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SubjectRe: [PATCH] vdpa/mlx5: fix param validation in mlx5_vdpa_get_config()
On Tue, Feb 09, 2021 at 11:24:03AM +0800, Jason Wang wrote:
>On 2021/2/9 上午2:38, Michael S. Tsirkin wrote:
>>On Mon, Feb 08, 2021 at 05:17:41PM +0100, Stefano Garzarella wrote:
>>>It's legal to have 'offset + len' equal to
>>>sizeof(struct virtio_net_config), since 'ndev->config' is a
>>>'struct virtio_net_config', so we can safely copy its content under
>>>this condition.
>>>Fixes: 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices")
>>>Signed-off-by: Stefano Garzarella <>
>>> drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>>>index dc88559a8d49..10e9b09932eb 100644
>>>--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
>>>+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>>>@@ -1820,7 +1820,7 @@ static void mlx5_vdpa_get_config(struct vdpa_device *vdev, unsigned int offset,
>>> struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
>>> struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
>>>- if (offset + len < sizeof(struct virtio_net_config))
>>>+ if (offset + len <= sizeof(struct virtio_net_config))
>>> memcpy(buf, (u8 *)&ndev->config + offset, len);
>>> }
>>Actually first I am not sure we need these checks at all.
>>vhost_vdpa_config_validate already validates the values, right?
>I think they're working at different levels. There's no guarantee that
>vhost-vdpa is the driver for this vdpa device.

Maybe we can do these checks in the vdpa_get_config() helper and we can
also add a vdpa_set_config() to do the same.


>>Second, what will happen when we extend the struct and then
>>run new userspace on an old kernel? Looks like it will just
>>fail right? So what is the plan?
>In this case, get_config() should match the spec behaviour. That is to
>say the size of config space depends on the feature negotiated.
>> I think we should
>>allow a bigger size, and return the copied config size to userspace.

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