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Re: Kernel oops when clearing bgp neighbor info with TCP MD5SUM enabled

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From: Anirban Sinha
Subject: Re: Kernel oops when clearing bgp neighbor info with TCP MD5SUM enabled
Date: Monday, October 19, 2009 - 5:56 pm

> I'd suppose that this unbalance comes from inet_twdr_hangman() pathes.


Yes, I have now verified this. There is indeed an issue with one of the
functions called by inet_twdr_hangman(). The call sequence is:

inet_twdr_hangman() -> inet_twdr_do_twkill_work() -> inet_twsk_put() ->
twsk_destructor().

In this case, the destructor callback is tcp_twsk_destructor() (installed
from line 1208 in net/ipv4/tcp_ipv4.c and line 906 in net/ipv6/tcp_ipv6.c) .
Without the TCP_MD5SUM compiled in, the function is a no-op. However, with the MD5SUM
compiled in, it calls tcp_put_md5_sig_pool() (when keylen is non zero) which
does an unbalanced put_cpu(). I did a grep across the entire tree.
tcp_put_md5_sig_pool() is a matching function for tcp_get_md5_sig_pool() and
in all other TCP IPV4 cases, it is called from net/ipv4/tcp_ipv4.c from
functions tcp_v4_md5_hash_hdr() and

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Messages in current thread:
Kernel oops when clearing bgp neighbor info with TCP MD5SU ..., Anirban Sinha, (Thu Oct 8, 3:19 pm)
Re: Kernel oops when clearing bgp neighbor info with TCP M ..., David Miller, (Thu Oct 8, 3:54 pm)
Re: Kernel oops when clearing bgp neighbor info with TCP M ..., Anirban Sinha, (Thu Oct 8, 4:33 pm)
Re: Kernel oops when clearing bgp neighbor info with TCP M ..., David Miller, (Thu Oct 8, 5:57 pm)
Re: Kernel oops when clearing bgp neighbor info with TCP M ..., Anirban Sinha, (Sat Oct 17, 10:57 am)
Re: Kernel oops when clearing bgp neighbor info with TCP M ..., Anirban Sinha, (Sat Oct 17, 7:35 pm)
Re: Kernel oops when clearing bgp neighbor info with TCP M ..., Anirban Sinha, (Sun Oct 18, 1:19 pm)
Re: Kernel oops when clearing bgp neighbor info with TCP M ..., Oleg Nesterov, (Mon Oct 19, 5:13 am)
Re: Kernel oops when clearing bgp neighbor info with TCP M ..., Anirban Sinha, (Mon Oct 19, 8:32 am)
Re: Kernel oops when clearing bgp neighbor info with TCP M ..., Oleg Nesterov, (Mon Oct 19, 8:36 am)
Re: Kernel oops when clearing bgp neighbor info with TCP M ..., Anirban Sinha, (Mon Oct 19, 9:01 am)
Re: Kernel oops when clearing bgp neighbor info with TCP M ..., Anirban Sinha, (Mon Oct 19, 5:56 pm)
[PATCH] Re: Kernel oops when clearing bgp neighbor info wi ..., Anirban Sinha, (Mon Oct 19, 6:08 pm)
Re: [PATCH] Re: Kernel oops when clearing bgp neighbor inf ..., David Miller, (Mon Oct 19, 6:13 pm)
Re: [PATCH] Re: Kernel oops when clearing bgp neighbor inf ..., Anirban Sinha, (Mon Oct 19, 6:17 pm)