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