/*
 * Implementation of the kernel access vector cache (AVC).
 *
 * Authors:  Stephen Smalley, <sds@epoch.ncsc.mil>
 *           James Morris <jmorris@redhat.com>
 *
 * Update:   KaiGai, Kohei <kaigai@ak.jp.nec.com>
 *     Replaced the avc_lock spinlock by RCU.
 *
 * Copyright (C) 2003 Red Hat, Inc., James Morris <jmorris@redhat.com>
 *
 *      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/types.h>
#include <linux/stddef.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/dcache.h>
#include <linux/init.h>
#include <linux/skbuff.h>
#include <linux/percpu.h>
#include <net/sock.h>
#include <linux/un.h>
#include <net/af_unix.h>
#include <linux/ip.h>
#include <linux/audit.h>
#include <linux/ipv6.h>
#include <net/ipv6.h>
#include "avc.h"
#include "avc_ss.h"

static const struct av_perm_to_string
{
  u16 tclass;
  u32 value;
  const char *name;
} av_perm_to_string[] = {
#define S_(c, v, s) { c, v, s },
#include "av_perm_to_string.h"
#undef S_
};

#ifdef CONFIG_AUDIT
static const char *class_to_string[] = {
#define S_(s) s,
#include "class_to_string.h"
#undef S_
};
#endif

#define TB_(s) static const char * s [] = {
#define TE_(s) };
#define S_(s) s,
#include "common_perm_to_string.h"
#undef TB_
#undef TE_
#undef S_

static const struct av_inherit
{
    u16 tclass;
    const char **common_pts;
    u32 common_base;
} av_inherit[] = {
#define S_(c, i, b) { c, common_##i##_perm_to_string, b },
#include "av_inherit.h"
#undef S_
};

#define AVC_CACHE_SLOTS                 512
#define AVC_DEF_CACHE_THRESHOLD         512
#define AVC_CACHE_RECLAIM               16

#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
#define avc_cache_stats_incr(field)                             \
do {                                                            \
        per_cpu(avc_cache_stats, get_cpu()).field++;            \
        put_cpu();                                              \
} while (0)
#else
#define avc_cache_stats_incr(field)     do {} while (0)
#endif

struct avc_entry {
        u32                     ssid;
        u32                     tsid;
        u16                     tclass;
        struct av_decision      avd;
        atomic_t                used;   /* used recently */
};

struct avc_node {
        struct avc_entry        ae;
        struct list_head        list;
        struct rcu_head         rhead;
};

struct avc_cache {
        struct list_head        slots[AVC_CACHE_SLOTS];
        spinlock_t              slots_lock[AVC_CACHE_SLOTS]; /* lock for writes */
        atomic_t                lru_hint;       /* LRU hint for reclaim scan */
        atomic_t                active_nodes;
        u32                     latest_notif;   /* latest revocation notification */
};

struct avc_callback_node {
        int (*callback) (u32 event, u32 ssid, u32 tsid,
                         u16 tclass, u32 perms,
                         u32 *out_retained);
        u32 events;
        u32 ssid;
        u32 tsid;
        u16 tclass;
        u32 perms;
        struct avc_callback_node *next;
};

/* Exported via selinufs */
unsigned int avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;

#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
#endif

static struct avc_cache avc_cache;
static struct avc_callback_node *avc_callbacks;
static kmem_cache_t *avc_node_cachep;

static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
{
        return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
}

/**
 * avc_dump_av - Display an access vector in human-readable form.
 * @tclass: target security class
 * @av: access vector
 */
void avc_dump_av(struct audit_buffer *ab, u16 tclass, u32 av)
{
        const char **common_pts = NULL;
        u32 common_base = 0;
        int i, i2, perm;

        if (av == 0) {
                audit_log_format(ab, " null");
                return;
        }

        for (i = 0; i < ARRAY_SIZE(av_inherit); i++) {
                if (av_inherit[i].tclass == tclass) {
                        common_pts = av_inherit[i].common_pts;
                        common_base = av_inherit[i].common_base;
                        break;
                }
        }

        audit_log_format(ab, " {");
        i = 0;
        perm = 1;
        while (perm < common_base) {
                if (perm & av) {
                        audit_log_format(ab, " %s", common_pts[i]);
                        av &= ~perm;
                }
                i++;
                perm <<= 1;
        }

        while (i < sizeof(av) * 8) {
                if (perm & av) {
                        for (i2 = 0; i2 < ARRAY_SIZE(av_perm_to_string); i2++) {
                                if ((av_perm_to_string[i2].tclass == tclass) &&
                                    (av_perm_to_string[i2].value == perm))
                                        break;
                        }
                        if (i2 < ARRAY_SIZE(av_perm_to_string)) {
                                audit_log_format(ab, " %s",
                                                 av_perm_to_string[i2].name);
                                av &= ~perm;
                        }
                }
                i++;
                perm <<= 1;
        }

        if (av)
                audit_log_format(ab, " 0x%x", av);

        audit_log_format(ab, " }");
}

/**
 * avc_dump_query - Display a SID pair and a class in human-readable form.
 * @ssid: source security identifier
 * @tsid: target security identifier
 * @tclass: target security class
 */
void avc_dump_query(struct audit_buffer *ab, u32 ssid, u32 tsid, u16 tclass)
{
        int rc;
        char *scontext;
        u32 scontext_len;

        rc = security_sid_to_context(ssid, &scontext, &scontext_len);
        if (rc)
                audit_log_format(ab, "ssid=%d", ssid);
        else {
                audit_log_format(ab, "scontext=%s", scontext);
                kfree(scontext);
        }

        rc = security_sid_to_context(tsid, &scontext, &scontext_len);
        if (rc)
                audit_log_format(ab, " tsid=%d", tsid);
        else {
                audit_log_format(ab, " tcontext=%s", scontext);
                kfree(scontext);
        }
        audit_log_format(ab, " tclass=%s", class_to_string[tclass]);
}

/**
 * avc_init - Initialize the AVC.
 *
 * Initialize the access vector cache.
 */
void __init avc_init(void)
{
        int i;

        for (i = 0; i < AVC_CACHE_SLOTS; i++) {
                INIT_LIST_HEAD(&avc_cache.slots[i]);
                spin_lock_init(&avc_cache.slots_lock[i]);
        }
        atomic_set(&avc_cache.active_nodes, 0);
        atomic_set(&avc_cache.lru_hint, 0);

        avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
                                             0, SLAB_PANIC, NULL, NULL);

        audit_log(current->audit_context, "AVC INITIALIZED\n");
}

int avc_get_hash_stats(char *page)
{
        int i, chain_len, max_chain_len, slots_used;
        struct avc_node *node;

        rcu_read_lock();

        slots_used = 0;
        max_chain_len = 0;
        for (i = 0; i < AVC_CACHE_SLOTS; i++) {
                if (!list_empty(&avc_cache.slots[i])) {
                        slots_used++;
                        chain_len = 0;
                        list_for_each_entry_rcu(node, &avc_cache.slots[i], list)
                                chain_len++;
                        if (chain_len > max_chain_len)
                                max_chain_len = chain_len;
                }
        }

        rcu_read_unlock();

        return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
                         "longest chain: %d\n",
                         atomic_read(&avc_cache.active_nodes),
                         slots_used, AVC_CACHE_SLOTS, max_chain_len);
}

static void avc_node_free(struct rcu_head *rhead)
{
        struct avc_node *node = container_of(rhead, struct avc_node, rhead);
        kmem_cache_free(avc_node_cachep, node);
        avc_cache_stats_incr(frees);
}

static void avc_node_delete(struct avc_node *node)
{
        list_del_rcu(&node->list);
        call_rcu(&node->rhead, avc_node_free);
        atomic_dec(&avc_cache.active_nodes);
}

static void avc_node_kill(struct avc_node *node)
{
        kmem_cache_free(avc_node_cachep, node);
        avc_cache_stats_incr(frees);
        atomic_dec(&avc_cache.active_nodes);
}

static void avc_node_replace(struct avc_node *new, struct avc_node *old)
{
        list_replace_rcu(&old->list, &new->list);
        call_rcu(&old->rhead, avc_node_free);
        atomic_dec(&avc_cache.active_nodes);
}

static inline int avc_reclaim_node(void)
{
        struct avc_node *node;
        int hvalue, try, ecx;
        unsigned long flags;

        for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++ ) {
                hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);

                if (!spin_trylock_irqsave(&avc_cache.slots_lock[hvalue], flags))
                        continue;

                list_for_each_entry(node, &avc_cache.slots[hvalue], list) {
                        if (atomic_dec_and_test(&node->ae.used)) {
                                /* Recently Unused */
                                avc_node_delete(node);
                                avc_cache_stats_incr(reclaims);
                                ecx++;
                                if (ecx >= AVC_CACHE_RECLAIM) {
                                        spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flags);
                                        goto out;
                                }
                        }
                }
                spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flags);
        }
out:
        return ecx;
}

static struct avc_node *avc_alloc_node(void)
{
        struct avc_node *node;

        node = kmem_cache_alloc(avc_node_cachep, SLAB_ATOMIC);
        if (!node)
                goto out;

        memset(node, 0, sizeof(*node));
        INIT_RCU_HEAD(&node->rhead);
        INIT_LIST_HEAD(&node->list);
        atomic_set(&node->ae.used, 1);
        avc_cache_stats_incr(allocations);

        if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
                avc_reclaim_node();

out:
        return node;
}

static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct avc_entry *ae)
{
        node->ae.ssid = ssid;
        node->ae.tsid = tsid;
        node->ae.tclass = tclass;
        memcpy(&node->ae.avd, &ae->avd, sizeof(node->ae.avd));
}

static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
{
        struct avc_node *node, *ret = NULL;
        int hvalue;

        hvalue = avc_hash(ssid, tsid, tclass);
        list_for_each_entry_rcu(node, &avc_cache.slots[hvalue], list) {
                if (ssid == node->ae.ssid &&
                    tclass == node->ae.tclass &&
                    tsid == node->ae.tsid) {
                        ret = node;
                        break;
                }
        }

        if (ret == NULL) {
                /* cache miss */
                goto out;
        }

        /* cache hit */
        if (atomic_read(&ret->ae.used) != 1)
                atomic_set(&ret->ae.used, 1);
out:
        return ret;
}

/**
 * avc_lookup - Look up an AVC entry.
 * @ssid: source security identifier
 * @tsid: target security identifier
 * @tclass: target security class
 * @requested: requested permissions, interpreted based on @tclass
 *
 * Look up an AVC entry that is valid for the
 * @requested permissions between the SID pair
 * (@ssid, @tsid), interpreting the permissions
 * based on @tclass.  If a valid AVC entry exists,
 * then this function return the avc_node.
 * Otherwise, this function returns NULL.
 */
static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass, u32 requested)
{
        struct avc_node *node;

        avc_cache_stats_incr(lookups);
        node = avc_search_node(ssid, tsid, tclass);

        if (node && ((node->ae.avd.decided & requested) == requested)) {
                avc_cache_stats_incr(hits);
                goto out;
        }

        node = NULL;
        avc_cache_stats_incr(misses);
out:
        return node;
}

static int avc_latest_notif_update(int seqno, int is_insert)
{
        int ret = 0;
        static DEFINE_SPINLOCK(notif_lock);
        unsigned long flag;

        spin_lock_irqsave(&notif_lock, flag);
        if (is_insert) {
                if (seqno < avc_cache.latest_notif) {
                        printk(KERN_WARNING "avc:  seqno %d < latest_notif %d\n",
                               seqno, avc_cache.latest_notif);
                        ret = -EAGAIN;
                }
        } else {
                if (seqno > avc_cache.latest_notif)
                        avc_cache.latest_notif = seqno;
        }
        spin_unlock_irqrestore(&notif_lock, flag);

        return ret;
}

/**
 * avc_insert - Insert an AVC entry.
 * @ssid: source security identifier
 * @tsid: target security identifier
 * @tclass: target security class
 * @ae: AVC entry
 *
 * Insert an AVC entry for the SID pair
 * (@ssid, @tsid) and class @tclass.
 * The access vectors and the sequence number are
 * normally provided by the security server in
 * response to a security_compute_av() call.  If the
 * sequence number @ae->avd.seqno is not less than the latest
 * revocation notification, then the function copies
 * the access vectors into a cache entry, returns
 * avc_node inserted. Otherwise, this function returns NULL.
 */
static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass, struct avc_entry *ae)
{
        struct avc_node *pos, *node = NULL;
        int hvalue;
        unsigned long flag;

        if (avc_latest_notif_update(ae->avd.seqno, 1))
                goto out;

        node = avc_alloc_node();
        if (node) {
                hvalue = avc_hash(ssid, tsid, tclass);
                avc_node_populate(node, ssid, tsid, tclass, ae);

                spin_lock_irqsave(&avc_cache.slots_lock[hvalue], flag);
                list_for_each_entry(pos, &avc_cache.slots[hvalue], list) {
                        if (pos->ae.ssid == ssid &&
                            pos->ae.tsid == tsid &&
                            pos->ae.tclass == tclass) {
                                avc_node_replace(node, pos);
                                goto found;
                        }
                }
                list_add_rcu(&node->list, &avc_cache.slots[hvalue]);
found:
                spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flag);
        }
out:
        return node;
}

static inline void avc_print_ipv6_addr(struct audit_buffer *ab,
                                       struct in6_addr *addr, u16 port,
                                       char *name1, char *name2)
{
        if (!ipv6_addr_any(addr))
                audit_log_format(ab, " %s=%04x:%04x:%04x:%04x:%04x:"
                                 "%04x:%04x:%04x", name1, NIP6(*addr));
        if (port)
                audit_log_format(ab, " %s=%d", name2, ntohs(port));
}

static inline void avc_print_ipv4_addr(struct audit_buffer *ab, u32 addr,
                                       u16 port, char *name1, char *name2)
{
        if (addr)
                audit_log_format(ab, " %s=%d.%d.%d.%d", name1, NIPQUAD(addr));
        if (port)
                audit_log_format(ab, " %s=%d", name2, ntohs(port));
}

/**
 * avc_audit - Audit the granting or denial of permissions.
 * @ssid: source security identifier
 * @tsid: target security identifier
 * @tclass: target security class
 * @requested: requested permissions
 * @avd: access vector decisions
 * @result: result from avc_has_perm_noaudit
 * @a:  auxiliary audit data
 *
 * Audit the granting or denial of permissions in accordance
 * with the policy.  This function is typically called by
 * avc_has_perm() after a permission check, but can also be
 * called directly by callers who use avc_has_perm_noaudit()
 * in order to separate the permission check from the auditing.
 * For example, this separation is useful when the permission check must
 * be performed under a lock, to allow the lock to be released
 * before calling the auditing code.
 */
void avc_audit(u32 ssid, u32 tsid,
               u16 tclass, u32 requested,
               struct av_decision *avd, int result, struct avc_audit_data *a)
{
        struct task_struct *tsk = current;
        struct inode *inode = NULL;
        u32 denied, audited;
        struct audit_buffer *ab;

        denied = requested & ~avd->allowed;
        if (denied) {
                audited = denied;
                if (!(audited & avd->auditdeny))
                        return;
        } else if (result) {
                audited = denied = requested;
        } else {
                audited = requested;
                if (!(audited & avd->auditallow))
                        return;
        }

        ab = audit_log_start(current->audit_context);
        if (!ab)
                return;         /* audit_panic has been called */
        audit_log_format(ab, "avc:  %s ", denied ? "denied" : "granted");
        avc_dump_av(ab, tclass,audited);
        audit_log_format(ab, " for ");
        if (a && a->tsk)
                tsk = a->tsk;
        if (tsk && tsk->pid) {
                struct mm_struct *mm;
                struct vm_area_struct *vma;
                audit_log_format(ab, " pid=%d", tsk->pid);
                if (tsk == current)
                        mm = current->mm;
                else
                        mm = get_task_mm(tsk);
                if (mm) {
                        if (down_read_trylock(&mm->mmap_sem)) {
                                vma = mm->mmap;
                                while (vma) {
                                        if ((vma->vm_flags & VM_EXECUTABLE) &&
                                            vma->vm_file) {
                                                audit_log_d_path(ab, "exe=",
                                                        vma->vm_file->f_dentry,
                                                        vma->vm_file->f_vfsmnt);
                                                break;
                                        }
                                        vma = vma->vm_next;
                                }
                                up_read(&mm->mmap_sem);
                        } else {
                                audit_log_format(ab, " comm=%s", tsk->comm);
                        }
                        if (tsk != current)
                                mmput(mm);
                } else {
                        audit_log_format(ab, " comm=%s", tsk->comm);
                }
        }
        if (a) {
                switch (a->type) {
                case AVC_AUDIT_DATA_IPC:
                        audit_log_format(ab, " key=%d", a->u.ipc_id);
                        break;
                case AVC_AUDIT_DATA_CAP:
                        audit_log_format(ab, " capability=%d", a->u.cap);
                        break;
                case AVC_AUDIT_DATA_FS:
                        if (a->u.fs.dentry) {
                                struct dentry *dentry = a->u.fs.dentry;
                                if (a->u.fs.mnt) {
                                        audit_log_d_path(ab, "path=", dentry,
                                                        a->u.fs.mnt);
                                } else {
                                        audit_log_format(ab, " name=%s",
                                                         dentry->d_name.name);
                                }
                                inode = dentry->d_inode;
                        } else if (a->u.fs.inode) {
                                struct dentry *dentry;
                                inode = a->u.fs.inode;
                                dentry = d_find_alias(inode);
                                if (dentry) {
                                        audit_log_format(ab, " name=%s",
                                                         dentry->d_name.name);
                                        dput(dentry);
                                }
                        }
                        if (inode)
                                audit_log_format(ab, " dev=%s ino=%ld",
                                                 inode->i_sb->s_id,
                                                 inode->i_ino);
                        break;
                case AVC_AUDIT_DATA_NET:
                        if (a->u.net.sk) {
                                struct sock *sk = a->u.net.sk;
                                struct unix_sock *u;
                                int len = 0;
                                char *p = NULL;

                                switch (sk->sk_family) {
                                case AF_INET: {
                                        struct inet_sock *inet = inet_sk(sk);

                                        avc_print_ipv4_addr(ab, inet->rcv_saddr,
                                                            inet->sport,
                                                            "laddr", "lport");
                                        avc_print_ipv4_addr(ab, inet->daddr,
                                                            inet->dport,
                                                            "faddr", "fport");
                                        break;
                                }
                                case AF_INET6: {
                                        struct inet_sock *inet = inet_sk(sk);
                                        struct ipv6_pinfo *inet6 = inet6_sk(sk);

                                        avc_print_ipv6_addr(ab, &inet6->rcv_saddr,
                                                            inet->sport,
                                                            "laddr", "lport");
                                        avc_print_ipv6_addr(ab, &inet6->daddr,
                                                            inet->dport,
                                                            "faddr", "fport");
                                        break;
                                }
                                case AF_UNIX:
                                        u = unix_sk(sk);
                                        if (u->dentry) {
                                                audit_log_d_path(ab, "path=",
                                                        u->dentry, u->mnt);
                                                break;
                                        }
                                        if (!u->addr)
                                                break;
                                        len = u->addr->len-sizeof(short);
                                        p = &u->addr->name->sun_path[0];
                                        if (*p)
                                                audit_log_format(ab,
                                                        "path=%*.*s", len,
                                                        len, p);
                                        else
                                                audit_log_format(ab,
                                                        "path=@%*.*s", len-1,
                                                        len-1, p+1);
                                        break;
                                }
                        }
                        
                        switch (a->u.net.family) {
                        case AF_INET:
                                avc_print_ipv4_addr(ab, a->u.net.v4info.saddr,
                                                    a->u.net.sport,
                                                    "saddr", "src");
                                avc_print_ipv4_addr(ab, a->u.net.v4info.daddr,
                                                    a->u.net.dport,
                                                    "daddr", "dest");
                                break;
                        case AF_INET6:
                                avc_print_ipv6_addr(ab, &a->u.net.v6info.saddr,
                                                    a->u.net.sport,
                                                    "saddr", "src");
                                avc_print_ipv6_addr(ab, &a->u.net.v6info.daddr,
                                                    a->u.net.dport,
                                                    "daddr", "dest");
                                break;
                        }
                        if (a->u.net.netif)
                                audit_log_format(ab, " netif=%s",
                                        a->u.net.netif);
                        break;
                }
        }
        audit_log_format(ab, " ");
        avc_dump_query(ab, ssid, tsid, tclass);
        audit_log_end(ab);
}

/**
 * avc_add_callback - Register a callback for security events.
 * @callback: callback function
 * @events: security events
 * @ssid: source security identifier or %SECSID_WILD
 * @tsid: target security identifier or %SECSID_WILD
 * @tclass: target security class
 * @perms: permissions
 *
 * Register a callback function for events in the set @events
 * related to the SID pair (@ssid, @tsid) and
 * and the permissions @perms, interpreting
 * @perms based on @tclass.  Returns %0 on success or
 * -%ENOMEM if insufficient memory exists to add the callback.
 */
int avc_add_callback(int (*callback)(u32 event, u32 ssid, u32 tsid,
                                     u16 tclass, u32 perms,
                                     u32 *out_retained),
                     u32 events, u32 ssid, u32 tsid,
                     u16 tclass, u32 perms)
{
        struct avc_callback_node *c;
        int rc = 0;

        c = kmalloc(sizeof(*c), GFP_ATOMIC);
        if (!c) {
                rc = -ENOMEM;
                goto out;
        }

        c->callback = callback;
        c->events = events;
        c->ssid = ssid;
        c->tsid = tsid;
        c->perms = perms;
        c->next = avc_callbacks;
        avc_callbacks = c;
out:
        return rc;
}

static inline int avc_sidcmp(u32 x, u32 y)
{
        return (x == y || x == SECSID_WILD || y == SECSID_WILD);
}

/**
 * avc_update_node Update an AVC entry
 * @event : Updating event
 * @perms : Permission mask bits
 * @ssid,@tsid,@tclass : identifier of an AVC entry
 *
 * if a valid AVC entry doesn't exist,this function returns -ENOENT.
 * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
 * otherwise, this function update the AVC entry. The original AVC-entry object
 * will release later by RCU.
 */
static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass)
{
        int hvalue, rc = 0;
        unsigned long flag;
        struct avc_node *pos, *node, *orig = NULL;

        node = avc_alloc_node();
        if (!node) {
                rc = -ENOMEM;
                goto out;
        }

        /* Lock the target slot */
        hvalue = avc_hash(ssid, tsid, tclass);
        spin_lock_irqsave(&avc_cache.slots_lock[hvalue], flag);

        list_for_each_entry(pos, &avc_cache.slots[hvalue], list){
                if ( ssid==pos->ae.ssid &&
                     tsid==pos->ae.tsid &&
                     tclass==pos->ae.tclass ){
                        orig = pos;
                        break;
                }
        }

        if (!orig) {
                rc = -ENOENT;
                avc_node_kill(node);
                goto out_unlock;
        }

        /*
         * Copy and replace original node.
         */

        avc_node_populate(node, ssid, tsid, tclass, &orig->ae);

        switch (event) {
        case AVC_CALLBACK_GRANT:
                node->ae.avd.allowed |= perms;
                break;
        case AVC_CALLBACK_TRY_REVOKE:
        case AVC_CALLBACK_REVOKE:
                node->ae.avd.allowed &= ~perms;
                break;
        case AVC_CALLBACK_AUDITALLOW_ENABLE:
                node->ae.avd.auditallow |= perms;
                break;
        case AVC_CALLBACK_AUDITALLOW_DISABLE:
                node->ae.avd.auditallow &= ~perms;
                break;
        case AVC_CALLBACK_AUDITDENY_ENABLE:
                node->ae.avd.auditdeny |= perms;
                break;
        case AVC_CALLBACK_AUDITDENY_DISABLE:
                node->ae.avd.auditdeny &= ~perms;
                break;
        }
        avc_node_replace(node, orig);
out_unlock:
        spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flag);
out:
        return rc;
}

static int avc_update_cache(u32 event, u32 ssid, u32 tsid,
                            u16 tclass, u32 perms)
{
        struct avc_node *node;
        int i;

        rcu_read_lock();

        if (ssid == SECSID_WILD || tsid == SECSID_WILD) {
                /* apply to all matching nodes */
                for (i = 0; i < AVC_CACHE_SLOTS; i++) {
                        list_for_each_entry_rcu(node, &avc_cache.slots[i], list) {
                                if (avc_sidcmp(ssid, node->ae.ssid) &&
                                    avc_sidcmp(tsid, node->ae.tsid) &&
                                    tclass == node->ae.tclass ) {
                                        avc_update_node(event, perms, node->ae.ssid,
                                                        node->ae.tsid, node->ae.tclass);
                                }
                        }
                }
        } else {
                /* apply to one node */
                avc_update_node(event, perms, ssid, tsid, tclass);
        }

        rcu_read_unlock();

        return 0;
}

static int avc_control(u32 event, u32 ssid, u32 tsid,
                       u16 tclass, u32 perms,
                       u32 seqno, u32 *out_retained)
{
        struct avc_callback_node *c;
        u32 tretained = 0, cretained = 0;
        int rc = 0;

        /*
         * try_revoke only removes permissions from the cache
         * state if they are not retained by the object manager.
         * Hence, try_revoke must wait until after the callbacks have
         * been invoked to update the cache state.
         */
        if (event != AVC_CALLBACK_TRY_REVOKE)
                avc_update_cache(event,ssid,tsid,tclass,perms);

        for (c = avc_callbacks; c; c = c->next)
        {
                if ((c->events & event) &&
                    avc_sidcmp(c->ssid, ssid) &&
                    avc_sidcmp(c->tsid, tsid) &&
                    c->tclass == tclass &&
                    (c->perms & perms)) {
                        cretained = 0;
                        rc = c->callback(event, ssid, tsid, tclass,
                                         (c->perms & perms),
                                         &cretained);
                        if (rc)
                                goto out;
                        tretained |= cretained;
                }
        }

        if (event == AVC_CALLBACK_TRY_REVOKE) {
                /* revoke any unretained permissions */
                perms &= ~tretained;
                avc_update_cache(event,ssid,tsid,tclass,perms);
                *out_retained = tretained;
        }

        avc_latest_notif_update(seqno, 0);

out:
        return rc;
}

/**
 * avc_ss_grant - Grant previously denied permissions.
 * @ssid: source security identifier or %SECSID_WILD
 * @tsid: target security identifier or %SECSID_WILD
 * @tclass: target security class
 * @perms: permissions to grant
 * @seqno: policy sequence number
 */
int avc_ss_grant(u32 ssid, u32 tsid, u16 tclass,
                 u32 perms, u32 seqno)
{
        return avc_control(AVC_CALLBACK_GRANT,
                           ssid, tsid, tclass, perms, seqno, NULL);
}

/**
 * avc_ss_try_revoke - Try to revoke previously granted permissions.
 * @ssid: source security identifier or %SECSID_WILD
 * @tsid: target security identifier or %SECSID_WILD
 * @tclass: target security class
 * @perms: permissions to grant
 * @seqno: policy sequence number
 * @out_retained: subset of @perms that are retained
 *
 * Try to revoke previously granted permissions, but
 * only if they are not retained as migrated permissions.
 * Return the subset of permissions that are retained via @out_retained.
 */
int avc_ss_try_revoke(u32 ssid, u32 tsid, u16 tclass,
                      u32 perms, u32 seqno, u32 *out_retained)
{
        return avc_control(AVC_CALLBACK_TRY_REVOKE,
                           ssid, tsid, tclass, perms, seqno, out_retained);
}

/**
 * avc_ss_revoke - Revoke previously granted permissions.
 * @ssid: source security identifier or %SECSID_WILD
 * @tsid: target security identifier or %SECSID_WILD
 * @tclass: target security class
 * @perms: permissions to grant
 * @seqno: policy sequence number
 *
 * Revoke previously granted permissions, even if
 * they are retained as migrated permissions.
 */
int avc_ss_revoke(u32 ssid, u32 tsid, u16 tclass,
                  u32 perms, u32 seqno)
{
        return avc_control(AVC_CALLBACK_REVOKE,
                           ssid, tsid, tclass, perms, seqno, NULL);
}

/**
 * avc_ss_reset - Flush the cache and revalidate migrated permissions.
 * @seqno: policy sequence number
 */
int avc_ss_reset(u32 seqno)
{
        struct avc_callback_node *c;
        int i, rc = 0;
        unsigned long flag;
        struct avc_node *node;

        for (i = 0; i < AVC_CACHE_SLOTS; i++) {
                spin_lock_irqsave(&avc_cache.slots_lock[i], flag);
                list_for_each_entry(node, &avc_cache.slots[i], list)
                        avc_node_delete(node);
                spin_unlock_irqrestore(&avc_cache.slots_lock[i], flag);
        }

        for (c = avc_callbacks; c; c = c->next) {
                if (c->events & AVC_CALLBACK_RESET) {
                        rc = c->callback(AVC_CALLBACK_RESET,
                                         0, 0, 0, 0, NULL);
                        if (rc)
                                goto out;
                }
        }

        avc_latest_notif_update(seqno, 0);
out:
        return rc;
}

/**
 * avc_ss_set_auditallow - Enable or disable auditing of granted permissions.
 * @ssid: source security identifier or %SECSID_WILD
 * @tsid: target security identifier or %SECSID_WILD
 * @tclass: target security class
 * @perms: permissions to grant
 * @seqno: policy sequence number
 * @enable: enable flag.

 */
int avc_ss_set_auditallow(u32 ssid, u32 tsid, u16 tclass,
                          u32 perms, u32 seqno, u32 enable)
{
        if (enable)
                return avc_control(AVC_CALLBACK_AUDITALLOW_ENABLE,
                                   ssid, tsid, tclass, perms, seqno, NULL);
        else
                return avc_control(AVC_CALLBACK_AUDITALLOW_DISABLE,
                                   ssid, tsid, tclass, perms, seqno, NULL);
}

/**
 * avc_ss_set_auditdeny - Enable or disable auditing of denied permissions.
 * @ssid: source security identifier or %SECSID_WILD
 * @tsid: target security identifier or %SECSID_WILD
 * @tclass: target security class
 * @perms: permissions to grant
 * @seqno: policy sequence number
 * @enable: enable flag.
 */
int avc_ss_set_auditdeny(u32 ssid, u32 tsid, u16 tclass,
                         u32 perms, u32 seqno, u32 enable)
{
        if (enable)
                return avc_control(AVC_CALLBACK_AUDITDENY_ENABLE,
                                   ssid, tsid, tclass, perms, seqno, NULL);
        else
                return avc_control(AVC_CALLBACK_AUDITDENY_DISABLE,
                                   ssid, tsid, tclass, perms, seqno, NULL);
}

/**
 * avc_has_perm_noaudit - Check permissions but perform no auditing.
 * @ssid: source security identifier
 * @tsid: target security identifier
 * @tclass: target security class
 * @requested: requested permissions, interpreted based on @tclass
 * @avd: access vector decisions
 *
 * Check the AVC to determine whether the @requested permissions are granted
 * for the SID pair (@ssid, @tsid), interpreting the permissions
 * based on @tclass, and call the security server on a cache miss to obtain
 * a new decision and add it to the cache.  Return a copy of the decisions
 * in @avd.  Return %0 if all @requested permissions are granted,
 * -%EACCES if any permissions are denied, or another -errno upon
 * other errors.  This function is typically called by avc_has_perm(),
 * but may also be called directly to separate permission checking from
 * auditing, e.g. in cases where a lock must be held for the check but
 * should be released for the auditing.
 */
int avc_has_perm_noaudit(u32 ssid, u32 tsid,
                         u16 tclass, u32 requested,
                         struct av_decision *avd)
{
        struct avc_node *node;
        struct avc_entry entry, *p_ae;
        int rc = 0;
        u32 denied;

        rcu_read_lock();

        node = avc_lookup(ssid, tsid, tclass, requested);
        if (!node) {
                rcu_read_unlock();
                rc = security_compute_av(ssid,tsid,tclass,requested,&entry.avd);
                if (rc)
                        goto out;
                rcu_read_lock();
                node = avc_insert(ssid,tsid,tclass,&entry);
        }

        p_ae = node ? &node->ae : &entry;

        if (avd)
                memcpy(avd, &p_ae->avd, sizeof(*avd));

        denied = requested & ~(p_ae->avd.allowed);

        if (!requested || denied) {
                if (selinux_enforcing)
                        rc = -EACCES;
                else
                        if (node)
                                avc_update_node(AVC_CALLBACK_GRANT,requested,
                                                ssid,tsid,tclass);
        }

        rcu_read_unlock();
out:
        return rc;
}

/**
 * avc_has_perm - Check permissions and perform any appropriate auditing.
 * @ssid: source security identifier
 * @tsid: target security identifier
 * @tclass: target security class
 * @requested: requested permissions, interpreted based on @tclass
 * @auditdata: auxiliary audit data
 *
 * Check the AVC to determine whether the @requested permissions are granted
 * for the SID pair (@ssid, @tsid), interpreting the permissions
 * based on @tclass, and call the security server on a cache miss to obtain
 * a new decision and add it to the cache.  Audit the granting or denial of
 * permissions in accordance with the policy.  Return %0 if all @requested
 * permissions are granted, -%EACCES if any permissions are denied, or
 * another -errno upon other errors.
 */
int avc_has_perm(u32 ssid, u32 tsid, u16 tclass,
                 u32 requested, struct avc_audit_data *auditdata)
{
        struct av_decision avd;
        int rc;

        rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, &avd);
        avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata);
        return rc;
}