Re: [BUG] power: supply: 88pm860x_battery: possible uninitialized-variable access in measure_vbatt()

[Sebastian Reichel <sre@kernel.org>]

[-- Attachment #1: Type: text/plain, Size: 1411 bytes --]

[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

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]