From: Heiner Kallweit <hkallweit1@gmail.com>
Date: Mon, 3 Dec 2018 08:19:33 +0100
Subject: net: phy: don't allow __set_phy_supported to add unsupported modes
Patch-mainline: v4.20-rc6
Git-commit: d2a36971ef595069b7a600d1144c2e0881a930a1
References: bsc#1119113 FATE#326472

Currently __set_phy_supported allows to add modes w/o checking whether
the PHY supports them. This is wrong, it should never add modes but
only remove modes we don't want to support.

The commit marked as fixed didn't do anything wrong, it just copied
existing functionality to the helper which is being fixed now.

Fixes: f3a6bd393c2c ("phylib: Add phy_set_max_speed helper")
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/phy/phy_device.c |   19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -1736,20 +1736,17 @@ EXPORT_SYMBOL(genphy_loopback);
 
 static int __set_phy_supported(struct phy_device *phydev, u32 max_speed)
 {
-	phydev->supported &= ~(PHY_1000BT_FEATURES | PHY_100BT_FEATURES |
-			       PHY_10BT_FEATURES);
-
 	switch (max_speed) {
-	default:
-		return -ENOTSUPP;
-	case SPEED_1000:
-		phydev->supported |= PHY_1000BT_FEATURES;
+	case SPEED_10:
+		phydev->supported &= ~PHY_100BT_FEATURES;
 		/* fall through */
 	case SPEED_100:
-		phydev->supported |= PHY_100BT_FEATURES;
-		/* fall through */
-	case SPEED_10:
-		phydev->supported |= PHY_10BT_FEATURES;
+		phydev->supported &= ~PHY_1000BT_FEATURES;
+		break;
+	case SPEED_1000:
+		break;
+	default:
+		return -ENOTSUPP;
 	}
 
 	return 0;