Audit: clean up audit_receive_skb

[safe/jmp/linux-2.6] / kernel / audit.c

/* audit.c -- Auditing support
 * Gateway between the kernel (e.g., selinux) and the user-space audit daemon.
 * System-call specific features have moved to auditsc.c
 *
 * Copyright 2003-2007 Red Hat Inc., Durham, North Carolina.
 * All Rights Reserved.
 *
 * 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
 *
 * Written by Rickard E. (Rik) Faith <faith@redhat.com>
 *
 * Goals: 1) Integrate fully with Security Modules.
 *        2) Minimal run-time overhead:
 *           a) Minimal when syscall auditing is disabled (audit_enable=0).
 *           b) Small when syscall auditing is enabled and no audit record
 *              is generated (defer as much work as possible to record
 *              generation time):
 *              i) context is allocated,
 *              ii) names from getname are stored without a copy, and
 *              iii) inode information stored from path_lookup.
 *        3) Ability to disable syscall auditing at boot time (audit=0).
 *        4) Usable by other parts of the kernel (if audit_log* is called,
 *           then a syscall record will be generated automatically for the
 *           current syscall).
 *        5) Netlink interface to user-space.
 *        6) Support low-overhead kernel-based filtering to minimize the
 *           information that must be passed to user-space.
 *
 * Example user-space utilities: http://people.redhat.com/sgrubb/audit/
 */

#include <linux/init.h>
#include <asm/types.h>
#include <asm/atomic.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/err.h>
#include <linux/kthread.h>

#include <linux/audit.h>

#include <net/sock.h>
#include <net/netlink.h>
#include <linux/skbuff.h>
#include <linux/netlink.h>
#include <linux/inotify.h>
#include <linux/freezer.h>
#include <linux/tty.h>

#include "audit.h"

/* No auditing will take place until audit_initialized == AUDIT_INITIALIZED.
 * (Initialization happens after skb_init is called.) */
#define AUDIT_DISABLED          -1
#define AUDIT_UNINITIALIZED     0
#define AUDIT_INITIALIZED       1
static int      audit_initialized;

#define AUDIT_OFF       0
#define AUDIT_ON        1
#define AUDIT_LOCKED    2
int             audit_enabled;
int             audit_ever_enabled;

/* Default state when kernel boots without any parameters. */
static int      audit_default;

/* If auditing cannot proceed, audit_failure selects what happens. */
static int      audit_failure = AUDIT_FAIL_PRINTK;

/*
 * If audit records are to be written to the netlink socket, audit_pid
 * contains the pid of the auditd process and audit_nlk_pid contains
 * the pid to use to send netlink messages to that process.
 */
int             audit_pid;
static int      audit_nlk_pid;

/* If audit_rate_limit is non-zero, limit the rate of sending audit records
 * to that number per second.  This prevents DoS attacks, but results in
 * audit records being dropped. */
static int      audit_rate_limit;

/* Number of outstanding audit_buffers allowed. */
static int      audit_backlog_limit = 64;
static int      audit_backlog_wait_time = 60 * HZ;
static int      audit_backlog_wait_overflow = 0;

/* The identity of the user shutting down the audit system. */
uid_t           audit_sig_uid = -1;
pid_t           audit_sig_pid = -1;
u32             audit_sig_sid = 0;

/* Records can be lost in several ways:
   0) [suppressed in audit_alloc]
   1) out of memory in audit_log_start [kmalloc of struct audit_buffer]
   2) out of memory in audit_log_move [alloc_skb]
   3) suppressed due to audit_rate_limit
   4) suppressed due to audit_backlog_limit
*/
static atomic_t    audit_lost = ATOMIC_INIT(0);

/* The netlink socket. */
static struct sock *audit_sock;

/* Inotify handle. */
struct inotify_handle *audit_ih;

/* Hash for inode-based rules */
struct list_head audit_inode_hash[AUDIT_INODE_BUCKETS];

/* The audit_freelist is a list of pre-allocated audit buffers (if more
 * than AUDIT_MAXFREE are in use, the audit buffer is freed instead of
 * being placed on the freelist). */
static DEFINE_SPINLOCK(audit_freelist_lock);
static int         audit_freelist_count;
static LIST_HEAD(audit_freelist);

static struct sk_buff_head audit_skb_queue;
/* queue of skbs to send to auditd when/if it comes back */
static struct sk_buff_head audit_skb_hold_queue;
static struct task_struct *kauditd_task;
static DECLARE_WAIT_QUEUE_HEAD(kauditd_wait);
static DECLARE_WAIT_QUEUE_HEAD(audit_backlog_wait);

/* Serialize requests from userspace. */
static DEFINE_MUTEX(audit_cmd_mutex);

/* AUDIT_BUFSIZ is the size of the temporary buffer used for formatting
 * audit records.  Since printk uses a 1024 byte buffer, this buffer
 * should be at least that large. */
#define AUDIT_BUFSIZ 1024

/* AUDIT_MAXFREE is the number of empty audit_buffers we keep on the
 * audit_freelist.  Doing so eliminates many kmalloc/kfree calls. */
#define AUDIT_MAXFREE  (2*NR_CPUS)

/* The audit_buffer is used when formatting an audit record.  The caller
 * locks briefly to get the record off the freelist or to allocate the
 * buffer, and locks briefly to send the buffer to the netlink layer or
 * to place it on a transmit queue.  Multiple audit_buffers can be in
 * use simultaneously. */
struct audit_buffer {
        struct list_head     list;
        struct sk_buff       *skb;      /* formatted skb ready to send */
        struct audit_context *ctx;      /* NULL or associated context */
        gfp_t                gfp_mask;
};

struct audit_reply {
        int pid;
        struct sk_buff *skb;
};

static void audit_set_pid(struct audit_buffer *ab, pid_t pid)
{
        if (ab) {
                struct nlmsghdr *nlh = nlmsg_hdr(ab->skb);
                nlh->nlmsg_pid = pid;
        }
}

void audit_panic(const char *message)
{
        switch (audit_failure)
        {
        case AUDIT_FAIL_SILENT:
                break;
        case AUDIT_FAIL_PRINTK:
                if (printk_ratelimit())
                        printk(KERN_ERR "audit: %s\n", message);
                break;
        case AUDIT_FAIL_PANIC:
                /* test audit_pid since printk is always losey, why bother? */
                if (audit_pid)
                        panic("audit: %s\n", message);
                break;
        }
}

static inline int audit_rate_check(void)
{
        static unsigned long    last_check = 0;
        static int              messages   = 0;
        static DEFINE_SPINLOCK(lock);
        unsigned long           flags;
        unsigned long           now;
        unsigned long           elapsed;
        int                     retval     = 0;

        if (!audit_rate_limit) return 1;

        spin_lock_irqsave(&lock, flags);
        if (++messages < audit_rate_limit) {
                retval = 1;
        } else {
                now     = jiffies;
                elapsed = now - last_check;
                if (elapsed > HZ) {
                        last_check = now;
                        messages   = 0;
                        retval     = 1;
                }
        }
        spin_unlock_irqrestore(&lock, flags);

        return retval;
}

/**
 * audit_log_lost - conditionally log lost audit message event
 * @message: the message stating reason for lost audit message
 *
 * Emit at least 1 message per second, even if audit_rate_check is
 * throttling.
 * Always increment the lost messages counter.
*/
void audit_log_lost(const char *message)
{
        static unsigned long    last_msg = 0;
        static DEFINE_SPINLOCK(lock);
        unsigned long           flags;
        unsigned long           now;
        int                     print;

        atomic_inc(&audit_lost);

        print = (audit_failure == AUDIT_FAIL_PANIC || !audit_rate_limit);

        if (!print) {
                spin_lock_irqsave(&lock, flags);
                now = jiffies;
                if (now - last_msg > HZ) {
                        print = 1;
                        last_msg = now;
                }
                spin_unlock_irqrestore(&lock, flags);
        }

        if (print) {
                if (printk_ratelimit())
                        printk(KERN_WARNING
                                "audit: audit_lost=%d audit_rate_limit=%d "
                                "audit_backlog_limit=%d\n",
                                atomic_read(&audit_lost),
                                audit_rate_limit,
                                audit_backlog_limit);
                audit_panic(message);
        }
}

static int audit_log_config_change(char *function_name, int new, int old,
                                   uid_t loginuid, u32 sessionid, u32 sid,
                                   int allow_changes)
{
        struct audit_buffer *ab;
        int rc = 0;

        ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE);
        audit_log_format(ab, "%s=%d old=%d auid=%u ses=%u", function_name, new,
                         old, loginuid, sessionid);
        if (sid) {
                char *ctx = NULL;
                u32 len;

                rc = security_secid_to_secctx(sid, &ctx, &len);
                if (rc) {
                        audit_log_format(ab, " sid=%u", sid);
                        allow_changes = 0; /* Something weird, deny request */
                } else {
                        audit_log_format(ab, " subj=%s", ctx);
                        security_release_secctx(ctx, len);
                }
        }
        audit_log_format(ab, " res=%d", allow_changes);
        audit_log_end(ab);
        return rc;
}

static int audit_do_config_change(char *function_name, int *to_change,
                                  int new, uid_t loginuid, u32 sessionid,
                                  u32 sid)
{
        int allow_changes, rc = 0, old = *to_change;

        /* check if we are locked */
        if (audit_enabled == AUDIT_LOCKED)
                allow_changes = 0;
        else
                allow_changes = 1;

        if (audit_enabled != AUDIT_OFF) {
                rc = audit_log_config_change(function_name, new, old, loginuid,
                                             sessionid, sid, allow_changes);
                if (rc)
                        allow_changes = 0;
        }

        /* If we are allowed, make the change */
        if (allow_changes == 1)
                *to_change = new;
        /* Not allowed, update reason */
        else if (rc == 0)
                rc = -EPERM;
        return rc;
}

static int audit_set_rate_limit(int limit, uid_t loginuid, u32 sessionid,
                                u32 sid)
{
        return audit_do_config_change("audit_rate_limit", &audit_rate_limit,
                                      limit, loginuid, sessionid, sid);
}

static int audit_set_backlog_limit(int limit, uid_t loginuid, u32 sessionid,
                                   u32 sid)
{
        return audit_do_config_change("audit_backlog_limit", &audit_backlog_limit,
                                      limit, loginuid, sessionid, sid);
}

static int audit_set_enabled(int state, uid_t loginuid, u32 sessionid, u32 sid)
{
        int rc;
        if (state < AUDIT_OFF || state > AUDIT_LOCKED)
                return -EINVAL;

        rc =  audit_do_config_change("audit_enabled", &audit_enabled, state,
                                     loginuid, sessionid, sid);

        if (!rc)
                audit_ever_enabled |= !!state;

        return rc;
}

static int audit_set_failure(int state, uid_t loginuid, u32 sessionid, u32 sid)
{
        if (state != AUDIT_FAIL_SILENT
            && state != AUDIT_FAIL_PRINTK
            && state != AUDIT_FAIL_PANIC)
                return -EINVAL;

        return audit_do_config_change("audit_failure", &audit_failure, state,
                                      loginuid, sessionid, sid);
}

/*
 * Queue skbs to be sent to auditd when/if it comes back.  These skbs should
 * already have been sent via prink/syslog and so if these messages are dropped
 * it is not a huge concern since we already passed the audit_log_lost()
 * notification and stuff.  This is just nice to get audit messages during
 * boot before auditd is running or messages generated while auditd is stopped.
 * This only holds messages is audit_default is set, aka booting with audit=1
 * or building your kernel that way.
 */
static void audit_hold_skb(struct sk_buff *skb)
{
        if (audit_default &&
            skb_queue_len(&audit_skb_hold_queue) < audit_backlog_limit)
                skb_queue_tail(&audit_skb_hold_queue, skb);
        else
                kfree_skb(skb);
}

/*
 * For one reason or another this nlh isn't getting delivered to the userspace
 * audit daemon, just send it to printk.
 */
static void audit_printk_skb(struct sk_buff *skb)
{
        struct nlmsghdr *nlh = nlmsg_hdr(skb);
        char *data = NLMSG_DATA(nlh);

        if (nlh->nlmsg_type != AUDIT_EOE) {
                if (printk_ratelimit())
                        printk(KERN_NOTICE "type=%d %s\n", nlh->nlmsg_type, data);
                else
                        audit_log_lost("printk limit exceeded\n");
        }

        audit_hold_skb(skb);
}

static void kauditd_send_skb(struct sk_buff *skb)
{
        int err;
        /* take a reference in case we can't send it and we want to hold it */
        skb_get(skb);
        err = netlink_unicast(audit_sock, skb, audit_nlk_pid, 0);
        if (err < 0) {
                BUG_ON(err != -ECONNREFUSED); /* Shoudn't happen */
                printk(KERN_ERR "audit: *NO* daemon at audit_pid=%d\n", audit_pid);
                audit_log_lost("auditd dissapeared\n");
                audit_pid = 0;
                /* we might get lucky and get this in the next auditd */
                audit_hold_skb(skb);
        } else
                /* drop the extra reference if sent ok */
                kfree_skb(skb);
}

static int kauditd_thread(void *dummy)
{
        struct sk_buff *skb;

        set_freezable();
        while (!kthread_should_stop()) {
                /*
                 * if auditd just started drain the queue of messages already
                 * sent to syslog/printk.  remember loss here is ok.  we already
                 * called audit_log_lost() if it didn't go out normally.  so the
                 * race between the skb_dequeue and the next check for audit_pid
                 * doesn't matter.
                 *
                 * if you ever find kauditd to be too slow we can get a perf win
                 * by doing our own locking and keeping better track if there
                 * are messages in this queue.  I don't see the need now, but
                 * in 5 years when I want to play with this again I'll see this
                 * note and still have no friggin idea what i'm thinking today.
                 */
                if (audit_default && audit_pid) {
                        skb = skb_dequeue(&audit_skb_hold_queue);
                        if (unlikely(skb)) {
                                while (skb && audit_pid) {
                                        kauditd_send_skb(skb);
                                        skb = skb_dequeue(&audit_skb_hold_queue);
                                }
                        }
                }

                skb = skb_dequeue(&audit_skb_queue);
                wake_up(&audit_backlog_wait);
                if (skb) {
                        if (audit_pid)
                                kauditd_send_skb(skb);
                        else
                                audit_printk_skb(skb);
                } else {
                        DECLARE_WAITQUEUE(wait, current);
                        set_current_state(TASK_INTERRUPTIBLE);
                        add_wait_queue(&kauditd_wait, &wait);

                        if (!skb_queue_len(&audit_skb_queue)) {
                                try_to_freeze();
                                schedule();
                        }

                        __set_current_state(TASK_RUNNING);
                        remove_wait_queue(&kauditd_wait, &wait);
                }
        }
        return 0;
}

static int audit_prepare_user_tty(pid_t pid, uid_t loginuid, u32 sessionid)
{
        struct task_struct *tsk;
        int err;

        read_lock(&tasklist_lock);
        tsk = find_task_by_vpid(pid);
        err = -ESRCH;
        if (!tsk)
                goto out;
        err = 0;

        spin_lock_irq(&tsk->sighand->siglock);
        if (!tsk->signal->audit_tty)
                err = -EPERM;
        spin_unlock_irq(&tsk->sighand->siglock);
        if (err)
                goto out;

        tty_audit_push_task(tsk, loginuid, sessionid);
out:
        read_unlock(&tasklist_lock);
        return err;
}

int audit_send_list(void *_dest)
{
        struct audit_netlink_list *dest = _dest;
        int pid = dest->pid;
        struct sk_buff *skb;

        /* wait for parent to finish and send an ACK */
        mutex_lock(&audit_cmd_mutex);
        mutex_unlock(&audit_cmd_mutex);

        while ((skb = __skb_dequeue(&dest->q)) != NULL)
                netlink_unicast(audit_sock, skb, pid, 0);

        kfree(dest);

        return 0;
}

#ifdef CONFIG_AUDIT_TREE
static int prune_tree_thread(void *unused)
{
        mutex_lock(&audit_cmd_mutex);
        audit_prune_trees();
        mutex_unlock(&audit_cmd_mutex);
        return 0;
}

void audit_schedule_prune(void)
{
        kthread_run(prune_tree_thread, NULL, "audit_prune_tree");
}
#endif

struct sk_buff *audit_make_reply(int pid, int seq, int type, int done,
                                 int multi, void *payload, int size)
{
        struct sk_buff  *skb;
        struct nlmsghdr *nlh;
        void            *data;
        int             flags = multi ? NLM_F_MULTI : 0;
        int             t     = done  ? NLMSG_DONE  : type;

        skb = nlmsg_new(size, GFP_KERNEL);
        if (!skb)
                return NULL;

        nlh     = NLMSG_NEW(skb, pid, seq, t, size, flags);
        data    = NLMSG_DATA(nlh);
        memcpy(data, payload, size);
        return skb;

nlmsg_failure:                  /* Used by NLMSG_NEW */
        if (skb)
                kfree_skb(skb);
        return NULL;
}

static int audit_send_reply_thread(void *arg)
{
        struct audit_reply *reply = (struct audit_reply *)arg;

        mutex_lock(&audit_cmd_mutex);
        mutex_unlock(&audit_cmd_mutex);

        /* Ignore failure. It'll only happen if the sender goes away,
           because our timeout is set to infinite. */
        netlink_unicast(audit_sock, reply->skb, reply->pid, 0);
        kfree(reply);
        return 0;
}
/**
 * audit_send_reply - send an audit reply message via netlink
 * @pid: process id to send reply to
 * @seq: sequence number
 * @type: audit message type
 * @done: done (last) flag
 * @multi: multi-part message flag
 * @payload: payload data
 * @size: payload size
 *
 * Allocates an skb, builds the netlink message, and sends it to the pid.
 * No failure notifications.
 */
void audit_send_reply(int pid, int seq, int type, int done, int multi,
                      void *payload, int size)
{
        struct sk_buff *skb;
        struct task_struct *tsk;
        struct audit_reply *reply = kmalloc(sizeof(struct audit_reply),
                                            GFP_KERNEL);

        if (!reply)
                return;

        skb = audit_make_reply(pid, seq, type, done, multi, payload, size);
        if (!skb)
                goto out;

        reply->pid = pid;
        reply->skb = skb;

        tsk = kthread_run(audit_send_reply_thread, reply, "audit_send_reply");
        if (!IS_ERR(tsk))
                return;
        kfree_skb(skb);
out:
        kfree(reply);
}

/*
 * Check for appropriate CAP_AUDIT_ capabilities on incoming audit
 * control messages.
 */
static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type)
{
        int err = 0;

        switch (msg_type) {
        case AUDIT_GET:
        case AUDIT_LIST:
        case AUDIT_LIST_RULES:
        case AUDIT_SET:
        case AUDIT_ADD:
        case AUDIT_ADD_RULE:
        case AUDIT_DEL:
        case AUDIT_DEL_RULE:
        case AUDIT_SIGNAL_INFO:
        case AUDIT_TTY_GET:
        case AUDIT_TTY_SET:
        case AUDIT_TRIM:
        case AUDIT_MAKE_EQUIV:
                if (security_netlink_recv(skb, CAP_AUDIT_CONTROL))
                        err = -EPERM;
                break;
        case AUDIT_USER:
        case AUDIT_FIRST_USER_MSG ... AUDIT_LAST_USER_MSG:
        case AUDIT_FIRST_USER_MSG2 ... AUDIT_LAST_USER_MSG2:
                if (security_netlink_recv(skb, CAP_AUDIT_WRITE))
                        err = -EPERM;
                break;
        default:  /* bad msg */
                err = -EINVAL;
        }

        return err;
}

static int audit_log_common_recv_msg(struct audit_buffer **ab, u16 msg_type,
                                     u32 pid, u32 uid, uid_t auid, u32 ses,
                                     u32 sid)
{
        int rc = 0;
        char *ctx = NULL;
        u32 len;

        if (!audit_enabled) {
                *ab = NULL;
                return rc;
        }

        *ab = audit_log_start(NULL, GFP_KERNEL, msg_type);
        audit_log_format(*ab, "user pid=%d uid=%u auid=%u ses=%u",
                         pid, uid, auid, ses);
        if (sid) {
                rc = security_secid_to_secctx(sid, &ctx, &len);
                if (rc)
                        audit_log_format(*ab, " ssid=%u", sid);
                else {
                        audit_log_format(*ab, " subj=%s", ctx);
                        security_release_secctx(ctx, len);
                }
        }

        return rc;
}

static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
{
        u32                     uid, pid, seq, sid;
        void                    *data;
        struct audit_status     *status_get, status_set;
        int                     err;
        struct audit_buffer     *ab;
        u16                     msg_type = nlh->nlmsg_type;
        uid_t                   loginuid; /* loginuid of sender */
        u32                     sessionid;
        struct audit_sig_info   *sig_data;
        char                    *ctx = NULL;
        u32                     len;

        err = audit_netlink_ok(skb, msg_type);
        if (err)
                return err;

        /* As soon as there's any sign of userspace auditd,
         * start kauditd to talk to it */
        if (!kauditd_task)
                kauditd_task = kthread_run(kauditd_thread, NULL, "kauditd");
        if (IS_ERR(kauditd_task)) {
                err = PTR_ERR(kauditd_task);
                kauditd_task = NULL;
                return err;
        }

        pid  = NETLINK_CREDS(skb)->pid;
        uid  = NETLINK_CREDS(skb)->uid;
        loginuid = NETLINK_CB(skb).loginuid;
        sessionid = NETLINK_CB(skb).sessionid;
        sid  = NETLINK_CB(skb).sid;
        seq  = nlh->nlmsg_seq;
        data = NLMSG_DATA(nlh);

        switch (msg_type) {
        case AUDIT_GET:
                status_set.enabled       = audit_enabled;
                status_set.failure       = audit_failure;
                status_set.pid           = audit_pid;
                status_set.rate_limit    = audit_rate_limit;
                status_set.backlog_limit = audit_backlog_limit;
                status_set.lost          = atomic_read(&audit_lost);
                status_set.backlog       = skb_queue_len(&audit_skb_queue);
                audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0,
                                 &status_set, sizeof(status_set));
                break;
        case AUDIT_SET:
                if (nlh->nlmsg_len < sizeof(struct audit_status))
                        return -EINVAL;
                status_get   = (struct audit_status *)data;
                if (status_get->mask & AUDIT_STATUS_ENABLED) {
                        err = audit_set_enabled(status_get->enabled,
                                                loginuid, sessionid, sid);
                        if (err < 0)
                                return err;
                }
                if (status_get->mask & AUDIT_STATUS_FAILURE) {
                        err = audit_set_failure(status_get->failure,
                                                loginuid, sessionid, sid);
                        if (err < 0)
                                return err;
                }
                if (status_get->mask & AUDIT_STATUS_PID) {
                        int new_pid = status_get->pid;

                        if (audit_enabled != AUDIT_OFF)
                                audit_log_config_change("audit_pid", new_pid,
                                                        audit_pid, loginuid,
                                                        sessionid, sid, 1);

                        audit_pid = new_pid;
                        audit_nlk_pid = NETLINK_CB(skb).pid;
                }
                if (status_get->mask & AUDIT_STATUS_RATE_LIMIT) {
                        err = audit_set_rate_limit(status_get->rate_limit,
                                                   loginuid, sessionid, sid);
                        if (err < 0)
                                return err;
                }
                if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT)
                        err = audit_set_backlog_limit(status_get->backlog_limit,
                                                      loginuid, sessionid, sid);
                break;
        case AUDIT_USER:
        case AUDIT_FIRST_USER_MSG ... AUDIT_LAST_USER_MSG:
        case AUDIT_FIRST_USER_MSG2 ... AUDIT_LAST_USER_MSG2:
                if (!audit_enabled && msg_type != AUDIT_USER_AVC)
                        return 0;

                err = audit_filter_user(&NETLINK_CB(skb));
                if (err == 1) {
                        err = 0;
                        if (msg_type == AUDIT_USER_TTY) {
                                err = audit_prepare_user_tty(pid, loginuid,
                                                             sessionid);
                                if (err)
                                        break;
                        }
                        audit_log_common_recv_msg(&ab, msg_type, pid, uid,
                                                  loginuid, sessionid, sid);

                        if (msg_type != AUDIT_USER_TTY)
                                audit_log_format(ab, " msg='%.1024s'",
                                                 (char *)data);
                        else {
                                int size;

                                audit_log_format(ab, " msg=");
                                size = nlmsg_len(nlh);
                                if (size > 0 &&
                                    ((unsigned char *)data)[size - 1] == '\0')
                                        size--;
                                audit_log_n_untrustedstring(ab, data, size);
                        }
                        audit_set_pid(ab, pid);
                        audit_log_end(ab);
                }
                break;
        case AUDIT_ADD:
        case AUDIT_DEL:
                if (nlmsg_len(nlh) < sizeof(struct audit_rule))
                        return -EINVAL;
                if (audit_enabled == AUDIT_LOCKED) {
                        audit_log_common_recv_msg(&ab, AUDIT_CONFIG_CHANGE, pid,
                                                  uid, loginuid, sessionid, sid);

                        audit_log_format(ab, " audit_enabled=%d res=0",
                                         audit_enabled);
                        audit_log_end(ab);
                        return -EPERM;
                }
                /* fallthrough */
        case AUDIT_LIST:
                err = audit_receive_filter(msg_type, NETLINK_CB(skb).pid,
                                           uid, seq, data, nlmsg_len(nlh),
                                           loginuid, sessionid, sid);
                break;
        case AUDIT_ADD_RULE:
        case AUDIT_DEL_RULE:
                if (nlmsg_len(nlh) < sizeof(struct audit_rule_data))
                        return -EINVAL;
                if (audit_enabled == AUDIT_LOCKED) {
                        audit_log_common_recv_msg(&ab, AUDIT_CONFIG_CHANGE, pid,
                                                  uid, loginuid, sessionid, sid);

                        audit_log_format(ab, " audit_enabled=%d res=0",
                                         audit_enabled);
                        audit_log_end(ab);
                        return -EPERM;
                }
                /* fallthrough */
        case AUDIT_LIST_RULES:
                err = audit_receive_filter(msg_type, NETLINK_CB(skb).pid,
                                           uid, seq, data, nlmsg_len(nlh),
                                           loginuid, sessionid, sid);
                break;
        case AUDIT_TRIM:
                audit_trim_trees();

                audit_log_common_recv_msg(&ab, AUDIT_CONFIG_CHANGE, pid,
                                          uid, loginuid, sessionid, sid);

                audit_log_format(ab, " op=trim res=1");
                audit_log_end(ab);
                break;
        case AUDIT_MAKE_EQUIV: {
                void *bufp = data;
                u32 sizes[2];
                size_t msglen = nlmsg_len(nlh);
                char *old, *new;

                err = -EINVAL;
                if (msglen < 2 * sizeof(u32))
                        break;
                memcpy(sizes, bufp, 2 * sizeof(u32));
                bufp += 2 * sizeof(u32);
                msglen -= 2 * sizeof(u32);
                old = audit_unpack_string(&bufp, &msglen, sizes[0]);
                if (IS_ERR(old)) {
                        err = PTR_ERR(old);
                        break;
                }
                new = audit_unpack_string(&bufp, &msglen, sizes[1]);
                if (IS_ERR(new)) {
                        err = PTR_ERR(new);
                        kfree(old);
                        break;
                }
                /* OK, here comes... */
                err = audit_tag_tree(old, new);

                audit_log_common_recv_msg(&ab, AUDIT_CONFIG_CHANGE, pid,
                                          uid, loginuid, sessionid, sid);

                audit_log_format(ab, " op=make_equiv old=");
                audit_log_untrustedstring(ab, old);
                audit_log_format(ab, " new=");
                audit_log_untrustedstring(ab, new);
                audit_log_format(ab, " res=%d", !err);
                audit_log_end(ab);
                kfree(old);
                kfree(new);
                break;
        }
        case AUDIT_SIGNAL_INFO:
                err = security_secid_to_secctx(audit_sig_sid, &ctx, &len);
                if (err)
                        return err;
                sig_data = kmalloc(sizeof(*sig_data) + len, GFP_KERNEL);
                if (!sig_data) {
                        security_release_secctx(ctx, len);
                        return -ENOMEM;
                }
                sig_data->uid = audit_sig_uid;
                sig_data->pid = audit_sig_pid;
                memcpy(sig_data->ctx, ctx, len);
                security_release_secctx(ctx, len);
                audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_SIGNAL_INFO,
                                0, 0, sig_data, sizeof(*sig_data) + len);
                kfree(sig_data);
                break;
        case AUDIT_TTY_GET: {
                struct audit_tty_status s;
                struct task_struct *tsk;

                read_lock(&tasklist_lock);
                tsk = find_task_by_vpid(pid);
                if (!tsk)
                        err = -ESRCH;
                else {
                        spin_lock_irq(&tsk->sighand->siglock);
                        s.enabled = tsk->signal->audit_tty != 0;
                        spin_unlock_irq(&tsk->sighand->siglock);
                }
                read_unlock(&tasklist_lock);
                audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_TTY_GET, 0, 0,
                                 &s, sizeof(s));
                break;
        }
        case AUDIT_TTY_SET: {
                struct audit_tty_status *s;
                struct task_struct *tsk;

                if (nlh->nlmsg_len < sizeof(struct audit_tty_status))
                        return -EINVAL;
                s = data;
                if (s->enabled != 0 && s->enabled != 1)
                        return -EINVAL;
                read_lock(&tasklist_lock);
                tsk = find_task_by_vpid(pid);
                if (!tsk)
                        err = -ESRCH;
                else {
                        spin_lock_irq(&tsk->sighand->siglock);
                        tsk->signal->audit_tty = s->enabled != 0;
                        spin_unlock_irq(&tsk->sighand->siglock);
                }
                read_unlock(&tasklist_lock);
                break;
        }
        default:
                err = -EINVAL;
                break;
        }

        return err < 0 ? err : 0;
}

/*
 * Get message from skb.  Each message is processed by audit_receive_msg.
 * Malformed skbs with wrong length are discarded silently.
 */
static void audit_receive_skb(struct sk_buff *skb)
{
        struct nlmsghdr *nlh;
        /*
         * len MUST be signed for NLMSG_NEXT to be able to dec it below 0
         * if the nlmsg_len was not aligned
         */
        int len;
        int err;

        nlh = nlmsg_hdr(skb);
        len = skb->len;

        while (NLMSG_OK(nlh, len)) {
                err = audit_receive_msg(skb, nlh);
                /* if err or if this message says it wants a response */
                if (err || (nlh->nlmsg_flags & NLM_F_ACK))
                        netlink_ack(skb, nlh, err);

                nlh = NLMSG_NEXT(nlh, len);
        }
}

/* Receive messages from netlink socket. */
static void audit_receive(struct sk_buff  *skb)
{
        mutex_lock(&audit_cmd_mutex);
        audit_receive_skb(skb);
        mutex_unlock(&audit_cmd_mutex);
}

#ifdef CONFIG_AUDITSYSCALL
static const struct inotify_operations audit_inotify_ops = {
        .handle_event   = audit_handle_ievent,
        .destroy_watch  = audit_free_parent,
};
#endif

/* Initialize audit support at boot time. */
static int __init audit_init(void)
{
        int i;

        if (audit_initialized == AUDIT_DISABLED)
                return 0;

        printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
               audit_default ? "enabled" : "disabled");
        audit_sock = netlink_kernel_create(&init_net, NETLINK_AUDIT, 0,
                                           audit_receive, NULL, THIS_MODULE);
        if (!audit_sock)
                audit_panic("cannot initialize netlink socket");
        else
                audit_sock->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT;

        skb_queue_head_init(&audit_skb_queue);
        skb_queue_head_init(&audit_skb_hold_queue);
        audit_initialized = AUDIT_INITIALIZED;
        audit_enabled = audit_default;
        audit_ever_enabled |= !!audit_default;

        audit_log(NULL, GFP_KERNEL, AUDIT_KERNEL, "initialized");

#ifdef CONFIG_AUDITSYSCALL
        audit_ih = inotify_init(&audit_inotify_ops);
        if (IS_ERR(audit_ih))
                audit_panic("cannot initialize inotify handle");
#endif

        for (i = 0; i < AUDIT_INODE_BUCKETS; i++)
                INIT_LIST_HEAD(&audit_inode_hash[i]);

        return 0;
}
__initcall(audit_init);

/* Process kernel command-line parameter at boot time.  audit=0 or audit=1. */
static int __init audit_enable(char *str)
{
        audit_default = !!simple_strtol(str, NULL, 0);
        if (!audit_default)
                audit_initialized = AUDIT_DISABLED;

        printk(KERN_INFO "audit: %s", audit_default ? "enabled" : "disabled");

        if (audit_initialized == AUDIT_INITIALIZED) {
                audit_enabled = audit_default;
                audit_ever_enabled |= !!audit_default;
        } else if (audit_initialized == AUDIT_UNINITIALIZED) {
                printk(" (after initialization)");
        } else {
                printk(" (until reboot)");
        }
        printk("\n");

        return 1;
}

__setup("audit=", audit_enable);

static void audit_buffer_free(struct audit_buffer *ab)
{
        unsigned long flags;

        if (!ab)
                return;

        if (ab->skb)
                kfree_skb(ab->skb);

        spin_lock_irqsave(&audit_freelist_lock, flags);
        if (audit_freelist_count > AUDIT_MAXFREE)
                kfree(ab);
        else {
                audit_freelist_count++;
                list_add(&ab->list, &audit_freelist);
        }
        spin_unlock_irqrestore(&audit_freelist_lock, flags);
}

static struct audit_buffer * audit_buffer_alloc(struct audit_context *ctx,
                                                gfp_t gfp_mask, int type)
{
        unsigned long flags;
        struct audit_buffer *ab = NULL;
        struct nlmsghdr *nlh;

        spin_lock_irqsave(&audit_freelist_lock, flags);
        if (!list_empty(&audit_freelist)) {
                ab = list_entry(audit_freelist.next,
                                struct audit_buffer, list);
                list_del(&ab->list);
                --audit_freelist_count;
        }
        spin_unlock_irqrestore(&audit_freelist_lock, flags);

        if (!ab) {
                ab = kmalloc(sizeof(*ab), gfp_mask);
                if (!ab)
                        goto err;
        }

        ab->ctx = ctx;
        ab->gfp_mask = gfp_mask;

        ab->skb = nlmsg_new(AUDIT_BUFSIZ, gfp_mask);
        if (!ab->skb)
                goto nlmsg_failure;

        nlh = NLMSG_NEW(ab->skb, 0, 0, type, 0, 0);

        return ab;

nlmsg_failure:                  /* Used by NLMSG_NEW */
        kfree_skb(ab->skb);
        ab->skb = NULL;
err:
        audit_buffer_free(ab);
        return NULL;
}

/**
 * audit_serial - compute a serial number for the audit record
 *
 * Compute a serial number for the audit record.  Audit records are
 * written to user-space as soon as they are generated, so a complete
 * audit record may be written in several pieces.  The timestamp of the
 * record and this serial number are used by the user-space tools to
 * determine which pieces belong to the same audit record.  The
 * (timestamp,serial) tuple is unique for each syscall and is live from
 * syscall entry to syscall exit.
 *
 * NOTE: Another possibility is to store the formatted records off the
 * audit context (for those records that have a context), and emit them
 * all at syscall exit.  However, this could delay the reporting of
 * significant errors until syscall exit (or never, if the system
 * halts).
 */
unsigned int audit_serial(void)
{
        static DEFINE_SPINLOCK(serial_lock);
        static unsigned int serial = 0;

        unsigned long flags;
        unsigned int ret;

        spin_lock_irqsave(&serial_lock, flags);
        do {
                ret = ++serial;
        } while (unlikely(!ret));
        spin_unlock_irqrestore(&serial_lock, flags);

        return ret;
}

static inline void audit_get_stamp(struct audit_context *ctx,
                                   struct timespec *t, unsigned int *serial)
{
        if (!ctx || !auditsc_get_stamp(ctx, t, serial)) {
                *t = CURRENT_TIME;
                *serial = audit_serial();
        }
}

/* Obtain an audit buffer.  This routine does locking to obtain the
 * audit buffer, but then no locking is required for calls to
 * audit_log_*format.  If the tsk is a task that is currently in a
 * syscall, then the syscall is marked as auditable and an audit record
 * will be written at syscall exit.  If there is no associated task, tsk
 * should be NULL. */

/**
 * audit_log_start - obtain an audit buffer
 * @ctx: audit_context (may be NULL)
 * @gfp_mask: type of allocation
 * @type: audit message type
 *
 * Returns audit_buffer pointer on success or NULL on error.
 *
 * Obtain an audit buffer.  This routine does locking to obtain the
 * audit buffer, but then no locking is required for calls to
 * audit_log_*format.  If the task (ctx) is a task that is currently in a
 * syscall, then the syscall is marked as auditable and an audit record
 * will be written at syscall exit.  If there is no associated task, then
 * task context (ctx) should be NULL.
 */
struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
                                     int type)
{
        struct audit_buffer     *ab     = NULL;
        struct timespec         t;
        unsigned int            uninitialized_var(serial);
        int reserve;
        unsigned long timeout_start = jiffies;

        if (audit_initialized != AUDIT_INITIALIZED)
                return NULL;

        if (unlikely(audit_filter_type(type)))
                return NULL;

        if (gfp_mask & __GFP_WAIT)
                reserve = 0;
        else
                reserve = 5; /* Allow atomic callers to go up to five
                                entries over the normal backlog limit */

        while (audit_backlog_limit
               && skb_queue_len(&audit_skb_queue) > audit_backlog_limit + reserve) {
                if (gfp_mask & __GFP_WAIT && audit_backlog_wait_time
                    && time_before(jiffies, timeout_start + audit_backlog_wait_time)) {

                        /* Wait for auditd to drain the queue a little */
                        DECLARE_WAITQUEUE(wait, current);
                        set_current_state(TASK_INTERRUPTIBLE);
                        add_wait_queue(&audit_backlog_wait, &wait);

                        if (audit_backlog_limit &&
                            skb_queue_len(&audit_skb_queue) > audit_backlog_limit)
                                schedule_timeout(timeout_start + audit_backlog_wait_time - jiffies);

                        __set_current_state(TASK_RUNNING);
                        remove_wait_queue(&audit_backlog_wait, &wait);
                        continue;
                }
                if (audit_rate_check() && printk_ratelimit())
                        printk(KERN_WARNING
                               "audit: audit_backlog=%d > "
                               "audit_backlog_limit=%d\n",
                               skb_queue_len(&audit_skb_queue),
                               audit_backlog_limit);
                audit_log_lost("backlog limit exceeded");
                audit_backlog_wait_time = audit_backlog_wait_overflow;
                wake_up(&audit_backlog_wait);
                return NULL;
        }

        ab = audit_buffer_alloc(ctx, gfp_mask, type);
        if (!ab) {
                audit_log_lost("out of memory in audit_log_start");
                return NULL;
        }

        audit_get_stamp(ab->ctx, &t, &serial);

        audit_log_format(ab, "audit(%lu.%03lu:%u): ",
                         t.tv_sec, t.tv_nsec/1000000, serial);
        return ab;
}

/**
 * audit_expand - expand skb in the audit buffer
 * @ab: audit_buffer
 * @extra: space to add at tail of the skb
 *
 * Returns 0 (no space) on failed expansion, or available space if
 * successful.
 */
static inline int audit_expand(struct audit_buffer *ab, int extra)
{
        struct sk_buff *skb = ab->skb;
        int oldtail = skb_tailroom(skb);
        int ret = pskb_expand_head(skb, 0, extra, ab->gfp_mask);
        int newtail = skb_tailroom(skb);

        if (ret < 0) {
                audit_log_lost("out of memory in audit_expand");
                return 0;
        }

        skb->truesize += newtail - oldtail;
        return newtail;
}

/*
 * Format an audit message into the audit buffer.  If there isn't enough
 * room in the audit buffer, more room will be allocated and vsnprint
 * will be called a second time.  Currently, we assume that a printk
 * can't format message larger than 1024 bytes, so we don't either.
 */
static void audit_log_vformat(struct audit_buffer *ab, const char *fmt,
                              va_list args)
{
        int len, avail;
        struct sk_buff *skb;
        va_list args2;

        if (!ab)
                return;

        BUG_ON(!ab->skb);
        skb = ab->skb;
        avail = skb_tailroom(skb);
        if (avail == 0) {
                avail = audit_expand(ab, AUDIT_BUFSIZ);
                if (!avail)
                        goto out;
        }
        va_copy(args2, args);
        len = vsnprintf(skb_tail_pointer(skb), avail, fmt, args);
        if (len >= avail) {
                /* The printk buffer is 1024 bytes long, so if we get
                 * here and AUDIT_BUFSIZ is at least 1024, then we can
                 * log everything that printk could have logged. */
                avail = audit_expand(ab,
                        max_t(unsigned, AUDIT_BUFSIZ, 1+len-avail));
                if (!avail)
                        goto out;
                len = vsnprintf(skb_tail_pointer(skb), avail, fmt, args2);
        }
        va_end(args2);
        if (len > 0)
                skb_put(skb, len);
out:
        return;
}

/**
 * audit_log_format - format a message into the audit buffer.
 * @ab: audit_buffer
 * @fmt: format string
 * @...: optional parameters matching @fmt string
 *
 * All the work is done in audit_log_vformat.
 */
void audit_log_format(struct audit_buffer *ab, const char *fmt, ...)
{
        va_list args;

        if (!ab)
                return;
        va_start(args, fmt);
        audit_log_vformat(ab, fmt, args);
        va_end(args);
}

/**
 * audit_log_hex - convert a buffer to hex and append it to the audit skb
 * @ab: the audit_buffer
 * @buf: buffer to convert to hex
 * @len: length of @buf to be converted
 *
 * No return value; failure to expand is silently ignored.
 *
 * This function will take the passed buf and convert it into a string of
 * ascii hex digits. The new string is placed onto the skb.
 */
void audit_log_n_hex(struct audit_buffer *ab, const unsigned char *buf,
                size_t len)
{
        int i, avail, new_len;
        unsigned char *ptr;
        struct sk_buff *skb;
        static const unsigned char *hex = "0123456789ABCDEF";

        if (!ab)
                return;

        BUG_ON(!ab->skb);
        skb = ab->skb;
        avail = skb_tailroom(skb);
        new_len = len<<1;
        if (new_len >= avail) {
                /* Round the buffer request up to the next multiple */
                new_len = AUDIT_BUFSIZ*(((new_len-avail)/AUDIT_BUFSIZ) + 1);
                avail = audit_expand(ab, new_len);
                if (!avail)
                        return;
        }

        ptr = skb_tail_pointer(skb);
        for (i=0; i<len; i++) {
                *ptr++ = hex[(buf[i] & 0xF0)>>4]; /* Upper nibble */
                *ptr++ = hex[buf[i] & 0x0F];      /* Lower nibble */
        }
        *ptr = 0;
        skb_put(skb, len << 1); /* new string is twice the old string */
}

/*
 * Format a string of no more than slen characters into the audit buffer,
 * enclosed in quote marks.
 */
void audit_log_n_string(struct audit_buffer *ab, const char *string,
                        size_t slen)
{
        int avail, new_len;
        unsigned char *ptr;
        struct sk_buff *skb;

        if (!ab)
                return;

        BUG_ON(!ab->skb);
        skb = ab->skb;
        avail = skb_tailroom(skb);
        new_len = slen + 3;     /* enclosing quotes + null terminator */
        if (new_len > avail) {
                avail = audit_expand(ab, new_len);
                if (!avail)
                        return;
        }
        ptr = skb_tail_pointer(skb);
        *ptr++ = '"';
        memcpy(ptr, string, slen);
        ptr += slen;
        *ptr++ = '"';
        *ptr = 0;
        skb_put(skb, slen + 2); /* don't include null terminator */
}

/**
 * audit_string_contains_control - does a string need to be logged in hex
 * @string: string to be checked
 * @len: max length of the string to check
 */
int audit_string_contains_control(const char *string, size_t len)
{
        const unsigned char *p;
        for (p = string; p < (const unsigned char *)string + len; p++) {
                if (*p == '"' || *p < 0x21 || *p > 0x7e)
                        return 1;
        }
        return 0;
}

/**
 * audit_log_n_untrustedstring - log a string that may contain random characters
 * @ab: audit_buffer
 * @len: length of string (not including trailing null)
 * @string: string to be logged
 *
 * This code will escape a string that is passed to it if the string
 * contains a control character, unprintable character, double quote mark,
 * or a space. Unescaped strings will start and end with a double quote mark.
 * Strings that are escaped are printed in hex (2 digits per char).
 *
 * The caller specifies the number of characters in the string to log, which may
 * or may not be the entire string.
 */
void audit_log_n_untrustedstring(struct audit_buffer *ab, const char *string,
                                 size_t len)
{
        if (audit_string_contains_control(string, len))
                audit_log_n_hex(ab, string, len);
        else
                audit_log_n_string(ab, string, len);
}

/**
 * audit_log_untrustedstring - log a string that may contain random characters
 * @ab: audit_buffer
 * @string: string to be logged
 *
 * Same as audit_log_n_untrustedstring(), except that strlen is used to
 * determine string length.
 */
void audit_log_untrustedstring(struct audit_buffer *ab, const char *string)
{
        audit_log_n_untrustedstring(ab, string, strlen(string));
}

/* This is a helper-function to print the escaped d_path */
void audit_log_d_path(struct audit_buffer *ab, const char *prefix,
                      struct path *path)
{
        char *p, *pathname;

        if (prefix)
                audit_log_format(ab, " %s", prefix);

        /* We will allow 11 spaces for ' (deleted)' to be appended */
        pathname = kmalloc(PATH_MAX+11, ab->gfp_mask);
        if (!pathname) {
                audit_log_string(ab, "<no_memory>");
                return;
        }
        p = d_path(path, pathname, PATH_MAX+11);
        if (IS_ERR(p)) { /* Should never happen since we send PATH_MAX */
                /* FIXME: can we save some information here? */
                audit_log_string(ab, "<too_long>");
        } else
                audit_log_untrustedstring(ab, p);
        kfree(pathname);
}

/**
 * audit_log_end - end one audit record
 * @ab: the audit_buffer
 *
 * The netlink_* functions cannot be called inside an irq context, so
 * the audit buffer is placed on a queue and a tasklet is scheduled to
 * remove them from the queue outside the irq context.  May be called in
 * any context.
 */
void audit_log_end(struct audit_buffer *ab)
{
        if (!ab)
                return;
        if (!audit_rate_check()) {
                audit_log_lost("rate limit exceeded");
        } else {
                struct nlmsghdr *nlh = nlmsg_hdr(ab->skb);
                nlh->nlmsg_len = ab->skb->len - NLMSG_SPACE(0);

                if (audit_pid) {
                        skb_queue_tail(&audit_skb_queue, ab->skb);
                        wake_up_interruptible(&kauditd_wait);
                } else {
                        audit_printk_skb(ab->skb);
                }
                ab->skb = NULL;
        }
        audit_buffer_free(ab);
}

/**
 * audit_log - Log an audit record
 * @ctx: audit context
 * @gfp_mask: type of allocation
 * @type: audit message type
 * @fmt: format string to use
 * @...: variable parameters matching the format string
 *
 * This is a convenience function that calls audit_log_start,
 * audit_log_vformat, and audit_log_end.  It may be called
 * in any context.
 */
void audit_log(struct audit_context *ctx, gfp_t gfp_mask, int type,
               const char *fmt, ...)
{
        struct audit_buffer *ab;
        va_list args;

        ab = audit_log_start(ctx, gfp_mask, type);
        if (ab) {
                va_start(args, fmt);
                audit_log_vformat(ab, fmt, args);
                va_end(args);
                audit_log_end(ab);
        }
}

EXPORT_SYMBOL(audit_log_start);
EXPORT_SYMBOL(audit_log_end);
EXPORT_SYMBOL(audit_log_format);
EXPORT_SYMBOL(audit_log);