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/mm.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>
38 VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
41 static LIST_HEAD(entries);
42 static int enabled = 1;
44 enum {Enabled, Magic};
45 #define MISC_FMT_PRESERVE_ARGV0 (1 << 31)
46 #define MISC_FMT_OPEN_BINARY (1 << 30)
47 #define MISC_FMT_CREDENTIALS (1 << 29)
48 #define MISC_FMT_OPEN_FILE (1 << 28)
51 struct list_head list;
52 unsigned long flags; /* type, status, etc. */
53 int offset; /* offset of magic */
54 int size; /* size of magic/mask */
55 char *magic; /* magic or filename extension */
56 char *mask; /* mask, NULL for exact match */
57 char *interpreter; /* filename of interpreter */
59 struct dentry *dentry;
60 struct file *interp_file;
63 static DEFINE_RWLOCK(entries_lock);
64 static struct file_system_type bm_fs_type;
65 static struct vfsmount *bm_mnt;
66 static int entry_count;
69 * Max length of the register string. Determined by:
73 * - offset: 3 bytes (has to be smaller than BINPRM_BUF_SIZE)
74 * - magic: 128 bytes (512 in escaped form)
75 * - mask: 128 bytes (512 in escaped form)
78 * Round that up a bit, and then back off to hold the internal data
81 #define MAX_REGISTER_LENGTH 1920
84 * Check if we support the binfmt
85 * if we do, return the node, else NULL
86 * locking is done in load_misc_binary
88 static Node *check_file(struct linux_binprm *bprm)
90 char *p = strrchr(bprm->interp, '.');
93 /* Walk all the registered handlers. */
94 list_for_each(l, &entries) {
95 Node *e = list_entry(l, Node, list);
99 /* Make sure this one is currently enabled. */
100 if (!test_bit(Enabled, &e->flags))
103 /* Do matching based on extension if applicable. */
104 if (!test_bit(Magic, &e->flags)) {
105 if (p && !strcmp(e->magic, p + 1))
110 /* Do matching based on magic & mask. */
111 s = bprm->buf + e->offset;
113 for (j = 0; j < e->size; j++)
114 if ((*s++ ^ e->magic[j]) & e->mask[j])
117 for (j = 0; j < e->size; j++)
118 if ((*s++ ^ e->magic[j]))
130 static int load_misc_binary(struct linux_binprm *bprm)
133 struct file *interp_file = NULL;
134 char iname[BINPRM_BUF_SIZE];
135 const char *iname_addr = iname;
143 /* to keep locking time low, we copy the interpreter string */
144 read_lock(&entries_lock);
145 fmt = check_file(bprm);
148 strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
150 read_unlock(&entries_lock);
154 /* Need to be able to load the file after exec */
156 if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
159 if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
160 retval = remove_arg_zero(bprm);
165 if (fmt->flags & MISC_FMT_OPEN_BINARY) {
167 /* if the binary should be opened on behalf of the
168 * interpreter than keep it open and assign descriptor
171 fd_binary = get_unused_fd_flags(0);
176 fd_install(fd_binary, bprm->file);
178 /* if the binary is not readable than enforce mm->dumpable=0
179 regardless of the interpreter's permissions */
180 would_dump(bprm, bprm->file);
182 allow_write_access(bprm->file);
185 /* mark the bprm that fd should be passed to interp */
186 bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
187 bprm->interp_data = fd_binary;
190 allow_write_access(bprm->file);
194 /* make argv[1] be the path to the binary */
195 retval = copy_strings_kernel(1, &bprm->interp, bprm);
200 /* add the interp as argv[0] */
201 retval = copy_strings_kernel(1, &iname_addr, bprm);
206 /* Update interp in case binfmt_script needs it. */
207 retval = bprm_change_interp(iname, bprm);
211 if (fmt->flags & MISC_FMT_OPEN_FILE) {
212 interp_file = filp_clone_open(fmt->interp_file);
213 if (!IS_ERR(interp_file))
214 deny_write_access(interp_file);
216 interp_file = open_exec(iname);
218 retval = PTR_ERR(interp_file);
219 if (IS_ERR(interp_file))
222 bprm->file = interp_file;
223 if (fmt->flags & MISC_FMT_CREDENTIALS) {
227 * No need to call prepare_binprm(), it's already been
228 * done. bprm->buf is stale, update from interp_file.
230 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
231 retval = kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE,
234 retval = prepare_binprm(bprm);
239 retval = search_binary_handler(bprm);
248 sys_close(fd_binary);
249 bprm->interp_flags = 0;
250 bprm->interp_data = 0;
254 /* Command parsers */
257 * parses and copies one argument enclosed in del from *sp to *dp,
258 * recognising the \x special.
259 * returns pointer to the copied argument or NULL in case of an
260 * error (and sets err) or null argument length.
262 static char *scanarg(char *s, char del)
266 while ((c = *s++) != del) {
267 if (c == '\\' && *s == 'x') {
279 static char *check_special_flags(char *sfs, Node *e)
288 pr_debug("register: flag: P (preserve argv0)\n");
290 e->flags |= MISC_FMT_PRESERVE_ARGV0;
293 pr_debug("register: flag: O (open binary)\n");
295 e->flags |= MISC_FMT_OPEN_BINARY;
298 pr_debug("register: flag: C (preserve creds)\n");
300 /* this flags also implies the
302 e->flags |= (MISC_FMT_CREDENTIALS |
303 MISC_FMT_OPEN_BINARY);
306 pr_debug("register: flag: F: open interpreter file now\n");
308 e->flags |= MISC_FMT_OPEN_FILE;
319 * This registers a new binary format, it recognises the syntax
320 * ':name:type:offset:magic:mask:interpreter:flags'
321 * where the ':' is the IFS, that can be chosen with the first char
323 static Node *create_entry(const char __user *buffer, size_t count)
330 pr_debug("register: received %zu bytes\n", count);
332 /* some sanity checks */
334 if ((count < 11) || (count > MAX_REGISTER_LENGTH))
338 memsize = sizeof(Node) + count + 8;
339 e = kmalloc(memsize, GFP_KERNEL);
343 p = buf = (char *)e + sizeof(Node);
345 memset(e, 0, sizeof(Node));
346 if (copy_from_user(buf, buffer, count))
349 del = *p++; /* delimeter */
351 pr_debug("register: delim: %#x {%c}\n", del, del);
353 /* Pad the buffer with the delim to simplify parsing below. */
354 memset(buf + count, del, 8);
356 /* Parse the 'name' field. */
363 !strcmp(e->name, ".") ||
364 !strcmp(e->name, "..") ||
365 strchr(e->name, '/'))
368 pr_debug("register: name: {%s}\n", e->name);
370 /* Parse the 'type' field. */
373 pr_debug("register: type: E (extension)\n");
374 e->flags = 1 << Enabled;
377 pr_debug("register: type: M (magic)\n");
378 e->flags = (1 << Enabled) | (1 << Magic);
386 if (test_bit(Magic, &e->flags)) {
387 /* Handle the 'M' (magic) format. */
390 /* Parse the 'offset' field. */
395 e->offset = simple_strtoul(p, &p, 10);
398 pr_debug("register: offset: %#x\n", e->offset);
400 /* Parse the 'magic' field. */
408 print_hex_dump_bytes(
409 KBUILD_MODNAME ": register: magic[raw]: ",
410 DUMP_PREFIX_NONE, e->magic, p - e->magic);
412 /* Parse the 'mask' field. */
419 pr_debug("register: mask[raw]: none\n");
420 } else if (USE_DEBUG)
421 print_hex_dump_bytes(
422 KBUILD_MODNAME ": register: mask[raw]: ",
423 DUMP_PREFIX_NONE, e->mask, p - e->mask);
426 * Decode the magic & mask fields.
427 * Note: while we might have accepted embedded NUL bytes from
428 * above, the unescape helpers here will stop at the first one
431 e->size = string_unescape_inplace(e->magic, UNESCAPE_HEX);
433 string_unescape_inplace(e->mask, UNESCAPE_HEX) != e->size)
435 if (e->size + e->offset > BINPRM_BUF_SIZE)
437 pr_debug("register: magic/mask length: %i\n", e->size);
439 print_hex_dump_bytes(
440 KBUILD_MODNAME ": register: magic[decoded]: ",
441 DUMP_PREFIX_NONE, e->magic, e->size);
445 char *masked = kmalloc(e->size, GFP_KERNEL);
447 print_hex_dump_bytes(
448 KBUILD_MODNAME ": register: mask[decoded]: ",
449 DUMP_PREFIX_NONE, e->mask, e->size);
452 for (i = 0; i < e->size; ++i)
453 masked[i] = e->magic[i] & e->mask[i];
454 print_hex_dump_bytes(
455 KBUILD_MODNAME ": register: magic[masked]: ",
456 DUMP_PREFIX_NONE, masked, e->size);
463 /* Handle the 'E' (extension) format. */
465 /* Skip the 'offset' field. */
471 /* Parse the 'magic' field. */
477 if (!e->magic[0] || strchr(e->magic, '/'))
479 pr_debug("register: extension: {%s}\n", e->magic);
481 /* Skip the 'mask' field. */
488 /* Parse the 'interpreter' field. */
494 if (!e->interpreter[0])
496 pr_debug("register: interpreter: {%s}\n", e->interpreter);
498 /* Parse the 'flags' field. */
499 p = check_special_flags(p, e);
502 if (p != buf + count)
512 return ERR_PTR(-EFAULT);
515 return ERR_PTR(-EINVAL);
519 * Set status of entry/binfmt_misc:
520 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
522 static int parse_command(const char __user *buffer, size_t count)
528 if (copy_from_user(s, buffer, count))
532 if (s[count - 1] == '\n')
534 if (count == 1 && s[0] == '0')
536 if (count == 1 && s[0] == '1')
538 if (count == 2 && s[0] == '-' && s[1] == '1')
545 static void entry_status(Node *e, char *page)
548 const char *status = "disabled";
550 if (test_bit(Enabled, &e->flags))
553 if (!VERBOSE_STATUS) {
554 sprintf(page, "%s\n", status);
558 dp += sprintf(dp, "%s\ninterpreter %s\n", status, e->interpreter);
560 /* print the special flags */
561 dp += sprintf(dp, "flags: ");
562 if (e->flags & MISC_FMT_PRESERVE_ARGV0)
564 if (e->flags & MISC_FMT_OPEN_BINARY)
566 if (e->flags & MISC_FMT_CREDENTIALS)
568 if (e->flags & MISC_FMT_OPEN_FILE)
572 if (!test_bit(Magic, &e->flags)) {
573 sprintf(dp, "extension .%s\n", e->magic);
575 dp += sprintf(dp, "offset %i\nmagic ", e->offset);
576 dp = bin2hex(dp, e->magic, e->size);
578 dp += sprintf(dp, "\nmask ");
579 dp = bin2hex(dp, e->mask, e->size);
586 static struct inode *bm_get_inode(struct super_block *sb, int mode)
588 struct inode *inode = new_inode(sb);
591 inode->i_ino = get_next_ino();
592 inode->i_mode = mode;
593 inode->i_atime = inode->i_mtime = inode->i_ctime =
599 static void bm_evict_inode(struct inode *inode)
601 Node *e = inode->i_private;
603 if (e->flags & MISC_FMT_OPEN_FILE)
604 filp_close(e->interp_file, NULL);
610 static void kill_node(Node *e)
612 struct dentry *dentry;
614 write_lock(&entries_lock);
615 list_del_init(&e->list);
616 write_unlock(&entries_lock);
619 drop_nlink(d_inode(dentry));
622 simple_release_fs(&bm_mnt, &entry_count);
628 bm_entry_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
630 Node *e = file_inode(file)->i_private;
634 page = (char *) __get_free_page(GFP_KERNEL);
638 entry_status(e, page);
640 res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
642 free_page((unsigned long) page);
646 static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
647 size_t count, loff_t *ppos)
650 Node *e = file_inode(file)->i_private;
651 int res = parse_command(buffer, count);
655 /* Disable this handler. */
656 clear_bit(Enabled, &e->flags);
659 /* Enable this handler. */
660 set_bit(Enabled, &e->flags);
663 /* Delete this handler. */
664 root = file_inode(file)->i_sb->s_root;
665 inode_lock(d_inode(root));
667 if (!list_empty(&e->list))
670 inode_unlock(d_inode(root));
679 static const struct file_operations bm_entry_operations = {
680 .read = bm_entry_read,
681 .write = bm_entry_write,
682 .llseek = default_llseek,
687 static ssize_t bm_register_write(struct file *file, const char __user *buffer,
688 size_t count, loff_t *ppos)
692 struct super_block *sb = file_inode(file)->i_sb;
693 struct dentry *root = sb->s_root, *dentry;
696 e = create_entry(buffer, count);
701 inode_lock(d_inode(root));
702 dentry = lookup_one_len(e->name, root, strlen(e->name));
703 err = PTR_ERR(dentry);
708 if (d_really_is_positive(dentry))
711 inode = bm_get_inode(sb, S_IFREG | 0644);
717 err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
724 if (e->flags & MISC_FMT_OPEN_FILE) {
727 f = open_exec(e->interpreter);
730 pr_notice("register: failed to install interpreter file %s\n", e->interpreter);
731 simple_release_fs(&bm_mnt, &entry_count);
739 e->dentry = dget(dentry);
740 inode->i_private = e;
741 inode->i_fop = &bm_entry_operations;
743 d_instantiate(dentry, inode);
744 write_lock(&entries_lock);
745 list_add(&e->list, &entries);
746 write_unlock(&entries_lock);
752 inode_unlock(d_inode(root));
761 static const struct file_operations bm_register_operations = {
762 .write = bm_register_write,
763 .llseek = noop_llseek,
769 bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
771 char *s = enabled ? "enabled\n" : "disabled\n";
773 return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
776 static ssize_t bm_status_write(struct file *file, const char __user *buffer,
777 size_t count, loff_t *ppos)
779 int res = parse_command(buffer, count);
784 /* Disable all handlers. */
788 /* Enable all handlers. */
792 /* Delete all handlers. */
793 root = file_inode(file)->i_sb->s_root;
794 inode_lock(d_inode(root));
796 while (!list_empty(&entries))
797 kill_node(list_first_entry(&entries, Node, list));
799 inode_unlock(d_inode(root));
808 static const struct file_operations bm_status_operations = {
809 .read = bm_status_read,
810 .write = bm_status_write,
811 .llseek = default_llseek,
814 /* Superblock handling */
816 static const struct super_operations s_ops = {
817 .statfs = simple_statfs,
818 .evict_inode = bm_evict_inode,
821 static int bm_fill_super(struct super_block *sb, void *data, int silent)
824 static const struct tree_descr bm_files[] = {
825 [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
826 [3] = {"register", &bm_register_operations, S_IWUSR},
830 err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files);
836 static struct dentry *bm_mount(struct file_system_type *fs_type,
837 int flags, const char *dev_name, void *data)
839 return mount_single(fs_type, flags, data, bm_fill_super);
842 static struct linux_binfmt misc_format = {
843 .module = THIS_MODULE,
844 .load_binary = load_misc_binary,
847 static struct file_system_type bm_fs_type = {
848 .owner = THIS_MODULE,
849 .name = "binfmt_misc",
851 .kill_sb = kill_litter_super,
853 MODULE_ALIAS_FS("binfmt_misc");
855 static int __init init_misc_binfmt(void)
857 int err = register_filesystem(&bm_fs_type);
859 insert_binfmt(&misc_format);
863 static void __exit exit_misc_binfmt(void)
865 unregister_binfmt(&misc_format);
866 unregister_filesystem(&bm_fs_type);
869 core_initcall(init_misc_binfmt);
870 module_exit(exit_misc_binfmt);
871 MODULE_LICENSE("GPL");