ipv4/udp: Verify multicast group is ours in upd_v4_early_demux() (6e540309) · Commits · 戴 / test

"udp: ipv4: Add udp early demux" introduced a regression that allowed sockets bound to INADDR_ANY to receive packets from multicast groups that the socket had not joined. For example a socket that had joined 224.168.2.9 could also receive packets from 225.168.2.9 despite not having joined that group if ip_early_demux is enabled. Fix this by calling ip_check_mc_rcu() in udp_v4_early_demux() to verify that the multicast packet is indeed ours. Signed-off-by:

Shawn Bohrer <sbohrer@rgmadvisors.com> Reported-by:

Yurij M. Plotnikov <Yurij.Plotnikov@oktetlabs.ru> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv4/udp.c

+15 −3

Original line number	Diff line number	Diff line
		@@ -90,6 +90,7 @@
		#include <linux/socket.h>
		#include <linux/sockios.h>
		#include <linux/igmp.h>
		#include <linux/inetdevice.h>
		#include <linux/in.h>
		#include <linux/errno.h>
		#include <linux/timer.h>
		@@ -1960,6 +1961,7 @@ void udp_v4_early_demux(struct sk_buff *skb)
		struct sock *sk;
		struct dst_entry *dst;
		int dif = skb->dev->ifindex;
		int ours;

		/* validate the packet */
		if (!pskb_may_pull(skb, skb_transport_offset(skb) + sizeof(struct udphdr)))
		@@ -1969,14 +1971,24 @@ void udp_v4_early_demux(struct sk_buff *skb)
		uh = udp_hdr(skb);

		if (skb->pkt_type == PACKET_BROADCAST \|\|
		skb->pkt_type == PACKET_MULTICAST)
		skb->pkt_type == PACKET_MULTICAST) {
		struct in_device *in_dev = __in_dev_get_rcu(skb->dev);

		if (!in_dev)
		return;

		ours = ip_check_mc_rcu(in_dev, iph->daddr, iph->saddr,
		iph->protocol);
		if (!ours)
		return;
		sk = __udp4_lib_mcast_demux_lookup(net, uh->dest, iph->daddr,
		uh->source, iph->saddr, dif);
		else if (skb->pkt_type == PACKET_HOST)
		} else if (skb->pkt_type == PACKET_HOST) {
		sk = __udp4_lib_demux_lookup(net, uh->dest, iph->daddr,
		uh->source, iph->saddr, dif);
		else
		} else {
		return;
		}

		if (!sk)
		return;

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