linux-kernel - Re: [PATCH] USB: EHCI: tegra: Fix use-after-free in .remove()

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Message-ID: <53A0653F.7090001@wwwdotorg.org>
Date:	Tue, 17 Jun 2014 09:56:47 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Tuomas Tynkkynen <ttynkkynen@...dia.com>,
	Alan Stern <stern@...land.harvard.edu>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-tegra@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] USB: EHCI: tegra: Fix use-after-free in .remove()

On 06/17/2014 08:17 AM, Tuomas Tynkkynen wrote:
> The tegra_ehci_hcd structure is located in the private space allocated
> by the core USB code so it must not be accessed after the HCD is
> freed.

> diff --git a/drivers/usb/host/ehci-tegra.c b/drivers/usb/host/ehci-tegra.c

This seems to be a persistent problem. Witness commit ecc8a0cdca18 "usb:
host: tegra: fix warning messages in ehci_remove". So, I wonder if ...

> @@ -479,10 +479,11 @@ static int tegra_ehci_remove(struct platform_device *pdev)
>  
>  	usb_phy_shutdown(hcd->phy);
>  	usb_remove_hcd(hcd);
> -	usb_put_hcd(hcd);
>  
>  	clk_disable_unprepare(tegra->clk);
>  

It's worth putting a comment here:

	/* This must be last, since *tegra is part of *hcd */
> +	usb_put_hcd(hcd);
> +
>  	return 0;
>  }

Of course, that could be a separate commit if you want.
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