From: Oliver Neukum <oneukum@suse.de>
To: Mathy Vanhoef <vanhoefm@gmail.com>
Cc: brudley@broadcom.com, Arend van Spriel <arend@broadcom.com>,
Franky Lin <frankyl@broadcom.com>,
meuleman@broadcom.com, John Linville <linville@tuxdriver.com>,
pieterpg@broadcom.com, linux-wireless@vger.kernel.org,
brcm80211-dev-list@broadcom.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] brcmfmac: unlink URB when request timed out
Date: Wed, 12 Nov 2014 08:00:44 +0100 [thread overview]
Message-ID: <1415775644.1761.1.camel@linux-0dmf.site> (raw)
In-Reply-To: <5462B1A3.9020401@gmail.com>
On Tue, 2014-11-11 at 20:02 -0500, Mathy Vanhoef wrote:
> On 11/10/2014 04:08 AM, Oliver Neukum wrote:
> > Which means that you are freeing memory that may still be used by DMA
> > at this time.
> > In addition you have no guarantee that the unlink is indeed finished
> > by the time the URB is reused.
> > If you wish to take this approach you better forget about this URB
> > and allocate a new one and free the buffer from the callback.
>
> Hi Oliver,
>
> Good catch. I think the DMA issue is also present in the current driver: it
> frees the buffer without unlinking/killing the URB at all. Can a malicious USB
Yes, it is present.
> device force a timeout to occur (i.e. delay the call to the completion
> handler)? If so this might be a use-after-free vulnerability.
>
> It seems using usb_kill_urb instead of usb_unlink_urb in the patch prevents any
> possible use-after-free. Can someone double check?
usb_kill_urb() will do the job.
Regards
Oliver
next prev parent reply other threads:[~2014-11-12 7:00 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-09 18:10 [PATCH] brcmfmac: unlink URB when request timed out Mathy Vanhoef
2014-11-10 9:08 ` Oliver Neukum
2014-11-12 1:02 ` Mathy Vanhoef
2014-11-12 7:00 ` Oliver Neukum [this message]
2014-11-10 11:18 ` Arend van Spriel
2014-11-10 16:08 ` Mathy Vanhoef
2014-11-10 18:03 ` Arend van Spriel
2014-11-11 11:05 ` Arend van Spriel
2014-11-11 17:35 ` Mathy Vanhoef
2014-11-11 18:00 ` Arend van Spriel
2014-11-12 0:40 ` Mathy Vanhoef
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