[PATCH net v3] broadcom: b44: prevent uninitialized value usage

[Alexey Simakov <bigalex934@gmail.com>]

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")
Reviewed-by: Jonas Gorski <jonas.gorski@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Alexey Simakov <bigalex934@gmail.com>
---

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

v3 - add needed mailing list into Cc.

link to v1: https://lore.kernel.org/all/20251204052243.5824-1-bigalex934@gmail.com/
link to v2: https://lore.kernel.org/all/20251205071759.5054-1-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