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

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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 <trond.myklebust@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Trond Myklebust 2016-07-26 09:51:19 -04:00 committed by J. Bruce Fields
parent 8a4c392688
commit b2f21f7d85
1 changed files with 10 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
net/sunrpc/svcsock.c
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@ -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);
}
}
}