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Date:   Tue, 10 Aug 2021 10:16:24 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     "Ivan T. Ivanov" <iivanov@...e.de>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, netdev@...r.kernel.org,
        linux-usb@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 11/11] net: usb: lan78xx: don't modify phy_device state concurrently

From: "Ivan T. Ivanov" <iivanov@...e.de>

[ Upstream commit 6b67d4d63edece1033972214704c04f36c5be89a ]

Currently phy_device state could be left in inconsistent state shown
by following alert message[1]. This is because phy_read_status could
be called concurrently from lan78xx_delayedwork, phy_state_machine and
__ethtool_get_link. Fix this by making sure that phy_device state is
updated atomically.

[1] lan78xx 1-1.1.1:1.0 eth0: No phy led trigger registered for speed(-1)

Signed-off-by: Ivan T. Ivanov <iivanov@...e.de>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/usb/lan78xx.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index 5bd07cdb3e6e..ac5f72077b26 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -1172,7 +1172,7 @@ static int lan78xx_link_reset(struct lan78xx_net *dev)
 {
 	struct phy_device *phydev = dev->net->phydev;
 	struct ethtool_link_ksettings ecmd;
-	int ladv, radv, ret;
+	int ladv, radv, ret, link;
 	u32 buf;
 
 	/* clear LAN78xx interrupt status */
@@ -1180,9 +1180,12 @@ static int lan78xx_link_reset(struct lan78xx_net *dev)
 	if (unlikely(ret < 0))
 		return -EIO;
 
+	mutex_lock(&phydev->lock);
 	phy_read_status(phydev);
+	link = phydev->link;
+	mutex_unlock(&phydev->lock);
 
-	if (!phydev->link && dev->link_on) {
+	if (!link && dev->link_on) {
 		dev->link_on = false;
 
 		/* reset MAC */
@@ -1195,7 +1198,7 @@ static int lan78xx_link_reset(struct lan78xx_net *dev)
 			return -EIO;
 
 		del_timer(&dev->stat_monitor);
-	} else if (phydev->link && !dev->link_on) {
+	} else if (link && !dev->link_on) {
 		dev->link_on = true;
 
 		phy_ethtool_ksettings_get(phydev, &ecmd);
@@ -1485,9 +1488,14 @@ static int lan78xx_set_eee(struct net_device *net, struct ethtool_eee *edata)
 
 static u32 lan78xx_get_link(struct net_device *net)
 {
+	u32 link;
+
+	mutex_lock(&net->phydev->lock);
 	phy_read_status(net->phydev);
+	link = net->phydev->link;
+	mutex_unlock(&net->phydev->lock);
 
-	return net->phydev->link;
+	return link;
 }
 
 static void lan78xx_get_drvinfo(struct net_device *net,
-- 
2.30.2

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