netdev - [PATCH AUTOSEL 4.9 30/34] vhost/vsock: fix reset orphans race with close timeout

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Message-Id: <20181213043200.76295-30-sashal@kernel.org>
Date:   Wed, 12 Dec 2018 23:31:56 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Stefan Hajnoczi <stefanha@...hat.com>,
        Graham Whaley <graham.whaley@...il.com>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Sasha Levin <sashal@...nel.org>, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.9 30/34] vhost/vsock: fix reset orphans race with close timeout

From: Stefan Hajnoczi <stefanha@...hat.com>

[ 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@...ami.net>
Cc: Graham Whaley <graham.whaley@...il.com>
Signed-off-by: Stefan Hajnoczi <stefanha@...hat.com>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.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 0ec970ca64ce..5d77a7491edb 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -551,13 +551,21 @@ 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