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netlink: Add netns check on taps 

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>
This commit is contained in:
Kevin Cernekee 2017-12-06 12:12:27 -08:00 committed by David S. Miller
parent 2aab6b40b0
commit 93c647643b
1 changed files with 3 additions and 0 deletions
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3
net/netlink/af_netlink.c
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@ -253,6 +253,9 @@ static int __netlink_deliver_tap_skb(struct sk_buff *skb,
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))