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>

3 files changed, 86 insertions, 41 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)
diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
index f03667213ea8..5b92c0219207 100644
--- a/security/selinux/ss/policydb.c
+++ b/security/selinux/ss/policydb.c
@@ -177,6 +177,21 @@ out_free_role:
         goto out;
 }
 
+static u32 rangetr_hash(struct hashtab *h, const void *k)
+{
+        const struct range_trans *key = k;
+        return (key->source_type + (key->target_type << 3) +
+                (key->target_class << 5)) & (h->size - 1);
+}
+
+static int rangetr_cmp(struct hashtab *h, const void *k1, const void *k2)
+{
+        const struct range_trans *key1 = k1, *key2 = k2;
+        return (key1->source_type != key2->source_type ||
+                key1->target_type != key2->target_type ||
+                key1->target_class != key2->target_class);
+}
+
 /*
  * Initialize a policy database structure.
  */
@@ -204,6 +219,10 @@ static int policydb_init(struct policydb *p)
         if (rc)
                 goto out_free_symtab;
 
+        p->range_tr = hashtab_create(rangetr_hash, rangetr_cmp, 256);
+        if (!p->range_tr)
+                goto out_free_symtab;
+
         ebitmap_init(&p->policycaps);
         ebitmap_init(&p->permissive_map);
 
@@ -408,6 +427,20 @@ static void symtab_hash_eval(struct symtab *s)
                        info.slots_used, h->size, info.max_chain_len);
         }
 }
+
+static void rangetr_hash_eval(struct hashtab *h)
+{
+        struct hashtab_info info;
+
+        hashtab_stat(h, &info);
+        printk(KERN_DEBUG "SELinux: rangetr:  %d entries and %d/%d buckets used, "
+               "longest chain length %d\n", h->nel,
+               info.slots_used, h->size, info.max_chain_len);
+}
+#else
+static inline void rangetr_hash_eval(struct hashtab *h)
+{
+}
 #endif
 
 /*
@@ -612,6 +645,17 @@ static int (*destroy_f[SYM_NUM]) (void *key, void *datum, void *datap) =
         cat_destroy,
 };
 
+static int range_tr_destroy(void *key, void *datum, void *p)
+{
+        struct mls_range *rt = datum;
+        kfree(key);
+        ebitmap_destroy(&rt->level[0].cat);
+        ebitmap_destroy(&rt->level[1].cat);
+        kfree(datum);
+        cond_resched();
+        return 0;
+}
+
 static void ocontext_destroy(struct ocontext *c, int i)
 {
         context_destroy(&c->context[0]);
@@ -632,7 +676,6 @@ void policydb_destroy(struct policydb *p)
         int i;
         struct role_allow *ra, *lra = NULL;
         struct role_trans *tr, *ltr = NULL;
-        struct range_trans *rt, *lrt = NULL;
 
         for (i = 0; i < SYM_NUM; i++) {
                 cond_resched();
@@ -693,20 +736,8 @@ void policydb_destroy(struct policydb *p)
         }
         kfree(lra);
 
-        for (rt = p->range_tr; rt; rt = rt->next) {
-                cond_resched();
-                if (lrt) {
-                        ebitmap_destroy(&lrt->target_range.level[0].cat);
-                        ebitmap_destroy(&lrt->target_range.level[1].cat);
-                        kfree(lrt);
-                }
-                lrt = rt;
-        }
-        if (lrt) {
-                ebitmap_destroy(&lrt->target_range.level[0].cat);
-                ebitmap_destroy(&lrt->target_range.level[1].cat);
-                kfree(lrt);
-        }
+        hashtab_map(p->range_tr, range_tr_destroy, NULL);
+        hashtab_destroy(p->range_tr);
 
         if (p->type_attr_map) {
                 for (i = 0; i < p->p_types.nprim; i++)
@@ -1689,7 +1720,8 @@ int policydb_read(struct policydb *p, void *fp)
         u32 len, len2, config, nprim, nel, nel2;
         char *policydb_str;
         struct policydb_compat_info *info;
-        struct range_trans *rt, *lrt;
+        struct range_trans *rt;
+        struct mls_range *r;
 
         config = 0;
 
@@ -2122,44 +2154,61 @@ int policydb_read(struct policydb *p, void *fp)
                 if (rc < 0)
                         goto bad;
                 nel = le32_to_cpu(buf[0]);
-                lrt = NULL;
                 for (i = 0; i < nel; i++) {
                         rt = kzalloc(sizeof(*rt), GFP_KERNEL);
                         if (!rt) {
                                 rc = -ENOMEM;
                                 goto bad;
                         }
-                        if (lrt)
-                                lrt->next = rt;
-                        else
-                                p->range_tr = rt;
                         rc = next_entry(buf, fp, (sizeof(u32) * 2));
-                        if (rc < 0)
+                        if (rc < 0) {
+                                kfree(rt);
                                 goto bad;
+                        }
                         rt->source_type = le32_to_cpu(buf[0]);
                         rt->target_type = le32_to_cpu(buf[1]);
                         if (new_rangetr) {
                                 rc = next_entry(buf, fp, sizeof(u32));
-                                if (rc < 0)
+                                if (rc < 0) {
+                                        kfree(rt);
                                         goto bad;
+                                }
                                 rt->target_class = le32_to_cpu(buf[0]);
                         } else
                                 rt->target_class = p->process_class;
                         if (!policydb_type_isvalid(p, rt->source_type) ||
                             !policydb_type_isvalid(p, rt->target_type) ||
                             !policydb_class_isvalid(p, rt->target_class)) {
+                                kfree(rt);
                                 rc = -EINVAL;
                                 goto bad;
                         }
-                        rc = mls_read_range_helper(&rt->target_range, fp);
-                        if (rc)
+                        r = kzalloc(sizeof(*r), GFP_KERNEL);
+                        if (!r) {
+                                kfree(rt);
+                                rc = -ENOMEM;
                                 goto bad;
-                        if (!mls_range_isvalid(p, &rt->target_range)) {
+                        }
+                        rc = mls_read_range_helper(r, fp);
+                        if (rc) {
+                                kfree(rt);
+                                kfree(r);
+                                goto bad;
+                        }
+                        if (!mls_range_isvalid(p, r)) {
                                 printk(KERN_WARNING "SELinux:  rangetrans:  invalid range\n");
+                                kfree(rt);
+                                kfree(r);
+                                goto bad;
+                        }
+                        rc = hashtab_insert(p->range_tr, rt, r);
+                        if (rc) {
+                                kfree(rt);
+                                kfree(r);
                                 goto bad;
                         }
-                        lrt = rt;
                 }
+                rangetr_hash_eval(p->range_tr);
         }
 
         p->type_attr_map = kmalloc(p->p_types.nprim*sizeof(struct ebitmap), GFP_KERNEL);
diff --git a/security/selinux/ss/policydb.h b/security/selinux/ss/policydb.h
index cdcc5700946f..193736b64de8 100644
--- a/security/selinux/ss/policydb.h
+++ b/security/selinux/ss/policydb.h
@@ -113,8 +113,6 @@ struct range_trans {
         u32 source_type;
         u32 target_type;
         u32 target_class;
-        struct mls_range target_range;
-        struct range_trans *next;
 };
 
 /* Boolean data type */
@@ -240,8 +238,8 @@ struct policydb {
            fixed labeling behavior. */
         struct genfs *genfs;
 
-        /* range transitions */
-        struct range_trans *range_tr;
+        /* range transitions table (range_trans_key -> mls_range) */
+        struct hashtab *range_tr;
 
         /* type -> attribute reverse mapping */
         struct ebitmap *type_attr_map;