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    Subject[PATCH 3.19.y-ckt 143/146] ipv4/udp: Verify multicast group is ours in upd_v4_early_demux()
    Date
    3.19.8-ckt2 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Shawn Bohrer <sbohrer@rgmadvisors.com>

    [ Upstream commit 6e540309326188f769e03bb4c6dd8ff6752930c2 ]

    421b3885bf6d56391297844f43fb7154a6396e12 "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>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    net/ipv4/udp.c | 18 +++++++++++++++---
    1 file changed, 15 insertions(+), 3 deletions(-)

    diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
    index 089d334..e0737ac 100644
    --- a/net/ipv4/udp.c
    +++ b/net/ipv4/udp.c
    @@ -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>
    @@ -1966,6 +1967,7 @@ 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)))
    @@ -1975,14 +1977,24 @@ 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;
    --
    1.9.1


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