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From 5af86b090e2f17b97c02d0bf9098f6edc3195935 Mon Sep 17 00:00:00 2001
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From: Kevin Cernekee <cernekee@chromium.org>
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Date: Wed, 6 Dec 2017 12:12:27 -0800
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Subject: [PATCH] netlink: Add netns check on taps
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Currently, a nlmon link inside a child namespace can observe systemwide
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netlink activity. Filter the traffic so that nlmon can only sniff
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netlink messages from its own netns.
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Test case:
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vpnns -- bash -c "ip link add nlmon0 type nlmon; \
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ip link set nlmon0 up; \
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tcpdump -i nlmon0 -q -w /tmp/nlmon.pcap -U" &
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sudo ip xfrm state add src 10.1.1.1 dst 10.1.1.2 proto esp \
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spi 0x1 mode transport \
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auth sha1 0x6162633132330000000000000000000000000000 \
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enc aes 0x00000000000000000000000000000000
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grep --binary abc123 /tmp/nlmon.pcap
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Signed-off-by: Kevin Cernekee <cernekee@chromium.org>
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---
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net/netlink/af_netlink.c | 3 +++
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1 file changed, 3 insertions(+)
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diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
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index 15c99dfa3d72..aac9d68b4636 100644
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--- a/net/netlink/af_netlink.c
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+++ b/net/netlink/af_netlink.c
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@@ -254,6 +254,9 @@ static int __netlink_deliver_tap_skb(struct sk_buff *skb,
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struct sock *sk = skb->sk;
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int ret = -ENOMEM;
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+ if (!net_eq(dev_net(dev), sock_net(sk)))
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+ return 0;
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+
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dev_hold(dev);
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if (is_vmalloc_addr(skb->head))
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--
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2.14.3
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