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Message-ID: <b372ef8c-7f3f-483b-8cc2-d927a60050be@baylibre.com>
Date:   Fri, 20 Oct 2023 12:32:22 +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, angelogioacchino.delregno@collabora.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,
        wenst@chromium.org, stable@vger.kernel.org
References: <20231020040732.2499269-1-zyytlz.wz@163.com>
From:   Alexandre Mergnat <amergnat@baylibre.com>
In-Reply-To: <20231020040732.2499269-1-zyytlz.wz@163.com>
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Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>

On 20/10/2023 06:07, Zheng Wang wrote:
> 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.

-- 
Regards,
Alexandre