netdev - Re: [PATCH net-next] mptcp: fix tracking issue in mptcp_subflow_create

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Date:   Tue, 25 Oct 2022 15:53:10 -0700 (PDT)
From:   Mat Martineau <mathew.j.martineau@...ux.intel.com>
To:     Eric Dumazet <edumazet@...gle.com>
cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        eric.dumazet@...il.com, syzbot <syzkaller@...glegroups.com>,
        Matthieu Baerts <matthieu.baerts@...sares.net>,
        Kuniyuki Iwashima <kuniyu@...zon.com>
Subject: Re: [PATCH net-next] mptcp: fix tracking issue in
 mptcp_subflow_create_socket()

On Tue, 25 Oct 2022, Eric Dumazet wrote:

> My recent patch missed that mptcp_subflow_create_socket()
> was creating a 'kernel' socket, then converted it to 'user' socket.
>
> Fixes: 0cafd77dcd03 ("net: add a refcount tracker for kernel sockets")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Mat Martineau <mathew.j.martineau@...ux.intel.com>
> Cc: Matthieu Baerts <matthieu.baerts@...sares.net>
> Cc: Kuniyuki Iwashima <kuniyu@...zon.com>
> ---

Hi Eric -

I also missed this quirk in MPTCP subflow handling, thanks for the fix:

Reviewed-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>



> net/mptcp/subflow.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
> index 07dd23d0fe04ac37f4cc66c0c21d4d41f50fb3f4..120f792fda9764271f020771b36d27c6e44d8618 100644
> --- a/net/mptcp/subflow.c
> +++ b/net/mptcp/subflow.c
> @@ -1595,7 +1595,9 @@ int mptcp_subflow_create_socket(struct sock *sk, struct socket **new_sock)
>
> 	/* kernel sockets do not by default acquire net ref, but TCP timer
> 	 * needs it.
> +	 * Update ns_tracker to current stack trace and refcounted tracker.
> 	 */
> +	__netns_tracker_free(net, &sf->sk->ns_tracker, false);
> 	sf->sk->sk_net_refcnt = 1;
> 	get_net_track(net, &sf->sk->ns_tracker, GFP_KERNEL);
> 	sock_inuse_add(net, 1);
> -- 
> 2.38.0.135.g90850a2211-goog
>
>

--
Mat Martineau
Intel