[-next,1/3] PCI: fix double put_device() in error case in pci_create_root_bus()

If device_add() fails in pci_register_host_bridge(), the brigde device will
be put once, and it will be put again in error path of pci_create_root_bus().
Move the put_device() from pci_create_root_bus() to pci_register_host_bridge()
to fix this problem. And use device_unregister() instead of del_device() and
put_device().

Fixes: 9885440b16b8 ("PCI: Fix pci_host_bridge struct device release/free handling")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
 drivers/pci/probe.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

[+cc Rob]

On Thu, Aug 25, 2022 at 08:27:51PM +0800, Yang Yingliang wrote:
> If device_add() fails in pci_register_host_bridge(), the brigde device will
> be put once, and it will be put again in error path of pci_create_root_bus().
> Move the put_device() from pci_create_root_bus() to pci_register_host_bridge()
> to fix this problem. And use device_unregister() instead of del_device() and
> put_device().

s/brigde/bridge/

> Fixes: 9885440b16b8 ("PCI: Fix pci_host_bridge struct device release/free handling")

If you're fixing a commit from somebody else, please always cc: the
author because the author can help review the change.

> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
> ---
>  drivers/pci/probe.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index c5286b027f00..e500eb9d6468 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1027,7 +1027,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
>  
>  unregister:
>  	put_device(&bridge->dev);
> -	device_del(&bridge->dev);
> +	device_unregister(&bridge->dev);

I don't understand this part.  device_unregister() looks like this:

  void device_unregister(struct device *dev)
  {
    device_del(dev);
    put_device(dev);
  }

So this calls put_device(&bridge->dev) twice, doesn't it?

The "unregister" label looks poorly named.  We only get there if
device_register() *failed*.  We shouldn't need to unregister anything
in that case.

>  free:
>  	kfree(bus);
> @@ -3037,13 +3037,9 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
>  
>  	error = pci_register_host_bridge(bridge);
>  	if (error < 0)
> -		goto err_out;
> +		return NULL;
>  
>  	return bridge->bus;
> -
> -err_out:
> -	put_device(&bridge->dev);
> -	return NULL;

This part looks right to me.  The get_device() is in
pci_register_host_bridge(), and if pci_register_host_bridge() returns
failure, I think it should first do the corresponding put_device().

>  }
>  EXPORT_SYMBOL_GPL(pci_create_root_bus);
>  
> -- 
> 2.25.1
>

Hi,

On 2022/8/27 5:14, Bjorn Helgaas wrote:
> [+cc Rob]
>
> On Thu, Aug 25, 2022 at 08:27:51PM +0800, Yang Yingliang wrote:
>> If device_add() fails in pci_register_host_bridge(), the brigde device will
>> be put once, and it will be put again in error path of pci_create_root_bus().
>> Move the put_device() from pci_create_root_bus() to pci_register_host_bridge()
>> to fix this problem. And use device_unregister() instead of del_device() and
>> put_device().
> s/brigde/bridge/
>
>> Fixes: 9885440b16b8 ("PCI: Fix pci_host_bridge struct device release/free handling")
> If you're fixing a commit from somebody else, please always cc: the
> author because the author can help review the change.
OK.
>
>> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
>> ---
>>   drivers/pci/probe.c | 8 ++------
>>   1 file changed, 2 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
>> index c5286b027f00..e500eb9d6468 100644
>> --- a/drivers/pci/probe.c
>> +++ b/drivers/pci/probe.c
>> @@ -1027,7 +1027,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
>>   
>>   unregister:
>>   	put_device(&bridge->dev);
>> -	device_del(&bridge->dev);
>> +	device_unregister(&bridge->dev);
> I don't understand this part.  device_unregister() looks like this:
>
>    void device_unregister(struct device *dev)
>    {
>      device_del(dev);
>      put_device(dev);
>    }
>
> So this calls put_device(&bridge->dev) twice, doesn't it?
>
> The "unregister" label looks poorly named.  We only get there if
> device_register() *failed*.  We shouldn't need to unregister anything
> in that case.
If it goes to the 'unregister' label, the bridge->dev has been register 
sucessfully (device_initialize() called from pci_alloc_host_bridge()
and device_add() called from pci_register_host_bridge()), so it need be 
unregister, and another put_device() is for decreasing
refcount of 'bus->bridge'.

Thanks,
Yang
>
>>   free:
>>   	kfree(bus);
>> @@ -3037,13 +3037,9 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
>>   
>>   	error = pci_register_host_bridge(bridge);
>>   	if (error < 0)
>> -		goto err_out;
>> +		return NULL;
>>   
>>   	return bridge->bus;
>> -
>> -err_out:
>> -	put_device(&bridge->dev);
>> -	return NULL;
> This part looks right to me.  The get_device() is in
> pci_register_host_bridge(), and if pci_register_host_bridge() returns
> failure, I think it should first do the corresponding put_device().
>
>>   }
>>   EXPORT_SYMBOL_GPL(pci_create_root_bus);
>>   
>> -- 
>> 2.25.1
>>
> .