Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [BUG] power: supply: 88pm860x_battery: possible
 uninitialized-variable access in measure_vbatt()
To:     Sebastian Reichel <sre@kernel.org>
Cc:     linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
        baijiaju1990@gmail.com, "Jett.Zhou" <jtzhou@marvell.com>
References: <e2080eb9-bbe2-5077-761d-b5594edb6006@gmail.com>
 <20210805174908.ctg6n5iwmg5izap3@earth.universe>
From:   Tuo Li <islituo@gmail.com>
Message-ID: <94bb8568-3f3b-b3af-c98f-9d9bf36528e1@gmail.com>
Date:   Fri, 6 Aug 2021 11:29:53 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101
 Thunderbird/78.12.0
MIME-Version: 1.0
In-Reply-To: <20210805174908.ctg6n5iwmg5izap3@earth.universe>
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-US
Precedence: bulk

Thanks for your feedback, and any further feedback about this problem 
would be appreciated.

Best wishes,
Tuo Li

On 2021/8/6 1:49, Sebastian Reichel wrote:
> [adding Jett Zhou to Cc who introduced the driver]
>
> Hi,
>
> On Wed, Jul 28, 2021 at 06:24:12PM +0800, Li Tuo wrote:
>> Our static analysis tool finds a possible uninitialized-variable access in
>> the 88pm860x_battery driver in Linux 5.14.0-rc3:
>>
>> In calc_soc():
>> 369:??? int ocv;
>> 376:??? switch (state) {
>> 380:??? case OCV_MODE_SLEEP:
>> 381:??????? ret = measure_vbatt(info, OCV_MODE_SLEEP, &ocv);
>>
>> In measure_vbatt(struct pm860x_battery_info *info, int state, int *data)
>> 176:??? switch (state) {
>> 184:??? case OCV_MODE_SLEEP:
>> 201:??????? *data = ((*data & 0xff) * 27 * 25) >> 9;
>>
>> If the variable state is OCV_MODE_SLEEP, the function measure_vbatt() is
>> called with the argument &ocv, and the corresponding parameter is data.
>> Thus *data is uninitialized but it is used at line 201.
>>
>> I am not quite sure whether this possible uninitialized-variable access is
>> real and how to fix it if it is real.
>> Any feedback would be appreciated, thanks!
>>
>> Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
> I suppose the code is suppose to look like this:
>
> 201:??????? *data = ((ret & 0xff) * 27 * 25) >> 9;
>
> Considering quite some code is spent before to setup ret, which is
> never used. I don't have the device (nor datasheets) though. Considering
> the driver has only seen trivial cleanups over the last 9 years, maybe
> it can just be removed?
>
> -- Sebastian