[PATCH] elf: Do not signal LA_ACT_CONSISTENT for an empty namespace [BZ #26076]

[H.J. Lu]

On Mon, Jul 6, 2020 at 12:45 PM Florian Weimer via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> The auditing interface identifies namespaces by their first loaded
> module.  Once the namespace is empty, it is no longer possible to signal
> LA_ACT_CONSISTENT for it because the first loaded module is already gone
> at that point.
>
> Tested on i686-linux-gnu and x86_64-linux-gnu.
>
> ---
>  elf/dl-close.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/elf/dl-close.c b/elf/dl-close.c
> index 73b2817bbf..8e146ecee1 100644
> --- a/elf/dl-close.c
> +++ b/elf/dl-close.c
> @@ -781,8 +781,14 @@ _dl_close_worker (struct link_map *map, bool force)
>    if (__glibc_unlikely (do_audit))
>      {
>        struct link_map *head = ns->_ns_loaded;
> -      /* Do not call the functions for any auditing object.  */
> -      if (head->l_auditing == 0)

I assume that "head" can be NULL.  Do you have a testcase?

> +      /* If head is NULL, the namespace has become empty, and the
> +        audit interface does not give us a way to signal
> +        LA_ACT_CONSISTENT for it because the first loaded module is
> +        used to identify the namespace.
> +
> +        Furthermore, do not notify auditors of the cleanup of a
> +        failed audit module loading attempt.  */
> +      if (head != NULL && head->l_auditing == 0)
>         {
>           struct audit_ifaces *afct = GLRO(dl_audit);
>           for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
>


-- 
H.J.