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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>
This commit is contained in:
Stephen Smalley 2015-03-24 16:54:16 -04:00 committed by Paul Moore
parent da8026fa0f
commit ba39db6e05
2 changed files with 22 additions and 13 deletions
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31
security/selinux/ss/avtab.c
View File

@ -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;

4
security/selinux/ss/avtab.h
View File

@ -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 */