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;
  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                 strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
 118         read_unlock(&entries_lock);
 119         if (!fmt)
 120                 goto _ret;
 121
 122         allow_write_access(bprm->file);
 123         fput(bprm->file);
 124         bprm->file = NULL;
 125
 126         /* Build args for interpreter */
 127         if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
 128                 remove_arg_zero(bprm);
 129         }
 130         retval = copy_strings_kernel(1, &bprm->filename, bprm);
 131         if (retval < 0) goto _ret;
 132         bprm->argc++;
 133         retval = copy_strings_kernel(1, &iname_addr, bprm);
 134         if (retval < 0) goto _ret;
 135         bprm->argc++;
 136         bprm->filename = iname; /* for binfmt_script */
 137
 138         file = open_exec(iname);
 139         retval = PTR_ERR(file);
 140         if (IS_ERR(file))
 141                 goto _ret;
 142         bprm->file = file;
 143
 144         retval = prepare_binprm(bprm);
 145         if (retval >= 0)
 146                 retval = search_binary_handler(bprm, regs);
 147 _ret:
 148         return retval;
 149 }
 150
 151 /* Command parsers */
 152
 153 /*
 154  * parses and copies one argument enclosed in del from *sp to *dp,
 155  * recognising the \x special.
 156  * returns pointer to the copied argument or NULL in case of an
 157  * error (and sets err) or null argument length.
 158  */
 159 static char *scanarg(char *s, char del)
 160 {
 161         char c;
 162
 163         while ((c = *s++) != del) {
 164                 if (c == '\\' && *s == 'x') {
 165                         s++;
 166                         if (!isxdigit(*s++))
 167                                 return NULL;
 168                         if (!isxdigit(*s++))
 169                                 return NULL;
 170                 }
 171         }
 172         return s;
 173 }
 174
 175 static int unquote(char *from)
 176 {
 177         char c = 0, *s = from, *p = from;
 178
 179         while ((c = *s++) != '\0') {
 180                 if (c == '\\' && *s == 'x') {
 181                         s++;
 182                         c = toupper(*s++);
 183                         *p = (c - (isdigit(c) ? '0' : 'A' - 10)) << 4;
 184                         c = toupper(*s++);
 185                         *p++ |= c - (isdigit(c) ? '0' : 'A' - 10);
 186                         continue;
 187                 }
 188                 *p++ = c;
 189         }
 190         return p - from;
 191 }
 192
 193 /*
 194  * This registers a new binary format, it recognises the syntax
 195  * ':name:type:offset:magic:mask:interpreter:'
 196  * where the ':' is the IFS, that can be chosen with the first char
 197  */
 198 static Node *create_entry(const char *buffer, size_t count)
 199 {
 200         Node *e;
 201         int memsize, err;
 202         char *buf, *p;
 203         char del;
 204
 205         /* some sanity checks */
 206         err = -EINVAL;
 207         if ((count < 11) || (count > 256))
 208                 goto out;
 209
 210         err = -ENOMEM;
 211         memsize = sizeof(Node) + count + 8;
 212         e = (Node *) kmalloc(memsize, GFP_USER);
 213         if (!e)
 214                 goto out;
 215
 216         p = buf = (char *)e + sizeof(Node);
 217
 218         memset(e, 0, sizeof(Node));
 219         if (copy_from_user(buf, buffer, count))
 220                 goto Efault;
 221
 222         del = *p++;     /* delimeter */
 223
 224         memset(buf+count, del, 8);
 225
 226         e->name = p;
 227         p = strchr(p, del);
 228         if (!p)
 229                 goto Einval;
 230         *p++ = '\0';
 231         if (!e->name[0] ||
 232             !strcmp(e->name, ".") ||
 233             !strcmp(e->name, "..") ||
 234             strchr(e->name, '/'))
 235                 goto Einval;
 236         switch (*p++) {
 237                 case 'E': e->flags = 1<<Enabled; break;
 238                 case 'M': e->flags = (1<<Enabled) | (1<<Magic); break;
 239                 default: goto Einval;
 240         }
 241         if (*p++ != del)
 242                 goto Einval;
 243         if (test_bit(Magic, &e->flags)) {
 244                 char *s = strchr(p, del);
 245                 if (!s)
 246                         goto Einval;
 247                 *s++ = '\0';
 248                 e->offset = simple_strtoul(p, &p, 10);
 249                 if (*p++)
 250                         goto Einval;
 251                 e->magic = p;
 252                 p = scanarg(p, del);
 253                 if (!p)
 254                         goto Einval;
 255                 p[-1] = '\0';
 256                 if (!e->magic[0])
 257                         goto Einval;
 258                 e->mask = p;
 259                 p = scanarg(p, del);
 260                 if (!p)
 261                         goto Einval;
 262                 p[-1] = '\0';
 263                 if (!e->mask[0])
 264                         e->mask = NULL;
 265                 e->size = unquote(e->magic);
 266                 if (e->mask && unquote(e->mask) != e->size)
 267                         goto Einval;
 268                 if (e->size + e->offset > BINPRM_BUF_SIZE)
 269                         goto Einval;
 270         } else {
 271                 p = strchr(p, del);
 272                 if (!p)
 273                         goto Einval;
 274                 *p++ = '\0';
 275                 e->magic = p;
 276                 p = strchr(p, del);
 277                 if (!p)
 278                         goto Einval;
 279                 *p++ = '\0';
 280                 if (!e->magic[0] || strchr(e->magic, '/'))
 281                         goto Einval;
 282                 p = strchr(p, del);
 283                 if (!p)
 284                         goto Einval;
 285                 *p++ = '\0';
 286         }
 287         e->interpreter = p;
 288         p = strchr(p, del);
 289         if (!p)
 290                 goto Einval;
 291         *p++ = '\0';
 292         if (!e->interpreter[0])
 293                 goto Einval;
 294
 295         if (*p == 'P') {
 296                 p++;
 297                 e->flags |= MISC_FMT_PRESERVE_ARGV0;
 298         }
 299
 300         if (*p == '\n')
 301                 p++;
 302         if (p != buf + count)
 303                 goto Einval;
 304         return e;
 305
 306 out:
 307         return ERR_PTR(err);
 308
 309 Efault:
 310         kfree(e);
 311         return ERR_PTR(-EFAULT);
 312 Einval:
 313         kfree(e);
 314         return ERR_PTR(-EINVAL);
 315 }
 316
 317 /*
 318  * Set status of entry/binfmt_misc:
 319  * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
 320  */
 321 static int parse_command(const char *buffer, size_t count)
 322 {
 323         char s[4];
 324
 325         if (!count)
 326                 return 0;
 327         if (count > 3)
 328                 return -EINVAL;
 329         if (copy_from_user(s, buffer, count))
 330                 return -EFAULT;
 331         if (s[count-1] == '\n')
 332                 count--;
 333         if (count == 1 && s[0] == '0')
 334                 return 1;
 335         if (count == 1 && s[0] == '1')
 336                 return 2;
 337         if (count == 2 && s[0] == '-' && s[1] == '1')
 338                 return 3;
 339         return -EINVAL;
 340 }
 341
 342 /* generic stuff */
 343
 344 static void entry_status(Node *e, char *page)
 345 {
 346         char *dp;
 347         char *status = "disabled";
 348
 349         if (test_bit(Enabled, &e->flags))
 350                 status = "enabled";
 351
 352         if (!VERBOSE_STATUS) {
 353                 sprintf(page, "%s\n", status);
 354                 return;
 355         }
 356
 357         sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter);
 358         dp = page + strlen(page);
 359         if (!test_bit(Magic, &e->flags)) {
 360                 sprintf(dp, "extension .%s\n", e->magic);
 361         } else {
 362                 int i;
 363
 364                 sprintf(dp, "offset %i\nmagic ", e->offset);
 365                 dp = page + strlen(page);
 366                 for (i = 0; i < e->size; i++) {
 367                         sprintf(dp, "%02x", 0xff & (int) (e->magic[i]));
 368                         dp += 2;
 369                 }
 370                 if (e->mask) {
 371                         sprintf(dp, "\nmask ");
 372                         dp += 6;
 373                         for (i = 0; i < e->size; i++) {
 374                                 sprintf(dp, "%02x", 0xff & (int) (e->mask[i]));
 375                                 dp += 2;
 376                         }
 377                 }
 378                 *dp++ = '\n';
 379                 *dp = '\0';
 380         }
 381 }
 382
 383 static struct inode *bm_get_inode(struct super_block *sb, int mode)
 384 {
 385         struct inode * inode = new_inode(sb);
 386
 387         if (inode) {
 388                 inode->i_mode = mode;
 389                 inode->i_uid = 0;
 390                 inode->i_gid = 0;
 391                 inode->i_blksize = PAGE_CACHE_SIZE;
 392                 inode->i_blocks = 0;
 393                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 394         }
 395         return inode;
 396 }
 397
 398 static void bm_clear_inode(struct inode *inode)
 399 {
 400         kfree(inode->u.generic_ip);
 401 }
 402
 403 static void kill_node(Node *e)
 404 {
 405         struct dentry *dentry;
 406
 407         write_lock(&entries_lock);
 408         dentry = e->dentry;
 409         if (dentry) {
 410                 list_del_init(&e->list);
 411                 e->dentry = NULL;
 412         }
 413         write_unlock(&entries_lock);
 414
 415         if (dentry) {
 416                 dentry->d_inode->i_nlink--;
 417                 d_drop(dentry);
 418                 dput(dentry);
 419                 simple_release_fs(&bm_mnt, &entry_count);
 420         }
 421 }
 422
 423 /* /<entry> */
 424
 425 static ssize_t
 426 bm_entry_read(struct file * file, char * buf, size_t nbytes, loff_t *ppos)
 427 {
 428         Node *e = file->f_dentry->d_inode->u.generic_ip;
 429         loff_t pos = *ppos;
 430         ssize_t res;
 431         char *page;
 432         int len;
 433
 434         if (!(page = (char*) __get_free_page(GFP_KERNEL)))
 435                 return -ENOMEM;
 436
 437         entry_status(e, page);
 438         len = strlen(page);
 439
 440         res = -EINVAL;
 441         if (pos < 0)
 442                 goto out;
 443         res = 0;
 444         if (pos >= len)
 445                 goto out;
 446         if (len < pos + nbytes)
 447                 nbytes = len - pos;
 448         res = -EFAULT;
 449         if (copy_to_user(buf, page + pos, nbytes))
 450                 goto out;
 451         *ppos = pos + nbytes;
 452         res = nbytes;
 453 out:
 454         free_page((unsigned long) page);
 455         return res;
 456 }
 457
 458 static ssize_t bm_entry_write(struct file *file, const char *buffer,
 459                                 size_t count, loff_t *ppos)
 460 {
 461         struct dentry *root;
 462         Node *e = file->f_dentry->d_inode->u.generic_ip;
 463         int res = parse_command(buffer, count);
 464
 465         switch (res) {
 466                 case 1: clear_bit(Enabled, &e->flags);
 467                         break;
 468                 case 2: set_bit(Enabled, &e->flags);
 469                         break;
 470                 case 3: root = dget(file->f_vfsmnt->mnt_sb->s_root);
 471                         down(&root->d_inode->i_sem);
 472
 473                         kill_node(e);
 474
 475                         up(&root->d_inode->i_sem);
 476                         dput(root);
 477                         break;
 478                 default: return res;
 479         }
 480         return count;
 481 }
 482
 483 static struct file_operations bm_entry_operations = {
 484         .read           = bm_entry_read,
 485         .write          = bm_entry_write,
 486 };
 487
 488 /* /register */
 489
 490 static ssize_t bm_register_write(struct file *file, const char *buffer,
 491                                size_t count, loff_t *ppos)
 492 {
 493         Node *e;
 494         struct inode *inode;
 495         struct dentry *root, *dentry;
 496         struct super_block *sb = file->f_vfsmnt->mnt_sb;
 497         int err = 0;
 498
 499         e = create_entry(buffer, count);
 500
 501         if (IS_ERR(e))
 502                 return PTR_ERR(e);
 503
 504         root = dget(sb->s_root);
 505         down(&root->d_inode->i_sem);
 506         dentry = lookup_one_len(e->name, root, strlen(e->name));
 507         err = PTR_ERR(dentry);
 508         if (IS_ERR(dentry))
 509                 goto out;
 510
 511         err = -EEXIST;
 512         if (dentry->d_inode)
 513                 goto out2;
 514
 515         inode = bm_get_inode(sb, S_IFREG | 0644);
 516
 517         err = -ENOMEM;
 518         if (!inode)
 519                 goto out2;
 520
 521         err = simple_pin_fs("binfmt_misc", &bm_mnt, &entry_count);
 522         if (err) {
 523                 iput(inode);
 524                 inode = NULL;
 525                 goto out2;
 526         }
 527
 528         e->dentry = dget(dentry);
 529         inode->u.generic_ip = e;
 530         inode->i_fop = &bm_entry_operations;
 531
 532         write_lock(&entries_lock);
 533         d_instantiate(dentry, inode);
 534         list_add(&e->list, &entries);
 535         write_unlock(&entries_lock);
 536
 537         err = 0;
 538 out2:
 539         dput(dentry);
 540 out:
 541         up(&root->d_inode->i_sem);
 542         dput(root);
 543
 544         if (err) {
 545                 kfree(e);
 546                 return -EINVAL;
 547         }
 548         return count;
 549 }
 550
 551 static struct file_operations bm_register_operations = {
 552         .write          = bm_register_write,
 553 };
 554
 555 /* /status */
 556
 557 static ssize_t
 558 bm_status_read(struct file * file, char * buf, size_t nbytes, loff_t *ppos)
 559 {
 560         char *s = enabled ? "enabled" : "disabled";
 561         int len = strlen(s);
 562         loff_t pos = *ppos;
 563
 564         if (pos < 0)
 565                 return -EINVAL;
 566         if (pos >= len)
 567                 return 0;
 568         if (len < pos + nbytes)
 569                 nbytes = len - pos;
 570         if (copy_to_user(buf, s + pos, nbytes))
 571                 return -EFAULT;
 572         *ppos = pos + nbytes;
 573         return nbytes;
 574 }
 575
 576 static ssize_t bm_status_write(struct file * file, const char * buffer,
 577                 size_t count, loff_t *ppos)
 578 {
 579         int res = parse_command(buffer, count);
 580         struct dentry *root;
 581
 582         switch (res) {
 583                 case 1: enabled = 0; break;
 584                 case 2: enabled = 1; break;
 585                 case 3: root = dget(file->f_vfsmnt->mnt_sb->s_root);
 586                         down(&root->d_inode->i_sem);
 587
 588                         while (!list_empty(&entries))
 589                                 kill_node(list_entry(entries.next, Node, list));
 590
 591                         up(&root->d_inode->i_sem);
 592                         dput(root);
 593                 default: return res;
 594         }
 595         return count;
 596 }
 597
 598 static struct file_operations bm_status_operations = {
 599         .read           = bm_status_read,
 600         .write          = bm_status_write,
 601 };
 602
 603 /* Superblock handling */
 604
 605 static struct super_operations s_ops = {
 606         .statfs         = simple_statfs,
 607         .clear_inode    = bm_clear_inode,
 608 };
 609
 610 static int bm_fill_super(struct super_block * sb, void * data, int silent)
 611 {
 612         static struct tree_descr bm_files[] = {
 613                 [1] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
 614                 [2] = {"register", &bm_register_operations, S_IWUSR},
 615                 /* last one */ {""}
 616         };
 617         int err = simple_fill_super(sb, 0x42494e4d, bm_files);
 618         if (!err)
 619                 sb->s_op = &s_ops;
 620         return err;
 621 }
 622
 623 static struct super_block *bm_get_sb(struct file_system_type *fs_type,
 624         int flags, const char *dev_name, void *data)
 625 {
 626         return get_sb_single(fs_type, flags, data, bm_fill_super);
 627 }
 628
 629 static struct linux_binfmt misc_format = {
 630         .module = THIS_MODULE,
 631         .load_binary = load_misc_binary,
 632 };
 633
 634 static struct file_system_type bm_fs_type = {
 635         .owner          = THIS_MODULE,
 636         .name           = "binfmt_misc",
 637         .get_sb         = bm_get_sb,
 638         .kill_sb        = kill_litter_super,
 639 };
 640
 641 static int __init init_misc_binfmt(void)
 642 {
 643         int err = register_filesystem(&bm_fs_type);
 644         if (!err) {
 645                 err = register_binfmt(&misc_format);
 646                 if (err)
 647                         unregister_filesystem(&bm_fs_type);
 648         }
 649         return err;
 650 }
 651
 652 static void __exit exit_misc_binfmt(void)
 653 {
 654         unregister_binfmt(&misc_format);
 655         unregister_filesystem(&bm_fs_type);
 656 }
 657
 658 module_init(init_misc_binfmt);
 659 module_exit(exit_misc_binfmt);
 660 MODULE_LICENSE("GPL");