Commit 8ca2a1ee authored by Jiayuan Chen's avatar Jiayuan Chen Committed by Jakub Kicinski
Browse files

bpf: fix recursive lock when verdict program return SK_PASS 

When the stream_verdict program returns SK_PASS, it places the received skb
into its own receive queue, but a recursive lock eventually occurs, leading
to an operating system deadlock. This issue has been present since v6.9.

'''
sk_psock_strp_data_ready
    write_lock_bh(&sk->sk_callback_lock)
    strp_data_ready
      strp_read_sock
        read_sock -> tcp_read_sock
          strp_recv
            cb.rcv_msg -> sk_psock_strp_read
              # now stream_verdict return SK_PASS without peer sock assign
              __SK_PASS = sk_psock_map_verd(SK_PASS, NULL)
              sk_psock_verdict_apply
                sk_psock_skb_ingress_self
                  sk_psock_skb_ingress_enqueue
                    sk_psock_data_ready
                      read_lock_bh(&sk->sk_callback_lock) <= dead lock

'''

This topic has been discussed before, but it has not been fixed.
Previous discussion:
https://lore.kernel.org/all/6684a5864ec86_403d20898@john.notmuch



Fixes: 6648e613 ("bpf, skmsg: Fix NULL pointer dereference in sk_psock_skb_ingress_enqueue")
Reported-by: default avatarVincent Whitchurch <vincent.whitchurch@datadoghq.com>
Signed-off-by: default avatarJiayuan Chen <mrpre@163.com>
Signed-off-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Acked-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20241118030910.36230-2-mrpre@163.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 21742be8

net/core/skmsg.c

+2 −2
Original line number Diff line number Diff line
@@ -1117,9 +1117,9 @@ static void sk_psock_strp_data_ready(struct sock *sk) 
		if (tls_sw_has_ctx_rx(sk)) {

			psock->saved_data_ready(sk);

		} else {

			write_lock_bh(&sk->sk_callback_lock);

			read_lock_bh(&sk->sk_callback_lock);

			strp_data_ready(&psock->strp);

			write_unlock_bh(&sk->sk_callback_lock);

			read_unlock_bh(&sk->sk_callback_lock);

		}

	}

	rcu_read_unlock();