linux-kernel - Re: [PATCH] clk: uniphier: Fix potential infinite loop

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Date:   Fri, 9 Apr 2021 15:46:47 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Colin King <colin.king@...onical.com>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        kernel-janitors@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] clk: uniphier: Fix potential infinite loop

On Thu, Apr 8, 2021 at 12:25 AM Colin King <colin.king@...onical.com> wrote:
>
> From: Colin Ian King <colin.king@...onical.com>
>
> The for-loop iterates with a u8 loop counter i and compares this
> with the loop upper limit of num_parents that is an int type.
> There is a potential infinite loop if num_parents is larger than
> the u8 loop counter. Fix this by making the loop counter the same
> type as num_parents.
>
> Addresses-Coverity: ("Infinite loop")
> Fixes: 734d82f4a678 ("clk: uniphier: add core support code for UniPhier clock driver")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/clk/uniphier/clk-uniphier-mux.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/clk/uniphier/clk-uniphier-mux.c b/drivers/clk/uniphier/clk-uniphier-mux.c
> index 462c84321b2d..ce219e0d2a85 100644
> --- a/drivers/clk/uniphier/clk-uniphier-mux.c
> +++ b/drivers/clk/uniphier/clk-uniphier-mux.c
> @@ -34,7 +34,7 @@ static u8 uniphier_clk_mux_get_parent(struct clk_hw *hw)
>         int num_parents = clk_hw_get_num_parents(hw);
>         int ret;
>         unsigned int val;
> -       u8 i;
> +       int i;
>
>         ret = regmap_read(mux->regmap, mux->reg, &val);
>         if (ret)
> --
> 2.30.2
>

clk_hw_get_num_parents() returns 'unsigned int', so
I think 'num_parents' should also have been 'unsigned int'.

Maybe, the loop counter 'i' also should be 'unsigned int' then?


-- 
Best Regards
Masahiro Yamada