Re: Boot regression caused by kauditd

From	Cong Wang <xiyou.wangcong@gmail.com>
Newsgroups	linux.kernel
Subject	Re: Boot regression caused by kauditd
Date	2017-04-27 22:40 +0200
Message-ID	<tAYmJ-5JM-1@gated-at.bofh.it> (permalink)
References	<tAC2R-7gR-5@gated-at.bofh.it> <tACFz-7Oy-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Wed, Apr 26, 2017 at 2:20 PM, Paul Moore <paul@paul-moore.com> wrote:
> Thanks for the report, this is the only one like it that I've seen.
> I'm looking at the code in Linus' tree and I'm not seeing anything
> obvious ... looking at the trace above it appears that the problem is
> when get_net() goes to bump the refcount and the passed net pointer is
> NULL; unless I'm missing something, the only way this would happen in
> kauditd_thread() is if the auditd_conn.pid value is non-zero but the
> auditd_conn.net pointer is NULL.
>
> That shouldn't happen.
>

Looking at the code that reads/writes the global auditd_conn,
I don't see how it even works with RCU+spinlock, RCU plays
with pointers and you have to make a copy as its name implies.
But it looks like you simply use RCU+spinlock as a traditional
rwlock, it doesn't work.

Thread

Boot regression caused by kauditd Cong Wang <xiyou.wangcong@gmail.com> - 2017-04-26 22:50 +0200
  Re: Boot regression caused by kauditd Paul Moore <paul@paul-moore.com> - 2017-04-26 23:30 +0200
    Re: Boot regression caused by kauditd Cong Wang <xiyou.wangcong@gmail.com> - 2017-04-27 07:10 +0200
    Re: Boot regression caused by kauditd Cong Wang <xiyou.wangcong@gmail.com> - 2017-04-27 22:40 +0200
      Re: Boot regression caused by kauditd Cong Wang <xiyou.wangcong@gmail.com> - 2017-04-27 23:40 +0200
        Re: Boot regression caused by kauditd Cong Wang <xiyou.wangcong@gmail.com> - 2017-04-27 23:50 +0200
          Re: Boot regression caused by kauditd Paul Moore <paul@paul-moore.com> - 2017-04-28 00:40 +0200
            Re: Boot regression caused by kauditd Cong Wang <xiyou.wangcong@gmail.com> - 2017-04-28 01:50 +0200
              Re: Boot regression caused by kauditd Paul Moore <paul@paul-moore.com> - 2017-04-28 02:50 +0200
                Re: Boot regression caused by kauditd Paul Moore <paul@paul-moore.com> - 2017-04-28 17:40 +0200
                Re: Boot regression caused by kauditd Cong Wang <xiyou.wangcong@gmail.com> - 2017-04-28 18:20 +0200
                Re: Boot regression caused by kauditd Paul Moore <paul@paul-moore.com> - 2017-04-28 18:30 +0200
                Re: Boot regression caused by kauditd Cong Wang <xiyou.wangcong@gmail.com> - 2017-05-02 08:00 +0200

csiph-web