security/selinux/ss/hashtab.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Implementation of the hash table type.
   4  *
   5  * Author : Stephen Smalley, <stephen.smalley.work@gmail.com>
   6  */
   7
   8 #include <linux/kernel.h>
   9 #include <linux/slab.h>
  10 #include <linux/errno.h>
  11 #include "hashtab.h"
  12 #include "security.h"
  13
  14 static struct kmem_cache *hashtab_node_cachep __ro_after_init;
  15
  16 /*
  17  * Here we simply round the number of elements up to the nearest power of two.
  18  * I tried also other options like rounding down or rounding to the closest
  19  * power of two (up or down based on which is closer), but I was unable to
  20  * find any significant difference in lookup/insert performance that would
  21  * justify switching to a different (less intuitive) formula. It could be that
  22  * a different formula is actually more optimal, but any future changes here
  23  * should be supported with performance/memory usage data.
  24  *
  25  * The total memory used by the htable arrays (only) with Fedora policy loaded
  26  * is approximately 163 KB at the time of writing.
  27  */
  28 static u32 hashtab_compute_size(u32 nel)
  29 {
  30         return nel == 0 ? 0 : roundup_pow_of_two(nel);
  31 }
  32
  33 int hashtab_init(struct hashtab *h, u32 nel_hint)
  34 {
  35         u32 size = hashtab_compute_size(nel_hint);
  36
  37         /* should already be zeroed, but better be safe */
  38         h->nel = 0;
  39         h->size = 0;
  40         h->htable = NULL;
  41
  42         if (size) {
  43                 h->htable = kcalloc(size, sizeof(*h->htable), GFP_KERNEL);
  44                 if (!h->htable)
  45                         return -ENOMEM;
  46                 h->size = size;
  47         }
  48         return 0;
  49 }
  50
  51 int __hashtab_insert(struct hashtab *h, struct hashtab_node **dst, void *key,
  52                      void *datum)
  53 {
  54         struct hashtab_node *newnode;
  55
  56         newnode = kmem_cache_zalloc(hashtab_node_cachep, GFP_KERNEL);
  57         if (!newnode)
  58                 return -ENOMEM;
  59         newnode->key = key;
  60         newnode->datum = datum;
  61         newnode->next = *dst;
  62         *dst = newnode;
  63
  64         h->nel++;
  65         return 0;
  66 }
  67
  68 void hashtab_destroy(struct hashtab *h)
  69 {
  70         u32 i;
  71         struct hashtab_node *cur, *temp;
  72
  73         for (i = 0; i < h->size; i++) {
  74                 cur = h->htable[i];
  75                 while (cur) {
  76                         temp = cur;
  77                         cur = cur->next;
  78                         kmem_cache_free(hashtab_node_cachep, temp);
  79                 }
  80                 h->htable[i] = NULL;
  81         }
  82
  83         kfree(h->htable);
  84         h->htable = NULL;
  85 }
  86
  87 int hashtab_map(struct hashtab *h, int (*apply)(void *k, void *d, void *args),
  88                 void *args)
  89 {
  90         u32 i;
  91         int ret;
  92         struct hashtab_node *cur;
  93
  94         for (i = 0; i < h->size; i++) {
  95                 cur = h->htable[i];
  96                 while (cur) {
  97                         ret = apply(cur->key, cur->datum, args);
  98                         if (ret)
  99                                 return ret;
 100                         cur = cur->next;
 101                 }
 102         }
 103         return 0;
 104 }
 105
 106 #ifdef CONFIG_SECURITY_SELINUX_DEBUG
 107 void hashtab_stat(struct hashtab *h, struct hashtab_info *info)
 108 {
 109         u32 i, chain_len, slots_used, max_chain_len;
 110         u64 chain2_len_sum;
 111         struct hashtab_node *cur;
 112
 113         slots_used = 0;
 114         max_chain_len = 0;
 115         chain2_len_sum = 0;
 116         for (i = 0; i < h->size; i++) {
 117                 cur = h->htable[i];
 118                 if (cur) {
 119                         slots_used++;
 120                         chain_len = 0;
 121                         while (cur) {
 122                                 chain_len++;
 123                                 cur = cur->next;
 124                         }
 125
 126                         if (chain_len > max_chain_len)
 127                                 max_chain_len = chain_len;
 128
 129                         chain2_len_sum += (u64)chain_len * chain_len;
 130                 }
 131         }
 132
 133         info->slots_used = slots_used;
 134         info->max_chain_len = max_chain_len;
 135         info->chain2_len_sum = chain2_len_sum;
 136 }
 137 #endif /* CONFIG_SECURITY_SELINUX_DEBUG */
 138
 139 int hashtab_duplicate(struct hashtab *new, struct hashtab *orig,
 140                       int (*copy)(struct hashtab_node *new,
 141                                   struct hashtab_node *orig, void *args),
 142                       int (*destroy)(void *k, void *d, void *args), void *args)
 143 {
 144         struct hashtab_node *cur, *tmp, *tail;
 145         u32 i;
 146         int rc;
 147
 148         memset(new, 0, sizeof(*new));
 149
 150         new->htable = kcalloc(orig->size, sizeof(*new->htable), GFP_KERNEL);
 151         if (!new->htable)
 152                 return -ENOMEM;
 153
 154         new->size = orig->size;
 155
 156         for (i = 0; i < orig->size; i++) {
 157                 tail = NULL;
 158                 for (cur = orig->htable[i]; cur; cur = cur->next) {
 159                         tmp = kmem_cache_zalloc(hashtab_node_cachep,
 160                                                 GFP_KERNEL);
 161                         if (!tmp)
 162                                 goto error;
 163                         rc = copy(tmp, cur, args);
 164                         if (rc) {
 165                                 kmem_cache_free(hashtab_node_cachep, tmp);
 166                                 goto error;
 167                         }
 168                         tmp->next = NULL;
 169                         if (!tail)
 170                                 new->htable[i] = tmp;
 171                         else
 172                                 tail->next = tmp;
 173                         tail = tmp;
 174                         new->nel++;
 175                 }
 176         }
 177
 178         return 0;
 179
 180 error:
 181         for (i = 0; i < new->size; i++) {
 182                 for (cur = new->htable[i]; cur; cur = tmp) {
 183                         tmp = cur->next;
 184                         destroy(cur->key, cur->datum, args);
 185                         kmem_cache_free(hashtab_node_cachep, cur);
 186                 }
 187         }
 188         kfree(new->htable);
 189         memset(new, 0, sizeof(*new));
 190         return -ENOMEM;
 191 }
 192
 193 void __init hashtab_cache_init(void)
 194 {
 195         hashtab_node_cachep = kmem_cache_create("hashtab_node",
 196                                                 sizeof(struct hashtab_node), 0,
 197                                                 SLAB_PANIC, NULL);
 198 }