Re: AW: AW: KASAN: use-after-free Read in usbhid_power

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On Fri, Aug 09, 2019 at 12:38:35PM +0000, Schmid, Carsten wrote:
> Hi again,
> 
> >>
> >> Hey, i did not want to trigger an eartquake in the basement of the kernel ;-)
> >> My intention was to prevent some crashes, and help developers to find their bugs.
> >> I think my patch exactly does this.
> > 
> > Hehe, actually drivers not being able to block unbind has been bugging me
> > for
> > a while now, because there are cases where this would be really helpful.
> >>> 1) make resources refcounted, have child resources take a ref on the parent
> >>> 2) Disallow unbind on devices with bound child-devices?
> >>>
> >> Exactly what i was thinking of in first attempts.
> >> But i fear that would break even more use cases.
> >>
> >> Hans, directly regarding the driver:
> >> The problem i see is that the xhci_intel_unregister_pdev which is added
> >> as an action with devm_add_action_or_reset() is called late by the framework,
> >> later than the usb_hcd_pci_remove() in xhci_pci_remove.
> >> Is there any chance to trigger this before?
> >> This is what Greg meant with "right order".
> > 
> > Ah, I missed that part, sure that should be easy, just stop using
> > devm_add_action_or_reset() and do the xhci_intel_unregister_pdev()
> > manually at the right time. The downside of this is that you also
> > need to make sure it happens at the right time from probe error-paths
> > but given the bug you are hitting, I guess that is probably
> > already a problem.
> > 
> @Hans:
> Sure, will have a look at this. I think i have found where to do that,
> but need to check how to get the pdev pointer there ....
> 
> @Greg:
> I am still confident that my patch in __release_region should be taken in.

Ok, submit it in a "real" way and we can consider it :)

thanks,

greg k-h



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