selinux: export initial SID contexts via selinuxfs

Make the initial SID contexts accessible to userspace via selinuxfs.
An initial use of this support will be to make the unlabeled context
available to libselinux for use for invalidated userspace SIDs.

Signed-off-by: James Carter <jwcart2@tycho.nsa.gov>
Acked-by:  Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index d3698568a213..21b8318979e3 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -593,6 +593,13 @@ static int context_struct_to_string(struct context *context, char **scontext, u3
 
 #include "initial_sid_to_string.h"
 
+const char *security_get_initial_sid_context(u32 sid)
+{
+        if (unlikely(sid > SECINITSID_NUM))
+                return NULL;
+        return initial_sid_to_string[sid];
+}
+
 /**
  * security_sid_to_context - Obtain a context for a given SID.
  * @sid: security identifier, SID