There is no check if stream size and start_clu are invalid.
If start_clu is EOF cluster and stream size is 4096, It will
cause uninit value access. because ei->hint_femp.eidx could
be 128(if cluster size is 4K) and wrong hint will allocate
next cluster. and this cluster will be same with the cluster
that is allocated by exfat_extend_valid_size(). The previous
patch will check invalid start_clu, but for clarity, initialize
hint_femp.eidx to zero.
Reported-by: syzbot+01218003be74b5e1213a@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested-by: syzbot+01218003be74b5e1213a@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Namjae Jeon <linkinjeon@xxxxxxxxxx>
Reviewed-by: Yuezhang Mo <Yuezhang.Mo@xxxxxxxx>
---
fs/exfat/namei.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/exfat/namei.c b/fs/exfat/namei.c
index 98f67e632ad1..337197ece599 100644
--- a/fs/exfat/namei.c
+++ b/fs/exfat/namei.c
@@ -345,6 +345,7 @@ static int exfat_find_empty_entry(struct inode *inode,
if (ei->start_clu == EXFAT_EOF_CLUSTER) {
ei->start_clu = clu.dir;
p_dir->dir = clu.dir;
+ hint_femp.eidx = 0;
}
/* append to the FAT chain */
--
2.43.0
