linux-kernel - Re: [RFC][PATCH] IRQ: Fix oneshot irq race between irq_finalize_oneshot and handle_level

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, 9 Mar 2010 16:08:00 +0800
From:	Yong Zhang <yong.zhang@...driver.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Lars-Peter Clausen <lars@...afoo.de>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH] IRQ: Fix oneshot irq race between
 irq_finalize_oneshot and handle_level_irq

On Tue, Mar 09, 2010 at 08:58:11AM +0100, Thomas Gleixner wrote:
> On Tue, 9 Mar 2010, Lars-Peter Clausen wrote:
> 
> > If the kernel has been compiled with preemtion support and handle_level_irq is
> > called from process context for a oneshot irq there is a race between
> > irq_finalize_oneshot and handle_level_irq which results in the irq not being
> > unmasked after its handlers have been run.
> > 
> > irq_finalize_oneshot is expected to unmask the irq after the threaded irq
> > handler has been run. It only does so if IRQ_MASKED is set for the irqs status.
> > IRQ_MASKED gets set in the lower part of handle_level_irq after handle_IRQ_event
> > has been called.
> > handle_IRQ_event will wakeup the oneshot irqs threaded handler and if the
> > kernel has been build with preemption there is a chance that the threaded irq
> > handler will finish before execution is returned to handle_level_irq.
> > As a result irq_finalize_oneshot will not unmask the irq and handle_level_irq
> > will set the IRQ_MASKED flag. Thus the irq will stay masked and stalls.
> > 
> > In case of an race the call-graph would look like this:
> >  handle_level_irq
> >  |- mask_ack_irq
> >  |- handle_IRQ_event
> >     |- wake_up_process
> >        |- irq_thread
> >           |- action->thread_fn
> >           |- irq_finalize_oneshot # Does not unmask the irq
> > |- # Set IRQ_MASKED status flag
> 
> Errm, a thread _CANNOT_ preempt a hard interrupt handler.

But on SMP, an irq thread could run on another cpu, right?

Thanks,
Yong

> 
> Thanks,
> 
> 	tglx
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@...r.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/