linux-kernel - Re: [PATCH v6] psi: fix race between psi_trigger

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:   Fri, 21 May 2021 13:10:17 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     Huangzhaoyang <huangzhaoyang@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Zhaoyang Huang <zhaoyang.huang@...soc.com>,
        Ziwei Dai <ziwei.dai@...soc.com>, Ke Wang <ke.wang@...soc.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        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>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: Re: [PATCH v6] psi: fix race between psi_trigger_create/destroy

On Thu, May 20, 2021 at 07:11:08PM -0700, Suren Baghdasaryan wrote:
> On Thu, May 20, 2021 at 7:07 PM Huangzhaoyang <huangzhaoyang@...il.com> wrote:
> >
> > From: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> >
> > Race detected between psi_trigger_destroy/create as shown below, which
> > cause panic by accessing invalid psi_system->poll_wait->wait_queue_entry
> > and psi_system->poll_timer->entry->next. Under this modification, the
> > race window is removed by initialising poll_wait and poll_timer in
> > group_init which are executed only once at beginning.
> >
> > psi_trigger_destroy                      psi_trigger_create
> > mutex_lock(trigger_lock);
> > rcu_assign_pointer(poll_task, NULL);
> > mutex_unlock(trigger_lock);
> >                                         mutex_lock(trigger_lock);
> >                                         if (!rcu_access_pointer(group->poll_task)) {
> >
> >                                                 timer_setup(poll_timer, poll_timer_fn, 0);
> >
> >                                                 rcu_assign_pointer(poll_task, task);
> >                                         }
> >                                         mutex_unlock(trigger_lock);
> >
> > synchronize_rcu();
> > del_timer_sync(poll_timer); <-- poll_timer has been reinitialized by
> > psi_trigger_create
> >
> > So, trigger_lock/RCU correctly protects destruction of group->poll_task but
> > misses this race affecting poll_timer and poll_wait.
> >
> > Fixes: 461daba06bdc ("psi: eliminate kthread_worker from psi trigger
> > scheduling mechanism")
> >
> > Signed-off-by: ziwei.dai <ziwei.dai@...soc.com>
> > Signed-off-by: ke.wang <ke.wang@...soc.com>
> > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...soc.com>

This is not a valid SoB chain though; please (re)read Documentation/process/submitting-patches.rst.

> Looks good. Thanks!
> Reviewed-by: Suren Baghdasaryan <surenb@...gle.com>