Root/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
18static 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
26static 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 */
118int 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;
131errout:
132    return err;
133}
134
135/**
136 * nla_policy_len - Determin the max. length of a policy
137 * @policy: policy to use
138 * @n: number of policies
139 *
140 * Determines the max. length of the policy. It is currently used
141 * to allocated Netlink buffers roughly the size of the actual
142 * message.
143 *
144 * Returns 0 on success or a negative error code.
145 */
146int
147nla_policy_len(const struct nla_policy *p, int n)
148{
149    int i, len = 0;
150
151    for (i = 0; i < n; i++) {
152        if (p->len)
153            len += nla_total_size(p->len);
154        else if (nla_attr_minlen[p->type])
155            len += nla_total_size(nla_attr_minlen[p->type]);
156    }
157
158    return len;
159}
160
161/**
162 * nla_parse - Parse a stream of attributes into a tb buffer
163 * @tb: destination array with maxtype+1 elements
164 * @maxtype: maximum attribute type to be expected
165 * @head: head of attribute stream
166 * @len: length of attribute stream
167 * @policy: validation policy
168 *
169 * Parses a stream of attributes and stores a pointer to each attribute in
170 * the tb array accessable via the attribute type. Attributes with a type
171 * exceeding maxtype will be silently ignored for backwards compatibility
172 * reasons. policy may be set to NULL if no validation is required.
173 *
174 * Returns 0 on success or a negative error code.
175 */
176int nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len,
177          const struct nla_policy *policy)
178{
179    struct nlattr *nla;
180    int rem, err;
181
182    memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
183
184    nla_for_each_attr(nla, head, len, rem) {
185        u16 type = nla_type(nla);
186
187        if (type > 0 && type <= maxtype) {
188            if (policy) {
189                err = validate_nla(nla, maxtype, policy);
190                if (err < 0)
191                    goto errout;
192            }
193
194            tb[type] = nla;
195        }
196    }
197
198    if (unlikely(rem > 0))
199        printk(KERN_WARNING "netlink: %d bytes leftover after parsing "
200               "attributes.\n", rem);
201
202    err = 0;
203errout:
204    return err;
205}
206
207/**
208 * nla_find - Find a specific attribute in a stream of attributes
209 * @head: head of attribute stream
210 * @len: length of attribute stream
211 * @attrtype: type of attribute to look for
212 *
213 * Returns the first attribute in the stream matching the specified type.
214 */
215struct nlattr *nla_find(struct nlattr *head, int len, int attrtype)
216{
217    struct nlattr *nla;
218    int rem;
219
220    nla_for_each_attr(nla, head, len, rem)
221        if (nla_type(nla) == attrtype)
222            return nla;
223
224    return NULL;
225}
226
227/**
228 * nla_strlcpy - Copy string attribute payload into a sized buffer
229 * @dst: where to copy the string to
230 * @nla: attribute to copy the string from
231 * @dstsize: size of destination buffer
232 *
233 * Copies at most dstsize - 1 bytes into the destination buffer.
234 * The result is always a valid NUL-terminated string. Unlike
235 * strlcpy the destination buffer is always padded out.
236 *
237 * Returns the length of the source buffer.
238 */
239size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
240{
241    size_t srclen = nla_len(nla);
242    char *src = nla_data(nla);
243
244    if (srclen > 0 && src[srclen - 1] == '\0')
245        srclen--;
246
247    if (dstsize > 0) {
248        size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
249
250        memset(dst, 0, dstsize);
251        memcpy(dst, src, len);
252    }
253
254    return srclen;
255}
256
257/**
258 * nla_memcpy - Copy a netlink attribute into another memory area
259 * @dest: where to copy to memcpy
260 * @src: netlink attribute to copy from
261 * @count: size of the destination area
262 *
263 * Note: The number of bytes copied is limited by the length of
264 * attribute's payload. memcpy
265 *
266 * Returns the number of bytes copied.
267 */
268int nla_memcpy(void *dest, const struct nlattr *src, int count)
269{
270    int minlen = min_t(int, count, nla_len(src));
271
272    memcpy(dest, nla_data(src), minlen);
273
274    return minlen;
275}
276
277/**
278 * nla_memcmp - Compare an attribute with sized memory area
279 * @nla: netlink attribute
280 * @data: memory area
281 * @size: size of memory area
282 */
283int nla_memcmp(const struct nlattr *nla, const void *data,
284                 size_t size)
285{
286    int d = nla_len(nla) - size;
287
288    if (d == 0)
289        d = memcmp(nla_data(nla), data, size);
290
291    return d;
292}
293
294/**
295 * nla_strcmp - Compare a string attribute against a string
296 * @nla: netlink string attribute
297 * @str: another string
298 */
299int nla_strcmp(const struct nlattr *nla, const char *str)
300{
301    int len = strlen(str) + 1;
302    int d = nla_len(nla) - len;
303
304    if (d == 0)
305        d = memcmp(nla_data(nla), str, len);
306
307    return d;
308}
309
310#ifdef CONFIG_NET
311/**
312 * __nla_reserve - reserve room for attribute on the skb
313 * @skb: socket buffer to reserve room on
314 * @attrtype: attribute type
315 * @attrlen: length of attribute payload
316 *
317 * Adds a netlink attribute header to a socket buffer and reserves
318 * room for the payload but does not copy it.
319 *
320 * The caller is responsible to ensure that the skb provides enough
321 * tailroom for the attribute header and payload.
322 */
323struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
324{
325    struct nlattr *nla;
326
327    nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
328    nla->nla_type = attrtype;
329    nla->nla_len = nla_attr_size(attrlen);
330
331    memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
332
333    return nla;
334}
335EXPORT_SYMBOL(__nla_reserve);
336
337/**
338 * __nla_reserve_nohdr - reserve room for attribute without header
339 * @skb: socket buffer to reserve room on
340 * @attrlen: length of attribute payload
341 *
342 * Reserves room for attribute payload without a header.
343 *
344 * The caller is responsible to ensure that the skb provides enough
345 * tailroom for the payload.
346 */
347void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
348{
349    void *start;
350
351    start = skb_put(skb, NLA_ALIGN(attrlen));
352    memset(start, 0, NLA_ALIGN(attrlen));
353
354    return start;
355}
356EXPORT_SYMBOL(__nla_reserve_nohdr);
357
358/**
359 * nla_reserve - reserve room for attribute on the skb
360 * @skb: socket buffer to reserve room on
361 * @attrtype: attribute type
362 * @attrlen: length of attribute payload
363 *
364 * Adds a netlink attribute header to a socket buffer and reserves
365 * room for the payload but does not copy it.
366 *
367 * Returns NULL if the tailroom of the skb is insufficient to store
368 * the attribute header and payload.
369 */
370struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
371{
372    if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
373        return NULL;
374
375    return __nla_reserve(skb, attrtype, attrlen);
376}
377EXPORT_SYMBOL(nla_reserve);
378
379/**
380 * nla_reserve_nohdr - reserve room for attribute without header
381 * @skb: socket buffer to reserve room on
382 * @attrlen: length of attribute payload
383 *
384 * Reserves room for attribute payload without a header.
385 *
386 * Returns NULL if the tailroom of the skb is insufficient to store
387 * the attribute payload.
388 */
389void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
390{
391    if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
392        return NULL;
393
394    return __nla_reserve_nohdr(skb, attrlen);
395}
396EXPORT_SYMBOL(nla_reserve_nohdr);
397
398/**
399 * __nla_put - Add a netlink attribute to a socket buffer
400 * @skb: socket buffer to add attribute to
401 * @attrtype: attribute type
402 * @attrlen: length of attribute payload
403 * @data: head of attribute payload
404 *
405 * The caller is responsible to ensure that the skb provides enough
406 * tailroom for the attribute header and payload.
407 */
408void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
409                 const void *data)
410{
411    struct nlattr *nla;
412
413    nla = __nla_reserve(skb, attrtype, attrlen);
414    memcpy(nla_data(nla), data, attrlen);
415}
416EXPORT_SYMBOL(__nla_put);
417
418/**
419 * __nla_put_nohdr - Add a netlink attribute without header
420 * @skb: socket buffer to add attribute to
421 * @attrlen: length of attribute payload
422 * @data: head of attribute payload
423 *
424 * The caller is responsible to ensure that the skb provides enough
425 * tailroom for the attribute payload.
426 */
427void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
428{
429    void *start;
430
431    start = __nla_reserve_nohdr(skb, attrlen);
432    memcpy(start, data, attrlen);
433}
434EXPORT_SYMBOL(__nla_put_nohdr);
435
436/**
437 * nla_put - Add a netlink attribute to a socket buffer
438 * @skb: socket buffer to add attribute to
439 * @attrtype: attribute type
440 * @attrlen: length of attribute payload
441 * @data: head of attribute payload
442 *
443 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
444 * the attribute header and payload.
445 */
446int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
447{
448    if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
449        return -EMSGSIZE;
450
451    __nla_put(skb, attrtype, attrlen, data);
452    return 0;
453}
454EXPORT_SYMBOL(nla_put);
455
456/**
457 * nla_put_nohdr - Add a netlink attribute without header
458 * @skb: socket buffer to add attribute to
459 * @attrlen: length of attribute payload
460 * @data: head of attribute payload
461 *
462 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
463 * the attribute payload.
464 */
465int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
466{
467    if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
468        return -EMSGSIZE;
469
470    __nla_put_nohdr(skb, attrlen, data);
471    return 0;
472}
473EXPORT_SYMBOL(nla_put_nohdr);
474
475/**
476 * nla_append - Add a netlink attribute without header or padding
477 * @skb: socket buffer to add attribute to
478 * @attrlen: length of attribute payload
479 * @data: head of attribute payload
480 *
481 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
482 * the attribute payload.
483 */
484int nla_append(struct sk_buff *skb, int attrlen, const void *data)
485{
486    if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
487        return -EMSGSIZE;
488
489    memcpy(skb_put(skb, attrlen), data, attrlen);
490    return 0;
491}
492EXPORT_SYMBOL(nla_append);
493#endif
494
495EXPORT_SYMBOL(nla_validate);
496EXPORT_SYMBOL(nla_policy_len);
497EXPORT_SYMBOL(nla_parse);
498EXPORT_SYMBOL(nla_find);
499EXPORT_SYMBOL(nla_strlcpy);
500EXPORT_SYMBOL(nla_memcpy);
501EXPORT_SYMBOL(nla_memcmp);
502EXPORT_SYMBOL(nla_strcmp);
503

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