linux-kernel - Re: [PATCH v2] usb: gadget: Fix double free of device descriptor pointers

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Date:   Thu, 22 Apr 2021 14:01:42 +0300
From:   Felipe Balbi <balbi@...nel.org>
To:     Wesley Cheng <wcheng@...eaurora.org>, gregkh@...uxfoundation.org,
        peter.chen@...nel.org
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Hemant Kumar <hemantk@...eaurora.org>, stable@...r.kernel.org,
        Wesley Cheng <wcheng@...eaurora.org>
Subject: Re: [PATCH v2] usb: gadget: Fix double free of device descriptor
 pointers


Hi,

Wesley Cheng <wcheng@...eaurora.org> writes:

> From: Hemant Kumar <hemantk@...eaurora.org>
>
> Upon driver unbind usb_free_all_descriptors() function frees all
> speed descriptor pointers without setting them to NULL. In case
> gadget speed changes (i.e from super speed plus to super speed)
> after driver unbind only upto super speed descriptor pointers get
> populated. Super speed plus desc still holds the stale (already
> freed) pointer. Fix this issue by setting all descriptor pointers
> to NULL after freeing them in usb_free_all_descriptors().

could you describe this a little better? How can one trigger this case?
Is the speed demotion happening after unbinding? It's not clear how to
cause this bug.

-- 
balbi

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