mac80211: fix bug in ieee80211_build_probe_req

commit 5b2bbf75a24d6b06afff6de0eb4819413fd81971 upstream.

ieee80211_probereq_get() can return NULL in
which case we should clean up & return NULL
in ieee80211_build_probe_req() as well.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index d3fe2d2..2124db8 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -1047,6 +1047,8 @@
 	skb = ieee80211_probereq_get(&local->hw, &sdata->vif,
 				     ssid, ssid_len,
 				     buf, buf_len);
+	if (!skb)
+		goto out;
 
 	if (dst) {
 		mgmt = (struct ieee80211_mgmt *) skb->data;
@@ -1055,6 +1057,8 @@
 	}
 
 	IEEE80211_SKB_CB(skb)->flags |= IEEE80211_TX_INTFL_DONT_ENCRYPT;
+
+ out:
 	kfree(buf);
 
 	return skb;