ip_mroute: Avoid leaking uninitialized bytes to the routing daemon

Reported by:	KMSAN
MFC after:	1 week

1 files changed, 8 insertions, 7 deletions

diff --git a/sys/netinet/ip_mroute.c b/sys/netinet/ip_mroute.c
index 359755b19e95..14bd458b74f3 100644
--- a/sys/netinet/ip_mroute.c
+++ b/sys/netinet/ip_mroute.c
@@ -2459,13 +2459,14 @@ pim_register_send_upcall(struct mfctable *mfct, struct ip *ip, struct vif *vifp,
 
 	/* Send message to routing daemon */
 	im = mtod(mb_first, struct igmpmsg *);
-	im->im_msgtype	= IGMPMSG_WHOLEPKT;
-	im->im_mbz		= 0;
-	im->im_vif		= vifp - mfct->viftable;
-	im->im_src		= ip->ip_src;
-	im->im_dst		= ip->ip_dst;
-
-	k_igmpsrc.sin_addr	= ip->ip_src;
+	memset(im, 0, sizeof(*im));
+	im->im_msgtype = IGMPMSG_WHOLEPKT;
+	im->im_mbz = 0;
+	im->im_vif = vifp - mfct->viftable;
+	im->im_src = ip->ip_src;
+	im->im_dst = ip->ip_dst;
+
+	k_igmpsrc.sin_addr = ip->ip_src;
 
 	MRTSTAT_INC(mrts_upcalls);