linux-kernel - [PATCH net] vsock/virtio: update credit only if socket is not closed

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Date:   Mon,  8 Feb 2021 15:44:54 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     kuba@...nel.org
Cc:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Asias He <asias@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.vnet.ibm.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Stefano Garzarella <sgarzare@...hat.com>
Subject: [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@...hat.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