[PATCH v6 19/20] elf: Fix runtime linker auditing on aarch64 (BZ #26643)

[Florian Weimer]

* Adhemerval Zanella:

> On 20/12/2021 18:32, Florian Weimer wrote:
>> * Adhemerval Zanella:
>> 
>>> diff --git a/elf/rtld.c b/elf/rtld.c
>>> index 29a37f51d3..1a13ae6314 100644
>>> --- a/elf/rtld.c
>>> +++ b/elf/rtld.c
>>> @@ -990,10 +990,10 @@ file=%s [%lu]; audit interface function la_version returned zero; ignored.\n",
>>>        return;
>>>      }
>>>  
>>> -  if (lav > LAV_CURRENT)
>>> +  if (lav != LAV_CURRENT)
>>>      {
>>>        _dl_debug_printf ("\
>>> -ERROR: audit interface '%s' requires version %d (maximum supported version %d); ignored.\n",
>>> +ERROR: audit interface '%s' requires version %d (current supported version %d); ignored.\n",
>>>  			name, lav, LAV_CURRENT);
>>>        unload_audit_module (dlmargs.map, original_tls_idx);
>>>        return;
>> 
>> Sorry, this is not what I had in mind.  I'd like to increase LAV_CURRENT
>> and pretend that the old and new versions have the same behavior, at
>> least as far as aarch64 is concerned.  We need not write the
>> compatibility code for the old <link.h> at this time, only if there
>> actual users out there that demand it.
>
> Do you mean to only check if lav >= LAV_CURRENT and allow old audit modules
> as well?

Yes.

> At least for aarch64 old audit modules are error-prone and potentially adds
> more subtle issues since they do not save/restore some return register that
> I don't see any real gain to keep supporting them.

I disagree.  la_objsearch alone is a significant use case, and I don't
see why it wouldn't work today.  It does not need any
architecture-specific code whatsoever.

Thanks,
Florian