linux-kernel - Re: [PATCH v3 3/3] sched: BUG when stack end location is over written

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Date:	Fri, 12 Sep 2014 10:50:21 +0100
From:	Aaron Tomlin <atomlin@...hat.com>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	peterz@...radead.org, dzickus@...hat.com, jcastillo@...hat.com,
	riel@...hat.com, x86@...nel.org, akpm@...ux-foundation.org,
	minchan@...nel.org, bmr@...hat.com, prarit@...hat.com,
	oleg@...hat.com, rostedt@...dmis.org, linux-kernel@...r.kernel.org,
	hannes@...xchg.org, mingo@...hat.com,
	aneesh.kumar@...ux.vnet.ibm.com, akpm@...gle.com, jgh@...hat.com,
	linuxppc-dev@...ts.ozlabs.org, tglx@...utronix.de
Subject: Re: [PATCH v3 3/3] sched: BUG when stack end location is over written

On Fri, Sep 12, 2014 at 04:04:51PM +1000, Michael Ellerman wrote:
> On Thu, 2014-09-11 at 16:41 +0100, Aaron Tomlin wrote:
> > Currently in the event of a stack overrun a call to schedule()
> > does not check for this type of corruption. This corruption is
> > often silent and can go unnoticed. However once the corrupted
> > region is examined at a later stage, the outcome is undefined
> > and often results in a sporadic page fault which cannot be
> > handled.
> > 
> > This patch checks for a stack overrun and takes appropriate
> > action since the damage is already done, there is no point
> > in continuing.
> > 
> > Signed-off-by: Aaron Tomlin <atomlin@...hat.com>
> > ---
> >  kernel/sched/core.c |  3 +++
> >  lib/Kconfig.debug   | 12 ++++++++++++
> >  2 files changed, 15 insertions(+)
> > 
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index ec1a286..0b70b73 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -2660,6 +2660,9 @@ static noinline void __schedule_bug(struct task_struct *prev)
> >   */
> >  static inline void schedule_debug(struct task_struct *prev)
> >  {
> > +#ifdef CONFIG_SCHED_STACK_END_CHECK
> > +	BUG_ON(unlikely(task_stack_end_corrupted(prev)))
> > +#endif
> 
> Spot the bug? Please compile your code in future.

Oops! Sorry about that.

-- 
Aaron Tomlin
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