// SPDX-License-Identifier: GPL-2.0-or-later

  /* 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.
   *

   * 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.
   *

   * Audit userspace, documentation, tests, and bug/issue trackers:
   * 	https://github.com/linux-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/spinlock.h>
  #include <linux/rcupdate.h>
  #include <linux/mutex.h>
  #include <linux/gfp.h>

  #include <linux/pid.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;

  u32		audit_enabled = AUDIT_OFF;

  bool		audit_ever_enabled = !!AUDIT_OFF;

  EXPORT_SYMBOL_GPL(audit_enabled);

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

  static u32	audit_default = AUDIT_OFF;

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

  static u32	audit_failure = AUDIT_FAIL_PRINTK;

  /* private audit network namespace index */
  static unsigned int audit_net_id;
  
  /**
   * struct audit_net - audit private network namespace data
   * @sk: communication socket
   */
  struct audit_net {
  	struct sock *sk;
  };
  
  /**
   * struct auditd_connection - kernel/auditd connection state
   * @pid: auditd PID
   * @portid: netlink portid
   * @net: the associated network namespace

   * @rcu: RCU head

   *
   * Description:
   * This struct is RCU protected; you must either hold the RCU lock for reading

   * or the associated spinlock for writing.

   */

  static struct auditd_connection {

  	struct pid *pid;

  	u32 portid;
  	struct net *net;

  	struct rcu_head rcu;
  } *auditd_conn = NULL;
  static DEFINE_SPINLOCK(auditd_conn_lock);

  /* 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 = 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);

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

  static struct kmem_cache *audit_buffer_cache;

  /* queue msgs to send via kauditd_task */

  static struct sk_buff_head audit_queue;

  /* queue msgs due to temporary unicast send problems */
  static struct sk_buff_head audit_retry_queue;
  /* queue msgs waiting for new auditd connection */

  static struct sk_buff_head audit_hold_queue;

  
  /* queue servicing thread */

  static struct task_struct *kauditd_task;
  static DECLARE_WAIT_QUEUE_HEAD(kauditd_wait);

  
  /* waitqueue for callers who are blocked on the audit backlog */

  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",

  };

  /**
   * struct audit_ctl_mutex - serialize requests from userspace
   * @lock: the mutex used for locking
   * @owner: the task which owns the lock
   *
   * Description:
   * This is the lock struct used to ensure we only process userspace requests
   * in an orderly fashion.  We can't simply use a mutex/lock here because we
   * need to track lock ownership so we don't end up blocking the lock owner in
   * audit_log_start() or similar.
   */
  static struct audit_ctl_mutex {
  	struct mutex lock;
  	void *owner;
  } 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

  /* 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 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;
  };

  /**
   * auditd_test_task - Check to see if a given task is an audit daemon
   * @task: the task to check
   *
   * Description:
   * Return 1 if the task is a registered audit daemon, 0 otherwise.
   */

  int auditd_test_task(struct task_struct *task)

  {
  	int rc;

  	struct auditd_connection *ac;

  
  	rcu_read_lock();

  	ac = rcu_dereference(auditd_conn);
  	rc = (ac && ac->pid == task_tgid(task) ? 1 : 0);

  	rcu_read_unlock();
  
  	return rc;
  }
  
  /**

   * audit_ctl_lock - Take the audit control lock
   */
  void audit_ctl_lock(void)
  {
  	mutex_lock(&audit_cmd_mutex.lock);
  	audit_cmd_mutex.owner = current;
  }
  
  /**
   * audit_ctl_unlock - Drop the audit control lock
   */
  void audit_ctl_unlock(void)
  {
  	audit_cmd_mutex.owner = NULL;
  	mutex_unlock(&audit_cmd_mutex.lock);
  }
  
  /**
   * audit_ctl_owner_current - Test to see if the current task owns the lock
   *
   * Description:
   * Return true if the current task owns the audit control lock, false if it
   * doesn't own the lock.
   */
  static bool audit_ctl_owner_current(void)
  {
  	return (current == audit_cmd_mutex.owner);
  }
  
  /**

   * auditd_pid_vnr - Return the auditd PID relative to the namespace

   *
   * Description:

   * Returns the PID in relation to the namespace, 0 on failure.

   */

  static pid_t auditd_pid_vnr(void)

  {
  	pid_t pid;

  	const struct auditd_connection *ac;

  
  	rcu_read_lock();

  	ac = rcu_dereference(auditd_conn);
  	if (!ac || !ac->pid)

  		pid = 0;
  	else

  		pid = pid_vnr(ac->pid);

  	rcu_read_unlock();
  
  	return pid;
  }
  
  /**

   * audit_get_sk - Return the audit socket for the given network namespace
   * @net: the destination network namespace
   *
   * Description:
   * Returns the sock pointer if valid, NULL otherwise.  The caller must ensure
   * that a reference is held for the network namespace while the sock is in use.
   */
  static struct sock *audit_get_sk(const struct net *net)
  {
  	struct audit_net *aunet;
  
  	if (!net)
  		return NULL;
  
  	aunet = net_generic(net, audit_net_id);
  	return aunet->sk;
  }

  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:

  		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(audit_context(), GFP_KERNEL, AUDIT_CONFIG_CHANGE);

  	if (unlikely(!ab))
  		return rc;

  	audit_log_format(ab, "op=set %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, 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);

  }

  /**

   * auditd_conn_free - RCU helper to release an auditd connection struct
   * @rcu: RCU head
   *
   * Description:
   * Drop any references inside the auditd connection tracking struct and free
   * the memory.
   */

  static void auditd_conn_free(struct rcu_head *rcu)
  {

  	struct auditd_connection *ac;
  
  	ac = container_of(rcu, struct auditd_connection, rcu);
  	put_pid(ac->pid);
  	put_net(ac->net);
  	kfree(ac);

  }

  
  /**

   * auditd_set - Set/Reset the auditd connection state
   * @pid: auditd PID
   * @portid: auditd netlink portid
   * @net: auditd network namespace pointer
   *
   * Description:
   * This function will obtain and drop network namespace references as

   * necessary.  Returns zero on success, negative values on failure.

   */

  static int auditd_set(struct pid *pid, u32 portid, struct net *net)

  {
  	unsigned long flags;

  	struct auditd_connection *ac_old, *ac_new;

  	if (!pid || !net)
  		return -EINVAL;
  
  	ac_new = kzalloc(sizeof(*ac_new), GFP_KERNEL);
  	if (!ac_new)
  		return -ENOMEM;
  	ac_new->pid = get_pid(pid);
  	ac_new->portid = portid;
  	ac_new->net = get_net(net);
  
  	spin_lock_irqsave(&auditd_conn_lock, flags);
  	ac_old = rcu_dereference_protected(auditd_conn,
  					   lockdep_is_held(&auditd_conn_lock));
  	rcu_assign_pointer(auditd_conn, ac_new);
  	spin_unlock_irqrestore(&auditd_conn_lock, flags);
  
  	if (ac_old)
  		call_rcu(&ac_old->rcu, auditd_conn_free);
  
  	return 0;

  }
  
  /**

   * kauditd_print_skb - Print the audit record to the ring buffer
   * @skb: audit record
   *
   * Whatever the reason, this packet may not make it to the auditd connection
   * so write it via printk so the information isn't completely lost.

   */

  static void kauditd_printk_skb(struct sk_buff *skb)

  {
  	struct nlmsghdr *nlh = nlmsg_hdr(skb);

  	char *data = nlmsg_data(nlh);

  	if (nlh->nlmsg_type != AUDIT_EOE && printk_ratelimit())
  		pr_notice("type=%d %s
  ", nlh->nlmsg_type, data);
  }
  
  /**
   * kauditd_rehold_skb - Handle a audit record send failure in the hold queue
   * @skb: audit record
   *
   * Description:
   * This should only be used by the kauditd_thread when it fails to flush the
   * hold queue.
   */
  static void kauditd_rehold_skb(struct sk_buff *skb)
  {
  	/* put the record back in the queue at the same place */
  	skb_queue_head(&audit_hold_queue, skb);

  }
  
  /**
   * kauditd_hold_skb - Queue an audit record, waiting for auditd
   * @skb: audit record
   *
   * Description:
   * Queue the audit record, waiting for an instance of auditd.  When this
   * function is called we haven't given up yet on sending the record, but things
   * are not looking good.  The first thing we want to do is try to write the
   * record via printk and then see if we want to try and hold on to the record
   * and queue it, if we have room.  If we want to hold on to the record, but we
   * don't have room, record a record lost message.
   */
  static void kauditd_hold_skb(struct sk_buff *skb)
  {
  	/* at this point it is uncertain if we will ever send this to auditd so
  	 * try to send the message via printk before we go any further */
  	kauditd_printk_skb(skb);
  
  	/* can we just silently drop the message? */
  	if (!audit_default) {
  		kfree_skb(skb);
  		return;
  	}
  
  	/* if we have room, queue the message */
  	if (!audit_backlog_limit ||
  	    skb_queue_len(&audit_hold_queue) < audit_backlog_limit) {
  		skb_queue_tail(&audit_hold_queue, skb);
  		return;
  	}

  	/* we have no other options - drop the message */
  	audit_log_lost("kauditd hold queue overflow");
  	kfree_skb(skb);

  }

  /**
   * kauditd_retry_skb - Queue an audit record, attempt to send again to auditd
   * @skb: audit record
   *
   * Description:
   * Not as serious as kauditd_hold_skb() as we still have a connected auditd,
   * but for some reason we are having problems sending it audit records so
   * queue the given record and attempt to resend.
   */
  static void kauditd_retry_skb(struct sk_buff *skb)

  {

  	/* NOTE: because records should only live in the retry queue for a
  	 * short period of time, before either being sent or moved to the hold
  	 * queue, we don't currently enforce a limit on this queue */
  	skb_queue_tail(&audit_retry_queue, skb);
  }

  /**

   * auditd_reset - Disconnect the auditd connection

   * @ac: auditd connection state

   *
   * Description:
   * Break the auditd/kauditd connection and move all the queued records into the

   * hold queue in case auditd reconnects.  It is important to note that the @ac
   * pointer should never be dereferenced inside this function as it may be NULL
   * or invalid, you can only compare the memory address!  If @ac is NULL then
   * the connection will always be reset.

   */

  static void auditd_reset(const struct auditd_connection *ac)

  {

  	unsigned long flags;

  	struct sk_buff *skb;

  	struct auditd_connection *ac_old;

  
  	/* if it isn't already broken, break the connection */

  	spin_lock_irqsave(&auditd_conn_lock, flags);
  	ac_old = rcu_dereference_protected(auditd_conn,
  					   lockdep_is_held(&auditd_conn_lock));

  	if (ac && ac != ac_old) {
  		/* someone already registered a new auditd connection */
  		spin_unlock_irqrestore(&auditd_conn_lock, flags);
  		return;
  	}

  	rcu_assign_pointer(auditd_conn, NULL);
  	spin_unlock_irqrestore(&auditd_conn_lock, flags);
  
  	if (ac_old)
  		call_rcu(&ac_old->rcu, auditd_conn_free);

  	/* flush the retry queue to the hold queue, but don't touch the main
  	 * queue since we need to process that normally for multicast */

  	while ((skb = skb_dequeue(&audit_retry_queue)))
  		kauditd_hold_skb(skb);

  }
  
  /**

   * auditd_send_unicast_skb - Send a record via unicast to auditd
   * @skb: audit record

   *
   * Description:

   * Send a skb to the audit daemon, returns positive/zero values on success and
   * negative values on failure; in all cases the skb will be consumed by this
   * function.  If the send results in -ECONNREFUSED the connection with auditd
   * will be reset.  This function may sleep so callers should not hold any locks
   * where this would cause a problem.

   */

  static int auditd_send_unicast_skb(struct sk_buff *skb)

  {

  	int rc;
  	u32 portid;
  	struct net *net;
  	struct sock *sk;

  	struct auditd_connection *ac;

  
  	/* NOTE: we can't call netlink_unicast while in the RCU section so
  	 *       take a reference to the network namespace and grab local
  	 *       copies of the namespace, the sock, and the portid; the
  	 *       namespace and sock aren't going to go away while we hold a
  	 *       reference and if the portid does become invalid after the RCU
  	 *       section netlink_unicast() should safely return an error */
  
  	rcu_read_lock();

  	ac = rcu_dereference(auditd_conn);
  	if (!ac) {

  		rcu_read_unlock();

  		kfree_skb(skb);

  		rc = -ECONNREFUSED;
  		goto err;

  	}

  	net = get_net(ac->net);

  	sk = audit_get_sk(net);

  	portid = ac->portid;

  	rcu_read_unlock();

  	rc = netlink_unicast(sk, skb, portid, 0);
  	put_net(net);
  	if (rc < 0)
  		goto err;
  
  	return rc;
  
  err:

  	if (ac && rc == -ECONNREFUSED)
  		auditd_reset(ac);

  	return rc;

  }
  
  /**

   * kauditd_send_queue - Helper for kauditd_thread to flush skb queues
   * @sk: the sending sock
   * @portid: the netlink destination
   * @queue: the skb queue to process
   * @retry_limit: limit on number of netlink unicast failures
   * @skb_hook: per-skb hook for additional processing
   * @err_hook: hook called if the skb fails the netlink unicast send
   *
   * Description:
   * Run through the given queue and attempt to send the audit records to auditd,
   * returns zero on success, negative values on failure.  It is up to the caller
   * to ensure that the @sk is valid for the duration of this function.
   *

   */

  static int kauditd_send_queue(struct sock *sk, u32 portid,
  			      struct sk_buff_head *queue,
  			      unsigned int retry_limit,
  			      void (*skb_hook)(struct sk_buff *skb),
  			      void (*err_hook)(struct sk_buff *skb))

  {

  	int rc = 0;
  	struct sk_buff *skb;
  	static unsigned int failed = 0;

  	/* NOTE: kauditd_thread takes care of all our locking, we just use
  	 *       the netlink info passed to us (e.g. sk and portid) */
  
  	while ((skb = skb_dequeue(queue))) {
  		/* call the skb_hook for each skb we touch */
  		if (skb_hook)
  			(*skb_hook)(skb);
  
  		/* can we send to anyone via unicast? */
  		if (!sk) {
  			if (err_hook)
  				(*err_hook)(skb);
  			continue;
  		}

  		/* grab an extra skb reference in case of error */
  		skb_get(skb);
  		rc = netlink_unicast(sk, skb, portid, 0);
  		if (rc < 0) {
  			/* fatal failure for our queue flush attempt? */
  			if (++failed >= retry_limit ||
  			    rc == -ECONNREFUSED || rc == -EPERM) {
  				/* yes - error processing for the queue */
  				sk = NULL;
  				if (err_hook)
  					(*err_hook)(skb);
  				if (!skb_hook)
  					goto out;
  				/* keep processing with the skb_hook */
  				continue;
  			} else
  				/* no - requeue to preserve ordering */
  				skb_queue_head(queue, skb);
  		} else {
  			/* it worked - drop the extra reference and continue */
  			consume_skb(skb);
  			failed = 0;
  		}

  	}

  out:
  	return (rc >= 0 ? 0 : rc);

  }

  /*

   * kauditd_send_multicast_skb - Send a record to any multicast listeners
   * @skb: audit record

   *

   * Description:

   * Write a multicast message to anyone listening in the initial network
   * namespace.  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)

  {

  	struct sk_buff *copy;

  	struct sock *sock = audit_get_sk(&init_net);

  	struct nlmsghdr *nlh;

  	/* NOTE: we are not taking an additional reference for init_net since
  	 *       we don't have to worry about it going away */

  	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_KERNEL);

  	if (!copy)
  		return;

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

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

  }

  /**

   * kauditd_thread - Worker thread to send audit records to userspace
   * @dummy: unused

   */

  static int kauditd_thread(void *dummy)

  {

  	int rc;

  	u32 portid = 0;
  	struct net *net = NULL;
  	struct sock *sk = NULL;

  	struct auditd_connection *ac;

  #define UNICAST_RETRIES 5

  	set_freezable();

  	while (!kthread_should_stop()) {

  		/* NOTE: see the lock comments in auditd_send_unicast_skb() */
  		rcu_read_lock();

  		ac = rcu_dereference(auditd_conn);
  		if (!ac) {

  			rcu_read_unlock();
  			goto main_queue;
  		}

  		net = get_net(ac->net);

  		sk = audit_get_sk(net);

  		portid = ac->portid;

  		rcu_read_unlock();

  
  		/* attempt to flush the hold queue */

  		rc = kauditd_send_queue(sk, portid,
  					&audit_hold_queue, UNICAST_RETRIES,
  					NULL, kauditd_rehold_skb);

  		if (ac && rc < 0) {

  			sk = NULL;

  			auditd_reset(ac);

  			goto main_queue;

  		}

  		/* attempt to flush the retry queue */

  		rc = kauditd_send_queue(sk, portid,
  					&audit_retry_queue, UNICAST_RETRIES,
  					NULL, kauditd_hold_skb);

  		if (ac && rc < 0) {

  			sk = NULL;

  			auditd_reset(ac);

  			goto main_queue;

  		}

  main_queue:
  		/* process the main queue - do the multicast send and attempt
  		 * unicast, dump failed record sends to the retry queue; if
  		 * sk == NULL due to previous failures we will just do the

  		 * multicast send and move the record to the hold queue */

  		rc = kauditd_send_queue(sk, portid, &audit_queue, 1,
  					kauditd_send_multicast_skb,

  					(sk ?
  					 kauditd_retry_skb : kauditd_hold_skb));
  		if (ac && rc < 0)
  			auditd_reset(ac);

  		sk = NULL;

  
  		/* drop our netns reference, no auditd sends past this line */
  		if (net) {
  			put_net(net);
  			net = NULL;

  		}

  
  		/* we have processed all the queues so wake everyone */
  		wake_up(&audit_backlog_wait);
  
  		/* NOTE: we want to wake up if there is anything on the queue,
  		 *       regardless of if an auditd is connected, as we need to
  		 *       do the multicast send and rotate records from the
  		 *       main queue to the retry/hold queues */
  		wait_event_freezable(kauditd_wait,
  				     (skb_queue_len(&audit_queue) ? 1 : 0));

  	}

  	return 0;

  }

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

  	struct sk_buff *skb;

  	struct sock *sk = audit_get_sk(dest->net);

  
  	/* wait for parent to finish and send an ACK */

  	audit_ctl_lock();
  	audit_ctl_unlock();

  
  	while ((skb = __skb_dequeue(&dest->q)) != NULL)

  		netlink_unicast(sk, skb, dest->portid, 0);

  	put_net(dest->net);

  	kfree(dest);
  
  	return 0;
  }

  struct sk_buff *audit_make_reply(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, 0, 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 sock *sk = audit_get_sk(reply->net);

  	audit_ctl_lock();
  	audit_ctl_unlock();

  
  	/* Ignore failure. It'll only happen if the sender goes away,
  	   because our timeout is set to infinite. */

  	netlink_unicast(sk, reply->skb, reply->portid, 0);
  	put_net(reply->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)

  {

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

  	if (!skb)

  		goto out;

  	reply->net = get_net(net);

  	reply->portid = NETLINK_CB(request_skb).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_context *context,
  					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(context, 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);

  }

  static inline void audit_log_user_recv_msg(struct audit_buffer **ab,
  					   u16 msg_type)
  {
  	audit_log_common_recv_msg(NULL, ab, msg_type);
  }

  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(audit_context(), GFP_KERNEL, AUDIT_FEATURE_CHANGE);

  	if (!ab)
  		return;

  	audit_log_task_info(ab);

  	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 audit_features *uaf)

  {

  	int i;

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

  
  	/* 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(struct pid *pid)

  {

  	pid_t pvnr;

  	struct sk_buff *skb;

  	pvnr = pid_vnr(pid);
  	skb = audit_make_reply(0, AUDIT_REPLACE, 0, 0, &pvnr, sizeof(pvnr));

  	if (!skb)
  		return -ENOMEM;

  	return auditd_send_unicast_skb(skb);

  }

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

  	u32			seq;

  	void			*data;

  	int			data_len;

  	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;

  	seq  = nlh->nlmsg_seq;

  	data = nlmsg_data(nlh);

  	data_len = nlmsg_len(nlh);

  
  	switch (msg_type) {

  	case AUDIT_GET: {
  		struct audit_status	s;
  		memset(&s, 0, sizeof(s));
  		s.enabled		= audit_enabled;
  		s.failure		= audit_failure;

  		/* NOTE: use pid_vnr() so the PID is relative to the current
  		 *       namespace */

  		s.pid			= auditd_pid_vnr();

  		s.rate_limit		= audit_rate_limit;
  		s.backlog_limit		= audit_backlog_limit;
  		s.lost			= atomic_read(&audit_lost);

  		s.backlog		= skb_queue_len(&audit_queue);

  		s.feature_bitmap	= AUDIT_FEATURE_BITMAP_ALL;

  		s.backlog_wait_time	= audit_backlog_wait_time;

  		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), data_len));

  		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 the vnr PID functions 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 */
  			pid_t new_pid = s.pid;

  			pid_t auditd_pid;

  			struct pid *req_pid = task_tgid(current);

  			/* Sanity check - PID values must match. Setting
  			 * pid to 0 is how auditd ends auditing. */
  			if (new_pid && (new_pid != pid_vnr(req_pid)))

  				return -EINVAL;

  			/* test the auditd connection */

  			audit_replace(req_pid);

  			auditd_pid = auditd_pid_vnr();

  			if (auditd_pid) {
  				/* replacing a healthy auditd is not allowed */
  				if (new_pid) {
  					audit_log_config_change("audit_pid",
  							new_pid, auditd_pid, 0);
  					return -EEXIST;
  				}
  				/* only current auditd can unregister itself */
  				if (pid_vnr(req_pid) != auditd_pid) {
  					audit_log_config_change("audit_pid",
  							new_pid, auditd_pid, 0);
  					return -EACCES;
  				}

  			}

  			if (new_pid) {

  				/* register a new auditd connection */

  				err = auditd_set(req_pid,
  						 NETLINK_CB(skb).portid,
  						 sock_net(NETLINK_CB(skb).sk));
  				if (audit_enabled != AUDIT_OFF)
  					audit_log_config_change("audit_pid",
  								new_pid,
  								auditd_pid,
  								err ? 0 : 1);
  				if (err)
  					return err;

  				/* try to process any backlog */
  				wake_up_interruptible(&kauditd_wait);

  			} else {
  				if (audit_enabled != AUDIT_OFF)
  					audit_log_config_change("audit_pid",
  								new_pid,
  								auditd_pid, 1);

  				/* unregister the auditd connection */

  				auditd_reset(NULL);

  			}

  		}

  		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;

  		}

  		if (s.mask == AUDIT_STATUS_LOST) {
  			u32 lost = atomic_xchg(&audit_lost, 0);
  
  			audit_log_config_change("lost", 0, lost, 1);
  			return lost;
  		}

  		break;

  	}

  	case AUDIT_GET_FEATURE:
  		err = audit_get_feature(skb);
  		if (err)
  			return err;
  		break;
  	case AUDIT_SET_FEATURE:

  		if (data_len < sizeof(struct audit_features))
  			return -EINVAL;
  		err = audit_set_feature(data);

  		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 */

  			char *str = data;

  			err = 0;

  			if (msg_type == AUDIT_USER_TTY) {

  				err = tty_audit_push();

  				if (err)
  					break;
  			}

  			audit_log_user_recv_msg(&ab, msg_type);

  			if (msg_type != AUDIT_USER_TTY) {
  				/* ensure NULL termination */
  				str[data_len - 1] = '\0';

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

  						 str);
  			} else {

  				audit_log_format(ab, " data=");

  				if (data_len > 0 && str[data_len - 1] == '\0')
  					data_len--;
  				audit_log_n_untrustedstring(ab, str, data_len);

  			}

  			audit_log_end(ab);

  		}

  		break;

  	case AUDIT_ADD_RULE:
  	case AUDIT_DEL_RULE:

  		if (data_len < sizeof(struct audit_rule_data))

  			return -EINVAL;

  		if (audit_enabled == AUDIT_LOCKED) {

  			audit_log_common_recv_msg(audit_context(), &ab,
  						  AUDIT_CONFIG_CHANGE);

  			audit_log_format(ab, " op=%s audit_enabled=%d res=0",
  					 msg_type == AUDIT_ADD_RULE ?
  						"add_rule" : "remove_rule",
  					 audit_enabled);

  			audit_log_end(ab);

  			return -EPERM;
  		}

  		err = audit_rule_change(msg_type, seq, data, data_len);

  		break;

  	case AUDIT_LIST_RULES:

  		err = audit_list_rules_send(skb, seq);

  		break;

  	case AUDIT_TRIM:
  		audit_trim_trees();

  		audit_log_common_recv_msg(audit_context(), &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 = data_len;

  		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(audit_context(), &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), data_len));

  		/* 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(audit_context(), &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;
  }

  /**
   * audit_receive - receive messages from a netlink control socket
   * @skb: the message buffer
   *
   * Parse the provided skb and deal with any messages that may be present,
   * malformed skbs are discarded.

   */

  static void audit_receive(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;

  	audit_ctl_lock();

  	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, NULL);

  		nlh = nlmsg_next(nlh, &len);

  	}

  	audit_ctl_unlock();

  }

  /* 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->sk = netlink_kernel_create(net, NETLINK_AUDIT, &cfg);
  	if (aunet->sk == NULL) {

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

  		return -ENOMEM;
  	}

  	aunet->sk->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);

  	/* NOTE: you would think that we would want to check the auditd
  	 * connection and potentially reset it here if it lives in this
  	 * namespace, but since the auditd connection tracking struct holds a
  	 * reference to this namespace (see auditd_set()) we are only ever
  	 * going to get here after that connection has been released */

  	netlink_kernel_release(aunet->sk);

  }

  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;

  	audit_buffer_cache = kmem_cache_create("audit_buffer",
  					       sizeof(struct audit_buffer),
  					       0, SLAB_PANIC, NULL);

  	skb_queue_head_init(&audit_queue);

  	skb_queue_head_init(&audit_retry_queue);

  	skb_queue_head_init(&audit_hold_queue);