Re: nct6775: UBSAN: shift exponent 32 is too large for 32-bit type 'long unsigned int'

[Paul Menzel]

Dear Guenter,


Am 13.06.2018 um 00:12 schrieb Guenter Roeck:

> On Tue, Jun 12, 2018 at 11:50:45PM +0200, Paul Menzel wrote:

> > Building Linux with the undefined behavior sanitizer (UBSAN), loading the
> > module *nct6775* on the ASRock E350M1 shows the error below.
> >
> > ```
> > [   28.322775] UBSAN: Undefined behaviour in drivers/hwmon/nct6775.c:4179:27
> > [   28.322833] shift exponent 32 is too large for 32-bit type 'long unsigned int'
> > ```
> >
> > I believe this was introduced by commit cc66b3038254 (hwmon: (nct6775)
> > Rework temperature source and label handling), but the same issue was
> > already present before.
>
> I don't think so. The code used to be
> 	for (i = 0; i < data->temp_label_num - 1; i++) {
> Notice the "- 1". So it should be
> 	for (i = 0; i < 31; i++) {
>
> In practice it doesn't matter because "data->temp_mask & BIT(31 + 1)"
> will always be false, causing the last loop iteration to abort, but
> it is nevertheless wrong.
>
> Thanks a lot for the report. I'll prepare a patch.

Thank you for the instant response. I tested your proposed change, and, 
as expected, the error is gone.


Kind regards,

Paul