linux-kernel - Re: [PATCH] virtio-vdpa: Fix unchecked call to NULL set_vq

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Date:   Thu, 4 May 2023 18:47:29 -0400
From:   Feng Liu <feliu@...dia.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Dragos Tatulea <dtatulea@...dia.com>,
        Jason Wang <jasowang@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        Xie Yongji <xieyongji@...edance.com>,
        Gal Pressman <gal@...dia.com>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] virtio-vdpa: Fix unchecked call to NULL set_vq_affinity



On 2023-05-04 p.m.2:51, Michael S. Tsirkin wrote:
> External email: Use caution opening links or attachments
> 
> 
> On Thu, May 04, 2023 at 01:08:54PM -0400, Feng Liu wrote:
>>
>>
>> On 2023-05-04 a.m.9:50, Dragos Tatulea wrote:
>>> External email: Use caution opening links or attachments
>>>
>>>
>>> The referenced patch calls set_vq_affinity without checking if the op is
>>> valid. This patch adds the check.
>>>
>>> Fixes: 3dad56823b53 ("virtio-vdpa: Support interrupt affinity spreading mechanism")
>>> Reviewed-by: Gal Pressman <gal@...dia.com>
>>> Signed-off-by: Dragos Tatulea <dtatulea@...dia.com>
>>> ---
>>>    drivers/virtio/virtio_vdpa.c | 4 +++-
>>>    1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/virtio/virtio_vdpa.c b/drivers/virtio/virtio_vdpa.c
>>> index eb6aee8c06b2..989e2d7184ce 100644
>>> --- a/drivers/virtio/virtio_vdpa.c
>>> +++ b/drivers/virtio/virtio_vdpa.c
>>> @@ -385,7 +385,9 @@ static int virtio_vdpa_find_vqs(struct virtio_device *vdev, unsigned int nvqs,
>>>                           err = PTR_ERR(vqs[i]);
>>>                           goto err_setup_vq;
>>>                   }
>>> -               ops->set_vq_affinity(vdpa, i, &masks[i]);
>>> +
>>> +               if (ops->set_vq_affinity)
>>> +                       ops->set_vq_affinity(vdpa, i, &masks[i]);
>> if ops->set_vq_affinity is NULL, should give an error code to err, and
>> return err
> 
> Given we ignore return code, hardly seems like a critical thing to do.
> Is it really important? affinity is an optimization isn't it?
> 
Yes, it is an optimization, got it.

>>>           }
>>>
>>>           cb.callback = virtio_vdpa_config_cb;
>>> --
>>> 2.40.1
>>>
>