netdev - Re: [Patch bpf-next] skmsg: pass psock pointer to ->psock_update_sk

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Message-ID: <87r1jg2aik.fsf@cloudflare.com>
Date:   Mon, 12 Apr 2021 10:05:23 +0200
From:   Jakub Sitnicki <jakub@...udflare.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        Cong Wang <cong.wang@...edance.com>,
        syzbot+320a3bc8d80f478c37e4@...kaller.appspotmail.com,
        John Fastabend <john.fastabend@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Lorenz Bauer <lmb@...udflare.com>
Subject: Re: [Patch bpf-next] skmsg: pass psock pointer to
 ->psock_update_sk_prot()

On Wed, Apr 07, 2021 at 05:21 AM CEST, Cong Wang wrote:
> From: Cong Wang <cong.wang@...edance.com>
>
> Using sk_psock() to retrieve psock pointer from sock requires
> RCU read lock, but we already get psock pointer before calling
> ->psock_update_sk_prot() in both cases, so we can just pass it
> without bothering sk_psock().
>
> Reported-and-tested-by: syzbot+320a3bc8d80f478c37e4@...kaller.appspotmail.com
> Fixes: 8a59f9d1e3d4 ("sock: Introduce sk->sk_prot->psock_update_sk_prot()")
> Cc: John Fastabend <john.fastabend@...il.com>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Daniel Borkmann <daniel@...earbox.net>
> Cc: Jakub Sitnicki <jakub@...udflare.com>
> Cc: Lorenz Bauer <lmb@...udflare.com>
> Signed-off-by: Cong Wang <cong.wang@...edance.com>
> ---

We don't necessarily need to pass both sk and psock.  psock has a
backpointer to sk that owns it.

Reviewed-by: Jakub Sitnicki <jakub@...udflare.com>