diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 92310b07cb98..a41858db1441 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -113,11 +113,14 @@ static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
 	} else if (value_size / 8 > sysctl_perf_event_max_stack)
 		return ERR_PTR(-EINVAL);
 
-	/* hash table size must be power of 2 */
-	n_buckets = roundup_pow_of_two(attr->max_entries);
-	if (!n_buckets)
+	/* hash table size must be power of 2; roundup_pow_of_two() can overflow
+	 * into UB on 32-bit arches, so check that first
+	 */
+	if (attr->max_entries > 1UL << 31)
 		return ERR_PTR(-E2BIG);
 
+	n_buckets = roundup_pow_of_two(attr->max_entries);
+
 	cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
 	if (cost >= U32_MAX - PAGE_SIZE)
 		return ERR_PTR(-E2BIG);