1 /* 2 * binfmt_misc.c 3 * 4 * Copyright (C) 1997 Richard Günther 5 * 6 * binfmt_misc detects binaries via a magic or filename extension and invokes 7 * a specified wrapper. This should obsolete binfmt_java, binfmt_em86 and 8 * binfmt_mz. 9 * 10 * 1997-04-25 first version 11 * [...] 12 * 1997-05-19 cleanup 13 * 1997-06-26 hpa: pass the real filename rather than argv[0] 14 * 1997-06-30 minor cleanup 15 * 1997-08-09 removed extension stripping, locking cleanup 16 * 2001-02-28 AV: rewritten into something that resembles C. Original didn't. 17 */ 18 19 #include <linux/module.h> 20 #include <linux/init.h> 21 #include <linux/sched.h> 22 #include <linux/magic.h> 23 #include <linux/binfmts.h> 24 #include <linux/slab.h> 25 #include <linux/ctype.h> 26 #include <linux/string_helpers.h> 27 #include <linux/file.h> 28 #include <linux/pagemap.h> 29 #include <linux/namei.h> 30 #include <linux/mount.h> 31 #include <linux/syscalls.h> 32 #include <linux/fs.h> 33 34 #include <asm/uaccess.h> 35 36 enum { 37 VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */ 38 }; 39 40 static LIST_HEAD(entries); 41 static int enabled = 1; 42 43 enum {Enabled, Magic}; 44 #define MISC_FMT_PRESERVE_ARGV0 (1<<31) 45 #define MISC_FMT_OPEN_BINARY (1<<30) 46 #define MISC_FMT_CREDENTIALS (1<<29) 47 48 typedef struct { 49 struct list_head list; 50 unsigned long flags; /* type, status, etc. */ 51 int offset; /* offset of magic */ 52 int size; /* size of magic/mask */ 53 char *magic; /* magic or filename extension */ 54 char *mask; /* mask, NULL for exact match */ 55 char *interpreter; /* filename of interpreter */ 56 char *name; 57 struct dentry *dentry; 58 } Node; 59 60 static DEFINE_RWLOCK(entries_lock); 61 static struct file_system_type bm_fs_type; 62 static struct vfsmount *bm_mnt; 63 static int entry_count; 64 65 /* 66 * Max length of the register string. Determined by: 67 * - 7 delimiters 68 * - name: ~50 bytes 69 * - type: 1 byte 70 * - offset: 3 bytes (has to be smaller than BINPRM_BUF_SIZE) 71 * - magic: 128 bytes (512 in escaped form) 72 * - mask: 128 bytes (512 in escaped form) 73 * - interp: ~50 bytes 74 * - flags: 5 bytes 75 * Round that up a bit, and then back off to hold the internal data 76 * (like struct Node). 77 */ 78 #define MAX_REGISTER_LENGTH 1920 79 80 /* 81 * Check if we support the binfmt 82 * if we do, return the node, else NULL 83 * locking is done in load_misc_binary 84 */ 85 static Node *check_file(struct linux_binprm *bprm) 86 { 87 char *p = strrchr(bprm->interp, '.'); 88 struct list_head *l; 89 90 list_for_each(l, &entries) { 91 Node *e = list_entry(l, Node, list); 92 char *s; 93 int j; 94 95 if (!test_bit(Enabled, &e->flags)) 96 continue; 97 98 if (!test_bit(Magic, &e->flags)) { 99 if (p && !strcmp(e->magic, p + 1)) 100 return e; 101 continue; 102 } 103 104 s = bprm->buf + e->offset; 105 if (e->mask) { 106 for (j = 0; j < e->size; j++) 107 if ((*s++ ^ e->magic[j]) & e->mask[j]) 108 break; 109 } else { 110 for (j = 0; j < e->size; j++) 111 if ((*s++ ^ e->magic[j])) 112 break; 113 } 114 if (j == e->size) 115 return e; 116 } 117 return NULL; 118 } 119 120 /* 121 * the loader itself 122 */ 123 static int load_misc_binary(struct linux_binprm *bprm) 124 { 125 Node *fmt; 126 struct file * interp_file = NULL; 127 char iname[BINPRM_BUF_SIZE]; 128 const char *iname_addr = iname; 129 int retval; 130 int fd_binary = -1; 131 132 retval = -ENOEXEC; 133 if (!enabled) 134 goto _ret; 135 136 /* to keep locking time low, we copy the interpreter string */ 137 read_lock(&entries_lock); 138 fmt = check_file(bprm); 139 if (fmt) 140 strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE); 141 read_unlock(&entries_lock); 142 if (!fmt) 143 goto _ret; 144 145 if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) { 146 retval = remove_arg_zero(bprm); 147 if (retval) 148 goto _ret; 149 } 150 151 if (fmt->flags & MISC_FMT_OPEN_BINARY) { 152 153 /* if the binary should be opened on behalf of the 154 * interpreter than keep it open and assign descriptor 155 * to it */ 156 fd_binary = get_unused_fd(); 157 if (fd_binary < 0) { 158 retval = fd_binary; 159 goto _ret; 160 } 161 fd_install(fd_binary, bprm->file); 162 163 /* if the binary is not readable than enforce mm->dumpable=0 164 regardless of the interpreter's permissions */ 165 would_dump(bprm, bprm->file); 166 167 allow_write_access(bprm->file); 168 bprm->file = NULL; 169 170 /* mark the bprm that fd should be passed to interp */ 171 bprm->interp_flags |= BINPRM_FLAGS_EXECFD; 172 bprm->interp_data = fd_binary; 173 174 } else { 175 allow_write_access(bprm->file); 176 fput(bprm->file); 177 bprm->file = NULL; 178 } 179 /* make argv[1] be the path to the binary */ 180 retval = copy_strings_kernel (1, &bprm->interp, bprm); 181 if (retval < 0) 182 goto _error; 183 bprm->argc++; 184 185 /* add the interp as argv[0] */ 186 retval = copy_strings_kernel (1, &iname_addr, bprm); 187 if (retval < 0) 188 goto _error; 189 bprm->argc ++; 190 191 /* Update interp in case binfmt_script needs it. */ 192 retval = bprm_change_interp(iname, bprm); 193 if (retval < 0) 194 goto _error; 195 196 interp_file = open_exec (iname); 197 retval = PTR_ERR (interp_file); 198 if (IS_ERR (interp_file)) 199 goto _error; 200 201 bprm->file = interp_file; 202 if (fmt->flags & MISC_FMT_CREDENTIALS) { 203 /* 204 * No need to call prepare_binprm(), it's already been 205 * done. bprm->buf is stale, update from interp_file. 206 */ 207 memset(bprm->buf, 0, BINPRM_BUF_SIZE); 208 retval = kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE); 209 } else 210 retval = prepare_binprm (bprm); 211 212 if (retval < 0) 213 goto _error; 214 215 retval = search_binary_handler(bprm); 216 if (retval < 0) 217 goto _error; 218 219 _ret: 220 return retval; 221 _error: 222 if (fd_binary > 0) 223 sys_close(fd_binary); 224 bprm->interp_flags = 0; 225 bprm->interp_data = 0; 226 goto _ret; 227 } 228 229 /* Command parsers */ 230 231 /* 232 * parses and copies one argument enclosed in del from *sp to *dp, 233 * recognising the \x special. 234 * returns pointer to the copied argument or NULL in case of an 235 * error (and sets err) or null argument length. 236 */ 237 static char *scanarg(char *s, char del) 238 { 239 char c; 240 241 while ((c = *s++) != del) { 242 if (c == '\\' && *s == 'x') { 243 s++; 244 if (!isxdigit(*s++)) 245 return NULL; 246 if (!isxdigit(*s++)) 247 return NULL; 248 } 249 } 250 return s; 251 } 252 253 static char * check_special_flags (char * sfs, Node * e) 254 { 255 char * p = sfs; 256 int cont = 1; 257 258 /* special flags */ 259 while (cont) { 260 switch (*p) { 261 case 'P': 262 p++; 263 e->flags |= MISC_FMT_PRESERVE_ARGV0; 264 break; 265 case 'O': 266 p++; 267 e->flags |= MISC_FMT_OPEN_BINARY; 268 break; 269 case 'C': 270 p++; 271 /* this flags also implies the 272 open-binary flag */ 273 e->flags |= (MISC_FMT_CREDENTIALS | 274 MISC_FMT_OPEN_BINARY); 275 break; 276 default: 277 cont = 0; 278 } 279 } 280 281 return p; 282 } 283 /* 284 * This registers a new binary format, it recognises the syntax 285 * ':name:type:offset:magic:mask:interpreter:flags' 286 * where the ':' is the IFS, that can be chosen with the first char 287 */ 288 static Node *create_entry(const char __user *buffer, size_t count) 289 { 290 Node *e; 291 int memsize, err; 292 char *buf, *p; 293 char del; 294 295 /* some sanity checks */ 296 err = -EINVAL; 297 if ((count < 11) || (count > MAX_REGISTER_LENGTH)) 298 goto out; 299 300 err = -ENOMEM; 301 memsize = sizeof(Node) + count + 8; 302 e = kmalloc(memsize, GFP_USER); 303 if (!e) 304 goto out; 305 306 p = buf = (char *)e + sizeof(Node); 307 308 memset(e, 0, sizeof(Node)); 309 if (copy_from_user(buf, buffer, count)) 310 goto Efault; 311 312 del = *p++; /* delimeter */ 313 314 memset(buf+count, del, 8); 315 316 e->name = p; 317 p = strchr(p, del); 318 if (!p) 319 goto Einval; 320 *p++ = '\0'; 321 if (!e->name[0] || 322 !strcmp(e->name, ".") || 323 !strcmp(e->name, "..") || 324 strchr(e->name, '/')) 325 goto Einval; 326 switch (*p++) { 327 case 'E': e->flags = 1<<Enabled; break; 328 case 'M': e->flags = (1<<Enabled) | (1<<Magic); break; 329 default: goto Einval; 330 } 331 if (*p++ != del) 332 goto Einval; 333 if (test_bit(Magic, &e->flags)) { 334 char *s = strchr(p, del); 335 if (!s) 336 goto Einval; 337 *s++ = '\0'; 338 e->offset = simple_strtoul(p, &p, 10); 339 if (*p++) 340 goto Einval; 341 e->magic = p; 342 p = scanarg(p, del); 343 if (!p) 344 goto Einval; 345 p[-1] = '\0'; 346 if (!e->magic[0]) 347 goto Einval; 348 e->mask = p; 349 p = scanarg(p, del); 350 if (!p) 351 goto Einval; 352 p[-1] = '\0'; 353 if (!e->mask[0]) 354 e->mask = NULL; 355 e->size = string_unescape_inplace(e->magic, UNESCAPE_HEX); 356 if (e->mask && 357 string_unescape_inplace(e->mask, UNESCAPE_HEX) != e->size) 358 goto Einval; 359 if (e->size + e->offset > BINPRM_BUF_SIZE) 360 goto Einval; 361 } else { 362 p = strchr(p, del); 363 if (!p) 364 goto Einval; 365 *p++ = '\0'; 366 e->magic = p; 367 p = strchr(p, del); 368 if (!p) 369 goto Einval; 370 *p++ = '\0'; 371 if (!e->magic[0] || strchr(e->magic, '/')) 372 goto Einval; 373 p = strchr(p, del); 374 if (!p) 375 goto Einval; 376 *p++ = '\0'; 377 } 378 e->interpreter = p; 379 p = strchr(p, del); 380 if (!p) 381 goto Einval; 382 *p++ = '\0'; 383 if (!e->interpreter[0]) 384 goto Einval; 385 386 387 p = check_special_flags (p, e); 388 389 if (*p == '\n') 390 p++; 391 if (p != buf + count) 392 goto Einval; 393 return e; 394 395 out: 396 return ERR_PTR(err); 397 398 Efault: 399 kfree(e); 400 return ERR_PTR(-EFAULT); 401 Einval: 402 kfree(e); 403 return ERR_PTR(-EINVAL); 404 } 405 406 /* 407 * Set status of entry/binfmt_misc: 408 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc 409 */ 410 static int parse_command(const char __user *buffer, size_t count) 411 { 412 char s[4]; 413 414 if (count > 3) 415 return -EINVAL; 416 if (copy_from_user(s, buffer, count)) 417 return -EFAULT; 418 if (!count) 419 return 0; 420 if (s[count-1] == '\n') 421 count--; 422 if (count == 1 && s[0] == '0') 423 return 1; 424 if (count == 1 && s[0] == '1') 425 return 2; 426 if (count == 2 && s[0] == '-' && s[1] == '1') 427 return 3; 428 return -EINVAL; 429 } 430 431 /* generic stuff */ 432 433 static void entry_status(Node *e, char *page) 434 { 435 char *dp; 436 char *status = "disabled"; 437 const char * flags = "flags: "; 438 439 if (test_bit(Enabled, &e->flags)) 440 status = "enabled"; 441 442 if (!VERBOSE_STATUS) { 443 sprintf(page, "%s\n", status); 444 return; 445 } 446 447 sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter); 448 dp = page + strlen(page); 449 450 /* print the special flags */ 451 sprintf (dp, "%s", flags); 452 dp += strlen (flags); 453 if (e->flags & MISC_FMT_PRESERVE_ARGV0) { 454 *dp ++ = 'P'; 455 } 456 if (e->flags & MISC_FMT_OPEN_BINARY) { 457 *dp ++ = 'O'; 458 } 459 if (e->flags & MISC_FMT_CREDENTIALS) { 460 *dp ++ = 'C'; 461 } 462 *dp ++ = '\n'; 463 464 465 if (!test_bit(Magic, &e->flags)) { 466 sprintf(dp, "extension .%s\n", e->magic); 467 } else { 468 int i; 469 470 sprintf(dp, "offset %i\nmagic ", e->offset); 471 dp = page + strlen(page); 472 for (i = 0; i < e->size; i++) { 473 sprintf(dp, "%02x", 0xff & (int) (e->magic[i])); 474 dp += 2; 475 } 476 if (e->mask) { 477 sprintf(dp, "\nmask "); 478 dp += 6; 479 for (i = 0; i < e->size; i++) { 480 sprintf(dp, "%02x", 0xff & (int) (e->mask[i])); 481 dp += 2; 482 } 483 } 484 *dp++ = '\n'; 485 *dp = '\0'; 486 } 487 } 488 489 static struct inode *bm_get_inode(struct super_block *sb, int mode) 490 { 491 struct inode * inode = new_inode(sb); 492 493 if (inode) { 494 inode->i_ino = get_next_ino(); 495 inode->i_mode = mode; 496 inode->i_atime = inode->i_mtime = inode->i_ctime = 497 current_fs_time(inode->i_sb); 498 } 499 return inode; 500 } 501 502 static void bm_evict_inode(struct inode *inode) 503 { 504 clear_inode(inode); 505 kfree(inode->i_private); 506 } 507 508 static void kill_node(Node *e) 509 { 510 struct dentry *dentry; 511 512 write_lock(&entries_lock); 513 dentry = e->dentry; 514 if (dentry) { 515 list_del_init(&e->list); 516 e->dentry = NULL; 517 } 518 write_unlock(&entries_lock); 519 520 if (dentry) { 521 drop_nlink(dentry->d_inode); 522 d_drop(dentry); 523 dput(dentry); 524 simple_release_fs(&bm_mnt, &entry_count); 525 } 526 } 527 528 /* /<entry> */ 529 530 static ssize_t 531 bm_entry_read(struct file * file, char __user * buf, size_t nbytes, loff_t *ppos) 532 { 533 Node *e = file_inode(file)->i_private; 534 ssize_t res; 535 char *page; 536 537 if (!(page = (char*) __get_free_page(GFP_KERNEL))) 538 return -ENOMEM; 539 540 entry_status(e, page); 541 542 res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page)); 543 544 free_page((unsigned long) page); 545 return res; 546 } 547 548 static ssize_t bm_entry_write(struct file *file, const char __user *buffer, 549 size_t count, loff_t *ppos) 550 { 551 struct dentry *root; 552 Node *e = file_inode(file)->i_private; 553 int res = parse_command(buffer, count); 554 555 switch (res) { 556 case 1: clear_bit(Enabled, &e->flags); 557 break; 558 case 2: set_bit(Enabled, &e->flags); 559 break; 560 case 3: root = dget(file->f_path.dentry->d_sb->s_root); 561 mutex_lock(&root->d_inode->i_mutex); 562 563 kill_node(e); 564 565 mutex_unlock(&root->d_inode->i_mutex); 566 dput(root); 567 break; 568 default: return res; 569 } 570 return count; 571 } 572 573 static const struct file_operations bm_entry_operations = { 574 .read = bm_entry_read, 575 .write = bm_entry_write, 576 .llseek = default_llseek, 577 }; 578 579 /* /register */ 580 581 static ssize_t bm_register_write(struct file *file, const char __user *buffer, 582 size_t count, loff_t *ppos) 583 { 584 Node *e; 585 struct inode *inode; 586 struct dentry *root, *dentry; 587 struct super_block *sb = file->f_path.dentry->d_sb; 588 int err = 0; 589 590 e = create_entry(buffer, count); 591 592 if (IS_ERR(e)) 593 return PTR_ERR(e); 594 595 root = dget(sb->s_root); 596 mutex_lock(&root->d_inode->i_mutex); 597 dentry = lookup_one_len(e->name, root, strlen(e->name)); 598 err = PTR_ERR(dentry); 599 if (IS_ERR(dentry)) 600 goto out; 601 602 err = -EEXIST; 603 if (dentry->d_inode) 604 goto out2; 605 606 inode = bm_get_inode(sb, S_IFREG | 0644); 607 608 err = -ENOMEM; 609 if (!inode) 610 goto out2; 611 612 err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count); 613 if (err) { 614 iput(inode); 615 inode = NULL; 616 goto out2; 617 } 618 619 e->dentry = dget(dentry); 620 inode->i_private = e; 621 inode->i_fop = &bm_entry_operations; 622 623 d_instantiate(dentry, inode); 624 write_lock(&entries_lock); 625 list_add(&e->list, &entries); 626 write_unlock(&entries_lock); 627 628 err = 0; 629 out2: 630 dput(dentry); 631 out: 632 mutex_unlock(&root->d_inode->i_mutex); 633 dput(root); 634 635 if (err) { 636 kfree(e); 637 return -EINVAL; 638 } 639 return count; 640 } 641 642 static const struct file_operations bm_register_operations = { 643 .write = bm_register_write, 644 .llseek = noop_llseek, 645 }; 646 647 /* /status */ 648 649 static ssize_t 650 bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) 651 { 652 char *s = enabled ? "enabled\n" : "disabled\n"; 653 654 return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s)); 655 } 656 657 static ssize_t bm_status_write(struct file * file, const char __user * buffer, 658 size_t count, loff_t *ppos) 659 { 660 int res = parse_command(buffer, count); 661 struct dentry *root; 662 663 switch (res) { 664 case 1: enabled = 0; break; 665 case 2: enabled = 1; break; 666 case 3: root = dget(file->f_path.dentry->d_sb->s_root); 667 mutex_lock(&root->d_inode->i_mutex); 668 669 while (!list_empty(&entries)) 670 kill_node(list_entry(entries.next, Node, list)); 671 672 mutex_unlock(&root->d_inode->i_mutex); 673 dput(root); 674 break; 675 default: return res; 676 } 677 return count; 678 } 679 680 static const struct file_operations bm_status_operations = { 681 .read = bm_status_read, 682 .write = bm_status_write, 683 .llseek = default_llseek, 684 }; 685 686 /* Superblock handling */ 687 688 static const struct super_operations s_ops = { 689 .statfs = simple_statfs, 690 .evict_inode = bm_evict_inode, 691 }; 692 693 static int bm_fill_super(struct super_block * sb, void * data, int silent) 694 { 695 static struct tree_descr bm_files[] = { 696 [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO}, 697 [3] = {"register", &bm_register_operations, S_IWUSR}, 698 /* last one */ {""} 699 }; 700 int err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files); 701 if (!err) 702 sb->s_op = &s_ops; 703 return err; 704 } 705 706 static struct dentry *bm_mount(struct file_system_type *fs_type, 707 int flags, const char *dev_name, void *data) 708 { 709 return mount_single(fs_type, flags, data, bm_fill_super); 710 } 711 712 static struct linux_binfmt misc_format = { 713 .module = THIS_MODULE, 714 .load_binary = load_misc_binary, 715 }; 716 717 static struct file_system_type bm_fs_type = { 718 .owner = THIS_MODULE, 719 .name = "binfmt_misc", 720 .mount = bm_mount, 721 .kill_sb = kill_litter_super, 722 }; 723 MODULE_ALIAS_FS("binfmt_misc"); 724 725 static int __init init_misc_binfmt(void) 726 { 727 int err = register_filesystem(&bm_fs_type); 728 if (!err) 729 insert_binfmt(&misc_format); 730 return err; 731 } 732 733 static void __exit exit_misc_binfmt(void) 734 { 735 unregister_binfmt(&misc_format); 736 unregister_filesystem(&bm_fs_type); 737 } 738 739 core_initcall(init_misc_binfmt); 740 module_exit(exit_misc_binfmt); 741 MODULE_LICENSE("GPL"); 742