/* 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 2003-2004 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 * * 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/sgrubb/audit/ */ #include #include #include #include #include #include #include #include #include #include #include /* 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. */ 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; /* The identity of the user shutting down the audit system. */ uid_t audit_sig_uid = -1; pid_t audit_sig_pid = -1; /* 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; /* The audit_freelist is a list of pre-allocated audit buffers (if more * than AUDIT_MAXFREE are in use, the audit buffer is freed instead of * being placed on the freelist). */ static DEFINE_SPINLOCK(audit_freelist_lock); static int audit_freelist_count = 0; static LIST_HEAD(audit_freelist); static struct sk_buff_head audit_skb_queue; static struct task_struct *kauditd_task; static DECLARE_WAIT_QUEUE_HEAD(kauditd_wait); /* The netlink socket is only to be read by 1 CPU, which lets us assume * that list additions and deletions never happen simultaneously 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 *skb; /* formatted skb ready to send */ struct audit_context *ctx; /* NULL or associated context */ }; static void audit_set_pid(struct audit_buffer *ab, pid_t pid) { struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data; nlh->nlmsg_pid = pid; } struct audit_entry { struct list_head list; struct audit_rule rule; }; 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_rate_limit=%d audit_backlog_limit=%d\n", atomic_read(&audit_lost), audit_rate_limit, audit_backlog_limit); audit_panic(message); } } static int audit_set_rate_limit(int limit, uid_t loginuid) { int old = audit_rate_limit; audit_rate_limit = limit; audit_log(NULL, AUDIT_CONFIG_CHANGE, "audit_rate_limit=%d old=%d by auid=%u", audit_rate_limit, old, loginuid); return old; } static int audit_set_backlog_limit(int limit, uid_t loginuid) { int old = audit_backlog_limit; audit_backlog_limit = limit; audit_log(NULL, AUDIT_CONFIG_CHANGE, "audit_backlog_limit=%d old=%d by auid=%u", audit_backlog_limit, old, loginuid); return old; } static int audit_set_enabled(int state, uid_t loginuid) { int old = audit_enabled; if (state != 0 && state != 1) return -EINVAL; audit_enabled = state; audit_log(NULL, AUDIT_CONFIG_CHANGE, "audit_enabled=%d old=%d by auid=%u", audit_enabled, old, loginuid); return old; } static int audit_set_failure(int state, uid_t loginuid) { int old = audit_failure; if (state != AUDIT_FAIL_SILENT && state != AUDIT_FAIL_PRINTK && state != AUDIT_FAIL_PANIC) return -EINVAL; audit_failure = state; audit_log(NULL, AUDIT_CONFIG_CHANGE, "audit_failure=%d old=%d by auid=%u", audit_failure, old, loginuid); return old; } int kauditd_thread(void *dummy) { struct sk_buff *skb; while (1) { skb = skb_dequeue(&audit_skb_queue); if (skb) { if (audit_pid) { int err = netlink_unicast(audit_sock, skb, audit_pid, 0); if (err < 0) { BUG_ON(err != -ECONNREFUSED); /* Shoudn't happen */ printk(KERN_ERR "audit: *NO* daemon at audit_pid=%d\n", audit_pid); audit_pid = 0; } } else { printk(KERN_ERR "%s\n", skb->data + NLMSG_SPACE(0)); kfree_skb(skb); } } else { DECLARE_WAITQUEUE(wait, current); set_current_state(TASK_INTERRUPTIBLE); add_wait_queue(&kauditd_wait, &wait); if (!skb_queue_len(&audit_skb_queue)) schedule(); __set_current_state(TASK_RUNNING); remove_wait_queue(&kauditd_wait, &wait); } } } 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) return; nlh = NLMSG_PUT(skb, pid, seq, t, size); nlh->nlmsg_flags = flags; data = NLMSG_DATA(nlh); memcpy(data, payload, size); /* Ignore failure. It'll only happen if the sender goes away, because our timeout is set to infinite. */ netlink_unicast(audit_sock, skb, pid, 0); 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: case AUDIT_SIGNAL_INFO: if (!cap_raised(eff_cap, CAP_AUDIT_CONTROL)) err = -EPERM; break; case AUDIT_USER: case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG: 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; uid_t loginuid; /* loginuid of sender */ struct audit_sig_info sig_data; struct task_struct *tsk; err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type); if (err) return err; /* As soon as there's any sign of userspace auditd, start kauditd to talk to it */ if (!kauditd_task) kauditd_task = kthread_run(kauditd_thread, NULL, "kauditd"); if (IS_ERR(kauditd_task)) { err = PTR_ERR(kauditd_task); kauditd_task = NULL; return err; } pid = NETLINK_CREDS(skb)->pid; uid = NETLINK_CREDS(skb)->uid; loginuid = NETLINK_CB(skb).loginuid; seq = nlh->nlmsg_seq; data = NLMSG_DATA(nlh); switch (msg_type) { case AUDIT_GET: status_set.enabled = audit_enabled; status_set.failure = audit_failure; status_set.pid = audit_pid; status_set.rate_limit = audit_rate_limit; status_set.backlog_limit = audit_backlog_limit; status_set.lost = atomic_read(&audit_lost); status_set.backlog = skb_queue_len(&audit_skb_queue); audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0, &status_set, sizeof(status_set)); break; case AUDIT_SET: if (nlh->nlmsg_len < sizeof(struct audit_status)) return -EINVAL; status_get = (struct audit_status *)data; if (status_get->mask & AUDIT_STATUS_ENABLED) { err = audit_set_enabled(status_get->enabled, loginuid); if (err < 0) return err; } if (status_get->mask & AUDIT_STATUS_FAILURE) { err = audit_set_failure(status_get->failure, loginuid); if (err < 0) return err; } if (status_get->mask & AUDIT_STATUS_PID) { int old = audit_pid; audit_pid = status_get->pid; audit_log(NULL, AUDIT_CONFIG_CHANGE, "audit_pid=%d old=%d by auid=%u", audit_pid, old, loginuid); } if (status_get->mask & AUDIT_STATUS_RATE_LIMIT) audit_set_rate_limit(status_get->rate_limit, loginuid); if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT) audit_set_backlog_limit(status_get->backlog_limit, loginuid); break; case AUDIT_USER: case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG: read_lock(&tasklist_lock); tsk = find_task_by_pid(pid); if (tsk) get_task_struct(tsk); read_unlock(&tasklist_lock); if (!tsk) return -ESRCH; if (audit_filter_user(tsk, msg_type)) { ab = audit_log_start(NULL, msg_type); if (ab) { audit_log_format(ab, "user pid=%d uid=%u auid=%u msg='%.1024s'", pid, uid, loginuid, (char *)data); audit_set_pid(ab, pid); audit_log_end(ab); } } put_task_struct(tsk); break; case AUDIT_ADD: case AUDIT_DEL: if (nlh->nlmsg_len < sizeof(struct audit_rule)) return -EINVAL; /* fallthrough */ case AUDIT_LIST: err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid, uid, seq, data, loginuid); break; case AUDIT_SIGNAL_INFO: sig_data.uid = audit_sig_uid; sig_data.pid = audit_sig_pid; audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_SIGNAL_INFO, 0, 0, &sig_data, sizeof(sig_data)); 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 void 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; 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); } } /* Receive messages from netlink socket. */ static void audit_receive(struct sock *sk, int length) { struct sk_buff *skb; unsigned int qlen; down(&audit_netlink_sem); for (qlen = skb_queue_len(&sk->sk_receive_queue); qlen; qlen--) { skb = skb_dequeue(&sk->sk_receive_queue); audit_receive_skb(skb); kfree_skb(skb); } up(&audit_netlink_sem); } /* 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_sock->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT; skb_queue_head_init(&audit_skb_queue); audit_initialized = 1; audit_enabled = audit_default; audit_log(NULL, AUDIT_KERNEL, "initialized"); return 0; } __initcall(audit_init); /* Process kernel command-line parameter at boot time. audit=0 or audit=1. */ static int __init audit_enable(char *str) { audit_default = !!simple_strtol(str, NULL, 0); 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); static void audit_buffer_free(struct audit_buffer *ab) { unsigned long flags; if (!ab) return; if (ab->skb) kfree_skb(ab->skb); spin_lock_irqsave(&audit_freelist_lock, flags); if (++audit_freelist_count > AUDIT_MAXFREE) kfree(ab); else list_add(&ab->list, &audit_freelist); spin_unlock_irqrestore(&audit_freelist_lock, flags); } static struct audit_buffer * audit_buffer_alloc(struct audit_context *ctx, int gfp_mask, int type) { unsigned long flags; struct audit_buffer *ab = NULL; struct nlmsghdr *nlh; spin_lock_irqsave(&audit_freelist_lock, flags); if (!list_empty(&audit_freelist)) { ab = list_entry(audit_freelist.next, struct audit_buffer, list); list_del(&ab->list); --audit_freelist_count; } spin_unlock_irqrestore(&audit_freelist_lock, flags); if (!ab) { ab = kmalloc(sizeof(*ab), gfp_mask); if (!ab) goto err; } ab->skb = alloc_skb(AUDIT_BUFSIZ, gfp_mask); if (!ab->skb) goto err; ab->ctx = ctx; nlh = (struct nlmsghdr *)skb_put(ab->skb, NLMSG_SPACE(0)); nlh->nlmsg_type = type; nlh->nlmsg_flags = 0; nlh->nlmsg_pid = 0; nlh->nlmsg_seq = 0; return ab; err: audit_buffer_free(ab); return NULL; } /* 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. * * Atomic values are only guaranteed to be 24-bit, so we count down. * * 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(0xffffff); unsigned int a, b; do { a = atomic_read(&serial); if (atomic_dec_and_test(&serial)) atomic_set(&serial, 0xffffff); b = atomic_read(&serial); } while (b != a - 1); return 0xffffff - b; } static inline void audit_get_stamp(struct audit_context *ctx, struct timespec *t, unsigned int *serial) { if (ctx) auditsc_get_stamp(ctx, t, serial); else { *t = CURRENT_TIME; *serial = audit_serial(); } } /* Obtain an audit buffer. This routine does locking to obtain the * audit buffer, but then no locking is required for calls to * audit_log_*format. If the tsk is a task that is currently in a * syscall, then the syscall is marked as auditable and an audit record * will be written at syscall exit. If there is no associated task, tsk * should be NULL. */ struct audit_buffer *audit_log_start(struct audit_context *ctx, int type) { struct audit_buffer *ab = NULL; struct timespec t; unsigned int serial; if (!audit_initialized) return NULL; if (audit_backlog_limit && skb_queue_len(&audit_skb_queue) > audit_backlog_limit) { if (audit_rate_check()) printk(KERN_WARNING "audit: audit_backlog=%d > " "audit_backlog_limit=%d\n", skb_queue_len(&audit_skb_queue), audit_backlog_limit); audit_log_lost("backlog limit exceeded"); return NULL; } ab = audit_buffer_alloc(ctx, GFP_ATOMIC, type); if (!ab) { audit_log_lost("out of memory in audit_log_start"); return NULL; } audit_get_stamp(ab->ctx, &t, &serial); audit_log_format(ab, "audit(%lu.%03lu:%u): ", t.tv_sec, t.tv_nsec/1000000, serial); return ab; } /** * audit_expand - expand skb in the audit buffer * @ab: audit_buffer * * 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 ret = pskb_expand_head(skb, skb_headroom(skb), extra, GFP_ATOMIC); if (ret < 0) { audit_log_lost("out of memory in audit_expand"); return 0; } return skb_tailroom(skb); } /* 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, avail, fmt, args); if (len >= avail) { /* The printk buffer is 1024 bytes long, so if we get * here and AUDIT_BUFSIZ is at least 1024, then we can * log everything that printk could have logged. */ avail = audit_expand(ab, max_t(unsigned, AUDIT_BUFSIZ, 1+len-avail)); if (!avail) goto out; len = vsnprintf(skb->tail, avail, fmt, args2); } if (len > 0) skb_put(skb, len); out: return; } /* 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 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_hex(struct audit_buffer *ab, const unsigned char *buf, size_t len) { int i, avail, new_len; unsigned char *ptr; struct sk_buff *skb; static const unsigned char *hex = "0123456789ABCDEF"; 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; for (i=0; i>4]; /* Upper nibble */ *ptr++ = hex[buf[i] & 0x0F]; /* Lower nibble */ } *ptr = 0; skb_put(skb, len << 1); /* new string is twice the old string */ } /* 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). */ void audit_log_untrustedstring(struct audit_buffer *ab, const char *string) { const unsigned char *p = string; while (*p) { if (*p == '"' || *p < 0x21 || *p > 0x7f) { audit_log_hex(ab, string, strlen(string)); return; } p++; } audit_log_format(ab, "\"%s\"", string); } /* This is a helper-function to print the escaped d_path */ void audit_log_d_path(struct audit_buffer *ab, const char *prefix, struct dentry *dentry, struct vfsmount *vfsmnt) { char *p, *path; if (prefix) audit_log_format(ab, " %s", prefix); /* We will allow 11 spaces for ' (deleted)' to be appended */ path = kmalloc(PATH_MAX+11, GFP_KERNEL); if (!path) { audit_log_format(ab, ""); return; } p = d_path(dentry, vfsmnt, path, 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, ""); } else audit_log_untrustedstring(ab, p); kfree(path); } /* 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. */ void audit_log_end(struct audit_buffer *ab) { if (!ab) return; if (!audit_rate_check()) { audit_log_lost("rate limit exceeded"); } else { if (audit_pid) { struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data; nlh->nlmsg_len = ab->skb->len - NLMSG_SPACE(0); skb_queue_tail(&audit_skb_queue, ab->skb); ab->skb = NULL; wake_up_interruptible(&kauditd_wait); } else { printk("%s\n", ab->skb->data + NLMSG_SPACE(0)); } } audit_buffer_free(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, int type, const char *fmt, ...) { struct audit_buffer *ab; va_list args; ab = audit_log_start(ctx, type); if (ab) { va_start(args, fmt); audit_log_vformat(ab, fmt, args); va_end(args); audit_log_end(ab); } }