Re: [dpdk-dev] [PATCH 1/3] vhost: fix dead loop in enqueue path

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 01/22/2017 09:46 AM, Yuanhan Liu wrote:
> If a malicious guest forges a dead loop desc chain (let desc->next point
> to itself) and desc->len is zero, this could lead to a dead loop in
> copy_mbuf_to_desc(following is a simplified code to show this issue
> clearly):
>
>     while (mbuf_is_not_totally_consumed) {
>         if (desc_avail == 0) {
>             desc = &descs[desc->next];
>             desc_avail = desc->len;
>         }
>
>         COPY(desc, mbuf, desc_avail);
>     }
>
> I have actually fixed a same issue before: a436f53ebfeb ("vhost: avoid
> dead loop chain"); it fixes the dequeue path though, leaving the enqueue
> path still vulnerable.
>
> The fix is the same. Add a var nr_desc to avoid the dead loop.
>
> Fixes: f1a519ad981c ("vhost: fix enqueue/dequeue to handle chained vring descriptors")
>
> Cc: stable@dpdk.org
> Reported-by: Xieming Katty <katty.xieming@huawei.com>
> Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> ---
>  lib/librte_vhost/virtio_net.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Thanks for the fix:
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

  - Maxime