On Friday, June 24, 2016 09:35:32 AM Hoan Tran wrote: > On Tue, May 31, 2016 at 12:29 PM, Ashwin Chaugule > <ashwin.chaugule@xxxxxxxxxx> wrote: > > > > On 27 May 2016 at 12:41, Hoan Tran <hotran@xxxxxxx> 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 > > > <ashwin.chaugule@xxxxxxxxxx> wrote: > > >> On 25 May 2016 at 15:09, Hoan Tran <hotran@xxxxxxx> 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 <hotran@xxxxxxx> > > >>> --- > > >>> 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 <ashwin.chaugule@xxxxxxxxxx> > > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
