1 /*
2 * binfmt_misc.c
3 *
4 * Copyright (C) 1997 Richard Günther
5 *
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
8 * binfmt_mz.
9 *
10 * 1997-04-25 first version
11 * [...]
12 * 1997-05-19 cleanup
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.
17 */
18
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/string_helpers.h>
27 #include <linux/file.h>
28 #include <linux/pagemap.h>
29 #include <linux/namei.h>
30 #include <linux/mount.h>
31 #include <linux/syscalls.h>
32 #include <linux/fs.h>
33
34 #include <asm/uaccess.h>
35
36 enum {
37 VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
38 };
39
40 static LIST_HEAD(entries);
41 static int enabled = 1;
42
43 enum {Enabled, Magic};
44 #define MISC_FMT_PRESERVE_ARGV0 (1<<31)
45 #define MISC_FMT_OPEN_BINARY (1<<30)
46 #define MISC_FMT_CREDENTIALS (1<<29)
47
48 typedef struct {
49 struct list_head list;
50 unsigned long flags; /* type, status, etc. */
51 int offset; /* offset of magic */
52 int size; /* size of magic/mask */
53 char *magic; /* magic or filename extension */
54 char *mask; /* mask, NULL for exact match */
55 char *interpreter; /* filename of interpreter */
56 char *name;
57 struct dentry *dentry;
58 } Node;
59
60 static DEFINE_RWLOCK(entries_lock);
61 static struct file_system_type bm_fs_type;
62 static struct vfsmount *bm_mnt;
63 static int entry_count;
64
65 /*
66 * Max length of the register string. Determined by:
67 * - 7 delimiters
68 * - name: ~50 bytes
69 * - type: 1 byte
70 * - offset: 3 bytes (has to be smaller than BINPRM_BUF_SIZE)
71 * - magic: 128 bytes (512 in escaped form)
72 * - mask: 128 bytes (512 in escaped form)
73 * - interp: ~50 bytes
74 * - flags: 5 bytes
75 * Round that up a bit, and then back off to hold the internal data
76 * (like struct Node).
77 */
78 #define MAX_REGISTER_LENGTH 1920
79
80 /*
81 * Check if we support the binfmt
82 * if we do, return the node, else NULL
83 * locking is done in load_misc_binary
84 */
check_file(struct linux_binprm * bprm)85 static Node *check_file(struct linux_binprm *bprm)
86 {
87 char *p = strrchr(bprm->interp, '.');
88 struct list_head *l;
89
90 list_for_each(l, &entries) {
91 Node *e = list_entry(l, Node, list);
92 char *s;
93 int j;
94
95 if (!test_bit(Enabled, &e->flags))
96 continue;
97
98 if (!test_bit(Magic, &e->flags)) {
99 if (p && !strcmp(e->magic, p + 1))
100 return e;
101 continue;
102 }
103
104 s = bprm->buf + e->offset;
105 if (e->mask) {
106 for (j = 0; j < e->size; j++)
107 if ((*s++ ^ e->magic[j]) & e->mask[j])
108 break;
109 } else {
110 for (j = 0; j < e->size; j++)
111 if ((*s++ ^ e->magic[j]))
112 break;
113 }
114 if (j == e->size)
115 return e;
116 }
117 return NULL;
118 }
119
120 /*
121 * the loader itself
122 */
load_misc_binary(struct linux_binprm * bprm)123 static int load_misc_binary(struct linux_binprm *bprm)
124 {
125 Node *fmt;
126 struct file * interp_file = NULL;
127 char iname[BINPRM_BUF_SIZE];
128 const char *iname_addr = iname;
129 int retval;
130 int fd_binary = -1;
131
132 retval = -ENOEXEC;
133 if (!enabled)
134 goto _ret;
135
136 /* to keep locking time low, we copy the interpreter string */
137 read_lock(&entries_lock);
138 fmt = check_file(bprm);
139 if (fmt)
140 strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
141 read_unlock(&entries_lock);
142 if (!fmt)
143 goto _ret;
144
145 if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
146 retval = remove_arg_zero(bprm);
147 if (retval)
148 goto _ret;
149 }
150
151 if (fmt->flags & MISC_FMT_OPEN_BINARY) {
152
153 /* if the binary should be opened on behalf of the
154 * interpreter than keep it open and assign descriptor
155 * to it */
156 fd_binary = get_unused_fd();
157 if (fd_binary < 0) {
158 retval = fd_binary;
159 goto _ret;
160 }
161 fd_install(fd_binary, bprm->file);
162
163 /* if the binary is not readable than enforce mm->dumpable=0
164 regardless of the interpreter's permissions */
165 would_dump(bprm, bprm->file);
166
167 allow_write_access(bprm->file);
168 bprm->file = NULL;
169
170 /* mark the bprm that fd should be passed to interp */
171 bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
172 bprm->interp_data = fd_binary;
173
174 } else {
175 allow_write_access(bprm->file);
176 fput(bprm->file);
177 bprm->file = NULL;
178 }
179 /* make argv[1] be the path to the binary */
180 retval = copy_strings_kernel (1, &bprm->interp, bprm);
181 if (retval < 0)
182 goto _error;
183 bprm->argc++;
184
185 /* add the interp as argv[0] */
186 retval = copy_strings_kernel (1, &iname_addr, bprm);
187 if (retval < 0)
188 goto _error;
189 bprm->argc ++;
190
191 /* Update interp in case binfmt_script needs it. */
192 retval = bprm_change_interp(iname, bprm);
193 if (retval < 0)
194 goto _error;
195
196 interp_file = open_exec (iname);
197 retval = PTR_ERR (interp_file);
198 if (IS_ERR (interp_file))
199 goto _error;
200
201 bprm->file = interp_file;
202 if (fmt->flags & MISC_FMT_CREDENTIALS) {
203 /*
204 * No need to call prepare_binprm(), it's already been
205 * done. bprm->buf is stale, update from interp_file.
206 */
207 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
208 retval = kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
209 } else
210 retval = prepare_binprm (bprm);
211
212 if (retval < 0)
213 goto _error;
214
215 retval = search_binary_handler(bprm);
216 if (retval < 0)
217 goto _error;
218
219 _ret:
220 return retval;
221 _error:
222 if (fd_binary > 0)
223 sys_close(fd_binary);
224 bprm->interp_flags = 0;
225 bprm->interp_data = 0;
226 goto _ret;
227 }
228
229 /* Command parsers */
230
231 /*
232 * parses and copies one argument enclosed in del from *sp to *dp,
233 * recognising the \x special.
234 * returns pointer to the copied argument or NULL in case of an
235 * error (and sets err) or null argument length.
236 */
scanarg(char * s,char del)237 static char *scanarg(char *s, char del)
238 {
239 char c;
240
241 while ((c = *s++) != del) {
242 if (c == '\\' && *s == 'x') {
243 s++;
244 if (!isxdigit(*s++))
245 return NULL;
246 if (!isxdigit(*s++))
247 return NULL;
248 }
249 }
250 return s;
251 }
252
check_special_flags(char * sfs,Node * e)253 static char * check_special_flags (char * sfs, Node * e)
254 {
255 char * p = sfs;
256 int cont = 1;
257
258 /* special flags */
259 while (cont) {
260 switch (*p) {
261 case 'P':
262 p++;
263 e->flags |= MISC_FMT_PRESERVE_ARGV0;
264 break;
265 case 'O':
266 p++;
267 e->flags |= MISC_FMT_OPEN_BINARY;
268 break;
269 case 'C':
270 p++;
271 /* this flags also implies the
272 open-binary flag */
273 e->flags |= (MISC_FMT_CREDENTIALS |
274 MISC_FMT_OPEN_BINARY);
275 break;
276 default:
277 cont = 0;
278 }
279 }
280
281 return p;
282 }
283 /*
284 * This registers a new binary format, it recognises the syntax
285 * ':name:type:offset:magic:mask:interpreter:flags'
286 * where the ':' is the IFS, that can be chosen with the first char
287 */
create_entry(const char __user * buffer,size_t count)288 static Node *create_entry(const char __user *buffer, size_t count)
289 {
290 Node *e;
291 int memsize, err;
292 char *buf, *p;
293 char del;
294
295 /* some sanity checks */
296 err = -EINVAL;
297 if ((count < 11) || (count > MAX_REGISTER_LENGTH))
298 goto out;
299
300 err = -ENOMEM;
301 memsize = sizeof(Node) + count + 8;
302 e = kmalloc(memsize, GFP_USER);
303 if (!e)
304 goto out;
305
306 p = buf = (char *)e + sizeof(Node);
307
308 memset(e, 0, sizeof(Node));
309 if (copy_from_user(buf, buffer, count))
310 goto Efault;
311
312 del = *p++; /* delimeter */
313
314 memset(buf+count, del, 8);
315
316 e->name = p;
317 p = strchr(p, del);
318 if (!p)
319 goto Einval;
320 *p++ = '\0';
321 if (!e->name[0] ||
322 !strcmp(e->name, ".") ||
323 !strcmp(e->name, "..") ||
324 strchr(e->name, '/'))
325 goto Einval;
326 switch (*p++) {
327 case 'E': e->flags = 1<<Enabled; break;
328 case 'M': e->flags = (1<<Enabled) | (1<<Magic); break;
329 default: goto Einval;
330 }
331 if (*p++ != del)
332 goto Einval;
333 if (test_bit(Magic, &e->flags)) {
334 char *s = strchr(p, del);
335 if (!s)
336 goto Einval;
337 *s++ = '\0';
338 e->offset = simple_strtoul(p, &p, 10);
339 if (*p++)
340 goto Einval;
341 e->magic = p;
342 p = scanarg(p, del);
343 if (!p)
344 goto Einval;
345 p[-1] = '\0';
346 if (!e->magic[0])
347 goto Einval;
348 e->mask = p;
349 p = scanarg(p, del);
350 if (!p)
351 goto Einval;
352 p[-1] = '\0';
353 if (!e->mask[0])
354 e->mask = NULL;
355 e->size = string_unescape_inplace(e->magic, UNESCAPE_HEX);
356 if (e->mask &&
357 string_unescape_inplace(e->mask, UNESCAPE_HEX) != e->size)
358 goto Einval;
359 if (e->size + e->offset > BINPRM_BUF_SIZE)
360 goto Einval;
361 } else {
362 p = strchr(p, del);
363 if (!p)
364 goto Einval;
365 *p++ = '\0';
366 e->magic = p;
367 p = strchr(p, del);
368 if (!p)
369 goto Einval;
370 *p++ = '\0';
371 if (!e->magic[0] || strchr(e->magic, '/'))
372 goto Einval;
373 p = strchr(p, del);
374 if (!p)
375 goto Einval;
376 *p++ = '\0';
377 }
378 e->interpreter = p;
379 p = strchr(p, del);
380 if (!p)
381 goto Einval;
382 *p++ = '\0';
383 if (!e->interpreter[0])
384 goto Einval;
385
386
387 p = check_special_flags (p, e);
388
389 if (*p == '\n')
390 p++;
391 if (p != buf + count)
392 goto Einval;
393 return e;
394
395 out:
396 return ERR_PTR(err);
397
398 Efault:
399 kfree(e);
400 return ERR_PTR(-EFAULT);
401 Einval:
402 kfree(e);
403 return ERR_PTR(-EINVAL);
404 }
405
406 /*
407 * Set status of entry/binfmt_misc:
408 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
409 */
parse_command(const char __user * buffer,size_t count)410 static int parse_command(const char __user *buffer, size_t count)
411 {
412 char s[4];
413
414 if (count > 3)
415 return -EINVAL;
416 if (copy_from_user(s, buffer, count))
417 return -EFAULT;
418 if (!count)
419 return 0;
420 if (s[count-1] == '\n')
421 count--;
422 if (count == 1 && s[0] == '0')
423 return 1;
424 if (count == 1 && s[0] == '1')
425 return 2;
426 if (count == 2 && s[0] == '-' && s[1] == '1')
427 return 3;
428 return -EINVAL;
429 }
430
431 /* generic stuff */
432
entry_status(Node * e,char * page)433 static void entry_status(Node *e, char *page)
434 {
435 char *dp;
436 char *status = "disabled";
437 const char * flags = "flags: ";
438
439 if (test_bit(Enabled, &e->flags))
440 status = "enabled";
441
442 if (!VERBOSE_STATUS) {
443 sprintf(page, "%s\n", status);
444 return;
445 }
446
447 sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter);
448 dp = page + strlen(page);
449
450 /* print the special flags */
451 sprintf (dp, "%s", flags);
452 dp += strlen (flags);
453 if (e->flags & MISC_FMT_PRESERVE_ARGV0) {
454 *dp ++ = 'P';
455 }
456 if (e->flags & MISC_FMT_OPEN_BINARY) {
457 *dp ++ = 'O';
458 }
459 if (e->flags & MISC_FMT_CREDENTIALS) {
460 *dp ++ = 'C';
461 }
462 *dp ++ = '\n';
463
464
465 if (!test_bit(Magic, &e->flags)) {
466 sprintf(dp, "extension .%s\n", e->magic);
467 } else {
468 int i;
469
470 sprintf(dp, "offset %i\nmagic ", e->offset);
471 dp = page + strlen(page);
472 for (i = 0; i < e->size; i++) {
473 sprintf(dp, "%02x", 0xff & (int) (e->magic[i]));
474 dp += 2;
475 }
476 if (e->mask) {
477 sprintf(dp, "\nmask ");
478 dp += 6;
479 for (i = 0; i < e->size; i++) {
480 sprintf(dp, "%02x", 0xff & (int) (e->mask[i]));
481 dp += 2;
482 }
483 }
484 *dp++ = '\n';
485 *dp = '\0';
486 }
487 }
488
bm_get_inode(struct super_block * sb,int mode)489 static struct inode *bm_get_inode(struct super_block *sb, int mode)
490 {
491 struct inode * inode = new_inode(sb);
492
493 if (inode) {
494 inode->i_ino = get_next_ino();
495 inode->i_mode = mode;
496 inode->i_atime = inode->i_mtime = inode->i_ctime =
497 current_fs_time(inode->i_sb);
498 }
499 return inode;
500 }
501
bm_evict_inode(struct inode * inode)502 static void bm_evict_inode(struct inode *inode)
503 {
504 clear_inode(inode);
505 kfree(inode->i_private);
506 }
507
kill_node(Node * e)508 static void kill_node(Node *e)
509 {
510 struct dentry *dentry;
511
512 write_lock(&entries_lock);
513 dentry = e->dentry;
514 if (dentry) {
515 list_del_init(&e->list);
516 e->dentry = NULL;
517 }
518 write_unlock(&entries_lock);
519
520 if (dentry) {
521 drop_nlink(dentry->d_inode);
522 d_drop(dentry);
523 dput(dentry);
524 simple_release_fs(&bm_mnt, &entry_count);
525 }
526 }
527
528 /* /<entry> */
529
530 static ssize_t
bm_entry_read(struct file * file,char __user * buf,size_t nbytes,loff_t * ppos)531 bm_entry_read(struct file * file, char __user * buf, size_t nbytes, loff_t *ppos)
532 {
533 Node *e = file_inode(file)->i_private;
534 ssize_t res;
535 char *page;
536
537 if (!(page = (char*) __get_free_page(GFP_KERNEL)))
538 return -ENOMEM;
539
540 entry_status(e, page);
541
542 res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
543
544 free_page((unsigned long) page);
545 return res;
546 }
547
bm_entry_write(struct file * file,const char __user * buffer,size_t count,loff_t * ppos)548 static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
549 size_t count, loff_t *ppos)
550 {
551 struct dentry *root;
552 Node *e = file_inode(file)->i_private;
553 int res = parse_command(buffer, count);
554
555 switch (res) {
556 case 1: clear_bit(Enabled, &e->flags);
557 break;
558 case 2: set_bit(Enabled, &e->flags);
559 break;
560 case 3: root = dget(file->f_path.dentry->d_sb->s_root);
561 mutex_lock(&root->d_inode->i_mutex);
562
563 kill_node(e);
564
565 mutex_unlock(&root->d_inode->i_mutex);
566 dput(root);
567 break;
568 default: return res;
569 }
570 return count;
571 }
572
573 static const struct file_operations bm_entry_operations = {
574 .read = bm_entry_read,
575 .write = bm_entry_write,
576 .llseek = default_llseek,
577 };
578
579 /* /register */
580
bm_register_write(struct file * file,const char __user * buffer,size_t count,loff_t * ppos)581 static ssize_t bm_register_write(struct file *file, const char __user *buffer,
582 size_t count, loff_t *ppos)
583 {
584 Node *e;
585 struct inode *inode;
586 struct dentry *root, *dentry;
587 struct super_block *sb = file->f_path.dentry->d_sb;
588 int err = 0;
589
590 e = create_entry(buffer, count);
591
592 if (IS_ERR(e))
593 return PTR_ERR(e);
594
595 root = dget(sb->s_root);
596 mutex_lock(&root->d_inode->i_mutex);
597 dentry = lookup_one_len(e->name, root, strlen(e->name));
598 err = PTR_ERR(dentry);
599 if (IS_ERR(dentry))
600 goto out;
601
602 err = -EEXIST;
603 if (dentry->d_inode)
604 goto out2;
605
606 inode = bm_get_inode(sb, S_IFREG | 0644);
607
608 err = -ENOMEM;
609 if (!inode)
610 goto out2;
611
612 err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
613 if (err) {
614 iput(inode);
615 inode = NULL;
616 goto out2;
617 }
618
619 e->dentry = dget(dentry);
620 inode->i_private = e;
621 inode->i_fop = &bm_entry_operations;
622
623 d_instantiate(dentry, inode);
624 write_lock(&entries_lock);
625 list_add(&e->list, &entries);
626 write_unlock(&entries_lock);
627
628 err = 0;
629 out2:
630 dput(dentry);
631 out:
632 mutex_unlock(&root->d_inode->i_mutex);
633 dput(root);
634
635 if (err) {
636 kfree(e);
637 return -EINVAL;
638 }
639 return count;
640 }
641
642 static const struct file_operations bm_register_operations = {
643 .write = bm_register_write,
644 .llseek = noop_llseek,
645 };
646
647 /* /status */
648
649 static ssize_t
bm_status_read(struct file * file,char __user * buf,size_t nbytes,loff_t * ppos)650 bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
651 {
652 char *s = enabled ? "enabled\n" : "disabled\n";
653
654 return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
655 }
656
bm_status_write(struct file * file,const char __user * buffer,size_t count,loff_t * ppos)657 static ssize_t bm_status_write(struct file * file, const char __user * buffer,
658 size_t count, loff_t *ppos)
659 {
660 int res = parse_command(buffer, count);
661 struct dentry *root;
662
663 switch (res) {
664 case 1: enabled = 0; break;
665 case 2: enabled = 1; break;
666 case 3: root = dget(file->f_path.dentry->d_sb->s_root);
667 mutex_lock(&root->d_inode->i_mutex);
668
669 while (!list_empty(&entries))
670 kill_node(list_entry(entries.next, Node, list));
671
672 mutex_unlock(&root->d_inode->i_mutex);
673 dput(root);
674 break;
675 default: return res;
676 }
677 return count;
678 }
679
680 static const struct file_operations bm_status_operations = {
681 .read = bm_status_read,
682 .write = bm_status_write,
683 .llseek = default_llseek,
684 };
685
686 /* Superblock handling */
687
688 static const struct super_operations s_ops = {
689 .statfs = simple_statfs,
690 .evict_inode = bm_evict_inode,
691 };
692
bm_fill_super(struct super_block * sb,void * data,int silent)693 static int bm_fill_super(struct super_block * sb, void * data, int silent)
694 {
695 static struct tree_descr bm_files[] = {
696 [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
697 [3] = {"register", &bm_register_operations, S_IWUSR},
698 /* last one */ {""}
699 };
700 int err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files);
701 if (!err)
702 sb->s_op = &s_ops;
703 return err;
704 }
705
bm_mount(struct file_system_type * fs_type,int flags,const char * dev_name,void * data)706 static struct dentry *bm_mount(struct file_system_type *fs_type,
707 int flags, const char *dev_name, void *data)
708 {
709 return mount_single(fs_type, flags, data, bm_fill_super);
710 }
711
712 static struct linux_binfmt misc_format = {
713 .module = THIS_MODULE,
714 .load_binary = load_misc_binary,
715 };
716
717 static struct file_system_type bm_fs_type = {
718 .owner = THIS_MODULE,
719 .name = "binfmt_misc",
720 .mount = bm_mount,
721 .kill_sb = kill_litter_super,
722 };
723 MODULE_ALIAS_FS("binfmt_misc");
724
init_misc_binfmt(void)725 static int __init init_misc_binfmt(void)
726 {
727 int err = register_filesystem(&bm_fs_type);
728 if (!err)
729 insert_binfmt(&misc_format);
730 return err;
731 }
732
exit_misc_binfmt(void)733 static void __exit exit_misc_binfmt(void)
734 {
735 unregister_binfmt(&misc_format);
736 unregister_filesystem(&bm_fs_type);
737 }
738
739 core_initcall(init_misc_binfmt);
740 module_exit(exit_misc_binfmt);
741 MODULE_LICENSE("GPL");
742