Re: [PATCH] PM / devfreq: Fix potential NULL pointer dereference in governor_store
From: Gustavo A. R. Silva
Date: Thu Dec 07 2017 - 18:56:06 EST
Hi Chanwoo,
Quoting Chanwoo Choi <cw00.choi@xxxxxxxxxxx>:
On 2017ë 12ì 07ì 05:20, Gustavo A. R. Silva wrote:
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@xxxxxxxxxxxxxx>
---
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 78fb496..14fe76b 100644
--- 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;
}
Actually, df->governor would be never NULL because devfreq_add_device()
initializes the ->governor always. But, governor_store() doesn't know it.
I got it.
So, looks good to me.
Reviewed-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx>
Thank you
--
Gustavo A. R. Silva