Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 839 insertions, 0 deletions

diff --git a/kernel/audit.c b/kernel/audit.c
new file mode 100644
index 000000000000..0f84dd7af2c8
--- /dev/null
+++ b/kernel/audit.c
@@ -0,0 +1,839 @@
+/* audit.c -- Auditing support -*- linux-c -*-
+ * Gateway between the kernel (e.g., selinux) and the user-space audit daemon.
+ * System-call specific features have moved to auditsc.c
+ *
+ * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
+ * All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * Written by Rickard E. (Rik) Faith <faith@redhat.com>
+ *
+ * Goals: 1) Integrate fully with SELinux.
+ *        2) Minimal run-time overhead:
+ *           a) Minimal when syscall auditing is disabled (audit_enable=0).
+ *           b) Small when syscall auditing is enabled and no audit record
+ *              is generated (defer as much work as possible to record
+ *              generation time):
+ *              i) context is allocated,
+ *              ii) names from getname are stored without a copy, and
+ *              iii) inode information stored from path_lookup.
+ *        3) Ability to disable syscall auditing at boot time (audit=0).
+ *        4) Usable by other parts of the kernel (if audit_log* is called,
+ *           then a syscall record will be generated automatically for the
+ *           current syscall).
+ *        5) Netlink interface to user-space.
+ *        6) Support low-overhead kernel-based filtering to minimize the
+ *           information that must be passed to user-space.
+ *
+ * Example user-space utilities: http://people.redhat.com/faith/audit/
+ */
+
+#include <linux/init.h>
+#include <asm/atomic.h>
+#include <asm/types.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+
+#include <linux/audit.h>
+
+#include <net/sock.h>
+#include <linux/skbuff.h>
+#include <linux/netlink.h>
+
+/* No auditing will take place until audit_initialized != 0.
+ * (Initialization happens after skb_init is called.) */
+static int      audit_initialized;
+
+/* No syscall auditing will take place unless audit_enabled != 0. */
+int             audit_enabled;
+
+/* Default state when kernel boots without any parameters. */
+static int      audit_default;
+
+/* If auditing cannot proceed, audit_failure selects what happens. */
+static int      audit_failure = AUDIT_FAIL_PRINTK;
+
+/* If audit records are to be written to the netlink socket, audit_pid
+ * contains the (non-zero) pid. */
+static int      audit_pid;
+
+/* If audit_limit is non-zero, limit the rate of sending audit records
+ * to that number per second.  This prevents DoS attacks, but results in
+ * audit records being dropped. */
+static int      audit_rate_limit;
+
+/* Number of outstanding audit_buffers allowed. */
+static int      audit_backlog_limit = 64;
+static atomic_t audit_backlog       = ATOMIC_INIT(0);
+
+/* Records can be lost in several ways:
+   0) [suppressed in audit_alloc]
+   1) out of memory in audit_log_start [kmalloc of struct audit_buffer]
+   2) out of memory in audit_log_move [alloc_skb]
+   3) suppressed due to audit_rate_limit
+   4) suppressed due to audit_backlog_limit
+*/
+static atomic_t    audit_lost = ATOMIC_INIT(0);
+
+/* The netlink socket. */
+static struct sock *audit_sock;
+
+/* There are two lists of audit buffers.  The txlist contains audit
+ * buffers that cannot be sent immediately to the netlink device because
+ * we are in an irq context (these are sent later in a tasklet).
+ *
+ * The second list is a list of pre-allocated audit buffers (if more
+ * than AUDIT_MAXFREE are in use, the audit buffer is freed instead of
+ * being placed on the freelist). */
+static DEFINE_SPINLOCK(audit_txlist_lock);
+static DEFINE_SPINLOCK(audit_freelist_lock);
+static int         audit_freelist_count = 0;
+static LIST_HEAD(audit_txlist);
+static LIST_HEAD(audit_freelist);
+
+/* There are three lists of rules -- one to search at task creation
+ * time, one to search at syscall entry time, and another to search at
+ * syscall exit time. */
+static LIST_HEAD(audit_tsklist);
+static LIST_HEAD(audit_entlist);
+static LIST_HEAD(audit_extlist);
+
+/* The netlink socket is only to be read by 1 CPU, which lets us assume
+ * that list additions and deletions never happen simultaneiously in
+ * auditsc.c */
+static DECLARE_MUTEX(audit_netlink_sem);
+
+/* AUDIT_BUFSIZ is the size of the temporary buffer used for formatting
+ * audit records.  Since printk uses a 1024 byte buffer, this buffer
+ * should be at least that large. */
+#define AUDIT_BUFSIZ 1024
+
+/* AUDIT_MAXFREE is the number of empty audit_buffers we keep on the
+ * audit_freelist.  Doing so eliminates many kmalloc/kfree calls. */
+#define AUDIT_MAXFREE  (2*NR_CPUS)
+
+/* The audit_buffer is used when formatting an audit record.  The caller
+ * locks briefly to get the record off the freelist or to allocate the
+ * buffer, and locks briefly to send the buffer to the netlink layer or
+ * to place it on a transmit queue.  Multiple audit_buffers can be in
+ * use simultaneously. */
+struct audit_buffer {
+        struct list_head     list;
+        struct sk_buff_head  sklist;    /* formatted skbs ready to send */
+        struct audit_context *ctx;      /* NULL or associated context */
+        int                  len;       /* used area of tmp */
+        char                 tmp[AUDIT_BUFSIZ];
+
+                                /* Pointer to header and contents */
+        struct nlmsghdr      *nlh;
+        int                  total;
+        int                  type;
+        int                  pid;
+        int                  count; /* Times requeued */
+};
+
+void audit_set_type(struct audit_buffer *ab, int type)
+{
+        ab->type = type;
+}
+
+struct audit_entry {
+        struct list_head  list;
+        struct audit_rule rule;
+};
+
+static void audit_log_end_irq(struct audit_buffer *ab);
+static void audit_log_end_fast(struct audit_buffer *ab);
+
+static void audit_panic(const char *message)
+{
+        switch (audit_failure)
+        {
+        case AUDIT_FAIL_SILENT:
+                break;
+        case AUDIT_FAIL_PRINTK:
+                printk(KERN_ERR "audit: %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;
+}
+
+/* Emit at least 1 message per second, even if audit_rate_check is
+ * throttling. */
+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) {
+                printk(KERN_WARNING
+                       "audit: audit_lost=%d audit_backlog=%d"
+                       " audit_rate_limit=%d audit_backlog_limit=%d\n",
+                       atomic_read(&audit_lost),
+                       atomic_read(&audit_backlog),
+                       audit_rate_limit,
+                       audit_backlog_limit);
+                audit_panic(message);
+        }
+
+}
+
+static int audit_set_rate_limit(int limit)
+{
+        int old          = audit_rate_limit;
+        audit_rate_limit = limit;
+        audit_log(current->audit_context, "audit_rate_limit=%d old=%d",
+                  audit_rate_limit, old);
+        return old;
+}
+
+static int audit_set_backlog_limit(int limit)
+{
+        int old          = audit_backlog_limit;
+        audit_backlog_limit = limit;
+        audit_log(current->audit_context, "audit_backlog_limit=%d old=%d",
+                  audit_backlog_limit, old);
+        return old;
+}
+
+static int audit_set_enabled(int state)
+{
+        int old          = audit_enabled;
+        if (state != 0 && state != 1)
+                return -EINVAL;
+        audit_enabled = state;
+        audit_log(current->audit_context, "audit_enabled=%d old=%d",
+                  audit_enabled, old);
+        return old;
+}
+
+static int audit_set_failure(int state)
+{
+        int old          = audit_failure;
+        if (state != AUDIT_FAIL_SILENT
+            && state != AUDIT_FAIL_PRINTK
+            && state != AUDIT_FAIL_PANIC)
+                return -EINVAL;
+        audit_failure = state;
+        audit_log(current->audit_context, "audit_failure=%d old=%d",
+                  audit_failure, old);
+        return old;
+}
+
+#ifdef CONFIG_NET
+void audit_send_reply(int pid, int seq, int type, int done, int multi,
+                      void *payload, int size)
+{
+        struct sk_buff  *skb;
+        struct nlmsghdr *nlh;
+        int             len = NLMSG_SPACE(size);
+        void            *data;
+        int             flags = multi ? NLM_F_MULTI : 0;
+        int             t     = done  ? NLMSG_DONE  : type;
+
+        skb = alloc_skb(len, GFP_KERNEL);
+        if (!skb)
+                goto nlmsg_failure;
+
+        nlh              = NLMSG_PUT(skb, pid, seq, t, len - sizeof(*nlh));
+        nlh->nlmsg_flags = flags;
+        data             = NLMSG_DATA(nlh);
+        memcpy(data, payload, size);
+        netlink_unicast(audit_sock, skb, pid, MSG_DONTWAIT);
+        return;
+
+nlmsg_failure:                  /* Used by NLMSG_PUT */
+        if (skb)
+                kfree_skb(skb);
+}
+
+/*
+ * Check for appropriate CAP_AUDIT_ capabilities on incoming audit
+ * control messages.
+ */
+static int audit_netlink_ok(kernel_cap_t eff_cap, u16 msg_type)
+{
+        int err = 0;
+
+        switch (msg_type) {
+        case AUDIT_GET:
+        case AUDIT_LIST:
+        case AUDIT_SET:
+        case AUDIT_ADD:
+        case AUDIT_DEL:
+                if (!cap_raised(eff_cap, CAP_AUDIT_CONTROL))
+                        err = -EPERM;
+                break;
+        case AUDIT_USER:
+                if (!cap_raised(eff_cap, CAP_AUDIT_WRITE))
+                        err = -EPERM;
+                break;
+        default:  /* bad msg */
+                err = -EINVAL;
+        }
+
+        return err;
+}
+
+static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
+{
+        u32                     uid, pid, seq;
+        void                    *data;
+        struct audit_status     *status_get, status_set;
+        int                     err;
+        struct audit_buffer     *ab;
+        u16                     msg_type = nlh->nlmsg_type;
+
+        err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
+        if (err)
+                return err;
+
+        pid  = NETLINK_CREDS(skb)->pid;
+        uid  = NETLINK_CREDS(skb)->uid;
+        seq  = nlh->nlmsg_seq;
+        data = NLMSG_DATA(nlh);
+
+        switch (msg_type) {
+        case AUDIT_GET:
+                status_set.enabled       = audit_enabled;
+                status_set.failure       = audit_failure;
+                status_set.pid           = audit_pid;
+                status_set.rate_limit    = audit_rate_limit;
+                status_set.backlog_limit = audit_backlog_limit;
+                status_set.lost          = atomic_read(&audit_lost);
+                status_set.backlog       = atomic_read(&audit_backlog);
+                audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0,
+                                 &status_set, sizeof(status_set));
+                break;
+        case AUDIT_SET:
+                if (nlh->nlmsg_len < sizeof(struct audit_status))
+                        return -EINVAL;
+                status_get   = (struct audit_status *)data;
+                if (status_get->mask & AUDIT_STATUS_ENABLED) {
+                        err = audit_set_enabled(status_get->enabled);
+                        if (err < 0) return err;
+                }
+                if (status_get->mask & AUDIT_STATUS_FAILURE) {
+                        err = audit_set_failure(status_get->failure);
+                        if (err < 0) return err;
+                }
+                if (status_get->mask & AUDIT_STATUS_PID) {
+                        int old   = audit_pid;
+                        audit_pid = status_get->pid;
+                        audit_log(current->audit_context,
+                                  "audit_pid=%d old=%d", audit_pid, old);
+                }
+                if (status_get->mask & AUDIT_STATUS_RATE_LIMIT)
+                        audit_set_rate_limit(status_get->rate_limit);
+                if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT)
+                        audit_set_backlog_limit(status_get->backlog_limit);
+                break;
+        case AUDIT_USER:
+                ab = audit_log_start(NULL);
+                if (!ab)
+                        break;  /* audit_panic has been called */
+                audit_log_format(ab,
+                                 "user pid=%d uid=%d length=%d msg='%.1024s'",
+                                 pid, uid,
+                                 (int)(nlh->nlmsg_len
+                                       - ((char *)data - (char *)nlh)),
+                                 (char *)data);
+                ab->type = AUDIT_USER;
+                ab->pid  = pid;
+                audit_log_end(ab);
+                break;
+        case AUDIT_ADD:
+        case AUDIT_DEL:
+                if (nlh->nlmsg_len < sizeof(struct audit_rule))
+                        return -EINVAL;
+                /* fallthrough */
+        case AUDIT_LIST:
+#ifdef CONFIG_AUDITSYSCALL
+                err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
+                                           uid, seq, data);
+#else
+                err = -EOPNOTSUPP;
+#endif
+                break;
+        default:
+                err = -EINVAL;
+                break;
+        }
+
+        return err < 0 ? err : 0;
+}
+
+/* Get message from skb (based on rtnetlink_rcv_skb).  Each message is
+ * processed by audit_receive_msg.  Malformed skbs with wrong length are
+ * discarded silently.  */
+static int audit_receive_skb(struct sk_buff *skb)
+{
+        int             err;
+        struct nlmsghdr *nlh;
+        u32             rlen;
+
+        while (skb->len >= NLMSG_SPACE(0)) {
+                nlh = (struct nlmsghdr *)skb->data;
+                if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
+                        return 0;
+                rlen = NLMSG_ALIGN(nlh->nlmsg_len);
+                if (rlen > skb->len)
+                        rlen = skb->len;
+                if ((err = audit_receive_msg(skb, nlh))) {
+                        netlink_ack(skb, nlh, err);
+                } else if (nlh->nlmsg_flags & NLM_F_ACK)
+                        netlink_ack(skb, nlh, 0);
+                skb_pull(skb, rlen);
+        }
+        return 0;
+}
+
+/* Receive messages from netlink socket. */
+static void audit_receive(struct sock *sk, int length)
+{
+        struct sk_buff  *skb;
+
+        if (down_trylock(&audit_netlink_sem))
+                return;
+
+                                /* FIXME: this must not cause starvation */
+        while ((skb = skb_dequeue(&sk->sk_receive_queue))) {
+                if (audit_receive_skb(skb) && skb->len)
+                        skb_queue_head(&sk->sk_receive_queue, skb);
+                else
+                        kfree_skb(skb);
+        }
+        up(&audit_netlink_sem);
+}
+
+/* Move data from tmp buffer into an skb.  This is an extra copy, and
+ * that is unfortunate.  However, the copy will only occur when a record
+ * is being written to user space, which is already a high-overhead
+ * operation.  (Elimination of the copy is possible, for example, by
+ * writing directly into a pre-allocated skb, at the cost of wasting
+ * memory. */
+static void audit_log_move(struct audit_buffer *ab)
+{
+        struct sk_buff  *skb;
+        char            *start;
+        int             extra = ab->nlh ? 0 : NLMSG_SPACE(0);
+
+        /* possible resubmission */
+        if (ab->len == 0)
+                return;
+
+        skb = skb_peek(&ab->sklist);
+        if (!skb || skb_tailroom(skb) <= ab->len + extra) {
+                skb = alloc_skb(2 * ab->len + extra, GFP_ATOMIC);
+                if (!skb) {
+                        ab->len = 0; /* Lose information in ab->tmp */
+                        audit_log_lost("out of memory in audit_log_move");
+                        return;
+                }
+                __skb_queue_tail(&ab->sklist, skb);
+                if (!ab->nlh)
+                        ab->nlh = (struct nlmsghdr *)skb_put(skb,
+                                                             NLMSG_SPACE(0));
+        }
+        start = skb_put(skb, ab->len);
+        memcpy(start, ab->tmp, ab->len);
+        ab->len = 0;
+}
+
+/* Iterate over the skbuff in the audit_buffer, sending their contents
+ * to user space. */
+static inline int audit_log_drain(struct audit_buffer *ab)
+{
+        struct sk_buff *skb;
+
+        while ((skb = skb_dequeue(&ab->sklist))) {
+                int retval = 0;
+
+                if (audit_pid) {
+                        if (ab->nlh) {
+                                ab->nlh->nlmsg_len   = ab->total;
+                                ab->nlh->nlmsg_type  = ab->type;
+                                ab->nlh->nlmsg_flags = 0;
+                                ab->nlh->nlmsg_seq   = 0;
+                                ab->nlh->nlmsg_pid   = ab->pid;
+                        }
+                        skb_get(skb); /* because netlink_* frees */
+                        retval = netlink_unicast(audit_sock, skb, audit_pid,
+                                                 MSG_DONTWAIT);
+                }
+                if (retval == -EAGAIN && ab->count < 5) {
+                        ++ab->count;
+                        skb_queue_tail(&ab->sklist, skb);
+                        audit_log_end_irq(ab);
+                        return 1;
+                }
+                if (retval < 0) {
+                        if (retval == -ECONNREFUSED) {
+                                printk(KERN_ERR
+                                       "audit: *NO* daemon at audit_pid=%d\n",
+                                       audit_pid);
+                                audit_pid = 0;
+                        } else
+                                audit_log_lost("netlink socket too busy");
+                }
+                if (!audit_pid) { /* No daemon */
+                        int offset = ab->nlh ? NLMSG_SPACE(0) : 0;
+                        int len    = skb->len - offset;
+                        printk(KERN_ERR "%*.*s\n",
+                               len, len, skb->data + offset);
+                }
+                kfree_skb(skb);
+                ab->nlh = NULL;
+        }
+        return 0;
+}
+
+/* Initialize audit support at boot time. */
+static int __init audit_init(void)
+{
+        printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
+               audit_default ? "enabled" : "disabled");
+        audit_sock = netlink_kernel_create(NETLINK_AUDIT, audit_receive);
+        if (!audit_sock)
+                audit_panic("cannot initialize netlink socket");
+
+        audit_initialized = 1;
+        audit_enabled = audit_default;
+        audit_log(NULL, "initialized");
+        return 0;
+}
+
+#else
+/* Without CONFIG_NET, we have no skbuffs.  For now, print what we have
+ * in the buffer. */
+static void audit_log_move(struct audit_buffer *ab)
+{
+        printk(KERN_ERR "%*.*s\n", ab->len, ab->len, ab->tmp);
+        ab->len = 0;
+}
+
+static inline int audit_log_drain(struct audit_buffer *ab)
+{
+        return 0;
+}
+
+/* Initialize audit support at boot time. */
+int __init audit_init(void)
+{
+        printk(KERN_INFO "audit: initializing WITHOUT netlink support\n");
+        audit_sock = NULL;
+        audit_pid  = 0;
+
+        audit_initialized = 1;
+        audit_enabled = audit_default;
+        audit_log(NULL, "initialized");
+        return 0;
+}
+#endif
+
+__initcall(audit_init);
+
+/* Process kernel command-line parameter at boot time.  audit=0 or audit=1. */
+static int __init audit_enable(char *str)
+{
+        audit_default = !!simple_strtol(str, NULL, 0);
+        printk(KERN_INFO "audit: %s%s\n",
+               audit_default ? "enabled" : "disabled",
+               audit_initialized ? "" : " (after initialization)");
+        if (audit_initialized)
+                audit_enabled = audit_default;
+        return 0;
+}
+
+__setup("audit=", audit_enable);
+
+
+/* Obtain an audit buffer.  This routine does locking to obtain the
+ * audit buffer, but then no locking is required for calls to
+ * audit_log_*format.  If the tsk is a task that is currently in a
+ * syscall, then the syscall is marked as auditable and an audit record
+ * will be written at syscall exit.  If there is no associated task, tsk
+ * should be NULL. */
+struct audit_buffer *audit_log_start(struct audit_context *ctx)
+{
+        struct audit_buffer     *ab     = NULL;
+        unsigned long           flags;
+        struct timespec         t;
+        int                     serial  = 0;
+
+        if (!audit_initialized)
+                return NULL;
+
+        if (audit_backlog_limit
+            && atomic_read(&audit_backlog) > audit_backlog_limit) {
+                if (audit_rate_check())
+                        printk(KERN_WARNING
+                               "audit: audit_backlog=%d > "
+                               "audit_backlog_limit=%d\n",
+                               atomic_read(&audit_backlog),
+                               audit_backlog_limit);
+                audit_log_lost("backlog limit exceeded");
+                return NULL;
+        }
+
+        spin_lock_irqsave(&audit_freelist_lock, flags);
+        if (!list_empty(&audit_freelist)) {
+                ab = list_entry(audit_freelist.next,
+                                struct audit_buffer, list);
+                list_del(&ab->list);
+                --audit_freelist_count;
+        }
+        spin_unlock_irqrestore(&audit_freelist_lock, flags);
+
+        if (!ab)
+                ab = kmalloc(sizeof(*ab), GFP_ATOMIC);
+        if (!ab) {
+                audit_log_lost("out of memory in audit_log_start");
+                return NULL;
+        }
+
+        atomic_inc(&audit_backlog);
+        skb_queue_head_init(&ab->sklist);
+
+        ab->ctx   = ctx;
+        ab->len   = 0;
+        ab->nlh   = NULL;
+        ab->total = 0;
+        ab->type  = AUDIT_KERNEL;
+        ab->pid   = 0;
+        ab->count = 0;
+
+#ifdef CONFIG_AUDITSYSCALL
+        if (ab->ctx)
+                audit_get_stamp(ab->ctx, &t, &serial);
+        else
+#endif
+                t = CURRENT_TIME;
+
+        audit_log_format(ab, "audit(%lu.%03lu:%u): ",
+                         t.tv_sec, t.tv_nsec/1000000, serial);
+        return ab;
+}
+
+
+/* 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;
+
+        if (!ab)
+                return;
+
+        avail = sizeof(ab->tmp) - ab->len;
+        if (avail <= 0) {
+                audit_log_move(ab);
+                avail = sizeof(ab->tmp) - ab->len;
+        }
+        len   = vsnprintf(ab->tmp + ab->len, 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. */
+                audit_log_move(ab);
+                avail = sizeof(ab->tmp) - ab->len;
+                len   = vsnprintf(ab->tmp + ab->len, avail, fmt, args);
+        }
+        ab->len   += (len < avail) ? len : avail;
+        ab->total += (len < avail) ? len : avail;
+}
+
+/* Format a message into the audit buffer.  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);
+}
+
+/* This is a helper-function to print the d_path without using a static
+ * buffer or allocating another buffer in addition to the one in
+ * audit_buffer. */
+void audit_log_d_path(struct audit_buffer *ab, const char *prefix,
+                      struct dentry *dentry, struct vfsmount *vfsmnt)
+{
+        char *p;
+        int  len, avail;
+
+        if (prefix) audit_log_format(ab, " %s", prefix);
+
+        if (ab->len > 128)
+                audit_log_move(ab);
+        avail = sizeof(ab->tmp) - ab->len;
+        p = d_path(dentry, vfsmnt, ab->tmp + ab->len, avail);
+        if (IS_ERR(p)) {
+                /* FIXME: can we save some information here? */
+                audit_log_format(ab, "<toolong>");
+        } else {
+                                /* path isn't at start of buffer */
+                len        = (ab->tmp + sizeof(ab->tmp) - 1) - p;
+                memmove(ab->tmp + ab->len, p, len);
+                ab->len   += len;
+                ab->total += len;
+        }
+}
+
+/* Remove queued messages from the audit_txlist and send them to userspace. */
+static void audit_tasklet_handler(unsigned long arg)
+{
+        LIST_HEAD(list);
+        struct audit_buffer *ab;
+        unsigned long       flags;
+
+        spin_lock_irqsave(&audit_txlist_lock, flags);
+        list_splice_init(&audit_txlist, &list);
+        spin_unlock_irqrestore(&audit_txlist_lock, flags);
+
+        while (!list_empty(&list)) {
+                ab = list_entry(list.next, struct audit_buffer, list);
+                list_del(&ab->list);
+                audit_log_end_fast(ab);
+        }
+}
+
+static DECLARE_TASKLET(audit_tasklet, audit_tasklet_handler, 0);
+
+/* The netlink_* functions cannot be called inside an irq context, so
+ * the audit buffer is places on a queue and a tasklet is scheduled to
+ * remove them from the queue outside the irq context.  May be called in
+ * any context. */
+static void audit_log_end_irq(struct audit_buffer *ab)
+{
+        unsigned long flags;
+
+        if (!ab)
+                return;
+        spin_lock_irqsave(&audit_txlist_lock, flags);
+        list_add_tail(&ab->list, &audit_txlist);
+        spin_unlock_irqrestore(&audit_txlist_lock, flags);
+
+        tasklet_schedule(&audit_tasklet);
+}
+
+/* Send the message in the audit buffer directly to user space.  May not
+ * be called in an irq context. */
+static void audit_log_end_fast(struct audit_buffer *ab)
+{
+        unsigned long flags;
+
+        BUG_ON(in_irq());
+        if (!ab)
+                return;
+        if (!audit_rate_check()) {
+                audit_log_lost("rate limit exceeded");
+        } else {
+                audit_log_move(ab);
+                if (audit_log_drain(ab))
+                        return;
+        }
+
+        atomic_dec(&audit_backlog);
+        spin_lock_irqsave(&audit_freelist_lock, flags);
+        if (++audit_freelist_count > AUDIT_MAXFREE)
+                kfree(ab);
+        else
+                list_add(&ab->list, &audit_freelist);
+        spin_unlock_irqrestore(&audit_freelist_lock, flags);
+}
+
+/* Send or queue the message in the audit buffer, depending on the
+ * current context.  (A convenience function that may be called in any
+ * context.) */
+void audit_log_end(struct audit_buffer *ab)
+{
+        if (in_irq())
+                audit_log_end_irq(ab);
+        else
+                audit_log_end_fast(ab);
+}
+
+/* Log an audit record.  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, const char *fmt, ...)
+{
+        struct audit_buffer *ab;
+        va_list args;
+
+        ab = audit_log_start(ctx);
+        if (ab) {
+                va_start(args, fmt);
+                audit_log_vformat(ab, fmt, args);
+                va_end(args);
+                audit_log_end(ab);
+        }
+}