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. This should obsolete binfmt_java, binfmt_em86 and
   8  *  binfmt_mz.
   9  *
  10  *  1997-04-25 first version
  11  *  [...]
  12  *  1997-05-19 cleanup
  13  *  1997-06-26 hpa: pass the real filename rather than argv[0]
  14  *  1997-06-30 minor cleanup
  15  *  1997-08-09 removed extension stripping, locking cleanup
  16  *  2001-02-28 AV: rewritten into something that resembles C. Original didn't.
  17  */
  18
  19 #include <linux/module.h>
  20 #include <linux/init.h>
  21
  22 #include <linux/binfmts.h>
  23 #include <linux/slab.h>
  24 #include <linux/ctype.h>
  25 #include <linux/file.h>
  26 #include <linux/pagemap.h>
  27 #include <linux/namei.h>
  28 #include <linux/mount.h>
  29
  30 #include <asm/uaccess.h>
  31
  32 enum {
  33         VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
  34 };
  35
  36 static LIST_HEAD(entries);
  37 static int enabled = 1;
  38
  39 enum {Enabled, Magic};
  40 #define MISC_FMT_PRESERVE_ARGV0 (1<<31)
  41
  42 typedef struct {
  43         struct list_head list;
  44         unsigned long flags;            /* type, status, etc. */
  45         int offset;                     /* offset of magic */
  46         int size;                       /* size of magic/mask */
  47         char *magic;                    /* magic or filename extension */
  48         char *mask;                     /* mask, NULL for exact match */
  49         char *interpreter;              /* filename of interpreter */
  50         char *name;
  51         struct dentry *dentry;
  52 } Node;
  53
  54 static rwlock_t entries_lock __attribute__((unused)) = RW_LOCK_UNLOCKED;
  55 static struct vfsmount *bm_mnt;
  56 static int entry_count = 0;
  57
  58 /*
  59  * Check if we support the binfmt
  60  * if we do, return the node, else NULL
  61  * locking is done in load_misc_binary
  62  */
  63 static Node *check_file(struct linux_binprm *bprm)
  64 {
  65         char *p = strrchr(bprm->filename, '.');
  66         struct list_head *l;
  67
  68         list_for_each(l, &entries) {
  69                 Node *e = list_entry(l, Node, list);
  70                 char *s;
  71                 int j;
  72
  73                 if (!test_bit(Enabled, &e->flags))
  74                         continue;
  75
  76                 if (!test_bit(Magic, &e->flags)) {
  77                         if (p && !strcmp(e->magic, p + 1))
  78                                 return e;
  79                         continue;
  80                 }
  81
  82                 s = bprm->buf + e->offset;
  83                 if (e->mask) {
  84                         for (j = 0; j < e->size; j++)
  85                                 if ((*s++ ^ e->magic[j]) & e->mask[j])
  86                                         break;
  87                 } else {
  88                         for (j = 0; j < e->size; j++)
  89                                 if ((*s++ ^ e->magic[j]))
  90                                         break;
  91                 }
  92                 if (j == e->size)
  93                         return e;
  94         }
  95         return NULL;
  96 }
  97
  98 /*
  99  * the loader itself
 100  */
 101 static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs)
 102 {
 103         Node *fmt;
 104         struct file * file;
 105         char iname[BINPRM_BUF_SIZE];
 106         char *iname_addr = iname;
 107         int retval;
 108
 109         retval = -ENOEXEC;
 110         if (!enabled)
 111                 goto _ret;
 112
 113         /* to keep locking time low, we copy the interpreter string */
 114         read_lock(&entries_lock);
 115         fmt = check_file(bprm);
 116         if (fmt) {
 117                 strncpy(iname, fmt->interpreter, BINPRM_BUF_SIZE - 1);
 118                 iname[BINPRM_BUF_SIZE - 1] = '\0';
 119         }
 120         read_unlock(&entries_lock);
 121         if (!fmt)
 122                 goto _ret;
 123
 124         allow_write_access(bprm->file);
 125         fput(bprm->file);
 126         bprm->file = NULL;
 127
 128         /* Build args for interpreter */
 129         if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
 130                 remove_arg_zero(bprm);
 131         }
 132         retval = copy_strings_kernel(1, &bprm->filename, bprm);
 133         if (retval < 0) goto _ret;
 134         bprm->argc++;
 135         retval = copy_strings_kernel(1, &iname_addr, bprm);
 136         if (retval < 0) goto _ret;
 137         bprm->argc++;
 138         bprm->filename = iname; /* for binfmt_script */
 139
 140         file = open_exec(iname);
 141         retval = PTR_ERR(file);
 142         if (IS_ERR(file))
 143                 goto _ret;
 144         bprm->file = file;
 145
 146         retval = prepare_binprm(bprm);
 147         if (retval >= 0)
 148                 retval = search_binary_handler(bprm, regs);
 149 _ret:
 150         return retval;
 151 }
 152
 153 /* Command parsers */
 154
 155 /*
 156  * parses and copies one argument enclosed in del from *sp to *dp,
 157  * recognising the \x special.
 158  * returns pointer to the copied argument or NULL in case of an
 159  * error (and sets err) or null argument length.
 160  */
 161 static char *scanarg(char *s, char del)
 162 {
 163         char c;
 164
 165         while ((c = *s++) != del) {
 166                 if (c == '\\' && *s == 'x') {
 167                         s++;
 168                         if (!isxdigit(*s++))
 169                                 return NULL;
 170                         if (!isxdigit(*s++))
 171                                 return NULL;
 172                 }
 173         }
 174         return s;
 175 }
 176
 177 static int unquote(char *from)
 178 {
 179         char c = 0, *s = from, *p = from;
 180
 181         while ((c = *s++) != '\0') {
 182                 if (c == '\\' && *s == 'x') {
 183                         s++;
 184                         c = toupper(*s++);
 185                         *p = (c - (isdigit(c) ? '0' : 'A' - 10)) << 4;
 186                         c = toupper(*s++);
 187                         *p++ |= c - (isdigit(c) ? '0' : 'A' - 10);
 188                         continue;
 189                 }
 190                 *p++ = c;
 191         }
 192         return p - from;
 193 }
 194
 195 /*
 196  * This registers a new binary format, it recognises the syntax
 197  * ':name:type:offset:magic:mask:interpreter:'
 198  * where the ':' is the IFS, that can be chosen with the first char
 199  */
 200 static Node *create_entry(const char *buffer, size_t count)
 201 {
 202         Node *e;
 203         int memsize, err;
 204         char *buf, *p;
 205         char del;
 206
 207         /* some sanity checks */
 208         err = -EINVAL;
 209         if ((count < 11) || (count > 256))
 210                 goto out;
 211
 212         err = -ENOMEM;
 213         memsize = sizeof(Node) + count + 8;
 214         e = (Node *) kmalloc(memsize, GFP_USER);
 215         if (!e)
 216                 goto out;
 217
 218         p = buf = (char *)e + sizeof(Node);
 219
 220         memset(e, 0, sizeof(Node));
 221         if (copy_from_user(buf, buffer, count))
 222                 goto Efault;
 223
 224         del = *p++;     /* delimeter */
 225
 226         memset(buf+count, del, 8);
 227
 228         e->name = p;
 229         p = strchr(p, del);
 230         if (!p)
 231                 goto Einval;
 232         *p++ = '\0';
 233         if (!e->name[0] ||
 234             !strcmp(e->name, ".") ||
 235             !strcmp(e->name, "..") ||
 236             strchr(e->name, '/'))
 237                 goto Einval;
 238         switch (*p++) {
 239                 case 'E': e->flags = 1<<Enabled; break;
 240                 case 'M': e->flags = (1<<Enabled) | (1<<Magic); break;
 241                 default: goto Einval;
 242         }
 243         if (*p++ != del)
 244                 goto Einval;
 245         if (test_bit(Magic, &e->flags)) {
 246                 char *s = strchr(p, del);
 247                 if (!s)
 248                         goto Einval;
 249                 *s++ = '\0';
 250                 e->offset = simple_strtoul(p, &p, 10);
 251                 if (*p++)
 252                         goto Einval;
 253                 e->magic = p;
 254                 p = scanarg(p, del);
 255                 if (!p)
 256                         goto Einval;
 257                 p[-1] = '\0';
 258                 if (!e->magic[0])
 259                         goto Einval;
 260                 e->mask = p;
 261                 p = scanarg(p, del);
 262                 if (!p)
 263                         goto Einval;
 264                 p[-1] = '\0';
 265                 if (!e->mask[0])
 266                         e->mask = NULL;
 267                 e->size = unquote(e->magic);
 268                 if (e->mask && unquote(e->mask) != e->size)
 269                         goto Einval;
 270                 if (e->size + e->offset > BINPRM_BUF_SIZE)
 271                         goto Einval;
 272         } else {
 273                 p = strchr(p, del);
 274                 if (!p)
 275                         goto Einval;
 276                 *p++ = '\0';
 277                 e->magic = p;
 278                 p = strchr(p, del);
 279                 if (!p)
 280                         goto Einval;
 281                 *p++ = '\0';
 282                 if (!e->magic[0] || strchr(e->magic, '/'))
 283                         goto Einval;
 284                 p = strchr(p, del);
 285                 if (!p)
 286                         goto Einval;
 287                 *p++ = '\0';
 288         }
 289         e->interpreter = p;
 290         p = strchr(p, del);
 291         if (!p)
 292                 goto Einval;
 293         *p++ = '\0';
 294         if (!e->interpreter[0])
 295                 goto Einval;
 296
 297         if (*p == 'P') {
 298                 p++;
 299                 e->flags |= MISC_FMT_PRESERVE_ARGV0;
 300         }
 301
 302         if (*p == '\n')
 303                 p++;
 304         if (p != buf + count)
 305                 goto Einval;
 306         return e;
 307
 308 out:
 309         return ERR_PTR(err);
 310
 311 Efault:
 312         kfree(e);
 313         return ERR_PTR(-EFAULT);
 314 Einval:
 315         kfree(e);
 316         return ERR_PTR(-EINVAL);
 317 }
 318
 319 /*
 320  * Set status of entry/binfmt_misc:
 321  * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
 322  */
 323 static int parse_command(const char *buffer, size_t count)
 324 {
 325         char s[4];
 326
 327         if (!count)
 328                 return 0;
 329         if (count > 3)
 330                 return -EINVAL;
 331         if (copy_from_user(s, buffer, count))
 332                 return -EFAULT;
 333         if (s[count-1] == '\n')
 334                 count--;
 335         if (count == 1 && s[0] == '0')
 336                 return 1;
 337         if (count == 1 && s[0] == '1')
 338                 return 2;
 339         if (count == 2 && s[0] == '-' && s[1] == '1')
 340                 return 3;
 341         return -EINVAL;
 342 }
 343
 344 /* generic stuff */
 345
 346 static void entry_status(Node *e, char *page)
 347 {
 348         char *dp;
 349         char *status = "disabled";
 350
 351         if (test_bit(Enabled, &e->flags))
 352                 status = "enabled";
 353
 354         if (!VERBOSE_STATUS) {
 355                 sprintf(page, "%s\n", status);
 356                 return;
 357         }
 358
 359         sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter);
 360         dp = page + strlen(page);
 361         if (!test_bit(Magic, &e->flags)) {
 362                 sprintf(dp, "extension .%s\n", e->magic);
 363         } else {
 364                 int i;
 365
 366                 sprintf(dp, "offset %i\nmagic ", e->offset);
 367                 dp = page + strlen(page);
 368                 for (i = 0; i < e->size; i++) {
 369                         sprintf(dp, "%02x", 0xff & (int) (e->magic[i]));
 370                         dp += 2;
 371                 }
 372                 if (e->mask) {
 373                         sprintf(dp, "\nmask ");
 374                         dp += 6;
 375                         for (i = 0; i < e->size; i++) {
 376                                 sprintf(dp, "%02x", 0xff & (int) (e->mask[i]));
 377                                 dp += 2;
 378                         }
 379                 }
 380                 *dp++ = '\n';
 381                 *dp = '\0';
 382         }
 383 }
 384
 385 static struct inode *bm_get_inode(struct super_block *sb, int mode)
 386 {
 387         struct inode * inode = new_inode(sb);
 388
 389         if (inode) {
 390                 inode->i_mode = mode;
 391                 inode->i_uid = 0;
 392                 inode->i_gid = 0;
 393                 inode->i_blksize = PAGE_CACHE_SIZE;
 394                 inode->i_blocks = 0;
 395                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 396         }
 397         return inode;
 398 }
 399
 400 static void bm_clear_inode(struct inode *inode)
 401 {
 402         Node *e = inode->u.generic_ip;
 403
 404         if (e) {
 405                 struct vfsmount *mnt;
 406                 write_lock(&entries_lock);
 407                 list_del(&e->list);
 408                 mnt = bm_mnt;
 409                 if (!--entry_count)
 410                         bm_mnt = NULL;
 411                 write_unlock(&entries_lock);
 412                 kfree(e);
 413                 mntput(mnt);
 414         }
 415 }
 416
 417 static void kill_node(Node *e)
 418 {
 419         struct dentry *dentry;
 420
 421         write_lock(&entries_lock);
 422         dentry = e->dentry;
 423         if (dentry) {
 424                 list_del_init(&e->list);
 425                 e->dentry = NULL;
 426         }
 427         write_unlock(&entries_lock);
 428
 429         if (dentry) {
 430                 dentry->d_inode->i_nlink--;
 431                 d_drop(dentry);
 432                 dput(dentry);
 433         }
 434 }
 435
 436 /* /<entry> */
 437
 438 static ssize_t
 439 bm_entry_read(struct file * file, char * buf, size_t nbytes, loff_t *ppos)
 440 {
 441         Node *e = file->f_dentry->d_inode->u.generic_ip;
 442         loff_t pos = *ppos;
 443         ssize_t res;
 444         char *page;
 445         int len;
 446
 447         if (!(page = (char*) __get_free_page(GFP_KERNEL)))
 448                 return -ENOMEM;
 449
 450         entry_status(e, page);
 451         len = strlen(page);
 452
 453         res = -EINVAL;
 454         if (pos < 0)
 455                 goto out;
 456         res = 0;
 457         if (pos >= len)
 458                 goto out;
 459         if (len < pos + nbytes)
 460                 nbytes = len - pos;
 461         res = -EFAULT;
 462         if (copy_to_user(buf, page + pos, nbytes))
 463                 goto out;
 464         *ppos = pos + nbytes;
 465         res = nbytes;
 466 out:
 467         free_page((unsigned long) page);
 468         return res;
 469 }
 470
 471 static ssize_t bm_entry_write(struct file *file, const char *buffer,
 472                                 size_t count, loff_t *ppos)
 473 {
 474         struct dentry *root;
 475         Node *e = file->f_dentry->d_inode->u.generic_ip;
 476         int res = parse_command(buffer, count);
 477
 478         switch (res) {
 479                 case 1: clear_bit(Enabled, &e->flags);
 480                         break;
 481                 case 2: set_bit(Enabled, &e->flags);
 482                         break;
 483                 case 3: root = dget(file->f_vfsmnt->mnt_sb->s_root);
 484                         down(&root->d_inode->i_sem);
 485
 486                         kill_node(e);
 487
 488                         up(&root->d_inode->i_sem);
 489                         dput(root);
 490                         break;
 491                 default: return res;
 492         }
 493         return count;
 494 }
 495
 496 static struct file_operations bm_entry_operations = {
 497         .read           = bm_entry_read,
 498         .write          = bm_entry_write,
 499 };
 500
 501 static struct file_system_type bm_fs_type;
 502
 503 /* /register */
 504
 505 static ssize_t bm_register_write(struct file *file, const char *buffer,
 506                                size_t count, loff_t *ppos)
 507 {
 508         Node *e;
 509         struct inode *inode;
 510         struct vfsmount *mnt = NULL;
 511         struct dentry *root, *dentry;
 512         struct super_block *sb = file->f_vfsmnt->mnt_sb;
 513         int err = 0;
 514
 515         e = create_entry(buffer, count);
 516
 517         if (IS_ERR(e))
 518                 return PTR_ERR(e);
 519
 520         root = dget(sb->s_root);
 521         down(&root->d_inode->i_sem);
 522         dentry = lookup_one_len(e->name, root, strlen(e->name));
 523         err = PTR_ERR(dentry);
 524         if (IS_ERR(dentry))
 525                 goto out;
 526
 527         err = -EEXIST;
 528         if (dentry->d_inode)
 529                 goto out2;
 530
 531         inode = bm_get_inode(sb, S_IFREG | 0644);
 532
 533         err = -ENOMEM;
 534         if (!inode)
 535                 goto out2;
 536
 537         write_lock(&entries_lock);
 538         if (!bm_mnt) {
 539                 write_unlock(&entries_lock);
 540                 mnt = kern_mount(&bm_fs_type);
 541                 if (IS_ERR(mnt)) {
 542                         err = PTR_ERR(mnt);
 543                         iput(inode);
 544                         inode = NULL;
 545                         goto out2;
 546                 }
 547                 write_lock(&entries_lock);
 548                 if (!bm_mnt)
 549                         bm_mnt = mnt;
 550         }
 551         mntget(bm_mnt);
 552         entry_count++;
 553
 554         e->dentry = dget(dentry);
 555         inode->u.generic_ip = e;
 556         inode->i_fop = &bm_entry_operations;
 557         d_instantiate(dentry, inode);
 558
 559         list_add(&e->list, &entries);
 560         write_unlock(&entries_lock);
 561
 562         mntput(mnt);
 563         err = 0;
 564 out2:
 565         dput(dentry);
 566 out:
 567         up(&root->d_inode->i_sem);
 568         dput(root);
 569
 570         if (err) {
 571                 kfree(e);
 572                 return -EINVAL;
 573         }
 574         return count;
 575 }
 576
 577 static struct file_operations bm_register_operations = {
 578         .write          = bm_register_write,
 579 };
 580
 581 /* /status */
 582
 583 static ssize_t
 584 bm_status_read(struct file * file, char * buf, size_t nbytes, loff_t *ppos)
 585 {
 586         char *s = enabled ? "enabled" : "disabled";
 587         int len = strlen(s);
 588         loff_t pos = *ppos;
 589
 590         if (pos < 0)
 591                 return -EINVAL;
 592         if (pos >= len)
 593                 return 0;
 594         if (len < pos + nbytes)
 595                 nbytes = len - pos;
 596         if (copy_to_user(buf, s + pos, nbytes))
 597                 return -EFAULT;
 598         *ppos = pos + nbytes;
 599         return nbytes;
 600 }
 601
 602 static ssize_t bm_status_write(struct file * file, const char * buffer,
 603                 size_t count, loff_t *ppos)
 604 {
 605         int res = parse_command(buffer, count);
 606         struct dentry *root;
 607
 608         switch (res) {
 609                 case 1: enabled = 0; break;
 610                 case 2: enabled = 1; break;
 611                 case 3: root = dget(file->f_vfsmnt->mnt_sb->s_root);
 612                         down(&root->d_inode->i_sem);
 613
 614                         while (!list_empty(&entries))
 615                                 kill_node(list_entry(entries.next, Node, list));
 616
 617                         up(&root->d_inode->i_sem);
 618                         dput(root);
 619                 default: return res;
 620         }
 621         return count;
 622 }
 623
 624 static struct file_operations bm_status_operations = {
 625         .read           = bm_status_read,
 626         .write          = bm_status_write,
 627 };
 628
 629 /* Superblock handling */
 630
 631 static struct super_operations s_ops = {
 632         .statfs         = simple_statfs,
 633         .drop_inode     = generic_delete_inode,
 634         .clear_inode    = bm_clear_inode,
 635 };
 636
 637 static int bm_fill_super(struct super_block * sb, void * data, int silent)
 638 {
 639         struct qstr names[2] = {{.name = "status"}, {.name = "register"}};
 640         struct inode * inode;
 641         struct dentry * dentry[3];
 642         int i;
 643
 644         for (i=0; i<sizeof(names)/sizeof(names[0]); i++) {
 645                 names[i].len = strlen(names[i].name);
 646                 names[i].hash = full_name_hash(names[i].name, names[i].len);
 647         }
 648
 649         sb->s_blocksize = PAGE_CACHE_SIZE;
 650         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
 651         sb->s_magic = 0x42494e4d;
 652         sb->s_op = &s_ops;
 653
 654         inode = bm_get_inode(sb, S_IFDIR | 0755);
 655         if (!inode)
 656                 return -ENOMEM;
 657         inode->i_op = &simple_dir_inode_operations;
 658         inode->i_fop = &simple_dir_operations;
 659         dentry[0] = d_alloc_root(inode);
 660         if (!dentry[0]) {
 661                 iput(inode);
 662                 return -ENOMEM;
 663         }
 664         dentry[1] = d_alloc(dentry[0], &names[0]);
 665         if (!dentry[1])
 666                 goto out1;
 667         dentry[2] = d_alloc(dentry[0], &names[1]);
 668         if (!dentry[2])
 669                 goto out2;
 670         inode = bm_get_inode(sb, S_IFREG | 0644);
 671         if (!inode)
 672                 goto out3;
 673         inode->i_fop = &bm_status_operations;
 674         d_add(dentry[1], inode);
 675         inode = bm_get_inode(sb, S_IFREG | 0400);
 676         if (!inode)
 677                 goto out3;
 678         inode->i_fop = &bm_register_operations;
 679         d_add(dentry[2], inode);
 680
 681         sb->s_root = dentry[0];
 682         return 0;
 683
 684 out3:
 685         dput(dentry[2]);
 686 out2:
 687         dput(dentry[1]);
 688 out1:
 689         dput(dentry[0]);
 690         return -ENOMEM;
 691 }
 692
 693 static struct super_block *bm_get_sb(struct file_system_type *fs_type,
 694         int flags, char *dev_name, void *data)
 695 {
 696         return get_sb_single(fs_type, flags, data, bm_fill_super);
 697 }
 698
 699 static struct linux_binfmt misc_format = {
 700         .module = THIS_MODULE,
 701         .load_binary = load_misc_binary,
 702 };
 703
 704 static struct file_system_type bm_fs_type = {
 705         .owner          = THIS_MODULE,
 706         .name           = "binfmt_misc",
 707         .get_sb         = bm_get_sb,
 708         .kill_sb        = kill_litter_super,
 709 };
 710
 711 static int __init init_misc_binfmt(void)
 712 {
 713         int err = register_filesystem(&bm_fs_type);
 714         if (!err) {
 715                 err = register_binfmt(&misc_format);
 716                 if (err)
 717                         unregister_filesystem(&bm_fs_type);
 718         }
 719         return err;
 720 }
 721
 722 static void __exit exit_misc_binfmt(void)
 723 {
 724         unregister_binfmt(&misc_format);
 725         unregister_filesystem(&bm_fs_type);
 726 }
 727
 728 module_init(init_misc_binfmt);
 729 module_exit(exit_misc_binfmt);
 730 MODULE_LICENSE("GPL");