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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id q15-20020a170902a3cf00b0017c6959724asm7613471plb.258.2022.10.17.22.55.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Oct 2022 22:55:31 -0700 (PDT) Date: Mon, 17 Oct 2022 22:55:30 -0700 From: Kees Cook To: Paul Moore Cc: Casey Schaufler , Nicolas Iooss , =?iso-8859-1?Q?Micka=EBl_Sala=FCn?= , James Morris , "Serge E . Hallyn" , linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, =?iso-8859-1?Q?Micka=EBl_Sala=FCn?= Subject: Re: [PATCH v3 1/1] security: Add CONFIG_LSM_AUTO to handle default LSM stack ordering Message-ID: <202210172153.C65BF23D5E@keescook> References: <20210222150608.808146-1-mic@digikod.net> <20210222150608.808146-2-mic@digikod.net> <51725b44-bc40-0205-8583-285d3b35b5ca@schaufler-ca.com> <7b67163a-9de1-313f-5b5a-8c720cef9b73@schaufler-ca.com> <3b97e25b-303c-d732-3e5d-f1b1a446e090@schaufler-ca.com> <202210171111.21E3983165@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 17, 2022 at 09:45:21PM -0400, Paul Moore wrote: > The code sorta cares about ordering, at least to the extent that the > LSMs will behave differently depending on the ordering, e.g. a LSM Right -- this is why I've been so uncomfortable with allowing arbitrarily reordering of the LSM list from lsm=. There are orderings we know work, and others may have undesirable side-effects. I'd much rather the kernel be specific about the order. > I personally would like to preserve the existing concept where "built" > does *not* equate to "enabled" by default. Yup, understood. I didn't think I was going to win over anyone on that one, but figured I'd just point it out again. ;) > > I *still* think there should be a way to leave ordering alone and have > > separate enable/disable control. > > My current opinion is that enabling a LSM and specifying its place in > an ordered list are one in the same. The way LSM stacking as > currently done almost requires the ability to specify an order if an > admin is trying to meet an security relevant operation visibility > goal. As in an admin wants to see selinux rejections instead of loadpin rejections for a blocked module loading? Hmmm. Is this a realistic need? > We can have defaults, like we do know, but I'm in no hurry to remove > the ability to allow admins to change the ordering at boot time. My concern is with new LSMs vs the build system. A system builder will be prompted for a new CONFIG_SECURITY_SHINY, but won't be prompted about making changes to CONFIG_LSM to include it. Even booting with "lsm.debug" isn't entirely helpful to helping someone construct the "lsm=" option they actually want... I guess I can fix that part, at least. :) -- Kees Cook