/* 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/

   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/file.h>

  #include <linux/init.h>

  #include <linux/types.h>

  #include <linux/atomic.h>

  #include <linux/mm.h>

  #include <linux/export.h>

  #include <linux/slab.h>

  #include <linux/err.h>
  #include <linux/kthread.h>

  #include <linux/kernel.h>

  #include <linux/syscalls.h>

  
  #include <linux/audit.h>
  
  #include <net/sock.h>

  #include <net/netlink.h>

  #include <linux/skbuff.h>

  #ifdef CONFIG_SECURITY
  #include <linux/security.h>
  #endif

  #include <linux/freezer.h>

  #include <linux/pid_namespace.h>

  #include <net/netns/generic.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

  u32		audit_enabled;
  u32		audit_ever_enabled;

  EXPORT_SYMBOL_GPL(audit_enabled);

  /* Default state when kernel boots without any parameters. */

  static u32	audit_default;

  
  /* If auditing cannot proceed, audit_failure selects what happens. */

  static u32	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_portid contains
   * the portid to use to send netlink messages to that process.

   */

  int		audit_pid;

  static __u32	audit_nlk_portid;

  /* 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 u32	audit_rate_limit;

  /* Number of outstanding audit_buffers allowed.
   * When set to zero, this means unlimited. */

  static u32	audit_backlog_limit = 64;

  #define AUDIT_BACKLOG_WAIT_TIME (60 * HZ)

  static u32	audit_backlog_wait_time_master = AUDIT_BACKLOG_WAIT_TIME;

  static u32	audit_backlog_wait_time = AUDIT_BACKLOG_WAIT_TIME;

  /* The identity of the user shutting down the audit system. */

  kuid_t		audit_sig_uid = INVALID_UID;

  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;

  static int audit_net_id;

  /* 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);

  static struct audit_features af = {.vers = AUDIT_FEATURE_VERSION,
  				   .mask = -1,
  				   .features = 0,
  				   .lock = 0,};

  static char *audit_feature_names[2] = {

  	"only_unset_loginuid",

  	"loginuid_immutable",

  };

  /* Serialize requests from userspace. */

  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 {

  	__u32 portid;

  	struct net *net;

  	struct sk_buff *skb;
  };

  static void audit_set_portid(struct audit_buffer *ab, __u32 portid)

  {

  	if (ab) {
  		struct nlmsghdr *nlh = nlmsg_hdr(ab->skb);

  		nlh->nlmsg_pid = portid;

  	}

  }

  void audit_panic(const char *message)

  {

  	switch (audit_failure) {

  	case AUDIT_FAIL_SILENT:
  		break;
  	case AUDIT_FAIL_PRINTK:

  		if (printk_ratelimit())

  			pr_err("%s
  ", message);

  		break;
  	case AUDIT_FAIL_PANIC:

  		/* test audit_pid since printk is always losey, why bother? */
  		if (audit_pid)
  			panic("audit: %s
  ", 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())

  			pr_warn("audit_lost=%u audit_rate_limit=%u audit_backlog_limit=%u
  ",

  				atomic_read(&audit_lost),
  				audit_rate_limit,
  				audit_backlog_limit);

  		audit_panic(message);
  	}

  }

  static int audit_log_config_change(char *function_name, u32 new, u32 old,

  				   int allow_changes)

  {

  	struct audit_buffer *ab;
  	int rc = 0;

  	ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE);

  	if (unlikely(!ab))
  		return rc;

  	audit_log_format(ab, "%s=%u old=%u", function_name, new, old);

  	audit_log_session_info(ab);

  	rc = audit_log_task_context(ab);
  	if (rc)
  		allow_changes = 0; /* Something weird, deny request */

  	audit_log_format(ab, " res=%d", allow_changes);
  	audit_log_end(ab);

  	return rc;

  }

  static int audit_do_config_change(char *function_name, u32 *to_change, u32 new)

  {

  	int allow_changes, rc = 0;
  	u32 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, 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(u32 limit)

  {

  	return audit_do_config_change("audit_rate_limit", &audit_rate_limit, limit);

  }

  static int audit_set_backlog_limit(u32 limit)

  {

  	return audit_do_config_change("audit_backlog_limit", &audit_backlog_limit, limit);

  }

  static int audit_set_backlog_wait_time(u32 timeout)

  {
  	return audit_do_config_change("audit_backlog_wait_time",

  				      &audit_backlog_wait_time_master, timeout);

  }

  static int audit_set_enabled(u32 state)

  {

  	int rc;

  	if (state > AUDIT_LOCKED)

  		return -EINVAL;

  	rc =  audit_do_config_change("audit_enabled", &audit_enabled, state);

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

  }

  static int audit_set_failure(u32 state)

  {

  	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);

  }

  /*
   * 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 &&

  	    (!audit_backlog_limit ||
  	     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())

  			pr_notice("type=%d %s
  ", nlh->nlmsg_type, data);

  		else

  			audit_log_lost("printk limit exceeded");

  	}
  
  	audit_hold_skb(skb);
  }

  static void kauditd_send_skb(struct sk_buff *skb)
  {
  	int err;

  	int attempts = 0;
  #define AUDITD_RETRIES 5
  
  restart:

  	/* 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_portid, 0);

  	if (err < 0) {

  		pr_err("netlink_unicast sending to audit_pid=%d returned error: %d
  ",
  		       audit_pid, err);

  		if (audit_pid) {

  			if (err == -ECONNREFUSED || err == -EPERM
  			    || ++attempts >= AUDITD_RETRIES) {
  				char s[32];
  
  				snprintf(s, sizeof(s), "audit_pid=%d reset", audit_pid);
  				audit_log_lost(s);
  				audit_pid = 0;
  				audit_sock = NULL;
  			} else {
  				pr_warn("re-scheduling(#%d) write to audit_pid=%d
  ",
  					attempts, audit_pid);
  				set_current_state(TASK_INTERRUPTIBLE);
  				schedule();

  				goto restart;
  			}

  		}

  		/* we might get lucky and get this in the next auditd */
  		audit_hold_skb(skb);
  	} else
  		/* drop the extra reference if sent ok */

  		consume_skb(skb);

  }

  /*

   * kauditd_send_multicast_skb - send the skb to multicast userspace listeners
   *
   * This function doesn't consume an skb as might be expected since it has to
   * copy it anyways.
   */

  static void kauditd_send_multicast_skb(struct sk_buff *skb, gfp_t gfp_mask)

  {
  	struct sk_buff		*copy;
  	struct audit_net	*aunet = net_generic(&init_net, audit_net_id);
  	struct sock		*sock = aunet->nlsk;

  	if (!netlink_has_listeners(sock, AUDIT_NLGRP_READLOG))
  		return;

  	/*
  	 * The seemingly wasteful skb_copy() rather than bumping the refcount
  	 * using skb_get() is necessary because non-standard mods are made to
  	 * the skb by the original kaudit unicast socket send routine.  The
  	 * existing auditd daemon assumes this breakage.  Fixing this would
  	 * require co-ordinating a change in the established protocol between
  	 * the kaudit kernel subsystem and the auditd userspace code.  There is
  	 * no reason for new multicast clients to continue with this
  	 * non-compliance.
  	 */

  	copy = skb_copy(skb, gfp_mask);

  	if (!copy)
  		return;

  	nlmsg_multicast(sock, copy, 0, AUDIT_NLGRP_READLOG, gfp_mask);

  }
  
  /*

   * flush_hold_queue - empty the hold queue if auditd appears
   *
   * 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.
   */
  static void flush_hold_queue(void)

  {
  	struct sk_buff *skb;

  	if (!audit_default || !audit_pid)
  		return;
  
  	skb = skb_dequeue(&audit_skb_hold_queue);
  	if (likely(!skb))
  		return;
  
  	while (skb && audit_pid) {
  		kauditd_send_skb(skb);
  		skb = skb_dequeue(&audit_skb_hold_queue);
  	}
  
  	/*
  	 * if auditd just disappeared but we
  	 * dequeued an skb we need to drop ref
  	 */

  	consume_skb(skb);

  }

  static int kauditd_thread(void *dummy)

  {

  	set_freezable();

  	while (!kthread_should_stop()) {

  		struct sk_buff *skb;

  		flush_hold_queue();

  		skb = skb_dequeue(&audit_skb_queue);

  		if (skb) {

  			if (!audit_backlog_limit ||
  			    (skb_queue_len(&audit_skb_queue) <= audit_backlog_limit))

  				wake_up(&audit_backlog_wait);

  			if (audit_pid)
  				kauditd_send_skb(skb);

  			else
  				audit_printk_skb(skb);

  			continue;
  		}

  		wait_event_freezable(kauditd_wait, skb_queue_len(&audit_skb_queue));

  	}

  	return 0;

  }

  int audit_send_list(void *_dest)
  {
  	struct audit_netlink_list *dest = _dest;

  	struct sk_buff *skb;

  	struct net *net = dest->net;

  	struct audit_net *aunet = net_generic(net, audit_net_id);

  
  	/* 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(aunet->nlsk, skb, dest->portid, 0);

  	put_net(net);

  	kfree(dest);
  
  	return 0;
  }

  struct sk_buff *audit_make_reply(__u32 portid, int seq, int type, int done,

  				 int multi, const 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_put(skb, portid, seq, t, size, flags);

  	if (!nlh)
  		goto out_kfree_skb;
  	data = nlmsg_data(nlh);

  	memcpy(data, payload, size);
  	return skb;

  out_kfree_skb:
  	kfree_skb(skb);

  	return NULL;
  }

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

  	struct net *net = reply->net;

  	struct audit_net *aunet = net_generic(net, audit_net_id);

  
  	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(aunet->nlsk , reply->skb, reply->portid, 0);

  	put_net(net);

  	kfree(reply);
  	return 0;
  }

  /**
   * audit_send_reply - send an audit reply message via netlink

   * @request_skb: skb of request we are replying to (used to target the reply)

   * @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 port id.

   * No failure notifications.
   */

  static void audit_send_reply(struct sk_buff *request_skb, int seq, int type, int done,

  			     int multi, const void *payload, int size)

  {

  	u32 portid = NETLINK_CB(request_skb).portid;
  	struct net *net = sock_net(NETLINK_CB(request_skb).sk);

  	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(portid, seq, type, done, multi, payload, size);

  	if (!skb)

  		goto out;

  	reply->net = get_net(net);

  	reply->portid = portid;

  	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;

  	/* Only support initial user namespace for now. */

  	/*
  	 * We return ECONNREFUSED because it tricks userspace into thinking
  	 * that audit was not configured into the kernel.  Lots of users
  	 * configure their PAM stack (because that's what the distro does)
  	 * to reject login if unable to send messages to audit.  If we return
  	 * ECONNREFUSED the PAM stack thinks the kernel does not have audit
  	 * configured in and will let login proceed.  If we return EPERM
  	 * userspace will reject all logins.  This should be removed when we
  	 * support non init namespaces!!
  	 */

  	if (current_user_ns() != &init_user_ns)

  		return -ECONNREFUSED;

  	switch (msg_type) {

  	case AUDIT_LIST:

  	case AUDIT_ADD:
  	case AUDIT_DEL:

  		return -EOPNOTSUPP;
  	case AUDIT_GET:
  	case AUDIT_SET:

  	case AUDIT_GET_FEATURE:
  	case AUDIT_SET_FEATURE:

  	case AUDIT_LIST_RULES:
  	case AUDIT_ADD_RULE:

  	case AUDIT_DEL_RULE:

  	case AUDIT_SIGNAL_INFO:

  	case AUDIT_TTY_GET:
  	case AUDIT_TTY_SET:

  	case AUDIT_TRIM:
  	case AUDIT_MAKE_EQUIV:

  		/* Only support auditd and auditctl in initial pid namespace
  		 * for now. */

  		if (task_active_pid_ns(current) != &init_pid_ns)

  			return -EPERM;

  		if (!netlink_capable(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 (!netlink_capable(skb, CAP_AUDIT_WRITE))

  			err = -EPERM;
  		break;
  	default:  /* bad msg */
  		err = -EINVAL;
  	}
  
  	return err;
  }

  static void audit_log_common_recv_msg(struct audit_buffer **ab, u16 msg_type)

  {

  	uid_t uid = from_kuid(&init_user_ns, current_uid());

  	pid_t pid = task_tgid_nr(current);

  	if (!audit_enabled && msg_type != AUDIT_USER_AVC) {

  		*ab = NULL;

  		return;

  	}
  
  	*ab = audit_log_start(NULL, GFP_KERNEL, msg_type);

  	if (unlikely(!*ab))

  		return;

  	audit_log_format(*ab, "pid=%d uid=%u", pid, uid);

  	audit_log_session_info(*ab);

  	audit_log_task_context(*ab);

  }

  int is_audit_feature_set(int i)
  {
  	return af.features & AUDIT_FEATURE_TO_MASK(i);
  }
  
  
  static int audit_get_feature(struct sk_buff *skb)
  {
  	u32 seq;
  
  	seq = nlmsg_hdr(skb)->nlmsg_seq;

  	audit_send_reply(skb, seq, AUDIT_GET_FEATURE, 0, 0, &af, sizeof(af));

  
  	return 0;
  }
  
  static void audit_log_feature_change(int which, u32 old_feature, u32 new_feature,
  				     u32 old_lock, u32 new_lock, int res)
  {
  	struct audit_buffer *ab;

  	if (audit_enabled == AUDIT_OFF)
  		return;

  	ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_FEATURE_CHANGE);

  	audit_log_task_info(ab, current);

  	audit_log_format(ab, " feature=%s old=%u new=%u old_lock=%u new_lock=%u res=%d",

  			 audit_feature_names[which], !!old_feature, !!new_feature,
  			 !!old_lock, !!new_lock, res);
  	audit_log_end(ab);
  }
  
  static int audit_set_feature(struct sk_buff *skb)
  {
  	struct audit_features *uaf;
  	int i;

  	BUILD_BUG_ON(AUDIT_LAST_FEATURE + 1 > ARRAY_SIZE(audit_feature_names));

  	uaf = nlmsg_data(nlmsg_hdr(skb));
  
  	/* if there is ever a version 2 we should handle that here */
  
  	for (i = 0; i <= AUDIT_LAST_FEATURE; i++) {
  		u32 feature = AUDIT_FEATURE_TO_MASK(i);
  		u32 old_feature, new_feature, old_lock, new_lock;
  
  		/* if we are not changing this feature, move along */
  		if (!(feature & uaf->mask))
  			continue;
  
  		old_feature = af.features & feature;
  		new_feature = uaf->features & feature;
  		new_lock = (uaf->lock | af.lock) & feature;
  		old_lock = af.lock & feature;
  
  		/* are we changing a locked feature? */

  		if (old_lock && (new_feature != old_feature)) {

  			audit_log_feature_change(i, old_feature, new_feature,
  						 old_lock, new_lock, 0);
  			return -EPERM;
  		}
  	}
  	/* nothing invalid, do the changes */
  	for (i = 0; i <= AUDIT_LAST_FEATURE; i++) {
  		u32 feature = AUDIT_FEATURE_TO_MASK(i);
  		u32 old_feature, new_feature, old_lock, new_lock;
  
  		/* if we are not changing this feature, move along */
  		if (!(feature & uaf->mask))
  			continue;
  
  		old_feature = af.features & feature;
  		new_feature = uaf->features & feature;
  		old_lock = af.lock & feature;
  		new_lock = (uaf->lock | af.lock) & feature;
  
  		if (new_feature != old_feature)
  			audit_log_feature_change(i, old_feature, new_feature,
  						 old_lock, new_lock, 1);
  
  		if (new_feature)
  			af.features |= feature;
  		else
  			af.features &= ~feature;
  		af.lock |= new_lock;
  	}
  
  	return 0;
  }

  static int audit_replace(pid_t pid)
  {
  	struct sk_buff *skb = audit_make_reply(0, 0, AUDIT_REPLACE, 0, 0,
  					       &pid, sizeof(pid));
  
  	if (!skb)
  		return -ENOMEM;
  	return netlink_unicast(audit_sock, skb, audit_nlk_portid, 0);
  }

  static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
  {

  	u32			seq;

  	void			*data;

  	int			err;

  	struct audit_buffer	*ab;

  	u16			msg_type = nlh->nlmsg_type;

  	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;
  		}

  	}

  	seq  = nlh->nlmsg_seq;

  	data = nlmsg_data(nlh);

  
  	switch (msg_type) {

  	case AUDIT_GET: {
  		struct audit_status	s;
  		memset(&s, 0, sizeof(s));
  		s.enabled		= audit_enabled;
  		s.failure		= audit_failure;
  		s.pid			= audit_pid;
  		s.rate_limit		= audit_rate_limit;
  		s.backlog_limit		= audit_backlog_limit;
  		s.lost			= atomic_read(&audit_lost);
  		s.backlog		= skb_queue_len(&audit_skb_queue);

  		s.feature_bitmap	= AUDIT_FEATURE_BITMAP_ALL;

  		s.backlog_wait_time	= audit_backlog_wait_time_master;

  		audit_send_reply(skb, seq, AUDIT_GET, 0, 0, &s, sizeof(s));

  		break;

  	}
  	case AUDIT_SET: {
  		struct audit_status	s;
  		memset(&s, 0, sizeof(s));
  		/* guard against past and future API changes */
  		memcpy(&s, data, min_t(size_t, sizeof(s), nlmsg_len(nlh)));
  		if (s.mask & AUDIT_STATUS_ENABLED) {
  			err = audit_set_enabled(s.enabled);

  			if (err < 0)
  				return err;

  		}

  		if (s.mask & AUDIT_STATUS_FAILURE) {
  			err = audit_set_failure(s.failure);

  			if (err < 0)
  				return err;

  		}

  		if (s.mask & AUDIT_STATUS_PID) {

  			/* NOTE: we are using task_tgid_vnr() below because
  			 *       the s.pid value is relative to the namespace
  			 *       of the caller; at present this doesn't matter
  			 *       much since you can really only run auditd
  			 *       from the initial pid namespace, but something
  			 *       to keep in mind if this changes */

  			int new_pid = s.pid;

  			pid_t requesting_pid = task_tgid_vnr(current);

  			if ((!new_pid) && (requesting_pid != audit_pid)) {
  				audit_log_config_change("audit_pid", new_pid, audit_pid, 0);

  				return -EACCES;

  			}

  			if (audit_pid && new_pid &&

  			    audit_replace(requesting_pid) != -ECONNREFUSED) {
  				audit_log_config_change("audit_pid", new_pid, audit_pid, 0);

  				return -EEXIST;

  			}

  			if (audit_enabled != AUDIT_OFF)

  				audit_log_config_change("audit_pid", new_pid, audit_pid, 1);

  			audit_pid = new_pid;

  			audit_nlk_portid = NETLINK_CB(skb).portid;

  			audit_sock = skb->sk;

  		}

  		if (s.mask & AUDIT_STATUS_RATE_LIMIT) {
  			err = audit_set_rate_limit(s.rate_limit);

  			if (err < 0)
  				return err;
  		}

  		if (s.mask & AUDIT_STATUS_BACKLOG_LIMIT) {

  			err = audit_set_backlog_limit(s.backlog_limit);

  			if (err < 0)
  				return err;
  		}

  		if (s.mask & AUDIT_STATUS_BACKLOG_WAIT_TIME) {
  			if (sizeof(s) > (size_t)nlh->nlmsg_len)
  				return -EINVAL;

  			if (s.backlog_wait_time > 10*AUDIT_BACKLOG_WAIT_TIME)

  				return -EINVAL;
  			err = audit_set_backlog_wait_time(s.backlog_wait_time);
  			if (err < 0)
  				return err;

  		}

  		break;

  	}

  	case AUDIT_GET_FEATURE:
  		err = audit_get_feature(skb);
  		if (err)
  			return err;
  		break;
  	case AUDIT_SET_FEATURE:
  		err = audit_set_feature(skb);
  		if (err)
  			return err;
  		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(msg_type, AUDIT_FILTER_USER);

  		if (err == 1) { /* match or error */

  			err = 0;

  			if (msg_type == AUDIT_USER_TTY) {

  				err = tty_audit_push();

  				if (err)
  					break;
  			}

  			mutex_unlock(&audit_cmd_mutex);

  			audit_log_common_recv_msg(&ab, msg_type);

  			if (msg_type != AUDIT_USER_TTY)

  				audit_log_format(ab, " msg='%.*s'",
  						 AUDIT_MESSAGE_TEXT_MAX,

  						 (char *)data);
  			else {
  				int size;

  				audit_log_format(ab, " data=");

  				size = nlmsg_len(nlh);

  				if (size > 0 &&
  				    ((unsigned char *)data)[size - 1] == '\0')
  					size--;

  				audit_log_n_untrustedstring(ab, data, size);

  			}

  			audit_set_portid(ab, NETLINK_CB(skb).portid);

  			audit_log_end(ab);

  			mutex_lock(&audit_cmd_mutex);

  		}

  		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);
  			audit_log_format(ab, " audit_enabled=%d res=0", audit_enabled);

  			audit_log_end(ab);

  			return -EPERM;
  		}

  		err = audit_rule_change(msg_type, NETLINK_CB(skb).portid,

  					   seq, data, nlmsg_len(nlh));

  		break;

  	case AUDIT_LIST_RULES:

  		err = audit_list_rules_send(skb, seq);

  		break;

  	case AUDIT_TRIM:
  		audit_trim_trees();

  		audit_log_common_recv_msg(&ab, AUDIT_CONFIG_CHANGE);

  		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);

  		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:

  		len = 0;
  		if (audit_sig_sid) {
  			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) {

  			if (audit_sig_sid)
  				security_release_secctx(ctx, len);

  			return -ENOMEM;
  		}

  		sig_data->uid = from_kuid(&init_user_ns, audit_sig_uid);

  		sig_data->pid = audit_sig_pid;

  		if (audit_sig_sid) {
  			memcpy(sig_data->ctx, ctx, len);
  			security_release_secctx(ctx, len);
  		}

  		audit_send_reply(skb, 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;

  		unsigned int t;

  		t = READ_ONCE(current->signal->audit_tty);
  		s.enabled = t & AUDIT_TTY_ENABLE;
  		s.log_passwd = !!(t & AUDIT_TTY_LOG_PASSWD);

  		audit_send_reply(skb, seq, AUDIT_TTY_GET, 0, 0, &s, sizeof(s));

  		break;
  	}
  	case AUDIT_TTY_SET: {

  		struct audit_tty_status s, old;

  		struct audit_buffer	*ab;

  		unsigned int t;

  
  		memset(&s, 0, sizeof(s));
  		/* guard against past and future API changes */
  		memcpy(&s, data, min_t(size_t, sizeof(s), nlmsg_len(nlh)));
  		/* check if new data is valid */
  		if ((s.enabled != 0 && s.enabled != 1) ||
  		    (s.log_passwd != 0 && s.log_passwd != 1))
  			err = -EINVAL;

  		if (err)
  			t = READ_ONCE(current->signal->audit_tty);
  		else {
  			t = s.enabled | (-s.log_passwd & AUDIT_TTY_LOG_PASSWD);
  			t = xchg(&current->signal->audit_tty, t);

  		}

  		old.enabled = t & AUDIT_TTY_ENABLE;
  		old.log_passwd = !!(t & AUDIT_TTY_LOG_PASSWD);

  		audit_log_common_recv_msg(&ab, AUDIT_CONFIG_CHANGE);

  		audit_log_format(ab, " op=tty_set old-enabled=%d new-enabled=%d"
  				 " old-log_passwd=%d new-log_passwd=%d res=%d",
  				 old.enabled, s.enabled, old.log_passwd,
  				 s.log_passwd, !err);

  		audit_log_end(ab);

  		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);

  }

  /* Run custom bind function on netlink socket group connect or bind requests. */

  static int audit_bind(struct net *net, int group)

  {
  	if (!capable(CAP_AUDIT_READ))
  		return -EPERM;
  
  	return 0;
  }

  static int __net_init audit_net_init(struct net *net)

  {

  	struct netlink_kernel_cfg cfg = {
  		.input	= audit_receive,

  		.bind	= audit_bind,

  		.flags	= NL_CFG_F_NONROOT_RECV,
  		.groups	= AUDIT_NLGRP_MAX,

  	};

  	struct audit_net *aunet = net_generic(net, audit_net_id);

  	aunet->nlsk = netlink_kernel_create(net, NETLINK_AUDIT, &cfg);

  	if (aunet->nlsk == NULL) {

  		audit_panic("cannot initialize netlink socket in namespace");

  		return -ENOMEM;
  	}
  	aunet->nlsk->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT;

  	return 0;
  }
  
  static void __net_exit audit_net_exit(struct net *net)
  {
  	struct audit_net *aunet = net_generic(net, audit_net_id);
  	struct sock *sock = aunet->nlsk;
  	if (sock == audit_sock) {
  		audit_pid = 0;
  		audit_sock = NULL;
  	}

  	RCU_INIT_POINTER(aunet->nlsk, NULL);

  	synchronize_net();
  	netlink_kernel_release(sock);
  }

  static struct pernet_operations audit_net_ops __net_initdata = {

  	.init = audit_net_init,
  	.exit = audit_net_exit,
  	.id = &audit_net_id,
  	.size = sizeof(struct audit_net),
  };
  
  /* Initialize audit support at boot time. */
  static int __init audit_init(void)
  {
  	int i;

  	if (audit_initialized == AUDIT_DISABLED)
  		return 0;

  	pr_info("initializing netlink subsys (%s)
  ",
  		audit_default ? "enabled" : "disabled");

  	register_pernet_subsys(&audit_net_ops);

  	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");

  	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;

  	pr_info("%s
  ", audit_default ?

  		"enabled (after initialization)" : "disabled (until reboot)");

  	return 1;

  }

  __setup("audit=", audit_enable);

  /* Process kernel command-line parameter at boot time.
   * audit_backlog_limit=<n> */
  static int __init audit_backlog_limit_set(char *str)
  {

  	u32 audit_backlog_limit_arg;

  	pr_info("audit_backlog_limit: ");

  	if (kstrtouint(str, 0, &audit_backlog_limit_arg)) {
  		pr_cont("using default of %u, unable to parse %s
  ",

  			audit_backlog_limit, str);

  		return 1;
  	}

  
  	audit_backlog_limit = audit_backlog_limit_arg;

  	pr_cont("%d
  ", audit_backlog_limit);

  
  	return 1;
  }
  __setup("audit_backlog_limit=", audit_backlog_limit_set);

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

  	if (!ab)
  		return;

  	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 err;

  	nlh = nlmsg_put(ab->skb, 0, 0, type, 0, 0);
  	if (!nlh)
  		goto out_kfree_skb;

  	return ab;

  out_kfree_skb:

  	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 atomic_t serial = ATOMIC_INIT(0);

  	return atomic_add_return(1, &serial);

  }

  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();
  	}
  }

  /*
   * Wait for auditd to drain the queue a little
   */

  static long wait_for_auditd(long sleep_time)

  {
  	DECLARE_WAITQUEUE(wait, current);

  
  	if (audit_backlog_limit &&

  	    skb_queue_len(&audit_skb_queue) > audit_backlog_limit) {
  		add_wait_queue_exclusive(&audit_backlog_wait, &wait);
  		set_current_state(TASK_UNINTERRUPTIBLE);

  		sleep_time = schedule_timeout(sleep_time);

  		remove_wait_queue(&audit_backlog_wait, &wait);
  	}

  	return sleep_time;

  }

  /**
   * 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 = 5; /* Allow atomic callers to go up to five
  			    entries over the normal backlog limit */

  	unsigned long timeout_start = jiffies;

  	if (audit_initialized != AUDIT_INITIALIZED)

  		return NULL;

  	if (unlikely(!audit_filter(type, AUDIT_FILTER_TYPE)))

  		return NULL;

  	if (gfp_mask & __GFP_DIRECT_RECLAIM) {

  		if (audit_pid && audit_pid == current->tgid)

  			gfp_mask &= ~__GFP_DIRECT_RECLAIM;

  		else
  			reserve = 0;
  	}

  
  	while (audit_backlog_limit
  	       && skb_queue_len(&audit_skb_queue) > audit_backlog_limit + reserve) {

  		if (gfp_mask & __GFP_DIRECT_RECLAIM && audit_backlog_wait_time) {

  			long sleep_time;

  			sleep_time = timeout_start + audit_backlog_wait_time - jiffies;
  			if (sleep_time > 0) {

  				sleep_time = wait_for_auditd(sleep_time);

  				if (sleep_time > 0)

  					continue;

  			}

  		}

  		if (audit_rate_check() && printk_ratelimit())

  			pr_warn("audit_backlog=%d > audit_backlog_limit=%d
  ",
  				skb_queue_len(&audit_skb_queue),
  				audit_backlog_limit);

  		audit_log_lost("backlog limit exceeded");

  		audit_backlog_wait_time = 0;

  		wake_up(&audit_backlog_wait);

  		return NULL;
  	}

  	if (!reserve && !audit_backlog_wait_time)

  		audit_backlog_wait_time = audit_backlog_wait_time_master;

  	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