Re: [PATCH 06/15] elf: Fix comments and logic in _dl_add_to_slotinfo

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 15/02/2021 08:59, Szabolcs Nagy via Libc-alpha wrote:
> From: Szabolcs Nagy <szabolcs dot nagy at arm dot com>
> 
> Since
> 
>   commit a509eb117fac1d764b15eba64993f4bdb63d7f3c
>   Avoid late dlopen failure due to scope, TLS slotinfo updates [BZ #25112]
> 
> the generation counter update is not needed in the failure path.

It is not clear to me from just the commit reference why it would
be safe to remove the GL(dl_tls_generation) update on 
_dl_add_to_slotinfo.

The dl_open_worker calls update_tls_slotinfo which in turn call
might call _dl_add_to_slotinfo *after* the demarcation point.  Will
it terminate the process?

> ---
>  elf/dl-tls.c | 11 +----------
>  1 file changed, 1 insertion(+), 10 deletions(-)
> 
> diff --git a/elf/dl-tls.c b/elf/dl-tls.c
> index 79b93ad91b..24d00c14ef 100644
> --- a/elf/dl-tls.c
> +++ b/elf/dl-tls.c
> @@ -998,16 +998,7 @@ _dl_add_to_slotinfo (struct link_map *l, bool do_add)
>  		+ TLS_SLOTINFO_SURPLUS * sizeof (struct dtv_slotinfo));
>        if (listp == NULL)
>  	{
> -	  /* We ran out of memory.  We will simply fail this
> -	     call but don't undo anything we did so far.  The
> -	     application will crash or be terminated anyway very
> -	     soon.  */
> -
> -	  /* We have to do this since some entries in the dtv
> -	     slotinfo array might already point to this
> -	     generation.  */
> -	  ++GL(dl_tls_generation);
> -
> +	  /* We ran out of memory while resizing the dtv slotinfo list.  */
>  	  _dl_signal_error (ENOMEM, "dlopen", NULL, N_("\
>  cannot create TLS data structures"));
>  	}
>