linux-kernel - [PATCH net] bonding: only set speed/duplex to unknown, if getting speed failed

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Message-ID: <20260130111904.144024-1-tbogendoerfer@suse.de>
Date: Fri, 30 Jan 2026 12:19:04 +0100
From: Thomas Bogendoerfer <tbogendoerfer@...e.de>
To: Jay Vosburgh <jv@...sburgh.net>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Hangbin Liu <liuhangbin@...il.com>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH net] bonding: only set speed/duplex to unknown, if getting speed failed

bond_update_speed_duplex() first set speed/duplex to unknown and
then asks slave driver for current speed/duplex. Since getting
speed/duplex might take longer there is a race, where this false state
is visible by /proc/net/bonding. With commit 691b2bf14946 ("bonding:
 update port speed when getting bond speed") this race gets more visible,
if user space is calling ethtool on a regular base.

Fix this by only setting speed/duplex to unknown, if link speed is
really unknown/unusable.

Fixes: 691b2bf14946 ("bonding: update port speed when getting bond speed")
Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@...e.de>
---
 drivers/net/bonding/bond_main.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index e7caf400a59c..4cdf89b21ca0 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -791,26 +791,29 @@ static int bond_update_speed_duplex(struct slave *slave)
 	struct ethtool_link_ksettings ecmd;
 	int res;
 
-	slave->speed = SPEED_UNKNOWN;
-	slave->duplex = DUPLEX_UNKNOWN;
-
 	res = __ethtool_get_link_ksettings(slave_dev, &ecmd);
 	if (res < 0)
-		return 1;
+		goto speed_duplex_unknown;
 	if (ecmd.base.speed == 0 || ecmd.base.speed == ((__u32)-1))
-		return 1;
+		goto speed_duplex_unknown;
 	switch (ecmd.base.duplex) {
 	case DUPLEX_FULL:
 	case DUPLEX_HALF:
 		break;
 	default:
-		return 1;
+		goto speed_duplex_unknown;
 	}
 
 	slave->speed = ecmd.base.speed;
 	slave->duplex = ecmd.base.duplex;
 
 	return 0;
+
+speed_duplex_unknown:
+	slave->speed = SPEED_UNKNOWN;
+	slave->duplex = DUPLEX_UNKNOWN;
+
+	return 1;
 }
 
 const char *bond_slave_link_status(s8 link)
-- 
2.43.0