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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. See Documentation/binfmt_misc.txt for more details.
8 */
9
10#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11
12#include <linux/kernel.h>
13#include <linux/module.h>
14#include <linux/init.h>
15#include <linux/sched.h>
16#include <linux/magic.h>
17#include <linux/binfmts.h>
18#include <linux/slab.h>
19#include <linux/ctype.h>
20#include <linux/string_helpers.h>
21#include <linux/file.h>
22#include <linux/pagemap.h>
23#include <linux/namei.h>
24#include <linux/mount.h>
25#include <linux/syscalls.h>
26#include <linux/fs.h>
27#include <linux/uaccess.h>
28
29#include "internal.h"
30
31#ifdef DEBUG
32# define USE_DEBUG 1
33#else
34# define USE_DEBUG 0
35#endif
36
37enum {
38 VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
39};
40
41static LIST_HEAD(entries);
42static int enabled = 1;
43
44enum {Enabled, Magic};
45#define MISC_FMT_PRESERVE_ARGV0 (1 << 31)
46#define MISC_FMT_OPEN_BINARY (1 << 30)
47#define MISC_FMT_CREDENTIALS (1 << 29)
48#define MISC_FMT_OPEN_FILE (1 << 28)
49
50typedef struct {
51 struct list_head list;
52 unsigned long flags; /* type, status, etc. */
53 int offset; /* offset of magic */
54 int size; /* size of magic/mask */
55 char *magic; /* magic or filename extension */
56 char *mask; /* mask, NULL for exact match */
57 char *interpreter; /* filename of interpreter */
58 char *name;
59 struct dentry *dentry;
60 struct file *interp_file;
61} Node;
62
63static DEFINE_RWLOCK(entries_lock);
64static struct file_system_type bm_fs_type;
65static struct vfsmount *bm_mnt;
66static int entry_count;
67
68/*
69 * Max length of the register string. Determined by:
70 * - 7 delimiters
71 * - name: ~50 bytes
72 * - type: 1 byte
73 * - offset: 3 bytes (has to be smaller than BINPRM_BUF_SIZE)
74 * - magic: 128 bytes (512 in escaped form)
75 * - mask: 128 bytes (512 in escaped form)
76 * - interp: ~50 bytes
77 * - flags: 5 bytes
78 * Round that up a bit, and then back off to hold the internal data
79 * (like struct Node).
80 */
81#define MAX_REGISTER_LENGTH 1920
82
83/*
84 * Check if we support the binfmt
85 * if we do, return the node, else NULL
86 * locking is done in load_misc_binary
87 */
88static Node *check_file(struct linux_binprm *bprm)
89{
90 char *p = strrchr(bprm->interp, '.');
91 struct list_head *l;
92
93 /* Walk all the registered handlers. */
94 list_for_each(l, &entries) {
95 Node *e = list_entry(l, Node, list);
96 char *s;
97 int j;
98
99 /* Make sure this one is currently enabled. */
100 if (!test_bit(Enabled, &e->flags))
101 continue;
102
103 /* Do matching based on extension if applicable. */
104 if (!test_bit(Magic, &e->flags)) {
105 if (p && !strcmp(e->magic, p + 1))
106 return e;
107 continue;
108 }
109
110 /* Do matching based on magic & mask. */
111 s = bprm->buf + e->offset;
112 if (e->mask) {
113 for (j = 0; j < e->size; j++)
114 if ((*s++ ^ e->magic[j]) & e->mask[j])
115 break;
116 } else {
117 for (j = 0; j < e->size; j++)
118 if ((*s++ ^ e->magic[j]))
119 break;
120 }
121 if (j == e->size)
122 return e;
123 }
124 return NULL;
125}
126
127/*
128 * the loader itself
129 */
130static int load_misc_binary(struct linux_binprm *bprm)
131{
132 Node *fmt;
133 struct file *interp_file = NULL;
134 char iname[BINPRM_BUF_SIZE];
135 const char *iname_addr = iname;
136 int retval;
137 int fd_binary = -1;
138
139 retval = -ENOEXEC;
140 if (!enabled)
141 goto ret;
142
143 /* to keep locking time low, we copy the interpreter string */
144 read_lock(&entries_lock);
145 fmt = check_file(bprm);
146 if (fmt)
147 strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
148 read_unlock(&entries_lock);
149 if (!fmt)
150 goto ret;
151
152 /* Need to be able to load the file after exec */
153 if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
154 return -ENOENT;
155
156 if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
157 retval = remove_arg_zero(bprm);
158 if (retval)
159 goto ret;
160 }
161
162 if (fmt->flags & MISC_FMT_OPEN_BINARY) {
163
164 /* if the binary should be opened on behalf of the
165 * interpreter than keep it open and assign descriptor
166 * to it
167 */
168 fd_binary = get_unused_fd_flags(0);
169 if (fd_binary < 0) {
170 retval = fd_binary;
171 goto ret;
172 }
173 fd_install(fd_binary, bprm->file);
174
175 /* if the binary is not readable than enforce mm->dumpable=0
176 regardless of the interpreter's permissions */
177 would_dump(bprm, bprm->file);
178
179 allow_write_access(bprm->file);
180 bprm->file = NULL;
181
182 /* mark the bprm that fd should be passed to interp */
183 bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
184 bprm->interp_data = fd_binary;
185
186 } else {
187 allow_write_access(bprm->file);
188 fput(bprm->file);
189 bprm->file = NULL;
190 }
191 /* make argv[1] be the path to the binary */
192 retval = copy_strings_kernel(1, &bprm->interp, bprm);
193 if (retval < 0)
194 goto error;
195 bprm->argc++;
196
197 /* add the interp as argv[0] */
198 retval = copy_strings_kernel(1, &iname_addr, bprm);
199 if (retval < 0)
200 goto error;
201 bprm->argc++;
202
203 /* Update interp in case binfmt_script needs it. */
204 retval = bprm_change_interp(iname, bprm);
205 if (retval < 0)
206 goto error;
207
208 if (fmt->flags & MISC_FMT_OPEN_FILE && fmt->interp_file) {
209 interp_file = filp_clone_open(fmt->interp_file);
210 if (!IS_ERR(interp_file))
211 deny_write_access(interp_file);
212 } else {
213 interp_file = open_exec(iname);
214 }
215 retval = PTR_ERR(interp_file);
216 if (IS_ERR(interp_file))
217 goto error;
218
219 bprm->file = interp_file;
220 if (fmt->flags & MISC_FMT_CREDENTIALS) {
221 /*
222 * No need to call prepare_binprm(), it's already been
223 * done. bprm->buf is stale, update from interp_file.
224 */
225 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
226 retval = kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
227 } else
228 retval = prepare_binprm(bprm);
229
230 if (retval < 0)
231 goto error;
232
233 retval = search_binary_handler(bprm);
234 if (retval < 0)
235 goto error;
236
237ret:
238 return retval;
239error:
240 if (fd_binary > 0)
241 sys_close(fd_binary);
242 bprm->interp_flags = 0;
243 bprm->interp_data = 0;
244 goto ret;
245}
246
247/* Command parsers */
248
249/*
250 * parses and copies one argument enclosed in del from *sp to *dp,
251 * recognising the \x special.
252 * returns pointer to the copied argument or NULL in case of an
253 * error (and sets err) or null argument length.
254 */
255static char *scanarg(char *s, char del)
256{
257 char c;
258
259 while ((c = *s++) != del) {
260 if (c == '\\' && *s == 'x') {
261 s++;
262 if (!isxdigit(*s++))
263 return NULL;
264 if (!isxdigit(*s++))
265 return NULL;
266 }
267 }
268 s[-1] ='\0';
269 return s;
270}
271
272static char *check_special_flags(char *sfs, Node *e)
273{
274 char *p = sfs;
275 int cont = 1;
276
277 /* special flags */
278 while (cont) {
279 switch (*p) {
280 case 'P':
281 pr_debug("register: flag: P (preserve argv0)\n");
282 p++;
283 e->flags |= MISC_FMT_PRESERVE_ARGV0;
284 break;
285 case 'O':
286 pr_debug("register: flag: O (open binary)\n");
287 p++;
288 e->flags |= MISC_FMT_OPEN_BINARY;
289 break;
290 case 'C':
291 pr_debug("register: flag: C (preserve creds)\n");
292 p++;
293 /* this flags also implies the
294 open-binary flag */
295 e->flags |= (MISC_FMT_CREDENTIALS |
296 MISC_FMT_OPEN_BINARY);
297 break;
298 case 'F':
299 pr_debug("register: flag: F: open interpreter file now\n");
300 p++;
301 e->flags |= MISC_FMT_OPEN_FILE;
302 break;
303 default:
304 cont = 0;
305 }
306 }
307
308 return p;
309}
310
311/*
312 * This registers a new binary format, it recognises the syntax
313 * ':name:type:offset:magic:mask:interpreter:flags'
314 * where the ':' is the IFS, that can be chosen with the first char
315 */
316static Node *create_entry(const char __user *buffer, size_t count)
317{
318 Node *e;
319 int memsize, err;
320 char *buf, *p;
321 char del;
322
323 pr_debug("register: received %zu bytes\n", count);
324
325 /* some sanity checks */
326 err = -EINVAL;
327 if ((count < 11) || (count > MAX_REGISTER_LENGTH))
328 goto out;
329
330 err = -ENOMEM;
331 memsize = sizeof(Node) + count + 8;
332 e = kmalloc(memsize, GFP_KERNEL);
333 if (!e)
334 goto out;
335
336 p = buf = (char *)e + sizeof(Node);
337
338 memset(e, 0, sizeof(Node));
339 if (copy_from_user(buf, buffer, count))
340 goto efault;
341
342 del = *p++; /* delimeter */
343
344 pr_debug("register: delim: %#x {%c}\n", del, del);
345
346 /* Pad the buffer with the delim to simplify parsing below. */
347 memset(buf + count, del, 8);
348
349 /* Parse the 'name' field. */
350 e->name = p;
351 p = strchr(p, del);
352 if (!p)
353 goto einval;
354 *p++ = '\0';
355 if (!e->name[0] ||
356 !strcmp(e->name, ".") ||
357 !strcmp(e->name, "..") ||
358 strchr(e->name, '/'))
359 goto einval;
360
361 pr_debug("register: name: {%s}\n", e->name);
362
363 /* Parse the 'type' field. */
364 switch (*p++) {
365 case 'E':
366 pr_debug("register: type: E (extension)\n");
367 e->flags = 1 << Enabled;
368 break;
369 case 'M':
370 pr_debug("register: type: M (magic)\n");
371 e->flags = (1 << Enabled) | (1 << Magic);
372 break;
373 default:
374 goto einval;
375 }
376 if (*p++ != del)
377 goto einval;
378
379 if (test_bit(Magic, &e->flags)) {
380 /* Handle the 'M' (magic) format. */
381 char *s;
382
383 /* Parse the 'offset' field. */
384 s = strchr(p, del);
385 if (!s)
386 goto einval;
387 *s++ = '\0';
388 e->offset = simple_strtoul(p, &p, 10);
389 if (*p++)
390 goto einval;
391 pr_debug("register: offset: %#x\n", e->offset);
392
393 /* Parse the 'magic' field. */
394 e->magic = p;
395 p = scanarg(p, del);
396 if (!p)
397 goto einval;
398 if (!e->magic[0])
399 goto einval;
400 if (USE_DEBUG)
401 print_hex_dump_bytes(
402 KBUILD_MODNAME ": register: magic[raw]: ",
403 DUMP_PREFIX_NONE, e->magic, p - e->magic);
404
405 /* Parse the 'mask' field. */
406 e->mask = p;
407 p = scanarg(p, del);
408 if (!p)
409 goto einval;
410 if (!e->mask[0]) {
411 e->mask = NULL;
412 pr_debug("register: mask[raw]: none\n");
413 } else if (USE_DEBUG)
414 print_hex_dump_bytes(
415 KBUILD_MODNAME ": register: mask[raw]: ",
416 DUMP_PREFIX_NONE, e->mask, p - e->mask);
417
418 /*
419 * Decode the magic & mask fields.
420 * Note: while we might have accepted embedded NUL bytes from
421 * above, the unescape helpers here will stop at the first one
422 * it encounters.
423 */
424 e->size = string_unescape_inplace(e->magic, UNESCAPE_HEX);
425 if (e->mask &&
426 string_unescape_inplace(e->mask, UNESCAPE_HEX) != e->size)
427 goto einval;
428 if (e->size + e->offset > BINPRM_BUF_SIZE)
429 goto einval;
430 pr_debug("register: magic/mask length: %i\n", e->size);
431 if (USE_DEBUG) {
432 print_hex_dump_bytes(
433 KBUILD_MODNAME ": register: magic[decoded]: ",
434 DUMP_PREFIX_NONE, e->magic, e->size);
435
436 if (e->mask) {
437 int i;
438 char *masked = kmalloc(e->size, GFP_KERNEL);
439
440 print_hex_dump_bytes(
441 KBUILD_MODNAME ": register: mask[decoded]: ",
442 DUMP_PREFIX_NONE, e->mask, e->size);
443
444 if (masked) {
445 for (i = 0; i < e->size; ++i)
446 masked[i] = e->magic[i] & e->mask[i];
447 print_hex_dump_bytes(
448 KBUILD_MODNAME ": register: magic[masked]: ",
449 DUMP_PREFIX_NONE, masked, e->size);
450
451 kfree(masked);
452 }
453 }
454 }
455 } else {
456 /* Handle the 'E' (extension) format. */
457
458 /* Skip the 'offset' field. */
459 p = strchr(p, del);
460 if (!p)
461 goto einval;
462 *p++ = '\0';
463
464 /* Parse the 'magic' field. */
465 e->magic = p;
466 p = strchr(p, del);
467 if (!p)
468 goto einval;
469 *p++ = '\0';
470 if (!e->magic[0] || strchr(e->magic, '/'))
471 goto einval;
472 pr_debug("register: extension: {%s}\n", e->magic);
473
474 /* Skip the 'mask' field. */
475 p = strchr(p, del);
476 if (!p)
477 goto einval;
478 *p++ = '\0';
479 }
480
481 /* Parse the 'interpreter' field. */
482 e->interpreter = p;
483 p = strchr(p, del);
484 if (!p)
485 goto einval;
486 *p++ = '\0';
487 if (!e->interpreter[0])
488 goto einval;
489 pr_debug("register: interpreter: {%s}\n", e->interpreter);
490
491 /* Parse the 'flags' field. */
492 p = check_special_flags(p, e);
493 if (*p == '\n')
494 p++;
495 if (p != buf + count)
496 goto einval;
497
498 return e;
499
500out:
501 return ERR_PTR(err);
502
503efault:
504 kfree(e);
505 return ERR_PTR(-EFAULT);
506einval:
507 kfree(e);
508 return ERR_PTR(-EINVAL);
509}
510
511/*
512 * Set status of entry/binfmt_misc:
513 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
514 */
515static int parse_command(const char __user *buffer, size_t count)
516{
517 char s[4];
518
519 if (count > 3)
520 return -EINVAL;
521 if (copy_from_user(s, buffer, count))
522 return -EFAULT;
523 if (!count)
524 return 0;
525 if (s[count - 1] == '\n')
526 count--;
527 if (count == 1 && s[0] == '0')
528 return 1;
529 if (count == 1 && s[0] == '1')
530 return 2;
531 if (count == 2 && s[0] == '-' && s[1] == '1')
532 return 3;
533 return -EINVAL;
534}
535
536/* generic stuff */
537
538static void entry_status(Node *e, char *page)
539{
540 char *dp = page;
541 const char *status = "disabled";
542
543 if (test_bit(Enabled, &e->flags))
544 status = "enabled";
545
546 if (!VERBOSE_STATUS) {
547 sprintf(page, "%s\n", status);
548 return;
549 }
550
551 dp += sprintf(dp, "%s\ninterpreter %s\n", status, e->interpreter);
552
553 /* print the special flags */
554 dp += sprintf(dp, "flags: ");
555 if (e->flags & MISC_FMT_PRESERVE_ARGV0)
556 *dp++ = 'P';
557 if (e->flags & MISC_FMT_OPEN_BINARY)
558 *dp++ = 'O';
559 if (e->flags & MISC_FMT_CREDENTIALS)
560 *dp++ = 'C';
561 if (e->flags & MISC_FMT_OPEN_FILE)
562 *dp++ = 'F';
563 *dp++ = '\n';
564
565 if (!test_bit(Magic, &e->flags)) {
566 sprintf(dp, "extension .%s\n", e->magic);
567 } else {
568 dp += sprintf(dp, "offset %i\nmagic ", e->offset);
569 dp = bin2hex(dp, e->magic, e->size);
570 if (e->mask) {
571 dp += sprintf(dp, "\nmask ");
572 dp = bin2hex(dp, e->mask, e->size);
573 }
574 *dp++ = '\n';
575 *dp = '\0';
576 }
577}
578
579static struct inode *bm_get_inode(struct super_block *sb, int mode)
580{
581 struct inode *inode = new_inode(sb);
582
583 if (inode) {
584 inode->i_ino = get_next_ino();
585 inode->i_mode = mode;
586 inode->i_atime = inode->i_mtime = inode->i_ctime =
587 current_time(inode);
588 }
589 return inode;
590}
591
592static void bm_evict_inode(struct inode *inode)
593{
594 clear_inode(inode);
595 kfree(inode->i_private);
596}
597
598static void kill_node(Node *e)
599{
600 struct dentry *dentry;
601
602 write_lock(&entries_lock);
603 dentry = e->dentry;
604 if (dentry) {
605 list_del_init(&e->list);
606 e->dentry = NULL;
607 }
608 write_unlock(&entries_lock);
609
610 if ((e->flags & MISC_FMT_OPEN_FILE) && e->interp_file) {
611 filp_close(e->interp_file, NULL);
612 e->interp_file = NULL;
613 }
614
615 if (dentry) {
616 drop_nlink(d_inode(dentry));
617 d_drop(dentry);
618 dput(dentry);
619 simple_release_fs(&bm_mnt, &entry_count);
620 }
621}
622
623/* /<entry> */
624
625static ssize_t
626bm_entry_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
627{
628 Node *e = file_inode(file)->i_private;
629 ssize_t res;
630 char *page;
631
632 page = (char *) __get_free_page(GFP_KERNEL);
633 if (!page)
634 return -ENOMEM;
635
636 entry_status(e, page);
637
638 res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
639
640 free_page((unsigned long) page);
641 return res;
642}
643
644static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
645 size_t count, loff_t *ppos)
646{
647 struct dentry *root;
648 Node *e = file_inode(file)->i_private;
649 int res = parse_command(buffer, count);
650
651 switch (res) {
652 case 1:
653 /* Disable this handler. */
654 clear_bit(Enabled, &e->flags);
655 break;
656 case 2:
657 /* Enable this handler. */
658 set_bit(Enabled, &e->flags);
659 break;
660 case 3:
661 /* Delete this handler. */
662 root = file_inode(file)->i_sb->s_root;
663 inode_lock(d_inode(root));
664
665 kill_node(e);
666
667 inode_unlock(d_inode(root));
668 break;
669 default:
670 return res;
671 }
672
673 return count;
674}
675
676static const struct file_operations bm_entry_operations = {
677 .read = bm_entry_read,
678 .write = bm_entry_write,
679 .llseek = default_llseek,
680};
681
682/* /register */
683
684static ssize_t bm_register_write(struct file *file, const char __user *buffer,
685 size_t count, loff_t *ppos)
686{
687 Node *e;
688 struct inode *inode;
689 struct super_block *sb = file_inode(file)->i_sb;
690 struct dentry *root = sb->s_root, *dentry;
691 int err = 0;
692
693 e = create_entry(buffer, count);
694
695 if (IS_ERR(e))
696 return PTR_ERR(e);
697
698 inode_lock(d_inode(root));
699 dentry = lookup_one_len(e->name, root, strlen(e->name));
700 err = PTR_ERR(dentry);
701 if (IS_ERR(dentry))
702 goto out;
703
704 err = -EEXIST;
705 if (d_really_is_positive(dentry))
706 goto out2;
707
708 inode = bm_get_inode(sb, S_IFREG | 0644);
709
710 err = -ENOMEM;
711 if (!inode)
712 goto out2;
713
714 err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
715 if (err) {
716 iput(inode);
717 inode = NULL;
718 goto out2;
719 }
720
721 if (e->flags & MISC_FMT_OPEN_FILE) {
722 struct file *f;
723
724 f = open_exec(e->interpreter);
725 if (IS_ERR(f)) {
726 err = PTR_ERR(f);
727 pr_notice("register: failed to install interpreter file %s\n", e->interpreter);
728 simple_release_fs(&bm_mnt, &entry_count);
729 iput(inode);
730 inode = NULL;
731 goto out2;
732 }
733 e->interp_file = f;
734 }
735
736 e->dentry = dget(dentry);
737 inode->i_private = e;
738 inode->i_fop = &bm_entry_operations;
739
740 d_instantiate(dentry, inode);
741 write_lock(&entries_lock);
742 list_add(&e->list, &entries);
743 write_unlock(&entries_lock);
744
745 err = 0;
746out2:
747 dput(dentry);
748out:
749 inode_unlock(d_inode(root));
750
751 if (err) {
752 kfree(e);
753 return err;
754 }
755 return count;
756}
757
758static const struct file_operations bm_register_operations = {
759 .write = bm_register_write,
760 .llseek = noop_llseek,
761};
762
763/* /status */
764
765static ssize_t
766bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
767{
768 char *s = enabled ? "enabled\n" : "disabled\n";
769
770 return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
771}
772
773static ssize_t bm_status_write(struct file *file, const char __user *buffer,
774 size_t count, loff_t *ppos)
775{
776 int res = parse_command(buffer, count);
777 struct dentry *root;
778
779 switch (res) {
780 case 1:
781 /* Disable all handlers. */
782 enabled = 0;
783 break;
784 case 2:
785 /* Enable all handlers. */
786 enabled = 1;
787 break;
788 case 3:
789 /* Delete all handlers. */
790 root = file_inode(file)->i_sb->s_root;
791 inode_lock(d_inode(root));
792
793 while (!list_empty(&entries))
794 kill_node(list_entry(entries.next, Node, list));
795
796 inode_unlock(d_inode(root));
797 break;
798 default:
799 return res;
800 }
801
802 return count;
803}
804
805static const struct file_operations bm_status_operations = {
806 .read = bm_status_read,
807 .write = bm_status_write,
808 .llseek = default_llseek,
809};
810
811/* Superblock handling */
812
813static const struct super_operations s_ops = {
814 .statfs = simple_statfs,
815 .evict_inode = bm_evict_inode,
816};
817
818static int bm_fill_super(struct super_block *sb, void *data, int silent)
819{
820 int err;
821 static struct tree_descr bm_files[] = {
822 [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
823 [3] = {"register", &bm_register_operations, S_IWUSR},
824 /* last one */ {""}
825 };
826
827 err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files);
828 if (!err)
829 sb->s_op = &s_ops;
830 return err;
831}
832
833static struct dentry *bm_mount(struct file_system_type *fs_type,
834 int flags, const char *dev_name, void *data)
835{
836 return mount_single(fs_type, flags, data, bm_fill_super);
837}
838
839static struct linux_binfmt misc_format = {
840 .module = THIS_MODULE,
841 .load_binary = load_misc_binary,
842};
843
844static struct file_system_type bm_fs_type = {
845 .owner = THIS_MODULE,
846 .name = "binfmt_misc",
847 .mount = bm_mount,
848 .kill_sb = kill_litter_super,
849};
850MODULE_ALIAS_FS("binfmt_misc");
851
852static int __init init_misc_binfmt(void)
853{
854 int err = register_filesystem(&bm_fs_type);
855 if (!err)
856 insert_binfmt(&misc_format);
857 return err;
858}
859
860static void __exit exit_misc_binfmt(void)
861{
862 unregister_binfmt(&misc_format);
863 unregister_filesystem(&bm_fs_type);
864}
865
866core_initcall(init_misc_binfmt);
867module_exit(exit_misc_binfmt);
868MODULE_LICENSE("GPL");
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * binfmt_misc.c
4 *
5 * Copyright (C) 1997 Richard Günther
6 *
7 * binfmt_misc detects binaries via a magic or filename extension and invokes
8 * a specified wrapper. See Documentation/admin-guide/binfmt-misc.rst for more details.
9 */
10
11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12
13#include <linux/kernel.h>
14#include <linux/module.h>
15#include <linux/init.h>
16#include <linux/sched/mm.h>
17#include <linux/magic.h>
18#include <linux/binfmts.h>
19#include <linux/slab.h>
20#include <linux/ctype.h>
21#include <linux/string_helpers.h>
22#include <linux/file.h>
23#include <linux/pagemap.h>
24#include <linux/namei.h>
25#include <linux/mount.h>
26#include <linux/fs_context.h>
27#include <linux/syscalls.h>
28#include <linux/fs.h>
29#include <linux/uaccess.h>
30
31#include "internal.h"
32
33#ifdef DEBUG
34# define USE_DEBUG 1
35#else
36# define USE_DEBUG 0
37#endif
38
39enum {
40 VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
41};
42
43static LIST_HEAD(entries);
44static int enabled = 1;
45
46enum {Enabled, Magic};
47#define MISC_FMT_PRESERVE_ARGV0 (1 << 31)
48#define MISC_FMT_OPEN_BINARY (1 << 30)
49#define MISC_FMT_CREDENTIALS (1 << 29)
50#define MISC_FMT_OPEN_FILE (1 << 28)
51
52typedef struct {
53 struct list_head list;
54 unsigned long flags; /* type, status, etc. */
55 int offset; /* offset of magic */
56 int size; /* size of magic/mask */
57 char *magic; /* magic or filename extension */
58 char *mask; /* mask, NULL for exact match */
59 const char *interpreter; /* filename of interpreter */
60 char *name;
61 struct dentry *dentry;
62 struct file *interp_file;
63} Node;
64
65static DEFINE_RWLOCK(entries_lock);
66static struct file_system_type bm_fs_type;
67static struct vfsmount *bm_mnt;
68static int entry_count;
69
70/*
71 * Max length of the register string. Determined by:
72 * - 7 delimiters
73 * - name: ~50 bytes
74 * - type: 1 byte
75 * - offset: 3 bytes (has to be smaller than BINPRM_BUF_SIZE)
76 * - magic: 128 bytes (512 in escaped form)
77 * - mask: 128 bytes (512 in escaped form)
78 * - interp: ~50 bytes
79 * - flags: 5 bytes
80 * Round that up a bit, and then back off to hold the internal data
81 * (like struct Node).
82 */
83#define MAX_REGISTER_LENGTH 1920
84
85/*
86 * Check if we support the binfmt
87 * if we do, return the node, else NULL
88 * locking is done in load_misc_binary
89 */
90static Node *check_file(struct linux_binprm *bprm)
91{
92 char *p = strrchr(bprm->interp, '.');
93 struct list_head *l;
94
95 /* Walk all the registered handlers. */
96 list_for_each(l, &entries) {
97 Node *e = list_entry(l, Node, list);
98 char *s;
99 int j;
100
101 /* Make sure this one is currently enabled. */
102 if (!test_bit(Enabled, &e->flags))
103 continue;
104
105 /* Do matching based on extension if applicable. */
106 if (!test_bit(Magic, &e->flags)) {
107 if (p && !strcmp(e->magic, p + 1))
108 return e;
109 continue;
110 }
111
112 /* Do matching based on magic & mask. */
113 s = bprm->buf + e->offset;
114 if (e->mask) {
115 for (j = 0; j < e->size; j++)
116 if ((*s++ ^ e->magic[j]) & e->mask[j])
117 break;
118 } else {
119 for (j = 0; j < e->size; j++)
120 if ((*s++ ^ e->magic[j]))
121 break;
122 }
123 if (j == e->size)
124 return e;
125 }
126 return NULL;
127}
128
129/*
130 * the loader itself
131 */
132static int load_misc_binary(struct linux_binprm *bprm)
133{
134 Node *fmt;
135 struct file *interp_file = NULL;
136 int retval;
137 int fd_binary = -1;
138
139 retval = -ENOEXEC;
140 if (!enabled)
141 return retval;
142
143 /* to keep locking time low, we copy the interpreter string */
144 read_lock(&entries_lock);
145 fmt = check_file(bprm);
146 if (fmt)
147 dget(fmt->dentry);
148 read_unlock(&entries_lock);
149 if (!fmt)
150 return retval;
151
152 /* Need to be able to load the file after exec */
153 retval = -ENOENT;
154 if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
155 goto ret;
156
157 if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
158 retval = remove_arg_zero(bprm);
159 if (retval)
160 goto ret;
161 }
162
163 if (fmt->flags & MISC_FMT_OPEN_BINARY) {
164
165 /* if the binary should be opened on behalf of the
166 * interpreter than keep it open and assign descriptor
167 * to it
168 */
169 fd_binary = get_unused_fd_flags(0);
170 if (fd_binary < 0) {
171 retval = fd_binary;
172 goto ret;
173 }
174 fd_install(fd_binary, bprm->file);
175
176 /* if the binary is not readable than enforce mm->dumpable=0
177 regardless of the interpreter's permissions */
178 would_dump(bprm, bprm->file);
179
180 allow_write_access(bprm->file);
181 bprm->file = NULL;
182
183 /* mark the bprm that fd should be passed to interp */
184 bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
185 bprm->interp_data = fd_binary;
186
187 } else {
188 allow_write_access(bprm->file);
189 fput(bprm->file);
190 bprm->file = NULL;
191 }
192 /* make argv[1] be the path to the binary */
193 retval = copy_strings_kernel(1, &bprm->interp, bprm);
194 if (retval < 0)
195 goto error;
196 bprm->argc++;
197
198 /* add the interp as argv[0] */
199 retval = copy_strings_kernel(1, &fmt->interpreter, bprm);
200 if (retval < 0)
201 goto error;
202 bprm->argc++;
203
204 /* Update interp in case binfmt_script needs it. */
205 retval = bprm_change_interp(fmt->interpreter, bprm);
206 if (retval < 0)
207 goto error;
208
209 if (fmt->flags & MISC_FMT_OPEN_FILE) {
210 interp_file = file_clone_open(fmt->interp_file);
211 if (!IS_ERR(interp_file))
212 deny_write_access(interp_file);
213 } else {
214 interp_file = open_exec(fmt->interpreter);
215 }
216 retval = PTR_ERR(interp_file);
217 if (IS_ERR(interp_file))
218 goto error;
219
220 bprm->file = interp_file;
221 if (fmt->flags & MISC_FMT_CREDENTIALS) {
222 loff_t pos = 0;
223
224 /*
225 * No need to call prepare_binprm(), it's already been
226 * done. bprm->buf is stale, update from interp_file.
227 */
228 memset(bprm->buf, 0, BINPRM_BUF_SIZE);
229 retval = kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE,
230 &pos);
231 } else
232 retval = prepare_binprm(bprm);
233
234 if (retval < 0)
235 goto error;
236
237 retval = search_binary_handler(bprm);
238 if (retval < 0)
239 goto error;
240
241ret:
242 dput(fmt->dentry);
243 return retval;
244error:
245 if (fd_binary > 0)
246 ksys_close(fd_binary);
247 bprm->interp_flags = 0;
248 bprm->interp_data = 0;
249 goto ret;
250}
251
252/* Command parsers */
253
254/*
255 * parses and copies one argument enclosed in del from *sp to *dp,
256 * recognising the \x special.
257 * returns pointer to the copied argument or NULL in case of an
258 * error (and sets err) or null argument length.
259 */
260static char *scanarg(char *s, char del)
261{
262 char c;
263
264 while ((c = *s++) != del) {
265 if (c == '\\' && *s == 'x') {
266 s++;
267 if (!isxdigit(*s++))
268 return NULL;
269 if (!isxdigit(*s++))
270 return NULL;
271 }
272 }
273 s[-1] ='\0';
274 return s;
275}
276
277static char *check_special_flags(char *sfs, Node *e)
278{
279 char *p = sfs;
280 int cont = 1;
281
282 /* special flags */
283 while (cont) {
284 switch (*p) {
285 case 'P':
286 pr_debug("register: flag: P (preserve argv0)\n");
287 p++;
288 e->flags |= MISC_FMT_PRESERVE_ARGV0;
289 break;
290 case 'O':
291 pr_debug("register: flag: O (open binary)\n");
292 p++;
293 e->flags |= MISC_FMT_OPEN_BINARY;
294 break;
295 case 'C':
296 pr_debug("register: flag: C (preserve creds)\n");
297 p++;
298 /* this flags also implies the
299 open-binary flag */
300 e->flags |= (MISC_FMT_CREDENTIALS |
301 MISC_FMT_OPEN_BINARY);
302 break;
303 case 'F':
304 pr_debug("register: flag: F: open interpreter file now\n");
305 p++;
306 e->flags |= MISC_FMT_OPEN_FILE;
307 break;
308 default:
309 cont = 0;
310 }
311 }
312
313 return p;
314}
315
316/*
317 * This registers a new binary format, it recognises the syntax
318 * ':name:type:offset:magic:mask:interpreter:flags'
319 * where the ':' is the IFS, that can be chosen with the first char
320 */
321static Node *create_entry(const char __user *buffer, size_t count)
322{
323 Node *e;
324 int memsize, err;
325 char *buf, *p;
326 char del;
327
328 pr_debug("register: received %zu bytes\n", count);
329
330 /* some sanity checks */
331 err = -EINVAL;
332 if ((count < 11) || (count > MAX_REGISTER_LENGTH))
333 goto out;
334
335 err = -ENOMEM;
336 memsize = sizeof(Node) + count + 8;
337 e = kmalloc(memsize, GFP_KERNEL);
338 if (!e)
339 goto out;
340
341 p = buf = (char *)e + sizeof(Node);
342
343 memset(e, 0, sizeof(Node));
344 if (copy_from_user(buf, buffer, count))
345 goto efault;
346
347 del = *p++; /* delimeter */
348
349 pr_debug("register: delim: %#x {%c}\n", del, del);
350
351 /* Pad the buffer with the delim to simplify parsing below. */
352 memset(buf + count, del, 8);
353
354 /* Parse the 'name' field. */
355 e->name = p;
356 p = strchr(p, del);
357 if (!p)
358 goto einval;
359 *p++ = '\0';
360 if (!e->name[0] ||
361 !strcmp(e->name, ".") ||
362 !strcmp(e->name, "..") ||
363 strchr(e->name, '/'))
364 goto einval;
365
366 pr_debug("register: name: {%s}\n", e->name);
367
368 /* Parse the 'type' field. */
369 switch (*p++) {
370 case 'E':
371 pr_debug("register: type: E (extension)\n");
372 e->flags = 1 << Enabled;
373 break;
374 case 'M':
375 pr_debug("register: type: M (magic)\n");
376 e->flags = (1 << Enabled) | (1 << Magic);
377 break;
378 default:
379 goto einval;
380 }
381 if (*p++ != del)
382 goto einval;
383
384 if (test_bit(Magic, &e->flags)) {
385 /* Handle the 'M' (magic) format. */
386 char *s;
387
388 /* Parse the 'offset' field. */
389 s = strchr(p, del);
390 if (!s)
391 goto einval;
392 *s = '\0';
393 if (p != s) {
394 int r = kstrtoint(p, 10, &e->offset);
395 if (r != 0 || e->offset < 0)
396 goto einval;
397 }
398 p = s;
399 if (*p++)
400 goto einval;
401 pr_debug("register: offset: %#x\n", e->offset);
402
403 /* Parse the 'magic' field. */
404 e->magic = p;
405 p = scanarg(p, del);
406 if (!p)
407 goto einval;
408 if (!e->magic[0])
409 goto einval;
410 if (USE_DEBUG)
411 print_hex_dump_bytes(
412 KBUILD_MODNAME ": register: magic[raw]: ",
413 DUMP_PREFIX_NONE, e->magic, p - e->magic);
414
415 /* Parse the 'mask' field. */
416 e->mask = p;
417 p = scanarg(p, del);
418 if (!p)
419 goto einval;
420 if (!e->mask[0]) {
421 e->mask = NULL;
422 pr_debug("register: mask[raw]: none\n");
423 } else if (USE_DEBUG)
424 print_hex_dump_bytes(
425 KBUILD_MODNAME ": register: mask[raw]: ",
426 DUMP_PREFIX_NONE, e->mask, p - e->mask);
427
428 /*
429 * Decode the magic & mask fields.
430 * Note: while we might have accepted embedded NUL bytes from
431 * above, the unescape helpers here will stop at the first one
432 * it encounters.
433 */
434 e->size = string_unescape_inplace(e->magic, UNESCAPE_HEX);
435 if (e->mask &&
436 string_unescape_inplace(e->mask, UNESCAPE_HEX) != e->size)
437 goto einval;
438 if (e->size > BINPRM_BUF_SIZE ||
439 BINPRM_BUF_SIZE - e->size < e->offset)
440 goto einval;
441 pr_debug("register: magic/mask length: %i\n", e->size);
442 if (USE_DEBUG) {
443 print_hex_dump_bytes(
444 KBUILD_MODNAME ": register: magic[decoded]: ",
445 DUMP_PREFIX_NONE, e->magic, e->size);
446
447 if (e->mask) {
448 int i;
449 char *masked = kmalloc(e->size, GFP_KERNEL);
450
451 print_hex_dump_bytes(
452 KBUILD_MODNAME ": register: mask[decoded]: ",
453 DUMP_PREFIX_NONE, e->mask, e->size);
454
455 if (masked) {
456 for (i = 0; i < e->size; ++i)
457 masked[i] = e->magic[i] & e->mask[i];
458 print_hex_dump_bytes(
459 KBUILD_MODNAME ": register: magic[masked]: ",
460 DUMP_PREFIX_NONE, masked, e->size);
461
462 kfree(masked);
463 }
464 }
465 }
466 } else {
467 /* Handle the 'E' (extension) format. */
468
469 /* Skip the 'offset' field. */
470 p = strchr(p, del);
471 if (!p)
472 goto einval;
473 *p++ = '\0';
474
475 /* Parse the 'magic' field. */
476 e->magic = p;
477 p = strchr(p, del);
478 if (!p)
479 goto einval;
480 *p++ = '\0';
481 if (!e->magic[0] || strchr(e->magic, '/'))
482 goto einval;
483 pr_debug("register: extension: {%s}\n", e->magic);
484
485 /* Skip the 'mask' field. */
486 p = strchr(p, del);
487 if (!p)
488 goto einval;
489 *p++ = '\0';
490 }
491
492 /* Parse the 'interpreter' field. */
493 e->interpreter = p;
494 p = strchr(p, del);
495 if (!p)
496 goto einval;
497 *p++ = '\0';
498 if (!e->interpreter[0])
499 goto einval;
500 pr_debug("register: interpreter: {%s}\n", e->interpreter);
501
502 /* Parse the 'flags' field. */
503 p = check_special_flags(p, e);
504 if (*p == '\n')
505 p++;
506 if (p != buf + count)
507 goto einval;
508
509 return e;
510
511out:
512 return ERR_PTR(err);
513
514efault:
515 kfree(e);
516 return ERR_PTR(-EFAULT);
517einval:
518 kfree(e);
519 return ERR_PTR(-EINVAL);
520}
521
522/*
523 * Set status of entry/binfmt_misc:
524 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
525 */
526static int parse_command(const char __user *buffer, size_t count)
527{
528 char s[4];
529
530 if (count > 3)
531 return -EINVAL;
532 if (copy_from_user(s, buffer, count))
533 return -EFAULT;
534 if (!count)
535 return 0;
536 if (s[count - 1] == '\n')
537 count--;
538 if (count == 1 && s[0] == '0')
539 return 1;
540 if (count == 1 && s[0] == '1')
541 return 2;
542 if (count == 2 && s[0] == '-' && s[1] == '1')
543 return 3;
544 return -EINVAL;
545}
546
547/* generic stuff */
548
549static void entry_status(Node *e, char *page)
550{
551 char *dp = page;
552 const char *status = "disabled";
553
554 if (test_bit(Enabled, &e->flags))
555 status = "enabled";
556
557 if (!VERBOSE_STATUS) {
558 sprintf(page, "%s\n", status);
559 return;
560 }
561
562 dp += sprintf(dp, "%s\ninterpreter %s\n", status, e->interpreter);
563
564 /* print the special flags */
565 dp += sprintf(dp, "flags: ");
566 if (e->flags & MISC_FMT_PRESERVE_ARGV0)
567 *dp++ = 'P';
568 if (e->flags & MISC_FMT_OPEN_BINARY)
569 *dp++ = 'O';
570 if (e->flags & MISC_FMT_CREDENTIALS)
571 *dp++ = 'C';
572 if (e->flags & MISC_FMT_OPEN_FILE)
573 *dp++ = 'F';
574 *dp++ = '\n';
575
576 if (!test_bit(Magic, &e->flags)) {
577 sprintf(dp, "extension .%s\n", e->magic);
578 } else {
579 dp += sprintf(dp, "offset %i\nmagic ", e->offset);
580 dp = bin2hex(dp, e->magic, e->size);
581 if (e->mask) {
582 dp += sprintf(dp, "\nmask ");
583 dp = bin2hex(dp, e->mask, e->size);
584 }
585 *dp++ = '\n';
586 *dp = '\0';
587 }
588}
589
590static struct inode *bm_get_inode(struct super_block *sb, int mode)
591{
592 struct inode *inode = new_inode(sb);
593
594 if (inode) {
595 inode->i_ino = get_next_ino();
596 inode->i_mode = mode;
597 inode->i_atime = inode->i_mtime = inode->i_ctime =
598 current_time(inode);
599 }
600 return inode;
601}
602
603static void bm_evict_inode(struct inode *inode)
604{
605 Node *e = inode->i_private;
606
607 if (e && e->flags & MISC_FMT_OPEN_FILE)
608 filp_close(e->interp_file, NULL);
609
610 clear_inode(inode);
611 kfree(e);
612}
613
614static void kill_node(Node *e)
615{
616 struct dentry *dentry;
617
618 write_lock(&entries_lock);
619 list_del_init(&e->list);
620 write_unlock(&entries_lock);
621
622 dentry = e->dentry;
623 drop_nlink(d_inode(dentry));
624 d_drop(dentry);
625 dput(dentry);
626 simple_release_fs(&bm_mnt, &entry_count);
627}
628
629/* /<entry> */
630
631static ssize_t
632bm_entry_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
633{
634 Node *e = file_inode(file)->i_private;
635 ssize_t res;
636 char *page;
637
638 page = (char *) __get_free_page(GFP_KERNEL);
639 if (!page)
640 return -ENOMEM;
641
642 entry_status(e, page);
643
644 res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
645
646 free_page((unsigned long) page);
647 return res;
648}
649
650static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
651 size_t count, loff_t *ppos)
652{
653 struct dentry *root;
654 Node *e = file_inode(file)->i_private;
655 int res = parse_command(buffer, count);
656
657 switch (res) {
658 case 1:
659 /* Disable this handler. */
660 clear_bit(Enabled, &e->flags);
661 break;
662 case 2:
663 /* Enable this handler. */
664 set_bit(Enabled, &e->flags);
665 break;
666 case 3:
667 /* Delete this handler. */
668 root = file_inode(file)->i_sb->s_root;
669 inode_lock(d_inode(root));
670
671 if (!list_empty(&e->list))
672 kill_node(e);
673
674 inode_unlock(d_inode(root));
675 break;
676 default:
677 return res;
678 }
679
680 return count;
681}
682
683static const struct file_operations bm_entry_operations = {
684 .read = bm_entry_read,
685 .write = bm_entry_write,
686 .llseek = default_llseek,
687};
688
689/* /register */
690
691static ssize_t bm_register_write(struct file *file, const char __user *buffer,
692 size_t count, loff_t *ppos)
693{
694 Node *e;
695 struct inode *inode;
696 struct super_block *sb = file_inode(file)->i_sb;
697 struct dentry *root = sb->s_root, *dentry;
698 int err = 0;
699
700 e = create_entry(buffer, count);
701
702 if (IS_ERR(e))
703 return PTR_ERR(e);
704
705 inode_lock(d_inode(root));
706 dentry = lookup_one_len(e->name, root, strlen(e->name));
707 err = PTR_ERR(dentry);
708 if (IS_ERR(dentry))
709 goto out;
710
711 err = -EEXIST;
712 if (d_really_is_positive(dentry))
713 goto out2;
714
715 inode = bm_get_inode(sb, S_IFREG | 0644);
716
717 err = -ENOMEM;
718 if (!inode)
719 goto out2;
720
721 err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
722 if (err) {
723 iput(inode);
724 inode = NULL;
725 goto out2;
726 }
727
728 if (e->flags & MISC_FMT_OPEN_FILE) {
729 struct file *f;
730
731 f = open_exec(e->interpreter);
732 if (IS_ERR(f)) {
733 err = PTR_ERR(f);
734 pr_notice("register: failed to install interpreter file %s\n", e->interpreter);
735 simple_release_fs(&bm_mnt, &entry_count);
736 iput(inode);
737 inode = NULL;
738 goto out2;
739 }
740 e->interp_file = f;
741 }
742
743 e->dentry = dget(dentry);
744 inode->i_private = e;
745 inode->i_fop = &bm_entry_operations;
746
747 d_instantiate(dentry, inode);
748 write_lock(&entries_lock);
749 list_add(&e->list, &entries);
750 write_unlock(&entries_lock);
751
752 err = 0;
753out2:
754 dput(dentry);
755out:
756 inode_unlock(d_inode(root));
757
758 if (err) {
759 kfree(e);
760 return err;
761 }
762 return count;
763}
764
765static const struct file_operations bm_register_operations = {
766 .write = bm_register_write,
767 .llseek = noop_llseek,
768};
769
770/* /status */
771
772static ssize_t
773bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
774{
775 char *s = enabled ? "enabled\n" : "disabled\n";
776
777 return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
778}
779
780static ssize_t bm_status_write(struct file *file, const char __user *buffer,
781 size_t count, loff_t *ppos)
782{
783 int res = parse_command(buffer, count);
784 struct dentry *root;
785
786 switch (res) {
787 case 1:
788 /* Disable all handlers. */
789 enabled = 0;
790 break;
791 case 2:
792 /* Enable all handlers. */
793 enabled = 1;
794 break;
795 case 3:
796 /* Delete all handlers. */
797 root = file_inode(file)->i_sb->s_root;
798 inode_lock(d_inode(root));
799
800 while (!list_empty(&entries))
801 kill_node(list_first_entry(&entries, Node, list));
802
803 inode_unlock(d_inode(root));
804 break;
805 default:
806 return res;
807 }
808
809 return count;
810}
811
812static const struct file_operations bm_status_operations = {
813 .read = bm_status_read,
814 .write = bm_status_write,
815 .llseek = default_llseek,
816};
817
818/* Superblock handling */
819
820static const struct super_operations s_ops = {
821 .statfs = simple_statfs,
822 .evict_inode = bm_evict_inode,
823};
824
825static int bm_fill_super(struct super_block *sb, struct fs_context *fc)
826{
827 int err;
828 static const struct tree_descr bm_files[] = {
829 [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
830 [3] = {"register", &bm_register_operations, S_IWUSR},
831 /* last one */ {""}
832 };
833
834 err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files);
835 if (!err)
836 sb->s_op = &s_ops;
837 return err;
838}
839
840static int bm_get_tree(struct fs_context *fc)
841{
842 return get_tree_single(fc, bm_fill_super);
843}
844
845static const struct fs_context_operations bm_context_ops = {
846 .get_tree = bm_get_tree,
847};
848
849static int bm_init_fs_context(struct fs_context *fc)
850{
851 fc->ops = &bm_context_ops;
852 return 0;
853}
854
855static struct linux_binfmt misc_format = {
856 .module = THIS_MODULE,
857 .load_binary = load_misc_binary,
858};
859
860static struct file_system_type bm_fs_type = {
861 .owner = THIS_MODULE,
862 .name = "binfmt_misc",
863 .init_fs_context = bm_init_fs_context,
864 .kill_sb = kill_litter_super,
865};
866MODULE_ALIAS_FS("binfmt_misc");
867
868static int __init init_misc_binfmt(void)
869{
870 int err = register_filesystem(&bm_fs_type);
871 if (!err)
872 insert_binfmt(&misc_format);
873 return err;
874}
875
876static void __exit exit_misc_binfmt(void)
877{
878 unregister_binfmt(&misc_format);
879 unregister_filesystem(&bm_fs_type);
880}
881
882core_initcall(init_misc_binfmt);
883module_exit(exit_misc_binfmt);
884MODULE_LICENSE("GPL");