From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752020AbcKNAWR convert rfc822-to-8bit (ORCPT ); Sun, 13 Nov 2016 19:22:17 -0500 Received: from cloudserver094114.home.net.pl ([79.96.170.134]:62451 "EHLO cloudserver094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750866AbcKNAWP (ORCPT ); Sun, 13 Nov 2016 19:22:15 -0500 From: "Rafael J. Wysocki" To: Arnd Bergmann Cc: Andy Henroid , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] intel_idle: avoid theoretical uninitialized data usage Date: Mon, 14 Nov 2016 01:29:47 +0100 Message-ID: <18262381.8nEl38huXk@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/4.9.0-rc5+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <20161024155259.3041159-1-arnd@arndb.de> References: <20161024155259.3041159-1-arnd@arndb.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday, October 24, 2016 05:52:37 PM Arnd Bergmann wrote: > When CONFIG_PCI is disabled, pci_read_config_byte() may not update > its result, as indicated by this warning: > > drivers/idle/i7300_idle.c: In function ‘i7300_idle_notifier’: > drivers/idle/i7300_idle.c:423:141: warning: ‘got_ctl’ may be used uninitialized in this function [-Wmaybe-uninitialized] > drivers/idle/i7300_idle.c:415:5: note: ‘got_ctl’ was declared here > > We know the function is never called if CONFIG_PCI is not set, so > this is harmless, but we can avoid the problem by checking the > return value of the config space accessor before using the result. > > Signed-off-by: Arnd Bergmann > --- > drivers/idle/i7300_idle.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > diff --git a/drivers/idle/i7300_idle.c b/drivers/idle/i7300_idle.c > index ffeebc7e9f1c..9a104e558c77 100644 > --- a/drivers/idle/i7300_idle.c > +++ b/drivers/idle/i7300_idle.c > @@ -347,6 +347,7 @@ static int i7300_idle_thrt_save(void) > { > u32 new_mc_val; > u8 gblactlm; > + int ret; > > pci_read_config_byte(fbd_dev, DIMM_THRTCTL, &i7300_idle_thrtctl_saved); > pci_read_config_byte(fbd_dev, DIMM_THRTLOW, &i7300_idle_thrtlow_saved); > @@ -364,7 +365,9 @@ static int i7300_idle_thrt_save(void) > * unlimited-activations while in open-loop throttling (i.e., when > * Global Activation Throttle Limit is zero). > */ > - pci_read_config_byte(fbd_dev, DIMM_GBLACT, &gblactlm); > + ret = pci_read_config_byte(fbd_dev, DIMM_GBLACT, &gblactlm); > + if (ret) > + return ret; > dprintk("thrtctl_saved = 0x%02x, thrtlow_saved = 0x%02x\n", > i7300_idle_thrtctl_saved, > i7300_idle_thrtlow_saved); > @@ -413,14 +416,16 @@ static void i7300_idle_stop(void) > { > u8 new_ctl; > u8 got_ctl; > + int ret; > > new_ctl = i7300_idle_thrtctl_saved & ~DIMM_THRTCTL_THRMHUNT; > pci_write_config_byte(fbd_dev, DIMM_THRTCTL, new_ctl); > > pci_write_config_byte(fbd_dev, DIMM_THRTLOW, i7300_idle_thrtlow_saved); > pci_write_config_byte(fbd_dev, DIMM_THRTCTL, i7300_idle_thrtctl_saved); > - pci_read_config_byte(fbd_dev, DIMM_THRTCTL, &got_ctl); > - WARN_ON_ONCE(got_ctl != i7300_idle_thrtctl_saved); > + ret = pci_read_config_byte(fbd_dev, DIMM_THRTCTL, &got_ctl); > + > + WARN_ON_ONCE(ret || (got_ctl != i7300_idle_thrtctl_saved)); > } > Applied (with a minor subject tweak). Thanks, Rafael