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

John Johansen
2020-11-09T22:47:18Z

On 11/9/20 2:28 PM, Casey Schaufler wrote:
> On 11/7/2020 2:05 PM, John Johansen wrote:
>> 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@canonical.com>
>>>>>> SELinux hook provided by Stephen Smalley <sds@tycho.nsa.gov>
>>>>>>
>>>>>> Reviewed-by: Kees Cook <keescook@chromium.org>
>>>>>> Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
>>>>>> Acked-by: Paul Moore <paul@paul-moore.com>
>>>>>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>>>>>> Cc: linux-api@vger.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
>
> I was hoping for a single word, but I see how something more descriptive
> might be in order. How about "lsm_of_current"? Or "lsm_of_dot_slash_current",
> if you want to be pedantic. "format_of_current" isn't quite accurate, but
> might be easier for some people to understand. Maybe "interface_owning_lsm".
>
> /proc/*/attr/display answers the question "Which LSM is providing the data
> I see if I look in /proc/*/attr/current, prev or exec or if that process uses
> SO_PEERSEC".
>

lsm_of_current or interface_lsm or interface_owning_lsm all wfm

>
>>> documentation will help clear it up?
>>>
>> yeah this needs documented.
>
> Agreed. I've noticed that nothing in /proc/*/attr seems documented
> in an orderly (documentation/ABI) fashion. I will have to fix some of
> that for a description of /proc/*/attr/whatever_it_ends_up_getting_called
> to make sense. Working on it.
>
>>> thanks,
>>>
>>> greg k-h
>>>
>