netdev - RE: [PATCH] virtio-net: fix the kzalloc/kfree mismatch problem

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Date:   Mon, 24 May 2021 01:48:53 +0000
From:   "Guodeqing (A)" <geffrey.guo@...wei.com>
To:     Max Gurtovoy <mgurtovoy@...dia.com>,
        "mst@...hat.com" <mst@...hat.com>
CC:     "jasowang@...hat.com" <jasowang@...hat.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH] virtio-net: fix the kzalloc/kfree mismatch problem



> -----Original Message-----
> From: Max Gurtovoy [mailto:mgurtovoy@...dia.com]
> Sent: Sunday, May 23, 2021 15:25
> To: Guodeqing (A) <geffrey.guo@...wei.com>; mst@...hat.com
> Cc: jasowang@...hat.com; davem@...emloft.net; kuba@...nel.org;
> virtualization@...ts.linux-foundation.org; netdev@...r.kernel.org
> Subject: Re: [PATCH] virtio-net: fix the kzalloc/kfree mismatch problem
> 
> 
> On 5/22/2021 11:02 AM, guodeqing wrote:
> > If the virtio_net device does not suppurt the ctrl queue feature, the
> > vi->ctrl was not allocated, so there is no need to free it.
> 
> you don't need this check.
> 
> from kfree doc:
> 
> "If @objp is NULL, no operation is performed."
> 
> This is not a bug. I've set vi->ctrl to be NULL in case !vi->has_cvq.
> 
> 
  yes,  this is not a bug, the patch is just a optimization, because the vi->ctrl maybe 
  be freed which  was not allocated, this may give people a misunderstanding. 
  Thanks.
> >
> > Here I adjust the initialization sequence and the check of vi->has_cvq
> > to slove this problem.
> >
> > Fixes: 	122b84a1267a ("virtio-net: don't allocate control_buf if not
> supported")
> > Signed-off-by: guodeqing <geffrey.guo@...wei.com>
> > ---
> >   drivers/net/virtio_net.c | 20 ++++++++++----------
> >   1 file changed, 10 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index
> > 9b6a4a875c55..894f894d3a29 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -2691,7 +2691,8 @@ static void virtnet_free_queues(struct
> > virtnet_info *vi)
> >
> >   	kfree(vi->rq);
> >   	kfree(vi->sq);
> > -	kfree(vi->ctrl);
> > +	if (vi->has_cvq)
> > +		kfree(vi->ctrl);
> >   }
> >
> >   static void _free_receive_bufs(struct virtnet_info *vi) @@ -2870,13
> > +2871,6 @@ static int virtnet_alloc_queues(struct virtnet_info *vi)
> >   {
> >   	int i;
> >
> > -	if (vi->has_cvq) {
> > -		vi->ctrl = kzalloc(sizeof(*vi->ctrl), GFP_KERNEL);
> > -		if (!vi->ctrl)
> > -			goto err_ctrl;
> > -	} else {
> > -		vi->ctrl = NULL;
> > -	}
> >   	vi->sq = kcalloc(vi->max_queue_pairs, sizeof(*vi->sq), GFP_KERNEL);
> >   	if (!vi->sq)
> >   		goto err_sq;
> > @@ -2884,6 +2878,12 @@ static int virtnet_alloc_queues(struct
> virtnet_info *vi)
> >   	if (!vi->rq)
> >   		goto err_rq;
> >
> > +	if (vi->has_cvq) {
> > +		vi->ctrl = kzalloc(sizeof(*vi->ctrl), GFP_KERNEL);
> > +		if (!vi->ctrl)
> > +			goto err_ctrl;
> > +	}
> > +
> >   	INIT_DELAYED_WORK(&vi->refill, refill_work);
> >   	for (i = 0; i < vi->max_queue_pairs; i++) {
> >   		vi->rq[i].pages = NULL;
> > @@ -2902,11 +2902,11 @@ static int virtnet_alloc_queues(struct
> > virtnet_info *vi)
> >
> >   	return 0;
> >
> > +err_ctrl:
> > +	kfree(vi->rq);
> >   err_rq:
> >   	kfree(vi->sq);
> >   err_sq:
> > -	kfree(vi->ctrl);
> > -err_ctrl:
> >   	return -ENOMEM;
> >   }
> >