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
  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, uid_t loginuid)
 243 {
 244         int old          = audit_rate_limit;
 245         audit_rate_limit = limit;
 246         audit_log(NULL, "audit_rate_limit=%d old=%d by auid %u",
 247                         audit_rate_limit, old, loginuid);
 248         return old;
 249 }
 250
 251 static int audit_set_backlog_limit(int limit, uid_t loginuid)
 252 {
 253         int old          = audit_backlog_limit;
 254         audit_backlog_limit = limit;
 255         audit_log(NULL, "audit_backlog_limit=%d old=%d by auid %u",
 256                         audit_backlog_limit, old, loginuid);
 257         return old;
 258 }
 259
 260 static int audit_set_enabled(int state, uid_t loginuid)
 261 {
 262         int old          = audit_enabled;
 263         if (state != 0 && state != 1)
 264                 return -EINVAL;
 265         audit_enabled = state;
 266         audit_log(NULL, "audit_enabled=%d old=%d by auid %u",
 267                   audit_enabled, old, loginuid);
 268         return old;
 269 }
 270
 271 static int audit_set_failure(int state, uid_t loginuid)
 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(NULL, "audit_failure=%d old=%d by auid %u",
 280                   audit_failure, old, loginuid);
 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         uid_t                   loginuid; /* loginuid of sender */
 348
 349         err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
 350         if (err)
 351                 return err;
 352
 353         pid  = NETLINK_CREDS(skb)->pid;
 354         uid  = NETLINK_CREDS(skb)->uid;
 355         loginuid = NETLINK_CB(skb).loginuid;
 356         seq  = nlh->nlmsg_seq;
 357         data = NLMSG_DATA(nlh);
 358
 359         switch (msg_type) {
 360         case AUDIT_GET:
 361                 status_set.enabled       = audit_enabled;
 362                 status_set.failure       = audit_failure;
 363                 status_set.pid           = audit_pid;
 364                 status_set.rate_limit    = audit_rate_limit;
 365                 status_set.backlog_limit = audit_backlog_limit;
 366                 status_set.lost          = atomic_read(&audit_lost);
 367                 status_set.backlog       = atomic_read(&audit_backlog);
 368                 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0,
 369                                  &status_set, sizeof(status_set));
 370                 break;
 371         case AUDIT_SET:
 372                 if (nlh->nlmsg_len < sizeof(struct audit_status))
 373                         return -EINVAL;
 374                 status_get   = (struct audit_status *)data;
 375                 if (status_get->mask & AUDIT_STATUS_ENABLED) {
 376                         err = audit_set_enabled(status_get->enabled, loginuid);
 377                         if (err < 0) return err;
 378                 }
 379                 if (status_get->mask & AUDIT_STATUS_FAILURE) {
 380                         err = audit_set_failure(status_get->failure, loginuid);
 381                         if (err < 0) return err;
 382                 }
 383                 if (status_get->mask & AUDIT_STATUS_PID) {
 384                         int old   = audit_pid;
 385                         audit_pid = status_get->pid;
 386                         audit_log(NULL, "audit_pid=%d old=%d by auid %u",
 387                                   audit_pid, old, loginuid);
 388                 }
 389                 if (status_get->mask & AUDIT_STATUS_RATE_LIMIT)
 390                         audit_set_rate_limit(status_get->rate_limit, loginuid);
 391                 if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT)
 392                         audit_set_backlog_limit(status_get->backlog_limit,
 393                                                         loginuid);
 394                 break;
 395         case AUDIT_USER:
 396                 ab = audit_log_start(NULL);
 397                 if (!ab)
 398                         break;  /* audit_panic has been called */
 399                 audit_log_format(ab,
 400                                  "user pid=%d uid=%d length=%d loginuid=%u"
 401                                  " msg='%.1024s'",
 402                                  pid, uid,
 403                                  (int)(nlh->nlmsg_len
 404                                        - ((char *)data - (char *)nlh)),
 405                                  loginuid, (char *)data);
 406                 ab->type = AUDIT_USER;
 407                 ab->pid  = pid;
 408                 audit_log_end(ab);
 409                 break;
 410         case AUDIT_ADD:
 411         case AUDIT_DEL:
 412                 if (nlh->nlmsg_len < sizeof(struct audit_rule))
 413                         return -EINVAL;
 414                 /* fallthrough */
 415         case AUDIT_LIST:
 416 #ifdef CONFIG_AUDITSYSCALL
 417                 err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
 418                                            uid, seq, data, loginuid);
 419 #else
 420                 err = -EOPNOTSUPP;
 421 #endif
 422                 break;
 423         default:
 424                 err = -EINVAL;
 425                 break;
 426         }
 427
 428         return err < 0 ? err : 0;
 429 }
 430
 431 /* Get message from skb (based on rtnetlink_rcv_skb).  Each message is
 432  * processed by audit_receive_msg.  Malformed skbs with wrong length are
 433  * discarded silently.  */
 434 static int audit_receive_skb(struct sk_buff *skb)
 435 {
 436         int             err;
 437         struct nlmsghdr *nlh;
 438         u32             rlen;
 439
 440         while (skb->len >= NLMSG_SPACE(0)) {
 441                 nlh = (struct nlmsghdr *)skb->data;
 442                 if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
 443                         return 0;
 444                 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
 445                 if (rlen > skb->len)
 446                         rlen = skb->len;
 447                 if ((err = audit_receive_msg(skb, nlh))) {
 448                         netlink_ack(skb, nlh, err);
 449                 } else if (nlh->nlmsg_flags & NLM_F_ACK)
 450                         netlink_ack(skb, nlh, 0);
 451                 skb_pull(skb, rlen);
 452         }
 453         return 0;
 454 }
 455
 456 /* Receive messages from netlink socket. */
 457 static void audit_receive(struct sock *sk, int length)
 458 {
 459         struct sk_buff  *skb;
 460
 461         if (down_trylock(&audit_netlink_sem))
 462                 return;
 463
 464                                 /* FIXME: this must not cause starvation */
 465         while ((skb = skb_dequeue(&sk->sk_receive_queue))) {
 466                 if (audit_receive_skb(skb) && skb->len)
 467                         skb_queue_head(&sk->sk_receive_queue, skb);
 468                 else
 469                         kfree_skb(skb);
 470         }
 471         up(&audit_netlink_sem);
 472 }
 473
 474 /* Move data from tmp buffer into an skb.  This is an extra copy, and
 475  * that is unfortunate.  However, the copy will only occur when a record
 476  * is being written to user space, which is already a high-overhead
 477  * operation.  (Elimination of the copy is possible, for example, by
 478  * writing directly into a pre-allocated skb, at the cost of wasting
 479  * memory. */
 480 static void audit_log_move(struct audit_buffer *ab)
 481 {
 482         struct sk_buff  *skb;
 483         char            *start;
 484         int             extra = ab->nlh ? 0 : NLMSG_SPACE(0);
 485
 486         /* possible resubmission */
 487         if (ab->len == 0)
 488                 return;
 489
 490         skb = skb_peek(&ab->sklist);
 491         if (!skb || skb_tailroom(skb) <= ab->len + extra) {
 492                 skb = alloc_skb(2 * ab->len + extra, GFP_ATOMIC);
 493                 if (!skb) {
 494                         ab->len = 0; /* Lose information in ab->tmp */
 495                         audit_log_lost("out of memory in audit_log_move");
 496                         return;
 497                 }
 498                 __skb_queue_tail(&ab->sklist, skb);
 499                 if (!ab->nlh)
 500                         ab->nlh = (struct nlmsghdr *)skb_put(skb,
 501                                                              NLMSG_SPACE(0));
 502         }
 503         start = skb_put(skb, ab->len);
 504         memcpy(start, ab->tmp, ab->len);
 505         ab->len = 0;
 506 }
 507
 508 /* Iterate over the skbuff in the audit_buffer, sending their contents
 509  * to user space. */
 510 static inline int audit_log_drain(struct audit_buffer *ab)
 511 {
 512         struct sk_buff *skb;
 513
 514         while ((skb = skb_dequeue(&ab->sklist))) {
 515                 int retval = 0;
 516
 517                 if (audit_pid) {
 518                         if (ab->nlh) {
 519                                 ab->nlh->nlmsg_len   = ab->total;
 520                                 ab->nlh->nlmsg_type  = ab->type;
 521                                 ab->nlh->nlmsg_flags = 0;
 522                                 ab->nlh->nlmsg_seq   = 0;
 523                                 ab->nlh->nlmsg_pid   = ab->pid;
 524                         }
 525                         skb_get(skb); /* because netlink_* frees */
 526                         retval = netlink_unicast(audit_sock, skb, audit_pid,
 527                                                  MSG_DONTWAIT);
 528                 }
 529                 if (retval == -EAGAIN && ab->count < 5) {
 530                         ++ab->count;
 531                         skb_queue_tail(&ab->sklist, skb);
 532                         audit_log_end_irq(ab);
 533                         return 1;
 534                 }
 535                 if (retval < 0) {
 536                         if (retval == -ECONNREFUSED) {
 537                                 printk(KERN_ERR
 538                                        "audit: *NO* daemon at audit_pid=%d\n",
 539                                        audit_pid);
 540                                 audit_pid = 0;
 541                         } else
 542                                 audit_log_lost("netlink socket too busy");
 543                 }
 544                 if (!audit_pid) { /* No daemon */
 545                         int offset = ab->nlh ? NLMSG_SPACE(0) : 0;
 546                         int len    = skb->len - offset;
 547                         skb->data[offset + len] = '\0';
 548                         printk(KERN_ERR "%s\n", skb->data + offset);
 549                 }
 550                 kfree_skb(skb);
 551                 ab->nlh = NULL;
 552         }
 553         return 0;
 554 }
 555
 556 /* Initialize audit support at boot time. */
 557 static int __init audit_init(void)
 558 {
 559         printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
 560                audit_default ? "enabled" : "disabled");
 561         audit_sock = netlink_kernel_create(NETLINK_AUDIT, audit_receive);
 562         if (!audit_sock)
 563                 audit_panic("cannot initialize netlink socket");
 564
 565         audit_initialized = 1;
 566         audit_enabled = audit_default;
 567         audit_log(NULL, "initialized");
 568         return 0;
 569 }
 570
 571 #else
 572 /* Without CONFIG_NET, we have no skbuffs.  For now, print what we have
 573  * in the buffer. */
 574 static void audit_log_move(struct audit_buffer *ab)
 575 {
 576         printk(KERN_ERR "%*.*s\n", ab->len, ab->len, ab->tmp);
 577         ab->len = 0;
 578 }
 579
 580 static inline int audit_log_drain(struct audit_buffer *ab)
 581 {
 582         return 0;
 583 }
 584
 585 /* Initialize audit support at boot time. */
 586 int __init audit_init(void)
 587 {
 588         printk(KERN_INFO "audit: initializing WITHOUT netlink support\n");
 589         audit_sock = NULL;
 590         audit_pid  = 0;
 591
 592         audit_initialized = 1;
 593         audit_enabled = audit_default;
 594         audit_log(NULL, "initialized");
 595         return 0;
 596 }
 597 #endif
 598
 599 __initcall(audit_init);
 600
 601 /* Process kernel command-line parameter at boot time.  audit=0 or audit=1. */
 602 static int __init audit_enable(char *str)
 603 {
 604         audit_default = !!simple_strtol(str, NULL, 0);
 605         printk(KERN_INFO "audit: %s%s\n",
 606                audit_default ? "enabled" : "disabled",
 607                audit_initialized ? "" : " (after initialization)");
 608         if (audit_initialized)
 609                 audit_enabled = audit_default;
 610         return 0;
 611 }
 612
 613 __setup("audit=", audit_enable);
 614
 615
 616 /* Obtain an audit buffer.  This routine does locking to obtain the
 617  * audit buffer, but then no locking is required for calls to
 618  * audit_log_*format.  If the tsk is a task that is currently in a
 619  * syscall, then the syscall is marked as auditable and an audit record
 620  * will be written at syscall exit.  If there is no associated task, tsk
 621  * should be NULL. */
 622 struct audit_buffer *audit_log_start(struct audit_context *ctx)
 623 {
 624         struct audit_buffer     *ab     = NULL;
 625         unsigned long           flags;
 626         struct timespec         t;
 627         unsigned int            serial;
 628
 629         if (!audit_initialized)
 630                 return NULL;
 631
 632         if (audit_backlog_limit
 633             && atomic_read(&audit_backlog) > audit_backlog_limit) {
 634                 if (audit_rate_check())
 635                         printk(KERN_WARNING
 636                                "audit: audit_backlog=%d > "
 637                                "audit_backlog_limit=%d\n",
 638                                atomic_read(&audit_backlog),
 639                                audit_backlog_limit);
 640                 audit_log_lost("backlog limit exceeded");
 641                 return NULL;
 642         }
 643
 644         spin_lock_irqsave(&audit_freelist_lock, flags);
 645         if (!list_empty(&audit_freelist)) {
 646                 ab = list_entry(audit_freelist.next,
 647                                 struct audit_buffer, list);
 648                 list_del(&ab->list);
 649                 --audit_freelist_count;
 650         }
 651         spin_unlock_irqrestore(&audit_freelist_lock, flags);
 652
 653         if (!ab)
 654                 ab = kmalloc(sizeof(*ab), GFP_ATOMIC);
 655         if (!ab) {
 656                 audit_log_lost("out of memory in audit_log_start");
 657                 return NULL;
 658         }
 659
 660         atomic_inc(&audit_backlog);
 661         skb_queue_head_init(&ab->sklist);
 662
 663         ab->ctx   = ctx;
 664         ab->len   = 0;
 665         ab->nlh   = NULL;
 666         ab->total = 0;
 667         ab->type  = AUDIT_KERNEL;
 668         ab->pid   = 0;
 669         ab->count = 0;
 670
 671 #ifdef CONFIG_AUDITSYSCALL
 672         if (ab->ctx)
 673                 audit_get_stamp(ab->ctx, &t, &serial);
 674         else
 675 #endif
 676         {
 677                 t = CURRENT_TIME;
 678                 serial = 0;
 679         }
 680         audit_log_format(ab, "audit(%lu.%03lu:%u): ",
 681                          t.tv_sec, t.tv_nsec/1000000, serial);
 682         return ab;
 683 }
 684
 685
 686 /* Format an audit message into the audit buffer.  If there isn't enough
 687  * room in the audit buffer, more room will be allocated and vsnprint
 688  * will be called a second time.  Currently, we assume that a printk
 689  * can't format message larger than 1024 bytes, so we don't either. */
 690 static void audit_log_vformat(struct audit_buffer *ab, const char *fmt,
 691                               va_list args)
 692 {
 693         int len, avail;
 694
 695         if (!ab)
 696                 return;
 697
 698         avail = sizeof(ab->tmp) - ab->len;
 699         if (avail <= 0) {
 700                 audit_log_move(ab);
 701                 avail = sizeof(ab->tmp) - ab->len;
 702         }
 703         len   = vsnprintf(ab->tmp + ab->len, avail, fmt, args);
 704         if (len >= avail) {
 705                 /* The printk buffer is 1024 bytes long, so if we get
 706                  * here and AUDIT_BUFSIZ is at least 1024, then we can
 707                  * log everything that printk could have logged. */
 708                 audit_log_move(ab);
 709                 avail = sizeof(ab->tmp) - ab->len;
 710                 len   = vsnprintf(ab->tmp + ab->len, avail, fmt, args);
 711         }
 712         ab->len   += (len < avail) ? len : avail;
 713         ab->total += (len < avail) ? len : avail;
 714 }
 715
 716 /* Format a message into the audit buffer.  All the work is done in
 717  * audit_log_vformat. */
 718 void audit_log_format(struct audit_buffer *ab, const char *fmt, ...)
 719 {
 720         va_list args;
 721
 722         if (!ab)
 723                 return;
 724         va_start(args, fmt);
 725         audit_log_vformat(ab, fmt, args);
 726         va_end(args);
 727 }
 728
 729 void audit_log_hex(struct audit_buffer *ab, const unsigned char *buf, size_t len)
 730 {
 731         int i;
 732
 733         for (i=0; i<len; i++)
 734                 audit_log_format(ab, "%02x", buf[i]);
 735 }
 736
 737 void audit_log_untrustedstring(struct audit_buffer *ab, const char *string)
 738 {
 739         const unsigned char *p = string;
 740
 741         while (*p) {
 742                 if (*p == '"' || *p == ' ' || *p < 0x20 || *p > 0x7f) {
 743                         audit_log_hex(ab, string, strlen(string));
 744                         return;
 745                 }
 746                 p++;
 747         }
 748         audit_log_format(ab, "\"%s\"", string);
 749 }
 750
 751
 752 /* This is a helper-function to print the d_path without using a static
 753  * buffer or allocating another buffer in addition to the one in
 754  * audit_buffer. */
 755 void audit_log_d_path(struct audit_buffer *ab, const char *prefix,
 756                       struct dentry *dentry, struct vfsmount *vfsmnt)
 757 {
 758         char *p;
 759         int  len, avail;
 760
 761         if (prefix) audit_log_format(ab, " %s", prefix);
 762
 763         if (ab->len > 128)
 764                 audit_log_move(ab);
 765         avail = sizeof(ab->tmp) - ab->len;
 766         p = d_path(dentry, vfsmnt, ab->tmp + ab->len, avail);
 767         if (IS_ERR(p)) {
 768                 /* FIXME: can we save some information here? */
 769                 audit_log_format(ab, "<toolong>");
 770         } else {
 771                                 /* path isn't at start of buffer */
 772                 len        = (ab->tmp + sizeof(ab->tmp) - 1) - p;
 773                 memmove(ab->tmp + ab->len, p, len);
 774                 ab->len   += len;
 775                 ab->total += len;
 776         }
 777 }
 778
 779 /* Remove queued messages from the audit_txlist and send them to userspace. */
 780 static void audit_tasklet_handler(unsigned long arg)
 781 {
 782         LIST_HEAD(list);
 783         struct audit_buffer *ab;
 784         unsigned long       flags;
 785
 786         spin_lock_irqsave(&audit_txlist_lock, flags);
 787         list_splice_init(&audit_txlist, &list);
 788         spin_unlock_irqrestore(&audit_txlist_lock, flags);
 789
 790         while (!list_empty(&list)) {
 791                 ab = list_entry(list.next, struct audit_buffer, list);
 792                 list_del(&ab->list);
 793                 audit_log_end_fast(ab);
 794         }
 795 }
 796
 797 static DECLARE_TASKLET(audit_tasklet, audit_tasklet_handler, 0);
 798
 799 /* The netlink_* functions cannot be called inside an irq context, so
 800  * the audit buffer is places on a queue and a tasklet is scheduled to
 801  * remove them from the queue outside the irq context.  May be called in
 802  * any context. */
 803 static void audit_log_end_irq(struct audit_buffer *ab)
 804 {
 805         unsigned long flags;
 806
 807         if (!ab)
 808                 return;
 809         spin_lock_irqsave(&audit_txlist_lock, flags);
 810         list_add_tail(&ab->list, &audit_txlist);
 811         spin_unlock_irqrestore(&audit_txlist_lock, flags);
 812
 813         tasklet_schedule(&audit_tasklet);
 814 }
 815
 816 /* Send the message in the audit buffer directly to user space.  May not
 817  * be called in an irq context. */
 818 static void audit_log_end_fast(struct audit_buffer *ab)
 819 {
 820         unsigned long flags;
 821
 822         BUG_ON(in_irq());
 823         if (!ab)
 824                 return;
 825         if (!audit_rate_check()) {
 826                 audit_log_lost("rate limit exceeded");
 827         } else {
 828                 audit_log_move(ab);
 829                 if (audit_log_drain(ab))
 830                         return;
 831         }
 832
 833         atomic_dec(&audit_backlog);
 834         spin_lock_irqsave(&audit_freelist_lock, flags);
 835         if (++audit_freelist_count > AUDIT_MAXFREE)
 836                 kfree(ab);
 837         else
 838                 list_add(&ab->list, &audit_freelist);
 839         spin_unlock_irqrestore(&audit_freelist_lock, flags);
 840 }
 841
 842 /* Send or queue the message in the audit buffer, depending on the
 843  * current context.  (A convenience function that may be called in any
 844  * context.) */
 845 void audit_log_end(struct audit_buffer *ab)
 846 {
 847         if (in_irq())
 848                 audit_log_end_irq(ab);
 849         else
 850                 audit_log_end_fast(ab);
 851 }
 852
 853 /* Log an audit record.  This is a convenience function that calls
 854  * audit_log_start, audit_log_vformat, and audit_log_end.  It may be
 855  * called in any context. */
 856 void audit_log(struct audit_context *ctx, const char *fmt, ...)
 857 {
 858         struct audit_buffer *ab;
 859         va_list args;
 860
 861         ab = audit_log_start(ctx);
 862         if (ab) {
 863                 va_start(args, fmt);
 864                 audit_log_vformat(ab, fmt, args);
 865                 va_end(args);
 866                 audit_log_end(ab);
 867         }
 868 }