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 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: netfilter-xt_osf-add-missing-permission-checks.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 916a27901de01446bcf57ecca4783f6cff493309 Mon Sep 17 00:00:00 2001 From: Kevin Cernekee <cernekee@xxxxxxxxxxxx> Date: Tue, 5 Dec 2017 15:42:41 -0800 Subject: netfilter: xt_osf: Add missing permission checks From: Kevin Cernekee <cernekee@xxxxxxxxxxxx> 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@xxxxxxxxxxxx> Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> Acked-by: Michal Kubecek <mkubecek@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 ne 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; @@ -113,6 +117,9 @@ 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@xxxxxxxxxxxx are queue-4.9/netfilter-xt_osf-add-missing-permission-checks.patch queue-4.9/netfilter-nfnetlink_cthelper-add-missing-permission-checks.patch