--- x/mm/shmem_quota.c
+++ y/mm/shmem_quota.c
@@ -116,7 +116,7 @@ static int shmem_free_file_info(struct s
 static int shmem_get_next_id(struct super_block *sb, struct kqid *qid)
 {
 	struct mem_dqinfo *info = sb_dqinfo(sb, qid->type);
-	struct rb_node *node = ((struct rb_root *)info->dqi_priv)->rb_node;
+	struct rb_node *node;
 	qid_t id = from_kqid(&init_user_ns, *qid);
 	struct quota_info *dqopt = sb_dqopt(sb);
 	struct quota_id *entry = NULL;
@@ -126,6 +126,11 @@ static int shmem_get_next_id(struct supe
 		return -ESRCH;
 
 	down_read(&dqopt->dqio_sem);
+	if (!info->dqi_priv) {
+		ret = -ENOENT;
+		goto out_unlock;
+	}
+	node = ((struct rb_root *)info->dqi_priv)->rb_node;
 	while (node) {
 		entry = rb_entry(node, struct quota_id, node);