[PATCH v2] batman-adv: Get inet(6) device inside RCU protected region

[Sven Eckelmann]

It is not necessary to get the inet(6)_dev outside of the rcu protected
region by using reference counting. Instead, the in(6)_dev_get can be
replaced by the non-refcnt function and everything can be moved inside the
rcu protected region.

Fixes: 0a7733468f95 ("batman-adv: mcast: detect, distribute and maintain 
multicast router presence")
Reported-by: David Miller <da...@davemloft.net>
Signed-off-by: Sven Eckelmann <s...@narfation.org>
---
v2:

* leave read_lock_bh for in6_dev->mc_list

 net/batman-adv/multicast.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/net/batman-adv/multicast.c b/net/batman-adv/multicast.c
index 40ceab95..67d7f830 100644
--- a/net/batman-adv/multicast.c
+++ b/net/batman-adv/multicast.c
@@ -379,11 +379,14 @@ batadv_mcast_mla_softif_get_ipv4(struct net_device *dev,
        if (flags->tvlv_flags & BATADV_MCAST_WANT_ALL_IPV4)
                return 0;
 
-       in_dev = in_dev_get(dev);
-       if (!in_dev)
+       rcu_read_lock();
+
+       in_dev = __in_dev_get_rcu(dev);
+       if (!in_dev) {
+               rcu_read_unlock();
                return 0;
+       }
 
-       rcu_read_lock();
        for (pmc = rcu_dereference(in_dev->mc_list); pmc;
             pmc = rcu_dereference(pmc->next_rcu)) {
                if (flags->tvlv_flags & BATADV_MCAST_WANT_ALL_UNSNOOPABLES &&
@@ -410,7 +413,6 @@ batadv_mcast_mla_softif_get_ipv4(struct net_device *dev,
                ret++;
        }
        rcu_read_unlock();
-       in_dev_put(in_dev);
 
        return ret;
 }
@@ -444,9 +446,13 @@ batadv_mcast_mla_softif_get_ipv6(struct net_device *dev,
        if (flags->tvlv_flags & BATADV_MCAST_WANT_ALL_IPV6)
                return 0;
 
-       in6_dev = in6_dev_get(dev);
-       if (!in6_dev)
+       rcu_read_lock();
+
+       in6_dev = __in6_dev_get(dev);
+       if (!in6_dev) {
+               rcu_read_unlock();
                return 0;
+       }
 
        read_lock_bh(&in6_dev->lock);
        for (pmc6 = in6_dev->mc_list; pmc6; pmc6 = pmc6->next) {
@@ -479,7 +485,7 @@ batadv_mcast_mla_softif_get_ipv6(struct net_device *dev,
                ret++;
        }
        read_unlock_bh(&in6_dev->lock);
-       in6_dev_put(in6_dev);
+       rcu_read_unlock();
 
        return ret;
 }
-- 
2.20.1