[PATCH 06/11] udp: use limited socket backlog CVE-2010-4251

[Paolo Pisati]

From: Zhu Yi <yi.zhu at intel.com>

udp: use limited socket backlog

BugLink: http://bugs.launchpad.net.bugs/807462

commit upstream 55349790d7cbf0d381873a7ece1dcafcffd4aaa9

Make udp adapt to the limited socket backlog change.

CVE-2010-4251

Cc: "David S. Miller" <davem at davemloft.net>
Cc: Alexey Kuznetsov <kuznet at ms2.inr.ac.ru>
Cc: "Pekka Savola (ipv6)" <pekkas at netcore.fi>
Cc: Patrick McHardy <kaber at trash.net>
Signed-off-by: Zhu Yi <yi.zhu at intel.com>
Acked-by: Eric Dumazet <eric.dumazet at gmail.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Paolo Pisati <paolo.pisati at canonical.com>
---
 net/ipv4/udp.c |    6 ++++--
 net/ipv6/udp.c |   28 ++++++++++++++++++----------
 2 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 595144d..4b3ab69 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1174,8 +1174,10 @@ int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 	bh_lock_sock(sk);
 	if (!sock_owned_by_user(sk))
 		rc = __udp_queue_rcv_skb(sk, skb);
-	else
-		sk_add_backlog(sk, skb);
+	else if (sk_add_backlog_limited(sk, skb)) {
+		bh_unlock_sock(sk);
+		goto drop;
+	}
 	bh_unlock_sock(sk);
 
 	return rc;
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 6fe1846..e72dfa3 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -455,16 +455,20 @@ static void flush_stack(struct sock **stack, unsigned int count,
 			bh_lock_sock(sk);
 			if (!sock_owned_by_user(sk))
 				udpv6_queue_rcv_skb(sk, skb1);
-			else
-				sk_add_backlog(sk, skb1);
+			else if (sk_add_backlog_limited(sk, skb1)) {
+				kfree_skb(skb1);
+				bh_unlock_sock(sk);
+				goto drop;
+			}
 			bh_unlock_sock(sk);
-		} else {
-			atomic_inc(&sk->sk_drops);
-			UDP6_INC_STATS_BH(sock_net(sk),
-					UDP_MIB_RCVBUFERRORS, IS_UDPLITE(sk));
-			UDP6_INC_STATS_BH(sock_net(sk),
-					UDP_MIB_INERRORS, IS_UDPLITE(sk));
+			continue;
 		}
+drop:
+		atomic_inc(&sk->sk_drops);
+		UDP6_INC_STATS_BH(sock_net(sk),
+				UDP_MIB_RCVBUFERRORS, IS_UDPLITE(sk));
+		UDP6_INC_STATS_BH(sock_net(sk),
+				UDP_MIB_INERRORS, IS_UDPLITE(sk));
 	}
 }
 /*
@@ -627,8 +631,12 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 	bh_lock_sock(sk);
 	if (!sock_owned_by_user(sk))
 		udpv6_queue_rcv_skb(sk, skb);
-	else
-		sk_add_backlog(sk, skb);
+	else if (sk_add_backlog_limited(sk, skb)) {
+		atomic_inc(&sk->sk_drops);
+		bh_unlock_sock(sk);
+		sock_put(sk);
+		goto discard;
+	}
 	bh_unlock_sock(sk);
 	sock_put(sk);
 	return 0;
-- 
1.7.5.3