linux-kernel - Re: [PATCH] platform/x86/intel: pmc: fix ltr decode in pmc_core_ltr

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Message-ID: <d4be773d-a2fe-686c-8769-800a309e5783@linux.intel.com>
Date: Fri, 20 Dec 2024 13:28:14 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Dmitry Kandybka <d.kandybka@...il.com>
cc: Rajneesh Bhardwaj <irenic.rajneesh@...il.com>, 
    David E Box <david.e.box@...el.com>, Hans de Goede <hdegoede@...hat.com>, 
    platform-driver-x86@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>, 
    lvc-project@...uxtesting.org
Subject: Re: [PATCH] platform/x86/intel: pmc: fix ltr decode in
 pmc_core_ltr_show()

On Fri, 20 Dec 2024, Dmitry Kandybka wrote:

> In pmc_core_ltr_show(), promote 'val' to 'u64' to avoid possible integer
> overflow. Values (10 bit) are multiplied by the scale, the result of
> expression is in a range from 1 to 34,326,183,936 which is bigger then
> UINT32_MAX. Compile tested only.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Dmitry Kandybka <d.kandybka@...il.com>
> ---
>  drivers/platform/x86/intel/pmc/core.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/platform/x86/intel/pmc/core.c b/drivers/platform/x86/intel/pmc/core.c
> index 3e7f99ac8c94..f06ba9636b03 100644
> --- a/drivers/platform/x86/intel/pmc/core.c
> +++ b/drivers/platform/x86/intel/pmc/core.c
> @@ -660,12 +660,12 @@ static int pmc_core_ltr_show(struct seq_file *s, void *unused)
>  			if (FIELD_GET(LTR_REQ_NONSNOOP, ltr_raw_data)) {
>  				scale = FIELD_GET(LTR_DECODED_SCALE, nonsnoop_ltr);
>  				val = FIELD_GET(LTR_DECODED_VAL, nonsnoop_ltr);
> -				decoded_non_snoop_ltr = val * convert_ltr_scale(scale);
> +				decoded_non_snoop_ltr = (u64)val * convert_ltr_scale(scale);
>  			}
>  			if (FIELD_GET(LTR_REQ_SNOOP, ltr_raw_data)) {
>  				scale = FIELD_GET(LTR_DECODED_SCALE, snoop_ltr);
>  				val = FIELD_GET(LTR_DECODED_VAL, snoop_ltr);
> -				decoded_snoop_ltr = val * convert_ltr_scale(scale);
> +				decoded_snoop_ltr = (u64)val * convert_ltr_scale(scale);

Please change val to u64 instead so casting won't be necessary.

-- 
 i.