From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:47704 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751738AbeBTNcV (ORCPT ); Tue, 20 Feb 2018 08:32:21 -0500 Subject: [net PATCH 4/4] virtio_net: fix ndo_xdp_xmit crash towards dev not ready for XDP From: Jesper Dangaard Brouer To: Jason Wang Cc: "Michael S. Tsirkin" , netdev@vger.kernel.org, John Fastabend , Alexei Starovoitov , Saeed Mahameed , Jesper Dangaard Brouer , Daniel Borkmann , "David S. Miller" , Tariq Toukan Date: Tue, 20 Feb 2018 14:32:20 +0100 Message-ID: <151913354012.28247.1462800242440559823.stgit@firesoul> In-Reply-To: <151913348634.28247.17519468037896960567.stgit@firesoul> References: <151913348634.28247.17519468037896960567.stgit@firesoul> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org List-ID: When a driver implements the ndo_xdp_xmit() function, there is (currently) no generic way to determine whether it is safe to call. It is e.g. unsafe to call the drivers ndo_xdp_xmit, if it have not allocated the needed XDP TX queues yet. This is the case for virtio_net, which first allocates the XDP TX queues once an XDP/bpf prog is attached (in virtnet_xdp_set()). Thus, a crash will occur for virtio_net when redirecting to another virtio_net device's ndo_xdp_xmit, which have not attached a XDP prog. The sample xdp_redirect_map tries to attach a dummy XDP prog to take this into account, but it can also easily fail if the virtio_net (or actually underlying vhost driver) have not allocated enough extra queues for the device. Allocating more queue this is currently a manual config. Hint for libvirt XML add: The solution in this patch is to check that the device have loaded an XDP/bpf prog before proceeding. This is similar to the check performed in driver ixgbe. Signed-off-by: Jesper Dangaard Brouer --- drivers/net/virtio_net.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 1e0e0fce3ab2..9bb9e562b893 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -452,8 +452,18 @@ static bool __virtnet_xdp_xmit(struct virtnet_info *vi, static int virtnet_xdp_xmit(struct net_device *dev, struct xdp_buff *xdp) { struct virtnet_info *vi = netdev_priv(dev); - bool sent = __virtnet_xdp_xmit(vi, xdp); + struct receive_queue *rq = vi->rq; + struct bpf_prog *xdp_prog; + bool sent; + + /* Only allow ndo_xdp_xmit if XDP is loaded on dev, as this + * indicate XDP resources have been successfully allocated. + */ + xdp_prog = rcu_dereference(rq->xdp_prog); + if (!xdp_prog) + return -ENXIO; + sent = __virtnet_xdp_xmit(vi, xdp); if (!sent) return -ENOSPC; return 0;