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authorEric Dumazet <edumazet@google.com>2013-12-11 14:46:51 -0800
committerDavid S. Miller <davem@davemloft.net>2013-12-11 20:21:10 -0500
commit975022310233fb0f0193873d79a7b8438070fa82 (patch)
tree2658e9259ca6a53e07a25fe399a4f61d15093220
parenta1bf1750871a6f242b0fdb174cc55d2c57e7ed66 (diff)
downloadblackbird-op-linux-975022310233fb0f0193873d79a7b8438070fa82.tar.gz
blackbird-op-linux-975022310233fb0f0193873d79a7b8438070fa82.zip
udp: ipv4: must add synchronization in udp_sk_rx_dst_set()
Unlike TCP, UDP input path does not hold the socket lock. Before messing with sk->sk_rx_dst, we must use a spinlock, otherwise multiple cpus could leak a refcount. This patch also takes care of renewing a stale dst entry. (When the sk->sk_rx_dst would not be used by IP early demux) Fixes: 421b3885bf6d ("udp: ipv4: Add udp early demux") Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Shawn Bohrer <sbohrer@rgmadvisors.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/ipv4/udp.c22
1 files changed, 16 insertions, 6 deletions
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 16d246a51a02..62c19fdd102d 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1599,12 +1599,21 @@ static void flush_stack(struct sock **stack, unsigned int count,
kfree_skb(skb1);
}
-static void udp_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
+/* For TCP sockets, sk_rx_dst is protected by socket lock
+ * For UDP, we use sk_dst_lock to guard against concurrent changes.
+ */
+static void udp_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst)
{
- struct dst_entry *dst = skb_dst(skb);
+ struct dst_entry *old;
- dst_hold(dst);
- sk->sk_rx_dst = dst;
+ spin_lock(&sk->sk_dst_lock);
+ old = sk->sk_rx_dst;
+ if (likely(old != dst)) {
+ dst_hold(dst);
+ sk->sk_rx_dst = dst;
+ dst_release(old);
+ }
+ spin_unlock(&sk->sk_dst_lock);
}
/*
@@ -1737,10 +1746,11 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
sk = skb_steal_sock(skb);
if (sk) {
+ struct dst_entry *dst = skb_dst(skb);
int ret;
- if (unlikely(sk->sk_rx_dst == NULL))
- udp_sk_rx_dst_set(sk, skb);
+ if (unlikely(sk->sk_rx_dst != dst))
+ udp_sk_rx_dst_set(sk, dst);
ret = udp_queue_rcv_skb(sk, skb);
sock_put(sk);
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