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};
  26
  27static int validate_nla(const struct nlattr *nla, int maxtype,
  28                        const struct nla_policy *policy)
  29{
  30        const struct nla_policy *pt;
  31        int minlen = 0, attrlen = nla_len(nla), type = nla_type(nla);
  32
  33        if (type <= 0 || type > maxtype)
  34                return 0;
  35
  36        pt = &policy[type];
  37
  38        BUG_ON(pt->type > NLA_TYPE_MAX);
  39
  40        switch (pt->type) {
  41        case NLA_FLAG:
  42                if (attrlen > 0)
  43                        return -ERANGE;
  44                break;
  45
  46        case NLA_NUL_STRING:
  47                if (pt->len)
  48                        minlen = min_t(int, attrlen, pt->len + 1);
  49                else
  50                        minlen = attrlen;
  51
  52                if (!minlen || memchr(nla_data(nla), '\0', minlen) == NULL)
  53                        return -EINVAL;
  54                /* fall through */
  55
  56        case NLA_STRING:
  57                if (attrlen < 1)
  58                        return -ERANGE;
  59
  60                if (pt->len) {
  61                        char *buf = nla_data(nla);
  62
  63                        if (buf[attrlen - 1] == '\0')
  64                                attrlen--;
  65
  66                        if (attrlen > pt->len)
  67                                return -ERANGE;
  68                }
  69                break;
  70
  71        case NLA_BINARY:
  72                if (pt->len && attrlen > pt->len)
  73                        return -ERANGE;
  74                break;
  75
  76        case NLA_NESTED_COMPAT:
  77                if (attrlen < pt->len)
  78                        return -ERANGE;
  79                if (attrlen < NLA_ALIGN(pt->len))
  80                        break;
  81                if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN)
  82                        return -ERANGE;
  83                nla = nla_data(nla) + NLA_ALIGN(pt->len);
  84                if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN + nla_len(nla))
  85                        return -ERANGE;
  86                break;
  87        case NLA_NESTED:
  88                /* a nested attributes is allowed to be empty; if its not,
  89                 * it must have a size of at least NLA_HDRLEN.
  90                 */
  91                if (attrlen == 0)
  92                        break;
  93        default:
  94                if (pt->len)
  95                        minlen = pt->len;
  96                else if (pt->type != NLA_UNSPEC)
  97                        minlen = nla_attr_minlen[pt->type];
  98
  99                if (attrlen < minlen)
 100                        return -ERANGE;
 101        }
 102
 103        return 0;
 104}
 105
 106/**
 107 * nla_validate - Validate a stream of attributes
 108 * @head: head of attribute stream
 109 * @len: length of attribute stream
 110 * @maxtype: maximum attribute type to be expected
 111 * @policy: validation policy
 112 *
 113 * Validates all attributes in the specified attribute stream against the
 114 * specified policy. Attributes with a type exceeding maxtype will be
 115 * ignored. See documenation of struct nla_policy for more details.
 116 *
 117 * Returns 0 on success or a negative error code.
 118 */
 119int nla_validate(const struct nlattr *head, int len, int maxtype,
 120                 const struct nla_policy *policy)
 121{
 122        const struct nlattr *nla;
 123        int rem, err;
 124
 125        nla_for_each_attr(nla, head, len, rem) {
 126                err = validate_nla(nla, maxtype, policy);
 127                if (err < 0)
 128                        goto errout;
 129        }
 130
 131        err = 0;
 132errout:
 133        return err;
 134}
 135
 136/**
 137 * nla_policy_len - Determin the max. length of a policy
 138 * @policy: policy to use
 139 * @n: number of policies
 140 *
 141 * Determines the max. length of the policy.  It is currently used
 142 * to allocated Netlink buffers roughly the size of the actual
 143 * message.
 144 *
 145 * Returns 0 on success or a negative error code.
 146 */
 147int
 148nla_policy_len(const struct nla_policy *p, int n)
 149{
 150        int i, len = 0;
 151
 152        for (i = 0; i < n; i++, p++) {
 153                if (p->len)
 154                        len += nla_total_size(p->len);
 155                else if (nla_attr_minlen[p->type])
 156                        len += nla_total_size(nla_attr_minlen[p->type]);
 157        }
 158
 159        return len;
 160}
 161
 162/**
 163 * nla_parse - Parse a stream of attributes into a tb buffer
 164 * @tb: destination array with maxtype+1 elements
 165 * @maxtype: maximum attribute type to be expected
 166 * @head: head of attribute stream
 167 * @len: length of attribute stream
 168 * @policy: validation policy
 169 *
 170 * Parses a stream of attributes and stores a pointer to each attribute in
 171 * the tb array accessible via the attribute type. Attributes with a type
 172 * exceeding maxtype will be silently ignored for backwards compatibility
 173 * reasons. policy may be set to NULL if no validation is required.
 174 *
 175 * Returns 0 on success or a negative error code.
 176 */
 177int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
 178              int len, const struct nla_policy *policy)
 179{
 180        const struct nlattr *nla;
 181        int rem, err;
 182
 183        memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 184
 185        nla_for_each_attr(nla, head, len, rem) {
 186                u16 type = nla_type(nla);
 187
 188                if (type > 0 && type <= maxtype) {
 189                        if (policy) {
 190                                err = validate_nla(nla, maxtype, policy);
 191                                if (err < 0)
 192                                        goto errout;
 193                        }
 194
 195                        tb[type] = (struct nlattr *)nla;
 196                }
 197        }
 198
 199        if (unlikely(rem > 0))
 200                printk(KERN_WARNING "netlink: %d bytes leftover after parsing "
 201                       "attributes.\n", rem);
 202
 203        err = 0;
 204errout:
 205        return err;
 206}
 207
 208/**
 209 * nla_find - Find a specific attribute in a stream of attributes
 210 * @head: head of attribute stream
 211 * @len: length of attribute stream
 212 * @attrtype: type of attribute to look for
 213 *
 214 * Returns the first attribute in the stream matching the specified type.
 215 */
 216struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype)
 217{
 218        const struct nlattr *nla;
 219        int rem;
 220
 221        nla_for_each_attr(nla, head, len, rem)
 222                if (nla_type(nla) == attrtype)
 223                        return (struct nlattr *)nla;
 224
 225        return NULL;
 226}
 227
 228/**
 229 * nla_strlcpy - Copy string attribute payload into a sized buffer
 230 * @dst: where to copy the string to
 231 * @nla: attribute to copy the string from
 232 * @dstsize: size of destination buffer
 233 *
 234 * Copies at most dstsize - 1 bytes into the destination buffer.
 235 * The result is always a valid NUL-terminated string. Unlike
 236 * strlcpy the destination buffer is always padded out.
 237 *
 238 * Returns the length of the source buffer.
 239 */
 240size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
 241{
 242        size_t srclen = nla_len(nla);
 243        char *src = nla_data(nla);
 244
 245        if (srclen > 0 && src[srclen - 1] == '\0')
 246                srclen--;
 247
 248        if (dstsize > 0) {
 249                size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
 250
 251                memset(dst, 0, dstsize);
 252                memcpy(dst, src, len);
 253        }
 254
 255        return srclen;
 256}
 257
 258/**
 259 * nla_memcpy - Copy a netlink attribute into another memory area
 260 * @dest: where to copy to memcpy
 261 * @src: netlink attribute to copy from
 262 * @count: size of the destination area
 263 *
 264 * Note: The number of bytes copied is limited by the length of
 265 *       attribute's payload. memcpy
 266 *
 267 * Returns the number of bytes copied.
 268 */
 269int nla_memcpy(void *dest, const struct nlattr *src, int count)
 270{
 271        int minlen = min_t(int, count, nla_len(src));
 272
 273        memcpy(dest, nla_data(src), minlen);
 274
 275        return minlen;
 276}
 277
 278/**
 279 * nla_memcmp - Compare an attribute with sized memory area
 280 * @nla: netlink attribute
 281 * @data: memory area
 282 * @size: size of memory area
 283 */
 284int nla_memcmp(const struct nlattr *nla, const void *data,
 285                             size_t size)
 286{
 287        int d = nla_len(nla) - size;
 288
 289        if (d == 0)
 290                d = memcmp(nla_data(nla), data, size);
 291
 292        return d;
 293}
 294
 295/**
 296 * nla_strcmp - Compare a string attribute against a string
 297 * @nla: netlink string attribute
 298 * @str: another string
 299 */
 300int nla_strcmp(const struct nlattr *nla, const char *str)
 301{
 302        int len = strlen(str) + 1;
 303        int d = nla_len(nla) - len;
 304
 305        if (d == 0)
 306                d = memcmp(nla_data(nla), str, len);
 307
 308        return d;
 309}
 310
 311#ifdef CONFIG_NET
 312/**
 313 * __nla_reserve - reserve room for attribute on the skb
 314 * @skb: socket buffer to reserve room on
 315 * @attrtype: attribute type
 316 * @attrlen: length of attribute payload
 317 *
 318 * Adds a netlink attribute header to a socket buffer and reserves
 319 * room for the payload but does not copy it.
 320 *
 321 * The caller is responsible to ensure that the skb provides enough
 322 * tailroom for the attribute header and payload.
 323 */
 324struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 325{
 326        struct nlattr *nla;
 327
 328        nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
 329        nla->nla_type = attrtype;
 330        nla->nla_len = nla_attr_size(attrlen);
 331
 332        memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
 333
 334        return nla;
 335}
 336EXPORT_SYMBOL(__nla_reserve);
 337
 338/**
 339 * __nla_reserve_nohdr - reserve room for attribute without header
 340 * @skb: socket buffer to reserve room on
 341 * @attrlen: length of attribute payload
 342 *
 343 * Reserves room for attribute payload without a header.
 344 *
 345 * The caller is responsible to ensure that the skb provides enough
 346 * tailroom for the payload.
 347 */
 348void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 349{
 350        void *start;
 351
 352        start = skb_put(skb, NLA_ALIGN(attrlen));
 353        memset(start, 0, NLA_ALIGN(attrlen));
 354
 355        return start;
 356}
 357EXPORT_SYMBOL(__nla_reserve_nohdr);
 358
 359/**
 360 * nla_reserve - reserve room for attribute on the skb
 361 * @skb: socket buffer to reserve room on
 362 * @attrtype: attribute type
 363 * @attrlen: length of attribute payload
 364 *
 365 * Adds a netlink attribute header to a socket buffer and reserves
 366 * room for the payload but does not copy it.
 367 *
 368 * Returns NULL if the tailroom of the skb is insufficient to store
 369 * the attribute header and payload.
 370 */
 371struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 372{
 373        if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 374                return NULL;
 375
 376        return __nla_reserve(skb, attrtype, attrlen);
 377}
 378EXPORT_SYMBOL(nla_reserve);
 379
 380/**
 381 * nla_reserve_nohdr - reserve room for attribute without header
 382 * @skb: socket buffer to reserve room on
 383 * @attrlen: length of attribute payload
 384 *
 385 * Reserves room for attribute payload without a header.
 386 *
 387 * Returns NULL if the tailroom of the skb is insufficient to store
 388 * the attribute payload.
 389 */
 390void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 391{
 392        if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 393                return NULL;
 394
 395        return __nla_reserve_nohdr(skb, attrlen);
 396}
 397EXPORT_SYMBOL(nla_reserve_nohdr);
 398
 399/**
 400 * __nla_put - Add a netlink attribute to a socket buffer
 401 * @skb: socket buffer to add attribute to
 402 * @attrtype: attribute type
 403 * @attrlen: length of attribute payload
 404 * @data: head of attribute payload
 405 *
 406 * The caller is responsible to ensure that the skb provides enough
 407 * tailroom for the attribute header and payload.
 408 */
 409void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 410                             const void *data)
 411{
 412        struct nlattr *nla;
 413
 414        nla = __nla_reserve(skb, attrtype, attrlen);
 415        memcpy(nla_data(nla), data, attrlen);
 416}
 417EXPORT_SYMBOL(__nla_put);
 418
 419/**
 420 * __nla_put_nohdr - Add a netlink attribute without header
 421 * @skb: socket buffer to add attribute to
 422 * @attrlen: length of attribute payload
 423 * @data: head of attribute payload
 424 *
 425 * The caller is responsible to ensure that the skb provides enough
 426 * tailroom for the attribute payload.
 427 */
 428void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 429{
 430        void *start;
 431
 432        start = __nla_reserve_nohdr(skb, attrlen);
 433        memcpy(start, data, attrlen);
 434}
 435EXPORT_SYMBOL(__nla_put_nohdr);
 436
 437/**
 438 * nla_put - Add a netlink attribute to a socket buffer
 439 * @skb: socket buffer to add attribute to
 440 * @attrtype: attribute type
 441 * @attrlen: length of attribute payload
 442 * @data: head of attribute payload
 443 *
 444 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 445 * the attribute header and payload.
 446 */
 447int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
 448{
 449        if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 450                return -EMSGSIZE;
 451
 452        __nla_put(skb, attrtype, attrlen, data);
 453        return 0;
 454}
 455EXPORT_SYMBOL(nla_put);
 456
 457/**
 458 * nla_put_nohdr - Add a netlink attribute without header
 459 * @skb: socket buffer to add attribute to
 460 * @attrlen: length of attribute payload
 461 * @data: head of attribute payload
 462 *
 463 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 464 * the attribute payload.
 465 */
 466int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 467{
 468        if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 469                return -EMSGSIZE;
 470
 471        __nla_put_nohdr(skb, attrlen, data);
 472        return 0;
 473}
 474EXPORT_SYMBOL(nla_put_nohdr);
 475
 476/**
 477 * nla_append - Add a netlink attribute without header or padding
 478 * @skb: socket buffer to add attribute to
 479 * @attrlen: length of attribute payload
 480 * @data: head of attribute payload
 481 *
 482 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 483 * the attribute payload.
 484 */
 485int nla_append(struct sk_buff *skb, int attrlen, const void *data)
 486{
 487        if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 488                return -EMSGSIZE;
 489
 490        memcpy(skb_put(skb, attrlen), data, attrlen);
 491        return 0;
 492}
 493EXPORT_SYMBOL(nla_append);
 494#endif
 495
 496EXPORT_SYMBOL(nla_validate);
 497EXPORT_SYMBOL(nla_policy_len);
 498EXPORT_SYMBOL(nla_parse);
 499EXPORT_SYMBOL(nla_find);
 500EXPORT_SYMBOL(nla_strlcpy);
 501EXPORT_SYMBOL(nla_memcpy);
 502EXPORT_SYMBOL(nla_memcmp);
 503EXPORT_SYMBOL(nla_strcmp);
 504
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