The timer function was inited 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 triigering 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 is also a worker which is inited 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 use jpeg->m2m_dev after freeing it in
mtk_jpeg_remove, it wll cause 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
Zheng Hacker <hackerzheng666@xxxxxxxxx> 于2023年3月7日周二 17:27写道：
>
> Hi,
>
> Is there anyone who can help with this? I can provide more details
> like invoking chain if needed.
>
> 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
> >
