[PATCH] elf: Make non-executable stack disable by default

[Florian Weimer]

* Adhemerval Zanella Netto:

> On 13/06/24 02:55, Florian Weimer wrote:
>> * Adhemerval Zanella:
>> 
>>> +* A new tunable, glibc.rtld.noexecstack, can be used to enable executable
>>> +  stacks from either main program, dependencies, or dynamically loadeed
>>> +  libraries.  The default is to disable executable stacks.
>> 
>> Typo: “load[e]d”
>> 
>> Should we refuse to enable executable stack on dlopen by default?  
>
> That's the idea of this change.
>
>> And
>> only enable it if the initial set of objects request executable stack?
>
> No, I think we should only allow it if user explicit enables it with the
> tunable.  Non-executable stack should not be allowed by silent dlopen a
> bogus shared library.

I think dlopen and initial executable are different scenarios.  It's
much easier to disable dlopen support by default if we keep the initial
execstack support present.

Thanks,
Florian