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

Uwe Kleine-König
2024-06-26T07:56:09Z

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>
---
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
--
2.43.0