Re: [syzbot] [io-uring?] INFO: task hung in io_uring_del_tctx_node (5)

[Jens Axboe <axboe@kernel.dk>]

On 10/27/25 4:57 PM, Keith Busch wrote:
> On Mon, Oct 27, 2025 at 04:04:05PM -0600, Jens Axboe wrote:
>>
>> commit 1cba30bf9fdd6c982708f3587f609a30c370d889
>> Author: Keith Busch <kbusch@kernel.org>
>> Date:   Thu Oct 16 11:09:38 2025 -0700
>>
>>     io_uring: add support for IORING_SETUP_SQE_MIXED
>>
>> leaves fdinfo open up to being broken. Before, we had:
>>
>> sq_entries = min(sq_tail - sq_head, ctx->sq_entries);
>>
>> as a cap for the loop, now you just have:
>>
>> while (sq_head < sq_tail) {
>>
>> which seems like a bad idea. It's also missing an sq_head increment if
>> we hit this condition:
> 
> This would have to mean the application did an invalid head ring-wrap,
> right?

Right, it's a malicious use case. But you always have to be able to deal
with those, it's not like broken hardware in that sense.

> Regardless, I messed up and the wrong thing will happen here in
> that case as well as the one you mentioned.

Yep I think so too, was more interested in your opinion on the patch :-)

-- 
Jens Axboe