netdev - Re: [PATCH net-next v4] vsock/test: Add test for null ptr deref when transport changes

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Message-ID: <0ea1ac72-a914-4a64-b82e-39b78685f51a@linux.ibm.com>
Date: Wed, 9 Jul 2025 11:45:21 -0500
From: Konstantin Shkolnyy <kshk@...ux.ibm.com>
To: Luigi Leonardi <leonardi@...hat.com>
Cc: mhal@...x.co, sgarzare@...hat.com, virtualization@...ts.linux.dev,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org, v4bel@...ori.io
Subject: Re: [PATCH net-next v4] vsock/test: Add test for null ptr deref when
 transport changes

On 09-Jul-25 09:57, Luigi Leonardi wrote:
> Hi Konstantin,
> 
> On Wed, Jul 09, 2025 at 09:54:03AM -0500, Konstantin Shkolnyy wrote:
>> 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.
>>
> 
> Thanks for pointing this out!
> I had an offline discussion with Stefano about this issue.
> This patch[1] should address it.
> Please let us know if it works on s390 too.
> 
> Cheers,
> Luigi
> 
> [1]https://lore.kernel.org/netdev/20250708111701.129585-1- 
> sgarzare@...hat.com/
> 
I've run it 40 times with this patch, and it seems OK now. You can add 
my "Tested-by" if you wish.