From d08311dd6fd8444e39710dd2fb97562895aed8fa Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Mon, 8 Aug 2016 14:25:30 -0500 Subject: cgroupns: Add a limit on the number of cgroup namespaces Acked-by: Kees Cook Signed-off-by: "Eric W. Biederman" --- kernel/cgroup.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'kernel/cgroup.c') diff --git a/kernel/cgroup.c b/kernel/cgroup.c index d1c51b7f5221..e9e4427fec46 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -6295,6 +6295,16 @@ void cgroup_sk_free(struct sock_cgroup_data *skcd) /* cgroup namespaces */ +static struct ucounts *inc_cgroup_namespaces(struct user_namespace *ns) +{ + return inc_ucount(ns, current_euid(), UCOUNT_CGROUP_NAMESPACES); +} + +static void dec_cgroup_namespaces(struct ucounts *ucounts) +{ + dec_ucount(ucounts, UCOUNT_CGROUP_NAMESPACES); +} + static struct cgroup_namespace *alloc_cgroup_ns(void) { struct cgroup_namespace *new_ns; @@ -6316,6 +6326,7 @@ static struct cgroup_namespace *alloc_cgroup_ns(void) void free_cgroup_ns(struct cgroup_namespace *ns) { put_css_set(ns->root_cset); + dec_cgroup_namespaces(ns->ucounts); put_user_ns(ns->user_ns); ns_free_inum(&ns->ns); kfree(ns); @@ -6327,6 +6338,7 @@ struct cgroup_namespace *copy_cgroup_ns(unsigned long flags, struct cgroup_namespace *old_ns) { struct cgroup_namespace *new_ns; + struct ucounts *ucounts; struct css_set *cset; BUG_ON(!old_ns); @@ -6340,6 +6352,10 @@ struct cgroup_namespace *copy_cgroup_ns(unsigned long flags, if (!ns_capable(user_ns, CAP_SYS_ADMIN)) return ERR_PTR(-EPERM); + ucounts = inc_cgroup_namespaces(user_ns); + if (!ucounts) + return ERR_PTR(-ENFILE); + /* It is not safe to take cgroup_mutex here */ spin_lock_irq(&css_set_lock); cset = task_css_set(current); @@ -6349,10 +6365,12 @@ struct cgroup_namespace *copy_cgroup_ns(unsigned long flags, new_ns = alloc_cgroup_ns(); if (IS_ERR(new_ns)) { put_css_set(cset); + dec_cgroup_namespaces(ucounts); return new_ns; } new_ns->user_ns = get_user_ns(user_ns); + new_ns->ucounts = ucounts; new_ns->root_cset = cset; return new_ns; -- cgit