Re: [PATCH][next] perf/x86/amd: fix potential integer overflow on shift of a int

[Ian Rogers <irogers@google.com>]

On Fri, Dec 2, 2022 at 5:52 AM Colin Ian King <colin.i.king@gmail.com> wrote:
>
> The left shift of int 32 bit integer constant 1 is evaluated using 32 bit
> arithmetic and then passed as a 64 bit function argument. In the case where
> i is 32 or more this can lead to an overflow.  Avoid this by shifting
> using the BIT_ULL macro instead.
>
> Fixes: 471af006a747 ("perf/x86/amd: Constrain Large Increment per Cycle events")
> Signed-off-by: Colin Ian King <colin.i.king@gmail.com>

Acked-by: Ian Rogers <irogers@google.com>

Thanks,
Ian

> ---
>  arch/x86/events/amd/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
> index d6f3703e4119..4386b10682ce 100644
> --- a/arch/x86/events/amd/core.c
> +++ b/arch/x86/events/amd/core.c
> @@ -1387,7 +1387,7 @@ static int __init amd_core_pmu_init(void)
>                  * numbered counter following it.
>                  */
>                 for (i = 0; i < x86_pmu.num_counters - 1; i += 2)
> -                       even_ctr_mask |= 1 << i;
> +                       even_ctr_mask |= BIT_ULL(i);
>
>                 pair_constraint = (struct event_constraint)
>                                     __EVENT_CONSTRAINT(0, even_ctr_mask, 0,
> --
> 2.38.1
>