linux-kernel - [PATCH net v2] broadcom: b44: prevent uninitialized value usage

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Message-Id: <20251205071759.5054-1-bigalex934@gmail.com>
Date: Fri,  5 Dec 2025 10:17:58 +0300
From: Alexey Simakov <bigalex934@...il.com>
To: Michael Chan <michael.chan@...adcom.com>
Cc: Alexey Simakov <bigalex934@...il.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Jonas Gorski <jonas.gorski@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	"John W. Linville" <linville@...driver.com>,
	Michael Buesch <mb@...sch.de>,
	linux-kernel@...r.kernel.org,
	lvc-project@...uxtesting.org
Subject: [PATCH net v2] broadcom: b44: prevent uninitialized value usage

On execution path with raised B44_FLAG_EXTERNAL_PHY, b44_readphy()
leaves bmcr value uninitialized and it is used later in the code.

Add check of this flag at the beginning of the b44_nway_reset() and
exit early of the function with restarting autonegotiation if an
external PHY is used.

Found by Linux Verification Center (linuxtesting.org) with Svace.

Fixes: 753f492093da ("[B44]: port to native ssb support")
Signed-off-by: Alexey Simakov <bigalex934@...il.com>
---

v2 - add restarting of autonegotiations by phy_ethtool_nway_reset(),
instead of returning with 0 code (suggested by Jonas Gorski).

link to v1: https://lore.kernel.org/all/20251204052243.5824-1-bigalex934@gmail.com/

 drivers/net/ethernet/broadcom/b44.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/broadcom/b44.c b/drivers/net/ethernet/broadcom/b44.c
index 0353359c3fe9..073d7d490d4b 100644
--- a/drivers/net/ethernet/broadcom/b44.c
+++ b/drivers/net/ethernet/broadcom/b44.c
@@ -1789,6 +1789,9 @@ static int b44_nway_reset(struct net_device *dev)
 	u32 bmcr;
 	int r;
 
+	if (bp->flags & B44_FLAG_EXTERNAL_PHY)
+		return phy_ethtool_nway_reset(dev);
+
 	spin_lock_irq(&bp->lock);
 	b44_readphy(bp, MII_BMCR, &bmcr);
 	b44_readphy(bp, MII_BMCR, &bmcr);
-- 
2.34.1