kernel/audit.c

   1 /* audit.c -- Auditing support
   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/sgrubb/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 #include <linux/err.h>
  50 #include <linux/kthread.h>
  51
  52 #include <linux/audit.h>
  53
  54 #include <net/sock.h>
  55 #include <linux/skbuff.h>
  56 #include <linux/netlink.h>
  57
  58 /* No auditing will take place until audit_initialized != 0.
  59  * (Initialization happens after skb_init is called.) */
  60 static int      audit_initialized;
  61
  62 /* No syscall auditing will take place unless audit_enabled != 0. */
  63 int             audit_enabled;
  64
  65 /* Default state when kernel boots without any parameters. */
  66 static int      audit_default;
  67
  68 /* If auditing cannot proceed, audit_failure selects what happens. */
  69 static int      audit_failure = AUDIT_FAIL_PRINTK;
  70
  71 /* If audit records are to be written to the netlink socket, audit_pid
  72  * contains the (non-zero) pid. */
  73 int             audit_pid;
  74
  75 /* If audit_limit is non-zero, limit the rate of sending audit records
  76  * to that number per second.  This prevents DoS attacks, but results in
  77  * audit records being dropped. */
  78 static int      audit_rate_limit;
  79
  80 /* Number of outstanding audit_buffers allowed. */
  81 static int      audit_backlog_limit = 64;
  82 static int      audit_backlog_wait_time = 60 * HZ;
  83 static int      audit_backlog_wait_overflow = 0;
  84
  85 /* The identity of the user shutting down the audit system. */
  86 uid_t           audit_sig_uid = -1;
  87 pid_t           audit_sig_pid = -1;
  88
  89 /* Records can be lost in several ways:
  90    0) [suppressed in audit_alloc]
  91    1) out of memory in audit_log_start [kmalloc of struct audit_buffer]
  92    2) out of memory in audit_log_move [alloc_skb]
  93    3) suppressed due to audit_rate_limit
  94    4) suppressed due to audit_backlog_limit
  95 */
  96 static atomic_t    audit_lost = ATOMIC_INIT(0);
  97
  98 /* The netlink socket. */
  99 static struct sock *audit_sock;
 100
 101 /* The audit_freelist is a list of pre-allocated audit buffers (if more
 102  * than AUDIT_MAXFREE are in use, the audit buffer is freed instead of
 103  * being placed on the freelist). */
 104 static DEFINE_SPINLOCK(audit_freelist_lock);
 105 static int         audit_freelist_count = 0;
 106 static LIST_HEAD(audit_freelist);
 107
 108 static struct sk_buff_head audit_skb_queue;
 109 static struct task_struct *kauditd_task;
 110 static DECLARE_WAIT_QUEUE_HEAD(kauditd_wait);
 111 static DECLARE_WAIT_QUEUE_HEAD(audit_backlog_wait);
 112
 113 /* The netlink socket is only to be read by 1 CPU, which lets us assume
 114  * that list additions and deletions never happen simultaneously in
 115  * auditsc.c */
 116 DECLARE_MUTEX(audit_netlink_sem);
 117
 118 /* AUDIT_BUFSIZ is the size of the temporary buffer used for formatting
 119  * audit records.  Since printk uses a 1024 byte buffer, this buffer
 120  * should be at least that large. */
 121 #define AUDIT_BUFSIZ 1024
 122
 123 /* AUDIT_MAXFREE is the number of empty audit_buffers we keep on the
 124  * audit_freelist.  Doing so eliminates many kmalloc/kfree calls. */
 125 #define AUDIT_MAXFREE  (2*NR_CPUS)
 126
 127 /* The audit_buffer is used when formatting an audit record.  The caller
 128  * locks briefly to get the record off the freelist or to allocate the
 129  * buffer, and locks briefly to send the buffer to the netlink layer or
 130  * to place it on a transmit queue.  Multiple audit_buffers can be in
 131  * use simultaneously. */
 132 struct audit_buffer {
 133         struct list_head     list;
 134         struct sk_buff       *skb;      /* formatted skb ready to send */
 135         struct audit_context *ctx;      /* NULL or associated context */
 136         gfp_t                gfp_mask;
 137 };
 138
 139 static void audit_set_pid(struct audit_buffer *ab, pid_t pid)
 140 {
 141         struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data;
 142         nlh->nlmsg_pid = pid;
 143 }
 144
 145 static void audit_panic(const char *message)
 146 {
 147         switch (audit_failure)
 148         {
 149         case AUDIT_FAIL_SILENT:
 150                 break;
 151         case AUDIT_FAIL_PRINTK:
 152                 printk(KERN_ERR "audit: %s\n", message);
 153                 break;
 154         case AUDIT_FAIL_PANIC:
 155                 panic("audit: %s\n", message);
 156                 break;
 157         }
 158 }
 159
 160 static inline int audit_rate_check(void)
 161 {
 162         static unsigned long    last_check = 0;
 163         static int              messages   = 0;
 164         static DEFINE_SPINLOCK(lock);
 165         unsigned long           flags;
 166         unsigned long           now;
 167         unsigned long           elapsed;
 168         int                     retval     = 0;
 169
 170         if (!audit_rate_limit) return 1;
 171
 172         spin_lock_irqsave(&lock, flags);
 173         if (++messages < audit_rate_limit) {
 174                 retval = 1;
 175         } else {
 176                 now     = jiffies;
 177                 elapsed = now - last_check;
 178                 if (elapsed > HZ) {
 179                         last_check = now;
 180                         messages   = 0;
 181                         retval     = 1;
 182                 }
 183         }
 184         spin_unlock_irqrestore(&lock, flags);
 185
 186         return retval;
 187 }
 188
 189 /* Emit at least 1 message per second, even if audit_rate_check is
 190  * throttling. */
 191 void audit_log_lost(const char *message)
 192 {
 193         static unsigned long    last_msg = 0;
 194         static DEFINE_SPINLOCK(lock);
 195         unsigned long           flags;
 196         unsigned long           now;
 197         int                     print;
 198
 199         atomic_inc(&audit_lost);
 200
 201         print = (audit_failure == AUDIT_FAIL_PANIC || !audit_rate_limit);
 202
 203         if (!print) {
 204                 spin_lock_irqsave(&lock, flags);
 205                 now = jiffies;
 206                 if (now - last_msg > HZ) {
 207                         print = 1;
 208                         last_msg = now;
 209                 }
 210                 spin_unlock_irqrestore(&lock, flags);
 211         }
 212
 213         if (print) {
 214                 printk(KERN_WARNING
 215                        "audit: audit_lost=%d audit_rate_limit=%d audit_backlog_limit=%d\n",
 216                        atomic_read(&audit_lost),
 217                        audit_rate_limit,
 218                        audit_backlog_limit);
 219                 audit_panic(message);
 220         }
 221
 222 }
 223
 224 static int audit_set_rate_limit(int limit, uid_t loginuid)
 225 {
 226         int old          = audit_rate_limit;
 227         audit_rate_limit = limit;
 228         audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 229                         "audit_rate_limit=%d old=%d by auid=%u",
 230                         audit_rate_limit, old, loginuid);
 231         return old;
 232 }
 233
 234 static int audit_set_backlog_limit(int limit, uid_t loginuid)
 235 {
 236         int old          = audit_backlog_limit;
 237         audit_backlog_limit = limit;
 238         audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 239                         "audit_backlog_limit=%d old=%d by auid=%u",
 240                         audit_backlog_limit, old, loginuid);
 241         return old;
 242 }
 243
 244 static int audit_set_enabled(int state, uid_t loginuid)
 245 {
 246         int old          = audit_enabled;
 247         if (state != 0 && state != 1)
 248                 return -EINVAL;
 249         audit_enabled = state;
 250         audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 251                         "audit_enabled=%d old=%d by auid=%u",
 252                         audit_enabled, old, loginuid);
 253         return old;
 254 }
 255
 256 static int audit_set_failure(int state, uid_t loginuid)
 257 {
 258         int old          = audit_failure;
 259         if (state != AUDIT_FAIL_SILENT
 260             && state != AUDIT_FAIL_PRINTK
 261             && state != AUDIT_FAIL_PANIC)
 262                 return -EINVAL;
 263         audit_failure = state;
 264         audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 265                         "audit_failure=%d old=%d by auid=%u",
 266                         audit_failure, old, loginuid);
 267         return old;
 268 }
 269
 270 int kauditd_thread(void *dummy)
 271 {
 272         struct sk_buff *skb;
 273
 274         while (1) {
 275                 skb = skb_dequeue(&audit_skb_queue);
 276                 wake_up(&audit_backlog_wait);
 277                 if (skb) {
 278                         if (audit_pid) {
 279                                 int err = netlink_unicast(audit_sock, skb, audit_pid, 0);
 280                                 if (err < 0) {
 281                                         BUG_ON(err != -ECONNREFUSED); /* Shoudn't happen */
 282                                         printk(KERN_ERR "audit: *NO* daemon at audit_pid=%d\n", audit_pid);
 283                                         audit_pid = 0;
 284                                 }
 285                         } else {
 286                                 printk(KERN_NOTICE "%s\n", skb->data + NLMSG_SPACE(0));
 287                                 kfree_skb(skb);
 288                         }
 289                 } else {
 290                         DECLARE_WAITQUEUE(wait, current);
 291                         set_current_state(TASK_INTERRUPTIBLE);
 292                         add_wait_queue(&kauditd_wait, &wait);
 293
 294                         if (!skb_queue_len(&audit_skb_queue))
 295                                 schedule();
 296
 297                         __set_current_state(TASK_RUNNING);
 298                         remove_wait_queue(&kauditd_wait, &wait);
 299                 }
 300         }
 301 }
 302
 303 void audit_send_reply(int pid, int seq, int type, int done, int multi,
 304                       void *payload, int size)
 305 {
 306         struct sk_buff  *skb;
 307         struct nlmsghdr *nlh;
 308         int             len = NLMSG_SPACE(size);
 309         void            *data;
 310         int             flags = multi ? NLM_F_MULTI : 0;
 311         int             t     = done  ? NLMSG_DONE  : type;
 312
 313         skb = alloc_skb(len, GFP_KERNEL);
 314         if (!skb)
 315                 return;
 316
 317         nlh              = NLMSG_PUT(skb, pid, seq, t, size);
 318         nlh->nlmsg_flags = flags;
 319         data             = NLMSG_DATA(nlh);
 320         memcpy(data, payload, size);
 321
 322         /* Ignore failure. It'll only happen if the sender goes away,
 323            because our timeout is set to infinite. */
 324         netlink_unicast(audit_sock, skb, pid, 0);
 325         return;
 326
 327 nlmsg_failure:                  /* Used by NLMSG_PUT */
 328         if (skb)
 329                 kfree_skb(skb);
 330 }
 331
 332 /*
 333  * Check for appropriate CAP_AUDIT_ capabilities on incoming audit
 334  * control messages.
 335  */
 336 static int audit_netlink_ok(kernel_cap_t eff_cap, u16 msg_type)
 337 {
 338         int err = 0;
 339
 340         switch (msg_type) {
 341         case AUDIT_GET:
 342         case AUDIT_LIST:
 343         case AUDIT_SET:
 344         case AUDIT_ADD:
 345         case AUDIT_DEL:
 346         case AUDIT_SIGNAL_INFO:
 347                 if (!cap_raised(eff_cap, CAP_AUDIT_CONTROL))
 348                         err = -EPERM;
 349                 break;
 350         case AUDIT_USER:
 351         case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG:
 352                 if (!cap_raised(eff_cap, CAP_AUDIT_WRITE))
 353                         err = -EPERM;
 354                 break;
 355         default:  /* bad msg */
 356                 err = -EINVAL;
 357         }
 358
 359         return err;
 360 }
 361
 362 static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 363 {
 364         u32                     uid, pid, seq;
 365         void                    *data;
 366         struct audit_status     *status_get, status_set;
 367         int                     err;
 368         struct audit_buffer     *ab;
 369         u16                     msg_type = nlh->nlmsg_type;
 370         uid_t                   loginuid; /* loginuid of sender */
 371         struct audit_sig_info   sig_data;
 372
 373         err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
 374         if (err)
 375                 return err;
 376
 377         /* As soon as there's any sign of userspace auditd, start kauditd to talk to it */
 378         if (!kauditd_task)
 379                 kauditd_task = kthread_run(kauditd_thread, NULL, "kauditd");
 380         if (IS_ERR(kauditd_task)) {
 381                 err = PTR_ERR(kauditd_task);
 382                 kauditd_task = NULL;
 383                 return err;
 384         }
 385
 386         pid  = NETLINK_CREDS(skb)->pid;
 387         uid  = NETLINK_CREDS(skb)->uid;
 388         loginuid = NETLINK_CB(skb).loginuid;
 389         seq  = nlh->nlmsg_seq;
 390         data = NLMSG_DATA(nlh);
 391
 392         switch (msg_type) {
 393         case AUDIT_GET:
 394                 status_set.enabled       = audit_enabled;
 395                 status_set.failure       = audit_failure;
 396                 status_set.pid           = audit_pid;
 397                 status_set.rate_limit    = audit_rate_limit;
 398                 status_set.backlog_limit = audit_backlog_limit;
 399                 status_set.lost          = atomic_read(&audit_lost);
 400                 status_set.backlog       = skb_queue_len(&audit_skb_queue);
 401                 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0,
 402                                  &status_set, sizeof(status_set));
 403                 break;
 404         case AUDIT_SET:
 405                 if (nlh->nlmsg_len < sizeof(struct audit_status))
 406                         return -EINVAL;
 407                 status_get   = (struct audit_status *)data;
 408                 if (status_get->mask & AUDIT_STATUS_ENABLED) {
 409                         err = audit_set_enabled(status_get->enabled, loginuid);
 410                         if (err < 0) return err;
 411                 }
 412                 if (status_get->mask & AUDIT_STATUS_FAILURE) {
 413                         err = audit_set_failure(status_get->failure, loginuid);
 414                         if (err < 0) return err;
 415                 }
 416                 if (status_get->mask & AUDIT_STATUS_PID) {
 417                         int old   = audit_pid;
 418                         audit_pid = status_get->pid;
 419                         audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 420                                 "audit_pid=%d old=%d by auid=%u",
 421                                   audit_pid, old, loginuid);
 422                 }
 423                 if (status_get->mask & AUDIT_STATUS_RATE_LIMIT)
 424                         audit_set_rate_limit(status_get->rate_limit, loginuid);
 425                 if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT)
 426                         audit_set_backlog_limit(status_get->backlog_limit,
 427                                                         loginuid);
 428                 break;
 429         case AUDIT_USER:
 430         case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG:
 431                 if (!audit_enabled && msg_type != AUDIT_USER_AVC)
 432                         return 0;
 433
 434                 err = audit_filter_user(&NETLINK_CB(skb), msg_type);
 435                 if (err == 1) {
 436                         err = 0;
 437                         ab = audit_log_start(NULL, GFP_KERNEL, msg_type);
 438                         if (ab) {
 439                                 audit_log_format(ab,
 440                                                  "user pid=%d uid=%u auid=%u msg='%.1024s'",
 441                                                  pid, uid, loginuid, (char *)data);
 442                                 audit_set_pid(ab, pid);
 443                                 audit_log_end(ab);
 444                         }
 445                 }
 446                 break;
 447         case AUDIT_ADD:
 448         case AUDIT_DEL:
 449                 if (nlh->nlmsg_len < sizeof(struct audit_rule))
 450                         return -EINVAL;
 451                 /* fallthrough */
 452         case AUDIT_LIST:
 453                 err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
 454                                            uid, seq, data, loginuid);
 455                 break;
 456         case AUDIT_SIGNAL_INFO:
 457                 sig_data.uid = audit_sig_uid;
 458                 sig_data.pid = audit_sig_pid;
 459                 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_SIGNAL_INFO,
 460                                 0, 0, &sig_data, sizeof(sig_data));
 461                 break;
 462         default:
 463                 err = -EINVAL;
 464                 break;
 465         }
 466
 467         return err < 0 ? err : 0;
 468 }
 469
 470 /* Get message from skb (based on rtnetlink_rcv_skb).  Each message is
 471  * processed by audit_receive_msg.  Malformed skbs with wrong length are
 472  * discarded silently.  */
 473 static void audit_receive_skb(struct sk_buff *skb)
 474 {
 475         int             err;
 476         struct nlmsghdr *nlh;
 477         u32             rlen;
 478
 479         while (skb->len >= NLMSG_SPACE(0)) {
 480                 nlh = (struct nlmsghdr *)skb->data;
 481                 if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
 482                         return;
 483                 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
 484                 if (rlen > skb->len)
 485                         rlen = skb->len;
 486                 if ((err = audit_receive_msg(skb, nlh))) {
 487                         netlink_ack(skb, nlh, err);
 488                 } else if (nlh->nlmsg_flags & NLM_F_ACK)
 489                         netlink_ack(skb, nlh, 0);
 490                 skb_pull(skb, rlen);
 491         }
 492 }
 493
 494 /* Receive messages from netlink socket. */
 495 static void audit_receive(struct sock *sk, int length)
 496 {
 497         struct sk_buff  *skb;
 498         unsigned int qlen;
 499
 500         down(&audit_netlink_sem);
 501
 502         for (qlen = skb_queue_len(&sk->sk_receive_queue); qlen; qlen--) {
 503                 skb = skb_dequeue(&sk->sk_receive_queue);
 504                 audit_receive_skb(skb);
 505                 kfree_skb(skb);
 506         }
 507         up(&audit_netlink_sem);
 508 }
 509
 510
 511 /* Initialize audit support at boot time. */
 512 static int __init audit_init(void)
 513 {
 514         printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
 515                audit_default ? "enabled" : "disabled");
 516         audit_sock = netlink_kernel_create(NETLINK_AUDIT, 0, audit_receive,
 517                                            THIS_MODULE);
 518         if (!audit_sock)
 519                 audit_panic("cannot initialize netlink socket");
 520
 521         audit_sock->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT;
 522         skb_queue_head_init(&audit_skb_queue);
 523         audit_initialized = 1;
 524         audit_enabled = audit_default;
 525         audit_log(NULL, GFP_KERNEL, AUDIT_KERNEL, "initialized");
 526         return 0;
 527 }
 528 __initcall(audit_init);
 529
 530 /* Process kernel command-line parameter at boot time.  audit=0 or audit=1. */
 531 static int __init audit_enable(char *str)
 532 {
 533         audit_default = !!simple_strtol(str, NULL, 0);
 534         printk(KERN_INFO "audit: %s%s\n",
 535                audit_default ? "enabled" : "disabled",
 536                audit_initialized ? "" : " (after initialization)");
 537         if (audit_initialized)
 538                 audit_enabled = audit_default;
 539         return 0;
 540 }
 541
 542 __setup("audit=", audit_enable);
 543
 544 static void audit_buffer_free(struct audit_buffer *ab)
 545 {
 546         unsigned long flags;
 547
 548         if (!ab)
 549                 return;
 550
 551         if (ab->skb)
 552                 kfree_skb(ab->skb);
 553
 554         spin_lock_irqsave(&audit_freelist_lock, flags);
 555         if (++audit_freelist_count > AUDIT_MAXFREE)
 556                 kfree(ab);
 557         else
 558                 list_add(&ab->list, &audit_freelist);
 559         spin_unlock_irqrestore(&audit_freelist_lock, flags);
 560 }
 561
 562 static struct audit_buffer * audit_buffer_alloc(struct audit_context *ctx,
 563                                                 gfp_t gfp_mask, int type)
 564 {
 565         unsigned long flags;
 566         struct audit_buffer *ab = NULL;
 567         struct nlmsghdr *nlh;
 568
 569         spin_lock_irqsave(&audit_freelist_lock, flags);
 570         if (!list_empty(&audit_freelist)) {
 571                 ab = list_entry(audit_freelist.next,
 572                                 struct audit_buffer, list);
 573                 list_del(&ab->list);
 574                 --audit_freelist_count;
 575         }
 576         spin_unlock_irqrestore(&audit_freelist_lock, flags);
 577
 578         if (!ab) {
 579                 ab = kmalloc(sizeof(*ab), gfp_mask);
 580                 if (!ab)
 581                         goto err;
 582         }
 583
 584         ab->skb = alloc_skb(AUDIT_BUFSIZ, gfp_mask);
 585         if (!ab->skb)
 586                 goto err;
 587
 588         ab->ctx = ctx;
 589         ab->gfp_mask = gfp_mask;
 590         nlh = (struct nlmsghdr *)skb_put(ab->skb, NLMSG_SPACE(0));
 591         nlh->nlmsg_type = type;
 592         nlh->nlmsg_flags = 0;
 593         nlh->nlmsg_pid = 0;
 594         nlh->nlmsg_seq = 0;
 595         return ab;
 596 err:
 597         audit_buffer_free(ab);
 598         return NULL;
 599 }
 600
 601 /* Compute a serial number for the audit record.  Audit records are
 602  * written to user-space as soon as they are generated, so a complete
 603  * audit record may be written in several pieces.  The timestamp of the
 604  * record and this serial number are used by the user-space tools to
 605  * determine which pieces belong to the same audit record.  The
 606  * (timestamp,serial) tuple is unique for each syscall and is live from
 607  * syscall entry to syscall exit.
 608  *
 609  * NOTE: Another possibility is to store the formatted records off the
 610  * audit context (for those records that have a context), and emit them
 611  * all at syscall exit.  However, this could delay the reporting of
 612  * significant errors until syscall exit (or never, if the system
 613  * halts). */
 614
 615 unsigned int audit_serial(void)
 616 {
 617         static spinlock_t serial_lock = SPIN_LOCK_UNLOCKED;
 618         static unsigned int serial = 0;
 619
 620         unsigned long flags;
 621         unsigned int ret;
 622
 623         spin_lock_irqsave(&serial_lock, flags);
 624         do {
 625                 ret = ++serial;
 626         } while (unlikely(!ret));
 627         spin_unlock_irqrestore(&serial_lock, flags);
 628
 629         return ret;
 630 }
 631
 632 static inline void audit_get_stamp(struct audit_context *ctx,
 633                                    struct timespec *t, unsigned int *serial)
 634 {
 635         if (ctx)
 636                 auditsc_get_stamp(ctx, t, serial);
 637         else {
 638                 *t = CURRENT_TIME;
 639                 *serial = audit_serial();
 640         }
 641 }
 642
 643 /* Obtain an audit buffer.  This routine does locking to obtain the
 644  * audit buffer, but then no locking is required for calls to
 645  * audit_log_*format.  If the tsk is a task that is currently in a
 646  * syscall, then the syscall is marked as auditable and an audit record
 647  * will be written at syscall exit.  If there is no associated task, tsk
 648  * should be NULL. */
 649
 650 struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
 651                                      int type)
 652 {
 653         struct audit_buffer     *ab     = NULL;
 654         struct timespec         t;
 655         unsigned int            serial;
 656         int reserve;
 657         unsigned long timeout_start = jiffies;
 658
 659         if (!audit_initialized)
 660                 return NULL;
 661
 662         if (gfp_mask & __GFP_WAIT)
 663                 reserve = 0;
 664         else
 665                 reserve = 5; /* Allow atomic callers to go up to five
 666                                 entries over the normal backlog limit */
 667
 668         while (audit_backlog_limit
 669                && skb_queue_len(&audit_skb_queue) > audit_backlog_limit + reserve) {
 670                 if (gfp_mask & __GFP_WAIT && audit_backlog_wait_time
 671                     && time_before(jiffies, timeout_start + audit_backlog_wait_time)) {
 672
 673                         /* Wait for auditd to drain the queue a little */
 674                         DECLARE_WAITQUEUE(wait, current);
 675                         set_current_state(TASK_INTERRUPTIBLE);
 676                         add_wait_queue(&audit_backlog_wait, &wait);
 677
 678                         if (audit_backlog_limit &&
 679                             skb_queue_len(&audit_skb_queue) > audit_backlog_limit)
 680                                 schedule_timeout(timeout_start + audit_backlog_wait_time - jiffies);
 681
 682                         __set_current_state(TASK_RUNNING);
 683                         remove_wait_queue(&audit_backlog_wait, &wait);
 684                         continue;
 685                 }
 686                 if (audit_rate_check())
 687                         printk(KERN_WARNING
 688                                "audit: audit_backlog=%d > "
 689                                "audit_backlog_limit=%d\n",
 690                                skb_queue_len(&audit_skb_queue),
 691                                audit_backlog_limit);
 692                 audit_log_lost("backlog limit exceeded");
 693                 audit_backlog_wait_time = audit_backlog_wait_overflow;
 694                 wake_up(&audit_backlog_wait);
 695                 return NULL;
 696         }
 697
 698         ab = audit_buffer_alloc(ctx, gfp_mask, type);
 699         if (!ab) {
 700                 audit_log_lost("out of memory in audit_log_start");
 701                 return NULL;
 702         }
 703
 704         audit_get_stamp(ab->ctx, &t, &serial);
 705
 706         audit_log_format(ab, "audit(%lu.%03lu:%u): ",
 707                          t.tv_sec, t.tv_nsec/1000000, serial);
 708         return ab;
 709 }
 710
 711 /**
 712  * audit_expand - expand skb in the audit buffer
 713  * @ab: audit_buffer
 714  *
 715  * Returns 0 (no space) on failed expansion, or available space if
 716  * successful.
 717  */
 718 static inline int audit_expand(struct audit_buffer *ab, int extra)
 719 {
 720         struct sk_buff *skb = ab->skb;
 721         int ret = pskb_expand_head(skb, skb_headroom(skb), extra,
 722                                    ab->gfp_mask);
 723         if (ret < 0) {
 724                 audit_log_lost("out of memory in audit_expand");
 725                 return 0;
 726         }
 727         return skb_tailroom(skb);
 728 }
 729
 730 /* Format an audit message into the audit buffer.  If there isn't enough
 731  * room in the audit buffer, more room will be allocated and vsnprint
 732  * will be called a second time.  Currently, we assume that a printk
 733  * can't format message larger than 1024 bytes, so we don't either. */
 734 static void audit_log_vformat(struct audit_buffer *ab, const char *fmt,
 735                               va_list args)
 736 {
 737         int len, avail;
 738         struct sk_buff *skb;
 739         va_list args2;
 740
 741         if (!ab)
 742                 return;
 743
 744         BUG_ON(!ab->skb);
 745         skb = ab->skb;
 746         avail = skb_tailroom(skb);
 747         if (avail == 0) {
 748                 avail = audit_expand(ab, AUDIT_BUFSIZ);
 749                 if (!avail)
 750                         goto out;
 751         }
 752         va_copy(args2, args);
 753         len = vsnprintf(skb->tail, avail, fmt, args);
 754         if (len >= avail) {
 755                 /* The printk buffer is 1024 bytes long, so if we get
 756                  * here and AUDIT_BUFSIZ is at least 1024, then we can
 757                  * log everything that printk could have logged. */
 758                 avail = audit_expand(ab, max_t(unsigned, AUDIT_BUFSIZ, 1+len-avail));
 759                 if (!avail)
 760                         goto out;
 761                 len = vsnprintf(skb->tail, avail, fmt, args2);
 762         }
 763         if (len > 0)
 764                 skb_put(skb, len);
 765 out:
 766         return;
 767 }
 768
 769 /* Format a message into the audit buffer.  All the work is done in
 770  * audit_log_vformat. */
 771 void audit_log_format(struct audit_buffer *ab, const char *fmt, ...)
 772 {
 773         va_list args;
 774
 775         if (!ab)
 776                 return;
 777         va_start(args, fmt);
 778         audit_log_vformat(ab, fmt, args);
 779         va_end(args);
 780 }
 781
 782 /* This function will take the passed buf and convert it into a string of
 783  * ascii hex digits. The new string is placed onto the skb. */
 784 void audit_log_hex(struct audit_buffer *ab, const unsigned char *buf,
 785                 size_t len)
 786 {
 787         int i, avail, new_len;
 788         unsigned char *ptr;
 789         struct sk_buff *skb;
 790         static const unsigned char *hex = "0123456789ABCDEF";
 791
 792         BUG_ON(!ab->skb);
 793         skb = ab->skb;
 794         avail = skb_tailroom(skb);
 795         new_len = len<<1;
 796         if (new_len >= avail) {
 797                 /* Round the buffer request up to the next multiple */
 798                 new_len = AUDIT_BUFSIZ*(((new_len-avail)/AUDIT_BUFSIZ) + 1);
 799                 avail = audit_expand(ab, new_len);
 800                 if (!avail)
 801                         return;
 802         }
 803
 804         ptr = skb->tail;
 805         for (i=0; i<len; i++) {
 806                 *ptr++ = hex[(buf[i] & 0xF0)>>4]; /* Upper nibble */
 807                 *ptr++ = hex[buf[i] & 0x0F];      /* Lower nibble */
 808         }
 809         *ptr = 0;
 810         skb_put(skb, len << 1); /* new string is twice the old string */
 811 }
 812
 813 /* This code will escape a string that is passed to it if the string
 814  * contains a control character, unprintable character, double quote mark,
 815  * or a space. Unescaped strings will start and end with a double quote mark.
 816  * Strings that are escaped are printed in hex (2 digits per char). */
 817 void audit_log_untrustedstring(struct audit_buffer *ab, const char *string)
 818 {
 819         const unsigned char *p = string;
 820
 821         while (*p) {
 822                 if (*p == '"' || *p < 0x21 || *p > 0x7f) {
 823                         audit_log_hex(ab, string, strlen(string));
 824                         return;
 825                 }
 826                 p++;
 827         }
 828         audit_log_format(ab, "\"%s\"", string);
 829 }
 830
 831 /* This is a helper-function to print the escaped d_path */
 832 void audit_log_d_path(struct audit_buffer *ab, const char *prefix,
 833                       struct dentry *dentry, struct vfsmount *vfsmnt)
 834 {
 835         char *p, *path;
 836
 837         if (prefix)
 838                 audit_log_format(ab, " %s", prefix);
 839
 840         /* We will allow 11 spaces for ' (deleted)' to be appended */
 841         path = kmalloc(PATH_MAX+11, ab->gfp_mask);
 842         if (!path) {
 843                 audit_log_format(ab, "<no memory>");
 844                 return;
 845         }
 846         p = d_path(dentry, vfsmnt, path, PATH_MAX+11);
 847         if (IS_ERR(p)) { /* Should never happen since we send PATH_MAX */
 848                 /* FIXME: can we save some information here? */
 849                 audit_log_format(ab, "<too long>");
 850         } else
 851                 audit_log_untrustedstring(ab, p);
 852         kfree(path);
 853 }
 854
 855 /* The netlink_* functions cannot be called inside an irq context, so
 856  * the audit buffer is places on a queue and a tasklet is scheduled to
 857  * remove them from the queue outside the irq context.  May be called in
 858  * any context. */
 859 void audit_log_end(struct audit_buffer *ab)
 860 {
 861         if (!ab)
 862                 return;
 863         if (!audit_rate_check()) {
 864                 audit_log_lost("rate limit exceeded");
 865         } else {
 866                 if (audit_pid) {
 867                         struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data;
 868                         nlh->nlmsg_len = ab->skb->len - NLMSG_SPACE(0);
 869                         skb_queue_tail(&audit_skb_queue, ab->skb);
 870                         ab->skb = NULL;
 871                         wake_up_interruptible(&kauditd_wait);
 872                 } else {
 873                         printk(KERN_NOTICE "%s\n", ab->skb->data + NLMSG_SPACE(0));
 874                 }
 875         }
 876         audit_buffer_free(ab);
 877 }
 878
 879 /* Log an audit record.  This is a convenience function that calls
 880  * audit_log_start, audit_log_vformat, and audit_log_end.  It may be
 881  * called in any context. */
 882 void audit_log(struct audit_context *ctx, gfp_t gfp_mask, int type,
 883                const char *fmt, ...)
 884 {
 885         struct audit_buffer *ab;
 886         va_list args;
 887
 888         ab = audit_log_start(ctx, gfp_mask, type);
 889         if (ab) {
 890                 va_start(args, fmt);
 891                 audit_log_vformat(ab, fmt, args);
 892                 va_end(args);
 893                 audit_log_end(ab);
 894         }
 895 }