From: Ryder Lee <ryder.lee@mediatek.com>
To: Felix Fietkau <nbd@nbd.name>
Cc: <linux-mediatek@lists.infradead.org>,
<linux-wireless@vger.kernel.org>,
Shayne Chen <shayne.chen@mediatek.com>,
Ryder Lee <ryder.lee@mediatek.com>
Subject: [PATCH] wifi: mt76: fix potential tx_retries underflow
Date: Thu, 4 Jun 2026 19:42:22 -0700 [thread overview]
Message-ID: <20260605024222.3388222-1-ryder.lee@mediatek.com> (raw)
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 or 255 for u8).
Fix by checking if count is non-zero before subtracting 1.
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
---
drivers/net/wireless/mediatek/mt76/mt7915/mac.c | 10 +++++-----
drivers/net/wireless/mediatek/mt76/mt7921/mac.c | 5 +++--
drivers/net/wireless/mediatek/mt76/mt7925/mac.c | 5 +++--
drivers/net/wireless/mediatek/mt76/mt7996/mac.c | 6 +++---
4 files changed, 14 insertions(+), 12 deletions(-)
diff --git a/drivers/net/wireless/mediatek/mt76/mt7915/mac.c b/drivers/net/wireless/mediatek/mt76/mt7915/mac.c
index cec2c4208..334c19ab2 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7915/mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7915/mac.c
@@ -912,16 +912,16 @@ mt7915_mac_tx_free(struct mt7915_dev *dev, void *data, int len)
}
if (!mtk_wed_device_active(&mdev->mmio.wed) && wcid) {
- u32 tx_retries = 0, tx_failed = 0;
+ u32 tx_retries = 0, tx_failed = 0, count;
if (v3 && (info & MT_TX_FREE_MPDU_HEADER_V3)) {
- tx_retries =
- FIELD_GET(MT_TX_FREE_COUNT_V3, info) - 1;
+ count = FIELD_GET(MT_TX_FREE_COUNT_V3, info);
+ tx_retries = count ? count - 1 : 0;
tx_failed = tx_retries +
!!FIELD_GET(MT_TX_FREE_STAT_V3, info);
} else if (!v3 && (info & MT_TX_FREE_MPDU_HEADER)) {
- tx_retries =
- FIELD_GET(MT_TX_FREE_COUNT, info) - 1;
+ count = FIELD_GET(MT_TX_FREE_COUNT, info);
+ tx_retries = count ? count - 1 : 0;
tx_failed = tx_retries +
!!FIELD_GET(MT_TX_FREE_STAT, info);
}
diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/mac.c b/drivers/net/wireless/mediatek/mt76/mt7921/mac.c
index 03b4960db..668bfa195 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7921/mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7921/mac.c
@@ -530,8 +530,9 @@ static void mt7921_mac_tx_free(struct mt792x_dev *dev, void *data, int len)
stat = FIELD_GET(MT_TX_FREE_STATUS, info);
if (wcid) {
- wcid->stats.tx_retries +=
- FIELD_GET(MT_TX_FREE_COUNT, info) - 1;
+ u32 count = FIELD_GET(MT_TX_FREE_COUNT, info);
+
+ wcid->stats.tx_retries += count ? count - 1 : 0;
wcid->stats.tx_failed += !!stat;
}
diff --git a/drivers/net/wireless/mediatek/mt76/mt7925/mac.c b/drivers/net/wireless/mediatek/mt76/mt7925/mac.c
index c47bd812b..c56a9e530 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7925/mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7925/mac.c
@@ -1141,8 +1141,9 @@ 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);
}
diff --git a/drivers/net/wireless/mediatek/mt76/mt7996/mac.c b/drivers/net/wireless/mediatek/mt76/mt7996/mac.c
index a59c14c8f..3fad977ba 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7996/mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7996/mac.c
@@ -1361,13 +1361,13 @@ mt7996_mac_tx_free(struct mt7996_dev *dev, void *data, int len)
cur_info++;
continue;
} else if (info & MT_TXFREE_INFO_HEADER) {
- u32 tx_retries = 0, tx_failed = 0;
+ u32 tx_retries = 0, tx_failed = 0, count;
if (!wcid)
continue;
- tx_retries =
- FIELD_GET(MT_TXFREE_INFO_COUNT, info) - 1;
+ count = FIELD_GET(MT_TXFREE_INFO_COUNT, info);
+ tx_retries = count ? count - 1 : 0;
tx_failed = tx_retries +
!!FIELD_GET(MT_TXFREE_INFO_STAT, info);
--
2.45.2
next reply other threads:[~2026-06-05 2:42 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-05 2:42 Ryder Lee [this message]
2026-06-05 10:17 ` [PATCH] wifi: mt76: fix potential tx_retries underflow Lorenzo Bianconi
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