linux-kernel - Re: [PATCH] io_uring: gate personality per opcode to fix TOCTOU check in io_msg_ring

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Message-ID: <cea5285e-061b-4e5e-8c06-82461e8eeb62@kernel.dk>
Date: Sun, 25 Jan 2026 07:16:43 -0700
From: Jens Axboe <axboe@...nel.dk>
To: clingfei <clf700383@...il.com>
Cc: io-uring@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] io_uring: gate personality per opcode to fix TOCTOU check
 in io_msg_ring_prep

On 1/25/26 12:53 AM, clingfei wrote:
> From: Cheng Lingfei <clf700383@...il.com>
> 
> Add allow_personality io_issue_def and reject personality use in
> io_init_req for opcodes that do not permit it. This fixes a TOCTOU
> window in the prior implementation: userspace could race-update
> sqe->personality and bypass the __io_msg_ring_prep personality check.

Please do detail what the bug is here, this looks like some kind of
AI hallucination. The check in msg_ring prep exists just to reject
commands with it set, for future expansion. The only thing that
matters is the ordering and use in io_init_req(), which is fine.

-- 
Jens Axboe