1 files changed, 34 insertions, 11 deletions

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ea9890d61967..f36584616e7d 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2230,14 +2230,8 @@ static bool virtnet_validate_features(struct virtio_device *vdev)
 #define MIN_MTU ETH_MIN_MTU
 #define MAX_MTU ETH_MAX_MTU
 
-static int virtnet_probe(struct virtio_device *vdev)
+static int virtnet_validate(struct virtio_device *vdev)
 {
-        int i, err;
-        struct net_device *dev;
-        struct virtnet_info *vi;
-        u16 max_queue_pairs;
-        int mtu;
-
         if (!vdev->config->get) {
                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
                         __func__);
@@ -2247,6 +2241,25 @@ static int virtnet_probe(struct virtio_device *vdev)
         if (!virtnet_validate_features(vdev))
                 return -EINVAL;
 
+        if (virtio_has_feature(vdev, VIRTIO_NET_F_MTU)) {
+                int mtu = virtio_cread16(vdev,
+                                         offsetof(struct virtio_net_config,
+                                                  mtu));
+                if (mtu < MIN_MTU)
+                        __virtio_clear_bit(vdev, VIRTIO_NET_F_MTU);
+        }
+
+        return 0;
+}
+
+static int virtnet_probe(struct virtio_device *vdev)
+{
+        int i, err;
+        struct net_device *dev;
+        struct virtnet_info *vi;
+        u16 max_queue_pairs;
+        int mtu;
+
         /* Find if host supports multiqueue virtio_net device */
         err = virtio_cread_feature(vdev, VIRTIO_NET_F_MQ,
                                    struct virtio_net_config,
@@ -2362,11 +2375,20 @@ static int virtnet_probe(struct virtio_device *vdev)
                                      offsetof(struct virtio_net_config,
                                               mtu));
                 if (mtu < dev->min_mtu) {
-                        __virtio_clear_bit(vdev, VIRTIO_NET_F_MTU);
-                } else {
-                        dev->mtu = mtu;
-                        dev->max_mtu = mtu;
+                        /* Should never trigger: MTU was previously validated
+                         * in virtnet_validate.
+                         */
+                        dev_err(&vdev->dev, "device MTU appears to have changed "
+                                "it is now %d < %d", mtu, dev->min_mtu);
+                        goto free_stats;
                 }
+
+                dev->mtu = mtu;
+                dev->max_mtu = mtu;
+
+                /* TODO: size buffers correctly in this case. */
+                if (dev->mtu > ETH_DATA_LEN)
+                        vi->big_packets = true;
         }
 
         if (vi->any_header_sg)
@@ -2544,6 +2566,7 @@ static struct virtio_driver virtio_net_driver = {
         .driver.name =  KBUILD_MODNAME,
         .driver.owner = THIS_MODULE,
         .id_table =     id_table,
+        .validate =     virtnet_validate,
         .probe =        virtnet_probe,
         .remove =       virtnet_remove,
         .config_changed = virtnet_config_changed,