linux-kernel - RE: [PATCH v3 2/2] clk:mmp: clk-mix.c fix divide-by-zero

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Message-ID: <E490CD805F7529488761C40FD9D26EF12AB29F8A@dggemm507-mbx.china.huawei.com>
Date:   Wed, 24 Apr 2019 15:34:54 +0000
From:   Nixiaoming <nixiaoming@...wei.com>
To:     Stephen Boyd <sboyd@...nel.org>,
        "chao.xie@...vell.com" <chao.xie@...vell.com>,
        "jbrunet@...libre.com" <jbrunet@...libre.com>,
        "mojha@...eaurora.org" <mojha@...eaurora.org>,
        "mturquette@...libre.com" <mturquette@...libre.com>,
        "sboyd@...eaurora.org" <sboyd@...eaurora.org>,
        "soren.brinkmann@...inx.com" <soren.brinkmann@...inx.com>
CC:     "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 2/2] clk:mmp: clk-mix.c fix divide-by-zero

On Wed, Apr 24, 2019 at 7:00 AM Stephen Boyd <sboyd@...nel.org> wrote:
>Quoting nixiaoming (2019-03-30 06:55:42)
>> The _get_div() function has a branch with a return value of 0
>> Add a check on the return value of _get_div() to avoid divide-by-zero
>> 
>
>Are you seeing this in practice? Or just trying to avoid a div-by-zero
>case that you've found from inspection? 
>
This potential bug is found by code inspection.
_get_div() is defined as a static function which is only refered twice 
in drivers/clk/mmp/clk-mix.c. In both cases the return value of _get_div()
 is used as divider without any check.
 If _get_div() never returns 0, then the branch returning 0 is dead code,
or the return value should be check to avoid dividing by zero error. 

thanks

>> Signed-off-by: nixiaoming <nixiaoming@...wei.com>
>> Reviewed-by: Mukesh Ojha <mojha@...eaurora.org>
>