--- x/kernel/futex/core.c
+++ y/kernel/futex/core.c
@@ -205,6 +205,8 @@ static void futex_rehash_private(struct
 	unsigned int slots = old->hash_mask + 1;
 	unsigned int i;
 
+	if (!old->hash_mask)
+		return;
 	for (i = 0; i < slots; i++) {
 		struct futex_q *this, *tmp;