[PATCH] vhost: fix null pointer dereference

[PATCH] vhost: fix null pointer dereference

[Jiayu Hu]

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;
+
 	ret = vq->async->pkts_inflight_n;
 	rte_spinlock_unlock(&vq->access_lock);
 
-- 
2.25.1

Re: [PATCH] vhost: fix null pointer dereference

[David Marchand]

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

Re: [PATCH] vhost: fix null pointer dereference

[Maxime Coquelin]

HI Jiayu,

On 3/28/22 09:04, David Marchand wrote:
> 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.

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

RE: [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@redhat.com>
> Sent: Wednesday, June 1, 2022 3:58 PM
> To: Hu, Jiayu <jiayu.hu@intel.com>
> Cc: dev <dev@dpdk.org>; dpdk stable <stable@dpdk.org>; David Marchand
> <david.marchand@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@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.
> 
> 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