SUNRPC: accept() may return sockets that are still in SYN_RECV

We're seeing traces of the following form: [10952.396347] svc: transport ffff88042ba4a 000 dequeued, inuse=2 [10952.396351] svc: tcp_accept ffff88042ba4 a000 sock ffff88042a6e4c80 [10952.396362] nfsd: connect from 10.2.6.1, port=187 [10952.396364] svc: svc_setup_socket ffff8800b99bcf00 [10952.396368] setting up TCP socket for reading [10952.396370] svc: svc_setup_socket created ffff8803eb10a000 (inet ffff88042b75b800) [10952.396373] svc: transport ffff8803eb10a000 put into queue [10952.396375] svc: transport ffff88042ba4a000 put into queue [10952.396377] svc: server ffff8800bb0ec000 waiting for data (to = 3600000) [10952.396380] svc: transport ffff8803eb10a000 dequeued, inuse=2 [10952.396381] svc_recv: found XPT_CLOSE [10952.396397] svc: svc_delete_xprt(ffff8803eb10a000) [10952.396398] svc: svc_tcp_sock_detach(ffff8803eb10a000) [10952.396399] svc: svc_sock_detach(ffff8803eb10a000) [10952.396412] svc: svc_sock_free(ffff8803eb10a000) i.e. an immediate close of the socket after initialisation. The culprit appears to be the test at the end of svc_tcp_init, which checks if the newly created socket is in the TCP_ESTABLISHED state, and immediately closes it if not. The evidence appears to suggest that the socket might still be in the SYN_RECV state at this time. The fix is to check for both states, and then to add a check in svc_tcp_state_change() to ensure we don't close the socket when it transitions into TCP_ESTABLISHED. Signed-off-by: Trond Myklebust <[email protected]> Signed-off-by: J. Bruce Fields <[email protected]>
CamonZ · Aug 1, 2016 · b2f21f7 · b2f21f7
1 parent 8a4c392
commit b2f21f7
Showing 1 changed file with 10 additions and 3 deletions.
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
@@ -763,8 +763,10 @@ static void svc_tcp_state_change(struct sock *sk)
 		printk("svc: socket %p: no user data\n", sk);
 	else {
 		svsk->sk_ostate(sk);
-		set_bit(XPT_CLOSE, &svsk->sk_xprt.xpt_flags);
-		svc_xprt_enqueue(&svsk->sk_xprt);
+		if (sk->sk_state != TCP_ESTABLISHED) {
+			set_bit(XPT_CLOSE, &svsk->sk_xprt.xpt_flags);
+			svc_xprt_enqueue(&svsk->sk_xprt);
+		}
 	}
 }
 
@@ -1290,8 +1292,13 @@ static void svc_tcp_init(struct svc_sock *svsk, struct svc_serv *serv)
 		tcp_sk(sk)->nonagle |= TCP_NAGLE_OFF;
 
 		set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
-		if (sk->sk_state != TCP_ESTABLISHED)
+		switch (sk->sk_state) {
+		case TCP_SYN_RECV:
+		case TCP_ESTABLISHED:
+			break;
+		default:
 			set_bit(XPT_CLOSE, &svsk->sk_xprt.xpt_flags);
+		}
 	}
 }