NetLabel: fix a cache race condition

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / net / ipv4 / cipso_ipv4.c

/*
 * CIPSO - Commercial IP Security Option
 *
 * This is an implementation of the CIPSO 2.2 protocol as specified in
 * draft-ietf-cipso-ipsecurity-01.txt with additional tag types as found in
 * FIPS-188, copies of both documents can be found in the Documentation
 * directory.  While CIPSO never became a full IETF RFC standard many vendors
 * have chosen to adopt the protocol and over the years it has become a
 * de-facto standard for labeled networking.
 *
 * Author: Paul Moore <paul.moore@hp.com>
 *
 */

/*
 * (c) Copyright Hewlett-Packard Development Company, L.P., 2006
 *
 * This program is free software;  you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY;  without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
 * the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program;  if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 */

#include <linux/init.h>
#include <linux/types.h>
#include <linux/rcupdate.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/jhash.h>
#include <net/ip.h>
#include <net/icmp.h>
#include <net/tcp.h>
#include <net/netlabel.h>
#include <net/cipso_ipv4.h>
#include <asm/atomic.h>
#include <asm/bug.h>

struct cipso_v4_domhsh_entry {
        char *domain;
        u32 valid;
        struct list_head list;
        struct rcu_head rcu;
};

/* List of available DOI definitions */
/* XXX - Updates should be minimal so having a single lock for the
 * cipso_v4_doi_list and the cipso_v4_doi_list->dom_list should be
 * okay. */
/* XXX - This currently assumes a minimal number of different DOIs in use,
 * if in practice there are a lot of different DOIs this list should
 * probably be turned into a hash table or something similar so we
 * can do quick lookups. */
static DEFINE_SPINLOCK(cipso_v4_doi_list_lock);
static struct list_head cipso_v4_doi_list = LIST_HEAD_INIT(cipso_v4_doi_list);

/* Label mapping cache */
int cipso_v4_cache_enabled = 1;
int cipso_v4_cache_bucketsize = 10;
#define CIPSO_V4_CACHE_BUCKETBITS     7
#define CIPSO_V4_CACHE_BUCKETS        (1 << CIPSO_V4_CACHE_BUCKETBITS)
#define CIPSO_V4_CACHE_REORDERLIMIT   10
struct cipso_v4_map_cache_bkt {
        spinlock_t lock;
        u32 size;
        struct list_head list;
};
struct cipso_v4_map_cache_entry {
        u32 hash;
        unsigned char *key;
        size_t key_len;

        struct netlbl_lsm_cache *lsm_data;

        u32 activity;
        struct list_head list;
};
static struct cipso_v4_map_cache_bkt *cipso_v4_cache = NULL;

/* Restricted bitmap (tag #1) flags */
int cipso_v4_rbm_optfmt = 0;
int cipso_v4_rbm_strictvalid = 1;

/*
 * Helper Functions
 */

/**
 * cipso_v4_bitmap_walk - Walk a bitmap looking for a bit
 * @bitmap: the bitmap
 * @bitmap_len: length in bits
 * @offset: starting offset
 * @state: if non-zero, look for a set (1) bit else look for a cleared (0) bit
 *
 * Description:
 * Starting at @offset, walk the bitmap from left to right until either the
 * desired bit is found or we reach the end.  Return the bit offset, -1 if
 * not found, or -2 if error.
 */
static int cipso_v4_bitmap_walk(const unsigned char *bitmap,
                                u32 bitmap_len,
                                u32 offset,
                                u8 state)
{
        u32 bit_spot;
        u32 byte_offset;
        unsigned char bitmask;
        unsigned char byte;

        /* gcc always rounds to zero when doing integer division */
        byte_offset = offset / 8;
        byte = bitmap[byte_offset];
        bit_spot = offset;
        bitmask = 0x80 >> (offset % 8);

        while (bit_spot < bitmap_len) {
                if ((state && (byte & bitmask) == bitmask) ||
                    (state == 0 && (byte & bitmask) == 0))
                        return bit_spot;

                bit_spot++;
                bitmask >>= 1;
                if (bitmask == 0) {
                        byte = bitmap[++byte_offset];
                        bitmask = 0x80;
                }
        }

        return -1;
}

/**
 * cipso_v4_bitmap_setbit - Sets a single bit in a bitmap
 * @bitmap: the bitmap
 * @bit: the bit
 * @state: if non-zero, set the bit (1) else clear the bit (0)
 *
 * Description:
 * Set a single bit in the bitmask.  Returns zero on success, negative values
 * on error.
 */
static void cipso_v4_bitmap_setbit(unsigned char *bitmap,
                                   u32 bit,
                                   u8 state)
{
        u32 byte_spot;
        u8 bitmask;

        /* gcc always rounds to zero when doing integer division */
        byte_spot = bit / 8;
        bitmask = 0x80 >> (bit % 8);
        if (state)
                bitmap[byte_spot] |= bitmask;
        else
                bitmap[byte_spot] &= ~bitmask;
}

/**
 * cipso_v4_doi_domhsh_free - Frees a domain list entry
 * @entry: the entry's RCU field
 *
 * Description:
 * This function is designed to be used as a callback to the call_rcu()
 * function so that the memory allocated to a domain list entry can be released
 * safely.
 *
 */
static void cipso_v4_doi_domhsh_free(struct rcu_head *entry)
{
        struct cipso_v4_domhsh_entry *ptr;

        ptr = container_of(entry, struct cipso_v4_domhsh_entry, rcu);
        kfree(ptr->domain);
        kfree(ptr);
}

/**
 * cipso_v4_cache_entry_free - Frees a cache entry
 * @entry: the entry to free
 *
 * Description:
 * This function frees the memory associated with a cache entry including the
 * LSM cache data if there are no longer any users, i.e. reference count == 0.
 *
 */
static void cipso_v4_cache_entry_free(struct cipso_v4_map_cache_entry *entry)
{
        if (entry->lsm_data)
                netlbl_secattr_cache_free(entry->lsm_data);
        kfree(entry->key);
        kfree(entry);
}

/**
 * cipso_v4_map_cache_hash - Hashing function for the CIPSO cache
 * @key: the hash key
 * @key_len: the length of the key in bytes
 *
 * Description:
 * The CIPSO tag hashing function.  Returns a 32-bit hash value.
 *
 */
static u32 cipso_v4_map_cache_hash(const unsigned char *key, u32 key_len)
{
        return jhash(key, key_len, 0);
}

/*
 * Label Mapping Cache Functions
 */

/**
 * cipso_v4_cache_init - Initialize the CIPSO cache
 *
 * Description:
 * Initializes the CIPSO label mapping cache, this function should be called
 * before any of the other functions defined in this file.  Returns zero on
 * success, negative values on error.
 *
 */
static int cipso_v4_cache_init(void)
{
        u32 iter;

        cipso_v4_cache = kcalloc(CIPSO_V4_CACHE_BUCKETS,
                                 sizeof(struct cipso_v4_map_cache_bkt),
                                 GFP_KERNEL);
        if (cipso_v4_cache == NULL)
                return -ENOMEM;

        for (iter = 0; iter < CIPSO_V4_CACHE_BUCKETS; iter++) {
                spin_lock_init(&cipso_v4_cache[iter].lock);
                cipso_v4_cache[iter].size = 0;
                INIT_LIST_HEAD(&cipso_v4_cache[iter].list);
        }

        return 0;
}

/**
 * cipso_v4_cache_invalidate - Invalidates the current CIPSO cache
 *
 * Description:
 * Invalidates and frees any entries in the CIPSO cache.  Returns zero on
 * success and negative values on failure.
 *
 */
void cipso_v4_cache_invalidate(void)
{
        struct cipso_v4_map_cache_entry *entry, *tmp_entry;
        u32 iter;

        for (iter = 0; iter < CIPSO_V4_CACHE_BUCKETS; iter++) {
                spin_lock_bh(&cipso_v4_cache[iter].lock);
                list_for_each_entry_safe(entry,
                                         tmp_entry,
                                         &cipso_v4_cache[iter].list, list) {
                        list_del(&entry->list);
                        cipso_v4_cache_entry_free(entry);
                }
                cipso_v4_cache[iter].size = 0;
                spin_unlock_bh(&cipso_v4_cache[iter].lock);
        }

        return;
}

/**
 * cipso_v4_cache_check - Check the CIPSO cache for a label mapping
 * @key: the buffer to check
 * @key_len: buffer length in bytes
 * @secattr: the security attribute struct to use
 *
 * Description:
 * This function checks the cache to see if a label mapping already exists for
 * the given key.  If there is a match then the cache is adjusted and the
 * @secattr struct is populated with the correct LSM security attributes.  The
 * cache is adjusted in the following manner if the entry is not already the
 * first in the cache bucket:
 *
 *  1. The cache entry's activity counter is incremented
 *  2. The previous (higher ranking) entry's activity counter is decremented
 *  3. If the difference between the two activity counters is geater than
 *     CIPSO_V4_CACHE_REORDERLIMIT the two entries are swapped
 *
 * Returns zero on success, -ENOENT for a cache miss, and other negative values
 * on error.
 *
 */
static int cipso_v4_cache_check(const unsigned char *key,
                                u32 key_len,
                                struct netlbl_lsm_secattr *secattr)
{
        u32 bkt;
        struct cipso_v4_map_cache_entry *entry;
        struct cipso_v4_map_cache_entry *prev_entry = NULL;
        u32 hash;

        if (!cipso_v4_cache_enabled)
                return -ENOENT;

        hash = cipso_v4_map_cache_hash(key, key_len);
        bkt = hash & (CIPSO_V4_CACHE_BUCKETBITS - 1);
        spin_lock_bh(&cipso_v4_cache[bkt].lock);
        list_for_each_entry(entry, &cipso_v4_cache[bkt].list, list) {
                if (entry->hash == hash &&
                    entry->key_len == key_len &&
                    memcmp(entry->key, key, key_len) == 0) {
                        entry->activity += 1;
                        atomic_inc(&entry->lsm_data->refcount);
                        secattr->cache = entry->lsm_data;
                        if (prev_entry == NULL) {
                                spin_unlock_bh(&cipso_v4_cache[bkt].lock);
                                return 0;
                        }

                        if (prev_entry->activity > 0)
                                prev_entry->activity -= 1;
                        if (entry->activity > prev_entry->activity &&
                            entry->activity - prev_entry->activity >
                            CIPSO_V4_CACHE_REORDERLIMIT) {
                                __list_del(entry->list.prev, entry->list.next);
                                __list_add(&entry->list,
                                           prev_entry->list.prev,
                                           &prev_entry->list);
                        }

                        spin_unlock_bh(&cipso_v4_cache[bkt].lock);
                        return 0;
                }
                prev_entry = entry;
        }
        spin_unlock_bh(&cipso_v4_cache[bkt].lock);

        return -ENOENT;
}

/**
 * cipso_v4_cache_add - Add an entry to the CIPSO cache
 * @skb: the packet
 * @secattr: the packet's security attributes
 *
 * Description:
 * Add a new entry into the CIPSO label mapping cache.  Add the new entry to
 * head of the cache bucket's list, if the cache bucket is out of room remove
 * the last entry in the list first.  It is important to note that there is
 * currently no checking for duplicate keys.  Returns zero on success,
 * negative values on failure.
 *
 */
int cipso_v4_cache_add(const struct sk_buff *skb,
                       const struct netlbl_lsm_secattr *secattr)
{
        int ret_val = -EPERM;
        u32 bkt;
        struct cipso_v4_map_cache_entry *entry = NULL;
        struct cipso_v4_map_cache_entry *old_entry = NULL;
        unsigned char *cipso_ptr;
        u32 cipso_ptr_len;

        if (!cipso_v4_cache_enabled || cipso_v4_cache_bucketsize <= 0)
                return 0;

        cipso_ptr = CIPSO_V4_OPTPTR(skb);
        cipso_ptr_len = cipso_ptr[1];

        entry = kzalloc(sizeof(*entry), GFP_ATOMIC);
        if (entry == NULL)
                return -ENOMEM;
        entry->key = kmalloc(cipso_ptr_len, GFP_ATOMIC);
        if (entry->key == NULL) {
                ret_val = -ENOMEM;
                goto cache_add_failure;
        }
        memcpy(entry->key, cipso_ptr, cipso_ptr_len);
        entry->key_len = cipso_ptr_len;
        entry->hash = cipso_v4_map_cache_hash(cipso_ptr, cipso_ptr_len);
        atomic_inc(&secattr->cache->refcount);
        entry->lsm_data = secattr->cache;

        bkt = entry->hash & (CIPSO_V4_CACHE_BUCKETBITS - 1);
        spin_lock_bh(&cipso_v4_cache[bkt].lock);
        if (cipso_v4_cache[bkt].size < cipso_v4_cache_bucketsize) {
                list_add(&entry->list, &cipso_v4_cache[bkt].list);
                cipso_v4_cache[bkt].size += 1;
        } else {
                old_entry = list_entry(cipso_v4_cache[bkt].list.prev,
                                       struct cipso_v4_map_cache_entry, list);
                list_del(&old_entry->list);
                list_add(&entry->list, &cipso_v4_cache[bkt].list);
                cipso_v4_cache_entry_free(old_entry);
        }
        spin_unlock_bh(&cipso_v4_cache[bkt].lock);

        return 0;

cache_add_failure:
        if (entry)
                cipso_v4_cache_entry_free(entry);
        return ret_val;
}

/*
 * DOI List Functions
 */

/**
 * cipso_v4_doi_search - Searches for a DOI definition
 * @doi: the DOI to search for
 *
 * Description:
 * Search the DOI definition list for a DOI definition with a DOI value that
 * matches @doi.  The caller is responsibile for calling rcu_read_[un]lock().
 * Returns a pointer to the DOI definition on success and NULL on failure.
 */
static struct cipso_v4_doi *cipso_v4_doi_search(u32 doi)
{
        struct cipso_v4_doi *iter;

        list_for_each_entry_rcu(iter, &cipso_v4_doi_list, list)
                if (iter->doi == doi && iter->valid)
                        return iter;
        return NULL;
}

/**
 * cipso_v4_doi_add - Add a new DOI to the CIPSO protocol engine
 * @doi_def: the DOI structure
 *
 * Description:
 * The caller defines a new DOI for use by the CIPSO engine and calls this
 * function to add it to the list of acceptable domains.  The caller must
 * ensure that the mapping table specified in @doi_def->map meets all of the
 * requirements of the mapping type (see cipso_ipv4.h for details).  Returns
 * zero on success and non-zero on failure.
 *
 */
int cipso_v4_doi_add(struct cipso_v4_doi *doi_def)
{
        if (doi_def == NULL || doi_def->doi == CIPSO_V4_DOI_UNKNOWN)
                return -EINVAL;

        doi_def->valid = 1;
        INIT_RCU_HEAD(&doi_def->rcu);
        INIT_LIST_HEAD(&doi_def->dom_list);

        rcu_read_lock();
        if (cipso_v4_doi_search(doi_def->doi) != NULL)
                goto doi_add_failure_rlock;
        spin_lock(&cipso_v4_doi_list_lock);
        if (cipso_v4_doi_search(doi_def->doi) != NULL)
                goto doi_add_failure_slock;
        list_add_tail_rcu(&doi_def->list, &cipso_v4_doi_list);
        spin_unlock(&cipso_v4_doi_list_lock);
        rcu_read_unlock();

        return 0;

doi_add_failure_slock:
        spin_unlock(&cipso_v4_doi_list_lock);
doi_add_failure_rlock:
        rcu_read_unlock();
        return -EEXIST;
}

/**
 * cipso_v4_doi_remove - Remove an existing DOI from the CIPSO protocol engine
 * @doi: the DOI value
 * @audit_secid: the LSM secid to use in the audit message
 * @callback: the DOI cleanup/free callback
 *
 * Description:
 * Removes a DOI definition from the CIPSO engine, @callback is called to
 * free any memory.  The NetLabel routines will be called to release their own
 * LSM domain mappings as well as our own domain list.  Returns zero on
 * success and negative values on failure.
 *
 */
int cipso_v4_doi_remove(u32 doi,
                        struct netlbl_audit *audit_info,
                        void (*callback) (struct rcu_head * head))
{
        struct cipso_v4_doi *doi_def;
        struct cipso_v4_domhsh_entry *dom_iter;

        rcu_read_lock();
        if (cipso_v4_doi_search(doi) != NULL) {
                spin_lock(&cipso_v4_doi_list_lock);
                doi_def = cipso_v4_doi_search(doi);
                if (doi_def == NULL) {
                        spin_unlock(&cipso_v4_doi_list_lock);
                        rcu_read_unlock();
                        return -ENOENT;
                }
                doi_def->valid = 0;
                list_del_rcu(&doi_def->list);
                spin_unlock(&cipso_v4_doi_list_lock);
                list_for_each_entry_rcu(dom_iter, &doi_def->dom_list, list)
                        if (dom_iter->valid)
                                netlbl_domhsh_remove(dom_iter->domain,
                                                     audit_info);
                cipso_v4_cache_invalidate();
                rcu_read_unlock();

                call_rcu(&doi_def->rcu, callback);
                return 0;
        }
        rcu_read_unlock();

        return -ENOENT;
}

/**
 * cipso_v4_doi_getdef - Returns a pointer to a valid DOI definition
 * @doi: the DOI value
 *
 * Description:
 * Searches for a valid DOI definition and if one is found it is returned to
 * the caller.  Otherwise NULL is returned.  The caller must ensure that
 * rcu_read_lock() is held while accessing the returned definition.
 *
 */
struct cipso_v4_doi *cipso_v4_doi_getdef(u32 doi)
{
        return cipso_v4_doi_search(doi);
}

/**
 * cipso_v4_doi_walk - Iterate through the DOI definitions
 * @skip_cnt: skip past this number of DOI definitions, updated
 * @callback: callback for each DOI definition
 * @cb_arg: argument for the callback function
 *
 * Description:
 * Iterate over the DOI definition list, skipping the first @skip_cnt entries.
 * For each entry call @callback, if @callback returns a negative value stop
 * 'walking' through the list and return.  Updates the value in @skip_cnt upon
 * return.  Returns zero on success, negative values on failure.
 *
 */
int cipso_v4_doi_walk(u32 *skip_cnt,
                     int (*callback) (struct cipso_v4_doi *doi_def, void *arg),
                     void *cb_arg)
{
        int ret_val = -ENOENT;
        u32 doi_cnt = 0;
        struct cipso_v4_doi *iter_doi;

        rcu_read_lock();
        list_for_each_entry_rcu(iter_doi, &cipso_v4_doi_list, list)
                if (iter_doi->valid) {
                        if (doi_cnt++ < *skip_cnt)
                                continue;
                        ret_val = callback(iter_doi, cb_arg);
                        if (ret_val < 0) {
                                doi_cnt--;
                                goto doi_walk_return;
                        }
                }

doi_walk_return:
        rcu_read_unlock();
        *skip_cnt = doi_cnt;
        return ret_val;
}

/**
 * cipso_v4_doi_domhsh_add - Adds a domain entry to a DOI definition
 * @doi_def: the DOI definition
 * @domain: the domain to add
 *
 * Description:
 * Adds the @domain to the the DOI specified by @doi_def, this function
 * should only be called by external functions (i.e. NetLabel).  This function
 * does allocate memory.  Returns zero on success, negative values on failure.
 *
 */
int cipso_v4_doi_domhsh_add(struct cipso_v4_doi *doi_def, const char *domain)
{
        struct cipso_v4_domhsh_entry *iter;
        struct cipso_v4_domhsh_entry *new_dom;

        new_dom = kzalloc(sizeof(*new_dom), GFP_KERNEL);
        if (new_dom == NULL)
                return -ENOMEM;
        if (domain) {
                new_dom->domain = kstrdup(domain, GFP_KERNEL);
                if (new_dom->domain == NULL) {
                        kfree(new_dom);
                        return -ENOMEM;
                }
        }
        new_dom->valid = 1;
        INIT_RCU_HEAD(&new_dom->rcu);

        rcu_read_lock();
        spin_lock(&cipso_v4_doi_list_lock);
        list_for_each_entry_rcu(iter, &doi_def->dom_list, list)
                if (iter->valid &&
                    ((domain != NULL && iter->domain != NULL &&
                      strcmp(iter->domain, domain) == 0) ||
                     (domain == NULL && iter->domain == NULL))) {
                        spin_unlock(&cipso_v4_doi_list_lock);
                        rcu_read_unlock();
                        kfree(new_dom->domain);
                        kfree(new_dom);
                        return -EEXIST;
                }
        list_add_tail_rcu(&new_dom->list, &doi_def->dom_list);
        spin_unlock(&cipso_v4_doi_list_lock);
        rcu_read_unlock();

        return 0;
}

/**
 * cipso_v4_doi_domhsh_remove - Removes a domain entry from a DOI definition
 * @doi_def: the DOI definition
 * @domain: the domain to remove
 *
 * Description:
 * Removes the @domain from the DOI specified by @doi_def, this function
 * should only be called by external functions (i.e. NetLabel).   Returns zero
 * on success and negative values on error.
 *
 */
int cipso_v4_doi_domhsh_remove(struct cipso_v4_doi *doi_def,
                               const char *domain)
{
        struct cipso_v4_domhsh_entry *iter;

        rcu_read_lock();
        spin_lock(&cipso_v4_doi_list_lock);
        list_for_each_entry_rcu(iter, &doi_def->dom_list, list)
                if (iter->valid &&
                    ((domain != NULL && iter->domain != NULL &&
                      strcmp(iter->domain, domain) == 0) ||
                     (domain == NULL && iter->domain == NULL))) {
                        iter->valid = 0;
                        list_del_rcu(&iter->list);
                        spin_unlock(&cipso_v4_doi_list_lock);
                        rcu_read_unlock();
                        call_rcu(&iter->rcu, cipso_v4_doi_domhsh_free);

                        return 0;
                }
        spin_unlock(&cipso_v4_doi_list_lock);
        rcu_read_unlock();

        return -ENOENT;
}

/*
 * Label Mapping Functions
 */

/**
 * cipso_v4_map_lvl_valid - Checks to see if the given level is understood
 * @doi_def: the DOI definition
 * @level: the level to check
 *
 * Description:
 * Checks the given level against the given DOI definition and returns a
 * negative value if the level does not have a valid mapping and a zero value
 * if the level is defined by the DOI.
 *
 */
static int cipso_v4_map_lvl_valid(const struct cipso_v4_doi *doi_def, u8 level)
{
        switch (doi_def->type) {
        case CIPSO_V4_MAP_PASS:
                return 0;
        case CIPSO_V4_MAP_STD:
                if (doi_def->map.std->lvl.cipso[level] < CIPSO_V4_INV_LVL)
                        return 0;
                break;
        }

        return -EFAULT;
}

/**
 * cipso_v4_map_lvl_hton - Perform a level mapping from the host to the network
 * @doi_def: the DOI definition
 * @host_lvl: the host MLS level
 * @net_lvl: the network/CIPSO MLS level
 *
 * Description:
 * Perform a label mapping to translate a local MLS level to the correct
 * CIPSO level using the given DOI definition.  Returns zero on success,
 * negative values otherwise.
 *
 */
static int cipso_v4_map_lvl_hton(const struct cipso_v4_doi *doi_def,
                                 u32 host_lvl,
                                 u32 *net_lvl)
{
        switch (doi_def->type) {
        case CIPSO_V4_MAP_PASS:
                *net_lvl = host_lvl;
                return 0;
        case CIPSO_V4_MAP_STD:
                if (host_lvl < doi_def->map.std->lvl.local_size) {
                        *net_lvl = doi_def->map.std->lvl.local[host_lvl];
                        return 0;
                }
                break;
        }

        return -EINVAL;
}

/**
 * cipso_v4_map_lvl_ntoh - Perform a level mapping from the network to the host
 * @doi_def: the DOI definition
 * @net_lvl: the network/CIPSO MLS level
 * @host_lvl: the host MLS level
 *
 * Description:
 * Perform a label mapping to translate a CIPSO level to the correct local MLS
 * level using the given DOI definition.  Returns zero on success, negative
 * values otherwise.
 *
 */
static int cipso_v4_map_lvl_ntoh(const struct cipso_v4_doi *doi_def,
                                 u32 net_lvl,
                                 u32 *host_lvl)
{
        struct cipso_v4_std_map_tbl *map_tbl;

        switch (doi_def->type) {
        case CIPSO_V4_MAP_PASS:
                *host_lvl = net_lvl;
                return 0;
        case CIPSO_V4_MAP_STD:
                map_tbl = doi_def->map.std;
                if (net_lvl < map_tbl->lvl.cipso_size &&
                    map_tbl->lvl.cipso[net_lvl] < CIPSO_V4_INV_LVL) {
                        *host_lvl = doi_def->map.std->lvl.cipso[net_lvl];
                        return 0;
                }
                break;
        }

        return -EINVAL;
}

/**
 * cipso_v4_map_cat_rbm_valid - Checks to see if the category bitmap is valid
 * @doi_def: the DOI definition
 * @bitmap: category bitmap
 * @bitmap_len: bitmap length in bytes
 *
 * Description:
 * Checks the given category bitmap against the given DOI definition and
 * returns a negative value if any of the categories in the bitmap do not have
 * a valid mapping and a zero value if all of the categories are valid.
 *
 */
static int cipso_v4_map_cat_rbm_valid(const struct cipso_v4_doi *doi_def,
                                      const unsigned char *bitmap,
                                      u32 bitmap_len)
{
        int cat = -1;
        u32 bitmap_len_bits = bitmap_len * 8;
        u32 cipso_cat_size = doi_def->map.std->cat.cipso_size;
        u32 *cipso_array = doi_def->map.std->cat.cipso;

        switch (doi_def->type) {
        case CIPSO_V4_MAP_PASS:
                return 0;
        case CIPSO_V4_MAP_STD:
                for (;;) {
                        cat = cipso_v4_bitmap_walk(bitmap,
                                                   bitmap_len_bits,
                                                   cat + 1,
                                                   1);
                        if (cat < 0)
                                break;
                        if (cat >= cipso_cat_size ||
                            cipso_array[cat] >= CIPSO_V4_INV_CAT)
                                return -EFAULT;
                }

                if (cat == -1)
                        return 0;
                break;
        }

        return -EFAULT;
}

/**
 * cipso_v4_map_cat_rbm_hton - Perform a category mapping from host to network
 * @doi_def: the DOI definition
 * @host_cat: the category bitmap in host format
 * @host_cat_len: the length of the host's category bitmap in bytes
 * @net_cat: the zero'd out category bitmap in network/CIPSO format
 * @net_cat_len: the length of the CIPSO bitmap in bytes
 *
 * Description:
 * Perform a label mapping to translate a local MLS category bitmap to the
 * correct CIPSO bitmap using the given DOI definition.  Returns the minimum
 * size in bytes of the network bitmap on success, negative values otherwise.
 *
 */
static int cipso_v4_map_cat_rbm_hton(const struct cipso_v4_doi *doi_def,
                                     const unsigned char *host_cat,
                                     u32 host_cat_len,
                                     unsigned char *net_cat,
                                     u32 net_cat_len)
{
        int host_spot = -1;
        u32 net_spot;
        u32 net_spot_max = 0;
        u32 host_clen_bits = host_cat_len * 8;
        u32 net_clen_bits = net_cat_len * 8;
        u32 host_cat_size = doi_def->map.std->cat.local_size;
        u32 *host_cat_array = doi_def->map.std->cat.local;

        switch (doi_def->type) {
        case CIPSO_V4_MAP_PASS:
                net_spot_max = host_cat_len - 1;
                while (net_spot_max > 0 && host_cat[net_spot_max] == 0)
                        net_spot_max--;
                if (net_spot_max > net_cat_len)
                        return -EINVAL;
                memcpy(net_cat, host_cat, net_spot_max);
                return net_spot_max;
        case CIPSO_V4_MAP_STD:
                for (;;) {
                        host_spot = cipso_v4_bitmap_walk(host_cat,
                                                         host_clen_bits,
                                                         host_spot + 1,
                                                         1);
                        if (host_spot < 0)
                                break;
                        if (host_spot >= host_cat_size)
                                return -EPERM;

                        net_spot = host_cat_array[host_spot];
                        if (net_spot >= net_clen_bits)
                                return -ENOSPC;
                        cipso_v4_bitmap_setbit(net_cat, net_spot, 1);

                        if (net_spot > net_spot_max)
                                net_spot_max = net_spot;
                }

                if (host_spot == -2)
                        return -EFAULT;

                if (++net_spot_max % 8)
                        return net_spot_max / 8 + 1;
                return net_spot_max / 8;
        }

        return -EINVAL;
}

/**
 * cipso_v4_map_cat_rbm_ntoh - Perform a category mapping from network to host
 * @doi_def: the DOI definition
 * @net_cat: the category bitmap in network/CIPSO format
 * @net_cat_len: the length of the CIPSO bitmap in bytes
 * @host_cat: the zero'd out category bitmap in host format
 * @host_cat_len: the length of the host's category bitmap in bytes
 *
 * Description:
 * Perform a label mapping to translate a CIPSO bitmap to the correct local
 * MLS category bitmap using the given DOI definition.  Returns the minimum
 * size in bytes of the host bitmap on success, negative values otherwise.
 *
 */
static int cipso_v4_map_cat_rbm_ntoh(const struct cipso_v4_doi *doi_def,
                                     const unsigned char *net_cat,
                                     u32 net_cat_len,
                                     unsigned char *host_cat,
                                     u32 host_cat_len)
{
        u32 host_spot;
        u32 host_spot_max = 0;
        int net_spot = -1;
        u32 net_clen_bits = net_cat_len * 8;
        u32 host_clen_bits = host_cat_len * 8;
        u32 net_cat_size = doi_def->map.std->cat.cipso_size;
        u32 *net_cat_array = doi_def->map.std->cat.cipso;

        switch (doi_def->type) {
        case CIPSO_V4_MAP_PASS:
                if (net_cat_len > host_cat_len)
                        return -EINVAL;
                memcpy(host_cat, net_cat, net_cat_len);
                return net_cat_len;
        case CIPSO_V4_MAP_STD:
                for (;;) {
                        net_spot = cipso_v4_bitmap_walk(net_cat,
                                                        net_clen_bits,
                                                        net_spot + 1,
                                                        1);
                        if (net_spot < 0)
                                break;
                        if (net_spot >= net_cat_size ||
                            net_cat_array[net_spot] >= CIPSO_V4_INV_CAT)
                                return -EPERM;

                        host_spot = net_cat_array[net_spot];
                        if (host_spot >= host_clen_bits)
                                return -ENOSPC;
                        cipso_v4_bitmap_setbit(host_cat, host_spot, 1);

                        if (host_spot > host_spot_max)
                                host_spot_max = host_spot;
                }

                if (net_spot == -2)
                        return -EFAULT;

                if (++host_spot_max % 8)
                        return host_spot_max / 8 + 1;
                return host_spot_max / 8;
        }

        return -EINVAL;
}

/*
 * Protocol Handling Functions
 */

#define CIPSO_V4_HDR_LEN              6

/**
 * cipso_v4_gentag_hdr - Generate a CIPSO option header
 * @doi_def: the DOI definition
 * @len: the total tag length in bytes
 * @buf: the CIPSO option buffer
 *
 * Description:
 * Write a CIPSO header into the beginning of @buffer.  Return zero on success,
 * negative values on failure.
 *
 */
static int cipso_v4_gentag_hdr(const struct cipso_v4_doi *doi_def,
                               u32 len,
                               unsigned char *buf)
{
        if (CIPSO_V4_HDR_LEN + len > 40)
                return -ENOSPC;

        buf[0] = IPOPT_CIPSO;
        buf[1] = CIPSO_V4_HDR_LEN + len;
        *(u32 *)&buf[2] = htonl(doi_def->doi);

        return 0;
}

#define CIPSO_V4_TAG1_CAT_LEN         30

/**
 * cipso_v4_gentag_rbm - Generate a CIPSO restricted bitmap tag (type #1)
 * @doi_def: the DOI definition
 * @secattr: the security attributes
 * @buffer: the option buffer
 * @buffer_len: length of buffer in bytes
 *
 * Description:
 * Generate a CIPSO option using the restricted bitmap tag, tag type #1.  The
 * actual buffer length may be larger than the indicated size due to
 * translation between host and network category bitmaps.  Returns zero on
 * success, negative values on failure.
 *
 */
static int cipso_v4_gentag_rbm(const struct cipso_v4_doi *doi_def,
                               const struct netlbl_lsm_secattr *secattr,
                               unsigned char **buffer,
                               u32 *buffer_len)
{
        int ret_val = -EPERM;
        unsigned char *buf = NULL;
        u32 buf_len;
        u32 level;

        if (secattr->mls_cat) {
                buf = kzalloc(CIPSO_V4_HDR_LEN + 4 + CIPSO_V4_TAG1_CAT_LEN,
                              GFP_ATOMIC);
                if (buf == NULL)
                        return -ENOMEM;

                ret_val = cipso_v4_map_cat_rbm_hton(doi_def,
                                                    secattr->mls_cat,
                                                    secattr->mls_cat_len,
                                                    &buf[CIPSO_V4_HDR_LEN + 4],
                                                    CIPSO_V4_TAG1_CAT_LEN);
                if (ret_val < 0)
                        goto gentag_failure;

                /* This will send packets using the "optimized" format when
                 * possibile as specified in  section 3.4.2.6 of the
                 * CIPSO draft. */
                if (cipso_v4_rbm_optfmt && (ret_val > 0 && ret_val < 10))
                        ret_val = 10;

                buf_len = 4 + ret_val;
        } else {
                buf = kzalloc(CIPSO_V4_HDR_LEN + 4, GFP_ATOMIC);
                if (buf == NULL)
                        return -ENOMEM;
                buf_len = 4;
        }

        ret_val = cipso_v4_map_lvl_hton(doi_def, secattr->mls_lvl, &level);
        if (ret_val != 0)
                goto gentag_failure;

        ret_val = cipso_v4_gentag_hdr(doi_def, buf_len, buf);
        if (ret_val != 0)
                goto gentag_failure;

        buf[CIPSO_V4_HDR_LEN] = 0x01;
        buf[CIPSO_V4_HDR_LEN + 1] = buf_len;
        buf[CIPSO_V4_HDR_LEN + 3] = level;

        *buffer = buf;
        *buffer_len = CIPSO_V4_HDR_LEN + buf_len;

        return 0;

gentag_failure:
        kfree(buf);
        return ret_val;
}

/**
 * cipso_v4_parsetag_rbm - Parse a CIPSO restricted bitmap tag
 * @doi_def: the DOI definition
 * @tag: the CIPSO tag
 * @secattr: the security attributes
 *
 * Description:
 * Parse a CIPSO restricted bitmap tag (tag type #1) and return the security
 * attributes in @secattr.  Return zero on success, negatives values on
 * failure.
 *
 */
static int cipso_v4_parsetag_rbm(const struct cipso_v4_doi *doi_def,
                                 const unsigned char *tag,
                                 struct netlbl_lsm_secattr *secattr)
{
        int ret_val;
        u8 tag_len = tag[1];
        u32 level;

        ret_val = cipso_v4_map_lvl_ntoh(doi_def, tag[3], &level);
        if (ret_val != 0)
                return ret_val;
        secattr->mls_lvl = level;
        secattr->mls_lvl_vld = 1;

        if (tag_len > 4) {
                switch (doi_def->type) {
                case CIPSO_V4_MAP_PASS:
                        secattr->mls_cat_len = tag_len - 4;
                        break;
                case CIPSO_V4_MAP_STD:
                        secattr->mls_cat_len =
                                doi_def->map.std->cat.local_size;
                        break;
                }
                secattr->mls_cat = kzalloc(secattr->mls_cat_len, GFP_ATOMIC);
                if (secattr->mls_cat == NULL)
                        return -ENOMEM;

                ret_val = cipso_v4_map_cat_rbm_ntoh(doi_def,
                                                    &tag[4],
                                                    tag_len - 4,
                                                    secattr->mls_cat,
                                                    secattr->mls_cat_len);
                if (ret_val < 0) {
                        kfree(secattr->mls_cat);
                        return ret_val;
                }
                secattr->mls_cat_len = ret_val;
        }

        return 0;
}

/**
 * cipso_v4_validate - Validate a CIPSO option
 * @option: the start of the option, on error it is set to point to the error
 *
 * Description:
 * This routine is called to validate a CIPSO option, it checks all of the
 * fields to ensure that they are at least valid, see the draft snippet below
 * for details.  If the option is valid then a zero value is returned and
 * the value of @option is unchanged.  If the option is invalid then a
 * non-zero value is returned and @option is adjusted to point to the
 * offending portion of the option.  From the IETF draft ...
 *
 *  "If any field within the CIPSO options, such as the DOI identifier, is not
 *   recognized the IP datagram is discarded and an ICMP 'parameter problem'
 *   (type 12) is generated and returned.  The ICMP code field is set to 'bad
 *   parameter' (code 0) and the pointer is set to the start of the CIPSO field
 *   that is unrecognized."
 *
 */
int cipso_v4_validate(unsigned char **option)
{
        unsigned char *opt = *option;
        unsigned char *tag;
        unsigned char opt_iter;
        unsigned char err_offset = 0;
        u8 opt_len;
        u8 tag_len;
        struct cipso_v4_doi *doi_def = NULL;
        u32 tag_iter;

        /* caller already checks for length values that are too large */
        opt_len = opt[1];
        if (opt_len < 8) {
                err_offset = 1;
                goto validate_return;
        }

        rcu_read_lock();
        doi_def = cipso_v4_doi_getdef(ntohl(*((u32 *)&opt[2])));
        if (doi_def == NULL) {
                err_offset = 2;
                goto validate_return_locked;
        }

        opt_iter = 6;
        tag = opt + opt_iter;
        while (opt_iter < opt_len) {
                for (tag_iter = 0; doi_def->tags[tag_iter] != tag[0];)
                        if (doi_def->tags[tag_iter] == CIPSO_V4_TAG_INVALID ||
                            ++tag_iter == CIPSO_V4_TAG_MAXCNT) {
                                err_offset = opt_iter;
                                goto validate_return_locked;
                        }

                tag_len = tag[1];
                if (tag_len > (opt_len - opt_iter)) {
                        err_offset = opt_iter + 1;
                        goto validate_return_locked;
                }

                switch (tag[0]) {
                case CIPSO_V4_TAG_RBITMAP:
                        if (tag_len < 4) {
                                err_offset = opt_iter + 1;
                                goto validate_return_locked;
                        }

                        /* We are already going to do all the verification
                         * necessary at the socket layer so from our point of
                         * view it is safe to turn these checks off (and less
                         * work), however, the CIPSO draft says we should do
                         * all the CIPSO validations here but it doesn't
                         * really specify _exactly_ what we need to validate
                         * ... so, just make it a sysctl tunable. */
                        if (cipso_v4_rbm_strictvalid) {
                                if (cipso_v4_map_lvl_valid(doi_def,
                                                           tag[3]) < 0) {
                                        err_offset = opt_iter + 3;
                                        goto validate_return_locked;
                                }
                                if (tag_len > 4 &&
                                    cipso_v4_map_cat_rbm_valid(doi_def,
                                                            &tag[4],
                                                            tag_len - 4) < 0) {
                                        err_offset = opt_iter + 4;
                                        goto validate_return_locked;
                                }
                        }
                        break;
                default:
                        err_offset = opt_iter;
                        goto validate_return_locked;
                }

                tag += tag_len;
                opt_iter += tag_len;
        }

validate_return_locked:
        rcu_read_unlock();
validate_return:
        *option = opt + err_offset;
        return err_offset;
}

/**
 * cipso_v4_error - Send the correct reponse for a bad packet
 * @skb: the packet
 * @error: the error code
 * @gateway: CIPSO gateway flag
 *
 * Description:
 * Based on the error code given in @error, send an ICMP error message back to
 * the originating host.  From the IETF draft ...
 *
 *  "If the contents of the CIPSO [option] are valid but the security label is
 *   outside of the configured host or port label range, the datagram is
 *   discarded and an ICMP 'destination unreachable' (type 3) is generated and
 *   returned.  The code field of the ICMP is set to 'communication with
 *   destination network administratively prohibited' (code 9) or to
 *   'communication with destination host administratively prohibited'
 *   (code 10).  The value of the code is dependent on whether the originator
 *   of the ICMP message is acting as a CIPSO host or a CIPSO gateway.  The
 *   recipient of the ICMP message MUST be able to handle either value.  The
 *   same procedure is performed if a CIPSO [option] can not be added to an
 *   IP packet because it is too large to fit in the IP options area."
 *
 *  "If the error is triggered by receipt of an ICMP message, the message is
 *   discarded and no response is permitted (consistent with general ICMP
 *   processing rules)."
 *
 */
void cipso_v4_error(struct sk_buff *skb, int error, u32 gateway)
{
        if (skb->nh.iph->protocol == IPPROTO_ICMP || error != -EACCES)
                return;

        if (gateway)
                icmp_send(skb, ICMP_DEST_UNREACH, ICMP_NET_ANO, 0);
        else
                icmp_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_ANO, 0);
}

/**
 * cipso_v4_socket_setattr - Add a CIPSO option to a socket
 * @sock: the socket
 * @doi_def: the CIPSO DOI to use
 * @secattr: the specific security attributes of the socket
 *
 * Description:
 * Set the CIPSO option on the given socket using the DOI definition and
 * security attributes passed to the function.  This function requires
 * exclusive access to @sock->sk, which means it either needs to be in the
 * process of being created or locked via lock_sock(sock->sk).  Returns zero on
 * success and negative values on failure.
 *
 */
int cipso_v4_socket_setattr(const struct socket *sock,
                            const struct cipso_v4_doi *doi_def,
                            const struct netlbl_lsm_secattr *secattr)
{
        int ret_val = -EPERM;
        u32 iter;
        unsigned char *buf = NULL;
        u32 buf_len = 0;
        u32 opt_len;
        struct ip_options *opt = NULL;
        struct sock *sk;
        struct inet_sock *sk_inet;
        struct inet_connection_sock *sk_conn;

        /* In the case of sock_create_lite(), the sock->sk field is not
         * defined yet but it is not a problem as the only users of these
         * "lite" PF_INET sockets are functions which do an accept() call
         * afterwards so we will label the socket as part of the accept(). */
        sk = sock->sk;
        if (sk == NULL)
                return 0;

        /* XXX - This code assumes only one tag per CIPSO option which isn't
         * really a good assumption to make but since we only support the MAC
         * tags right now it is a safe assumption. */
        iter = 0;
        do {
                switch (doi_def->tags[iter]) {
                case CIPSO_V4_TAG_RBITMAP:
                        ret_val = cipso_v4_gentag_rbm(doi_def,
                                                      secattr,
                                                      &buf,
                                                      &buf_len);
                        break;
                default:
                        ret_val = -EPERM;
                        goto socket_setattr_failure;
                }

                iter++;
        } while (ret_val != 0 &&
                 iter < CIPSO_V4_TAG_MAXCNT &&
                 doi_def->tags[iter] != CIPSO_V4_TAG_INVALID);
        if (ret_val != 0)
                goto socket_setattr_failure;

        /* We can't use ip_options_get() directly because it makes a call to
         * ip_options_get_alloc() which allocates memory with GFP_KERNEL and
         * we can't block here. */
        opt_len = (buf_len + 3) & ~3;
        opt = kzalloc(sizeof(*opt) + opt_len, GFP_ATOMIC);
        if (opt == NULL) {
                ret_val = -ENOMEM;
                goto socket_setattr_failure;
        }
        memcpy(opt->__data, buf, buf_len);
        opt->optlen = opt_len;
        opt->is_data = 1;
        kfree(buf);
        buf = NULL;
        ret_val = ip_options_compile(opt, NULL);
        if (ret_val != 0)
                goto socket_setattr_failure;

        sk_inet = inet_sk(sk);
        if (sk_inet->is_icsk) {
                sk_conn = inet_csk(sk);
                if (sk_inet->opt)
                        sk_conn->icsk_ext_hdr_len -= sk_inet->opt->optlen;
                sk_conn->icsk_ext_hdr_len += opt->optlen;
                sk_conn->icsk_sync_mss(sk, sk_conn->icsk_pmtu_cookie);
        }
        opt = xchg(&sk_inet->opt, opt);
        kfree(opt);

        return 0;

socket_setattr_failure:
        kfree(buf);
        kfree(opt);
        return ret_val;
}

/**
 * cipso_v4_sock_getattr - Get the security attributes from a sock
 * @sk: the sock
 * @secattr: the security attributes
 *
 * Description:
 * Query @sk to see if there is a CIPSO option attached to the sock and if
 * there is return the CIPSO security attributes in @secattr.  This function
 * requires that @sk be locked, or privately held, but it does not do any
 * locking itself.  Returns zero on success and negative values on failure.
 *
 */
int cipso_v4_sock_getattr(struct sock *sk, struct netlbl_lsm_secattr *secattr)
{
        int ret_val = -ENOMSG;
        struct inet_sock *sk_inet;
        unsigned char *cipso_ptr;
        u32 doi;
        struct cipso_v4_doi *doi_def;

        sk_inet = inet_sk(sk);
        if (sk_inet->opt == NULL || sk_inet->opt->cipso == 0)
                return -ENOMSG;
        cipso_ptr = sk_inet->opt->__data + sk_inet->opt->cipso -
                sizeof(struct iphdr);
        ret_val = cipso_v4_cache_check(cipso_ptr, cipso_ptr[1], secattr);
        if (ret_val == 0)
                return ret_val;

        doi = ntohl(*(u32 *)&cipso_ptr[2]);
        rcu_read_lock();
        doi_def = cipso_v4_doi_getdef(doi);
        if (doi_def == NULL) {
                rcu_read_unlock();
                return -ENOMSG;
        }
        switch (cipso_ptr[6]) {
        case CIPSO_V4_TAG_RBITMAP:
                ret_val = cipso_v4_parsetag_rbm(doi_def,
                                                &cipso_ptr[6],
                                                secattr);
                break;
        }
        rcu_read_unlock();

        return ret_val;
}

/**
 * cipso_v4_socket_getattr - Get the security attributes from a socket
 * @sock: the socket
 * @secattr: the security attributes
 *
 * Description:
 * Query @sock to see if there is a CIPSO option attached to the socket and if
 * there is return the CIPSO security attributes in @secattr.  Returns zero on
 * success and negative values on failure.
 *
 */
int cipso_v4_socket_getattr(const struct socket *sock,
                            struct netlbl_lsm_secattr *secattr)
{
        int ret_val;

        lock_sock(sock->sk);
        ret_val = cipso_v4_sock_getattr(sock->sk, secattr);
        release_sock(sock->sk);

        return ret_val;
}

/**
 * cipso_v4_skbuff_getattr - Get the security attributes from the CIPSO option
 * @skb: the packet
 * @secattr: the security attributes
 *
 * Description:
 * Parse the given packet's CIPSO option and return the security attributes.
 * Returns zero on success and negative values on failure.
 *
 */
int cipso_v4_skbuff_getattr(const struct sk_buff *skb,
                            struct netlbl_lsm_secattr *secattr)
{
        int ret_val = -ENOMSG;
        unsigned char *cipso_ptr;
        u32 doi;
        struct cipso_v4_doi *doi_def;

        if (!CIPSO_V4_OPTEXIST(skb))
                return -ENOMSG;
        cipso_ptr = CIPSO_V4_OPTPTR(skb);
        if (cipso_v4_cache_check(cipso_ptr, cipso_ptr[1], secattr) == 0)
                return 0;

        doi = ntohl(*(u32 *)&cipso_ptr[2]);
        rcu_read_lock();
        doi_def = cipso_v4_doi_getdef(doi);
        if (doi_def == NULL)
                goto skbuff_getattr_return;
        switch (cipso_ptr[6]) {
        case CIPSO_V4_TAG_RBITMAP:
                ret_val = cipso_v4_parsetag_rbm(doi_def,
                                                &cipso_ptr[6],
                                                secattr);
                break;
        }

skbuff_getattr_return:
        rcu_read_unlock();
        return ret_val;
}

/*
 * Setup Functions
 */

/**
 * cipso_v4_init - Initialize the CIPSO module
 *
 * Description:
 * Initialize the CIPSO module and prepare it for use.  Returns zero on success
 * and negative values on failure.
 *
 */
static int __init cipso_v4_init(void)
{
        int ret_val;

        ret_val = cipso_v4_cache_init();
        if (ret_val != 0)
                panic("Failed to initialize the CIPSO/IPv4 cache (%d)\n",
                      ret_val);

        return 0;
}

subsys_initcall(cipso_v4_init);