Re: [PATCH -next 2/3] PCI: fix possible memory leak in error case in pci_register_host_bridge()

[Yang Yingliang]

On 2022/8/27 6:38, Bjorn Helgaas wrote:
> [+cc Arnd, Rob]
>
> On Thu, Aug 25, 2022 at 08:27:52PM +0800, Yang Yingliang wrote:
> > If device_register() fails in pci_register_host_bridge(), the refcount
> > of bus device is leaked, so device name that set by dev_set_name() can
> > not be freed. Fix this by calling put_device() when device_register()
> > fails, so the device name will be freed in kobject_cleanup().
> >
> > Fixes: 37d6a0a6f470 ("PCI: Add pci_register_host_bridge() interface")
> > Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
> > ---
> >   drivers/pci/probe.c | 17 +++++++++++------
> >   1 file changed, 11 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> > index e500eb9d6468..292d9da146ce 100644
> > --- a/drivers/pci/probe.c
> > +++ b/drivers/pci/probe.c
> > @@ -948,8 +948,17 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
> >   	name = dev_name(&bus->dev);
> >   
> >   	err = device_register(&bus->dev);
> > -	if (err)
> > -		goto unregister;
> > +	if (err) {
> > +		/*
> > +		 * release_pcibus_dev() will decrease the refcount of bridge
> > +		 * device and free the memory of bus.
> > +		 * The memory of bus device name will be freed when the refcount
> > +		 * get to zero.
> > +		 */
> > +		put_device(&bus->dev);
> > +		device_unregister(&bridge->dev);
> > +		return err;
> > +	}
> Calling put_device(X) after device_register(X) returns failure doesn't
> need explanation because that's the standard pattern.  I think that
> was just missing before.
>
> In this error case, we previously did called put_device() for the
> *bridge* instead of the bus.  That was likely a typo and seems like
> the important thing here.
put_device() for the bridge will be called in the callback of put for 
the bus.
So it doesn't call put bridge device here.

Thanks,
Yang
> >   	pcibios_add_bus(bus);
> >   
> > @@ -1025,10 +1034,6 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
> >   
> >   	return 0;
> >   
> > -unregister:
> > -	put_device(&bridge->dev);
> > -	device_unregister(&bridge->dev);
> > -
> >   free:
> >   	kfree(bus);
> >   	return err;
> > --
> > 2.25.1
> .