bpf: Fix values type used in test_maps

Maps of per-cpu type have their value element size adjusted to 8 if it
is specified smaller during various map operations.

This makes test_maps as a 32-bit binary fail, in fact the kernel
writes past the end of the value's array on the user's stack.

To be quite honest, I think the kernel should reject creation of a
per-cpu map that doesn't have a value size of at least 8 if that's
what the kernel is going to silently adjust to later.

If the user passed something smaller, it is a sizeof() calcualtion
based upon the type they will actually use (just like in this testcase
code) in later calls to the map operations.

Fixes: df570f5 ("samples/bpf: unit test for BPF_MAP_TYPE_PERCPU_ARRAY")
Signed-off-by: David S. Miller <[email protected]>
Acked-by: Daniel Borkmann <[email protected]>
Acked-by: Alexei Starovoitov <[email protected]>

tools/testing/selftests/bpf/test_maps.c

@@ -282,7 +282,7 @@ static void test_arraymap_percpu(int task, void *data)
 {
 	unsigned int nr_cpus = bpf_num_possible_cpus();
 	int key, next_key, fd, i;
-	long values[nr_cpus];
+	long long values[nr_cpus];
 
 	fd = bpf_create_map(BPF_MAP_TYPE_PERCPU_ARRAY, sizeof(key),
 			    sizeof(values[0]), 2, 0);
@@ -340,7 +340,7 @@ static void test_arraymap_percpu_many_keys(void)
 	 * allocator more than anything else
 	 */
 	unsigned int nr_keys = 2000;
-	long values[nr_cpus];
+	long long values[nr_cpus];
 	int key, fd, i;
 
 	fd = bpf_create_map(BPF_MAP_TYPE_PERCPU_ARRAY, sizeof(key),