linux-kernel - Re: [PATCH] usb: dwc3: qcom: fix NULL pointer dereference on dwc3_qcom_read_usb2

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Message-ID: <2024082315-astride-footrest-ab04@gregkh>
Date: Fri, 23 Aug 2024 14:14:35 +0800
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Faisal Hassan <quic_faisalh@...cinc.com>
Cc: Johan Hovold <johan@...nel.org>,
	Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
	linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] usb: dwc3: qcom: fix NULL pointer dereference on
 dwc3_qcom_read_usb2_speed

On Fri, Aug 23, 2024 at 09:26:18AM +0530, Faisal Hassan wrote:
> 
> 
> On 8/22/2024 4:55 PM, Johan Hovold wrote:
> > On Tue, Aug 13, 2024 at 04:48:47PM +0530, Faisal Hassan wrote:
> >> Null pointer dereference occurs when accessing 'hcd' to detect speed
> >> from dwc3_qcom_suspend after the xhci-hcd is unbound.
> > 
> > Why are you unbinding the xhci driver?
> > 
> 
> On our automotive platforms, when preparing for suspend, a script
> unbinds the xhci driver to remove all devices, ensuring the platform
> reaches the lowest power state.

That used to be the case a decade or so ago, but shouldn't be needed
anymore if your hardware is "sane" and can properly go to sleep.  Why
not just fix the driver to correctly sleep instead of unloading
everything?  This would require you to go through the whole
initialization sequence again when waking up and that can be a long time
overall, right?

thanks,

greg k-h