Re: [PATCH] proc: allow restricting /proc/pid/mem writes

From: Kees Cook <keescook@chromium.org>
To: Doug Anderson <dianders@chromium.org>
Cc: Adrian Ratiu <adrian.ratiu@collabora.com>,
	jannh@google.com, linux-security-module@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	kernel@collabora.com, Guenter Roeck <groeck@chromium.org>,
	Mike Frysinger <vapier@chromium.org>,
	linux-hardening@vger.kernel.org
Subject: Re: [PATCH] proc: allow restricting /proc/pid/mem writes
Date: Mon, 26 Feb 2024 16:53:00 -0800	[thread overview]
Message-ID: <202402261650.DE0601F01@keescook> (raw)
In-Reply-To: <CAD=FV=Vh7Ctaj6N_k9gdkrqpb687zJqQN19qTZXMyDw6TujvLQ@mail.gmail.com>

On Mon, Feb 26, 2024 at 02:37:29PM -0800, Doug Anderson wrote:
> Hi,
> 
> On Mon, Feb 26, 2024 at 2:33 PM Adrian Ratiu <adrian.ratiu@collabora.com> wrote:
> >
> > > > [...]
> > > > +config SECURITY_PROC_MEM_RESTRICT_WRITES
> > >
> > > Instead of a build-time CONFIG, I'd prefer a boot-time config (or a
> > > sysctl, but that's be harder given the perms). That this is selectable
> > > by distro users, etc, and they don't need to rebuild their kernel to
> > > benefit from it.
> >
> > Ack, I'll implement a cmdline arg in v2.
> 
> Any objections to doing both? Have a CONFIG option for a default and a
> cmdline to override it? This way if a distro wants to restrict writes
> by default then don't need to jam more stuff into the kernel command
> line.

For an example, take a look at randomize_kstack_offset and
CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.

-- 
Kees Cook