commit 916a27901de01446bcf57ecca4783f6cff493309
Author: Kevin Cernekee <cernekee@chromium.org>
Date:   Tue Dec 5 15:42:41 2017 -0800

    netfilter: xt_osf: Add missing permission checks
    
    The capability check in nfnetlink_rcv() verifies that the caller
    has CAP_NET_ADMIN in the namespace that "owns" the netlink socket.
    However, xt_osf_fingers is shared by all net namespaces on the
    system.  An unprivileged user can create user and net namespaces
    in which he holds CAP_NET_ADMIN to bypass the netlink_net_capable()
    check:
    
        vpnns -- nfnl_osf -f /tmp/pf.os
    
        vpnns -- nfnl_osf -f /tmp/pf.os -d
    
    These non-root operations successfully modify the systemwide OS
    fingerprint list.  Add new capable() checks so that they can't.
    
    Signed-off-by: Kevin Cernekee <cernekee@chromium.org>
    Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/xt_osf.c b/net/netfilter/xt_osf.c
index 36e14b1..a34f314 100644
--- a/net/netfilter/xt_osf.c
+++ b/net/netfilter/xt_osf.c
@@ -19,6 +19,7 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 
+#include <linux/capability.h>
 #include <linux/if.h>
 #include <linux/inetdevice.h>
 #include <linux/ip.h>
@@ -70,6 +71,9 @@ static int xt_osf_add_callback(struct net *net, struct sock *ctnl,
 	struct xt_osf_finger *kf = NULL, *sf;
 	int err = 0;
 
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
 	if (!osf_attrs[OSF_ATTR_FINGER])
 		return -EINVAL;
 
@@ -115,6 +119,9 @@ static int xt_osf_remove_callback(struct net *net, struct sock *ctnl,
 	struct xt_osf_finger *sf;
 	int err = -ENOENT;
 
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
 	if (!osf_attrs[OSF_ATTR_FINGER])
 		return -EINVAL;