[PATCH v2 08/10] cgroupns: Add a limit on the number of cgroup namespaces

From: Eric W. Biederman
Date: Thu Jul 21 2016 - 12:55:04 EST


Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
---
include/linux/user_namespace.h | 1 +
kernel/cgroup.c | 15 +++++++++++++++
kernel/user_namespace.c | 1 +
3 files changed, 17 insertions(+)

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 367cf08ff63d..1a3a9cb93277 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -27,6 +27,7 @@ enum ucounts {
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 86cb5c6e8932..240eec43390b 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -6260,6 +6260,16 @@ void cgroup_sk_free(struct sock_cgroup_data *skcd)

/* cgroup namespaces */

+static bool inc_cgroup_namespaces(struct user_namespace *ns)
+{
+ return inc_ucount(ns, UCOUNT_CGROUP_NAMESPACES);
+}
+
+static void dec_cgroup_namespaces(struct user_namespace *ns)
+{
+ dec_ucount(ns, UCOUNT_CGROUP_NAMESPACES);
+}
+
static struct cgroup_namespace *alloc_cgroup_ns(void)
{
struct cgroup_namespace *new_ns;
@@ -6281,6 +6291,7 @@ 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->user_ns);
put_user_ns(ns->user_ns);
ns_free_inum(&ns->ns);
kfree(ns);
@@ -6305,6 +6316,9 @@ struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
if (!ns_capable(user_ns, CAP_SYS_ADMIN))
return ERR_PTR(-EPERM);

+ if (!inc_cgroup_namespaces(user_ns))
+ return ERR_PTR(-ENFILE);
+
mutex_lock(&cgroup_mutex);
spin_lock_bh(&css_set_lock);

@@ -6317,6 +6331,7 @@ 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(user_ns);
return new_ns;
}

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 060d3e099f87..1cf074cb47e2 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -80,6 +80,7 @@ static struct ctl_table userns_table[] = {
UCOUNT_ENTRY("max_pid_namespaces"),
UCOUNT_ENTRY("max_uts_namespaces"),
UCOUNT_ENTRY("max_ipc_namespaces"),
+ UCOUNT_ENTRY("max_cgroup_namespaces"),
{ }
};
#endif /* CONFIG_SYSCTL */
--
2.8.3