[3.16.y-ckt stable] Patch "ipv6: replacing a rt6_info needs to purge possible propagated rt6_infos too" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    ipv6: replacing a rt6_info needs to purge possible propagated rt6_infos too

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt7.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 00f5e7530e2e7f50915492f755f26c99f72bd6ae Mon Sep 17 00:00:00 2001
From: Hannes Frederic Sowa <hannes at stressinduktion.org>
Date: Mon, 26 Jan 2015 15:11:17 +0100
Subject: ipv6: replacing a rt6_info needs to purge possible propagated
 rt6_infos too

commit 6e9e16e6143b725662e47026a1d0f270721cdd24 upstream.

Lubomir Rintel reported that during replacing a route the interface
reference counter isn't correctly decremented.

To quote bug <https://bugzilla.kernel.org/show_bug.cgi?id=91941>:
| [root at rhel7-5 lkundrak]# sh -x lal
| + ip link add dev0 type dummy
| + ip link set dev0 up
| + ip link add dev1 type dummy
| + ip link set dev1 up
| + ip addr add 2001:db8:8086::2/64 dev dev0
| + ip route add 2001:db8:8086::/48 dev dev0 proto static metric 20
| + ip route add 2001:db8:8088::/48 dev dev1 proto static metric 10
| + ip route replace 2001:db8:8086::/48 dev dev1 proto static metric 20
| + ip link del dev0 type dummy
| Message from syslogd at rhel7-5 at Jan 23 10:54:41 ...
|  kernel:unregister_netdevice: waiting for dev0 to become free. Usage count = 2
|
| Message from syslogd at rhel7-5 at Jan 23 10:54:51 ...
|  kernel:unregister_netdevice: waiting for dev0 to become free. Usage count = 2

During replacement of a rt6_info we must walk all parent nodes and check
if the to be replaced rt6_info got propagated. If so, replace it with
an alive one.

Fixes: 4a287eba2de3957 ("IPv6 routing, NLM_F_* flag support: REPLACE and EXCL flags support, warn about missing CREATE flag")
Reported-by: Lubomir Rintel <lkundrak at v3.sk>
Signed-off-by: Hannes Frederic Sowa <hannes at stressinduktion.org>
Tested-by: Lubomir Rintel <lkundrak at v3.sk>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/ipv6/ip6_fib.c | 45 ++++++++++++++++++++++++++-------------------
 1 file changed, 26 insertions(+), 19 deletions(-)

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 97b9fa8de377..4bffae914120 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -662,6 +662,29 @@ static int fib6_commit_metrics(struct dst_entry *dst,
 	return 0;
 }

+static void fib6_purge_rt(struct rt6_info *rt, struct fib6_node *fn,
+			  struct net *net)
+{
+	if (atomic_read(&rt->rt6i_ref) != 1) {
+		/* This route is used as dummy address holder in some split
+		 * nodes. It is not leaked, but it still holds other resources,
+		 * which must be released in time. So, scan ascendant nodes
+		 * and replace dummy references to this route with references
+		 * to still alive ones.
+		 */
+		while (fn) {
+			if (!(fn->fn_flags & RTN_RTINFO) && fn->leaf == rt) {
+				fn->leaf = fib6_find_prefix(net, fn);
+				atomic_inc(&fn->leaf->rt6i_ref);
+				rt6_release(rt);
+			}
+			fn = fn->parent;
+		}
+		/* No more references are possible at this point. */
+		BUG_ON(atomic_read(&rt->rt6i_ref) != 1);
+	}
+}
+
 /*
  *	Insert routing information in a node.
  */
@@ -810,11 +833,12 @@ add:
 		rt->dst.rt6_next = iter->dst.rt6_next;
 		atomic_inc(&rt->rt6i_ref);
 		inet6_rt_notify(RTM_NEWROUTE, rt, info);
-		rt6_release(iter);
 		if (!(fn->fn_flags & RTN_RTINFO)) {
 			info->nl_net->ipv6.rt6_stats->fib_route_nodes++;
 			fn->fn_flags |= RTN_RTINFO;
 		}
+		fib6_purge_rt(iter, fn, info->nl_net);
+		rt6_release(iter);
 	}

 	return 0;
@@ -1324,24 +1348,7 @@ static void fib6_del_route(struct fib6_node *fn, struct rt6_info **rtp,
 		fn = fib6_repair_tree(net, fn);
 	}

-	if (atomic_read(&rt->rt6i_ref) != 1) {
-		/* This route is used as dummy address holder in some split
-		 * nodes. It is not leaked, but it still holds other resources,
-		 * which must be released in time. So, scan ascendant nodes
-		 * and replace dummy references to this route with references
-		 * to still alive ones.
-		 */
-		while (fn) {
-			if (!(fn->fn_flags & RTN_RTINFO) && fn->leaf == rt) {
-				fn->leaf = fib6_find_prefix(net, fn);
-				atomic_inc(&fn->leaf->rt6i_ref);
-				rt6_release(rt);
-			}
-			fn = fn->parent;
-		}
-		/* No more references are possible at this point. */
-		BUG_ON(atomic_read(&rt->rt6i_ref) != 1);
-	}
+	fib6_purge_rt(rt, fn, net);

 	inet6_rt_notify(RTM_DELROUTE, rt, info);
 	rt6_release(rt);
--
2.1.4