Re: [PATCH v3] usb: dwc3: core: Prevent USB core invalid event buffer address access

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Aug 16, 2024 at 09:13:09PM +0530, Selvarasu Ganesan wrote:
> 
> On 8/16/2024 3:25 PM, Greg KH wrote:
> > On Thu, Aug 15, 2024 at 12:18:31PM +0530, Selvarasu Ganesan wrote:
> >> This commit addresses an issue where the USB core could access an
> >> invalid event buffer address during runtime suspend, potentially causing
> >> SMMU faults and other memory issues in Exynos platforms. The problem
> >> arises from the following sequence.
> >>          1. In dwc3_gadget_suspend, there is a chance of a timeout when
> >>          moving the USB core to the halt state after clearing the
> >>          run/stop bit by software.
> >>          2. In dwc3_core_exit, the event buffer is cleared regardless of
> >>          the USB core's status, which may lead to an SMMU faults and
> >>          other memory issues. if the USB core tries to access the event
> >>          buffer address.
> >>
> >> To prevent this hardware quirk on Exynos platforms, this commit ensures
> >> that the event buffer address is not cleared by software  when the USB
> >> core is active during runtime suspend by checking its status before
> >> clearing the buffer address.
> >>
> >> Cc: stable@vger.kernel.org # v6.1+
> > Any hint as to what commit id this fixes?
> >
> > thanks,
> >
> > greg k-h
> 
> 
> Hi Greg,
> 
> This issue is not related to any particular commit. The given fix is 
> address a hardware quirk on the Exynos platform. And we require it to be 
> backported on stable kernel 6.1 and above all stable kernel.

If it's a hardware quirk issue, why are you restricting it to a specific
kernel release and not a specific kernel commit?  Why not 5.15?  5.4?

thanks,

greg k-h