wifi: mt76: mt7925: fix potential tx_retries underflow

When FIELD_GET returns 0 for the retry count, subtracting 1 causes
an unsigned integer underflow, resulting in tx_retries becoming a
very large value (0xFFFFFFFF for u32).

Fix by checking if count is non-zero before subtracting 1.

Fixes: c948b5da6bbe ("wifi: mt76: mt7925: add Mediatek Wi-Fi7 driver for mt7925 chips")
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Link: https://patch.msgid.link/20260605113306.3485554-3-ryder.lee@mediatek.com
Signed-off-by: Felix Fietkau <nbd@nbd.name>

diff --git a/drivers/net/wireless/mediatek/mt76/mt7925/mac.c b/drivers/net/wireless/mediatek/mt76/mt7925/mac.c
index 5dd895c3f2054025fd7c3eb920c3785aa1176998..0641a7131d7c7bda76a38a2d321405a80d4f5419 100644 (file)
--- a/drivers/net/wireless/mediatek/mt76/mt7925/mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7925/mac.c
@@ -1149,8 +1149,9 @@ mt7925_mac_tx_free(struct mt792x_dev *dev, void *data, int len)
 
                if (info & MT_TXFREE_INFO_HEADER) {
                        if (wcid) {
-                               wcid->stats.tx_retries +=
-                                       FIELD_GET(MT_TXFREE_INFO_COUNT, info) - 1;
+                               u32 count = FIELD_GET(MT_TXFREE_INFO_COUNT, info);
+
+                               wcid->stats.tx_retries += count ? count - 1 : 0;
                                wcid->stats.tx_failed +=
                                        !!FIELD_GET(MT_TXFREE_INFO_STAT, info);
                        }