selinux: reduce the use of hard-coded hash sizes

Instead allocate hash tables with just the right size based on the
actual number of elements (which is almost always known beforehand, we
just need to defer the hashtab allocation to the right time). The only
case when we don't know the size (with the current policy format) is the
new filename transitions hashtable. Here I just left the existing value.

After this patch, the time to load Fedora policy on x86_64 decreases
from 790 ms to 167 ms. If the unconfined module is removed, it decreases
from 750 ms to 122 ms. It is also likely that other operations are going
to be faster, mainly string_to_context_struct() or mls_compute_sid(),
but I didn't try to quantify that.

The memory usage of all hash table arrays increases from ~58 KB to
~163 KB (with Fedora policy on x86_64).

Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>

diff --git a/security/selinux/ss/hashtab.c b/security/selinux/ss/hashtab.c
index ebfdaa31ee326906da7826011546dd3cdc2f2b66..883f19d32c28458600332d1e02fb9907337c8d84 100644 (file)
--- a/security/selinux/ss/hashtab.c
+++ b/security/selinux/ss/hashtab.c
@@ -12,12 +12,29 @@
 
 static struct kmem_cache *hashtab_node_cachep;
 
+/*
+ * Here we simply round the number of elements up to the nearest power of two.
+ * I tried also other options like rouding down or rounding to the closest
+ * power of two (up or down based on which is closer), but I was unable to
+ * find any significant difference in lookup/insert performance that would
+ * justify switching to a different (less intuitive) formula. It could be that
+ * a different formula is actually more optimal, but any future changes here
+ * should be supported with performance/memory usage data.
+ *
+ * The total memory used by the htable arrays (only) with Fedora policy loaded
+ * is approximately 163 KB at the time of writing.
+ */
+static u32 hashtab_compute_size(u32 nel)
+{
+       return nel == 0 ? 0 : roundup_pow_of_two(nel);
+}
+
 struct hashtab *hashtab_create(u32 (*hash_value)(struct hashtab *h, const void *key),
                               int (*keycmp)(struct hashtab *h, const void *key1, const void *key2),
-                              u32 size)
+                              u32 nel_hint)
 {
        struct hashtab *p;
-       u32 i;
+       u32 i, size = hashtab_compute_size(nel_hint);
 
        p = kzalloc(sizeof(*p), GFP_KERNEL);
        if (!p)
@@ -27,6 +44,9 @@ struct hashtab *hashtab_create(u32 (*hash_value)(struct hashtab *h, const void *
        p->nel = 0;
        p->hash_value = hash_value;
        p->keycmp = keycmp;
+       if (!size)
+               return p;
+
        p->htable = kmalloc_array(size, sizeof(*p->htable), GFP_KERNEL);
        if (!p->htable) {
                kfree(p);
@@ -46,7 +66,7 @@ int hashtab_insert(struct hashtab *h, void *key, void *datum)
 
        cond_resched();
 
-       if (!h || h->nel == HASHTAB_MAX_NODES)
+       if (!h || !h->size || h->nel == HASHTAB_MAX_NODES)
                return -EINVAL;
 
        hvalue = h->hash_value(h, key);
@@ -82,7 +102,7 @@ void *hashtab_search(struct hashtab *h, const void *key)
        u32 hvalue;
        struct hashtab_node *cur;
 
-       if (!h)
+       if (!h || !h->size)
                return NULL;
 
        hvalue = h->hash_value(h, key);

diff --git a/security/selinux/ss/hashtab.h b/security/selinux/ss/hashtab.h
index 3e3e42bfd150cbb9f2fd5d5ca4a6aed29c84972b..dde54d9ff01c7e9d4994368dd3b731e82d217f38 100644 (file)
--- a/security/selinux/ss/hashtab.h
+++ b/security/selinux/ss/hashtab.h
@@ -42,7 +42,7 @@ struct hashtab_info {
  */
 struct hashtab *hashtab_create(u32 (*hash_value)(struct hashtab *h, const void *key),
                               int (*keycmp)(struct hashtab *h, const void *key1, const void *key2),
-                              u32 size);
+                              u32 nel_hint);
 
 /*
  * Inserts the specified (key, datum) pair into the specified hash table.

diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
index 32b3a8acf96f18d026fba1d9387f3fd4007070e1..7ca8c74efba33ae034b591ec08d1a9c9e6f54352 100644 (file)
--- a/security/selinux/ss/policydb.c
+++ b/security/selinux/ss/policydb.c
@@ -56,17 +56,6 @@ static const char *symtab_name[SYM_NUM] = {
 };
 #endif
 
-static unsigned int symtab_sizes[SYM_NUM] = {
-       2,
-       32,
-       16,
-       512,
-       128,
-       16,
-       16,
-       16,
-};
-
 struct policydb_compat_info {
        int version;
        int sym_num;
@@ -478,20 +467,10 @@ static int policydb_init(struct policydb *p)
 
        memset(p, 0, sizeof(*p));
 
-       for (i = 0; i < SYM_NUM; i++) {
-               rc = symtab_init(&p->symtab[i], symtab_sizes[i]);
-               if (rc)
-                       goto out;
-       }
-
        rc = avtab_init(&p->te_avtab);
        if (rc)
                goto out;
 
-       rc = roles_init(p);
-       if (rc)
-               goto out;
-
        rc = cond_policydb_init(p);
        if (rc)
                goto out;
@@ -503,20 +482,12 @@ static int policydb_init(struct policydb *p)
                goto out;
        }
 
-       p->range_tr = hashtab_create(rangetr_hash, rangetr_cmp, 256);
-       if (!p->range_tr) {
-               rc = -ENOMEM;
-               goto out;
-       }
-
        ebitmap_init(&p->filename_trans_ttypes);
        ebitmap_init(&p->policycaps);
        ebitmap_init(&p->permissive_map);
 
        return 0;
 out:
-       hashtab_destroy(p->filename_trans);
-       hashtab_destroy(p->range_tr);
        for (i = 0; i < SYM_NUM; i++) {
                hashtab_map(p->symtab[i].table, destroy_f[i], NULL);
                hashtab_destroy(p->symtab[i].table);
@@ -1142,12 +1113,12 @@ static int common_read(struct policydb *p, struct hashtab *h, void *fp)
 
        len = le32_to_cpu(buf[0]);
        comdatum->value = le32_to_cpu(buf[1]);
+       nel = le32_to_cpu(buf[3]);
 
-       rc = symtab_init(&comdatum->permissions, PERM_SYMTAB_SIZE);
+       rc = symtab_init(&comdatum->permissions, nel);
        if (rc)
                goto bad;
        comdatum->permissions.nprim = le32_to_cpu(buf[2]);
-       nel = le32_to_cpu(buf[3]);
 
        rc = str_read(&key, GFP_KERNEL, fp, len);
        if (rc)
@@ -1308,12 +1279,12 @@ static int class_read(struct policydb *p, struct hashtab *h, void *fp)
        len = le32_to_cpu(buf[0]);
        len2 = le32_to_cpu(buf[1]);
        cladatum->value = le32_to_cpu(buf[2]);
+       nel = le32_to_cpu(buf[4]);
 
-       rc = symtab_init(&cladatum->permissions, PERM_SYMTAB_SIZE);
+       rc = symtab_init(&cladatum->permissions, nel);
        if (rc)
                goto bad;
        cladatum->permissions.nprim = le32_to_cpu(buf[3]);
-       nel = le32_to_cpu(buf[4]);
 
        ncons = le32_to_cpu(buf[5]);
 
@@ -1826,6 +1797,11 @@ static int range_read(struct policydb *p, void *fp)
                return rc;
 
        nel = le32_to_cpu(buf[0]);
+
+       p->range_tr = hashtab_create(rangetr_hash, rangetr_cmp, nel);
+       if (!p->range_tr)
+               return -ENOMEM;
+
        for (i = 0; i < nel; i++) {
                rc = -ENOMEM;
                rt = kzalloc(sizeof(*rt), GFP_KERNEL);
@@ -2418,6 +2394,17 @@ int policydb_read(struct policydb *p, void *fp)
                        goto bad;
                nprim = le32_to_cpu(buf[0]);
                nel = le32_to_cpu(buf[1]);
+
+               rc = symtab_init(&p->symtab[i], nel);
+               if (rc)
+                       goto out;
+
+               if (i == SYM_ROLES) {
+                       rc = roles_init(p);
+                       if (rc)
+                               goto out;
+               }
+
                for (j = 0; j < nel; j++) {
                        rc = read_f[i](p, p->symtab[i].table, fp);
                        if (rc)

diff --git a/security/selinux/ss/policydb.h b/security/selinux/ss/policydb.h
index 41ad78a1f17bac7261bb694a8b3fad76fc35ee57..72e2932fb12d21f33de2742c42539656b9e02e6b 100644 (file)
--- a/security/selinux/ss/policydb.h
+++ b/security/selinux/ss/policydb.h
@@ -321,8 +321,6 @@ extern int policydb_role_isvalid(struct policydb *p, unsigned int role);
 extern int policydb_read(struct policydb *p, void *fp);
 extern int policydb_write(struct policydb *p, void *fp);
 
-#define PERM_SYMTAB_SIZE 32
-
 #define POLICYDB_CONFIG_MLS    1
 
 /* the config flags related to unknown classes/perms are bits 2 and 3 */