Subject: Re: [PATCH v2] usb: core: Warn if an URB's transfer_buffer is on
 stack
To: Florian Fainelli <f.fainelli@gmail.com>, linux-kernel@vger.kernel.org
Cc: arnd@arndb.de, maksim.salau@gmail.com,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Alan Stern <stern@rowland.harvard.edu>,
        Mathias Nyman <mathias.nyman@linux.intel.com>,
        Peter Chen <peter.chen@nxp.com>, Roger Quadros <rogerq@ti.com>,
        Baoyou Xie <baoyou.xie@linaro.org>, Sekhar Nori <nsekhar@ti.com>,
        Chris Bainbridge <chris.bainbridge@gmail.com>,
        Wolfram Sang <wsa-dev@sang-engineering.com>,
        "open list:USB SUBSYSTEM" <linux-usb@vger.kernel.org>
References: <20170424012939.29929-1-f.fainelli@gmail.com>
From: Clemens Ladisch <clemens@ladisch.de>
Message-ID: <1f64fcfb-10b0-0407-8f6e-86f94601003f@ladisch.de>
Date: Mon, 24 Apr 2017 09:15:55 +0200
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Florian Fainelli wrote:
> We see a large number of fixes to several drivers to remove the usage of
> on-stack buffers feeding into USB transfer functions. Make it easier to spot
> the offenders by adding a warning in usb_hcd_map_urb_for_dma() checking that
> urb->transfer_buffer is not a stack object.

This description is incomplete.

> +			} else if (object_is_on_stack(urb->transfer_buffer)) {
> +				WARN_ONCE(1, "transfer buffer is on stack\n");
> +				ret = -EAGAIN;
>  			} else {
>  				urb->transfer_dma = dma_map_single(

Not only is there a warning, but the check also forces all those URBs
to abort with an error.

Well, that makes it even easier to spot the offenders ...


Regards,
Clemens