linux-kernel - Re: [PATCH v22 12/23] LSM: Specify which LSM to display

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Message-ID: <04b4adf9-9313-7f5a-e7fe-6132e0c5fc4f@canonical.com>
Date:   Sat, 7 Nov 2020 14:05:20 -0800
From:   John Johansen <john.johansen@...onical.com>
To:     Greg KH <gregkh@...uxfoundation.org>,
        Casey Schaufler <casey@...aufler-ca.com>
Cc:     casey.schaufler@...el.com, jmorris@...ei.org,
        linux-security-module@...r.kernel.org, selinux@...r.kernel.org,
        linux-audit@...hat.com, keescook@...omium.org,
        penguin-kernel@...ove.sakura.ne.jp, paul@...l-moore.com,
        sds@...ho.nsa.gov, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org
Subject: Re: [PATCH v22 12/23] LSM: Specify which LSM to display

On 11/7/20 1:15 AM, Greg KH wrote:
> On Fri, Nov 06, 2020 at 04:20:43PM -0800, Casey Schaufler wrote:
>> On 11/5/2020 1:22 AM, Greg KH wrote:
>>> On Wed, Nov 04, 2020 at 03:41:03PM -0800, Casey Schaufler wrote:
>>>> Create a new entry "display" in the procfs attr directory for
>>>> controlling which LSM security information is displayed for a
>>>> process. A process can only read or write its own display value.
>>>>
>>>> The name of an active LSM that supplies hooks for
>>>> human readable data may be written to "display" to set the
>>>> value. The name of the LSM currently in use can be read from
>>>> "display". At this point there can only be one LSM capable
>>>> of display active. A helper function lsm_task_display() is
>>>> provided to get the display slot for a task_struct.
>>>>
>>>> Setting the "display" requires that all security modules using
>>>> setprocattr hooks allow the action. Each security module is
>>>> responsible for defining its policy.
>>>>
>>>> AppArmor hook provided by John Johansen <john.johansen@...onical.com>
>>>> SELinux hook provided by Stephen Smalley <sds@...ho.nsa.gov>
>>>>
>>>> Reviewed-by: Kees Cook <keescook@...omium.org>
>>>> Acked-by: Stephen Smalley <sds@...ho.nsa.gov>
>>>> Acked-by: Paul Moore <paul@...l-moore.com>
>>>> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
>>>> Cc: linux-api@...r.kernel.org
>>>> ---
>>>>  fs/proc/base.c                       |   1 +
>>>>  include/linux/lsm_hooks.h            |  17 +++
>>>>  security/apparmor/include/apparmor.h |   3 +-
>>>>  security/apparmor/lsm.c              |  32 +++++
>>>>  security/security.c                  | 169 ++++++++++++++++++++++++---
>>>>  security/selinux/hooks.c             |  11 ++
>>>>  security/selinux/include/classmap.h  |   2 +-
>>>>  security/smack/smack_lsm.c           |   7 ++
>>>>  8 files changed, 223 insertions(+), 19 deletions(-)
>>>>
>>>> diff --git a/fs/proc/base.c b/fs/proc/base.c
>>>> index 0f707003dda5..7432f24f0132 100644
>>>> --- a/fs/proc/base.c
>>>> +++ b/fs/proc/base.c
>>>> @@ -2806,6 +2806,7 @@ static const struct pid_entry attr_dir_stuff[] = {
>>>>  	ATTR(NULL, "fscreate",		0666),
>>>>  	ATTR(NULL, "keycreate",		0666),
>>>>  	ATTR(NULL, "sockcreate",	0666),
>>>> +	ATTR(NULL, "display",		0666),
>>> That's a vague name, any chance it can be more descriptive?
>>
>> Sure. How about lsm_display, or display_lsm? I wouldn't say that
>> any of the files in /proc/*/attr have especially descriptive names,
>> but that's hardly an excuse.
> 
> I still don't understand what "display" means in this context.  Perhaps

its the LSM thats context is being displayed on the shared interface,
ie. /proc/*/attr/*

thinking about it more owner or even interface_owner might be a better
name


> documentation will help clear it up?
> 

yeah this needs documented.

> thanks,
> 
> greg k-h
>