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/kernel.h>
13 #include <linux/module.h>
14 #include <linux/init.h>
15 #include <linux/sched.h>
16 #include <linux/magic.h>
17 #include <linux/binfmts.h>
18 #include <linux/slab.h>
19 #include <linux/ctype.h>
20 #include <linux/string_helpers.h>
21 #include <linux/file.h>
22 #include <linux/pagemap.h>
23 #include <linux/namei.h>
24 #include <linux/mount.h>
25 #include <linux/syscalls.h>
27 #include <linux/uaccess.h>
36 VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
39 static LIST_HEAD(entries);
40 static int enabled = 1;
42 enum {Enabled, Magic};
43 #define MISC_FMT_PRESERVE_ARGV0 (1 << 31)
44 #define MISC_FMT_OPEN_BINARY (1 << 30)
45 #define MISC_FMT_CREDENTIALS (1 << 29)
48 struct list_head list;
49 unsigned long flags; /* type, status, etc. */
50 int offset; /* offset of magic */
51 int size; /* size of magic/mask */
52 char *magic; /* magic or filename extension */
53 char *mask; /* mask, NULL for exact match */
54 char *interpreter; /* filename of interpreter */
56 struct dentry *dentry;
59 static DEFINE_RWLOCK(entries_lock);
60 static struct file_system_type bm_fs_type;
61 static struct vfsmount *bm_mnt;
62 static int entry_count;
65 * Max length of the register string. Determined by:
69 * - offset: 3 bytes (has to be smaller than BINPRM_BUF_SIZE)
70 * - magic: 128 bytes (512 in escaped form)
71 * - mask: 128 bytes (512 in escaped form)
74 * Round that up a bit, and then back off to hold the internal data
77 #define MAX_REGISTER_LENGTH 1920
80 * Check if we support the binfmt
81 * if we do, return the node, else NULL
82 * locking is done in load_misc_binary
84 static Node *check_file(struct linux_binprm *bprm)
86 char *p = strrchr(bprm->interp, '.');
89 /* Walk all the registered handlers. */
90 list_for_each(l, &entries) {
91 Node *e = list_entry(l, Node, list);
95 /* Make sure this one is currently enabled. */
96 if (!test_bit(Enabled, &e->flags))
99 /* Do matching based on extension if applicable. */
100 if (!test_bit(Magic, &e->flags)) {
101 if (p && !strcmp(e->magic, p + 1))
106 /* Do matching based on magic & mask. */
107 s = bprm->buf + e->offset;
109 for (j = 0; j < e->size; j++)
110 if ((*s++ ^ e->magic[j]) & e->mask[j])
113 for (j = 0; j < e->size; j++)
114 if ((*s++ ^ e->magic[j]))
126 static int load_misc_binary(struct linux_binprm *bprm)
129 struct file *interp_file = NULL;
130 char iname[BINPRM_BUF_SIZE];
131 const char *iname_addr = iname;
139 /* to keep locking time low, we copy the interpreter string */
140 read_lock(&entries_lock);
141 fmt = check_file(bprm);
143 strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
144 read_unlock(&entries_lock);
148 /* Need to be able to load the file after exec */
149 if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
152 if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
153 retval = remove_arg_zero(bprm);
158 if (fmt->flags & MISC_FMT_OPEN_BINARY) {
160 /* if the binary should be opened on behalf of the
161 * interpreter than keep it open and assign descriptor
164 fd_binary = get_unused_fd_flags(0);
169 fd_install(fd_binary, bprm->file);
171 /* if the binary is not readable than enforce mm->dumpable=0
172 regardless of the interpreter's permissions */
173 would_dump(bprm, bprm->file);
175 allow_write_access(bprm->file);
178 /* mark the bprm that fd should be passed to interp */
179 bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
180 bprm->interp_data = fd_binary;
183 allow_write_access(bprm->file);
187 /* make argv[1] be the path to the binary */
188 retval = copy_strings_kernel(1, &bprm->interp, bprm);
193 /* add the interp as argv[0] */
194 retval = copy_strings_kernel(1, &iname_addr, bprm);
199 /* Update interp in case binfmt_script needs it. */
200 retval = bprm_change_interp(iname, bprm);
204 interp_file = open_exec(iname);
205 retval = PTR_ERR(interp_file);
206 if (IS_ERR(interp_file))
209 bprm->file = interp_file;
210 if (fmt->flags & MISC_FMT_CREDENTIALS) {
212 * No need to call prepare_binprm(), it's already been
213 * done. bprm->buf is stale, update from interp_file.
215 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
216 retval = kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
218 retval = prepare_binprm(bprm);
223 retval = search_binary_handler(bprm);
231 sys_close(fd_binary);
232 bprm->interp_flags = 0;
233 bprm->interp_data = 0;
237 /* Command parsers */
240 * parses and copies one argument enclosed in del from *sp to *dp,
241 * recognising the \x special.
242 * returns pointer to the copied argument or NULL in case of an
243 * error (and sets err) or null argument length.
245 static char *scanarg(char *s, char del)
249 while ((c = *s++) != del) {
250 if (c == '\\' && *s == 'x') {
262 static char *check_special_flags(char *sfs, Node *e)
271 pr_debug("register: flag: P (preserve argv0)\n");
273 e->flags |= MISC_FMT_PRESERVE_ARGV0;
276 pr_debug("register: flag: O (open binary)\n");
278 e->flags |= MISC_FMT_OPEN_BINARY;
281 pr_debug("register: flag: C (preserve creds)\n");
283 /* this flags also implies the
285 e->flags |= (MISC_FMT_CREDENTIALS |
286 MISC_FMT_OPEN_BINARY);
297 * This registers a new binary format, it recognises the syntax
298 * ':name:type:offset:magic:mask:interpreter:flags'
299 * where the ':' is the IFS, that can be chosen with the first char
301 static Node *create_entry(const char __user *buffer, size_t count)
308 pr_debug("register: received %zu bytes\n", count);
310 /* some sanity checks */
312 if ((count < 11) || (count > MAX_REGISTER_LENGTH))
316 memsize = sizeof(Node) + count + 8;
317 e = kmalloc(memsize, GFP_KERNEL);
321 p = buf = (char *)e + sizeof(Node);
323 memset(e, 0, sizeof(Node));
324 if (copy_from_user(buf, buffer, count))
327 del = *p++; /* delimeter */
329 pr_debug("register: delim: %#x {%c}\n", del, del);
331 /* Pad the buffer with the delim to simplify parsing below. */
332 memset(buf + count, del, 8);
334 /* Parse the 'name' field. */
341 !strcmp(e->name, ".") ||
342 !strcmp(e->name, "..") ||
343 strchr(e->name, '/'))
346 pr_debug("register: name: {%s}\n", e->name);
348 /* Parse the 'type' field. */
351 pr_debug("register: type: E (extension)\n");
352 e->flags = 1 << Enabled;
355 pr_debug("register: type: M (magic)\n");
356 e->flags = (1 << Enabled) | (1 << Magic);
364 if (test_bit(Magic, &e->flags)) {
365 /* Handle the 'M' (magic) format. */
368 /* Parse the 'offset' field. */
374 int r = kstrtoint(p, 10, &e->offset);
375 if (r != 0 || e->offset < 0)
381 pr_debug("register: offset: %#x\n", e->offset);
383 /* Parse the 'magic' field. */
391 print_hex_dump_bytes(
392 KBUILD_MODNAME ": register: magic[raw]: ",
393 DUMP_PREFIX_NONE, e->magic, p - e->magic);
395 /* Parse the 'mask' field. */
402 pr_debug("register: mask[raw]: none\n");
403 } else if (USE_DEBUG)
404 print_hex_dump_bytes(
405 KBUILD_MODNAME ": register: mask[raw]: ",
406 DUMP_PREFIX_NONE, e->mask, p - e->mask);
409 * Decode the magic & mask fields.
410 * Note: while we might have accepted embedded NUL bytes from
411 * above, the unescape helpers here will stop at the first one
414 e->size = string_unescape_inplace(e->magic, UNESCAPE_HEX);
416 string_unescape_inplace(e->mask, UNESCAPE_HEX) != e->size)
418 if (e->size > BINPRM_BUF_SIZE ||
419 BINPRM_BUF_SIZE - e->size < e->offset)
421 pr_debug("register: magic/mask length: %i\n", e->size);
423 print_hex_dump_bytes(
424 KBUILD_MODNAME ": register: magic[decoded]: ",
425 DUMP_PREFIX_NONE, e->magic, e->size);
429 char *masked = kmalloc(e->size, GFP_KERNEL);
431 print_hex_dump_bytes(
432 KBUILD_MODNAME ": register: mask[decoded]: ",
433 DUMP_PREFIX_NONE, e->mask, e->size);
436 for (i = 0; i < e->size; ++i)
437 masked[i] = e->magic[i] & e->mask[i];
438 print_hex_dump_bytes(
439 KBUILD_MODNAME ": register: magic[masked]: ",
440 DUMP_PREFIX_NONE, masked, e->size);
447 /* Handle the 'E' (extension) format. */
449 /* Skip the 'offset' field. */
455 /* Parse the 'magic' field. */
461 if (!e->magic[0] || strchr(e->magic, '/'))
463 pr_debug("register: extension: {%s}\n", e->magic);
465 /* Skip the 'mask' field. */
472 /* Parse the 'interpreter' field. */
478 if (!e->interpreter[0])
480 pr_debug("register: interpreter: {%s}\n", e->interpreter);
482 /* Parse the 'flags' field. */
483 p = check_special_flags(p, e);
486 if (p != buf + count)
496 return ERR_PTR(-EFAULT);
499 return ERR_PTR(-EINVAL);
503 * Set status of entry/binfmt_misc:
504 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
506 static int parse_command(const char __user *buffer, size_t count)
512 if (copy_from_user(s, buffer, count))
516 if (s[count - 1] == '\n')
518 if (count == 1 && s[0] == '0')
520 if (count == 1 && s[0] == '1')
522 if (count == 2 && s[0] == '-' && s[1] == '1')
529 static void entry_status(Node *e, char *page)
532 const char *status = "disabled";
534 if (test_bit(Enabled, &e->flags))
537 if (!VERBOSE_STATUS) {
538 sprintf(page, "%s\n", status);
542 dp += sprintf(dp, "%s\ninterpreter %s\n", status, e->interpreter);
544 /* print the special flags */
545 dp += sprintf(dp, "flags: ");
546 if (e->flags & MISC_FMT_PRESERVE_ARGV0)
548 if (e->flags & MISC_FMT_OPEN_BINARY)
550 if (e->flags & MISC_FMT_CREDENTIALS)
554 if (!test_bit(Magic, &e->flags)) {
555 sprintf(dp, "extension .%s\n", e->magic);
557 dp += sprintf(dp, "offset %i\nmagic ", e->offset);
558 dp = bin2hex(dp, e->magic, e->size);
560 dp += sprintf(dp, "\nmask ");
561 dp = bin2hex(dp, e->mask, e->size);
568 static struct inode *bm_get_inode(struct super_block *sb, int mode)
570 struct inode *inode = new_inode(sb);
573 inode->i_ino = get_next_ino();
574 inode->i_mode = mode;
575 inode->i_atime = inode->i_mtime = inode->i_ctime =
576 current_fs_time(inode->i_sb);
581 static void bm_evict_inode(struct inode *inode)
584 kfree(inode->i_private);
587 static void kill_node(Node *e)
589 struct dentry *dentry;
591 write_lock(&entries_lock);
594 list_del_init(&e->list);
597 write_unlock(&entries_lock);
600 drop_nlink(d_inode(dentry));
603 simple_release_fs(&bm_mnt, &entry_count);
610 bm_entry_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
612 Node *e = file_inode(file)->i_private;
616 page = (char *) __get_free_page(GFP_KERNEL);
620 entry_status(e, page);
622 res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
624 free_page((unsigned long) page);
628 static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
629 size_t count, loff_t *ppos)
632 Node *e = file_inode(file)->i_private;
633 int res = parse_command(buffer, count);
637 /* Disable this handler. */
638 clear_bit(Enabled, &e->flags);
641 /* Enable this handler. */
642 set_bit(Enabled, &e->flags);
645 /* Delete this handler. */
646 root = dget(file->f_path.dentry->d_sb->s_root);
647 mutex_lock(&d_inode(root)->i_mutex);
651 mutex_unlock(&d_inode(root)->i_mutex);
661 static const struct file_operations bm_entry_operations = {
662 .read = bm_entry_read,
663 .write = bm_entry_write,
664 .llseek = default_llseek,
669 static ssize_t bm_register_write(struct file *file, const char __user *buffer,
670 size_t count, loff_t *ppos)
674 struct dentry *root, *dentry;
675 struct super_block *sb = file->f_path.dentry->d_sb;
678 e = create_entry(buffer, count);
683 root = dget(sb->s_root);
684 mutex_lock(&d_inode(root)->i_mutex);
685 dentry = lookup_one_len(e->name, root, strlen(e->name));
686 err = PTR_ERR(dentry);
691 if (d_really_is_positive(dentry))
694 inode = bm_get_inode(sb, S_IFREG | 0644);
700 err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
707 e->dentry = dget(dentry);
708 inode->i_private = e;
709 inode->i_fop = &bm_entry_operations;
711 d_instantiate(dentry, inode);
712 write_lock(&entries_lock);
713 list_add(&e->list, &entries);
714 write_unlock(&entries_lock);
720 mutex_unlock(&d_inode(root)->i_mutex);
730 static const struct file_operations bm_register_operations = {
731 .write = bm_register_write,
732 .llseek = noop_llseek,
738 bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
740 char *s = enabled ? "enabled\n" : "disabled\n";
742 return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
745 static ssize_t bm_status_write(struct file *file, const char __user *buffer,
746 size_t count, loff_t *ppos)
748 int res = parse_command(buffer, count);
753 /* Disable all handlers. */
757 /* Enable all handlers. */
761 /* Delete all handlers. */
762 root = dget(file->f_path.dentry->d_sb->s_root);
763 mutex_lock(&d_inode(root)->i_mutex);
765 while (!list_empty(&entries))
766 kill_node(list_entry(entries.next, Node, list));
768 mutex_unlock(&d_inode(root)->i_mutex);
778 static const struct file_operations bm_status_operations = {
779 .read = bm_status_read,
780 .write = bm_status_write,
781 .llseek = default_llseek,
784 /* Superblock handling */
786 static const struct super_operations s_ops = {
787 .statfs = simple_statfs,
788 .evict_inode = bm_evict_inode,
791 static int bm_fill_super(struct super_block *sb, void *data, int silent)
794 static struct tree_descr bm_files[] = {
795 [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
796 [3] = {"register", &bm_register_operations, S_IWUSR},
800 err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files);
806 static struct dentry *bm_mount(struct file_system_type *fs_type,
807 int flags, const char *dev_name, void *data)
809 return mount_single(fs_type, flags, data, bm_fill_super);
812 static struct linux_binfmt misc_format = {
813 .module = THIS_MODULE,
814 .load_binary = load_misc_binary,
817 static struct file_system_type bm_fs_type = {
818 .owner = THIS_MODULE,
819 .name = "binfmt_misc",
821 .kill_sb = kill_litter_super,
823 MODULE_ALIAS_FS("binfmt_misc");
825 static int __init init_misc_binfmt(void)
827 int err = register_filesystem(&bm_fs_type);
829 insert_binfmt(&misc_format);
833 static void __exit exit_misc_binfmt(void)
835 unregister_binfmt(&misc_format);
836 unregister_filesystem(&bm_fs_type);
839 core_initcall(init_misc_binfmt);
840 module_exit(exit_misc_binfmt);
841 MODULE_LICENSE("GPL");