--- zzzz-none-000/linux-4.4.60/kernel/bpf/arraymap.c	2017-04-08 07:53:53.000000000 +0000
+++ wasp-540e-714/linux-4.4.60/kernel/bpf/arraymap.c	2019-07-03 09:21:34.000000000 +0000
@@ -22,6 +22,8 @@
 {
 	struct bpf_array *array;
 	u32 elem_size, array_size;
+	u32 index_mask, max_entries;
+	bool unpriv = !capable(CAP_SYS_ADMIN);
 
 	/* check sanity of attributes */
 	if (attr->max_entries == 0 || attr->key_size != 4 ||
@@ -36,12 +38,22 @@
 
 	elem_size = round_up(attr->value_size, 8);
 
+	max_entries = attr->max_entries;
+	index_mask = roundup_pow_of_two(max_entries) - 1;
+
+	if (unpriv)
+		/* round up array size to nearest power of 2,
+		 * since cpu will speculate within index_mask limits
+		 */
+		max_entries = index_mask + 1;
+
+
 	/* check round_up into zero and u32 overflow */
 	if (elem_size == 0 ||
 	    attr->max_entries > (U32_MAX - PAGE_SIZE - sizeof(*array)) / elem_size)
 		return ERR_PTR(-ENOMEM);
 
-	array_size = sizeof(*array) + attr->max_entries * elem_size;
+	array_size = sizeof(*array) + max_entries * elem_size;
 
 	/* allocate all map elements and zero-initialize them */
 	array = kzalloc(array_size, GFP_USER | __GFP_NOWARN);
@@ -51,6 +63,9 @@
 			return ERR_PTR(-ENOMEM);
 	}
 
+	array->index_mask = index_mask;
+	array->map.unpriv_array = unpriv;
+
 	/* copy mandatory map attributes */
 	array->map.key_size = attr->key_size;
 	array->map.value_size = attr->value_size;
@@ -70,7 +85,7 @@
 	if (index >= array->map.max_entries)
 		return NULL;
 
-	return array->value + array->elem_size * index;
+	return array->value + array->elem_size * (index & array->index_mask);
 }
 
 /* Called from syscall */
@@ -111,7 +126,9 @@
 		/* all elements already exist */
 		return -EEXIST;
 
-	memcpy(array->value + array->elem_size * index, value, map->value_size);
+	memcpy(array->value +
+		array->elem_size * (index & array->index_mask),
+		value, map->value_size);
 	return 0;
 }