linux-kernel - [PATCH] drm/mediatek: Initialize pointer in mtk_drm_of_ddp_path_build

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Message-ID: <20241112105030.93337-1-angelogioacchino.delregno@collabora.com>
Date: Tue, 12 Nov 2024 11:50:30 +0100
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: chunkuang.hu@...nel.org
Cc: p.zabel@...gutronix.de,
	airlied@...il.com,
	simona@...ll.ch,
	matthias.bgg@...il.com,
	angelogioacchino.delregno@...labora.com,
	sui.jingfeng@...ux.dev,
	ck.hu@...iatek.com,
	amergnat@...libre.com,
	dri-devel@...ts.freedesktop.org,
	linux-mediatek@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	kernel@...labora.com,
	dan.carpenter@...aro.org
Subject: [PATCH] drm/mediatek: Initialize pointer in mtk_drm_of_ddp_path_build_one()

The struct device_node *next pointer is not initialized, and it is
used in an error path in which it may have never been modified by
function mtk_drm_of_get_ddp_ep_cid().

Since the error path is relying on that pointer being NULL for the
OVL Adaptor and/or invalid component check and since said pointer
is being used in prints for %pOF, in the case that it points to a
bogus address, the print may cause a KP.

To resolve that, initialize the *next pointer to NULL before usage.

Fixes: 4c932840db1d ("drm/mediatek: Implement OF graphs support for display paths")
Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
---
 drivers/gpu/drm/mediatek/mtk_drm_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
index 9a8ef8558da9..bc06c664e80f 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
@@ -900,7 +900,7 @@ static int mtk_drm_of_ddp_path_build_one(struct device *dev, enum mtk_crtc_path
 					 const unsigned int **out_path,
 					 unsigned int *out_path_len)
 {
-	struct device_node *next, *prev, *vdo = dev->parent->of_node;
+	struct device_node *next = NULL, *prev, *vdo = dev->parent->of_node;
 	unsigned int temp_path[DDP_COMPONENT_DRM_ID_MAX] = { 0 };
 	unsigned int *final_ddp_path;
 	unsigned short int idx = 0;
-- 
2.47.0