[PATCH wireless v2] wifi: mt76: mt76x02: validate TX-status rate index before mac80211 handoff

[PATCH wireless v2] wifi: mt76: mt76x02: validate TX-status rate index before mac80211 handoff

[Mark Anthony Agarro]

mt76x02_mac_process_tx_rate() extracts the rate index straight from
the hardware's raw TX-status word with no bounds check for the
HT/HT_GF/VHT cases, and mt76x02_mac_fill_tx_status() ignores its
return value. A stale or corrupt hardware index reaches mac80211's
minstrel_ht rate control, whose per-group rate array is a fixed 10
entries (MCS_GROUP_RATES), causing an out-of-bounds write.

Validate the index in mt76x02_mac_process_tx_rate() (HT: 0-31,
VHT: MCS nibble 0-9) and have mt76x02_mac_fill_tx_status() bail out
cleanly on failure instead of passing an invalid index through.

Fixes: 7c1f88812690 ("mt76: unify send_tx_status and related helpers")
Cc: stable@vger.kernel.org
Closes: https://github.com/morrownr/mt76/issues/88
Tested-by: Devin Wittmayer <lucid_duck@justthetip.ca>
Signed-off-by: Mark Anthony Agarro <markanthonyagarro@gmail.com>
---
v2: Drop the Reported-by tag. It named an invented
    users.noreply.github.com address for the reporter that isn't a
    real, deliverable mailbox (v1's Cc bounced with NXDOMAIN on that
    domain). Closes: already credits and links the original report;
    no functional change.

 .../net/wireless/mediatek/mt76/mt76x02_mac.c  | 27 ++++++++++++++-----
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt76x02_mac.c b/drivers/net/wireless/mediatek/mt76/mt76x02_mac.c
index 14ee5b3b9..d77356a2e 100644
--- a/drivers/net/wireless/mediatek/mt76/mt76x02_mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt76x02_mac.c
@@ -302,10 +302,22 @@ mt76x02_mac_process_tx_rate(struct ieee80211_tx_rate *txrate, u16 rate,
 		txrate->flags |= IEEE80211_TX_RC_GREEN_FIELD;
 		fallthrough;
 	case MT_PHY_TYPE_HT:
+		/* Raw hardware TX-status index is unvalidated; a stale or
+		 * corrupt value here overflows mac80211/minstrel_ht's
+		 * per-group rate array (MCS_GROUP_RATES == 10) and crashes.
+		 * Valid 802.11n MCS indices are 0-31 (four streams x 8).
+		 */
+		if (idx > 31)
+			return -EINVAL;
 		txrate->flags |= IEEE80211_TX_RC_MCS;
 		txrate->idx = idx;
 		break;
 	case MT_PHY_TYPE_VHT:
+		/* Same overflow risk for VHT: mac80211 expects the MCS
+		 * nibble (bits 3:0) in range 0-9, nss packed above it.
+		 */
+		if ((idx & 0xf) > 9)
+			return -EINVAL;
 		txrate->flags |= IEEE80211_TX_RC_VHT_MCS;
 		txrate->idx = idx;
 		break;
@@ -493,18 +505,21 @@ mt76x02_mac_fill_tx_status(struct mt76x02_dev *dev, struct mt76x02_sta *msta,
 		first_rate = st->rate & ~MT_PKTID_RATE;
 		first_rate |= st->pktid & MT_PKTID_RATE;
 
-		mt76x02_mac_process_tx_rate(&rate[0], first_rate,
-					    dev->mphy.chandef.chan->band);
+		if (mt76x02_mac_process_tx_rate(&rate[0], first_rate,
+						dev->mphy.chandef.chan->band))
+			return;
 	} else if (rate[0].idx < 0) {
 		if (!msta)
 			return;
 
-		mt76x02_mac_process_tx_rate(&rate[0], msta->wcid.tx_info,
-					    dev->mphy.chandef.chan->band);
+		if (mt76x02_mac_process_tx_rate(&rate[0], msta->wcid.tx_info,
+						dev->mphy.chandef.chan->band))
+			return;
 	}
 
-	mt76x02_mac_process_tx_rate(&last_rate, st->rate,
-				    dev->mphy.chandef.chan->band);
+	if (mt76x02_mac_process_tx_rate(&last_rate, st->rate,
+					dev->mphy.chandef.chan->band))
+		return;
 
 	for (i = 0; i < ARRAY_SIZE(info->status.rates); i++) {
 		retry--;
-- 
2.47.3