[PATCH bpf 5/5] selftests/bpf: add tests for write-only stacks/queues

[Anton Protopopov]

For write-only stacks and queues bpf_map_update_elem should be allowed, but
bpf_map_lookup_elem and bpf_map_lookup_and_delete_elem should fail with EPERM.

Signed-off-by: Anton Protopopov <a.s.protopo...@gmail.com>
---
 tools/testing/selftests/bpf/test_maps.c | 40 ++++++++++++++++++++++++-
 1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/test_maps.c 
b/tools/testing/selftests/bpf/test_maps.c
index 08d63948514a..6a12a0e01e07 100644
--- a/tools/testing/selftests/bpf/test_maps.c
+++ b/tools/testing/selftests/bpf/test_maps.c
@@ -1405,7 +1405,7 @@ static void test_map_rdonly(void)
        close(fd);
 }
 
-static void test_map_wronly(void)
+static void test_map_wronly_hash(void)
 {
        int fd, key = 0, value = 0;
 
@@ -1429,6 +1429,44 @@ static void test_map_wronly(void)
        close(fd);
 }
 
+static void test_map_wronly_stack_or_queue(enum bpf_map_type map_type)
+{
+       int fd, value = 0;
+
+       assert(map_type == BPF_MAP_TYPE_QUEUE ||
+              map_type == BPF_MAP_TYPE_STACK);
+       fd = bpf_create_map(map_type, 0, sizeof(value), MAP_SIZE,
+                           map_flags | BPF_F_WRONLY);
+       /* Stack/Queue maps do not support BPF_F_NO_PREALLOC */
+       if (map_flags & BPF_F_NO_PREALLOC) {
+               assert(fd < 0 && errno == EINVAL);
+               return;
+       }
+       if (fd < 0) {
+               printf("Failed to create map '%s'!\n", strerror(errno));
+               exit(1);
+       }
+
+       value = 1234;
+       assert(bpf_map_update_elem(fd, NULL, &value, BPF_ANY) == 0);
+
+       /* Peek element should fail */
+       assert(bpf_map_lookup_elem(fd, NULL, &value) == -1 && errno == EPERM);
+
+       /* Pop element should fail */
+       assert(bpf_map_lookup_and_delete_elem(fd, NULL, &value) == -1 &&
+              errno == EPERM);
+
+       close(fd);
+}
+
+static void test_map_wronly(void)
+{
+       test_map_wronly_hash();
+       test_map_wronly_stack_or_queue(BPF_MAP_TYPE_STACK);
+       test_map_wronly_stack_or_queue(BPF_MAP_TYPE_QUEUE);
+}
+
 static void prepare_reuseport_grp(int type, int map_fd, size_t map_elem_size,
                                  __s64 *fds64, __u64 *sk_cookies,
                                  unsigned int n)
-- 
2.20.1