net: phy: fix race in genphy_update_link

In phy_start_aneg() autoneg is started, and immediately after that
link and autoneg status are read. As reported in [0] it can happen that
at time of this read the PHY has reset the "aneg complete" bit but not
yet the "link up" bit, what can result in a false link-up detection.
To fix this don't report link as up if we're in aneg mode and PHY
doesn't signal "aneg complete".

[0] https://marc.info/?t=156413509900003&r=1&w=2

Fixes: 4950c2ba49cc ("net: phy: fix autoneg mismatch case in genphy_read_status")
Reported-by: liuyonglong <liuyonglong@huawei.com>
Tested-by: liuyonglong <liuyonglong@huawei.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 6b5cb87..7ddd91d 100644 (file)
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -1774,6 +1774,12 @@ done:
        phydev->link = status & BMSR_LSTATUS ? 1 : 0;
        phydev->autoneg_complete = status & BMSR_ANEGCOMPLETE ? 1 : 0;
 
+       /* Consider the case that autoneg was started and "aneg complete"
+        * bit has been reset, but "link up" bit not yet.
+        */
+       if (phydev->autoneg == AUTONEG_ENABLE && !phydev->autoneg_complete)
+               phydev->link = 0;
+
        return 0;
 }
 EXPORT_SYMBOL(genphy_update_link);