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

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

From: Pan Bian <bianpan2...@163.com>


[ 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 <bianpan2...@163.com>
Signed-off-by: Hans Verkuil <hans.verk...@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mche...@s-opensource.com>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 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);
@@ -631,11 +633,13 @@ 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.
@@ -746,11 +750,13 @@ 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);
 


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