linux/lib/nlattr.c
David Ahern a5f6cba291 netlink: Add strict version of nlmsg_parse and nla_parse
nla_parse is currently lenient on message parsing, allowing type to be 0
or greater than max expected and only logging a message

    "netlink: %d bytes leftover after parsing attributes in process `%s'."

if the netlink message has unknown data at the end after parsing. What this
could mean is that the header at the front of the attributes is actually
wrong and the parsing is shifted from what is expected.

Add a new strict version that actually fails with EINVAL if there are any
bytes remaining after the parsing loop completes, if the atttrbitue type
is 0 or greater than max expected.

Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Christian Brauner <christian@brauner.io>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-10-08 10:39:04 -07:00

873 lines
22 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* NETLINK Netlink attributes
*
* Authors: Thomas Graf <tgraf@suug.ch>
* Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
*/
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/jiffies.h>
#include <linux/skbuff.h>
#include <linux/string.h>
#include <linux/types.h>
#include <net/netlink.h>
/* For these data types, attribute length should be exactly the given
* size. However, to maintain compatibility with broken commands, if the
* attribute length does not match the expected size a warning is emitted
* to the user that the command is sending invalid data and needs to be fixed.
*/
static const u8 nla_attr_len[NLA_TYPE_MAX+1] = {
[NLA_U8] = sizeof(u8),
[NLA_U16] = sizeof(u16),
[NLA_U32] = sizeof(u32),
[NLA_U64] = sizeof(u64),
[NLA_S8] = sizeof(s8),
[NLA_S16] = sizeof(s16),
[NLA_S32] = sizeof(s32),
[NLA_S64] = sizeof(s64),
};
static const u8 nla_attr_minlen[NLA_TYPE_MAX+1] = {
[NLA_U8] = sizeof(u8),
[NLA_U16] = sizeof(u16),
[NLA_U32] = sizeof(u32),
[NLA_U64] = sizeof(u64),
[NLA_MSECS] = sizeof(u64),
[NLA_NESTED] = NLA_HDRLEN,
[NLA_S8] = sizeof(s8),
[NLA_S16] = sizeof(s16),
[NLA_S32] = sizeof(s32),
[NLA_S64] = sizeof(s64),
};
static int validate_nla_bitfield32(const struct nlattr *nla,
const u32 *valid_flags_mask)
{
const struct nla_bitfield32 *bf = nla_data(nla);
if (!valid_flags_mask)
return -EINVAL;
/*disallow invalid bit selector */
if (bf->selector & ~*valid_flags_mask)
return -EINVAL;
/*disallow invalid bit values */
if (bf->value & ~*valid_flags_mask)
return -EINVAL;
/*disallow valid bit values that are not selected*/
if (bf->value & ~bf->selector)
return -EINVAL;
return 0;
}
static int nla_validate_array(const struct nlattr *head, int len, int maxtype,
const struct nla_policy *policy,
struct netlink_ext_ack *extack)
{
const struct nlattr *entry;
int rem;
nla_for_each_attr(entry, head, len, rem) {
int ret;
if (nla_len(entry) == 0)
continue;
if (nla_len(entry) < NLA_HDRLEN) {
NL_SET_ERR_MSG_ATTR(extack, entry,
"Array element too short");
return -ERANGE;
}
ret = nla_validate(nla_data(entry), nla_len(entry),
maxtype, policy, extack);
if (ret < 0)
return ret;
}
return 0;
}
static int nla_validate_int_range(const struct nla_policy *pt,
const struct nlattr *nla,
struct netlink_ext_ack *extack)
{
bool validate_min, validate_max;
s64 value;
validate_min = pt->validation_type == NLA_VALIDATE_RANGE ||
pt->validation_type == NLA_VALIDATE_MIN;
validate_max = pt->validation_type == NLA_VALIDATE_RANGE ||
pt->validation_type == NLA_VALIDATE_MAX;
switch (pt->type) {
case NLA_U8:
value = nla_get_u8(nla);
break;
case NLA_U16:
value = nla_get_u16(nla);
break;
case NLA_U32:
value = nla_get_u32(nla);
break;
case NLA_S8:
value = nla_get_s8(nla);
break;
case NLA_S16:
value = nla_get_s16(nla);
break;
case NLA_S32:
value = nla_get_s32(nla);
break;
case NLA_S64:
value = nla_get_s64(nla);
break;
case NLA_U64:
/* treat this one specially, since it may not fit into s64 */
if ((validate_min && nla_get_u64(nla) < pt->min) ||
(validate_max && nla_get_u64(nla) > pt->max)) {
NL_SET_ERR_MSG_ATTR(extack, nla,
"integer out of range");
return -ERANGE;
}
return 0;
default:
WARN_ON(1);
return -EINVAL;
}
if ((validate_min && value < pt->min) ||
(validate_max && value > pt->max)) {
NL_SET_ERR_MSG_ATTR(extack, nla,
"integer out of range");
return -ERANGE;
}
return 0;
}
static int validate_nla(const struct nlattr *nla, int maxtype,
const struct nla_policy *policy,
struct netlink_ext_ack *extack)
{
const struct nla_policy *pt;
int minlen = 0, attrlen = nla_len(nla), type = nla_type(nla);
int err = -ERANGE;
if (type <= 0 || type > maxtype)
return 0;
pt = &policy[type];
BUG_ON(pt->type > NLA_TYPE_MAX);
if ((nla_attr_len[pt->type] && attrlen != nla_attr_len[pt->type]) ||
(pt->type == NLA_EXACT_LEN_WARN && attrlen != pt->len)) {
pr_warn_ratelimited("netlink: '%s': attribute type %d has an invalid length.\n",
current->comm, type);
}
switch (pt->type) {
case NLA_EXACT_LEN:
if (attrlen != pt->len)
goto out_err;
break;
case NLA_REJECT:
if (extack && pt->validation_data) {
NL_SET_BAD_ATTR(extack, nla);
extack->_msg = pt->validation_data;
return -EINVAL;
}
err = -EINVAL;
goto out_err;
case NLA_FLAG:
if (attrlen > 0)
goto out_err;
break;
case NLA_BITFIELD32:
if (attrlen != sizeof(struct nla_bitfield32))
goto out_err;
err = validate_nla_bitfield32(nla, pt->validation_data);
if (err)
goto out_err;
break;
case NLA_NUL_STRING:
if (pt->len)
minlen = min_t(int, attrlen, pt->len + 1);
else
minlen = attrlen;
if (!minlen || memchr(nla_data(nla), '\0', minlen) == NULL) {
err = -EINVAL;
goto out_err;
}
/* fall through */
case NLA_STRING:
if (attrlen < 1)
goto out_err;
if (pt->len) {
char *buf = nla_data(nla);
if (buf[attrlen - 1] == '\0')
attrlen--;
if (attrlen > pt->len)
goto out_err;
}
break;
case NLA_BINARY:
if (pt->len && attrlen > pt->len)
goto out_err;
break;
case NLA_NESTED:
/* a nested attributes is allowed to be empty; if its not,
* it must have a size of at least NLA_HDRLEN.
*/
if (attrlen == 0)
break;
if (attrlen < NLA_HDRLEN)
goto out_err;
if (pt->validation_data) {
err = nla_validate(nla_data(nla), nla_len(nla), pt->len,
pt->validation_data, extack);
if (err < 0) {
/*
* return directly to preserve the inner
* error message/attribute pointer
*/
return err;
}
}
break;
case NLA_NESTED_ARRAY:
/* a nested array attribute is allowed to be empty; if its not,
* it must have a size of at least NLA_HDRLEN.
*/
if (attrlen == 0)
break;
if (attrlen < NLA_HDRLEN)
goto out_err;
if (pt->validation_data) {
int err;
err = nla_validate_array(nla_data(nla), nla_len(nla),
pt->len, pt->validation_data,
extack);
if (err < 0) {
/*
* return directly to preserve the inner
* error message/attribute pointer
*/
return err;
}
}
break;
default:
if (pt->len)
minlen = pt->len;
else if (pt->type != NLA_UNSPEC)
minlen = nla_attr_minlen[pt->type];
if (attrlen < minlen)
goto out_err;
}
/* further validation */
switch (pt->validation_type) {
case NLA_VALIDATE_NONE:
/* nothing to do */
break;
case NLA_VALIDATE_RANGE:
case NLA_VALIDATE_MIN:
case NLA_VALIDATE_MAX:
err = nla_validate_int_range(pt, nla, extack);
if (err)
return err;
break;
case NLA_VALIDATE_FUNCTION:
if (pt->validate) {
err = pt->validate(nla, extack);
if (err)
return err;
}
break;
}
return 0;
out_err:
NL_SET_ERR_MSG_ATTR(extack, nla, "Attribute failed policy validation");
return err;
}
/**
* nla_validate - Validate a stream of attributes
* @head: head of attribute stream
* @len: length of attribute stream
* @maxtype: maximum attribute type to be expected
* @policy: validation policy
* @extack: extended ACK report struct
*
* Validates all attributes in the specified attribute stream against the
* specified policy. Attributes with a type exceeding maxtype will be
* ignored. See documenation of struct nla_policy for more details.
*
* Returns 0 on success or a negative error code.
*/
int nla_validate(const struct nlattr *head, int len, int maxtype,
const struct nla_policy *policy,
struct netlink_ext_ack *extack)
{
const struct nlattr *nla;
int rem;
nla_for_each_attr(nla, head, len, rem) {
int err = validate_nla(nla, maxtype, policy, extack);
if (err < 0)
return err;
}
return 0;
}
EXPORT_SYMBOL(nla_validate);
/**
* nla_policy_len - Determin the max. length of a policy
* @policy: policy to use
* @n: number of policies
*
* Determines the max. length of the policy. It is currently used
* to allocated Netlink buffers roughly the size of the actual
* message.
*
* Returns 0 on success or a negative error code.
*/
int
nla_policy_len(const struct nla_policy *p, int n)
{
int i, len = 0;
for (i = 0; i < n; i++, p++) {
if (p->len)
len += nla_total_size(p->len);
else if (nla_attr_len[p->type])
len += nla_total_size(nla_attr_len[p->type]);
else if (nla_attr_minlen[p->type])
len += nla_total_size(nla_attr_minlen[p->type]);
}
return len;
}
EXPORT_SYMBOL(nla_policy_len);
/**
* nla_parse - Parse a stream of attributes into a tb buffer
* @tb: destination array with maxtype+1 elements
* @maxtype: maximum attribute type to be expected
* @head: head of attribute stream
* @len: length of attribute stream
* @policy: validation policy
*
* Parses a stream of attributes and stores a pointer to each attribute in
* the tb array accessible via the attribute type. Attributes with a type
* exceeding maxtype will be silently ignored for backwards compatibility
* reasons. policy may be set to NULL if no validation is required.
*
* Returns 0 on success or a negative error code.
*/
static int __nla_parse(struct nlattr **tb, int maxtype,
const struct nlattr *head, int len,
bool strict, const struct nla_policy *policy,
struct netlink_ext_ack *extack)
{
const struct nlattr *nla;
int rem;
memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
nla_for_each_attr(nla, head, len, rem) {
u16 type = nla_type(nla);
if (type == 0 || type > maxtype) {
if (strict) {
NL_SET_ERR_MSG(extack, "Unknown attribute type");
return -EINVAL;
}
continue;
}
if (policy) {
int err = validate_nla(nla, maxtype, policy, extack);
if (err < 0)
return err;
}
tb[type] = (struct nlattr *)nla;
}
if (unlikely(rem > 0)) {
pr_warn_ratelimited("netlink: %d bytes leftover after parsing attributes in process `%s'.\n",
rem, current->comm);
NL_SET_ERR_MSG(extack, "bytes leftover after parsing attributes");
if (strict)
return -EINVAL;
}
return 0;
}
int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
int len, const struct nla_policy *policy,
struct netlink_ext_ack *extack)
{
return __nla_parse(tb, maxtype, head, len, false, policy, extack);
}
EXPORT_SYMBOL(nla_parse);
int nla_parse_strict(struct nlattr **tb, int maxtype, const struct nlattr *head,
int len, const struct nla_policy *policy,
struct netlink_ext_ack *extack)
{
return __nla_parse(tb, maxtype, head, len, true, policy, extack);
}
EXPORT_SYMBOL(nla_parse_strict);
/**
* nla_find - Find a specific attribute in a stream of attributes
* @head: head of attribute stream
* @len: length of attribute stream
* @attrtype: type of attribute to look for
*
* Returns the first attribute in the stream matching the specified type.
*/
struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype)
{
const struct nlattr *nla;
int rem;
nla_for_each_attr(nla, head, len, rem)
if (nla_type(nla) == attrtype)
return (struct nlattr *)nla;
return NULL;
}
EXPORT_SYMBOL(nla_find);
/**
* nla_strlcpy - Copy string attribute payload into a sized buffer
* @dst: where to copy the string to
* @nla: attribute to copy the string from
* @dstsize: size of destination buffer
*
* Copies at most dstsize - 1 bytes into the destination buffer.
* The result is always a valid NUL-terminated string. Unlike
* strlcpy the destination buffer is always padded out.
*
* Returns the length of the source buffer.
*/
size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
{
size_t srclen = nla_len(nla);
char *src = nla_data(nla);
if (srclen > 0 && src[srclen - 1] == '\0')
srclen--;
if (dstsize > 0) {
size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
memset(dst, 0, dstsize);
memcpy(dst, src, len);
}
return srclen;
}
EXPORT_SYMBOL(nla_strlcpy);
/**
* nla_strdup - Copy string attribute payload into a newly allocated buffer
* @nla: attribute to copy the string from
* @flags: the type of memory to allocate (see kmalloc).
*
* Returns a pointer to the allocated buffer or NULL on error.
*/
char *nla_strdup(const struct nlattr *nla, gfp_t flags)
{
size_t srclen = nla_len(nla);
char *src = nla_data(nla), *dst;
if (srclen > 0 && src[srclen - 1] == '\0')
srclen--;
dst = kmalloc(srclen + 1, flags);
if (dst != NULL) {
memcpy(dst, src, srclen);
dst[srclen] = '\0';
}
return dst;
}
EXPORT_SYMBOL(nla_strdup);
/**
* nla_memcpy - Copy a netlink attribute into another memory area
* @dest: where to copy to memcpy
* @src: netlink attribute to copy from
* @count: size of the destination area
*
* Note: The number of bytes copied is limited by the length of
* attribute's payload. memcpy
*
* Returns the number of bytes copied.
*/
int nla_memcpy(void *dest, const struct nlattr *src, int count)
{
int minlen = min_t(int, count, nla_len(src));
memcpy(dest, nla_data(src), minlen);
if (count > minlen)
memset(dest + minlen, 0, count - minlen);
return minlen;
}
EXPORT_SYMBOL(nla_memcpy);
/**
* nla_memcmp - Compare an attribute with sized memory area
* @nla: netlink attribute
* @data: memory area
* @size: size of memory area
*/
int nla_memcmp(const struct nlattr *nla, const void *data,
size_t size)
{
int d = nla_len(nla) - size;
if (d == 0)
d = memcmp(nla_data(nla), data, size);
return d;
}
EXPORT_SYMBOL(nla_memcmp);
/**
* nla_strcmp - Compare a string attribute against a string
* @nla: netlink string attribute
* @str: another string
*/
int nla_strcmp(const struct nlattr *nla, const char *str)
{
int len = strlen(str);
char *buf = nla_data(nla);
int attrlen = nla_len(nla);
int d;
if (attrlen > 0 && buf[attrlen - 1] == '\0')
attrlen--;
d = attrlen - len;
if (d == 0)
d = memcmp(nla_data(nla), str, len);
return d;
}
EXPORT_SYMBOL(nla_strcmp);
#ifdef CONFIG_NET
/**
* __nla_reserve - reserve room for attribute on the skb
* @skb: socket buffer to reserve room on
* @attrtype: attribute type
* @attrlen: length of attribute payload
*
* Adds a netlink attribute header to a socket buffer and reserves
* room for the payload but does not copy it.
*
* The caller is responsible to ensure that the skb provides enough
* tailroom for the attribute header and payload.
*/
struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
{
struct nlattr *nla;
nla = skb_put(skb, nla_total_size(attrlen));
nla->nla_type = attrtype;
nla->nla_len = nla_attr_size(attrlen);
memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
return nla;
}
EXPORT_SYMBOL(__nla_reserve);
/**
* __nla_reserve_64bit - reserve room for attribute on the skb and align it
* @skb: socket buffer to reserve room on
* @attrtype: attribute type
* @attrlen: length of attribute payload
* @padattr: attribute type for the padding
*
* Adds a netlink attribute header to a socket buffer and reserves
* room for the payload but does not copy it. It also ensure that this
* attribute will have a 64-bit aligned nla_data() area.
*
* The caller is responsible to ensure that the skb provides enough
* tailroom for the attribute header and payload.
*/
struct nlattr *__nla_reserve_64bit(struct sk_buff *skb, int attrtype,
int attrlen, int padattr)
{
if (nla_need_padding_for_64bit(skb))
nla_align_64bit(skb, padattr);
return __nla_reserve(skb, attrtype, attrlen);
}
EXPORT_SYMBOL(__nla_reserve_64bit);
/**
* __nla_reserve_nohdr - reserve room for attribute without header
* @skb: socket buffer to reserve room on
* @attrlen: length of attribute payload
*
* Reserves room for attribute payload without a header.
*
* The caller is responsible to ensure that the skb provides enough
* tailroom for the payload.
*/
void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
{
return skb_put_zero(skb, NLA_ALIGN(attrlen));
}
EXPORT_SYMBOL(__nla_reserve_nohdr);
/**
* nla_reserve - reserve room for attribute on the skb
* @skb: socket buffer to reserve room on
* @attrtype: attribute type
* @attrlen: length of attribute payload
*
* Adds a netlink attribute header to a socket buffer and reserves
* room for the payload but does not copy it.
*
* Returns NULL if the tailroom of the skb is insufficient to store
* the attribute header and payload.
*/
struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
{
if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
return NULL;
return __nla_reserve(skb, attrtype, attrlen);
}
EXPORT_SYMBOL(nla_reserve);
/**
* nla_reserve_64bit - reserve room for attribute on the skb and align it
* @skb: socket buffer to reserve room on
* @attrtype: attribute type
* @attrlen: length of attribute payload
* @padattr: attribute type for the padding
*
* Adds a netlink attribute header to a socket buffer and reserves
* room for the payload but does not copy it. It also ensure that this
* attribute will have a 64-bit aligned nla_data() area.
*
* Returns NULL if the tailroom of the skb is insufficient to store
* the attribute header and payload.
*/
struct nlattr *nla_reserve_64bit(struct sk_buff *skb, int attrtype, int attrlen,
int padattr)
{
size_t len;
if (nla_need_padding_for_64bit(skb))
len = nla_total_size_64bit(attrlen);
else
len = nla_total_size(attrlen);
if (unlikely(skb_tailroom(skb) < len))
return NULL;
return __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
}
EXPORT_SYMBOL(nla_reserve_64bit);
/**
* nla_reserve_nohdr - reserve room for attribute without header
* @skb: socket buffer to reserve room on
* @attrlen: length of attribute payload
*
* Reserves room for attribute payload without a header.
*
* Returns NULL if the tailroom of the skb is insufficient to store
* the attribute payload.
*/
void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
{
if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
return NULL;
return __nla_reserve_nohdr(skb, attrlen);
}
EXPORT_SYMBOL(nla_reserve_nohdr);
/**
* __nla_put - Add a netlink attribute to a socket buffer
* @skb: socket buffer to add attribute to
* @attrtype: attribute type
* @attrlen: length of attribute payload
* @data: head of attribute payload
*
* The caller is responsible to ensure that the skb provides enough
* tailroom for the attribute header and payload.
*/
void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
const void *data)
{
struct nlattr *nla;
nla = __nla_reserve(skb, attrtype, attrlen);
memcpy(nla_data(nla), data, attrlen);
}
EXPORT_SYMBOL(__nla_put);
/**
* __nla_put_64bit - Add a netlink attribute to a socket buffer and align it
* @skb: socket buffer to add attribute to
* @attrtype: attribute type
* @attrlen: length of attribute payload
* @data: head of attribute payload
* @padattr: attribute type for the padding
*
* The caller is responsible to ensure that the skb provides enough
* tailroom for the attribute header and payload.
*/
void __nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
const void *data, int padattr)
{
struct nlattr *nla;
nla = __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
memcpy(nla_data(nla), data, attrlen);
}
EXPORT_SYMBOL(__nla_put_64bit);
/**
* __nla_put_nohdr - Add a netlink attribute without header
* @skb: socket buffer to add attribute to
* @attrlen: length of attribute payload
* @data: head of attribute payload
*
* The caller is responsible to ensure that the skb provides enough
* tailroom for the attribute payload.
*/
void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
{
void *start;
start = __nla_reserve_nohdr(skb, attrlen);
memcpy(start, data, attrlen);
}
EXPORT_SYMBOL(__nla_put_nohdr);
/**
* nla_put - Add a netlink attribute to a socket buffer
* @skb: socket buffer to add attribute to
* @attrtype: attribute type
* @attrlen: length of attribute payload
* @data: head of attribute payload
*
* Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
* the attribute header and payload.
*/
int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
{
if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
return -EMSGSIZE;
__nla_put(skb, attrtype, attrlen, data);
return 0;
}
EXPORT_SYMBOL(nla_put);
/**
* nla_put_64bit - Add a netlink attribute to a socket buffer and align it
* @skb: socket buffer to add attribute to
* @attrtype: attribute type
* @attrlen: length of attribute payload
* @data: head of attribute payload
* @padattr: attribute type for the padding
*
* Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
* the attribute header and payload.
*/
int nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
const void *data, int padattr)
{
size_t len;
if (nla_need_padding_for_64bit(skb))
len = nla_total_size_64bit(attrlen);
else
len = nla_total_size(attrlen);
if (unlikely(skb_tailroom(skb) < len))
return -EMSGSIZE;
__nla_put_64bit(skb, attrtype, attrlen, data, padattr);
return 0;
}
EXPORT_SYMBOL(nla_put_64bit);
/**
* nla_put_nohdr - Add a netlink attribute without header
* @skb: socket buffer to add attribute to
* @attrlen: length of attribute payload
* @data: head of attribute payload
*
* Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
* the attribute payload.
*/
int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
{
if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
return -EMSGSIZE;
__nla_put_nohdr(skb, attrlen, data);
return 0;
}
EXPORT_SYMBOL(nla_put_nohdr);
/**
* nla_append - Add a netlink attribute without header or padding
* @skb: socket buffer to add attribute to
* @attrlen: length of attribute payload
* @data: head of attribute payload
*
* Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
* the attribute payload.
*/
int nla_append(struct sk_buff *skb, int attrlen, const void *data)
{
if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
return -EMSGSIZE;
skb_put_data(skb, data, attrlen);
return 0;
}
EXPORT_SYMBOL(nla_append);
#endif