[PATCH] vhost: fix null pointer dereference

[Hu, Jiayu]

Hi Maxime,

This issue has fixed in https://patches.dpdk.org/project/dpdk/patch/20220411110013.18624-4-david.marchand@redhat.com/.

Thanks,
Jiayu

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin at redhat.com>
> Sent: Wednesday, June 1, 2022 3:58 PM
> To: Hu, Jiayu <jiayu.hu at intel.com>
> Cc: dev <dev at dpdk.org>; dpdk stable <stable at dpdk.org>; David Marchand
> <david.marchand at redhat.com>
> Subject: Re: [PATCH] vhost: fix null pointer dereference
> 
> HI Jiayu,
> 
> On 3/28/22 09:04, David Marchand wrote:
> > On Mon, Mar 28, 2022 at 4:08 AM Jiayu Hu <jiayu.hu at intel.com> wrote:
> >>
> >> NULL check for vq->async must be protected by lock. Otherwise, it is
> >> possible that the data plane thread dereferences vq->async with NULL
> >> value, since the control plane thread is freeing vq->async.
> >>
> >> Fixes: ee8024b3d4ad (vhost: move async data in dedicated structure)
> >> Cc: stable at dpdk.org
> >>
> >> Signed-off-by: Jiayu Hu <jiayu.hu at intel.com>
> >> ---
> >>   lib/vhost/vhost.c | 6 +++---
> >>   1 file changed, 3 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c index
> >> bc88148347..7f60c2824f 100644
> >> --- a/lib/vhost/vhost.c
> >> +++ b/lib/vhost/vhost.c
> >> @@ -1887,9 +1887,6 @@ rte_vhost_async_get_inflight(int vid, uint16_t
> queue_id)
> >>          if (vq == NULL)
> >>                  return ret;
> >>
> >> -       if (!vq->async)
> >> -               return ret;
> >> -
> >>          if (!rte_spinlock_trylock(&vq->access_lock)) {
> >>                  VHOST_LOG_CONFIG(DEBUG,
> >>                          "(%s) failed to check in-flight packets.
> >> virtqueue busy.\n", @@ -1897,6 +1894,9 @@
> rte_vhost_async_get_inflight(int vid, uint16_t queue_id)
> >>                  return ret;
> >>          }
> >>
> >> +       if (!vq->async)
> >> +               return ret;
> >
> > Lock is still taken at this point.
> >
> > FYI, I'll post a series to instrument locks in vhost, soon.
> 
> Could you please send a v2 which does not return with the lock taken?
> 
> >> +
> >>          ret = vq->async->pkts_inflight_n;
> >>          rte_spinlock_unlock(&vq->access_lock);
> >>
> >
> >
> 
> Thanks,
> Maxime