ath9k: fix spurious MIC failure reports

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
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 11 insertions, 8 deletions

diff --git a/drivers/net/wireless/ath/ath9k/recv.c b/drivers/net/wireless/ath/ath9k/recv.c
index a3fc987ebab0..534a91bcc1d9 100644
--- 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_common *common,
                 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