[PATCH 3/4] media: mediatek: vcodec: Fix potential crash in mtk_vcodec_dbgfs_remove()

From: Dan Carpenter <dan.carpenter@linaro.org>
To: Yunfei Dong <yunfei.dong@mediatek.com>
Cc: Tiffany Lin <tiffany.lin@mediatek.com>,
	Andrew-CT Chen <andrew-ct.chen@mediatek.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	AngeloGioacchino Del Regno
	<angelogioacchino.delregno@collabora.com>,
	Hans Verkuil <hverkuil-cisco@xs4all.nl>,
	linux-media@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org,
	kernel-janitors@vger.kernel.org
Subject: [PATCH 3/4] media: mediatek: vcodec: Fix potential crash in mtk_vcodec_dbgfs_remove()
Date: Wed, 14 Jun 2023 16:07:15 +0300	[thread overview]
Message-ID: <d4fffbaa-f01d-4e2e-9b1b-45d996236642@moroto.mountain> (raw)
In-Reply-To: <ca491aaa-cfc4-4a84-b7fc-b64f3adc6550@moroto.mountain>

The list iterator "dbgfs_inst" is always non-NULL.  This means that the
test for NULL inside the loop is unnecessary and it also means that the
test for NULL outside the loop will not work.  If we do not find the item
on the list with the correct the ctx_id then it will free invalid memory
leading to a crash.

Fixes: cd403a6a0419 ("media: mediatek: vcodec: Add a debugfs file to get different useful information")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
---
 .../media/platform/mediatek/vcodec/mtk_vcodec_dbgfs.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/media/platform/mediatek/vcodec/mtk_vcodec_dbgfs.c b/drivers/media/platform/mediatek/vcodec/mtk_vcodec_dbgfs.c
index 2151c3967684..2ebf68d33d57 100644
--- a/drivers/media/platform/mediatek/vcodec/mtk_vcodec_dbgfs.c
+++ b/drivers/media/platform/mediatek/vcodec/mtk_vcodec_dbgfs.c
@@ -166,16 +166,13 @@ void mtk_vcodec_dbgfs_remove(struct mtk_vcodec_dev *vcodec_dev, int ctx_id)
 	struct mtk_vcodec_dbgfs_inst *dbgfs_inst;
 
 	list_for_each_entry(dbgfs_inst, &vcodec_dev->dbgfs.dbgfs_head, node) {
-		if (dbgfs_inst && dbgfs_inst->inst_id == ctx_id) {
+		if (dbgfs_inst->inst_id == ctx_id) {
 			vcodec_dev->dbgfs.inst_count--;
-			break;
+			list_del(&dbgfs_inst->node);
+			kfree(dbgfs_inst);
+			return;
 		}
 	}
-
-	if (dbgfs_inst) {
-		list_del(&dbgfs_inst->node);
-		kfree(dbgfs_inst);
-	}
 }
 EXPORT_SYMBOL_GPL(mtk_vcodec_dbgfs_remove);
 
-- 
2.39.2


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