lib/nlattr.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * NETLINK      Netlink attributes
   4  *
   5  *              Authors:        Thomas Graf <tgraf@suug.ch>
   6  *                              Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
   7  */
   8
   9 #include <linux/export.h>
  10 #include <linux/kernel.h>
  11 #include <linux/errno.h>
  12 #include <linux/jiffies.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/string.h>
  15 #include <linux/types.h>
  16 #include <net/netlink.h>
  17
  18 /* For these data types, attribute length should be exactly the given
  19  * size. However, to maintain compatibility with broken commands, if the
  20  * attribute length does not match the expected size a warning is emitted
  21  * to the user that the command is sending invalid data and needs to be fixed.
  22  */
  23 static const u8 nla_attr_len[NLA_TYPE_MAX+1] = {
  24         [NLA_U8]        = sizeof(u8),
  25         [NLA_U16]       = sizeof(u16),
  26         [NLA_U32]       = sizeof(u32),
  27         [NLA_U64]       = sizeof(u64),
  28         [NLA_S8]        = sizeof(s8),
  29         [NLA_S16]       = sizeof(s16),
  30         [NLA_S32]       = sizeof(s32),
  31         [NLA_S64]       = sizeof(s64),
  32 };
  33
  34 static const u8 nla_attr_minlen[NLA_TYPE_MAX+1] = {
  35         [NLA_U8]        = sizeof(u8),
  36         [NLA_U16]       = sizeof(u16),
  37         [NLA_U32]       = sizeof(u32),
  38         [NLA_U64]       = sizeof(u64),
  39         [NLA_MSECS]     = sizeof(u64),
  40         [NLA_NESTED]    = NLA_HDRLEN,
  41         [NLA_S8]        = sizeof(s8),
  42         [NLA_S16]       = sizeof(s16),
  43         [NLA_S32]       = sizeof(s32),
  44         [NLA_S64]       = sizeof(s64),
  45 };
  46
  47 /*
  48  * Nested policies might refer back to the original
  49  * policy in some cases, and userspace could try to
  50  * abuse that and recurse by nesting in the right
  51  * ways. Limit recursion to avoid this problem.
  52  */
  53 #define MAX_POLICY_RECURSION_DEPTH      10
  54
  55 static int __nla_validate_parse(const struct nlattr *head, int len, int maxtype,
  56                                 const struct nla_policy *policy,
  57                                 unsigned int validate,
  58                                 struct netlink_ext_ack *extack,
  59                                 struct nlattr **tb, unsigned int depth);
  60
  61 static int validate_nla_bitfield32(const struct nlattr *nla,
  62                                    const u32 valid_flags_mask)
  63 {
  64         const struct nla_bitfield32 *bf = nla_data(nla);
  65
  66         if (!valid_flags_mask)
  67                 return -EINVAL;
  68
  69         /*disallow invalid bit selector */
  70         if (bf->selector & ~valid_flags_mask)
  71                 return -EINVAL;
  72
  73         /*disallow invalid bit values */
  74         if (bf->value & ~valid_flags_mask)
  75                 return -EINVAL;
  76
  77         /*disallow valid bit values that are not selected*/
  78         if (bf->value & ~bf->selector)
  79                 return -EINVAL;
  80
  81         return 0;
  82 }
  83
  84 static int nla_validate_array(const struct nlattr *head, int len, int maxtype,
  85                               const struct nla_policy *policy,
  86                               struct netlink_ext_ack *extack,
  87                               unsigned int validate, unsigned int depth)
  88 {
  89         const struct nlattr *entry;
  90         int rem;
  91
  92         nla_for_each_attr(entry, head, len, rem) {
  93                 int ret;
  94
  95                 if (nla_len(entry) == 0)
  96                         continue;
  97
  98                 if (nla_len(entry) < NLA_HDRLEN) {
  99                         NL_SET_ERR_MSG_ATTR_POL(extack, entry, policy,
 100                                                 "Array element too short");
 101                         return -ERANGE;
 102                 }
 103
 104                 ret = __nla_validate_parse(nla_data(entry), nla_len(entry),
 105                                            maxtype, policy, validate, extack,
 106                                            NULL, depth + 1);
 107                 if (ret < 0)
 108                         return ret;
 109         }
 110
 111         return 0;
 112 }
 113
 114 void nla_get_range_unsigned(const struct nla_policy *pt,
 115                             struct netlink_range_validation *range)
 116 {
 117         WARN_ON_ONCE(pt->validation_type != NLA_VALIDATE_RANGE_PTR &&
 118                      (pt->min < 0 || pt->max < 0));
 119
 120         range->min = 0;
 121
 122         switch (pt->type) {
 123         case NLA_U8:
 124                 range->max = U8_MAX;
 125                 break;
 126         case NLA_U16:
 127         case NLA_BINARY:
 128                 range->max = U16_MAX;
 129                 break;
 130         case NLA_U32:
 131                 range->max = U32_MAX;
 132                 break;
 133         case NLA_U64:
 134         case NLA_MSECS:
 135                 range->max = U64_MAX;
 136                 break;
 137         default:
 138                 WARN_ON_ONCE(1);
 139                 return;
 140         }
 141
 142         switch (pt->validation_type) {
 143         case NLA_VALIDATE_RANGE:
 144         case NLA_VALIDATE_RANGE_WARN_TOO_LONG:
 145                 range->min = pt->min;
 146                 range->max = pt->max;
 147                 break;
 148         case NLA_VALIDATE_RANGE_PTR:
 149                 *range = *pt->range;
 150                 break;
 151         case NLA_VALIDATE_MIN:
 152                 range->min = pt->min;
 153                 break;
 154         case NLA_VALIDATE_MAX:
 155                 range->max = pt->max;
 156                 break;
 157         default:
 158                 break;
 159         }
 160 }
 161
 162 static int nla_validate_range_unsigned(const struct nla_policy *pt,
 163                                        const struct nlattr *nla,
 164                                        struct netlink_ext_ack *extack,
 165                                        unsigned int validate)
 166 {
 167         struct netlink_range_validation range;
 168         u64 value;
 169
 170         switch (pt->type) {
 171         case NLA_U8:
 172                 value = nla_get_u8(nla);
 173                 break;
 174         case NLA_U16:
 175                 value = nla_get_u16(nla);
 176                 break;
 177         case NLA_U32:
 178                 value = nla_get_u32(nla);
 179                 break;
 180         case NLA_U64:
 181         case NLA_MSECS:
 182                 value = nla_get_u64(nla);
 183                 break;
 184         case NLA_BINARY:
 185                 value = nla_len(nla);
 186                 break;
 187         default:
 188                 return -EINVAL;
 189         }
 190
 191         nla_get_range_unsigned(pt, &range);
 192
 193         if (pt->validation_type == NLA_VALIDATE_RANGE_WARN_TOO_LONG &&
 194             pt->type == NLA_BINARY && value > range.max) {
 195                 pr_warn_ratelimited("netlink: '%s': attribute type %d has an invalid length.\n",
 196                                     current->comm, pt->type);
 197                 if (validate & NL_VALIDATE_STRICT_ATTRS) {
 198                         NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
 199                                                 "invalid attribute length");
 200                         return -EINVAL;
 201                 }
 202
 203                 /* this assumes min <= max (don't validate against min) */
 204                 return 0;
 205         }
 206
 207         if (value < range.min || value > range.max) {
 208                 bool binary = pt->type == NLA_BINARY;
 209
 210                 if (binary)
 211                         NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
 212                                                 "binary attribute size out of range");
 213                 else
 214                         NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
 215                                                 "integer out of range");
 216
 217                 return -ERANGE;
 218         }
 219
 220         return 0;
 221 }
 222
 223 void nla_get_range_signed(const struct nla_policy *pt,
 224                           struct netlink_range_validation_signed *range)
 225 {
 226         switch (pt->type) {
 227         case NLA_S8:
 228                 range->min = S8_MIN;
 229                 range->max = S8_MAX;
 230                 break;
 231         case NLA_S16:
 232                 range->min = S16_MIN;
 233                 range->max = S16_MAX;
 234                 break;
 235         case NLA_S32:
 236                 range->min = S32_MIN;
 237                 range->max = S32_MAX;
 238                 break;
 239         case NLA_S64:
 240                 range->min = S64_MIN;
 241                 range->max = S64_MAX;
 242                 break;
 243         default:
 244                 WARN_ON_ONCE(1);
 245                 return;
 246         }
 247
 248         switch (pt->validation_type) {
 249         case NLA_VALIDATE_RANGE:
 250                 range->min = pt->min;
 251                 range->max = pt->max;
 252                 break;
 253         case NLA_VALIDATE_RANGE_PTR:
 254                 *range = *pt->range_signed;
 255                 break;
 256         case NLA_VALIDATE_MIN:
 257                 range->min = pt->min;
 258                 break;
 259         case NLA_VALIDATE_MAX:
 260                 range->max = pt->max;
 261                 break;
 262         default:
 263                 break;
 264         }
 265 }
 266
 267 static int nla_validate_int_range_signed(const struct nla_policy *pt,
 268                                          const struct nlattr *nla,
 269                                          struct netlink_ext_ack *extack)
 270 {
 271         struct netlink_range_validation_signed range;
 272         s64 value;
 273
 274         switch (pt->type) {
 275         case NLA_S8:
 276                 value = nla_get_s8(nla);
 277                 break;
 278         case NLA_S16:
 279                 value = nla_get_s16(nla);
 280                 break;
 281         case NLA_S32:
 282                 value = nla_get_s32(nla);
 283                 break;
 284         case NLA_S64:
 285                 value = nla_get_s64(nla);
 286                 break;
 287         default:
 288                 return -EINVAL;
 289         }
 290
 291         nla_get_range_signed(pt, &range);
 292
 293         if (value < range.min || value > range.max) {
 294                 NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
 295                                         "integer out of range");
 296                 return -ERANGE;
 297         }
 298
 299         return 0;
 300 }
 301
 302 static int nla_validate_int_range(const struct nla_policy *pt,
 303                                   const struct nlattr *nla,
 304                                   struct netlink_ext_ack *extack,
 305                                   unsigned int validate)
 306 {
 307         switch (pt->type) {
 308         case NLA_U8:
 309         case NLA_U16:
 310         case NLA_U32:
 311         case NLA_U64:
 312         case NLA_MSECS:
 313         case NLA_BINARY:
 314                 return nla_validate_range_unsigned(pt, nla, extack, validate);
 315         case NLA_S8:
 316         case NLA_S16:
 317         case NLA_S32:
 318         case NLA_S64:
 319                 return nla_validate_int_range_signed(pt, nla, extack);
 320         default:
 321                 WARN_ON(1);
 322                 return -EINVAL;
 323         }
 324 }
 325
 326 static int nla_validate_mask(const struct nla_policy *pt,
 327                              const struct nlattr *nla,
 328                              struct netlink_ext_ack *extack)
 329 {
 330         u64 value;
 331
 332         switch (pt->type) {
 333         case NLA_U8:
 334                 value = nla_get_u8(nla);
 335                 break;
 336         case NLA_U16:
 337                 value = nla_get_u16(nla);
 338                 break;
 339         case NLA_U32:
 340                 value = nla_get_u32(nla);
 341                 break;
 342         case NLA_U64:
 343                 value = nla_get_u64(nla);
 344                 break;
 345         default:
 346                 return -EINVAL;
 347         }
 348
 349         if (value & ~(u64)pt->mask) {
 350                 NL_SET_ERR_MSG_ATTR(extack, nla, "reserved bit set");
 351                 return -EINVAL;
 352         }
 353
 354         return 0;
 355 }
 356
 357 static int validate_nla(const struct nlattr *nla, int maxtype,
 358                         const struct nla_policy *policy, unsigned int validate,
 359                         struct netlink_ext_ack *extack, unsigned int depth)
 360 {
 361         u16 strict_start_type = policy[0].strict_start_type;
 362         const struct nla_policy *pt;
 363         int minlen = 0, attrlen = nla_len(nla), type = nla_type(nla);
 364         int err = -ERANGE;
 365
 366         if (strict_start_type && type >= strict_start_type)
 367                 validate |= NL_VALIDATE_STRICT;
 368
 369         if (type <= 0 || type > maxtype)
 370                 return 0;
 371
 372         pt = &policy[type];
 373
 374         BUG_ON(pt->type > NLA_TYPE_MAX);
 375
 376         if (nla_attr_len[pt->type] && attrlen != nla_attr_len[pt->type]) {
 377                 pr_warn_ratelimited("netlink: '%s': attribute type %d has an invalid length.\n",
 378                                     current->comm, type);
 379                 if (validate & NL_VALIDATE_STRICT_ATTRS) {
 380                         NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
 381                                                 "invalid attribute length");
 382                         return -EINVAL;
 383                 }
 384         }
 385
 386         if (validate & NL_VALIDATE_NESTED) {
 387                 if ((pt->type == NLA_NESTED || pt->type == NLA_NESTED_ARRAY) &&
 388                     !(nla->nla_type & NLA_F_NESTED)) {
 389                         NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
 390                                                 "NLA_F_NESTED is missing");
 391                         return -EINVAL;
 392                 }
 393                 if (pt->type != NLA_NESTED && pt->type != NLA_NESTED_ARRAY &&
 394                     pt->type != NLA_UNSPEC && (nla->nla_type & NLA_F_NESTED)) {
 395                         NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
 396                                                 "NLA_F_NESTED not expected");
 397                         return -EINVAL;
 398                 }
 399         }
 400
 401         switch (pt->type) {
 402         case NLA_REJECT:
 403                 if (extack && pt->reject_message) {
 404                         NL_SET_BAD_ATTR(extack, nla);
 405                         extack->_msg = pt->reject_message;
 406                         return -EINVAL;
 407                 }
 408                 err = -EINVAL;
 409                 goto out_err;
 410
 411         case NLA_FLAG:
 412                 if (attrlen > 0)
 413                         goto out_err;
 414                 break;
 415
 416         case NLA_BITFIELD32:
 417                 if (attrlen != sizeof(struct nla_bitfield32))
 418                         goto out_err;
 419
 420                 err = validate_nla_bitfield32(nla, pt->bitfield32_valid);
 421                 if (err)
 422                         goto out_err;
 423                 break;
 424
 425         case NLA_NUL_STRING:
 426                 if (pt->len)
 427                         minlen = min_t(int, attrlen, pt->len + 1);
 428                 else
 429                         minlen = attrlen;
 430
 431                 if (!minlen || memchr(nla_data(nla), '\0', minlen) == NULL) {
 432                         err = -EINVAL;
 433                         goto out_err;
 434                 }
 435                 fallthrough;
 436
 437         case NLA_STRING:
 438                 if (attrlen < 1)
 439                         goto out_err;
 440
 441                 if (pt->len) {
 442                         char *buf = nla_data(nla);
 443
 444                         if (buf[attrlen - 1] == '\0')
 445                                 attrlen--;
 446
 447                         if (attrlen > pt->len)
 448                                 goto out_err;
 449                 }
 450                 break;
 451
 452         case NLA_BINARY:
 453                 if (pt->len && attrlen > pt->len)
 454                         goto out_err;
 455                 break;
 456
 457         case NLA_NESTED:
 458                 /* a nested attributes is allowed to be empty; if its not,
 459                  * it must have a size of at least NLA_HDRLEN.
 460                  */
 461                 if (attrlen == 0)
 462                         break;
 463                 if (attrlen < NLA_HDRLEN)
 464                         goto out_err;
 465                 if (pt->nested_policy) {
 466                         err = __nla_validate_parse(nla_data(nla), nla_len(nla),
 467                                                    pt->len, pt->nested_policy,
 468                                                    validate, extack, NULL,
 469                                                    depth + 1);
 470                         if (err < 0) {
 471                                 /*
 472                                  * return directly to preserve the inner
 473                                  * error message/attribute pointer
 474                                  */
 475                                 return err;
 476                         }
 477                 }
 478                 break;
 479         case NLA_NESTED_ARRAY:
 480                 /* a nested array attribute is allowed to be empty; if its not,
 481                  * it must have a size of at least NLA_HDRLEN.
 482                  */
 483                 if (attrlen == 0)
 484                         break;
 485                 if (attrlen < NLA_HDRLEN)
 486                         goto out_err;
 487                 if (pt->nested_policy) {
 488                         int err;
 489
 490                         err = nla_validate_array(nla_data(nla), nla_len(nla),
 491                                                  pt->len, pt->nested_policy,
 492                                                  extack, validate, depth);
 493                         if (err < 0) {
 494                                 /*
 495                                  * return directly to preserve the inner
 496                                  * error message/attribute pointer
 497                                  */
 498                                 return err;
 499                         }
 500                 }
 501                 break;
 502
 503         case NLA_UNSPEC:
 504                 if (validate & NL_VALIDATE_UNSPEC) {
 505                         NL_SET_ERR_MSG_ATTR(extack, nla,
 506                                             "Unsupported attribute");
 507                         return -EINVAL;
 508                 }
 509                 if (attrlen < pt->len)
 510                         goto out_err;
 511                 break;
 512
 513         default:
 514                 if (pt->len)
 515                         minlen = pt->len;
 516                 else
 517                         minlen = nla_attr_minlen[pt->type];
 518
 519                 if (attrlen < minlen)
 520                         goto out_err;
 521         }
 522
 523         /* further validation */
 524         switch (pt->validation_type) {
 525         case NLA_VALIDATE_NONE:
 526                 /* nothing to do */
 527                 break;
 528         case NLA_VALIDATE_RANGE_PTR:
 529         case NLA_VALIDATE_RANGE:
 530         case NLA_VALIDATE_RANGE_WARN_TOO_LONG:
 531         case NLA_VALIDATE_MIN:
 532         case NLA_VALIDATE_MAX:
 533                 err = nla_validate_int_range(pt, nla, extack, validate);
 534                 if (err)
 535                         return err;
 536                 break;
 537         case NLA_VALIDATE_MASK:
 538                 err = nla_validate_mask(pt, nla, extack);
 539                 if (err)
 540                         return err;
 541                 break;
 542         case NLA_VALIDATE_FUNCTION:
 543                 if (pt->validate) {
 544                         err = pt->validate(nla, extack);
 545                         if (err)
 546                                 return err;
 547                 }
 548                 break;
 549         }
 550
 551         return 0;
 552 out_err:
 553         NL_SET_ERR_MSG_ATTR_POL(extack, nla, pt,
 554                                 "Attribute failed policy validation");
 555         return err;
 556 }
 557
 558 static int __nla_validate_parse(const struct nlattr *head, int len, int maxtype,
 559                                 const struct nla_policy *policy,
 560                                 unsigned int validate,
 561                                 struct netlink_ext_ack *extack,
 562                                 struct nlattr **tb, unsigned int depth)
 563 {
 564         const struct nlattr *nla;
 565         int rem;
 566
 567         if (depth >= MAX_POLICY_RECURSION_DEPTH) {
 568                 NL_SET_ERR_MSG(extack,
 569                                "allowed policy recursion depth exceeded");
 570                 return -EINVAL;
 571         }
 572
 573         if (tb)
 574                 memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 575
 576         nla_for_each_attr(nla, head, len, rem) {
 577                 u16 type = nla_type(nla);
 578
 579                 if (type == 0 || type > maxtype) {
 580                         if (validate & NL_VALIDATE_MAXTYPE) {
 581                                 NL_SET_ERR_MSG_ATTR(extack, nla,
 582                                                     "Unknown attribute type");
 583                                 return -EINVAL;
 584                         }
 585                         continue;
 586                 }
 587                 if (policy) {
 588                         int err = validate_nla(nla, maxtype, policy,
 589                                                validate, extack, depth);
 590
 591                         if (err < 0)
 592                                 return err;
 593                 }
 594
 595                 if (tb)
 596                         tb[type] = (struct nlattr *)nla;
 597         }
 598
 599         if (unlikely(rem > 0)) {
 600                 pr_warn_ratelimited("netlink: %d bytes leftover after parsing attributes in process `%s'.\n",
 601                                     rem, current->comm);
 602                 NL_SET_ERR_MSG(extack, "bytes leftover after parsing attributes");
 603                 if (validate & NL_VALIDATE_TRAILING)
 604                         return -EINVAL;
 605         }
 606
 607         return 0;
 608 }
 609
 610 /**
 611  * __nla_validate - Validate a stream of attributes
 612  * @head: head of attribute stream
 613  * @len: length of attribute stream
 614  * @maxtype: maximum attribute type to be expected
 615  * @policy: validation policy
 616  * @validate: validation strictness
 617  * @extack: extended ACK report struct
 618  *
 619  * Validates all attributes in the specified attribute stream against the
 620  * specified policy. Validation depends on the validate flags passed, see
 621  * &enum netlink_validation for more details on that.
 622  * See documenation of struct nla_policy for more details.
 623  *
 624  * Returns 0 on success or a negative error code.
 625  */
 626 int __nla_validate(const struct nlattr *head, int len, int maxtype,
 627                    const struct nla_policy *policy, unsigned int validate,
 628                    struct netlink_ext_ack *extack)
 629 {
 630         return __nla_validate_parse(head, len, maxtype, policy, validate,
 631                                     extack, NULL, 0);
 632 }
 633 EXPORT_SYMBOL(__nla_validate);
 634
 635 /**
 636  * nla_policy_len - Determin the max. length of a policy
 637  * @policy: policy to use
 638  * @n: number of policies
 639  *
 640  * Determines the max. length of the policy.  It is currently used
 641  * to allocated Netlink buffers roughly the size of the actual
 642  * message.
 643  *
 644  * Returns 0 on success or a negative error code.
 645  */
 646 int
 647 nla_policy_len(const struct nla_policy *p, int n)
 648 {
 649         int i, len = 0;
 650
 651         for (i = 0; i < n; i++, p++) {
 652                 if (p->len)
 653                         len += nla_total_size(p->len);
 654                 else if (nla_attr_len[p->type])
 655                         len += nla_total_size(nla_attr_len[p->type]);
 656                 else if (nla_attr_minlen[p->type])
 657                         len += nla_total_size(nla_attr_minlen[p->type]);
 658         }
 659
 660         return len;
 661 }
 662 EXPORT_SYMBOL(nla_policy_len);
 663
 664 /**
 665  * __nla_parse - Parse a stream of attributes into a tb buffer
 666  * @tb: destination array with maxtype+1 elements
 667  * @maxtype: maximum attribute type to be expected
 668  * @head: head of attribute stream
 669  * @len: length of attribute stream
 670  * @policy: validation policy
 671  * @validate: validation strictness
 672  * @extack: extended ACK pointer
 673  *
 674  * Parses a stream of attributes and stores a pointer to each attribute in
 675  * the tb array accessible via the attribute type.
 676  * Validation is controlled by the @validate parameter.
 677  *
 678  * Returns 0 on success or a negative error code.
 679  */
 680 int __nla_parse(struct nlattr **tb, int maxtype,
 681                 const struct nlattr *head, int len,
 682                 const struct nla_policy *policy, unsigned int validate,
 683                 struct netlink_ext_ack *extack)
 684 {
 685         return __nla_validate_parse(head, len, maxtype, policy, validate,
 686                                     extack, tb, 0);
 687 }
 688 EXPORT_SYMBOL(__nla_parse);
 689
 690 /**
 691  * nla_find - Find a specific attribute in a stream of attributes
 692  * @head: head of attribute stream
 693  * @len: length of attribute stream
 694  * @attrtype: type of attribute to look for
 695  *
 696  * Returns the first attribute in the stream matching the specified type.
 697  */
 698 struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype)
 699 {
 700         const struct nlattr *nla;
 701         int rem;
 702
 703         nla_for_each_attr(nla, head, len, rem)
 704                 if (nla_type(nla) == attrtype)
 705                         return (struct nlattr *)nla;
 706
 707         return NULL;
 708 }
 709 EXPORT_SYMBOL(nla_find);
 710
 711 /**
 712  * nla_strscpy - Copy string attribute payload into a sized buffer
 713  * @dst: Where to copy the string to.
 714  * @nla: Attribute to copy the string from.
 715  * @dstsize: Size of destination buffer.
 716  *
 717  * Copies at most dstsize - 1 bytes into the destination buffer.
 718  * Unlike strlcpy the destination buffer is always padded out.
 719  *
 720  * Return:
 721  * * srclen - Returns @nla length (not including the trailing %NUL).
 722  * * -E2BIG - If @dstsize is 0 or greater than U16_MAX or @nla length greater
 723  *            than @dstsize.
 724  */
 725 ssize_t nla_strscpy(char *dst, const struct nlattr *nla, size_t dstsize)
 726 {
 727         size_t srclen = nla_len(nla);
 728         char *src = nla_data(nla);
 729         ssize_t ret;
 730         size_t len;
 731
 732         if (dstsize == 0 || WARN_ON_ONCE(dstsize > U16_MAX))
 733                 return -E2BIG;
 734
 735         if (srclen > 0 && src[srclen - 1] == '\0')
 736                 srclen--;
 737
 738         if (srclen >= dstsize) {
 739                 len = dstsize - 1;
 740                 ret = -E2BIG;
 741         } else {
 742                 len = srclen;
 743                 ret = len;
 744         }
 745
 746         memcpy(dst, src, len);
 747         /* Zero pad end of dst. */
 748         memset(dst + len, 0, dstsize - len);
 749
 750         return ret;
 751 }
 752 EXPORT_SYMBOL(nla_strscpy);
 753
 754 /**
 755  * nla_strdup - Copy string attribute payload into a newly allocated buffer
 756  * @nla: attribute to copy the string from
 757  * @flags: the type of memory to allocate (see kmalloc).
 758  *
 759  * Returns a pointer to the allocated buffer or NULL on error.
 760  */
 761 char *nla_strdup(const struct nlattr *nla, gfp_t flags)
 762 {
 763         size_t srclen = nla_len(nla);
 764         char *src = nla_data(nla), *dst;
 765
 766         if (srclen > 0 && src[srclen - 1] == '\0')
 767                 srclen--;
 768
 769         dst = kmalloc(srclen + 1, flags);
 770         if (dst != NULL) {
 771                 memcpy(dst, src, srclen);
 772                 dst[srclen] = '\0';
 773         }
 774         return dst;
 775 }
 776 EXPORT_SYMBOL(nla_strdup);
 777
 778 /**
 779  * nla_memcpy - Copy a netlink attribute into another memory area
 780  * @dest: where to copy to memcpy
 781  * @src: netlink attribute to copy from
 782  * @count: size of the destination area
 783  *
 784  * Note: The number of bytes copied is limited by the length of
 785  *       attribute's payload. memcpy
 786  *
 787  * Returns the number of bytes copied.
 788  */
 789 int nla_memcpy(void *dest, const struct nlattr *src, int count)
 790 {
 791         int minlen = min_t(int, count, nla_len(src));
 792
 793         memcpy(dest, nla_data(src), minlen);
 794         if (count > minlen)
 795                 memset(dest + minlen, 0, count - minlen);
 796
 797         return minlen;
 798 }
 799 EXPORT_SYMBOL(nla_memcpy);
 800
 801 /**
 802  * nla_memcmp - Compare an attribute with sized memory area
 803  * @nla: netlink attribute
 804  * @data: memory area
 805  * @size: size of memory area
 806  */
 807 int nla_memcmp(const struct nlattr *nla, const void *data,
 808                              size_t size)
 809 {
 810         int d = nla_len(nla) - size;
 811
 812         if (d == 0)
 813                 d = memcmp(nla_data(nla), data, size);
 814
 815         return d;
 816 }
 817 EXPORT_SYMBOL(nla_memcmp);
 818
 819 /**
 820  * nla_strcmp - Compare a string attribute against a string
 821  * @nla: netlink string attribute
 822  * @str: another string
 823  */
 824 int nla_strcmp(const struct nlattr *nla, const char *str)
 825 {
 826         int len = strlen(str);
 827         char *buf = nla_data(nla);
 828         int attrlen = nla_len(nla);
 829         int d;
 830
 831         if (attrlen > 0 && buf[attrlen - 1] == '\0')
 832                 attrlen--;
 833
 834         d = attrlen - len;
 835         if (d == 0)
 836                 d = memcmp(nla_data(nla), str, len);
 837
 838         return d;
 839 }
 840 EXPORT_SYMBOL(nla_strcmp);
 841
 842 #ifdef CONFIG_NET
 843 /**
 844  * __nla_reserve - reserve room for attribute on the skb
 845  * @skb: socket buffer to reserve room on
 846  * @attrtype: attribute type
 847  * @attrlen: length of attribute payload
 848  *
 849  * Adds a netlink attribute header to a socket buffer and reserves
 850  * room for the payload but does not copy it.
 851  *
 852  * The caller is responsible to ensure that the skb provides enough
 853  * tailroom for the attribute header and payload.
 854  */
 855 struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 856 {
 857         struct nlattr *nla;
 858
 859         nla = skb_put(skb, nla_total_size(attrlen));
 860         nla->nla_type = attrtype;
 861         nla->nla_len = nla_attr_size(attrlen);
 862
 863         memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
 864
 865         return nla;
 866 }
 867 EXPORT_SYMBOL(__nla_reserve);
 868
 869 /**
 870  * __nla_reserve_64bit - reserve room for attribute on the skb and align it
 871  * @skb: socket buffer to reserve room on
 872  * @attrtype: attribute type
 873  * @attrlen: length of attribute payload
 874  * @padattr: attribute type for the padding
 875  *
 876  * Adds a netlink attribute header to a socket buffer and reserves
 877  * room for the payload but does not copy it. It also ensure that this
 878  * attribute will have a 64-bit aligned nla_data() area.
 879  *
 880  * The caller is responsible to ensure that the skb provides enough
 881  * tailroom for the attribute header and payload.
 882  */
 883 struct nlattr *__nla_reserve_64bit(struct sk_buff *skb, int attrtype,
 884                                    int attrlen, int padattr)
 885 {
 886         nla_align_64bit(skb, padattr);
 887
 888         return __nla_reserve(skb, attrtype, attrlen);
 889 }
 890 EXPORT_SYMBOL(__nla_reserve_64bit);
 891
 892 /**
 893  * __nla_reserve_nohdr - reserve room for attribute without header
 894  * @skb: socket buffer to reserve room on
 895  * @attrlen: length of attribute payload
 896  *
 897  * Reserves room for attribute payload without a header.
 898  *
 899  * The caller is responsible to ensure that the skb provides enough
 900  * tailroom for the payload.
 901  */
 902 void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 903 {
 904         return skb_put_zero(skb, NLA_ALIGN(attrlen));
 905 }
 906 EXPORT_SYMBOL(__nla_reserve_nohdr);
 907
 908 /**
 909  * nla_reserve - reserve room for attribute on the skb
 910  * @skb: socket buffer to reserve room on
 911  * @attrtype: attribute type
 912  * @attrlen: length of attribute payload
 913  *
 914  * Adds a netlink attribute header to a socket buffer and reserves
 915  * room for the payload but does not copy it.
 916  *
 917  * Returns NULL if the tailroom of the skb is insufficient to store
 918  * the attribute header and payload.
 919  */
 920 struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 921 {
 922         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 923                 return NULL;
 924
 925         return __nla_reserve(skb, attrtype, attrlen);
 926 }
 927 EXPORT_SYMBOL(nla_reserve);
 928
 929 /**
 930  * nla_reserve_64bit - reserve room for attribute on the skb and align it
 931  * @skb: socket buffer to reserve room on
 932  * @attrtype: attribute type
 933  * @attrlen: length of attribute payload
 934  * @padattr: attribute type for the padding
 935  *
 936  * Adds a netlink attribute header to a socket buffer and reserves
 937  * room for the payload but does not copy it. It also ensure that this
 938  * attribute will have a 64-bit aligned nla_data() area.
 939  *
 940  * Returns NULL if the tailroom of the skb is insufficient to store
 941  * the attribute header and payload.
 942  */
 943 struct nlattr *nla_reserve_64bit(struct sk_buff *skb, int attrtype, int attrlen,
 944                                  int padattr)
 945 {
 946         size_t len;
 947
 948         if (nla_need_padding_for_64bit(skb))
 949                 len = nla_total_size_64bit(attrlen);
 950         else
 951                 len = nla_total_size(attrlen);
 952         if (unlikely(skb_tailroom(skb) < len))
 953                 return NULL;
 954
 955         return __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
 956 }
 957 EXPORT_SYMBOL(nla_reserve_64bit);
 958
 959 /**
 960  * nla_reserve_nohdr - reserve room for attribute without header
 961  * @skb: socket buffer to reserve room on
 962  * @attrlen: length of attribute payload
 963  *
 964  * Reserves room for attribute payload without a header.
 965  *
 966  * Returns NULL if the tailroom of the skb is insufficient to store
 967  * the attribute payload.
 968  */
 969 void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 970 {
 971         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 972                 return NULL;
 973
 974         return __nla_reserve_nohdr(skb, attrlen);
 975 }
 976 EXPORT_SYMBOL(nla_reserve_nohdr);
 977
 978 /**
 979  * __nla_put - Add a netlink attribute to a socket buffer
 980  * @skb: socket buffer to add attribute to
 981  * @attrtype: attribute type
 982  * @attrlen: length of attribute payload
 983  * @data: head of attribute payload
 984  *
 985  * The caller is responsible to ensure that the skb provides enough
 986  * tailroom for the attribute header and payload.
 987  */
 988 void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 989                              const void *data)
 990 {
 991         struct nlattr *nla;
 992
 993         nla = __nla_reserve(skb, attrtype, attrlen);
 994         memcpy(nla_data(nla), data, attrlen);
 995 }
 996 EXPORT_SYMBOL(__nla_put);
 997
 998 /**
 999  * __nla_put_64bit - Add a netlink attribute to a socket buffer and align it
1000  * @skb: socket buffer to add attribute to
1001  * @attrtype: attribute type
1002  * @attrlen: length of attribute payload
1003  * @data: head of attribute payload
1004  * @padattr: attribute type for the padding
1005  *
1006  * The caller is responsible to ensure that the skb provides enough
1007  * tailroom for the attribute header and payload.
1008  */
1009 void __nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
1010                      const void *data, int padattr)
1011 {
1012         struct nlattr *nla;
1013
1014         nla = __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
1015         memcpy(nla_data(nla), data, attrlen);
1016 }
1017 EXPORT_SYMBOL(__nla_put_64bit);
1018
1019 /**
1020  * __nla_put_nohdr - Add a netlink attribute without header
1021  * @skb: socket buffer to add attribute to
1022  * @attrlen: length of attribute payload
1023  * @data: head of attribute payload
1024  *
1025  * The caller is responsible to ensure that the skb provides enough
1026  * tailroom for the attribute payload.
1027  */
1028 void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
1029 {
1030         void *start;
1031
1032         start = __nla_reserve_nohdr(skb, attrlen);
1033         memcpy(start, data, attrlen);
1034 }
1035 EXPORT_SYMBOL(__nla_put_nohdr);
1036
1037 /**
1038  * nla_put - Add a netlink attribute to a socket buffer
1039  * @skb: socket buffer to add attribute to
1040  * @attrtype: attribute type
1041  * @attrlen: length of attribute payload
1042  * @data: head of attribute payload
1043  *
1044  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
1045  * the attribute header and payload.
1046  */
1047 int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
1048 {
1049         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
1050                 return -EMSGSIZE;
1051
1052         __nla_put(skb, attrtype, attrlen, data);
1053         return 0;
1054 }
1055 EXPORT_SYMBOL(nla_put);
1056
1057 /**
1058  * nla_put_64bit - Add a netlink attribute to a socket buffer and align it
1059  * @skb: socket buffer to add attribute to
1060  * @attrtype: attribute type
1061  * @attrlen: length of attribute payload
1062  * @data: head of attribute payload
1063  * @padattr: attribute type for the padding
1064  *
1065  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
1066  * the attribute header and payload.
1067  */
1068 int nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
1069                   const void *data, int padattr)
1070 {
1071         size_t len;
1072
1073         if (nla_need_padding_for_64bit(skb))
1074                 len = nla_total_size_64bit(attrlen);
1075         else
1076                 len = nla_total_size(attrlen);
1077         if (unlikely(skb_tailroom(skb) < len))
1078                 return -EMSGSIZE;
1079
1080         __nla_put_64bit(skb, attrtype, attrlen, data, padattr);
1081         return 0;
1082 }
1083 EXPORT_SYMBOL(nla_put_64bit);
1084
1085 /**
1086  * nla_put_nohdr - Add a netlink attribute without header
1087  * @skb: socket buffer to add attribute to
1088  * @attrlen: length of attribute payload
1089  * @data: head of attribute payload
1090  *
1091  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
1092  * the attribute payload.
1093  */
1094 int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
1095 {
1096         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
1097                 return -EMSGSIZE;
1098
1099         __nla_put_nohdr(skb, attrlen, data);
1100         return 0;
1101 }
1102 EXPORT_SYMBOL(nla_put_nohdr);
1103
1104 /**
1105  * nla_append - Add a netlink attribute without header or padding
1106  * @skb: socket buffer to add attribute to
1107  * @attrlen: length of attribute payload
1108  * @data: head of attribute payload
1109  *
1110  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
1111  * the attribute payload.
1112  */
1113 int nla_append(struct sk_buff *skb, int attrlen, const void *data)
1114 {
1115         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
1116                 return -EMSGSIZE;
1117
1118         skb_put_data(skb, data, attrlen);
1119         return 0;
1120 }
1121 EXPORT_SYMBOL(nla_append);
1122 #endif