netdev - Re: [Bugme-new] [Bug 16268] New: kernel oops when rmmod the tcp

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Date:	Wed, 23 Jun 2010 00:02:42 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	netdev@...r.kernel.org, bugzilla-daemon@...zilla.kernel.org,
	bugme-daemon@...zilla.kernel.org, lyw@...fujitsu.com
Subject: Re: [Bugme-new] [Bug 16268] New: kernel oops when rmmod the
 tcp_diag modules

Le mardi 22 juin 2010 à 14:12 -0700, Andrew Morton a écrit :
> (switched to email.  Please respond via emailed reply-to-all, not via the
> bugzilla web interface).
> 
> On Tue, 22 Jun 2010 00:43:37 GMT
> bugzilla-daemon@...zilla.kernel.org wrote:
> 
> > https://bugzilla.kernel.org/show_bug.cgi?id=16268
> > 
> >            Summary: kernel oops when rmmod the tcp_diag modules
> >            Product: Networking
> >            Version: 2.5
> >     Kernel Version: 2.6.35-rc3
> >           Platform: All
> >         OS/Version: Linux
> >               Tree: Mainline
> >             Status: NEW
> >           Severity: high
> >           Priority: P1
> >          Component: IPV4
> >         AssignedTo: shemminger@...ux-foundation.org
> >         ReportedBy: lyw@...fujitsu.com
> >         Regression: No
> > 
> > 
> > I found a crash problem use following scripts and steps
> > 
> > #cat run_ss.sh
> >  while [ 1 ]
> >  do
> >      ss -a
> >  done
> > 
> > #cat rmmod.sh
> >  while [ 1 ]
> >  do 
> >      rmmod -f tcp_diag >/dev/null 2>&1
> >      rmmod -f inet_diag >/dev/null 2>&1
> >  done
> > 
> > step1:
> >   # sh run_sh.sh
> > step2:
> >   # sh rmmod.sh
> 
> I assume the rmmod script runs in pararallel with run_ss.sh.
> 
> What is "ss"?  Something which triggers a load of kernel modules,
> presumably.  Which ones?
> 

ss is kind of "netstat" with advanced features.

It loads inet_diag & tcp_diag modules.

> > After step2, the kernel oopsed.
> 
> yeah, that was a pretty nasty test ;)

Well, they are faster and more predictable ways to reboot a machine, if
you ask me :)

man rmmod

       -f --force
              This  option can be extremely dangerous: it has no effect unless
              CONFIG_MODULE_FORCE_UNLOAD was set when the kernel was compiled.
              With  this  option, you can remove modules which are being used,
              or which are not designed to be removed, or have been marked  as
              unsafe (see lsmod(8)).


I guess Linux is supposed to respect admin choice to live in a dangerous world.


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