Re: [PATCH] of: property: Fix of_fwnode_get_reference_args() with negative index

[Alban Bedel <alban.bedel@lht.dlh.de>]

On Mon, 15 Jun 2026 08:33:32 +0200
Krzysztof Kozlowski <krzk@kernel.org> wrote:

> On Thu, Jun 11, 2026 at 12:28:06PM +0200, Alban Bedel wrote:
> > fwnode_property_get_reference_args() should return -ENOENT when an out
> > of bound index is passed. An issue arised with the OF backend because
> > the OF API use signed indexes while the fwnode API use unsigned ones.
> > When an index value greater the INT_MAX was passed to the OF backend
> > it got casted to a negative value and it returned -EINVAL instead of  
> 
> INT_MAX is not out of bound for this function. It is invalid value,
> because OF code expects signed.

But this is fwnode code, it use the OF API but it should implement the
fwnode API which, unlike the OF API, use unsigned index.

> > -ENOENT. This patch add a check to of_fwnode_get_reference_args() to
> > catch negative index before they are passed to the OF API and return
> > -ENOENT right away.  
> 
> I do not understand why are you fixing this issue that way. For this
> API, the INT_MAX is correct value, but you claim that it is wrong and
> should be ENOENT (even if there is entry).
>
> Fine, if this is not a correct value, then EINVAL.

Indices larger than INT_MAX are valid in the fwnode API, so returning
-EINVAL is not appropriate here.

> But more important I think this should be just fixed in different way -
> why index in OF calls is signed in the first place? All indices are
> supposed to be unsigned in general, because that is both logical and
> readable when accessing arrays.
 
I agree that would be the better fix in the long run. But that would
impact a lot more code and I found it difficult to ensure it would not
potentially break some of its users. 

Alban