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 (file)
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -621,6 +621,7 @@ struct cgroup_namespace {
        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 (file)
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -29,6 +29,7 @@ enum ucount_type {
        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 (file)
--- 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;

diff --git a/kernel/ucount.c b/kernel/ucount.c
index fbab754..335cc5d 100644 (file)
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -71,6 +71,7 @@ static struct ctl_table user_table[] = {
        UCOUNT_ENTRY("max_pid_namespaces"),
        UCOUNT_ENTRY("max_uts_namespaces"),
        UCOUNT_ENTRY("max_ipc_namespaces"),
+       UCOUNT_ENTRY("max_cgroup_namespaces"),
        { }
 };
 #endif /* CONFIG_SYSCTL */