 } 997 mmdrop(active_mm); 998 return 0; 999 } 1000 1001 /* 1002 * This function makes sure the current process has its own signal table, 1003 * so that flush_signal_handlers can later reset the handlers without 1004 * disturbing other processes. (Other processes might share the signal 1005 * table via the CLONE_SIGHAND option to clone().) 1006 */ 1007 static int de_thread(struct task_struct *tsk) 1008 { 1009 struct signal_struct *sig = tsk->signal; 1010 struct sighand_struct *oldsighand = tsk->sighand; 1011 spinlock_t *lock = &oldsighand->siglock; 1012 1013 if (thread_group_empty(tsk)) 1014 goto no_thread_group; 1015 1016 /* 1017 * Kill all other threads in the thread group. 1018 */ 1019 spin_lock_irq(lock); 1020 if (signal_group_exit(sig)) { 1021 /* 1022 * Another group action in progress, just 1023 * return so that the signal is processed. 1024 */ 1025 spin_unlock_irq(lock); 1026 return -EAGAIN; 1027 } 1028 1029 sig->group_exit_task = tsk; 1030 sig->notify_count = zap_other_threads(tsk); 1031 if (!thread_group_leader(tsk)) 1032 sig->notify_count--; 1033 1034 while (sig->notify_count) { 1035 __set_current_state(TASK_KILLABLE); 1036 spin_unlock_irq(lock); 1037 schedule(); 1038 if (unlikely(__fatal_signal_pending(tsk))) 1039 goto killed; 1040 spin_lock_irq(lock); 1041 } 1042 spin_unlock_irq(lock); 1043 1044 /* 1045 * At this point all other threads have exited, all we have to 1046 * do is to wait for the thread group leader to become inactive, 1047 * and to assume its PID: 1048 */ 1049 if (!thread_group_leader(tsk)) { 1050 struct task_struct *leader = tsk->group_leader; 1051 1052 for (;;) { 1053 threadgroup_change_begin(tsk); 1054 write_lock_irq(&tasklist_lock); 1055 /* 1056 * Do this under tasklist_lock to ensure that 1057 * exit_notify() can't miss ->group_exit_task 1058 */ 1059 sig->notify_count = -1; 1060 if (likely(leader->exit_state)) 1061 break; 1062 __set_current_state(TASK_KILLABLE); 1063 write_unlock_irq(&tasklist_lock); 1064 threadgroup_change_end(tsk); 1065 schedule(); 1066 if (unlikely(__fatal_signal_pending(tsk))) 1067 goto killed; 1068 } 1069 1070 /* 1071 * The only record we have of the real-time age of a 1072 * process, regardless of execs it's done, is start_time. 1073 * All the past CPU time is accumulated in signal_struct 1074 * from sister threads now dead. But in this non-leader 1075 * exec, nothing survives from the original leader thread, 1076 * whose birth marks the true age of this process now. 1077 * When we take on its identity by switching to its PID, we 1078 * also take its birthdate (always earlier than our own). 1079 */ 1080 tsk->start_time = leader->start_time; 1081 tsk->real_start_time = leader->real_start_time; 1082 1083 BUG_ON(!same_thread_group(leader, tsk)); 1084 BUG_ON(has_group_leader_pid(tsk)); 1085 /* 1086 * An exec() starts a new thread group with the 1087 * TGID of the previous thread group. Rehash the 1088 * two threads with a switched PID, and release 1089 * the former thread group leader: 1090 */ 1091 1092 /* Become a process group leader with the old leader's pid. 1093 * The old leader becomes a thread of the this thread group. 1094 * Note: The old leader also uses this pid until release_task 1095 * is called. Odd but simple and correct. 1096 */ 1097 tsk->pid = leader->pid; 1098 change_pid(tsk, PIDTYPE_PID, task_pid(leader)); 1099 transfer_pid(leader, tsk, PIDTYPE_PGID); 1100 transfer_pid(leader, tsk, PIDTYPE_SID); 1101 1102 list_replace_rcu(&leader->tasks, &tsk->tasks); 1103 list_replace_init(&leader->sibling, &tsk->sibling); 1104 1105 tsk->group_leader = tsk; 1106 leader->group_leader = tsk; 1107 1108 tsk->exit_signal = SIGCHLD; 1109 leader->exit_signal = -1; 1110 1111 BUG_ON(leader->exit_state != EXIT_ZOMBIE); 1112 leader->exit_state = EXIT_DEAD; 1113 1114 /* 1115 * We are going to release_task()->ptrace_unlink() silently, 1116 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees 1117 * the tracer wont't block again waiting for this thread. 1118 */ 1119 if (unlikely(leader->ptrace)) 1120 __wake_up_parent(leader, leader->parent); 1121 write_unlock_irq(&tasklist_lock); 1122 threadgroup_change_end(tsk); 1123 1124 release_task(leader); 1125 } 1126 1127 sig->group_exit_task = NULL; 1128 sig->notify_count = 0; 1129 1130 no_thread_group: 1131 /* we have changed execution domain */ 1132 tsk->exit_signal = SIGCHLD; 1133 1134 exit_itimers(sig); 1135 flush_itimer_signals(); 1136 1137 if (atomic_read(&oldsighand->count) != 1) { 1138 struct sighand_struct *newsighand; 1139 /* 1140 * This ->sighand is shared with the CLONE_SIGHAND 1141 * but not CLONE_THREAD task, switch to the new one. 1142 */ 1143 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1144 if (!newsighand) 1145 return -ENOMEM; 1146 1147 atomic_set(&newsighand->count, 1); 1148 memcpy(newsighand->action, oldsighand->action, 1149 sizeof(newsighand->action)); 1150 1151 write_lock_irq(&tasklist_lock); 1152 spin_lock(&oldsighand->siglock); 1153 rcu_assign_pointer(tsk->sighand, newsighand); 1154 spin_unlock(&oldsighand->siglock); 1155 write_unlock_irq(&tasklist_lock); 1156 1157 __cleanup_sighand(oldsighand); 1158 } 1159 1160 BUG_ON(!thread_group_leader(tsk)); 1161 return 0; 1162 1163 killed: 1164 /* protects against exit_notify() and __exit_signal() */ 1165 read_lock(&tasklist_lock); 1166 sig->group_exit_task = NULL; 1167 sig->notify_count = 0; 1168 read_unlock(&tasklist_lock); 1169 return -EAGAIN; 1170 } 1171 1172 char *get_task_comm(char *buf, struct task_struct *tsk) 1173 { 1174 /* buf must be at least sizeof(tsk->comm) in size */ 1175 task_lock(tsk); 1176 strncpy(buf, tsk->comm, sizeof(tsk->comm)); 1177 task_unlock(tsk); 1178 return buf; 1179 } 1180 EXPORT_SYMBOL_GPL(get_task_comm); 1181 1182 /* 1183 * These functions flushes out all traces of the currently running executable 1184 * so that a new one can be started 1185 */ 1186 1187 void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec) 1188 { 1189 task_lock(tsk); 1190 trace_task_rename(tsk, buf); 1191 strlcpy(tsk->comm, buf, sizeof(tsk->comm)); 1192 task_unlock(tsk); 1193 perf_event_comm(tsk, exec); 1194 } 1195 1196 int flush_old_exec(struct linux_binprm * bprm) 1197 { 1198 int retval; 1199 1200 /* 1201 * Make sure we have a private signal table and that 1202 * we are unassociated from the previous thread group. 1203 */ 1204 retval = de_thread(current); 1205 if (retval) 1206 goto out; 1207 1208 /* 1209 * Must be called _before_ exec_mmap() as bprm->mm is 1210 * not visibile until then. This also enables the update 1211 * to be lockless. 1212 */ 1213 set_mm_exe_file(bprm->mm, bprm->file); 1214 1215 /* 1216 * Release all of the old mmap stuff 1217 */ 1218 acct_arg_size(bprm, 0); 1219 retval = exec_mmap(bprm->mm); 1220 if (retval) 1221 goto out; 1222 1223 bprm->mm = NULL; /* We're using it now */ 1224 1225 set_fs(USER_DS); 1226 current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD | 1227 PF_NOFREEZE | PF_NO_SETAFFINITY); 1228 flush_thread(); 1229 current->personality &= ~bprm->per_clear; 1230 1231 return 0; 1232 1233 out: 1234 return retval; 1235 } 1236 EXPORT_SYMBOL(flush_old_exec); 1237 1238 void would_dump(struct linux_binprm *bprm, struct file *file) 1239 { 1240 if (inode_permission(file_inode(file), MAY_READ) < 0) 1241 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP; 1242 } 1243 EXPORT_SYMBOL(would_dump); 1244 1245 void setup_new_exec(struct linux_binprm * bprm) 1246 { 1247 arch_pick_mmap_layout(current->mm); 1248 1249 /* This is the point of no return */ 1250 current->sas_ss_sp = current->sas_ss_size = 0; 1251 1252 if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid())) 1253 set_dumpable(current->mm, SUID_DUMP_USER); 1254 else 1255 set_dumpable(current->mm, suid_dumpable); 1256 1257 perf_event_exec(); 1258 __set_task_comm(current, kbasename(bprm->filename), true); 1259 1260 /* Set the new mm task size. We have to do that late because it may 1261 * depend on TIF_32BIT which is only updated in flush_thread() on 1262 * some architectures like powerpc 1263 */ 1264 current->mm->task_size = TASK_SIZE; 1265 1266 /* install the new credentials */ 1267 if (!uid_eq(bprm->cred->uid, current_euid()) || 1268 !gid_eq(bprm->cred->gid, current_egid())) { 1269 current->pdeath_signal = 0; 1270 } else { 1271 would_dump(bprm, bprm->file); 1272 if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) 1273 set_dumpable(current->mm, suid_dumpable); 1274 } 1275 1276 /* An exec changes our domain. We are no longer part of the thread 1277 group */ 1278 current->self_exec_id++; 1279 flush_signal_handlers(current, 0); 1280 do_close_on_exec(current->files); 1281 } 1282 EXPORT_SYMBOL(setup_new_exec); 1283 1284 /* 1285 * Prepare credentials and lock ->cred_guard_mutex. 1286 * install_exec_creds() commits the new creds and drops the lock. 1287 * Or, if exec fails before, free_bprm() should release ->cred and 1288 * and unlock. 1289 */ 1290 int prepare_bprm_creds(struct linux_binprm *bprm) 1291 { 1292 if (mutex_lock_interruptible(¤t->signal->cred_guard_mutex)) 1293 return -ERESTARTNOINTR; 1294 1295 bprm->cred = prepare_exec_creds(); 1296 if (likely(bprm->cred)) 1297 return 0; 1298 1299 mutex_unlock(¤t->signal->cred_guard_mutex); 1300 return -ENOMEM; 1301 } 1302 1303 static void free_bprm(struct linux_binprm *bprm) 1304 { 1305 free_arg_pages(bprm); 1306 if (bprm->cred) { 1307 mutex_unlock(¤t->signal->cred_guard_mutex); 1308 abort_creds(bprm->cred); 1309 } 1310 if (bprm->file) { 1311 allow_write_access(bprm->file); 1312 fput(bprm->file); 1313 } 1314 /* If a binfmt changed the interp, free it. */ 1315 if (bprm->interp != bprm->filename) 1316 kfree(bprm->interp); 1317 kfree(bprm); 1318 } 1319 1320 int bprm_change_interp(char *interp, struct linux_binprm *bprm) 1321 { 1322 /* If a binfmt changed the interp, free it first. */ 1323 if (bprm->interp != bprm->filename) 1324 kfree(bprm->interp); 1325 bprm->interp = kstrdup(interp, GFP_KERNEL); 1326 if (!bprm->interp) 1327 return -ENOMEM; 1328 return 0; 1329 } 1330 EXPORT_SYMBOL(bprm_change_interp); 1331 1332 /* 1333 * install the new credentials for this executable 1334 */ 1335 void install_exec_creds(struct linux_binprm *bprm) 1336 { 1337 security_bprm_committing_creds(bprm); 1338 1339 commit_creds(bprm->cred); 1340 bprm->cred = NULL; 1341 1342 /* 1343 * Disable monitoring for regular users 1344 * when executing setuid binaries. Must 1345 * wait until new credentials are committed 1346 * by commit_creds() above 1347 */ 1348 if (get_dumpable(current->mm) != SUID_DUMP_USER) 1349 perf_event_exit_task(current); 1350 /* 1351 * cred_guard_mutex must be held at least to this point to prevent 1352 * ptrace_attach() from altering our determination of the task's 1353 * credentials; any time after this it may be unlocked. 1354 */ 1355 security_bprm_committed_creds(bprm); 1356 mutex_unlock(¤t->signal->cred_guard_mutex); 1357 } 1358 EXPORT_SYMBOL(install_exec_creds); 1359 1360 /* 1361 * determine how safe it is to execute the proposed program 1362 * - the caller must hold ->cred_guard_mutex to protect against 1363 * PTRACE_ATTACH or seccomp thread-sync 1364 */ 1365 static void check_unsafe_exec(struct linux_binprm *bprm) 1366 { 1367 struct task_struct *p = current, *t; 1368 unsigned n_fs; 1369 1370 if (p->ptrace) { 1371 if (p->ptrace & PT_PTRACE_CAP) 1372 bprm->unsafe |= LSM_UNSAFE_PTRACE_CAP; 1373 else 1374 bprm->unsafe |= LSM_UNSAFE_PTRACE; 1375 } 1376 1377 /* 1378 * This isn't strictly necessary, but it makes it harder for LSMs to 1379 * mess up. 1380 */ 1381 if (task_no_new_privs(current)) 1382 bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS; 1383 1384 t = p; 1385 n_fs = 1; 1386 spin_lock(&p->fs->lock); 1387 rcu_read_lock(); 1388 while_each_thread(p, t) { 1389 if (t->fs == p->fs) 1390 n_fs++; 1391 } 1392 rcu_read_unlock(); 1393 1394 if (p->fs->users > n_fs) 1395 bprm->unsafe |= LSM_UNSAFE_SHARE; 1396 else 1397 p->fs->in_exec = 1; 1398 spin_unlock(&p->fs->lock); 1399 } 1400 1401 static void bprm_fill_uid(struct linux_binprm *bprm) 1402 { 1403 struct inode *inode; 1404 unsigned int mode; 1405 kuid_t uid; 1406 kgid_t gid; 1407 1408 /* 1409 * Since this can be called multiple times (via prepare_binprm), 1410 * we must clear any previous work done when setting set[ug]id 1411 * bits from any earlier bprm->file uses (for example when run 1412 * first for a setuid script then again for its interpreter). 1413 */ 1414 bprm->cred->euid = current_euid(); 1415 bprm->cred->egid = current_egid(); 1416 1417 if (!mnt_may_suid(bprm->file->f_path.mnt)) 1418 return; 1419 1420 if (task_no_new_privs(current)) 1421 return; 1422 1423 inode = file_inode(bprm->file); 1424 mode = READ_ONCE(inode->i_mode); 1425 if (!(mode & (S_ISUID|S_ISGID))) 1426 return; 1427 1428 /* Be careful if suid/sgid is set */ 1429 inode_lock(inode); 1430 1431 /* reload atomically mode/uid/gid now that lock held */ 1432 mode = inode->i_mode; 1433 uid = inode->i_uid; 1434 gid = inode->i_gid; 1435 inode_unlock(inode); 1436 1437 /* We ignore suid/sgid if there are no mappings for them in the ns */ 1438 if (!kuid_has_mapping(bprm->cred->user_ns, uid) || 1439 !kgid_has_mapping(bprm->cred->user_ns, gid)) 1440 return; 1441 1442 if (mode & S_ISUID) { 1443 bprm->per_clear |= PER_CLEAR_ON_SETID; 1444 bprm->cred->euid = uid; 1445 } 1446 1447 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { 1448 bprm->per_clear |= PER_CLEAR_ON_SETID; 1449 bprm->cred->egid = gid; 1450 } 1451 } 1452 1453 /* 1454 * Fill the binprm structure from the inode. 1455 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes 1456 * 1457 * This may be called multiple times for binary chains (scripts for example). 1458 */ 1459 int prepare_binprm(struct linux_binprm *bprm) 1460 { 1461 int retval; 1462 1463 bprm_fill_uid(bprm); 1464 1465 /* fill in binprm security blob */ 1466 retval = security_bprm_set_creds(bprm); 1467 if (retval) 1468 return retval; 1469 bprm->cred_prepared = 1; 1470 1471 memset(bprm->buf, 0, BINPRM_BUF_SIZE); 1472 return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE); 1473 } 1474 1475 EXPORT_SYMBOL(prepare_binprm); 1476 1477 /* 1478 * Arguments are '\0' separated strings found at the location bprm->p 1479 * points to; chop off the first by relocating brpm->p to right after 1480 * the first '\0' encountered. 1481 */ 1482 int remove_arg_zero(struct linux_binprm *bprm) 1483 { 1484 int ret = 0; 1485 unsigned long offset; 1486 char *kaddr; 1487 struct page *page; 1488 1489 if (!bprm->argc) 1490 return 0; 1491 1492 do { 1493 offset = bprm->p & ~PAGE_MASK; 1494 page = get_arg_page(bprm, bprm->p, 0); 1495 if (!page) { 1496 ret = -EFAULT; 1497 goto out; 1498 } 1499 kaddr = kmap_atomic(page); 1500 1501 for (; offset < PAGE_SIZE && kaddr[offset]; 1502 offset++, bprm->p++) 1503 ; 1504 1505 kunmap_atomic(kaddr); 1506 put_arg_page(page); 1507 } while (offset == PAGE_SIZE); 1508 1509 bprm->p++; 1510 bprm->argc--; 1511 ret = 0; 1512 1513 out: 1514 return ret; 1515 } 1516 EXPORT_SYMBOL(remove_arg_zero); 1517 1518 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e)) 1519 /* 1520 * cycle the list of binary formats handler, until one recognizes the image 1521 */ 1522 int search_binary_handler(struct linux_binprm *bprm) 1523 { 1524 bool need_retry = IS_ENABLED(CONFIG_MODULES); 1525 struct linux_binfmt *fmt; 1526 int retval; 1527 1528 /* This allows 4 levels of binfmt rewrites before failing hard. */ 1529 if (bprm->recursion_depth > 5) 1530 return -ELOOP; 1531 1532 retval = security_bprm_check(bprm); 1533 if (retval) 1534 return retval; 1535 1536 retval = -ENOENT; 1537 retry: 1538 read_lock(&binfmt_lock); 1539 list_for_each_entry(fmt, &formats, lh) { 1540 if (!try_module_get(fmt->module)) 1541 continue; 1542 read_unlock(&binfmt_lock); 1543 bprm->recursion_depth++; 1544 retval = fmt->load_binary(bprm); 1545 read_lock(&binfmt_lock); 1546 put_binfmt(fmt); 1547 bprm->recursion_depth--; 1548 if (retval < 0 && !bprm->mm) { 1549 /* we got to flush_old_exec() and failed after it */ 1550 read_unlock(&binfmt_lock); 1551 force_sigsegv(SIGSEGV, current); 1552 return retval; 1553 } 1554 if (retval != -ENOEXEC || !bprm->file) { 1555 read_unlock(&binfmt_lock); 1556 return retval; 1557 } 1558 } 1559 read_unlock(&binfmt_lock); 1560 1561 if (need_retry) { 1562 if (printable(bprm->buf[0]) && printable(bprm->buf[1]) && 1563 printable(bprm->buf[2]) && printable(bprm->buf[3])) 1564 return retval; 1565 if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0) 1566 return retval; 1567 need_retry = false; 1568 goto retry; 1569 } 1570 1571 return retval; 1572 } 1573 EXPORT_SYMBOL(search_binary_handler); 1574 1575 static int exec_binprm(struct linux_binprm *bprm) 1576 { 1577 pid_t old_pid, old_vpid; 1578 int ret; 1579 1580 /* Need to fetch pid before load_binary changes it */ 1581 old_pid = current->pid; 1582 rcu_read_lock(); 1583 old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent)); 1584 rcu_read_unlock(); 1585 1586 ret = search_binary_handler(bprm); 1587 if (ret >= 0) { 1588 audit_bprm(bprm); 1589 trace_sched_process_exec(current, old_pid, bprm); 1590 ptrace_event(PTRACE_EVENT_EXEC, old_vpid); 1591 proc_exec_connector(current); 1592 } 1593 1594 return ret; 1595 } 1596 1597 /* 1598 * sys_execve() executes a new program. 1599 */ 1600 static int do_execveat_common(int fd, struct filename *filename, 1601 struct user_arg_ptr argv, 1602 struct user_arg_ptr envp, 1603 int flags) 1604 { 1605 char *pathbuf = NULL; 1606 struct linux_binprm *bprm; 1607 struct file *file; 1608 struct files_struct *displaced; 1609 int retval; 1610 1611 if (IS_ERR(filename)) 1612 return PTR_ERR(filename); 1613 1614 /* 1615 * We move the actual failure in case of RLIMIT_NPROC excess from 1616 * set*uid() to execve() because too many poorly written programs 1617 * don't check setuid() return code. Here we additionally recheck 1618 * whether NPROC limit is still exceeded. 1619 */ 1620 if ((current->flags & PF_NPROC_EXCEEDED) && 1621 atomic_read(¤t_user()->processes) > rlimit(RLIMIT_NPROC)) { 1622 retval = -EAGAIN; 1623 goto out_ret; 1624 } 1625 1626 /* We're below the limit (still or again), so we don't want to make 1627 * further execve() calls fail. */ 1628 current->flags &= ~PF_NPROC_EXCEEDED; 1629 1630 retval = unshare_files(&displaced); 1631 if (retval) 1632 goto out_ret; 1633 1634 retval = -ENOMEM; 1635 bprm = kzalloc(sizeof(*bprm), GFP_KERNEL); 1636 if (!bprm) 1637 goto out_files; 1638 1639 retval = prepare_bprm_creds(bprm); 1640 if (retval) 1641 goto out_free; 1642 1643 check_unsafe_exec(bprm); 1644 current->in_execve = 1; 1645 1646 file = do_open_execat(fd, filename, flags); 1647 retval = PTR_ERR(file); 1648 if (IS_ERR(file)) 1649 goto out_unmark; 1650 1651 sched_exec(); 1652 1653 bprm->file = file; 1654 if (fd == AT_FDCWD || filename->name[0] == '/') { 1655 bprm->filename = filename->name; 1656 } else { 1657 if (filename->name[0] == '\0') 1658 pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d", fd); 1659 else 1660 pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d/%s", 1661 fd, filename->name); 1662 if (!pathbuf) { 1663 retval = -ENOMEM; 1664 goto out_unmark; 1665 } 1666 /* 1667 * Record that a name derived from an O_CLOEXEC fd will be 1668 * inaccessible after exec. Relies on having exclusive access to 1669 * current->files (due to unshare_files above). 1670 */ 1671 if (close_on_exec(fd, rcu_dereference_raw(current->files->fdt))) 1672 bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE; 1673 bprm->filename = pathbuf; 1674 } 1675 bprm->interp = bprm->filename; 1676 1677 retval = bprm_mm_init(bprm); 1678 if (retval) 1679 goto out_unmark; 1680 1681 bprm->argc = count(argv, MAX_ARG_STRINGS); 1682 if ((retval = bprm->argc) < 0) 1683 goto out; 1684 1685 bprm->envc = count(envp, MAX_ARG_STRINGS); 1686 if ((retval = bprm->envc) < 0) 1687 goto out; 1688 1689 retval = prepare_binprm(bprm); 1690 if (retval < 0) 1691 goto out; 1692 1693 retval = copy_strings_kernel(1, &bprm->filename, bprm); 1694 if (retval < 0) 1695 goto out; 1696 1697 bprm->exec = bprm->p; 1698 retval = copy_strings(bprm->envc, envp, bprm); 1699 if (retval < 0) 1700 goto out; 1701 1702 retval = copy_strings(bprm->argc, argv, bprm); 1703 if (retval < 0) 1704 goto out; 1705 1706 retval = exec_binprm(bprm); 1707 if (retval < 0) 1708 goto out; 1709 1710 /* execve succeeded */ 1711 current->fs->in_exec = 0; 1712 current->in_execve = 0; 1713 acct_update_integrals(current); 1714 task_numa_free(current); 1715 free_bprm(bprm); 1716 kfree(pathbuf); 1717 putname(filename); 1718 if (displaced) 1719 put_files_struct(displaced); 1720 return retval; 1721 1722 out: 1723 if (bprm->mm) { 1724 acct_arg_size(bprm, 0); 1725 mmput(bprm->mm); 1726 } 1727 1728 out_unmark: 1729 current->fs->in_exec = 0; 1730 current->in_execve = 0; 1731 1732 out_free: 1733 free_bprm(bprm); 1734 kfree(pathbuf); 1735 1736 out_files: 1737 if (displaced) 1738 reset_files_struct(displaced); 1739 out_ret: 1740 putname(filename); 1741 return retval; 1742 } 1743 1744 int do_execve(struct filename *filename, 1745 const char __user *const __user *__argv, 1746 const char __user *const __user *__envp) 1747 { 1748 struct user_arg_ptr argv = { .ptr.native = __argv }; 1749 struct user_arg_ptr envp = { .ptr.native = __envp }; 1750 return do_execveat_common(AT_FDCWD, filename, argv, envp, 0); 1751 } 1752 1753 int do_execveat(int fd, struct filename *filename, 1754 const char __user *const __user *__argv, 1755 const char __user *const __user *__envp, 1756 int flags) 1757 { 1758 struct user_arg_ptr argv = { .ptr.native = __argv }; 1759 struct user_arg_ptr envp = { .ptr.native = __envp }; 1760 1761 return do_execveat_common(fd, filename, argv, envp, flags); 1762 } 1763 1764 #ifdef CONFIG_COMPAT 1765 static int compat_do_execve(struct filename *filename, 1766 const compat_uptr_t __user *__argv, 1767 const compat_uptr_t __user *__envp) 1768 { 1769 struct user_arg_ptr argv = { 1770 .is_compat = true, 1771 .ptr.compat = __argv, 1772 }; 1773 struct user_arg_ptr envp = { 1774 .is_compat = true, 1775 .ptr.compat = __envp, 1776 }; 1777 return do_execveat_common(AT_FDCWD, filename, argv, envp, 0); 1778 } 1779 1780 static int compat_do_execveat(int fd, struct filename *filename, 1781 const compat_uptr_t __user *__argv, 1782 const compat_uptr_t __user *__envp, 1783 int flags) 1784 { 1785 struct user_arg_ptr argv = { 1786 .is_compat = true, 1787 .ptr.compat = __argv, 1788 }; 1789 struct user_arg_ptr envp = { 1790 .is_compat = true, 1791 .ptr.compat = __envp, 1792 }; 1793 return do_execveat_common(fd, filename, argv, envp, flags); 1794 } 1795 #endif 1796 1797 void set_binfmt(struct linux_binfmt *new) 1798 { 1799 struct mm_struct *mm = current->mm; 1800 1801 if (mm->binfmt) 1802 module_put(mm->binfmt->module); 1803 1804 mm->binfmt = new; 1805 if (new) 1806 __module_get(new->module); 1807 } 1808 EXPORT_SYMBOL(set_binfmt); 1809 1810 /* 1811 * set_dumpable stores three-value SUID_DUMP_* into mm->flags. 1812 */ 1813 void set_dumpable(struct mm_struct *mm, int value) 1814 { 1815 unsigned long old, new; 1816 1817 if (WARN_ON((unsigned)value > SUID_DUMP_ROOT)) 1818 return; 1819 1820 do { 1821 old = ACCESS_ONCE(mm->flags); 1822 new = (old & ~MMF_DUMPABLE_MASK) | value; 1823 } while (cmpxchg(&mm->flags, old, new) != old); 1824 } 1825 1826 SYSCALL_DEFINE3(execve, 1827 const char __user *, filename, 1828 const char __user *const __user *, argv, 1829 const char __user *const __user *, envp) 1830 { 1831 return do_execve(getname(filename), argv, envp); 1832 } 1833 1834 SYSCALL_DEFINE5(execveat, 1835 int, fd, const char __user *, filename, 1836 const char __user *const __user *, argv, 1837 const char __user *const __user *, envp, 1838 int, flags) 1839 { 1840 int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0; 1841 1842 return do_execveat(fd, 1843 getname_flags(filename, lookup_flags, NULL), 1844 argv, envp, flags); 1845 } 1846 1847 #ifdef CONFIG_COMPAT 1848 COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename, 1849 const compat_uptr_t __user *, argv, 1850 const compat_uptr_t __user *, envp) 1851 { 1852 return compat_do_execve(getname(filename), argv, envp); 1853 } 1854 1855 COMPAT_SYSCALL_DEFINE5(execveat, int, fd, 1856 const char __user *, filename, 1857 const compat_uptr_t __user *, argv, 1858 const compat_uptr_t __user *, envp, 1859 int, flags) 1860 { 1861 int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0; 1862 1863 return compat_do_execveat(fd, 1864 getname_flags(filename, lookup_flags, NULL), 1865 argv, envp, flags); 1866 } 1867 #endif 1868