linux-kernel - Re: [PATCH net v2] net: mptcp: fix unreleased socket in accept queue

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Message-ID: <873298fe-7fc2-4417-2852-5180f81f94aa@tessares.net>
Date:   Wed, 7 Sep 2022 10:51:21 +0200
From:   Matthieu Baerts <matthieu.baerts@...sares.net>
To:     menglong8.dong@...il.com, pabeni@...hat.com
Cc:     mathew.j.martineau@...ux.intel.com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, fw@...len.de,
        peter.krystad@...ux.intel.com, netdev@...r.kernel.org,
        mptcp@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Menglong Dong <imagedong@...cent.com>,
        Jiang Biao <benbjiang@...cent.com>,
        Mengen Sun <mengensun@...cent.com>
Subject: Re: [PATCH net v2] net: mptcp: fix unreleased socket in accept queue

Hi Menglong,

On 07/09/2022 10:33, menglong8.dong@...il.com wrote:
> From: Menglong Dong <imagedong@...cent.com>
> 
> The mptcp socket and its subflow sockets in accept queue can't be
> released after the process exit.
> 
> While the release of a mptcp socket in listening state, the
> corresponding tcp socket will be released too. Meanwhile, the tcp
> socket in the unaccept queue will be released too. However, only init
> subflow is in the unaccept queue, and the joined subflow is not in the
> unaccept queue, which makes the joined subflow won't be released, and
> therefore the corresponding unaccepted mptcp socket will not be released
> to.

Thank you for the patch!

(...)

> ---
>  net/mptcp/protocol.c | 13 +++++++++----
>  net/mptcp/subflow.c  | 33 ++++++++-------------------------
>  2 files changed, 17 insertions(+), 29 deletions(-)
> 
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index d398f3810662..fe6b7fbb145c 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -2796,13 +2796,12 @@ static void __mptcp_destroy_sock(struct sock *sk)
>  	sock_put(sk);
>  }
>  
> -static void mptcp_close(struct sock *sk, long timeout)
> +void mptcp_close_nolock(struct sock *sk, long timeout)

I didn't look at it into details but like the previous previous, I don't
think this one compiles without errors: you define this (non static)
function here in protocol.c but you don't "expose" it in protocol.h ...
(see below)

> diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
> index c7d49fb6e7bd..cebabf2bb222 100644
> --- a/net/mptcp/subflow.c
> +++ b/net/mptcp/subflow.c

(...)

> @@ -1765,11 +1740,19 @@ void mptcp_subflow_queue_clean(struct sock *listener_ssk)
>  		struct sock *sk = (struct sock *)msk;
>  		bool slow;
>  
> +		sock_hold(sk);
>  		slow = lock_sock_fast_nested(sk);
>  		next = msk->dl_next;
>  		msk->first = NULL;
>  		msk->dl_next = NULL;
> +
> +		/* mptcp_close_nolock() will put a extra reference on sk,
> +		 * so we hold one here.
> +		 */
> +		sock_hold(sk);
> +		mptcp_close_nolock(sk, 0);

... I guess the compiler will complain if you try to use it here from
subflow.c, no?

Also, did you have the opportunity to run the different MPTCP selftests
with this patch?

Cheers,
Matt
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