Re: [PATCH] ACPI: scan: Make acpi_bus_get_device() clear the adev ptr on error

[Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>]

On 1/18/21 7:58 AM, Rafael J. Wysocki wrote:
> On Fri, Jan 15, 2021 at 10:59 PM Hans de Goede <hdegoede@redhat.com> wrote:
>>
>> Set the acpi_device pointer which acpi_bus_get_device()
>> returns-by-reference to NULL on error.
>>
>> We've recently had 2 cases where callers of acpi_bus_get_device()
>> did not properly error check the return value, using the
>> returned-by-reference acpi_device pointer blindly, set it to NULL
>> so that this will lead to an immediate oops, rather then following
>> a pointer to who knows what.
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> 
> This should fix the crash reported by Pierre-Louis, so let me apply it
> instead of the two debug changes posted by me
> (https://lore.kernel.org/linux-acpi/98e6ed8e-884e-adb4-a146-a66daefa94a7@redhat.com/T/#md5add2fe554a30e3a929d87a66b435f4cc8bf628).
> 
> Pierre-Louis, can you please double check that the issue goes away
> with this patch applied?

yep, tested twice

Tested-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>

Thanks Hans and Rafael for your work, much appreciated.

>> ---
>>   drivers/acpi/scan.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
>> index c575c9b67f76..c53e88deee1d 100644
>> --- a/drivers/acpi/scan.c
>> +++ b/drivers/acpi/scan.c
>> @@ -585,6 +585,8 @@ static int acpi_get_device_data(acpi_handle handle, struct acpi_device **device,
>>          if (!device)
>>                  return -EINVAL;
>>
>> +       *device = NULL;
>> +
>>          status = acpi_get_data_full(handle, acpi_scan_drop_device,
>>                                      (void **)device, callback);
>>          if (ACPI_FAILURE(status) || !*device) {
>> --
>> 2.28.0
>>