virtio-net: Fix DMA-from-the-stack in virtnet_set_mac_address()

With CONFIG_VMAP_STACK=y, virtnet_set_mac_address() can be passed a
pointer to the stack and it will OOPS.  Copy the address to the heap
to prevent the crash.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Laura Abbott <labbott@redhat.com>
Reported-by: zbyszek@in.waw.pl
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 5 deletions

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 7276d5a95bd0..cbf1c613c67a 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -969,12 +969,17 @@ static int virtnet_set_mac_address(struct net_device *dev, void *p)
         struct virtnet_info *vi = netdev_priv(dev);
         struct virtio_device *vdev = vi->vdev;
         int ret;
-        struct sockaddr *addr = p;
+        struct sockaddr *addr;
         struct scatterlist sg;
 
-        ret = eth_prepare_mac_addr_change(dev, p);
+        addr = kmalloc(sizeof(*addr), GFP_KERNEL);
+        if (!addr)
+                return -ENOMEM;
+        memcpy(addr, p, sizeof(*addr));
+
+        ret = eth_prepare_mac_addr_change(dev, addr);
         if (ret)
-                return ret;
+                goto out;
 
         if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_MAC_ADDR)) {
                 sg_init_one(&sg, addr->sa_data, dev->addr_len);
@@ -982,7 +987,8 @@ static int virtnet_set_mac_address(struct net_device *dev, void *p)
                                           VIRTIO_NET_CTRL_MAC_ADDR_SET, &sg)) {
                         dev_warn(&vdev->dev,
                                  "Failed to set mac address by vq command.\n");
-                        return -EINVAL;
+                        ret = -EINVAL;
+                        goto out;
                 }
         } else if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC) &&
                    !virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) {
@@ -996,8 +1002,11 @@ static int virtnet_set_mac_address(struct net_device *dev, void *p)
         }
 
         eth_commit_mac_addr_change(dev, p);
+        ret = 0;
 
-        return 0;
+out:
+        kfree(addr);
+        return ret;
 }
 
 static struct rtnl_link_stats64 *virtnet_stats(struct net_device *dev,