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 #include <linux/module.h>
20 #include <linux/init.h>
21 #include <linux/sched.h>
22 #include <linux/binfmts.h>
23 #include <linux/slab.h>
24 #include <linux/ctype.h>
25 #include <linux/file.h>
26 #include <linux/pagemap.h>
27 #include <linux/namei.h>
28 #include <linux/mount.h>
29 #include <linux/syscalls.h>
32 #include <asm/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 * Check if we support the binfmt
65 * if we do, return the node, else NULL
66 * locking is done in load_misc_binary
68 static Node *check_file(struct linux_binprm *bprm)
70 char *p = strrchr(bprm->interp, '.');
73 list_for_each(l, &entries) {
74 Node *e = list_entry(l, Node, list);
78 if (!test_bit(Enabled, &e->flags))
81 if (!test_bit(Magic, &e->flags)) {
82 if (p && !strcmp(e->magic, p + 1))
87 s = bprm->buf + e->offset;
89 for (j = 0; j < e->size; j++)
90 if ((*s++ ^ e->magic[j]) & e->mask[j])
93 for (j = 0; j < e->size; j++)
94 if ((*s++ ^ e->magic[j]))
106 static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs)
109 struct file * interp_file = NULL;
110 char iname[BINPRM_BUF_SIZE];
111 const char *iname_addr = iname;
120 if (bprm->recursion_depth > BINPRM_MAX_RECURSION)
123 /* to keep locking time low, we copy the interpreter string */
124 read_lock(&entries_lock);
125 fmt = check_file(bprm);
127 strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
128 read_unlock(&entries_lock);
132 if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
133 retval = remove_arg_zero(bprm);
138 if (fmt->flags & MISC_FMT_OPEN_BINARY) {
140 /* if the binary should be opened on behalf of the
141 * interpreter than keep it open and assign descriptor
143 fd_binary = get_unused_fd();
148 fd_install(fd_binary, bprm->file);
150 /* if the binary is not readable than enforce mm->dumpable=0
151 regardless of the interpreter's permissions */
152 would_dump(bprm, bprm->file);
154 allow_write_access(bprm->file);
157 /* mark the bprm that fd should be passed to interp */
158 bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
159 bprm->interp_data = fd_binary;
162 allow_write_access(bprm->file);
166 /* make argv[1] be the path to the binary */
167 retval = copy_strings_kernel (1, &bprm->interp, bprm);
172 /* add the interp as argv[0] */
173 retval = copy_strings_kernel (1, &iname_addr, bprm);
178 bprm->interp = iname; /* for binfmt_script */
180 interp_file = open_exec (iname);
181 retval = PTR_ERR (interp_file);
182 if (IS_ERR (interp_file))
185 bprm->file = interp_file;
186 if (fmt->flags & MISC_FMT_CREDENTIALS) {
188 * No need to call prepare_binprm(), it's already been
189 * done. bprm->buf is stale, update from interp_file.
191 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
192 retval = kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
194 retval = prepare_binprm (bprm);
199 bprm->recursion_depth++;
201 retval = search_binary_handler (bprm, regs);
209 sys_close(fd_binary);
210 bprm->interp_flags = 0;
211 bprm->interp_data = 0;
215 /* Command parsers */
218 * parses and copies one argument enclosed in del from *sp to *dp,
219 * recognising the \x special.
220 * returns pointer to the copied argument or NULL in case of an
221 * error (and sets err) or null argument length.
223 static char *scanarg(char *s, char del)
227 while ((c = *s++) != del) {
228 if (c == '\\' && *s == 'x') {
239 static int unquote(char *from)
241 char c = 0, *s = from, *p = from;
243 while ((c = *s++) != '\0') {
244 if (c == '\\' && *s == 'x') {
247 *p = (c - (isdigit(c) ? '0' : 'A' - 10)) << 4;
249 *p++ |= c - (isdigit(c) ? '0' : 'A' - 10);
257 static char * check_special_flags (char * sfs, Node * e)
267 e->flags |= MISC_FMT_PRESERVE_ARGV0;
271 e->flags |= MISC_FMT_OPEN_BINARY;
275 /* this flags also implies the
277 e->flags |= (MISC_FMT_CREDENTIALS |
278 MISC_FMT_OPEN_BINARY);
288 * This registers a new binary format, it recognises the syntax
289 * ':name:type:offset:magic:mask:interpreter:flags'
290 * where the ':' is the IFS, that can be chosen with the first char
292 static Node *create_entry(const char __user *buffer, size_t count)
299 /* some sanity checks */
301 if ((count < 11) || (count > 256))
305 memsize = sizeof(Node) + count + 8;
306 e = kmalloc(memsize, GFP_USER);
310 p = buf = (char *)e + sizeof(Node);
312 memset(e, 0, sizeof(Node));
313 if (copy_from_user(buf, buffer, count))
316 del = *p++; /* delimeter */
318 memset(buf+count, del, 8);
326 !strcmp(e->name, ".") ||
327 !strcmp(e->name, "..") ||
328 strchr(e->name, '/'))
331 case 'E': e->flags = 1<<Enabled; break;
332 case 'M': e->flags = (1<<Enabled) | (1<<Magic); break;
333 default: goto Einval;
337 if (test_bit(Magic, &e->flags)) {
338 char *s = strchr(p, del);
342 e->offset = simple_strtoul(p, &p, 10);
359 e->size = unquote(e->magic);
360 if (e->mask && unquote(e->mask) != e->size)
362 if (e->size + e->offset > BINPRM_BUF_SIZE)
374 if (!e->magic[0] || strchr(e->magic, '/'))
386 if (!e->interpreter[0])
390 p = check_special_flags (p, e);
394 if (p != buf + count)
403 return ERR_PTR(-EFAULT);
406 return ERR_PTR(-EINVAL);
410 * Set status of entry/binfmt_misc:
411 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
413 static int parse_command(const char __user *buffer, size_t count)
421 if (copy_from_user(s, buffer, count))
423 if (s[count-1] == '\n')
425 if (count == 1 && s[0] == '0')
427 if (count == 1 && s[0] == '1')
429 if (count == 2 && s[0] == '-' && s[1] == '1')
436 static void entry_status(Node *e, char *page)
439 char *status = "disabled";
440 const char * flags = "flags: ";
442 if (test_bit(Enabled, &e->flags))
445 if (!VERBOSE_STATUS) {
446 sprintf(page, "%s\n", status);
450 sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter);
451 dp = page + strlen(page);
453 /* print the special flags */
454 sprintf (dp, "%s", flags);
455 dp += strlen (flags);
456 if (e->flags & MISC_FMT_PRESERVE_ARGV0) {
459 if (e->flags & MISC_FMT_OPEN_BINARY) {
462 if (e->flags & MISC_FMT_CREDENTIALS) {
468 if (!test_bit(Magic, &e->flags)) {
469 sprintf(dp, "extension .%s\n", e->magic);
473 sprintf(dp, "offset %i\nmagic ", e->offset);
474 dp = page + strlen(page);
475 for (i = 0; i < e->size; i++) {
476 sprintf(dp, "%02x", 0xff & (int) (e->magic[i]));
480 sprintf(dp, "\nmask ");
482 for (i = 0; i < e->size; i++) {
483 sprintf(dp, "%02x", 0xff & (int) (e->mask[i]));
492 static struct inode *bm_get_inode(struct super_block *sb, int mode)
494 struct inode * inode = new_inode(sb);
497 inode->i_ino = get_next_ino();
498 inode->i_mode = mode;
499 inode->i_atime = inode->i_mtime = inode->i_ctime =
500 current_fs_time(inode->i_sb);
505 static void bm_evict_inode(struct inode *inode)
507 end_writeback(inode);
508 kfree(inode->i_private);
511 static void kill_node(Node *e)
513 struct dentry *dentry;
515 write_lock(&entries_lock);
518 list_del_init(&e->list);
521 write_unlock(&entries_lock);
524 drop_nlink(dentry->d_inode);
527 simple_release_fs(&bm_mnt, &entry_count);
534 bm_entry_read(struct file * file, char __user * buf, size_t nbytes, loff_t *ppos)
536 Node *e = file->f_path.dentry->d_inode->i_private;
540 if (!(page = (char*) __get_free_page(GFP_KERNEL)))
543 entry_status(e, page);
545 res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
547 free_page((unsigned long) page);
551 static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
552 size_t count, loff_t *ppos)
555 Node *e = file->f_path.dentry->d_inode->i_private;
556 int res = parse_command(buffer, count);
559 case 1: clear_bit(Enabled, &e->flags);
561 case 2: set_bit(Enabled, &e->flags);
563 case 3: root = dget(file->f_path.dentry->d_sb->s_root);
564 mutex_lock(&root->d_inode->i_mutex);
568 mutex_unlock(&root->d_inode->i_mutex);
576 static const struct file_operations bm_entry_operations = {
577 .read = bm_entry_read,
578 .write = bm_entry_write,
579 .llseek = default_llseek,
584 static ssize_t bm_register_write(struct file *file, const char __user *buffer,
585 size_t count, loff_t *ppos)
589 struct dentry *root, *dentry;
590 struct super_block *sb = file->f_path.dentry->d_sb;
593 e = create_entry(buffer, count);
598 root = dget(sb->s_root);
599 mutex_lock(&root->d_inode->i_mutex);
600 dentry = lookup_one_len(e->name, root, strlen(e->name));
601 err = PTR_ERR(dentry);
609 inode = bm_get_inode(sb, S_IFREG | 0644);
615 err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
622 e->dentry = dget(dentry);
623 inode->i_private = e;
624 inode->i_fop = &bm_entry_operations;
626 d_instantiate(dentry, inode);
627 write_lock(&entries_lock);
628 list_add(&e->list, &entries);
629 write_unlock(&entries_lock);
635 mutex_unlock(&root->d_inode->i_mutex);
645 static const struct file_operations bm_register_operations = {
646 .write = bm_register_write,
647 .llseek = noop_llseek,
653 bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
655 char *s = enabled ? "enabled\n" : "disabled\n";
657 return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
660 static ssize_t bm_status_write(struct file * file, const char __user * buffer,
661 size_t count, loff_t *ppos)
663 int res = parse_command(buffer, count);
667 case 1: enabled = 0; break;
668 case 2: enabled = 1; break;
669 case 3: root = dget(file->f_path.dentry->d_sb->s_root);
670 mutex_lock(&root->d_inode->i_mutex);
672 while (!list_empty(&entries))
673 kill_node(list_entry(entries.next, Node, list));
675 mutex_unlock(&root->d_inode->i_mutex);
682 static const struct file_operations bm_status_operations = {
683 .read = bm_status_read,
684 .write = bm_status_write,
685 .llseek = default_llseek,
688 /* Superblock handling */
690 static const struct super_operations s_ops = {
691 .statfs = simple_statfs,
692 .evict_inode = bm_evict_inode,
695 static int bm_fill_super(struct super_block * sb, void * data, int silent)
697 static struct tree_descr bm_files[] = {
698 [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
699 [3] = {"register", &bm_register_operations, S_IWUSR},
702 int err = simple_fill_super(sb, 0x42494e4d, bm_files);
708 static struct dentry *bm_mount(struct file_system_type *fs_type,
709 int flags, const char *dev_name, void *data)
711 return mount_single(fs_type, flags, data, bm_fill_super);
714 static struct linux_binfmt misc_format = {
715 .module = THIS_MODULE,
716 .load_binary = load_misc_binary,
719 static struct file_system_type bm_fs_type = {
720 .owner = THIS_MODULE,
721 .name = "binfmt_misc",
723 .kill_sb = kill_litter_super,
726 static int __init init_misc_binfmt(void)
728 int err = register_filesystem(&bm_fs_type);
730 err = insert_binfmt(&misc_format);
732 unregister_filesystem(&bm_fs_type);
737 static void __exit exit_misc_binfmt(void)
739 unregister_binfmt(&misc_format);
740 unregister_filesystem(&bm_fs_type);
743 core_initcall(init_misc_binfmt);
744 module_exit(exit_misc_binfmt);
745 MODULE_LICENSE("GPL");