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/magic.h>
23 #include <linux/binfmts.h>
24 #include <linux/slab.h>
25 #include <linux/ctype.h>
26 #include <linux/file.h>
27 #include <linux/pagemap.h>
28 #include <linux/namei.h>
29 #include <linux/mount.h>
30 #include <linux/syscalls.h>
33 #include <asm/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 * Check if we support the binfmt
66 * if we do, return the node, else NULL
67 * locking is done in load_misc_binary
69 static Node *check_file(struct linux_binprm *bprm)
71 char *p = strrchr(bprm->interp, '.');
74 list_for_each(l, &entries) {
75 Node *e = list_entry(l, Node, list);
79 if (!test_bit(Enabled, &e->flags))
82 if (!test_bit(Magic, &e->flags)) {
83 if (p && !strcmp(e->magic, p + 1))
88 s = bprm->buf + e->offset;
90 for (j = 0; j < e->size; j++)
91 if ((*s++ ^ e->magic[j]) & e->mask[j])
94 for (j = 0; j < e->size; j++)
95 if ((*s++ ^ e->magic[j]))
107 static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs)
110 struct file * interp_file = NULL;
111 char iname[BINPRM_BUF_SIZE];
112 const char *iname_addr = iname;
121 if (bprm->recursion_depth > BINPRM_MAX_RECURSION)
124 /* to keep locking time low, we copy the interpreter string */
125 read_lock(&entries_lock);
126 fmt = check_file(bprm);
128 strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
129 read_unlock(&entries_lock);
133 if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
134 retval = remove_arg_zero(bprm);
139 if (fmt->flags & MISC_FMT_OPEN_BINARY) {
141 /* if the binary should be opened on behalf of the
142 * interpreter than keep it open and assign descriptor
144 fd_binary = get_unused_fd();
149 fd_install(fd_binary, bprm->file);
151 /* if the binary is not readable than enforce mm->dumpable=0
152 regardless of the interpreter's permissions */
153 would_dump(bprm, bprm->file);
155 allow_write_access(bprm->file);
158 /* mark the bprm that fd should be passed to interp */
159 bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
160 bprm->interp_data = fd_binary;
163 allow_write_access(bprm->file);
167 /* make argv[1] be the path to the binary */
168 retval = copy_strings_kernel (1, &bprm->interp, bprm);
173 /* add the interp as argv[0] */
174 retval = copy_strings_kernel (1, &iname_addr, bprm);
179 /* Update interp in case binfmt_script needs it. */
180 retval = bprm_change_interp(iname, bprm);
184 interp_file = open_exec (iname);
185 retval = PTR_ERR (interp_file);
186 if (IS_ERR (interp_file))
189 bprm->file = interp_file;
190 if (fmt->flags & MISC_FMT_CREDENTIALS) {
192 * No need to call prepare_binprm(), it's already been
193 * done. bprm->buf is stale, update from interp_file.
195 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
196 retval = kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
198 retval = prepare_binprm (bprm);
203 bprm->recursion_depth++;
205 retval = search_binary_handler (bprm, regs);
213 sys_close(fd_binary);
214 bprm->interp_flags = 0;
215 bprm->interp_data = 0;
219 /* Command parsers */
222 * parses and copies one argument enclosed in del from *sp to *dp,
223 * recognising the \x special.
224 * returns pointer to the copied argument or NULL in case of an
225 * error (and sets err) or null argument length.
227 static char *scanarg(char *s, char del)
231 while ((c = *s++) != del) {
232 if (c == '\\' && *s == 'x') {
243 static int unquote(char *from)
245 char c = 0, *s = from, *p = from;
247 while ((c = *s++) != '\0') {
248 if (c == '\\' && *s == 'x') {
251 *p = (c - (isdigit(c) ? '0' : 'A' - 10)) << 4;
253 *p++ |= c - (isdigit(c) ? '0' : 'A' - 10);
261 static char * check_special_flags (char * sfs, Node * e)
271 e->flags |= MISC_FMT_PRESERVE_ARGV0;
275 e->flags |= MISC_FMT_OPEN_BINARY;
279 /* this flags also implies the
281 e->flags |= (MISC_FMT_CREDENTIALS |
282 MISC_FMT_OPEN_BINARY);
292 * This registers a new binary format, it recognises the syntax
293 * ':name:type:offset:magic:mask:interpreter:flags'
294 * where the ':' is the IFS, that can be chosen with the first char
296 static Node *create_entry(const char __user *buffer, size_t count)
303 /* some sanity checks */
305 if ((count < 11) || (count > 256))
309 memsize = sizeof(Node) + count + 8;
310 e = kmalloc(memsize, GFP_USER);
314 p = buf = (char *)e + sizeof(Node);
316 memset(e, 0, sizeof(Node));
317 if (copy_from_user(buf, buffer, count))
320 del = *p++; /* delimeter */
322 memset(buf+count, del, 8);
330 !strcmp(e->name, ".") ||
331 !strcmp(e->name, "..") ||
332 strchr(e->name, '/'))
335 case 'E': e->flags = 1<<Enabled; break;
336 case 'M': e->flags = (1<<Enabled) | (1<<Magic); break;
337 default: goto Einval;
341 if (test_bit(Magic, &e->flags)) {
342 char *s = strchr(p, del);
346 e->offset = simple_strtoul(p, &p, 10);
363 e->size = unquote(e->magic);
364 if (e->mask && unquote(e->mask) != e->size)
366 if (e->size + e->offset > BINPRM_BUF_SIZE)
378 if (!e->magic[0] || strchr(e->magic, '/'))
390 if (!e->interpreter[0])
394 p = check_special_flags (p, e);
398 if (p != buf + count)
407 return ERR_PTR(-EFAULT);
410 return ERR_PTR(-EINVAL);
414 * Set status of entry/binfmt_misc:
415 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
417 static int parse_command(const char __user *buffer, size_t count)
425 if (copy_from_user(s, buffer, count))
427 if (s[count-1] == '\n')
429 if (count == 1 && s[0] == '0')
431 if (count == 1 && s[0] == '1')
433 if (count == 2 && s[0] == '-' && s[1] == '1')
440 static void entry_status(Node *e, char *page)
443 char *status = "disabled";
444 const char * flags = "flags: ";
446 if (test_bit(Enabled, &e->flags))
449 if (!VERBOSE_STATUS) {
450 sprintf(page, "%s\n", status);
454 sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter);
455 dp = page + strlen(page);
457 /* print the special flags */
458 sprintf (dp, "%s", flags);
459 dp += strlen (flags);
460 if (e->flags & MISC_FMT_PRESERVE_ARGV0) {
463 if (e->flags & MISC_FMT_OPEN_BINARY) {
466 if (e->flags & MISC_FMT_CREDENTIALS) {
472 if (!test_bit(Magic, &e->flags)) {
473 sprintf(dp, "extension .%s\n", e->magic);
477 sprintf(dp, "offset %i\nmagic ", e->offset);
478 dp = page + strlen(page);
479 for (i = 0; i < e->size; i++) {
480 sprintf(dp, "%02x", 0xff & (int) (e->magic[i]));
484 sprintf(dp, "\nmask ");
486 for (i = 0; i < e->size; i++) {
487 sprintf(dp, "%02x", 0xff & (int) (e->mask[i]));
496 static struct inode *bm_get_inode(struct super_block *sb, int mode)
498 struct inode * inode = new_inode(sb);
501 inode->i_ino = get_next_ino();
502 inode->i_mode = mode;
503 inode->i_atime = inode->i_mtime = inode->i_ctime =
504 current_fs_time(inode->i_sb);
509 static void bm_evict_inode(struct inode *inode)
512 kfree(inode->i_private);
515 static void kill_node(Node *e)
517 struct dentry *dentry;
519 write_lock(&entries_lock);
522 list_del_init(&e->list);
525 write_unlock(&entries_lock);
528 drop_nlink(dentry->d_inode);
531 simple_release_fs(&bm_mnt, &entry_count);
538 bm_entry_read(struct file * file, char __user * buf, size_t nbytes, loff_t *ppos)
540 Node *e = file->f_path.dentry->d_inode->i_private;
544 if (!(page = (char*) __get_free_page(GFP_KERNEL)))
547 entry_status(e, page);
549 res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
551 free_page((unsigned long) page);
555 static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
556 size_t count, loff_t *ppos)
559 Node *e = file->f_path.dentry->d_inode->i_private;
560 int res = parse_command(buffer, count);
563 case 1: clear_bit(Enabled, &e->flags);
565 case 2: set_bit(Enabled, &e->flags);
567 case 3: root = dget(file->f_path.dentry->d_sb->s_root);
568 mutex_lock(&root->d_inode->i_mutex);
572 mutex_unlock(&root->d_inode->i_mutex);
580 static const struct file_operations bm_entry_operations = {
581 .read = bm_entry_read,
582 .write = bm_entry_write,
583 .llseek = default_llseek,
588 static ssize_t bm_register_write(struct file *file, const char __user *buffer,
589 size_t count, loff_t *ppos)
593 struct dentry *root, *dentry;
594 struct super_block *sb = file->f_path.dentry->d_sb;
597 e = create_entry(buffer, count);
602 root = dget(sb->s_root);
603 mutex_lock(&root->d_inode->i_mutex);
604 dentry = lookup_one_len(e->name, root, strlen(e->name));
605 err = PTR_ERR(dentry);
613 inode = bm_get_inode(sb, S_IFREG | 0644);
619 err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
626 e->dentry = dget(dentry);
627 inode->i_private = e;
628 inode->i_fop = &bm_entry_operations;
630 d_instantiate(dentry, inode);
631 write_lock(&entries_lock);
632 list_add(&e->list, &entries);
633 write_unlock(&entries_lock);
639 mutex_unlock(&root->d_inode->i_mutex);
649 static const struct file_operations bm_register_operations = {
650 .write = bm_register_write,
651 .llseek = noop_llseek,
657 bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
659 char *s = enabled ? "enabled\n" : "disabled\n";
661 return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
664 static ssize_t bm_status_write(struct file * file, const char __user * buffer,
665 size_t count, loff_t *ppos)
667 int res = parse_command(buffer, count);
671 case 1: enabled = 0; break;
672 case 2: enabled = 1; break;
673 case 3: root = dget(file->f_path.dentry->d_sb->s_root);
674 mutex_lock(&root->d_inode->i_mutex);
676 while (!list_empty(&entries))
677 kill_node(list_entry(entries.next, Node, list));
679 mutex_unlock(&root->d_inode->i_mutex);
686 static const struct file_operations bm_status_operations = {
687 .read = bm_status_read,
688 .write = bm_status_write,
689 .llseek = default_llseek,
692 /* Superblock handling */
694 static const struct super_operations s_ops = {
695 .statfs = simple_statfs,
696 .evict_inode = bm_evict_inode,
699 static int bm_fill_super(struct super_block * sb, void * data, int silent)
701 static struct tree_descr bm_files[] = {
702 [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
703 [3] = {"register", &bm_register_operations, S_IWUSR},
706 int err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files);
712 static struct dentry *bm_mount(struct file_system_type *fs_type,
713 int flags, const char *dev_name, void *data)
715 return mount_single(fs_type, flags, data, bm_fill_super);
718 static struct linux_binfmt misc_format = {
719 .module = THIS_MODULE,
720 .load_binary = load_misc_binary,
723 static struct file_system_type bm_fs_type = {
724 .owner = THIS_MODULE,
725 .name = "binfmt_misc",
727 .kill_sb = kill_litter_super,
730 static int __init init_misc_binfmt(void)
732 int err = register_filesystem(&bm_fs_type);
734 insert_binfmt(&misc_format);
738 static void __exit exit_misc_binfmt(void)
740 unregister_binfmt(&misc_format);
741 unregister_filesystem(&bm_fs_type);
744 core_initcall(init_misc_binfmt);
745 module_exit(exit_misc_binfmt);
746 MODULE_LICENSE("GPL");