linux-kernel - [V2 PATCH 6/9] vhost_net: zerocopy: fix possible NULL pointer dereference of vq->bufs

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Message-ID: <20120502034223.11782.31222.stgit@amd-6168-8-1.englab.nay.redhat.com>
Date:	Wed, 02 May 2012 11:42:23 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	eric.dumazet@...il.com, mst@...hat.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, ebiederm@...ssion.com,
	davem@...emloft.net
Subject: [V2 PATCH 6/9] vhost_net: zerocopy: fix possible NULL pointer
 dereference of vq->bufs

When we want to disable vhost_net backend while there's a tx work, a possible
NULL pointer defernece may happen we we try to deference the vq->bufs after
vhost_net_set_backend() assign a NULL to it.

As suggested by Michael, fix this by checking the vq->bufs instead of
vhost_sock_zcopy().
---
 drivers/vhost/net.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index f0da2c3..ffdc0d8 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -166,7 +166,7 @@ static void handle_tx(struct vhost_net *net)
 	if (wmem < sock->sk->sk_sndbuf / 2)
 		tx_poll_stop(net);
 	hdr_size = vq->vhost_hlen;
-	zcopy = vhost_sock_zcopy(sock);
+	zcopy = vq->ubufs;
 
 	for (;;) {
 		/* Release DMAs done buffers first */

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