selinux: convert range transition list to a hashtab

Per https://bugzilla.redhat.com/show_bug.cgi?id=548145
there are sufficient range transition rules in modern (Fedora) policy to
make mls_compute_sid a significant factor on the shmem file setup path
due to the length of the range_tr list.  Replace the simple range_tr
list with a hashtab inside the security server to help mitigate this
problem.

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

1 files changed, 8 insertions, 10 deletions

diff --git a/security/selinux/ss/mls.c b/security/selinux/ss/mls.c
index e6654b543aed..443ae7370144 100644
--- a/security/selinux/ss/mls.c
+++ b/security/selinux/ss/mls.c
@@ -513,7 +513,8 @@ int mls_compute_sid(struct context *scontext,
                     u32 specified,
                     struct context *newcontext)
 {
-        struct range_trans *rtr;
+        struct range_trans rtr;
+        struct mls_range *r;
 
         if (!selinux_mls_enabled)
                 return 0;
@@ -521,15 +522,12 @@ int mls_compute_sid(struct context *scontext,
         switch (specified) {
         case AVTAB_TRANSITION:
                 /* Look for a range transition rule. */
-                for (rtr = policydb.range_tr; rtr; rtr = rtr->next) {
-                        if (rtr->source_type == scontext->type &&
-                            rtr->target_type == tcontext->type &&
-                            rtr->target_class == tclass) {
-                                /* Set the range from the rule */
-                                return mls_range_set(newcontext,
-                                                     &rtr->target_range);
-                        }
-                }
+                rtr.source_type = scontext->type;
+                rtr.target_type = tcontext->type;
+                rtr.target_class = tclass;
+                r = hashtab_search(policydb.range_tr, &rtr);
+                if (r)
+                        return mls_range_set(newcontext, r);
                 /* Fallthrough */
         case AVTAB_CHANGE:
                 if (tclass == policydb.process_class)