Re: [Qemu-devel] [PATCH 1/2] tests/tpm: fix tpm_util_swtpm_has_tpm2()

[Stefan Berger <stefanb@linux.vnet.ibm.com>]

On 10/3/18 9:21 AM, Marc-André Lureau wrote:
> 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: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>   tests/tpm-util.c | 46 ++++++++++++++++++++--------------------------
>   1 file changed, 20 insertions(+), 26 deletions(-)
>
> diff --git a/tests/tpm-util.c b/tests/tpm-util.c
> index 9f3f156e42..ae4aaf35ca 100644
> --- a/tests/tpm-util.c
> +++ b/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,

Reviewed-by: Stefan Berger <stefanb@linux.vnet.ibm.com>