Hi Paul,
On Tue, Jun 12, 2018 at 11:50:45PM +0200, Paul Menzel wrote:
> Dear Guenther, dear Jean,
>
>
> 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.
Guenter
> ```
> - for (i = 0; i < data->temp_label_num - 1; i++) {
> + for (i = 0; i < 32; i++) {
> + if (!(data->temp_mask & BIT(i + 1)))
> + continue;
> ```
>
> `include/linux/bitops.h` has the macros below.
>
> ```
> #define BIT(nr) (1UL << (nr))
> #define BIT_ULL(nr) (1ULL << (nr))
> ```
>
> Maybe `BIT_ULL` should be used, but I do not know, if that’d would work with
> `data->temp_mask`, which has type `u32`.
>
>
> Kind regards,
>
> Paul
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