Re: [PATCH] vhost: fix null pointer dereference

[David Marchand <david.marchand@redhat.com>]

On Mon, Mar 28, 2022 at 4:08 AM Jiayu Hu <jiayu.hu@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@dpdk.org
>
> Signed-off-by: Jiayu Hu <jiayu.hu@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.

> +
>         ret = vq->async->pkts_inflight_n;
>         rte_spinlock_unlock(&vq->access_lock);
>


-- 
David Marchand