linux-kernel - Re: [PATCH] USB: core: of: Check device_node before parsing in usb_of_get_child

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Date:	Mon, 15 Aug 2016 20:41:17 +0200
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Vaibhav Hiremath <vaibhav.hiremath@...aro.org>
Cc:	linux-usb@...r.kernel.org, robh@...nel.org, p.zabel@...gutronix.de,
	stern@...land.harvard.edu, arnd@...db.de, peter.chen@...escale.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] USB: core: of: Check device_node before parsing in
 usb_of_get_child_node()

On Mon, Aug 15, 2016 at 11:31:10AM -0700, Vaibhav Hiremath wrote:
> In case of HUB devices connected to USB ports, we may not have DT
> node representing it inside USB, and when devices connected to hub
> gets enumerated, call to usb_of_get_child_node() leads to NULL pointer
> dereference.

Really?  That seems messed up.

> In the usecase we have, where EHCI port is connected to USB HUB
> device, and downward ports of HUB are connected to further USB
> devices. When those devices gets enumerated, in order,
>  1. USB HUB ->
> 	-> Call to usb_of_get_child_node() is OK, as
> 	parent->dev.of_node is pointing to host node.
>  2. Devices connected to downward port of USB HUB
>  	-> Call to usb_of_get_child_node() leads to NULL
> 	pointer dereference as parent->dev.of_node = NULL,
> 	as USB HUB DTS node may be empty.

Why is the hub DTS empty?  Shouldn't that be the fix here?

thanks,

greg k-h