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

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

From: Vladimir Zapolskiy <vz@mleia.com>

commit 91e630d9ae6de6f740ef7c8176736eb55366833e upstream.

The kthread_run() function returns either a valid task_struct or
ERR_PTR() value, check for NULL is invalid.  This change fixes potential
for oops, e.g. in OOM situation.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Signed-off-by: Mike Snitzer <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/md/dm-log-writes.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/md/dm-log-writes.c
+++ b/drivers/md/dm-log-writes.c

@@ -456,9 +456,9 @@ static int log_writes_ctr(struct dm_targ
 		goto bad;
 	}
 
-	ret = -EINVAL;
 	lc->log_kthread = kthread_run(log_writes_kthread, lc, "log-write");
-	if (!lc->log_kthread) {
+	if (IS_ERR(lc->log_kthread)) {
+		ret = PTR_ERR(lc->log_kthread);
 		ti->error = "Couldn't alloc kthread";
 		dm_put_device(ti, lc->dev);
 		dm_put_device(ti, lc->logdev);