[PATCH 4.9 208/310] [media] cx25840: fix unchecked return values

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Pan Bian <bianpan2016@xxxxxxx>


[ Upstream commit 35378ce143071c2a6bad4b59a000e9b9f8f6ea67 ]

In functions cx25840_initialize(), cx231xx_initialize(), and
cx23885_initialize(), the return value of create_singlethread_workqueue()
is used without validation. This may result in NULL dereference and cause
kernel crash. This patch fixes it.

Signed-off-by: Pan Bian <bianpan2016@xxxxxxx>
Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/media/i2c/cx25840/cx25840-core.c |   36 ++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 15 deletions(-)

--- a/drivers/media/i2c/cx25840/cx25840-core.c
+++ b/drivers/media/i2c/cx25840/cx25840-core.c
@@ -420,11 +420,13 @@ static void cx25840_initialize(struct i2
 	INIT_WORK(&state->fw_work, cx25840_work_handler);
 	init_waitqueue_head(&state->fw_wait);
 	q = create_singlethread_workqueue("cx25840_fw");
-	prepare_to_wait(&state->fw_wait, &wait, TASK_UNINTERRUPTIBLE);
-	queue_work(q, &state->fw_work);
-	schedule();
-	finish_wait(&state->fw_wait, &wait);
-	destroy_workqueue(q);
+	if (q) {
+		prepare_to_wait(&state->fw_wait, &wait, TASK_UNINTERRUPTIBLE);
+		queue_work(q, &state->fw_work);
+		schedule();
+		finish_wait(&state->fw_wait, &wait);
+		destroy_workqueue(q);
+	}
 
 	/* 6. */
 	cx25840_write(client, 0x115, 0x8c);
@@ -634,11 +636,13 @@ static void cx23885_initialize(struct i2
 	INIT_WORK(&state->fw_work, cx25840_work_handler);
 	init_waitqueue_head(&state->fw_wait);
 	q = create_singlethread_workqueue("cx25840_fw");
-	prepare_to_wait(&state->fw_wait, &wait, TASK_UNINTERRUPTIBLE);
-	queue_work(q, &state->fw_work);
-	schedule();
-	finish_wait(&state->fw_wait, &wait);
-	destroy_workqueue(q);
+	if (q) {
+		prepare_to_wait(&state->fw_wait, &wait, TASK_UNINTERRUPTIBLE);
+		queue_work(q, &state->fw_work);
+		schedule();
+		finish_wait(&state->fw_wait, &wait);
+		destroy_workqueue(q);
+	}
 
 	/* Call the cx23888 specific std setup func, we no longer rely on
 	 * the generic cx24840 func.
@@ -752,11 +756,13 @@ static void cx231xx_initialize(struct i2
 	INIT_WORK(&state->fw_work, cx25840_work_handler);
 	init_waitqueue_head(&state->fw_wait);
 	q = create_singlethread_workqueue("cx25840_fw");
-	prepare_to_wait(&state->fw_wait, &wait, TASK_UNINTERRUPTIBLE);
-	queue_work(q, &state->fw_work);
-	schedule();
-	finish_wait(&state->fw_wait, &wait);
-	destroy_workqueue(q);
+	if (q) {
+		prepare_to_wait(&state->fw_wait, &wait, TASK_UNINTERRUPTIBLE);
+		queue_work(q, &state->fw_work);
+		schedule();
+		finish_wait(&state->fw_wait, &wait);
+		destroy_workqueue(q);
+	}
 
 	cx25840_std_setup(client);