[PATCH net v4 4/5] ip6mr: Lock RCU before ip6mr_get_table() call in ip6mr_get_route()

[Stefan Wiehler <stefan.wiehler@nokia.com>]

When IPV6_MROUTE_MULTIPLE_TABLES is enabled, calls to ip6mr_get_table()
must be done under RCU or RTNL lock.

Signed-off-by: Stefan Wiehler <stefan.wiehler@nokia.com>
Fixes: d1db275dd3f6 ("ipv6: ip6mr: support multiple tables")
---
 net/ipv6/ip6mr.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index 1e233ee15d43..a817b688473a 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -2300,11 +2300,13 @@ int ip6mr_get_route(struct net *net, struct sk_buff *skb, struct rtmsg *rtm,
 	struct mfc6_cache *cache;
 	struct rt6_info *rt = dst_rt6_info(skb_dst(skb));
 
+	rcu_read_lock();
 	mrt = ip6mr_get_table(net, RT6_TABLE_DFLT);
-	if (!mrt)
-		return -ENOENT;
+	if (!mrt) {
+		err = -ENOENT;
+		goto out;
+	}
 
-	rcu_read_lock();
 	cache = ip6mr_cache_find(mrt, &rt->rt6i_src.addr, &rt->rt6i_dst.addr);
 	if (!cache && skb->dev) {
 		int vif = ip6mr_find_vif(mrt, skb->dev);
@@ -2322,15 +2324,15 @@ int ip6mr_get_route(struct net *net, struct sk_buff *skb, struct rtmsg *rtm,
 
 		dev = skb->dev;
 		if (!dev || (vif = ip6mr_find_vif(mrt, dev)) < 0) {
-			rcu_read_unlock();
-			return -ENODEV;
+			err = -ENODEV;
+			goto out;
 		}
 
 		/* really correct? */
 		skb2 = alloc_skb(sizeof(struct ipv6hdr), GFP_ATOMIC);
 		if (!skb2) {
-			rcu_read_unlock();
-			return -ENOMEM;
+			err = -ENOMEM;
+			goto out;
 		}
 
 		NETLINK_CB(skb2).portid = portid;
@@ -2352,12 +2354,13 @@ int ip6mr_get_route(struct net *net, struct sk_buff *skb, struct rtmsg *rtm,
 		iph->daddr = rt->rt6i_dst.addr;
 
 		err = ip6mr_cache_unresolved(mrt, vif, skb2, dev);
-		rcu_read_unlock();
 
-		return err;
+		goto out;
 	}
 
 	err = mr_fill_mroute(mrt, skb, &cache->_c, rtm);
+
+out:
 	rcu_read_unlock();
 	return err;
 }
-- 
2.42.0