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

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Date:   Fri, 9 Apr 2021 09:42:14 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
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 09/04/2021 07:46, Masahiro Yamada wrote:
> 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?
> 
> 
Good point. I'll send a V2.