[Devel] [PATCH RHEL7 COMMIT] ms/ipv6: only call ip6_route_dev_notify() once for NETDEV_UNREGISTER

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-514.26.1.vz7.33.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-514.26.1.vz7.33.9
------>
commit 7b1c8329b82cff08f8a0c2e686b9b66de668a18c
Author: WANG Cong <xiyou.wangcong at gmail.com>
Date:   Tue Jun 20 11:42:27 2017 -0700

    ms/ipv6: only call ip6_route_dev_notify() once for NETDEV_UNREGISTER
    
    In commit 242d3a49a2a1 ("ipv6: reorder ip6_route_dev_notifier after ipv6_dev_notf")
    I assumed NETDEV_REGISTER and NETDEV_UNREGISTER are paired,
    unfortunately, as reported by jeffy, netdev_wait_allrefs()
    could rebroadcast NETDEV_UNREGISTER event until all refs are
    gone.
    
    We have to add an additional check to avoid this corner case.
    For netdev_wait_allrefs() dev->reg_state is NETREG_UNREGISTERED,
    for dev_change_net_namespace(), dev->reg_state is
    NETREG_REGISTERED. So check for dev->reg_state != NETREG_UNREGISTERED.
    
    Fixes: 242d3a49a2a1 ("ipv6: reorder ip6_route_dev_notifier after ipv6_dev_notf")
    Reported-by: jeffy <jeffy.chen at rock-chips.com>
    Cc: David Ahern <dsahern at gmail.com>
    Signed-off-by: Cong Wang <xiyou.wangcong at gmail.com>
    Acked-by: David Ahern <dsahern at gmail.com>
    Signed-off-by: David S. Miller <davem at davemloft.net>
    
    https://jira.sw.ru/browse/PSBM-66197
    
    (cherry picked from commit 76da0704507bbc51875013f6557877ab308cfd0a)
    Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
---
 net/ipv6/route.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 3d4d519..fa0e036 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3228,7 +3228,11 @@ static int ip6_route_dev_notify(struct notifier_block *this,
 		net->ipv6.ip6_blk_hole_entry->dst.dev = dev;
 		net->ipv6.ip6_blk_hole_entry->rt6i_idev = in6_dev_get(dev);
 #endif
-	 } else if (event == NETDEV_UNREGISTER) {
+	 } else if (event == NETDEV_UNREGISTER &&
+		    dev->reg_state != NETREG_UNREGISTERED) {
+		/* NETDEV_UNREGISTER could be fired for multiple times by
+		 * netdev_wait_allrefs(). Make sure we only call this once.
+		 */
 		in6_dev_put(net->ipv6.ip6_null_entry->rt6i_idev);
 #ifdef CONFIG_IPV6_MULTIPLE_TABLES
 		in6_dev_put(net->ipv6.ip6_prohibit_entry->rt6i_idev);