netif.c

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/*
 * Network interface table.
 *
 * Network interfaces (devices) do not have a security field, so we
 * maintain a table associating each interface with a SID.
 *
 * Author: James Morris <[email protected]>
 *
 * Copyright (C) 2003 Red Hat, Inc., James Morris <[email protected]>
 * Copyright (C) 2007 Hewlett-Packard Development Company, L.P.
 *            Paul Moore <[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/list.h>
#include <linux/notifier.h>
#include <linux/netdevice.h>
#include <linux/rcupdate.h>
#include <net/net_namespace.h>

#include "security.h"
#include "objsec.h"
#include "netif.h"

#define SEL_NETIF_HASH_SIZE 64
#define SEL_NETIF_HASH_MAX  1024

struct sel_netif {
    struct list_head list;
    struct netif_security_struct nsec;
    struct rcu_head rcu_head;
};

static u32 sel_netif_total;
static LIST_HEAD(sel_netif_list);
static DEFINE_SPINLOCK(sel_netif_lock);
static struct list_head sel_netif_hash[SEL_NETIF_HASH_SIZE];

static inline u32 sel_netif_hashfn(int ifindex)
{
    return (ifindex & (SEL_NETIF_HASH_SIZE - 1));
}

static inline struct sel_netif *sel_netif_find(int ifindex)
{
    int idx = sel_netif_hashfn(ifindex);
    struct sel_netif *netif;

    list_for_each_entry_rcu(netif, &sel_netif_hash[idx], list)
        /* all of the devices should normally fit in the hash, so we
         * optimize for that case */
        if (likely(netif->nsec.ifindex == ifindex))
            return netif;

    return NULL;
}

static int sel_netif_insert(struct sel_netif *netif)
{
    int idx;

    if (sel_netif_total >= SEL_NETIF_HASH_MAX)
        return -ENOSPC;

    idx = sel_netif_hashfn(netif->nsec.ifindex);
    list_add_rcu(&netif->list, &sel_netif_hash[idx]);
    sel_netif_total++;

    return 0;
}

static void sel_netif_destroy(struct sel_netif *netif)
{
    list_del_rcu(&netif->list);
    sel_netif_total--;
    kfree_rcu(netif, rcu_head);
}

static int sel_netif_sid_slow(int ifindex, u32 *sid)
{
    int ret;
    struct sel_netif *netif;
    struct sel_netif *new = NULL;
    struct net_device *dev;

    /* NOTE: we always use init's network namespace since we don't
     * currently support containers */

    dev = dev_get_by_index(&init_net, ifindex);
    if (unlikely(dev == NULL)) {
        printk(KERN_WARNING
               "SELinux: failure in sel_netif_sid_slow(),"
               " invalid network interface (%d)\n", ifindex);
        return -ENOENT;
    }

    spin_lock_bh(&sel_netif_lock);
    netif = sel_netif_find(ifindex);
    if (netif != NULL) {
        *sid = netif->nsec.sid;
        ret = 0;
        goto out;
    }
    new = kzalloc(sizeof(*new), GFP_ATOMIC);
    if (new == NULL) {
        ret = -ENOMEM;
        goto out;
    }
    ret = security_netif_sid(dev->name, &new->nsec.sid);
    if (ret != 0)
        goto out;
    new->nsec.ifindex = ifindex;
    ret = sel_netif_insert(new);
    if (ret != 0)
        goto out;
    *sid = new->nsec.sid;

out:
    spin_unlock_bh(&sel_netif_lock);
    dev_put(dev);
    if (unlikely(ret)) {
        printk(KERN_WARNING
               "SELinux: failure in sel_netif_sid_slow(),"
               " unable to determine network interface label (%d)\n",
               ifindex);
        kfree(new);
    }
    return ret;
}

int sel_netif_sid(int ifindex, u32 *sid)
{
    struct sel_netif *netif;

    rcu_read_lock();
    netif = sel_netif_find(ifindex);
    if (likely(netif != NULL)) {
        *sid = netif->nsec.sid;
        rcu_read_unlock();
        return 0;
    }
    rcu_read_unlock();

    return sel_netif_sid_slow(ifindex, sid);
}

static void sel_netif_kill(int ifindex)
{
    struct sel_netif *netif;

    rcu_read_lock();
    spin_lock_bh(&sel_netif_lock);
    netif = sel_netif_find(ifindex);
    if (netif)
        sel_netif_destroy(netif);
    spin_unlock_bh(&sel_netif_lock);
    rcu_read_unlock();
}

static void sel_netif_flush(void)
{
    int idx;
    struct sel_netif *netif;

    spin_lock_bh(&sel_netif_lock);
    for (idx = 0; idx < SEL_NETIF_HASH_SIZE; idx++)
        list_for_each_entry(netif, &sel_netif_hash[idx], list)
            sel_netif_destroy(netif);
    spin_unlock_bh(&sel_netif_lock);
}

static int sel_netif_avc_callback(u32 event)
{
    if (event == AVC_CALLBACK_RESET) {
        sel_netif_flush();
        synchronize_net();
    }
    return 0;
}

static int sel_netif_netdev_notifier_handler(struct notifier_block *this,
                         unsigned long event, void *ptr)
{
    struct net_device *dev = ptr;

    if (dev_net(dev) != &init_net)
        return NOTIFY_DONE;

    if (event == NETDEV_DOWN)
        sel_netif_kill(dev->ifindex);

    return NOTIFY_DONE;
}

static struct notifier_block sel_netif_netdev_notifier = {
    .notifier_call = sel_netif_netdev_notifier_handler,
};

static __init int sel_netif_init(void)
{
    int i, err;

    if (!selinux_enabled)
        return 0;

    for (i = 0; i < SEL_NETIF_HASH_SIZE; i++)
        INIT_LIST_HEAD(&sel_netif_hash[i]);

    register_netdevice_notifier(&sel_netif_netdev_notifier);

    err = avc_add_callback(sel_netif_avc_callback, AVC_CALLBACK_RESET);
    if (err)
        panic("avc_add_callback() failed, error %d\n", err);

    return err;
}

__initcall(sel_netif_init);