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Tue, 13 May 2025 04:10:55 -0700 (PDT) Received: from [192.168.0.20] ([212.21.133.65]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ad24121e992sm496096766b.14.2025.05.13.04.10.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 13 May 2025 04:10:55 -0700 (PDT) Message-ID: Date: Tue, 13 May 2025 14:10:54 +0300 Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/2] Allow individual features to be locked down To: Paul Moore , Dan Williams Cc: linux-security-module@vger.kernel.org, serge@hallyn.com, kees@kernel.org, linux-kernel@vger.kernel.org, kirill.shutemov@linux.intel.com, linux-coco@lists.linux.dev References: <20250321102422.640271-1-nik.borisov@suse.com> <67f69600ed221_71fe2946f@dwillia2-xfh.jf.intel.com.notmuch> <68226ad551afd_29032945b@dwillia2-xfh.jf.intel.com.notmuch> From: Nikolay Borisov Content-Language: en-US Autocrypt: addr=nik.borisov@suse.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 5/13/25 01:01, Paul Moore wrote: > On Mon, May 12, 2025 at 5:41 PM Dan Williams wrote: >> Dan Williams wrote: >>> Paul Moore wrote: >>>> On Fri, Mar 21, 2025 at 6:24 AM Nikolay Borisov wrote: >>>>> >>>>> This simple change allows usecases where someone might want to lock only specific >>>>> feature at a finer granularity than integrity/confidentiality levels allows. >>>>> The first likely user of this is the CoCo subsystem where certain features will be >>>>> disabled. >>>>> >>>>> Nikolay Borisov (2): >>>>> lockdown: Switch implementation to using bitmap >>>>> lockdown/kunit: Introduce kunit tests >>>> >>>> Hi Nikolay, >>>> >>>> Thanks for the patches! With the merge window opening in a few days, >>>> it is too late to consider this for the upcoming merge window so >>>> realistically this patchset is two weeks out and I'm hopeful we'll >>>> have a dedicated Lockdown maintainer by then so I'm going to defer the >>>> ultimate decision on acceptance to them. >>> >>> The patches in this thread proposed to selectively disable /dev/mem >>> independent of all the other lockdown mitigations. That goal can be >>> achieved with more precision with this proposed patch: >>> >>> http://lore.kernel.org/67f5b75c37143_71fe2949b@dwillia2-xfh.jf.intel.com.notmuch >> >> Just wanted to circle back here and repair the damage I caused to the >> momentum of this "lockdown feature bitmap" proposal. It turns out that >> devmem maintainers are not looking to add yet more arch-specific hacks >> [1]. >> >> "Restricting /dev/mem further is a good idea, but it would be nice >> if that could be done without adding yet another special case." >> >> security_locked_down() is already plumbed into all the places that >> confidential VMs may need to manage userspace access to confidential / >> private memory. >> >> I considered registering a new "coco-LSM" to hook >> security_locked_down(), but that immediately raises the next question of >> how does userspace discover what is currently locked_down. So just teach >> the native lockdown LSM how to be more fine-grained rather than >> complicate the situation with a new LSM. > > Historically Linus has bristled at LSMs with alternative > security_locked_down() implementations/security-models, therefore I'd > probably give a nod to refining the existing Lockdown approach over a > new LSM. > > Related update, there are new Lockdown maintainers coming, there is > just an issue of sorting out some email addresses first. Hopefully > we'll see something on-list soon. > So I guess the most sensible way forward will be to resend these 2 patches after the new maintainer has been officially announced?