linux-kernel - Re: [PATCH v2 0/6] LSM: Replace secctx/len pairs with lsm

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Message-ID: <88bc4a97-562d-4cb2-ac12-a7549cb20583@schaufler-ca.com>
Date: Mon, 14 Oct 2024 14:54:24 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: "Serge E. Hallyn" <serge@...lyn.com>
Cc: paul@...l-moore.com, linux-security-module@...r.kernel.org,
 jmorris@...ei.org, keescook@...omium.org, john.johansen@...onical.com,
 penguin-kernel@...ove.sakura.ne.jp, stephen.smalley.work@...il.com,
 linux-kernel@...r.kernel.org, selinux@...r.kernel.org, mic@...ikod.net,
 Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH v2 0/6] LSM: Replace secctx/len pairs with lsm_context

On 10/14/2024 2:35 PM, Serge E. Hallyn wrote:
> On Mon, Oct 14, 2024 at 04:29:37PM -0500, Serge E. Hallyn wrote:
>> On Mon, Oct 14, 2024 at 08:14:44AM -0700, Casey Schaufler wrote:
>>> LSM: Replace secctx/len pairs with lsm_context
>>>
>>> Several of the Linux Security Module (LSM) interfaces use a pair of
>>> pointers for transmitting security context data and data length. The
>>> data passed is refered to as a security context.  While all existing
>>> modules provide nul terminated strings, there is no requirement that
>>> they to so. Hence, the length is necessary.
>>>
>>> Security contexts are provided by a number of interfaces. The interface
>>> security_release_secctx() is used when the caller is finished with the
>>> data. Each of the security modules that provide security contexts manages
>>> them differently. This was safe in the past, because only one security
>>> module that provides security contexts is allowed to be active. To allow
>>> multiple active modules that use security contexts it is necessary to
>>> identify which security module created a security context. Adding a third
>>> pointer to the interfaces for the LSM identification is not appealing.
>>>
>>> A new structure, lsm_context, is created for use in these interfaces.
>>> It includes three members: the data pointer, the data length and
>>> the LSM ID of its creator. The interfaces that create contexts and
>>> security_release_secctx() now use a pointer to an lsm_context instead
>>> of a pointer pair.
>>>
>>> The changes are mostly mechanical, and some scaffolding is used within
>>> the patch set to allow for smaller individual patches.
>> Hey Casey,
>>
>> so this set is not bisectable.  Applying just patch 1 will no compile, right?
>> What is your plan for getting past that?  Squash some or all of them into one?
>> Or are you planning a wider reorg of the patches down the line, once the
>> basics of the end result are agreed upon?
> Sorry, I may have misread that.  secids make my eyes glaze over.

They make my skin crawl, and have since I first saw them circa 1986.
I would love to eradicate them, but they're like bad tattoos, showing
up in embarrassing places for which removal would be too painful.