Dear Kyrie, Guenter gave some advice about this issue in [1]. As we are not familiar with the code here, could you please see if the bug really exists? [1] https://lore.kernel.org/all/e03134f9-9433-ab6b-170a-8ce752fccdeb@xxxxxxxxxxxx/ Best regards, Zheng Zheng Hacker <hackerzheng666@xxxxxxxxx> 于2023年3月8日周三 17:11写道： > > Dear Kyrie, > > Sorry for my misunderstanding. I've seen the timeout worker is bound > with mtk_jpegdec_timeout_work rather than mtk_jpeg_job_timeout_work.So > the competition won't happen. > > Back to the beginning scene, I still don't know if it's a UAF issue or > not. The normal schedule is very strong to me. If we can call > mtk_jpeg_remove directly without calling mtk_jpeg_release, > The UAF is still possible. Otherwis, I think it's safe here. > > Best regards, > Zheng > > Kyrie Wu (吴晗) <Kyrie.Wu@xxxxxxxxxxxx> 于2023年3月8日周三 15:39写道： > > > > On Wed, 2023-03-08 at 14:10 +0800, Zheng Hacker wrote: > > > Hi Kyrie, > > > > > > After reviewing the code, I found anothe possible code path. As I am > > > not familiar with the module. It has high possibility it's wrong. > > > Could please help me check this? Very much appreciated for your > > > valuable time. > > > > > > In summary, mtk_jpegdec_worker was set in mtk_jpeg_open and started > > > in > > > mtk_jpeg_multicore_dec_device_run, which made it running on cpu1. > > > Inside the mtk_jpeg_multicore_dec_device_run, it will call > > > schedule_delayed_work to start the timeout_work, which will make it > > > running on cpu2. Meanwhile, we can call > > > mtk_jpeg_release to cancel the job. But there might be a race between > > > mtk_jpegdec_worker and v4l2_m2m_cancel_job. It may call > > > v4l2_m2m_job_finish too early to wake up the event. > > > The remove will go on, the other race is as described earlier. > > > > > > cpu0 cpu1 cpu2 > > > (1)->device_run > > > mtk_jpeg_multicore > > > _dec_device_run > > > queue_work > > > (jpeg->workqueue, > > > &ctx->jpeg_work); > > > (2)mtk_jpegdec_worker > > > (3)mtk_jpeg_release > > > v4l2_m2m_cancel_job > > > wait event > > > > > > schedule_delayed_work > > > (4)mtk_jpeg_job_timeout_w > > > ork > > > (5)v4l2_m2m_job_finish > > > wake up > > > (6)mtk_jpeg_remove > > > v4l2_m2m_release > > > kfree(m2m_dev) > > > (7)v4l2_m2m_get_curr_priv > > > > > Dear zheng, > > > > The mtk_jpeg_multicore_dec_device_run function is used for multi-hw > > jpeg decoding. Instead of scheduling mtk_jpeg_job_timeout_work, > > mtk_jpegdec_worker is scheduled in this function. > > > > The mtk_jpeg_dec_device_run function is used for single hw jpeg > > decoding, which schedules mtk_jpeg_job_timeout_work. > > > > A driver is either a single hw driver or a multi-hw driver and cannot > > represent both at the same time. > > mtk_jpeg_job_timeout_work and mtk_jpegdec_worker cannot be scheduled at > > the same time. > > So mtk_jpeg_job_timeout_work calls v4l2_m2m_job_finish would not cause > > competition between the mtk_jpegdec_worker and v4l2_m2m_cancel_job. > > > > Regards, > > Kyrie. > > > > > > > Kyrie Wu (吴晗) <Kyrie.Wu@xxxxxxxxxxxx> 于2023年3月8日周三 11:32写道： > > > > > > > > On Wed, 2023-03-08 at 10:20 +0800, Zheng Hacker wrote: > > > > > Hi Kyrie, > > > > > > > > > > Thank you for your careful analysis and response. I still have > > > > > some > > > > > areas that I don't quite understand and would like to ask for > > > > > clarification. That is, how do the function pointers for stop > > > > > streaming, initialized as mtk_jpeg_enc_stop_streaming and > > > > > mtk_jpeg_dec_stop_streaming, ensure that the worker is canceled? > > > > > I > > > > > would greatly appreciate your response. > > > > > > > > > > Best regards, > > > > > Zheng > > > > > > > > Dear zheng, > > > > > > > > For stop streaming, what I mean is that stoppping jpeg decoding or > > > > encoding. > > > > Ok, let me introduce the sw flow of stop streaming: > > > > Firstly, the app will call v4l2_m2m_ioctl_streamoff, which will > > > > call > > > > v4l2_m2m_cancel_job, if it finds a job running(as you note, cpu1 is > > > > running), it will wait event, the event is wake up by > > > > v4l2_m2m_job_finish function. And v4l2_m2m_job_finish is called by > > > > jpeg > > > > dec/enc irq handler, which means that the waitting would result mtk > > > > hw > > > > to finish dec/enc, irq will occur and irq handler would cancel > > > > timeout > > > > worker. The follow is shown as blow. > > > > v4l2_m2m_ioctl_streamoff > > > > v4l2_m2m_cancel_job mtk_jpeg_enc_irq/mtk_jpeg_dec > > > > _irq > > > > wait evnet <------ wake up ------v4l2_m2m_job_finish > > > > cancel timeout work > > > > > > > > As mentioned above, if it is normal stop streaming action, there > > > > will > > > > be no happen that the timeout worker does not canceled. > > > > > > > > But if mtk_jpeg_remove is called directly without above flow, it > > > > would > > > > cause lots of issues. > > > > > > > > Regards, > > > > Kyrie. > > > > > > > > > > Kyrie Wu (吴晗) <Kyrie.Wu@xxxxxxxxxxxx> 于2023年3月8日周三 10:02写道： > > > > > > > > > > > > On Tue, 2023-03-07 at 23:03 +0800, Zheng Hacker wrote: > > > > > > > The timer function was set in mtk_jpeg_probe with > > > > > > > mtk_jpeg_job_timeout_work function. > > > > > > > And the worker is started in mtk_jpeg_dec_device_run. > > > > > > > There are two functions (mtk_jpeg_enc_irq and > > > > > > > mtk_jpeg_dec_irq) > > > > > > > which > > > > > > > may cancel the worker. > > > > > > > They are used as IRQ handler function which is saved as > > > > > > > function > > > > > > > pointer in a variable. > > > > > > > In mtk_jpeg_probe, they are registered by devm_request_irq: > > > > > > > > > > > > > > ret = devm_request_irq(&pdev->dev, > > > > > > > jpeg_irq, > > > > > > > jpeg->variant->irq_handler, > > > > > > > 0, > > > > > > > pdev->name, jpeg); > > > > > > > if (ret) { > > > > > > > dev_err(&pdev->dev, "Failed to request jpeg_irq %d > > > > > > > (%d)\n", > > > > > > > jpeg_irq, ret); > > > > > > > return ret; > > > > > > > } > > > > > > > > > > > > > > However, if we remove the module without triggering the irq, > > > > > > > the > > > > > > > worker will never be removed. > > > > > > > > > > > > > > As for the schedule, mtk_jpeg_dec_device_run and > > > > > > > mtk_jpeg_enc_device_run will start the worker. > > > > > > > The schedule invoking is quite complicated. As far as I know, > > > > > > > the > > > > > > > invoking chain is as follows: > > > > > > > > > > > > > > v4l2_m2m_init->v4l2_m2m_device_run_work->v4l2_m2m_try_run > > > > > > > > > > > > > > the v4l2_m2m_device_run_work function is also a worker which > > > > > > > is > > > > > > > set > > > > > > > in > > > > > > > v4l2_m2m_init and started in > > > > > > > v4l2_m2m_schedule_next_job. > > > > > > > > > > > > > > Before calling remove function, the mtk_jpeg_release was > > > > > > > invoked > > > > > > > to > > > > > > > release the related resource. > > > > > > > > > > > > > > v4l2_m2m_cancel_job will cancel the job by calling > > > > > > > m2m_dev->m2m_ops->job_abort(m2m_ctx->priv). > > > > > > > > > > > > > > But this will only cancel the current queue by > > > > > > > list_del(&m2m_dev->curr_ctx->queue); > > > > > > > > > > > > > > I think this can not cancel the posted task mentioned before. > > > > > > > So > > > > > > > I > > > > > > > think if mtk_jpeg_job_timeout_work > > > > > > > > > > > > > > is working on, and using jpeg->m2m_dev after freeing it in > > > > > > > mtk_jpeg_remove, it will cause a UAF bug. > > > > > > > > > > > > > > static int mtk_jpeg_release(struct file *file) > > > > > > > { > > > > > > > struct mtk_jpeg_dev *jpeg = video_drvdata(file); > > > > > > > struct mtk_jpeg_ctx *ctx = mtk_jpeg_fh_to_ctx(file- > > > > > > > > private_data); > > > > > > > > > > > > > > mutex_lock(&jpeg->lock); > > > > > > > v4l2_ctrl_handler_free(&ctx->ctrl_hdl); > > > > > > > [1] v4l2_m2m_ctx_release(ctx->fh.m2m_ctx); > > > > > > > v4l2_fh_del(&ctx->fh); > > > > > > > v4l2_fh_exit(&ctx->fh); > > > > > > > kfree(ctx); > > > > > > > mutex_unlock(&jpeg->lock); > > > > > > > return 0; > > > > > > > } > > > > > > > > > > > > > > void v4l2_m2m_ctx_release(struct v4l2_m2m_ctx *m2m_ctx) > > > > > > > { > > > > > > > /* wait until the current context is dequeued from > > > > > > > job_queue */ > > > > > > > [2] v4l2_m2m_cancel_job(m2m_ctx); > > > > > > > > > > > > > > vb2_queue_release(&m2m_ctx->cap_q_ctx.q); > > > > > > > vb2_queue_release(&m2m_ctx->out_q_ctx.q); > > > > > > > > > > > > > > kfree(m2m_ctx); > > > > > > > } > > > > > > > > > > > > > > Note that all of this is static analysis, which may be false > > > > > > > positive. > > > > > > > Feel free to tell me if there is something I've missed. > > > > > > > > > > > > > > Regard, > > > > > > > Zheng > > > > > > > > > > > > Dear Zheng, > > > > > > > > > > > > You set up an application scenario: > > > > > > cpu1 is using the mtk-jpeg driver and timeout work has been > > > > > > scheduled. > > > > > > At the same time cpu0 wanted to remove the mtk-jpeg driver, > > > > > > which > > > > > > caused the UAF bug. > > > > > > I wonder if such an irrational application scenario could > > > > > > exist. > > > > > > This > > > > > > scenario, as you described, not only leads to the problems you > > > > > > mentioned, but also to output&capture memory leaks and > > > > > > unreleased > > > > > > resources, such as spinlock. > > > > > > Typically, if we want to remove the driver, we firstly do stop > > > > > > streaming, which ensures that the worker has been canceled. > > > > > > I agree with your changes from the perspective of strengthening > > > > > > the > > > > > > robustness of the driver code. > > > > > > > > > > > > Regards, > > > > > > Kyrie. > > > > > > > > > > > > > > Irui Wang (王瑞) <Irui.Wang@xxxxxxxxxxxx> 于2023年3月7日周二 18:23写道： > > > > > > > > > > > > > > > > Dear Angelo and Zheng, > > > > > > > > > > > > > > > > Thanks for your patch and comments. > > > > > > > > > > > > > > > > Dear Kyrie, > > > > > > > > > > > > > > > > Please help to check this, thanks. > > > > > > > > > > > > > > > > Best Regards > > > > > > > > > > > > > > > > On Tue, 2023-03-07 at 10:49 +0100, AngeloGioacchino Del > > > > > > > > Regno > > > > > > > > wrote: > > > > > > > > > Il 07/03/23 10:27, Zheng Hacker ha scritto: > > > > > > > > > > Hi, > > > > > > > > > > > > > > > > > > > > Is there anyone who can help with this? I can provide > > > > > > > > > > more > > > > > > > > > > details > > > > > > > > > > like invoking chain if needed. > > > > > > > > > > > > > > > > > > > > > > > > > > > > Providing more details is always good. Please do. > > > > > > > > > > > > > > > > > > Meanwhile, adding Irui Wang to the loop: he's doing mtk- > > > > > > > > > jpeg. > > > > > > > > > > > > > > > > > > Regards, > > > > > > > > > Angelo > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > Zheng > > > > > > > > > > > > > > > > > > > > Zheng Wang <zyytlz.wz@xxxxxxx> 于2023年3月6日周一 14:28写道： > > > > > > > > > > > > > > > > > > > > > > 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@xxxxxxx> > > > > > > > > > > > --- > > > > > > > > > > > > > > > > > > > > > > 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); > > > > > > > > > > > pm_runtime_disable(&pdev->dev); > > > > > > > > > > > video_unregister_device(jpeg->vdev); > > > > > > > > > > > v4l2_m2m_release(jpeg->m2m_dev); > > > > > > > > > > > -- > > > > > > > > > > > 2.25.1 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
