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

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Message-ID: <CANn89iLC6F3P6PcP4cKG9=f7+ymW1By1EyhFH+Q0V6V-xXn7jA@mail.gmail.com>
Date: Tue, 16 Sep 2025 00:30:45 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: xuanqiang.luo@...ux.dev
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

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.

>
> 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
>