Re: [PATCH] driver core: Don't match device with NULL of_node/fwnode

[Rob Herring]

On Mon, Dec 9, 2024 at 5:47 PM Brian Norris <briannorris@xxxxxxxxxxxx> wrote:
>
> Hi Greg,
>
> On Wed, Dec 04, 2024 at 10:37:06AM +0100, Greg Kroah-Hartman wrote:
> > On Tue, Dec 03, 2024 at 06:02:59PM -0600, Rob Herring (Arm) wrote:
> > > It recently came up that of_find_device_by_node() will match a device
> > > with a NULL of_node pointer. This is not desired behavior. The returned
> > > struct device is also not deterministic.
> >
> > It's not deterministic because a NULL pointer will cause that to happen,
> > or for some other reason?
>
> It'll pick the first platform device with no of_node. That likely yields
> something very wrong, but doesn't produce a visible problem until a
> caller does something with the result. Commit 5c8418cf4025
> ("PCI/pwrctrl: Unregister platform device only if one actually exists")
> has plenty of explanation of what really goes wrong.
>
> > > Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> > > Signed-off-by: Rob Herring (Arm) <robh@xxxxxxxxxx>
> > > ---
> > > It would be a bit more efficient to check this up front before we
> > > iterate thru devices, but there's a number of users of these functions
> > > and this isn't really a hot path.
> >
> > Yeah, this should be fine.  Does this fix a problem now and we need it
> > merged for 6.13-final and backported, or can it just wait for 6.14-rc1?
>
> It's a preventive measure to help head off future confusing bugs. It
> doesn't need expedited merging or backporting.
>
> FWIW, last week, I also cooked this change locally (+ the ACPI change;
> and a kunit test for added fun), before I noticed Rob submitted this
> one. If you'd rather, I can submit my patch series. Or I can submit my
> patch series on top of this. Whichever you'd prefer.

If you have a kunit test, you win. :)

Rob