From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751394AbcFXXBH (ORCPT ); Fri, 24 Jun 2016 19:01:07 -0400 Received: from cloudserver094114.home.net.pl ([79.96.170.134]:51614 "HELO cloudserver094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751037AbcFXXBE (ORCPT ); Fri, 24 Jun 2016 19:01:04 -0400 From: "Rafael J. Wysocki" To: Hoan Tran Cc: Ashwin Chaugule , Len Brown , linux acpi , lkml , Duc Dang , Loc Ho Subject: Re: [PATCH] acpi: cppc: Prevent cpc_desc_ptr points to the invalid data Date: Sat, 25 Jun 2016 01:05:25 +0200 Message-ID: <1558142.bgzLy2HxBR@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/4.5.0-rc1+; KDE/4.11.5; x86_64; ; ) In-Reply-To: References: <1464203363-20599-1-git-send-email-hotran@apm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit 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 Friday, June 24, 2016 09:35:32 AM Hoan Tran wrote: > On Tue, May 31, 2016 at 12:29 PM, Ashwin Chaugule > wrote: > > > > On 27 May 2016 at 12:41, Hoan Tran wrote: > > > Hi Ashwin, > > > > Hi, > > > > > > > > Yes, I saw kernel crash. > > > As cpc_desc_ptr is not NULL, cppc_cpufreq_init() still can pass then > > > crash during cppc_get_perf_caps() access CPPC shared memory. > > > > > > It's not only "PCC channel request fail" can create this issue but > > > "acpi_get_psd() fail" also creates it > > > > > > Thanks > > > Hoan > > > > > > Just for future reference. :) > > > > https://web.archive.org/web/20080722025748/http://www.zip.com.au/~akpm/linux/patches/stuff/top-posting.txt > > > > > > > > > > On Fri, May 27, 2016 at 9:10 AM, Ashwin Chaugule > > > wrote: > > >> On 25 May 2016 at 15:09, Hoan Tran wrote: > > >>> When CPPC fails to request PCC channel, the CPC data is freed > > >>> and cpc_desc_ptr points to the invalid data. This change prevents > > >>> this issue by moving cpc_desc_ptr assignment after PCC channel > > >>> request. > > >>> > > >>> Signed-off-by: Hoan Tran > > >>> --- > > >>> drivers/acpi/cppc_acpi.c | 6 +++--- > > >>> 1 file changed, 3 insertions(+), 3 deletions(-) > > >>> > > >>> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c > > >>> index 8adac69..85fd8f7 100644 > > >>> --- a/drivers/acpi/cppc_acpi.c > > >>> +++ b/drivers/acpi/cppc_acpi.c > > >>> @@ -595,9 +595,6 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr) > > >>> /* Store CPU Logical ID */ > > >>> cpc_ptr->cpu_id = pr->id; > > >>> > > >>> - /* Plug it into this CPUs CPC descriptor. */ > > >>> - per_cpu(cpc_desc_ptr, pr->id) = cpc_ptr; > > >>> - > > >>> /* Parse PSD data for this CPU */ > > >>> ret = acpi_get_psd(cpc_ptr, handle); > > >>> if (ret) > > >>> @@ -610,6 +607,9 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr) > > >>> goto out_free; > > >>> } > > >>> > > >>> + /* Plug PSD data into this CPUs CPC descriptor. */ > > >>> + per_cpu(cpc_desc_ptr, pr->id) = cpc_ptr; > > >>> + > > >> > > >> Are you seeing a real problem without this change? I'm missing where > > >> this pointer is dereferenced if the PCC channel request fails. > > >> > > > > So, after freeing the cpc_ptr, we need to NULL the per-cpu pointer as > > well. Alternately, not assign it until everything passes and rely on > > the static declaration, which is the path you've taken here. > > > > Acked-by: Ashwin Chaugule > > Hi Rafael, > > Do you have plan to apply this patch ? I do now. :-) I've overlooked the Ashwin's ACK, so thanks for the reminder. Thanks, Rafael