net/netlink/attr.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         default:
  87                 if (pt->len)
  88                         minlen = pt->len;
  89                 else if (pt->type != NLA_UNSPEC)
  90                         minlen = nla_attr_minlen[pt->type];
  91
  92                 if (attrlen < minlen)
  93                         return -ERANGE;
  94         }
  95
  96         return 0;
  97 }
  98
  99 /**
 100  * nla_validate - Validate a stream of attributes
 101  * @head: head of attribute stream
 102  * @len: length of attribute stream
 103  * @maxtype: maximum attribute type to be expected
 104  * @policy: validation policy
 105  *
 106  * Validates all attributes in the specified attribute stream against the
 107  * specified policy. Attributes with a type exceeding maxtype will be
 108  * ignored. See documenation of struct nla_policy for more details.
 109  *
 110  * Returns 0 on success or a negative error code.
 111  */
 112 int nla_validate(struct nlattr *head, int len, int maxtype,
 113                  const struct nla_policy *policy)
 114 {
 115         struct nlattr *nla;
 116         int rem, err;
 117
 118         nla_for_each_attr(nla, head, len, rem) {
 119                 err = validate_nla(nla, maxtype, policy);
 120                 if (err < 0)
 121                         goto errout;
 122         }
 123
 124         err = 0;
 125 errout:
 126         return err;
 127 }
 128
 129 /**
 130  * nla_parse - Parse a stream of attributes into a tb buffer
 131  * @tb: destination array with maxtype+1 elements
 132  * @maxtype: maximum attribute type to be expected
 133  * @head: head of attribute stream
 134  * @len: length of attribute stream
 135  *
 136  * Parses a stream of attributes and stores a pointer to each attribute in
 137  * the tb array accessable via the attribute type. Attributes with a type
 138  * exceeding maxtype will be silently ignored for backwards compatibility
 139  * reasons. policy may be set to NULL if no validation is required.
 140  *
 141  * Returns 0 on success or a negative error code.
 142  */
 143 int nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len,
 144               const struct nla_policy *policy)
 145 {
 146         struct nlattr *nla;
 147         int rem, err;
 148
 149         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 150
 151         nla_for_each_attr(nla, head, len, rem) {
 152                 u16 type = nla_type(nla);
 153
 154                 if (type > 0 && type <= maxtype) {
 155                         if (policy) {
 156                                 err = validate_nla(nla, maxtype, policy);
 157                                 if (err < 0)
 158                                         goto errout;
 159                         }
 160
 161                         tb[type] = nla;
 162                 }
 163         }
 164
 165         if (unlikely(rem > 0))
 166                 printk(KERN_WARNING "netlink: %d bytes leftover after parsing "
 167                        "attributes.\n", rem);
 168
 169         err = 0;
 170 errout:
 171         return err;
 172 }
 173
 174 /**
 175  * nla_find - Find a specific attribute in a stream of attributes
 176  * @head: head of attribute stream
 177  * @len: length of attribute stream
 178  * @attrtype: type of attribute to look for
 179  *
 180  * Returns the first attribute in the stream matching the specified type.
 181  */
 182 struct nlattr *nla_find(struct nlattr *head, int len, int attrtype)
 183 {
 184         struct nlattr *nla;
 185         int rem;
 186
 187         nla_for_each_attr(nla, head, len, rem)
 188                 if (nla_type(nla) == attrtype)
 189                         return nla;
 190
 191         return NULL;
 192 }
 193
 194 /**
 195  * nla_strlcpy - Copy string attribute payload into a sized buffer
 196  * @dst: where to copy the string to
 197  * @src: attribute to copy the string from
 198  * @dstsize: size of destination buffer
 199  *
 200  * Copies at most dstsize - 1 bytes into the destination buffer.
 201  * The result is always a valid NUL-terminated string. Unlike
 202  * strlcpy the destination buffer is always padded out.
 203  *
 204  * Returns the length of the source buffer.
 205  */
 206 size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
 207 {
 208         size_t srclen = nla_len(nla);
 209         char *src = nla_data(nla);
 210
 211         if (srclen > 0 && src[srclen - 1] == '\0')
 212                 srclen--;
 213
 214         if (dstsize > 0) {
 215                 size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
 216
 217                 memset(dst, 0, dstsize);
 218                 memcpy(dst, src, len);
 219         }
 220
 221         return srclen;
 222 }
 223
 224 /**
 225  * nla_memcpy - Copy a netlink attribute into another memory area
 226  * @dest: where to copy to memcpy
 227  * @src: netlink attribute to copy from
 228  * @count: size of the destination area
 229  *
 230  * Note: The number of bytes copied is limited by the length of
 231  *       attribute's payload. memcpy
 232  *
 233  * Returns the number of bytes copied.
 234  */
 235 int nla_memcpy(void *dest, struct nlattr *src, int count)
 236 {
 237         int minlen = min_t(int, count, nla_len(src));
 238
 239         memcpy(dest, nla_data(src), minlen);
 240
 241         return minlen;
 242 }
 243
 244 /**
 245  * nla_memcmp - Compare an attribute with sized memory area
 246  * @nla: netlink attribute
 247  * @data: memory area
 248  * @size: size of memory area
 249  */
 250 int nla_memcmp(const struct nlattr *nla, const void *data,
 251                              size_t size)
 252 {
 253         int d = nla_len(nla) - size;
 254
 255         if (d == 0)
 256                 d = memcmp(nla_data(nla), data, size);
 257
 258         return d;
 259 }
 260
 261 /**
 262  * nla_strcmp - Compare a string attribute against a string
 263  * @nla: netlink string attribute
 264  * @str: another string
 265  */
 266 int nla_strcmp(const struct nlattr *nla, const char *str)
 267 {
 268         int len = strlen(str) + 1;
 269         int d = nla_len(nla) - len;
 270
 271         if (d == 0)
 272                 d = memcmp(nla_data(nla), str, len);
 273
 274         return d;
 275 }
 276
 277 /**
 278  * __nla_reserve - reserve room for attribute on the skb
 279  * @skb: socket buffer to reserve room on
 280  * @attrtype: attribute type
 281  * @attrlen: length of attribute payload
 282  *
 283  * Adds a netlink attribute header to a socket buffer and reserves
 284  * room for the payload but does not copy it.
 285  *
 286  * The caller is responsible to ensure that the skb provides enough
 287  * tailroom for the attribute header and payload.
 288  */
 289 struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 290 {
 291         struct nlattr *nla;
 292
 293         nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
 294         nla->nla_type = attrtype;
 295         nla->nla_len = nla_attr_size(attrlen);
 296
 297         memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
 298
 299         return nla;
 300 }
 301
 302 /**
 303  * __nla_reserve_nohdr - reserve room for attribute without header
 304  * @skb: socket buffer to reserve room on
 305  * @attrlen: length of attribute payload
 306  *
 307  * Reserves room for attribute payload without a header.
 308  *
 309  * The caller is responsible to ensure that the skb provides enough
 310  * tailroom for the payload.
 311  */
 312 void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 313 {
 314         void *start;
 315
 316         start = skb_put(skb, NLA_ALIGN(attrlen));
 317         memset(start, 0, NLA_ALIGN(attrlen));
 318
 319         return start;
 320 }
 321
 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  * Returns NULL if the tailroom of the skb is insufficient to store
 332  * the attribute header and payload.
 333  */
 334 struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 335 {
 336         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 337                 return NULL;
 338
 339         return __nla_reserve(skb, attrtype, attrlen);
 340 }
 341
 342 /**
 343  * nla_reserve - reserve room for attribute without header
 344  * @skb: socket buffer to reserve room on
 345  * @len: length of attribute payload
 346  *
 347  * Reserves room for attribute payload without a header.
 348  *
 349  * Returns NULL if the tailroom of the skb is insufficient to store
 350  * the attribute payload.
 351  */
 352 void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 353 {
 354         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 355                 return NULL;
 356
 357         return __nla_reserve_nohdr(skb, attrlen);
 358 }
 359
 360 /**
 361  * __nla_put - Add a netlink attribute to a socket buffer
 362  * @skb: socket buffer to add attribute to
 363  * @attrtype: attribute type
 364  * @attrlen: length of attribute payload
 365  * @data: head of attribute payload
 366  *
 367  * The caller is responsible to ensure that the skb provides enough
 368  * tailroom for the attribute header and payload.
 369  */
 370 void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 371                              const void *data)
 372 {
 373         struct nlattr *nla;
 374
 375         nla = __nla_reserve(skb, attrtype, attrlen);
 376         memcpy(nla_data(nla), data, attrlen);
 377 }
 378
 379 /**
 380  * __nla_put_nohdr - Add a netlink attribute without header
 381  * @skb: socket buffer to add attribute to
 382  * @attrlen: length of attribute payload
 383  * @data: head of attribute payload
 384  *
 385  * The caller is responsible to ensure that the skb provides enough
 386  * tailroom for the attribute payload.
 387  */
 388 void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 389 {
 390         void *start;
 391
 392         start = __nla_reserve_nohdr(skb, attrlen);
 393         memcpy(start, data, attrlen);
 394 }
 395
 396 /**
 397  * nla_put - Add a netlink attribute to a socket buffer
 398  * @skb: socket buffer to add attribute to
 399  * @attrtype: attribute type
 400  * @attrlen: length of attribute payload
 401  * @data: head of attribute payload
 402  *
 403  * Returns -1 if the tailroom of the skb is insufficient to store
 404  * the attribute header and payload.
 405  */
 406 int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
 407 {
 408         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 409                 return -1;
 410
 411         __nla_put(skb, attrtype, attrlen, data);
 412         return 0;
 413 }
 414
 415 /**
 416  * nla_put_nohdr - Add a netlink attribute without header
 417  * @skb: socket buffer to add attribute to
 418  * @attrlen: length of attribute payload
 419  * @data: head of attribute payload
 420  *
 421  * Returns -1 if the tailroom of the skb is insufficient to store
 422  * the attribute payload.
 423  */
 424 int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 425 {
 426         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 427                 return -1;
 428
 429         __nla_put_nohdr(skb, attrlen, data);
 430         return 0;
 431 }
 432
 433 EXPORT_SYMBOL(nla_validate);
 434 EXPORT_SYMBOL(nla_parse);
 435 EXPORT_SYMBOL(nla_find);
 436 EXPORT_SYMBOL(nla_strlcpy);
 437 EXPORT_SYMBOL(__nla_reserve);
 438 EXPORT_SYMBOL(__nla_reserve_nohdr);
 439 EXPORT_SYMBOL(nla_reserve);
 440 EXPORT_SYMBOL(nla_reserve_nohdr);
 441 EXPORT_SYMBOL(__nla_put);
 442 EXPORT_SYMBOL(__nla_put_nohdr);
 443 EXPORT_SYMBOL(nla_put);
 444 EXPORT_SYMBOL(nla_put_nohdr);
 445 EXPORT_SYMBOL(nla_memcpy);
 446 EXPORT_SYMBOL(nla_memcmp);
 447 EXPORT_SYMBOL(nla_strcmp);