PM / devfreq: Fix potential NULL pointer dereference in governor_store

BugLink: http://bugs.launchpad.net/bugs/1763366
[ 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 <garsilva@embeddedor.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 99c4021fc33b0ba4e79fb8453584dd6c56e0e962..fe2af6aa88fc2b0cec9a103fcc2ca682f073659a 100644 (file)
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -996,7 +996,8 @@ 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;
        }