From: Kevin Cernekee Date: Wed, 6 Dec 2017 12:12:27 -0800 Subject: netlink: Add netns check on taps Origin: https://git.kernel.org/linus/93c647643b48f0131f02e45da3bd367d80443291 Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2017-17449 Currently, a nlmon link inside a child namespace can observe systemwide netlink activity. Filter the traffic so that nlmon can only sniff netlink messages from its own netns. Test case: vpnns -- bash -c "ip link add nlmon0 type nlmon; \ ip link set nlmon0 up; \ tcpdump -i nlmon0 -q -w /tmp/nlmon.pcap -U" & sudo ip xfrm state add src 10.1.1.1 dst 10.1.1.2 proto esp \ spi 0x1 mode transport \ auth sha1 0x6162633132330000000000000000000000000000 \ enc aes 0x00000000000000000000000000000000 grep --binary abc123 /tmp/nlmon.pcap Signed-off-by: Kevin Cernekee Signed-off-by: David S. Miller --- net/netlink/af_netlink.c | 3 +++ 1 file changed, 3 insertions(+) --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -254,6 +254,9 @@ static int __netlink_deliver_tap_skb(str struct sock *sk = skb->sk; int ret = -ENOMEM; + if (!net_eq(dev_net(dev), sock_net(sk))) + return 0; + dev_hold(dev); if (is_vmalloc_addr(skb->head))