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

[Greg KH]

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@xxxxxxxxxxxxx>
> >> SELinux hook provided by Stephen Smalley <sds@xxxxxxxxxxxxx>
> >>
> >> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
> >> Acked-by: Stephen Smalley <sds@xxxxxxxxxxxxx>
> >> Acked-by: Paul Moore <paul@xxxxxxxxxxxxxx>
> >> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
> >> Cc: linux-api@xxxxxxxxxxxxxxx
> >> ---
> >>  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
documentation will help clear it up?

thanks,

greg k-h