[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 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