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

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Date:   Fri, 12 May 2023 12:51:21 +0000
From:   Dragos Tatulea <dtatulea@...dia.com>
To:     Feng Liu <feliu@...dia.com>, "mst@...hat.com" <mst@...hat.com>
CC:     "xieyongji@...edance.com" <xieyongji@...edance.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        Gal Pressman <gal@...dia.com>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "xuanzhuo@...ux.alibaba.com" <xuanzhuo@...ux.alibaba.com>
Subject: Re: [PATCH] virtio-vdpa: Fix unchecked call to NULL set_vq_affinity

On Thu, 2023-05-04 at 14:51 -0400, Michael S. Tsirkin wrote:
> 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?
> 
> > > 
set_vq_affinity is optional so it's not an error if the op is not implemented.

Is there anything else that needs to be done for this fix?

Thanks,
Dragos