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>
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 DEFINE_RWLOCK(entries_lock);
58 static struct file_system_type bm_fs_type;
59 static struct vfsmount *bm_mnt;
60 static int entry_count;
63 * Check if we support the binfmt
64 * if we do, return the node, else NULL
65 * locking is done in load_misc_binary
67 static Node *check_file(struct linux_binprm *bprm)
69 char *p = strrchr(bprm->interp, '.');
72 list_for_each(l, &entries) {
73 Node *e = list_entry(l, Node, list);
77 if (!test_bit(Enabled, &e->flags))
80 if (!test_bit(Magic, &e->flags)) {
81 if (p && !strcmp(e->magic, p + 1))
86 s = bprm->buf + e->offset;
88 for (j = 0; j < e->size; j++)
89 if ((*s++ ^ e->magic[j]) & e->mask[j])
92 for (j = 0; j < e->size; j++)
93 if ((*s++ ^ e->magic[j]))
105 static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs)
108 struct file * interp_file = NULL;
109 char iname[BINPRM_BUF_SIZE];
110 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 retval = remove_arg_zero(bprm);
134 if (fmt->flags & MISC_FMT_OPEN_BINARY) {
136 files = current->files;
137 retval = unshare_files();
140 if (files == current->files) {
141 put_files_struct(files);
144 /* if the binary should be opened on behalf of the
145 * interpreter than keep it open and assign descriptor
147 fd_binary = get_unused_fd();
152 fd_install(fd_binary, bprm->file);
154 /* if the binary is not readable than enforce mm->dumpable=0
155 regardless of the interpreter's permissions */
156 if (file_permission(bprm->file, MAY_READ))
157 bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
159 allow_write_access(bprm->file);
162 /* mark the bprm that fd should be passed to interp */
163 bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
164 bprm->interp_data = fd_binary;
167 allow_write_access(bprm->file);
171 /* make argv[1] be the path to the binary */
172 retval = copy_strings_kernel (1, &bprm->interp, bprm);
177 /* add the interp as argv[0] */
178 retval = copy_strings_kernel (1, &iname_addr, bprm);
183 bprm->interp = iname; /* for binfmt_script */
185 interp_file = open_exec (iname);
186 retval = PTR_ERR (interp_file);
187 if (IS_ERR (interp_file))
190 bprm->file = interp_file;
191 if (fmt->flags & MISC_FMT_CREDENTIALS) {
193 * No need to call prepare_binprm(), it's already been
194 * done. bprm->buf is stale, update from interp_file.
196 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
197 retval = kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
199 retval = prepare_binprm (bprm);
204 retval = search_binary_handler (bprm, regs);
209 put_files_struct(files);
216 sys_close(fd_binary);
217 bprm->interp_flags = 0;
218 bprm->interp_data = 0;
221 reset_files_struct(current, files);
225 /* Command parsers */
228 * parses and copies one argument enclosed in del from *sp to *dp,
229 * recognising the \x special.
230 * returns pointer to the copied argument or NULL in case of an
231 * error (and sets err) or null argument length.
233 static char *scanarg(char *s, char del)
237 while ((c = *s++) != del) {
238 if (c == '\\' && *s == 'x') {
249 static int unquote(char *from)
251 char c = 0, *s = from, *p = from;
253 while ((c = *s++) != '\0') {
254 if (c == '\\' && *s == 'x') {
257 *p = (c - (isdigit(c) ? '0' : 'A' - 10)) << 4;
259 *p++ |= c - (isdigit(c) ? '0' : 'A' - 10);
267 static char * check_special_flags (char * sfs, Node * e)
277 e->flags |= MISC_FMT_PRESERVE_ARGV0;
281 e->flags |= MISC_FMT_OPEN_BINARY;
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 /* some sanity checks */
311 if ((count < 11) || (count > 256))
315 memsize = sizeof(Node) + count + 8;
316 e = kmalloc(memsize, GFP_USER);
320 p = buf = (char *)e + sizeof(Node);
322 memset(e, 0, sizeof(Node));
323 if (copy_from_user(buf, buffer, count))
326 del = *p++; /* delimeter */
328 memset(buf+count, del, 8);
336 !strcmp(e->name, ".") ||
337 !strcmp(e->name, "..") ||
338 strchr(e->name, '/'))
341 case 'E': e->flags = 1<<Enabled; break;
342 case 'M': e->flags = (1<<Enabled) | (1<<Magic); break;
343 default: goto Einval;
347 if (test_bit(Magic, &e->flags)) {
348 char *s = strchr(p, del);
352 e->offset = simple_strtoul(p, &p, 10);
369 e->size = unquote(e->magic);
370 if (e->mask && unquote(e->mask) != e->size)
372 if (e->size + e->offset > BINPRM_BUF_SIZE)
384 if (!e->magic[0] || strchr(e->magic, '/'))
396 if (!e->interpreter[0])
400 p = check_special_flags (p, e);
404 if (p != buf + count)
413 return ERR_PTR(-EFAULT);
416 return ERR_PTR(-EINVAL);
420 * Set status of entry/binfmt_misc:
421 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
423 static int parse_command(const char __user *buffer, size_t count)
431 if (copy_from_user(s, buffer, count))
433 if (s[count-1] == '\n')
435 if (count == 1 && s[0] == '0')
437 if (count == 1 && s[0] == '1')
439 if (count == 2 && s[0] == '-' && s[1] == '1')
446 static void entry_status(Node *e, char *page)
449 char *status = "disabled";
450 const char * flags = "flags: ";
452 if (test_bit(Enabled, &e->flags))
455 if (!VERBOSE_STATUS) {
456 sprintf(page, "%s\n", status);
460 sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter);
461 dp = page + strlen(page);
463 /* print the special flags */
464 sprintf (dp, "%s", flags);
465 dp += strlen (flags);
466 if (e->flags & MISC_FMT_PRESERVE_ARGV0) {
469 if (e->flags & MISC_FMT_OPEN_BINARY) {
472 if (e->flags & MISC_FMT_CREDENTIALS) {
478 if (!test_bit(Magic, &e->flags)) {
479 sprintf(dp, "extension .%s\n", e->magic);
483 sprintf(dp, "offset %i\nmagic ", e->offset);
484 dp = page + strlen(page);
485 for (i = 0; i < e->size; i++) {
486 sprintf(dp, "%02x", 0xff & (int) (e->magic[i]));
490 sprintf(dp, "\nmask ");
492 for (i = 0; i < e->size; i++) {
493 sprintf(dp, "%02x", 0xff & (int) (e->mask[i]));
502 static struct inode *bm_get_inode(struct super_block *sb, int mode)
504 struct inode * inode = new_inode(sb);
507 inode->i_mode = mode;
511 inode->i_atime = inode->i_mtime = inode->i_ctime =
512 current_fs_time(inode->i_sb);
517 static void bm_clear_inode(struct inode *inode)
519 kfree(inode->i_private);
522 static void kill_node(Node *e)
524 struct dentry *dentry;
526 write_lock(&entries_lock);
529 list_del_init(&e->list);
532 write_unlock(&entries_lock);
535 dentry->d_inode->i_nlink--;
538 simple_release_fs(&bm_mnt, &entry_count);
545 bm_entry_read(struct file * file, char __user * buf, size_t nbytes, loff_t *ppos)
547 Node *e = file->f_path.dentry->d_inode->i_private;
553 if (!(page = (char*) __get_free_page(GFP_KERNEL)))
556 entry_status(e, page);
565 if (len < pos + nbytes)
568 if (copy_to_user(buf, page + pos, nbytes))
570 *ppos = pos + nbytes;
573 free_page((unsigned long) page);
577 static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
578 size_t count, loff_t *ppos)
581 Node *e = file->f_path.dentry->d_inode->i_private;
582 int res = parse_command(buffer, count);
585 case 1: clear_bit(Enabled, &e->flags);
587 case 2: set_bit(Enabled, &e->flags);
589 case 3: root = dget(file->f_path.mnt->mnt_sb->s_root);
590 mutex_lock(&root->d_inode->i_mutex);
594 mutex_unlock(&root->d_inode->i_mutex);
602 static const struct file_operations bm_entry_operations = {
603 .read = bm_entry_read,
604 .write = bm_entry_write,
609 static ssize_t bm_register_write(struct file *file, const char __user *buffer,
610 size_t count, loff_t *ppos)
614 struct dentry *root, *dentry;
615 struct super_block *sb = file->f_path.mnt->mnt_sb;
618 e = create_entry(buffer, count);
623 root = dget(sb->s_root);
624 mutex_lock(&root->d_inode->i_mutex);
625 dentry = lookup_one_len(e->name, root, strlen(e->name));
626 err = PTR_ERR(dentry);
634 inode = bm_get_inode(sb, S_IFREG | 0644);
640 err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
647 e->dentry = dget(dentry);
648 inode->i_private = e;
649 inode->i_fop = &bm_entry_operations;
651 d_instantiate(dentry, inode);
652 write_lock(&entries_lock);
653 list_add(&e->list, &entries);
654 write_unlock(&entries_lock);
660 mutex_unlock(&root->d_inode->i_mutex);
670 static const struct file_operations bm_register_operations = {
671 .write = bm_register_write,
677 bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
679 char *s = enabled ? "enabled" : "disabled";
681 return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
684 static ssize_t bm_status_write(struct file * file, const char __user * buffer,
685 size_t count, loff_t *ppos)
687 int res = parse_command(buffer, count);
691 case 1: enabled = 0; break;
692 case 2: enabled = 1; break;
693 case 3: root = dget(file->f_path.mnt->mnt_sb->s_root);
694 mutex_lock(&root->d_inode->i_mutex);
696 while (!list_empty(&entries))
697 kill_node(list_entry(entries.next, Node, list));
699 mutex_unlock(&root->d_inode->i_mutex);
706 static const struct file_operations bm_status_operations = {
707 .read = bm_status_read,
708 .write = bm_status_write,
711 /* Superblock handling */
713 static const struct super_operations s_ops = {
714 .statfs = simple_statfs,
715 .clear_inode = bm_clear_inode,
718 static int bm_fill_super(struct super_block * sb, void * data, int silent)
720 static struct tree_descr bm_files[] = {
721 [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
722 [3] = {"register", &bm_register_operations, S_IWUSR},
725 int err = simple_fill_super(sb, 0x42494e4d, bm_files);
731 static int bm_get_sb(struct file_system_type *fs_type,
732 int flags, const char *dev_name, void *data, struct vfsmount *mnt)
734 return get_sb_single(fs_type, flags, data, bm_fill_super, mnt);
737 static struct linux_binfmt misc_format = {
738 .module = THIS_MODULE,
739 .load_binary = load_misc_binary,
742 static struct file_system_type bm_fs_type = {
743 .owner = THIS_MODULE,
744 .name = "binfmt_misc",
746 .kill_sb = kill_litter_super,
749 static int __init init_misc_binfmt(void)
751 int err = register_filesystem(&bm_fs_type);
753 err = register_binfmt(&misc_format);
755 unregister_filesystem(&bm_fs_type);
760 static void __exit exit_misc_binfmt(void)
762 unregister_binfmt(&misc_format);
763 unregister_filesystem(&bm_fs_type);
766 core_initcall(init_misc_binfmt);
767 module_exit(exit_misc_binfmt);
768 MODULE_LICENSE("GPL");