Ezequiel Garcia <ezequiel@xxxxxxxxxxxxxxxxxxxx> 于2023年3月31日周五 10:38写道： > > 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. > Hi Ezequiel, Thanks for your detailed analysis. Got it :) Best regards, Zheng > 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 > >
