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

Greg KH
2020-11-05T09:22:03Z

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?

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