This is a note to let you know that I've just added the patch titled

netfilter: xt_osf: Add missing permission checks

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: netfilter-xt_osf-add-missing-permission-checks.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 916a27901de01446bcf57ecca4783f6cff493309 Mon Sep 17 00:00:00 2001

From: Kevin Cernekee cernekee@chromium.org Date: Tue, 5 Dec 2017 15:42:41 -0800 Subject: netfilter: xt_osf: Add missing permission checks

From: Kevin Cernekee cernekee@chromium.org

commit 916a27901de01446bcf57ecca4783f6cff493309 upstream.

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 Acked-by: Michal Kubecek mkubecek@suse.cz Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- net/netfilter/xt_osf.c | 7 +++++++ 1 file changed, 7 insertions(+)

--- 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> @@ -69,6 +70,9 @@ static int xt_osf_add_callback(struct so 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;

@@ -112,6 +116,9 @@ static int xt_osf_remove_callback(struct struct xt_osf_finger *sf; int err = -ENOENT;

+ if (!capable(CAP_NET_ADMIN)) + return -EPERM; + if (!osf_attrs[OSF_ATTR_FINGER]) return -EINVAL;

Patches currently in stable-queue which might be from cernekee@chromium.org are

queue-4.4/netfilter-xt_osf-add-missing-permission-checks.patch queue-4.4/netfilter-nfnetlink_cthelper-add-missing-permission-checks.patch