Re: [PATCH] Revert "PCI: Fix reference leak in pci_register_host_bridge()"

[liwei (JK)]

在 2025/4/12 11:18, liwei (JK) 写道:
> 在 2025/4/10 19:19, Su Hui 写道:
> > On 2025/4/10 11:28, Xiangwei Li wrote:
> > > This reverts commit 804443c1f27883926de94c849d91f5b7d7d696e9.
> > >
> > > The newly added logic incorrectly sets bus_registered to true even when
> > > device_register returns an error, this is incorrect.
> > >
> > > When device_register fails, there is no need to release the reference 
> > > count,
> > I think you missed some thing about device_register(). This patch is 
> > wrong.
> >
> > device_register()
> >      -> device_initialize()
> >                -> kobject_init()
> >                      -> kobject_init_internal()
> >                          -> kref_init(&kobj->kref);  //set 
> > kref->refcount to 1
> >                             ^^^^^^^^^^^^^^^^^^^^^
> Sorry, I missed the initialization of refcount in device_initialize,
> but I’m confused about the branch logic for bus_registered. Why isn’t
> free(bus) executed when bus_registered == true? My understanding is
> that the kobject_cleanup operation triggered when refcount reaches zero
> does not clean up the allocated bus. Could you clarify this further?
>
> Thanks,
> Xiangwei Li
Hi Su,

Thank you very much for your explanation. Based on your response and an
analysis of the corresponding release paths, this confirms that the
issue I previously raised does not exist in your patch.

Release path:
 kobject_cleanup
	->device_release  // device_ktype.device_release
		->release_pcibus_dev  // pcibus_class.release_pcibus_dev
			->kfree(pci_bus)   // free(bus)

Thanks,
Xiangwei Li

> > device_register() only  fails when device_add() fails, and 
> > kerf->refcount can be 1
> > at this time ,  so we need to call put_deivce() to release  memory.
> > > and there are no direct error-handling operations following its 
> > > execution.
> > >
> > > Therefore, this patch is meaningless and should be reverted.
> > >
> > > Fixes: 804443c1f278 ("PCI: Fix reference leak in 
> > > pci_register_host_bridge()")
> > > Signed-off-by: Xiangwei Li <liwei728@xxxxxxxxxx>
> > > Signed-off-by: Xiongfeng Wang <wangxiongfeng2@xxxxxxxxxx>