Re: [PATCH AUTOSEL 5.14 04/25] cxl/pci: Introduce cdevm_file_operations

[Sasha Levin]

On Tue, Sep 14, 2021 at 08:42:04AM -0700, Dan Williams wrote:
> On Mon, Sep 13, 2021 at 3:33 PM Sasha Levin <sashal@xxxxxxxxxx> wrote:
> > From: Dan Williams <dan.j.williams@xxxxxxxxx>
> >
> > [ Upstream commit 9cc238c7a526dba9ee8c210fa2828886fc65db66 ]
> >
> > In preparation for moving cxl_memdev allocation to the core, introduce
> > cdevm_file_operations to coordinate file operations shutdown relative to
> > driver data release.
> >
> > The motivation for moving cxl_memdev allocation to the core (beyond
> > better file organization of sysfs attributes in core/ and drivers in
> > cxl/), is that device lifetime is longer than module lifetime. The cxl_pci
> > module should be free to come and go without needing to coordinate with
> > devices that need the text associated with cxl_memdev_release() to stay
> > resident. The move will fix a use after free bug when looping driver
> > load / unload with CONFIG_DEBUG_KOBJECT_RELEASE=y.
> >
> > Another motivation for passing in file_operations to the core cxl_memdev
> > creation flow is to allow for alternate drivers, like unit test code, to
> > define their own ioctl backends.
>
> Hi Sasha,
>
> Please drop this. It's not a fix, it's just a reorganization for
> easing the addition of new features and capabilities.

I'll drop it, but just to satisfy my curiousity: the description says it
fixes a use-after-free bug in the existing code, is it not the case?

--
Thanks,
Sasha