linux-kernel - Re: [PATCH] usb: don't trust report

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Message-ID: <20101011191119.GN4991@outflux.net>
Date:	Mon, 11 Oct 2010 12:11:19 -0700
From:	Kees Cook <kees.cook@...onical.com>
To:	Németh Márton <nm127@...email.hu>
Cc:	linux-kernel@...r.kernel.org, Greg Kroah-Hartman <gregkh@...e.de>,
	Oliver Neukum <oliver@...kum.org>,
	Joe Perches <joe@...ches.com>, linux-usb@...r.kernel.org
Subject: Re: [PATCH] usb: don't trust report_size for buffer size

Hi Németh,

On Mon, Oct 11, 2010 at 08:54:04PM +0200, Németh Márton wrote:
> There might be similar problem also in the case USB_DEVICE_ID_CODEMERCS_IOW56. There
> is buf is allocated with usb_alloc_coherent() to the size dev->report_size. However,
> some lines later the copy_from_user() function tries to copy "count" number of
> bytes to the dev->report_size allocated buffer. Unfortunately I don't have such
> devices to try the driver so these are just coming from "static analysis".

I don't think the USB_DEVICE_ID_CODEMERCS_IOW56 path is a problem:

        if (count != dev->report_size) {
                retval = -EINVAL;
                goto exit;
        }
        switch (dev->product_id) {
...
        case USB_DEVICE_ID_CODEMERCS_IOW56:
...
                buf = usb_alloc_coherent(dev->udev, dev->report_size,
                                         GFP_KERNEL, &int_out_urb->transfer_dma);
...
                if (copy_from_user(buf, user_buffer, count)) {

i.e. count must == dev->report_size, and the buf is allocated with size
dev->report_size even though copy_from_user uses "count".

-Kees

-- 
Kees Cook
Ubuntu Security Team
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