From: Felix Fietkau <nbd@nbd.name>
Date: Wed, 17 Jan 2018 11:11:17 +0100
Subject: [PATCH] ath9k: discard undersized packets

Sometimes the hardware will push small packets that trigger a WARN_ON
in mac80211. Discard them early to avoid this issue.

Reported-by: Stijn Tintel <stijn@linux-ipv6.be>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---

--- a/drivers/net/wireless/ath/ath9k/recv.c
+++ b/drivers/net/wireless/ath/ath9k/recv.c
@@ -826,9 +826,9 @@ static int ath9k_rx_skb_preprocess(struc
 	sc->rx.discard_next = false;
 
 	/*
-	 * Discard zero-length packets.
+	 * Discard zero-length packets and packets smaller than an ACK
 	 */
-	if (!rx_stats->rs_datalen) {
+	if (rx_stats->rs_datalen < 10) {
 		RX_STAT_INC(rx_len_err);
 		goto corrupt;
 	}