virtio-net: add a missing synchronize_net()

[ Upstream commit 963abe5c8a0273a1cf5913556da1b1189de0e57a ]

It seems many drivers do not respect napi_hash_del() contract.

When napi_hash_del() is used before netif_napi_del(), an RCU grace
period is needed before freeing NAPI object.

Fixes: 91815639d880 ("virtio-net: rx busy polling support")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index f94ab78..0e2a19e 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1465,6 +1465,11 @@ static void virtnet_free_queues(struct virtnet_info *vi)
                netif_napi_del(&vi->rq[i].napi);
        }
 
+       /* We called napi_hash_del() before netif_napi_del(),
+        * we need to respect an RCU grace period before freeing vi->rq
+        */
+       synchronize_net();
+
        kfree(vi->rq);
        kfree(vi->sq);
 }