1/*
2 * Copyright (C) 1995, 1996, 1997 Wolfgang Solfrank
3 * Copyright (c) 1995 Martin Husemann
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26
27#include <sys/cdefs.h>
28#ifndef lint
29__RCSID("$NetBSD: fat.c,v 1.18 2006/06/05 16:51:18 christos Exp $");
30static const char rcsid[] =
31 "$FreeBSD: head/sbin/fsck_msdosfs/fat.c 268631 2014-07-14 20:17:09Z pfg $";
32#endif /* not lint */
33
34#include <stdlib.h>
35#include <string.h>
36#include <ctype.h>
37#include <stdio.h>
38#include <unistd.h>
39
40#include "ext.h"
41#include "fsutil.h"
42
43static int checkclnum(struct bootblock *, u_int, cl_t, cl_t *);
44static int clustdiffer(cl_t, cl_t *, cl_t *, u_int);
45static int tryclear(struct bootblock *, struct fatEntry *, cl_t, cl_t *);
46static int _readfat(int, struct bootblock *, u_int, u_char **);
47
48/*-
49 * The first 2 FAT entries contain pseudo-cluster numbers with the following
50 * layout:
51 *
52 * 31...... ........ ........ .......0
53 * rrrr1111 11111111 11111111 mmmmmmmm FAT32 entry 0
54 * rrrrsh11 11111111 11111111 11111xxx FAT32 entry 1
55 *
56 * 11111111 mmmmmmmm FAT16 entry 0
57 * sh111111 11111xxx FAT16 entry 1
58 *
59 * r = reserved
60 * m = BPB media ID byte
61 * s = clean flag (1 = dismounted; 0 = still mounted)
62 * h = hard error flag (1 = ok; 0 = I/O error)
63 * x = any value ok
64 */
65
66int
67checkdirty(int fs, struct bootblock *boot)
68{
69 off_t off;
70 u_char *buffer;
71 int ret = 0;
72 size_t len;
73
74 if (boot->ClustMask != CLUST16_MASK && boot->ClustMask != CLUST32_MASK)
75 return 0;
76
77 off = boot->bpbResSectors;
78 off *= boot->bpbBytesPerSec;
79
80 buffer = malloc(len = boot->bpbBytesPerSec);
81 if (buffer == NULL) {
82 perr("No space for FAT sectors (%zu)", len);
83 return 1;
84 }
85
86 if (lseek(fs, off, SEEK_SET) != off) {
87 perr("Unable to read FAT");
88 goto err;
89 }
90
91 if ((size_t)read(fs, buffer, boot->bpbBytesPerSec) !=
92 boot->bpbBytesPerSec) {
93 perr("Unable to read FAT");
94 goto err;
95 }
96
97 /*
98 * If we don't understand the FAT, then the file system must be
99 * assumed to be unclean.
100 */
101 if (buffer[0] != boot->bpbMedia || buffer[1] != 0xff)
102 goto err;
103 if (boot->ClustMask == CLUST16_MASK) {
104 if ((buffer[2] & 0xf8) != 0xf8 || (buffer[3] & 0x3f) != 0x3f)
105 goto err;
106 } else {
107 if (buffer[2] != 0xff || (buffer[3] & 0x0f) != 0x0f
108 || (buffer[4] & 0xf8) != 0xf8 || buffer[5] != 0xff
109 || buffer[6] != 0xff || (buffer[7] & 0x03) != 0x03)
110 goto err;
111 }
112
113 /*
114 * Now check the actual clean flag (and the no-error flag).
115 */
116 if (boot->ClustMask == CLUST16_MASK) {
117 if ((buffer[3] & 0xc0) == 0xc0)
118 ret = 1;
119 } else {
120 if ((buffer[7] & 0x0c) == 0x0c)
121 ret = 1;
122 }
123
124err:
125 free(buffer);
126 return ret;
127}
128
129/*
130 * Check a cluster number for valid value
131 */
132static int
133checkclnum(struct bootblock *boot, u_int fat, cl_t cl, cl_t *next)
134{
135 if (*next >= (CLUST_RSRVD&boot->ClustMask))
136 *next |= ~boot->ClustMask;
137 if (*next == CLUST_FREE) {
138 boot->NumFree++;
139 return FSOK;
140 }
141 if (*next == CLUST_BAD) {
142 boot->NumBad++;
143 return FSOK;
144 }
145 if (*next < CLUST_FIRST
146 || (*next >= boot->NumClusters && *next < CLUST_EOFS)) {
147 pwarn("Cluster %u in FAT %d continues with %s cluster number %u\n",
148 cl, fat,
149 *next < CLUST_RSRVD ? "out of range" : "reserved",
150 *next&boot->ClustMask);
151 if (ask(0, "Truncate")) {
152 *next = CLUST_EOF;
153 return FSFATMOD;
154 }
155 return FSERROR;
156 }
157 return FSOK;
158}
159
160/*
161 * Read a FAT from disk. Returns 1 if successful, 0 otherwise.
162 */
163static int
164_readfat(int fs, struct bootblock *boot, u_int no, u_char **buffer)
165{
166 off_t off;
167 size_t len;
168
169 *buffer = malloc(len = boot->FATsecs * boot->bpbBytesPerSec);
170 if (*buffer == NULL) {
171 perr("No space for FAT sectors (%zu)", len);
172 return 0;
173 }
174
175 off = boot->bpbResSectors + no * boot->FATsecs;
176 off *= boot->bpbBytesPerSec;
177
178 if (lseek(fs, off, SEEK_SET) != off) {
179 perr("Unable to read FAT");
180 goto err;
181 }
182
183 if ((size_t)read(fs, *buffer, boot->FATsecs * boot->bpbBytesPerSec)
184 != boot->FATsecs * boot->bpbBytesPerSec) {
185 perr("Unable to read FAT");
186 goto err;
187 }
188
189 return 1;
190
191 err:
192 free(*buffer);
193 return 0;
194}
195
196/*
197 * Read a FAT and decode it into internal format
198 */
199int
200readfat(int fs, struct bootblock *boot, u_int no, struct fatEntry **fp)
201{
202 struct fatEntry *fat;
203 u_char *buffer, *p;
204 cl_t cl;
205 int ret = FSOK;
206 size_t len;
207
208 boot->NumFree = boot->NumBad = 0;
209
210 if (!_readfat(fs, boot, no, &buffer))
211 return FSFATAL;
212
213 fat = malloc(len = boot->NumClusters * sizeof(struct fatEntry));
214 if (fat == NULL) {
215 perr("No space for FAT clusters (%zu)", len);
216 free(buffer);
217 return FSFATAL;
218 }
219 (void)memset(fat, 0, len);
220
221 if (buffer[0] != boot->bpbMedia
222 || buffer[1] != 0xff || buffer[2] != 0xff
223 || (boot->ClustMask == CLUST16_MASK && buffer[3] != 0xff)
224 || (boot->ClustMask == CLUST32_MASK
225 && ((buffer[3]&0x0f) != 0x0f
226 || buffer[4] != 0xff || buffer[5] != 0xff
227 || buffer[6] != 0xff || (buffer[7]&0x0f) != 0x0f))) {
228
229 /* Windows 95 OSR2 (and possibly any later) changes
230 * the FAT signature to 0xXXffff7f for FAT16 and to
231 * 0xXXffff0fffffff07 for FAT32 upon boot, to know that the
232 * file system is dirty if it doesn't reboot cleanly.
233 * Check this special condition before errorring out.
234 */
235 if (buffer[0] == boot->bpbMedia && buffer[1] == 0xff
236 && buffer[2] == 0xff
237 && ((boot->ClustMask == CLUST16_MASK && buffer[3] == 0x7f)
238 || (boot->ClustMask == CLUST32_MASK
239 && buffer[3] == 0x0f && buffer[4] == 0xff
240 && buffer[5] == 0xff && buffer[6] == 0xff
241 && buffer[7] == 0x07)))
242 ret |= FSDIRTY;
243 else {
244 /* just some odd byte sequence in FAT */
245
246 switch (boot->ClustMask) {
247 case CLUST32_MASK:
248 pwarn("%s (%02x%02x%02x%02x%02x%02x%02x%02x)\n",
249 "FAT starts with odd byte sequence",
250 buffer[0], buffer[1], buffer[2], buffer[3],
251 buffer[4], buffer[5], buffer[6], buffer[7]);
252 break;
253 case CLUST16_MASK:
254 pwarn("%s (%02x%02x%02x%02x)\n",
255 "FAT starts with odd byte sequence",
256 buffer[0], buffer[1], buffer[2], buffer[3]);
257 break;
258 default:
259 pwarn("%s (%02x%02x%02x)\n",
260 "FAT starts with odd byte sequence",
261 buffer[0], buffer[1], buffer[2]);
262 break;
263 }
264
265
266 if (ask(1, "Correct"))
267 ret |= FSFIXFAT;
268 }
269 }
270 switch (boot->ClustMask) {
271 case CLUST32_MASK:
272 p = buffer + 8;
273 break;
274 case CLUST16_MASK:
275 p = buffer + 4;
276 break;
277 default:
278 p = buffer + 3;
279 break;
280 }
281 for (cl = CLUST_FIRST; cl < boot->NumClusters;) {
282 switch (boot->ClustMask) {
283 case CLUST32_MASK:
284 fat[cl].next = p[0] + (p[1] << 8)
285 + (p[2] << 16) + (p[3] << 24);
286 fat[cl].next &= boot->ClustMask;
287 ret |= checkclnum(boot, no, cl, &fat[cl].next);
288 cl++;
289 p += 4;
290 break;
291 case CLUST16_MASK:
292 fat[cl].next = p[0] + (p[1] << 8);
293 ret |= checkclnum(boot, no, cl, &fat[cl].next);
294 cl++;
295 p += 2;
296 break;
297 default:
298 fat[cl].next = (p[0] + (p[1] << 8)) & 0x0fff;
299 ret |= checkclnum(boot, no, cl, &fat[cl].next);
300 cl++;
301 if (cl >= boot->NumClusters)
302 break;
303 fat[cl].next = ((p[1] >> 4) + (p[2] << 4)) & 0x0fff;
304 ret |= checkclnum(boot, no, cl, &fat[cl].next);
305 cl++;
306 p += 3;
307 break;
308 }
309 }
310
311 free(buffer);
312 if (ret & FSFATAL) {
313 free(fat);
314 *fp = NULL;
315 } else
316 *fp = fat;
317 return ret;
318}
319
320/*
321 * Get type of reserved cluster
322 */
323const char *
324rsrvdcltype(cl_t cl)
325{
326 if (cl == CLUST_FREE)
327 return "free";
328 if (cl < CLUST_BAD)
329 return "reserved";
330 if (cl > CLUST_BAD)
331 return "as EOF";
332 return "bad";
333}
334
335static int
336clustdiffer(cl_t cl, cl_t *cp1, cl_t *cp2, u_int fatnum)
337{
338 if (*cp1 == CLUST_FREE || *cp1 >= CLUST_RSRVD) {
339 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
340 if ((*cp1 != CLUST_FREE && *cp1 < CLUST_BAD
341 && *cp2 != CLUST_FREE && *cp2 < CLUST_BAD)
342 || (*cp1 > CLUST_BAD && *cp2 > CLUST_BAD)) {
343 pwarn("Cluster %u is marked %s with different indicators\n",
344 cl, rsrvdcltype(*cp1));
345 if (ask(1, "Fix")) {
346 *cp2 = *cp1;
347 return FSFATMOD;
348 }
349 return FSFATAL;
350 }
351 pwarn("Cluster %u is marked %s in FAT 0, %s in FAT %u\n",
352 cl, rsrvdcltype(*cp1), rsrvdcltype(*cp2), fatnum);
353 if (ask(0, "Use FAT 0's entry")) {
354 *cp2 = *cp1;
355 return FSFATMOD;
356 }
357 if (ask(0, "Use FAT %u's entry", fatnum)) {
358 *cp1 = *cp2;
359 return FSFATMOD;
360 }
361 return FSFATAL;
362 }
363 pwarn("Cluster %u is marked %s in FAT 0, but continues with cluster %u in FAT %d\n",
364 cl, rsrvdcltype(*cp1), *cp2, fatnum);
365 if (ask(0, "Use continuation from FAT %u", fatnum)) {
366 *cp1 = *cp2;
367 return FSFATMOD;
368 }
369 if (ask(0, "Use mark from FAT 0")) {
370 *cp2 = *cp1;
371 return FSFATMOD;
372 }
373 return FSFATAL;
374 }
375 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
376 pwarn("Cluster %u continues with cluster %u in FAT 0, but is marked %s in FAT %u\n",
377 cl, *cp1, rsrvdcltype(*cp2), fatnum);
378 if (ask(0, "Use continuation from FAT 0")) {
379 *cp2 = *cp1;
380 return FSFATMOD;
381 }
382 if (ask(0, "Use mark from FAT %d", fatnum)) {
383 *cp1 = *cp2;
384 return FSFATMOD;
385 }
386 return FSERROR;
387 }
388 pwarn("Cluster %u continues with cluster %u in FAT 0, but with cluster %u in FAT %u\n",
389 cl, *cp1, *cp2, fatnum);
390 if (ask(0, "Use continuation from FAT 0")) {
391 *cp2 = *cp1;
392 return FSFATMOD;
393 }
394 if (ask(0, "Use continuation from FAT %u", fatnum)) {
395 *cp1 = *cp2;
396 return FSFATMOD;
397 }
398 return FSERROR;
399}
400
401/*
402 * Compare two FAT copies in memory. Resolve any conflicts and merge them
403 * into the first one.
404 */
405int
406comparefat(struct bootblock *boot, struct fatEntry *first,
407 struct fatEntry *second, u_int fatnum)
408{
409 cl_t cl;
410 int ret = FSOK;
411
412 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++)
413 if (first[cl].next != second[cl].next)
414 ret |= clustdiffer(cl, &first[cl].next, &second[cl].next, fatnum);
415 return ret;
416}
417
418void
419clearchain(struct bootblock *boot, struct fatEntry *fat, cl_t head)
420{
421 cl_t p, q;
422
423 for (p = head; p >= CLUST_FIRST && p < boot->NumClusters; p = q) {
424 if (fat[p].head != head)
425 break;
426 q = fat[p].next;
427 fat[p].next = fat[p].head = CLUST_FREE;
428 fat[p].length = 0;
429 }
430}
431
432int
433tryclear(struct bootblock *boot, struct fatEntry *fat, cl_t head, cl_t *truncp)
434{
435 if (ask(0, "Clear chain starting at %u", head)) {
436 clearchain(boot, fat, head);
437 return FSFATMOD;
438 } else if (ask(0, "Truncate")) {
439 *truncp = CLUST_EOF;
440 return FSFATMOD;
441 } else
442 return FSERROR;
443}
444
445/*
446 * Check a complete FAT in-memory for crosslinks
447 */
448int
449checkfat(struct bootblock *boot, struct fatEntry *fat)
450{
451 cl_t head, p, h, n;
452 u_int len;
453 int ret = 0;
454 int conf;
455
456 /*
457 * pass 1: figure out the cluster chains.
458 */
459 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
460 /* find next untravelled chain */
461 if (fat[head].head != 0 /* cluster already belongs to some chain */
462 || fat[head].next == CLUST_FREE
463 || fat[head].next == CLUST_BAD)
464 continue; /* skip it. */
465
466 /* follow the chain and mark all clusters on the way */
467 for (len = 0, p = head;
468 p >= CLUST_FIRST && p < boot->NumClusters;
469 p = fat[p].next) {
470 fat[p].head = head;
471 len++;
472 }
473
474 /* the head record gets the length */
475 fat[head].length = fat[head].next == CLUST_FREE ? 0 : len;
476 }
477
478 /*
479 * pass 2: check for crosslinked chains (we couldn't do this in pass 1 because
480 * we didn't know the real start of the chain then - would have treated partial
481 * chains as interlinked with their main chain)
482 */
483 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
484 /* find next untravelled chain */
485 if (fat[head].head != head)
486 continue;
487
488 /* follow the chain to its end (hopefully) */
489 for (p = head;
490 (n = fat[p].next) >= CLUST_FIRST && n < boot->NumClusters;
491 p = n)
492 if (fat[n].head != head)
493 break;
494 if (n >= CLUST_EOFS)
495 continue;
496
497 if (n == CLUST_FREE || n >= CLUST_RSRVD) {
498 pwarn("Cluster chain starting at %u ends with cluster marked %s\n",
499 head, rsrvdcltype(n));
500 ret |= tryclear(boot, fat, head, &fat[p].next);
501 continue;
502 }
503 if (n < CLUST_FIRST || n >= boot->NumClusters) {
504 pwarn("Cluster chain starting at %u ends with cluster out of range (%u)\n",
505 head, n);
506 ret |= tryclear(boot, fat, head, &fat[p].next);
507 continue;
508 }
509 pwarn("Cluster chains starting at %u and %u are linked at cluster %u\n",
510 head, fat[n].head, n);
511 conf = tryclear(boot, fat, head, &fat[p].next);
512 if (ask(0, "Clear chain starting at %u", h = fat[n].head)) {
513 if (conf == FSERROR) {
514 /*
515 * Transfer the common chain to the one not cleared above.
516 */
517 for (p = n;
518 p >= CLUST_FIRST && p < boot->NumClusters;
519 p = fat[p].next) {
520 if (h != fat[p].head) {
521 /*
522 * Have to reexamine this chain.
523 */
524 head--;
525 break;
526 }
527 fat[p].head = head;
528 }
529 }
530 clearchain(boot, fat, h);
531 conf |= FSFATMOD;
532 }
533 ret |= conf;
534 }
535
536 return ret;
537}
538
539/*
540 * Write out FATs encoding them from the internal format
541 */
542int
543writefat(int fs, struct bootblock *boot, struct fatEntry *fat, int correct_fat)
544{
545 u_char *buffer, *p;
546 cl_t cl;
547 u_int i;
548 size_t fatsz;
549 off_t off;
550 int ret = FSOK;
551
552 buffer = malloc(fatsz = boot->FATsecs * boot->bpbBytesPerSec);
553 if (buffer == NULL) {
554 perr("No space for FAT sectors (%zu)", fatsz);
555 return FSFATAL;
556 }
557 memset(buffer, 0, fatsz);
558 boot->NumFree = 0;
559 p = buffer;
560 if (correct_fat) {
561 *p++ = (u_char)boot->bpbMedia;
562 *p++ = 0xff;
563 *p++ = 0xff;
564 switch (boot->ClustMask) {
565 case CLUST16_MASK:
566 *p++ = 0xff;
567 break;
568 case CLUST32_MASK:
569 *p++ = 0x0f;
570 *p++ = 0xff;
571 *p++ = 0xff;
572 *p++ = 0xff;
573 *p++ = 0x0f;
574 break;
575 }
576 } else {
577 /* use same FAT signature as the old FAT has */
578 int count;
579 u_char *old_fat;
580
581 switch (boot->ClustMask) {
582 case CLUST32_MASK:
583 count = 8;
584 break;
585 case CLUST16_MASK:
586 count = 4;
587 break;
588 default:
589 count = 3;
590 break;
591 }
592
593 if (!_readfat(fs, boot, boot->ValidFat >= 0 ? boot->ValidFat :0,
594 &old_fat)) {
595 free(buffer);
596 return FSFATAL;
597 }
598
599 memcpy(p, old_fat, count);
600 free(old_fat);
601 p += count;
602 }
603
604 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) {
605 switch (boot->ClustMask) {
606 case CLUST32_MASK:
607 if (fat[cl].next == CLUST_FREE)
608 boot->NumFree++;
609 *p++ = (u_char)fat[cl].next;
610 *p++ = (u_char)(fat[cl].next >> 8);
611 *p++ = (u_char)(fat[cl].next >> 16);
612 *p &= 0xf0;
613 *p++ |= (fat[cl].next >> 24)&0x0f;
614 break;
615 case CLUST16_MASK:
616 if (fat[cl].next == CLUST_FREE)
617 boot->NumFree++;
618 *p++ = (u_char)fat[cl].next;
619 *p++ = (u_char)(fat[cl].next >> 8);
620 break;
621 default:
622 if (fat[cl].next == CLUST_FREE)
623 boot->NumFree++;
624 if (cl + 1 < boot->NumClusters
625 && fat[cl + 1].next == CLUST_FREE)
626 boot->NumFree++;
627 *p++ = (u_char)fat[cl].next;
628 *p++ = (u_char)((fat[cl].next >> 8) & 0xf)
629 |(u_char)(fat[cl+1].next << 4);
630 *p++ = (u_char)(fat[++cl].next >> 4);
631 break;
632 }
633 }
634 for (i = 0; i < boot->bpbFATs; i++) {
635 off = boot->bpbResSectors + i * boot->FATsecs;
636 off *= boot->bpbBytesPerSec;
637 if (lseek(fs, off, SEEK_SET) != off
638 || (size_t)write(fs, buffer, fatsz) != fatsz) {
639 perr("Unable to write FAT");
640 ret = FSFATAL; /* Return immediately? XXX */
641 }
642 }
643 free(buffer);
644 return ret;
645}
646
647/*
648 * Check a complete in-memory FAT for lost cluster chains
649 */
650int
651checklost(int dosfs, struct bootblock *boot, struct fatEntry *fat)
652{
653 cl_t head;
654 int mod = FSOK;
655 int ret;
656
657 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
658 /* find next untravelled chain */
659 if (fat[head].head != head
660 || fat[head].next == CLUST_FREE
661 || (fat[head].next >= CLUST_RSRVD
662 && fat[head].next < CLUST_EOFS)
663 || (fat[head].flags & FAT_USED))
664 continue;
665
666 pwarn("Lost cluster chain at cluster %u\n%d Cluster(s) lost\n",
667 head, fat[head].length);
668 mod |= ret = reconnect(dosfs, boot, fat, head);
669 if (mod & FSFATAL)
670 break;
671 if (ret == FSERROR && ask(0, "Clear")) {
672 clearchain(boot, fat, head);
673 mod |= FSFATMOD;
674 }
675 }
676 finishlf();
677
678 if (boot->bpbFSInfo) {
679 ret = 0;
680 if (boot->FSFree != 0xffffffffU &&
681 boot->FSFree != boot->NumFree) {
682 pwarn("Free space in FSInfo block (%u) not correct (%u)\n",
683 boot->FSFree, boot->NumFree);
684 if (ask(1, "Fix")) {
685 boot->FSFree = boot->NumFree;
686 ret = 1;
687 }
688 }
689 if (ret)
690 mod |= writefsinfo(dosfs, boot);
691 }
692
693 return mod;
694}
2 * Copyright (C) 1995, 1996, 1997 Wolfgang Solfrank
3 * Copyright (c) 1995 Martin Husemann
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26
27#include <sys/cdefs.h>
28#ifndef lint
29__RCSID("$NetBSD: fat.c,v 1.18 2006/06/05 16:51:18 christos Exp $");
30static const char rcsid[] =
31 "$FreeBSD: head/sbin/fsck_msdosfs/fat.c 268631 2014-07-14 20:17:09Z pfg $";
32#endif /* not lint */
33
34#include <stdlib.h>
35#include <string.h>
36#include <ctype.h>
37#include <stdio.h>
38#include <unistd.h>
39
40#include "ext.h"
41#include "fsutil.h"
42
43static int checkclnum(struct bootblock *, u_int, cl_t, cl_t *);
44static int clustdiffer(cl_t, cl_t *, cl_t *, u_int);
45static int tryclear(struct bootblock *, struct fatEntry *, cl_t, cl_t *);
46static int _readfat(int, struct bootblock *, u_int, u_char **);
47
48/*-
49 * The first 2 FAT entries contain pseudo-cluster numbers with the following
50 * layout:
51 *
52 * 31...... ........ ........ .......0
53 * rrrr1111 11111111 11111111 mmmmmmmm FAT32 entry 0
54 * rrrrsh11 11111111 11111111 11111xxx FAT32 entry 1
55 *
56 * 11111111 mmmmmmmm FAT16 entry 0
57 * sh111111 11111xxx FAT16 entry 1
58 *
59 * r = reserved
60 * m = BPB media ID byte
61 * s = clean flag (1 = dismounted; 0 = still mounted)
62 * h = hard error flag (1 = ok; 0 = I/O error)
63 * x = any value ok
64 */
65
66int
67checkdirty(int fs, struct bootblock *boot)
68{
69 off_t off;
70 u_char *buffer;
71 int ret = 0;
72 size_t len;
73
74 if (boot->ClustMask != CLUST16_MASK && boot->ClustMask != CLUST32_MASK)
75 return 0;
76
77 off = boot->bpbResSectors;
78 off *= boot->bpbBytesPerSec;
79
80 buffer = malloc(len = boot->bpbBytesPerSec);
81 if (buffer == NULL) {
82 perr("No space for FAT sectors (%zu)", len);
83 return 1;
84 }
85
86 if (lseek(fs, off, SEEK_SET) != off) {
87 perr("Unable to read FAT");
88 goto err;
89 }
90
91 if ((size_t)read(fs, buffer, boot->bpbBytesPerSec) !=
92 boot->bpbBytesPerSec) {
93 perr("Unable to read FAT");
94 goto err;
95 }
96
97 /*
98 * If we don't understand the FAT, then the file system must be
99 * assumed to be unclean.
100 */
101 if (buffer[0] != boot->bpbMedia || buffer[1] != 0xff)
102 goto err;
103 if (boot->ClustMask == CLUST16_MASK) {
104 if ((buffer[2] & 0xf8) != 0xf8 || (buffer[3] & 0x3f) != 0x3f)
105 goto err;
106 } else {
107 if (buffer[2] != 0xff || (buffer[3] & 0x0f) != 0x0f
108 || (buffer[4] & 0xf8) != 0xf8 || buffer[5] != 0xff
109 || buffer[6] != 0xff || (buffer[7] & 0x03) != 0x03)
110 goto err;
111 }
112
113 /*
114 * Now check the actual clean flag (and the no-error flag).
115 */
116 if (boot->ClustMask == CLUST16_MASK) {
117 if ((buffer[3] & 0xc0) == 0xc0)
118 ret = 1;
119 } else {
120 if ((buffer[7] & 0x0c) == 0x0c)
121 ret = 1;
122 }
123
124err:
125 free(buffer);
126 return ret;
127}
128
129/*
130 * Check a cluster number for valid value
131 */
132static int
133checkclnum(struct bootblock *boot, u_int fat, cl_t cl, cl_t *next)
134{
135 if (*next >= (CLUST_RSRVD&boot->ClustMask))
136 *next |= ~boot->ClustMask;
137 if (*next == CLUST_FREE) {
138 boot->NumFree++;
139 return FSOK;
140 }
141 if (*next == CLUST_BAD) {
142 boot->NumBad++;
143 return FSOK;
144 }
145 if (*next < CLUST_FIRST
146 || (*next >= boot->NumClusters && *next < CLUST_EOFS)) {
147 pwarn("Cluster %u in FAT %d continues with %s cluster number %u\n",
148 cl, fat,
149 *next < CLUST_RSRVD ? "out of range" : "reserved",
150 *next&boot->ClustMask);
151 if (ask(0, "Truncate")) {
152 *next = CLUST_EOF;
153 return FSFATMOD;
154 }
155 return FSERROR;
156 }
157 return FSOK;
158}
159
160/*
161 * Read a FAT from disk. Returns 1 if successful, 0 otherwise.
162 */
163static int
164_readfat(int fs, struct bootblock *boot, u_int no, u_char **buffer)
165{
166 off_t off;
167 size_t len;
168
169 *buffer = malloc(len = boot->FATsecs * boot->bpbBytesPerSec);
170 if (*buffer == NULL) {
171 perr("No space for FAT sectors (%zu)", len);
172 return 0;
173 }
174
175 off = boot->bpbResSectors + no * boot->FATsecs;
176 off *= boot->bpbBytesPerSec;
177
178 if (lseek(fs, off, SEEK_SET) != off) {
179 perr("Unable to read FAT");
180 goto err;
181 }
182
183 if ((size_t)read(fs, *buffer, boot->FATsecs * boot->bpbBytesPerSec)
184 != boot->FATsecs * boot->bpbBytesPerSec) {
185 perr("Unable to read FAT");
186 goto err;
187 }
188
189 return 1;
190
191 err:
192 free(*buffer);
193 return 0;
194}
195
196/*
197 * Read a FAT and decode it into internal format
198 */
199int
200readfat(int fs, struct bootblock *boot, u_int no, struct fatEntry **fp)
201{
202 struct fatEntry *fat;
203 u_char *buffer, *p;
204 cl_t cl;
205 int ret = FSOK;
206 size_t len;
207
208 boot->NumFree = boot->NumBad = 0;
209
210 if (!_readfat(fs, boot, no, &buffer))
211 return FSFATAL;
212
213 fat = malloc(len = boot->NumClusters * sizeof(struct fatEntry));
214 if (fat == NULL) {
215 perr("No space for FAT clusters (%zu)", len);
216 free(buffer);
217 return FSFATAL;
218 }
219 (void)memset(fat, 0, len);
220
221 if (buffer[0] != boot->bpbMedia
222 || buffer[1] != 0xff || buffer[2] != 0xff
223 || (boot->ClustMask == CLUST16_MASK && buffer[3] != 0xff)
224 || (boot->ClustMask == CLUST32_MASK
225 && ((buffer[3]&0x0f) != 0x0f
226 || buffer[4] != 0xff || buffer[5] != 0xff
227 || buffer[6] != 0xff || (buffer[7]&0x0f) != 0x0f))) {
228
229 /* Windows 95 OSR2 (and possibly any later) changes
230 * the FAT signature to 0xXXffff7f for FAT16 and to
231 * 0xXXffff0fffffff07 for FAT32 upon boot, to know that the
232 * file system is dirty if it doesn't reboot cleanly.
233 * Check this special condition before errorring out.
234 */
235 if (buffer[0] == boot->bpbMedia && buffer[1] == 0xff
236 && buffer[2] == 0xff
237 && ((boot->ClustMask == CLUST16_MASK && buffer[3] == 0x7f)
238 || (boot->ClustMask == CLUST32_MASK
239 && buffer[3] == 0x0f && buffer[4] == 0xff
240 && buffer[5] == 0xff && buffer[6] == 0xff
241 && buffer[7] == 0x07)))
242 ret |= FSDIRTY;
243 else {
244 /* just some odd byte sequence in FAT */
245
246 switch (boot->ClustMask) {
247 case CLUST32_MASK:
248 pwarn("%s (%02x%02x%02x%02x%02x%02x%02x%02x)\n",
249 "FAT starts with odd byte sequence",
250 buffer[0], buffer[1], buffer[2], buffer[3],
251 buffer[4], buffer[5], buffer[6], buffer[7]);
252 break;
253 case CLUST16_MASK:
254 pwarn("%s (%02x%02x%02x%02x)\n",
255 "FAT starts with odd byte sequence",
256 buffer[0], buffer[1], buffer[2], buffer[3]);
257 break;
258 default:
259 pwarn("%s (%02x%02x%02x)\n",
260 "FAT starts with odd byte sequence",
261 buffer[0], buffer[1], buffer[2]);
262 break;
263 }
264
265
266 if (ask(1, "Correct"))
267 ret |= FSFIXFAT;
268 }
269 }
270 switch (boot->ClustMask) {
271 case CLUST32_MASK:
272 p = buffer + 8;
273 break;
274 case CLUST16_MASK:
275 p = buffer + 4;
276 break;
277 default:
278 p = buffer + 3;
279 break;
280 }
281 for (cl = CLUST_FIRST; cl < boot->NumClusters;) {
282 switch (boot->ClustMask) {
283 case CLUST32_MASK:
284 fat[cl].next = p[0] + (p[1] << 8)
285 + (p[2] << 16) + (p[3] << 24);
286 fat[cl].next &= boot->ClustMask;
287 ret |= checkclnum(boot, no, cl, &fat[cl].next);
288 cl++;
289 p += 4;
290 break;
291 case CLUST16_MASK:
292 fat[cl].next = p[0] + (p[1] << 8);
293 ret |= checkclnum(boot, no, cl, &fat[cl].next);
294 cl++;
295 p += 2;
296 break;
297 default:
298 fat[cl].next = (p[0] + (p[1] << 8)) & 0x0fff;
299 ret |= checkclnum(boot, no, cl, &fat[cl].next);
300 cl++;
301 if (cl >= boot->NumClusters)
302 break;
303 fat[cl].next = ((p[1] >> 4) + (p[2] << 4)) & 0x0fff;
304 ret |= checkclnum(boot, no, cl, &fat[cl].next);
305 cl++;
306 p += 3;
307 break;
308 }
309 }
310
311 free(buffer);
312 if (ret & FSFATAL) {
313 free(fat);
314 *fp = NULL;
315 } else
316 *fp = fat;
317 return ret;
318}
319
320/*
321 * Get type of reserved cluster
322 */
323const char *
324rsrvdcltype(cl_t cl)
325{
326 if (cl == CLUST_FREE)
327 return "free";
328 if (cl < CLUST_BAD)
329 return "reserved";
330 if (cl > CLUST_BAD)
331 return "as EOF";
332 return "bad";
333}
334
335static int
336clustdiffer(cl_t cl, cl_t *cp1, cl_t *cp2, u_int fatnum)
337{
338 if (*cp1 == CLUST_FREE || *cp1 >= CLUST_RSRVD) {
339 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
340 if ((*cp1 != CLUST_FREE && *cp1 < CLUST_BAD
341 && *cp2 != CLUST_FREE && *cp2 < CLUST_BAD)
342 || (*cp1 > CLUST_BAD && *cp2 > CLUST_BAD)) {
343 pwarn("Cluster %u is marked %s with different indicators\n",
344 cl, rsrvdcltype(*cp1));
345 if (ask(1, "Fix")) {
346 *cp2 = *cp1;
347 return FSFATMOD;
348 }
349 return FSFATAL;
350 }
351 pwarn("Cluster %u is marked %s in FAT 0, %s in FAT %u\n",
352 cl, rsrvdcltype(*cp1), rsrvdcltype(*cp2), fatnum);
353 if (ask(0, "Use FAT 0's entry")) {
354 *cp2 = *cp1;
355 return FSFATMOD;
356 }
357 if (ask(0, "Use FAT %u's entry", fatnum)) {
358 *cp1 = *cp2;
359 return FSFATMOD;
360 }
361 return FSFATAL;
362 }
363 pwarn("Cluster %u is marked %s in FAT 0, but continues with cluster %u in FAT %d\n",
364 cl, rsrvdcltype(*cp1), *cp2, fatnum);
365 if (ask(0, "Use continuation from FAT %u", fatnum)) {
366 *cp1 = *cp2;
367 return FSFATMOD;
368 }
369 if (ask(0, "Use mark from FAT 0")) {
370 *cp2 = *cp1;
371 return FSFATMOD;
372 }
373 return FSFATAL;
374 }
375 if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
376 pwarn("Cluster %u continues with cluster %u in FAT 0, but is marked %s in FAT %u\n",
377 cl, *cp1, rsrvdcltype(*cp2), fatnum);
378 if (ask(0, "Use continuation from FAT 0")) {
379 *cp2 = *cp1;
380 return FSFATMOD;
381 }
382 if (ask(0, "Use mark from FAT %d", fatnum)) {
383 *cp1 = *cp2;
384 return FSFATMOD;
385 }
386 return FSERROR;
387 }
388 pwarn("Cluster %u continues with cluster %u in FAT 0, but with cluster %u in FAT %u\n",
389 cl, *cp1, *cp2, fatnum);
390 if (ask(0, "Use continuation from FAT 0")) {
391 *cp2 = *cp1;
392 return FSFATMOD;
393 }
394 if (ask(0, "Use continuation from FAT %u", fatnum)) {
395 *cp1 = *cp2;
396 return FSFATMOD;
397 }
398 return FSERROR;
399}
400
401/*
402 * Compare two FAT copies in memory. Resolve any conflicts and merge them
403 * into the first one.
404 */
405int
406comparefat(struct bootblock *boot, struct fatEntry *first,
407 struct fatEntry *second, u_int fatnum)
408{
409 cl_t cl;
410 int ret = FSOK;
411
412 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++)
413 if (first[cl].next != second[cl].next)
414 ret |= clustdiffer(cl, &first[cl].next, &second[cl].next, fatnum);
415 return ret;
416}
417
418void
419clearchain(struct bootblock *boot, struct fatEntry *fat, cl_t head)
420{
421 cl_t p, q;
422
423 for (p = head; p >= CLUST_FIRST && p < boot->NumClusters; p = q) {
424 if (fat[p].head != head)
425 break;
426 q = fat[p].next;
427 fat[p].next = fat[p].head = CLUST_FREE;
428 fat[p].length = 0;
429 }
430}
431
432int
433tryclear(struct bootblock *boot, struct fatEntry *fat, cl_t head, cl_t *truncp)
434{
435 if (ask(0, "Clear chain starting at %u", head)) {
436 clearchain(boot, fat, head);
437 return FSFATMOD;
438 } else if (ask(0, "Truncate")) {
439 *truncp = CLUST_EOF;
440 return FSFATMOD;
441 } else
442 return FSERROR;
443}
444
445/*
446 * Check a complete FAT in-memory for crosslinks
447 */
448int
449checkfat(struct bootblock *boot, struct fatEntry *fat)
450{
451 cl_t head, p, h, n;
452 u_int len;
453 int ret = 0;
454 int conf;
455
456 /*
457 * pass 1: figure out the cluster chains.
458 */
459 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
460 /* find next untravelled chain */
461 if (fat[head].head != 0 /* cluster already belongs to some chain */
462 || fat[head].next == CLUST_FREE
463 || fat[head].next == CLUST_BAD)
464 continue; /* skip it. */
465
466 /* follow the chain and mark all clusters on the way */
467 for (len = 0, p = head;
468 p >= CLUST_FIRST && p < boot->NumClusters;
469 p = fat[p].next) {
470 fat[p].head = head;
471 len++;
472 }
473
474 /* the head record gets the length */
475 fat[head].length = fat[head].next == CLUST_FREE ? 0 : len;
476 }
477
478 /*
479 * pass 2: check for crosslinked chains (we couldn't do this in pass 1 because
480 * we didn't know the real start of the chain then - would have treated partial
481 * chains as interlinked with their main chain)
482 */
483 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
484 /* find next untravelled chain */
485 if (fat[head].head != head)
486 continue;
487
488 /* follow the chain to its end (hopefully) */
489 for (p = head;
490 (n = fat[p].next) >= CLUST_FIRST && n < boot->NumClusters;
491 p = n)
492 if (fat[n].head != head)
493 break;
494 if (n >= CLUST_EOFS)
495 continue;
496
497 if (n == CLUST_FREE || n >= CLUST_RSRVD) {
498 pwarn("Cluster chain starting at %u ends with cluster marked %s\n",
499 head, rsrvdcltype(n));
500 ret |= tryclear(boot, fat, head, &fat[p].next);
501 continue;
502 }
503 if (n < CLUST_FIRST || n >= boot->NumClusters) {
504 pwarn("Cluster chain starting at %u ends with cluster out of range (%u)\n",
505 head, n);
506 ret |= tryclear(boot, fat, head, &fat[p].next);
507 continue;
508 }
509 pwarn("Cluster chains starting at %u and %u are linked at cluster %u\n",
510 head, fat[n].head, n);
511 conf = tryclear(boot, fat, head, &fat[p].next);
512 if (ask(0, "Clear chain starting at %u", h = fat[n].head)) {
513 if (conf == FSERROR) {
514 /*
515 * Transfer the common chain to the one not cleared above.
516 */
517 for (p = n;
518 p >= CLUST_FIRST && p < boot->NumClusters;
519 p = fat[p].next) {
520 if (h != fat[p].head) {
521 /*
522 * Have to reexamine this chain.
523 */
524 head--;
525 break;
526 }
527 fat[p].head = head;
528 }
529 }
530 clearchain(boot, fat, h);
531 conf |= FSFATMOD;
532 }
533 ret |= conf;
534 }
535
536 return ret;
537}
538
539/*
540 * Write out FATs encoding them from the internal format
541 */
542int
543writefat(int fs, struct bootblock *boot, struct fatEntry *fat, int correct_fat)
544{
545 u_char *buffer, *p;
546 cl_t cl;
547 u_int i;
548 size_t fatsz;
549 off_t off;
550 int ret = FSOK;
551
552 buffer = malloc(fatsz = boot->FATsecs * boot->bpbBytesPerSec);
553 if (buffer == NULL) {
554 perr("No space for FAT sectors (%zu)", fatsz);
555 return FSFATAL;
556 }
557 memset(buffer, 0, fatsz);
558 boot->NumFree = 0;
559 p = buffer;
560 if (correct_fat) {
561 *p++ = (u_char)boot->bpbMedia;
562 *p++ = 0xff;
563 *p++ = 0xff;
564 switch (boot->ClustMask) {
565 case CLUST16_MASK:
566 *p++ = 0xff;
567 break;
568 case CLUST32_MASK:
569 *p++ = 0x0f;
570 *p++ = 0xff;
571 *p++ = 0xff;
572 *p++ = 0xff;
573 *p++ = 0x0f;
574 break;
575 }
576 } else {
577 /* use same FAT signature as the old FAT has */
578 int count;
579 u_char *old_fat;
580
581 switch (boot->ClustMask) {
582 case CLUST32_MASK:
583 count = 8;
584 break;
585 case CLUST16_MASK:
586 count = 4;
587 break;
588 default:
589 count = 3;
590 break;
591 }
592
593 if (!_readfat(fs, boot, boot->ValidFat >= 0 ? boot->ValidFat :0,
594 &old_fat)) {
595 free(buffer);
596 return FSFATAL;
597 }
598
599 memcpy(p, old_fat, count);
600 free(old_fat);
601 p += count;
602 }
603
604 for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) {
605 switch (boot->ClustMask) {
606 case CLUST32_MASK:
607 if (fat[cl].next == CLUST_FREE)
608 boot->NumFree++;
609 *p++ = (u_char)fat[cl].next;
610 *p++ = (u_char)(fat[cl].next >> 8);
611 *p++ = (u_char)(fat[cl].next >> 16);
612 *p &= 0xf0;
613 *p++ |= (fat[cl].next >> 24)&0x0f;
614 break;
615 case CLUST16_MASK:
616 if (fat[cl].next == CLUST_FREE)
617 boot->NumFree++;
618 *p++ = (u_char)fat[cl].next;
619 *p++ = (u_char)(fat[cl].next >> 8);
620 break;
621 default:
622 if (fat[cl].next == CLUST_FREE)
623 boot->NumFree++;
624 if (cl + 1 < boot->NumClusters
625 && fat[cl + 1].next == CLUST_FREE)
626 boot->NumFree++;
627 *p++ = (u_char)fat[cl].next;
628 *p++ = (u_char)((fat[cl].next >> 8) & 0xf)
629 |(u_char)(fat[cl+1].next << 4);
630 *p++ = (u_char)(fat[++cl].next >> 4);
631 break;
632 }
633 }
634 for (i = 0; i < boot->bpbFATs; i++) {
635 off = boot->bpbResSectors + i * boot->FATsecs;
636 off *= boot->bpbBytesPerSec;
637 if (lseek(fs, off, SEEK_SET) != off
638 || (size_t)write(fs, buffer, fatsz) != fatsz) {
639 perr("Unable to write FAT");
640 ret = FSFATAL; /* Return immediately? XXX */
641 }
642 }
643 free(buffer);
644 return ret;
645}
646
647/*
648 * Check a complete in-memory FAT for lost cluster chains
649 */
650int
651checklost(int dosfs, struct bootblock *boot, struct fatEntry *fat)
652{
653 cl_t head;
654 int mod = FSOK;
655 int ret;
656
657 for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
658 /* find next untravelled chain */
659 if (fat[head].head != head
660 || fat[head].next == CLUST_FREE
661 || (fat[head].next >= CLUST_RSRVD
662 && fat[head].next < CLUST_EOFS)
663 || (fat[head].flags & FAT_USED))
664 continue;
665
666 pwarn("Lost cluster chain at cluster %u\n%d Cluster(s) lost\n",
667 head, fat[head].length);
668 mod |= ret = reconnect(dosfs, boot, fat, head);
669 if (mod & FSFATAL)
670 break;
671 if (ret == FSERROR && ask(0, "Clear")) {
672 clearchain(boot, fat, head);
673 mod |= FSFATMOD;
674 }
675 }
676 finishlf();
677
678 if (boot->bpbFSInfo) {
679 ret = 0;
680 if (boot->FSFree != 0xffffffffU &&
681 boot->FSFree != boot->NumFree) {
682 pwarn("Free space in FSInfo block (%u) not correct (%u)\n",
683 boot->FSFree, boot->NumFree);
684 if (ask(1, "Fix")) {
685 boot->FSFree = boot->NumFree;
686 ret = 1;
687 }
688 }
689 if (ret)
690 mod |= writefsinfo(dosfs, boot);
691 }
692
693 return mod;
694}