4 * Copyright (C) 1997 Richard Günther
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
10 * 1997-04-25 first version
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.
19 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
21 #include <linux/module.h>
22 #include <linux/init.h>
23 #include <linux/sched.h>
24 #include <linux/magic.h>
25 #include <linux/binfmts.h>
26 #include <linux/slab.h>
27 #include <linux/ctype.h>
28 #include <linux/string_helpers.h>
29 #include <linux/file.h>
30 #include <linux/pagemap.h>
31 #include <linux/namei.h>
32 #include <linux/mount.h>
33 #include <linux/syscalls.h>
35 #include <linux/uaccess.h>
44 VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
47 static LIST_HEAD(entries);
48 static int enabled = 1;
50 enum {Enabled, Magic};
51 #define MISC_FMT_PRESERVE_ARGV0 (1<<31)
52 #define MISC_FMT_OPEN_BINARY (1<<30)
53 #define MISC_FMT_CREDENTIALS (1<<29)
56 struct list_head list;
57 unsigned long flags; /* type, status, etc. */
58 int offset; /* offset of magic */
59 int size; /* size of magic/mask */
60 char *magic; /* magic or filename extension */
61 char *mask; /* mask, NULL for exact match */
62 char *interpreter; /* filename of interpreter */
64 struct dentry *dentry;
67 static DEFINE_RWLOCK(entries_lock);
68 static struct file_system_type bm_fs_type;
69 static struct vfsmount *bm_mnt;
70 static int entry_count;
73 * Max length of the register string. Determined by:
77 * - offset: 3 bytes (has to be smaller than BINPRM_BUF_SIZE)
78 * - magic: 128 bytes (512 in escaped form)
79 * - mask: 128 bytes (512 in escaped form)
82 * Round that up a bit, and then back off to hold the internal data
85 #define MAX_REGISTER_LENGTH 1920
88 * Check if we support the binfmt
89 * if we do, return the node, else NULL
90 * locking is done in load_misc_binary
92 static Node *check_file(struct linux_binprm *bprm)
94 char *p = strrchr(bprm->interp, '.');
97 /* Walk all the registered handlers. */
98 list_for_each(l, &entries) {
99 Node *e = list_entry(l, Node, list);
103 /* Make sure this one is currently enabled. */
104 if (!test_bit(Enabled, &e->flags))
107 /* Do matching based on extension if applicable. */
108 if (!test_bit(Magic, &e->flags)) {
109 if (p && !strcmp(e->magic, p + 1))
114 /* Do matching based on magic & mask. */
115 s = bprm->buf + e->offset;
117 for (j = 0; j < e->size; j++)
118 if ((*s++ ^ e->magic[j]) & e->mask[j])
121 for (j = 0; j < e->size; j++)
122 if ((*s++ ^ e->magic[j]))
134 static int load_misc_binary(struct linux_binprm *bprm)
137 struct file * interp_file = NULL;
138 char iname[BINPRM_BUF_SIZE];
139 const char *iname_addr = iname;
147 /* to keep locking time low, we copy the interpreter string */
148 read_lock(&entries_lock);
149 fmt = check_file(bprm);
151 strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
152 read_unlock(&entries_lock);
156 if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
157 retval = remove_arg_zero(bprm);
162 if (fmt->flags & MISC_FMT_OPEN_BINARY) {
164 /* if the binary should be opened on behalf of the
165 * interpreter than keep it open and assign descriptor
167 fd_binary = get_unused_fd_flags(0);
172 fd_install(fd_binary, bprm->file);
174 /* if the binary is not readable than enforce mm->dumpable=0
175 regardless of the interpreter's permissions */
176 would_dump(bprm, bprm->file);
178 allow_write_access(bprm->file);
181 /* mark the bprm that fd should be passed to interp */
182 bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
183 bprm->interp_data = fd_binary;
186 allow_write_access(bprm->file);
190 /* make argv[1] be the path to the binary */
191 retval = copy_strings_kernel (1, &bprm->interp, bprm);
196 /* add the interp as argv[0] */
197 retval = copy_strings_kernel (1, &iname_addr, bprm);
202 /* Update interp in case binfmt_script needs it. */
203 retval = bprm_change_interp(iname, bprm);
207 interp_file = open_exec (iname);
208 retval = PTR_ERR (interp_file);
209 if (IS_ERR (interp_file))
212 bprm->file = interp_file;
213 if (fmt->flags & MISC_FMT_CREDENTIALS) {
215 * No need to call prepare_binprm(), it's already been
216 * done. bprm->buf is stale, update from interp_file.
218 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
219 retval = kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
221 retval = prepare_binprm (bprm);
226 retval = search_binary_handler(bprm);
234 sys_close(fd_binary);
235 bprm->interp_flags = 0;
236 bprm->interp_data = 0;
240 /* Command parsers */
243 * parses and copies one argument enclosed in del from *sp to *dp,
244 * recognising the \x special.
245 * returns pointer to the copied argument or NULL in case of an
246 * error (and sets err) or null argument length.
248 static char *scanarg(char *s, char del)
252 while ((c = *s++) != del) {
253 if (c == '\\' && *s == 'x') {
264 static char * check_special_flags (char * sfs, Node * e)
273 pr_debug("register: flag: P (preserve argv0)\n");
275 e->flags |= MISC_FMT_PRESERVE_ARGV0;
278 pr_debug("register: flag: O (open binary)\n");
280 e->flags |= MISC_FMT_OPEN_BINARY;
283 pr_debug("register: flag: C (preserve creds)\n");
285 /* this flags also implies the
287 e->flags |= (MISC_FMT_CREDENTIALS |
288 MISC_FMT_OPEN_BINARY);
298 * This registers a new binary format, it recognises the syntax
299 * ':name:type:offset:magic:mask:interpreter:flags'
300 * where the ':' is the IFS, that can be chosen with the first char
302 static Node *create_entry(const char __user *buffer, size_t count)
309 pr_debug("register: received %zu bytes\n", count);
311 /* some sanity checks */
313 if ((count < 11) || (count > MAX_REGISTER_LENGTH))
317 memsize = sizeof(Node) + count + 8;
318 e = kmalloc(memsize, GFP_USER);
322 p = buf = (char *)e + sizeof(Node);
324 memset(e, 0, sizeof(Node));
325 if (copy_from_user(buf, buffer, count))
328 del = *p++; /* delimeter */
330 pr_debug("register: delim: %#x {%c}\n", del, del);
332 /* Pad the buffer with the delim to simplify parsing below. */
333 memset(buf+count, del, 8);
335 /* Parse the 'name' field. */
342 !strcmp(e->name, ".") ||
343 !strcmp(e->name, "..") ||
344 strchr(e->name, '/'))
347 pr_debug("register: name: {%s}\n", e->name);
349 /* Parse the 'type' field. */
352 pr_debug("register: type: E (extension)\n");
353 e->flags = 1 << Enabled;
356 pr_debug("register: type: M (magic)\n");
357 e->flags = (1 << Enabled) | (1 << Magic);
365 if (test_bit(Magic, &e->flags)) {
366 /* Handle the 'M' (magic) format. */
369 /* Parse the 'offset' field. */
374 e->offset = simple_strtoul(p, &p, 10);
377 pr_debug("register: offset: %#x\n", e->offset);
379 /* Parse the 'magic' field. */
388 print_hex_dump_bytes(
389 KBUILD_MODNAME ": register: magic[raw]: ",
390 DUMP_PREFIX_NONE, e->magic, p - e->magic);
392 /* Parse the 'mask' field. */
400 pr_debug("register: mask[raw]: none\n");
401 } else if (USE_DEBUG)
402 print_hex_dump_bytes(
403 KBUILD_MODNAME ": register: mask[raw]: ",
404 DUMP_PREFIX_NONE, e->mask, p - e->mask);
407 * Decode the magic & mask fields.
408 * Note: while we might have accepted embedded NUL bytes from
409 * above, the unescape helpers here will stop at the first one
412 e->size = string_unescape_inplace(e->magic, UNESCAPE_HEX);
414 string_unescape_inplace(e->mask, UNESCAPE_HEX) != e->size)
416 if (e->size + e->offset > BINPRM_BUF_SIZE)
418 pr_debug("register: magic/mask length: %i\n", e->size);
420 print_hex_dump_bytes(
421 KBUILD_MODNAME ": register: magic[decoded]: ",
422 DUMP_PREFIX_NONE, e->magic, e->size);
426 char *masked = kmalloc(e->size, GFP_USER);
428 print_hex_dump_bytes(
429 KBUILD_MODNAME ": register: mask[decoded]: ",
430 DUMP_PREFIX_NONE, e->mask, e->size);
433 for (i = 0; i < e->size; ++i)
434 masked[i] = e->magic[i] & e->mask[i];
435 print_hex_dump_bytes(
436 KBUILD_MODNAME ": register: magic[masked]: ",
437 DUMP_PREFIX_NONE, masked, e->size);
444 /* Handle the 'E' (extension) format. */
446 /* Skip the 'offset' field. */
452 /* Parse the 'magic' field. */
458 if (!e->magic[0] || strchr(e->magic, '/'))
460 pr_debug("register: extension: {%s}\n", e->magic);
462 /* Skip the 'mask' field. */
469 /* Parse the 'interpreter' field. */
475 if (!e->interpreter[0])
477 pr_debug("register: interpreter: {%s}\n", e->interpreter);
479 /* Parse the 'flags' field. */
480 p = check_special_flags (p, e);
483 if (p != buf + count)
492 return ERR_PTR(-EFAULT);
495 return ERR_PTR(-EINVAL);
499 * Set status of entry/binfmt_misc:
500 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
502 static int parse_command(const char __user *buffer, size_t count)
508 if (copy_from_user(s, buffer, count))
512 if (s[count-1] == '\n')
514 if (count == 1 && s[0] == '0')
516 if (count == 1 && s[0] == '1')
518 if (count == 2 && s[0] == '-' && s[1] == '1')
525 static void entry_status(Node *e, char *page)
528 char *status = "disabled";
529 const char * flags = "flags: ";
531 if (test_bit(Enabled, &e->flags))
534 if (!VERBOSE_STATUS) {
535 sprintf(page, "%s\n", status);
539 sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter);
540 dp = page + strlen(page);
542 /* print the special flags */
543 sprintf (dp, "%s", flags);
544 dp += strlen (flags);
545 if (e->flags & MISC_FMT_PRESERVE_ARGV0) {
548 if (e->flags & MISC_FMT_OPEN_BINARY) {
551 if (e->flags & MISC_FMT_CREDENTIALS) {
557 if (!test_bit(Magic, &e->flags)) {
558 sprintf(dp, "extension .%s\n", e->magic);
562 sprintf(dp, "offset %i\nmagic ", e->offset);
563 dp = page + strlen(page);
564 for (i = 0; i < e->size; i++) {
565 sprintf(dp, "%02x", 0xff & (int) (e->magic[i]));
569 sprintf(dp, "\nmask ");
571 for (i = 0; i < e->size; i++) {
572 sprintf(dp, "%02x", 0xff & (int) (e->mask[i]));
581 static struct inode *bm_get_inode(struct super_block *sb, int mode)
583 struct inode * inode = new_inode(sb);
586 inode->i_ino = get_next_ino();
587 inode->i_mode = mode;
588 inode->i_atime = inode->i_mtime = inode->i_ctime =
589 current_fs_time(inode->i_sb);
594 static void bm_evict_inode(struct inode *inode)
597 kfree(inode->i_private);
600 static void kill_node(Node *e)
602 struct dentry *dentry;
604 write_lock(&entries_lock);
607 list_del_init(&e->list);
610 write_unlock(&entries_lock);
613 drop_nlink(dentry->d_inode);
616 simple_release_fs(&bm_mnt, &entry_count);
623 bm_entry_read(struct file * file, char __user * buf, size_t nbytes, loff_t *ppos)
625 Node *e = file_inode(file)->i_private;
629 if (!(page = (char*) __get_free_page(GFP_KERNEL)))
632 entry_status(e, page);
634 res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
636 free_page((unsigned long) page);
640 static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
641 size_t count, loff_t *ppos)
644 Node *e = file_inode(file)->i_private;
645 int res = parse_command(buffer, count);
649 /* Disable this handler. */
650 clear_bit(Enabled, &e->flags);
653 /* Enable this handler. */
654 set_bit(Enabled, &e->flags);
657 /* Delete this handler. */
658 root = dget(file->f_path.dentry->d_sb->s_root);
659 mutex_lock(&root->d_inode->i_mutex);
663 mutex_unlock(&root->d_inode->i_mutex);
671 static const struct file_operations bm_entry_operations = {
672 .read = bm_entry_read,
673 .write = bm_entry_write,
674 .llseek = default_llseek,
679 static ssize_t bm_register_write(struct file *file, const char __user *buffer,
680 size_t count, loff_t *ppos)
684 struct dentry *root, *dentry;
685 struct super_block *sb = file->f_path.dentry->d_sb;
688 e = create_entry(buffer, count);
693 root = dget(sb->s_root);
694 mutex_lock(&root->d_inode->i_mutex);
695 dentry = lookup_one_len(e->name, root, strlen(e->name));
696 err = PTR_ERR(dentry);
704 inode = bm_get_inode(sb, S_IFREG | 0644);
710 err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
717 e->dentry = dget(dentry);
718 inode->i_private = e;
719 inode->i_fop = &bm_entry_operations;
721 d_instantiate(dentry, inode);
722 write_lock(&entries_lock);
723 list_add(&e->list, &entries);
724 write_unlock(&entries_lock);
730 mutex_unlock(&root->d_inode->i_mutex);
740 static const struct file_operations bm_register_operations = {
741 .write = bm_register_write,
742 .llseek = noop_llseek,
748 bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
750 char *s = enabled ? "enabled\n" : "disabled\n";
752 return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
755 static ssize_t bm_status_write(struct file * file, const char __user * buffer,
756 size_t count, loff_t *ppos)
758 int res = parse_command(buffer, count);
763 /* Disable all handlers. */
767 /* Enable all handlers. */
771 /* Delete all handlers. */
772 root = dget(file->f_path.dentry->d_sb->s_root);
773 mutex_lock(&root->d_inode->i_mutex);
775 while (!list_empty(&entries))
776 kill_node(list_entry(entries.next, Node, list));
778 mutex_unlock(&root->d_inode->i_mutex);
786 static const struct file_operations bm_status_operations = {
787 .read = bm_status_read,
788 .write = bm_status_write,
789 .llseek = default_llseek,
792 /* Superblock handling */
794 static const struct super_operations s_ops = {
795 .statfs = simple_statfs,
796 .evict_inode = bm_evict_inode,
799 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},
806 int err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files);
812 static struct dentry *bm_mount(struct file_system_type *fs_type,
813 int flags, const char *dev_name, void *data)
815 return mount_single(fs_type, flags, data, bm_fill_super);
818 static struct linux_binfmt misc_format = {
819 .module = THIS_MODULE,
820 .load_binary = load_misc_binary,
823 static struct file_system_type bm_fs_type = {
824 .owner = THIS_MODULE,
825 .name = "binfmt_misc",
827 .kill_sb = kill_litter_super,
829 MODULE_ALIAS_FS("binfmt_misc");
831 static int __init init_misc_binfmt(void)
833 int err = register_filesystem(&bm_fs_type);
835 insert_binfmt(&misc_format);
839 static void __exit exit_misc_binfmt(void)
841 unregister_binfmt(&misc_format);
842 unregister_filesystem(&bm_fs_type);
845 core_initcall(init_misc_binfmt);
846 module_exit(exit_misc_binfmt);
847 MODULE_LICENSE("GPL");