Version:  2.0.40 2.2.26 2.4.37 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

Linux/fs/binfmt_misc.c

  1 /*
  2  * binfmt_misc.c
  3  *
  4  * Copyright (C) 1997 Richard G√ľnther
  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 
 37 enum {
 38         VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
 39 };
 40 
 41 static LIST_HEAD(entries);
 42 static int enabled = 1;
 43 
 44 enum {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 
 50 typedef 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 
 63 static DEFINE_RWLOCK(entries_lock);
 64 static struct file_system_type bm_fs_type;
 65 static struct vfsmount *bm_mnt;
 66 static 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  */
 88 static 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  */
130 static 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 
237 ret:
238         return retval;
239 error:
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  */
255 static 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 
272 static 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  */
316 static 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 
500 out:
501         return ERR_PTR(err);
502 
503 efault:
504         kfree(e);
505         return ERR_PTR(-EFAULT);
506 einval:
507         kfree(e);
508         return ERR_PTR(-EINVAL);
509 }
510 
511 /*
512  * Set status of entry/binfmt_misc:
513  * '1' enables, '' disables and '-1' clears entry/binfmt_misc
514  */
515 static 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] == '')
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 
538 static 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 
579 static 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 
592 static void bm_evict_inode(struct inode *inode)
593 {
594         clear_inode(inode);
595         kfree(inode->i_private);
596 }
597 
598 static 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 
625 static ssize_t
626 bm_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 
644 static 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 
676 static 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 
684 static 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;
746 out2:
747         dput(dentry);
748 out:
749         inode_unlock(d_inode(root));
750 
751         if (err) {
752                 kfree(e);
753                 return err;
754         }
755         return count;
756 }
757 
758 static const struct file_operations bm_register_operations = {
759         .write          = bm_register_write,
760         .llseek         = noop_llseek,
761 };
762 
763 /* /status */
764 
765 static ssize_t
766 bm_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 
773 static 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 
805 static 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 
813 static const struct super_operations s_ops = {
814         .statfs         = simple_statfs,
815         .evict_inode    = bm_evict_inode,
816 };
817 
818 static 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 
833 static 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 
839 static struct linux_binfmt misc_format = {
840         .module = THIS_MODULE,
841         .load_binary = load_misc_binary,
842 };
843 
844 static 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 };
850 MODULE_ALIAS_FS("binfmt_misc");
851 
852 static 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 
860 static void __exit exit_misc_binfmt(void)
861 {
862         unregister_binfmt(&misc_format);
863         unregister_filesystem(&bm_fs_type);
864 }
865 
866 core_initcall(init_misc_binfmt);
867 module_exit(exit_misc_binfmt);
868 MODULE_LICENSE("GPL");
869 

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