netdev - [PATCH] net/vmw_vsock: improve locking in vsock_connect

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Message-ID: <trinity-f8e0937a-cf0e-4d80-a76e-d9a958ba3ef1-1612535522360@3c-app-gmx-bap12>
Date:   Fri, 5 Feb 2021 15:32:02 +0100
From:   Norbert Slusarek <nslusarek@....net>
To:     sgarzare@...hat.com, kuba@...nel.org, alex.popov@...ux.com,
        eric.dumazet@...il.com
Cc:     netdev@...r.kernel.org
Subject: [PATCH] net/vmw_vsock: improve locking in vsock_connect_timeout()

From: Norbert Slusarek <nslusarek@....net>
Date: Fri, 5 Feb 2021 13:14:05 +0100
Subject: [PATCH] net/vmw_vsock: improve locking in vsock_connect_timeout()

A possible locking issue in vsock_connect_timeout() was recognized by
Eric Dumazet which might cause a null pointer dereference in
vsock_transport_cancel_pkt(). This patch assures that
vsock_transport_cancel_pkt() will be called within the lock, so a race
condition won't occur which could result in vsk->transport to be set to NULL.

Fixes: 380feae0def7 ("vsock: cancel packets when failing to connect")
Reported-by: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: Norbert Slusarek <nslusarek@....net>
---
 net/vmw_vsock/af_vsock.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 6894f21dc147..ad7dd9d93b5b 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1243,7 +1243,6 @@ static void vsock_connect_timeout(struct work_struct *work)
 {
 	struct sock *sk;
 	struct vsock_sock *vsk;
-	int cancel = 0;

 	vsk = container_of(work, struct vsock_sock, connect_work.work);
 	sk = sk_vsock(vsk);
@@ -1254,11 +1253,9 @@ static void vsock_connect_timeout(struct work_struct *work)
 		sk->sk_state = TCP_CLOSE;
 		sk->sk_err = ETIMEDOUT;
 		sk->sk_error_report(sk);
-		cancel = 1;
+		vsock_transport_cancel_pkt(vsk);
 	}
 	release_sock(sk);
-	if (cancel)
-		vsock_transport_cancel_pkt(vsk);

 	sock_put(sk);
 }
--
2.30.0