[PATCH 4.4 01/28] virtio-net: add a missing synchronize_net()

From: Greg Kroah-Hartman
Date: Fri Dec 09 2016 - 11:18:18 EST


4.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@xxxxxxxxxx>


[ 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@xxxxxxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/virtio_net.c | 5 +++++
1 file changed, 5 insertions(+)

--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1465,6 +1465,11 @@ static void virtnet_free_queues(struct v
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);
}