netdev - Re: [PATCH bpf-next 1/4] bpf, sockmap: Fix memleak in sk_psock_queue

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Date:   Sun, 27 Feb 2022 11:21:12 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Wang Yufen <wangyufen@...wei.com>
Cc:     john.fastabend@...il.com, daniel@...earbox.net,
        jakub@...udflare.com, lmb@...udflare.com, davem@...emloft.net,
        bpf@...r.kernel.org, edumazet@...gle.com, yoshfuji@...ux-ipv6.org,
        dsahern@...nel.org, kuba@...nel.org, ast@...nel.org,
        andrii@...nel.org, kafai@...com, songliubraving@...com, yhs@...com,
        kpsingh@...nel.org, netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next 1/4] bpf, sockmap: Fix memleak in
 sk_psock_queue_msg

On Fri, Feb 25, 2022 at 09:49:26AM +0800, Wang Yufen wrote:
> If tcp_bpf_sendmsg is running during a tear down operation we may enqueue
> data on the ingress msg queue while tear down is trying to free it.
> 
>  sk1 (redirect sk2)                         sk2
>  -------------------                      ---------------
> tcp_bpf_sendmsg()
>  tcp_bpf_send_verdict()
>   tcp_bpf_sendmsg_redir()
>    bpf_tcp_ingress()
>                                           sock_map_close()
>                                            lock_sock()
>     lock_sock() ... blocking
>                                            sk_psock_stop
>                                             sk_psock_clear_state(psock, SK_PSOCK_TX_ENABLED);
>                                            release_sock(sk);
>     lock_sock()	
>     sk_mem_charge()
>     get_page()
>     sk_psock_queue_msg()
>      sk_psock_test_state(psock, SK_PSOCK_TX_ENABLED);
>       drop_sk_msg()
>     release_sock()
> 
> While drop_sk_msg(), the msg has charged memory form sk by sk_mem_charge
> and has sg pages need to put. To fix we use sk_msg_free() and then kfee()
> msg.
> 

What about the other code path? That is, sk_psock_skb_ingress_enqueue().
I don't see skmsg is charged there.

Thanks.