ath5k: warn and correct rate for unknown hw rate indexes

ath5k sets up a mapping table from the hardware rate index to
the rate index used by mac80211; however, we have seen some
received frames with incorrect rate indexes.  Such frames
normally get dropped with a warning in __ieee80211_rx(),
but it doesn't include enough information to track down the
error.

This patch adds a warning to hw_to_driver_rix for any lookups
that result in a rate index of -1, then returns a valid rate so
the frame can be processed.

Changes-licensed-under: 3-Clause-BSD

Signed-off-by: Bob Copeland <me@bobcopeland.com>
Cc: stable@kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath5k/base.c b/drivers/net/wireless/ath5k/base.c
index f28b86c..6580df2 100644
--- a/drivers/net/wireless/ath5k/base.c
+++ b/drivers/net/wireless/ath5k/base.c
@@ -1088,9 +1088,18 @@
 static inline int
 ath5k_hw_to_driver_rix(struct ath5k_softc *sc, int hw_rix)
 {
-	WARN(hw_rix < 0 || hw_rix >= AR5K_MAX_RATES,
-			"hw_rix out of bounds: %x\n", hw_rix);
-	return sc->rate_idx[sc->curband->band][hw_rix];
+	int rix;
+
+	/* return base rate on errors */
+	if (WARN(hw_rix < 0 || hw_rix >= AR5K_MAX_RATES,
+			"hw_rix out of bounds: %x\n", hw_rix))
+		return 0;
+
+	rix = sc->rate_idx[sc->curband->band][hw_rix];
+	if (WARN(rix < 0, "invalid hw_rix: %x\n", hw_rix))
+		rix = 0;
+
+	return rix;
 }
 
 /***************\