[Bug dynamic-link/31076] Extra struct vm_area_struct with ---p created when PAGE_SIZE < max-page-size

["fweimer at redhat dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=31076

--- Comment #10 from Florian Weimer <fweimer at redhat dot com> ---
(In reply to Adhemerval Zanella from comment #9)
> (In reply to Florian Weimer from comment #8)
> > (In reply to Adhemerval Zanella from comment #7)
> > > So the mprotect is essentially a hardening feature, assuming that the
> > > dynamic object padding/holes might contain gadgets.  It still does not
> > > happen for loader and main program itself, since normally they would be
> > > mapped by the kernel and its does do anything with holes,
> > 
> > There's no expectation that these are contiguous in memory, yes. Such an
> > expectation exists for shared objects loaded by glibc.
> 
> Right, but my point is if this is a hardening feature that glibc aims to
> provide it does not help if the kernel still does not provide it for the
> loader (if this is built with a different page size) and the main program
> itself. Should we push for kernel to implement a similar handling?

The kernel effectively implements the munmap behavior, I think. It creates
unmapped holes, not PROT_MEM reserved holes.

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