On Thu, Jun 08, 2023 at 03:49:58PM +0200, Johan Hovold wrote: > On Thu, Jun 08, 2023 at 06:53:13PM +0530, Manivannan Sadhasivam wrote: > > On Thu, Jun 08, 2023 at 03:09:27PM +0200, Johan Hovold wrote: > > > On Thu, Jun 08, 2023 at 06:32:46PM +0530, Manivannan Sadhasivam wrote: > > > > On Wed, Jun 07, 2023 at 12:05:40PM +0200, Johan Hovold wrote: > > > > > Some dwc3 glue drivers are currently accessing the driver data of the > > > > > child core device directly, which is clearly a bad idea as the child may > > > > > not have probed yet or may have been unbound from its driver. > > > > > > > > > > As a workaround until the glue drivers have been fixed, clear the driver > > > > > data pointer before allowing the glue parent device to runtime suspend > > > > > to prevent its driver from accessing data that has been freed during > > > > > unbind. > > > > > > > > @@ -1929,6 +1929,11 @@ static int dwc3_remove(struct platform_device *pdev) > > > > > pm_runtime_disable(&pdev->dev); > > > > > pm_runtime_dont_use_autosuspend(&pdev->dev); > > > > > pm_runtime_put_noidle(&pdev->dev); > > > > > + /* > > > > > + * HACK: Clear the driver data, which is currently accessed by parent > > > > > + * glue drivers, before allowing the parent to suspend. > > > > > + */ > > > > > + platform_set_drvdata(pdev, NULL); > > > > > > > > This is required because you have seen the glue driver going to runtime suspend > > > > once the below pm_runtime_set_suspended() is completed? > > > > > > This is based on analysis of the code. The parent (glue) can not suspend > > > while the child (core) is in the active state, but once we set the > > > suspended state that could happen. > > > > I could see that the driver core is setting drvdata to NULL during > > device_unbind_cleanup(), so not sure if this scenario could be met otherwise it > > will be redundant. > > If this was redundant I wouldn't have added it. ;) > > The parent driver has no business accessing the driver data of the child > in the first place, but it must absolutely not do so after the child has > been unbound from its driver and the driver data is getting freed. > > Relying on the clean up in driver core that resets this pointer does not > work as that would still leave a window where the parent could access > this stale data. > Well, I agree with the small window here. Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx> - Mani > Johan -- மணிவண்ணன் சதாசிவம்
