Re: [kernel-hardening] Re: [PATCH v3 3/3] SROP mitigation: Add sysctl to disable SROP protection.

[Andy Lutomirski]

On Wed, Mar 9, 2016 at 10:36 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> On Tue, Mar 8, 2016 at 1:00 PM, One Thousand Gnomes
> <gnomes@xxxxxxxxxxxxxxxxxxx> wrote:
>> On Tue,  8 Mar 2016 13:47:55 -0700
>> Scott Bauer <sbauer@xxxxxxxxxxxx> wrote:
>>
>>> This patch adds a sysctl argument to disable SROP protection.
>>
>> Shouldn't it be a sysctl to enable it irrevocably, otherwise if I have DAC
>> capability I can turn off SROP and attack something to get to higher
>> capability levels ?
>>
>> (The way almost all distros are set up its kind of academic but for a
>> properly secured system it might matter).
>
> Perhaps use proc_dointvec_minmax_sysadmin instead to tie changes
> strictly to CAP_SYS_ADMIN?

I don't see why this needs to be irrevocable.  If you have
CAP_SYS_ADMIN or write access to /proc or whatever, you can do much
worse things than turning off a user-level mitigation.  For example,
you can ptrace things.  Also, you're already root, so what's the
point?

--Andy