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_log_end_irq(struct audit_buffer *ab); 159 static void audit_log_end_fast(struct audit_buffer *ab); 160 161 static void audit_panic(const char *message) 162 { 163 switch (audit_failure) 164 { 165 case AUDIT_FAIL_SILENT: 166 break; 167 case AUDIT_FAIL_PRINTK: 168 printk(KERN_ERR "audit: %s\n", message); 169 break; 170 case AUDIT_FAIL_PANIC: 171 panic("audit: %s\n", message); 172 break; 173 } 174 } 175 176 static inline int audit_rate_check(void) 177 { 178 static unsigned long last_check = 0; 179 static int messages = 0; 180 static DEFINE_SPINLOCK(lock); 181 unsigned long flags; 182 unsigned long now; 183 unsigned long elapsed; 184 int retval = 0; 185 186 if (!audit_rate_limit) return 1; 187 188 spin_lock_irqsave(&lock, flags); 189 if (++messages < audit_rate_limit) { 190 retval = 1; 191 } else { 192 now = jiffies; 193 elapsed = now - last_check; 194 if (elapsed > HZ) { 195 last_check = now; 196 messages = 0; 197 retval = 1; 198 } 199 } 200 spin_unlock_irqrestore(&lock, flags); 201 202 return retval; 203 } 204 205 /* Emit at least 1 message per second, even if audit_rate_check is 206 * throttling. */ 207 void audit_log_lost(const char *message) 208 { 209 static unsigned long last_msg = 0; 210 static DEFINE_SPINLOCK(lock); 211 unsigned long flags; 212 unsigned long now; 213 int print; 214 215 atomic_inc(&audit_lost); 216 217 print = (audit_failure == AUDIT_FAIL_PANIC || !audit_rate_limit); 218 219 if (!print) { 220 spin_lock_irqsave(&lock, flags); 221 now = jiffies; 222 if (now - last_msg > HZ) { 223 print = 1; 224 last_msg = now; 225 } 226 spin_unlock_irqrestore(&lock, flags); 227 } 228 229 if (print) { 230 printk(KERN_WARNING 231 "audit: audit_lost=%d audit_backlog=%d" 232 " audit_rate_limit=%d audit_backlog_limit=%d\n", 233 atomic_read(&audit_lost), 234 atomic_read(&audit_backlog), 235 audit_rate_limit, 236 audit_backlog_limit); 237 audit_panic(message); 238 } 239 240 } 241 242 static int audit_set_rate_limit(int limit) 243 { 244 int old = audit_rate_limit; 245 audit_rate_limit = limit; 246 audit_log(current->audit_context, "audit_rate_limit=%d old=%d", 247 audit_rate_limit, old); 248 return old; 249 } 250 251 static int audit_set_backlog_limit(int limit) 252 { 253 int old = audit_backlog_limit; 254 audit_backlog_limit = limit; 255 audit_log(current->audit_context, "audit_backlog_limit=%d old=%d", 256 audit_backlog_limit, old); 257 return old; 258 } 259 260 static int audit_set_enabled(int state) 261 { 262 int old = audit_enabled; 263 if (state != 0 && state != 1) 264 return -EINVAL; 265 audit_enabled = state; 266 audit_log(current->audit_context, "audit_enabled=%d old=%d", 267 audit_enabled, old); 268 return old; 269 } 270 271 static int audit_set_failure(int state) 272 { 273 int old = audit_failure; 274 if (state != AUDIT_FAIL_SILENT 275 && state != AUDIT_FAIL_PRINTK 276 && state != AUDIT_FAIL_PANIC) 277 return -EINVAL; 278 audit_failure = state; 279 audit_log(current->audit_context, "audit_failure=%d old=%d", 280 audit_failure, old); 281 return old; 282 } 283 284 #ifdef CONFIG_NET 285 void audit_send_reply(int pid, int seq, int type, int done, int multi, 286 void *payload, int size) 287 { 288 struct sk_buff *skb; 289 struct nlmsghdr *nlh; 290 int len = NLMSG_SPACE(size); 291 void *data; 292 int flags = multi ? NLM_F_MULTI : 0; 293 int t = done ? NLMSG_DONE : type; 294 295 skb = alloc_skb(len, GFP_KERNEL); 296 if (!skb) 297 goto nlmsg_failure; 298 299 nlh = NLMSG_PUT(skb, pid, seq, t, len - sizeof(*nlh)); 300 nlh->nlmsg_flags = flags; 301 data = NLMSG_DATA(nlh); 302 memcpy(data, payload, size); 303 netlink_unicast(audit_sock, skb, pid, MSG_DONTWAIT); 304 return; 305 306 nlmsg_failure: /* Used by NLMSG_PUT */ 307 if (skb) 308 kfree_skb(skb); 309 } 310 311 /* 312 * Check for appropriate CAP_AUDIT_ capabilities on incoming audit 313 * control messages. 314 */ 315 static int audit_netlink_ok(kernel_cap_t eff_cap, u16 msg_type) 316 { 317 int err = 0; 318 319 switch (msg_type) { 320 case AUDIT_GET: 321 case AUDIT_LIST: 322 case AUDIT_SET: 323 case AUDIT_ADD: 324 case AUDIT_DEL: 325 if (!cap_raised(eff_cap, CAP_AUDIT_CONTROL)) 326 err = -EPERM; 327 break; 328 case AUDIT_USER: 329 if (!cap_raised(eff_cap, CAP_AUDIT_WRITE)) 330 err = -EPERM; 331 break; 332 default: /* bad msg */ 333 err = -EINVAL; 334 } 335 336 return err; 337 } 338 339 static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh) 340 { 341 u32 uid, pid, seq; 342 void *data; 343 struct audit_status *status_get, status_set; 344 int err; 345 struct audit_buffer *ab; 346 u16 msg_type = nlh->nlmsg_type; 347 348 err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type); 349 if (err) 350 return err; 351 352 pid = NETLINK_CREDS(skb)->pid; 353 uid = NETLINK_CREDS(skb)->uid; 354 seq = nlh->nlmsg_seq; 355 data = NLMSG_DATA(nlh); 356 357 switch (msg_type) { 358 case AUDIT_GET: 359 status_set.enabled = audit_enabled; 360 status_set.failure = audit_failure; 361 status_set.pid = audit_pid; 362 status_set.rate_limit = audit_rate_limit; 363 status_set.backlog_limit = audit_backlog_limit; 364 status_set.lost = atomic_read(&audit_lost); 365 status_set.backlog = atomic_read(&audit_backlog); 366 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0, 367 &status_set, sizeof(status_set)); 368 break; 369 case AUDIT_SET: 370 if (nlh->nlmsg_len < sizeof(struct audit_status)) 371 return -EINVAL; 372 status_get = (struct audit_status *)data; 373 if (status_get->mask & AUDIT_STATUS_ENABLED) { 374 err = audit_set_enabled(status_get->enabled); 375 if (err < 0) return err; 376 } 377 if (status_get->mask & AUDIT_STATUS_FAILURE) { 378 err = audit_set_failure(status_get->failure); 379 if (err < 0) return err; 380 } 381 if (status_get->mask & AUDIT_STATUS_PID) { 382 int old = audit_pid; 383 audit_pid = status_get->pid; 384 audit_log(current->audit_context, 385 "audit_pid=%d old=%d", audit_pid, old); 386 } 387 if (status_get->mask & AUDIT_STATUS_RATE_LIMIT) 388 audit_set_rate_limit(status_get->rate_limit); 389 if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT) 390 audit_set_backlog_limit(status_get->backlog_limit); 391 break; 392 case AUDIT_USER: 393 ab = audit_log_start(NULL); 394 if (!ab) 395 break; /* audit_panic has been called */ 396 audit_log_format(ab, 397 "user pid=%d uid=%d length=%d msg='%.1024s'", 398 pid, uid, 399 (int)(nlh->nlmsg_len 400 - ((char *)data - (char *)nlh)), 401 (char *)data); 402 ab->type = AUDIT_USER; 403 ab->pid = pid; 404 audit_log_end(ab); 405 break; 406 case AUDIT_ADD: 407 case AUDIT_DEL: 408 if (nlh->nlmsg_len < sizeof(struct audit_rule)) 409 return -EINVAL; 410 /* fallthrough */ 411 case AUDIT_LIST: 412 #ifdef CONFIG_AUDITSYSCALL 413 err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid, 414 uid, seq, data); 415 #else 416 err = -EOPNOTSUPP; 417 #endif 418 break; 419 default: 420 err = -EINVAL; 421 break; 422 } 423 424 return err < 0 ? err : 0; 425 } 426 427 /* Get message from skb (based on rtnetlink_rcv_skb). Each message is 428 * processed by audit_receive_msg. Malformed skbs with wrong length are 429 * discarded silently. */ 430 static int audit_receive_skb(struct sk_buff *skb) 431 { 432 int err; 433 struct nlmsghdr *nlh; 434 u32 rlen; 435 436 while (skb->len >= NLMSG_SPACE(0)) { 437 nlh = (struct nlmsghdr *)skb->data; 438 if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len) 439 return 0; 440 rlen = NLMSG_ALIGN(nlh->nlmsg_len); 441 if (rlen > skb->len) 442 rlen = skb->len; 443 if ((err = audit_receive_msg(skb, nlh))) { 444 netlink_ack(skb, nlh, err); 445 } else if (nlh->nlmsg_flags & NLM_F_ACK) 446 netlink_ack(skb, nlh, 0); 447 skb_pull(skb, rlen); 448 } 449 return 0; 450 } 451 452 /* Receive messages from netlink socket. */ 453 static void audit_receive(struct sock *sk, int length) 454 { 455 struct sk_buff *skb; 456 457 if (down_trylock(&audit_netlink_sem)) 458 return; 459 460 /* FIXME: this must not cause starvation */ 461 while ((skb = skb_dequeue(&sk->sk_receive_queue))) { 462 if (audit_receive_skb(skb) && skb->len) 463 skb_queue_head(&sk->sk_receive_queue, skb); 464 else 465 kfree_skb(skb); 466 } 467 up(&audit_netlink_sem); 468 } 469 470 /* Move data from tmp buffer into an skb. This is an extra copy, and 471 * that is unfortunate. However, the copy will only occur when a record 472 * is being written to user space, which is already a high-overhead 473 * operation. (Elimination of the copy is possible, for example, by 474 * writing directly into a pre-allocated skb, at the cost of wasting 475 * memory. */ 476 static void audit_log_move(struct audit_buffer *ab) 477 { 478 struct sk_buff *skb; 479 char *start; 480 int extra = ab->nlh ? 0 : NLMSG_SPACE(0); 481 482 /* possible resubmission */ 483 if (ab->len == 0) 484 return; 485 486 skb = skb_peek(&ab->sklist); 487 if (!skb || skb_tailroom(skb) <= ab->len + extra) { 488 skb = alloc_skb(2 * ab->len + extra, GFP_ATOMIC); 489 if (!skb) { 490 ab->len = 0; /* Lose information in ab->tmp */ 491 audit_log_lost("out of memory in audit_log_move"); 492 return; 493 } 494 __skb_queue_tail(&ab->sklist, skb); 495 if (!ab->nlh) 496 ab->nlh = (struct nlmsghdr *)skb_put(skb, 497 NLMSG_SPACE(0)); 498 } 499 start = skb_put(skb, ab->len); 500 memcpy(start, ab->tmp, ab->len); 501 ab->len = 0; 502 } 503 504 /* Iterate over the skbuff in the audit_buffer, sending their contents 505 * to user space. */ 506 static inline int audit_log_drain(struct audit_buffer *ab) 507 { 508 struct sk_buff *skb; 509 510 while ((skb = skb_dequeue(&ab->sklist))) { 511 int retval = 0; 512 513 if (audit_pid) { 514 if (ab->nlh) { 515 ab->nlh->nlmsg_len = ab->total; 516 ab->nlh->nlmsg_type = ab->type; 517 ab->nlh->nlmsg_flags = 0; 518 ab->nlh->nlmsg_seq = 0; 519 ab->nlh->nlmsg_pid = ab->pid; 520 } 521 skb_get(skb); /* because netlink_* frees */ 522 retval = netlink_unicast(audit_sock, skb, audit_pid, 523 MSG_DONTWAIT); 524 } 525 if (retval == -EAGAIN && ab->count < 5) { 526 ++ab->count; 527 skb_queue_tail(&ab->sklist, skb); 528 audit_log_end_irq(ab); 529 return 1; 530 } 531 if (retval < 0) { 532 if (retval == -ECONNREFUSED) { 533 printk(KERN_ERR 534 "audit: *NO* daemon at audit_pid=%d\n", 535 audit_pid); 536 audit_pid = 0; 537 } else 538 audit_log_lost("netlink socket too busy"); 539 } 540 if (!audit_pid) { /* No daemon */ 541 int offset = ab->nlh ? NLMSG_SPACE(0) : 0; 542 int len = skb->len - offset; 543 printk(KERN_ERR "%*.*s\n", 544 len, len, skb->data + offset); 545 } 546 kfree_skb(skb); 547 ab->nlh = NULL; 548 } 549 return 0; 550 } 551 552 /* Initialize audit support at boot time. */ 553 static int __init audit_init(void) 554 { 555 printk(KERN_INFO "audit: initializing netlink socket (%s)\n", 556 audit_default ? "enabled" : "disabled"); 557 audit_sock = netlink_kernel_create(NETLINK_AUDIT, audit_receive); 558 if (!audit_sock) 559 audit_panic("cannot initialize netlink socket"); 560 561 audit_initialized = 1; 562 audit_enabled = audit_default; 563 audit_log(NULL, "initialized"); 564 return 0; 565 } 566 567 #else 568 /* Without CONFIG_NET, we have no skbuffs. For now, print what we have 569 * in the buffer. */ 570 static void audit_log_move(struct audit_buffer *ab) 571 { 572 printk(KERN_ERR "%*.*s\n", ab->len, ab->len, ab->tmp); 573 ab->len = 0; 574 } 575 576 static inline int audit_log_drain(struct audit_buffer *ab) 577 { 578 return 0; 579 } 580 581 /* Initialize audit support at boot time. */ 582 int __init audit_init(void) 583 { 584 printk(KERN_INFO "audit: initializing WITHOUT netlink support\n"); 585 audit_sock = NULL; 586 audit_pid = 0; 587 588 audit_initialized = 1; 589 audit_enabled = audit_default; 590 audit_log(NULL, "initialized"); 591 return 0; 592 } 593 #endif 594 595 __initcall(audit_init); 596 597 /* Process kernel command-line parameter at boot time. audit=0 or audit=1. */ 598 static int __init audit_enable(char *str) 599 { 600 audit_default = !!simple_strtol(str, NULL, 0); 601 printk(KERN_INFO "audit: %s%s\n", 602 audit_default ? "enabled" : "disabled", 603 audit_initialized ? "" : " (after initialization)"); 604 if (audit_initialized) 605 audit_enabled = audit_default; 606 return 0; 607 } 608 609 __setup("audit=", audit_enable); 610 611 612 /* Obtain an audit buffer. This routine does locking to obtain the 613 * audit buffer, but then no locking is required for calls to 614 * audit_log_*format. If the tsk is a task that is currently in a 615 * syscall, then the syscall is marked as auditable and an audit record 616 * will be written at syscall exit. If there is no associated task, tsk 617 * should be NULL. */ 618 struct audit_buffer *audit_log_start(struct audit_context *ctx) 619 { 620 struct audit_buffer *ab = NULL; 621 unsigned long flags; 622 struct timespec t; 623 int serial = 0; 624 625 if (!audit_initialized) 626 return NULL; 627 628 if (audit_backlog_limit 629 && atomic_read(&audit_backlog) > audit_backlog_limit) { 630 if (audit_rate_check()) 631 printk(KERN_WARNING 632 "audit: audit_backlog=%d > " 633 "audit_backlog_limit=%d\n", 634 atomic_read(&audit_backlog), 635 audit_backlog_limit); 636 audit_log_lost("backlog limit exceeded"); 637 return NULL; 638 } 639 640 spin_lock_irqsave(&audit_freelist_lock, flags); 641 if (!list_empty(&audit_freelist)) { 642 ab = list_entry(audit_freelist.next, 643 struct audit_buffer, list); 644 list_del(&ab->list); 645 --audit_freelist_count; 646 } 647 spin_unlock_irqrestore(&audit_freelist_lock, flags); 648 649 if (!ab) 650 ab = kmalloc(sizeof(*ab), GFP_ATOMIC); 651 if (!ab) { 652 audit_log_lost("out of memory in audit_log_start"); 653 return NULL; 654 } 655 656 atomic_inc(&audit_backlog); 657 skb_queue_head_init(&ab->sklist); 658 659 ab->ctx = ctx; 660 ab->len = 0; 661 ab->nlh = NULL; 662 ab->total = 0; 663 ab->type = AUDIT_KERNEL; 664 ab->pid = 0; 665 ab->count = 0; 666 667 #ifdef CONFIG_AUDITSYSCALL 668 if (ab->ctx) 669 audit_get_stamp(ab->ctx, &t, &serial); 670 else 671 #endif 672 t = CURRENT_TIME; 673 674 audit_log_format(ab, "audit(%lu.%03lu:%u): ", 675 t.tv_sec, t.tv_nsec/1000000, serial); 676 return ab; 677 } 678 679 680 /* Format an audit message into the audit buffer. If there isn't enough 681 * room in the audit buffer, more room will be allocated and vsnprint 682 * will be called a second time. Currently, we assume that a printk 683 * can't format message larger than 1024 bytes, so we don't either. */ 684 static void audit_log_vformat(struct audit_buffer *ab, const char *fmt, 685 va_list args) 686 { 687 int len, avail; 688 689 if (!ab) 690 return; 691 692 avail = sizeof(ab->tmp) - ab->len; 693 if (avail <= 0) { 694 audit_log_move(ab); 695 avail = sizeof(ab->tmp) - ab->len; 696 } 697 len = vsnprintf(ab->tmp + ab->len, avail, fmt, args); 698 if (len >= avail) { 699 /* The printk buffer is 1024 bytes long, so if we get 700 * here and AUDIT_BUFSIZ is at least 1024, then we can 701 * log everything that printk could have logged. */ 702 audit_log_move(ab); 703 avail = sizeof(ab->tmp) - ab->len; 704 len = vsnprintf(ab->tmp + ab->len, avail, fmt, args); 705 } 706 ab->len += (len < avail) ? len : avail; 707 ab->total += (len < avail) ? len : avail; 708 } 709 710 /* Format a message into the audit buffer. All the work is done in 711 * audit_log_vformat. */ 712 void audit_log_format(struct audit_buffer *ab, const char *fmt, ...) 713 { 714 va_list args; 715 716 if (!ab) 717 return; 718 va_start(args, fmt); 719 audit_log_vformat(ab, fmt, args); 720 va_end(args); 721 } 722 723 /* This is a helper-function to print the d_path without using a static 724 * buffer or allocating another buffer in addition to the one in 725 * audit_buffer. */ 726 void audit_log_d_path(struct audit_buffer *ab, const char *prefix, 727 struct dentry *dentry, struct vfsmount *vfsmnt) 728 { 729 char *p; 730 int len, avail; 731 732 if (prefix) audit_log_format(ab, " %s", prefix); 733 734 if (ab->len > 128) 735 audit_log_move(ab); 736 avail = sizeof(ab->tmp) - ab->len; 737 p = d_path(dentry, vfsmnt, ab->tmp + ab->len, avail); 738 if (IS_ERR(p)) { 739 /* FIXME: can we save some information here? */ 740 audit_log_format(ab, "<toolong>"); 741 } else { 742 /* path isn't at start of buffer */ 743 len = (ab->tmp + sizeof(ab->tmp) - 1) - p; 744 memmove(ab->tmp + ab->len, p, len); 745 ab->len += len; 746 ab->total += len; 747 } 748 } 749 750 /* Remove queued messages from the audit_txlist and send them to userspace. */ 751 static void audit_tasklet_handler(unsigned long arg) 752 { 753 LIST_HEAD(list); 754 struct audit_buffer *ab; 755 unsigned long flags; 756 757 spin_lock_irqsave(&audit_txlist_lock, flags); 758 list_splice_init(&audit_txlist, &list); 759 spin_unlock_irqrestore(&audit_txlist_lock, flags); 760 761 while (!list_empty(&list)) { 762 ab = list_entry(list.next, struct audit_buffer, list); 763 list_del(&ab->list); 764 audit_log_end_fast(ab); 765 } 766 } 767 768 static DECLARE_TASKLET(audit_tasklet, audit_tasklet_handler, 0); 769 770 /* The netlink_* functions cannot be called inside an irq context, so 771 * the audit buffer is places on a queue and a tasklet is scheduled to 772 * remove them from the queue outside the irq context. May be called in 773 * any context. */ 774 static void audit_log_end_irq(struct audit_buffer *ab) 775 { 776 unsigned long flags; 777 778 if (!ab) 779 return; 780 spin_lock_irqsave(&audit_txlist_lock, flags); 781 list_add_tail(&ab->list, &audit_txlist); 782 spin_unlock_irqrestore(&audit_txlist_lock, flags); 783 784 tasklet_schedule(&audit_tasklet); 785 } 786 787 /* Send the message in the audit buffer directly to user space. May not 788 * be called in an irq context. */ 789 static void audit_log_end_fast(struct audit_buffer *ab) 790 { 791 unsigned long flags; 792 793 BUG_ON(in_irq()); 794 if (!ab) 795 return; 796 if (!audit_rate_check()) { 797 audit_log_lost("rate limit exceeded"); 798 } else { 799 audit_log_move(ab); 800 if (audit_log_drain(ab)) 801 return; 802 } 803 804 atomic_dec(&audit_backlog); 805 spin_lock_irqsave(&audit_freelist_lock, flags); 806 if (++audit_freelist_count > AUDIT_MAXFREE) 807 kfree(ab); 808 else 809 list_add(&ab->list, &audit_freelist); 810 spin_unlock_irqrestore(&audit_freelist_lock, flags); 811 } 812 813 /* Send or queue the message in the audit buffer, depending on the 814 * current context. (A convenience function that may be called in any 815 * context.) */ 816 void audit_log_end(struct audit_buffer *ab) 817 { 818 if (in_irq()) 819 audit_log_end_irq(ab); 820 else 821 audit_log_end_fast(ab); 822 } 823 824 /* Log an audit record. This is a convenience function that calls 825 * audit_log_start, audit_log_vformat, and audit_log_end. It may be 826 * called in any context. */ 827 void audit_log(struct audit_context *ctx, const char *fmt, ...) 828 { 829 struct audit_buffer *ab; 830 va_list args; 831 832 ab = audit_log_start(ctx); 833 if (ab) { 834 va_start(args, fmt); 835 audit_log_vformat(ab, fmt, args); 836 va_end(args); 837 audit_log_end(ab); 838 } 839 } 840