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 // 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 = AUDIT_UNINITIALIZED;
 
 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.
  */
 struct auditd_connection {
     struct pid *pid;
     u32 portid;
     struct net *net;
     struct rcu_head rcu;
 };
 static struct auditd_connection __rcu *auditd_conn;
 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. */
 static kuid_t       audit_sig_uid = INVALID_UID;
 static pid_t        audit_sig_pid = -1;
 static u32      audit_sig_sid;
 
 /* 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);
 
 /* Monotonically increasing sum of time the kernel has spent
  * waiting while the backlog limit is exceeded.
  */
 static atomic_t audit_backlog_wait_time_actual = 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\n", message);
         break;
     case AUDIT_FAIL_PANIC:
         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())
             pr_warn("audit_lost=%u audit_rate_limit=%u audit_backlog_limit=%u\n",
                 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_printk_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\n", nlh->nlmsg_type, data);
 }
 
 /**
  * kauditd_rehold_skb - Handle a audit record send failure in the hold queue
  * @skb: audit record
  * @error: error code (unused)
  *
  * 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, __always_unused int error)
 {
     /* put the record back in the queue */
     skb_queue_tail(&audit_hold_queue, skb);
 }
 
 /**
  * kauditd_hold_skb - Queue an audit record, waiting for auditd
  * @skb: audit record
  * @error: error code
  *
  * 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, int error)
 {
     /* 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)
         goto drop;
 
     /* the hold queue is only for when the daemon goes away completely,
      * not -EAGAIN failures; if we are in a -EAGAIN state requeue the
      * record on the retry queue unless it's full, in which case drop it
      */
     if (error == -EAGAIN) {
         if (!audit_backlog_limit ||
             skb_queue_len(&audit_retry_queue) < audit_backlog_limit) {
             skb_queue_tail(&audit_retry_queue, skb);
             return;
         }
         audit_log_lost("kauditd retry queue overflow");
         goto drop;
     }
 
     /* if we have room in the hold queue, 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");
 drop:
     kfree_skb(skb);
 }
 
 /**
  * kauditd_retry_skb - Queue an audit record, attempt to send again to auditd
  * @skb: audit record
  * @error: error code (unused)
  *
  * 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, __always_unused int error)
 {
     if (!audit_backlog_limit ||
         skb_queue_len(&audit_retry_queue) < audit_backlog_limit) {
         skb_queue_tail(&audit_retry_queue, skb);
         return;
     }
 
     /* we have to drop the record, send it via printk as a last effort */
     kauditd_printk_skb(skb);
     audit_log_lost("kauditd retry queue overflow");
     kfree_skb(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, -ECONNREFUSED);
 }
 
 /**
  * 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 error))
 {
     int rc = 0;
     struct sk_buff *skb = NULL;
     struct sk_buff *skb_tail;
     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) */
 
     skb_tail = skb_peek_tail(queue);
     while ((skb != skb_tail) && (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, -ECONNREFUSED);
             continue;
         }
 
 retry:
         /* grab an extra skb reference in case of error */
         skb_get(skb);
         rc = netlink_unicast(sk, skb, portid, 0);
         if (rc < 0) {
             /* send failed - try a few times unless fatal error */
             if (++failed >= retry_limit ||
                 rc == -ECONNREFUSED || rc == -EPERM) {
                 sk = NULL;
                 if (err_hook)
                     (*err_hook)(skb, rc);
                 if (rc == -EAGAIN)
                     rc = 0;
                 /* continue to drain the queue */
                 continue;
             } else
                 goto retry;
         } else {
             /* skb sent - drop the extra reference and continue */
             consume_skb(skb);
             failed = 0;
         }
     }
 
     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 (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 (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_thread(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 void audit_free_reply(struct audit_reply *reply)
 {
     if (!reply)
         return;
 
     kfree_skb(reply->skb);
     if (reply->net)
         put_net(reply->net);
     kfree(reply);
 }
 
 static int audit_send_reply_thread(void *arg)
 {
     struct audit_reply *reply = (struct audit_reply *)arg;
 
     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(audit_get_sk(reply->net), reply->skb, reply->portid, 0);
     reply->skb = NULL;
     audit_free_reply(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 a skb, builds the netlink message, and sends it to the port id.
  */
 static void audit_send_reply(struct sk_buff *request_skb, int seq, int type, int done,
                  int multi, const void *payload, int size)
 {
     struct task_struct *tsk;
     struct audit_reply *reply;
 
     reply = kzalloc(sizeof(*reply), GFP_KERNEL);
     if (!reply)
         return;
 
     reply->skb = audit_make_reply(seq, type, done, multi, payload, size);
     if (!reply->skb)
         goto err;
     reply->net = get_net(sock_net(NETLINK_CB(request_skb).sk));
     reply->portid = NETLINK_CB(request_skb).portid;
 
     tsk = kthread_run(audit_send_reply_thread, reply, "audit_send_reply");
     if (IS_ERR(tsk))
         goto err;
 
     return;
 
 err:
     audit_free_reply(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);
 }
 
 static 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;
         s.backlog_wait_time_actual = atomic_read(&audit_backlog_wait_time_actual);
         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;
         }
         if (s.mask == AUDIT_STATUS_BACKLOG_WAIT_TIME_ACTUAL) {
             u32 actual = atomic_xchg(&audit_backlog_wait_time_actual, 0);
 
             audit_log_config_change("backlog_wait_time_actual", 0, actual, 1);
             return actual;
         }
         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;
         /* exit early if there isn't at least one character to print */
         if (data_len < 2)
             return -EINVAL;
 
         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 (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(struct_size(sig_data, ctx, 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, struct_size(sig_data, ctx, 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();
 
     /* can't block with the ctrl lock, so penalize the sender now */
     if (audit_backlog_limit &&
         (skb_queue_len(&audit_queue) > audit_backlog_limit)) {
         DECLARE_WAITQUEUE(wait, current);
 
         /* wake kauditd to try and flush the queue */
         wake_up_interruptible(&kauditd_wait);
 
         add_wait_queue_exclusive(&audit_backlog_wait, &wait);
         set_current_state(TASK_UNINTERRUPTIBLE);
         schedule_timeout(audit_backlog_wait_time);
         remove_wait_queue(&audit_backlog_wait, &wait);
     }
 }
 
 /* Log information about who is connecting to the audit multicast socket */
 static void audit_log_multicast(int group, const char *op, int err)
 {
     const struct cred *cred;
     struct tty_struct *tty;
     char comm[sizeof(current->comm)];
     struct audit_buffer *ab;
 
     if (!audit_enabled)
         return;
 
     ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_EVENT_LISTENER);
     if (!ab)
         return;
 
     cred = current_cred();
     tty = audit_get_tty();
     audit_log_format(ab, "pid=%u uid=%u auid=%u tty=%s ses=%u",
              task_pid_nr(current),
              from_kuid(&init_user_ns, cred->uid),
              from_kuid(&init_user_ns, audit_get_loginuid(current)),
              tty ? tty_name(tty) : "(none)",
              audit_get_sessionid(current));
     audit_put_tty(tty);
     audit_log_task_context(ab); /* subj= */
     audit_log_format(ab, " comm=");
     audit_log_untrustedstring(ab, get_task_comm(comm, current));
     audit_log_d_path_exe(ab, current->mm); /* exe= */
     audit_log_format(ab, " nl-mcgrp=%d op=%s res=%d", group, op, !err);
     audit_log_end(ab);
 }
 
 /* Run custom bind function on netlink socket group connect or bind requests. */
 static int audit_multicast_bind(struct net *net, int group)
 {
     int err = 0;
 
     if (!capable(CAP_AUDIT_READ))
         err = -EPERM;
     audit_log_multicast(group, "connect", err);
     return err;
 }
 
 static void audit_multicast_unbind(struct net *net, int group)
 {
     audit_log_multicast(group, "disconnect", 0);
 }
 
 static int __net_init audit_net_init(struct net *net)
 {
     struct netlink_kernel_cfg cfg = {
         .input  = audit_receive,
         .bind   = audit_multicast_bind,
         .unbind = audit_multicast_unbind,
         .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;
     }
     /* limit the timeout in case auditd is blocked/stopped */
     aunet->sk->sk_sndtimeo = HZ / 10;
 
     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);
 
     for (i = 0; i < AUDIT_INODE_BUCKETS; i++)
         INIT_LIST_HEAD(&audit_inode_hash[i]);
 
     mutex_init(&audit_cmd_mutex.lock);
     audit_cmd_mutex.owner = NULL;
 
     pr_info("initializing netlink subsys (%s)\n",
         audit_default ? "enabled" : "disabled");
     register_pernet_subsys(&audit_net_ops);
 
     audit_initialized = AUDIT_INITIALIZED;
 
     kauditd_task = kthread_run(kauditd_thread, NULL, "kauditd");
     if (IS_ERR(kauditd_task)) {
         int err = PTR_ERR(kauditd_task);
         panic("audit: failed to start the kauditd thread (%d)\n", err);
     }
 
     audit_log(NULL, GFP_KERNEL, AUDIT_KERNEL,
         "state=initialized audit_enabled=%u res=1",
          audit_enabled);
 
     return 0;
 }
 postcore_initcall(audit_init);
 
 /*
  * Process kernel command-line parameter at boot time.
  * audit={0|off} or audit={1|on}.
  */
 static int __init audit_enable(char *str)
 {
     if (!strcasecmp(str, "off") || !strcmp(str, "0"))
         audit_default = AUDIT_OFF;
     else if (!strcasecmp(str, "on") || !strcmp(str, "1"))
         audit_default = AUDIT_ON;
     else {
         pr_err("audit: invalid 'audit' parameter value (%s)\n", str);
         audit_default = AUDIT_ON;
     }
 
     if (audit_default == AUDIT_OFF)
         audit_initialized = AUDIT_DISABLED;
     if (audit_set_enabled(audit_default))
         pr_err("audit: error setting audit state (%d)\n",
                audit_default);
 
     pr_info("%s\n", 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\n",
             audit_backlog_limit, str);
         return 1;
     }
 
     audit_backlog_limit = audit_backlog_limit_arg;
     pr_cont("%d\n", audit_backlog_limit);
 
     return 1;
 }
 __setup("audit_backlog_limit=", audit_backlog_limit_set);
 
 static void audit_buffer_free(struct audit_buffer *ab)
 {
     if (!ab)
         return;
 
     kfree_skb(ab->skb);
     kmem_cache_free(audit_buffer_cache, ab);
 }
 
 static struct audit_buffer *audit_buffer_alloc(struct audit_context *ctx,
                            gfp_t gfp_mask, int type)
 {
     struct audit_buffer *ab;
 
     ab = kmem_cache_alloc(audit_buffer_cache, gfp_mask);
     if (!ab)
         return NULL;
 
     ab->skb = nlmsg_new(AUDIT_BUFSIZ, gfp_mask);
     if (!ab->skb)
         goto err;
     if (!nlmsg_put(ab->skb, 0, 0, type, 0, 0))
         goto err;
 
     ab->ctx = ctx;
     ab->gfp_mask = gfp_mask;
 
     return ab;
 
 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_inc_return(&serial);
 }
 
 static inline void audit_get_stamp(struct audit_context *ctx,
                    struct timespec64 *t, unsigned int *serial)
 {
     if (!ctx || !auditsc_get_stamp(ctx, t, serial)) {
         ktime_get_coarse_real_ts64(t);
         *serial = audit_serial();
     }
 }
 
 /**
  * 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;
     struct timespec64 t;
     unsigned int serial;
 
     if (audit_initialized != AUDIT_INITIALIZED)
         return NULL;
 
     if (unlikely(!audit_filter(type, AUDIT_FILTER_EXCLUDE)))
         return NULL;
 
     /* NOTE: don't ever fail/sleep on these two conditions:
      * 1. auditd generated record - since we need auditd to drain the
      *    queue; also, when we are checking for auditd, compare PIDs using
      *    task_tgid_vnr() since auditd_pid is set in audit_receive_msg()
      *    using a PID anchored in the caller's namespace
      * 2. generator holding the audit_cmd_mutex - we don't want to block
      *    while holding the mutex, although we do penalize the sender
      *    later in audit_receive() when it is safe to block
      */
     if (!(auditd_test_task(current) || audit_ctl_owner_current())) {
         long stime = audit_backlog_wait_time;
 
         while (audit_backlog_limit &&
                (skb_queue_len(&audit_queue) > audit_backlog_limit)) {
             /* wake kauditd to try and flush the queue */
             wake_up_interruptible(&kauditd_wait);
 
             /* sleep if we are allowed and we haven't exhausted our
              * backlog wait limit */
             if (gfpflags_allow_blocking(gfp_mask) && (stime > 0)) {
                 long rtime = stime;
 
                 DECLARE_WAITQUEUE(wait, current);
 
                 add_wait_queue_exclusive(&audit_backlog_wait,
                              &wait);
                 set_current_state(TASK_UNINTERRUPTIBLE);
                 stime = schedule_timeout(rtime);
                 atomic_add(rtime - stime, &audit_backlog_wait_time_actual);
                 remove_wait_queue(&audit_backlog_wait, &wait);
             } else {
                 if (audit_rate_check() && printk_ratelimit())
                     pr_warn("audit_backlog=%d > audit_backlog_limit=%d\n",
                         skb_queue_len(&audit_queue),
                         audit_backlog_limit);
                 audit_log_lost("backlog limit exceeded");
                 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);
     /* cancel dummy context to enable supporting records */
     if (ctx)
         ctx->dummy = 0;
     audit_log_format(ab, "audit(%llu.%03lu:%u): ",
              (unsigned long long)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_va_end;
         len = vsnprintf(skb_tail_pointer(skb), avail, fmt, args2);
     }
     if (len > 0)
         skb_put(skb, len);
 out_va_end:
     va_end(args2);
 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_n_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;
 
     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_byte_pack_upper(ptr, buf[i]);
     *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
  */
 bool 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 true;
     }
     return false;
 }
 
 /**
  * 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,
               const 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_format(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_format(ab, "\"<too_long>\"");
     } else
         audit_log_untrustedstring(ab, p);
     kfree(pathname);
 }
 
 void audit_log_session_info(struct audit_buffer *ab)
 {
     unsigned int sessionid = audit_get_sessionid(current);
     uid_t auid = from_kuid(&init_user_ns, audit_get_loginuid(current));
 
     audit_log_format(ab, "auid=%u ses=%u", auid, sessionid);
 }
 
 void audit_log_key(struct audit_buffer *ab, char *key)
 {
     audit_log_format(ab, " key=");
     if (key)
         audit_log_untrustedstring(ab, key);
     else
         audit_log_format(ab, "(null)");
 }
 
 int audit_log_task_context(struct audit_buffer *ab)
 {
     char *ctx = NULL;
     unsigned len;
     int error;
     u32 sid;
 
     security_current_getsecid_subj(&sid);
     if (!sid)
         return 0;
 
     error = security_secid_to_secctx(sid, &ctx, &len);
     if (error) {
         if (error != -EINVAL)
             goto error_path;
         return 0;
     }
 
     audit_log_format(ab, " subj=%s", ctx);
     security_release_secctx(ctx, len);
     return 0;
 
 error_path:
     audit_panic("error in audit_log_task_context");
     return error;
 }
 EXPORT_SYMBOL(audit_log_task_context);
 
 void audit_log_d_path_exe(struct audit_buffer *ab,
               struct mm_struct *mm)
 {
     struct file *exe_file;
 
     if (!mm)
         goto out_null;
 
     exe_file = get_mm_exe_file(mm);
     if (!exe_file)
         goto out_null;
 
     audit_log_d_path(ab, " exe=", &exe_file->f_path);
     fput(exe_file);
     return;
 out_null:
     audit_log_format(ab, " exe=(null)");
 }
 
 struct tty_struct *audit_get_tty(void)
 {
     struct tty_struct *tty = NULL;
     unsigned long flags;
 
     spin_lock_irqsave(&current->sighand->siglock, flags);
     if (current->signal)
         tty = tty_kref_get(current->signal->tty);
     spin_unlock_irqrestore(&current->sighand->siglock, flags);
     return tty;
 }
 
 void audit_put_tty(struct tty_struct *tty)
 {
     tty_kref_put(tty);
 }
 
 void audit_log_task_info(struct audit_buffer *ab)
 {
     const struct cred *cred;
     char comm[sizeof(current->comm)];
     struct tty_struct *tty;
 
     if (!ab)
         return;
 
     cred = current_cred();
     tty = audit_get_tty();
     audit_log_format(ab,
              " ppid=%d pid=%d auid=%u uid=%u gid=%u"
              " euid=%u suid=%u fsuid=%u"
              " egid=%u sgid=%u fsgid=%u tty=%s ses=%u",
              task_ppid_nr(current),
              task_tgid_nr(current),
              from_kuid(&init_user_ns, audit_get_loginuid(current)),
              from_kuid(&init_user_ns, cred->uid),
              from_kgid(&init_user_ns, cred->gid),
              from_kuid(&init_user_ns, cred->euid),
              from_kuid(&init_user_ns, cred->suid),
              from_kuid(&init_user_ns, cred->fsuid),
              from_kgid(&init_user_ns, cred->egid),
              from_kgid(&init_user_ns, cred->sgid),
              from_kgid(&init_user_ns, cred->fsgid),
              tty ? tty_name(tty) : "(none)",
              audit_get_sessionid(current));
     audit_put_tty(tty);
     audit_log_format(ab, " comm=");
     audit_log_untrustedstring(ab, get_task_comm(comm, current));
     audit_log_d_path_exe(ab, current->mm);
     audit_log_task_context(ab);
 }
 EXPORT_SYMBOL(audit_log_task_info);
 
 /**
  * audit_log_path_denied - report a path restriction denial
  * @type: audit message type (AUDIT_ANOM_LINK, AUDIT_ANOM_CREAT, etc)
  * @operation: specific operation name
  */
 void audit_log_path_denied(int type, const char *operation)
 {
     struct audit_buffer *ab;
 
     if (!audit_enabled || audit_dummy_context())
         return;
 
     /* Generate log with subject, operation, outcome. */
     ab = audit_log_start(audit_context(), GFP_KERNEL, type);
     if (!ab)
         return;
     audit_log_format(ab, "op=%s", operation);
     audit_log_task_info(ab);
     audit_log_format(ab, " res=0");
     audit_log_end(ab);
 }
 
 /* global counter which is incremented every time something logs in */
 static atomic_t session_id = ATOMIC_INIT(0);
 
 static int audit_set_loginuid_perm(kuid_t loginuid)
 {
     /* if we are unset, we don't need privs */
     if (!audit_loginuid_set(current))
         return 0;
     /* if AUDIT_FEATURE_LOGINUID_IMMUTABLE means never ever allow a change*/
     if (is_audit_feature_set(AUDIT_FEATURE_LOGINUID_IMMUTABLE))
         return -EPERM;
     /* it is set, you need permission */
     if (!capable(CAP_AUDIT_CONTROL))
         return -EPERM;
     /* reject if this is not an unset and we don't allow that */
     if (is_audit_feature_set(AUDIT_FEATURE_ONLY_UNSET_LOGINUID)
                  && uid_valid(loginuid))
         return -EPERM;
     return 0;
 }
 
 static void audit_log_set_loginuid(kuid_t koldloginuid, kuid_t kloginuid,
                    unsigned int oldsessionid,
                    unsigned int sessionid, int rc)
 {
     struct audit_buffer *ab;
     uid_t uid, oldloginuid, loginuid;
     struct tty_struct *tty;
 
     if (!audit_enabled)
         return;
 
     ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_LOGIN);
     if (!ab)
         return;
 
     uid = from_kuid(&init_user_ns, task_uid(current));
     oldloginuid = from_kuid(&init_user_ns, koldloginuid);
     loginuid = from_kuid(&init_user_ns, kloginuid);
     tty = audit_get_tty();
 
     audit_log_format(ab, "pid=%d uid=%u", task_tgid_nr(current), uid);
     audit_log_task_context(ab);
     audit_log_format(ab, " old-auid=%u auid=%u tty=%s old-ses=%u ses=%u res=%d",
              oldloginuid, loginuid, tty ? tty_name(tty) : "(none)",
              oldsessionid, sessionid, !rc);
     audit_put_tty(tty);
     audit_log_end(ab);
 }
 
 /**
  * audit_set_loginuid - set current task's loginuid
  * @loginuid: loginuid value
  *
  * Returns 0.
  *
  * Called (set) from fs/proc/base.c::proc_loginuid_write().
  */
 int audit_set_loginuid(kuid_t loginuid)
 {
     unsigned int oldsessionid, sessionid = AUDIT_SID_UNSET;
     kuid_t oldloginuid;
     int rc;
 
     oldloginuid = audit_get_loginuid(current);
     oldsessionid = audit_get_sessionid(current);
 
     rc = audit_set_loginuid_perm(loginuid);
     if (rc)
         goto out;
 
     /* are we setting or clearing? */
     if (uid_valid(loginuid)) {
         sessionid = (unsigned int)atomic_inc_return(&session_id);
         if (unlikely(sessionid == AUDIT_SID_UNSET))
             sessionid = (unsigned int)atomic_inc_return(&session_id);
     }
 
     current->sessionid = sessionid;
     current->loginuid = loginuid;
 out:
     audit_log_set_loginuid(oldloginuid, loginuid, oldsessionid, sessionid, rc);
     return rc;
 }
 
 /**
  * audit_signal_info - record signal info for shutting down audit subsystem
  * @sig: signal value
  * @t: task being signaled
  *
  * If the audit subsystem is being terminated, record the task (pid)
  * and uid that is doing that.
  */
 int audit_signal_info(int sig, struct task_struct *t)
 {
     kuid_t uid = current_uid(), auid;
 
     if (auditd_test_task(t) &&
         (sig == SIGTERM || sig == SIGHUP ||
          sig == SIGUSR1 || sig == SIGUSR2)) {
         audit_sig_pid = task_tgid_nr(current);
         auid = audit_get_loginuid(current);
         if (uid_valid(auid))
             audit_sig_uid = auid;
         else
             audit_sig_uid = uid;
         security_current_getsecid_subj(&audit_sig_sid);
     }
 
     return audit_signal_info_syscall(t);
 }
 
 /**
  * audit_log_end - end one audit record
  * @ab: the audit_buffer
  *
  * We can not do a netlink send inside an irq context because it blocks (last
  * arg, flags, is not set to MSG_DONTWAIT), so the audit buffer is placed on a
  * queue and a kthread 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)
 {
     struct sk_buff *skb;
     struct nlmsghdr *nlh;
 
     if (!ab)
         return;
 
     if (audit_rate_check()) {
         skb = ab->skb;
         ab->skb = NULL;
 
         /* setup the netlink header, see the comments in
          * kauditd_send_multicast_skb() for length quirks */
         nlh = nlmsg_hdr(skb);
         nlh->nlmsg_len = skb->len - NLMSG_HDRLEN;
 
         /* queue the netlink packet and poke the kauditd thread */
         skb_queue_tail(&audit_queue, skb);
         wake_up_interruptible(&kauditd_wait);
     } else
         audit_log_lost("rate limit exceeded");
 
     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);

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