mac80211: clear sequence/fragment number in QoS-null frames

Avoid leaking data by sending uninitialized memory and setting an
invalid (non-zero) fragment number (the sequence number is ignored
anyway) by setting the seq_ctrl field to zero.

Cc: stable@vger.kernel.org
Fixes: 3f52b7e328c5 ("mac80211: mesh power save basics")
Fixes: ce662b44ce22 ("mac80211: send (QoS) Null if no buffered frames")
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/mesh_ps.c b/net/mac80211/mesh_ps.c
index 2802f9d..ad8b377 100644
--- a/net/mac80211/mesh_ps.c
+++ b/net/mac80211/mesh_ps.c
@@ -36,6 +36,7 @@
 				      sdata->vif.addr);
 	nullfunc->frame_control = fc;
 	nullfunc->duration_id = 0;
+	nullfunc->seq_ctrl = 0;
 	/* no address resolution for this frame -> set addr 1 immediately */
 	memcpy(nullfunc->addr1, sta->sta.addr, ETH_ALEN);
 	memset(skb_put(skb, 2), 0, 2); /* append QoS control field */