| Message ID | 20230302093715.811758-1-zyytlz.wz@163.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | media: mtk-jpeg: Fix use after free bug due to uncanceled work | expand |
On Thu, Mar 02, 2023 at 05:37:15PM +0800, Zheng Wang wrote: > 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 > > Signed-off-by: Zheng Wang <zyytlz.wz@163.com> > --- > drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c > index 969516a940ba..364513e7897e 100644 > --- a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c > +++ b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c > @@ -1793,7 +1793,7 @@ static int mtk_jpeg_probe(struct platform_device *pdev) > static int mtk_jpeg_remove(struct platform_device *pdev) > { > struct mtk_jpeg_dev *jpeg = platform_get_drvdata(pdev); > - > + cancel_delayed_work(&jpeg->job_timeout_work); The empty line is needed (coding style). Also, this doesn't cancel the worker if it is already running. This should probably be cancel_delayed_work_sync(). Even then the question is if it is possible that new work is queued before the device is unregistered. Guenter > pm_runtime_disable(&pdev->dev); > video_unregister_device(jpeg->vdev); > v4l2_m2m_release(jpeg->m2m_dev); > -- > 2.25.1 >
Hi, Thanks for your reply. I think you're right. I don't know if there is other method to stop new work from enqueing. Could you please give me some advice about the fix? Regards, Zheng Guenter Roeck <linux@roeck-us.net> 于2023年3月9日周四 08:27写道： > > On Thu, Mar 02, 2023 at 05:37:15PM +0800, Zheng Wang wrote: > > 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 > > > > Signed-off-by: Zheng Wang <zyytlz.wz@163.com> > > --- > > drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c > > index 969516a940ba..364513e7897e 100644 > > --- a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c > > +++ b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c > > @@ -1793,7 +1793,7 @@ static int mtk_jpeg_probe(struct platform_device *pdev) > > static int mtk_jpeg_remove(struct platform_device *pdev) > > { > > struct mtk_jpeg_dev *jpeg = platform_get_drvdata(pdev); > > - > > + cancel_delayed_work(&jpeg->job_timeout_work); > > The empty line is needed (coding style). Also, this doesn't cancel > the worker if it is already running. This should probably be > cancel_delayed_work_sync(). Even then the question is if it is > possible that new work is queued before the device is unregistered. > > Guenter > > > pm_runtime_disable(&pdev->dev); > > video_unregister_device(jpeg->vdev); > > v4l2_m2m_release(jpeg->m2m_dev); > > -- > > 2.25.1 > >
On 3/8/23 19:58, Zheng Hacker wrote: > Hi, > > Thanks for your reply. I think you're right. I don't know if there is > other method to stop new work from enqueing. Could you please give me > some advice about the fix? > Top-posting is discouraged. Anyway - I don't know the code well enough to suggest a solution. It all depends on the driver architecture. The maintainers might have a better idea. A worse problem appears to be that the worker is also canceled from mtk_jpeg_enc_irq() and mtk_jpeg_dec_irq(). Those are non-threaded interrupt handlers which, as far as I know, must not sleep and thus can not call cancel_delayed_work_sync(). I have no idea how to solve that problem either. Guenter > Regards, > Zheng > > Guenter Roeck <linux@roeck-us.net> 于2023年3月9日周四 08:27写道： >> >> On Thu, Mar 02, 2023 at 05:37:15PM +0800, Zheng Wang wrote: >>> 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 >>> >>> Signed-off-by: Zheng Wang <zyytlz.wz@163.com> >>> --- >>> drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c >>> index 969516a940ba..364513e7897e 100644 >>> --- a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c >>> +++ b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c >>> @@ -1793,7 +1793,7 @@ static int mtk_jpeg_probe(struct platform_device *pdev) >>> static int mtk_jpeg_remove(struct platform_device *pdev) >>> { >>> struct mtk_jpeg_dev *jpeg = platform_get_drvdata(pdev); >>> - >>> + cancel_delayed_work(&jpeg->job_timeout_work); >> >> The empty line is needed (coding style). Also, this doesn't cancel >> the worker if it is already running. This should probably be >> cancel_delayed_work_sync(). Even then the question is if it is >> possible that new work is queued before the device is unregistered. >> >> Guenter >> >>> pm_runtime_disable(&pdev->dev); >>> video_unregister_device(jpeg->vdev); >>> v4l2_m2m_release(jpeg->m2m_dev); >>> -- >>> 2.25.1 >>>
Guenter Roeck <linux@roeck-us.net> 于2023年3月9日周四 13:30写道： > > On 3/8/23 19:58, Zheng Hacker wrote: > > Hi, > > > > Thanks for your reply. I think you're right. I don't know if there is > > other method to stop new work from enqueing. Could you please give me > > some advice about the fix? > > > > Top-posting is discouraged. > Sorry I forgot that. Thanks for the kind reminder. > Anyway - > I don't know the code well enough to suggest a solution. > It all depends on the driver architecture. The maintainers might > have a better idea. > Yes, some related developers have reached out to me and discussed fixes with me. > A worse problem appears to be that the worker is also canceled > from mtk_jpeg_enc_irq() and mtk_jpeg_dec_irq(). Those are non-threaded > interrupt handlers which, as far as I know, must not sleep and thus > can not call cancel_delayed_work_sync(). I have no idea how to solve > that problem either. > I'd be glad to pass along your thoughts and recommendations to the relevant parties. Best regards, Zheng
diff --git a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c index 969516a940ba..364513e7897e 100644 --- a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c +++ b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c @@ -1793,7 +1793,7 @@ static int mtk_jpeg_probe(struct platform_device *pdev) static int mtk_jpeg_remove(struct platform_device *pdev) { struct mtk_jpeg_dev *jpeg = platform_get_drvdata(pdev); - + cancel_delayed_work(&jpeg->job_timeout_work); pm_runtime_disable(&pdev->dev); video_unregister_device(jpeg->vdev); v4l2_m2m_release(jpeg->m2m_dev);
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 Signed-off-by: Zheng Wang <zyytlz.wz@163.com> --- drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)