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 /* Need to be able to load the file after exec */
148 if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
151 if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
152 retval = remove_arg_zero(bprm);
157 if (fmt->flags & MISC_FMT_OPEN_BINARY) {
159 /* if the binary should be opened on behalf of the
160 * interpreter than keep it open and assign descriptor
163 fd_binary = get_unused_fd_flags(0);
168 fd_install(fd_binary, bprm->file);
170 /* if the binary is not readable than enforce mm->dumpable=0
171 regardless of the interpreter's permissions */
172 would_dump(bprm, bprm->file);
174 allow_write_access(bprm->file);
177 /* mark the bprm that fd should be passed to interp */
178 bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
179 bprm->interp_data = fd_binary;
182 allow_write_access(bprm->file);
186 /* make argv[1] be the path to the binary */
187 retval = copy_strings_kernel(1, &bprm->interp, bprm);
192 /* add the interp as argv[0] */
193 retval = copy_strings_kernel(1, &iname_addr, bprm);
198 /* Update interp in case binfmt_script needs it. */
199 retval = bprm_change_interp(iname, bprm);
203 interp_file = open_exec(iname);
204 retval = PTR_ERR(interp_file);
205 if (IS_ERR(interp_file))
208 bprm->file = interp_file;
209 if (fmt->flags & MISC_FMT_CREDENTIALS) {
211 * No need to call prepare_binprm(), it's already been
212 * done. bprm->buf is stale, update from interp_file.
214 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
215 retval = kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
217 retval = prepare_binprm(bprm);
222 retval = search_binary_handler(bprm);
230 sys_close(fd_binary);
231 bprm->interp_flags = 0;
232 bprm->interp_data = 0;
236 /* Command parsers */
239 * parses and copies one argument enclosed in del from *sp to *dp,
240 * recognising the \x special.
241 * returns pointer to the copied argument or NULL in case of an
242 * error (and sets err) or null argument length.
244 static char *scanarg(char *s, char del)
248 while ((c = *s++) != del) {
249 if (c == '\\' && *s == 'x') {
260 static char *check_special_flags(char *sfs, Node *e)
269 pr_debug("register: flag: P (preserve argv0)\n");
271 e->flags |= MISC_FMT_PRESERVE_ARGV0;
274 pr_debug("register: flag: O (open binary)\n");
276 e->flags |= MISC_FMT_OPEN_BINARY;
279 pr_debug("register: flag: C (preserve creds)\n");
281 /* this flags also implies the
283 e->flags |= (MISC_FMT_CREDENTIALS |
284 MISC_FMT_OPEN_BINARY);
295 * This registers a new binary format, it recognises the syntax
296 * ':name:type:offset:magic:mask:interpreter:flags'
297 * where the ':' is the IFS, that can be chosen with the first char
299 static Node *create_entry(const char __user *buffer, size_t count)
306 pr_debug("register: received %zu bytes\n", count);
308 /* some sanity checks */
310 if ((count < 11) || (count > MAX_REGISTER_LENGTH))
314 memsize = sizeof(Node) + count + 8;
315 e = kmalloc(memsize, GFP_KERNEL);
319 p = buf = (char *)e + sizeof(Node);
321 memset(e, 0, sizeof(Node));
322 if (copy_from_user(buf, buffer, count))
325 del = *p++; /* delimeter */
327 pr_debug("register: delim: %#x {%c}\n", del, del);
329 /* Pad the buffer with the delim to simplify parsing below. */
330 memset(buf + count, del, 8);
332 /* Parse the 'name' field. */
339 !strcmp(e->name, ".") ||
340 !strcmp(e->name, "..") ||
341 strchr(e->name, '/'))
344 pr_debug("register: name: {%s}\n", e->name);
346 /* Parse the 'type' field. */
349 pr_debug("register: type: E (extension)\n");
350 e->flags = 1 << Enabled;
353 pr_debug("register: type: M (magic)\n");
354 e->flags = (1 << Enabled) | (1 << Magic);
362 if (test_bit(Magic, &e->flags)) {
363 /* Handle the 'M' (magic) format. */
366 /* Parse the 'offset' field. */
371 e->offset = simple_strtoul(p, &p, 10);
374 pr_debug("register: offset: %#x\n", e->offset);
376 /* Parse the 'magic' field. */
385 print_hex_dump_bytes(
386 KBUILD_MODNAME ": register: magic[raw]: ",
387 DUMP_PREFIX_NONE, e->magic, p - e->magic);
389 /* Parse the 'mask' field. */
397 pr_debug("register: mask[raw]: none\n");
398 } else if (USE_DEBUG)
399 print_hex_dump_bytes(
400 KBUILD_MODNAME ": register: mask[raw]: ",
401 DUMP_PREFIX_NONE, e->mask, p - e->mask);
404 * Decode the magic & mask fields.
405 * Note: while we might have accepted embedded NUL bytes from
406 * above, the unescape helpers here will stop at the first one
409 e->size = string_unescape_inplace(e->magic, UNESCAPE_HEX);
411 string_unescape_inplace(e->mask, UNESCAPE_HEX) != e->size)
413 if (e->size + e->offset > BINPRM_BUF_SIZE)
415 pr_debug("register: magic/mask length: %i\n", e->size);
417 print_hex_dump_bytes(
418 KBUILD_MODNAME ": register: magic[decoded]: ",
419 DUMP_PREFIX_NONE, e->magic, e->size);
423 char *masked = kmalloc(e->size, GFP_KERNEL);
425 print_hex_dump_bytes(
426 KBUILD_MODNAME ": register: mask[decoded]: ",
427 DUMP_PREFIX_NONE, e->mask, e->size);
430 for (i = 0; i < e->size; ++i)
431 masked[i] = e->magic[i] & e->mask[i];
432 print_hex_dump_bytes(
433 KBUILD_MODNAME ": register: magic[masked]: ",
434 DUMP_PREFIX_NONE, masked, e->size);
441 /* Handle the 'E' (extension) format. */
443 /* Skip the 'offset' field. */
449 /* Parse the 'magic' field. */
455 if (!e->magic[0] || strchr(e->magic, '/'))
457 pr_debug("register: extension: {%s}\n", e->magic);
459 /* Skip the 'mask' field. */
466 /* Parse the 'interpreter' field. */
472 if (!e->interpreter[0])
474 pr_debug("register: interpreter: {%s}\n", e->interpreter);
476 /* Parse the 'flags' field. */
477 p = check_special_flags(p, e);
480 if (p != buf + count)
490 return ERR_PTR(-EFAULT);
493 return ERR_PTR(-EINVAL);
497 * Set status of entry/binfmt_misc:
498 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
500 static int parse_command(const char __user *buffer, size_t count)
506 if (copy_from_user(s, buffer, count))
510 if (s[count - 1] == '\n')
512 if (count == 1 && s[0] == '0')
514 if (count == 1 && s[0] == '1')
516 if (count == 2 && s[0] == '-' && s[1] == '1')
523 static void entry_status(Node *e, char *page)
526 char *status = "disabled";
527 const char *flags = "flags: ";
529 if (test_bit(Enabled, &e->flags))
532 if (!VERBOSE_STATUS) {
533 sprintf(page, "%s\n", status);
537 sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter);
538 dp = page + strlen(page);
540 /* print the special flags */
541 sprintf(dp, "%s", flags);
543 if (e->flags & MISC_FMT_PRESERVE_ARGV0)
545 if (e->flags & MISC_FMT_OPEN_BINARY)
547 if (e->flags & MISC_FMT_CREDENTIALS)
551 if (!test_bit(Magic, &e->flags)) {
552 sprintf(dp, "extension .%s\n", e->magic);
556 sprintf(dp, "offset %i\nmagic ", e->offset);
557 dp = page + strlen(page);
558 for (i = 0; i < e->size; i++) {
559 sprintf(dp, "%02x", 0xff & (int) (e->magic[i]));
563 sprintf(dp, "\nmask ");
565 for (i = 0; i < e->size; i++) {
566 sprintf(dp, "%02x", 0xff & (int) (e->mask[i]));
575 static struct inode *bm_get_inode(struct super_block *sb, int mode)
577 struct inode *inode = new_inode(sb);
580 inode->i_ino = get_next_ino();
581 inode->i_mode = mode;
582 inode->i_atime = inode->i_mtime = inode->i_ctime =
583 current_fs_time(inode->i_sb);
588 static void bm_evict_inode(struct inode *inode)
591 kfree(inode->i_private);
594 static void kill_node(Node *e)
596 struct dentry *dentry;
598 write_lock(&entries_lock);
601 list_del_init(&e->list);
604 write_unlock(&entries_lock);
607 drop_nlink(dentry->d_inode);
610 simple_release_fs(&bm_mnt, &entry_count);
617 bm_entry_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
619 Node *e = file_inode(file)->i_private;
623 page = (char *) __get_free_page(GFP_KERNEL);
627 entry_status(e, page);
629 res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
631 free_page((unsigned long) page);
635 static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
636 size_t count, loff_t *ppos)
639 Node *e = file_inode(file)->i_private;
640 int res = parse_command(buffer, count);
644 /* Disable this handler. */
645 clear_bit(Enabled, &e->flags);
648 /* Enable this handler. */
649 set_bit(Enabled, &e->flags);
652 /* Delete this handler. */
653 root = dget(file->f_path.dentry->d_sb->s_root);
654 mutex_lock(&root->d_inode->i_mutex);
658 mutex_unlock(&root->d_inode->i_mutex);
668 static const struct file_operations bm_entry_operations = {
669 .read = bm_entry_read,
670 .write = bm_entry_write,
671 .llseek = default_llseek,
676 static ssize_t bm_register_write(struct file *file, const char __user *buffer,
677 size_t count, loff_t *ppos)
681 struct dentry *root, *dentry;
682 struct super_block *sb = file->f_path.dentry->d_sb;
685 e = create_entry(buffer, count);
690 root = dget(sb->s_root);
691 mutex_lock(&root->d_inode->i_mutex);
692 dentry = lookup_one_len(e->name, root, strlen(e->name));
693 err = PTR_ERR(dentry);
701 inode = bm_get_inode(sb, S_IFREG | 0644);
707 err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
714 e->dentry = dget(dentry);
715 inode->i_private = e;
716 inode->i_fop = &bm_entry_operations;
718 d_instantiate(dentry, inode);
719 write_lock(&entries_lock);
720 list_add(&e->list, &entries);
721 write_unlock(&entries_lock);
727 mutex_unlock(&root->d_inode->i_mutex);
737 static const struct file_operations bm_register_operations = {
738 .write = bm_register_write,
739 .llseek = noop_llseek,
745 bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
747 char *s = enabled ? "enabled\n" : "disabled\n";
749 return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
752 static ssize_t bm_status_write(struct file *file, const char __user *buffer,
753 size_t count, loff_t *ppos)
755 int res = parse_command(buffer, count);
760 /* Disable all handlers. */
764 /* Enable all handlers. */
768 /* Delete all handlers. */
769 root = dget(file->f_path.dentry->d_sb->s_root);
770 mutex_lock(&root->d_inode->i_mutex);
772 while (!list_empty(&entries))
773 kill_node(list_entry(entries.next, Node, list));
775 mutex_unlock(&root->d_inode->i_mutex);
785 static const struct file_operations bm_status_operations = {
786 .read = bm_status_read,
787 .write = bm_status_write,
788 .llseek = default_llseek,
791 /* Superblock handling */
793 static const struct super_operations s_ops = {
794 .statfs = simple_statfs,
795 .evict_inode = bm_evict_inode,
798 static int bm_fill_super(struct super_block *sb, void *data, int silent)
801 static struct tree_descr bm_files[] = {
802 [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
803 [3] = {"register", &bm_register_operations, S_IWUSR},
807 err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files);
813 static struct dentry *bm_mount(struct file_system_type *fs_type,
814 int flags, const char *dev_name, void *data)
816 return mount_single(fs_type, flags, data, bm_fill_super);
819 static struct linux_binfmt misc_format = {
820 .module = THIS_MODULE,
821 .load_binary = load_misc_binary,
824 static struct file_system_type bm_fs_type = {
825 .owner = THIS_MODULE,
826 .name = "binfmt_misc",
828 .kill_sb = kill_litter_super,
830 MODULE_ALIAS_FS("binfmt_misc");
832 static int __init init_misc_binfmt(void)
834 int err = register_filesystem(&bm_fs_type);
836 insert_binfmt(&misc_format);
840 static void __exit exit_misc_binfmt(void)
842 unregister_binfmt(&misc_format);
843 unregister_filesystem(&bm_fs_type);
846 core_initcall(init_misc_binfmt);
847 module_exit(exit_misc_binfmt);
848 MODULE_LICENSE("GPL");