linux-kernel - Re: [PATCH v2] vduse: Validate vq_num in vduse_validate

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Message-ID: <Y4SUOPX2WRFiuB7n@kadam>
Date:   Mon, 28 Nov 2022 13:58:00 +0300
From:   Dan Carpenter <error27@...il.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>,
        harshit.m.mogalapalli@...il.com,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Xie Yongji <xieyongji@...edance.com>,
        Gautam Dawar <gautam.dawar@...inx.com>,
        Parav Pandit <parav@...dia.com>, Eli Cohen <elic@...dia.com>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] vduse: Validate vq_num in vduse_validate_config()

On Mon, Nov 28, 2022 at 11:53:12AM +0100, Stefano Garzarella wrote:
> On Mon, Nov 28, 2022 at 12:36:26AM -0800, Harshit Mogalapalli wrote:
> > Add a limit to 'config->vq_num' which is user controlled data which
> > comes from an vduse_ioctl to prevent large memory allocations.
> > 
> > This is found using static analysis with smatch.
> > 
> > Suggested-by: Michael S. Tsirkin <mst@...hat.com>
> > Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
> > ---
> > v1->v2: Change title of the commit and description, add a limit to
> > 	vq_num.
> > 
> > Note: I think here 0xffff is the max size of vring =  no: of vqueues.
> > Only compile and boot tested.
> > ---
> > drivers/vdpa/vdpa_user/vduse_dev.c | 3 +++
> > 1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> > index 35dceee3ed56..31017ebc4d7c 100644
> > --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> > @@ -1440,6 +1440,9 @@ static bool vduse_validate_config(struct vduse_dev_config *config)
> > 	if (config->config_size > PAGE_SIZE)
> > 		return false;
> > 
> > +	if (config->vq_num > 0xffff)
> 
> What about using U16_MAX here?

Where is the ->vq_num stored in a u16?  I looked for this but didn't
see it.

regards,
dan carpenter