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/export.h>
   9 #include <linux/kernel.h>
  10 #include <linux/errno.h>
  11 #include <linux/jiffies.h>
  12 #include <linux/skbuff.h>
  13 #include <linux/string.h>
  14 #include <linux/types.h>
  15 #include <net/netlink.h>
  16
  17 static const u8 nla_attr_minlen[NLA_TYPE_MAX+1] = {
  18         [NLA_U8]        = sizeof(u8),
  19         [NLA_U16]       = sizeof(u16),
  20         [NLA_U32]       = sizeof(u32),
  21         [NLA_U64]       = sizeof(u64),
  22         [NLA_MSECS]     = sizeof(u64),
  23         [NLA_NESTED]    = NLA_HDRLEN,
  24         [NLA_S8]        = sizeof(s8),
  25         [NLA_S16]       = sizeof(s16),
  26         [NLA_S32]       = sizeof(s32),
  27         [NLA_S64]       = sizeof(s64),
  28 };
  29
  30 static int validate_nla(const struct nlattr *nla, int maxtype,
  31                         const struct nla_policy *policy)
  32 {
  33         const struct nla_policy *pt;
  34         int minlen = 0, attrlen = nla_len(nla), type = nla_type(nla);
  35
  36         if (type <= 0 || type > maxtype)
  37                 return 0;
  38
  39         pt = &policy[type];
  40
  41         BUG_ON(pt->type > NLA_TYPE_MAX);
  42
  43         switch (pt->type) {
  44         case NLA_FLAG:
  45                 if (attrlen > 0)
  46                         return -ERANGE;
  47                 break;
  48
  49         case NLA_NUL_STRING:
  50                 if (pt->len)
  51                         minlen = min_t(int, attrlen, pt->len + 1);
  52                 else
  53                         minlen = attrlen;
  54
  55                 if (!minlen || memchr(nla_data(nla), '\0', minlen) == NULL)
  56                         return -EINVAL;
  57                 /* fall through */
  58
  59         case NLA_STRING:
  60                 if (attrlen < 1)
  61                         return -ERANGE;
  62
  63                 if (pt->len) {
  64                         char *buf = nla_data(nla);
  65
  66                         if (buf[attrlen - 1] == '\0')
  67                                 attrlen--;
  68
  69                         if (attrlen > pt->len)
  70                                 return -ERANGE;
  71                 }
  72                 break;
  73
  74         case NLA_BINARY:
  75                 if (pt->len && attrlen > pt->len)
  76                         return -ERANGE;
  77                 break;
  78
  79         case NLA_NESTED_COMPAT:
  80                 if (attrlen < pt->len)
  81                         return -ERANGE;
  82                 if (attrlen < NLA_ALIGN(pt->len))
  83                         break;
  84                 if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN)
  85                         return -ERANGE;
  86                 nla = nla_data(nla) + NLA_ALIGN(pt->len);
  87                 if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN + nla_len(nla))
  88                         return -ERANGE;
  89                 break;
  90         case NLA_NESTED:
  91                 /* a nested attributes is allowed to be empty; if its not,
  92                  * it must have a size of at least NLA_HDRLEN.
  93                  */
  94                 if (attrlen == 0)
  95                         break;
  96         default:
  97                 if (pt->len)
  98                         minlen = pt->len;
  99                 else if (pt->type != NLA_UNSPEC)
 100                         minlen = nla_attr_minlen[pt->type];
 101
 102                 if (attrlen < minlen)
 103                         return -ERANGE;
 104         }
 105
 106         return 0;
 107 }
 108
 109 /**
 110  * nla_validate - Validate a stream of attributes
 111  * @head: head of attribute stream
 112  * @len: length of attribute stream
 113  * @maxtype: maximum attribute type to be expected
 114  * @policy: validation policy
 115  * @extack: extended ACK report struct
 116  *
 117  * Validates all attributes in the specified attribute stream against the
 118  * specified policy. Attributes with a type exceeding maxtype will be
 119  * ignored. See documenation of struct nla_policy for more details.
 120  *
 121  * Returns 0 on success or a negative error code.
 122  */
 123 int nla_validate(const struct nlattr *head, int len, int maxtype,
 124                  const struct nla_policy *policy,
 125                  struct netlink_ext_ack *extack)
 126 {
 127         const struct nlattr *nla;
 128         int rem;
 129
 130         nla_for_each_attr(nla, head, len, rem) {
 131                 int err = validate_nla(nla, maxtype, policy);
 132
 133                 if (err < 0) {
 134                         if (extack)
 135                                 extack->bad_attr = nla;
 136                         return err;
 137                 }
 138         }
 139
 140         return 0;
 141 }
 142 EXPORT_SYMBOL(nla_validate);
 143
 144 /**
 145  * nla_policy_len - Determin the max. length of a policy
 146  * @policy: policy to use
 147  * @n: number of policies
 148  *
 149  * Determines the max. length of the policy.  It is currently used
 150  * to allocated Netlink buffers roughly the size of the actual
 151  * message.
 152  *
 153  * Returns 0 on success or a negative error code.
 154  */
 155 int
 156 nla_policy_len(const struct nla_policy *p, int n)
 157 {
 158         int i, len = 0;
 159
 160         for (i = 0; i < n; i++, p++) {
 161                 if (p->len)
 162                         len += nla_total_size(p->len);
 163                 else if (nla_attr_minlen[p->type])
 164                         len += nla_total_size(nla_attr_minlen[p->type]);
 165         }
 166
 167         return len;
 168 }
 169 EXPORT_SYMBOL(nla_policy_len);
 170
 171 /**
 172  * nla_parse - Parse a stream of attributes into a tb buffer
 173  * @tb: destination array with maxtype+1 elements
 174  * @maxtype: maximum attribute type to be expected
 175  * @head: head of attribute stream
 176  * @len: length of attribute stream
 177  * @policy: validation policy
 178  *
 179  * Parses a stream of attributes and stores a pointer to each attribute in
 180  * the tb array accessible via the attribute type. Attributes with a type
 181  * exceeding maxtype will be silently ignored for backwards compatibility
 182  * reasons. policy may be set to NULL if no validation is required.
 183  *
 184  * Returns 0 on success or a negative error code.
 185  */
 186 int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
 187               int len, const struct nla_policy *policy,
 188               struct netlink_ext_ack *extack)
 189 {
 190         const struct nlattr *nla;
 191         int rem, err;
 192
 193         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 194
 195         nla_for_each_attr(nla, head, len, rem) {
 196                 u16 type = nla_type(nla);
 197
 198                 if (type > 0 && type <= maxtype) {
 199                         if (policy) {
 200                                 err = validate_nla(nla, maxtype, policy);
 201                                 if (err < 0) {
 202                                         if (extack)
 203                                                 extack->bad_attr = nla;
 204                                         goto errout;
 205                                 }
 206                         }
 207
 208                         tb[type] = (struct nlattr *)nla;
 209                 }
 210         }
 211
 212         if (unlikely(rem > 0))
 213                 pr_warn_ratelimited("netlink: %d bytes leftover after parsing attributes in process `%s'.\n",
 214                                     rem, current->comm);
 215
 216         err = 0;
 217 errout:
 218         return err;
 219 }
 220 EXPORT_SYMBOL(nla_parse);
 221
 222 /**
 223  * nla_find - Find a specific attribute in a stream of attributes
 224  * @head: head of attribute stream
 225  * @len: length of attribute stream
 226  * @attrtype: type of attribute to look for
 227  *
 228  * Returns the first attribute in the stream matching the specified type.
 229  */
 230 struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype)
 231 {
 232         const struct nlattr *nla;
 233         int rem;
 234
 235         nla_for_each_attr(nla, head, len, rem)
 236                 if (nla_type(nla) == attrtype)
 237                         return (struct nlattr *)nla;
 238
 239         return NULL;
 240 }
 241 EXPORT_SYMBOL(nla_find);
 242
 243 /**
 244  * nla_strlcpy - Copy string attribute payload into a sized buffer
 245  * @dst: where to copy the string to
 246  * @nla: attribute to copy the string from
 247  * @dstsize: size of destination buffer
 248  *
 249  * Copies at most dstsize - 1 bytes into the destination buffer.
 250  * The result is always a valid NUL-terminated string. Unlike
 251  * strlcpy the destination buffer is always padded out.
 252  *
 253  * Returns the length of the source buffer.
 254  */
 255 size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
 256 {
 257         size_t srclen = nla_len(nla);
 258         char *src = nla_data(nla);
 259
 260         if (srclen > 0 && src[srclen - 1] == '\0')
 261                 srclen--;
 262
 263         if (dstsize > 0) {
 264                 size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
 265
 266                 memset(dst, 0, dstsize);
 267                 memcpy(dst, src, len);
 268         }
 269
 270         return srclen;
 271 }
 272 EXPORT_SYMBOL(nla_strlcpy);
 273
 274 /**
 275  * nla_memcpy - Copy a netlink attribute into another memory area
 276  * @dest: where to copy to memcpy
 277  * @src: netlink attribute to copy from
 278  * @count: size of the destination area
 279  *
 280  * Note: The number of bytes copied is limited by the length of
 281  *       attribute's payload. memcpy
 282  *
 283  * Returns the number of bytes copied.
 284  */
 285 int nla_memcpy(void *dest, const struct nlattr *src, int count)
 286 {
 287         int minlen = min_t(int, count, nla_len(src));
 288
 289         memcpy(dest, nla_data(src), minlen);
 290         if (count > minlen)
 291                 memset(dest + minlen, 0, count - minlen);
 292
 293         return minlen;
 294 }
 295 EXPORT_SYMBOL(nla_memcpy);
 296
 297 /**
 298  * nla_memcmp - Compare an attribute with sized memory area
 299  * @nla: netlink attribute
 300  * @data: memory area
 301  * @size: size of memory area
 302  */
 303 int nla_memcmp(const struct nlattr *nla, const void *data,
 304                              size_t size)
 305 {
 306         int d = nla_len(nla) - size;
 307
 308         if (d == 0)
 309                 d = memcmp(nla_data(nla), data, size);
 310
 311         return d;
 312 }
 313 EXPORT_SYMBOL(nla_memcmp);
 314
 315 /**
 316  * nla_strcmp - Compare a string attribute against a string
 317  * @nla: netlink string attribute
 318  * @str: another string
 319  */
 320 int nla_strcmp(const struct nlattr *nla, const char *str)
 321 {
 322         int len = strlen(str);
 323         char *buf = nla_data(nla);
 324         int attrlen = nla_len(nla);
 325         int d;
 326
 327         if (attrlen > 0 && buf[attrlen - 1] == '\0')
 328                 attrlen--;
 329
 330         d = attrlen - len;
 331         if (d == 0)
 332                 d = memcmp(nla_data(nla), str, len);
 333
 334         return d;
 335 }
 336 EXPORT_SYMBOL(nla_strcmp);
 337
 338 #ifdef CONFIG_NET
 339 /**
 340  * __nla_reserve - reserve room for attribute on the skb
 341  * @skb: socket buffer to reserve room on
 342  * @attrtype: attribute type
 343  * @attrlen: length of attribute payload
 344  *
 345  * Adds a netlink attribute header to a socket buffer and reserves
 346  * room for the payload but does not copy it.
 347  *
 348  * The caller is responsible to ensure that the skb provides enough
 349  * tailroom for the attribute header and payload.
 350  */
 351 struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 352 {
 353         struct nlattr *nla;
 354
 355         nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
 356         nla->nla_type = attrtype;
 357         nla->nla_len = nla_attr_size(attrlen);
 358
 359         memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
 360
 361         return nla;
 362 }
 363 EXPORT_SYMBOL(__nla_reserve);
 364
 365 /**
 366  * __nla_reserve_64bit - reserve room for attribute on the skb and align it
 367  * @skb: socket buffer to reserve room on
 368  * @attrtype: attribute type
 369  * @attrlen: length of attribute payload
 370  * @padattr: attribute type for the padding
 371  *
 372  * Adds a netlink attribute header to a socket buffer and reserves
 373  * room for the payload but does not copy it. It also ensure that this
 374  * attribute will have a 64-bit aligned nla_data() area.
 375  *
 376  * The caller is responsible to ensure that the skb provides enough
 377  * tailroom for the attribute header and payload.
 378  */
 379 struct nlattr *__nla_reserve_64bit(struct sk_buff *skb, int attrtype,
 380                                    int attrlen, int padattr)
 381 {
 382         if (nla_need_padding_for_64bit(skb))
 383                 nla_align_64bit(skb, padattr);
 384
 385         return __nla_reserve(skb, attrtype, attrlen);
 386 }
 387 EXPORT_SYMBOL(__nla_reserve_64bit);
 388
 389 /**
 390  * __nla_reserve_nohdr - reserve room for attribute without header
 391  * @skb: socket buffer to reserve room on
 392  * @attrlen: length of attribute payload
 393  *
 394  * Reserves room for attribute payload without a header.
 395  *
 396  * The caller is responsible to ensure that the skb provides enough
 397  * tailroom for the payload.
 398  */
 399 void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 400 {
 401         void *start;
 402
 403         start = skb_put_zero(skb, NLA_ALIGN(attrlen));
 404
 405         return start;
 406 }
 407 EXPORT_SYMBOL(__nla_reserve_nohdr);
 408
 409 /**
 410  * nla_reserve - reserve room for attribute on the skb
 411  * @skb: socket buffer to reserve room on
 412  * @attrtype: attribute type
 413  * @attrlen: length of attribute payload
 414  *
 415  * Adds a netlink attribute header to a socket buffer and reserves
 416  * room for the payload but does not copy it.
 417  *
 418  * Returns NULL if the tailroom of the skb is insufficient to store
 419  * the attribute header and payload.
 420  */
 421 struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 422 {
 423         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 424                 return NULL;
 425
 426         return __nla_reserve(skb, attrtype, attrlen);
 427 }
 428 EXPORT_SYMBOL(nla_reserve);
 429
 430 /**
 431  * nla_reserve_64bit - reserve room for attribute on the skb and align it
 432  * @skb: socket buffer to reserve room on
 433  * @attrtype: attribute type
 434  * @attrlen: length of attribute payload
 435  * @padattr: attribute type for the padding
 436  *
 437  * Adds a netlink attribute header to a socket buffer and reserves
 438  * room for the payload but does not copy it. It also ensure that this
 439  * attribute will have a 64-bit aligned nla_data() area.
 440  *
 441  * Returns NULL if the tailroom of the skb is insufficient to store
 442  * the attribute header and payload.
 443  */
 444 struct nlattr *nla_reserve_64bit(struct sk_buff *skb, int attrtype, int attrlen,
 445                                  int padattr)
 446 {
 447         size_t len;
 448
 449         if (nla_need_padding_for_64bit(skb))
 450                 len = nla_total_size_64bit(attrlen);
 451         else
 452                 len = nla_total_size(attrlen);
 453         if (unlikely(skb_tailroom(skb) < len))
 454                 return NULL;
 455
 456         return __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
 457 }
 458 EXPORT_SYMBOL(nla_reserve_64bit);
 459
 460 /**
 461  * nla_reserve_nohdr - reserve room for attribute without header
 462  * @skb: socket buffer to reserve room on
 463  * @attrlen: length of attribute payload
 464  *
 465  * Reserves room for attribute payload without a header.
 466  *
 467  * Returns NULL if the tailroom of the skb is insufficient to store
 468  * the attribute payload.
 469  */
 470 void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 471 {
 472         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 473                 return NULL;
 474
 475         return __nla_reserve_nohdr(skb, attrlen);
 476 }
 477 EXPORT_SYMBOL(nla_reserve_nohdr);
 478
 479 /**
 480  * __nla_put - Add a netlink attribute to a socket buffer
 481  * @skb: socket buffer to add attribute to
 482  * @attrtype: attribute type
 483  * @attrlen: length of attribute payload
 484  * @data: head of attribute payload
 485  *
 486  * The caller is responsible to ensure that the skb provides enough
 487  * tailroom for the attribute header and payload.
 488  */
 489 void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 490                              const void *data)
 491 {
 492         struct nlattr *nla;
 493
 494         nla = __nla_reserve(skb, attrtype, attrlen);
 495         memcpy(nla_data(nla), data, attrlen);
 496 }
 497 EXPORT_SYMBOL(__nla_put);
 498
 499 /**
 500  * __nla_put_64bit - Add a netlink attribute to a socket buffer and align it
 501  * @skb: socket buffer to add attribute to
 502  * @attrtype: attribute type
 503  * @attrlen: length of attribute payload
 504  * @data: head of attribute payload
 505  * @padattr: attribute type for the padding
 506  *
 507  * The caller is responsible to ensure that the skb provides enough
 508  * tailroom for the attribute header and payload.
 509  */
 510 void __nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
 511                      const void *data, int padattr)
 512 {
 513         struct nlattr *nla;
 514
 515         nla = __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
 516         memcpy(nla_data(nla), data, attrlen);
 517 }
 518 EXPORT_SYMBOL(__nla_put_64bit);
 519
 520 /**
 521  * __nla_put_nohdr - Add a netlink attribute without header
 522  * @skb: socket buffer to add attribute to
 523  * @attrlen: length of attribute payload
 524  * @data: head of attribute payload
 525  *
 526  * The caller is responsible to ensure that the skb provides enough
 527  * tailroom for the attribute payload.
 528  */
 529 void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 530 {
 531         void *start;
 532
 533         start = __nla_reserve_nohdr(skb, attrlen);
 534         memcpy(start, data, attrlen);
 535 }
 536 EXPORT_SYMBOL(__nla_put_nohdr);
 537
 538 /**
 539  * nla_put - Add a netlink attribute to a socket buffer
 540  * @skb: socket buffer to add attribute to
 541  * @attrtype: attribute type
 542  * @attrlen: length of attribute payload
 543  * @data: head of attribute payload
 544  *
 545  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 546  * the attribute header and payload.
 547  */
 548 int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
 549 {
 550         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 551                 return -EMSGSIZE;
 552
 553         __nla_put(skb, attrtype, attrlen, data);
 554         return 0;
 555 }
 556 EXPORT_SYMBOL(nla_put);
 557
 558 /**
 559  * nla_put_64bit - Add a netlink attribute to a socket buffer and align it
 560  * @skb: socket buffer to add attribute to
 561  * @attrtype: attribute type
 562  * @attrlen: length of attribute payload
 563  * @data: head of attribute payload
 564  * @padattr: attribute type for the padding
 565  *
 566  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 567  * the attribute header and payload.
 568  */
 569 int nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
 570                   const void *data, int padattr)
 571 {
 572         size_t len;
 573
 574         if (nla_need_padding_for_64bit(skb))
 575                 len = nla_total_size_64bit(attrlen);
 576         else
 577                 len = nla_total_size(attrlen);
 578         if (unlikely(skb_tailroom(skb) < len))
 579                 return -EMSGSIZE;
 580
 581         __nla_put_64bit(skb, attrtype, attrlen, data, padattr);
 582         return 0;
 583 }
 584 EXPORT_SYMBOL(nla_put_64bit);
 585
 586 /**
 587  * nla_put_nohdr - Add a netlink attribute without header
 588  * @skb: socket buffer to add attribute to
 589  * @attrlen: length of attribute payload
 590  * @data: head of attribute payload
 591  *
 592  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 593  * the attribute payload.
 594  */
 595 int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 596 {
 597         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 598                 return -EMSGSIZE;
 599
 600         __nla_put_nohdr(skb, attrlen, data);
 601         return 0;
 602 }
 603 EXPORT_SYMBOL(nla_put_nohdr);
 604
 605 /**
 606  * nla_append - Add a netlink attribute without header or padding
 607  * @skb: socket buffer to add attribute to
 608  * @attrlen: length of attribute payload
 609  * @data: head of attribute payload
 610  *
 611  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 612  * the attribute payload.
 613  */
 614 int nla_append(struct sk_buff *skb, int attrlen, const void *data)
 615 {
 616         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 617                 return -EMSGSIZE;
 618
 619         skb_put_data(skb, data, attrlen);
 620         return 0;
 621 }
 622 EXPORT_SYMBOL(nla_append);
 623 #endif