netdev - Re: [PATCH net-next v8 2/3] inet: Avoid ehash lookup race in inet_ehash

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Message-ID: <CANn89iKvf6i7-Ku-iqYG0JoGqfiewx45ZVoYcCRzbDW7g=RDvQ@mail.gmail.com>
Date: Wed, 15 Oct 2025 02:00:19 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: xuanqiang.luo@...ux.dev
Cc: kuniyu@...gle.com, pabeni@...hat.com, kerneljasonxing@...il.com, 
	davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org, 
	horms@...nel.org, jiayuan.chen@...ux.dev, ncardwell@...gle.com, 
	dsahern@...nel.org, Xuanqiang Luo <luoxuanqiang@...inos.cn>
Subject: Re: [PATCH net-next v8 2/3] inet: Avoid ehash lookup race in inet_ehash_insert()

On Tue, Oct 14, 2025 at 7:04 PM <xuanqiang.luo@...ux.dev> wrote:
>
> From: Xuanqiang Luo <luoxuanqiang@...inos.cn>
>
> Since ehash lookups are lockless, if one CPU performs a lookup while
> another concurrently deletes and inserts (removing reqsk and inserting sk),
> the lookup may fail to find the socket, an RST may be sent.
>
> The call trace map is drawn as follows:
>    CPU 0                           CPU 1
>    -----                           -----
>                                 inet_ehash_insert()
>                                 spin_lock()
>                                 sk_nulls_del_node_init_rcu(osk)
> __inet_lookup_established()
>         (lookup failed)
>                                 __sk_nulls_add_node_rcu(sk, list)
>                                 spin_unlock()
>
> As both deletion and insertion operate on the same ehash chain, this patch
> introduces a new sk_nulls_replace_node_init_rcu() helper functions to
> implement atomic replacement.
>
> Fixes: 5e0724d027f0 ("tcp/dccp: fix hashdance race for passive sessions")
> Reviewed-by: Kuniyuki Iwashima <kuniyu@...gle.com>
> Reviewed-by: Jiayuan Chen <jiayuan.chen@...ux.dev>
> Signed-off-by: Xuanqiang Luo <luoxuanqiang@...inos.cn>

Reviewed-by: Eric Dumazet <edumazet@...gle.com>