linux-kernel - Re: [Openipmi-developer] [PATCH 0/1] Fix race in ipmi timer cleanup

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Date:   Sat, 14 Sep 2019 20:08:52 -0500
From:   Corey Minyard <minyard@....org>
To:     Jes Sorensen <jes.sorensen@...il.com>
Cc:     openipmi-developer@...ts.sourceforge.net, kernel-team@...com,
        linux-kernel@...r.kernel.org
Subject: Re: [Openipmi-developer] [PATCH 0/1] Fix race in ipmi timer cleanup

> 
> > 
> > {disable,enable}_si_irq() themselves are racy:
> > 
> > static inline bool disable_si_irq(struct smi_info *smi_info)
> > {
> >         if ((smi_info->io.irq) && (!smi_info->interrupt_disabled)) {
> >                 smi_info->interrupt_disabled = true;
> > 
> > Basically interrupt_disabled need to be atomic here to have any value,
> > unless you ensure to have a spin lock around every access to it.
> 
> It needs to be atomic, yes, but I think just adding the spinlock like
> I suggested will work.  You are right, the check for timer_running is
> not necessary here, and I'm fine with removing it, but there are other
> issues with interrupt_disabled (as you said) and with memory ordering
> in the timer case.  So even if you remove the timer running check, the
> lock is still required here.

It turns out you were right, all that really needs to be done is the
del_timer_sync().  I've added your patch to my queue.

Sorry for the trouble.

Thanks,

-corey