From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 468091A006C for ; Fri, 12 Sep 2014 16:04:53 +1000 (EST) Message-ID: <1410501891.17540.6.camel@concordia> Subject: Re: [PATCH v3 3/3] sched: BUG when stack end location is over written From: Michael Ellerman To: Aaron Tomlin Date: Fri, 12 Sep 2014 16:04:51 +1000 In-Reply-To: <1410450088-18236-4-git-send-email-atomlin@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> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Cc: dzickus@redhat.com, jcastillo@redhat.com, riel@redhat.com, prarit@redhat.com, pzijlstr@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 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. ../kernel/sched/core.c: In function ‘schedule_debug’: ../kernel/sched/core.c:2671:2: error: expected ‘;’ before ‘if’ if (unlikely(in_atomic_preempt_off() && prev->state != TASK_DEAD)) ^ ../kernel/sched/core.c: At top level: ../kernel/sched/core.c:2635:22: warning: ‘__schedule_bug’ defined but not used [-Wunused-function] static noinline void __schedule_bug(struct task_struct *prev) ^ make[3]: *** [kernel/sched/core.o] Error 1 make[2]: *** [kernel/sched] Error 2 make[1]: *** [kernel] Error 2 make: *** [sub-make] Error 2 cheers