linux-kernel - [PATCH] mt76: avoid uninitialized skb data

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Message-Id: <20250807205305.88394-1-arnd@kernel.org>
Date: Thu,  7 Aug 2025 22:52:57 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: Felix Fietkau <nbd@....name>,
	Lorenzo Bianconi <lorenzo@...nel.org>,
	Ryder Lee <ryder.lee@...iatek.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Nathan Chancellor <nathan@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>,
	Shayne Chen <shayne.chen@...iatek.com>,
	Sean Wang <sean.wang@...iatek.com>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Peter Chiu <chui-hao.chiu@...iatek.com>,
	Bo Jiao <Bo.Jiao@...iatek.com>,
	Howard Hsu <howard-yh.hsu@...iatek.com>,
	linux-wireless@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org,
	llvm@...ts.linux.dev
Subject: [PATCH] mt76: avoid uninitialized skb data

From: Arnd Bergmann <arnd@...db.de>

Two functions in the mt7996 driver cause a clang-21 build warning because
the pass uninitialized data into skb_put_data:

drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:1894:21: error: variable 'hdr' is uninitialized when passed as a const pointer argument here [-Werror,-Wuninitialized-const-pointer]
 1894 |         skb_put_data(skb, &hdr, sizeof(hdr));
      |                            ^~~
drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:3386:21: error: variable 'hdr' is uninitialized when passed as a const pointer argument here [-Werror,-Wuninitialized-const-pointer]
 3386 |         skb_put_data(skb, &hdr, sizeof(hdr));
      |                            ^~~

Remove the otherwise unused variables and instead use skb_put_zero() instead
to fill the header with zeroes.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/net/wireless/mediatek/mt76/mt7996/mcu.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7996/mcu.c b/drivers/net/wireless/mediatek/mt76/mt7996/mcu.c
index 3593fd40c51b..6a00df3c5343 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7996/mcu.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7996/mcu.c
@@ -1880,18 +1880,17 @@ int mt7996_mcu_set_fixed_rate_ctrl(struct mt7996_dev *dev,
 				   void *data, u16 version)
 {
 	struct ra_fixed_rate *req;
-	struct uni_header hdr;
 	struct sk_buff *skb;
 	struct tlv *tlv;
 	int len;
 
-	len = sizeof(hdr) + sizeof(*req);
+	len = sizeof(struct uni_header) + sizeof(*req);
 
 	skb = mt76_mcu_msg_alloc(&dev->mt76, NULL, len);
 	if (!skb)
 		return -ENOMEM;
 
-	skb_put_data(skb, &hdr, sizeof(hdr));
+	skb_put_zero(skb, sizeof(struct uni_header));
 
 	tlv = mt7996_mcu_add_uni_tlv(skb, UNI_RA_FIXED_RATE, sizeof(*req));
 	req = (struct ra_fixed_rate *)tlv;
@@ -3370,20 +3369,17 @@ void mt7996_mcu_exit(struct mt7996_dev *dev)
 
 int mt7996_mcu_set_hdr_trans(struct mt7996_dev *dev, bool hdr_trans)
 {
-	struct {
-		u8 __rsv[4];
-	} __packed hdr;
 	struct hdr_trans_blacklist *req_blacklist;
 	struct hdr_trans_en *req_en;
 	struct sk_buff *skb;
 	struct tlv *tlv;
-	int len = MT7996_HDR_TRANS_MAX_SIZE + sizeof(hdr);
+	int len = MT7996_HDR_TRANS_MAX_SIZE + 4;
 
 	skb = mt76_mcu_msg_alloc(&dev->mt76, NULL, len);
 	if (!skb)
 		return -ENOMEM;
 
-	skb_put_data(skb, &hdr, sizeof(hdr));
+	skb_put_zero(skb, 4);
 
 	tlv = mt7996_mcu_add_uni_tlv(skb, UNI_HDR_TRANS_EN, sizeof(*req_en));
 	req_en = (struct hdr_trans_en *)tlv;
-- 
2.39.5