selinux: convert avtab hash table to flex_array

Previously we shrank the avtab max hash buckets to avoid
high order memory allocations, but this causes avtab lookups to
degenerate to very long linear searches for the Fedora policy. Convert to
using a flex_array instead so that we can increase the buckets
without such limitations.

This change does not alter the max hash buckets; that is left to a
separate follow-on change.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <pmoore@redhat.com>

2 files changed, 22 insertions, 13 deletions

diff --git a/security/selinux/ss/avtab.c b/security/selinux/ss/avtab.c
index a3dd9faa19c0..3ea0198fc964 100644
--- a/security/selinux/ss/avtab.c
+++ b/security/selinux/ss/avtab.c
@@ -46,8 +46,12 @@ avtab_insert_node(struct avtab *h, int hvalue,
                 newnode->next = prev->next;
                 prev->next = newnode;
         } else {
-                newnode->next = h->htable[hvalue];
-                h->htable[hvalue] = newnode;
+                newnode->next = flex_array_get_ptr(h->htable, hvalue);
+                if (flex_array_put_ptr(h->htable, hvalue, newnode,
+                                       GFP_KERNEL|__GFP_ZERO)) {
+                        kmem_cache_free(avtab_node_cachep, newnode);
+                        return NULL;
+                }
         }
 
         h->nel++;
@@ -64,7 +68,7 @@ static int avtab_insert(struct avtab *h, struct avtab_key *key, struct avtab_dat
                 return -EINVAL;
 
         hvalue = avtab_hash(key, h->mask);
-        for (prev = NULL, cur = h->htable[hvalue];
+        for (prev = NULL, cur = flex_array_get_ptr(h->htable, hvalue);
              cur;
              prev = cur, cur = cur->next) {
                 if (key->source_type == cur->key.source_type &&
@@ -104,7 +108,7 @@ avtab_insert_nonunique(struct avtab *h, struct avtab_key *key, struct avtab_datu
         if (!h || !h->htable)
                 return NULL;
         hvalue = avtab_hash(key, h->mask);
-        for (prev = NULL, cur = h->htable[hvalue];
+        for (prev = NULL, cur = flex_array_get_ptr(h->htable, hvalue);
              cur;
              prev = cur, cur = cur->next) {
                 if (key->source_type == cur->key.source_type &&
@@ -135,7 +139,8 @@ struct avtab_datum *avtab_search(struct avtab *h, struct avtab_key *key)
                 return NULL;
 
         hvalue = avtab_hash(key, h->mask);
-        for (cur = h->htable[hvalue]; cur; cur = cur->next) {
+        for (cur = flex_array_get_ptr(h->htable, hvalue); cur;
+             cur = cur->next) {
                 if (key->source_type == cur->key.source_type &&
                     key->target_type == cur->key.target_type &&
                     key->target_class == cur->key.target_class &&
@@ -170,7 +175,8 @@ avtab_search_node(struct avtab *h, struct avtab_key *key)
                 return NULL;
 
         hvalue = avtab_hash(key, h->mask);
-        for (cur = h->htable[hvalue]; cur; cur = cur->next) {
+        for (cur = flex_array_get_ptr(h->htable, hvalue); cur;
+             cur = cur->next) {
                 if (key->source_type == cur->key.source_type &&
                     key->target_type == cur->key.target_type &&
                     key->target_class == cur->key.target_class &&
@@ -228,15 +234,14 @@ void avtab_destroy(struct avtab *h)
                 return;
 
         for (i = 0; i < h->nslot; i++) {
-                cur = h->htable[i];
+                cur = flex_array_get_ptr(h->htable, i);
                 while (cur) {
                         temp = cur;
                         cur = cur->next;
                         kmem_cache_free(avtab_node_cachep, temp);
                 }
-                h->htable[i] = NULL;
         }
-        kfree(h->htable);
+        flex_array_free(h->htable);
         h->htable = NULL;
         h->nslot = 0;
         h->mask = 0;
@@ -270,7 +275,8 @@ int avtab_alloc(struct avtab *h, u32 nrules)
                 nslot = MAX_AVTAB_HASH_BUCKETS;
         mask = nslot - 1;
 
-        h->htable = kcalloc(nslot, sizeof(*(h->htable)), GFP_KERNEL);
+        h->htable = flex_array_alloc(sizeof(struct avtab_node *), nslot,
+                                     GFP_KERNEL | __GFP_ZERO);
         if (!h->htable)
                 return -ENOMEM;
 
@@ -293,7 +299,7 @@ void avtab_hash_eval(struct avtab *h, char *tag)
         max_chain_len = 0;
         chain2_len_sum = 0;
         for (i = 0; i < h->nslot; i++) {
-                cur = h->htable[i];
+                cur = flex_array_get_ptr(h->htable, i);
                 if (cur) {
                         slots_used++;
                         chain_len = 0;
@@ -534,7 +540,8 @@ int avtab_write(struct policydb *p, struct avtab *a, void *fp)
                 return rc;
 
         for (i = 0; i < a->nslot; i++) {
-                for (cur = a->htable[i]; cur; cur = cur->next) {
+                for (cur = flex_array_get_ptr(a->htable, i); cur;
+                     cur = cur->next) {
                         rc = avtab_write_item(p, cur, fp);
                         if (rc)
                                 return rc;
diff --git a/security/selinux/ss/avtab.h b/security/selinux/ss/avtab.h
index 63ce2f9e441d..9318b2b8f6c9 100644
--- a/security/selinux/ss/avtab.h
+++ b/security/selinux/ss/avtab.h
@@ -23,6 +23,8 @@
 #ifndef _SS_AVTAB_H_
 #define _SS_AVTAB_H_
 
+#include <linux/flex_array.h>
+
 struct avtab_key {
         u16 source_type;        /* source type */
         u16 target_type;        /* target type */
@@ -51,7 +53,7 @@ struct avtab_node {
 };
 
 struct avtab {
-        struct avtab_node **htable;
+        struct flex_array *htable;
         u32 nel;        /* number of elements */
         u32 nslot;      /* number of hash slots */
         u16 mask;       /* mask to compute hash func */