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 };
  26
  27 static 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  */
 119 int 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;
 132 errout:
 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  */
 147 int
 148 nla_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  */
 177 int 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;
 204 errout:
 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  */
 216 struct 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  */
 240 size_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  */
 269 int 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  */
 284 int 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  */
 300 int 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  */
 324 struct 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 }
 336 EXPORT_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  */
 348 void *__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 }
 357 EXPORT_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  */
 371 struct 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 }
 378 EXPORT_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  */
 390 void *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 }
 397 EXPORT_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  */
 409 void __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 }
 417 EXPORT_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  */
 428 void __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 }
 435 EXPORT_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  */
 447 int 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 }
 455 EXPORT_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  */
 466 int 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 }
 474 EXPORT_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  */
 485 int 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 }
 493 EXPORT_SYMBOL(nla_append);
 494 #endif
 495
 496 EXPORT_SYMBOL(nla_validate);
 497 EXPORT_SYMBOL(nla_policy_len);
 498 EXPORT_SYMBOL(nla_parse);
 499 EXPORT_SYMBOL(nla_find);
 500 EXPORT_SYMBOL(nla_strlcpy);
 501 EXPORT_SYMBOL(nla_memcpy);
 502 EXPORT_SYMBOL(nla_memcmp);
 503 EXPORT_SYMBOL(nla_strcmp);