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>
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>
31 #include <asm/uaccess.h>
34 VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
37 static LIST_HEAD(entries);
38 static int enabled = 1;
40 enum {Enabled, Magic};
41 #define MISC_FMT_PRESERVE_ARGV0 (1<<31)
42 #define MISC_FMT_OPEN_BINARY (1<<30)
43 #define MISC_FMT_CREDENTIALS (1<<29)
46 struct list_head list;
47 unsigned long flags; /* type, status, etc. */
48 int offset; /* offset of magic */
49 int size; /* size of magic/mask */
50 char *magic; /* magic or filename extension */
51 char *mask; /* mask, NULL for exact match */
52 char *interpreter; /* filename of interpreter */
54 struct dentry *dentry;
57 static rwlock_t entries_lock = RW_LOCK_UNLOCKED;
58 static struct vfsmount *bm_mnt;
59 static int entry_count;
62 * Check if we support the binfmt
63 * if we do, return the node, else NULL
64 * locking is done in load_misc_binary
66 static Node *check_file(struct linux_binprm *bprm)
68 char *p = strrchr(bprm->interp, '.');
71 list_for_each(l, &entries) {
72 Node *e = list_entry(l, Node, list);
76 if (!test_bit(Enabled, &e->flags))
79 if (!test_bit(Magic, &e->flags)) {
80 if (p && !strcmp(e->magic, p + 1))
85 s = bprm->buf + e->offset;
87 for (j = 0; j < e->size; j++)
88 if ((*s++ ^ e->magic[j]) & e->mask[j])
91 for (j = 0; j < e->size; j++)
92 if ((*s++ ^ e->magic[j]))
104 static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs)
107 struct file * interp_file = NULL;
108 char iname[BINPRM_BUF_SIZE];
109 char *iname_addr = iname;
113 struct files_struct *files = NULL;
119 /* to keep locking time low, we copy the interpreter string */
120 read_lock(&entries_lock);
121 fmt = check_file(bprm);
123 strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
124 read_unlock(&entries_lock);
128 if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
129 remove_arg_zero(bprm);
132 if (fmt->flags & MISC_FMT_OPEN_BINARY) {
135 files = current->files;
136 retval = unshare_files();
139 if (files == current->files) {
140 put_files_struct(files);
143 /* if the binary should be opened on behalf of the
144 * interpreter than keep it open and assign descriptor
146 fd_binary = get_unused_fd();
151 fd_install(fd_binary, bprm->file);
153 /* if the binary is not readable than enforce mm->dumpable=0
154 regardless of the interpreter's permissions */
155 if (permission(bprm->file->f_dentry->d_inode, MAY_READ, NULL))
156 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
158 allow_write_access(bprm->file);
161 /* make argv[1] be the file descriptor of the binary */
162 snprintf(fd_str, sizeof(fd_str), "%d", fd_binary);
163 retval = copy_strings_kernel(1, &fdsp, bprm);
169 allow_write_access(bprm->file);
172 /* make argv[1] be the path to the binary */
173 retval = copy_strings_kernel (1, &bprm->interp, bprm);
178 retval = copy_strings_kernel (1, &iname_addr, bprm);
182 bprm->interp = iname; /* for binfmt_script */
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 retval = search_binary_handler (bprm, regs);
209 put_files_struct(files);
216 sys_close(fd_binary);
217 bprm->interp_flags = 0;
220 put_files_struct(current->files);
221 current->files = files;
226 /* Command parsers */
229 * parses and copies one argument enclosed in del from *sp to *dp,
230 * recognising the \x special.
231 * returns pointer to the copied argument or NULL in case of an
232 * error (and sets err) or null argument length.
234 static char *scanarg(char *s, char del)
238 while ((c = *s++) != del) {
239 if (c == '\\' && *s == 'x') {
250 static int unquote(char *from)
252 char c = 0, *s = from, *p = from;
254 while ((c = *s++) != '\0') {
255 if (c == '\\' && *s == 'x') {
258 *p = (c - (isdigit(c) ? '0' : 'A' - 10)) << 4;
260 *p++ |= c - (isdigit(c) ? '0' : 'A' - 10);
268 static inline char * check_special_flags (char * sfs, Node * e)
278 e->flags |= MISC_FMT_PRESERVE_ARGV0;
282 e->flags |= MISC_FMT_OPEN_BINARY;
286 /* this flags also implies the
288 e->flags |= (MISC_FMT_CREDENTIALS |
289 MISC_FMT_OPEN_BINARY);
299 * This registers a new binary format, it recognises the syntax
300 * ':name:type:offset:magic:mask:interpreter:flags'
301 * where the ':' is the IFS, that can be chosen with the first char
303 static Node *create_entry(const char __user *buffer, size_t count)
310 /* some sanity checks */
312 if ((count < 11) || (count > 256))
316 memsize = sizeof(Node) + count + 8;
317 e = (Node *) kmalloc(memsize, GFP_USER);
321 p = buf = (char *)e + sizeof(Node);
323 memset(e, 0, sizeof(Node));
324 if (copy_from_user(buf, buffer, count))
327 del = *p++; /* delimeter */
329 memset(buf+count, del, 8);
337 !strcmp(e->name, ".") ||
338 !strcmp(e->name, "..") ||
339 strchr(e->name, '/'))
342 case 'E': e->flags = 1<<Enabled; break;
343 case 'M': e->flags = (1<<Enabled) | (1<<Magic); break;
344 default: goto Einval;
348 if (test_bit(Magic, &e->flags)) {
349 char *s = strchr(p, del);
353 e->offset = simple_strtoul(p, &p, 10);
370 e->size = unquote(e->magic);
371 if (e->mask && unquote(e->mask) != e->size)
373 if (e->size + e->offset > BINPRM_BUF_SIZE)
385 if (!e->magic[0] || strchr(e->magic, '/'))
397 if (!e->interpreter[0])
401 p = check_special_flags (p, e);
405 if (p != buf + count)
414 return ERR_PTR(-EFAULT);
417 return ERR_PTR(-EINVAL);
421 * Set status of entry/binfmt_misc:
422 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
424 static int parse_command(const char __user *buffer, size_t count)
432 if (copy_from_user(s, buffer, count))
434 if (s[count-1] == '\n')
436 if (count == 1 && s[0] == '0')
438 if (count == 1 && s[0] == '1')
440 if (count == 2 && s[0] == '-' && s[1] == '1')
447 static void entry_status(Node *e, char *page)
450 char *status = "disabled";
451 const char * flags = "flags: ";
453 if (test_bit(Enabled, &e->flags))
456 if (!VERBOSE_STATUS) {
457 sprintf(page, "%s\n", status);
461 sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter);
462 dp = page + strlen(page);
464 /* print the special flags */
465 sprintf (dp, "%s", flags);
466 dp += strlen (flags);
467 if (e->flags & MISC_FMT_PRESERVE_ARGV0) {
470 if (e->flags & MISC_FMT_OPEN_BINARY) {
473 if (e->flags & MISC_FMT_CREDENTIALS) {
479 if (!test_bit(Magic, &e->flags)) {
480 sprintf(dp, "extension .%s\n", e->magic);
484 sprintf(dp, "offset %i\nmagic ", e->offset);
485 dp = page + strlen(page);
486 for (i = 0; i < e->size; i++) {
487 sprintf(dp, "%02x", 0xff & (int) (e->magic[i]));
491 sprintf(dp, "\nmask ");
493 for (i = 0; i < e->size; i++) {
494 sprintf(dp, "%02x", 0xff & (int) (e->mask[i]));
503 static struct inode *bm_get_inode(struct super_block *sb, int mode)
505 struct inode * inode = new_inode(sb);
508 inode->i_mode = mode;
511 inode->i_blksize = PAGE_CACHE_SIZE;
513 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
518 static void bm_clear_inode(struct inode *inode)
520 kfree(inode->u.generic_ip);
523 static void kill_node(Node *e)
525 struct dentry *dentry;
527 write_lock(&entries_lock);
530 list_del_init(&e->list);
533 write_unlock(&entries_lock);
536 dentry->d_inode->i_nlink--;
539 simple_release_fs(&bm_mnt, &entry_count);
546 bm_entry_read(struct file * file, char __user * buf, size_t nbytes, loff_t *ppos)
548 Node *e = file->f_dentry->d_inode->u.generic_ip;
554 if (!(page = (char*) __get_free_page(GFP_KERNEL)))
557 entry_status(e, page);
566 if (len < pos + nbytes)
569 if (copy_to_user(buf, page + pos, nbytes))
571 *ppos = pos + nbytes;
574 free_page((unsigned long) page);
578 static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
579 size_t count, loff_t *ppos)
582 Node *e = file->f_dentry->d_inode->u.generic_ip;
583 int res = parse_command(buffer, count);
586 case 1: clear_bit(Enabled, &e->flags);
588 case 2: set_bit(Enabled, &e->flags);
590 case 3: root = dget(file->f_vfsmnt->mnt_sb->s_root);
591 down(&root->d_inode->i_sem);
595 up(&root->d_inode->i_sem);
603 static struct file_operations bm_entry_operations = {
604 .read = bm_entry_read,
605 .write = bm_entry_write,
610 static ssize_t bm_register_write(struct file *file, const char __user *buffer,
611 size_t count, loff_t *ppos)
615 struct dentry *root, *dentry;
616 struct super_block *sb = file->f_vfsmnt->mnt_sb;
619 e = create_entry(buffer, count);
624 root = dget(sb->s_root);
625 down(&root->d_inode->i_sem);
626 dentry = lookup_one_len(e->name, root, strlen(e->name));
627 err = PTR_ERR(dentry);
635 inode = bm_get_inode(sb, S_IFREG | 0644);
641 err = simple_pin_fs("binfmt_misc", &bm_mnt, &entry_count);
648 e->dentry = dget(dentry);
649 inode->u.generic_ip = e;
650 inode->i_fop = &bm_entry_operations;
652 d_instantiate(dentry, inode);
653 write_lock(&entries_lock);
654 list_add(&e->list, &entries);
655 write_unlock(&entries_lock);
661 up(&root->d_inode->i_sem);
671 static struct file_operations bm_register_operations = {
672 .write = bm_register_write,
678 bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
680 char *s = enabled ? "enabled" : "disabled";
688 if (len < pos + nbytes)
690 if (copy_to_user(buf, s + pos, nbytes))
692 *ppos = pos + nbytes;
696 static ssize_t bm_status_write(struct file * file, const char __user * buffer,
697 size_t count, loff_t *ppos)
699 int res = parse_command(buffer, count);
703 case 1: enabled = 0; break;
704 case 2: enabled = 1; break;
705 case 3: root = dget(file->f_vfsmnt->mnt_sb->s_root);
706 down(&root->d_inode->i_sem);
708 while (!list_empty(&entries))
709 kill_node(list_entry(entries.next, Node, list));
711 up(&root->d_inode->i_sem);
718 static struct file_operations bm_status_operations = {
719 .read = bm_status_read,
720 .write = bm_status_write,
723 /* Superblock handling */
725 static struct super_operations s_ops = {
726 .statfs = simple_statfs,
727 .clear_inode = bm_clear_inode,
730 static int bm_fill_super(struct super_block * sb, void * data, int silent)
732 static struct tree_descr bm_files[] = {
733 [1] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
734 [2] = {"register", &bm_register_operations, S_IWUSR},
737 int err = simple_fill_super(sb, 0x42494e4d, bm_files);
743 static struct super_block *bm_get_sb(struct file_system_type *fs_type,
744 int flags, const char *dev_name, void *data)
746 return get_sb_single(fs_type, flags, data, bm_fill_super);
749 static struct linux_binfmt misc_format = {
750 .module = THIS_MODULE,
751 .load_binary = load_misc_binary,
754 static struct file_system_type bm_fs_type = {
755 .owner = THIS_MODULE,
756 .name = "binfmt_misc",
758 .kill_sb = kill_litter_super,
761 static int __init init_misc_binfmt(void)
763 int err = register_filesystem(&bm_fs_type);
765 err = register_binfmt(&misc_format);
767 unregister_filesystem(&bm_fs_type);
772 static void __exit exit_misc_binfmt(void)
774 unregister_binfmt(&misc_format);
775 unregister_filesystem(&bm_fs_type);
778 core_initcall(init_misc_binfmt);
779 module_exit(exit_misc_binfmt);
780 MODULE_LICENSE("GPL");