[PATCH] net/vmw_vsock: improve locking in vsock_connect_timeout()

From: Norbert Slusarek <redacted>
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 <redacted>
Signed-off-by: Norbert Slusarek <redacted>
---
 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

On Fri, Feb 05, 2021 at 03:32:02PM +0100, Norbert Slusarek wrote:

From: Norbert Slusarek <redacted>
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")

I have a doubt about the tag to use, since until we introduced 
transports in commit c0cfa2d8a788 ("vsock: add multi-transports 
support") this issue didn't cause many problems.

But it must be said that in the commit 380feae0def7 ("vsock: cancel 
packets when failing to connect") the vsock_transport_cancel_pkt() was 
called with the lock held in vsock_stream_connect() and without lock in 
vsock_connect_timeout(), so maybe this tag is okay.

Anyway, the patch LGTM:

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

On Fri, 5 Feb 2021 18:19:51 +0100 Stefano Garzarella wrote:

On Fri, Feb 05, 2021 at 03:32:02PM +0100, Norbert Slusarek wrote:

quoted

From: Norbert Slusarek <redacted>
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")  

I have a doubt about the tag to use, since until we introduced 
transports in commit c0cfa2d8a788 ("vsock: add multi-transports 
support") this issue didn't cause many problems.

But it must be said that in the commit 380feae0def7 ("vsock: cancel 
packets when failing to connect") the vsock_transport_cancel_pkt() was 
called with the lock held in vsock_stream_connect() and without lock in 
vsock_connect_timeout(), so maybe this tag is okay.

Anyway, the patch LGTM:

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

Applied, thanks!