ip6mr: do not acquire mrt_lock in pim6_rcv()

rcu_read_lock() protection is more than enough.

vif_dev_read() supports either mrt_lock or rcu_read_lock().

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index a6d97952bf5306c245996c612107d0c851bbc822..fa6720377e82d732ccafa02b37cc28e0ab1cea07 100644 (file)
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -559,12 +559,11 @@ static int pim6_rcv(struct sk_buff *skb)
 
        if (ip6mr_fib_lookup(net, &fl6, &mrt) < 0)
                goto drop;
-       reg_vif_num = mrt->mroute_reg_vif_num;
 
-       read_lock(&mrt_lock);
+       /* Pairs with WRITE_ONCE() in mif6_add()/mif6_delete() */
+       reg_vif_num = READ_ONCE(mrt->mroute_reg_vif_num);
        if (reg_vif_num >= 0)
                reg_dev = vif_dev_read(&mrt->vif_table[reg_vif_num]);
-       read_unlock(&mrt_lock);
 
        if (!reg_dev)
                goto drop;