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    Subject[PATCH 4.9 007/138] ipv6: only call ip6_route_dev_notify() once for NETDEV_UNREGISTER
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    From: WANG Cong <xiyou.wangcong@gmail.com>

    commit 76da0704507bbc51875013f6557877ab308cfd0a upstream.

    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@rock-chips.com>
    Cc: David Ahern <dsahern@gmail.com>
    Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
    Acked-by: David Ahern <dsahern@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    net/ipv6/route.c | 6 +++++-
    1 file changed, 5 insertions(+), 1 deletion(-)

    --- a/net/ipv6/route.c
    +++ b/net/ipv6/route.c
    @@ -3495,7 +3495,11 @@ static int ip6_route_dev_notify(struct n
    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);

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