1 files changed, 10 insertions, 3 deletions

diff --git a/fs/super.c b/fs/super.c
index ea662b0e5e78..b8b6a086c03b 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -469,7 +469,7 @@ struct super_block *sget_userns(struct file_system_type *type,
         struct super_block *old;
         int err;
 
-        if (!(flags & MS_KERNMOUNT) &&
+        if (!(flags & (MS_KERNMOUNT|MS_SUBMOUNT)) &&
             !(type->fs_flags & FS_USERNS_MOUNT) &&
             !capable(CAP_SYS_ADMIN))
                 return ERR_PTR(-EPERM);
@@ -499,7 +499,7 @@ retry:
         }
         if (!s) {
                 spin_unlock(&sb_lock);
-                s = alloc_super(type, flags, user_ns);
+                s = alloc_super(type, (flags & ~MS_SUBMOUNT), user_ns);
                 if (!s)
                         return ERR_PTR(-ENOMEM);
                 goto retry;
@@ -540,8 +540,15 @@ struct super_block *sget(struct file_system_type *type,
 {
         struct user_namespace *user_ns = current_user_ns();
 
+        /* We don't yet pass the user namespace of the parent
+         * mount through to here so always use &init_user_ns
+         * until that changes.
+         */
+        if (flags & MS_SUBMOUNT)
+                user_ns = &init_user_ns;
+
         /* Ensure the requestor has permissions over the target filesystem */
-        if (!(flags & MS_KERNMOUNT) && !ns_capable(user_ns, CAP_SYS_ADMIN))
+        if (!(flags & (MS_KERNMOUNT|MS_SUBMOUNT)) && !ns_capable(user_ns, CAP_SYS_ADMIN))
                 return ERR_PTR(-EPERM);
 
         return sget_userns(type, test, set, flags, user_ns, data);