From: "Michael S. Tsirkin" <mst@redhat.com>
To: Jason Wang <jasowang@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org
Subject: Re: [RFC PATCH untested] vhost: block speculation of translated descriptors
Date: Tue, 10 Sep 2019 02:48:55 -0400 [thread overview]
Message-ID: <20190910024814-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <9ab48e0f-50a9-bed4-1801-73c37a7da27c@redhat.com>
On Tue, Sep 10, 2019 at 09:52:10AM +0800, Jason Wang wrote:
>
> On 2019/9/9 下午10:45, Michael S. Tsirkin wrote:
> > On Mon, Sep 09, 2019 at 03:19:55PM +0800, Jason Wang wrote:
> > > On 2019/9/8 下午7:05, Michael S. Tsirkin wrote:
> > > > iovec addresses coming from vhost are assumed to be
> > > > pre-validated, but in fact can be speculated to a value
> > > > out of range.
> > > >
> > > > Userspace address are later validated with array_index_nospec so we can
> > > > be sure kernel info does not leak through these addresses, but vhost
> > > > must also not leak userspace info outside the allowed memory table to
> > > > guests.
> > > >
> > > > Following the defence in depth principle, make sure
> > > > the address is not validated out of node range.
> > > >
> > > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > > > ---
> > > > drivers/vhost/vhost.c | 4 +++-
> > > > 1 file changed, 3 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> > > > index 5dc174ac8cac..0ee375fb7145 100644
> > > > --- a/drivers/vhost/vhost.c
> > > > +++ b/drivers/vhost/vhost.c
> > > > @@ -2072,7 +2072,9 @@ static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
> > > > size = node->size - addr + node->start;
> > > > _iov->iov_len = min((u64)len - s, size);
> > > > _iov->iov_base = (void __user *)(unsigned long)
> > > > - (node->userspace_addr + addr - node->start);
> > > > + (node->userspace_addr +
> > > > + array_index_nospec(addr - node->start,
> > > > + node->size));
> > > > s += size;
> > > > addr += size;
> > > > ++ret;
> > >
> > > I've tried this on Kaby Lake smap off metadata acceleration off using
> > > testpmd (virtio-user) + vhost_net. I don't see obvious performance
> > > difference with TX PPS.
> > >
> > > Thanks
> > Should I push this to Linus right now then? It's a security thing so
> > maybe we better do it ASAP ... what's your opinion?
>
>
> Yes, you can.
>
> Acked-by: Jason Wang <jasowang@redhat.com>
And should I include
Tested-by: Jason Wang <jasowang@redhat.com>
?
>
>
> >
next prev parent reply other threads:[~2019-09-10 6:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-08 11:05 [RFC PATCH untested] vhost: block speculation of translated descriptors Michael S. Tsirkin
2019-09-09 7:19 ` Jason Wang
2019-09-09 14:45 ` Michael S. Tsirkin
2019-09-10 1:52 ` Jason Wang
2019-09-10 6:48 ` Michael S. Tsirkin [this message]
2019-09-10 7:28 ` Jason Wang
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