netlink.c

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/*
 * Netlink event notifications for SELinux.
 *
 * Author: James Morris <[email protected]>
 *
 * Copyright (C) 2004 Red Hat, Inc., James Morris <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2,
 * as published by the Free Software Foundation.
 */
#include <linux/init.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/stddef.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/skbuff.h>
#include <linux/netlink.h>
#include <linux/selinux_netlink.h>
#include <net/net_namespace.h>
#include <net/netlink.h>

#include "security.h"

static struct sock *selnl;

static int selnl_msglen(int msgtype)
{
    int ret = 0;

    switch (msgtype) {
    case SELNL_MSG_SETENFORCE:
        ret = sizeof(struct selnl_msg_setenforce);
        break;

    case SELNL_MSG_POLICYLOAD:
        ret = sizeof(struct selnl_msg_policyload);
        break;

    default:
        BUG();
    }
    return ret;
}

static void selnl_add_payload(struct nlmsghdr *nlh, int len, int msgtype, void *data)
{
    switch (msgtype) {
    case SELNL_MSG_SETENFORCE: {
        struct selnl_msg_setenforce *msg = nlmsg_data(nlh);

        memset(msg, 0, len);
        msg->val = *((int *)data);
        break;
    }

    case SELNL_MSG_POLICYLOAD: {
        struct selnl_msg_policyload *msg = nlmsg_data(nlh);

        memset(msg, 0, len);
        msg->seqno = *((u32 *)data);
        break;
    }

    default:
        BUG();
    }
}

static void selnl_notify(int msgtype, void *data)
{
    int len;
    sk_buff_data_t tmp;
    struct sk_buff *skb;
    struct nlmsghdr *nlh;

    len = selnl_msglen(msgtype);

    skb = alloc_skb(NLMSG_SPACE(len), GFP_USER);
    if (!skb)
        goto oom;

    tmp = skb->tail;
    nlh = nlmsg_put(skb, 0, 0, msgtype, len, 0);
    if (!nlh)
        goto out_kfree_skb;
    selnl_add_payload(nlh, len, msgtype, data);
    nlh->nlmsg_len = skb->tail - tmp;
    NETLINK_CB(skb).dst_group = SELNLGRP_AVC;
    netlink_broadcast(selnl, skb, 0, SELNLGRP_AVC, GFP_USER);
out:
    return;

out_kfree_skb:
    kfree_skb(skb);
oom:
    printk(KERN_ERR "SELinux:  OOM in %s\n", __func__);
    goto out;
}

void selnl_notify_setenforce(int val)
{
    selnl_notify(SELNL_MSG_SETENFORCE, &val);
}

void selnl_notify_policyload(u32 seqno)
{
    selnl_notify(SELNL_MSG_POLICYLOAD, &seqno);
}

static int __init selnl_init(void)
{
    struct netlink_kernel_cfg cfg = {
        .groups = SELNLGRP_MAX,
        .flags  = NL_CFG_F_NONROOT_RECV,
    };

    selnl = netlink_kernel_create(&init_net, NETLINK_SELINUX, &cfg);
    if (selnl == NULL)
        panic("SELinux:  Cannot create netlink socket.");
    return 0;
}

__initcall(selnl_init);