[PATCH] media: imon: Fix null-ptr-deref in imon_probe

[Colin King]

From: Arvind Yadav <arvind.yadav.cs at gmail.com>

CVE-2017-16537

It seems that the return value of usb_ifnum_to_if() can be NULL and
needs to be checked.

Signed-off-by: Arvind Yadav <arvind.yadav.cs at gmail.com>
Tested-by: Andrey Konovalov <andreyknvl at google.com>
Signed-off-by: Sean Young <sean at mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab at osg.samsung.com>
(clean upstream cherry pick from commit 58fd55e838276a0c13d1dc7c387f90f25063cbf3)
Signed-off-by: Colin Ian King <colin.king at canonical.com>
---
 drivers/media/rc/imon.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/media/rc/imon.c b/drivers/media/rc/imon.c
index 9724fe8..9fef8cc 100644
--- a/drivers/media/rc/imon.c
+++ b/drivers/media/rc/imon.c
@@ -2515,6 +2515,11 @@ static int imon_probe(struct usb_interface *interface,
 	mutex_lock(&driver_lock);
 
 	first_if = usb_ifnum_to_if(usbdev, 0);
+	if (!first_if) {
+		ret = -ENODEV;
+		goto fail;
+	}
+
 	first_if_ctx = usb_get_intfdata(first_if);
 
 	if (ifnum == 0) {
-- 
1.9.1