Patch "udp: never accept GSO_FRAGLIST packets" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    udp: never accept GSO_FRAGLIST packets

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     udp-never-accept-gso_fraglist-packets.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit fa9b0e2ca65bcd9dfaa0c29c43aee0cef61c8152
Author: Paolo Abeni <pabeni@xxxxxxxxxx>
Date:   Tue Mar 30 12:28:52 2021 +0200

    udp: never accept GSO_FRAGLIST packets
    
    [ Upstream commit 78352f73dc5047f3f744764cc45912498c52f3c9 ]
    
    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@xxxxxxxxxx>
    Reviewed-by: Willem de Bruijn <willemb@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/linux/udp.h b/include/linux/udp.h
index aa84597bdc33..ae58ff3b6b5b 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 4a2fd286787c..9d28b2778e8f 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2657,9 +2657,12 @@ 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;