linux-kernel - Re: [patch 02/20] posix-timers: Ensure timer ID search-loop limit is valid

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Message-ID: <877cth1xyd.ffs@tglx>
Date:   Tue, 09 May 2023 14:38:50 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        syzbot+5c54bd3eb218bb595aa9@...kaller.appspotmail.com,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        Michael Kerrisk <mtk.manpages@...il.com>
Subject: Re: [patch 02/20] posix-timers: Ensure timer ID search-loop limit
 is valid

On Tue, May 09 2023 at 11:42, Frederic Weisbecker wrote:
> On Sat, May 06, 2023 at 01:36:22AM +0200, Thomas Gleixner wrote:
>> Unless you think about the theoretical case of an unlimited number of
>> threads sharing the signal_struct which all concurrently try to allocate
>> a timer id and then releasing it immediately again (to avoid resource
>> limit exhaustion). Theoretically possible, but is this a real concern
>> with a timer ID space of 2G?
>
> I didn't go that far actually, it was just me misunderstanding that loop and
> especially the (id =~start) part. Now I got it.
>
> I guess the for statement can just be:
>
> for (; start != id; id++)

My brain based compiler complains about uninitialized usage of @id. I'm
pretty sure it's rightfully complaining and a real compiler would agree,
no?

Thanks,

        tglx