Hi Zheng, On Mon, Mar 13, 2023 at 12:42 PM Zheng Wang <zyytlz.wz@xxxxxxx> wrote: > > In hantro_probe, vpu->watchdog_work is bound with > hantro_watchdog. Then hantro_end_prepare_run may > be called to start the work. > > If we close the file or remove the module which will > call hantro_release and hantro_remove to make cleanup, It's not possible to close the file or remove the module while a watchdog is scheduled. That's because the watchdog is active only during a mem2mem job, and the file won't be closed until the job is done. v4l2_m2m_ctx_release calls v4l2_m2m_cancel_jobw which waits until the job is done. If you can confirm it's possible to remove or close the file while a job is running, that would be a driver bug. Thanks for the patch, but it's not needed. Regards, Ezequiel > there may be an unfinished work. The possible sequence > is as follows, which will cause a typical UAF bug. > > The same thing will happen in hantro_release, and use > ctx after freeing it. > > Fix it by canceling the work before cleanup in hantro_release. > > CPU0 CPU1 > > |hantro_watchdog > hantro_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> > --- > v3: > - use cancel_delayed_work_sync instead of cancel_delayed_work and add it to > hantro_release suggested by Hans Verkuil > > v2: > - move the cancel-work-related code to hantro_remove suggested by Hans Verkuil > --- > drivers/media/platform/verisilicon/hantro_drv.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/media/platform/verisilicon/hantro_drv.c b/drivers/media/platform/verisilicon/hantro_drv.c > index b0aeedae7b65..86a4c0fa8c7d 100644 > --- a/drivers/media/platform/verisilicon/hantro_drv.c > +++ b/drivers/media/platform/verisilicon/hantro_drv.c > @@ -597,6 +597,7 @@ static int hantro_release(struct file *filp) > struct hantro_ctx *ctx = > container_of(filp->private_data, struct hantro_ctx, fh); > > + cancel_delayed_work_sync(&ctx->dev->watchdog_work); > /* > * No need for extra locking because this was the last reference > * to this file. > @@ -1099,6 +1100,7 @@ static int hantro_remove(struct platform_device *pdev) > > v4l2_info(&vpu->v4l2_dev, "Removing %s\n", pdev->name); > > + cancel_delayed_work_sync(&vpu->watchdog_work); > media_device_unregister(&vpu->mdev); > hantro_remove_dec_func(vpu); > hantro_remove_enc_func(vpu); > -- > 2.25.1 >
