linux/fs/isofs/rock.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *  linux/fs/isofs/rock.c
   4 *
   5 *  (C) 1992, 1993  Eric Youngdale
   6 *
   7 *  Rock Ridge Extensions to iso9660
   8 */
   9
  10#include <linux/slab.h>
  11#include <linux/pagemap.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
  27struct 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        int cont_loops;
  35        struct inode *inode;
  36};
  37
  38/*
  39 * This is a way of ensuring that we have something in the system
  40 * use fields that is compatible with Rock Ridge.  Return zero on success.
  41 */
  42
  43static int check_sp(struct rock_ridge *rr, struct inode *inode)
  44{
  45        if (rr->u.SP.magic[0] != 0xbe)
  46                return -1;
  47        if (rr->u.SP.magic[1] != 0xef)
  48                return -1;
  49        ISOFS_SB(inode->i_sb)->s_rock_offset = rr->u.SP.skip;
  50        return 0;
  51}
  52
  53static void setup_rock_ridge(struct iso_directory_record *de,
  54                        struct inode *inode, struct rock_state *rs)
  55{
  56        rs->len = sizeof(struct iso_directory_record) + de->name_len[0];
  57        if (rs->len & 1)
  58                (rs->len)++;
  59        rs->chr = (unsigned char *)de + rs->len;
  60        rs->len = *((unsigned char *)de) - rs->len;
  61        if (rs->len < 0)
  62                rs->len = 0;
  63
  64        if (ISOFS_SB(inode->i_sb)->s_rock_offset != -1) {
  65                rs->len -= ISOFS_SB(inode->i_sb)->s_rock_offset;
  66                rs->chr += ISOFS_SB(inode->i_sb)->s_rock_offset;
  67                if (rs->len < 0)
  68                        rs->len = 0;
  69        }
  70}
  71
  72static void init_rock_state(struct rock_state *rs, struct inode *inode)
  73{
  74        memset(rs, 0, sizeof(*rs));
  75        rs->inode = inode;
  76}
  77
  78/* Maximum number of Rock Ridge continuation entries */
  79#define RR_MAX_CE_ENTRIES 32
  80
  81/*
  82 * Returns 0 if the caller should continue scanning, 1 if the scan must end
  83 * and -ve on error.
  84 */
  85static int rock_continue(struct rock_state *rs)
  86{
  87        int ret = 1;
  88        int blocksize = 1 << rs->inode->i_blkbits;
  89        const int min_de_size = offsetof(struct rock_ridge, u);
  90
  91        kfree(rs->buffer);
  92        rs->buffer = NULL;
  93
  94        if ((unsigned)rs->cont_offset > blocksize - min_de_size ||
  95            (unsigned)rs->cont_size > blocksize ||
  96            (unsigned)(rs->cont_offset + rs->cont_size) > blocksize) {
  97                printk(KERN_NOTICE "rock: corrupted directory entry. "
  98                        "extent=%d, offset=%d, size=%d\n",
  99                        rs->cont_extent, rs->cont_offset, rs->cont_size);
 100                ret = -EIO;
 101                goto out;
 102        }
 103
 104        if (rs->cont_extent) {
 105                struct buffer_head *bh;
 106
 107                rs->buffer = kmalloc(rs->cont_size, GFP_KERNEL);
 108                if (!rs->buffer) {
 109                        ret = -ENOMEM;
 110                        goto out;
 111                }
 112                ret = -EIO;
 113                if (++rs->cont_loops >= RR_MAX_CE_ENTRIES)
 114                        goto out;
 115                bh = sb_bread(rs->inode->i_sb, rs->cont_extent);
 116                if (bh) {
 117                        memcpy(rs->buffer, bh->b_data + rs->cont_offset,
 118                                        rs->cont_size);
 119                        put_bh(bh);
 120                        rs->chr = rs->buffer;
 121                        rs->len = rs->cont_size;
 122                        rs->cont_extent = 0;
 123                        rs->cont_size = 0;
 124                        rs->cont_offset = 0;
 125                        return 0;
 126                }
 127                printk("Unable to read rock-ridge attributes\n");
 128        }
 129out:
 130        kfree(rs->buffer);
 131        rs->buffer = NULL;
 132        return ret;
 133}
 134
 135/*
 136 * We think there's a record of type `sig' at rs->chr.  Parse the signature
 137 * and make sure that there's really room for a record of that type.
 138 */
 139static int rock_check_overflow(struct rock_state *rs, int sig)
 140{
 141        int len;
 142
 143        switch (sig) {
 144        case SIG('S', 'P'):
 145                len = sizeof(struct SU_SP_s);
 146                break;
 147        case SIG('C', 'E'):
 148                len = sizeof(struct SU_CE_s);
 149                break;
 150        case SIG('E', 'R'):
 151                len = sizeof(struct SU_ER_s);
 152                break;
 153        case SIG('R', 'R'):
 154                len = sizeof(struct RR_RR_s);
 155                break;
 156        case SIG('P', 'X'):
 157                len = sizeof(struct RR_PX_s);
 158                break;
 159        case SIG('P', 'N'):
 160                len = sizeof(struct RR_PN_s);
 161                break;
 162        case SIG('S', 'L'):
 163                len = sizeof(struct RR_SL_s);
 164                break;
 165        case SIG('N', 'M'):
 166                len = sizeof(struct RR_NM_s);
 167                break;
 168        case SIG('C', 'L'):
 169                len = sizeof(struct RR_CL_s);
 170                break;
 171        case SIG('P', 'L'):
 172                len = sizeof(struct RR_PL_s);
 173                break;
 174        case SIG('T', 'F'):
 175                len = sizeof(struct RR_TF_s);
 176                break;
 177        case SIG('Z', 'F'):
 178                len = sizeof(struct RR_ZF_s);
 179                break;
 180        default:
 181                len = 0;
 182                break;
 183        }
 184        len += offsetof(struct rock_ridge, u);
 185        if (len > rs->len) {
 186                printk(KERN_NOTICE "rock: directory entry would overflow "
 187                                "storage\n");
 188                printk(KERN_NOTICE "rock: sig=0x%02x, size=%d, remaining=%d\n",
 189                                sig, len, rs->len);
 190                return -EIO;
 191        }
 192        return 0;
 193}
 194
 195/*
 196 * return length of name field; 0: not found, -1: to be ignored
 197 */
 198int get_rock_ridge_filename(struct iso_directory_record *de,
 199                            char *retname, struct inode *inode)
 200{
 201        struct rock_state rs;
 202        struct rock_ridge *rr;
 203        int sig;
 204        int retnamlen = 0;
 205        int truncate = 0;
 206        int ret = 0;
 207        char *p;
 208        int len;
 209
 210        if (!ISOFS_SB(inode->i_sb)->s_rock)
 211                return 0;
 212        *retname = 0;
 213
 214        init_rock_state(&rs, inode);
 215        setup_rock_ridge(de, inode, &rs);
 216repeat:
 217
 218        while (rs.len > 2) { /* There may be one byte for padding somewhere */
 219                rr = (struct rock_ridge *)rs.chr;
 220                /*
 221                 * Ignore rock ridge info if rr->len is out of range, but
 222                 * don't return -EIO because that would make the file
 223                 * invisible.
 224                 */
 225                if (rr->len < 3)
 226                        goto out;       /* Something got screwed up here */
 227                sig = isonum_721(rs.chr);
 228                if (rock_check_overflow(&rs, sig))
 229                        goto eio;
 230                rs.chr += rr->len;
 231                rs.len -= rr->len;
 232                /*
 233                 * As above, just ignore the rock ridge info if rr->len
 234                 * is bogus.
 235                 */
 236                if (rs.len < 0)
 237                        goto out;       /* Something got screwed up here */
 238
 239                switch (sig) {
 240                case SIG('R', 'R'):
 241                        if ((rr->u.RR.flags[0] & RR_NM) == 0)
 242                                goto out;
 243                        break;
 244                case SIG('S', 'P'):
 245                        if (check_sp(rr, inode))
 246                                goto out;
 247                        break;
 248                case SIG('C', 'E'):
 249                        rs.cont_extent = isonum_733(rr->u.CE.extent);
 250                        rs.cont_offset = isonum_733(rr->u.CE.offset);
 251                        rs.cont_size = isonum_733(rr->u.CE.size);
 252                        break;
 253                case SIG('N', 'M'):
 254                        if (truncate)
 255                                break;
 256                        if (rr->len < 5)
 257                                break;
 258                        /*
 259                         * If the flags are 2 or 4, this indicates '.' or '..'.
 260                         * We don't want to do anything with this, because it
 261                         * screws up the code that calls us.  We don't really
 262                         * care anyways, since we can just use the non-RR
 263                         * name.
 264                         */
 265                        if (rr->u.NM.flags & 6)
 266                                break;
 267
 268                        if (rr->u.NM.flags & ~1) {
 269                                printk("Unsupported NM flag settings (%d)\n",
 270                                        rr->u.NM.flags);
 271                                break;
 272                        }
 273                        len = rr->len - 5;
 274                        if (retnamlen + len >= 254) {
 275                                truncate = 1;
 276                                break;
 277                        }
 278                        p = memchr(rr->u.NM.name, '\0', len);
 279                        if (unlikely(p))
 280                                len = p - rr->u.NM.name;
 281                        memcpy(retname + retnamlen, rr->u.NM.name, len);
 282                        retnamlen += len;
 283                        retname[retnamlen] = '\0';
 284                        break;
 285                case SIG('R', 'E'):
 286                        kfree(rs.buffer);
 287                        return -1;
 288                default:
 289                        break;
 290                }
 291        }
 292        ret = rock_continue(&rs);
 293        if (ret == 0)
 294                goto repeat;
 295        if (ret == 1)
 296                return retnamlen; /* If 0, this file did not have a NM field */
 297out:
 298        kfree(rs.buffer);
 299        return ret;
 300eio:
 301        ret = -EIO;
 302        goto out;
 303}
 304
 305#define RR_REGARD_XA 1
 306#define RR_RELOC_DE 2
 307
 308static int
 309parse_rock_ridge_inode_internal(struct iso_directory_record *de,
 310                                struct inode *inode, int flags)
 311{
 312        int symlink_len = 0;
 313        int cnt, sig;
 314        unsigned int reloc_block;
 315        struct inode *reloc;
 316        struct rock_ridge *rr;
 317        int rootflag;
 318        struct rock_state rs;
 319        int ret = 0;
 320
 321        if (!ISOFS_SB(inode->i_sb)->s_rock)
 322                return 0;
 323
 324        init_rock_state(&rs, inode);
 325        setup_rock_ridge(de, inode, &rs);
 326        if (flags & RR_REGARD_XA) {
 327                rs.chr += 14;
 328                rs.len -= 14;
 329                if (rs.len < 0)
 330                        rs.len = 0;
 331        }
 332
 333repeat:
 334        while (rs.len > 2) { /* There may be one byte for padding somewhere */
 335                rr = (struct rock_ridge *)rs.chr;
 336                /*
 337                 * Ignore rock ridge info if rr->len is out of range, but
 338                 * don't return -EIO because that would make the file
 339                 * invisible.
 340                 */
 341                if (rr->len < 3)
 342                        goto out;       /* Something got screwed up here */
 343                sig = isonum_721(rs.chr);
 344                if (rock_check_overflow(&rs, sig))
 345                        goto eio;
 346                rs.chr += rr->len;
 347                rs.len -= rr->len;
 348                /*
 349                 * As above, just ignore the rock ridge info if rr->len
 350                 * is bogus.
 351                 */
 352                if (rs.len < 0)
 353                        goto out;       /* Something got screwed up here */
 354
 355                switch (sig) {
 356#ifndef CONFIG_ZISOFS           /* No flag for SF or ZF */
 357                case SIG('R', 'R'):
 358                        if ((rr->u.RR.flags[0] &
 359                             (RR_PX | RR_TF | RR_SL | RR_CL)) == 0)
 360                                goto out;
 361                        break;
 362#endif
 363                case SIG('S', 'P'):
 364                        if (check_sp(rr, inode))
 365                                goto out;
 366                        break;
 367                case SIG('C', 'E'):
 368                        rs.cont_extent = isonum_733(rr->u.CE.extent);
 369                        rs.cont_offset = isonum_733(rr->u.CE.offset);
 370                        rs.cont_size = isonum_733(rr->u.CE.size);
 371                        break;
 372                case SIG('E', 'R'):
 373                        /* Invalid length of ER tag id? */
 374                        if (rr->u.ER.len_id + offsetof(struct rock_ridge, u.ER.data) > rr->len)
 375                                goto out;
 376                        ISOFS_SB(inode->i_sb)->s_rock = 1;
 377                        printk(KERN_DEBUG "ISO 9660 Extensions: ");
 378                        {
 379                                int p;
 380                                for (p = 0; p < rr->u.ER.len_id; p++)
 381                                        printk(KERN_CONT "%c", rr->u.ER.data[p]);
 382                        }
 383                        printk(KERN_CONT "\n");
 384                        break;
 385                case SIG('P', 'X'):
 386                        inode->i_mode = isonum_733(rr->u.PX.mode);
 387                        set_nlink(inode, isonum_733(rr->u.PX.n_links));
 388                        i_uid_write(inode, isonum_733(rr->u.PX.uid));
 389                        i_gid_write(inode, isonum_733(rr->u.PX.gid));
 390                        break;
 391                case SIG('P', 'N'):
 392                        {
 393                                int high, low;
 394                                high = isonum_733(rr->u.PN.dev_high);
 395                                low = isonum_733(rr->u.PN.dev_low);
 396                                /*
 397                                 * The Rock Ridge standard specifies that if
 398                                 * sizeof(dev_t) <= 4, then the high field is
 399                                 * unused, and the device number is completely
 400                                 * stored in the low field.  Some writers may
 401                                 * ignore this subtlety,
 402                                 * and as a result we test to see if the entire
 403                                 * device number is
 404                                 * stored in the low field, and use that.
 405                                 */
 406                                if ((low & ~0xff) && high == 0) {
 407                                        inode->i_rdev =
 408                                            MKDEV(low >> 8, low & 0xff);
 409                                } else {
 410                                        inode->i_rdev =
 411                                            MKDEV(high, low);
 412                                }
 413                        }
 414                        break;
 415                case SIG('T', 'F'):
 416                        /*
 417                         * Some RRIP writers incorrectly place ctime in the
 418                         * TF_CREATE field. Try to handle this correctly for
 419                         * either case.
 420                         */
 421                        /* Rock ridge never appears on a High Sierra disk */
 422                        cnt = 0;
 423                        if (rr->u.TF.flags & TF_CREATE) {
 424                                inode->i_ctime.tv_sec =
 425                                    iso_date(rr->u.TF.times[cnt++].time,
 426                                             0);
 427                                inode->i_ctime.tv_nsec = 0;
 428                        }
 429                        if (rr->u.TF.flags & TF_MODIFY) {
 430                                inode->i_mtime.tv_sec =
 431                                    iso_date(rr->u.TF.times[cnt++].time,
 432                                             0);
 433                                inode->i_mtime.tv_nsec = 0;
 434                        }
 435                        if (rr->u.TF.flags & TF_ACCESS) {
 436                                inode->i_atime.tv_sec =
 437                                    iso_date(rr->u.TF.times[cnt++].time,
 438                                             0);
 439                                inode->i_atime.tv_nsec = 0;
 440                        }
 441                        if (rr->u.TF.flags & TF_ATTRIBUTES) {
 442                                inode->i_ctime.tv_sec =
 443                                    iso_date(rr->u.TF.times[cnt++].time,
 444                                             0);
 445                                inode->i_ctime.tv_nsec = 0;
 446                        }
 447                        break;
 448                case SIG('S', 'L'):
 449                        {
 450                                int slen;
 451                                struct SL_component *slp;
 452                                struct SL_component *oldslp;
 453                                slen = rr->len - 5;
 454                                slp = &rr->u.SL.link;
 455                                inode->i_size = symlink_len;
 456                                while (slen > 1) {
 457                                        rootflag = 0;
 458                                        switch (slp->flags & ~1) {
 459                                        case 0:
 460                                                inode->i_size +=
 461                                                    slp->len;
 462                                                break;
 463                                        case 2:
 464                                                inode->i_size += 1;
 465                                                break;
 466                                        case 4:
 467                                                inode->i_size += 2;
 468                                                break;
 469                                        case 8:
 470                                                rootflag = 1;
 471                                                inode->i_size += 1;
 472                                                break;
 473                                        default:
 474                                                printk("Symlink component flag "
 475                                                        "not implemented\n");
 476                                        }
 477                                        slen -= slp->len + 2;
 478                                        oldslp = slp;
 479                                        slp = (struct SL_component *)
 480                                                (((char *)slp) + slp->len + 2);
 481
 482                                        if (slen < 2) {
 483                                                if (((rr->u.SL.
 484                                                      flags & 1) != 0)
 485                                                    &&
 486                                                    ((oldslp->
 487                                                      flags & 1) == 0))
 488                                                        inode->i_size +=
 489                                                            1;
 490                                                break;
 491                                        }
 492
 493                                        /*
 494                                         * If this component record isn't
 495                                         * continued, then append a '/'.
 496                                         */
 497                                        if (!rootflag
 498                                            && (oldslp->flags & 1) == 0)
 499                                                inode->i_size += 1;
 500                                }
 501                        }
 502                        symlink_len = inode->i_size;
 503                        break;
 504                case SIG('R', 'E'):
 505                        printk(KERN_WARNING "Attempt to read inode for "
 506                                        "relocated directory\n");
 507                        goto out;
 508                case SIG('C', 'L'):
 509                        if (flags & RR_RELOC_DE) {
 510                                printk(KERN_ERR
 511                                       "ISOFS: Recursive directory relocation "
 512                                       "is not supported\n");
 513                                goto eio;
 514                        }
 515                        reloc_block = isonum_733(rr->u.CL.location);
 516                        if (reloc_block == ISOFS_I(inode)->i_iget5_block &&
 517                            ISOFS_I(inode)->i_iget5_offset == 0) {
 518                                printk(KERN_ERR
 519                                       "ISOFS: Directory relocation points to "
 520                                       "itself\n");
 521                                goto eio;
 522                        }
 523                        ISOFS_I(inode)->i_first_extent = reloc_block;
 524                        reloc = isofs_iget_reloc(inode->i_sb, reloc_block, 0);
 525                        if (IS_ERR(reloc)) {
 526                                ret = PTR_ERR(reloc);
 527                                goto out;
 528                        }
 529                        inode->i_mode = reloc->i_mode;
 530                        set_nlink(inode, reloc->i_nlink);
 531                        inode->i_uid = reloc->i_uid;
 532                        inode->i_gid = reloc->i_gid;
 533                        inode->i_rdev = reloc->i_rdev;
 534                        inode->i_size = reloc->i_size;
 535                        inode->i_blocks = reloc->i_blocks;
 536                        inode->i_atime = reloc->i_atime;
 537                        inode->i_ctime = reloc->i_ctime;
 538                        inode->i_mtime = reloc->i_mtime;
 539                        iput(reloc);
 540                        break;
 541#ifdef CONFIG_ZISOFS
 542                case SIG('Z', 'F'): {
 543                        int algo;
 544
 545                        if (ISOFS_SB(inode->i_sb)->s_nocompress)
 546                                break;
 547                        algo = isonum_721(rr->u.ZF.algorithm);
 548                        if (algo == SIG('p', 'z')) {
 549                                int block_shift =
 550                                        isonum_711(&rr->u.ZF.parms[1]);
 551                                if (block_shift > 17) {
 552                                        printk(KERN_WARNING "isofs: "
 553                                                "Can't handle ZF block "
 554                                                "size of 2^%d\n",
 555                                                block_shift);
 556                                } else {
 557                                        /*
 558                                         * Note: we don't change
 559                                         * i_blocks here
 560                                         */
 561                                        ISOFS_I(inode)->i_file_format =
 562                                                isofs_file_compressed;
 563                                        /*
 564                                         * Parameters to compression
 565                                         * algorithm (header size,
 566                                         * block size)
 567                                         */
 568                                        ISOFS_I(inode)->i_format_parm[0] =
 569                                                isonum_711(&rr->u.ZF.parms[0]);
 570                                        ISOFS_I(inode)->i_format_parm[1] =
 571                                                isonum_711(&rr->u.ZF.parms[1]);
 572                                        inode->i_size =
 573                                            isonum_733(rr->u.ZF.
 574                                                       real_size);
 575                                }
 576                        } else {
 577                                printk(KERN_WARNING
 578                                       "isofs: Unknown ZF compression "
 579                                                "algorithm: %c%c\n",
 580                                       rr->u.ZF.algorithm[0],
 581                                       rr->u.ZF.algorithm[1]);
 582                        }
 583                        break;
 584                }
 585#endif
 586                default:
 587                        break;
 588                }
 589        }
 590        ret = rock_continue(&rs);
 591        if (ret == 0)
 592                goto repeat;
 593        if (ret == 1)
 594                ret = 0;
 595out:
 596        kfree(rs.buffer);
 597        return ret;
 598eio:
 599        ret = -EIO;
 600        goto out;
 601}
 602
 603static char *get_symlink_chunk(char *rpnt, struct rock_ridge *rr, char *plimit)
 604{
 605        int slen;
 606        int rootflag;
 607        struct SL_component *oldslp;
 608        struct SL_component *slp;
 609        slen = rr->len - 5;
 610        slp = &rr->u.SL.link;
 611        while (slen > 1) {
 612                rootflag = 0;
 613                switch (slp->flags & ~1) {
 614                case 0:
 615                        if (slp->len > plimit - rpnt)
 616                                return NULL;
 617                        memcpy(rpnt, slp->text, slp->len);
 618                        rpnt += slp->len;
 619                        break;
 620                case 2:
 621                        if (rpnt >= plimit)
 622                                return NULL;
 623                        *rpnt++ = '.';
 624                        break;
 625                case 4:
 626                        if (2 > plimit - rpnt)
 627                                return NULL;
 628                        *rpnt++ = '.';
 629                        *rpnt++ = '.';
 630                        break;
 631                case 8:
 632                        if (rpnt >= plimit)
 633                                return NULL;
 634                        rootflag = 1;
 635                        *rpnt++ = '/';
 636                        break;
 637                default:
 638                        printk("Symlink component flag not implemented (%d)\n",
 639                               slp->flags);
 640                }
 641                slen -= slp->len + 2;
 642                oldslp = slp;
 643                slp = (struct SL_component *)((char *)slp + slp->len + 2);
 644
 645                if (slen < 2) {
 646                        /*
 647                         * If there is another SL record, and this component
 648                         * record isn't continued, then add a slash.
 649                         */
 650                        if ((!rootflag) && (rr->u.SL.flags & 1) &&
 651                            !(oldslp->flags & 1)) {
 652                                if (rpnt >= plimit)
 653                                        return NULL;
 654                                *rpnt++ = '/';
 655                        }
 656                        break;
 657                }
 658
 659                /*
 660                 * If this component record isn't continued, then append a '/'.
 661                 */
 662                if (!rootflag && !(oldslp->flags & 1)) {
 663                        if (rpnt >= plimit)
 664                                return NULL;
 665                        *rpnt++ = '/';
 666                }
 667        }
 668        return rpnt;
 669}
 670
 671int parse_rock_ridge_inode(struct iso_directory_record *de, struct inode *inode,
 672                           int relocated)
 673{
 674        int flags = relocated ? RR_RELOC_DE : 0;
 675        int result = parse_rock_ridge_inode_internal(de, inode, flags);
 676
 677        /*
 678         * if rockridge flag was reset and we didn't look for attributes
 679         * behind eventual XA attributes, have a look there
 680         */
 681        if ((ISOFS_SB(inode->i_sb)->s_rock_offset == -1)
 682            && (ISOFS_SB(inode->i_sb)->s_rock == 2)) {
 683                result = parse_rock_ridge_inode_internal(de, inode,
 684                                                         flags | RR_REGARD_XA);
 685        }
 686        return result;
 687}
 688
 689/*
 690 * readpage() for symlinks: reads symlink contents into the page and either
 691 * makes it uptodate and returns 0 or returns error (-EIO)
 692 */
 693static int rock_ridge_symlink_readpage(struct file *file, struct page *page)
 694{
 695        struct inode *inode = page->mapping->host;
 696        struct iso_inode_info *ei = ISOFS_I(inode);
 697        struct isofs_sb_info *sbi = ISOFS_SB(inode->i_sb);
 698        char *link = page_address(page);
 699        unsigned long bufsize = ISOFS_BUFFER_SIZE(inode);
 700        struct buffer_head *bh;
 701        char *rpnt = link;
 702        unsigned char *pnt;
 703        struct iso_directory_record *raw_de;
 704        unsigned long block, offset;
 705        int sig;
 706        struct rock_ridge *rr;
 707        struct rock_state rs;
 708        int ret;
 709
 710        if (!sbi->s_rock)
 711                goto error;
 712
 713        init_rock_state(&rs, inode);
 714        block = ei->i_iget5_block;
 715        bh = sb_bread(inode->i_sb, block);
 716        if (!bh)
 717                goto out_noread;
 718
 719        offset = ei->i_iget5_offset;
 720        pnt = (unsigned char *)bh->b_data + offset;
 721
 722        raw_de = (struct iso_directory_record *)pnt;
 723
 724        /*
 725         * If we go past the end of the buffer, there is some sort of error.
 726         */
 727        if (offset + *pnt > bufsize)
 728                goto out_bad_span;
 729
 730        /*
 731         * Now test for possible Rock Ridge extensions which will override
 732         * some of these numbers in the inode structure.
 733         */
 734
 735        setup_rock_ridge(raw_de, inode, &rs);
 736
 737repeat:
 738        while (rs.len > 2) { /* There may be one byte for padding somewhere */
 739                rr = (struct rock_ridge *)rs.chr;
 740                if (rr->len < 3)
 741                        goto out;       /* Something got screwed up here */
 742                sig = isonum_721(rs.chr);
 743                if (rock_check_overflow(&rs, sig))
 744                        goto out;
 745                rs.chr += rr->len;
 746                rs.len -= rr->len;
 747                if (rs.len < 0)
 748                        goto out;       /* corrupted isofs */
 749
 750                switch (sig) {
 751                case SIG('R', 'R'):
 752                        if ((rr->u.RR.flags[0] & RR_SL) == 0)
 753                                goto out;
 754                        break;
 755                case SIG('S', 'P'):
 756                        if (check_sp(rr, inode))
 757                                goto out;
 758                        break;
 759                case SIG('S', 'L'):
 760                        rpnt = get_symlink_chunk(rpnt, rr,
 761                                                 link + (PAGE_SIZE - 1));
 762                        if (rpnt == NULL)
 763                                goto out;
 764                        break;
 765                case SIG('C', 'E'):
 766                        /* This tells is if there is a continuation record */
 767                        rs.cont_extent = isonum_733(rr->u.CE.extent);
 768                        rs.cont_offset = isonum_733(rr->u.CE.offset);
 769                        rs.cont_size = isonum_733(rr->u.CE.size);
 770                default:
 771                        break;
 772                }
 773        }
 774        ret = rock_continue(&rs);
 775        if (ret == 0)
 776                goto repeat;
 777        if (ret < 0)
 778                goto fail;
 779
 780        if (rpnt == link)
 781                goto fail;
 782        brelse(bh);
 783        *rpnt = '\0';
 784        SetPageUptodate(page);
 785        unlock_page(page);
 786        return 0;
 787
 788        /* error exit from macro */
 789out:
 790        kfree(rs.buffer);
 791        goto fail;
 792out_noread:
 793        printk("unable to read i-node block");
 794        goto fail;
 795out_bad_span:
 796        printk("symlink spans iso9660 blocks\n");
 797fail:
 798        brelse(bh);
 799error:
 800        SetPageError(page);
 801        unlock_page(page);
 802        return -EIO;
 803}
 804
 805const struct address_space_operations isofs_symlink_aops = {
 806        .readpage = rock_ridge_symlink_readpage
 807};
 808