Hi Ashwin, 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 My mistake and will fix in future :) > > >> >> 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> 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
