cgroupns: Add a limit on the number of cgroup namespaces
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 984f73b..1ed9281 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -621,6 +621,7 @@
atomic_t count;
struct ns_common ns;
struct user_namespace *user_ns;
+ struct ucounts *ucounts;
struct css_set *root_cset;
};
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index e1d6721..d067f0d 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -29,6 +29,7 @@
UCOUNT_PID_NAMESPACES,
UCOUNT_UTS_NAMESPACES,
UCOUNT_IPC_NAMESPACES,
+ UCOUNT_CGROUP_NAMESPACES,
UCOUNT_COUNTS,
};
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index d1c51b7..e9e4427 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -6295,6 +6295,16 @@
/* 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 @@
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 *old_ns)
{
struct cgroup_namespace *new_ns;
+ struct ucounts *ucounts;
struct css_set *cset;
BUG_ON(!old_ns);
@@ -6340,6 +6352,10 @@
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 @@
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;
diff --git a/kernel/ucount.c b/kernel/ucount.c
index fbab754..335cc5d 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -71,6 +71,7 @@
UCOUNT_ENTRY("max_pid_namespaces"),
UCOUNT_ENTRY("max_uts_namespaces"),
UCOUNT_ENTRY("max_ipc_namespaces"),
+ UCOUNT_ENTRY("max_cgroup_namespaces"),
{ }
};
#endif /* CONFIG_SYSCTL */