From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5BEF2175A62; Tue, 19 May 2026 00:31:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779150681; cv=none; b=ljPVZBaOHVF84yx7bifvpuPGr/Ixo++U2xgRRjgnm+BpBPeE8ogV+0WgLYF+9nRRBm+T6CbnPv4lwtVURrJ5qxyyVFqUE2gWfbifgrbPlHbS+Sc+RIj5Tio1dG4p4HhLX2/4MWuWlxm+bT3Mme6+NN8FVXirtaQVIcq0VsNpyB4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779150681; c=relaxed/simple; bh=ugd6OYM13lrewg3RCk4+7fzTmJDDbeyPBjaxq5puXrE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=jVg9OZcmORizfr70XSO/6dl355RpJNe4aA83yQPVxH2qlhb35dsJ3O821h7uViBMAXZ9JM2A52HfOHBX4bOiADedWiL6vt4Pib52eHX3/uF7Y2qDISqztBXhjtbhuOFjwAgA5bAjrBShviFF6ja6k482afikTbYuU56aFFSm7Cw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Q8p4I1CK; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Q8p4I1CK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DFBB3C2BCB8; Tue, 19 May 2026 00:31:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1779150681; bh=ugd6OYM13lrewg3RCk4+7fzTmJDDbeyPBjaxq5puXrE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Q8p4I1CKRGuATsYVFUBxxv418bj8L8Be74qaPtvPea3MG6MkN250M3FXNdfeLoiN9 EuJkQhvk1vEdmYZ/En+uT2xo6nEhtDl48zDtZTX8RxCeIvwHmJCWU/c7Kn76RYyUiz evDpqldZ59lIB2BC3SQ49+P65rq1jtRa4LXVUFgTZovvMw2hSr/J86xgAybVI73gI1 drFqze+7Aib4PVPzcyQyWJgSJKE+Igk58GGKyLwoiJZ8qbISBoEt7pqXgYe2WMx5Fz nNaeErOkSNp0y9yCKwOmHhxtMSYnUtFM0rxyVZSykPHyYfzxo6MsCi7kR0e64KcBP7 cI5xevaMAJILw== Date: Mon, 18 May 2026 20:31:19 -0400 From: Sasha Levin To: Paul Moore Cc: Song Liu , corbet@lwn.net, akpm@linux-foundation.org, skhan@linuxfoundation.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, gregkh@linuxfoundation.org, linux-security-module@vger.kernel.org Subject: Re: [PATCH] killswitch: add per-function short-circuit mitigation primitive Message-ID: References: <20260507070547.2268452-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: On Mon, May 18, 2026 at 05:29:32PM -0400, Paul Moore wrote: >>From my perspective there are two different issues here: should >killswitch be a LSM, and should killswitch leverage kprobes to be able >to "kill" security related symbols. After all, are we okay with >killswitch killing capable() and friends? killswitch doesn't do it on it's own. It may be instructed by root to do that, at which point that is root's problem. >In my opinion, making killswitch an LSM is more of a procedural item >that deals with how we view a capability like killswitch. I >personally view killswitch as somewhat similar to Lockdown, which is >why I made the suggestion. Maybe I'm not all that familiar with LSMs, but we would need to be able to stop "random" code paths from executing, and I don't think we can create LSM hooks at that granularity, no? >The use of kprobes, while an interesting idea, presents problems as >allowing any kernel symbol to be killed introduces the potential for >security regressions. As a reminder, some LSMs, as well as other >kernel subsystems, have mechanisms in place to restrict root and/or >enforce one-way configuration locks; while many people equate "root" >with full control, in many cases today that is not strictly correct. killswitch "complies" with lockdown. Is there a different scenario which we should be blocking? >Yes, kprobes have been around for some time, this is not a new >problem, but killswitch makes it far more convenient and accessible to >do dangerous things with kprobes. If killswitch makes it past the RFC >stage without any significant changes to its kill mechanism, we may >need to start considering more liberal usage of NOKPROBE_SYMBOL() >which I think would be an unfortunate casualty. Why? If I don't really mind the security impact, I want to be able to have a killswitch-like interface on my systems. If an attacker is in my systems, killswitch is the least of my concerns I think. If you are security concious, just don't enable CONFIG_KILLSWITCH? -- Thanks, Sasha