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Subject[PATCH 3.4 128/176] ipv6: replacing a rt6_info needs to purge possible propagated rt6_infos too
Date
From: Hannes Frederic Sowa <hannes@stressinduktion.org>

3.4.107-rc1 review patch. If anyone has any objections, please let me know.

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


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@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@rhel7-5 at Jan 23 10:54:41 ...
| kernel:unregister_netdevice: waiting for dev0 to become free. Usage count = 2
|
| Message from syslogd@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@v3.sk>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Tested-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Zefan Li <lizefan@huawei.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 5bb77a6..2cfcfb7 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -633,6 +633,29 @@ insert_above:
return ln;
}

+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.
*/
@@ -723,11 +746,12 @@ 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;
@@ -1229,24 +1253,7 @@ 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);
--
1.9.1


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