linux-kernel - Re: [PATCH] ACPI: acpi_pcc.c: Fix unintentional integer overflow

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Date:   Thu, 13 Oct 2022 13:42:48 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     pmanank200502@...il.com
Cc:     rafael@...nel.org, lenb@...nel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ACPI: acpi_pcc.c: Fix unintentional integer overflow

On Thu, Oct 13, 2022 at 7:50 AM <pmanank200502@...il.com> wrote:
>
> From: Manank Patel <pmanank200502@...il.com>
>
> Fixed unintentional u32 overflow by casting it to u64 before multiplication.
>
> Signed-off-by: Manank Patel <pmanank200502@...il.com>

A Fixes tag would be nice to have here.

> ---
>  drivers/acpi/acpi_pcc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/acpi_pcc.c b/drivers/acpi/acpi_pcc.c
> index ee4ce5ba1fb2..b929d2e5c622 100644
> --- a/drivers/acpi/acpi_pcc.c
> +++ b/drivers/acpi/acpi_pcc.c
> @@ -112,7 +112,7 @@ acpi_pcc_address_space_handler(u32 function, acpi_physical_address addr,
>                  * processor could be much slower to reply. So add an arbitrary
>                  * amount of wait on top of Nominal.
>                  */
> -               usecs_lat = PCC_CMD_WAIT_RETRIES_NUM * data->pcc_chan->latency;
> +               usecs_lat = PCC_CMD_WAIT_RETRIES_NUM * ((u64) data->pcc_chan->latency);

Or redefine PCC_CMD_WAIT_RETRIES_NUM as 500ULL?

>                 ret = wait_for_completion_timeout(&data->done,
>                                                   usecs_to_jiffies(usecs_lat));
>                 if (ret == 0) {
> --
> 2.38.0
>