linux-kernel - Re: [PATCH] clk: actions: prevent overflow in owl_pll_recalc

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Message-ID: <20240910165242.v6jcirmtbahxqggx@thinkpad>
Date: Tue, 10 Sep 2024 22:22:42 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Anastasia Belova <abelova@...ralinux.ru>
Cc: Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>,
	Andreas Färber <afaerber@...e.de>,
	"open list:COMMON CLK FRAMEWORK" <linux-clk@...r.kernel.org>,
	"moderated list:ARM/ACTIONS SEMI ARCHITECTURE" <linux-arm-kernel@...ts.infradead.org>,
	"moderated list:ARM/ACTIONS SEMI ARCHITECTURE" <linux-actions@...ts.infradead.org>,
	open list <linux-kernel@...r.kernel.org>,
	lvc-project@...uxtesting.org, stable@...r.kernel.org
Subject: Re: [PATCH] clk: actions: prevent overflow in owl_pll_recalc_rate

On Tue, Sep 10, 2024 at 04:06:40PM +0300, Anastasia Belova wrote:
> In case of OWL S900 SoC clock driver there are cases
> where bfreq = 24000000, shift = 0. If value read from
> CMU_COREPLL or CMU_DDRPLL to val is big enough, an
> overflow may occur.
> 
> Add explicit casting to prevent it.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: 2792c37e94c8 ("clk: actions: Add pll clock support")
> Cc: <stable@...r.kernel.org> 
> Signed-off-by: Anastasia Belova <abelova@...ralinux.ru>

Currently, val is limited to 8 bits max on the supported SoCs. So there won't be
any overflow. But for the sake of correctness, I'm OK with this patch.

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

- Mani

> ---
>  drivers/clk/actions/owl-pll.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/actions/owl-pll.c b/drivers/clk/actions/owl-pll.c
> index 155f313986b4..fa17567665ec 100644
> --- a/drivers/clk/actions/owl-pll.c
> +++ b/drivers/clk/actions/owl-pll.c
> @@ -104,7 +104,7 @@ static unsigned long owl_pll_recalc_rate(struct clk_hw *hw,
>  	val = val >> pll_hw->shift;
>  	val &= mul_mask(pll_hw);
>  
> -	return pll_hw->bfreq * val;
> +	return (unsigned long)pll_hw->bfreq * val;
>  }
>  
>  static int owl_pll_is_enabled(struct clk_hw *hw)
> -- 
> 2.30.2
> 

-- 
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