[PATCH net v4 1/5] ip6mr: Lock RCU before ip6mr_get_table() call in ip6mr_vif_seq_start()

[Stefan Wiehler]

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

In case ip6mr_vif_seq_start() fails with an error (currently not
possible, as RT6_TABLE_DFLT always exists, ip6mr_get_table() cannot fail
in this case), ip6mr_vif_seq_stop() would be called and release the RCU
lock.

Signed-off-by: Stefan Wiehler <stefan.wiehler@xxxxxxxxx>
Fixes: d1db275dd3f6 ("ipv6: ip6mr: support multiple tables")
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
---
 net/ipv6/ip6mr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index 2ce4ae0d8dc3..268e77196753 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -411,13 +411,13 @@ static void *ip6mr_vif_seq_start(struct seq_file *seq, loff_t *pos)
 	struct net *net = seq_file_net(seq);
 	struct mr_table *mrt;
 
+	rcu_read_lock();
 	mrt = ip6mr_get_table(net, RT6_TABLE_DFLT);
 	if (!mrt)
 		return ERR_PTR(-ENOENT);
 
 	iter->mrt = mrt;
 
-	rcu_read_lock();
 	return mr_vif_seq_start(seq, pos);
 }
 
-- 
2.42.0