net/mlx4_en: Protect MAC address modification with the state_lock mutex

This Patches solves an issue that could raise when modifying the
device's MAC. It occurs due to a simultaneous access to priv->mac_hash
from two contexts. The buggy scenario described below:
Context 1: copy the new mac address to the dev->dev_addr field.
Context 2: mlx4_en_do_uc_filter removes prev_mac entry from the mac_hash
           db since it is not in dev->uc and not equal to dev->dev_addr.
Context 1: mlx4_en_do_set_mac() calls mlx4_en_replace_mac() to replace
           prev_mac with dev_addr but it fails to update the mac_hash db
           since it no longer contains prev_mac, therefore it returns
           with an error.

The fix is to prevent mlx4_en_do_uc_filter from being executed by both
of the context 1 calls described above, This is done by putting them
both under the mdev->state_lock lock, it will solve this issue since
mlx4_en_do_uc_filter is already protected by the mdev->state_lock.
Reviewed-by: Eyal Perry <eyalpe@mellanox.com>
Signed-off-by: Shani Michaeli <shanim@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/en_netdev.c

@@ -789,9 +789,8 @@ static int mlx4_en_set_mac(struct net_device *dev, void *addr)
 	if (!is_valid_ether_addr(saddr->sa_data))
 		return -EADDRNOTAVAIL;
 
-	memcpy(dev->dev_addr, saddr->sa_data, ETH_ALEN);
-
 	mutex_lock(&mdev->state_lock);
+	memcpy(dev->dev_addr, saddr->sa_data, ETH_ALEN);
 	err = mlx4_en_do_set_mac(priv);
 	mutex_unlock(&mdev->state_lock);