linux-kernel - Re: [RFC PATCH 51/77] dtc: Avoid NULL fullpath for nodes in orphan trees

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Message-ID: <aWiPhz92DBQImUw1@zatzit>
Date: Thu, 15 Jan 2026 17:56:07 +1100
From: David Gibson <david@...son.dropbear.id.au>
To: Herve Codina <herve.codina@...tlin.com>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Ayush Singh <ayush@...gleboard.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	devicetree-compiler@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree-spec@...r.kernel.org,
	Hui Pu <hui.pu@...ealthcare.com>,
	Ian Ray <ian.ray@...ealthcare.com>,
	Luca Ceresoli <luca.ceresoli@...tlin.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [RFC PATCH 51/77] dtc: Avoid NULL fullpath for nodes in orphan
 trees

On Mon, Jan 12, 2026 at 03:19:41PM +0100, Herve Codina wrote:
> Orphan nodes have been introduced recently.
> 
> The process_checks() function uses fullpath in several places and
> crashes due NULL pointer dereferences if fullpath is NULL.
> 
> In order to have process_checks() function running without crashes with
> orphan trees (i.e. trees based on orphan nodes), the fullpath of node
> available in those orphan trees must not be NULL.
> 
> Fullpath values are built by dti_fill_fullpaths(). Update it to handle
> fullpath in trees based on orphan nodes.
> 
> Use a simple "__orphan__/" prefix to avoid the NULL pointer and to be
> distinct from the root node ("/" prefix).
> 
> It is worth noting that this "__orphan__/" prefix is a temporary prefix
> and it will be change later when support for reference by path involving
> nodes in orphan tree is added.

It might be simpler to eliminate the fullpath field entirely, and
instead have a function that calculates fullpaths at the point you
need them.

> 
> Signed-off-by: Herve Codina <herve.codina@...tlin.com>
> ---
>  dtc.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/dtc.c b/dtc.c
> index 59f4d77..5cf8f31 100644
> --- a/dtc.c
> +++ b/dtc.c
> @@ -47,9 +47,14 @@ static void fill_fullpaths(struct node *tree, const char *prefix)
>  
>  static void dti_fill_fullpaths(struct dt_info *dti)
>  {
> +	struct node *orphan;
> +
>  	/* Fill fullpaths for the root node */
>  	if (dti->dt)
>  		fill_fullpaths(dti->dt, "");
> +
> +	for_each_orphan(dti->orphanlist, orphan)
> +		fill_fullpaths(orphan, "__orphan__/");
>  }
>  
>  /* Usage related data. */
> -- 
> 2.52.0
> 
> 

-- 
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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