linux-kernel - Re: [PATCH -next 2/3] PCI: fix possible memory leak in error case in pci_register_host

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Message-ID: <83f42399-6dc3-d227-bb48-891172e061f9@huawei.com>
Date:   Sat, 27 Aug 2022 17:29:35 +0800
From:   Yang Yingliang <yangyingliang@...wei.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <bhelgaas@...gle.com>, Arnd Bergmann <arnd@...db.de>,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH -next 2/3] PCI: fix possible memory leak in error case in
 pci_register_host_bridge()


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@...wei.com>
>> ---
>>   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
>>
> .