Re: [PATCH v3] clk: sophgo: Cast an operand to u64 to prevent potential unsigned long overflow on 32-bit machine in sg2042_pll_recalc_rate()

[Zichen Xie <zichenxie0106@gmail.com>]

On 2024/10/23 2:41, Dan Carpenter wrote:
> I'm sorry, I have let you down in some ways.  This subject line is too long.
> It's 126 characters long.  Please change it so something like:
>
> clk: sophgo: avoid integer overflow in sg2042_pll_recalc_rate()
>
> On Tue, Oct 22, 2024 at 03:12:45PM -0500, Gax-c wrote:
>> From: Zichen Xie <zichenxie0106@gmail.com>
>>
>> This was found by a static analyzer.
>> There may be a potential integer overflow issue in
>> sg2042_pll_recalc_rate(). numerator is defined as u64 while
>> parent_rate is defined as unsigned long and ctrl_table.fbdiv
>> is defined as unsigned int. On 32-bit machine, the result of
>> the calculation will be limited to "u32" without correct casting.
>> Integer overflow may occur on high-performance systems.
>> We recommended that we cast the denominator as well but
>> Dan Carpenter said that it was a max of 3087 and was not even
>> vaguely close to the 4 billion mark needed to overflow a u32.
>> So, we only cast the numerator here.
> On second though, could we just leave this out.  Let's only mention the
> numerator.

Fine. I'll do it later.


>
> regards,
> dan carpenter
>