GIT: unionfs2-2.6.27.y: tcp: fix CONFIG_TCP_MD5SIG + CONFIG_PREEMPT timer BUG()

[Erez Zadok]

commit 7224283df47b5ff9f309371b60030f07037cd51e
Author: Robert Varga <nite at hq.alert.sk>
Date:   Tue Sep 15 23:49:21 2009 -0700

    tcp: fix CONFIG_TCP_MD5SIG + CONFIG_PREEMPT timer BUG()
    
    commit 657e9649e745b06675aa5063c84430986cdc3afa upstream.
    
    I have recently came across a preemption imbalance detected by:
    
    <4>huh, entered ffffffff80644630 with preempt_count 00000102, exited with 00000101?
    <0>------------[ cut here ]------------
    <2>kernel BUG at /usr/src/linux/kernel/timer.c:664!
    <0>invalid opcode: 0000 [1] PREEMPT SMP
    
    with ffffffff80644630 being inet_twdr_hangman().
    
    This appeared after I enabled CONFIG_TCP_MD5SIG and played with it a
    bit, so I looked at what might have caused it.
    
    One thing that struck me as strange is tcp_twsk_destructor(), as it
    calls tcp_put_md5sig_pool() -- which entails a put_cpu(), causing the
    detected imbalance. Found on 2.6.23.9, but 2.6.31 is affected as well,
    as far as I can tell.
    
    Signed-off-by: Robert Varga <nite at hq.alert.sk>
    Signed-off-by: David S. Miller <davem at davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh at suse.de>

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index f976fc5..6d108fb 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -362,7 +362,7 @@ void tcp_twsk_destructor(struct sock *sk)
 #ifdef CONFIG_TCP_MD5SIG
 	struct tcp_timewait_sock *twsk = tcp_twsk(sk);
 	if (twsk->tw_md5_keylen)
-		tcp_put_md5sig_pool();
+		tcp_free_md5sig_pool();
 #endif
 }