netdev - Re: net-next kernel NULL pointer dereference at fib_rules

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Message-Id: <20120710.094428.1167234955738653678.davem@davemloft.net>
Date:	Tue, 10 Jul 2012 09:44:28 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	ogerlitz@...lanox.com
Cc:	netdev@...r.kernel.org, shlomop@...lanox.com, amirv@...lanox.com,
	erezsh@...lanox.com
Subject: Re: net-next kernel NULL pointer dereference at fib_rules_tclass 

From: Or Gerlitz <ogerlitz@...lanox.com>
Date: Tue, 10 Jul 2012 10:16:55 +0300

> Starting system logger: BUG: unable to handle kernel NULL pointer dereference at 00000000000000ac
> IP: [<ffffffff81320393>] fib_rules_tclass+0xf/0x17

Ok, fib_rules_tclass() checks for res->r being NULL and only
dereferences it if it is not.

fib4_rule->tclassid has offset ~0x8c on x86-64, and this fault
address is 0x10 bytes off.

Does this patch fix the problem?

diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index 539c672..000c467 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -230,6 +230,7 @@ static inline int fib_lookup(struct net *net, struct flowi4 *flp,
 			     struct fib_result *res)
 {
 	if (!net->ipv4.fib_has_custom_rules) {
+		res->r = NULL;
 		if (net->ipv4.fib_local &&
 		    !fib_table_lookup(net->ipv4.fib_local, flp, res,
 				      FIB_LOOKUP_NOREF))
--
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