Re: [PATCH] hw/nubus/nubus-virtio-mmio: Fix missing ERRP_GUARD() in nubus_virtio_mmio_realize()

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

+Markus/Eric for review

On 17/7/24 13:27, Zhao Liu wrote:
> Hi Philippe,
> 
> If possible, can this one catch a ride with your PULL too?
> 
> Many thanks!
> Zhao
> 
> On Mon, Jul 15, 2024 at 05:59:37PM +0800, Zhao Liu wrote:
>> Date: Mon, 15 Jul 2024 17:59:37 +0800
>> From: Zhao Liu <zhao1.liu@intel.com>
>> Subject: [PATCH] hw/nubus/nubus-virtio-mmio: Fix missing ERRP_GUARD() in
>>   nubus_virtio_mmio_realize()
>> X-Mailer: git-send-email 2.34.1
>>
>> As the comment in qapi/error, dereferencing @errp requires
>> ERRP_GUARD():
>>
>> * = Why, when and how to use ERRP_GUARD() =
>> *
>> * Without ERRP_GUARD(), use of the @errp parameter is restricted:
>> * - It must not be dereferenced, because it may be null.
>> ...
>> * ERRP_GUARD() lifts these restrictions.
>> *
>> * To use ERRP_GUARD(), add it right at the beginning of the function.
>> * @errp can then be used without worrying about the argument being
>> * NULL or &error_fatal.
>> *
>> * Using it when it's not needed is safe, but please avoid cluttering
>> * the source with useless code.
>>
>> But in nubus_virtio_mmio_realize(), @errp is dereferenced without
>> ERRP_GUARD().
>>
>> Although nubus_virtio_mmio_realize() - as a DeviceClass.realize()
>> method - doesn't get the NULL @errp parameter, it hasn't triggered the
>> bug that dereferencing the NULL @errp. It's still necessary to follow
>> the requirement of @errp, so add missing ERRP_GUARD() in
>> nubus_virtio_mmio_realize().
>>
>> Cc: Laurent Vivier <laurent@vivier.eu>
>> Cc: Philippe Mathieu-Daudé <philmd@linaro.org>
>> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
>> ---
>>   hw/nubus/nubus-virtio-mmio.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/hw/nubus/nubus-virtio-mmio.c b/hw/nubus/nubus-virtio-mmio.c
>> index 58a63c84d0be..a5558d3ec28b 100644
>> --- a/hw/nubus/nubus-virtio-mmio.c
>> +++ b/hw/nubus/nubus-virtio-mmio.c
>> @@ -23,6 +23,7 @@ static void nubus_virtio_mmio_set_input_irq(void *opaque, int n, int level)
>>   
>>   static void nubus_virtio_mmio_realize(DeviceState *dev, Error **errp)
>>   {
>> +    ERRP_GUARD();
>>       NubusVirtioMMIODeviceClass *nvmdc = NUBUS_VIRTIO_MMIO_GET_CLASS(dev);
>>       NubusVirtioMMIO *s = NUBUS_VIRTIO_MMIO(dev);
>>       NubusDevice *nd = NUBUS_DEVICE(dev);
>> -- 
>> 2.34.1
>>