From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 6651C1A00CD for ; Fri, 12 Sep 2014 19:53:07 +1000 (EST) Date: Fri, 12 Sep 2014 10:50:21 +0100 From: Aaron Tomlin To: Michael Ellerman Subject: Re: [PATCH v3 3/3] sched: BUG when stack end location is over written Message-ID: <20140912095021.GE1873@atomlin.usersys.redhat.com> References: <1410255749-2956-1-git-send-email-atomlin@redhat.com> <1410450088-18236-1-git-send-email-atomlin@redhat.com> <1410450088-18236-4-git-send-email-atomlin@redhat.com> <1410501891.17540.6.camel@concordia> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 In-Reply-To: <1410501891.17540.6.camel@concordia> Cc: dzickus@redhat.com, jcastillo@redhat.com, riel@redhat.com, prarit@redhat.com, peterz@infradead.org, bmr@redhat.com, x86@kernel.org, oleg@redhat.com, rostedt@goodmis.org, linux-kernel@vger.kernel.org, minchan@kernel.org, mingo@redhat.com, tglx@linutronix.de, aneesh.kumar@linux.vnet.ibm.com, hannes@cmpxchg.org, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, jgh@redhat.com, akpm@google.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 > > --- > > 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