Re: [Patch v5] usb: hcd: use managed device resources

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On Fri, Aug 23, 2019 at 02:11:28PM +0000, Schmid, Carsten wrote:
> Using managed device resources in usb_hcd_pci_probe() allows devm usage for
> resource subranges, such as the mmio resource for the platform device
> created to control host/device mode mux, which is a xhci extended
> capability, and sits inside the xhci mmio region.
> 
> If managed device resources are not used then "parent" resource
> is released before subrange at driver removal as .remove callback is
> called before the devres list of resources for this device is walked
> and released.
> 
> This has been observed with the xhci extended capability driver causing a
> use-after-free which is now fixed.
> 
> An additional nice benefit is that error handling on driver initialisation
> is simplified much.
> 
> Signed-off-by: Carsten Schmid <carsten_schmid@xxxxxxxxxx>
> Tested-by: Carsten Schmid <carsten_schmid@xxxxxxxxxx>
> ---
> Rationale:
> Use-after-free was reproduced on 4.14.102 and 4.14.129 kernel
> using unbind mechanism.
> echo 0000:00:15.0 > /sys/bus/pci/drivers/xhci_hcd/unbind
> 
> Upstream version of driver is identical in the affected code.
> Fix was tested successfully on 4.14.129.
> Provided patch applies and compiles on v5.2.8 stable.
> As this is also a bugfix, please consider it to go to stable trees too.

How far back should it go, just 4.14?  Was this caused by a specific
commit that you happened to notice?

thanks,

greg k-h



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