netdev - Re: kernel panic in fib_rules_lookup [2.6.27.7 vendor-patched]

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Date:	Sat, 23 Oct 2010 17:11:09 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Joe Buehler <aspam@....net>
Cc:	netdev@...r.kernel.org
Subject: Re: kernel panic in fib_rules_lookup [2.6.27.7 vendor-patched]

Le samedi 23 octobre 2010 à 05:44 +0200, Eric Dumazet a écrit :
> Le vendredi 22 octobre 2010 à 16:30 -0400, Joe Buehler a écrit :
> > Eric Dumazet wrote:
> > 
> > > Could you provide a disassembly of function fib_rules_lookup ?
> > 
> > Try looking in http://68.100.141.95:3000/linux-crash/.  There should be
> > the source file I am using (not current release if you recall), the .o,
> > the disassembly, and a -S compile that makes deducing the line numbers a
> > little easier.
> > 
> 
> Hmm, I'll take a look sometime in the future, thanks

Did that... Hmm...

I am wondering if smp_rcu_assign_pointer() (or more precisely smp_wmb())
is correctly implemented on octeon platform.

Try to add in fib_nl_newrule() right after the kzalloc bloc :

	rule = kzalloc(ops->rule_size, GFP_KERNEL);
	if (rule == NULL) {
		err = -ENOMEM;
		goto errout;
	}
+       rule->list.next = LIST_POISON1;
+       rule->list.prev = LIST_POISON2;


So that we can actually see if the NULL dereference bug you hit becomes
a "LIST_POISON1" dereference bug...



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