Subject: [net 2/2] net/mlx5e: Fix wrong features assignment in case of error

From: Saeed Mahameed <[email-masked]>
Date: Tue, 28 Dec 2021 22:53:52 -0800

From: Gal Pressman <[email-masked]>

In case of an error in mlx5e_set_features(), 'netdev->features' must be
updated with the correct state of the device to indicate which features
were updated successfully.
To do that we maintain a copy of 'netdev->features' and update it after
successful feature changes, so we can assign it to back to
'netdev->features' if needed.

However, since not all netdev features are handled by the driver (e.g.
GRO/TSO/etc), some features may not be updated correctly in case of an
error updating another feature.

For example, while requesting to disable TSO (feature which is not
handled by the driver) and enable HW-GRO, if an error occurs during
HW-GRO enable, 'oper_features' will be assigned with 'netdev->features'
and HW-GRO turned off. TSO will remain enabled in such case, which is a
bug.

To solve that, instead of using 'netdev->features' as the baseline of
'oper_features' and changing it on set feature success, use 'features'
instead and update it in case of errors.

Fixes: 75b81ce719b7 ("net/mlx5e: Don't override netdev features field unless in error flow")
Signed-off-by: Gal Pressman <[email-masked]>
Signed-off-by: Saeed Mahameed <[email-masked]>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 3b0f3a831216..41379844eee1 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -3741,12 +3741,11 @@ static int set_feature_arfs(struct net_device *netdev, bool enable)
 
 static int mlx5e_handle_feature(struct net_device *netdev,
 				netdev_features_t *features,
-				netdev_features_t wanted_features,
 				netdev_features_t feature,
 				mlx5e_feature_handler feature_handler)
 {
-	netdev_features_t changes = wanted_features ^ netdev->features;
-	bool enable = !!(wanted_features & feature);
+	netdev_features_t changes = *features ^ netdev->features;
+	bool enable = !!(*features & feature);
 	int err;
 
 	if (!(changes & feature))
@@ -3754,22 +3753,22 @@ static int mlx5e_handle_feature(struct net_device *netdev,
 
 	err = feature_handler(netdev, enable);
 	if (err) {
+		MLX5E_SET_FEATURE(features, feature, !enable);
 		netdev_err(netdev, "%s feature %pNF failed, err %d\n",
 			   enable ? "Enable" : "Disable", &feature, err);
 		return err;
 	}
 
-	MLX5E_SET_FEATURE(features, feature, enable);
 	return 0;
 }
 
 int mlx5e_set_features(struct net_device *netdev, netdev_features_t features)
 {
-	netdev_features_t oper_features = netdev->features;
+	netdev_features_t oper_features = features;
 	int err = 0;
 
 #define MLX5E_HANDLE_FEATURE(feature, handler) \
-	mlx5e_handle_feature(netdev, &oper_features, features, feature, handler)
+	mlx5e_handle_feature(netdev, &oper_features, feature, handler)
 
 	err |= MLX5E_HANDLE_FEATURE(NETIF_F_LRO, set_feature_lro);
 	err |= MLX5E_HANDLE_FEATURE(NETIF_F_GRO_HW, set_feature_hw_gro);
-- 
2.33.1