[PATCH net-next v2 4/8] udp: never accept GSO_FRAGLIST packets

[Paolo Abeni <pabeni@redhat.com>]

Currently the UDP protocol delivers GSO_FRAGLIST packets to
the sockets without the expected segmentation.

This change addresses the issue introducing and maintaining
a couple of new fields to explicitly accept SKB_GSO_UDP_L4
or GSO_FRAGLIST packets. Additionally updates  udp_unexpected_gso()
accordingly.

UDP sockets enabling UDP_GRO stil keep accept_udp_fraglist
zeroed.

v1 -> v2:
 - use 2 bits instead of a whole GSO bitmask (Willem)

Fixes: 9fd1ff5d2ac7 ("udp: Support UDP fraglist GRO/GSO.")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 include/linux/udp.h | 16 +++++++++++++---
 net/ipv4/udp.c      |  3 +++
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/include/linux/udp.h b/include/linux/udp.h
index aa84597bdc33c..ae58ff3b6b5b8 100644
--- a/include/linux/udp.h
+++ b/include/linux/udp.h
@@ -51,7 +51,9 @@ struct udp_sock {
 					   * different encapsulation layer set
 					   * this
 					   */
-			 gro_enabled:1;	/* Can accept GRO packets */
+			 gro_enabled:1,	/* Request GRO aggregation */
+			 accept_udp_l4:1,
+			 accept_udp_fraglist:1;
 	/*
 	 * Following member retains the information to create a UDP header
 	 * when the socket is uncorked.
@@ -131,8 +133,16 @@ static inline void udp_cmsg_recv(struct msghdr *msg, struct sock *sk,
 
 static inline bool udp_unexpected_gso(struct sock *sk, struct sk_buff *skb)
 {
-	return !udp_sk(sk)->gro_enabled && skb_is_gso(skb) &&
-	       skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4;
+	if (!skb_is_gso(skb))
+		return false;
+
+	if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4 && !udp_sk(sk)->accept_udp_l4)
+		return true;
+
+	if (skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST && !udp_sk(sk)->accept_udp_fraglist)
+		return true;
+
+	return false;
 }
 
 #define udp_portaddr_for_each_entry(__sk, list) \
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index fe85dcf8c0087..c0695ce42dc53 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2666,9 +2666,12 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname,
 
 	case UDP_GRO:
 		lock_sock(sk);
+
+		/* when enabling GRO, accept the related GSO packet type */
 		if (valbool)
 			udp_tunnel_encap_enable(sk->sk_socket);
 		up->gro_enabled = valbool;
+		up->accept_udp_l4 = valbool;
 		release_sock(sk);
 		break;
 
-- 
2.26.2