[PATCH] ath9k: fix spurious MIC failure reports

[Felix Fietkau <nbd@openwrt.org>]

According to the hardware documentation, the MIC failure bit is only
valid if the frame was decrypted using a valid TKIP key and is not a
fragment.
In some setups I've seen hardware-reported MIC failures on an AP that
was configured for CCMP only, so it's clear that additional checks are
necessary.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Cc: stable@kernel.org
---
--- a/drivers/net/wireless/ath/ath.h
+++ b/drivers/net/wireless/ath/ath.h
@@ -119,6 +119,7 @@ struct ath_common {
 
 	u32 keymax;
 	DECLARE_BITMAP(keymap, ATH_KEYMAX);
+	DECLARE_BITMAP(tkip_keymap, ATH_KEYMAX);
 	u8 splitmic;
 
 	struct ath_regulatory regulatory;
--- a/drivers/net/wireless/ath/ath9k/common.c
+++ b/drivers/net/wireless/ath/ath9k/common.c
@@ -366,9 +366,13 @@ int ath9k_cmn_key_config(struct ath_comm
 	set_bit(idx, common->keymap);
 	if (key->alg == ALG_TKIP) {
 		set_bit(idx + 64, common->keymap);
+		set_bit(idx, common->tkip_keymap);
+		set_bit(idx + 64, common->tkip_keymap);
 		if (common->splitmic) {
 			set_bit(idx + 32, common->keymap);
 			set_bit(idx + 64 + 32, common->keymap);
+			set_bit(idx + 32, common->tkip_keymap);
+			set_bit(idx + 64 + 32, common->tkip_keymap);
 		}
 	}
 
@@ -393,10 +397,17 @@ void ath9k_cmn_key_delete(struct ath_com
 		return;
 
 	clear_bit(key->hw_key_idx + 64, common->keymap);
+
+	clear_bit(key->hw_key_idx, common->tkip_keymap);
+	clear_bit(key->hw_key_idx + 64, common->tkip_keymap);
+
 	if (common->splitmic) {
 		ath9k_hw_keyreset(ah, key->hw_key_idx + 32);
 		clear_bit(key->hw_key_idx + 32, common->keymap);
 		clear_bit(key->hw_key_idx + 64 + 32, common->keymap);
+
+		clear_bit(key->hw_key_idx + 32, common->tkip_keymap);
+		clear_bit(key->hw_key_idx + 64 + 32, common->tkip_keymap);
 	}
 }
 EXPORT_SYMBOL(ath9k_cmn_key_delete);
--- a/drivers/net/wireless/ath/ath9k/recv.c
+++ b/drivers/net/wireless/ath/ath9k/recv.c
@@ -870,15 +870,18 @@ static bool ath9k_rx_accept(struct ath_c
 		if (rx_stats->rs_status & ATH9K_RXERR_DECRYPT) {
 			*decrypt_error = true;
 		} else if (rx_stats->rs_status & ATH9K_RXERR_MIC) {
-			if (ieee80211_is_ctl(fc))
-				/*
-				 * Sometimes, we get invalid
-				 * MIC failures on valid control frames.
-				 * Remove these mic errors.
-				 */
-				rx_stats->rs_status &= ~ATH9K_RXERR_MIC;
-			else
+			/*
+			 * The MIC error bit is only valid if the frame
+			 * is not a control frame or fragment, and it was
+			 * decrypted using a valid TKIP key.
+			 */
+			if (!ieee80211_is_ctl(fc) &&
+			    !ieee80211_has_morefrags(fc) &&
+			    !(le16_to_cpu(hdr->seq_ctrl) & IEEE80211_SCTL_FRAG) &&
+			    test_bit(rx_stats->rs_keyix, common->tkip_keymap))
 				rxs->flag |= RX_FLAG_MMIC_ERROR;
+			else
+				rx_stats->rs_status &= ~ATH9K_RXERR_MIC;
 		}
 		/*
 		 * Reject error frames with the exception of
--- a/drivers/net/wireless/ath/ath9k/mac.c
+++ b/drivers/net/wireless/ath/ath9k/mac.c
@@ -711,7 +711,8 @@ int ath9k_hw_rxprocdesc(struct ath_hw *a
 			rs->rs_phyerr = phyerr;
 		} else if (ads.ds_rxstatus8 & AR_DecryptCRCErr)
 			rs->rs_status |= ATH9K_RXERR_DECRYPT;
-		else if (ads.ds_rxstatus8 & AR_MichaelErr)
+		else if ((ads.ds_rxstatus8 & AR_MichaelErr) &&
+		         rs->rs_keyix != ATH9K_RXKEYIX_INVALID)
 			rs->rs_status |= ATH9K_RXERR_MIC;
 		else if (ads.ds_rxstatus8 & AR_KeyMiss)
 			rs->rs_status |= ATH9K_RXERR_DECRYPT;