tests/tpm: fix tpm_util_swtpm_has_tpm2()

Using g_spawn_async_with_pipes() is more complicated than running the
sync version. The async version returns a file descriptor for stdout, which may
not be fully read. Sometime "--tpm2" will failed to be read, and will
cause the related test to be silently skipped.

Use g_spawn_sync() instead, simplifying the code and fixing the race.
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NStefan Berger <stefanb@linux.vnet.ibm.com>
Signed-off-by: NStefan Berger <stefanb@linux.vnet.ibm.com>

tests/tpm-util.c

@@ -145,39 +145,33 @@ void tpm_util_pcrread(QTestState *s, tx_func *tx,
     g_assert_cmpmem(buffer, exp_resp_size, exp_resp, exp_resp_size);
 }
 
-static gboolean tpm_util_swtpm_has_tpm2(void)
+static bool tpm_util_swtpm_has_tpm2(void)
 {
-    gint mystdout;
-    gboolean succ;
-    unsigned i;
-    char buffer[10240];
-    ssize_t n;
-    gchar *swtpm_argv[] = {
-        g_strdup("swtpm"), g_strdup("socket"), g_strdup("--help"), NULL
+    bool has_tpm2 = false;
+    char *out = NULL;
+    static const char *argv[] = {
+        "swtpm", "socket", "--help", NULL
     };
 
-    succ = g_spawn_async_with_pipes(NULL, swtpm_argv, NULL,
-                                    G_SPAWN_SEARCH_PATH, NULL, NULL, NULL,
-                                    NULL, &mystdout, NULL, NULL);
-    if (!succ) {
-        goto cleanup;
+    if (!g_spawn_sync(NULL /* working_dir */,
+                      (char **)argv,
+                      NULL /* envp */,
+                      G_SPAWN_SEARCH_PATH,
+                      NULL /* child_setup */,
+                      NULL /* user_data */,
+                      &out,
+                      NULL /* err */,
+                      NULL /* exit_status */,
+                      NULL)) {
+        return false;
     }
 
-    n = read(mystdout, buffer, sizeof(buffer) - 1);
-    if (n < 0) {
-        goto cleanup;
-    }
-    buffer[n] = 0;
-    if (!strstr(buffer, "--tpm2")) {
-        succ = false;
-    }
-
- cleanup:
-    for (i = 0; swtpm_argv[i]; i++) {
-        g_free(swtpm_argv[i]);
+    if (strstr(out, "--tpm2")) {
+        has_tpm2 = true;
     }
 
-    return succ;
+    g_free(out);
+    return has_tpm2;
 }
 
 gboolean tpm_util_swtpm_start(const char *path, GPid *pid,