Re: [PATCH] vsock: use sock_error() to consume sk_err after connect timeout

[Michal Luczaj <mhal@rbox.co>]

On 7/29/26 15:03, Stefano Garzarella wrote:
> On Wed, Jul 29, 2026 at 05:46:29PM +0800, Nguyen Dinh Phi [SG] wrote:
>> On 28/7/26 16:21, Stefano Garzarella wrote:
>>> On Fri, Jul 24, 2026 at 03:34:23PM +0800, Nguyen Dinh Phi [SG] wrote:
>>>> On 24/7/26 05:43, Michal Luczaj wrote:
>>>>> On 7/23/26 12:26, Nguyen Dinh Phi [SG] wrote:
>>>>>>>>>> ...
>>>>>>>>>> Yeah, we need to handle that part better, I think it's 
>>>>>>>>>> a leftover when
>>>>>>>>>> we generalized AF_VSOCK to support more transport than vmci.
>>>>>>>>
>>>>>>>> Speaking of leftovers, I have trouble understanding where 
>>>>>>>> does vsock set
>>>>>>>> sk_err on listener sockets anyway. If it doesn't, why vsock_accept()
>>>>>>>> checks for it?
>>>>>>>
>>>>>>> I can't also see where it can be set TBH. Should we remove it ?
>>>>>>
>>>>>> I couldn't find it for listener side too.
>>>>>
>>>>> Removing sk_err handling from vsock_accept() solves the problem, right?
>>>>>
>>>>> thanks,
>>>>> Michal
>>>>
>>>> Yes, confirmed, removing sk_err checks from vsock_accept() does 
>>>> solve the problem.
>>>
>>> Okay, so maybe better on going on this direction. WDYT?
>>>
>>> Stefano
>>>
>>
>> I'm still a bit concerned about how connect() and poll() interact 
>> here, even with the sk_err checks removed from vsock_accept().
>>
>> For example:
>> vsock_accept() now lets us reuse a socket whose connect() failed (call 
>> it r0) as syzbot reproducer does. After listen(), r0 becomes a 
>> listener (sk_state == TCP_LISTEN) and works correctly -- it accepts 
>> connections.
>>
>> But poll() on r0 still marks POLLERR, even though there is no error on 
>> that socket at that point.
>>
>> As I understand it, sk_err holds an error that has not yet been 
>> reported to userspace. In the blocking vsock_connect() case we have 
>> already read that error and returned it to the caller, so it is no 
>> longer pending
>> Shouldn't sk_err be consumed/cleared when vsock_connect() returns it 
>> to userspace?
> 
> Yeah, makes sense to me, I'll ack the v2.
> @Michal WDYT?

I'm worried this patch does not address the non-blocking connect() case.
Could vsock_connect_timeout() set `sk->sk_err = ETIMEDOUT` after connect()
returns?

> As cleanup (separate patch), should we remove the `sk_err` check in 
> vsock_accept() ?