[PATCH AUTOSEL for 4.9 131/281] PM / devfreq: Fix potential NULL pointer dereference in governor_store

[Sasha Levin]

From: "Gustavo A. R. Silva" <garsi...@embeddedor.com>

[ Upstream commit 63f1e05f7fe9ca509c60154d6a833abf96eecdc9 ]

df->governor is being dereferenced before it is null checked,
hence there is a potential null pointer dereference.

Notice that df->governor is being null checked at line 1004:
if (df->governor) {, which implies it might be null.

Fix this by null checking df->governor before dereferencing it.

Addresses-Coverity-ID: 1401988 ("Dereference before null check")
Fixes: bcf23c79c4e4 ("PM / devfreq: Fix available_governor sysfs")
Signed-off-by: Gustavo A. R. Silva <garsi...@embeddedor.com>
Reviewed-by: Chanwoo Choi <cw00.c...@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo....@samsung.com>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
---
 drivers/devfreq/devfreq.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 9e5674c5a07b..db70cee71caa 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -943,7 +943,8 @@ static ssize_t governor_store(struct device *dev, struct 
device_attribute *attr,
        if (df->governor == governor) {
                ret = 0;
                goto out;
-       } else if (df->governor->immutable || governor->immutable) {
+       } else if ((df->governor && df->governor->immutable) ||
+                                       governor->immutable) {
                ret = -EINVAL;
                goto out;
        }
-- 
2.14.1