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From:   Zhou Qingyang <zhou1615@umn.edu>
To:     zhou1615@umn.edu
Cc:     kjlu@umn.edu, 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>,
        Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        Alexandre Courbot <acourbot@chromium.org>,
        linux-media@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH] media: mtk-vcodec: media: mtk-vcodec: Fix a NULL pointer dereference in mtk_vcodec_fw_vpu_init()
Date:   Tue, 25 Jan 2022 01:15:03 +0800
Message-Id: <20220124171503.61098-1-zhou1615@umn.edu>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

In mtk_vcodec_fw_vpu_init(), devm_kzalloc() is assigned to fw and there is
a dereference of it right after that, which could lead to NULL pointer
dereference on failure of devm_kzalloc().

Fix this bug by adding a NULL check of fw.

This bug was found by a static analyzer.

Builds with 'make allyesconfig' show no new warnings,
and our static analyzer no longer warns about this code.

Fixes: 46233e91fa24 ("media: mtk-vcodec: move firmware implementations into their own files")
Signed-off-by: Zhou Qingyang <zhou1615@umn.edu>
---
The analysis employs differential checking to identify inconsistent 
security operations (e.g., checks or kfrees) between two code paths 
and confirms that the inconsistent operations are not recovered in the
current function or the callers, so they constitute bugs. 

Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.

 drivers/media/platform/mtk-vcodec/mtk_vcodec_fw_vpu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/media/platform/mtk-vcodec/mtk_vcodec_fw_vpu.c b/drivers/media/platform/mtk-vcodec/mtk_vcodec_fw_vpu.c
index cd27f637dbe7..33ae88a9f9da 100644
--- a/drivers/media/platform/mtk-vcodec/mtk_vcodec_fw_vpu.c
+++ b/drivers/media/platform/mtk-vcodec/mtk_vcodec_fw_vpu.c
@@ -102,6 +102,9 @@ struct mtk_vcodec_fw *mtk_vcodec_fw_vpu_init(struct mtk_vcodec_dev *dev,
 	vpu_wdt_reg_handler(fw_pdev, mtk_vcodec_vpu_reset_handler, dev, rst_id);
 
 	fw = devm_kzalloc(&dev->plat_dev->dev, sizeof(*fw), GFP_KERNEL);
+	if (!fw)
+		return ERR_PTR(-ENOMEM);
+
 	fw->type = VPU;
 	fw->ops = &mtk_vcodec_vpu_msg;
 	fw->pdev = fw_pdev;
-- 
2.25.1