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                 e->offset = simple_strtoul(p, &p, 10);
 374                 if (*p++)
 375                         goto einval;
 376                 pr_debug("register: offset: %#x\n", e->offset);
 377
 378                 /* Parse the 'magic' field. */
 379                 e->magic = p;
 380                 p = scanarg(p, del);
 381                 if (!p)
 382                         goto einval;
 383                 if (!e->magic[0])
 384                         goto einval;
 385                 if (USE_DEBUG)
 386                         print_hex_dump_bytes(
 387                                 KBUILD_MODNAME ": register: magic[raw]: ",
 388                                 DUMP_PREFIX_NONE, e->magic, p - e->magic);
 389
 390                 /* Parse the 'mask' field. */
 391                 e->mask = p;
 392                 p = scanarg(p, del);
 393                 if (!p)
 394                         goto einval;
 395                 if (!e->mask[0]) {
 396                         e->mask = NULL;
 397                         pr_debug("register:  mask[raw]: none\n");
 398                 } else if (USE_DEBUG)
 399                         print_hex_dump_bytes(
 400                                 KBUILD_MODNAME ": register:  mask[raw]: ",
 401                                 DUMP_PREFIX_NONE, e->mask, p - e->mask);
 402
 403                 /*
 404                  * Decode the magic & mask fields.
 405                  * Note: while we might have accepted embedded NUL bytes from
 406                  * above, the unescape helpers here will stop at the first one
 407                  * it encounters.
 408                  */
 409                 e->size = string_unescape_inplace(e->magic, UNESCAPE_HEX);
 410                 if (e->mask &&
 411                     string_unescape_inplace(e->mask, UNESCAPE_HEX) != e->size)
 412                         goto einval;
 413                 if (e->size + e->offset > BINPRM_BUF_SIZE)
 414                         goto einval;
 415                 pr_debug("register: magic/mask length: %i\n", e->size);
 416                 if (USE_DEBUG) {
 417                         print_hex_dump_bytes(
 418                                 KBUILD_MODNAME ": register: magic[decoded]: ",
 419                                 DUMP_PREFIX_NONE, e->magic, e->size);
 420
 421                         if (e->mask) {
 422                                 int i;
 423                                 char *masked = kmalloc(e->size, GFP_KERNEL);
 424
 425                                 print_hex_dump_bytes(
 426                                         KBUILD_MODNAME ": register:  mask[decoded]: ",
 427                                         DUMP_PREFIX_NONE, e->mask, e->size);
 428
 429                                 if (masked) {
 430                                         for (i = 0; i < e->size; ++i)
 431                                                 masked[i] = e->magic[i] & e->mask[i];
 432                                         print_hex_dump_bytes(
 433                                                 KBUILD_MODNAME ": register:  magic[masked]: ",
 434                                                 DUMP_PREFIX_NONE, masked, e->size);
 435
 436                                         kfree(masked);
 437                                 }
 438                         }
 439                 }
 440         } else {
 441                 /* Handle the 'E' (extension) format. */
 442
 443                 /* Skip the 'offset' field. */
 444                 p = strchr(p, del);
 445                 if (!p)
 446                         goto einval;
 447                 *p++ = '\0';
 448
 449                 /* Parse the 'magic' field. */
 450                 e->magic = p;
 451                 p = strchr(p, del);
 452                 if (!p)
 453                         goto einval;
 454                 *p++ = '\0';
 455                 if (!e->magic[0] || strchr(e->magic, '/'))
 456                         goto einval;
 457                 pr_debug("register: extension: {%s}\n", e->magic);
 458
 459                 /* Skip the 'mask' field. */
 460                 p = strchr(p, del);
 461                 if (!p)
 462                         goto einval;
 463                 *p++ = '\0';
 464         }
 465
 466         /* Parse the 'interpreter' field. */
 467         e->interpreter = p;
 468         p = strchr(p, del);
 469         if (!p)
 470                 goto einval;
 471         *p++ = '\0';
 472         if (!e->interpreter[0])
 473                 goto einval;
 474         pr_debug("register: interpreter: {%s}\n", e->interpreter);
 475
 476         /* Parse the 'flags' field. */
 477         p = check_special_flags(p, e);
 478         if (*p == '\n')
 479                 p++;
 480         if (p != buf + count)
 481                 goto einval;
 482
 483         return e;
 484
 485 out:
 486         return ERR_PTR(err);
 487
 488 efault:
 489         kfree(e);
 490         return ERR_PTR(-EFAULT);
 491 einval:
 492         kfree(e);
 493         return ERR_PTR(-EINVAL);
 494 }
 495
 496 /*
 497  * Set status of entry/binfmt_misc:
 498  * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
 499  */
 500 static int parse_command(const char __user *buffer, size_t count)
 501 {
 502         char s[4];
 503
 504         if (count > 3)
 505                 return -EINVAL;
 506         if (copy_from_user(s, buffer, count))
 507                 return -EFAULT;
 508         if (!count)
 509                 return 0;
 510         if (s[count - 1] == '\n')
 511                 count--;
 512         if (count == 1 && s[0] == '0')
 513                 return 1;
 514         if (count == 1 && s[0] == '1')
 515                 return 2;
 516         if (count == 2 && s[0] == '-' && s[1] == '1')
 517                 return 3;
 518         return -EINVAL;
 519 }
 520
 521 /* generic stuff */
 522
 523 static void entry_status(Node *e, char *page)
 524 {
 525         char *dp = page;
 526         const char *status = "disabled";
 527
 528         if (test_bit(Enabled, &e->flags))
 529                 status = "enabled";
 530
 531         if (!VERBOSE_STATUS) {
 532                 sprintf(page, "%s\n", status);
 533                 return;
 534         }
 535
 536         dp += sprintf(dp, "%s\ninterpreter %s\n", status, e->interpreter);
 537
 538         /* print the special flags */
 539         dp += sprintf(dp, "flags: ");
 540         if (e->flags & MISC_FMT_PRESERVE_ARGV0)
 541                 *dp++ = 'P';
 542         if (e->flags & MISC_FMT_OPEN_BINARY)
 543                 *dp++ = 'O';
 544         if (e->flags & MISC_FMT_CREDENTIALS)
 545                 *dp++ = 'C';
 546         *dp++ = '\n';
 547
 548         if (!test_bit(Magic, &e->flags)) {
 549                 sprintf(dp, "extension .%s\n", e->magic);
 550         } else {
 551                 dp += sprintf(dp, "offset %i\nmagic ", e->offset);
 552                 dp = bin2hex(dp, e->magic, e->size);
 553                 if (e->mask) {
 554                         dp += sprintf(dp, "\nmask ");
 555                         dp = bin2hex(dp, e->mask, e->size);
 556                 }
 557                 *dp++ = '\n';
 558                 *dp = '\0';
 559         }
 560 }
 561
 562 static struct inode *bm_get_inode(struct super_block *sb, int mode)
 563 {
 564         struct inode *inode = new_inode(sb);
 565
 566         if (inode) {
 567                 inode->i_ino = get_next_ino();
 568                 inode->i_mode = mode;
 569                 inode->i_atime = inode->i_mtime = inode->i_ctime =
 570                         current_fs_time(inode->i_sb);
 571         }
 572         return inode;
 573 }
 574
 575 static void bm_evict_inode(struct inode *inode)
 576 {
 577         clear_inode(inode);
 578         kfree(inode->i_private);
 579 }
 580
 581 static void kill_node(Node *e)
 582 {
 583         struct dentry *dentry;
 584
 585         write_lock(&entries_lock);
 586         dentry = e->dentry;
 587         if (dentry) {
 588                 list_del_init(&e->list);
 589                 e->dentry = NULL;
 590         }
 591         write_unlock(&entries_lock);
 592
 593         if (dentry) {
 594                 drop_nlink(d_inode(dentry));
 595                 d_drop(dentry);
 596                 dput(dentry);
 597                 simple_release_fs(&bm_mnt, &entry_count);
 598         }
 599 }
 600
 601 /* /<entry> */
 602
 603 static ssize_t
 604 bm_entry_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
 605 {
 606         Node *e = file_inode(file)->i_private;
 607         ssize_t res;
 608         char *page;
 609
 610         page = (char *) __get_free_page(GFP_KERNEL);
 611         if (!page)
 612                 return -ENOMEM;
 613
 614         entry_status(e, page);
 615
 616         res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
 617
 618         free_page((unsigned long) page);
 619         return res;
 620 }
 621
 622 static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
 623                                 size_t count, loff_t *ppos)
 624 {
 625         struct dentry *root;
 626         Node *e = file_inode(file)->i_private;
 627         int res = parse_command(buffer, count);
 628
 629         switch (res) {
 630         case 1:
 631                 /* Disable this handler. */
 632                 clear_bit(Enabled, &e->flags);
 633                 break;
 634         case 2:
 635                 /* Enable this handler. */
 636                 set_bit(Enabled, &e->flags);
 637                 break;
 638         case 3:
 639                 /* Delete this handler. */
 640                 root = dget(file->f_path.dentry->d_sb->s_root);
 641                 inode_lock(d_inode(root));
 642
 643                 kill_node(e);
 644
 645                 inode_unlock(d_inode(root));
 646                 dput(root);
 647                 break;
 648         default:
 649                 return res;
 650         }
 651
 652         return count;
 653 }
 654
 655 static const struct file_operations bm_entry_operations = {
 656         .read           = bm_entry_read,
 657         .write          = bm_entry_write,
 658         .llseek         = default_llseek,
 659 };
 660
 661 /* /register */
 662
 663 static ssize_t bm_register_write(struct file *file, const char __user *buffer,
 664                                size_t count, loff_t *ppos)
 665 {
 666         Node *e;
 667         struct inode *inode;
 668         struct dentry *root, *dentry;
 669         struct super_block *sb = file->f_path.dentry->d_sb;
 670         int err = 0;
 671
 672         e = create_entry(buffer, count);
 673
 674         if (IS_ERR(e))
 675                 return PTR_ERR(e);
 676
 677         root = dget(sb->s_root);
 678         inode_lock(d_inode(root));
 679         dentry = lookup_one_len(e->name, root, strlen(e->name));
 680         err = PTR_ERR(dentry);
 681         if (IS_ERR(dentry))
 682                 goto out;
 683
 684         err = -EEXIST;
 685         if (d_really_is_positive(dentry))
 686                 goto out2;
 687
 688         inode = bm_get_inode(sb, S_IFREG | 0644);
 689
 690         err = -ENOMEM;
 691         if (!inode)
 692                 goto out2;
 693
 694         err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
 695         if (err) {
 696                 iput(inode);
 697                 inode = NULL;
 698                 goto out2;
 699         }
 700
 701         e->dentry = dget(dentry);
 702         inode->i_private = e;
 703         inode->i_fop = &bm_entry_operations;
 704
 705         d_instantiate(dentry, inode);
 706         write_lock(&entries_lock);
 707         list_add(&e->list, &entries);
 708         write_unlock(&entries_lock);
 709
 710         err = 0;
 711 out2:
 712         dput(dentry);
 713 out:
 714         inode_unlock(d_inode(root));
 715         dput(root);
 716
 717         if (err) {
 718                 kfree(e);
 719                 return -EINVAL;
 720         }
 721         return count;
 722 }
 723
 724 static const struct file_operations bm_register_operations = {
 725         .write          = bm_register_write,
 726         .llseek         = noop_llseek,
 727 };
 728
 729 /* /status */
 730
 731 static ssize_t
 732 bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
 733 {
 734         char *s = enabled ? "enabled\n" : "disabled\n";
 735
 736         return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
 737 }
 738
 739 static ssize_t bm_status_write(struct file *file, const char __user *buffer,
 740                 size_t count, loff_t *ppos)
 741 {
 742         int res = parse_command(buffer, count);
 743         struct dentry *root;
 744
 745         switch (res) {
 746         case 1:
 747                 /* Disable all handlers. */
 748                 enabled = 0;
 749                 break;
 750         case 2:
 751                 /* Enable all handlers. */
 752                 enabled = 1;
 753                 break;
 754         case 3:
 755                 /* Delete all handlers. */
 756                 root = dget(file->f_path.dentry->d_sb->s_root);
 757                 inode_lock(d_inode(root));
 758
 759                 while (!list_empty(&entries))
 760                         kill_node(list_entry(entries.next, Node, list));
 761
 762                 inode_unlock(d_inode(root));
 763                 dput(root);
 764                 break;
 765         default:
 766                 return res;
 767         }
 768
 769         return count;
 770 }
 771
 772 static const struct file_operations bm_status_operations = {
 773         .read           = bm_status_read,
 774         .write          = bm_status_write,
 775         .llseek         = default_llseek,
 776 };
 777
 778 /* Superblock handling */
 779
 780 static const struct super_operations s_ops = {
 781         .statfs         = simple_statfs,
 782         .evict_inode    = bm_evict_inode,
 783 };
 784
 785 static int bm_fill_super(struct super_block *sb, void *data, int silent)
 786 {
 787         int err;
 788         static struct tree_descr bm_files[] = {
 789                 [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
 790                 [3] = {"register", &bm_register_operations, S_IWUSR},
 791                 /* last one */ {""}
 792         };
 793
 794         err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files);
 795         if (!err)
 796                 sb->s_op = &s_ops;
 797         return err;
 798 }
 799
 800 static struct dentry *bm_mount(struct file_system_type *fs_type,
 801         int flags, const char *dev_name, void *data)
 802 {
 803         return mount_single(fs_type, flags, data, bm_fill_super);
 804 }
 805
 806 static struct linux_binfmt misc_format = {
 807         .module = THIS_MODULE,
 808         .load_binary = load_misc_binary,
 809 };
 810
 811 static struct file_system_type bm_fs_type = {
 812         .owner          = THIS_MODULE,
 813         .name           = "binfmt_misc",
 814         .mount          = bm_mount,
 815         .kill_sb        = kill_litter_super,
 816 };
 817 MODULE_ALIAS_FS("binfmt_misc");
 818
 819 static int __init init_misc_binfmt(void)
 820 {
 821         int err = register_filesystem(&bm_fs_type);
 822         if (!err)
 823                 insert_binfmt(&misc_format);
 824         return err;
 825 }
 826
 827 static void __exit exit_misc_binfmt(void)
 828 {
 829         unregister_binfmt(&misc_format);
 830         unregister_filesystem(&bm_fs_type);
 831 }
 832
 833 core_initcall(init_misc_binfmt);
 834 module_exit(exit_misc_binfmt);
 835 MODULE_LICENSE("GPL");