linux-kernel - RE: [char-misc-next v2] mei: bus: fix device leak

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Message-ID: <CY5PR11MB6366BBFF44C7F21C24292590ED46A@CY5PR11MB6366.namprd11.prod.outlook.com>
Date: Mon, 30 Jun 2025 11:27:14 +0000
From: "Usyskin, Alexander" <alexander.usyskin@...el.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC: "Abliyev, Reuven" <reuven.abliyev@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [char-misc-next v2] mei: bus: fix device leak

> Subject: Re: [char-misc-next v2] mei: bus: fix device leak
> 
> On Mon, Jun 30, 2025 at 10:52:08AM +0000, Usyskin, Alexander wrote:
> > > Subject: Re: [char-misc-next v2] mei: bus: fix device leak
> > >
> > > On Tue, Jun 24, 2025 at 02:05:20PM +0300, Alexander Usyskin wrote:
> > > > The bus rescan function creates bus devices for all clients.
> > > > The fixup routine is executed on all devices, unneeded
> > > > devices are removed and fully initialized once set
> > > > is_added flag to 1.
> > >
> > > I don't understand why the mei bus is so special that it has to have
> > > this type of flag, when no other bus has that for its devices.  The bus
> > > code should know if the device has been properly added or not, if not,
> > > then no release function can be called and the structure isn't even
> > > viable to be used or touched at all.
> > >
> > > So why is this needed?
> >
> > It seems that is_added can be replaced by device_is_registered().
> 
> Again, why do you need to track that?
> 
> But yes, that should work, although using it is usually a sign that
> something is a bit broken in the design.
> 

Mei bus uses device_initialize() and device_add() pair.
After device_initialize() there are different hooks and filters called,
that may lead to dropping the device or adding with device_add().
Thus, we should track if device_add() is called when destroying the device.
Not sure if this can be re-architected to use device_register().

> thanks
> 
> greg k-h


- - 
Thanks,
Sasha