diff --git a/ipc/sem.c b/ipc/sem.c
index 35952c0..d65e285 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -143,6 +143,7 @@
 void sem_exit_ns(struct ipc_namespace *ns)
 {
 	struct sem_array *sma;
+	struct kern_ipc_perm *perm;
 	int next_id;
 	int total, in_use;
 
@@ -151,10 +152,11 @@
 	in_use = sem_ids(ns).in_use;
 
 	for (total = 0, next_id = 0; total < in_use; next_id++) {
-		sma = idr_find(&sem_ids(ns).ipcs_idr, next_id);
-		if (sma == NULL)
+		perm = idr_find(&sem_ids(ns).ipcs_idr, next_id);
+		if (perm == NULL)
 			continue;
-		ipc_lock_by_ptr(&sma->sem_perm);
+		ipc_lock_by_ptr(perm);
+		sma = container_of(perm, struct sem_array, sem_perm);
 		freeary(ns, sma);
 		total++;
 	}
@@ -181,6 +183,9 @@
 {
 	struct kern_ipc_perm *ipcp = ipc_lock_check_down(&sem_ids(ns), id);
 
+	if (IS_ERR(ipcp))
+		return (struct sem_array *)ipcp;
+
 	return container_of(ipcp, struct sem_array, sem_perm);
 }
 
@@ -192,6 +197,9 @@
 {
 	struct kern_ipc_perm *ipcp = ipc_lock(&sem_ids(ns), id);
 
+	if (IS_ERR(ipcp))
+		return (struct sem_array *)ipcp;
+
 	return container_of(ipcp, struct sem_array, sem_perm);
 }
 
@@ -200,6 +208,9 @@
 {
 	struct kern_ipc_perm *ipcp = ipc_lock_check(&sem_ids(ns), id);
 
+	if (IS_ERR(ipcp))
+		return (struct sem_array *)ipcp;
+
 	return container_of(ipcp, struct sem_array, sem_perm);
 }