linux-kernel - Re: Bug in net/ipv6/ip6_fib.c:fib6_dump

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Message-ID: <1340388785.4604.11442.camel@edumazet-glaptop>
Date:	Fri, 22 Jun 2012 20:13:05 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Josh Hunt <johunt@...mai.com>
Cc:	"davem@...emloft.net" <davem@...emloft.net>,
	"kaber@...sh.net" <kaber@...sh.net>,
	Debabrata Banerjee <dbavatar@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"yoshfuji@...ux-ipv6.org" <yoshfuji@...ux-ipv6.org>,
	"jmorris@...ei.org" <jmorris@...ei.org>,
	"pekkas@...core.fi" <pekkas@...core.fi>,
	"kuznet@....inr.ac.ru" <kuznet@....inr.ac.ru>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Bug in net/ipv6/ip6_fib.c:fib6_dump_table()

On Fri, 2012-06-22 at 08:44 -0500, Josh Hunt wrote:

> Ahh. That makes sense and is what Alexey said before I just didn't put
> it all together. So we are OK reverting this patch? I cannot find a path
> where the walker's pointers are updated without the tb6_lock write_lock.
> 

There was a bug somewhere, not sure we want to NULL dereference again.

Following fix should at least avoid a never ending dump

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 74c21b9..6083276 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -1349,8 +1349,8 @@ static int fib6_walk_continue(struct fib6_walker_t *w)
 			if (w->leaf && fn->fn_flags & RTN_RTINFO) {
 				int err;
 
-				if (w->count < w->skip) {
-					w->count++;
+				if (w->skip) {
+					w->skip--;
 					continue;
 				}
 


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