linux-kernel - Re: [PATCH net v3] net: Refine key_len calculations in rhashtable

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Message-ID: <20241227111328.540ced11@kernel.org>
Date: Fri, 27 Dec 2024 11:13:28 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Liang Jie <buaajxlj@....com>
Cc: edumazet@...gle.com, davem@...emloft.net, pabeni@...hat.com,
 horms@...nel.org, anthony.l.nguyen@...el.com, andrew+netdev@...n.ch,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org, Liang Jie
 <liangjie@...iang.com>
Subject: Re: [PATCH net v3] net: Refine key_len calculations in
 rhashtable_params

On Fri, 20 Dec 2024 16:24:36 +0800 Liang Jie wrote:
> From: Liang Jie <liangjie@...iang.com>
> 
> This patch improves the calculation of key_len in the rhashtable_params
> structures across the net driver modules by replacing hardcoded sizes
> and previous calculations with appropriate macros like sizeof_field()
> and offsetofend().
> 
> Previously, key_len was set using hardcoded sizes like sizeof(u32) or
> sizeof(unsigned long), or using offsetof() calculations. This patch
> replaces these with sizeof_field() and correct use of offsetofend(),
> making the code more robust, maintainable, and improving readability.
> 
> Using sizeof_field() and offsetofend() provides several advantages:
> - They explicitly specify the size of the field or the end offset of a
>   member being used as a key.
> - They ensure that the key_len is accurate even if the structs change in
>   the future.
> - They improve code readability by clearly indicating which fields are used
>   and how their sizes are determined, making the code easier to understand
>   and maintain.
> 
> For example, instead of:
>     .key_len    = sizeof(u32),
> we now use:
>     .key_len    = sizeof_field(struct mae_mport_desc, mport_id),
> 
> And instead of:
>     .key_len    = offsetof(struct efx_tc_encap_match, linkage),
> we now use:
>     .key_len    = offsetofend(struct efx_tc_encap_match, ip_tos_mask),
> 
> These changes eliminate the risk in certain scenarios of including
> unintended padding or extra data in the key, ensuring the rhashtable
> functions correctly.

IMHO the change is not worth the churn. Does any upstream code checker
/ tool prevent from new instances of this pattern occurring?
-- 
pw-bot: reject