[PATCH 4.14 063/146] netlink: Add netns check on taps

Greg Kroah-Hartman
2018-01-01T14:42:27Z

From: Kevin Cernekee <cernekee@chromium.org>

[ Upstream commit 93c647643b48f0131f02e45da3bd367d80443291 ]

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 <cernekee@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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))