linux-kernel - Re: [PATCH v2] usb: core: Warn if an URB's transfer

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Date:   Mon, 24 Apr 2017 09:15:55 +0200
From:   Clemens Ladisch <clemens@...isch.de>
To:     Florian Fainelli <f.fainelli@...il.com>,
        linux-kernel@...r.kernel.org
Cc:     arnd@...db.de, maksim.salau@...il.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Peter Chen <peter.chen@....com>, Roger Quadros <rogerq@...com>,
        Baoyou Xie <baoyou.xie@...aro.org>,
        Sekhar Nori <nsekhar@...com>,
        Chris Bainbridge <chris.bainbridge@...il.com>,
        Wolfram Sang <wsa-dev@...g-engineering.com>,
        "open list:USB SUBSYSTEM" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v2] usb: core: Warn if an URB's transfer_buffer is on
 stack

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