From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chanwoo Choi Subject: Re: [PATCH] PM / devfreq: Fix potential NULL pointer dereference in governor_store Date: Thu, 07 Dec 2017 10:24:21 +0900 Message-ID: <5A289845.5040301@samsung.com> References: <20171206202015.GA15636@embeddedor.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Return-path: In-reply-to: <20171206202015.GA15636@embeddedor.com> Sender: linux-kernel-owner@vger.kernel.org To: "Gustavo A. R. Silva" , MyungJoo Ham , Kyungmin Park Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-pm@vger.kernel.org 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 > --- > 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 -- Best Regards, Chanwoo Choi Samsung Electronics