udp6: add missing checks on edumux packet processing

Currently the UDPv6 early demux rx code path lacks some mandatory
checks, already implemented into the normal RX code path - namely
the checksum conversion and no_check6_rx check.

Similar to the previous commit, we move the common processing to
an UDPv6 specific helper and call it from both edemux code path
and normal code path. In respect to the UDPv4, we need to add an
explicit check for non zero csum according to no_check6_rx value.

Reported-by: Jianlin Shi <jishi@redhat.com>
Suggested-by: Xin Long <lucien.xin@gmail.com>
Fixes: c9f2c1ae123a ("udp6: fix socket leak on early demux")
Fixes: 2abb7cdc0dc8 ("udp: Add support for doing checksum unnecessary conversion")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/udp.c

@@ -752,6 +752,28 @@ static void udp6_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst)
 	}
 }
 
+/* wrapper for udp_queue_rcv_skb tacking care of csum conversion and
+ * return code conversion for ip layer consumption
+ */
+static int udp6_unicast_rcv_skb(struct sock *sk, struct sk_buff *skb,
+				struct udphdr *uh)
+{
+	int ret;
+
+	if (inet_get_convert_csum(sk) && uh->check && !IS_UDPLITE(sk))
+		skb_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
+					 ip6_compute_pseudo);
+
+	ret = udpv6_queue_rcv_skb(sk, skb);
+
+	/* a return value > 0 means to resubmit the input, but
+	 * it wants the return to be -protocol, or 0
+	 */
+	if (ret > 0)
+		return -ret;
+	return 0;
+}
+
 int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 		   int proto)
 {
@@ -803,13 +825,14 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 		if (unlikely(sk->sk_rx_dst != dst))
 			udp6_sk_rx_dst_set(sk, dst);
 
-		ret = udpv6_queue_rcv_skb(sk, skb);
-		sock_put(sk);
+		if (!uh->check && !udp_sk(sk)->no_check6_rx) {
+			sock_put(sk);
+			goto report_csum_error;
+		}
 
-		/* a return value > 0 means to resubmit the input */
-		if (ret > 0)
-			return ret;
-		return 0;
+		ret = udp6_unicast_rcv_skb(sk, skb, uh);
+		sock_put(sk);
+		return ret;
 	}
 
 	/*
@@ -822,30 +845,13 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 	/* Unicast */
 	sk = __udp6_lib_lookup_skb(skb, uh->source, uh->dest, udptable);
 	if (sk) {
-		int ret;
-
-		if (!uh->check && !udp_sk(sk)->no_check6_rx) {
-			udp6_csum_zero_error(skb);
-			goto csum_error;
-		}
-
-		if (inet_get_convert_csum(sk) && uh->check && !IS_UDPLITE(sk))
-			skb_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
-						 ip6_compute_pseudo);
-
-		ret = udpv6_queue_rcv_skb(sk, skb);
-
-		/* a return value > 0 means to resubmit the input */
-		if (ret > 0)
-			return ret;
-
-		return 0;
+		if (!uh->check && !udp_sk(sk)->no_check6_rx)
+			goto report_csum_error;
+		return udp6_unicast_rcv_skb(sk, skb, uh);
 	}
 
-	if (!uh->check) {
-		udp6_csum_zero_error(skb);
-		goto csum_error;
-	}
+	if (!uh->check)
+		goto report_csum_error;
 
 	if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
 		goto discard;
@@ -866,6 +872,9 @@ short_packet:
 			    ulen, skb->len,
 			    daddr, ntohs(uh->dest));
 	goto discard;
+
+report_csum_error:
+	udp6_csum_zero_error(skb);
 csum_error:
 	__UDP6_INC_STATS(net, UDP_MIB_CSUMERRORS, proto == IPPROTO_UDPLITE);
 discard: