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Tsirkin" To: Alvaro Karsz Cc: jasowang@redhat.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net] virtio-net: reject small vring sizes Message-ID: <20230416163751-mutt-send-email-mst@kernel.org> References: <20230416074607.292616-1-alvaro.karsz@solid-run.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230416074607.292616-1-alvaro.karsz@solid-run.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sun, Apr 16, 2023 at 10:46:07AM +0300, Alvaro Karsz wrote: > Check vring size and fail probe if a transmit/receive vring size is > smaller than MAX_SKB_FRAGS + 2. > > At the moment, any vring size is accepted. This is problematic because > it may result in attempting to transmit a packet with more fragments > than there are descriptors in the ring. > > Furthermore, it leads to an immediate bug: > > The condition: (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) in > virtnet_poll_cleantx and virtnet_poll_tx always evaluates to false, > so netif_tx_wake_queue is not called, leading to TX timeouts. > > Signed-off-by: Alvaro Karsz > --- > drivers/net/virtio_net.c | 24 ++++++++++++++++++++++++ > 1 file changed, 24 insertions(+) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 2396c28c012..59676252c5c 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -3745,6 +3745,26 @@ static int init_vqs(struct virtnet_info *vi) > return ret; > } > > +static int virtnet_validate_vqs(struct virtnet_info *vi) > +{ > + u32 i, min_size = roundup_pow_of_two(MAX_SKB_FRAGS + 2); why power of two? > + > + /* Transmit/Receive vring size must be at least MAX_SKB_FRAGS + 2 > + * (fragments + linear part + virtio header) > + */ > + for (i = 0; i < vi->max_queue_pairs; i++) { > + if (virtqueue_get_vring_size(vi->sq[i].vq) < min_size || > + virtqueue_get_vring_size(vi->rq[i].vq) < min_size) { > + dev_warn(&vi->vdev->dev, > + "Transmit/Receive virtqueue vring size must be at least %u\n", > + min_size); > + return -EINVAL; > + } > + } > + > + return 0; > +} > + > #ifdef CONFIG_SYSFS > static ssize_t mergeable_rx_buffer_size_show(struct netdev_rx_queue *queue, > char *buf) > @@ -4056,6 +4076,10 @@ static int virtnet_probe(struct virtio_device *vdev) > if (err) > goto free; > > + err = virtnet_validate_vqs(vi); > + if (err) > + goto free_vqs; > + > #ifdef CONFIG_SYSFS > if (vi->mergeable_rx_bufs) > dev->sysfs_rx_queue_group = &virtio_net_mrg_rx_group; > -- > 2.34.1