linux-kernel - [PATCH v2] media: mtk-jpeg: Fix use after free bug due to uncanceled work

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Message-Id: <20230624145050.2471885-1-zyytlz.wz@163.com>
Date:   Sat, 24 Jun 2023 22:50:50 +0800
From:   Zheng Wang <zyytlz.wz@....com>
To:     Kyrie.Wu@...iatek.com
Cc:     bin.liu@...iatek.com, mchehab@...nel.org, matthias.bgg@...il.com,
        angelogioacchino.delregno@...labora.com,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, Irui.Wang@...iatek.com,
        security@...nel.org, hackerzheng666@...il.com,
        1395428693sheep@...il.com, alex000young@...il.com,
        Zheng Wang <zyytlz.wz@....com>
Subject: [PATCH v2] media: mtk-jpeg: Fix use after free bug due to uncanceled work

In mtk_jpeg_probe, &jpeg->job_timeout_work is bound with
mtk_jpeg_job_timeout_work. Then mtk_jpeg_dec_device_run
and mtk_jpeg_enc_device_run may be called to start the
work.
If we remove the module which will call mtk_jpeg_remove
to make cleanup, there may be a unfinished work. The
possible sequence is as follows, which will cause a
typical UAF bug.

Fix it by canceling the work before cleanup in the mtk_jpeg_remove

CPU0                  CPU1

                    |mtk_jpeg_job_timeout_work
mtk_jpeg_remove     |
  v4l2_m2m_release  |
    kfree(m2m_dev); |
                    |
                    | v4l2_m2m_get_curr_priv
                    |   m2m_dev->curr_ctx //use
Fixes: b2f0d2724ba4 ("[media] vcodec: mediatek: Add Mediatek JPEG Decoder Driver")
Signed-off-by: Zheng Wang <zyytlz.wz@....com>
---
- v2: use cancel_delayed_work_sync instead of cancel_delayed_work suggested by Kyrie.
---
 drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c
index 0051f372a66c..6069ecf420b0 100644
--- a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c
+++ b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c
@@ -1816,6 +1816,7 @@ static void mtk_jpeg_remove(struct platform_device *pdev)
 {
 	struct mtk_jpeg_dev *jpeg = platform_get_drvdata(pdev);
 
+	cancel_delayed_work_sync(&jpeg->job_timeout_work);
 	pm_runtime_disable(&pdev->dev);
 	video_unregister_device(jpeg->vdev);
 	v4l2_m2m_release(jpeg->m2m_dev);
-- 
2.25.1