Messages in this thread | | | Date | Wed, 22 Dec 2021 10:02:43 +0100 | Subject | Re: [PATCH] nvmem: fix unregistering device in nvmem_register() error path | From | Rafał Miłecki <> |
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On 22.12.2021 09:56, Greg Kroah-Hartman wrote: > On Wed, Dec 22, 2021 at 09:38:27AM +0100, Johan Hovold wrote: >> On Wed, Dec 22, 2021 at 08:44:44AM +0100, Greg Kroah-Hartman wrote: >>> On Tue, Dec 21, 2021 at 06:46:01PM +0100, Rafał Miłecki wrote: >>>> On 21.12.2021 17:06, Greg Kroah-Hartman wrote: >>>>> On Tue, Dec 21, 2021 at 04:45:50PM +0100, Rafał Miłecki wrote: >>>>>> From: Rafał Miłecki <rafal@milecki.pl> >>>>>> >>>>>> 1. Drop incorrect put_device() calls >>>>>> >>>>>> If device_register() fails then underlaying device_add() takes care of >>>>>> calling put_device() if needed. There is no need to do that in a driver. >>>>> >>>>> Did you read the documentation for device_register() that says: >>>>> >>>>> * NOTE: _Never_ directly free @dev after calling this function, even >>>>> * if it returned an error! Always use put_device() to give up the >>>>> * reference initialized in this function instead. >>>> >>>> I clearly tried to be too smart and ignored documentation. >>>> >>>> I'd say device_add() behaviour is rather uncommon and a bit unintuitive. >>>> Most kernel functions are safe to assume to do nothing that requires >>>> cleanup if they fail. >>>> >>>> E.g. if I call platform_device_register() and it fails I don't need to >>>> call anything like platform_device_put(). I just free previously >>>> allocated memory. >>> >>> And that is wrong. >> >> It seems Rafał is mistaken here too; you certainly need to call >> platform_device_put() if platform_device_register() fail, even if many >> current users do appear to get this wrong. > > A short search found almost everyone getting this wrong. Arguably > platform_device_register() can clean up properly on its own if we want > it to do so. Will take a lot of auditing of the current codebase first > to see if it's safe...
If so many people get it wrong maybe that is indded an unintuitive design?
I'll better hide now ;)
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