Author: delphij
Date: Tue Jan 28 07:49:52 2020
New Revision: 357196
URL: https://svnweb.freebsd.org/changeset/base/357196
Log:
MFC r356629, r356636
r356629:
Apply typo fix from NetBSD, we have already applied all NetBSD changes so
update the NetBSD tag while I'm there.
r356636:
Correct off-by-two issue when determining FAT type.
In the code we used NumClusters as the upper (non-inclusive) boundary
of valid cluster number, so the actual value was 2 (CLUST_FIRST) more
than the real number of clusters. This causes a FAT16 media with
65524 clusters be treated as FAT32 and might affect FAT12 media with
4084 clusters as well.
To fix this, we increment NumClusters by CLUST_FIRST after the type
determination.
PR: 243179
Modified:
stable/12/sbin/fsck_msdosfs/boot.c
Directory Properties:
stable/12/ (props changed)
Modified: stable/12/sbin/fsck_msdosfs/boot.c
==============================================================================
--- stable/12/sbin/fsck_msdosfs/boot.c Tue Jan 28 03:47:29 2020
(r357195)
+++ stable/12/sbin/fsck_msdosfs/boot.c Tue Jan 28 07:49:52 2020
(r357196)
@@ -28,7 +28,7 @@
#include <sys/cdefs.h>
#ifndef lint
-__RCSID("$NetBSD: boot.c,v 1.11 2006/06/05 16:51:18 christos Exp ");
+__RCSID("$NetBSD: boot.c,v 1.21 2018/02/08 09:05:17 dholland Exp $");
static const char rcsid[] =
"$FreeBSD$";
#endif /* not lint */
@@ -269,8 +269,11 @@ readboot(int dosfs, struct bootblock *boot)
return FSFATAL;
}
- boot->NumClusters = (boot->NumSectors - boot->FirstCluster) /
boot->bpbSecPerClust +
- CLUST_FIRST;
+ /*
+ * The number of clusters is derived from available data sectors,
divided
+ * by sectors per cluster.
+ */
+ boot->NumClusters = (boot->NumSectors - boot->FirstCluster) /
boot->bpbSecPerClust;
if (boot->flags & FAT32)
boot->ClustMask = CLUST32_MASK;
@@ -296,11 +299,19 @@ readboot(int dosfs, struct bootblock *boot)
break;
}
- if (boot->NumFatEntries < boot->NumClusters - CLUST_FIRST) {
+ if (boot->NumFatEntries < boot->NumClusters) {
pfatal("FAT size too small, %u entries won't fit into %u
sectors\n",
boot->NumClusters, boot->FATsecs);
return FSFATAL;
}
+
+ /*
+ * There are two reserved clusters. To avoid adding CLUST_FIRST every
time
+ * when we perform boundary checks, we increment the NumClusters by 2,
+ * which is CLUST_FIRST to denote the first out-of-range cluster number.
+ */
+ boot->NumClusters += CLUST_FIRST;
+
boot->ClusterSize = boot->bpbBytesPerSec * boot->bpbSecPerClust;
boot->NumFiles = 1;
@@ -342,7 +353,7 @@ writefsinfo(int dosfs, struct bootblock *boot)
* support for FAT32) doesn't maintain the FSINFO block
* correctly, it has to be fixed pretty often.
*
- * Therefor, we handle the FSINFO block only informally,
+ * Therefore, we handle the FSINFO block only informally,
* fixing it if necessary, but otherwise ignoring the
* fact that it was incorrect.
*/
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