From: Eric Dumazet <dada1@cosmosbay.com>
Date: Thu, 16 Oct 2008 21:18:29 +0000 (-0700)
Subject: ipv4: Add a missing rcu_assign_pointer() in routing cache.
X-Git-Tag: v2.6.28-rc1~264^2~1
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=00269b54edbf25f3bb0dccb558ae23a6fc77ed86;p=linux-2.6-omap-h63xx.git

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>
---

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index a6d7c584f53..8d23cc7efba 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;