Author: emaste
Date: Wed Aug 21 19:09:40 2019
New Revision: 351347
URL: https://svnweb.freebsd.org/changeset/base/351347
Log:
makefs: Verify that the BPB media descriptor and FAT ID match
From r322982 in sys/fs/msdosfs.
Modified:
head/usr.sbin/makefs/msdos/msdosfs_fat.c
Modified: head/usr.sbin/makefs/msdos/msdosfs_fat.c
==============================================================================
--- head/usr.sbin/makefs/msdos/msdosfs_fat.c Wed Aug 21 19:07:13 2019
(r351346)
+++ head/usr.sbin/makefs/msdos/msdosfs_fat.c Wed Aug 21 19:09:40 2019
(r351347)
@@ -887,19 +887,17 @@ fillinusemap(struct msdosfsmount *pmp)
* zero. These represent free clusters.
*/
pmp->pm_freeclustercount = 0;
- for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) {
+ for (cn = 0; cn <= pmp->pm_maxcluster; cn++) {
byteoffset = FATOFS(pmp, cn);
bo = byteoffset % pmp->pm_fatblocksize;
- if (bo == 0 || bp == NULL) {
+ if (bo == 0) {
/* Read new FAT block */
if (bp != NULL)
brelse(bp);
fatblock(pmp, byteoffset, &bn, &bsize, NULL);
error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
- if (error != 0) {
- brelse(bp);
+ if (error != 0)
return (error);
- }
}
if (FAT32(pmp))
readcn = getulong(bp->b_data + bo);
@@ -909,7 +907,19 @@ fillinusemap(struct msdosfsmount *pmp)
readcn >>= 4;
readcn &= pmp->pm_fatmask;
- if (readcn == CLUST_FREE)
+ /*
+ * Check if the FAT ID matches the BPB's media descriptor and
+ * all other bits are set to 1.
+ */
+ if (cn == 0 && readcn != ((pmp->pm_fatmask & 0xffffff00) |
+ pmp->pm_bpb.bpbMedia)) {
+#ifdef MSDOSFS_DEBUG
+ printf("mountmsdosfs(): Media descriptor in BPB"
+ "does not match FAT ID\n");
+#endif
+ brelse(bp);
+ return (EINVAL);
+ } else if (readcn == CLUST_FREE)
usemap_free(pmp, cn);
}
if (bp != NULL)
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