Re: [PATCH] virtio-net: check the existence of peer before accesing its config

[Jason Wang <jasowang@redhat.com>]

On 2020/7/27 下午6:13, Michael S. Tsirkin wrote:
> On Mon, Jul 27, 2020 at 11:53:22AM +0200, Cornelia Huck wrote:
>> On Mon, 27 Jul 2020 05:41:17 -0400
>> "Michael S. Tsirkin" <mst@redhat.com> wrote:
>>
>>> On Mon, Jul 27, 2020 at 03:43:28PM +0800, Jason Wang wrote:
>>>> We try to get config from peer unconditionally which may lead NULL
>>>> pointer dereference. Add a check before trying to access the config.
>>>>
>>>> Fixes: 108a64818e69b ("vhost-vdpa: introduce vhost-vdpa backend")
>>>> Cc: Cindy Lu <lulu@redhat.com>
>>>> Tested-by: Cornelia Huck <cohuck@redhat.com>
>>>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>>> I am a bit lost here. Isn't this invoked
>>> when guest attempts to read the config?
>>> With no peer, what do we return to guest?
>> Same as with a non-vdpa peer? It's the dereference that needs to be
>> guarded.
> So vdpa has a GET_CONFIG ioctl which to me hints that a peer needs to be
> notified on get config calls.
> If we return config from qemu memory here, then I guess we
> need to call GET_CONFIG on connect and validate it -
> does this make sense?
>
> Cindy, Jason?


For "connect" you meant connecting virtio-net to its peer (vDPA)? AFAIK, 
if we start with no peer, there's no way to set a peer afterwards.

Thanks


>
>>> A code comment might be helpful here.
>>>
>>>> ---
>>>>   hw/net/virtio-net.c | 22 +++++++++++-----------
>>>>   1 file changed, 11 insertions(+), 11 deletions(-)