Re: [PATCH] libfdt: overlay: Fix phandle overwrite check for new subtrees

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

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On Wed, Jun 26, 2024 at 09:55:52AM +0200, Uwe Kleine-König wrote:
> If the overlay's target is only created in a previous fragment, it
> doesn't exist in the unmodified base device tree. For the phandle
> overwrite check this can be ignored because in this case the base tree
> doesn't contain a phandle that could be overwritten.
> 
> Adapt the corresponding check to not error out if that happens but just
> continue with the next fragment.
> 
> This is currently triggered by
> arch/arm64/boot/dts/renesas/salvator-panel-aa104xd12.dtso in the kernel
> repository which creates /panel in its first fragment and modifies it in
> its second.
> 
> Reported-by: Rob Herring <robh@kernel.org>
> Link: https://lore.kernel.org/all/CAL_JsqL9MPycDjqQfPNAuGfC6EMrdzUivr+fuOS7YgU3biGd4A@mail.gmail.com/
> Fixes: 1fad065080e6 ("libfdt: overlay: ensure that existing phandles are not overwritten")
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>

Merged, thanks.

> ---
>  libfdt/fdt_overlay.c                | 8 +++++++-
>  tests/overlay_overlay_bypath.dts    | 4 ++++
>  tests/overlay_overlay_no_fixups.dts | 8 ++++++++
>  3 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/libfdt/fdt_overlay.c b/libfdt/fdt_overlay.c
> index e19506fb56a5..28b667ffc490 100644
> --- a/libfdt/fdt_overlay.c
> +++ b/libfdt/fdt_overlay.c
> @@ -729,7 +729,13 @@ static int overlay_prevent_phandle_overwrite(void *fdt, void *fdto)
>  			return overlay;
>  
>  		target = fdt_overlay_target_offset(fdt, fdto, fragment, NULL);
> -		if (target < 0)
> +		if (target == -FDT_ERR_NOTFOUND)
> +			/*
> +			 * The subtree doesn't exist in the base, so nothing
> +			 * will be overwritten.
> +			 */
> +			continue;
> +		else if (target < 0)
>  			return target;
>  
>  		ret = overlay_prevent_phandle_overwrite_node(fdt, target,
> diff --git a/tests/overlay_overlay_bypath.dts b/tests/overlay_overlay_bypath.dts
> index f23e7b6035e2..dfcb7cdb25a4 100644
> --- a/tests/overlay_overlay_bypath.dts
> +++ b/tests/overlay_overlay_bypath.dts
> @@ -46,3 +46,7 @@
>  		new-sub-test-property;
>  	};
>  };
> +
> +&{/new-local-node} {
> +	another-new-property;
> +};
> diff --git a/tests/overlay_overlay_no_fixups.dts b/tests/overlay_overlay_no_fixups.dts
> index e8d0f96d889c..1dbdcdc2b40f 100644
> --- a/tests/overlay_overlay_no_fixups.dts
> +++ b/tests/overlay_overlay_no_fixups.dts
> @@ -72,6 +72,14 @@
>  		};
>  	};
>  
> +	fragment@7 {
> +		target-path = "/new-local-node";
> +
> +		__overlay__ {
> +			another-new-property;
> +		};
> +	};
> +
>  	__local_fixups__ {
>  		fragment@5 {
>  			__overlay__ {
> 
> base-commit: ff4f17eb58650784ffb2e8a8fbefebce1038f80b

-- 
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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