4 * Copyright (C) 1997 Richard Günther
6 * binfmt_misc detects binaries via a magic or filename extension and invokes
7 * a specified wrapper. See Documentation/binfmt_misc.txt for more details.
10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/sched.h>
15 #include <linux/magic.h>
16 #include <linux/binfmts.h>
17 #include <linux/slab.h>
18 #include <linux/ctype.h>
19 #include <linux/string_helpers.h>
20 #include <linux/file.h>
21 #include <linux/pagemap.h>
22 #include <linux/namei.h>
23 #include <linux/mount.h>
24 #include <linux/syscalls.h>
26 #include <linux/uaccess.h>
35 VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
38 static LIST_HEAD(entries);
39 static int enabled = 1;
41 enum {Enabled, Magic};
42 #define MISC_FMT_PRESERVE_ARGV0 (1 << 31)
43 #define MISC_FMT_OPEN_BINARY (1 << 30)
44 #define MISC_FMT_CREDENTIALS (1 << 29)
47 struct list_head list;
48 unsigned long flags; /* type, status, etc. */
49 int offset; /* offset of magic */
50 int size; /* size of magic/mask */
51 char *magic; /* magic or filename extension */
52 char *mask; /* mask, NULL for exact match */
53 char *interpreter; /* filename of interpreter */
55 struct dentry *dentry;
58 static DEFINE_RWLOCK(entries_lock);
59 static struct file_system_type bm_fs_type;
60 static struct vfsmount *bm_mnt;
61 static int entry_count;
64 * Max length of the register string. Determined by:
68 * - offset: 3 bytes (has to be smaller than BINPRM_BUF_SIZE)
69 * - magic: 128 bytes (512 in escaped form)
70 * - mask: 128 bytes (512 in escaped form)
73 * Round that up a bit, and then back off to hold the internal data
76 #define MAX_REGISTER_LENGTH 1920
79 * Check if we support the binfmt
80 * if we do, return the node, else NULL
81 * locking is done in load_misc_binary
83 static Node *check_file(struct linux_binprm *bprm)
85 char *p = strrchr(bprm->interp, '.');
88 /* Walk all the registered handlers. */
89 list_for_each(l, &entries) {
90 Node *e = list_entry(l, Node, list);
94 /* Make sure this one is currently enabled. */
95 if (!test_bit(Enabled, &e->flags))
98 /* Do matching based on extension if applicable. */
99 if (!test_bit(Magic, &e->flags)) {
100 if (p && !strcmp(e->magic, p + 1))
105 /* Do matching based on magic & mask. */
106 s = bprm->buf + e->offset;
108 for (j = 0; j < e->size; j++)
109 if ((*s++ ^ e->magic[j]) & e->mask[j])
112 for (j = 0; j < e->size; j++)
113 if ((*s++ ^ e->magic[j]))
125 static int load_misc_binary(struct linux_binprm *bprm)
128 struct file *interp_file = NULL;
129 char iname[BINPRM_BUF_SIZE];
130 const char *iname_addr = iname;
138 /* to keep locking time low, we copy the interpreter string */
139 read_lock(&entries_lock);
140 fmt = check_file(bprm);
142 strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
143 read_unlock(&entries_lock);
147 if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
148 retval = remove_arg_zero(bprm);
153 if (fmt->flags & MISC_FMT_OPEN_BINARY) {
155 /* if the binary should be opened on behalf of the
156 * interpreter than keep it open and assign descriptor
159 fd_binary = get_unused_fd_flags(0);
164 fd_install(fd_binary, bprm->file);
166 /* if the binary is not readable than enforce mm->dumpable=0
167 regardless of the interpreter's permissions */
168 would_dump(bprm, bprm->file);
170 allow_write_access(bprm->file);
173 /* mark the bprm that fd should be passed to interp */
174 bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
175 bprm->interp_data = fd_binary;
178 allow_write_access(bprm->file);
182 /* make argv[1] be the path to the binary */
183 retval = copy_strings_kernel(1, &bprm->interp, bprm);
188 /* add the interp as argv[0] */
189 retval = copy_strings_kernel(1, &iname_addr, bprm);
194 /* Update interp in case binfmt_script needs it. */
195 retval = bprm_change_interp(iname, bprm);
199 interp_file = open_exec(iname);
200 retval = PTR_ERR(interp_file);
201 if (IS_ERR(interp_file))
204 bprm->file = interp_file;
205 if (fmt->flags & MISC_FMT_CREDENTIALS) {
207 * No need to call prepare_binprm(), it's already been
208 * done. bprm->buf is stale, update from interp_file.
210 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
211 retval = kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
213 retval = prepare_binprm(bprm);
218 retval = search_binary_handler(bprm);
226 sys_close(fd_binary);
227 bprm->interp_flags = 0;
228 bprm->interp_data = 0;
232 /* Command parsers */
235 * parses and copies one argument enclosed in del from *sp to *dp,
236 * recognising the \x special.
237 * returns pointer to the copied argument or NULL in case of an
238 * error (and sets err) or null argument length.
240 static char *scanarg(char *s, char del)
244 while ((c = *s++) != del) {
245 if (c == '\\' && *s == 'x') {
256 static char *check_special_flags(char *sfs, Node *e)
265 pr_debug("register: flag: P (preserve argv0)\n");
267 e->flags |= MISC_FMT_PRESERVE_ARGV0;
270 pr_debug("register: flag: O (open binary)\n");
272 e->flags |= MISC_FMT_OPEN_BINARY;
275 pr_debug("register: flag: C (preserve creds)\n");
277 /* this flags also implies the
279 e->flags |= (MISC_FMT_CREDENTIALS |
280 MISC_FMT_OPEN_BINARY);
291 * This registers a new binary format, it recognises the syntax
292 * ':name:type:offset:magic:mask:interpreter:flags'
293 * where the ':' is the IFS, that can be chosen with the first char
295 static Node *create_entry(const char __user *buffer, size_t count)
302 pr_debug("register: received %zu bytes\n", count);
304 /* some sanity checks */
306 if ((count < 11) || (count > MAX_REGISTER_LENGTH))
310 memsize = sizeof(Node) + count + 8;
311 e = kmalloc(memsize, GFP_KERNEL);
315 p = buf = (char *)e + sizeof(Node);
317 memset(e, 0, sizeof(Node));
318 if (copy_from_user(buf, buffer, count))
321 del = *p++; /* delimeter */
323 pr_debug("register: delim: %#x {%c}\n", del, del);
325 /* Pad the buffer with the delim to simplify parsing below. */
326 memset(buf + count, del, 8);
328 /* Parse the 'name' field. */
335 !strcmp(e->name, ".") ||
336 !strcmp(e->name, "..") ||
337 strchr(e->name, '/'))
340 pr_debug("register: name: {%s}\n", e->name);
342 /* Parse the 'type' field. */
345 pr_debug("register: type: E (extension)\n");
346 e->flags = 1 << Enabled;
349 pr_debug("register: type: M (magic)\n");
350 e->flags = (1 << Enabled) | (1 << Magic);
358 if (test_bit(Magic, &e->flags)) {
359 /* Handle the 'M' (magic) format. */
362 /* Parse the 'offset' field. */
367 e->offset = simple_strtoul(p, &p, 10);
370 pr_debug("register: offset: %#x\n", e->offset);
372 /* Parse the 'magic' field. */
381 print_hex_dump_bytes(
382 KBUILD_MODNAME ": register: magic[raw]: ",
383 DUMP_PREFIX_NONE, e->magic, p - e->magic);
385 /* Parse the 'mask' field. */
393 pr_debug("register: mask[raw]: none\n");
394 } else if (USE_DEBUG)
395 print_hex_dump_bytes(
396 KBUILD_MODNAME ": register: mask[raw]: ",
397 DUMP_PREFIX_NONE, e->mask, p - e->mask);
400 * Decode the magic & mask fields.
401 * Note: while we might have accepted embedded NUL bytes from
402 * above, the unescape helpers here will stop at the first one
405 e->size = string_unescape_inplace(e->magic, UNESCAPE_HEX);
407 string_unescape_inplace(e->mask, UNESCAPE_HEX) != e->size)
409 if (e->size + e->offset > BINPRM_BUF_SIZE)
411 pr_debug("register: magic/mask length: %i\n", e->size);
413 print_hex_dump_bytes(
414 KBUILD_MODNAME ": register: magic[decoded]: ",
415 DUMP_PREFIX_NONE, e->magic, e->size);
419 char *masked = kmalloc(e->size, GFP_KERNEL);
421 print_hex_dump_bytes(
422 KBUILD_MODNAME ": register: mask[decoded]: ",
423 DUMP_PREFIX_NONE, e->mask, e->size);
426 for (i = 0; i < e->size; ++i)
427 masked[i] = e->magic[i] & e->mask[i];
428 print_hex_dump_bytes(
429 KBUILD_MODNAME ": register: magic[masked]: ",
430 DUMP_PREFIX_NONE, masked, e->size);
437 /* Handle the 'E' (extension) format. */
439 /* Skip the 'offset' field. */
445 /* Parse the 'magic' field. */
451 if (!e->magic[0] || strchr(e->magic, '/'))
453 pr_debug("register: extension: {%s}\n", e->magic);
455 /* Skip the 'mask' field. */
462 /* Parse the 'interpreter' field. */
468 if (!e->interpreter[0])
470 pr_debug("register: interpreter: {%s}\n", e->interpreter);
472 /* Parse the 'flags' field. */
473 p = check_special_flags(p, e);
476 if (p != buf + count)
486 return ERR_PTR(-EFAULT);
489 return ERR_PTR(-EINVAL);
493 * Set status of entry/binfmt_misc:
494 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
496 static int parse_command(const char __user *buffer, size_t count)
502 if (copy_from_user(s, buffer, count))
506 if (s[count - 1] == '\n')
508 if (count == 1 && s[0] == '0')
510 if (count == 1 && s[0] == '1')
512 if (count == 2 && s[0] == '-' && s[1] == '1')
519 static void entry_status(Node *e, char *page)
522 char *status = "disabled";
523 const char *flags = "flags: ";
525 if (test_bit(Enabled, &e->flags))
528 if (!VERBOSE_STATUS) {
529 sprintf(page, "%s\n", status);
533 sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter);
534 dp = page + strlen(page);
536 /* print the special flags */
537 sprintf(dp, "%s", flags);
539 if (e->flags & MISC_FMT_PRESERVE_ARGV0)
541 if (e->flags & MISC_FMT_OPEN_BINARY)
543 if (e->flags & MISC_FMT_CREDENTIALS)
547 if (!test_bit(Magic, &e->flags)) {
548 sprintf(dp, "extension .%s\n", e->magic);
552 sprintf(dp, "offset %i\nmagic ", e->offset);
553 dp = page + strlen(page);
554 for (i = 0; i < e->size; i++) {
555 sprintf(dp, "%02x", 0xff & (int) (e->magic[i]));
559 sprintf(dp, "\nmask ");
561 for (i = 0; i < e->size; i++) {
562 sprintf(dp, "%02x", 0xff & (int) (e->mask[i]));
571 static struct inode *bm_get_inode(struct super_block *sb, int mode)
573 struct inode *inode = new_inode(sb);
576 inode->i_ino = get_next_ino();
577 inode->i_mode = mode;
578 inode->i_atime = inode->i_mtime = inode->i_ctime =
579 current_fs_time(inode->i_sb);
584 static void bm_evict_inode(struct inode *inode)
587 kfree(inode->i_private);
590 static void kill_node(Node *e)
592 struct dentry *dentry;
594 write_lock(&entries_lock);
597 list_del_init(&e->list);
600 write_unlock(&entries_lock);
603 drop_nlink(dentry->d_inode);
606 simple_release_fs(&bm_mnt, &entry_count);
613 bm_entry_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
615 Node *e = file_inode(file)->i_private;
619 page = (char *) __get_free_page(GFP_KERNEL);
623 entry_status(e, page);
625 res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
627 free_page((unsigned long) page);
631 static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
632 size_t count, loff_t *ppos)
635 Node *e = file_inode(file)->i_private;
636 int res = parse_command(buffer, count);
640 /* Disable this handler. */
641 clear_bit(Enabled, &e->flags);
644 /* Enable this handler. */
645 set_bit(Enabled, &e->flags);
648 /* Delete this handler. */
649 root = dget(file->f_path.dentry->d_sb->s_root);
650 mutex_lock(&root->d_inode->i_mutex);
654 mutex_unlock(&root->d_inode->i_mutex);
664 static const struct file_operations bm_entry_operations = {
665 .read = bm_entry_read,
666 .write = bm_entry_write,
667 .llseek = default_llseek,
672 static ssize_t bm_register_write(struct file *file, const char __user *buffer,
673 size_t count, loff_t *ppos)
677 struct dentry *root, *dentry;
678 struct super_block *sb = file->f_path.dentry->d_sb;
681 e = create_entry(buffer, count);
686 root = dget(sb->s_root);
687 mutex_lock(&root->d_inode->i_mutex);
688 dentry = lookup_one_len(e->name, root, strlen(e->name));
689 err = PTR_ERR(dentry);
697 inode = bm_get_inode(sb, S_IFREG | 0644);
703 err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
710 e->dentry = dget(dentry);
711 inode->i_private = e;
712 inode->i_fop = &bm_entry_operations;
714 d_instantiate(dentry, inode);
715 write_lock(&entries_lock);
716 list_add(&e->list, &entries);
717 write_unlock(&entries_lock);
723 mutex_unlock(&root->d_inode->i_mutex);
733 static const struct file_operations bm_register_operations = {
734 .write = bm_register_write,
735 .llseek = noop_llseek,
741 bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
743 char *s = enabled ? "enabled\n" : "disabled\n";
745 return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
748 static ssize_t bm_status_write(struct file *file, const char __user *buffer,
749 size_t count, loff_t *ppos)
751 int res = parse_command(buffer, count);
756 /* Disable all handlers. */
760 /* Enable all handlers. */
764 /* Delete all handlers. */
765 root = dget(file->f_path.dentry->d_sb->s_root);
766 mutex_lock(&root->d_inode->i_mutex);
768 while (!list_empty(&entries))
769 kill_node(list_entry(entries.next, Node, list));
771 mutex_unlock(&root->d_inode->i_mutex);
781 static const struct file_operations bm_status_operations = {
782 .read = bm_status_read,
783 .write = bm_status_write,
784 .llseek = default_llseek,
787 /* Superblock handling */
789 static const struct super_operations s_ops = {
790 .statfs = simple_statfs,
791 .evict_inode = bm_evict_inode,
794 static int bm_fill_super(struct super_block *sb, void *data, int silent)
797 static struct tree_descr bm_files[] = {
798 [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
799 [3] = {"register", &bm_register_operations, S_IWUSR},
803 err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files);
809 static struct dentry *bm_mount(struct file_system_type *fs_type,
810 int flags, const char *dev_name, void *data)
812 return mount_single(fs_type, flags, data, bm_fill_super);
815 static struct linux_binfmt misc_format = {
816 .module = THIS_MODULE,
817 .load_binary = load_misc_binary,
820 static struct file_system_type bm_fs_type = {
821 .owner = THIS_MODULE,
822 .name = "binfmt_misc",
824 .kill_sb = kill_litter_super,
826 MODULE_ALIAS_FS("binfmt_misc");
828 static int __init init_misc_binfmt(void)
830 int err = register_filesystem(&bm_fs_type);
832 insert_binfmt(&misc_format);
836 static void __exit exit_misc_binfmt(void)
838 unregister_binfmt(&misc_format);
839 unregister_filesystem(&bm_fs_type);
842 core_initcall(init_misc_binfmt);
843 module_exit(exit_misc_binfmt);
844 MODULE_LICENSE("GPL");