[3.11.y.z extended stable] Patch "staging: comedi: pcmuio: fix possible NULL deref on detach" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    staging: comedi: pcmuio: fix possible NULL deref on detach

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 4fb8e78b2a8a545757d79d0e50ff3e51d2346985 Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti at mev.co.uk>
Date: Tue, 20 Aug 2013 11:50:19 +0100
Subject: staging: comedi: pcmuio: fix possible NULL deref on detach

commit 2fd2bdfccae61efe18f6b92b6a45fbf936d75b48 upstream.

pcmuio_detach() is called by the comedi core even if pcmuio_attach()
returned an error, so `dev->private` might be `NULL`.  Check for that
before dereferencing it.

Also, as pointed out by Dan Carpenter, there is no need to check the
pointer passed to `kfree()` is non-NULL, so remove that check.

Signed-off-by: Ian Abbott <abbotti at mev.co.uk>
Cc: Dan Carpenter <dan.carpenter at oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/staging/comedi/drivers/pcmuio.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/staging/comedi/drivers/pcmuio.c b/drivers/staging/comedi/drivers/pcmuio.c
index c43b633..7211c6b 100644
--- a/drivers/staging/comedi/drivers/pcmuio.c
+++ b/drivers/staging/comedi/drivers/pcmuio.c
@@ -680,12 +680,13 @@ static void pcmuio_detach(struct comedi_device *dev)
 	struct pcmuio_private *devpriv = dev->private;
 	int i;

-	for (i = 0; i < PCMUIO_MAX_ASICS; ++i) {
-		if (devpriv->asics[i].irq)
-			free_irq(devpriv->asics[i].irq, dev);
-	}
-	if (devpriv && devpriv->sprivs)
+	if (devpriv) {
+		for (i = 0; i < PCMUIO_MAX_ASICS; ++i) {
+			if (devpriv->asics[i].irq)
+				free_irq(devpriv->asics[i].irq, dev);
+		}
 		kfree(devpriv->sprivs);
+	}
 	comedi_legacy_detach(dev);
 }

--
1.8.3.2