Virtualization - Feb 2021 - [PATCH net] vsock/virtio: update credit only if socket is not closed

If the socket is closed or is being released, some resources used by
virtio_transport_space_update() such as 'vsk->trans' may be released.

To avoid a use after free bug we should only update the available credit
when we are sure the socket is still open and we have the lock held.

Fixes: 06a8fc78367d ("VSOCK: Introduce virtio_vsock_common.ko")
Signed-off-by: Stefano Garzarella <sgarzare at redhat.com>
---
 net/vmw_vsock/virtio_transport_common.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport_common.c
b/net/vmw_vsock/virtio_transport_common.c
index 5956939eebb7..e4370b1b7494 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -1130,8 +1130,6 @@ void virtio_transport_recv_pkt(struct virtio_transport *t,
 
 	vsk = vsock_sk(sk);
 
-	space_available = virtio_transport_space_update(sk, pkt);
-
 	lock_sock(sk);
 
 	/* Check if sk has been closed before lock_sock */
@@ -1142,6 +1140,8 @@ void virtio_transport_recv_pkt(struct virtio_transport *t,
 		goto free_pkt;
 	}
 
+	space_available = virtio_transport_space_update(sk, pkt);
+
 	/* Update CID in case it has changed after a transport reset event */
 	vsk->local_addr.svm_cid = dst.svm_cid;
 
-- 
2.29.2

On Mon, Feb 08, 2021 at 03:44:54PM +0100, Stefano Garzarella
wrote:
> If the socket is closed or is being released, some resources used by
> virtio_transport_space_update() such as 'vsk->trans' may be
released.
> 
> To avoid a use after free bug we should only update the available credit
> when we are sure the socket is still open and we have the lock held.
> 
> Fixes: 06a8fc78367d ("VSOCK: Introduce virtio_vsock_common.ko")
> Signed-off-by: Stefano Garzarella <sgarzare at redhat.com>
Acked-by: Michael S. Tsirkin <mst at redhat.com>

Probably stable material.
> ---
>  net/vmw_vsock/virtio_transport_common.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/vmw_vsock/virtio_transport_common.c
b/net/vmw_vsock/virtio_transport_common.c
> index 5956939eebb7..e4370b1b7494 100644
> --- a/net/vmw_vsock/virtio_transport_common.c
> +++ b/net/vmw_vsock/virtio_transport_common.c
> @@ -1130,8 +1130,6 @@ void virtio_transport_recv_pkt(struct
virtio_transport *t,
>  
>  	vsk = vsock_sk(sk);
>  
> -	space_available = virtio_transport_space_update(sk, pkt);
> -
>  	lock_sock(sk);
>  
>  	/* Check if sk has been closed before lock_sock */
> @@ -1142,6 +1140,8 @@ void virtio_transport_recv_pkt(struct
virtio_transport *t,
>  		goto free_pkt;
>  	}
>  
> +	space_available = virtio_transport_space_update(sk, pkt);
> +
>  	/* Update CID in case it has changed after a transport reset event */
>  	vsk->local_addr.svm_cid = dst.svm_cid;
>  
> -- 
> 2.29.2