Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755285AbdD0JlL (ORCPT ); Thu, 27 Apr 2017 05:41:11 -0400 Received: from mga02.intel.com ([134.134.136.20]:34392 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752706AbdD0JlC (ORCPT ); Thu, 27 Apr 2017 05:41:02 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.37,383,1488873600"; d="scan'208";a="79533122" Message-ID: <1493285964.24567.225.camel@linux.intel.com> Subject: Re: [PATCH V2] cpuidle: check dev before usage in cpuidle_use_deepest_state From: Andy Shevchenko To: "Li, Fei" , "Shi, FengX" , "rjw@rjwysocki.net" , "daniel.lezcano@linaro.org" Cc: "linux-pm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Koul, Vinod" Date: Thu, 27 Apr 2017 12:39:24 +0300 In-Reply-To: References: Organization: Intel Finland Oy Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6-1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1601 Lines: 51 On Thu, 2017-04-27 at 01:47 +0000, Li, Fei wrote: > In case of there is no cpuidle devices registered, dev will be null, > and > panic will be triggered like below; > In this patch, add checking of dev before usage, like that done in > cpuidle_idle_call. > > Panic without fix: > [  184.961328] BUG: unable to handle kernel NULL pointer dereference > at >   (null) > [  184.961328] IP: cpuidle_use_deepest_state+0x30/0x60 > ... > [  184.961328]  play_idle+0x8d/0x210 > [  184.961328]  ? __schedule+0x359/0x8e0 > [  184.961328]  ? _raw_spin_unlock_irqrestore+0x28/0x50 > [  184.961328]  ? kthread_queue_delayed_work+0x41/0x80 > [  184.961328]  clamp_idle_injection_func+0x64/0x1e0 FWIW: Reviewed-by: Andy Shevchenko P.S. V2 is mistakenly left from internal review AFAIU. > > Fixes: bb8313b603eb8 ("cpuidle: Allow enforcing deepest idle state > selection") > Signed-off-by: Li, Fei > Tested-by: Shi, Feng > --- >  drivers/cpuidle/cpuidle.c | 3 ++- >  1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c > index 548b90b..2706be7 100644 > --- a/drivers/cpuidle/cpuidle.c > +++ b/drivers/cpuidle/cpuidle.c > @@ -111,7 +111,8 @@ void cpuidle_use_deepest_state(bool enable) >   >   preempt_disable(); >   dev = cpuidle_get_device(); > - dev->use_deepest_state = enable; > + if (dev) > + dev->use_deepest_state = enable; >   preempt_enable(); >  } >   -- Andy Shevchenko Intel Finland Oy