fs/binfmt_misc.c

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