Re: [PATCH] sunrpc: fix TLS connect_worker rpc_clnt lifetime UAF

[Chuck Lever <cel@kernel.org>]

On 3/11/26 10:18 AM, Benjamin Coddington wrote:
> On 9 Mar 2026, at 7:19, bsdhenrymartin@gmail.com wrote:

>> @@ -2805,7 +2811,11 @@ static void xs_connect(struct rpc_xprt *xprt, struct rpc_task *task)
>>         } else
>>                 dprintk("RPC:       xs_connect scheduled xprt %p\n", xprt);
>>
>> -       transport->clnt = task->tk_client;
>> +       if (transport->connect_worker.work.func == xs_tcp_tls_setup_socket) {
> 
> ^^ .. this seems a bit brittle..

This caught my eye as well.


> 
>> +               WARN_ON_ONCE(transport->clnt != NULL);
>> +               refcount_inc(&task->tk_client->cl_count);
>> +               transport->clnt = task->tk_client;
>> +       }
>>         queue_delayed_work(xprtiod_workqueue,
>>                         &transport->connect_worker,
>>                         delay);
> 
> This fix works and I think its great for stable:
> 
> Reviewed-by: Benjamin Coddington <bcodding@hammerspace.com>
> 
> But I think we ended up with this problem because we're re-using the
> rpc_clnt in order to set up the lower_transport, and maybe we don't have to
> actually mix those layers.
> 
> Chuck, Trond - can we use a "dummy" rpc_program to create the lower rpc_clnt,
> and keep the lifetime of the original rpc_clnt disconnected from the
> sock_xprt?  I can send a patch..

The upper/lower architecture was Trond's suggestion. I just implemented
it (poorly). Let's see whatcha got!


-- 
Chuck Lever