diff options
| author | Eric Dumazet <edumazet@google.com> | 2013-12-11 14:46:51 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2013-12-11 20:21:10 -0500 |
| commit | 975022310233fb0f0193873d79a7b8438070fa82 (patch) | |
| tree | 2658e9259ca6a53e07a25fe399a4f61d15093220 /net | |
| parent | a1bf1750871a6f242b0fdb174cc55d2c57e7ed66 (diff) | |
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>
Diffstat (limited to 'net')
| -rw-r--r-- | net/ipv4/udp.c | 22 |
1 files changed, 16 insertions, 6 deletions
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 16d246a51a0..62c19fdd102 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); |