linux-kernel - Re: [PATCH] linux/wait: Fix __wait_event

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 19 Jul 2022 10:47:52 +0200
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     Juri Lelli <juri.lelli@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Bruno Goncalves <bgoncalv@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Valentin Schneider <vschneid@...hat.com>
Subject: Re: [PATCH] linux/wait: Fix __wait_event_hrtimeout for RT/DL tasks

On 6/27/22 11:50, Juri Lelli wrote:
> Changes to hrtimer mode (potentially made by __hrtimer_init_sleeper on
> PREEMPT_RT) are not visible to hrtimer_start_range_ns, thus not
> accounted for by hrtimer_start_expires call paths. In particular,
> __wait_event_hrtimeout suffers from this problem as we have, for
> example:
> 
> fs/aio.c::read_events
>   wait_event_interruptible_hrtimeout
>     __wait_event_hrtimeout
>       hrtimer_init_sleeper_on_stack <- this might "mode |= HRTIMER_MODE_HARD"
>                                        on RT if task runs at RT/DL priority
>         hrtimer_start_range_ns
>           WARN_ON_ONCE(!(mode & HRTIMER_MODE_HARD) ^ !timer->is_hard)
>           fires since the latter doesn't see the change of mode done by
>           init_sleeper
> 
> Fix it by making __wait_event_hrtimeout call hrtimer_sleeper_start_expires,
> which is aware of the special RT/DL case, instead of hrtimer_start_range_ns.
> 
> Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> Reported-by: Bruno Goncalves <bgoncalv@...hat.com>
> Signed-off-by: Juri Lelli <juri.lelli@...hat.com>

Reviewed-by: Daniel Bristot de Oliveira <bristot@...nel.org>
-- Daniel