1 /* audit.c -- Auditing support -*- linux-c -*-
2 * Gateway between the kernel (e.g., selinux) and the user-space audit daemon.
3 * System-call specific features have moved to auditsc.c
4 *
5 * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
6 * All Rights Reserved.
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
21 *
22 * Written by Rickard E. (Rik) Faith <faith@redhat.com>
23 *
24 * Goals: 1) Integrate fully with SELinux.
25 * 2) Minimal run-time overhead:
26 * a) Minimal when syscall auditing is disabled (audit_enable=0).
27 * b) Small when syscall auditing is enabled and no audit record
28 * is generated (defer as much work as possible to record
29 * generation time):
30 * i) context is allocated,
31 * ii) names from getname are stored without a copy, and
32 * iii) inode information stored from path_lookup.
33 * 3) Ability to disable syscall auditing at boot time (audit=0).
34 * 4) Usable by other parts of the kernel (if audit_log* is called,
35 * then a syscall record will be generated automatically for the
36 * current syscall).
37 * 5) Netlink interface to user-space.
38 * 6) Support low-overhead kernel-based filtering to minimize the
39 * information that must be passed to user-space.
40 *
41 * Example user-space utilities: http://people.redhat.com/faith/audit/
42 */
43
44 #include <linux/init.h>
45 #include <asm/atomic.h>
46 #include <asm/types.h>
47 #include <linux/mm.h>
48 #include <linux/module.h>
49
50 #include <linux/audit.h>
51
52 #include <net/sock.h>
53 #include <linux/skbuff.h>
54 #include <linux/netlink.h>
55
56 /* No auditing will take place until audit_initialized != 0.
57 * (Initialization happens after skb_init is called.) */
58 static int audit_initialized;
59
60 /* No syscall auditing will take place unless audit_enabled != 0. */
61 int audit_enabled;
62
63 /* Default state when kernel boots without any parameters. */
64 static int audit_default;
65
66 /* If auditing cannot proceed, audit_failure selects what happens. */
67 static int audit_failure = AUDIT_FAIL_PRINTK;
68
69 /* If audit records are to be written to the netlink socket, audit_pid
70 * contains the (non-zero) pid. */
71 static int audit_pid;
72
73 /* If audit_limit is non-zero, limit the rate of sending audit records
74 * to that number per second. This prevents DoS attacks, but results in
75 * audit records being dropped. */
76 static int audit_rate_limit;
77
78 /* Number of outstanding audit_buffers allowed. */
79 static int audit_backlog_limit = 64;
80 static atomic_t audit_backlog = ATOMIC_INIT(0);
81
82 /* Records can be lost in several ways:
83 0) [suppressed in audit_alloc]
84 1) out of memory in audit_log_start [kmalloc of struct audit_buffer]
85 2) out of memory in audit_log_move [alloc_skb]
86 3) suppressed due to audit_rate_limit
87 4) suppressed due to audit_backlog_limit
88 */
89 static atomic_t audit_lost = ATOMIC_INIT(0);
90
91 /* The netlink socket. */
92 static struct sock *audit_sock;
93
94 /* There are two lists of audit buffers. The txlist contains audit
95 * buffers that cannot be sent immediately to the netlink device because
96 * we are in an irq context (these are sent later in a tasklet).
97 *
98 * The second list is a list of pre-allocated audit buffers (if more
99 * than AUDIT_MAXFREE are in use, the audit buffer is freed instead of
100 * being placed on the freelist). */
101 static DEFINE_SPINLOCK(audit_txlist_lock);
102 static DEFINE_SPINLOCK(audit_freelist_lock);
103 static int audit_freelist_count = 0;
104 static LIST_HEAD(audit_txlist);
105 static LIST_HEAD(audit_freelist);
106
107 /* There are three lists of rules -- one to search at task creation
108 * time, one to search at syscall entry time, and another to search at
109 * syscall exit time. */
110 static LIST_HEAD(audit_tsklist);
111 static LIST_HEAD(audit_entlist);
112 static LIST_HEAD(audit_extlist);
113
114 /* The netlink socket is only to be read by 1 CPU, which lets us assume
115 * that list additions and deletions never happen simultaneiously in
116 * auditsc.c */
117 static DECLARE_MUTEX(audit_netlink_sem);
118
119 /* AUDIT_BUFSIZ is the size of the temporary buffer used for formatting
120 * audit records. Since printk uses a 1024 byte buffer, this buffer
121 * should be at least that large. */
122 #define AUDIT_BUFSIZ 1024
123
124 /* AUDIT_MAXFREE is the number of empty audit_buffers we keep on the
125 * audit_freelist. Doing so eliminates many kmalloc/kfree calls. */
126 #define AUDIT_MAXFREE (2*NR_CPUS)
127
128 /* The audit_buffer is used when formatting an audit record. The caller
129 * locks briefly to get the record off the freelist or to allocate the
130 * buffer, and locks briefly to send the buffer to the netlink layer or
131 * to place it on a transmit queue. Multiple audit_buffers can be in
132 * use simultaneously. */
133 struct audit_buffer {
134 struct list_head list;
135 struct sk_buff_head sklist; /* formatted skbs ready to send */
136 struct audit_context *ctx; /* NULL or associated context */
137 int len; /* used area of tmp */
138 char tmp[AUDIT_BUFSIZ];
139
140 /* Pointer to header and contents */
141 struct nlmsghdr *nlh;
142 int total;
143 int type;
144 int pid;
145 int count; /* Times requeued */
146 };
147
148 void audit_set_type(struct audit_buffer *ab, int type)
149 {
150 ab->type = type;
151 }
152
153 struct audit_entry {
154 struct list_head list;
155 struct audit_rule rule;
156 };
157
158 static void audit_panic(const char *message)
159 {
160 switch (audit_failure)
161 {
162 case AUDIT_FAIL_SILENT:
163 break;
164 case AUDIT_FAIL_PRINTK:
165 printk(KERN_ERR "audit: %s\n", message);
166 break;
167 case AUDIT_FAIL_PANIC:
168 panic("audit: %s\n", message);
169 break;
170 }
171 }
172
173 static inline int audit_rate_check(void)
174 {
175 static unsigned long last_check = 0;
176 static int messages = 0;
177 static DEFINE_SPINLOCK(lock);
178 unsigned long flags;
179 unsigned long now;
180 unsigned long elapsed;
181 int retval = 0;
182
183 if (!audit_rate_limit) return 1;
184
185 spin_lock_irqsave(&lock, flags);
186 if (++messages < audit_rate_limit) {
187 retval = 1;
188 } else {
189 now = jiffies;
190 elapsed = now - last_check;
191 if (elapsed > HZ) {
192 last_check = now;
193 messages = 0;
194 retval = 1;
195 }
196 }
197 spin_unlock_irqrestore(&lock, flags);
198
199 return retval;
200 }
201
202 /* Emit at least 1 message per second, even if audit_rate_check is
203 * throttling. */
204 void audit_log_lost(const char *message)
205 {
206 static unsigned long last_msg = 0;
207 static DEFINE_SPINLOCK(lock);
208 unsigned long flags;
209 unsigned long now;
210 int print;
211
212 atomic_inc(&audit_lost);
213
214 print = (audit_failure == AUDIT_FAIL_PANIC || !audit_rate_limit);
215
216 if (!print) {
217 spin_lock_irqsave(&lock, flags);
218 now = jiffies;
219 if (now - last_msg > HZ) {
220 print = 1;
221 last_msg = now;
222 }
223 spin_unlock_irqrestore(&lock, flags);
224 }
225
226 if (print) {
227 printk(KERN_WARNING
228 "audit: audit_lost=%d audit_backlog=%d"
229 " audit_rate_limit=%d audit_backlog_limit=%d\n",
230 atomic_read(&audit_lost),
231 atomic_read(&audit_backlog),
232 audit_rate_limit,
233 audit_backlog_limit);
234 audit_panic(message);
235 }
236
237 }
238
239 int audit_set_rate_limit(int limit)
240 {
241 int old = audit_rate_limit;
242 audit_rate_limit = limit;
243 audit_log(current->audit_context, "audit_rate_limit=%d old=%d",
244 audit_rate_limit, old);
245 return old;
246 }
247
248 int audit_set_backlog_limit(int limit)
249 {
250 int old = audit_backlog_limit;
251 audit_backlog_limit = limit;
252 audit_log(current->audit_context, "audit_backlog_limit=%d old=%d",
253 audit_backlog_limit, old);
254 return old;
255 }
256
257 int audit_set_enabled(int state)
258 {
259 int old = audit_enabled;
260 if (state != 0 && state != 1)
261 return -EINVAL;
262 audit_enabled = state;
263 audit_log(current->audit_context, "audit_enabled=%d old=%d",
264 audit_enabled, old);
265 return old;
266 }
267
268 int audit_set_failure(int state)
269 {
270 int old = audit_failure;
271 if (state != AUDIT_FAIL_SILENT
272 && state != AUDIT_FAIL_PRINTK
273 && state != AUDIT_FAIL_PANIC)
274 return -EINVAL;
275 audit_failure = state;
276 audit_log(current->audit_context, "audit_failure=%d old=%d",
277 audit_failure, old);
278 return old;
279 }
280
281 #ifdef CONFIG_NET
282 void audit_send_reply(int pid, int seq, int type, int done, int multi,
283 void *payload, int size)
284 {
285 struct sk_buff *skb;
286 struct nlmsghdr *nlh;
287 int len = NLMSG_SPACE(size);
288 void *data;
289 int flags = multi ? NLM_F_MULTI : 0;
290 int t = done ? NLMSG_DONE : type;
291
292 skb = alloc_skb(len, GFP_KERNEL);
293 if (!skb)
294 goto nlmsg_failure;
295
296 nlh = NLMSG_PUT(skb, pid, seq, t, len - sizeof(*nlh));
297 nlh->nlmsg_flags = flags;
298 data = NLMSG_DATA(nlh);
299 memcpy(data, payload, size);
300 netlink_unicast(audit_sock, skb, pid, MSG_DONTWAIT);
301 return;
302
303 nlmsg_failure: /* Used by NLMSG_PUT */
304 if (skb)
305 kfree_skb(skb);
306 }
307
308 /*
309 * Check for appropriate CAP_AUDIT_ capabilities on incoming audit
310 * control messages.
311 */
312 static int audit_netlink_ok(kernel_cap_t eff_cap, u16 msg_type)
313 {
314 int err = 0;
315
316 switch (msg_type) {
317 case AUDIT_GET:
318 case AUDIT_LIST:
319 case AUDIT_SET:
320 case AUDIT_ADD:
321 case AUDIT_DEL:
322 if (!cap_raised(eff_cap, CAP_AUDIT_CONTROL))
323 err = -EPERM;
324 break;
325 case AUDIT_USER:
326 if (!cap_raised(eff_cap, CAP_AUDIT_WRITE))
327 err = -EPERM;
328 break;
329 default: /* bad msg */
330 err = -EINVAL;
331 }
332
333 return err;
334 }
335
336 static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
337 {
338 u32 uid, pid, seq;
339 void *data;
340 struct audit_status *status_get, status_set;
341 int err;
342 struct audit_buffer *ab;
343 u16 msg_type = nlh->nlmsg_type;
344
345 err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
346 if (err)
347 return err;
348
349 pid = NETLINK_CREDS(skb)->pid;
350 uid = NETLINK_CREDS(skb)->uid;
351 seq = nlh->nlmsg_seq;
352 data = NLMSG_DATA(nlh);
353
354 switch (msg_type) {
355 case AUDIT_GET:
356 status_set.enabled = audit_enabled;
357 status_set.failure = audit_failure;
358 status_set.pid = audit_pid;
359 status_set.rate_limit = audit_rate_limit;
360 status_set.backlog_limit = audit_backlog_limit;
361 status_set.lost = atomic_read(&audit_lost);
362 status_set.backlog = atomic_read(&audit_backlog);
363 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0,
364 &status_set, sizeof(status_set));
365 break;
366 case AUDIT_SET:
367 if (nlh->nlmsg_len < sizeof(struct audit_status))
368 return -EINVAL;
369 status_get = (struct audit_status *)data;
370 if (status_get->mask & AUDIT_STATUS_ENABLED) {
371 err = audit_set_enabled(status_get->enabled);
372 if (err < 0) return err;
373 }
374 if (status_get->mask & AUDIT_STATUS_FAILURE) {
375 err = audit_set_failure(status_get->failure);
376 if (err < 0) return err;
377 }
378 if (status_get->mask & AUDIT_STATUS_PID) {
379 int old = audit_pid;
380 audit_pid = status_get->pid;
381 audit_log(current->audit_context,
382 "audit_pid=%d old=%d", audit_pid, old);
383 }
384 if (status_get->mask & AUDIT_STATUS_RATE_LIMIT)
385 audit_set_rate_limit(status_get->rate_limit);
386 if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT)
387 audit_set_backlog_limit(status_get->backlog_limit);
388 break;
389 case AUDIT_USER:
390 ab = audit_log_start(NULL);
391 if (!ab)
392 break; /* audit_panic has been called */
393 audit_log_format(ab,
394 "user pid=%d uid=%d length=%d msg='%.1024s'",
395 pid, uid,
396 (int)(nlh->nlmsg_len
397 - ((char *)data - (char *)nlh)),
398 (char *)data);
399 ab->type = AUDIT_USER;
400 ab->pid = pid;
401 audit_log_end(ab);
402 break;
403 case AUDIT_ADD:
404 case AUDIT_DEL:
405 if (nlh->nlmsg_len < sizeof(struct audit_rule))
406 return -EINVAL;
407 /* fallthrough */
408 case AUDIT_LIST:
409 #ifdef CONFIG_AUDITSYSCALL
410 err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
411 uid, seq, data);
412 #else
413 err = -EOPNOTSUPP;
414 #endif
415 break;
416 default:
417 err = -EINVAL;
418 break;
419 }
420
421 return err < 0 ? err : 0;
422 }
423
424 /* Get message from skb (based on rtnetlink_rcv_skb). Each message is
425 * processed by audit_receive_msg. Malformed skbs with wrong length are
426 * discarded silently. */
427 static int audit_receive_skb(struct sk_buff *skb)
428 {
429 int err;
430 struct nlmsghdr *nlh;
431 u32 rlen;
432
433 while (skb->len >= NLMSG_SPACE(0)) {
434 nlh = (struct nlmsghdr *)skb->data;
435 if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
436 return 0;
437 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
438 if (rlen > skb->len)
439 rlen = skb->len;
440 if ((err = audit_receive_msg(skb, nlh))) {
441 netlink_ack(skb, nlh, err);
442 } else if (nlh->nlmsg_flags & NLM_F_ACK)
443 netlink_ack(skb, nlh, 0);
444 skb_pull(skb, rlen);
445 }
446 return 0;
447 }
448
449 /* Receive messages from netlink socket. */
450 static void audit_receive(struct sock *sk, int length)
451 {
452 struct sk_buff *skb;
453
454 if (down_trylock(&audit_netlink_sem))
455 return;
456
457 /* FIXME: this must not cause starvation */
458 while ((skb = skb_dequeue(&sk->sk_receive_queue))) {
459 if (audit_receive_skb(skb) && skb->len)
460 skb_queue_head(&sk->sk_receive_queue, skb);
461 else
462 kfree_skb(skb);
463 }
464 up(&audit_netlink_sem);
465 }
466
467 /* Move data from tmp buffer into an skb. This is an extra copy, and
468 * that is unfortunate. However, the copy will only occur when a record
469 * is being written to user space, which is already a high-overhead
470 * operation. (Elimination of the copy is possible, for example, by
471 * writing directly into a pre-allocated skb, at the cost of wasting
472 * memory. */
473 static void audit_log_move(struct audit_buffer *ab)
474 {
475 struct sk_buff *skb;
476 char *start;
477 int extra = ab->nlh ? 0 : NLMSG_SPACE(0);
478
479 /* possible resubmission */
480 if (ab->len == 0)
481 return;
482
483 skb = skb_peek(&ab->sklist);
484 if (!skb || skb_tailroom(skb) <= ab->len + extra) {
485 skb = alloc_skb(2 * ab->len + extra, GFP_ATOMIC);
486 if (!skb) {
487 ab->len = 0; /* Lose information in ab->tmp */
488 audit_log_lost("out of memory in audit_log_move");
489 return;
490 }
491 __skb_queue_tail(&ab->sklist, skb);
492 if (!ab->nlh)
493 ab->nlh = (struct nlmsghdr *)skb_put(skb,
494 NLMSG_SPACE(0));
495 }
496 start = skb_put(skb, ab->len);
497 memcpy(start, ab->tmp, ab->len);
498 ab->len = 0;
499 }
500
501 /* Iterate over the skbuff in the audit_buffer, sending their contents
502 * to user space. */
503 static inline int audit_log_drain(struct audit_buffer *ab)
504 {
505 struct sk_buff *skb;
506
507 while ((skb = skb_dequeue(&ab->sklist))) {
508 int retval = 0;
509
510 if (audit_pid) {
511 if (ab->nlh) {
512 ab->nlh->nlmsg_len = ab->total;
513 ab->nlh->nlmsg_type = ab->type;
514 ab->nlh->nlmsg_flags = 0;
515 ab->nlh->nlmsg_seq = 0;
516 ab->nlh->nlmsg_pid = ab->pid;
517 }
518 skb_get(skb); /* because netlink_* frees */
519 retval = netlink_unicast(audit_sock, skb, audit_pid,
520 MSG_DONTWAIT);
521 }
522 if (retval == -EAGAIN && ab->count < 5) {
523 ++ab->count;
524 skb_queue_tail(&ab->sklist, skb);
525 audit_log_end_irq(ab);
526 return 1;
527 }
528 if (retval < 0) {
529 if (retval == -ECONNREFUSED) {
530 printk(KERN_ERR
531 "audit: *NO* daemon at audit_pid=%d\n",
532 audit_pid);
533 audit_pid = 0;
534 } else
535 audit_log_lost("netlink socket too busy");
536 }
537 if (!audit_pid) { /* No daemon */
538 int offset = ab->nlh ? NLMSG_SPACE(0) : 0;
539 int len = skb->len - offset;
540 printk(KERN_ERR "%*.*s\n",
541 len, len, skb->data + offset);
542 }
543 kfree_skb(skb);
544 ab->nlh = NULL;
545 }
546 return 0;
547 }
548
549 /* Initialize audit support at boot time. */
550 int __init audit_init(void)
551 {
552 printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
553 audit_default ? "enabled" : "disabled");
554 audit_sock = netlink_kernel_create(NETLINK_AUDIT, audit_receive);
555 if (!audit_sock)
556 audit_panic("cannot initialize netlink socket");
557
558 audit_initialized = 1;
559 audit_enabled = audit_default;
560 audit_log(NULL, "initialized");
561 return 0;
562 }
563
564 #else
565 /* Without CONFIG_NET, we have no skbuffs. For now, print what we have
566 * in the buffer. */
567 static void audit_log_move(struct audit_buffer *ab)
568 {
569 printk(KERN_ERR "%*.*s\n", ab->len, ab->len, ab->tmp);
570 ab->len = 0;
571 }
572
573 static inline int audit_log_drain(struct audit_buffer *ab)
574 {
575 return 0;
576 }
577
578 /* Initialize audit support at boot time. */
579 int __init audit_init(void)
580 {
581 printk(KERN_INFO "audit: initializing WITHOUT netlink support\n");
582 audit_sock = NULL;
583 audit_pid = 0;
584
585 audit_initialized = 1;
586 audit_enabled = audit_default;
587 audit_log(NULL, "initialized");
588 return 0;
589 }
590 #endif
591
592 __initcall(audit_init);
593
594 /* Process kernel command-line parameter at boot time. audit=0 or audit=1. */
595 static int __init audit_enable(char *str)
596 {
597 audit_default = !!simple_strtol(str, NULL, 0);
598 printk(KERN_INFO "audit: %s%s\n",
599 audit_default ? "enabled" : "disabled",
600 audit_initialized ? "" : " (after initialization)");
601 if (audit_initialized)
602 audit_enabled = audit_default;
603 return 0;
604 }
605
606 __setup("audit=", audit_enable);
607
608
609 /* Obtain an audit buffer. This routine does locking to obtain the
610 * audit buffer, but then no locking is required for calls to
611 * audit_log_*format. If the tsk is a task that is currently in a
612 * syscall, then the syscall is marked as auditable and an audit record
613 * will be written at syscall exit. If there is no associated task, tsk
614 * should be NULL. */
615 struct audit_buffer *audit_log_start(struct audit_context *ctx)
616 {
617 struct audit_buffer *ab = NULL;
618 unsigned long flags;
619 struct timespec t;
620 int serial = 0;
621
622 if (!audit_initialized)
623 return NULL;
624
625 if (audit_backlog_limit
626 && atomic_read(&audit_backlog) > audit_backlog_limit) {
627 if (audit_rate_check())
628 printk(KERN_WARNING
629 "audit: audit_backlog=%d > "
630 "audit_backlog_limit=%d\n",
631 atomic_read(&audit_backlog),
632 audit_backlog_limit);
633 audit_log_lost("backlog limit exceeded");
634 return NULL;
635 }
636
637 spin_lock_irqsave(&audit_freelist_lock, flags);
638 if (!list_empty(&audit_freelist)) {
639 ab = list_entry(audit_freelist.next,
640 struct audit_buffer, list);
641 list_del(&ab->list);
642 --audit_freelist_count;
643 }
644 spin_unlock_irqrestore(&audit_freelist_lock, flags);
645
646 if (!ab)
647 ab = kmalloc(sizeof(*ab), GFP_ATOMIC);
648 if (!ab) {
649 audit_log_lost("out of memory in audit_log_start");
650 return NULL;
651 }
652
653 atomic_inc(&audit_backlog);
654 skb_queue_head_init(&ab->sklist);
655
656 ab->ctx = ctx;
657 ab->len = 0;
658 ab->nlh = NULL;
659 ab->total = 0;
660 ab->type = AUDIT_KERNEL;
661 ab->pid = 0;
662 ab->count = 0;
663
664 #ifdef CONFIG_AUDITSYSCALL
665 if (ab->ctx)
666 audit_get_stamp(ab->ctx, &t, &serial);
667 else
668 #endif
669 t = CURRENT_TIME;
670
671 audit_log_format(ab, "audit(%lu.%03lu:%u): ",
672 t.tv_sec, t.tv_nsec/1000000, serial);
673 return ab;
674 }
675
676
677 /* Format an audit message into the audit buffer. If there isn't enough
678 * room in the audit buffer, more room will be allocated and vsnprint
679 * will be called a second time. Currently, we assume that a printk
680 * can't format message larger than 1024 bytes, so we don't either. */
681 static void audit_log_vformat(struct audit_buffer *ab, const char *fmt,
682 va_list args)
683 {
684 int len, avail;
685
686 if (!ab)
687 return;
688
689 avail = sizeof(ab->tmp) - ab->len;
690 if (avail <= 0) {
691 audit_log_move(ab);
692 avail = sizeof(ab->tmp) - ab->len;
693 }
694 len = vsnprintf(ab->tmp + ab->len, avail, fmt, args);
695 if (len >= avail) {
696 /* The printk buffer is 1024 bytes long, so if we get
697 * here and AUDIT_BUFSIZ is at least 1024, then we can
698 * log everything that printk could have logged. */
699 audit_log_move(ab);
700 avail = sizeof(ab->tmp) - ab->len;
701 len = vsnprintf(ab->tmp + ab->len, avail, fmt, args);
702 }
703 ab->len += (len < avail) ? len : avail;
704 ab->total += (len < avail) ? len : avail;
705 }
706
707 /* Format a message into the audit buffer. All the work is done in
708 * audit_log_vformat. */
709 void audit_log_format(struct audit_buffer *ab, const char *fmt, ...)
710 {
711 va_list args;
712
713 if (!ab)
714 return;
715 va_start(args, fmt);
716 audit_log_vformat(ab, fmt, args);
717 va_end(args);
718 }
719
720 /* This is a helper-function to print the d_path without using a static
721 * buffer or allocating another buffer in addition to the one in
722 * audit_buffer. */
723 void audit_log_d_path(struct audit_buffer *ab, const char *prefix,
724 struct dentry *dentry, struct vfsmount *vfsmnt)
725 {
726 char *p;
727 int len, avail;
728
729 if (prefix) audit_log_format(ab, " %s", prefix);
730
731 if (ab->len > 128)
732 audit_log_move(ab);
733 avail = sizeof(ab->tmp) - ab->len;
734 p = d_path(dentry, vfsmnt, ab->tmp + ab->len, avail);
735 if (IS_ERR(p)) {
736 /* FIXME: can we save some information here? */
737 audit_log_format(ab, "<toolong>");
738 } else {
739 /* path isn't at start of buffer */
740 len = (ab->tmp + sizeof(ab->tmp) - 1) - p;
741 memmove(ab->tmp + ab->len, p, len);
742 ab->len += len;
743 ab->total += len;
744 }
745 }
746
747 /* Remove queued messages from the audit_txlist and send them to userspace. */
748 static void audit_tasklet_handler(unsigned long arg)
749 {
750 LIST_HEAD(list);
751 struct audit_buffer *ab;
752 unsigned long flags;
753
754 spin_lock_irqsave(&audit_txlist_lock, flags);
755 list_splice_init(&audit_txlist, &list);
756 spin_unlock_irqrestore(&audit_txlist_lock, flags);
757
758 while (!list_empty(&list)) {
759 ab = list_entry(list.next, struct audit_buffer, list);
760 list_del(&ab->list);
761 audit_log_end_fast(ab);
762 }
763 }
764
765 static DECLARE_TASKLET(audit_tasklet, audit_tasklet_handler, 0);
766
767 /* The netlink_* functions cannot be called inside an irq context, so
768 * the audit buffer is places on a queue and a tasklet is scheduled to
769 * remove them from the queue outside the irq context. May be called in
770 * any context. */
771 void audit_log_end_irq(struct audit_buffer *ab)
772 {
773 unsigned long flags;
774
775 if (!ab)
776 return;
777 spin_lock_irqsave(&audit_txlist_lock, flags);
778 list_add_tail(&ab->list, &audit_txlist);
779 spin_unlock_irqrestore(&audit_txlist_lock, flags);
780
781 tasklet_schedule(&audit_tasklet);
782 }
783
784 /* Send the message in the audit buffer directly to user space. May not
785 * be called in an irq context. */
786 void audit_log_end_fast(struct audit_buffer *ab)
787 {
788 unsigned long flags;
789
790 BUG_ON(in_irq());
791 if (!ab)
792 return;
793 if (!audit_rate_check()) {
794 audit_log_lost("rate limit exceeded");
795 } else {
796 audit_log_move(ab);
797 if (audit_log_drain(ab))
798 return;
799 }
800
801 atomic_dec(&audit_backlog);
802 spin_lock_irqsave(&audit_freelist_lock, flags);
803 if (++audit_freelist_count > AUDIT_MAXFREE)
804 kfree(ab);
805 else
806 list_add(&ab->list, &audit_freelist);
807 spin_unlock_irqrestore(&audit_freelist_lock, flags);
808 }
809
810 /* Send or queue the message in the audit buffer, depending on the
811 * current context. (A convenience function that may be called in any
812 * context.) */
813 void audit_log_end(struct audit_buffer *ab)
814 {
815 if (in_irq())
816 audit_log_end_irq(ab);
817 else
818 audit_log_end_fast(ab);
819 }
820
821 /* Log an audit record. This is a convenience function that calls
822 * audit_log_start, audit_log_vformat, and audit_log_end. It may be
823 * called in any context. */
824 void audit_log(struct audit_context *ctx, const char *fmt, ...)
825 {
826 struct audit_buffer *ab;
827 va_list args;
828
829 ab = audit_log_start(ctx);
830 if (ab) {
831 va_start(args, fmt);
832 audit_log_vformat(ab, fmt, args);
833 va_end(args);
834 audit_log_end(ab);
835 }
836 }
837
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