Re: [PATCH v2] libselinux: use designated initializers for label initfuncs

On Tue, Jul 14, 2026 at 7:25 PM Thiébaud Weksteen <[email protected]> wrote:
>
> Previously, the initfuncs array relied on implicit positional ordering
> to match backend context constants (e.g., SELABEL_CTX_FILE). If constants
> were reordered or added, array indexing could become misaligned.
>
> Use C99 designated initializers in initfuncs to explicitly bind each
> initialization function to its corresponding context constant.
>
> Additionally, define _SELABEL_CTX_NUM in include/selinux/label.h
> to count total backends, and add a compile-time static_assert ensuring
> initfuncs stays in sync with _SELABEL_CTX_NUM.
>
> Signed-off-by: Thiébaud Weksteen <[email protected]>

Acked-by: Stephen Smalley <[email protected]>


> ---
> v2: Rebase on selinux/main and format
>
>  libselinux/include/selinux/label.h |  5 +++++
>  libselinux/src/label.c             | 18 ++++++++++++------
>  2 files changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/libselinux/include/selinux/label.h b/libselinux/include/selinux/label.h
> index 748b0db0..bde2501f 100644
> --- a/libselinux/include/selinux/label.h
> +++ b/libselinux/include/selinux/label.h
> @@ -37,6 +37,11 @@ struct selabel_handle;
>  #define SELABEL_CTX_ANDROID_PROP 4
>  /* Android service contexts */
>  #define SELABEL_CTX_ANDROID_SERVICE 5
> +/*
> + * Total number of context backends. When adding a new backend,
> + * please increase this value.
> + */
> +#define _SELABEL_CTX_NUM 6
>
>  /*
>   * Available options
> diff --git a/libselinux/src/label.c b/libselinux/src/label.c
> index 1ccd1abe..991b9769 100644
> --- a/libselinux/src/label.c
> +++ b/libselinux/src/label.c
> @@ -4,6 +4,7 @@
>   * Author : Eamon Walsh <[email protected]>
>   */
>
> +#include <assert.h>
>  #include <sys/types.h>
>  #include <ctype.h>
>  #include <errno.h>
> @@ -45,14 +46,19 @@ typedef int (*selabel_initfunc)(struct selabel_handle *rec,
>                                 const struct selinux_opt *opts, unsigned nopts);
>
>  static const selabel_initfunc initfuncs[] = {
> -       &selabel_file_init,
> -       CONFIG_MEDIA_BACKEND(selabel_media_init),
> -       CONFIG_X_BACKEND(selabel_x_init),
> -       CONFIG_DB_BACKEND(selabel_db_init),
> -       CONFIG_ANDROID_BACKEND(selabel_property_init),
> -       CONFIG_ANDROID_BACKEND(selabel_service_init),
> +       [SELABEL_CTX_FILE] = &selabel_file_init,
> +       [SELABEL_CTX_MEDIA] = CONFIG_MEDIA_BACKEND(selabel_media_init),
> +       [SELABEL_CTX_X] = CONFIG_X_BACKEND(selabel_x_init),
> +       [SELABEL_CTX_DB] = CONFIG_DB_BACKEND(selabel_db_init),
> +       [SELABEL_CTX_ANDROID_PROP] =
> +               CONFIG_ANDROID_BACKEND(selabel_property_init),
> +       [SELABEL_CTX_ANDROID_SERVICE] =
> +               CONFIG_ANDROID_BACKEND(selabel_service_init),
>  };
>
> +static_assert(ARRAY_SIZE(initfuncs) == _SELABEL_CTX_NUM,
> +             "initfuncs array size does not match _SELABEL_CTX_NUM");
> +
>  static inline struct selabel_digest *
>  selabel_is_digest_set(const struct selinux_opt *opts, unsigned n)
>  {
> --
> 2.55.0.229.g6434b31f56-goog
>