security: avoid calling a NULL function pointer in drivers/video/tvaudio.c

NULL function pointers are very bad security wise. This one got caught by
kerneloops.org quite a few times, so it's happening in the field....

Fix is simple, check the function pointer for NULL, like 6 other places
in the same function are already doing.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/media/video/tvaudio.c b/drivers/media/video/tvaudio.c
index 463680b13289..b59e47272abf 100644
--- a/drivers/media/video/tvaudio.c
+++ b/drivers/media/video/tvaudio.c
@@ -1792,7 +1792,7 @@ static int chip_command(struct i2c_client *client,
                 break;
         case VIDIOC_S_FREQUENCY:
                 chip->mode = 0; /* automatic */
-                if (desc->checkmode) {
+                if (desc->checkmode && desc->setmode) {
                         desc->setmode(chip,V4L2_TUNER_MODE_MONO);
                         if (chip->prevmode != V4L2_TUNER_MODE_MONO)
                                 chip->prevmode = -1; /* reset previous mode */