super1: Clear memory allocated for superblock + bitmap before use

load_super1() did not clear memory allocated for the superblock +
bitmap. This causes issues if the superblock does not contain a bitmap
as later checks of bitmap features would rely on the bits being
cleared.

This bug has been around for a long time, but was only exposed in
mdadm-3.4 with the introduction of the clustering code.

Reported-by: Jan Stodola <jstodola@redhat.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/super1.c b/super1.c
index d6f3c93..8d5543f 100644
--- a/super1.c
+++ b/super1.c
@@ -2016,6 +2016,8 @@ static int load_super1(struct supertype *st, int fd, char *devname)
 		return 1;
 	}
 
+	memset(super, 0, SUPER1_SIZE);
+
 	if (aread(&afd, super, MAX_SB_SIZE) != MAX_SB_SIZE) {
 		if (devname)
 			pr_err("Cannot read superblock on %s\n",