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 4b380c42f7d00a395feede754f0bc2292eebe6e5 upstream.
The capability check in nfnetlink_rcv() verifies that the caller has CAP_NET_ADMIN in the namespace that "owns" the netlink socket. However, nfnl_cthelper_list 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:
$ nfct helper list nfct v1.4.4: netlink error: Operation not permitted $ vpnns -- nfct helper list { .name = ftp, .queuenum = 0, .l3protonum = 2, .l4protonum = 6, .priv_data_len = 24, .status = enabled, };
Add capable() checks in nfnetlink_cthelper, as this is cleaner than trying to generalize the solution.
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/nfnetlink_cthelper.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
--- a/net/netfilter/nfnetlink_cthelper.c +++ b/net/netfilter/nfnetlink_cthelper.c @@ -17,6 +17,7 @@ #include <linux/types.h> #include <linux/list.h> #include <linux/errno.h> +#include <linux/capability.h> #include <net/netlink.h> #include <net/sock.h>
@@ -392,6 +393,9 @@ static int nfnl_cthelper_new(struct net struct nfnl_cthelper *nlcth; int ret = 0;
+ if (!capable(CAP_NET_ADMIN)) + return -EPERM; + if (!tb[NFCTH_NAME] || !tb[NFCTH_TUPLE]) return -EINVAL;
@@ -595,6 +599,9 @@ static int nfnl_cthelper_get(struct net struct nfnl_cthelper *nlcth; bool tuple_set = false;
+ if (!capable(CAP_NET_ADMIN)) + return -EPERM; + if (nlh->nlmsg_flags & NLM_F_DUMP) { struct netlink_dump_control c = { .dump = nfnl_cthelper_dump_table, @@ -661,6 +668,9 @@ static int nfnl_cthelper_del(struct net struct nfnl_cthelper *nlcth, *n; int j = 0, ret;
+ if (!capable(CAP_NET_ADMIN)) + return -EPERM; + if (tb[NFCTH_NAME]) helper_name = nla_data(tb[NFCTH_NAME]);