linux-hardening - Re: [PATCH] proc: add config to block FOLL

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Message-ID: <202407171017.A0930117@keescook>
Date: Wed, 17 Jul 2024 10:22:58 -0700
From: Kees Cook <kees@...nel.org>
To: Adrian Ratiu <adrian.ratiu@...labora.com>
Cc: linux-fsdevel@...r.kernel.org, linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
	kernel@...labora.com, gbiv@...gle.com, inglorion@...gle.com,
	ajordanr@...gle.com, Doug Anderson <dianders@...omium.org>,
	Jeff Xu <jeffxu@...gle.com>, Jann Horn <jannh@...gle.com>,
	Christian Brauner <brauner@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] proc: add config to block FOLL_FORCE in mem writes

On Wed, Jul 17, 2024 at 02:13:58PM +0300, Adrian Ratiu wrote:
> This simple Kconfig option removes the FOLL_FORCE flag from
> procfs write calls because it can be abused.

For this to be available for general distros, I still want to have a
bootparam to control this, otherwise this mitigation will never see much
testing as most kernel deployments don't build their own kernels. A
simple __ro_after_init variable can be used.

In the future if folks want a more flexible version, we could make this
a one-way per-process flag, like no_new_privs.

-- 
Kees Cook