Re: [Question] Status of user-space dynamic overlays API

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Feb 24, 2025 at 09:37:56AM +0100, Geert Uytterhoeven wrote:
> Hi Ayush,
> 
> On Sat, 22 Feb 2025 at 21:14, Ayush Singh <ayush@beagleboard.org> wrote:
> > # Challenges
> >
> > ## Security
> >
> > The concerns regarding security seemed to show up in the other
> > proposals. There was a proposal to have a devicetree property to
> > allow/deny the application of overlays in some nodes, with default being
> > deny. Was it insufficient?
> 
> This is the most important issue: using DT overlays, you can change
> about anything.  There is no protection yet to limit this to e.g. the
> expansion connectors on your board.

Right.

> This is what the various WIP "connector" abstractions are trying
> to solve.

Exactly.

> > ## Memory Leaks
> >
> > Currently, updating/removing properties leaks memory. Was it one of the
> > reasons for the rejection of previous proposals?
> 
> IMO this is a minor issue. I am sure this can be improved upon.  We just
> need some way to keep track of which properties are part of the initial
> FDT (and thus can't be freed), and which were allocated dynamically.

Somewhat related to this, "unapplying" a DT overlay is not a natural
operation, but we need it for a sane update interface.  The normal way
of applying overlays is a lossy process.  Obviously, it's possible to
make it reversible by keeping around enough undo information, but it's
kind of a hack.

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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