git: e1ac02ff7adf - stable/13 - geom label msdosfs: sanity check BPB before using it for io request

The branch stable/13 has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=e1ac02ff7adf7a9749ca2a57d6da25e6a295a68f

commit e1ac02ff7adf7a9749ca2a57d6da25e6a295a68f
Author:     Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2021-12-30 13:17:59 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2022-01-14 18:11:01 +0000

    geom label msdosfs: sanity check BPB before using it for io request
    
    (cherry picked from commit 9f4073d44628bc70dbe67df5163266cbfbe37167)
---
 sys/geom/label/g_label_msdosfs.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/sys/geom/label/g_label_msdosfs.c b/sys/geom/label/g_label_msdosfs.c
index d6ccb8b334ee..67ac879d62c2 100644
--- a/sys/geom/label/g_label_msdosfs.c
+++ b/sys/geom/label/g_label_msdosfs.c
@@ -152,6 +152,12 @@ g_label_msdosfs_taste(struct g_consumer *cp, char *label, size_t size)
 		G_LABEL_DEBUG(2,
 		    "MSDOSFS: FAT_FirstDataSector=0x%x, FAT_BytesPerSector=%d",
 		    fat_FirstDataSector, fat_BytesPerSector);
+		if (fat_BytesPerSector == 0 ||
+		    fat_BytesPerSector % pp->sectorsize != 0) {
+			G_LABEL_DEBUG(1, "MSDOSFS: %s: corrupted BPB",
+			    pp->name);
+			goto error;
+		}
 
 		for (offset = fat_BytesPerSector * fat_FirstDataSector;;
 		    offset += fat_BytesPerSector) {