Patch "ipv6: Add reasons for skb drops to __udp6_lib_rcv" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    ipv6: Add reasons for skb drops to __udp6_lib_rcv

to the 5.15-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:
     ipv6-add-reasons-for-skb-drops-to-__udp6_lib_rcv.patch
and it can be found in the queue-5.15 subdirectory.

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



commit ca80e6dbddb257dc8ba700a753f9f4409c7858f3
Author: David Ahern <dsahern@xxxxxxxxxx>
Date:   Fri Feb 11 09:15:07 2022 -0800

    ipv6: Add reasons for skb drops to __udp6_lib_rcv
    
    [ Upstream commit 4cf91f825b2777f81799f98ce32172b829acd1b2 ]
    
    Add reasons to __udp6_lib_rcv for skb drops. The only twist is that the
    NO_SOCKET takes precedence over the CSUM or other counters for that
    path (motivation behind this patch - csum counter was misleading).
    
    Signed-off-by: David Ahern <dsahern@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Stable-dep-of: 9c02bec95954 ("bpf, net: Support SO_REUSEPORT sockets with bpf_sk_assign")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 2dab9aab551c3..d5d254ca2dfe6 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -936,6 +936,7 @@ static int udp6_unicast_rcv_skb(struct sock *sk, struct sk_buff *skb,
 int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 		   int proto)
 {
+	enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
 	const struct in6_addr *saddr, *daddr;
 	struct net *net = dev_net(skb->dev);
 	struct udphdr *uh;
@@ -1012,6 +1013,8 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 		return udp6_unicast_rcv_skb(sk, skb, uh);
 	}
 
+	reason = SKB_DROP_REASON_NO_SOCKET;
+
 	if (!uh->check)
 		goto report_csum_error;
 
@@ -1024,10 +1027,12 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 	__UDP6_INC_STATS(net, UDP_MIB_NOPORTS, proto == IPPROTO_UDPLITE);
 	icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0);
 
-	kfree_skb(skb);
+	kfree_skb_reason(skb, reason);
 	return 0;
 
 short_packet:
+	if (reason == SKB_DROP_REASON_NOT_SPECIFIED)
+		reason = SKB_DROP_REASON_PKT_TOO_SMALL;
 	net_dbg_ratelimited("UDP%sv6: short packet: From [%pI6c]:%u %d/%d to [%pI6c]:%u\n",
 			    proto == IPPROTO_UDPLITE ? "-Lite" : "",
 			    saddr, ntohs(uh->source),
@@ -1038,10 +1043,12 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 report_csum_error:
 	udp6_csum_zero_error(skb);
 csum_error:
+	if (reason == SKB_DROP_REASON_NOT_SPECIFIED)
+		reason = SKB_DROP_REASON_UDP_CSUM;
 	__UDP6_INC_STATS(net, UDP_MIB_CSUMERRORS, proto == IPPROTO_UDPLITE);
 discard:
 	__UDP6_INC_STATS(net, UDP_MIB_INERRORS, proto == IPPROTO_UDPLITE);
-	kfree_skb(skb);
+	kfree_skb_reason(skb, reason);
 	return 0;
 }