Re: [PATCH v2 06/11] firmware: move loading timeout under struct firmware_fallback_config

[Kees Cook]

On Fri, Feb 23, 2018 at 6:46 PM, Luis R. Rodriguez <mcgrof@xxxxxxxxxx> wrote:
> The timeout is a fallback construct, so we can just stuff the
> timeout configuration under struct firmware_fallback_config.
>
> While at it, add a few helpers which vets the use of getting or
> setting the timeout as an int. The main use of the timeout is
> to set a timeout for completion, and that is used as an unsigned
> long. There a few cases however where it makes sense to get or
> set the timeout as an int, the helpers annotate these use cases
> have been properly vetted for.
>
> Signed-off-by: Luis R. Rodriguez <mcgrof@xxxxxxxxxx>

Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>

-Kees

> ---
>  drivers/base/firmware_loader.c | 46 ++++++++++++++++++++++++++++++------------
>  1 file changed, 33 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/base/firmware_loader.c b/drivers/base/firmware_loader.c
> index 2d819875348d..9757f9fff01e 100644
> --- a/drivers/base/firmware_loader.c
> +++ b/drivers/base/firmware_loader.c
> @@ -266,21 +266,38 @@ static inline bool fw_state_is_aborted(struct fw_priv *fw_priv)
>   *
>   * @force_sysfs_fallback: force the sysfs fallback mechanism to be used
>   *     as if one had enabled CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y.
> + * @old_timeout: for internal use
> + * @loading_timeout: the timeout to wait for the fallback mechanism before
> + *     giving up, in seconds.
>   */
>  struct firmware_fallback_config {
> -       bool force_sysfs_fallback;
> +       const bool force_sysfs_fallback;
> +       int old_timeout;
> +       int loading_timeout;
>  };
>
> -static const struct firmware_fallback_config fw_fallback_config = {
> +static struct firmware_fallback_config fw_fallback_config = {
>         .force_sysfs_fallback = IS_ENABLED(CONFIG_FW_LOADER_USER_HELPER_FALLBACK),
> +       .loading_timeout = 60,
> +       .old_timeout = 60,
>  };
>
> -static int old_timeout;
> -static int loading_timeout = 60;       /* In seconds */
> +/* These getters are vetted to use int properly */
> +static inline int __firmware_loading_timeout(void)
> +{
> +       return fw_fallback_config.loading_timeout;
> +}
> +
> +/* These setters are vetted to use int properly */
> +static void __fw_fallback_set_timeout(int timeout)
> +{
> +       fw_fallback_config.loading_timeout = timeout;
> +}
>
>  static inline long firmware_loading_timeout(void)
>  {
> -       return loading_timeout > 0 ? loading_timeout * HZ : MAX_JIFFY_OFFSET;
> +       return __firmware_loading_timeout() > 0 ?
> +               __firmware_loading_timeout() * HZ : MAX_JIFFY_OFFSET;
>  }
>
>  /*
> @@ -291,14 +308,14 @@ static inline long firmware_loading_timeout(void)
>   */
>  static void fw_fallback_set_cache_timeout(void)
>  {
> -       old_timeout = loading_timeout;
> -       loading_timeout = 10;
> +       fw_fallback_config.old_timeout = __firmware_loading_timeout();
> +       __fw_fallback_set_timeout(10);
>  }
>
>  /* Restores the timeout to the value last configured during normal operation */
>  static void fw_fallback_set_default_timeout(void)
>  {
> -       loading_timeout =  old_timeout;
> +       __fw_fallback_set_timeout(fw_fallback_config.old_timeout);
>  }
>
>  static inline bool fw_sysfs_done(struct fw_priv *fw_priv)
> @@ -677,7 +694,7 @@ static void kill_pending_fw_fallback_reqs(bool only_kill_custom)
>  static ssize_t timeout_show(struct class *class, struct class_attribute *attr,
>                             char *buf)
>  {
> -       return sprintf(buf, "%d\n", loading_timeout);
> +       return sprintf(buf, "%d\n", __firmware_loading_timeout());
>  }
>
>  /**
> @@ -696,9 +713,12 @@ static ssize_t timeout_show(struct class *class, struct class_attribute *attr,
>  static ssize_t timeout_store(struct class *class, struct class_attribute *attr,
>                              const char *buf, size_t count)
>  {
> -       loading_timeout = simple_strtol(buf, NULL, 10);
> -       if (loading_timeout < 0)
> -               loading_timeout = 0;
> +       int tmp_loading_timeout = simple_strtol(buf, NULL, 10);
> +
> +       if (tmp_loading_timeout < 0)
> +               tmp_loading_timeout = 0;
> +
> +       __fw_fallback_set_timeout(tmp_loading_timeout);
>
>         return count;
>  }
> @@ -721,7 +741,7 @@ static int do_firmware_uevent(struct fw_sysfs *fw_sysfs, struct kobj_uevent_env
>  {
>         if (add_uevent_var(env, "FIRMWARE=%s", fw_sysfs->fw_priv->fw_name))
>                 return -ENOMEM;
> -       if (add_uevent_var(env, "TIMEOUT=%i", loading_timeout))
> +       if (add_uevent_var(env, "TIMEOUT=%i", __firmware_loading_timeout()))
>                 return -ENOMEM;
>         if (add_uevent_var(env, "ASYNC=%d", fw_sysfs->nowait))
>                 return -ENOMEM;
> --
> 2.16.2
>



-- 
Kees Cook
Pixel Security