From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751703AbcFXQfi (ORCPT ); Fri, 24 Jun 2016 12:35:38 -0400 Received: from mail-vk0-f54.google.com ([209.85.213.54]:33313 "EHLO mail-vk0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751605AbcFXQff (ORCPT ); Fri, 24 Jun 2016 12:35:35 -0400 MIME-Version: 1.0 In-Reply-To: References: <1464203363-20599-1-git-send-email-hotran@apm.com> From: Hoan Tran Date: Fri, 24 Jun 2016 09:35:32 -0700 Message-ID: Subject: Re: [PATCH] acpi: cppc: Prevent cpc_desc_ptr points to the invalid data To: Ashwin Chaugule Cc: "Rafael J. Wysocki" , Len Brown , linux acpi , lkml , Duc Dang , Loc Ho 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 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 ? Thanks Hoan