linux-hardening - Re: [PATCH v5 3/6] mm/memfd: add MFD_NOEXEC_SEAL and MFD

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Date:   Tue, 6 Dec 2022 08:26:30 -0800
From:   Jeff Xu <jeffxu@...gle.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     jeffxu@...omium.org, skhan@...uxfoundation.org,
        keescook@...omium.org, akpm@...ux-foundation.org,
        dmitry.torokhov@...il.com, dverkamp@...omium.org, hughd@...gle.com,
        jorgelo@...omium.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-mm@...ck.org,
        jannh@...gle.com, linux-hardening@...r.kernel.org,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v5 3/6] mm/memfd: add MFD_NOEXEC_SEAL and MFD_EXEC

On Tue, Dec 6, 2022 at 8:04 AM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Tue, Dec 06, 2022 at 03:23:55PM +0000, jeffxu@...omium.org wrote:
> > --- a/kernel/pid_namespace.c
> > +++ b/kernel/pid_namespace.c
> > @@ -110,6 +110,11 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns
> >       ns->ucounts = ucounts;
> >       ns->pid_allocated = PIDNS_ADDING;
> >
> > +#if defined(CONFIG_SYSCTL) && defined(CONFIG_MEMFD_CREATE)
> > +     ns->memfd_noexec_scope =
> > +             task_active_pid_ns(current)->memfd_noexec_scope;
> > +#endif
>
> .c files should never have #if in them.  Can't you put this in a .h file
> properly so that this does not get really messy over time?
>
>
Thanks for reviewing.
It seems to me that checking for CONFIG_XXX is  common in c code in
kernel/ path.
Do you have a sample code pattern (link/function) that I can follow?

Thanks
Jeff

>
> > +
> >       return ns;
> >
> >  out_free_idr:
> > @@ -255,6 +260,45 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
> >       return;
> >  }
> >
> > +#if defined(CONFIG_SYSCTL) && defined(CONFIG_MEMFD_CREATE)
>
> Same here.
>
> thanks,
>
> greg k-h