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

[Casey Schaufler <casey@schaufler-ca.com>]

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.

> And where is the Documentation/ABI/ entries for all of this, how does
> userspace know what these things are, and how to use them?

I'll add ABI descriptions and move some of the lsm.rst up from where it
is later in the patchset.

>
> thanks,
>
> greg k-h