[lvc-project] [PATCH] powercap: intel_rapl: use unsigned arithmetic in time window computation

[Fedor Pchelkin]

On Fri, 13. Feb 06:29, Ваторопин Андрей wrote:
> From: Andrey Vatoropin <a.vatoropin at crpt.ru>
> 
> In rapl_compute_time_window_core() the time window is calculated using the
> variable "y". This variable is limited by the mask 0x1F, however the
> result of the corner-case expression (1 << 0x1F) is 0x80000000 of signed
> integer type. Actually it's undefined in standard C language but the
> kernel is compiled with -fno-strict-overflow (-fwrapv) flag which does the
> trick.
> 
> Eventually the unexpected sign extension is possible when the result of
> type int is expanded to u64, like 0x80000000 -> 0xFFFFFFFF80000000 which
> leads to incorrect arithmetic.
> 
> Avoid sign extension by casting the left operand of the shift to the
> unsigned type before performing the shift.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: 3c2c08454ce9 ("powercap / RAPL: handle atom and core differences")
> Cc: stable at vger.kernel.org
> Signed-off-by: Andrey Vatoropin <a.vatoropin at crpt.ru>
> ---


Для веток 5.10 и 6.1 просьба выслать адаптированную версию патча только
в lvc-patches, отметив целевые ветки в теме письма.

>  drivers/powercap/intel_rapl_common.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/powercap/intel_rapl_common.c b/drivers/powercap/intel_rapl_common.c
> index 3ff6da3bf4e6..0f2d3d1a00c5 100644
> --- a/drivers/powercap/intel_rapl_common.c
> +++ b/drivers/powercap/intel_rapl_common.c
> @@ -1107,7 +1107,7 @@ static u64 rapl_compute_time_window_core(struct rapl_domain *rd, u64 value,
>  	if (!to_raw) {
>  		f = (value & 0x60) >> 5;
>  		y = value & 0x1f;
> -		value = (1 << y) * (4 + f) * rd->time_unit / 4;
> +		value = (1U << y) * (4 + f) * rd->time_unit / 4;
>  	} else {
>  		if (value < rd->time_unit)
>  			return 0;
> -- 
> 2.43.0