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