From: "Michael S. Tsirkin" <mst@redhat.com>
To: Stefano Garzarella <sgarzare@redhat.com>
Cc: Dan Carpenter <error27@gmail.com>,
Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>,
harshit.m.mogalapalli@gmail.com, Jason Wang <jasowang@redhat.com>,
Xie Yongji <xieyongji@bytedance.com>,
Gautam Dawar <gautam.dawar@xilinx.com>,
Parav Pandit <parav@nvidia.com>, Eli Cohen <elic@nvidia.com>,
virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] vduse: Validate vq_num in vduse_validate_config()
Date: Mon, 28 Nov 2022 08:10:09 -0500 [thread overview]
Message-ID: <20221128070238-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20221128111310.6exrqi26grwspqcz@sgarzare-redhat>
On Mon, Nov 28, 2022 at 12:13:10PM +0100, Stefano Garzarella wrote:
> On Mon, Nov 28, 2022 at 01:58:00PM +0300, Dan Carpenter wrote:
> > 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@redhat.com>
> > > > Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.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.
>
> I thought vq_num referred to the number of elements in the vq (like
> .get_vq_num_max), since this patch wants to limit to 0xffff.
>
> But it actually refers to the number of virtqueue, so @Harshit why do we
> limit it to 0xffff?
>
> Maybe we should explain it in the commit message or in a comment.
>
> Thanks,
> Stefano
This limit is somewhat arbitrary.
However, currently virtio pci and ccw are limited to a 16 bit vq number.
While MMIO isn't it is also isn't used with lots of VQs due to
current lack of support for per-vq interrupts.
Thus, the 0xffff limit on number of VQs corresponding
to a 16-bit VQ number seems sufficient for now.
Feel free to put the above in a code comment.
--
MST
prev parent reply other threads:[~2022-11-28 13:11 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-28 8:36 [PATCH v2] vduse: Validate vq_num in vduse_validate_config() Harshit Mogalapalli
2022-11-28 10:53 ` Stefano Garzarella
2022-11-28 10:58 ` Dan Carpenter
2022-11-28 11:13 ` Stefano Garzarella
2022-11-28 12:35 ` Harshit Mogalapalli
2022-11-28 13:10 ` Michael S. Tsirkin [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20221128070238-mutt-send-email-mst@kernel.org \
--to=mst@redhat.com \
--cc=elic@nvidia.com \
--cc=error27@gmail.com \
--cc=gautam.dawar@xilinx.com \
--cc=harshit.m.mogalapalli@gmail.com \
--cc=harshit.m.mogalapalli@oracle.com \
--cc=jasowang@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=parav@nvidia.com \
--cc=sgarzare@redhat.com \
--cc=virtualization@lists.linux-foundation.org \
--cc=xieyongji@bytedance.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).