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/[email protected]

Fixes: 6648e613226e ("bpf, skmsg: Fix NULL pointer dereference in sk_psock_skb_ingress_enqueue")
Reported-by: Vincent Whitchurch <[email protected]>
Signed-off-by: Jiayuan Chen <[email protected]>
Signed-off-by: John Fastabend <[email protected]>
Acked-by: Martin KaFai Lau <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index b1dcbd3be89e10a2c23072177b816a30f897de22..e90fbab703b2db1da49068b5a53338ce7ff99087 100644 (file)
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -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();