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
 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
 166 /**
 167  * nla_parse - Parse a stream of attributes into a tb buffer
 168  * @tb: destination array with maxtype+1 elements
 169  * @maxtype: maximum attribute type to be expected
 170  * @head: head of attribute stream
 171  * @len: length of attribute stream
 172  * @policy: validation policy
 173  *
 174  * Parses a stream of attributes and stores a pointer to each attribute in
 175  * the tb array accessible via the attribute type. Attributes with a type
 176  * exceeding maxtype will be silently ignored for backwards compatibility
 177  * reasons. policy may be set to NULL if no validation is required.
 178  *
 179  * Returns 0 on success or a negative error code.
 180  */
 181 int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
 182               int len, const struct nla_policy *policy)
 183 {
 184         const struct nlattr *nla;
 185         int rem, err;
 186
 187         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 188
 189         nla_for_each_attr(nla, head, len, rem) {
 190                 u16 type = nla_type(nla);
 191
 192                 if (type > 0 && type <= maxtype) {
 193                         if (policy) {
 194                                 err = validate_nla(nla, maxtype, policy);
 195                                 if (err < 0)
 196                                         goto errout;
 197                         }
 198
 199                         tb[type] = (struct nlattr *)nla;
 200                 }
 201         }
 202
 203         if (unlikely(rem > 0))
 204                 pr_warn_ratelimited("netlink: %d bytes leftover after parsing attributes in process `%s'.\n",
 205                                     rem, current->comm);
 206
 207         err = 0;
 208 errout:
 209         return err;
 210 }
 211
 212 /**
 213  * nla_find - Find a specific attribute in a stream of attributes
 214  * @head: head of attribute stream
 215  * @len: length of attribute stream
 216  * @attrtype: type of attribute to look for
 217  *
 218  * Returns the first attribute in the stream matching the specified type.
 219  */
 220 struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype)
 221 {
 222         const struct nlattr *nla;
 223         int rem;
 224
 225         nla_for_each_attr(nla, head, len, rem)
 226                 if (nla_type(nla) == attrtype)
 227                         return (struct nlattr *)nla;
 228
 229         return NULL;
 230 }
 231
 232 /**
 233  * nla_strlcpy - Copy string attribute payload into a sized buffer
 234  * @dst: where to copy the string to
 235  * @nla: attribute to copy the string from
 236  * @dstsize: size of destination buffer
 237  *
 238  * Copies at most dstsize - 1 bytes into the destination buffer.
 239  * The result is always a valid NUL-terminated string. Unlike
 240  * strlcpy the destination buffer is always padded out.
 241  *
 242  * Returns the length of the source buffer.
 243  */
 244 size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
 245 {
 246         size_t srclen = nla_len(nla);
 247         char *src = nla_data(nla);
 248
 249         if (srclen > 0 && src[srclen - 1] == '\0')
 250                 srclen--;
 251
 252         if (dstsize > 0) {
 253                 size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
 254
 255                 memset(dst, 0, dstsize);
 256                 memcpy(dst, src, len);
 257         }
 258
 259         return srclen;
 260 }
 261
 262 /**
 263  * nla_memcpy - Copy a netlink attribute into another memory area
 264  * @dest: where to copy to memcpy
 265  * @src: netlink attribute to copy from
 266  * @count: size of the destination area
 267  *
 268  * Note: The number of bytes copied is limited by the length of
 269  *       attribute's payload. memcpy
 270  *
 271  * Returns the number of bytes copied.
 272  */
 273 int nla_memcpy(void *dest, const struct nlattr *src, int count)
 274 {
 275         int minlen = min_t(int, count, nla_len(src));
 276
 277         memcpy(dest, nla_data(src), minlen);
 278
 279         return minlen;
 280 }
 281
 282 /**
 283  * nla_memcmp - Compare an attribute with sized memory area
 284  * @nla: netlink attribute
 285  * @data: memory area
 286  * @size: size of memory area
 287  */
 288 int nla_memcmp(const struct nlattr *nla, const void *data,
 289                              size_t size)
 290 {
 291         int d = nla_len(nla) - size;
 292
 293         if (d == 0)
 294                 d = memcmp(nla_data(nla), data, size);
 295
 296         return d;
 297 }
 298
 299 /**
 300  * nla_strcmp - Compare a string attribute against a string
 301  * @nla: netlink string attribute
 302  * @str: another string
 303  */
 304 int nla_strcmp(const struct nlattr *nla, const char *str)
 305 {
 306         int len = strlen(str);
 307         char *buf = nla_data(nla);
 308         int attrlen = nla_len(nla);
 309         int d;
 310
 311         if (attrlen > 0 && buf[attrlen - 1] == '\0')
 312                 attrlen--;
 313
 314         d = attrlen - len;
 315         if (d == 0)
 316                 d = memcmp(nla_data(nla), str, len);
 317
 318         return d;
 319 }
 320
 321 #ifdef CONFIG_NET
 322 /**
 323  * __nla_reserve - reserve room for attribute on the skb
 324  * @skb: socket buffer to reserve room on
 325  * @attrtype: attribute type
 326  * @attrlen: length of attribute payload
 327  *
 328  * Adds a netlink attribute header to a socket buffer and reserves
 329  * room for the payload but does not copy it.
 330  *
 331  * The caller is responsible to ensure that the skb provides enough
 332  * tailroom for the attribute header and payload.
 333  */
 334 struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 335 {
 336         struct nlattr *nla;
 337
 338         nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
 339         nla->nla_type = attrtype;
 340         nla->nla_len = nla_attr_size(attrlen);
 341
 342         memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
 343
 344         return nla;
 345 }
 346 EXPORT_SYMBOL(__nla_reserve);
 347
 348 /**
 349  * __nla_reserve_nohdr - reserve room for attribute without header
 350  * @skb: socket buffer to reserve room on
 351  * @attrlen: length of attribute payload
 352  *
 353  * Reserves room for attribute payload without a header.
 354  *
 355  * The caller is responsible to ensure that the skb provides enough
 356  * tailroom for the payload.
 357  */
 358 void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 359 {
 360         void *start;
 361
 362         start = skb_put(skb, NLA_ALIGN(attrlen));
 363         memset(start, 0, NLA_ALIGN(attrlen));
 364
 365         return start;
 366 }
 367 EXPORT_SYMBOL(__nla_reserve_nohdr);
 368
 369 /**
 370  * nla_reserve - reserve room for attribute on the skb
 371  * @skb: socket buffer to reserve room on
 372  * @attrtype: attribute type
 373  * @attrlen: length of attribute payload
 374  *
 375  * Adds a netlink attribute header to a socket buffer and reserves
 376  * room for the payload but does not copy it.
 377  *
 378  * Returns NULL if the tailroom of the skb is insufficient to store
 379  * the attribute header and payload.
 380  */
 381 struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 382 {
 383         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 384                 return NULL;
 385
 386         return __nla_reserve(skb, attrtype, attrlen);
 387 }
 388 EXPORT_SYMBOL(nla_reserve);
 389
 390 /**
 391  * nla_reserve_nohdr - reserve room for attribute without header
 392  * @skb: socket buffer to reserve room on
 393  * @attrlen: length of attribute payload
 394  *
 395  * Reserves room for attribute payload without a header.
 396  *
 397  * Returns NULL if the tailroom of the skb is insufficient to store
 398  * the attribute payload.
 399  */
 400 void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 401 {
 402         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 403                 return NULL;
 404
 405         return __nla_reserve_nohdr(skb, attrlen);
 406 }
 407 EXPORT_SYMBOL(nla_reserve_nohdr);
 408
 409 /**
 410  * __nla_put - Add a netlink attribute to a socket buffer
 411  * @skb: socket buffer to add attribute to
 412  * @attrtype: attribute type
 413  * @attrlen: length of attribute payload
 414  * @data: head of attribute payload
 415  *
 416  * The caller is responsible to ensure that the skb provides enough
 417  * tailroom for the attribute header and payload.
 418  */
 419 void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 420                              const void *data)
 421 {
 422         struct nlattr *nla;
 423
 424         nla = __nla_reserve(skb, attrtype, attrlen);
 425         memcpy(nla_data(nla), data, attrlen);
 426 }
 427 EXPORT_SYMBOL(__nla_put);
 428
 429 /**
 430  * __nla_put_nohdr - Add a netlink attribute without header
 431  * @skb: socket buffer to add attribute to
 432  * @attrlen: length of attribute payload
 433  * @data: head of attribute payload
 434  *
 435  * The caller is responsible to ensure that the skb provides enough
 436  * tailroom for the attribute payload.
 437  */
 438 void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 439 {
 440         void *start;
 441
 442         start = __nla_reserve_nohdr(skb, attrlen);
 443         memcpy(start, data, attrlen);
 444 }
 445 EXPORT_SYMBOL(__nla_put_nohdr);
 446
 447 /**
 448  * nla_put - Add a netlink attribute to a socket buffer
 449  * @skb: socket buffer to add attribute to
 450  * @attrtype: attribute type
 451  * @attrlen: length of attribute payload
 452  * @data: head of attribute payload
 453  *
 454  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 455  * the attribute header and payload.
 456  */
 457 int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
 458 {
 459         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 460                 return -EMSGSIZE;
 461
 462         __nla_put(skb, attrtype, attrlen, data);
 463         return 0;
 464 }
 465 EXPORT_SYMBOL(nla_put);
 466
 467 /**
 468  * nla_put_nohdr - Add a netlink attribute without header
 469  * @skb: socket buffer to add attribute to
 470  * @attrlen: length of attribute payload
 471  * @data: head of attribute payload
 472  *
 473  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 474  * the attribute payload.
 475  */
 476 int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 477 {
 478         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 479                 return -EMSGSIZE;
 480
 481         __nla_put_nohdr(skb, attrlen, data);
 482         return 0;
 483 }
 484 EXPORT_SYMBOL(nla_put_nohdr);
 485
 486 /**
 487  * nla_append - Add a netlink attribute without header or padding
 488  * @skb: socket buffer to add attribute to
 489  * @attrlen: length of attribute payload
 490  * @data: head of attribute payload
 491  *
 492  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 493  * the attribute payload.
 494  */
 495 int nla_append(struct sk_buff *skb, int attrlen, const void *data)
 496 {
 497         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 498                 return -EMSGSIZE;
 499
 500         memcpy(skb_put(skb, attrlen), data, attrlen);
 501         return 0;
 502 }
 503 EXPORT_SYMBOL(nla_append);
 504 #endif
 505
 506 EXPORT_SYMBOL(nla_validate);
 507 EXPORT_SYMBOL(nla_policy_len);
 508 EXPORT_SYMBOL(nla_parse);
 509 EXPORT_SYMBOL(nla_find);
 510 EXPORT_SYMBOL(nla_strlcpy);
 511 EXPORT_SYMBOL(nla_memcpy);
 512 EXPORT_SYMBOL(nla_memcmp);
 513 EXPORT_SYMBOL(nla_strcmp);