[PATCH net] bonding: fix feature flag setting at init time

[Jarod Wilson]

Have run into a case where bond_option_mode_set() gets called before
hw_features has been filled in, and very bad things happen when
netdev_change_features() then gets called, because the empty hw_features
wipes out almost all features. Further reading of netdev feature flag
documentation suggests drivers aren't supposed to touch wanted_features,
so this changes bond_option_mode_set() to use netdev_increment_features()
and &= ~BOND_XFRM_FEATURES on mode changes and then only calling
netdev_features_change() if there was actually a change of features. This
specifically fixes bonding on top of mlxsw interfaces, and has been
regression-tested with ixgbe interfaces. This change also simplifies the
xfrm-specific code in bond_setup() a little bit as well.

Fixes: a3b658cfb664 ("bonding: allow xfrm offload setup post-module-load")
Reported-by: Ivan Vecera <ivecera@xxxxxxxxxx>
Cc: Jay Vosburgh <j.vosburgh@xxxxxxxxx>
Cc: Veaceslav Falico <vfalico@xxxxxxxxx>
Cc: Andy Gospodarek <andy@xxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: Thomas Davis <tadavis@xxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Jarod Wilson <jarod@xxxxxxxxxx>
---
 drivers/net/bonding/bond_main.c    | 10 ++++------
 drivers/net/bonding/bond_options.c | 14 +++++++++++---
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 71c9677d135f..b8e0cb4f9480 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -4721,15 +4721,13 @@ void bond_setup(struct net_device *bond_dev)
 				NETIF_F_HW_VLAN_CTAG_FILTER;
 
 	bond_dev->hw_features |= NETIF_F_GSO_ENCAP_ALL;
-#ifdef CONFIG_XFRM_OFFLOAD
-	bond_dev->hw_features |= BOND_XFRM_FEATURES;
-#endif /* CONFIG_XFRM_OFFLOAD */
 	bond_dev->features |= bond_dev->hw_features;
 	bond_dev->features |= NETIF_F_HW_VLAN_CTAG_TX | NETIF_F_HW_VLAN_STAG_TX;
 #ifdef CONFIG_XFRM_OFFLOAD
-	/* Disable XFRM features if this isn't an active-backup config */
-	if (BOND_MODE(bond) != BOND_MODE_ACTIVEBACKUP)
-		bond_dev->features &= ~BOND_XFRM_FEATURES;
+	bond_dev->hw_features |= BOND_XFRM_FEATURES;
+	/* Only enable XFRM features if this is an active-backup config */
+	if (BOND_MODE(bond) == BOND_MODE_ACTIVEBACKUP)
+		bond_dev->features |= BOND_XFRM_FEATURES;
 #endif /* CONFIG_XFRM_OFFLOAD */
 }
 
diff --git a/drivers/net/bonding/bond_options.c b/drivers/net/bonding/bond_options.c
index 9abfaae1c6f7..bce34648d97d 100644
--- a/drivers/net/bonding/bond_options.c
+++ b/drivers/net/bonding/bond_options.c
@@ -748,6 +748,9 @@ const struct bond_option *bond_opt_get(unsigned int option)
 static int bond_option_mode_set(struct bonding *bond,
 				const struct bond_opt_value *newval)
 {
+	netdev_features_t features = bond->dev->features;
+	netdev_features_t mask = features & BOND_XFRM_FEATURES;
+
 	if (!bond_mode_uses_arp(newval->value)) {
 		if (bond->params.arp_interval) {
 			netdev_dbg(bond->dev, "%s mode is incompatible with arp monitoring, start mii monitoring\n",
@@ -769,10 +772,15 @@ static int bond_option_mode_set(struct bonding *bond,
 
 #ifdef CONFIG_XFRM_OFFLOAD
 	if (newval->value == BOND_MODE_ACTIVEBACKUP)
-		bond->dev->wanted_features |= BOND_XFRM_FEATURES;
+		features = netdev_increment_features(features,
+						     BOND_XFRM_FEATURES, mask);
 	else
-		bond->dev->wanted_features &= ~BOND_XFRM_FEATURES;
-	netdev_change_features(bond->dev);
+		features &= ~BOND_XFRM_FEATURES;
+
+	if (bond->dev->features != features) {
+		bond->dev->features = features;
+		netdev_features_change(bond->dev);
+	}
 #endif /* CONFIG_XFRM_OFFLOAD */
 
 	/* don't cache arp_validate between modes */
-- 
2.28.0