Re: [PATCH v2 1/2] MIPS: vpe-mt: fix possible memory leak while module exiting

[Yang Yingliang <yangyingliang@huawei.com>]

Hi,

On 2022/11/22 19:21, Thomas Bogendoerfer wrote:
> On Fri, Nov 04, 2022 at 11:39:44AM +0800, Yang Yingliang wrote:
>> Afer commit 1fa5ae857bb1 ("driver core: get rid of struct device's
>> bus_id string array"), the name of device is allocated dynamically,
>> it need be freed when module exiting, call put_device() to give up
>> reference, so that it can be freed in kobject_cleanup() when the
>> refcount hit to 0. The vpe_device is static, so remove kfree() from
>> vpe_device_release().
>>
>> Fixes: 1fa5ae857bb1 ("driver core: get rid of struct device's bus_id string array")
>> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
>> ---
>>   arch/mips/kernel/vpe-mt.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/mips/kernel/vpe-mt.c b/arch/mips/kernel/vpe-mt.c
>> index bad6b0891b2b..84a82b551ec3 100644
>> --- a/arch/mips/kernel/vpe-mt.c
>> +++ b/arch/mips/kernel/vpe-mt.c
>> @@ -313,7 +313,6 @@ ATTRIBUTE_GROUPS(vpe);
>>   
>>   static void vpe_device_release(struct device *cd)
>>   {
>> -	kfree(cd);
>>   }
> as this is empty now, we can IMHO remove the function completly. Same
> for the other patch in this series.
It can not be removed, or it will cause WARNING in device_release() when 
calling
put_device()/device_unregister().

static void device_release(struct kobject *kobj)
{
...

         if (dev->release)
                 dev->release(dev);
         else if (dev->type && dev->type->release)
                 dev->type->release(dev);
         else if (dev->class && dev->class->dev_release)
                 dev->class->dev_release(dev);
         else
                 WARN(1, KERN_ERR "Device '%s' does not have a release() 
function, it is broken and must be fixed. See 
Documentation/core-api/kobject.rst.\n",
                         dev_name(dev));  // WANING here
...
}

Thanks,
Yang
>
> Thomas.
>