Re: [musl] vfork()-based posix_spawn() has more failure modes than fork()-based one

[Carlos O'Donell <carlos@redhat.com>]

On 5/2/22 17:25, Florian Weimer wrote:
> * Rich Felker:
> 
>> I'm trying to understand how this comes to be. The child should
>> inherit the namespaces of the parent and thus should not be in a
>> different namespace that precludes spawn. I'm guessing this is some
>> oddity where unshare doesn't affect the process itself, only its
>> children? If so, it seems like a bug that it doesn't affect the
>> process itself after execve (after unshare(1) runs your test program),
>> but that probably can't be fixed now on the Linux side for stability
>> reasons. :(
> 
> It's about fundamentally conflicting requirements.
> 
> The vDSO data mapping needs to store the time offset, so it has to be
> distinct from the original namespace.  vfork preserves the VM sharing.
> It's not possible to do both things at the same time.
> 
> unshare(CLONE_NEWTIME) should have been specified to only take effect
> after execve, when the vDSO is remapped anyway.

Can we ask some kernel developers for an opinion?

-- 
Cheers,
Carlos.