* nct6775: UBSAN: shift exponent 32 is too large for 32-bit type 'long unsigned int'
@ 2018-06-12 21:50 Paul Menzel
2018-06-12 22:12 ` Guenter Roeck
0 siblings, 1 reply; 3+ messages in thread
From: Paul Menzel @ 2018-06-12 21:50 UTC (permalink / raw)
To: Guenter Roeck, Jean Delvare; +Cc: linux-hwmon, linux-kernel
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.
```
- 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
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: nct6775: UBSAN: shift exponent 32 is too large for 32-bit type 'long unsigned int'
2018-06-12 21:50 nct6775: UBSAN: shift exponent 32 is too large for 32-bit type 'long unsigned int' Paul Menzel
@ 2018-06-12 22:12 ` Guenter Roeck
2018-06-13 6:57 ` Paul Menzel
0 siblings, 1 reply; 3+ messages in thread
From: Guenter Roeck @ 2018-06-12 22:12 UTC (permalink / raw)
To: Paul Menzel; +Cc: Jean Delvare, linux-hwmon, linux-kernel
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
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: nct6775: UBSAN: shift exponent 32 is too large for 32-bit type 'long unsigned int'
2018-06-12 22:12 ` Guenter Roeck
@ 2018-06-13 6:57 ` Paul Menzel
0 siblings, 0 replies; 3+ messages in thread
From: Paul Menzel @ 2018-06-13 6:57 UTC (permalink / raw)
To: Guenter Roeck; +Cc: Jean Delvare, linux-hwmon, linux-kernel
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
^ permalink raw reply [flat|nested] 3+ messages in thread
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