netdev - Re: [PATCH net-next v2 0/3] net: Avoid ehash lookup races

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Message-ID: <09d9a014-5687-4b60-9646-95c3644efe19@linux.dev>
Date: Tue, 16 Sep 2025 16:11:25 +0800
From: luoxuanqiang <xuanqiang.luo@...ux.dev>
To: Eric Dumazet <edumazet@...gle.com>
Cc: kuniyu@...gle.com, kerneljasonxing@...il.com, davem@...emloft.net,
 kuba@...nel.org, netdev@...r.kernel.org,
 Xuanqiang Luo <luoxuanqiang@...inos.cn>
Subject: Re: [PATCH net-next v2 0/3] net: Avoid ehash lookup races


在 2025/9/16 15:30, Eric Dumazet 写道:
> On Mon, Sep 15, 2025 at 11:47 PM <xuanqiang.luo@...ux.dev> wrote:
>> From: Xuanqiang Luo <luoxuanqiang@...inos.cn>
>>
>> After replacing R/W locks with RCU in commit 3ab5aee7fe84 ("net: Convert
>> TCP & DCCP hash tables to use RCU / hlist_nulls"), a race window emerged
>> during the switch from reqsk/sk to sk/tw.
>>
>> Now that both timewait sock (tw) and full sock (sk) reside on the same
>> ehash chain, it is appropriate to introduce hlist_nulls replace
>> operations, to eliminate the race conditions caused by this window.
>>
>> ---
>> Changes:
>>    v2:
>>      * Patch 1
>>          * Use WRITE_ONCE() to initialize old->pprev.
>>      * Patch 2&3
>>          * Optimize sk hashed check. Thanks Kuni for pointing it out!
>>
>>    v1: https://lore.kernel.org/all/20250915070308.111816-1-xuanqiang.luo@linux.dev/
> Note : I think you sent an earlier version, you should have added a
> link to the discussion,
> and past feedback/suggestions.
>
> Lack of credit is a bit annoying frankly.
>
> I will take a look at your series, thanks.

This patch's solution isn't very related to previous ones, so I didn't
include prior discussions.

But to help others get the full picture, I'll share past links and
earlier discussions related to this type of issue in the next version
or a reply. Sorry for any oversight.

Thanks
Xuanqiang.

>> Xuanqiang Luo (3):
>>    rculist: Add __hlist_nulls_replace_rcu() and
>>      hlist_nulls_replace_init_rcu()
>>    inet: Avoid ehash lookup race in inet_ehash_insert()
>>    inet: Avoid ehash lookup race in inet_twsk_hashdance_schedule()
>>
>>   include/linux/rculist_nulls.h | 61 +++++++++++++++++++++++++++++++++++
>>   include/net/sock.h            | 23 +++++++++++++
>>   net/ipv4/inet_hashtables.c    |  4 ++-
>>   net/ipv4/inet_timewait_sock.c | 15 ++++-----
>>   4 files changed, 93 insertions(+), 10 deletions(-)
>>
>> --
>> 2.25.1
>>