linux-kernel - [PATCH 3.10 68/78] staging: comedi: pcmuio: fix possible NULL deref on detach

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Date:	Wed, 18 Dec 2013 13:11:36 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Ian Abbott <abbotti@....co.uk>,
	Dan Carpenter <dan.carpenter@...cle.com>
Subject: [PATCH 3.10 68/78] staging: comedi: pcmuio: fix possible NULL deref on detach

3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ian Abbott <abbotti@....co.uk>

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@....co.uk>
Cc: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/staging/comedi/drivers/pcmuio.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

--- a/drivers/staging/comedi/drivers/pcmuio.c
+++ b/drivers/staging/comedi/drivers/pcmuio.c
@@ -935,12 +935,13 @@ static void pcmuio_detach(struct comedi_
 	struct pcmuio_private *devpriv = dev->private;
 	int i;
 
-	for (i = 0; i < 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 < MAX_ASICS; ++i) {
+			if (devpriv->asics[i].irq)
+				free_irq(devpriv->asics[i].irq, dev);
+		}
 		kfree(devpriv->sprivs);
+	}
 	comedi_legacy_detach(dev);
 }
 


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