linux-kernel - Re: [PATCH] ISP1704 USB Charger: Fix use-after-free error in isp1704_charger

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Date:	Sun, 22 Apr 2012 22:34:59 +0200
From:	Marek Vasut <marex@...x.de>
To:	Jesper Juhl <jj@...osbits.net>
Cc:	linux-kernel@...r.kernel.org,
	Felipe Contreras <felipe.contreras@...il.com>,
	Felipe Balbi <balbi@...com>,
	Anton Vorontsov <anton.vorontsov@...aro.org>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Kalle Jokiniemi <kalle.jokiniemi@...ia.com>
Subject: Re: [PATCH] ISP1704 USB Charger: Fix use-after-free error in isp1704_charger_probe()

Dear Jesper Juhl,

> In isp1704_charger_probe() at the 'fail0:' label we kfree(isp) and
> then subsequently call isp1704_charger_set_power(isp, 0). That's a
> problem since isp1704_charger_set_power() dereferences the pointer it
> is passed as its first argument, which is 'isp', which we already
> freed.
> 
> Fixed by simply swapping the order of the two calls so that we only
> kfree() *after* the call to isp1704_charger_set_power().
> 
> Signed-off-by: Jesper Juhl <jj@...osbits.net>
> ---
>  drivers/power/isp1704_charger.c |    4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/power/isp1704_charger.c
> b/drivers/power/isp1704_charger.c index 39eb50f..8a610da 100644
> --- a/drivers/power/isp1704_charger.c
> +++ b/drivers/power/isp1704_charger.c
> @@ -476,11 +476,9 @@ fail2:
>  fail1:
>  	usb_put_transceiver(isp->phy);
>  fail0:
> -	kfree(isp);
> -
>  	dev_err(&pdev->dev, "failed to register isp1704 with error %d\n", ret);
> -
>  	isp1704_charger_set_power(isp, 0);
> +	kfree(isp);

Use devm_kzalloc() and be done with all this goo?

>  	return ret;
>  }

Best regards,
Marek Vasut
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