[lkml]   [2014]   [Nov]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] brcmfmac: unlink URB when request timed out
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.


 \ /
  Last update: 2014-11-12 08:41    [W:0.083 / U:0.800 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site