linux-kernel - Re: [syzbot] [io-uring?] INFO: task hung in io_uring_del_tctx

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Message-ID: <aQAIR9DQwiySzEj-@kbusch-mbp>
Date: Mon, 27 Oct 2025 18:03:19 -0600
From: Keith Busch <kbusch@...nel.org>
To: Jens Axboe <axboe@...nel.dk>
Cc: syzbot <syzbot+10a9b495f54a17b607a6@...kaller.appspotmail.com>,
	io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [io-uring?] INFO: task hung in io_uring_del_tctx_node
 (5)

On Mon, Oct 27, 2025 at 05:15:56PM -0600, Jens Axboe wrote:
> >> 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 :-)

Yeah, patch looks good. I plowed through this thinking the mixed CQE
showed the way, but didn't appreciate the subtle differences on the
submission side.