mac80211: check management frame header length

Due to pskb_may_pull() checking the skb length, all
non-management frames are checked on input whether
their 802.11 header is fully present. Also add that
check for management frames and remove a check that
is now duplicate. This prevents accessing skb data
beyond the frame end.

Cc: stable@vger.kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/rx.c

@@ -1470,7 +1470,6 @@ ieee80211_rx_h_defragment(struct ieee80211_rx_data *rx)
 	frag = sc & IEEE80211_SCTL_FRAG;
 
 	if (likely((!ieee80211_has_morefrags(fc) && frag == 0) ||
-		   (rx->skb)->len < 24 ||
 		   is_multicast_ether_addr(hdr->addr1))) {
 		/* not fragmented */
 		goto out;
@@ -2915,10 +2914,15 @@ static void __ieee80211_rx_handle_packet(struct ieee80211_hw *hw,
 	if (ieee80211_is_data(fc) || ieee80211_is_mgmt(fc))
 		local->dot11ReceivedFragmentCount++;
 
-	if (ieee80211_is_mgmt(fc))
-		err = skb_linearize(skb);
-	else
+	if (ieee80211_is_mgmt(fc)) {
+		/* drop frame if too short for header */
+		if (skb->len < ieee80211_hdrlen(fc))
+			err = -ENOBUFS;
+		else
+			err = skb_linearize(skb);
+	} else {
 		err = !pskb_may_pull(skb, ieee80211_hdrlen(fc));
+	}
 
 	if (err) {
 		dev_kfree_skb(skb);