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, 27 insertions, 0 deletions

diff --git a/lib/check_signature.c b/lib/check_signature.c
new file mode 100644
index 000000000..43a7301da
--- /dev/null
+++ b/lib/check_signature.c
@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/io.h>
+#include <linux/export.h>
+
+/**
+ *	check_signature		-	find BIOS signatures
+ *	@io_addr: mmio address to check
+ *	@signature:  signature block
+ *	@length: length of signature
+ *
+ *	Perform a signature comparison with the mmio address io_addr. This
+ *	address should have been obtained by ioremap.
+ *	Returns 1 on a match.
+ */
+
+int check_signature(const volatile void __iomem *io_addr,
+			const unsigned char *signature, int length)
+{
+	while (length--) {
+		if (readb(io_addr) != *signature)
+			return 0;
+		io_addr++;
+		signature++;
+	}
+	return 1;
+}
+EXPORT_SYMBOL(check_signature);