netdev - Re: [PATCH] net: ethernet: ti: Prevent divide-by-zero in cpts_calc_mult

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Message-ID: <e177027d-9286-4a30-9656-e0395094b2c1@linux.dev>
Date: Thu, 28 Aug 2025 14:01:23 +0100
From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To: 林妙倩 <linmq006@...il.com>
Cc: Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Matthias Brugger <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Thomas Gleixner <tglx@...utronix.de>,
 Grygorii Strashko <grygorii.strashko@...com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] net: ethernet: ti: Prevent divide-by-zero in
 cpts_calc_mult_shift()

On 28/08/2025 13:38, æå¦å© wrote:
> Hi, Vadim
> 
> Vadim Fedorenko <vadim.fedorenko@...ux.dev> 于2025年8月28日周四 20:06写道：
>>
>> On 28/08/2025 10:22, Miaoqian Lin wrote:
>>> cpts_calc_mult_shift() has a potential divide-by-zero in this line:
>>>
>>>           do_div(maxsec, freq);
>>>
>>> due to the fact that clk_get_rate() can return zero in certain error
>>> conditions.
>>
>> Have you seen this happening in the real environment, or is it just
>> analysis of the code? I don't see a reason for these "certain error
>> conditions" to happen...
> 
> This is from code analysis, not from real environment.
> The !CONFIG_HAVE_CLK version of clk_get_rate() returns zero.
> With CONFIG_COMPILE_TEST && !CONFIG_HAVE_CLK could have the problem.
> This may be theoretical.

!CONFIG_HAVE_CLK will have cpts_create() doing nothing as defined in
cpts.h and it means the patch fixes impossible scenario.

NAck