From df5c4150501ee7e86383be88f6490d970adcf157 Mon Sep 17 00:00:00 2001
From: Zefir Kurtisi <zefir.kurtisi@neratec.com>
Date: Tue, 11 Jun 2019 15:36:56 +0200
Subject: [PATCH] ath9k: correctly handle short radar pulses
Git-commit: df5c4150501ee7e86383be88f6490d970adcf157
Patch-mainline: v5.3-rc1
References: bsc#1111666

In commit 3c0efb745a17 ("ath9k: discard undersized packets")
the lower bound of RX packets was set to 10 (min ACK size) to
filter those that would otherwise be treated as invalid at
mac80211.

Alas, short radar pulses are reported as PHY_ERROR frames
with length set to 3. Therefore their detection stopped
working after that commit.

Note: ath9k drivers built thereafter will not pass DFS
certification.

This extends the criteria for short packets to explicitly
handle PHY_ERROR frames.

Fixes: 3c0efb745a17 ("ath9k: discard undersized packets")
Signed-off-by: Zefir Kurtisi <zefir.kurtisi@neratec.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/net/wireless/ath/ath9k/recv.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/net/wireless/ath/ath9k/recv.c
+++ b/drivers/net/wireless/ath/ath9k/recv.c
@@ -815,6 +815,7 @@ static int ath9k_rx_skb_preprocess(struc
 	struct ath_common *common = ath9k_hw_common(ah);
 	struct ieee80211_hdr *hdr;
 	bool discard_current = sc->rx.discard_next;
+	bool is_phyerr;
 
 	/*
 	 * Discard corrupt descriptors which are marked in
@@ -827,8 +828,11 @@ static int ath9k_rx_skb_preprocess(struc
 
 	/*
 	 * Discard zero-length packets and packets smaller than an ACK
+	 * which are not PHY_ERROR (short radar pulses have a length of 3)
 	 */
-	if (rx_stats->rs_datalen < 10) {
+	is_phyerr = rx_stats->rs_status & ATH9K_RXERR_PHY;
+	if (!rx_stats->rs_datalen ||
+	    (rx_stats->rs_datalen < 10 && !is_phyerr)) {
 		RX_STAT_INC(rx_len_err);
 		goto corrupt;
 	}