userns: Rename id_map_mutex to userns_state_mutex

Generalize id_map_mutex so it can be used for more state of a user namespace.

Cc: stable@vger.kernel.org
Reviewed-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

kernel/user_namespace.c

@@ -24,6 +24,7 @@
 #include <linux/fs_struct.h>
 
 static struct kmem_cache *user_ns_cachep __read_mostly;
+static DEFINE_MUTEX(userns_state_mutex);
 
 static bool new_idmap_permitted(const struct file *file,
 				struct user_namespace *ns, int cap_setid,
@@ -583,9 +584,6 @@ static bool mappings_overlap(struct uid_gid_map *new_map,
 	return false;
 }
 
-
-static DEFINE_MUTEX(id_map_mutex);
-
 static ssize_t map_write(struct file *file, const char __user *buf,
 			 size_t count, loff_t *ppos,
 			 int cap_setid,
@@ -602,7 +600,7 @@ static ssize_t map_write(struct file *file, const char __user *buf,
 	ssize_t ret = -EINVAL;
 
 	/*
-	 * The id_map_mutex serializes all writes to any given map.
+	 * The userns_state_mutex serializes all writes to any given map.
 	 *
 	 * Any map is only ever written once.
 	 *
@@ -620,7 +618,7 @@ static ssize_t map_write(struct file *file, const char __user *buf,
 	 * order and smp_rmb() is guaranteed that we don't have crazy
 	 * architectures returning stale data.
 	 */
-	mutex_lock(&id_map_mutex);
+	mutex_lock(&userns_state_mutex);
 
 	ret = -EPERM;
 	/* Only allow one successful write to the map */
@@ -750,7 +748,7 @@ static ssize_t map_write(struct file *file, const char __user *buf,
 	*ppos = count;
 	ret = count;
 out:
-	mutex_unlock(&id_map_mutex);
+	mutex_unlock(&userns_state_mutex);
 	if (page)
 		free_page(page);
 	return ret;
@@ -845,12 +843,12 @@ bool userns_may_setgroups(const struct user_namespace *ns)
 {
 	bool allowed;
 
-	mutex_lock(&id_map_mutex);
+	mutex_lock(&userns_state_mutex);
 	/* It is not safe to use setgroups until a gid mapping in
 	 * the user namespace has been established.
 	 */
 	allowed = ns->gid_map.nr_extents != 0;
-	mutex_unlock(&id_map_mutex);
+	mutex_unlock(&userns_state_mutex);
 
 	return allowed;
 }