IB/core: Clear AH attr variable to prevent garbage data

commit 8b0f93d9 upstream.

During create-ah from userspace, uverbs is sending garbage data in
attr.dmac and attr.vlan_id.  This patch sets attr.dmac and
attr.vlan_id to zero.

Fixes: dd5f03be ("IB/core: Ethernet L2 attributes in verbs/cm structures")
Signed-off-by: Devesh Sharma <devesh.sharma@emulex.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/infiniband/core/uverbs_cmd.c

@@ -2425,6 +2425,8 @@ ssize_t ib_uverbs_create_ah(struct ib_uverbs_file *file,
 	attr.grh.sgid_index    = cmd.attr.grh.sgid_index;
 	attr.grh.hop_limit     = cmd.attr.grh.hop_limit;
 	attr.grh.traffic_class = cmd.attr.grh.traffic_class;
+	attr.vlan_id           = 0;
+	memset(&attr.dmac, 0, sizeof(attr.dmac));
 	memcpy(attr.grh.dgid.raw, cmd.attr.grh.dgid, 16);
 
 	ah = ib_create_ah(pd, &attr);