ipv4: Add a missing rcu_assign_pointer() in routing cache.

rt_intern_hash() is doing an update of a RCU guarded hash chain
without using rcu_assign_pointer() or equivalent barrier.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 1 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index a6d7c584f53b..8d23cc7efbad 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1109,7 +1109,12 @@ restart:
                 printk("\n");
         }
 #endif
-        rt_hash_table[hash].chain = rt;
+        /*
+         * Since lookup is lockfree, we must make sure
+         * previous writes to rt are comitted to memory
+         * before making rt visible to other CPUS.
+         */
+        rcu_assign_pointer(rt_hash_table[hash].chain, rt);
         spin_unlock_bh(rt_hash_lock_addr(hash));
         *rp = rt;
         return 0;