bttv: Prevent NULL pointer dereference in radio_open

From: Jean Delvare <khali@linux-fr.org>

Fix the following crash in the bttv driver:

BUG: unable to handle kernel NULL pointer dereference at 000000000000036c
IP: [<ffffffffa037860a>] radio_open+0x3a/0x170 [bttv]

This happens because radio_open assumes that all present bttv devices
have a radio function. If a bttv device without radio and one with
radio are installed on the same system, and the one without radio is
registered first, then radio_open checks for the radio device number
of a bttv device that has no radio function, and this breaks. All we
have to do to fix it is to skip bttv devices without a radio function.

Priority: high

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/linux/drivers/media/video/bt8xx/bttv-driver.c b/linux/drivers/media/video/bt8xx/bttv-driver.c
index 1c8183c2c..8d398a4b0 100644
--- a/linux/drivers/media/video/bt8xx/bttv-driver.c
+++ b/linux/drivers/media/video/bt8xx/bttv-driver.c
@@ -3463,7 +3463,7 @@ static int radio_open(struct inode *inode, struct file *file)
 
 	lock_kernel();
 	for (i = 0; i < bttv_num; i++) {
-		if (bttvs[i].radio_dev->minor == minor) {
+		if (bttvs[i].radio_dev && bttvs[i].radio_dev->minor == minor) {
 			btv = &bttvs[i];
 			break;
 		}