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  * @policy: validation policy
 136  *
 137  * Parses a stream of attributes and stores a pointer to each attribute in
 138  * the tb array accessable via the attribute type. Attributes with a type
 139  * exceeding maxtype will be silently ignored for backwards compatibility
 140  * reasons. policy may be set to NULL if no validation is required.
 141  *
 142  * Returns 0 on success or a negative error code.
 143  */
 144 int nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len,
 145               const struct nla_policy *policy)
 146 {
 147         struct nlattr *nla;
 148         int rem, err;
 149
 150         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 151
 152         nla_for_each_attr(nla, head, len, rem) {
 153                 u16 type = nla_type(nla);
 154
 155                 if (type > 0 && type <= maxtype) {
 156                         if (policy) {
 157                                 err = validate_nla(nla, maxtype, policy);
 158                                 if (err < 0)
 159                                         goto errout;
 160                         }
 161
 162                         tb[type] = nla;
 163                 }
 164         }
 165
 166         if (unlikely(rem > 0))
 167                 printk(KERN_WARNING "netlink: %d bytes leftover after parsing "
 168                        "attributes.\n", rem);
 169
 170         err = 0;
 171 errout:
 172         return err;
 173 }
 174
 175 /**
 176  * nla_find - Find a specific attribute in a stream of attributes
 177  * @head: head of attribute stream
 178  * @len: length of attribute stream
 179  * @attrtype: type of attribute to look for
 180  *
 181  * Returns the first attribute in the stream matching the specified type.
 182  */
 183 struct nlattr *nla_find(struct nlattr *head, int len, int attrtype)
 184 {
 185         struct nlattr *nla;
 186         int rem;
 187
 188         nla_for_each_attr(nla, head, len, rem)
 189                 if (nla_type(nla) == attrtype)
 190                         return nla;
 191
 192         return NULL;
 193 }
 194
 195 /**
 196  * nla_strlcpy - Copy string attribute payload into a sized buffer
 197  * @dst: where to copy the string to
 198  * @nla: attribute to copy the string from
 199  * @dstsize: size of destination buffer
 200  *
 201  * Copies at most dstsize - 1 bytes into the destination buffer.
 202  * The result is always a valid NUL-terminated string. Unlike
 203  * strlcpy the destination buffer is always padded out.
 204  *
 205  * Returns the length of the source buffer.
 206  */
 207 size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
 208 {
 209         size_t srclen = nla_len(nla);
 210         char *src = nla_data(nla);
 211
 212         if (srclen > 0 && src[srclen - 1] == '\0')
 213                 srclen--;
 214
 215         if (dstsize > 0) {
 216                 size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
 217
 218                 memset(dst, 0, dstsize);
 219                 memcpy(dst, src, len);
 220         }
 221
 222         return srclen;
 223 }
 224
 225 /**
 226  * nla_memcpy - Copy a netlink attribute into another memory area
 227  * @dest: where to copy to memcpy
 228  * @src: netlink attribute to copy from
 229  * @count: size of the destination area
 230  *
 231  * Note: The number of bytes copied is limited by the length of
 232  *       attribute's payload. memcpy
 233  *
 234  * Returns the number of bytes copied.
 235  */
 236 int nla_memcpy(void *dest, struct nlattr *src, int count)
 237 {
 238         int minlen = min_t(int, count, nla_len(src));
 239
 240         memcpy(dest, nla_data(src), minlen);
 241
 242         return minlen;
 243 }
 244
 245 /**
 246  * nla_memcmp - Compare an attribute with sized memory area
 247  * @nla: netlink attribute
 248  * @data: memory area
 249  * @size: size of memory area
 250  */
 251 int nla_memcmp(const struct nlattr *nla, const void *data,
 252                              size_t size)
 253 {
 254         int d = nla_len(nla) - size;
 255
 256         if (d == 0)
 257                 d = memcmp(nla_data(nla), data, size);
 258
 259         return d;
 260 }
 261
 262 /**
 263  * nla_strcmp - Compare a string attribute against a string
 264  * @nla: netlink string attribute
 265  * @str: another string
 266  */
 267 int nla_strcmp(const struct nlattr *nla, const char *str)
 268 {
 269         int len = strlen(str) + 1;
 270         int d = nla_len(nla) - len;
 271
 272         if (d == 0)
 273                 d = memcmp(nla_data(nla), str, len);
 274
 275         return d;
 276 }
 277
 278 /**
 279  * __nla_reserve - reserve room for attribute on the skb
 280  * @skb: socket buffer to reserve room on
 281  * @attrtype: attribute type
 282  * @attrlen: length of attribute payload
 283  *
 284  * Adds a netlink attribute header to a socket buffer and reserves
 285  * room for the payload but does not copy it.
 286  *
 287  * The caller is responsible to ensure that the skb provides enough
 288  * tailroom for the attribute header and payload.
 289  */
 290 struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 291 {
 292         struct nlattr *nla;
 293
 294         nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
 295         nla->nla_type = attrtype;
 296         nla->nla_len = nla_attr_size(attrlen);
 297
 298         memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
 299
 300         return nla;
 301 }
 302
 303 /**
 304  * __nla_reserve_nohdr - reserve room for attribute without header
 305  * @skb: socket buffer to reserve room on
 306  * @attrlen: length of attribute payload
 307  *
 308  * Reserves room for attribute payload without a header.
 309  *
 310  * The caller is responsible to ensure that the skb provides enough
 311  * tailroom for the payload.
 312  */
 313 void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 314 {
 315         void *start;
 316
 317         start = skb_put(skb, NLA_ALIGN(attrlen));
 318         memset(start, 0, NLA_ALIGN(attrlen));
 319
 320         return start;
 321 }
 322
 323 /**
 324  * nla_reserve - reserve room for attribute on the skb
 325  * @skb: socket buffer to reserve room on
 326  * @attrtype: attribute type
 327  * @attrlen: length of attribute payload
 328  *
 329  * Adds a netlink attribute header to a socket buffer and reserves
 330  * room for the payload but does not copy it.
 331  *
 332  * Returns NULL if the tailroom of the skb is insufficient to store
 333  * the attribute header and payload.
 334  */
 335 struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 336 {
 337         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 338                 return NULL;
 339
 340         return __nla_reserve(skb, attrtype, attrlen);
 341 }
 342
 343 /**
 344  * nla_reserve_nohdr - reserve room for attribute without header
 345  * @skb: socket buffer to reserve room on
 346  * @attrlen: length of attribute payload
 347  *
 348  * Reserves room for attribute payload without a header.
 349  *
 350  * Returns NULL if the tailroom of the skb is insufficient to store
 351  * the attribute payload.
 352  */
 353 void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 354 {
 355         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 356                 return NULL;
 357
 358         return __nla_reserve_nohdr(skb, attrlen);
 359 }
 360
 361 /**
 362  * __nla_put - Add a netlink attribute to a socket buffer
 363  * @skb: socket buffer to add attribute to
 364  * @attrtype: attribute type
 365  * @attrlen: length of attribute payload
 366  * @data: head of attribute payload
 367  *
 368  * The caller is responsible to ensure that the skb provides enough
 369  * tailroom for the attribute header and payload.
 370  */
 371 void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 372                              const void *data)
 373 {
 374         struct nlattr *nla;
 375
 376         nla = __nla_reserve(skb, attrtype, attrlen);
 377         memcpy(nla_data(nla), data, attrlen);
 378 }
 379
 380 /**
 381  * __nla_put_nohdr - Add a netlink attribute without header
 382  * @skb: socket buffer to add attribute to
 383  * @attrlen: length of attribute payload
 384  * @data: head of attribute payload
 385  *
 386  * The caller is responsible to ensure that the skb provides enough
 387  * tailroom for the attribute payload.
 388  */
 389 void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 390 {
 391         void *start;
 392
 393         start = __nla_reserve_nohdr(skb, attrlen);
 394         memcpy(start, data, attrlen);
 395 }
 396
 397 /**
 398  * nla_put - Add a netlink attribute to a socket buffer
 399  * @skb: socket buffer to add attribute to
 400  * @attrtype: attribute type
 401  * @attrlen: length of attribute payload
 402  * @data: head of attribute payload
 403  *
 404  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 405  * the attribute header and payload.
 406  */
 407 int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
 408 {
 409         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 410                 return -EMSGSIZE;
 411
 412         __nla_put(skb, attrtype, attrlen, data);
 413         return 0;
 414 }
 415
 416 /**
 417  * nla_put_nohdr - Add a netlink attribute without header
 418  * @skb: socket buffer to add attribute to
 419  * @attrlen: length of attribute payload
 420  * @data: head of attribute payload
 421  *
 422  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 423  * the attribute payload.
 424  */
 425 int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 426 {
 427         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 428                 return -EMSGSIZE;
 429
 430         __nla_put_nohdr(skb, attrlen, data);
 431         return 0;
 432 }
 433
 434 /**
 435  * nla_append - Add a netlink attribute without header or padding
 436  * @skb: socket buffer to add attribute to
 437  * @attrlen: length of attribute payload
 438  * @data: head of attribute payload
 439  *
 440  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 441  * the attribute payload.
 442  */
 443 int nla_append(struct sk_buff *skb, int attrlen, const void *data)
 444 {
 445         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 446                 return -EMSGSIZE;
 447
 448         memcpy(skb_put(skb, attrlen), data, attrlen);
 449         return 0;
 450 }
 451
 452 EXPORT_SYMBOL(nla_validate);
 453 EXPORT_SYMBOL(nla_parse);
 454 EXPORT_SYMBOL(nla_find);
 455 EXPORT_SYMBOL(nla_strlcpy);
 456 EXPORT_SYMBOL(__nla_reserve);
 457 EXPORT_SYMBOL(__nla_reserve_nohdr);
 458 EXPORT_SYMBOL(nla_reserve);
 459 EXPORT_SYMBOL(nla_reserve_nohdr);
 460 EXPORT_SYMBOL(__nla_put);
 461 EXPORT_SYMBOL(__nla_put_nohdr);
 462 EXPORT_SYMBOL(nla_put);
 463 EXPORT_SYMBOL(nla_put_nohdr);
 464 EXPORT_SYMBOL(nla_memcpy);
 465 EXPORT_SYMBOL(nla_memcmp);
 466 EXPORT_SYMBOL(nla_strcmp);
 467 EXPORT_SYMBOL(nla_append);