security/selinux/ss/sidtab.c

   1 /*
   2  * Implementation of the SID table type.
   3  *
   4  * Author : Stephen Smalley, <sds@epoch.ncsc.mil>
   5  */
   6 #include <linux/kernel.h>
   7 #include <linux/slab.h>
   8 #include <linux/spinlock.h>
   9 #include <linux/errno.h>
  10 #include "flask.h"
  11 #include "security.h"
  12 #include "sidtab.h"
  13
  14 #define SIDTAB_HASH(sid) \
  15 (sid & SIDTAB_HASH_MASK)
  16
  17 int sidtab_init(struct sidtab *s)
  18 {
  19         int i;
  20
  21         s->htable = kmalloc_array(SIDTAB_SIZE, sizeof(*s->htable), GFP_ATOMIC);
  22         if (!s->htable)
  23                 return -ENOMEM;
  24         for (i = 0; i < SIDTAB_SIZE; i++)
  25                 s->htable[i] = NULL;
  26         s->nel = 0;
  27         s->next_sid = 1;
  28         s->shutdown = 0;
  29         spin_lock_init(&s->lock);
  30         return 0;
  31 }
  32
  33 int sidtab_insert(struct sidtab *s, u32 sid, struct context *context)
  34 {
  35         int hvalue;
  36         struct sidtab_node *prev, *cur, *newnode;
  37
  38         if (!s)
  39                 return -ENOMEM;
  40
  41         hvalue = SIDTAB_HASH(sid);
  42         prev = NULL;
  43         cur = s->htable[hvalue];
  44         while (cur && sid > cur->sid) {
  45                 prev = cur;
  46                 cur = cur->next;
  47         }
  48
  49         if (cur && sid == cur->sid)
  50                 return -EEXIST;
  51
  52         newnode = kmalloc(sizeof(*newnode), GFP_ATOMIC);
  53         if (!newnode)
  54                 return -ENOMEM;
  55
  56         newnode->sid = sid;
  57         if (context_cpy(&newnode->context, context)) {
  58                 kfree(newnode);
  59                 return -ENOMEM;
  60         }
  61
  62         if (prev) {
  63                 newnode->next = prev->next;
  64                 wmb();
  65                 prev->next = newnode;
  66         } else {
  67                 newnode->next = s->htable[hvalue];
  68                 wmb();
  69                 s->htable[hvalue] = newnode;
  70         }
  71
  72         s->nel++;
  73         if (sid >= s->next_sid)
  74                 s->next_sid = sid + 1;
  75         return 0;
  76 }
  77
  78 static struct context *sidtab_search_core(struct sidtab *s, u32 sid, int force)
  79 {
  80         int hvalue;
  81         struct sidtab_node *cur;
  82
  83         if (!s)
  84                 return NULL;
  85
  86         hvalue = SIDTAB_HASH(sid);
  87         cur = s->htable[hvalue];
  88         while (cur && sid > cur->sid)
  89                 cur = cur->next;
  90
  91         if (force && cur && sid == cur->sid && cur->context.len)
  92                 return &cur->context;
  93
  94         if (!cur || sid != cur->sid || cur->context.len) {
  95                 /* Remap invalid SIDs to the unlabeled SID. */
  96                 sid = SECINITSID_UNLABELED;
  97                 hvalue = SIDTAB_HASH(sid);
  98                 cur = s->htable[hvalue];
  99                 while (cur && sid > cur->sid)
 100                         cur = cur->next;
 101                 if (!cur || sid != cur->sid)
 102                         return NULL;
 103         }
 104
 105         return &cur->context;
 106 }
 107
 108 struct context *sidtab_search(struct sidtab *s, u32 sid)
 109 {
 110         return sidtab_search_core(s, sid, 0);
 111 }
 112
 113 struct context *sidtab_search_force(struct sidtab *s, u32 sid)
 114 {
 115         return sidtab_search_core(s, sid, 1);
 116 }
 117
 118 int sidtab_map(struct sidtab *s,
 119                int (*apply) (u32 sid,
 120                              struct context *context,
 121                              void *args),
 122                void *args)
 123 {
 124         int i, rc = 0;
 125         struct sidtab_node *cur;
 126
 127         if (!s)
 128                 goto out;
 129
 130         for (i = 0; i < SIDTAB_SIZE; i++) {
 131                 cur = s->htable[i];
 132                 while (cur) {
 133                         rc = apply(cur->sid, &cur->context, args);
 134                         if (rc)
 135                                 goto out;
 136                         cur = cur->next;
 137                 }
 138         }
 139 out:
 140         return rc;
 141 }
 142
 143 static void sidtab_update_cache(struct sidtab *s, struct sidtab_node *n, int loc)
 144 {
 145         BUG_ON(loc >= SIDTAB_CACHE_LEN);
 146
 147         while (loc > 0) {
 148                 s->cache[loc] = s->cache[loc - 1];
 149                 loc--;
 150         }
 151         s->cache[0] = n;
 152 }
 153
 154 static inline u32 sidtab_search_context(struct sidtab *s,
 155                                                   struct context *context)
 156 {
 157         int i;
 158         struct sidtab_node *cur;
 159
 160         for (i = 0; i < SIDTAB_SIZE; i++) {
 161                 cur = s->htable[i];
 162                 while (cur) {
 163                         if (context_cmp(&cur->context, context)) {
 164                                 sidtab_update_cache(s, cur, SIDTAB_CACHE_LEN - 1);
 165                                 return cur->sid;
 166                         }
 167                         cur = cur->next;
 168                 }
 169         }
 170         return 0;
 171 }
 172
 173 static inline u32 sidtab_search_cache(struct sidtab *s, struct context *context)
 174 {
 175         int i;
 176         struct sidtab_node *node;
 177
 178         for (i = 0; i < SIDTAB_CACHE_LEN; i++) {
 179                 node = s->cache[i];
 180                 if (unlikely(!node))
 181                         return 0;
 182                 if (context_cmp(&node->context, context)) {
 183                         sidtab_update_cache(s, node, i);
 184                         return node->sid;
 185                 }
 186         }
 187         return 0;
 188 }
 189
 190 int sidtab_context_to_sid(struct sidtab *s,
 191                           struct context *context,
 192                           u32 *out_sid)
 193 {
 194         u32 sid;
 195         int ret = 0;
 196         unsigned long flags;
 197
 198         *out_sid = SECSID_NULL;
 199
 200         sid  = sidtab_search_cache(s, context);
 201         if (!sid)
 202                 sid = sidtab_search_context(s, context);
 203         if (!sid) {
 204                 spin_lock_irqsave(&s->lock, flags);
 205                 /* Rescan now that we hold the lock. */
 206                 sid = sidtab_search_context(s, context);
 207                 if (sid)
 208                         goto unlock_out;
 209                 /* No SID exists for the context.  Allocate a new one. */
 210                 if (s->next_sid == UINT_MAX || s->shutdown) {
 211                         ret = -ENOMEM;
 212                         goto unlock_out;
 213                 }
 214                 sid = s->next_sid++;
 215                 if (context->len)
 216                         printk(KERN_INFO
 217                        "SELinux:  Context %s is not valid (left unmapped).\n",
 218                                context->str);
 219                 ret = sidtab_insert(s, sid, context);
 220                 if (ret)
 221                         s->next_sid--;
 222 unlock_out:
 223                 spin_unlock_irqrestore(&s->lock, flags);
 224         }
 225
 226         if (ret)
 227                 return ret;
 228
 229         *out_sid = sid;
 230         return 0;
 231 }
 232
 233 void sidtab_hash_eval(struct sidtab *h, char *tag)
 234 {
 235         int i, chain_len, slots_used, max_chain_len;
 236         struct sidtab_node *cur;
 237
 238         slots_used = 0;
 239         max_chain_len = 0;
 240         for (i = 0; i < SIDTAB_SIZE; i++) {
 241                 cur = h->htable[i];
 242                 if (cur) {
 243                         slots_used++;
 244                         chain_len = 0;
 245                         while (cur) {
 246                                 chain_len++;
 247                                 cur = cur->next;
 248                         }
 249
 250                         if (chain_len > max_chain_len)
 251                                 max_chain_len = chain_len;
 252                 }
 253         }
 254
 255         printk(KERN_DEBUG "%s:  %d entries and %d/%d buckets used, longest "
 256                "chain length %d\n", tag, h->nel, slots_used, SIDTAB_SIZE,
 257                max_chain_len);
 258 }
 259
 260 void sidtab_destroy(struct sidtab *s)
 261 {
 262         int i;
 263         struct sidtab_node *cur, *temp;
 264
 265         if (!s)
 266                 return;
 267
 268         for (i = 0; i < SIDTAB_SIZE; i++) {
 269                 cur = s->htable[i];
 270                 while (cur) {
 271                         temp = cur;
 272                         cur = cur->next;
 273                         context_destroy(&temp->context);
 274                         kfree(temp);
 275                 }
 276                 s->htable[i] = NULL;
 277         }
 278         kfree(s->htable);
 279         s->htable = NULL;
 280         s->nel = 0;
 281         s->next_sid = 1;
 282 }
 283
 284 void sidtab_set(struct sidtab *dst, struct sidtab *src)
 285 {
 286         unsigned long flags;
 287         int i;
 288
 289         spin_lock_irqsave(&src->lock, flags);
 290         dst->htable = src->htable;
 291         dst->nel = src->nel;
 292         dst->next_sid = src->next_sid;
 293         dst->shutdown = 0;
 294         for (i = 0; i < SIDTAB_CACHE_LEN; i++)
 295                 dst->cache[i] = NULL;
 296         spin_unlock_irqrestore(&src->lock, flags);
 297 }
 298
 299 void sidtab_shutdown(struct sidtab *s)
 300 {
 301         unsigned long flags;
 302
 303         spin_lock_irqsave(&s->lock, flags);
 304         s->shutdown = 1;
 305         spin_unlock_irqrestore(&s->lock, flags);
 306 }