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/skbuff.h>
  13 #include <linux/string.h>
  14 #include <linux/types.h>
  15 #include <net/netlink.h>
  16
  17 static const u16 nla_attr_minlen[NLA_TYPE_MAX+1] = {
  18         [NLA_U8]        = sizeof(u8),
  19         [NLA_U16]       = sizeof(u16),
  20         [NLA_U32]       = sizeof(u32),
  21         [NLA_U64]       = sizeof(u64),
  22         [NLA_MSECS]     = sizeof(u64),
  23         [NLA_NESTED]    = NLA_HDRLEN,
  24         [NLA_S8]        = sizeof(s8),
  25         [NLA_S16]       = sizeof(s16),
  26         [NLA_S32]       = sizeof(s32),
  27         [NLA_S64]       = sizeof(s64),
  28 };
  29
  30 static int validate_nla(const struct nlattr *nla, int maxtype,
  31                         const struct nla_policy *policy)
  32 {
  33         const struct nla_policy *pt;
  34         int minlen = 0, attrlen = nla_len(nla), type = nla_type(nla);
  35
  36         if (type <= 0 || type > maxtype)
  37                 return 0;
  38
  39         pt = &policy[type];
  40
  41         BUG_ON(pt->type > NLA_TYPE_MAX);
  42
  43         switch (pt->type) {
  44         case NLA_FLAG:
  45                 if (attrlen > 0)
  46                         return -ERANGE;
  47                 break;
  48
  49         case NLA_NUL_STRING:
  50                 if (pt->len)
  51                         minlen = min_t(int, attrlen, pt->len + 1);
  52                 else
  53                         minlen = attrlen;
  54
  55                 if (!minlen || memchr(nla_data(nla), '\0', minlen) == NULL)
  56                         return -EINVAL;
  57                 /* fall through */
  58
  59         case NLA_STRING:
  60                 if (attrlen < 1)
  61                         return -ERANGE;
  62
  63                 if (pt->len) {
  64                         char *buf = nla_data(nla);
  65
  66                         if (buf[attrlen - 1] == '\0')
  67                                 attrlen--;
  68
  69                         if (attrlen > pt->len)
  70                                 return -ERANGE;
  71                 }
  72                 break;
  73
  74         case NLA_BINARY:
  75                 if (pt->len && attrlen > pt->len)
  76                         return -ERANGE;
  77                 break;
  78
  79         case NLA_NESTED_COMPAT:
  80                 if (attrlen < pt->len)
  81                         return -ERANGE;
  82                 if (attrlen < NLA_ALIGN(pt->len))
  83                         break;
  84                 if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN)
  85                         return -ERANGE;
  86                 nla = nla_data(nla) + NLA_ALIGN(pt->len);
  87                 if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN + nla_len(nla))
  88                         return -ERANGE;
  89                 break;
  90         case NLA_NESTED:
  91                 /* a nested attributes is allowed to be empty; if its not,
  92                  * it must have a size of at least NLA_HDRLEN.
  93                  */
  94                 if (attrlen == 0)
  95                         break;
  96         default:
  97                 if (pt->len)
  98                         minlen = pt->len;
  99                 else if (pt->type != NLA_UNSPEC)
 100                         minlen = nla_attr_minlen[pt->type];
 101
 102                 if (attrlen < minlen)
 103                         return -ERANGE;
 104         }
 105
 106         return 0;
 107 }
 108
 109 /**
 110  * nla_validate - Validate a stream of attributes
 111  * @head: head of attribute stream
 112  * @len: length of attribute stream
 113  * @maxtype: maximum attribute type to be expected
 114  * @policy: validation policy
 115  *
 116  * Validates all attributes in the specified attribute stream against the
 117  * specified policy. Attributes with a type exceeding maxtype will be
 118  * ignored. See documenation of struct nla_policy for more details.
 119  *
 120  * Returns 0 on success or a negative error code.
 121  */
 122 int nla_validate(const struct nlattr *head, int len, int maxtype,
 123                  const struct nla_policy *policy)
 124 {
 125         const struct nlattr *nla;
 126         int rem, err;
 127
 128         nla_for_each_attr(nla, head, len, rem) {
 129                 err = validate_nla(nla, maxtype, policy);
 130                 if (err < 0)
 131                         goto errout;
 132         }
 133
 134         err = 0;
 135 errout:
 136         return err;
 137 }
 138 EXPORT_SYMBOL(nla_validate);
 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  */
 151 int
 152 nla_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 EXPORT_SYMBOL(nla_policy_len);
 166
 167 /**
 168  * nla_parse - Parse a stream of attributes into a tb buffer
 169  * @tb: destination array with maxtype+1 elements
 170  * @maxtype: maximum attribute type to be expected
 171  * @head: head of attribute stream
 172  * @len: length of attribute stream
 173  * @policy: validation policy
 174  *
 175  * Parses a stream of attributes and stores a pointer to each attribute in
 176  * the tb array accessible via the attribute type. Attributes with a type
 177  * exceeding maxtype will be silently ignored for backwards compatibility
 178  * reasons. policy may be set to NULL if no validation is required.
 179  *
 180  * Returns 0 on success or a negative error code.
 181  */
 182 int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
 183               int len, const struct nla_policy *policy)
 184 {
 185         const struct nlattr *nla;
 186         int rem, err;
 187
 188         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 189
 190         nla_for_each_attr(nla, head, len, rem) {
 191                 u16 type = nla_type(nla);
 192
 193                 if (type > 0 && type <= maxtype) {
 194                         if (policy) {
 195                                 err = validate_nla(nla, maxtype, policy);
 196                                 if (err < 0)
 197                                         goto errout;
 198                         }
 199
 200                         tb[type] = (struct nlattr *)nla;
 201                 }
 202         }
 203
 204         if (unlikely(rem > 0))
 205                 pr_warn_ratelimited("netlink: %d bytes leftover after parsing attributes in process `%s'.\n",
 206                                     rem, current->comm);
 207
 208         err = 0;
 209 errout:
 210         return err;
 211 }
 212 EXPORT_SYMBOL(nla_parse);
 213
 214 /**
 215  * nla_find - Find a specific attribute in a stream of attributes
 216  * @head: head of attribute stream
 217  * @len: length of attribute stream
 218  * @attrtype: type of attribute to look for
 219  *
 220  * Returns the first attribute in the stream matching the specified type.
 221  */
 222 struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype)
 223 {
 224         const struct nlattr *nla;
 225         int rem;
 226
 227         nla_for_each_attr(nla, head, len, rem)
 228                 if (nla_type(nla) == attrtype)
 229                         return (struct nlattr *)nla;
 230
 231         return NULL;
 232 }
 233 EXPORT_SYMBOL(nla_find);
 234
 235 /**
 236  * nla_strlcpy - Copy string attribute payload into a sized buffer
 237  * @dst: where to copy the string to
 238  * @nla: attribute to copy the string from
 239  * @dstsize: size of destination buffer
 240  *
 241  * Copies at most dstsize - 1 bytes into the destination buffer.
 242  * The result is always a valid NUL-terminated string. Unlike
 243  * strlcpy the destination buffer is always padded out.
 244  *
 245  * Returns the length of the source buffer.
 246  */
 247 size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
 248 {
 249         size_t srclen = nla_len(nla);
 250         char *src = nla_data(nla);
 251
 252         if (srclen > 0 && src[srclen - 1] == '\0')
 253                 srclen--;
 254
 255         if (dstsize > 0) {
 256                 size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
 257
 258                 memset(dst, 0, dstsize);
 259                 memcpy(dst, src, len);
 260         }
 261
 262         return srclen;
 263 }
 264 EXPORT_SYMBOL(nla_strlcpy);
 265
 266 /**
 267  * nla_memcpy - Copy a netlink attribute into another memory area
 268  * @dest: where to copy to memcpy
 269  * @src: netlink attribute to copy from
 270  * @count: size of the destination area
 271  *
 272  * Note: The number of bytes copied is limited by the length of
 273  *       attribute's payload. memcpy
 274  *
 275  * Returns the number of bytes copied.
 276  */
 277 int nla_memcpy(void *dest, const struct nlattr *src, int count)
 278 {
 279         int minlen = min_t(int, count, nla_len(src));
 280
 281         memcpy(dest, nla_data(src), minlen);
 282         if (count > minlen)
 283                 memset(dest + minlen, 0, count - minlen);
 284
 285         return minlen;
 286 }
 287 EXPORT_SYMBOL(nla_memcpy);
 288
 289 /**
 290  * nla_memcmp - Compare an attribute with sized memory area
 291  * @nla: netlink attribute
 292  * @data: memory area
 293  * @size: size of memory area
 294  */
 295 int nla_memcmp(const struct nlattr *nla, const void *data,
 296                              size_t size)
 297 {
 298         int d = nla_len(nla) - size;
 299
 300         if (d == 0)
 301                 d = memcmp(nla_data(nla), data, size);
 302
 303         return d;
 304 }
 305 EXPORT_SYMBOL(nla_memcmp);
 306
 307 /**
 308  * nla_strcmp - Compare a string attribute against a string
 309  * @nla: netlink string attribute
 310  * @str: another string
 311  */
 312 int nla_strcmp(const struct nlattr *nla, const char *str)
 313 {
 314         int len = strlen(str);
 315         char *buf = nla_data(nla);
 316         int attrlen = nla_len(nla);
 317         int d;
 318
 319         if (attrlen > 0 && buf[attrlen - 1] == '\0')
 320                 attrlen--;
 321
 322         d = attrlen - len;
 323         if (d == 0)
 324                 d = memcmp(nla_data(nla), str, len);
 325
 326         return d;
 327 }
 328 EXPORT_SYMBOL(nla_strcmp);
 329
 330 #ifdef CONFIG_NET
 331 /**
 332  * __nla_reserve - reserve room for attribute on the skb
 333  * @skb: socket buffer to reserve room on
 334  * @attrtype: attribute type
 335  * @attrlen: length of attribute payload
 336  *
 337  * Adds a netlink attribute header to a socket buffer and reserves
 338  * room for the payload but does not copy it.
 339  *
 340  * The caller is responsible to ensure that the skb provides enough
 341  * tailroom for the attribute header and payload.
 342  */
 343 struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 344 {
 345         struct nlattr *nla;
 346
 347         nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
 348         nla->nla_type = attrtype;
 349         nla->nla_len = nla_attr_size(attrlen);
 350
 351         memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
 352
 353         return nla;
 354 }
 355 EXPORT_SYMBOL(__nla_reserve);
 356
 357 /**
 358  * __nla_reserve_nohdr - reserve room for attribute without header
 359  * @skb: socket buffer to reserve room on
 360  * @attrlen: length of attribute payload
 361  *
 362  * Reserves room for attribute payload without a header.
 363  *
 364  * The caller is responsible to ensure that the skb provides enough
 365  * tailroom for the payload.
 366  */
 367 void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 368 {
 369         void *start;
 370
 371         start = skb_put(skb, NLA_ALIGN(attrlen));
 372         memset(start, 0, NLA_ALIGN(attrlen));
 373
 374         return start;
 375 }
 376 EXPORT_SYMBOL(__nla_reserve_nohdr);
 377
 378 /**
 379  * nla_reserve - reserve room for attribute on the skb
 380  * @skb: socket buffer to reserve room on
 381  * @attrtype: attribute type
 382  * @attrlen: length of attribute payload
 383  *
 384  * Adds a netlink attribute header to a socket buffer and reserves
 385  * room for the payload but does not copy it.
 386  *
 387  * Returns NULL if the tailroom of the skb is insufficient to store
 388  * the attribute header and payload.
 389  */
 390 struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 391 {
 392         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 393                 return NULL;
 394
 395         return __nla_reserve(skb, attrtype, attrlen);
 396 }
 397 EXPORT_SYMBOL(nla_reserve);
 398
 399 /**
 400  * nla_reserve_nohdr - reserve room for attribute without header
 401  * @skb: socket buffer to reserve room on
 402  * @attrlen: length of attribute payload
 403  *
 404  * Reserves room for attribute payload without a header.
 405  *
 406  * Returns NULL if the tailroom of the skb is insufficient to store
 407  * the attribute payload.
 408  */
 409 void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 410 {
 411         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 412                 return NULL;
 413
 414         return __nla_reserve_nohdr(skb, attrlen);
 415 }
 416 EXPORT_SYMBOL(nla_reserve_nohdr);
 417
 418 /**
 419  * __nla_put - Add a netlink attribute to a socket buffer
 420  * @skb: socket buffer to add attribute to
 421  * @attrtype: attribute type
 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 header and payload.
 427  */
 428 void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 429                              const void *data)
 430 {
 431         struct nlattr *nla;
 432
 433         nla = __nla_reserve(skb, attrtype, attrlen);
 434         memcpy(nla_data(nla), data, attrlen);
 435 }
 436 EXPORT_SYMBOL(__nla_put);
 437
 438 /**
 439  * __nla_put_nohdr - Add a netlink attribute without header
 440  * @skb: socket buffer to add attribute to
 441  * @attrlen: length of attribute payload
 442  * @data: head of attribute payload
 443  *
 444  * The caller is responsible to ensure that the skb provides enough
 445  * tailroom for the attribute payload.
 446  */
 447 void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 448 {
 449         void *start;
 450
 451         start = __nla_reserve_nohdr(skb, attrlen);
 452         memcpy(start, data, attrlen);
 453 }
 454 EXPORT_SYMBOL(__nla_put_nohdr);
 455
 456 /**
 457  * nla_put - Add a netlink attribute to a socket buffer
 458  * @skb: socket buffer to add attribute to
 459  * @attrtype: attribute type
 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 header and payload.
 465  */
 466 int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
 467 {
 468         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 469                 return -EMSGSIZE;
 470
 471         __nla_put(skb, attrtype, attrlen, data);
 472         return 0;
 473 }
 474 EXPORT_SYMBOL(nla_put);
 475
 476 /**
 477  * nla_put_nohdr - Add a netlink attribute without header
 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  */
 485 int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 486 {
 487         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 488                 return -EMSGSIZE;
 489
 490         __nla_put_nohdr(skb, attrlen, data);
 491         return 0;
 492 }
 493 EXPORT_SYMBOL(nla_put_nohdr);
 494
 495 /**
 496  * nla_append - Add a netlink attribute without header or padding
 497  * @skb: socket buffer to add attribute to
 498  * @attrlen: length of attribute payload
 499  * @data: head of attribute payload
 500  *
 501  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 502  * the attribute payload.
 503  */
 504 int nla_append(struct sk_buff *skb, int attrlen, const void *data)
 505 {
 506         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 507                 return -EMSGSIZE;
 508
 509         memcpy(skb_put(skb, attrlen), data, attrlen);
 510         return 0;
 511 }
 512 EXPORT_SYMBOL(nla_append);
 513 #endif