Re: x86/ldt: Prevent ldt inheritance on exec

[Linus Torvalds]

On Fri, Dec 8, 2017 at 12:02 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>
> The reason why this happens is that init_new_context_ldt() is called from
> init_new_context() which obviously needs to be called for both fork() and
> exec().
>
> It would be surprising if anything relies on that behaviour, so it seems to
> be safe to remove that misfeature.

Looks sane. That said, can't we separate this out into the copy_mm()
phase only?

We have "arch_dup_mmap()" that is called on fork() only, so that could
do the LDT copy from the old mm, and the actual init_new_context would
just zero it out.

Then there wouldn't be any odd "check if this is an execve" because
the copying would be done in the right place.

Hmm?

             Linus