[PATCH 1/1] NAX LSM: Add initial support support

[Igor Zhbanov]

Hi Simon,

Thanks for thorough review. Will post the corrected version soon.

> > @@ -278,11 +279,11 @@ endchoice
> >
> >  config LSM
> >       string "Ordered list of enabled LSMs"
> > -     default "landlock,lockdown,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor,bpf" if DEFAULT_SECURITY_SMACK
> > -     default "landlock,lockdown,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo,bpf" if DEFAULT_SECURITY_APPARMOR
> > -     default "landlock,lockdown,yama,loadpin,safesetid,integrity,tomoyo,bpf" if DEFAULT_SECURITY_TOMOYO
> > -     default "landlock,lockdown,yama,loadpin,safesetid,integrity,bpf" if DEFAULT_SECURITY_DAC
> > -     default "landlock,lockdown,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor,bpf"
> > +     default "nax,landlock,lockdown,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor,bpf" if DEFAULT_SECURITY_SMACK
> > +     default "nax,landlock,lockdown,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo,bpf" if DEFAULT_SECURITY_APPARMOR
> > +     default "nax,landlock,lockdown,yama,loadpin,safesetid,integrity,tomoyo,bpf" if DEFAULT_SECURITY_TOMOYO
> > +     default "nax,landlock,lockdown,yama,loadpin,safesetid,integrity,bpf" if DEFAULT_SECURITY_DAC
> > +     default "nax,landlock,lockdown,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor,bpf"
>
> I don't know the policy with regard to new LSMs, but enabling this one by default is maybe a bit violent?
> That said, considering the default mode is SECURITY_NAX_MODE_LOG, this would just log kernel messages and
> not break existing systems, so this shouldn't be a problem.

I've just oriended on landlock and lockdown. They are handled in the similar
way. But, yes, by default NAX module doesn't block anything.
If you suggest not to do that, I can remove it.

> > +__setup("nax_mode=", setup_mode);
> > +
> > +static int __init setup_quiet(char *str)
> > +{
> > +     unsigned long val;
> > +
> > +     if (!locked && !kstrtoul(str, 0, &val))
> > +             quiet = val ? 1 : 0;
>
> The order of the kernel parameters will have an impact on NAX behavior.
>
> "nax_mode=1 nax_locked=1" and "nax_locked=1 nax_mode=1" will end up with the same behavior.
> in the first case the mode is enforced, in the second case it isn't (well unless you changed
>  the kernel configuration from the default) and it can't be enabled later either.
>
> Is that desired?

Yes. The idea is that on boot you can set-up the proper options then block
further changing (especially turning the module off).
Initially it was implemented for sysctl parameters, so, you can change
something in init-scripts, then lock. Then, I've extended it to command-line
parameters.
I can ignore "locked" flag in setup_* functions to defer locking to sysctl
parsing. (Unless our command-line is glued by the bootloader from several
parts, so we want to lock it as early as possible...).

Thanks.