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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Stefano Garzarella <sgarzare@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jakub Kicinski <kuba@kernel.org>
Subject: [PATCH 4.19 32/50] vsock/virtio: update credit only if socket is not closed
Date:   Mon, 22 Feb 2021 13:13:23 +0100
Message-Id: <20210222121025.947666099@linuxfoundation.org>
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From: Stefano Garzarella <sgarzare@redhat.com>

commit ce7536bc7398e2ae552d2fabb7e0e371a9f1fe46 upstream.

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@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://lore.kernel.org/r/20210208144454.84438-1-sgarzare@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/vmw_vsock/virtio_transport_common.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -1033,10 +1033,10 @@ void virtio_transport_recv_pkt(struct vi
 
 	vsk = vsock_sk(sk);
 
-	space_available = virtio_transport_space_update(sk, pkt);
-
 	lock_sock(sk);
 
+	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;