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_bitfield32(const struct nlattr *nla,
  31                                    u32 *valid_flags_allowed)
  32 {
  33         const struct nla_bitfield32 *bf = nla_data(nla);
  34         u32 *valid_flags_mask = valid_flags_allowed;
  35
  36         if (!valid_flags_allowed)
  37                 return -EINVAL;
  38
  39         /*disallow invalid bit selector */
  40         if (bf->selector & ~*valid_flags_mask)
  41                 return -EINVAL;
  42
  43         /*disallow invalid bit values */
  44         if (bf->value & ~*valid_flags_mask)
  45                 return -EINVAL;
  46
  47         /*disallow valid bit values that are not selected*/
  48         if (bf->value & ~bf->selector)
  49                 return -EINVAL;
  50
  51         return 0;
  52 }
  53
  54 static int validate_nla(const struct nlattr *nla, int maxtype,
  55                         const struct nla_policy *policy)
  56 {
  57         const struct nla_policy *pt;
  58         int minlen = 0, attrlen = nla_len(nla), type = nla_type(nla);
  59
  60         if (type <= 0 || type > maxtype)
  61                 return 0;
  62
  63         pt = &policy[type];
  64
  65         BUG_ON(pt->type > NLA_TYPE_MAX);
  66
  67         switch (pt->type) {
  68         case NLA_FLAG:
  69                 if (attrlen > 0)
  70                         return -ERANGE;
  71                 break;
  72
  73         case NLA_BITFIELD32:
  74                 if (attrlen != sizeof(struct nla_bitfield32))
  75                         return -ERANGE;
  76
  77                 return validate_nla_bitfield32(nla, pt->validation_data);
  78
  79         case NLA_NUL_STRING:
  80                 if (pt->len)
  81                         minlen = min_t(int, attrlen, pt->len + 1);
  82                 else
  83                         minlen = attrlen;
  84
  85                 if (!minlen || memchr(nla_data(nla), '\0', minlen) == NULL)
  86                         return -EINVAL;
  87                 /* fall through */
  88
  89         case NLA_STRING:
  90                 if (attrlen < 1)
  91                         return -ERANGE;
  92
  93                 if (pt->len) {
  94                         char *buf = nla_data(nla);
  95
  96                         if (buf[attrlen - 1] == '\0')
  97                                 attrlen--;
  98
  99                         if (attrlen > pt->len)
 100                                 return -ERANGE;
 101                 }
 102                 break;
 103
 104         case NLA_BINARY:
 105                 if (pt->len && attrlen > pt->len)
 106                         return -ERANGE;
 107                 break;
 108
 109         case NLA_NESTED_COMPAT:
 110                 if (attrlen < pt->len)
 111                         return -ERANGE;
 112                 if (attrlen < NLA_ALIGN(pt->len))
 113                         break;
 114                 if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN)
 115                         return -ERANGE;
 116                 nla = nla_data(nla) + NLA_ALIGN(pt->len);
 117                 if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN + nla_len(nla))
 118                         return -ERANGE;
 119                 break;
 120         case NLA_NESTED:
 121                 /* a nested attributes is allowed to be empty; if its not,
 122                  * it must have a size of at least NLA_HDRLEN.
 123                  */
 124                 if (attrlen == 0)
 125                         break;
 126         default:
 127                 if (pt->len)
 128                         minlen = pt->len;
 129                 else if (pt->type != NLA_UNSPEC)
 130                         minlen = nla_attr_minlen[pt->type];
 131
 132                 if (attrlen < minlen)
 133                         return -ERANGE;
 134         }
 135
 136         return 0;
 137 }
 138
 139 /**
 140  * nla_validate - Validate a stream of attributes
 141  * @head: head of attribute stream
 142  * @len: length of attribute stream
 143  * @maxtype: maximum attribute type to be expected
 144  * @policy: validation policy
 145  * @extack: extended ACK report struct
 146  *
 147  * Validates all attributes in the specified attribute stream against the
 148  * specified policy. Attributes with a type exceeding maxtype will be
 149  * ignored. See documenation of struct nla_policy for more details.
 150  *
 151  * Returns 0 on success or a negative error code.
 152  */
 153 int nla_validate(const struct nlattr *head, int len, int maxtype,
 154                  const struct nla_policy *policy,
 155                  struct netlink_ext_ack *extack)
 156 {
 157         const struct nlattr *nla;
 158         int rem;
 159
 160         nla_for_each_attr(nla, head, len, rem) {
 161                 int err = validate_nla(nla, maxtype, policy);
 162
 163                 if (err < 0) {
 164                         if (extack)
 165                                 extack->bad_attr = nla;
 166                         return err;
 167                 }
 168         }
 169
 170         return 0;
 171 }
 172 EXPORT_SYMBOL(nla_validate);
 173
 174 /**
 175  * nla_policy_len - Determin the max. length of a policy
 176  * @policy: policy to use
 177  * @n: number of policies
 178  *
 179  * Determines the max. length of the policy.  It is currently used
 180  * to allocated Netlink buffers roughly the size of the actual
 181  * message.
 182  *
 183  * Returns 0 on success or a negative error code.
 184  */
 185 int
 186 nla_policy_len(const struct nla_policy *p, int n)
 187 {
 188         int i, len = 0;
 189
 190         for (i = 0; i < n; i++, p++) {
 191                 if (p->len)
 192                         len += nla_total_size(p->len);
 193                 else if (nla_attr_minlen[p->type])
 194                         len += nla_total_size(nla_attr_minlen[p->type]);
 195         }
 196
 197         return len;
 198 }
 199 EXPORT_SYMBOL(nla_policy_len);
 200
 201 /**
 202  * nla_parse - Parse a stream of attributes into a tb buffer
 203  * @tb: destination array with maxtype+1 elements
 204  * @maxtype: maximum attribute type to be expected
 205  * @head: head of attribute stream
 206  * @len: length of attribute stream
 207  * @policy: validation policy
 208  *
 209  * Parses a stream of attributes and stores a pointer to each attribute in
 210  * the tb array accessible via the attribute type. Attributes with a type
 211  * exceeding maxtype will be silently ignored for backwards compatibility
 212  * reasons. policy may be set to NULL if no validation is required.
 213  *
 214  * Returns 0 on success or a negative error code.
 215  */
 216 int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
 217               int len, const struct nla_policy *policy,
 218               struct netlink_ext_ack *extack)
 219 {
 220         const struct nlattr *nla;
 221         int rem, err;
 222
 223         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 224
 225         nla_for_each_attr(nla, head, len, rem) {
 226                 u16 type = nla_type(nla);
 227
 228                 if (type > 0 && type <= maxtype) {
 229                         if (policy) {
 230                                 err = validate_nla(nla, maxtype, policy);
 231                                 if (err < 0) {
 232                                         if (extack)
 233                                                 extack->bad_attr = nla;
 234                                         goto errout;
 235                                 }
 236                         }
 237
 238                         tb[type] = (struct nlattr *)nla;
 239                 }
 240         }
 241
 242         if (unlikely(rem > 0))
 243                 pr_warn_ratelimited("netlink: %d bytes leftover after parsing attributes in process `%s'.\n",
 244                                     rem, current->comm);
 245
 246         err = 0;
 247 errout:
 248         return err;
 249 }
 250 EXPORT_SYMBOL(nla_parse);
 251
 252 /**
 253  * nla_find - Find a specific attribute in a stream of attributes
 254  * @head: head of attribute stream
 255  * @len: length of attribute stream
 256  * @attrtype: type of attribute to look for
 257  *
 258  * Returns the first attribute in the stream matching the specified type.
 259  */
 260 struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype)
 261 {
 262         const struct nlattr *nla;
 263         int rem;
 264
 265         nla_for_each_attr(nla, head, len, rem)
 266                 if (nla_type(nla) == attrtype)
 267                         return (struct nlattr *)nla;
 268
 269         return NULL;
 270 }
 271 EXPORT_SYMBOL(nla_find);
 272
 273 /**
 274  * nla_strlcpy - Copy string attribute payload into a sized buffer
 275  * @dst: where to copy the string to
 276  * @nla: attribute to copy the string from
 277  * @dstsize: size of destination buffer
 278  *
 279  * Copies at most dstsize - 1 bytes into the destination buffer.
 280  * The result is always a valid NUL-terminated string. Unlike
 281  * strlcpy the destination buffer is always padded out.
 282  *
 283  * Returns the length of the source buffer.
 284  */
 285 size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
 286 {
 287         size_t srclen = nla_len(nla);
 288         char *src = nla_data(nla);
 289
 290         if (srclen > 0 && src[srclen - 1] == '\0')
 291                 srclen--;
 292
 293         if (dstsize > 0) {
 294                 size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
 295
 296                 memset(dst, 0, dstsize);
 297                 memcpy(dst, src, len);
 298         }
 299
 300         return srclen;
 301 }
 302 EXPORT_SYMBOL(nla_strlcpy);
 303
 304 /**
 305  * nla_memcpy - Copy a netlink attribute into another memory area
 306  * @dest: where to copy to memcpy
 307  * @src: netlink attribute to copy from
 308  * @count: size of the destination area
 309  *
 310  * Note: The number of bytes copied is limited by the length of
 311  *       attribute's payload. memcpy
 312  *
 313  * Returns the number of bytes copied.
 314  */
 315 int nla_memcpy(void *dest, const struct nlattr *src, int count)
 316 {
 317         int minlen = min_t(int, count, nla_len(src));
 318
 319         memcpy(dest, nla_data(src), minlen);
 320         if (count > minlen)
 321                 memset(dest + minlen, 0, count - minlen);
 322
 323         return minlen;
 324 }
 325 EXPORT_SYMBOL(nla_memcpy);
 326
 327 /**
 328  * nla_memcmp - Compare an attribute with sized memory area
 329  * @nla: netlink attribute
 330  * @data: memory area
 331  * @size: size of memory area
 332  */
 333 int nla_memcmp(const struct nlattr *nla, const void *data,
 334                              size_t size)
 335 {
 336         int d = nla_len(nla) - size;
 337
 338         if (d == 0)
 339                 d = memcmp(nla_data(nla), data, size);
 340
 341         return d;
 342 }
 343 EXPORT_SYMBOL(nla_memcmp);
 344
 345 /**
 346  * nla_strcmp - Compare a string attribute against a string
 347  * @nla: netlink string attribute
 348  * @str: another string
 349  */
 350 int nla_strcmp(const struct nlattr *nla, const char *str)
 351 {
 352         int len = strlen(str);
 353         char *buf = nla_data(nla);
 354         int attrlen = nla_len(nla);
 355         int d;
 356
 357         if (attrlen > 0 && buf[attrlen - 1] == '\0')
 358                 attrlen--;
 359
 360         d = attrlen - len;
 361         if (d == 0)
 362                 d = memcmp(nla_data(nla), str, len);
 363
 364         return d;
 365 }
 366 EXPORT_SYMBOL(nla_strcmp);
 367
 368 #ifdef CONFIG_NET
 369 /**
 370  * __nla_reserve - reserve room for attribute on the skb
 371  * @skb: socket buffer to reserve room on
 372  * @attrtype: attribute type
 373  * @attrlen: length of attribute payload
 374  *
 375  * Adds a netlink attribute header to a socket buffer and reserves
 376  * room for the payload but does not copy it.
 377  *
 378  * The caller is responsible to ensure that the skb provides enough
 379  * tailroom for the attribute header and payload.
 380  */
 381 struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 382 {
 383         struct nlattr *nla;
 384
 385         nla = skb_put(skb, nla_total_size(attrlen));
 386         nla->nla_type = attrtype;
 387         nla->nla_len = nla_attr_size(attrlen);
 388
 389         memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
 390
 391         return nla;
 392 }
 393 EXPORT_SYMBOL(__nla_reserve);
 394
 395 /**
 396  * __nla_reserve_64bit - reserve room for attribute on the skb and align it
 397  * @skb: socket buffer to reserve room on
 398  * @attrtype: attribute type
 399  * @attrlen: length of attribute payload
 400  * @padattr: attribute type for the padding
 401  *
 402  * Adds a netlink attribute header to a socket buffer and reserves
 403  * room for the payload but does not copy it. It also ensure that this
 404  * attribute will have a 64-bit aligned nla_data() area.
 405  *
 406  * The caller is responsible to ensure that the skb provides enough
 407  * tailroom for the attribute header and payload.
 408  */
 409 struct nlattr *__nla_reserve_64bit(struct sk_buff *skb, int attrtype,
 410                                    int attrlen, int padattr)
 411 {
 412         if (nla_need_padding_for_64bit(skb))
 413                 nla_align_64bit(skb, padattr);
 414
 415         return __nla_reserve(skb, attrtype, attrlen);
 416 }
 417 EXPORT_SYMBOL(__nla_reserve_64bit);
 418
 419 /**
 420  * __nla_reserve_nohdr - reserve room for attribute without header
 421  * @skb: socket buffer to reserve room on
 422  * @attrlen: length of attribute payload
 423  *
 424  * Reserves room for attribute payload without a header.
 425  *
 426  * The caller is responsible to ensure that the skb provides enough
 427  * tailroom for the payload.
 428  */
 429 void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 430 {
 431         return skb_put_zero(skb, NLA_ALIGN(attrlen));
 432 }
 433 EXPORT_SYMBOL(__nla_reserve_nohdr);
 434
 435 /**
 436  * nla_reserve - reserve room for attribute on the skb
 437  * @skb: socket buffer to reserve room on
 438  * @attrtype: attribute type
 439  * @attrlen: length of attribute payload
 440  *
 441  * Adds a netlink attribute header to a socket buffer and reserves
 442  * room for the payload but does not copy it.
 443  *
 444  * Returns NULL if the tailroom of the skb is insufficient to store
 445  * the attribute header and payload.
 446  */
 447 struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 448 {
 449         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 450                 return NULL;
 451
 452         return __nla_reserve(skb, attrtype, attrlen);
 453 }
 454 EXPORT_SYMBOL(nla_reserve);
 455
 456 /**
 457  * nla_reserve_64bit - reserve room for attribute on the skb and align it
 458  * @skb: socket buffer to reserve room on
 459  * @attrtype: attribute type
 460  * @attrlen: length of attribute payload
 461  * @padattr: attribute type for the padding
 462  *
 463  * Adds a netlink attribute header to a socket buffer and reserves
 464  * room for the payload but does not copy it. It also ensure that this
 465  * attribute will have a 64-bit aligned nla_data() area.
 466  *
 467  * Returns NULL if the tailroom of the skb is insufficient to store
 468  * the attribute header and payload.
 469  */
 470 struct nlattr *nla_reserve_64bit(struct sk_buff *skb, int attrtype, int attrlen,
 471                                  int padattr)
 472 {
 473         size_t len;
 474
 475         if (nla_need_padding_for_64bit(skb))
 476                 len = nla_total_size_64bit(attrlen);
 477         else
 478                 len = nla_total_size(attrlen);
 479         if (unlikely(skb_tailroom(skb) < len))
 480                 return NULL;
 481
 482         return __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
 483 }
 484 EXPORT_SYMBOL(nla_reserve_64bit);
 485
 486 /**
 487  * nla_reserve_nohdr - reserve room for attribute without header
 488  * @skb: socket buffer to reserve room on
 489  * @attrlen: length of attribute payload
 490  *
 491  * Reserves room for attribute payload without a header.
 492  *
 493  * Returns NULL if the tailroom of the skb is insufficient to store
 494  * the attribute payload.
 495  */
 496 void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 497 {
 498         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 499                 return NULL;
 500
 501         return __nla_reserve_nohdr(skb, attrlen);
 502 }
 503 EXPORT_SYMBOL(nla_reserve_nohdr);
 504
 505 /**
 506  * __nla_put - Add a netlink attribute to a socket buffer
 507  * @skb: socket buffer to add attribute to
 508  * @attrtype: attribute type
 509  * @attrlen: length of attribute payload
 510  * @data: head of attribute payload
 511  *
 512  * The caller is responsible to ensure that the skb provides enough
 513  * tailroom for the attribute header and payload.
 514  */
 515 void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 516                              const void *data)
 517 {
 518         struct nlattr *nla;
 519
 520         nla = __nla_reserve(skb, attrtype, attrlen);
 521         memcpy(nla_data(nla), data, attrlen);
 522 }
 523 EXPORT_SYMBOL(__nla_put);
 524
 525 /**
 526  * __nla_put_64bit - Add a netlink attribute to a socket buffer and align it
 527  * @skb: socket buffer to add attribute to
 528  * @attrtype: attribute type
 529  * @attrlen: length of attribute payload
 530  * @data: head of attribute payload
 531  * @padattr: attribute type for the padding
 532  *
 533  * The caller is responsible to ensure that the skb provides enough
 534  * tailroom for the attribute header and payload.
 535  */
 536 void __nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
 537                      const void *data, int padattr)
 538 {
 539         struct nlattr *nla;
 540
 541         nla = __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
 542         memcpy(nla_data(nla), data, attrlen);
 543 }
 544 EXPORT_SYMBOL(__nla_put_64bit);
 545
 546 /**
 547  * __nla_put_nohdr - Add a netlink attribute without header
 548  * @skb: socket buffer to add attribute to
 549  * @attrlen: length of attribute payload
 550  * @data: head of attribute payload
 551  *
 552  * The caller is responsible to ensure that the skb provides enough
 553  * tailroom for the attribute payload.
 554  */
 555 void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 556 {
 557         void *start;
 558
 559         start = __nla_reserve_nohdr(skb, attrlen);
 560         memcpy(start, data, attrlen);
 561 }
 562 EXPORT_SYMBOL(__nla_put_nohdr);
 563
 564 /**
 565  * nla_put - Add a netlink attribute to a socket buffer
 566  * @skb: socket buffer to add attribute to
 567  * @attrtype: attribute type
 568  * @attrlen: length of attribute payload
 569  * @data: head of attribute payload
 570  *
 571  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 572  * the attribute header and payload.
 573  */
 574 int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
 575 {
 576         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 577                 return -EMSGSIZE;
 578
 579         __nla_put(skb, attrtype, attrlen, data);
 580         return 0;
 581 }
 582 EXPORT_SYMBOL(nla_put);
 583
 584 /**
 585  * nla_put_64bit - Add a netlink attribute to a socket buffer and align it
 586  * @skb: socket buffer to add attribute to
 587  * @attrtype: attribute type
 588  * @attrlen: length of attribute payload
 589  * @data: head of attribute payload
 590  * @padattr: attribute type for the padding
 591  *
 592  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 593  * the attribute header and payload.
 594  */
 595 int nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
 596                   const void *data, int padattr)
 597 {
 598         size_t len;
 599
 600         if (nla_need_padding_for_64bit(skb))
 601                 len = nla_total_size_64bit(attrlen);
 602         else
 603                 len = nla_total_size(attrlen);
 604         if (unlikely(skb_tailroom(skb) < len))
 605                 return -EMSGSIZE;
 606
 607         __nla_put_64bit(skb, attrtype, attrlen, data, padattr);
 608         return 0;
 609 }
 610 EXPORT_SYMBOL(nla_put_64bit);
 611
 612 /**
 613  * nla_put_nohdr - Add a netlink attribute without header
 614  * @skb: socket buffer to add attribute to
 615  * @attrlen: length of attribute payload
 616  * @data: head of attribute payload
 617  *
 618  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 619  * the attribute payload.
 620  */
 621 int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 622 {
 623         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 624                 return -EMSGSIZE;
 625
 626         __nla_put_nohdr(skb, attrlen, data);
 627         return 0;
 628 }
 629 EXPORT_SYMBOL(nla_put_nohdr);
 630
 631 /**
 632  * nla_append - Add a netlink attribute without header or padding
 633  * @skb: socket buffer to add attribute to
 634  * @attrlen: length of attribute payload
 635  * @data: head of attribute payload
 636  *
 637  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 638  * the attribute payload.
 639  */
 640 int nla_append(struct sk_buff *skb, int attrlen, const void *data)
 641 {
 642         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 643                 return -EMSGSIZE;
 644
 645         skb_put_data(skb, data, attrlen);
 646         return 0;
 647 }
 648 EXPORT_SYMBOL(nla_append);
 649 #endif