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