nlattr.c

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/*
 * NETLINK      Netlink attributes
 *
 *      Authors:    Thomas Graf <[email protected]>
 *              Alexey Kuznetsov <[email protected]>
 */

#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/jiffies.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/string.h>
#include <linux/types.h>
#include <net/netlink.h>

static const u16 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(const struct nlattr *nla, int maxtype,
            const struct nla_policy *policy)
{
    const struct nla_policy *pt;
    int minlen = 0, attrlen = nla_len(nla), type = nla_type(nla);

    if (type <= 0 || type > maxtype)
        return 0;

    pt = &policy[type];

    BUG_ON(pt->type > NLA_TYPE_MAX);

    switch (pt->type) {
    case NLA_FLAG:
        if (attrlen > 0)
            return -ERANGE;
        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)
            return -EINVAL;
        /* fall through */

    case NLA_STRING:
        if (attrlen < 1)
            return -ERANGE;

        if (pt->len) {
            char *buf = nla_data(nla);

            if (buf[attrlen - 1] == '\0')
                attrlen--;

            if (attrlen > pt->len)
                return -ERANGE;
        }
        break;

    case NLA_BINARY:
        if (pt->len && attrlen > pt->len)
            return -ERANGE;
        break;

    case NLA_NESTED_COMPAT:
        if (attrlen < pt->len)
            return -ERANGE;
        if (attrlen < NLA_ALIGN(pt->len))
            break;
        if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN)
            return -ERANGE;
        nla = nla_data(nla) + NLA_ALIGN(pt->len);
        if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN + nla_len(nla))
            return -ERANGE;
        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;
    default:
        if (pt->len)
            minlen = pt->len;
        else if (pt->type != NLA_UNSPEC)
            minlen = nla_attr_minlen[pt->type];

        if (attrlen < minlen)
            return -ERANGE;
    }

    return 0;
}

int nla_validate(const struct nlattr *head, int len, int maxtype,
         const struct nla_policy *policy)
{
    const struct nlattr *nla;
    int rem, err;

    nla_for_each_attr(nla, head, len, rem) {
        err = validate_nla(nla, maxtype, policy);
        if (err < 0)
            goto errout;
    }

    err = 0;
errout:
    return err;
}

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_minlen[p->type])
            len += nla_total_size(nla_attr_minlen[p->type]);
    }

    return len;
}

int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
          int len, const struct nla_policy *policy)
{
    const struct nlattr *nla;
    int rem, err;

    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 (policy) {
                err = validate_nla(nla, maxtype, policy);
                if (err < 0)
                    goto errout;
            }

            tb[type] = (struct nlattr *)nla;
        }
    }

    if (unlikely(rem > 0))
        printk(KERN_WARNING "netlink: %d bytes leftover after parsing "
               "attributes.\n", rem);

    err = 0;
errout:
    return err;
}

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;
}

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;
}

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);

    return minlen;
}

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;
}

int nla_strcmp(const struct nlattr *nla, const char *str)
{
    int len = strlen(str) + 1;
    int d = nla_len(nla) - len;

    if (d == 0)
        d = memcmp(nla_data(nla), str, len);

    return d;
}

#ifdef CONFIG_NET

struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
{
    struct nlattr *nla;

    nla = (struct nlattr *) 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);

void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
{
    void *start;

    start = skb_put(skb, NLA_ALIGN(attrlen));
    memset(start, 0, NLA_ALIGN(attrlen));

    return start;
}
EXPORT_SYMBOL(__nla_reserve_nohdr);

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);

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);

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);

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);

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);

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);

int nla_append(struct sk_buff *skb, int attrlen, const void *data)
{
    if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
        return -EMSGSIZE;

    memcpy(skb_put(skb, attrlen), data, attrlen);
    return 0;
}
EXPORT_SYMBOL(nla_append);
#endif

EXPORT_SYMBOL(nla_validate);
EXPORT_SYMBOL(nla_policy_len);
EXPORT_SYMBOL(nla_parse);
EXPORT_SYMBOL(nla_find);
EXPORT_SYMBOL(nla_strlcpy);
EXPORT_SYMBOL(nla_memcpy);
EXPORT_SYMBOL(nla_memcmp);
EXPORT_SYMBOL(nla_strcmp);