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SubjectRe: [PATCH] PM / devfreq: Fix potential NULL pointer dereference in governor_store
On 2017년 12월 07일 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@embeddedor.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 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.

So, looks good to me.
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>

--
Best Regards,
Chanwoo Choi
Samsung Electronics

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