Re: [PATCH] sysctl: add config to make randomize_va_space RO

[Paul Moore]

On Fri, May 5, 2023 at 11:15 AM David Hildenbrand <david@xxxxxxxxxx> wrote:
> On 05.05.23 09:46, Sam James wrote:
> > David Hildenbrand <david@xxxxxxxxxx> writes:
> >> On 04.05.23 23:30, Michael McCracken wrote:
> >>> Add config RO_RANDMAP_SYSCTL to set the mode of the randomize_va_space
> >>> sysctl to 0444 to disallow all runtime changes. This will prevent
> >>> accidental changing of this value by a root service.
> >>> The config is disabled by default to avoid surprises.

...

> If we really care, not sure what's better: maybe we want to disallow
> disabling it only in a security lockdown kernel?

If we're bringing up the idea of Lockdown, controlling access to
randomize_va_space is possible with the use of LSMs.  One could easily
remove write access to randomize_va_space, even for tasks running as
root.

(On my Rawhide system with SELinux enabled)
% ls -Z /proc/sys/kernel/randomize_va_space
system_u:object_r:proc_security_t:s0 /proc/sys/kernel/randomize_va_space

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