4.9-stable review patch. If anyone has any objections, please let me know.
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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 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;