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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,
        Maximilian Riemensberger <riemensberger@cadami.net>,
        Graham Whaley <graham.whaley@gmail.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 56/61] vhost/vsock: fix reset orphans race with close timeout
Date:   Thu, 20 Dec 2018 10:18:56 +0100
Message-Id: <20181220085846.019914336@linuxfoundation.org>
In-Reply-To: <20181220085843.743900603@linuxfoundation.org>
References: <20181220085843.743900603@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit c38f57da428b033f2721b611d84b1f40bde674a8 ]

If a local process has closed a connected socket and hasn't received a
RST packet yet, then the socket remains in the table until a timeout
expires.

When a vhost_vsock instance is released with the timeout still pending,
the socket is never freed because vhost_vsock has already set the
SOCK_DONE flag.

Check if the close timer is pending and let it close the socket.  This
prevents the race which can leak sockets.

Reported-by: Maximilian Riemensberger <riemensberger@cadami.net>
Cc: Graham Whaley <graham.whaley@gmail.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/vhost/vsock.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index f800f89068db..46f966d7c328 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -559,13 +559,21 @@ static void vhost_vsock_reset_orphans(struct sock *sk)
 	 * executing.
 	 */
 
-	if (!vhost_vsock_get(vsk->remote_addr.svm_cid)) {
-		sock_set_flag(sk, SOCK_DONE);
-		vsk->peer_shutdown = SHUTDOWN_MASK;
-		sk->sk_state = SS_UNCONNECTED;
-		sk->sk_err = ECONNRESET;
-		sk->sk_error_report(sk);
-	}
+	/* If the peer is still valid, no need to reset connection */
+	if (vhost_vsock_get(vsk->remote_addr.svm_cid))
+		return;
+
+	/* If the close timeout is pending, let it expire.  This avoids races
+	 * with the timeout callback.
+	 */
+	if (vsk->close_work_scheduled)
+		return;
+
+	sock_set_flag(sk, SOCK_DONE);
+	vsk->peer_shutdown = SHUTDOWN_MASK;
+	sk->sk_state = SS_UNCONNECTED;
+	sk->sk_err = ECONNRESET;
+	sk->sk_error_report(sk);
 }
 
 static int vhost_vsock_dev_release(struct inode *inode, struct file *file)
-- 
2.19.1