ath9k: detect more kinds of invalid descriptors

If AR_CRCErr, AR_PHYErr, AR_DecryptCRCErr or AR_MichaelErr is indicated
in the rx status word, but AR_RxFrameOK is also set, the descriptor
contents are typically invalid. This can show up as a warning about
invalid MCS rates in a frame. Even with those checks in place, a
descriptor with invalid MCS rates can still sometimes make it through to
the driver (mostly on older hardware like AR91xx).

Detect such errors in the last descriptor of a frame and discard the
whole frame if present.
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -615,6 +615,14 @@ 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_CRCErr | AR_PHYErr | AR_DecryptCRCErr | AR_MichaelErr))
+			rs->rs_status |= ATH9K_RXERR_CORRUPT_DESC;
+
+		/* Only up to MCS16 supported, everything above is invalid */
+		if (rs->rs_rate >= 0x90)
+			rs->rs_status |= ATH9K_RXERR_CORRUPT_DESC;
 	}
 
 	if (ads.ds_rxstatus8 & AR_KeyMiss)

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

@@ -183,6 +183,7 @@ struct ath_htc_rx_status {
 #define ATH9K_RXERR_DECRYPT       0x08
 #define ATH9K_RXERR_MIC           0x10
 #define ATH9K_RXERR_KEYMISS       0x20
+#define ATH9K_RXERR_CORRUPT_DESC  0x40
 
 #define ATH9K_RX_MORE             0x01
 #define ATH9K_RX_MORE_AGGR        0x02

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

@@ -1319,6 +1319,8 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
 			sc->rx.frag = skb;
 			goto requeue;
 		}
+		if (rs.rs_status & ATH9K_RXERR_CORRUPT_DESC)
+			goto requeue_drop_frag;
 
 		if (sc->rx.frag) {
 			int space = skb->len - skb_tailroom(hdr_skb);