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

[Greg KH]

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?

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

thanks,

greg k-h