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 ? Thanks Hoan -- 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
