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authorEric Dumazet <dada1@cosmosbay.com>2008-11-01 21:19:18 -0700
committerDavid S. Miller <davem@davemloft.net>2008-11-01 21:19:18 -0700
commitc37ccc0d4e2a4ee52f1a40cff1be0049f2104bba (patch)
tree8ed76232d7debc5f63f5b80dac7b8a9ba44eb4ce
parent7e3a42a12c4b9d99bfe81cb929cadf0e08a37c49 (diff)
udp: add a missing smp_wmb() in udp_lib_get_port()
Corey Minyard spotted a missing memory barrier in udp_lib_get_port() We need to make sure a reader cannot read the new 'sk->sk_next' value and previous value of 'sk->sk_hash'. Or else, an item could be deleted from a chain, and inserted into another chain. If new chain was empty before the move, 'next' pointer is NULL, and lockless reader can not detect it missed following items in original chain. This patch is temporary, since we expect an upcoming patch to introduce another way of handling the problem. Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/ipv4/udp.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index bcb5def2b09..7e4d9c87115 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -189,6 +189,11 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
inet_sk(sk)->num = snum;
sk->sk_hash = snum;
if (sk_unhashed(sk)) {
+ /*
+ * We need that previous write to sk->sk_hash committed
+ * before write to sk->next done in following add_node() variant
+ */
+ smp_wmb();
sk_add_node_rcu(sk, &hslot->head);
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
}