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

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Message-ID: <aP_48DOFFdm4kB7Q@kbusch-mbp>
Date: Mon, 27 Oct 2025 16:57:52 -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 04:04:05PM -0600, Jens Axboe wrote:
> 
> commit 1cba30bf9fdd6c982708f3587f609a30c370d889
> Author: Keith Busch <kbusch@...nel.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? Regardless, I messed up and the wrong thing will happen here in
that case as well as the one you mentioned.