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Message-ID: <8b799079-fd98-46ba-a2cd-04ecf0c0df1d@collabora.com>
Date:   Fri, 20 Oct 2023 10:20:13 +0200
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Subject: Re: [PATCH] media: mtk-jpeg: Fix use after free bug due to error path
 handling in mtk_jpeg_dec_device_run
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To:     Zheng Wang <zyytlz.wz@163.com>, dmitry.osipenko@collabora.com
Cc:     Kyrie.Wu@mediatek.com, bin.liu@mediatek.com, mchehab@kernel.org,
        matthias.bgg@gmail.com, linux-media@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, Irui.Wang@mediatek.com,
        security@kernel.org, hackerzheng666@gmail.com,
        1395428693sheep@gmail.com, alex000young@gmail.com,
        amergnat@baylibre.com, wenst@chromium.org, stable@vger.kernel.org
References: <20231020040732.2499269-1-zyytlz.wz@163.com>
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>
In-Reply-To: <20231020040732.2499269-1-zyytlz.wz@163.com>
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Il 20/10/23 06:07, Zheng Wang ha scritto:
> In mtk_jpeg_probe, &jpeg->job_timeout_work is bound with
> mtk_jpeg_job_timeout_work.
> 
> In mtk_jpeg_dec_device_run, if error happens in
> mtk_jpeg_set_dec_dst, it will finally start the worker while
> mark the job as finished by invoking v4l2_m2m_job_finish.
> 
> There are two methods to trigger the bug. If we remove the
> module, it which will call mtk_jpeg_remove to make cleanup.
> The possible sequence is as follows, which will cause a
> use-after-free bug.
> 
> CPU0                  CPU1
> mtk_jpeg_dec_...    |
>    start worker	    |
>                      |mtk_jpeg_job_timeout_work
> mtk_jpeg_remove     |
>    v4l2_m2m_release  |
>      kfree(m2m_dev); |
>                      |
>                      | v4l2_m2m_get_curr_priv
>                      |   m2m_dev->curr_ctx //use
> 
> If we close the file descriptor, which will call mtk_jpeg_release,
> it will have a similar sequence.
> 
> Fix this bug by start timeout worker only if started jpegdec worker
> successfully so the v4l2_m2m_job_finish will only be called on
> either mtk_jpeg_job_timeout_work or mtk_jpeg_dec_device_run.
> 
> This patch also reverts commit c677d7ae8314
> ("media: mtk-jpeg: Fix use after free bug due to uncanceled work")
> for this patch also fixed the use-after-free bug mentioned before.
> Before mtk_jpeg_remove is invoked, mtk_jpeg_release must be invoked
> to close opened files. And it will call v4l2_m2m_cancel_job to wait
> for the timeout worker finished so the canceling in mtk_jpeg_remove
> is unnecessary.
> 
> Fixes: b2f0d2724ba4 ("[media] vcodec: mediatek: Add Mediatek JPEG Decoder Driver")
> Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>