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/netdevice.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/string.h>
  15 #include <linux/types.h>
  16 #include <net/netlink.h>
  17
  18 static 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
  31 static 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  */
 123 int 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;
 136 errout:
 137         return err;
 138 }
 139 EXPORT_SYMBOL(nla_validate);
 140
 141 /**
 142  * nla_policy_len - Determin the max. length of a policy
 143  * @policy: policy to use
 144  * @n: number of policies
 145  *
 146  * Determines the max. length of the policy.  It is currently used
 147  * to allocated Netlink buffers roughly the size of the actual
 148  * message.
 149  *
 150  * Returns 0 on success or a negative error code.
 151  */
 152 int
 153 nla_policy_len(const struct nla_policy *p, int n)
 154 {
 155         int i, len = 0;
 156
 157         for (i = 0; i < n; i++, p++) {
 158                 if (p->len)
 159                         len += nla_total_size(p->len);
 160                 else if (nla_attr_minlen[p->type])
 161                         len += nla_total_size(nla_attr_minlen[p->type]);
 162         }
 163
 164         return len;
 165 }
 166 EXPORT_SYMBOL(nla_policy_len);
 167
 168 /**
 169  * nla_parse - Parse a stream of attributes into a tb buffer
 170  * @tb: destination array with maxtype+1 elements
 171  * @maxtype: maximum attribute type to be expected
 172  * @head: head of attribute stream
 173  * @len: length of attribute stream
 174  * @policy: validation policy
 175  *
 176  * Parses a stream of attributes and stores a pointer to each attribute in
 177  * the tb array accessible via the attribute type. Attributes with a type
 178  * exceeding maxtype will be silently ignored for backwards compatibility
 179  * reasons. policy may be set to NULL if no validation is required.
 180  *
 181  * Returns 0 on success or a negative error code.
 182  */
 183 int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
 184               int len, const struct nla_policy *policy)
 185 {
 186         const struct nlattr *nla;
 187         int rem, err;
 188
 189         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 190
 191         nla_for_each_attr(nla, head, len, rem) {
 192                 u16 type = nla_type(nla);
 193
 194                 if (type > 0 && type <= maxtype) {
 195                         if (policy) {
 196                                 err = validate_nla(nla, maxtype, policy);
 197                                 if (err < 0)
 198                                         goto errout;
 199                         }
 200
 201                         tb[type] = (struct nlattr *)nla;
 202                 }
 203         }
 204
 205         if (unlikely(rem > 0))
 206                 pr_warn_ratelimited("netlink: %d bytes leftover after parsing attributes in process `%s'.\n",
 207                                     rem, current->comm);
 208
 209         err = 0;
 210 errout:
 211         return err;
 212 }
 213 EXPORT_SYMBOL(nla_parse);
 214
 215 /**
 216  * nla_find - Find a specific attribute in a stream of attributes
 217  * @head: head of attribute stream
 218  * @len: length of attribute stream
 219  * @attrtype: type of attribute to look for
 220  *
 221  * Returns the first attribute in the stream matching the specified type.
 222  */
 223 struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype)
 224 {
 225         const struct nlattr *nla;
 226         int rem;
 227
 228         nla_for_each_attr(nla, head, len, rem)
 229                 if (nla_type(nla) == attrtype)
 230                         return (struct nlattr *)nla;
 231
 232         return NULL;
 233 }
 234 EXPORT_SYMBOL(nla_find);
 235
 236 /**
 237  * nla_strlcpy - Copy string attribute payload into a sized buffer
 238  * @dst: where to copy the string to
 239  * @nla: attribute to copy the string from
 240  * @dstsize: size of destination buffer
 241  *
 242  * Copies at most dstsize - 1 bytes into the destination buffer.
 243  * The result is always a valid NUL-terminated string. Unlike
 244  * strlcpy the destination buffer is always padded out.
 245  *
 246  * Returns the length of the source buffer.
 247  */
 248 size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
 249 {
 250         size_t srclen = nla_len(nla);
 251         char *src = nla_data(nla);
 252
 253         if (srclen > 0 && src[srclen - 1] == '\0')
 254                 srclen--;
 255
 256         if (dstsize > 0) {
 257                 size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
 258
 259                 memset(dst, 0, dstsize);
 260                 memcpy(dst, src, len);
 261         }
 262
 263         return srclen;
 264 }
 265 EXPORT_SYMBOL(nla_strlcpy);
 266
 267 /**
 268  * nla_memcpy - Copy a netlink attribute into another memory area
 269  * @dest: where to copy to memcpy
 270  * @src: netlink attribute to copy from
 271  * @count: size of the destination area
 272  *
 273  * Note: The number of bytes copied is limited by the length of
 274  *       attribute's payload. memcpy
 275  *
 276  * Returns the number of bytes copied.
 277  */
 278 int nla_memcpy(void *dest, const struct nlattr *src, int count)
 279 {
 280         int minlen = min_t(int, count, nla_len(src));
 281
 282         memcpy(dest, nla_data(src), minlen);
 283
 284         return minlen;
 285 }
 286 EXPORT_SYMBOL(nla_memcpy);
 287
 288 /**
 289  * nla_memcmp - Compare an attribute with sized memory area
 290  * @nla: netlink attribute
 291  * @data: memory area
 292  * @size: size of memory area
 293  */
 294 int nla_memcmp(const struct nlattr *nla, const void *data,
 295                              size_t size)
 296 {
 297         int d = nla_len(nla) - size;
 298
 299         if (d == 0)
 300                 d = memcmp(nla_data(nla), data, size);
 301
 302         return d;
 303 }
 304 EXPORT_SYMBOL(nla_memcmp);
 305
 306 /**
 307  * nla_strcmp - Compare a string attribute against a string
 308  * @nla: netlink string attribute
 309  * @str: another string
 310  */
 311 int nla_strcmp(const struct nlattr *nla, const char *str)
 312 {
 313         int len = strlen(str);
 314         char *buf = nla_data(nla);
 315         int attrlen = nla_len(nla);
 316         int d;
 317
 318         if (attrlen > 0 && buf[attrlen - 1] == '\0')
 319                 attrlen--;
 320
 321         d = attrlen - len;
 322         if (d == 0)
 323                 d = memcmp(nla_data(nla), str, len);
 324
 325         return d;
 326 }
 327 EXPORT_SYMBOL(nla_strcmp);
 328
 329 #ifdef CONFIG_NET
 330 /**
 331  * __nla_reserve - reserve room for attribute on the skb
 332  * @skb: socket buffer to reserve room on
 333  * @attrtype: attribute type
 334  * @attrlen: length of attribute payload
 335  *
 336  * Adds a netlink attribute header to a socket buffer and reserves
 337  * room for the payload but does not copy it.
 338  *
 339  * The caller is responsible to ensure that the skb provides enough
 340  * tailroom for the attribute header and payload.
 341  */
 342 struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 343 {
 344         struct nlattr *nla;
 345
 346         nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
 347         nla->nla_type = attrtype;
 348         nla->nla_len = nla_attr_size(attrlen);
 349
 350         memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
 351
 352         return nla;
 353 }
 354 EXPORT_SYMBOL(__nla_reserve);
 355
 356 /**
 357  * __nla_reserve_nohdr - reserve room for attribute without header
 358  * @skb: socket buffer to reserve room on
 359  * @attrlen: length of attribute payload
 360  *
 361  * Reserves room for attribute payload without a header.
 362  *
 363  * The caller is responsible to ensure that the skb provides enough
 364  * tailroom for the payload.
 365  */
 366 void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 367 {
 368         void *start;
 369
 370         start = skb_put(skb, NLA_ALIGN(attrlen));
 371         memset(start, 0, NLA_ALIGN(attrlen));
 372
 373         return start;
 374 }
 375 EXPORT_SYMBOL(__nla_reserve_nohdr);
 376
 377 /**
 378  * nla_reserve - reserve room for attribute on the skb
 379  * @skb: socket buffer to reserve room on
 380  * @attrtype: attribute type
 381  * @attrlen: length of attribute payload
 382  *
 383  * Adds a netlink attribute header to a socket buffer and reserves
 384  * room for the payload but does not copy it.
 385  *
 386  * Returns NULL if the tailroom of the skb is insufficient to store
 387  * the attribute header and payload.
 388  */
 389 struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 390 {
 391         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 392                 return NULL;
 393
 394         return __nla_reserve(skb, attrtype, attrlen);
 395 }
 396 EXPORT_SYMBOL(nla_reserve);
 397
 398 /**
 399  * nla_reserve_nohdr - reserve room for attribute without header
 400  * @skb: socket buffer to reserve room on
 401  * @attrlen: length of attribute payload
 402  *
 403  * Reserves room for attribute payload without a header.
 404  *
 405  * Returns NULL if the tailroom of the skb is insufficient to store
 406  * the attribute payload.
 407  */
 408 void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 409 {
 410         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 411                 return NULL;
 412
 413         return __nla_reserve_nohdr(skb, attrlen);
 414 }
 415 EXPORT_SYMBOL(nla_reserve_nohdr);
 416
 417 /**
 418  * __nla_put - Add a netlink attribute to a socket buffer
 419  * @skb: socket buffer to add attribute to
 420  * @attrtype: attribute type
 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 header and payload.
 426  */
 427 void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 428                              const void *data)
 429 {
 430         struct nlattr *nla;
 431
 432         nla = __nla_reserve(skb, attrtype, attrlen);
 433         memcpy(nla_data(nla), data, attrlen);
 434 }
 435 EXPORT_SYMBOL(__nla_put);
 436
 437 /**
 438  * __nla_put_nohdr - Add a netlink attribute without header
 439  * @skb: socket buffer to add attribute to
 440  * @attrlen: length of attribute payload
 441  * @data: head of attribute payload
 442  *
 443  * The caller is responsible to ensure that the skb provides enough
 444  * tailroom for the attribute payload.
 445  */
 446 void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 447 {
 448         void *start;
 449
 450         start = __nla_reserve_nohdr(skb, attrlen);
 451         memcpy(start, data, attrlen);
 452 }
 453 EXPORT_SYMBOL(__nla_put_nohdr);
 454
 455 /**
 456  * nla_put - Add a netlink attribute to a socket buffer
 457  * @skb: socket buffer to add attribute to
 458  * @attrtype: attribute type
 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 header and payload.
 464  */
 465 int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
 466 {
 467         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 468                 return -EMSGSIZE;
 469
 470         __nla_put(skb, attrtype, attrlen, data);
 471         return 0;
 472 }
 473 EXPORT_SYMBOL(nla_put);
 474
 475 /**
 476  * nla_put_nohdr - Add a netlink attribute without header
 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  */
 484 int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 485 {
 486         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 487                 return -EMSGSIZE;
 488
 489         __nla_put_nohdr(skb, attrlen, data);
 490         return 0;
 491 }
 492 EXPORT_SYMBOL(nla_put_nohdr);
 493
 494 /**
 495  * nla_append - Add a netlink attribute without header or padding
 496  * @skb: socket buffer to add attribute to
 497  * @attrlen: length of attribute payload
 498  * @data: head of attribute payload
 499  *
 500  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 501  * the attribute payload.
 502  */
 503 int nla_append(struct sk_buff *skb, int attrlen, const void *data)
 504 {
 505         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 506                 return -EMSGSIZE;
 507
 508         memcpy(skb_put(skb, attrlen), data, attrlen);
 509         return 0;
 510 }
 511 EXPORT_SYMBOL(nla_append);
 512 #endif