[patch 30/37] tcp: fix CONFIG_TCP_MD5SIG + CONFIG_PREEMPT timer BUG()

Greg KH
2009-10-09T23:42:27Z

[-- Attachment #1: tcp-fix-config_tcp_md5sig-config_preempt-timer-bug.patch --]
[-- Type: text/plain, Size: 1413 bytes --]

2.6.31-stable review patch. If anyone has any objections, please let us know.

------------------
From: Robert Varga <nite@hq.alert.sk>

[ Upstream commit 657e9649e745b06675aa5063c84430986cdc3afa ]

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@hq.alert.sk>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
net/ipv4/tcp_minisocks.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -363,7 +363,7 @@ 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
}