linux-kernel - RE: [PATCH net-next v4] vsock/test: Add test for null ptr deref when transport changes

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Message-ID: <472a5d43-4905-4fa4-8750-733bb848410d@linux.ibm.com>
Date: Wed, 9 Jul 2025 09:54:03 -0500
From: Konstantin Shkolnyy <kshk@...ux.ibm.com>
To: mhal@...x.co, sgarzare@...hat.com
Cc: virtualization@...ts.linux.dev, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, v4bel@...ori.io, leonardi@...hat.com
Subject: RE: [PATCH net-next v4] vsock/test: Add test for null ptr deref when
 transport changes

I'm seeing a problem on s390 with the new "SOCK_STREAM transport change 
null-ptr-deref" test. Here is how it appears to happen:

test_stream_transport_change_client() spins for 2s and sends 70K+ 
CONTROL_CONTINUE messages to the "control" socket.

test_stream_transport_change_server() spins calling accept() because it 
keeps receiving CONTROL_CONTINUE.

When the client exits, the server has received just under 1K of those 
70K CONTROL_CONTINUE, so it calls accept() again but the client has 
exited, so accept() never returns and the server never exits.