From 725a70d8a68ef5368652c0c49631fefb361d62cf Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti@mev.co.uk>
Date: Fri, 28 Jun 2013 17:09:17 +0100
Subject: [PATCH] staging: comedi: ni_labpc: fix possible double-free of
 dma_buffer

If `labpc_attach()` allocates memory for `devpriv->dma_buffer` but fails
to request a DMA channel, it frees `devpriv->dma_buffer` but leaves the
pointer set.  Later, `labpc_detach()` frees `devpriv->dma_buffer` again,
which means it has been freed twice in this case.

Fix it by only setting `devpriv->dma_buffer` in `labpc_attach()` if the
DMA channel was requested successfully.

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