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   1 /*
   2  *  linux/fs/isofs/rock.c
   3  *
   4  *  (C) 1992, 1993  Eric Youngdale
   5  *
   6  *  Rock Ridge Extensions to iso9660
   7  */
   8
   9 #include <linux/slab.h>
  10 #include <linux/pagemap.h>
  11 #include <linux/smp_lock.h>
  12
  13 #include "isofs.h"
  14 #include "rock.h"
  15
  16 /*
  17  * These functions are designed to read the system areas of a directory record
  18  * and extract relevant information.  There are different functions provided
  19  * depending upon what information we need at the time.  One function fills
  20  * out an inode structure, a second one extracts a filename, a third one
  21  * returns a symbolic link name, and a fourth one returns the extent number
  22  * for the file.
  23  */
  24
  25 #define SIG(A,B) ((A) | ((B) << 8))     /* isonum_721() */
  26
  27 struct rock_state {
  28         void *buffer;
  29         unsigned char *chr;
  30         int len;
  31         int cont_size;
  32         int cont_extent;
  33         int cont_offset;
  34         struct inode *inode;
  35 };
  36
  37 /*
  38  * This is a way of ensuring that we have something in the system
  39  * use fields that is compatible with Rock Ridge.  Return zero on success.
  40  */
  41
  42 static int check_sp(struct rock_ridge *rr, struct inode *inode)
  43 {
  44         if (rr->u.SP.magic[0] != 0xbe)
  45                 return -1;
  46         if (rr->u.SP.magic[1] != 0xef)
  47                 return -1;
  48         ISOFS_SB(inode->i_sb)->s_rock_offset = rr->u.SP.skip;
  49         return 0;
  50 }
  51
  52 static void setup_rock_ridge(struct iso_directory_record *de,
  53                         struct inode *inode, struct rock_state *rs)
  54 {
  55         rs->len = sizeof(struct iso_directory_record) + de->name_len[0];
  56         if (rs->len & 1)
  57                 (rs->len)++;
  58         rs->chr = (unsigned char *)de + rs->len;
  59         rs->len = *((unsigned char *)de) - rs->len;
  60         if (rs->len < 0)
  61                 rs->len = 0;
  62
  63         if (ISOFS_SB(inode->i_sb)->s_rock_offset != -1) {
  64                 rs->len -= ISOFS_SB(inode->i_sb)->s_rock_offset;
  65                 rs->chr += ISOFS_SB(inode->i_sb)->s_rock_offset;
  66                 if (rs->len < 0)
  67                         rs->len = 0;
  68         }
  69 }
  70
  71 static void init_rock_state(struct rock_state *rs, struct inode *inode)
  72 {
  73         memset(rs, 0, sizeof(*rs));
  74         rs->inode = inode;
  75 }
  76
  77 /*
  78  * Returns 0 if the caller should continue scanning, 1 if the scan must end
  79  * and -ve on error.
  80  */
  81 static int rock_continue(struct rock_state *rs)
  82 {
  83         int ret = 1;
  84         int blocksize = 1 << rs->inode->i_blkbits;
  85         const int min_de_size = offsetof(struct rock_ridge, u);
  86
  87         kfree(rs->buffer);
  88         rs->buffer = NULL;
  89
  90         if ((unsigned)rs->cont_offset > blocksize - min_de_size ||
  91             (unsigned)rs->cont_size > blocksize ||
  92             (unsigned)(rs->cont_offset + rs->cont_size) > blocksize) {
  93                 printk(KERN_NOTICE "rock: corrupted directory entry. "
  94                         "extent=%d, offset=%d, size=%d\n",
  95                         rs->cont_extent, rs->cont_offset, rs->cont_size);
  96                 ret = -EIO;
  97                 goto out;
  98         }
  99
 100         if (rs->cont_extent) {
 101                 struct buffer_head *bh;
 102
 103                 rs->buffer = kmalloc(rs->cont_size, GFP_KERNEL);
 104                 if (!rs->buffer) {
 105                         ret = -ENOMEM;
 106                         goto out;
 107                 }
 108                 ret = -EIO;
 109                 bh = sb_bread(rs->inode->i_sb, rs->cont_extent);
 110                 if (bh) {
 111                         memcpy(rs->buffer, bh->b_data + rs->cont_offset,
 112                                         rs->cont_size);
 113                         put_bh(bh);
 114                         rs->chr = rs->buffer;
 115                         rs->len = rs->cont_size;
 116                         rs->cont_extent = 0;
 117                         rs->cont_size = 0;
 118                         rs->cont_offset = 0;
 119                         return 0;
 120                 }
 121                 printk("Unable to read rock-ridge attributes\n");
 122         }
 123 out:
 124         kfree(rs->buffer);
 125         rs->buffer = NULL;
 126         return ret;
 127 }
 128
 129 /*
 130  * We think there's a record of type `sig' at rs->chr.  Parse the signature
 131  * and make sure that there's really room for a record of that type.
 132  */
 133 static int rock_check_overflow(struct rock_state *rs, int sig)
 134 {
 135         int len;
 136
 137         switch (sig) {
 138         case SIG('S', 'P'):
 139                 len = sizeof(struct SU_SP_s);
 140                 break;
 141         case SIG('C', 'E'):
 142                 len = sizeof(struct SU_CE_s);
 143                 break;
 144         case SIG('E', 'R'):
 145                 len = sizeof(struct SU_ER_s);
 146                 break;
 147         case SIG('R', 'R'):
 148                 len = sizeof(struct RR_RR_s);
 149                 break;
 150         case SIG('P', 'X'):
 151                 len = sizeof(struct RR_PX_s);
 152                 break;
 153         case SIG('P', 'N'):
 154                 len = sizeof(struct RR_PN_s);
 155                 break;
 156         case SIG('S', 'L'):
 157                 len = sizeof(struct RR_SL_s);
 158                 break;
 159         case SIG('N', 'M'):
 160                 len = sizeof(struct RR_NM_s);
 161                 break;
 162         case SIG('C', 'L'):
 163                 len = sizeof(struct RR_CL_s);
 164                 break;
 165         case SIG('P', 'L'):
 166                 len = sizeof(struct RR_PL_s);
 167                 break;
 168         case SIG('T', 'F'):
 169                 len = sizeof(struct RR_TF_s);
 170                 break;
 171         case SIG('Z', 'F'):
 172                 len = sizeof(struct RR_ZF_s);
 173                 break;
 174         default:
 175                 len = 0;
 176                 break;
 177         }
 178         len += offsetof(struct rock_ridge, u);
 179         if (len > rs->len) {
 180                 printk(KERN_NOTICE "rock: directory entry would overflow "
 181                                 "storage\n");
 182                 printk(KERN_NOTICE "rock: sig=0x%02x, size=%d, remaining=%d\n",
 183                                 sig, len, rs->len);
 184                 return -EIO;
 185         }
 186         return 0;
 187 }
 188
 189 /*
 190  * return length of name field; 0: not found, -1: to be ignored
 191  */
 192 int get_rock_ridge_filename(struct iso_directory_record *de,
 193                             char *retname, struct inode *inode)
 194 {
 195         struct rock_state rs;
 196         struct rock_ridge *rr;
 197         int sig;
 198         int retnamlen = 0;
 199         int truncate = 0;
 200         int ret = 0;
 201
 202         if (!ISOFS_SB(inode->i_sb)->s_rock)
 203                 return 0;
 204         *retname = 0;
 205
 206         init_rock_state(&rs, inode);
 207         setup_rock_ridge(de, inode, &rs);
 208 repeat:
 209
 210         while (rs.len > 2) { /* There may be one byte for padding somewhere */
 211                 rr = (struct rock_ridge *)rs.chr;
 212                 /*
 213                  * Ignore rock ridge info if rr->len is out of range, but
 214                  * don't return -EIO because that would make the file
 215                  * invisible.
 216                  */
 217                 if (rr->len < 3)
 218                         goto out;       /* Something got screwed up here */
 219                 sig = isonum_721(rs.chr);
 220                 if (rock_check_overflow(&rs, sig))
 221                         goto eio;
 222                 rs.chr += rr->len;
 223                 rs.len -= rr->len;
 224                 /*
 225                  * As above, just ignore the rock ridge info if rr->len
 226                  * is bogus.
 227                  */
 228                 if (rs.len < 0)
 229                         goto out;       /* Something got screwed up here */
 230
 231                 switch (sig) {
 232                 case SIG('R', 'R'):
 233                         if ((rr->u.RR.flags[0] & RR_NM) == 0)
 234                                 goto out;
 235                         break;
 236                 case SIG('S', 'P'):
 237                         if (check_sp(rr, inode))
 238                                 goto out;
 239                         break;
 240                 case SIG('C', 'E'):
 241                         rs.cont_extent = isonum_733(rr->u.CE.extent);
 242                         rs.cont_offset = isonum_733(rr->u.CE.offset);
 243                         rs.cont_size = isonum_733(rr->u.CE.size);
 244                         break;
 245                 case SIG('N', 'M'):
 246                         if (truncate)
 247                                 break;
 248                         if (rr->len < 5)
 249                                 break;
 250                         /*
 251                          * If the flags are 2 or 4, this indicates '.' or '..'.
 252                          * We don't want to do anything with this, because it
 253                          * screws up the code that calls us.  We don't really
 254                          * care anyways, since we can just use the non-RR
 255                          * name.
 256                          */
 257                         if (rr->u.NM.flags & 6)
 258                                 break;
 259
 260                         if (rr->u.NM.flags & ~1) {
 261                                 printk("Unsupported NM flag settings (%d)\n",
 262                                         rr->u.NM.flags);
 263                                 break;
 264                         }
 265                         if ((strlen(retname) + rr->len - 5) >= 254) {
 266                                 truncate = 1;
 267                                 break;
 268                         }
 269                         strncat(retname, rr->u.NM.name, rr->len - 5);
 270                         retnamlen += rr->len - 5;
 271                         break;
 272                 case SIG('R', 'E'):
 273                         kfree(rs.buffer);
 274                         return -1;
 275                 default:
 276                         break;
 277                 }
 278         }
 279         ret = rock_continue(&rs);
 280         if (ret == 0)
 281                 goto repeat;
 282         if (ret == 1)
 283                 return retnamlen; /* If 0, this file did not have a NM field */
 284 out:
 285         kfree(rs.buffer);
 286         return ret;
 287 eio:
 288         ret = -EIO;
 289         goto out;
 290 }
 291
 292 static int
 293 parse_rock_ridge_inode_internal(struct iso_directory_record *de,
 294                                 struct inode *inode, int regard_xa)
 295 {
 296         int symlink_len = 0;
 297         int cnt, sig;
 298         struct inode *reloc;
 299         struct rock_ridge *rr;
 300         int rootflag;
 301         struct rock_state rs;
 302         int ret = 0;
 303
 304         if (!ISOFS_SB(inode->i_sb)->s_rock)
 305                 return 0;
 306
 307         init_rock_state(&rs, inode);
 308         setup_rock_ridge(de, inode, &rs);
 309         if (regard_xa) {
 310                 rs.chr += 14;
 311                 rs.len -= 14;
 312                 if (rs.len < 0)
 313                         rs.len = 0;
 314         }
 315
 316 repeat:
 317         while (rs.len > 2) { /* There may be one byte for padding somewhere */
 318                 rr = (struct rock_ridge *)rs.chr;
 319                 /*
 320                  * Ignore rock ridge info if rr->len is out of range, but
 321                  * don't return -EIO because that would make the file
 322                  * invisible.
 323                  */
 324                 if (rr->len < 3)
 325                         goto out;       /* Something got screwed up here */
 326                 sig = isonum_721(rs.chr);
 327                 if (rock_check_overflow(&rs, sig))
 328                         goto eio;
 329                 rs.chr += rr->len;
 330                 rs.len -= rr->len;
 331                 /*
 332                  * As above, just ignore the rock ridge info if rr->len
 333                  * is bogus.
 334                  */
 335                 if (rs.len < 0)
 336                         goto out;       /* Something got screwed up here */
 337
 338                 switch (sig) {
 339 #ifndef CONFIG_ZISOFS           /* No flag for SF or ZF */
 340                 case SIG('R', 'R'):
 341                         if ((rr->u.RR.flags[0] &
 342                              (RR_PX | RR_TF | RR_SL | RR_CL)) == 0)
 343                                 goto out;
 344                         break;
 345 #endif
 346                 case SIG('S', 'P'):
 347                         if (check_sp(rr, inode))
 348                                 goto out;
 349                         break;
 350                 case SIG('C', 'E'):
 351                         rs.cont_extent = isonum_733(rr->u.CE.extent);
 352                         rs.cont_offset = isonum_733(rr->u.CE.offset);
 353                         rs.cont_size = isonum_733(rr->u.CE.size);
 354                         break;
 355                 case SIG('E', 'R'):
 356                         ISOFS_SB(inode->i_sb)->s_rock = 1;
 357                         printk(KERN_DEBUG "ISO 9660 Extensions: ");
 358                         {
 359                                 int p;
 360                                 for (p = 0; p < rr->u.ER.len_id; p++)
 361                                         printk("%c", rr->u.ER.data[p]);
 362                         }
 363                         printk("\n");
 364                         break;
 365                 case SIG('P', 'X'):
 366                         inode->i_mode = isonum_733(rr->u.PX.mode);
 367                         inode->i_nlink = isonum_733(rr->u.PX.n_links);
 368                         inode->i_uid = isonum_733(rr->u.PX.uid);
 369                         inode->i_gid = isonum_733(rr->u.PX.gid);
 370                         break;
 371                 case SIG('P', 'N'):
 372                         {
 373                                 int high, low;
 374                                 high = isonum_733(rr->u.PN.dev_high);
 375                                 low = isonum_733(rr->u.PN.dev_low);
 376                                 /*
 377                                  * The Rock Ridge standard specifies that if
 378                                  * sizeof(dev_t) <= 4, then the high field is
 379                                  * unused, and the device number is completely
 380                                  * stored in the low field.  Some writers may
 381                                  * ignore this subtlety,
 382                                  * and as a result we test to see if the entire
 383                                  * device number is
 384                                  * stored in the low field, and use that.
 385                                  */
 386                                 if ((low & ~0xff) && high == 0) {
 387                                         inode->i_rdev =
 388                                             MKDEV(low >> 8, low & 0xff);
 389                                 } else {
 390                                         inode->i_rdev =
 391                                             MKDEV(high, low);
 392                                 }
 393                         }
 394                         break;
 395                 case SIG('T', 'F'):
 396                         /*
 397                          * Some RRIP writers incorrectly place ctime in the
 398                          * TF_CREATE field. Try to handle this correctly for
 399                          * either case.
 400                          */
 401                         /* Rock ridge never appears on a High Sierra disk */
 402                         cnt = 0;
 403                         if (rr->u.TF.flags & TF_CREATE) {
 404                                 inode->i_ctime.tv_sec =
 405                                     iso_date(rr->u.TF.times[cnt++].time,
 406                                              0);
 407                                 inode->i_ctime.tv_nsec = 0;
 408                         }
 409                         if (rr->u.TF.flags & TF_MODIFY) {
 410                                 inode->i_mtime.tv_sec =
 411                                     iso_date(rr->u.TF.times[cnt++].time,
 412                                              0);
 413                                 inode->i_mtime.tv_nsec = 0;
 414                         }
 415                         if (rr->u.TF.flags & TF_ACCESS) {
 416                                 inode->i_atime.tv_sec =
 417                                     iso_date(rr->u.TF.times[cnt++].time,
 418                                              0);
 419                                 inode->i_atime.tv_nsec = 0;
 420                         }
 421                         if (rr->u.TF.flags & TF_ATTRIBUTES) {
 422                                 inode->i_ctime.tv_sec =
 423                                     iso_date(rr->u.TF.times[cnt++].time,
 424                                              0);
 425                                 inode->i_ctime.tv_nsec = 0;
 426                         }
 427                         break;
 428                 case SIG('S', 'L'):
 429                         {
 430                                 int slen;
 431                                 struct SL_component *slp;
 432                                 struct SL_component *oldslp;
 433                                 slen = rr->len - 5;
 434                                 slp = &rr->u.SL.link;
 435                                 inode->i_size = symlink_len;
 436                                 while (slen > 1) {
 437                                         rootflag = 0;
 438                                         switch (slp->flags & ~1) {
 439                                         case 0:
 440                                                 inode->i_size +=
 441                                                     slp->len;
 442                                                 break;
 443                                         case 2:
 444                                                 inode->i_size += 1;
 445                                                 break;
 446                                         case 4:
 447                                                 inode->i_size += 2;
 448                                                 break;
 449                                         case 8:
 450                                                 rootflag = 1;
 451                                                 inode->i_size += 1;
 452                                                 break;
 453                                         default:
 454                                                 printk("Symlink component flag "
 455                                                         "not implemented\n");
 456                                         }
 457                                         slen -= slp->len + 2;
 458                                         oldslp = slp;
 459                                         slp = (struct SL_component *)
 460                                                 (((char *)slp) + slp->len + 2);
 461
 462                                         if (slen < 2) {
 463                                                 if (((rr->u.SL.
 464                                                       flags & 1) != 0)
 465                                                     &&
 466                                                     ((oldslp->
 467                                                       flags & 1) == 0))
 468                                                         inode->i_size +=
 469                                                             1;
 470                                                 break;
 471                                         }
 472
 473                                         /*
 474                                          * If this component record isn't
 475                                          * continued, then append a '/'.
 476                                          */
 477                                         if (!rootflag
 478                                             && (oldslp->flags & 1) == 0)
 479                                                 inode->i_size += 1;
 480                                 }
 481                         }
 482                         symlink_len = inode->i_size;
 483                         break;
 484                 case SIG('R', 'E'):
 485                         printk(KERN_WARNING "Attempt to read inode for "
 486                                         "relocated directory\n");
 487                         goto out;
 488                 case SIG('C', 'L'):
 489                         ISOFS_I(inode)->i_first_extent =
 490                             isonum_733(rr->u.CL.location);
 491                         reloc =
 492                             isofs_iget(inode->i_sb,
 493                                        ISOFS_I(inode)->i_first_extent,
 494                                        0);
 495                         if (IS_ERR(reloc)) {
 496                                 ret = PTR_ERR(reloc);
 497                                 goto out;
 498                         }
 499                         inode->i_mode = reloc->i_mode;
 500                         inode->i_nlink = reloc->i_nlink;
 501                         inode->i_uid = reloc->i_uid;
 502                         inode->i_gid = reloc->i_gid;
 503                         inode->i_rdev = reloc->i_rdev;
 504                         inode->i_size = reloc->i_size;
 505                         inode->i_blocks = reloc->i_blocks;
 506                         inode->i_atime = reloc->i_atime;
 507                         inode->i_ctime = reloc->i_ctime;
 508                         inode->i_mtime = reloc->i_mtime;
 509                         iput(reloc);
 510                         break;
 511 #ifdef CONFIG_ZISOFS
 512                 case SIG('Z', 'F'): {
 513                         int algo;
 514
 515                         if (ISOFS_SB(inode->i_sb)->s_nocompress)
 516                                 break;
 517                         algo = isonum_721(rr->u.ZF.algorithm);
 518                         if (algo == SIG('p', 'z')) {
 519                                 int block_shift =
 520                                         isonum_711(&rr->u.ZF.parms[1]);
 521                                 if (block_shift > 17) {
 522                                         printk(KERN_WARNING "isofs: "
 523                                                 "Can't handle ZF block "
 524                                                 "size of 2^%d\n",
 525                                                 block_shift);
 526                                 } else {
 527                                         /*
 528                                          * Note: we don't change
 529                                          * i_blocks here
 530                                          */
 531                                         ISOFS_I(inode)->i_file_format =
 532                                                 isofs_file_compressed;
 533                                         /*
 534                                          * Parameters to compression
 535                                          * algorithm (header size,
 536                                          * block size)
 537                                          */
 538                                         ISOFS_I(inode)->i_format_parm[0] =
 539                                                 isonum_711(&rr->u.ZF.parms[0]);
 540                                         ISOFS_I(inode)->i_format_parm[1] =
 541                                                 isonum_711(&rr->u.ZF.parms[1]);
 542                                         inode->i_size =
 543                                             isonum_733(rr->u.ZF.
 544                                                        real_size);
 545                                 }
 546                         } else {
 547                                 printk(KERN_WARNING
 548                                        "isofs: Unknown ZF compression "
 549                                                 "algorithm: %c%c\n",
 550                                        rr->u.ZF.algorithm[0],
 551                                        rr->u.ZF.algorithm[1]);
 552                         }
 553                         break;
 554                 }
 555 #endif
 556                 default:
 557                         break;
 558                 }
 559         }
 560         ret = rock_continue(&rs);
 561         if (ret == 0)
 562                 goto repeat;
 563         if (ret == 1)
 564                 ret = 0;
 565 out:
 566         kfree(rs.buffer);
 567         return ret;
 568 eio:
 569         ret = -EIO;
 570         goto out;
 571 }
 572
 573 static char *get_symlink_chunk(char *rpnt, struct rock_ridge *rr, char *plimit)
 574 {
 575         int slen;
 576         int rootflag;
 577         struct SL_component *oldslp;
 578         struct SL_component *slp;
 579         slen = rr->len - 5;
 580         slp = &rr->u.SL.link;
 581         while (slen > 1) {
 582                 rootflag = 0;
 583                 switch (slp->flags & ~1) {
 584                 case 0:
 585                         if (slp->len > plimit - rpnt)
 586                                 return NULL;
 587                         memcpy(rpnt, slp->text, slp->len);
 588                         rpnt += slp->len;
 589                         break;
 590                 case 2:
 591                         if (rpnt >= plimit)
 592                                 return NULL;
 593                         *rpnt++ = '.';
 594                         break;
 595                 case 4:
 596                         if (2 > plimit - rpnt)
 597                                 return NULL;
 598                         *rpnt++ = '.';
 599                         *rpnt++ = '.';
 600                         break;
 601                 case 8:
 602                         if (rpnt >= plimit)
 603                                 return NULL;
 604                         rootflag = 1;
 605                         *rpnt++ = '/';
 606                         break;
 607                 default:
 608                         printk("Symlink component flag not implemented (%d)\n",
 609                                slp->flags);
 610                 }
 611                 slen -= slp->len + 2;
 612                 oldslp = slp;
 613                 slp = (struct SL_component *)((char *)slp + slp->len + 2);
 614
 615                 if (slen < 2) {
 616                         /*
 617                          * If there is another SL record, and this component
 618                          * record isn't continued, then add a slash.
 619                          */
 620                         if ((!rootflag) && (rr->u.SL.flags & 1) &&
 621                             !(oldslp->flags & 1)) {
 622                                 if (rpnt >= plimit)
 623                                         return NULL;
 624                                 *rpnt++ = '/';
 625                         }
 626                         break;
 627                 }
 628
 629                 /*
 630                  * If this component record isn't continued, then append a '/'.
 631                  */
 632                 if (!rootflag && !(oldslp->flags & 1)) {
 633                         if (rpnt >= plimit)
 634                                 return NULL;
 635                         *rpnt++ = '/';
 636                 }
 637         }
 638         return rpnt;
 639 }
 640
 641 int parse_rock_ridge_inode(struct iso_directory_record *de, struct inode *inode)
 642 {
 643         int result = parse_rock_ridge_inode_internal(de, inode, 0);
 644
 645         /*
 646          * if rockridge flag was reset and we didn't look for attributes
 647          * behind eventual XA attributes, have a look there
 648          */
 649         if ((ISOFS_SB(inode->i_sb)->s_rock_offset == -1)
 650             && (ISOFS_SB(inode->i_sb)->s_rock == 2)) {
 651                 result = parse_rock_ridge_inode_internal(de, inode, 14);
 652         }
 653         return result;
 654 }
 655
 656 /*
 657  * readpage() for symlinks: reads symlink contents into the page and either
 658  * makes it uptodate and returns 0 or returns error (-EIO)
 659  */
 660 static int rock_ridge_symlink_readpage(struct file *file, struct page *page)
 661 {
 662         struct inode *inode = page->mapping->host;
 663         struct iso_inode_info *ei = ISOFS_I(inode);
 664         char *link = kmap(page);
 665         unsigned long bufsize = ISOFS_BUFFER_SIZE(inode);
 666         struct buffer_head *bh;
 667         char *rpnt = link;
 668         unsigned char *pnt;
 669         struct iso_directory_record *raw_de;
 670         unsigned long block, offset;
 671         int sig;
 672         struct rock_ridge *rr;
 673         struct rock_state rs;
 674         int ret;
 675
 676         if (!ISOFS_SB(inode->i_sb)->s_rock)
 677                 goto error;
 678
 679         init_rock_state(&rs, inode);
 680         block = ei->i_iget5_block;
 681         lock_kernel();
 682         bh = sb_bread(inode->i_sb, block);
 683         if (!bh)
 684                 goto out_noread;
 685
 686         offset = ei->i_iget5_offset;
 687         pnt = (unsigned char *)bh->b_data + offset;
 688
 689         raw_de = (struct iso_directory_record *)pnt;
 690
 691         /*
 692          * If we go past the end of the buffer, there is some sort of error.
 693          */
 694         if (offset + *pnt > bufsize)
 695                 goto out_bad_span;
 696
 697         /*
 698          * Now test for possible Rock Ridge extensions which will override
 699          * some of these numbers in the inode structure.
 700          */
 701
 702         setup_rock_ridge(raw_de, inode, &rs);
 703
 704 repeat:
 705         while (rs.len > 2) { /* There may be one byte for padding somewhere */
 706                 rr = (struct rock_ridge *)rs.chr;
 707                 if (rr->len < 3)
 708                         goto out;       /* Something got screwed up here */
 709                 sig = isonum_721(rs.chr);
 710                 if (rock_check_overflow(&rs, sig))
 711                         goto out;
 712                 rs.chr += rr->len;
 713                 rs.len -= rr->len;
 714                 if (rs.len < 0)
 715                         goto out;       /* corrupted isofs */
 716
 717                 switch (sig) {
 718                 case SIG('R', 'R'):
 719                         if ((rr->u.RR.flags[0] & RR_SL) == 0)
 720                                 goto out;
 721                         break;
 722                 case SIG('S', 'P'):
 723                         if (check_sp(rr, inode))
 724                                 goto out;
 725                         break;
 726                 case SIG('S', 'L'):
 727                         rpnt = get_symlink_chunk(rpnt, rr,
 728                                                  link + (PAGE_SIZE - 1));
 729                         if (rpnt == NULL)
 730                                 goto out;
 731                         break;
 732                 case SIG('C', 'E'):
 733                         /* This tells is if there is a continuation record */
 734                         rs.cont_extent = isonum_733(rr->u.CE.extent);
 735                         rs.cont_offset = isonum_733(rr->u.CE.offset);
 736                         rs.cont_size = isonum_733(rr->u.CE.size);
 737                 default:
 738                         break;
 739                 }
 740         }
 741         ret = rock_continue(&rs);
 742         if (ret == 0)
 743                 goto repeat;
 744         if (ret < 0)
 745                 goto fail;
 746
 747         if (rpnt == link)
 748                 goto fail;
 749         brelse(bh);
 750         *rpnt = '\0';
 751         unlock_kernel();
 752         SetPageUptodate(page);
 753         kunmap(page);
 754         unlock_page(page);
 755         return 0;
 756
 757         /* error exit from macro */
 758 out:
 759         kfree(rs.buffer);
 760         goto fail;
 761 out_noread:
 762         printk("unable to read i-node block");
 763         goto fail;
 764 out_bad_span:
 765         printk("symlink spans iso9660 blocks\n");
 766 fail:
 767         brelse(bh);
 768         unlock_kernel();
 769 error:
 770         SetPageError(page);
 771         kunmap(page);
 772         unlock_page(page);
 773         return -EIO;
 774 }
 775
 776 const struct address_space_operations isofs_symlink_aops = {
 777         .readpage = rock_ridge_symlink_readpage
 778 };