ath9k_hw: fix a regression in key miss handling

The commit "ath9k_hw: Fix incorrect key_miss handling" changed the code
to only report key miss errors if a MIC error wasn't reported.
When checking the flags in that order in the MAC code, it might miss some
real events, because the value of the MIC error flag is undefined under
some conditions.

The primary issue addressed by the previous commit is making sure that
MIC errors are properly reported on the STA side. This can be fixed in
a better way by adding a separate rx status flag for key miss and
ignoring it for multicast frames.

This fix slightly improves stability in AP mode on some older hardware,
like AR9132.
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Cc: stable@kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/ar9003_mac.c

@@ -525,8 +525,8 @@ int ath9k_hw_process_rxdesc_edma(struct ath_hw *ah, struct ath_rx_status *rxs,
 			rxs->rs_status |= ATH9K_RXERR_DECRYPT;
 		else if (rxsp->status11 & AR_MichaelErr)
 			rxs->rs_status |= ATH9K_RXERR_MIC;
-		else if (rxsp->status11 & AR_KeyMiss)
-			rxs->rs_status |= ATH9K_RXERR_DECRYPT;
+		if (rxsp->status11 & AR_KeyMiss)
+			rxs->rs_status |= ATH9K_RXERR_KEYMISS;
 	}
 
 	return 0;

drivers/net/wireless/ath/ath9k/mac.c

@@ -620,8 +620,8 @@ int ath9k_hw_rxprocdesc(struct ath_hw *ah, struct ath_desc *ds,
 			rs->rs_status |= ATH9K_RXERR_DECRYPT;
 		else if (ads.ds_rxstatus8 & AR_MichaelErr)
 			rs->rs_status |= ATH9K_RXERR_MIC;
-		else if (ads.ds_rxstatus8 & AR_KeyMiss)
-			rs->rs_status |= ATH9K_RXERR_DECRYPT;
+		if (ads.ds_rxstatus8 & AR_KeyMiss)
+			rs->rs_status |= ATH9K_RXERR_KEYMISS;
 	}
 
 	return 0;

drivers/net/wireless/ath/ath9k/mac.h

@@ -182,6 +182,7 @@ struct ath_htc_rx_status {
 #define ATH9K_RXERR_FIFO          0x04
 #define ATH9K_RXERR_DECRYPT       0x08
 #define ATH9K_RXERR_MIC           0x10
+#define ATH9K_RXERR_KEYMISS       0x20
 
 #define ATH9K_RX_MORE             0x01
 #define ATH9K_RX_MORE_AGGR        0x02

drivers/net/wireless/ath/ath9k/recv.c

@@ -820,7 +820,8 @@ static bool ath9k_rx_accept(struct ath_common *common,
 		test_bit(rx_stats->rs_keyix, common->tkip_keymap);
 	strip_mic = is_valid_tkip && ieee80211_is_data(fc) &&
 		!(rx_stats->rs_status &
-		(ATH9K_RXERR_DECRYPT | ATH9K_RXERR_CRC | ATH9K_RXERR_MIC));
+		(ATH9K_RXERR_DECRYPT | ATH9K_RXERR_CRC | ATH9K_RXERR_MIC |
+		 ATH9K_RXERR_KEYMISS));
 
 	if (!rx_stats->rs_datalen)
 		return false;
@@ -848,6 +849,8 @@ static bool ath9k_rx_accept(struct ath_common *common,
 	 * descriptors.
 	 */
 	if (rx_stats->rs_status != 0) {
+		u8 status_mask;
+
 		if (rx_stats->rs_status & ATH9K_RXERR_CRC) {
 			rxs->flag |= RX_FLAG_FAILED_FCS_CRC;
 			mic_error = false;
@@ -855,7 +858,8 @@ static bool ath9k_rx_accept(struct ath_common *common,
 		if (rx_stats->rs_status & ATH9K_RXERR_PHY)
 			return false;
 
-		if (rx_stats->rs_status & ATH9K_RXERR_DECRYPT) {
+		if ((rx_stats->rs_status & ATH9K_RXERR_DECRYPT) ||
+		    (!is_mc && (rx_stats->rs_status & ATH9K_RXERR_KEYMISS))) {
 			*decrypt_error = true;
 			mic_error = false;
 		}
@@ -865,18 +869,15 @@ static bool ath9k_rx_accept(struct ath_common *common,
 		 * decryption and MIC failures. For monitor mode,
 		 * we also ignore the CRC error.
 		 */
-		if (ah->is_monitoring) {
-			if (rx_stats->rs_status &
-			    ~(ATH9K_RXERR_DECRYPT | ATH9K_RXERR_MIC |
-			      ATH9K_RXERR_CRC))
-				return false;
-		} else {
-			if (rx_stats->rs_status &
-			    ~(ATH9K_RXERR_DECRYPT | ATH9K_RXERR_MIC)) {
+		status_mask = ATH9K_RXERR_DECRYPT | ATH9K_RXERR_MIC |
+			      ATH9K_RXERR_KEYMISS;
+
+		if (ah->is_monitoring)
+			status_mask |= ATH9K_RXERR_CRC;
+
+		if (rx_stats->rs_status & ~status_mask)
 			return false;
 	}
-		}
-	}
 
 	/*
 	 * For unicast frames the MIC error bit can have false positives,