diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index ff21980..74706b6 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -841,6 +841,9 @@
 	unsigned int hashent = hashfn(sb, qid);
 	struct dquot *dquot, *empty = NULL;
 
+	if (!qid_has_mapping(sb->s_user_ns, qid))
+		return ERR_PTR(-EINVAL);
+
         if (!sb_has_quota_active(sb, qid.type))
 		return ERR_PTR(-ESRCH);
 we_slept:
diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index 0f10ee9..73f6f4c 100644
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -211,7 +211,7 @@
 	if (!sb->s_qcop->get_dqblk)
 		return -ENOSYS;
 	qid = make_kqid(current_user_ns(), type, id);
-	if (!qid_valid(qid))
+	if (!qid_has_mapping(sb->s_user_ns, qid))
 		return -EINVAL;
 	ret = sb->s_qcop->get_dqblk(sb, qid, &fdq);
 	if (ret)
@@ -237,7 +237,7 @@
 	if (!sb->s_qcop->get_nextdqblk)
 		return -ENOSYS;
 	qid = make_kqid(current_user_ns(), type, id);
-	if (!qid_valid(qid))
+	if (!qid_has_mapping(sb->s_user_ns, qid))
 		return -EINVAL;
 	ret = sb->s_qcop->get_nextdqblk(sb, &qid, &fdq);
 	if (ret)
@@ -288,7 +288,7 @@
 	if (!sb->s_qcop->set_dqblk)
 		return -ENOSYS;
 	qid = make_kqid(current_user_ns(), type, id);
-	if (!qid_valid(qid))
+	if (!qid_has_mapping(sb->s_user_ns, qid))
 		return -EINVAL;
 	copy_from_if_dqblk(&fdq, &idq);
 	return sb->s_qcop->set_dqblk(sb, qid, &fdq);
@@ -581,7 +581,7 @@
 	if (!sb->s_qcop->set_dqblk)
 		return -ENOSYS;
 	qid = make_kqid(current_user_ns(), type, id);
-	if (!qid_valid(qid))
+	if (!qid_has_mapping(sb->s_user_ns, qid))
 		return -EINVAL;
 	/* Are we actually setting timer / warning limits for all users? */
 	if (from_kqid(&init_user_ns, qid) == 0 &&
@@ -642,7 +642,7 @@
 	if (!sb->s_qcop->get_dqblk)
 		return -ENOSYS;
 	qid = make_kqid(current_user_ns(), type, id);
-	if (!qid_valid(qid))
+	if (!qid_has_mapping(sb->s_user_ns, qid))
 		return -EINVAL;
 	ret = sb->s_qcop->get_dqblk(sb, qid, &qdq);
 	if (ret)
@@ -669,7 +669,7 @@
 	if (!sb->s_qcop->get_nextdqblk)
 		return -ENOSYS;
 	qid = make_kqid(current_user_ns(), type, id);
-	if (!qid_valid(qid))
+	if (!qid_has_mapping(sb->s_user_ns, qid))
 		return -EINVAL;
 	ret = sb->s_qcop->get_nextdqblk(sb, &qid, &qdq);
 	if (ret)
diff --git a/include/linux/quota.h b/include/linux/quota.h
index 9dfb6bc..1db16ee 100644
--- a/include/linux/quota.h
+++ b/include/linux/quota.h
@@ -179,6 +179,16 @@
 	return kqid;
 }
 
+/**
+ *	qid_has_mapping - Report if a qid maps into a user namespace.
+ *	@ns:  The user namespace to see if a value maps into.
+ *	@qid: The kernel internal quota identifier to test.
+ */
+static inline bool qid_has_mapping(struct user_namespace *ns, struct kqid qid)
+{
+	return from_kqid(ns, qid) != (qid_t) -1;
+}
+
 
 extern spinlock_t dq_data_lock;