linux-kernel - [PATCH 3.12 12/19] ipv6: reset dst.expires value when clearing expire flag

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Date:	Mon, 18 Nov 2013 10:37:25 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	"Steinar H. Gunderson" <sgunderson@...foot.com>,
	Valentijn Sessink <valentyn@...b.net>,
	YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.12 12/19] ipv6: reset dst.expires value when clearing expire flag

3.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hannes Frederic Sowa <hannes@...essinduktion.org>

[ Upstream commit 01ba16d6ec85a1ec4669c75513a76b61ec53ee50 ]

On receiving a packet too big icmp error we update the expire value by
calling rt6_update_expires. This function uses dst_set_expires which is
implemented that it can only reduce the expiration value of the dst entry.

If we insert new routing non-expiry information into the ipv6 fib where
we already have a matching rt6_info we only clear the RTF_EXPIRES flag
in rt6i_flags and leave the dst.expires value as is.

When new mtu information arrives for that cached dst_entry we again
call dst_set_expires. This time it won't update the dst.expire value
because we left the dst.expire value intact from the last update. So
dst_set_expires won't touch dst.expires.

Fix this by resetting dst.expires when clearing the RTF_EXPIRE flag.
dst_set_expires checks for a zero expiration and updates the
dst.expires.

In the past this (not updating dst.expires) was necessary because
dst.expire was placed in a union with the dst_entry *from reference
and rt6_clean_expires did assign NULL to it. This split happend in
ecd9883724b78cc72ed92c98bcb1a46c764fff21 ("ipv6: fix race condition
regarding dst->expires and dst->from").

Reported-by: Steinar H. Gunderson <sgunderson@...foot.com>
Reported-by: Valentijn Sessink <valentyn@...b.net>
Cc: YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>
Acked-by: Eric Dumazet <edumazet@...gle.com>
Tested-by: Valentijn Sessink <valentyn@...b.net>
Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 include/net/ip6_fib.h |    1 +
 1 file changed, 1 insertion(+)

--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -165,6 +165,7 @@ static inline struct inet6_dev *ip6_dst_
 static inline void rt6_clean_expires(struct rt6_info *rt)
 {
 	rt->rt6i_flags &= ~RTF_EXPIRES;
+	rt->dst.expires = 0;
 }

 static inline void rt6_set_expires(struct rt6_info *rt, unsigned long expires)

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