vhost:fix crash on port deletion and VM shutdown at same time

  The vhost_user_read_cb() and rte_vhost_driver_unregister() can be
called at the same time by 2 threads. Eg thread1 calls vhost_user_read_cb()
and removes the vsocket from conn_list, then thread2 calls
rte_vhost_driver_unregister() and frees the vsocket since it is NOT in the
conn_list. So thread1 will access invalid memory when trying to reconnect.

The fix is to move the "removing of vsocket from conn_list" to end of the
vhost_user_read_cb(), then avoid the race condition.

The core trace is
Program terminated with signal 11, Segmentation fault.

Signed-off-by: Zhike Wang <wangzhike@jd.com>
---
 lib/librte_vhost/socket.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)
  

On 1/16/20 3:07 AM, Zhike Wang wrote:
> The vhost_user_read_cb() and rte_vhost_driver_unregister() can be
> called at the same time by 2 threads. Eg thread1 calls vhost_user_read_cb()
> and removes the vsocket from conn_list, then thread2 calls
> rte_vhost_driver_unregister() and frees the vsocket since it is NOT in the
> conn_list. So thread1 will access invalid memory when trying to reconnect.
> 
> The fix is to move the "removing of vsocket from conn_list" to end of the
> vhost_user_read_cb(), then avoid the race condition.
> 
> The core trace is
> Program terminated with signal 11, Segmentation fault.

Need to add the Fixes tag;

Fixes: af1475918124 ("vhost: introduce API to start a specific driver")
Cc: stable@dpdk.org

> Signed-off-by: Zhike Wang <wangzhike@jd.com>
> ---
>  lib/librte_vhost/socket.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c
> index ebb2ff6..01a9dec 100644
> --- a/lib/librte_vhost/socket.c
> +++ b/lib/librte_vhost/socket.c
> @@ -318,16 +318,16 @@ struct vhost_user {
>  
>  		vhost_destroy_device(conn->vid);
>  
> +		if (vsocket->reconnect) {
> +			create_unix_socket(vsocket);
> +			vhost_user_start_client(vsocket);
> +		}
> +
>  		pthread_mutex_lock(&vsocket->conn_mutex);
>  		TAILQ_REMOVE(&vsocket->conn_list, conn, next);
>  		pthread_mutex_unlock(&vsocket->conn_mutex);
>  
>  		free(conn);
> -
> -		if (vsocket->reconnect) {
> -			create_unix_socket(vsocket);
> -			vhost_user_start_client(vsocket);
> -		}
>  	}
>  }
>  
> 

No need to send v2, I'll add it when applying to my tree.

Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

Thanks,
Maxime
  

On 1/16/20 3:07 AM, Zhike Wang wrote:
> The vhost_user_read_cb() and rte_vhost_driver_unregister() can be
> called at the same time by 2 threads. Eg thread1 calls vhost_user_read_cb()
> and removes the vsocket from conn_list, then thread2 calls
> rte_vhost_driver_unregister() and frees the vsocket since it is NOT in the
> conn_list. So thread1 will access invalid memory when trying to reconnect.
> 
> The fix is to move the "removing of vsocket from conn_list" to end of the
> vhost_user_read_cb(), then avoid the race condition.
> 
> The core trace is
> Program terminated with signal 11, Segmentation fault.
> 
> Signed-off-by: Zhike Wang <wangzhike@jd.com>
> ---
>  lib/librte_vhost/socket.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)

Applied to dpdk-next-virtio tree.

Thanks,
Maxime