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 <ivec...@redhat.com>
Cc: Jay Vosburgh <j.vosbu...@gmail.com>
Cc: Veaceslav Falico <vfal...@gmail.com>
Cc: Andy Gospodarek <a...@greyhouse.net>
Cc: "David S. Miller" <da...@davemloft.net>
Cc: Jakub Kicinski <k...@kernel.org>
Cc: Thomas Davis <tada...@lbl.gov>
Cc: net...@vger.kernel.org
Signed-off-by: Jarod Wilson <ja...@redhat.com>
---
 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

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