2 files changed, 18 insertions, 4 deletions

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 315bcd375224..cc4f45361dbb 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -13,6 +13,7 @@ struct user_namespace {
         struct kref             kref;
         struct hlist_head       uidhash_table[UIDHASH_SZ];
         struct user_struct      *creator;
+        struct work_struct      destroyer;
 };
 
 extern struct user_namespace init_user_ns;
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 79084311ee57..076c7c8215b0 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -60,12 +60,25 @@ int create_user_ns(struct cred *new)
         return 0;
 }
 
-void free_user_ns(struct kref *kref)
+/*
+ * Deferred destructor for a user namespace.  This is required because
+ * free_user_ns() may be called with uidhash_lock held, but we need to call
+ * back to free_uid() which will want to take the lock again.
+ */
+static void free_user_ns_work(struct work_struct *work)
 {
-        struct user_namespace *ns;
-
-        ns = container_of(kref, struct user_namespace, kref);
+        struct user_namespace *ns =
+                container_of(work, struct user_namespace, destroyer);
         free_uid(ns->creator);
         kfree(ns);
 }
+
+void free_user_ns(struct kref *kref)
+{
+        struct user_namespace *ns =
+                container_of(kref, struct user_namespace, kref);
+
+        INIT_WORK(&ns->destroyer, free_user_ns_work);
+        schedule_work(&ns->destroyer);
+}
 EXPORT_SYMBOL(free_user_ns);