inet: ping: avoid skb_clone() dance in ping_rcv()

ping_rcv() callers currently call skb_free() or consume_skb(),
forcing ping_rcv() to clone the skb.

After this patch ping_rcv() is now 'consuming' the original skb,
either moving to a socket receive queue, or dropping it.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20250226183437.1457318-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/icmp.c

@@ -1274,9 +1274,10 @@ int icmp_rcv(struct sk_buff *skb)
 		}
 	}
 
-	if (icmph->type == ICMP_EXT_ECHOREPLY) {
+	if (icmph->type == ICMP_EXT_ECHOREPLY ||
+	    icmph->type == ICMP_ECHOREPLY) {
 		reason = ping_rcv(skb);
-		goto reason_check;
+		return reason ? NET_RX_DROP : NET_RX_SUCCESS;
 	}
 
 	/*

net/ipv4/ping.c

@@ -966,10 +966,9 @@ EXPORT_SYMBOL_GPL(ping_queue_rcv_skb);
 
 enum skb_drop_reason ping_rcv(struct sk_buff *skb)
 {
-	enum skb_drop_reason reason = SKB_DROP_REASON_NO_SOCKET;
-	struct sock *sk;
 	struct net *net = dev_net(skb->dev);
 	struct icmphdr *icmph = icmp_hdr(skb);
+	struct sock *sk;
 
 	/* We assume the packet has already been checked by icmp_rcv */
 
@@ -980,20 +979,11 @@ enum skb_drop_reason ping_rcv(struct sk_buff *skb)
 	skb_push(skb, skb->data - (u8 *)icmph);
 
 	sk = ping_lookup(net, skb, ntohs(icmph->un.echo.id));
-	if (sk) {
-		struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
-
-		pr_debug("rcv on socket %p\n", sk);
-		if (skb2)
-			reason = __ping_queue_rcv_skb(sk, skb2);
-		else
-			reason = SKB_DROP_REASON_NOMEM;
-	}
-
-	if (reason)
-		pr_debug("no socket, dropping\n");
+	if (sk)
+		return __ping_queue_rcv_skb(sk, skb);
 
-	return reason;
+	kfree_skb_reason(skb, SKB_DROP_REASON_NO_SOCKET);
+	return SKB_DROP_REASON_NO_SOCKET;
 }
 EXPORT_SYMBOL_GPL(ping_rcv);
 

net/ipv6/icmp.c

@@ -957,12 +957,9 @@ static int icmpv6_rcv(struct sk_buff *skb)
 		break;
 
 	case ICMPV6_ECHO_REPLY:
-		reason = ping_rcv(skb);
-		break;
-
 	case ICMPV6_EXT_ECHO_REPLY:
-		reason = ping_rcv(skb);
-		break;
+		ping_rcv(skb);
+		return 0;
 
 	case ICMPV6_PKT_TOOBIG:
 		/* BUGGG_FUTURE: if packet contains rthdr, we cannot update