linux-kernel - Re: [PATCH] media: mtk-jpeg: Fix use after free bug due to error path handling in mtk_jpeg_dec_device

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Date:   Fri, 20 Oct 2023 12:32:22 +0200
From:   Alexandre Mergnat <amergnat@...libre.com>
To:     Zheng Wang <zyytlz.wz@....com>, dmitry.osipenko@...labora.com
Cc:     Kyrie.Wu@...iatek.com, 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,
        wenst@...omium.org, stable@...r.kernel.org
Subject: Re: [PATCH] media: mtk-jpeg: Fix use after free bug due to error path
 handling in mtk_jpeg_dec_device_run

Reviewed-by: Alexandre Mergnat <amergnat@...libre.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