ethtool: Fix preserving of wanted feature bits in netlink interface

Currently, ethtool-netlink calculates new wanted bits as:
(req_wanted & req_mask) | (old_active & ~req_mask)

It completely discards the old wanted bits, so they are forgotten with
the next ethtool command. Sample steps to reproduce:

1. ethtool -k eth0
   tx-tcp-segmentation: on # TSO is on from the beginning
2. ethtool -K eth0 tx off
   tx-tcp-segmentation: off [not requested]
3. ethtool -k eth0
   tx-tcp-segmentation: off [requested on]
4. ethtool -K eth0 rx off # Some change unrelated to TSO
5. ethtool -k eth0
   tx-tcp-segmentation: off # "Wanted on" is forgotten

This commit fixes it by changing the formula to:
(req_wanted & req_mask) | (old_wanted & ~req_mask),
where old_active was replaced by old_wanted to account for the wanted
bits.

The shortcut condition for the case where nothing was changed now
compares wanted bitmasks, instead of wanted to active.

Fixes: 0980bfcd6954 ("ethtool: set netdev features with FEATURES_SET request")
Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Reviewed-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ethtool/features.c b/net/ethtool/features.c
index 4e632dc987d859d7599c1c8b9a084c9fd01c76ea..ec196f0fddc924f0784683121ebe3c49a83d8432 100644 (file)
--- a/net/ethtool/features.c
+++ b/net/ethtool/features.c
@@ -224,7 +224,9 @@ int ethnl_set_features(struct sk_buff *skb, struct genl_info *info)
        DECLARE_BITMAP(wanted_diff_mask, NETDEV_FEATURE_COUNT);
        DECLARE_BITMAP(active_diff_mask, NETDEV_FEATURE_COUNT);
        DECLARE_BITMAP(old_active, NETDEV_FEATURE_COUNT);
+       DECLARE_BITMAP(old_wanted, NETDEV_FEATURE_COUNT);
        DECLARE_BITMAP(new_active, NETDEV_FEATURE_COUNT);
+       DECLARE_BITMAP(new_wanted, NETDEV_FEATURE_COUNT);
        DECLARE_BITMAP(req_wanted, NETDEV_FEATURE_COUNT);
        DECLARE_BITMAP(req_mask, NETDEV_FEATURE_COUNT);
        struct nlattr *tb[ETHTOOL_A_FEATURES_MAX + 1];
@@ -250,6 +252,7 @@ int ethnl_set_features(struct sk_buff *skb, struct genl_info *info)
 
        rtnl_lock();
        ethnl_features_to_bitmap(old_active, dev->features);
+       ethnl_features_to_bitmap(old_wanted, dev->wanted_features);
        ret = ethnl_parse_bitset(req_wanted, req_mask, NETDEV_FEATURE_COUNT,
                                 tb[ETHTOOL_A_FEATURES_WANTED],
                                 netdev_features_strings, info->extack);
@@ -261,11 +264,11 @@ int ethnl_set_features(struct sk_buff *skb, struct genl_info *info)
                goto out_rtnl;
        }
 
-       /* set req_wanted bits not in req_mask from old_active */
+       /* set req_wanted bits not in req_mask from old_wanted */
        bitmap_and(req_wanted, req_wanted, req_mask, NETDEV_FEATURE_COUNT);
-       bitmap_andnot(new_active, old_active, req_mask, NETDEV_FEATURE_COUNT);
-       bitmap_or(req_wanted, new_active, req_wanted, NETDEV_FEATURE_COUNT);
-       if (bitmap_equal(req_wanted, old_active, NETDEV_FEATURE_COUNT)) {
+       bitmap_andnot(new_wanted, old_wanted, req_mask, NETDEV_FEATURE_COUNT);
+       bitmap_or(req_wanted, new_wanted, req_wanted, NETDEV_FEATURE_COUNT);
+       if (bitmap_equal(req_wanted, old_wanted, NETDEV_FEATURE_COUNT)) {
                ret = 0;
                goto out_rtnl;
        }