Re: [PATCH 3/3] x86: kernel base offset ASLR

["H. Peter Anvin" <hpa@zytor.com>]

On 04/04/2013 01:23 PM, Julien Tinnes wrote:
> On Thu, Apr 4, 2013 at 1:19 PM, Julien Tinnes <jln@google.com> wrote:
>> On Thu, Apr 4, 2013 at 1:12 PM, H. Peter Anvin <hpa@zytor.com> wrote:
>>> On 04/04/2013 01:07 PM, Kees Cook wrote:
>>>> However, the benefits of
>>>> this feature in certain environments exceed the perceived weaknesses[2].
>>>
>>> Could you clarify?
>>
>> I think privilege reduction in general, and sandboxing in particular,
>> can make KASLR even more useful. A lot of the information leaks can be
>> mitigated in the same way as attack surface and vulnerabilities can be
>> mitigated.
> 
> Case in point:
> - leaks of 64 bits kernel values to userland in compatibility
> sub-mode. Sandboxing by using seccomp-bpf can restrict a process to
> the 64-bit mode API.
> - restricting access to the syslog() system call
> 

That doesn't really speak to the value proposition.  My concern is that
we're going to spend a lot of time chasing/plugging infoleaks instead of
tackling bigger problems.

8 bits of entropy is not a lot.

	-hpa