Re: [PATCH v2] virtio_vsock: Fix race condition in virtio_transport_recv_pkt

[Stefano Garzarella <sgarzare@xxxxxxxxxx>]

On Fri, Jun 05, 2020 at 02:10:49PM +0000, Sasha Levin wrote:
> Hi
> 
> [This is an automated email]
> 
> This commit has been processed because it contains a -stable tag.
> The stable tag indicates that it's relevant for the following trees: all
> 
> The bot has tested the following trees: v5.6.15, v5.4.43, v4.19.125, v4.14.182, v4.9.225, v4.4.225.
> 
> v5.6.15: Build OK!
> v5.4.43: Build failed! Errors:
>     net/vmw_vsock/virtio_transport_common.c:1109:40: error: ???????????????t?????????????????? undeclared (first use in this function); did you mean ???????????????tm???????????????????
>     net/vmw_vsock/virtio_transport_common.c:1109:9: error: too many arguments to function ???????????????virtio_transport_reset_no_sock??????????????????
> 
> v4.19.125: Build failed! Errors:
>     net/vmw_vsock/virtio_transport_common.c:1042:40: error: ???????????????t?????????????????? undeclared (first use in this function); did you mean ???????????????tm???????????????????
>     net/vmw_vsock/virtio_transport_common.c:1042:9: error: too many arguments to function ???????????????virtio_transport_reset_no_sock??????????????????
> 
> v4.14.182: Build failed! Errors:
>     net/vmw_vsock/virtio_transport_common.c:1038:40: error: ???????????????t?????????????????? undeclared (first use in this function); did you mean ???????????????tm???????????????????
>     net/vmw_vsock/virtio_transport_common.c:1038:9: error: too many arguments to function ???????????????virtio_transport_reset_no_sock??????????????????
> 
> v4.9.225: Build failed! Errors:
>     net/vmw_vsock/virtio_transport_common.c:968:40: error: ???????????????t?????????????????? undeclared (first use in this function); did you mean ???????????????tm???????????????????
>     net/vmw_vsock/virtio_transport_common.c:968:9: error: too many arguments to function ???????????????virtio_transport_reset_no_sock??????????????????
> 
> v4.4.225: Failed to apply! Possible dependencies:
>     06a8fc78367d ("VSOCK: Introduce virtio_vsock_common.ko")
> 
> 
> NOTE: The patch will not be queued to stable trees until it is upstream.
> 
> How should we proceed with this patch?

I think we can simply remove the 't' from virtio_transport_reset_no_sock(),
the following patch should work:

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index fb2060dffb0a..17f4c93f5e75 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -1104,6 +1104,14 @@ void virtio_transport_recv_pkt(struct virtio_vsock_pkt *pkt)

        lock_sock(sk);

+       /* Check if sk has been released before lock_sock */
+       if (sk->sk_shutdown == SHUTDOWN_MASK) {
+               (void)virtio_transport_reset_no_sock(pkt);
+               release_sock(sk);
+               sock_put(sk);
+               goto free_pkt;
+       }
+
        /* Update CID in case it has changed after a transport reset event */
        vsk->local_addr.svm_cid = dst.svm_cid;

Thanks,
Stefano