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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Frederic Weisbecker <frederic@kernel.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Anna-Maria Behnsen <anna-maria@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        syzbot+5c54bd3eb218bb595aa9@syzkaller.appspotmail.com,
        Dmitry Vyukov <dvyukov@google.com>,
        Sebastian Siewior <bigeasy@linutronix.de>,
        Michael Kerrisk <mtk.manpages@gmail.com>
Subject: Re: [patch 02/20] posix-timers: Ensure timer ID search-loop limit
 is valid
In-Reply-To: <ZFoVg9UmItpIaA69@lothringen>
References: <20230425181827.219128101@linutronix.de>
 <20230425183312.932345089@linutronix.de> <ZFUXrCZtWyNG3Esi@lothringen>
 <87zg6i2xn3.ffs@tglx> <87v8h62vwp.ffs@tglx> <ZFoVg9UmItpIaA69@lothringen>
Date:   Tue, 09 May 2023 14:38:50 +0200
Message-ID: <877cth1xyd.ffs@tglx>
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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