linux-kernel - [PATCH 3.2 178/200] staging: comedi: pcmuio: fix possible NULL deref on detach

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Date:	Mon, 31 Mar 2014 00:23:35 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
	"Ian Abbott" <abbotti@....co.uk>,
	"Dan Carpenter" <dan.carpenter@...cle.com>
Subject: [PATCH 3.2 178/200] staging: comedi: pcmuio: fix possible NULL
 deref on detach

3.2.56-rc1 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>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/staging/comedi/drivers/pcmuio.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/staging/comedi/drivers/pcmuio.c b/drivers/staging/comedi/drivers/pcmuio.c
index 661ba2e..6e936c5 100644
--- a/drivers/staging/comedi/drivers/pcmuio.c
+++ b/drivers/staging/comedi/drivers/pcmuio.c
@@ -464,13 +464,13 @@ static int pcmuio_detach(struct comedi_device *dev)
 	if (dev->iobase)
 		release_region(dev->iobase, ASIC_IOSIZE * thisboard->num_asics);
 
-	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);
+	}
 
 	return 0;
 }

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