linux-kernel - Re: [PATCH] staging: comedi: ni_tio: Adjust clock period calculation in ni_tio_set_clock

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Message-ID: <5c3172d8-517f-4d23-a713-fc41406c00d8@mev.co.uk>
Date: Tue, 17 Sep 2024 11:22:21 +0100
From: Ian Abbott <abbotti@....co.uk>
To: Aleksandr Mishin <amishin@...rgos.ru>,
 H Hartley Sweeten <hsweeten@...ionengravers.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: Re: [PATCH] staging: comedi: ni_tio: Adjust clock period calculation
 in ni_tio_set_clock_src()

On 17/09/2024 07:23, Aleksandr Mishin wrote:
> In ni_tio_set_clock_src() clock period is a subject to overflow because
> 'period_ns' (which comes from user, may have any value and is not
> validated anywhere) is not cast to a larger data type before performing
> arithmetic.
> 
> Cast 'period_ns' to u64 to prevent overflow.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: 3e90b1c7ebe9 ("staging: comedi: ni_tio: tidy up ni_tio_set_clock_src() and helpers")
> Signed-off-by: Aleksandr Mishin <amishin@...rgos.ru>
> ---
>   drivers/comedi/drivers/ni_tio.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/comedi/drivers/ni_tio.c b/drivers/comedi/drivers/ni_tio.c
> index da6826d77e60..98b5b44416cf 100644
> --- a/drivers/comedi/drivers/ni_tio.c
> +++ b/drivers/comedi/drivers/ni_tio.c
> @@ -800,7 +800,7 @@ static int ni_tio_set_clock_src(struct ni_gpct *counter,
>   				GI_PRESCALE_X2(counter_dev->variant) |
>   				GI_PRESCALE_X8(counter_dev->variant), bits);
>   	}
> -	counter->clock_period_ps = period_ns * 1000;
> +	counter->clock_period_ps = (u64)period_ns * 1000;
>   	ni_tio_set_sync_mode(counter);
>   	return 0;
>   }

Thanks.  The patch looks good but since comedi was migrated out of 
staging, it should no longer be tagged as "staging:" in the title.

Reviewed-by: Ian Abbott <abbotti@....co.uk>

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