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

[Dmitry Osipenko <dmitry.osipenko@collabora.com>]

On 10/20/23 07:07, 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.
> 
> 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>
> Cc: stable@vger.kernel.org
> ---
>  .../media/platform/mediatek/jpeg/mtk_jpeg_core.c    | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c
> index 7194f88edc0f..c3456c700c07 100644
> --- a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c
> +++ b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c
> @@ -1021,13 +1021,13 @@ static void mtk_jpeg_dec_device_run(void *priv)
>  	if (ret < 0)
>  		goto dec_end;
>  
> -	schedule_delayed_work(&jpeg->job_timeout_work,
> -			      msecs_to_jiffies(MTK_JPEG_HW_TIMEOUT_MSEC));
> -
>  	mtk_jpeg_set_dec_src(ctx, &src_buf->vb2_buf, &bs);
>  	if (mtk_jpeg_set_dec_dst(ctx, &jpeg_src_buf->dec_param, &dst_buf->vb2_buf, &fb))
>  		goto dec_end;
>  
> +	schedule_delayed_work(&jpeg->job_timeout_work,
> +			      msecs_to_jiffies(MTK_JPEG_HW_TIMEOUT_MSEC));
> +
>  	spin_lock_irqsave(&jpeg->hw_lock, flags);
>  	mtk_jpeg_dec_reset(jpeg->reg_base);
>  	mtk_jpeg_dec_set_config(jpeg->reg_base,
> @@ -1403,7 +1403,6 @@ 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);
> @@ -1750,9 +1749,6 @@ static void mtk_jpegdec_worker(struct work_struct *work)
>  	v4l2_m2m_src_buf_remove(ctx->fh.m2m_ctx);
>  	v4l2_m2m_dst_buf_remove(ctx->fh.m2m_ctx);
>  
> -	schedule_delayed_work(&comp_jpeg[hw_id]->job_timeout_work,
> -			      msecs_to_jiffies(MTK_JPEG_HW_TIMEOUT_MSEC));
> -
>  	mtk_jpeg_set_dec_src(ctx, &src_buf->vb2_buf, &bs);
>  	if (mtk_jpeg_set_dec_dst(ctx,
>  				 &jpeg_src_buf->dec_param,
> @@ -1762,6 +1758,9 @@ static void mtk_jpegdec_worker(struct work_struct *work)
>  		goto setdst_end;
>  	}
>  
> +	schedule_delayed_work(&comp_jpeg[hw_id]->job_timeout_work,
> +			      msecs_to_jiffies(MTK_JPEG_HW_TIMEOUT_MSEC));
> +
>  	spin_lock_irqsave(&comp_jpeg[hw_id]->hw_lock, flags);
>  	ctx->total_frame_num++;
>  	mtk_jpeg_dec_reset(comp_jpeg[hw_id]->reg_base);

What about to split this patch into 3 patches:

1. will remove cancel_delayed_work_sync()
2. will update mtk_jpeg_dec_device_run()
3. will update mtk_jpegdec_worker()

The reason for splitting is because the multi-core mtk_jpegdec_worker()
doesn't present in older stable kernels, and thus, the patch isn't
backportable as-is.

-- 
Best regards,
Dmitry