linux-kernel - [PATCH v3 14/15] [media] lirc

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Date:	Wed, 06 Jul 2016 18:01:26 +0900
From:	Andi Shyti <andi.shyti@...sung.com>
To:	Mauro Carvalho Chehab <mchehab@....samsung.com>
Cc:	Joe Perches <joe@...ches.com>, Sean Young <sean@...s.org>,
	Hans Verkuil <hverkuil@...all.nl>, linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org, Andi Shyti <andi.shyti@...sung.com>,
	Andi Shyti <andi@...zian.org>
Subject: [PATCH v3 14/15] [media] lirc_dev: fix potential segfault

When opening or closing a lirc character device, the framework
provides to the user the possibility to keep track of opening or
closing of the device by calling two functions:

 - set_use_inc() when opening the device
 - set_use_dec() when closing the device

if those are not set by the lirc user, the system segfaults.
Check the pointer value before calling the above functions.

Signed-off-by: Andi Shyti <andi.shyti@...sung.com>
---
 drivers/media/rc/lirc_dev.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/media/rc/lirc_dev.c b/drivers/media/rc/lirc_dev.c
index c78fe2b..8cf5e6b 100644
--- a/drivers/media/rc/lirc_dev.c
+++ b/drivers/media/rc/lirc_dev.c
@@ -408,7 +408,10 @@ int lirc_unregister_driver(int minor)
 			ir->d.name, ir->d.minor);
 		wake_up_interruptible(&ir->buf->wait_poll);
 		mutex_lock(&ir->irctl_lock);
-		ir->d.set_use_dec(ir->d.data);
+
+		if (ir->d.set_use_dec)
+			ir->d.set_use_dec(ir->d.data);
+
 		module_put(cdev->owner);
 		mutex_unlock(&ir->irctl_lock);
 	} else {
@@ -466,7 +469,8 @@ int lirc_dev_fop_open(struct inode *inode, struct file *file)
 	cdev = ir->cdev;
 	if (try_module_get(cdev->owner)) {
 		ir->open++;
-		retval = ir->d.set_use_inc(ir->d.data);
+		if (ir->d.set_use_inc)
+			retval = ir->d.set_use_inc(ir->d.data);
 
 		if (retval) {
 			module_put(cdev->owner);
@@ -507,7 +511,8 @@ int lirc_dev_fop_close(struct inode *inode, struct file *file)
 
 	ir->open--;
 	if (ir->attached) {
-		ir->d.set_use_dec(ir->d.data);
+		if (ir->d.set_use_dec)
+			ir->d.set_use_dec(ir->d.data);
 		module_put(cdev->owner);
 	} else {
 		lirc_irctl_cleanup(ir);
-- 
2.8.1