From e56b1401056288a725d50942ef300dcbed5e519a Mon Sep 17 00:00:00 2001
From: Bernd Porr <mail@berndporr.me.uk>
Date: Wed, 11 Dec 2013 16:06:15 +0000
Subject: [PATCH] staging: comedi: fix result of memdup_user for user chanlist

If the channel list is not set in userspace we get an error at
PTR_ERR(async->cmd.chanlist). However, do_become_nonbusy(dev, s) cleans
up this pointer which causes a kernel ooops. Setting the channel list in
async to NULL and checking this in do_become_nonbusy prevents the oops.

[Ian Abbott] Also do the same for the chanlist allocated in
do_cmdtest_ioctl().

Signed-off-by: Bernd Porr <mail@berndporr.me.uk>
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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