Subject: [PATCH 01/19] virtio-net: add a missing synchronize_net()

From: Eric Dumazet <[email-masked]>
Date: Tue, 15 Nov 2016 22:24:12 -0800

[ 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 <[email-masked]>
Cc: Jason Wang <[email-masked]>
Cc: Michael S. Tsirkin <[email-masked]>
Acked-by: Michael S. Tsirkin <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 drivers/net/virtio_net.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index f94ab78..0e2a19e 100644
--- 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);
 }
-- 
2.7.4