net/netlink/attr.c

   1 /*
   2  * NETLINK      Netlink attributes
   3  *
   4  *              Authors:        Thomas Graf <tgraf@suug.ch>
   5  *                              Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
   6  */
   7
   8 #include <linux/module.h>
   9 #include <linux/kernel.h>
  10 #include <linux/errno.h>
  11 #include <linux/jiffies.h>
  12 #include <linux/netdevice.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/string.h>
  15 #include <linux/types.h>
  16 #include <net/netlink.h>
  17
  18 static u16 nla_attr_minlen[NLA_TYPE_MAX+1] __read_mostly = {
  19         [NLA_U8]        = sizeof(u8),
  20         [NLA_U16]       = sizeof(u16),
  21         [NLA_U32]       = sizeof(u32),
  22         [NLA_U64]       = sizeof(u64),
  23         [NLA_NESTED]    = NLA_HDRLEN,
  24 };
  25
  26 static int validate_nla(struct nlattr *nla, int maxtype,
  27                         const struct nla_policy *policy)
  28 {
  29         const struct nla_policy *pt;
  30         int minlen = 0, attrlen = nla_len(nla), type = nla_type(nla);
  31
  32         if (type <= 0 || type > maxtype)
  33                 return 0;
  34
  35         pt = &policy[type];
  36
  37         BUG_ON(pt->type > NLA_TYPE_MAX);
  38
  39         switch (pt->type) {
  40         case NLA_FLAG:
  41                 if (attrlen > 0)
  42                         return -ERANGE;
  43                 break;
  44
  45         case NLA_NUL_STRING:
  46                 if (pt->len)
  47                         minlen = min_t(int, attrlen, pt->len + 1);
  48                 else
  49                         minlen = attrlen;
  50
  51                 if (!minlen || memchr(nla_data(nla), '\0', minlen) == NULL)
  52                         return -EINVAL;
  53                 /* fall through */
  54
  55         case NLA_STRING:
  56                 if (attrlen < 1)
  57                         return -ERANGE;
  58
  59                 if (pt->len) {
  60                         char *buf = nla_data(nla);
  61
  62                         if (buf[attrlen - 1] == '\0')
  63                                 attrlen--;
  64
  65                         if (attrlen > pt->len)
  66                                 return -ERANGE;
  67                 }
  68                 break;
  69
  70         case NLA_BINARY:
  71                 if (pt->len && attrlen > pt->len)
  72                         return -ERANGE;
  73                 break;
  74
  75         case NLA_NESTED_COMPAT:
  76                 if (attrlen < pt->len)
  77                         return -ERANGE;
  78                 if (attrlen < NLA_ALIGN(pt->len))
  79                         break;
  80                 if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN)
  81                         return -ERANGE;
  82                 nla = nla_data(nla) + NLA_ALIGN(pt->len);
  83                 if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN + nla_len(nla))
  84                         return -ERANGE;
  85                 break;
  86         case NLA_NESTED:
  87                 /* a nested attributes is allowed to be empty; if its not,
  88                  * it must have a size of at least NLA_HDRLEN.
  89                  */
  90                 if (attrlen == 0)
  91                         break;
  92         default:
  93                 if (pt->len)
  94                         minlen = pt->len;
  95                 else if (pt->type != NLA_UNSPEC)
  96                         minlen = nla_attr_minlen[pt->type];
  97
  98                 if (attrlen < minlen)
  99                         return -ERANGE;
 100         }
 101
 102         return 0;
 103 }
 104
 105 /**
 106  * nla_validate - Validate a stream of attributes
 107  * @head: head of attribute stream
 108  * @len: length of attribute stream
 109  * @maxtype: maximum attribute type to be expected
 110  * @policy: validation policy
 111  *
 112  * Validates all attributes in the specified attribute stream against the
 113  * specified policy. Attributes with a type exceeding maxtype will be
 114  * ignored. See documenation of struct nla_policy for more details.
 115  *
 116  * Returns 0 on success or a negative error code.
 117  */
 118 int nla_validate(struct nlattr *head, int len, int maxtype,
 119                  const struct nla_policy *policy)
 120 {
 121         struct nlattr *nla;
 122         int rem, err;
 123
 124         nla_for_each_attr(nla, head, len, rem) {
 125                 err = validate_nla(nla, maxtype, policy);
 126                 if (err < 0)
 127                         goto errout;
 128         }
 129
 130         err = 0;
 131 errout:
 132         return err;
 133 }
 134
 135 /**
 136  * nla_parse - Parse a stream of attributes into a tb buffer
 137  * @tb: destination array with maxtype+1 elements
 138  * @maxtype: maximum attribute type to be expected
 139  * @head: head of attribute stream
 140  * @len: length of attribute stream
 141  * @policy: validation policy
 142  *
 143  * Parses a stream of attributes and stores a pointer to each attribute in
 144  * the tb array accessable via the attribute type. Attributes with a type
 145  * exceeding maxtype will be silently ignored for backwards compatibility
 146  * reasons. policy may be set to NULL if no validation is required.
 147  *
 148  * Returns 0 on success or a negative error code.
 149  */
 150 int nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len,
 151               const struct nla_policy *policy)
 152 {
 153         struct nlattr *nla;
 154         int rem, err;
 155
 156         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 157
 158         nla_for_each_attr(nla, head, len, rem) {
 159                 u16 type = nla_type(nla);
 160
 161                 if (type > 0 && type <= maxtype) {
 162                         if (policy) {
 163                                 err = validate_nla(nla, maxtype, policy);
 164                                 if (err < 0)
 165                                         goto errout;
 166                         }
 167
 168                         tb[type] = nla;
 169                 }
 170         }
 171
 172         if (unlikely(rem > 0))
 173                 printk(KERN_WARNING "netlink: %d bytes leftover after parsing "
 174                        "attributes.\n", rem);
 175
 176         err = 0;
 177 errout:
 178         return err;
 179 }
 180
 181 /**
 182  * nla_find - Find a specific attribute in a stream of attributes
 183  * @head: head of attribute stream
 184  * @len: length of attribute stream
 185  * @attrtype: type of attribute to look for
 186  *
 187  * Returns the first attribute in the stream matching the specified type.
 188  */
 189 struct nlattr *nla_find(struct nlattr *head, int len, int attrtype)
 190 {
 191         struct nlattr *nla;
 192         int rem;
 193
 194         nla_for_each_attr(nla, head, len, rem)
 195                 if (nla_type(nla) == attrtype)
 196                         return nla;
 197
 198         return NULL;
 199 }
 200
 201 /**
 202  * nla_strlcpy - Copy string attribute payload into a sized buffer
 203  * @dst: where to copy the string to
 204  * @nla: attribute to copy the string from
 205  * @dstsize: size of destination buffer
 206  *
 207  * Copies at most dstsize - 1 bytes into the destination buffer.
 208  * The result is always a valid NUL-terminated string. Unlike
 209  * strlcpy the destination buffer is always padded out.
 210  *
 211  * Returns the length of the source buffer.
 212  */
 213 size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
 214 {
 215         size_t srclen = nla_len(nla);
 216         char *src = nla_data(nla);
 217
 218         if (srclen > 0 && src[srclen - 1] == '\0')
 219                 srclen--;
 220
 221         if (dstsize > 0) {
 222                 size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
 223
 224                 memset(dst, 0, dstsize);
 225                 memcpy(dst, src, len);
 226         }
 227
 228         return srclen;
 229 }
 230
 231 /**
 232  * nla_memcpy - Copy a netlink attribute into another memory area
 233  * @dest: where to copy to memcpy
 234  * @src: netlink attribute to copy from
 235  * @count: size of the destination area
 236  *
 237  * Note: The number of bytes copied is limited by the length of
 238  *       attribute's payload. memcpy
 239  *
 240  * Returns the number of bytes copied.
 241  */
 242 int nla_memcpy(void *dest, const struct nlattr *src, int count)
 243 {
 244         int minlen = min_t(int, count, nla_len(src));
 245
 246         memcpy(dest, nla_data(src), minlen);
 247
 248         return minlen;
 249 }
 250
 251 /**
 252  * nla_memcmp - Compare an attribute with sized memory area
 253  * @nla: netlink attribute
 254  * @data: memory area
 255  * @size: size of memory area
 256  */
 257 int nla_memcmp(const struct nlattr *nla, const void *data,
 258                              size_t size)
 259 {
 260         int d = nla_len(nla) - size;
 261
 262         if (d == 0)
 263                 d = memcmp(nla_data(nla), data, size);
 264
 265         return d;
 266 }
 267
 268 /**
 269  * nla_strcmp - Compare a string attribute against a string
 270  * @nla: netlink string attribute
 271  * @str: another string
 272  */
 273 int nla_strcmp(const struct nlattr *nla, const char *str)
 274 {
 275         int len = strlen(str) + 1;
 276         int d = nla_len(nla) - len;
 277
 278         if (d == 0)
 279                 d = memcmp(nla_data(nla), str, len);
 280
 281         return d;
 282 }
 283
 284 /**
 285  * __nla_reserve - reserve room for attribute on the skb
 286  * @skb: socket buffer to reserve room on
 287  * @attrtype: attribute type
 288  * @attrlen: length of attribute payload
 289  *
 290  * Adds a netlink attribute header to a socket buffer and reserves
 291  * room for the payload but does not copy it.
 292  *
 293  * The caller is responsible to ensure that the skb provides enough
 294  * tailroom for the attribute header and payload.
 295  */
 296 struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 297 {
 298         struct nlattr *nla;
 299
 300         nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
 301         nla->nla_type = attrtype;
 302         nla->nla_len = nla_attr_size(attrlen);
 303
 304         memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
 305
 306         return nla;
 307 }
 308
 309 /**
 310  * __nla_reserve_nohdr - reserve room for attribute without header
 311  * @skb: socket buffer to reserve room on
 312  * @attrlen: length of attribute payload
 313  *
 314  * Reserves room for attribute payload without a header.
 315  *
 316  * The caller is responsible to ensure that the skb provides enough
 317  * tailroom for the payload.
 318  */
 319 void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 320 {
 321         void *start;
 322
 323         start = skb_put(skb, NLA_ALIGN(attrlen));
 324         memset(start, 0, NLA_ALIGN(attrlen));
 325
 326         return start;
 327 }
 328
 329 /**
 330  * nla_reserve - reserve room for attribute on the skb
 331  * @skb: socket buffer to reserve room on
 332  * @attrtype: attribute type
 333  * @attrlen: length of attribute payload
 334  *
 335  * Adds a netlink attribute header to a socket buffer and reserves
 336  * room for the payload but does not copy it.
 337  *
 338  * Returns NULL if the tailroom of the skb is insufficient to store
 339  * the attribute header and payload.
 340  */
 341 struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 342 {
 343         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 344                 return NULL;
 345
 346         return __nla_reserve(skb, attrtype, attrlen);
 347 }
 348
 349 /**
 350  * nla_reserve_nohdr - reserve room for attribute without header
 351  * @skb: socket buffer to reserve room on
 352  * @attrlen: length of attribute payload
 353  *
 354  * Reserves room for attribute payload without a header.
 355  *
 356  * Returns NULL if the tailroom of the skb is insufficient to store
 357  * the attribute payload.
 358  */
 359 void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 360 {
 361         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 362                 return NULL;
 363
 364         return __nla_reserve_nohdr(skb, attrlen);
 365 }
 366
 367 /**
 368  * __nla_put - Add a netlink attribute to a socket buffer
 369  * @skb: socket buffer to add attribute to
 370  * @attrtype: attribute type
 371  * @attrlen: length of attribute payload
 372  * @data: head of attribute payload
 373  *
 374  * The caller is responsible to ensure that the skb provides enough
 375  * tailroom for the attribute header and payload.
 376  */
 377 void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 378                              const void *data)
 379 {
 380         struct nlattr *nla;
 381
 382         nla = __nla_reserve(skb, attrtype, attrlen);
 383         memcpy(nla_data(nla), data, attrlen);
 384 }
 385
 386 /**
 387  * __nla_put_nohdr - Add a netlink attribute without header
 388  * @skb: socket buffer to add attribute to
 389  * @attrlen: length of attribute payload
 390  * @data: head of attribute payload
 391  *
 392  * The caller is responsible to ensure that the skb provides enough
 393  * tailroom for the attribute payload.
 394  */
 395 void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 396 {
 397         void *start;
 398
 399         start = __nla_reserve_nohdr(skb, attrlen);
 400         memcpy(start, data, attrlen);
 401 }
 402
 403 /**
 404  * nla_put - Add a netlink attribute to a socket buffer
 405  * @skb: socket buffer to add attribute to
 406  * @attrtype: attribute type
 407  * @attrlen: length of attribute payload
 408  * @data: head of attribute payload
 409  *
 410  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 411  * the attribute header and payload.
 412  */
 413 int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
 414 {
 415         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 416                 return -EMSGSIZE;
 417
 418         __nla_put(skb, attrtype, attrlen, data);
 419         return 0;
 420 }
 421
 422 /**
 423  * nla_put_nohdr - Add a netlink attribute without header
 424  * @skb: socket buffer to add attribute to
 425  * @attrlen: length of attribute payload
 426  * @data: head of attribute payload
 427  *
 428  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 429  * the attribute payload.
 430  */
 431 int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 432 {
 433         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 434                 return -EMSGSIZE;
 435
 436         __nla_put_nohdr(skb, attrlen, data);
 437         return 0;
 438 }
 439
 440 /**
 441  * nla_append - Add a netlink attribute without header or padding
 442  * @skb: socket buffer to add attribute to
 443  * @attrlen: length of attribute payload
 444  * @data: head of attribute payload
 445  *
 446  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 447  * the attribute payload.
 448  */
 449 int nla_append(struct sk_buff *skb, int attrlen, const void *data)
 450 {
 451         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 452                 return -EMSGSIZE;
 453
 454         memcpy(skb_put(skb, attrlen), data, attrlen);
 455         return 0;
 456 }
 457
 458 EXPORT_SYMBOL(nla_validate);
 459 EXPORT_SYMBOL(nla_parse);
 460 EXPORT_SYMBOL(nla_find);
 461 EXPORT_SYMBOL(nla_strlcpy);
 462 EXPORT_SYMBOL(__nla_reserve);
 463 EXPORT_SYMBOL(__nla_reserve_nohdr);
 464 EXPORT_SYMBOL(nla_reserve);
 465 EXPORT_SYMBOL(nla_reserve_nohdr);
 466 EXPORT_SYMBOL(__nla_put);
 467 EXPORT_SYMBOL(__nla_put_nohdr);
 468 EXPORT_SYMBOL(nla_put);
 469 EXPORT_SYMBOL(nla_put_nohdr);
 470 EXPORT_SYMBOL(nla_memcpy);
 471 EXPORT_SYMBOL(nla_memcmp);
 472 EXPORT_SYMBOL(nla_strcmp);
 473 EXPORT_SYMBOL(nla_append);