[PATCH net 0/4] ksettings_{get|set} lock fixes

[PATCH net 0/4] ksettings_{get|set} lock fixes

[Andrew Lunn]

Walter Stoll <Walter.Stoll@duagon.com> reported a race condition
between "ethtool -s eth0 speed 100 duplex full autoneg off" and phylib
reading the current status from the PHY. Both ksetting_get and
ksetting_set fail the take the phydev mutex, and as a result, there is
a small window of time where the phydev members are not self
consistent.

Patch 1 fixes phy_ethtool_ksettings_get by adding the needed lock.
Patches 2 and 3 move code around and perform to refactoring, to allow
patch 4 to fix phy_ethtool_ksettings_set by added the lock.

Thanks go to Walter for the detailed origional report, suggested fix,
and testing of the proposed patches.

Andrew Lunn (4):
  phy: phy_ethtool_ksettings_get: Lock the phy for consistency
  phy: phy_ethtool_ksettings_set: Move after phy_start_aneg
  phy: phy_start_aneg: Add an unlocked version
  phy: phy_ethtool_ksettings_set: Lock the PHY while changing settings

 drivers/net/phy/phy.c | 140 ++++++++++++++++++++++++------------------
 1 file changed, 81 insertions(+), 59 deletions(-)

-- 
2.33.0

[PATCH net 1/4] phy: phy_ethtool_ksettings_get: Lock the phy for consistency

[Andrew Lunn]

The PHY structure should be locked while copying information out if
it, otherwise there is no guarantee of self consistency. Without the
lock the PHY state machine could be updating the structure.

Fixes: 2d55173e71b0 ("phy: add generic function to support ksetting support")
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
---
 drivers/net/phy/phy.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index f124a8a58bd4..8457b829667e 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -299,6 +299,7 @@ EXPORT_SYMBOL(phy_ethtool_ksettings_set);
 void phy_ethtool_ksettings_get(struct phy_device *phydev,
 			       struct ethtool_link_ksettings *cmd)
 {
+	mutex_lock(&phydev->lock);
 	linkmode_copy(cmd->link_modes.supported, phydev->supported);
 	linkmode_copy(cmd->link_modes.advertising, phydev->advertising);
 	linkmode_copy(cmd->link_modes.lp_advertising, phydev->lp_advertising);
@@ -317,6 +318,7 @@ void phy_ethtool_ksettings_get(struct phy_device *phydev,
 	cmd->base.autoneg = phydev->autoneg;
 	cmd->base.eth_tp_mdix_ctrl = phydev->mdix_ctrl;
 	cmd->base.eth_tp_mdix = phydev->mdix;
+	mutex_unlock(&phydev->lock);
 }
 EXPORT_SYMBOL(phy_ethtool_ksettings_get);
 
-- 
2.33.0

[PATCH net 2/4] phy: phy_ethtool_ksettings_set: Move after phy_start_aneg

[Andrew Lunn]

This allows it to make use of a helper which assume the PHY is already
locked.

Fixes: 2d55173e71b0 ("phy: add generic function to support ksetting support")
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
---
 drivers/net/phy/phy.c | 106 +++++++++++++++++++++---------------------
 1 file changed, 53 insertions(+), 53 deletions(-)

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index 8457b829667e..ee584fa8b76d 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -243,59 +243,6 @@ static void phy_sanitize_settings(struct phy_device *phydev)
 	}
 }
 
-int phy_ethtool_ksettings_set(struct phy_device *phydev,
-			      const struct ethtool_link_ksettings *cmd)
-{
-	__ETHTOOL_DECLARE_LINK_MODE_MASK(advertising);
-	u8 autoneg = cmd->base.autoneg;
-	u8 duplex = cmd->base.duplex;
-	u32 speed = cmd->base.speed;
-
-	if (cmd->base.phy_address != phydev->mdio.addr)
-		return -EINVAL;
-
-	linkmode_copy(advertising, cmd->link_modes.advertising);
-
-	/* We make sure that we don't pass unsupported values in to the PHY */
-	linkmode_and(advertising, advertising, phydev->supported);
-
-	/* Verify the settings we care about. */
-	if (autoneg != AUTONEG_ENABLE && autoneg != AUTONEG_DISABLE)
-		return -EINVAL;
-
-	if (autoneg == AUTONEG_ENABLE && linkmode_empty(advertising))
-		return -EINVAL;
-
-	if (autoneg == AUTONEG_DISABLE &&
-	    ((speed != SPEED_1000 &&
-	      speed != SPEED_100 &&
-	      speed != SPEED_10) ||
-	     (duplex != DUPLEX_HALF &&
-	      duplex != DUPLEX_FULL)))
-		return -EINVAL;
-
-	phydev->autoneg = autoneg;
-
-	if (autoneg == AUTONEG_DISABLE) {
-		phydev->speed = speed;
-		phydev->duplex = duplex;
-	}
-
-	linkmode_copy(phydev->advertising, advertising);
-
-	linkmode_mod_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
-			 phydev->advertising, autoneg == AUTONEG_ENABLE);
-
-	phydev->master_slave_set = cmd->base.master_slave_cfg;
-	phydev->mdix_ctrl = cmd->base.eth_tp_mdix_ctrl;
-
-	/* Restart the PHY */
-	phy_start_aneg(phydev);
-
-	return 0;
-}
-EXPORT_SYMBOL(phy_ethtool_ksettings_set);
-
 void phy_ethtool_ksettings_get(struct phy_device *phydev,
 			       struct ethtool_link_ksettings *cmd)
 {
@@ -802,6 +749,59 @@ static int phy_poll_aneg_done(struct phy_device *phydev)
 	return ret < 0 ? ret : 0;
 }
 
+int phy_ethtool_ksettings_set(struct phy_device *phydev,
+			      const struct ethtool_link_ksettings *cmd)
+{
+	__ETHTOOL_DECLARE_LINK_MODE_MASK(advertising);
+	u8 autoneg = cmd->base.autoneg;
+	u8 duplex = cmd->base.duplex;
+	u32 speed = cmd->base.speed;
+
+	if (cmd->base.phy_address != phydev->mdio.addr)
+		return -EINVAL;
+
+	linkmode_copy(advertising, cmd->link_modes.advertising);
+
+	/* We make sure that we don't pass unsupported values in to the PHY */
+	linkmode_and(advertising, advertising, phydev->supported);
+
+	/* Verify the settings we care about. */
+	if (autoneg != AUTONEG_ENABLE && autoneg != AUTONEG_DISABLE)
+		return -EINVAL;
+
+	if (autoneg == AUTONEG_ENABLE && linkmode_empty(advertising))
+		return -EINVAL;
+
+	if (autoneg == AUTONEG_DISABLE &&
+	    ((speed != SPEED_1000 &&
+	      speed != SPEED_100 &&
+	      speed != SPEED_10) ||
+	     (duplex != DUPLEX_HALF &&
+	      duplex != DUPLEX_FULL)))
+		return -EINVAL;
+
+	phydev->autoneg = autoneg;
+
+	if (autoneg == AUTONEG_DISABLE) {
+		phydev->speed = speed;
+		phydev->duplex = duplex;
+	}
+
+	linkmode_copy(phydev->advertising, advertising);
+
+	linkmode_mod_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
+			 phydev->advertising, autoneg == AUTONEG_ENABLE);
+
+	phydev->master_slave_set = cmd->base.master_slave_cfg;
+	phydev->mdix_ctrl = cmd->base.eth_tp_mdix_ctrl;
+
+	/* Restart the PHY */
+	phy_start_aneg(phydev);
+
+	return 0;
+}
+EXPORT_SYMBOL(phy_ethtool_ksettings_set);
+
 /**
  * phy_speed_down - set speed to lowest speed supported by both link partners
  * @phydev: the phy_device struct
-- 
2.33.0

[PATCH net 3/4] phy: phy_start_aneg: Add an unlocked version

[Andrew Lunn]

Split phy_start_aneg into a wrapper which takes the PHY lock, and a
helper doing the real work. This will be needed when
phy_ethtook_ksettings_set takes the lock.

Fixes: 2d55173e71b0 ("phy: add generic function to support ksetting support")
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
---
 drivers/net/phy/phy.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index ee584fa8b76d..d845afab1af7 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -700,7 +700,7 @@ static int phy_check_link_status(struct phy_device *phydev)
 }
 
 /**
- * phy_start_aneg - start auto-negotiation for this PHY device
+ * _phy_start_aneg - start auto-negotiation for this PHY device
  * @phydev: the phy_device struct
  *
  * Description: Sanitizes the settings (if we're not autonegotiating
@@ -708,25 +708,43 @@ static int phy_check_link_status(struct phy_device *phydev)
  *   If the PHYCONTROL Layer is operating, we change the state to
  *   reflect the beginning of Auto-negotiation or forcing.
  */
-int phy_start_aneg(struct phy_device *phydev)
+static int _phy_start_aneg(struct phy_device *phydev)
 {
 	int err;
 
+	lockdep_assert_held(&phydev->lock);
+
 	if (!phydev->drv)
 		return -EIO;
 
-	mutex_lock(&phydev->lock);
-
 	if (AUTONEG_DISABLE == phydev->autoneg)
 		phy_sanitize_settings(phydev);
 
 	err = phy_config_aneg(phydev);
 	if (err < 0)
-		goto out_unlock;
+		return err;
 
 	if (phy_is_started(phydev))
 		err = phy_check_link_status(phydev);
-out_unlock:
+
+	return err;
+}
+
+/**
+ * phy_start_aneg - start auto-negotiation for this PHY device
+ * @phydev: the phy_device struct
+ *
+ * Description: Sanitizes the settings (if we're not autonegotiating
+ *   them), and then calls the driver's config_aneg function.
+ *   If the PHYCONTROL Layer is operating, we change the state to
+ *   reflect the beginning of Auto-negotiation or forcing.
+ */
+int phy_start_aneg(struct phy_device *phydev)
+{
+	int err;
+
+	mutex_lock(&phydev->lock);
+	err = _phy_start_aneg(phydev);
 	mutex_unlock(&phydev->lock);
 
 	return err;
-- 
2.33.0

[PATCH net 4/4] phy: phy_ethtool_ksettings_set: Lock the PHY while changing settings

[Andrew Lunn]

There is a race condition where the PHY state machine can change
members of the phydev structure at the same time userspace requests a
change via ethtool. To prevent this, have phy_ethtool_ksettings_set
take the PHY lock.

Fixes: 2d55173e71b0 ("phy: add generic function to support ksetting support")
Reported-by: Walter Stoll <Walter.Stoll@duagon.com>
Suggested-by: Walter Stoll <Walter.Stoll@duagon.com>
Tested-by: Walter Stoll <Walter.Stoll@duagon.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
---
 drivers/net/phy/phy.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index d845afab1af7..a3bfb156c83d 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -798,6 +798,7 @@ int phy_ethtool_ksettings_set(struct phy_device *phydev,
 	      duplex != DUPLEX_FULL)))
 		return -EINVAL;
 
+	mutex_lock(&phydev->lock);
 	phydev->autoneg = autoneg;
 
 	if (autoneg == AUTONEG_DISABLE) {
@@ -814,8 +815,9 @@ int phy_ethtool_ksettings_set(struct phy_device *phydev,
 	phydev->mdix_ctrl = cmd->base.eth_tp_mdix_ctrl;
 
 	/* Restart the PHY */
-	phy_start_aneg(phydev);
+	_phy_start_aneg(phydev);
 
+	mutex_unlock(&phydev->lock);
 	return 0;
 }
 EXPORT_SYMBOL(phy_ethtool_ksettings_set);
-- 
2.33.0