lib/nlattr.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 const u16 nla_attr_minlen[NLA_TYPE_MAX+1] = {
  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(const 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(const struct nlattr *head, int len, int maxtype,
 119                  const struct nla_policy *policy)
 120 {
 121         const 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_policy_len - Determin the max. length of a policy
 137  * @policy: policy to use
 138  * @n: number of policies
 139  *
 140  * Determines the max. length of the policy.  It is currently used
 141  * to allocated Netlink buffers roughly the size of the actual
 142  * message.
 143  *
 144  * Returns 0 on success or a negative error code.
 145  */
 146 int
 147 nla_policy_len(const struct nla_policy *p, int n)
 148 {
 149         int i, len = 0;
 150
 151         for (i = 0; i < n; i++, p++) {
 152                 if (p->len)
 153                         len += nla_total_size(p->len);
 154                 else if (nla_attr_minlen[p->type])
 155                         len += nla_total_size(nla_attr_minlen[p->type]);
 156         }
 157
 158         return len;
 159 }
 160
 161 /**
 162  * nla_parse - Parse a stream of attributes into a tb buffer
 163  * @tb: destination array with maxtype+1 elements
 164  * @maxtype: maximum attribute type to be expected
 165  * @head: head of attribute stream
 166  * @len: length of attribute stream
 167  * @policy: validation policy
 168  *
 169  * Parses a stream of attributes and stores a pointer to each attribute in
 170  * the tb array accessible via the attribute type. Attributes with a type
 171  * exceeding maxtype will be silently ignored for backwards compatibility
 172  * reasons. policy may be set to NULL if no validation is required.
 173  *
 174  * Returns 0 on success or a negative error code.
 175  */
 176 int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
 177               int len, const struct nla_policy *policy)
 178 {
 179         const struct nlattr *nla;
 180         int rem, err;
 181
 182         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 183
 184         nla_for_each_attr(nla, head, len, rem) {
 185                 u16 type = nla_type(nla);
 186
 187                 if (type > 0 && type <= maxtype) {
 188                         if (policy) {
 189                                 err = validate_nla(nla, maxtype, policy);
 190                                 if (err < 0)
 191                                         goto errout;
 192                         }
 193
 194                         tb[type] = (struct nlattr *)nla;
 195                 }
 196         }
 197
 198         if (unlikely(rem > 0))
 199                 printk(KERN_WARNING "netlink: %d bytes leftover after parsing "
 200                        "attributes.\n", rem);
 201
 202         err = 0;
 203 errout:
 204         return err;
 205 }
 206
 207 /**
 208  * nla_find - Find a specific attribute in a stream of attributes
 209  * @head: head of attribute stream
 210  * @len: length of attribute stream
 211  * @attrtype: type of attribute to look for
 212  *
 213  * Returns the first attribute in the stream matching the specified type.
 214  */
 215 struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype)
 216 {
 217         const struct nlattr *nla;
 218         int rem;
 219
 220         nla_for_each_attr(nla, head, len, rem)
 221                 if (nla_type(nla) == attrtype)
 222                         return (struct nlattr *)nla;
 223
 224         return NULL;
 225 }
 226
 227 /**
 228  * nla_strlcpy - Copy string attribute payload into a sized buffer
 229  * @dst: where to copy the string to
 230  * @nla: attribute to copy the string from
 231  * @dstsize: size of destination buffer
 232  *
 233  * Copies at most dstsize - 1 bytes into the destination buffer.
 234  * The result is always a valid NUL-terminated string. Unlike
 235  * strlcpy the destination buffer is always padded out.
 236  *
 237  * Returns the length of the source buffer.
 238  */
 239 size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
 240 {
 241         size_t srclen = nla_len(nla);
 242         char *src = nla_data(nla);
 243
 244         if (srclen > 0 && src[srclen - 1] == '\0')
 245                 srclen--;
 246
 247         if (dstsize > 0) {
 248                 size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
 249
 250                 memset(dst, 0, dstsize);
 251                 memcpy(dst, src, len);
 252         }
 253
 254         return srclen;
 255 }
 256
 257 /**
 258  * nla_memcpy - Copy a netlink attribute into another memory area
 259  * @dest: where to copy to memcpy
 260  * @src: netlink attribute to copy from
 261  * @count: size of the destination area
 262  *
 263  * Note: The number of bytes copied is limited by the length of
 264  *       attribute's payload. memcpy
 265  *
 266  * Returns the number of bytes copied.
 267  */
 268 int nla_memcpy(void *dest, const struct nlattr *src, int count)
 269 {
 270         int minlen = min_t(int, count, nla_len(src));
 271
 272         memcpy(dest, nla_data(src), minlen);
 273
 274         return minlen;
 275 }
 276
 277 /**
 278  * nla_memcmp - Compare an attribute with sized memory area
 279  * @nla: netlink attribute
 280  * @data: memory area
 281  * @size: size of memory area
 282  */
 283 int nla_memcmp(const struct nlattr *nla, const void *data,
 284                              size_t size)
 285 {
 286         int d = nla_len(nla) - size;
 287
 288         if (d == 0)
 289                 d = memcmp(nla_data(nla), data, size);
 290
 291         return d;
 292 }
 293
 294 /**
 295  * nla_strcmp - Compare a string attribute against a string
 296  * @nla: netlink string attribute
 297  * @str: another string
 298  */
 299 int nla_strcmp(const struct nlattr *nla, const char *str)
 300 {
 301         int len = strlen(str) + 1;
 302         int d = nla_len(nla) - len;
 303
 304         if (d == 0)
 305                 d = memcmp(nla_data(nla), str, len);
 306
 307         return d;
 308 }
 309
 310 #ifdef CONFIG_NET
 311 /**
 312  * __nla_reserve - reserve room for attribute on the skb
 313  * @skb: socket buffer to reserve room on
 314  * @attrtype: attribute type
 315  * @attrlen: length of attribute payload
 316  *
 317  * Adds a netlink attribute header to a socket buffer and reserves
 318  * room for the payload but does not copy it.
 319  *
 320  * The caller is responsible to ensure that the skb provides enough
 321  * tailroom for the attribute header and payload.
 322  */
 323 struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 324 {
 325         struct nlattr *nla;
 326
 327         nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
 328         nla->nla_type = attrtype;
 329         nla->nla_len = nla_attr_size(attrlen);
 330
 331         memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
 332
 333         return nla;
 334 }
 335 EXPORT_SYMBOL(__nla_reserve);
 336
 337 /**
 338  * __nla_reserve_nohdr - reserve room for attribute without header
 339  * @skb: socket buffer to reserve room on
 340  * @attrlen: length of attribute payload
 341  *
 342  * Reserves room for attribute payload without a header.
 343  *
 344  * The caller is responsible to ensure that the skb provides enough
 345  * tailroom for the payload.
 346  */
 347 void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 348 {
 349         void *start;
 350
 351         start = skb_put(skb, NLA_ALIGN(attrlen));
 352         memset(start, 0, NLA_ALIGN(attrlen));
 353
 354         return start;
 355 }
 356 EXPORT_SYMBOL(__nla_reserve_nohdr);
 357
 358 /**
 359  * nla_reserve - reserve room for attribute on the skb
 360  * @skb: socket buffer to reserve room on
 361  * @attrtype: attribute type
 362  * @attrlen: length of attribute payload
 363  *
 364  * Adds a netlink attribute header to a socket buffer and reserves
 365  * room for the payload but does not copy it.
 366  *
 367  * Returns NULL if the tailroom of the skb is insufficient to store
 368  * the attribute header and payload.
 369  */
 370 struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 371 {
 372         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 373                 return NULL;
 374
 375         return __nla_reserve(skb, attrtype, attrlen);
 376 }
 377 EXPORT_SYMBOL(nla_reserve);
 378
 379 /**
 380  * nla_reserve_nohdr - reserve room for attribute without header
 381  * @skb: socket buffer to reserve room on
 382  * @attrlen: length of attribute payload
 383  *
 384  * Reserves room for attribute payload without a header.
 385  *
 386  * Returns NULL if the tailroom of the skb is insufficient to store
 387  * the attribute payload.
 388  */
 389 void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 390 {
 391         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 392                 return NULL;
 393
 394         return __nla_reserve_nohdr(skb, attrlen);
 395 }
 396 EXPORT_SYMBOL(nla_reserve_nohdr);
 397
 398 /**
 399  * __nla_put - Add a netlink attribute to a socket buffer
 400  * @skb: socket buffer to add attribute to
 401  * @attrtype: attribute type
 402  * @attrlen: length of attribute payload
 403  * @data: head of attribute payload
 404  *
 405  * The caller is responsible to ensure that the skb provides enough
 406  * tailroom for the attribute header and payload.
 407  */
 408 void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 409                              const void *data)
 410 {
 411         struct nlattr *nla;
 412
 413         nla = __nla_reserve(skb, attrtype, attrlen);
 414         memcpy(nla_data(nla), data, attrlen);
 415 }
 416 EXPORT_SYMBOL(__nla_put);
 417
 418 /**
 419  * __nla_put_nohdr - Add a netlink attribute without header
 420  * @skb: socket buffer to add attribute to
 421  * @attrlen: length of attribute payload
 422  * @data: head of attribute payload
 423  *
 424  * The caller is responsible to ensure that the skb provides enough
 425  * tailroom for the attribute payload.
 426  */
 427 void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 428 {
 429         void *start;
 430
 431         start = __nla_reserve_nohdr(skb, attrlen);
 432         memcpy(start, data, attrlen);
 433 }
 434 EXPORT_SYMBOL(__nla_put_nohdr);
 435
 436 /**
 437  * nla_put - Add a netlink attribute to a socket buffer
 438  * @skb: socket buffer to add attribute to
 439  * @attrtype: attribute type
 440  * @attrlen: length of attribute payload
 441  * @data: head of attribute payload
 442  *
 443  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 444  * the attribute header and payload.
 445  */
 446 int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
 447 {
 448         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 449                 return -EMSGSIZE;
 450
 451         __nla_put(skb, attrtype, attrlen, data);
 452         return 0;
 453 }
 454 EXPORT_SYMBOL(nla_put);
 455
 456 /**
 457  * nla_put_nohdr - Add a netlink attribute without header
 458  * @skb: socket buffer to add attribute to
 459  * @attrlen: length of attribute payload
 460  * @data: head of attribute payload
 461  *
 462  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 463  * the attribute payload.
 464  */
 465 int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 466 {
 467         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 468                 return -EMSGSIZE;
 469
 470         __nla_put_nohdr(skb, attrlen, data);
 471         return 0;
 472 }
 473 EXPORT_SYMBOL(nla_put_nohdr);
 474
 475 /**
 476  * nla_append - Add a netlink attribute without header or padding
 477  * @skb: socket buffer to add attribute to
 478  * @attrlen: length of attribute payload
 479  * @data: head of attribute payload
 480  *
 481  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 482  * the attribute payload.
 483  */
 484 int nla_append(struct sk_buff *skb, int attrlen, const void *data)
 485 {
 486         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 487                 return -EMSGSIZE;
 488
 489         memcpy(skb_put(skb, attrlen), data, attrlen);
 490         return 0;
 491 }
 492 EXPORT_SYMBOL(nla_append);
 493 #endif
 494
 495 EXPORT_SYMBOL(nla_validate);
 496 EXPORT_SYMBOL(nla_policy_len);
 497 EXPORT_SYMBOL(nla_parse);
 498 EXPORT_SYMBOL(nla_find);
 499 EXPORT_SYMBOL(nla_strlcpy);
 500 EXPORT_SYMBOL(nla_memcpy);
 501 EXPORT_SYMBOL(nla_memcmp);
 502 EXPORT_SYMBOL(nla_strcmp);