Re: [PATCH 1/5] elf: Fix audit regression

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

On 07/07/2021 17:07, Florian Weimer via Libc-alpha wrote:
> * Florian Weimer:
> 
>> * Andreas Schwab:
>>
>>> On Jul 07 2021, Adhemerval Zanella via Libc-alpha wrote:
>>>
>>>> @@ -771,7 +771,7 @@ dl_open_worker (void *a)
>>>>      {
>>>>        struct link_map *libc_map = GL(dl_ns)[args->nsid].libc_map;
>>>>  #ifdef SHARED
>>>> -      bool initial = libc_map->l_ns == LM_ID_BASE;
>>>> +      bool initial = libc_map != NULL ? libc_map->l_ns == LM_ID_BASE : false;
>>>
>>>          bool initial = libc_map != NULL && libc_map->l_ns == LM_ID_BASE;
>>
>> True … but:
>>
>> This is only used by dlopen/dlmopen, right?  And even if dlmopen is
>> called from an auditor (to load another libc), it is *never* the initial
>> libc in the base namespace.
>>
>> The actual base namespace libc is handled in elf/rtld.c:dl_main:
>>
>>   /* Relocation is complete.  Perform early libc initialization.  This
>>      is the initial libc, even if audit modules have been loaded with
>>      other libcs.  */
>>   _dl_call_libc_early_init (GL(dl_ns)[LM_ID_BASE].libc_map, true);
>>
>> And I think the dl_open_worker should mirror that and just do:
>>
>>   if (!args->libc_already_loaded)
>>     /* This is never the initial libc because it has been loaded via
>>        dlmopen.  */
>>     _dl_call_libc_early_init (libc_map, false);
> 
> Eh, or rather:
> 
>   if (!args->libc_already_loaded)
>     {
>       struct link_map *libc_map = GL(dl_ns)[args->nsid].libc_map;
>       /* This is never the initial libc because it has been loaded via
>          dlmopen.  */
>       _dl_call_libc_early_init (libc_map, false);
>     }
> 
> (_dl_call_libc_early_init checks for a null link map.)

I think this make sense and it also simplifes the code a bit. I will
adjust the patch.