xref: /openbmc/linux/fs/isofs/rock.c (revision 293d5b43)
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 
12 #include "isofs.h"
13 #include "rock.h"
14 
15 /*
16  * These functions are designed to read the system areas of a directory record
17  * and extract relevant information.  There are different functions provided
18  * depending upon what information we need at the time.  One function fills
19  * out an inode structure, a second one extracts a filename, a third one
20  * returns a symbolic link name, and a fourth one returns the extent number
21  * for the file.
22  */
23 
24 #define SIG(A,B) ((A) | ((B) << 8))	/* isonum_721() */
25 
26 struct rock_state {
27 	void *buffer;
28 	unsigned char *chr;
29 	int len;
30 	int cont_size;
31 	int cont_extent;
32 	int cont_offset;
33 	int cont_loops;
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 /* Maximum number of Rock Ridge continuation entries */
78 #define RR_MAX_CE_ENTRIES 32
79 
80 /*
81  * Returns 0 if the caller should continue scanning, 1 if the scan must end
82  * and -ve on error.
83  */
84 static int rock_continue(struct rock_state *rs)
85 {
86 	int ret = 1;
87 	int blocksize = 1 << rs->inode->i_blkbits;
88 	const int min_de_size = offsetof(struct rock_ridge, u);
89 
90 	kfree(rs->buffer);
91 	rs->buffer = NULL;
92 
93 	if ((unsigned)rs->cont_offset > blocksize - min_de_size ||
94 	    (unsigned)rs->cont_size > blocksize ||
95 	    (unsigned)(rs->cont_offset + rs->cont_size) > blocksize) {
96 		printk(KERN_NOTICE "rock: corrupted directory entry. "
97 			"extent=%d, offset=%d, size=%d\n",
98 			rs->cont_extent, rs->cont_offset, rs->cont_size);
99 		ret = -EIO;
100 		goto out;
101 	}
102 
103 	if (rs->cont_extent) {
104 		struct buffer_head *bh;
105 
106 		rs->buffer = kmalloc(rs->cont_size, GFP_KERNEL);
107 		if (!rs->buffer) {
108 			ret = -ENOMEM;
109 			goto out;
110 		}
111 		ret = -EIO;
112 		if (++rs->cont_loops >= RR_MAX_CE_ENTRIES)
113 			goto out;
114 		bh = sb_bread(rs->inode->i_sb, rs->cont_extent);
115 		if (bh) {
116 			memcpy(rs->buffer, bh->b_data + rs->cont_offset,
117 					rs->cont_size);
118 			put_bh(bh);
119 			rs->chr = rs->buffer;
120 			rs->len = rs->cont_size;
121 			rs->cont_extent = 0;
122 			rs->cont_size = 0;
123 			rs->cont_offset = 0;
124 			return 0;
125 		}
126 		printk("Unable to read rock-ridge attributes\n");
127 	}
128 out:
129 	kfree(rs->buffer);
130 	rs->buffer = NULL;
131 	return ret;
132 }
133 
134 /*
135  * We think there's a record of type `sig' at rs->chr.  Parse the signature
136  * and make sure that there's really room for a record of that type.
137  */
138 static int rock_check_overflow(struct rock_state *rs, int sig)
139 {
140 	int len;
141 
142 	switch (sig) {
143 	case SIG('S', 'P'):
144 		len = sizeof(struct SU_SP_s);
145 		break;
146 	case SIG('C', 'E'):
147 		len = sizeof(struct SU_CE_s);
148 		break;
149 	case SIG('E', 'R'):
150 		len = sizeof(struct SU_ER_s);
151 		break;
152 	case SIG('R', 'R'):
153 		len = sizeof(struct RR_RR_s);
154 		break;
155 	case SIG('P', 'X'):
156 		len = sizeof(struct RR_PX_s);
157 		break;
158 	case SIG('P', 'N'):
159 		len = sizeof(struct RR_PN_s);
160 		break;
161 	case SIG('S', 'L'):
162 		len = sizeof(struct RR_SL_s);
163 		break;
164 	case SIG('N', 'M'):
165 		len = sizeof(struct RR_NM_s);
166 		break;
167 	case SIG('C', 'L'):
168 		len = sizeof(struct RR_CL_s);
169 		break;
170 	case SIG('P', 'L'):
171 		len = sizeof(struct RR_PL_s);
172 		break;
173 	case SIG('T', 'F'):
174 		len = sizeof(struct RR_TF_s);
175 		break;
176 	case SIG('Z', 'F'):
177 		len = sizeof(struct RR_ZF_s);
178 		break;
179 	default:
180 		len = 0;
181 		break;
182 	}
183 	len += offsetof(struct rock_ridge, u);
184 	if (len > rs->len) {
185 		printk(KERN_NOTICE "rock: directory entry would overflow "
186 				"storage\n");
187 		printk(KERN_NOTICE "rock: sig=0x%02x, size=%d, remaining=%d\n",
188 				sig, len, rs->len);
189 		return -EIO;
190 	}
191 	return 0;
192 }
193 
194 /*
195  * return length of name field; 0: not found, -1: to be ignored
196  */
197 int get_rock_ridge_filename(struct iso_directory_record *de,
198 			    char *retname, struct inode *inode)
199 {
200 	struct rock_state rs;
201 	struct rock_ridge *rr;
202 	int sig;
203 	int retnamlen = 0;
204 	int truncate = 0;
205 	int ret = 0;
206 	char *p;
207 	int len;
208 
209 	if (!ISOFS_SB(inode->i_sb)->s_rock)
210 		return 0;
211 	*retname = 0;
212 
213 	init_rock_state(&rs, inode);
214 	setup_rock_ridge(de, inode, &rs);
215 repeat:
216 
217 	while (rs.len > 2) { /* There may be one byte for padding somewhere */
218 		rr = (struct rock_ridge *)rs.chr;
219 		/*
220 		 * Ignore rock ridge info if rr->len is out of range, but
221 		 * don't return -EIO because that would make the file
222 		 * invisible.
223 		 */
224 		if (rr->len < 3)
225 			goto out;	/* Something got screwed up here */
226 		sig = isonum_721(rs.chr);
227 		if (rock_check_overflow(&rs, sig))
228 			goto eio;
229 		rs.chr += rr->len;
230 		rs.len -= rr->len;
231 		/*
232 		 * As above, just ignore the rock ridge info if rr->len
233 		 * is bogus.
234 		 */
235 		if (rs.len < 0)
236 			goto out;	/* Something got screwed up here */
237 
238 		switch (sig) {
239 		case SIG('R', 'R'):
240 			if ((rr->u.RR.flags[0] & RR_NM) == 0)
241 				goto out;
242 			break;
243 		case SIG('S', 'P'):
244 			if (check_sp(rr, inode))
245 				goto out;
246 			break;
247 		case SIG('C', 'E'):
248 			rs.cont_extent = isonum_733(rr->u.CE.extent);
249 			rs.cont_offset = isonum_733(rr->u.CE.offset);
250 			rs.cont_size = isonum_733(rr->u.CE.size);
251 			break;
252 		case SIG('N', 'M'):
253 			if (truncate)
254 				break;
255 			if (rr->len < 5)
256 				break;
257 			/*
258 			 * If the flags are 2 or 4, this indicates '.' or '..'.
259 			 * We don't want to do anything with this, because it
260 			 * screws up the code that calls us.  We don't really
261 			 * care anyways, since we can just use the non-RR
262 			 * name.
263 			 */
264 			if (rr->u.NM.flags & 6)
265 				break;
266 
267 			if (rr->u.NM.flags & ~1) {
268 				printk("Unsupported NM flag settings (%d)\n",
269 					rr->u.NM.flags);
270 				break;
271 			}
272 			len = rr->len - 5;
273 			if (retnamlen + len >= 254) {
274 				truncate = 1;
275 				break;
276 			}
277 			p = memchr(rr->u.NM.name, '\0', len);
278 			if (unlikely(p))
279 				len = p - rr->u.NM.name;
280 			memcpy(retname + retnamlen, rr->u.NM.name, len);
281 			retnamlen += len;
282 			retname[retnamlen] = '\0';
283 			break;
284 		case SIG('R', 'E'):
285 			kfree(rs.buffer);
286 			return -1;
287 		default:
288 			break;
289 		}
290 	}
291 	ret = rock_continue(&rs);
292 	if (ret == 0)
293 		goto repeat;
294 	if (ret == 1)
295 		return retnamlen; /* If 0, this file did not have a NM field */
296 out:
297 	kfree(rs.buffer);
298 	return ret;
299 eio:
300 	ret = -EIO;
301 	goto out;
302 }
303 
304 #define RR_REGARD_XA 1
305 #define RR_RELOC_DE 2
306 
307 static int
308 parse_rock_ridge_inode_internal(struct iso_directory_record *de,
309 				struct inode *inode, int flags)
310 {
311 	int symlink_len = 0;
312 	int cnt, sig;
313 	unsigned int reloc_block;
314 	struct inode *reloc;
315 	struct rock_ridge *rr;
316 	int rootflag;
317 	struct rock_state rs;
318 	int ret = 0;
319 
320 	if (!ISOFS_SB(inode->i_sb)->s_rock)
321 		return 0;
322 
323 	init_rock_state(&rs, inode);
324 	setup_rock_ridge(de, inode, &rs);
325 	if (flags & RR_REGARD_XA) {
326 		rs.chr += 14;
327 		rs.len -= 14;
328 		if (rs.len < 0)
329 			rs.len = 0;
330 	}
331 
332 repeat:
333 	while (rs.len > 2) { /* There may be one byte for padding somewhere */
334 		rr = (struct rock_ridge *)rs.chr;
335 		/*
336 		 * Ignore rock ridge info if rr->len is out of range, but
337 		 * don't return -EIO because that would make the file
338 		 * invisible.
339 		 */
340 		if (rr->len < 3)
341 			goto out;	/* Something got screwed up here */
342 		sig = isonum_721(rs.chr);
343 		if (rock_check_overflow(&rs, sig))
344 			goto eio;
345 		rs.chr += rr->len;
346 		rs.len -= rr->len;
347 		/*
348 		 * As above, just ignore the rock ridge info if rr->len
349 		 * is bogus.
350 		 */
351 		if (rs.len < 0)
352 			goto out;	/* Something got screwed up here */
353 
354 		switch (sig) {
355 #ifndef CONFIG_ZISOFS		/* No flag for SF or ZF */
356 		case SIG('R', 'R'):
357 			if ((rr->u.RR.flags[0] &
358 			     (RR_PX | RR_TF | RR_SL | RR_CL)) == 0)
359 				goto out;
360 			break;
361 #endif
362 		case SIG('S', 'P'):
363 			if (check_sp(rr, inode))
364 				goto out;
365 			break;
366 		case SIG('C', 'E'):
367 			rs.cont_extent = isonum_733(rr->u.CE.extent);
368 			rs.cont_offset = isonum_733(rr->u.CE.offset);
369 			rs.cont_size = isonum_733(rr->u.CE.size);
370 			break;
371 		case SIG('E', 'R'):
372 			/* Invalid length of ER tag id? */
373 			if (rr->u.ER.len_id + offsetof(struct rock_ridge, u.ER.data) > rr->len)
374 				goto out;
375 			ISOFS_SB(inode->i_sb)->s_rock = 1;
376 			printk(KERN_DEBUG "ISO 9660 Extensions: ");
377 			{
378 				int p;
379 				for (p = 0; p < rr->u.ER.len_id; p++)
380 					printk("%c", rr->u.ER.data[p]);
381 			}
382 			printk("\n");
383 			break;
384 		case SIG('P', 'X'):
385 			inode->i_mode = isonum_733(rr->u.PX.mode);
386 			set_nlink(inode, isonum_733(rr->u.PX.n_links));
387 			i_uid_write(inode, isonum_733(rr->u.PX.uid));
388 			i_gid_write(inode, isonum_733(rr->u.PX.gid));
389 			break;
390 		case SIG('P', 'N'):
391 			{
392 				int high, low;
393 				high = isonum_733(rr->u.PN.dev_high);
394 				low = isonum_733(rr->u.PN.dev_low);
395 				/*
396 				 * The Rock Ridge standard specifies that if
397 				 * sizeof(dev_t) <= 4, then the high field is
398 				 * unused, and the device number is completely
399 				 * stored in the low field.  Some writers may
400 				 * ignore this subtlety,
401 				 * and as a result we test to see if the entire
402 				 * device number is
403 				 * stored in the low field, and use that.
404 				 */
405 				if ((low & ~0xff) && high == 0) {
406 					inode->i_rdev =
407 					    MKDEV(low >> 8, low & 0xff);
408 				} else {
409 					inode->i_rdev =
410 					    MKDEV(high, low);
411 				}
412 			}
413 			break;
414 		case SIG('T', 'F'):
415 			/*
416 			 * Some RRIP writers incorrectly place ctime in the
417 			 * TF_CREATE field. Try to handle this correctly for
418 			 * either case.
419 			 */
420 			/* Rock ridge never appears on a High Sierra disk */
421 			cnt = 0;
422 			if (rr->u.TF.flags & TF_CREATE) {
423 				inode->i_ctime.tv_sec =
424 				    iso_date(rr->u.TF.times[cnt++].time,
425 					     0);
426 				inode->i_ctime.tv_nsec = 0;
427 			}
428 			if (rr->u.TF.flags & TF_MODIFY) {
429 				inode->i_mtime.tv_sec =
430 				    iso_date(rr->u.TF.times[cnt++].time,
431 					     0);
432 				inode->i_mtime.tv_nsec = 0;
433 			}
434 			if (rr->u.TF.flags & TF_ACCESS) {
435 				inode->i_atime.tv_sec =
436 				    iso_date(rr->u.TF.times[cnt++].time,
437 					     0);
438 				inode->i_atime.tv_nsec = 0;
439 			}
440 			if (rr->u.TF.flags & TF_ATTRIBUTES) {
441 				inode->i_ctime.tv_sec =
442 				    iso_date(rr->u.TF.times[cnt++].time,
443 					     0);
444 				inode->i_ctime.tv_nsec = 0;
445 			}
446 			break;
447 		case SIG('S', 'L'):
448 			{
449 				int slen;
450 				struct SL_component *slp;
451 				struct SL_component *oldslp;
452 				slen = rr->len - 5;
453 				slp = &rr->u.SL.link;
454 				inode->i_size = symlink_len;
455 				while (slen > 1) {
456 					rootflag = 0;
457 					switch (slp->flags & ~1) {
458 					case 0:
459 						inode->i_size +=
460 						    slp->len;
461 						break;
462 					case 2:
463 						inode->i_size += 1;
464 						break;
465 					case 4:
466 						inode->i_size += 2;
467 						break;
468 					case 8:
469 						rootflag = 1;
470 						inode->i_size += 1;
471 						break;
472 					default:
473 						printk("Symlink component flag "
474 							"not implemented\n");
475 					}
476 					slen -= slp->len + 2;
477 					oldslp = slp;
478 					slp = (struct SL_component *)
479 						(((char *)slp) + slp->len + 2);
480 
481 					if (slen < 2) {
482 						if (((rr->u.SL.
483 						      flags & 1) != 0)
484 						    &&
485 						    ((oldslp->
486 						      flags & 1) == 0))
487 							inode->i_size +=
488 							    1;
489 						break;
490 					}
491 
492 					/*
493 					 * If this component record isn't
494 					 * continued, then append a '/'.
495 					 */
496 					if (!rootflag
497 					    && (oldslp->flags & 1) == 0)
498 						inode->i_size += 1;
499 				}
500 			}
501 			symlink_len = inode->i_size;
502 			break;
503 		case SIG('R', 'E'):
504 			printk(KERN_WARNING "Attempt to read inode for "
505 					"relocated directory\n");
506 			goto out;
507 		case SIG('C', 'L'):
508 			if (flags & RR_RELOC_DE) {
509 				printk(KERN_ERR
510 				       "ISOFS: Recursive directory relocation "
511 				       "is not supported\n");
512 				goto eio;
513 			}
514 			reloc_block = isonum_733(rr->u.CL.location);
515 			if (reloc_block == ISOFS_I(inode)->i_iget5_block &&
516 			    ISOFS_I(inode)->i_iget5_offset == 0) {
517 				printk(KERN_ERR
518 				       "ISOFS: Directory relocation points to "
519 				       "itself\n");
520 				goto eio;
521 			}
522 			ISOFS_I(inode)->i_first_extent = reloc_block;
523 			reloc = isofs_iget_reloc(inode->i_sb, reloc_block, 0);
524 			if (IS_ERR(reloc)) {
525 				ret = PTR_ERR(reloc);
526 				goto out;
527 			}
528 			inode->i_mode = reloc->i_mode;
529 			set_nlink(inode, reloc->i_nlink);
530 			inode->i_uid = reloc->i_uid;
531 			inode->i_gid = reloc->i_gid;
532 			inode->i_rdev = reloc->i_rdev;
533 			inode->i_size = reloc->i_size;
534 			inode->i_blocks = reloc->i_blocks;
535 			inode->i_atime = reloc->i_atime;
536 			inode->i_ctime = reloc->i_ctime;
537 			inode->i_mtime = reloc->i_mtime;
538 			iput(reloc);
539 			break;
540 #ifdef CONFIG_ZISOFS
541 		case SIG('Z', 'F'): {
542 			int algo;
543 
544 			if (ISOFS_SB(inode->i_sb)->s_nocompress)
545 				break;
546 			algo = isonum_721(rr->u.ZF.algorithm);
547 			if (algo == SIG('p', 'z')) {
548 				int block_shift =
549 					isonum_711(&rr->u.ZF.parms[1]);
550 				if (block_shift > 17) {
551 					printk(KERN_WARNING "isofs: "
552 						"Can't handle ZF block "
553 						"size of 2^%d\n",
554 						block_shift);
555 				} else {
556 					/*
557 					 * Note: we don't change
558 					 * i_blocks here
559 					 */
560 					ISOFS_I(inode)->i_file_format =
561 						isofs_file_compressed;
562 					/*
563 					 * Parameters to compression
564 					 * algorithm (header size,
565 					 * block size)
566 					 */
567 					ISOFS_I(inode)->i_format_parm[0] =
568 						isonum_711(&rr->u.ZF.parms[0]);
569 					ISOFS_I(inode)->i_format_parm[1] =
570 						isonum_711(&rr->u.ZF.parms[1]);
571 					inode->i_size =
572 					    isonum_733(rr->u.ZF.
573 						       real_size);
574 				}
575 			} else {
576 				printk(KERN_WARNING
577 				       "isofs: Unknown ZF compression "
578 						"algorithm: %c%c\n",
579 				       rr->u.ZF.algorithm[0],
580 				       rr->u.ZF.algorithm[1]);
581 			}
582 			break;
583 		}
584 #endif
585 		default:
586 			break;
587 		}
588 	}
589 	ret = rock_continue(&rs);
590 	if (ret == 0)
591 		goto repeat;
592 	if (ret == 1)
593 		ret = 0;
594 out:
595 	kfree(rs.buffer);
596 	return ret;
597 eio:
598 	ret = -EIO;
599 	goto out;
600 }
601 
602 static char *get_symlink_chunk(char *rpnt, struct rock_ridge *rr, char *plimit)
603 {
604 	int slen;
605 	int rootflag;
606 	struct SL_component *oldslp;
607 	struct SL_component *slp;
608 	slen = rr->len - 5;
609 	slp = &rr->u.SL.link;
610 	while (slen > 1) {
611 		rootflag = 0;
612 		switch (slp->flags & ~1) {
613 		case 0:
614 			if (slp->len > plimit - rpnt)
615 				return NULL;
616 			memcpy(rpnt, slp->text, slp->len);
617 			rpnt += slp->len;
618 			break;
619 		case 2:
620 			if (rpnt >= plimit)
621 				return NULL;
622 			*rpnt++ = '.';
623 			break;
624 		case 4:
625 			if (2 > plimit - rpnt)
626 				return NULL;
627 			*rpnt++ = '.';
628 			*rpnt++ = '.';
629 			break;
630 		case 8:
631 			if (rpnt >= plimit)
632 				return NULL;
633 			rootflag = 1;
634 			*rpnt++ = '/';
635 			break;
636 		default:
637 			printk("Symlink component flag not implemented (%d)\n",
638 			       slp->flags);
639 		}
640 		slen -= slp->len + 2;
641 		oldslp = slp;
642 		slp = (struct SL_component *)((char *)slp + slp->len + 2);
643 
644 		if (slen < 2) {
645 			/*
646 			 * If there is another SL record, and this component
647 			 * record isn't continued, then add a slash.
648 			 */
649 			if ((!rootflag) && (rr->u.SL.flags & 1) &&
650 			    !(oldslp->flags & 1)) {
651 				if (rpnt >= plimit)
652 					return NULL;
653 				*rpnt++ = '/';
654 			}
655 			break;
656 		}
657 
658 		/*
659 		 * If this component record isn't continued, then append a '/'.
660 		 */
661 		if (!rootflag && !(oldslp->flags & 1)) {
662 			if (rpnt >= plimit)
663 				return NULL;
664 			*rpnt++ = '/';
665 		}
666 	}
667 	return rpnt;
668 }
669 
670 int parse_rock_ridge_inode(struct iso_directory_record *de, struct inode *inode,
671 			   int relocated)
672 {
673 	int flags = relocated ? RR_RELOC_DE : 0;
674 	int result = parse_rock_ridge_inode_internal(de, inode, flags);
675 
676 	/*
677 	 * if rockridge flag was reset and we didn't look for attributes
678 	 * behind eventual XA attributes, have a look there
679 	 */
680 	if ((ISOFS_SB(inode->i_sb)->s_rock_offset == -1)
681 	    && (ISOFS_SB(inode->i_sb)->s_rock == 2)) {
682 		result = parse_rock_ridge_inode_internal(de, inode,
683 							 flags | RR_REGARD_XA);
684 	}
685 	return result;
686 }
687 
688 /*
689  * readpage() for symlinks: reads symlink contents into the page and either
690  * makes it uptodate and returns 0 or returns error (-EIO)
691  */
692 static int rock_ridge_symlink_readpage(struct file *file, struct page *page)
693 {
694 	struct inode *inode = page->mapping->host;
695 	struct iso_inode_info *ei = ISOFS_I(inode);
696 	struct isofs_sb_info *sbi = ISOFS_SB(inode->i_sb);
697 	char *link = page_address(page);
698 	unsigned long bufsize = ISOFS_BUFFER_SIZE(inode);
699 	struct buffer_head *bh;
700 	char *rpnt = link;
701 	unsigned char *pnt;
702 	struct iso_directory_record *raw_de;
703 	unsigned long block, offset;
704 	int sig;
705 	struct rock_ridge *rr;
706 	struct rock_state rs;
707 	int ret;
708 
709 	if (!sbi->s_rock)
710 		goto error;
711 
712 	init_rock_state(&rs, inode);
713 	block = ei->i_iget5_block;
714 	bh = sb_bread(inode->i_sb, block);
715 	if (!bh)
716 		goto out_noread;
717 
718 	offset = ei->i_iget5_offset;
719 	pnt = (unsigned char *)bh->b_data + offset;
720 
721 	raw_de = (struct iso_directory_record *)pnt;
722 
723 	/*
724 	 * If we go past the end of the buffer, there is some sort of error.
725 	 */
726 	if (offset + *pnt > bufsize)
727 		goto out_bad_span;
728 
729 	/*
730 	 * Now test for possible Rock Ridge extensions which will override
731 	 * some of these numbers in the inode structure.
732 	 */
733 
734 	setup_rock_ridge(raw_de, inode, &rs);
735 
736 repeat:
737 	while (rs.len > 2) { /* There may be one byte for padding somewhere */
738 		rr = (struct rock_ridge *)rs.chr;
739 		if (rr->len < 3)
740 			goto out;	/* Something got screwed up here */
741 		sig = isonum_721(rs.chr);
742 		if (rock_check_overflow(&rs, sig))
743 			goto out;
744 		rs.chr += rr->len;
745 		rs.len -= rr->len;
746 		if (rs.len < 0)
747 			goto out;	/* corrupted isofs */
748 
749 		switch (sig) {
750 		case SIG('R', 'R'):
751 			if ((rr->u.RR.flags[0] & RR_SL) == 0)
752 				goto out;
753 			break;
754 		case SIG('S', 'P'):
755 			if (check_sp(rr, inode))
756 				goto out;
757 			break;
758 		case SIG('S', 'L'):
759 			rpnt = get_symlink_chunk(rpnt, rr,
760 						 link + (PAGE_SIZE - 1));
761 			if (rpnt == NULL)
762 				goto out;
763 			break;
764 		case SIG('C', 'E'):
765 			/* This tells is if there is a continuation record */
766 			rs.cont_extent = isonum_733(rr->u.CE.extent);
767 			rs.cont_offset = isonum_733(rr->u.CE.offset);
768 			rs.cont_size = isonum_733(rr->u.CE.size);
769 		default:
770 			break;
771 		}
772 	}
773 	ret = rock_continue(&rs);
774 	if (ret == 0)
775 		goto repeat;
776 	if (ret < 0)
777 		goto fail;
778 
779 	if (rpnt == link)
780 		goto fail;
781 	brelse(bh);
782 	*rpnt = '\0';
783 	SetPageUptodate(page);
784 	unlock_page(page);
785 	return 0;
786 
787 	/* error exit from macro */
788 out:
789 	kfree(rs.buffer);
790 	goto fail;
791 out_noread:
792 	printk("unable to read i-node block");
793 	goto fail;
794 out_bad_span:
795 	printk("symlink spans iso9660 blocks\n");
796 fail:
797 	brelse(bh);
798 error:
799 	SetPageError(page);
800 	unlock_page(page);
801 	return -EIO;
802 }
803 
804 const struct address_space_operations isofs_symlink_aops = {
805 	.readpage = rock_ridge_symlink_readpage
806 };
807