linux-kernel - Re: [PATCH] vdpa/mlx5: fix param validation in mlx5_vdpa_get

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Date:   Tue, 9 Feb 2021 10:00:14 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Eli Cohen <elic@...dia.com>
Cc:     virtualization@...ts.linux-foundation.org,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Parav Pandit <parav@...dia.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vdpa/mlx5: fix param validation in mlx5_vdpa_get_config()

On Tue, Feb 09, 2021 at 07:43:02AM +0200, Eli Cohen 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")
>> Cc: stable@...r.kernel.org
>> Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
>
>Acked-by: Eli Cohen <elic@...dia.com>
>
>BTW, same error in vdpa_sim you may want to fix.
>

Commit 65b709586e22 ("vdpa_sim: add get_config callback in 
vdpasim_dev_attr") unintentionally solved it.

Since it's a simulator, maybe we can avoid solving it in the stable 
branches. Or does it matter?

Thanks,
Stefano

>> ---
>>  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);
>>  }
>>
>> --
>> 2.29.2
>>
>