tests: filter_kubernetes: Add a test case for preventing backtracks on regex

Signed-off-by: Hiroshi Hatake <hiroshi@chronosphere.io>

Author: cosmo0920

tests/runtime/data/kubernetes/log/core/core_uat-myapp-12345_fluent-bit.log

@@ -0,0 +1 @@
+{"log":"hello from uat pod","stream":"stdout","time":"2019-04-01T17:58:33.598656444Z"}

tests/runtime/data/kubernetes/meta/short-prefix-uat-podname.json

@@ -0,0 +1,17 @@
+{
+  "apiVersion": "v1",
+  "kind": "Pod",
+  "metadata": {
+    "name": "uat-myapp-12345",
+    "namespace": "core",
+    "uid": "00000000-0000-0000-0000-000000000000"
+  },
+  "spec": {
+    "containers": [
+      {
+        "name": "container"
+      }
+    ]
+  }
+}
+

tests/runtime/data/kubernetes/out/core/core_uat-myapp-12345_fluent-bit.out

@@ -0,0 +1 @@
+[1554141513.598656,{"log":"hello from uat pod","stream":"stdout","kubernetes":{"pod_name":"uat-myapp-12345","namespace_name":"core","container_name":"fluent-bit"}}]

tests/runtime/filter_kubernetes.c

@@ -86,7 +86,7 @@ static int file_to_buf(const char *path, char **out_buf, size_t *out_size)
         return -1;
     }
 
-    buf = flb_malloc(st.st_size);
+    buf = flb_malloc(st.st_size + 1);
     if (!buf) {
         flb_errno();
         fclose(fp);
@@ -100,6 +100,7 @@ static int file_to_buf(const char *path, char **out_buf, size_t *out_size)
         fclose(fp);
         return -1;
     }
+    buf[st.st_size] = '\0';
 
     fclose(fp);
     *out_buf = buf;
@@ -411,6 +412,17 @@ static void flb_test_core_base_with_namespace_labels_and_annotations()
     flb_test_namespace_labels_and_annotations("core_base-with-namespace-labels-and-annotations_fluent-bit", NULL, 1);
 }
 
+static void flb_test_kube_short_prefix_uat_podname()
+{
+    kube_test("core/core_uat-myapp-12345_fluent-bit",
+              KUBE_TAIL,
+              NULL,
+              1,
+              "Use_Tag_For_Meta", "On",
+              NULL);
+}
+
+
 #define flb_test_owner_references(target, suffix, nExpected) \
     kube_test("core/" target, KUBE_TAIL, suffix, nExpected, \
               "Labels", "Off", \
@@ -1113,5 +1125,6 @@ TEST_LIST = {
 #ifdef FLB_HAVE_SYSTEMD
     {"kube_systemd_logs", flb_test_systemd_logs},
 #endif
+    {"kube_short_prefix_uat_podname", flb_test_kube_short_prefix_uat_podname},
     {NULL, NULL}
 };