[PATCH 5.10 076/147] bonding: only set speed/duplex to unknown, if getting speed failed

Sasha Levin
2026-02-28T18:18:37Z

From: Thomas Bogendoerfer <tbogendoerfer@suse.de>

[ Upstream commit 48dec8d88af96039a4a17b8c2f148f2a4066e195 ]

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: 98f41f694f46 ("bonding:update speed/duplex for NETDEV_CHANGE")
Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Acked-by: Jay Vosburgh <jv@jvosburgh.net>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Reviewed-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://patch.msgid.link/20260203141153.51581-1-tbogendoerfer@suse.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 a6d552a83ca43..1d8a6690527aa 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -638,26 +638,29 @@ 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)
--
2.51.0