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/module.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 u16 nla_attr_minlen[NLA_TYPE_MAX+1] __read_mostly = {
  19         [NLA_U8]        = sizeof(u8),
  20         [NLA_U16]       = sizeof(u16),
  21         [NLA_U32]       = sizeof(u32),
  22         [NLA_U64]       = sizeof(u64),
  23         [NLA_NESTED]    = NLA_HDRLEN,
  24 };
  25
  26 static int validate_nla(struct nlattr *nla, int maxtype,
  27                         const struct nla_policy *policy)
  28 {
  29         const struct nla_policy *pt;
  30         int minlen = 0, attrlen = nla_len(nla), type = nla_type(nla);
  31
  32         if (type <= 0 || type > maxtype)
  33                 return 0;
  34
  35         pt = &policy[type];
  36
  37         BUG_ON(pt->type > NLA_TYPE_MAX);
  38
  39         switch (pt->type) {
  40         case NLA_FLAG:
  41                 if (attrlen > 0)
  42                         return -ERANGE;
  43                 break;
  44
  45         case NLA_NUL_STRING:
  46                 if (pt->len)
  47                         minlen = min_t(int, attrlen, pt->len + 1);
  48                 else
  49                         minlen = attrlen;
  50
  51                 if (!minlen || memchr(nla_data(nla), '\0', minlen) == NULL)
  52                         return -EINVAL;
  53                 /* fall through */
  54
  55         case NLA_STRING:
  56                 if (attrlen < 1)
  57                         return -ERANGE;
  58
  59                 if (pt->len) {
  60                         char *buf = nla_data(nla);
  61
  62                         if (buf[attrlen - 1] == '\0')
  63                                 attrlen--;
  64
  65                         if (attrlen > pt->len)
  66                                 return -ERANGE;
  67                 }
  68                 break;
  69
  70         case NLA_BINARY:
  71                 if (pt->len && attrlen > pt->len)
  72                         return -ERANGE;
  73                 break;
  74
  75         case NLA_NESTED_COMPAT:
  76                 if (attrlen < pt->len)
  77                         return -ERANGE;
  78                 if (attrlen < NLA_ALIGN(pt->len))
  79                         break;
  80                 if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN)
  81                         return -ERANGE;
  82                 nla = nla_data(nla) + NLA_ALIGN(pt->len);
  83                 if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN + nla_len(nla))
  84                         return -ERANGE;
  85                 break;
  86         case NLA_NESTED:
  87                 /* a nested attributes is allowed to be empty; if its not,
  88                  * it must have a size of at least NLA_HDRLEN.
  89                  */
  90                 if (attrlen == 0)
  91                         break;
  92         default:
  93                 if (pt->len)
  94                         minlen = pt->len;
  95                 else if (pt->type != NLA_UNSPEC)
  96                         minlen = nla_attr_minlen[pt->type];
  97
  98                 if (attrlen < minlen)
  99                         return -ERANGE;
 100         }
 101
 102         return 0;
 103 }
 104
 105 /**
 106  * nla_validate - Validate a stream of attributes
 107  * @head: head of attribute stream
 108  * @len: length of attribute stream
 109  * @maxtype: maximum attribute type to be expected
 110  * @policy: validation policy
 111  *
 112  * Validates all attributes in the specified attribute stream against the
 113  * specified policy. Attributes with a type exceeding maxtype will be
 114  * ignored. See documenation of struct nla_policy for more details.
 115  *
 116  * Returns 0 on success or a negative error code.
 117  */
 118 int nla_validate(struct nlattr *head, int len, int maxtype,
 119                  const struct nla_policy *policy)
 120 {
 121         struct nlattr *nla;
 122         int rem, err;
 123
 124         nla_for_each_attr(nla, head, len, rem) {
 125                 err = validate_nla(nla, maxtype, policy);
 126                 if (err < 0)
 127                         goto errout;
 128         }
 129
 130         err = 0;
 131 errout:
 132         return err;
 133 }
 134
 135 /**
 136  * nla_parse - Parse a stream of attributes into a tb buffer
 137  * @tb: destination array with maxtype+1 elements
 138  * @maxtype: maximum attribute type to be expected
 139  * @head: head of attribute stream
 140  * @len: length of attribute stream
 141  * @policy: validation policy
 142  *
 143  * Parses a stream of attributes and stores a pointer to each attribute in
 144  * the tb array accessable via the attribute type. Attributes with a type
 145  * exceeding maxtype will be silently ignored for backwards compatibility
 146  * reasons. policy may be set to NULL if no validation is required.
 147  *
 148  * Returns 0 on success or a negative error code.
 149  */
 150 int nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len,
 151               const struct nla_policy *policy)
 152 {
 153         struct nlattr *nla;
 154         int rem, err;
 155
 156         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 157
 158         nla_for_each_attr(nla, head, len, rem) {
 159                 u16 type = nla_type(nla);
 160
 161                 if (type > 0 && type <= maxtype) {
 162                         if (policy) {
 163                                 err = validate_nla(nla, maxtype, policy);
 164                                 if (err < 0)
 165                                         goto errout;
 166                         }
 167
 168                         tb[type] = nla;
 169                 }
 170         }
 171
 172         if (unlikely(rem > 0))
 173                 printk(KERN_WARNING "netlink: %d bytes leftover after parsing "
 174                        "attributes.\n", rem);
 175
 176         err = 0;
 177 errout:
 178         return err;
 179 }
 180
 181 /**
 182  * nla_find - Find a specific attribute in a stream of attributes
 183  * @head: head of attribute stream
 184  * @len: length of attribute stream
 185  * @attrtype: type of attribute to look for
 186  *
 187  * Returns the first attribute in the stream matching the specified type.
 188  */
 189 struct nlattr *nla_find(struct nlattr *head, int len, int attrtype)
 190 {
 191         struct nlattr *nla;
 192         int rem;
 193
 194         nla_for_each_attr(nla, head, len, rem)
 195                 if (nla_type(nla) == attrtype)
 196                         return nla;
 197
 198         return NULL;
 199 }
 200
 201 /**
 202  * nla_strlcpy - Copy string attribute payload into a sized buffer
 203  * @dst: where to copy the string to
 204  * @nla: attribute to copy the string from
 205  * @dstsize: size of destination buffer
 206  *
 207  * Copies at most dstsize - 1 bytes into the destination buffer.
 208  * The result is always a valid NUL-terminated string. Unlike
 209  * strlcpy the destination buffer is always padded out.
 210  *
 211  * Returns the length of the source buffer.
 212  */
 213 size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
 214 {
 215         size_t srclen = nla_len(nla);
 216         char *src = nla_data(nla);
 217
 218         if (srclen > 0 && src[srclen - 1] == '\0')
 219                 srclen--;
 220
 221         if (dstsize > 0) {
 222                 size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
 223
 224                 memset(dst, 0, dstsize);
 225                 memcpy(dst, src, len);
 226         }
 227
 228         return srclen;
 229 }
 230
 231 /**
 232  * nla_memcpy - Copy a netlink attribute into another memory area
 233  * @dest: where to copy to memcpy
 234  * @src: netlink attribute to copy from
 235  * @count: size of the destination area
 236  *
 237  * Note: The number of bytes copied is limited by the length of
 238  *       attribute's payload. memcpy
 239  *
 240  * Returns the number of bytes copied.
 241  */
 242 int nla_memcpy(void *dest, const struct nlattr *src, int count)
 243 {
 244         int minlen = min_t(int, count, nla_len(src));
 245
 246         memcpy(dest, nla_data(src), minlen);
 247
 248         return minlen;
 249 }
 250
 251 /**
 252  * nla_memcmp - Compare an attribute with sized memory area
 253  * @nla: netlink attribute
 254  * @data: memory area
 255  * @size: size of memory area
 256  */
 257 int nla_memcmp(const struct nlattr *nla, const void *data,
 258                              size_t size)
 259 {
 260         int d = nla_len(nla) - size;
 261
 262         if (d == 0)
 263                 d = memcmp(nla_data(nla), data, size);
 264
 265         return d;
 266 }
 267
 268 /**
 269  * nla_strcmp - Compare a string attribute against a string
 270  * @nla: netlink string attribute
 271  * @str: another string
 272  */
 273 int nla_strcmp(const struct nlattr *nla, const char *str)
 274 {
 275         int len = strlen(str) + 1;
 276         int d = nla_len(nla) - len;
 277
 278         if (d == 0)
 279                 d = memcmp(nla_data(nla), str, len);
 280
 281         return d;
 282 }
 283
 284 #ifdef CONFIG_NET
 285 /**
 286  * __nla_reserve - reserve room for attribute on the skb
 287  * @skb: socket buffer to reserve room on
 288  * @attrtype: attribute type
 289  * @attrlen: length of attribute payload
 290  *
 291  * Adds a netlink attribute header to a socket buffer and reserves
 292  * room for the payload but does not copy it.
 293  *
 294  * The caller is responsible to ensure that the skb provides enough
 295  * tailroom for the attribute header and payload.
 296  */
 297 struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 298 {
 299         struct nlattr *nla;
 300
 301         nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
 302         nla->nla_type = attrtype;
 303         nla->nla_len = nla_attr_size(attrlen);
 304
 305         memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
 306
 307         return nla;
 308 }
 309 EXPORT_SYMBOL(__nla_reserve);
 310
 311 /**
 312  * __nla_reserve_nohdr - reserve room for attribute without header
 313  * @skb: socket buffer to reserve room on
 314  * @attrlen: length of attribute payload
 315  *
 316  * Reserves room for attribute payload without a header.
 317  *
 318  * The caller is responsible to ensure that the skb provides enough
 319  * tailroom for the payload.
 320  */
 321 void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 322 {
 323         void *start;
 324
 325         start = skb_put(skb, NLA_ALIGN(attrlen));
 326         memset(start, 0, NLA_ALIGN(attrlen));
 327
 328         return start;
 329 }
 330 EXPORT_SYMBOL(__nla_reserve_nohdr);
 331
 332 /**
 333  * nla_reserve - reserve room for attribute on the skb
 334  * @skb: socket buffer to reserve room on
 335  * @attrtype: attribute type
 336  * @attrlen: length of attribute payload
 337  *
 338  * Adds a netlink attribute header to a socket buffer and reserves
 339  * room for the payload but does not copy it.
 340  *
 341  * Returns NULL if the tailroom of the skb is insufficient to store
 342  * the attribute header and payload.
 343  */
 344 struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 345 {
 346         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 347                 return NULL;
 348
 349         return __nla_reserve(skb, attrtype, attrlen);
 350 }
 351 EXPORT_SYMBOL(nla_reserve);
 352
 353 /**
 354  * nla_reserve_nohdr - reserve room for attribute without header
 355  * @skb: socket buffer to reserve room on
 356  * @attrlen: length of attribute payload
 357  *
 358  * Reserves room for attribute payload without a header.
 359  *
 360  * Returns NULL if the tailroom of the skb is insufficient to store
 361  * the attribute payload.
 362  */
 363 void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 364 {
 365         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 366                 return NULL;
 367
 368         return __nla_reserve_nohdr(skb, attrlen);
 369 }
 370 EXPORT_SYMBOL(nla_reserve_nohdr);
 371
 372 /**
 373  * __nla_put - Add a netlink attribute to a socket buffer
 374  * @skb: socket buffer to add attribute to
 375  * @attrtype: attribute type
 376  * @attrlen: length of attribute payload
 377  * @data: head of attribute payload
 378  *
 379  * The caller is responsible to ensure that the skb provides enough
 380  * tailroom for the attribute header and payload.
 381  */
 382 void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 383                              const void *data)
 384 {
 385         struct nlattr *nla;
 386
 387         nla = __nla_reserve(skb, attrtype, attrlen);
 388         memcpy(nla_data(nla), data, attrlen);
 389 }
 390 EXPORT_SYMBOL(__nla_put);
 391
 392 /**
 393  * __nla_put_nohdr - Add a netlink attribute without header
 394  * @skb: socket buffer to add attribute to
 395  * @attrlen: length of attribute payload
 396  * @data: head of attribute payload
 397  *
 398  * The caller is responsible to ensure that the skb provides enough
 399  * tailroom for the attribute payload.
 400  */
 401 void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 402 {
 403         void *start;
 404
 405         start = __nla_reserve_nohdr(skb, attrlen);
 406         memcpy(start, data, attrlen);
 407 }
 408 EXPORT_SYMBOL(__nla_put_nohdr);
 409
 410 /**
 411  * nla_put - Add a netlink attribute to a socket buffer
 412  * @skb: socket buffer to add attribute to
 413  * @attrtype: attribute type
 414  * @attrlen: length of attribute payload
 415  * @data: head of attribute payload
 416  *
 417  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 418  * the attribute header and payload.
 419  */
 420 int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
 421 {
 422         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 423                 return -EMSGSIZE;
 424
 425         __nla_put(skb, attrtype, attrlen, data);
 426         return 0;
 427 }
 428 EXPORT_SYMBOL(nla_put);
 429
 430 /**
 431  * nla_put_nohdr - Add a netlink attribute without header
 432  * @skb: socket buffer to add attribute to
 433  * @attrlen: length of attribute payload
 434  * @data: head of attribute payload
 435  *
 436  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 437  * the attribute payload.
 438  */
 439 int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 440 {
 441         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 442                 return -EMSGSIZE;
 443
 444         __nla_put_nohdr(skb, attrlen, data);
 445         return 0;
 446 }
 447 EXPORT_SYMBOL(nla_put_nohdr);
 448
 449 /**
 450  * nla_append - Add a netlink attribute without header or padding
 451  * @skb: socket buffer to add attribute to
 452  * @attrlen: length of attribute payload
 453  * @data: head of attribute payload
 454  *
 455  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 456  * the attribute payload.
 457  */
 458 int nla_append(struct sk_buff *skb, int attrlen, const void *data)
 459 {
 460         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 461                 return -EMSGSIZE;
 462
 463         memcpy(skb_put(skb, attrlen), data, attrlen);
 464         return 0;
 465 }
 466 EXPORT_SYMBOL(nla_append);
 467 #endif
 468
 469 EXPORT_SYMBOL(nla_validate);
 470 EXPORT_SYMBOL(nla_parse);
 471 EXPORT_SYMBOL(nla_find);
 472 EXPORT_SYMBOL(nla_strlcpy);
 473 EXPORT_SYMBOL(nla_memcpy);
 474 EXPORT_SYMBOL(nla_memcmp);
 475 EXPORT_SYMBOL(nla_strcmp);