Re: [PATCH] Gerd Hoffman's move-vsyscall-into-user-address-range patch

Ingo Molnar
2006-05-16T06:47:33Z

* Rusty Russell <rusty@rustcorp.com.au> wrote:

> AFAICT we'll pay one extra TLB entry for this patch. Zach had a patch
> which left the vsyscall page at the top of memory (minus hole for
> hypervisor) and patched the ELF header at boot.

i'd suggest the solution from exec-shield (which has been there for a
long time), which also randomizes the vsyscall vma. Exploits are already
starting to use the vsyscall page (with predictable addresses) to
circumvent randomization, it provides 'interesting' instructions to act
as a syscall-functionality building block. Moving that address to
another predictable place solves the virtualization problem, but doesnt
solve the address-space randomization problem.

Ingo