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/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
18static 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
31static 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 */
123int 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;
136errout:
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 */
151int
152nla_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 */
181int 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        printk(KERN_WARNING "netlink: %d bytes leftover after parsing "
205               "attributes.\n", rem);
206
207    err = 0;
208errout:
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 */
220struct 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 */
244size_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 */
273int 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 */
288int 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 */
304int nla_strcmp(const struct nlattr *nla, const char *str)
305{
306    int len = strlen(str) + 1;
307    int d = nla_len(nla) - len;
308
309    if (d == 0)
310        d = memcmp(nla_data(nla), str, len);
311
312    return d;
313}
314
315#ifdef CONFIG_NET
316/**
317 * __nla_reserve - reserve room for attribute on the skb
318 * @skb: socket buffer to reserve room on
319 * @attrtype: attribute type
320 * @attrlen: length of attribute payload
321 *
322 * Adds a netlink attribute header to a socket buffer and reserves
323 * room for the payload but does not copy it.
324 *
325 * The caller is responsible to ensure that the skb provides enough
326 * tailroom for the attribute header and payload.
327 */
328struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
329{
330    struct nlattr *nla;
331
332    nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
333    nla->nla_type = attrtype;
334    nla->nla_len = nla_attr_size(attrlen);
335
336    memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
337
338    return nla;
339}
340EXPORT_SYMBOL(__nla_reserve);
341
342/**
343 * __nla_reserve_nohdr - reserve room for attribute without header
344 * @skb: socket buffer to reserve room on
345 * @attrlen: length of attribute payload
346 *
347 * Reserves room for attribute payload without a header.
348 *
349 * The caller is responsible to ensure that the skb provides enough
350 * tailroom for the payload.
351 */
352void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
353{
354    void *start;
355
356    start = skb_put(skb, NLA_ALIGN(attrlen));
357    memset(start, 0, NLA_ALIGN(attrlen));
358
359    return start;
360}
361EXPORT_SYMBOL(__nla_reserve_nohdr);
362
363/**
364 * nla_reserve - reserve room for attribute on the skb
365 * @skb: socket buffer to reserve room on
366 * @attrtype: attribute type
367 * @attrlen: length of attribute payload
368 *
369 * Adds a netlink attribute header to a socket buffer and reserves
370 * room for the payload but does not copy it.
371 *
372 * Returns NULL if the tailroom of the skb is insufficient to store
373 * the attribute header and payload.
374 */
375struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
376{
377    if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
378        return NULL;
379
380    return __nla_reserve(skb, attrtype, attrlen);
381}
382EXPORT_SYMBOL(nla_reserve);
383
384/**
385 * nla_reserve_nohdr - reserve room for attribute without header
386 * @skb: socket buffer to reserve room on
387 * @attrlen: length of attribute payload
388 *
389 * Reserves room for attribute payload without a header.
390 *
391 * Returns NULL if the tailroom of the skb is insufficient to store
392 * the attribute payload.
393 */
394void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
395{
396    if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
397        return NULL;
398
399    return __nla_reserve_nohdr(skb, attrlen);
400}
401EXPORT_SYMBOL(nla_reserve_nohdr);
402
403/**
404 * __nla_put - Add a netlink attribute to a socket buffer
405 * @skb: socket buffer to add attribute to
406 * @attrtype: attribute type
407 * @attrlen: length of attribute payload
408 * @data: head of attribute payload
409 *
410 * The caller is responsible to ensure that the skb provides enough
411 * tailroom for the attribute header and payload.
412 */
413void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
414                 const void *data)
415{
416    struct nlattr *nla;
417
418    nla = __nla_reserve(skb, attrtype, attrlen);
419    memcpy(nla_data(nla), data, attrlen);
420}
421EXPORT_SYMBOL(__nla_put);
422
423/**
424 * __nla_put_nohdr - Add a netlink attribute without header
425 * @skb: socket buffer to add attribute to
426 * @attrlen: length of attribute payload
427 * @data: head of attribute payload
428 *
429 * The caller is responsible to ensure that the skb provides enough
430 * tailroom for the attribute payload.
431 */
432void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
433{
434    void *start;
435
436    start = __nla_reserve_nohdr(skb, attrlen);
437    memcpy(start, data, attrlen);
438}
439EXPORT_SYMBOL(__nla_put_nohdr);
440
441/**
442 * nla_put - Add a netlink attribute to a socket buffer
443 * @skb: socket buffer to add attribute to
444 * @attrtype: attribute type
445 * @attrlen: length of attribute payload
446 * @data: head of attribute payload
447 *
448 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
449 * the attribute header and payload.
450 */
451int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
452{
453    if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
454        return -EMSGSIZE;
455
456    __nla_put(skb, attrtype, attrlen, data);
457    return 0;
458}
459EXPORT_SYMBOL(nla_put);
460
461/**
462 * nla_put_nohdr - Add a netlink attribute without header
463 * @skb: socket buffer to add attribute to
464 * @attrlen: length of attribute payload
465 * @data: head of attribute payload
466 *
467 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
468 * the attribute payload.
469 */
470int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
471{
472    if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
473        return -EMSGSIZE;
474
475    __nla_put_nohdr(skb, attrlen, data);
476    return 0;
477}
478EXPORT_SYMBOL(nla_put_nohdr);
479
480/**
481 * nla_append - Add a netlink attribute without header or padding
482 * @skb: socket buffer to add attribute to
483 * @attrlen: length of attribute payload
484 * @data: head of attribute payload
485 *
486 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
487 * the attribute payload.
488 */
489int nla_append(struct sk_buff *skb, int attrlen, const void *data)
490{
491    if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
492        return -EMSGSIZE;
493
494    memcpy(skb_put(skb, attrlen), data, attrlen);
495    return 0;
496}
497EXPORT_SYMBOL(nla_append);
498#endif
499
500EXPORT_SYMBOL(nla_validate);
501EXPORT_SYMBOL(nla_policy_len);
502EXPORT_SYMBOL(nla_parse);
503EXPORT_SYMBOL(nla_find);
504EXPORT_SYMBOL(nla_strlcpy);
505EXPORT_SYMBOL(nla_memcpy);
506EXPORT_SYMBOL(nla_memcmp);
507EXPORT_SYMBOL(nla_strcmp);
508

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