Re: [PATCH] x86/vdso: Move vDSO to mmap region

[Kees Cook]

On Sat, Feb 10, 2024 at 01:18:35AM -0800, Kees Cook wrote:
> The vDSO (and its initial randomization) was introduced in commit
> 2aae950b21e4 ("x86_64: Add vDSO for x86-64 with gettimeofday/clock_gettime/getcpu"),
> but had very low entropy. The entropy was improved in commit
> 394f56fe4801 ("x86_64, vdso: Fix the vdso address randomization algorithm"),
> but there is still improvement to be made.
> 
> On principle there should not be executable code at a low entropy offset
> from the stack, since the stack and executable code having separate
> randomization is part of what makes ASLR stronger.
> 
> Remove the only executable code near the stack region and give the vDSO
> the same randomized base as other mmap mappings including the linker
> and other shared objects. This results in higher entropy being provided
> and there's little to no advantage in separating this from the existing
> executable code there. This is already how other architectures like
> arm64 handle the vDSO.

Thread ping. Anyone have thoughts on this? I can carry it in -next to
see if anything melts...

-- 
Kees Cook