drm/mediatek: Add missing IS_ERR check for ovl_adaptor platform devicegrafted

platform_device_register_data() can fail and return an ERR_PTR, but the
return value is used without checking, leading to an invalid pointer
being stored in ddp_comp[].dev and passed to component_match_add() and
mtk_ddp_comp_init(), which could result in a kernel crash.

Add an IS_ERR() check to jump to the error handling path on failure.

Fixes: 0d9eee9118b7 ("drm/mediatek: Add drm ovl_adaptor sub driver for MT8195")
Cc: stable@vger.kernel.org
Signed-off-by: Haojie Li <lihaojie@kylinos.cn>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20260825100845.438893-1-lihaojie@kylinos.cn/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

1 files changed, 57 insertions, 0 deletions

diff --git a/Documentation/kbuild/Kconfig.recursion-issue-01 b/Documentation/kbuild/Kconfig.recursion-issue-01
new file mode 100644
index 000000000..ac49836d8
--- /dev/null
+++ b/Documentation/kbuild/Kconfig.recursion-issue-01
@@ -0,0 +1,57 @@
+# Simple Kconfig recursive issue
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+#
+# Test with:
+#
+# make KBUILD_KCONFIG=Documentation/kbuild/Kconfig.recursion-issue-01 allnoconfig
+#
+# This Kconfig file has a simple recursive dependency issue. In order to
+# understand why this recursive dependency issue occurs lets consider what
+# Kconfig needs to address. We iterate over what Kconfig needs to address
+# by stepping through the questions it needs to address sequentially.
+#
+#  * What values are possible for CORE?
+#
+# CORE_BELL_A_ADVANCED selects CORE, which means that it influences the values
+# that are possible for CORE. So for example if CORE_BELL_A_ADVANCED is 'y',
+# CORE must be 'y' too.
+#
+#  * What influences CORE_BELL_A_ADVANCED?
+#
+# As the name implies CORE_BELL_A_ADVANCED is an advanced feature of
+# CORE_BELL_A so naturally it depends on CORE_BELL_A. So if CORE_BELL_A is 'y'
+# we know CORE_BELL_A_ADVANCED can be 'y' too.
+#
+#   * What influences CORE_BELL_A?
+#
+# CORE_BELL_A depends on CORE, so CORE influences CORE_BELL_A.
+#
+# But that is a problem, because this means that in order to determine
+# what values are possible for CORE we ended up needing to address questions
+# regarding possible values of CORE itself again. Answering the original
+# question of what are the possible values of CORE would make the kconfig
+# tools run in a loop. When this happens Kconfig exits and complains about
+# the "recursive dependency detected" error.
+#
+# Reading the Documentation/kbuild/Kconfig.recursion-issue-01 file it may be
+# obvious that an easy solution to this problem should just be the removal
+# of the "select CORE" from CORE_BELL_A_ADVANCED as that is implicit already
+# since CORE_BELL_A depends on CORE. Recursive dependency issues are not always
+# so trivial to resolve, we provide another example below of practical
+# implications of this recursive issue where the solution is perhaps not so
+# easy to understand. Note that matching semantics on the dependency on
+# CORE also consist of a solution to this recursive problem.
+
+mainmenu "Simple example to demo kconfig recursive dependency issue"
+
+config CORE
+	tristate
+
+config CORE_BELL_A
+	tristate
+	depends on CORE
+
+config CORE_BELL_A_ADVANCED
+	tristate
+	depends on CORE_BELL_A
+	select CORE