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 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 /* The identity of the user shutting down the audit system. */
  83 uid_t           audit_sig_uid = -1;
  84 pid_t           audit_sig_pid = -1;
  85
  86 /* Records can be lost in several ways:
  87    0) [suppressed in audit_alloc]
  88    1) out of memory in audit_log_start [kmalloc of struct audit_buffer]
  89    2) out of memory in audit_log_move [alloc_skb]
  90    3) suppressed due to audit_rate_limit
  91    4) suppressed due to audit_backlog_limit
  92 */
  93 static atomic_t    audit_lost = ATOMIC_INIT(0);
  94
  95 /* The netlink socket. */
  96 static struct sock *audit_sock;
  97
  98 /* There are two lists of audit buffers.  The txlist contains audit
  99  * buffers that cannot be sent immediately to the netlink device because
 100  * we are in an irq context (these are sent later in a tasklet).
 101  *
 102  * The second list is a list of pre-allocated audit buffers (if more
 103  * than AUDIT_MAXFREE are in use, the audit buffer is freed instead of
 104  * being placed on the freelist). */
 105 static DEFINE_SPINLOCK(audit_txlist_lock);
 106 static DEFINE_SPINLOCK(audit_freelist_lock);
 107 static int         audit_freelist_count = 0;
 108 static LIST_HEAD(audit_txlist);
 109 static LIST_HEAD(audit_freelist);
 110
 111 /* There are three lists of rules -- one to search at task creation
 112  * time, one to search at syscall entry time, and another to search at
 113  * syscall exit time. */
 114 static LIST_HEAD(audit_tsklist);
 115 static LIST_HEAD(audit_entlist);
 116 static LIST_HEAD(audit_extlist);
 117
 118 /* The netlink socket is only to be read by 1 CPU, which lets us assume
 119  * that list additions and deletions never happen simultaneiously in
 120  * auditsc.c */
 121 static DECLARE_MUTEX(audit_netlink_sem);
 122
 123 /* AUDIT_BUFSIZ is the size of the temporary buffer used for formatting
 124  * audit records.  Since printk uses a 1024 byte buffer, this buffer
 125  * should be at least that large. */
 126 #define AUDIT_BUFSIZ 1024
 127
 128 /* AUDIT_MAXFREE is the number of empty audit_buffers we keep on the
 129  * audit_freelist.  Doing so eliminates many kmalloc/kfree calls. */
 130 #define AUDIT_MAXFREE  (2*NR_CPUS)
 131
 132 /* The audit_buffer is used when formatting an audit record.  The caller
 133  * locks briefly to get the record off the freelist or to allocate the
 134  * buffer, and locks briefly to send the buffer to the netlink layer or
 135  * to place it on a transmit queue.  Multiple audit_buffers can be in
 136  * use simultaneously. */
 137 struct audit_buffer {
 138         struct list_head     list;
 139         struct sk_buff       *skb;      /* formatted skb ready to send */
 140         struct audit_context *ctx;      /* NULL or associated context */
 141 };
 142
 143 void audit_set_type(struct audit_buffer *ab, int type)
 144 {
 145         struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data;
 146         nlh->nlmsg_type = type;
 147 }
 148
 149 static void audit_set_pid(struct audit_buffer *ab, pid_t pid)
 150 {
 151         struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data;
 152         nlh->nlmsg_pid = pid;
 153 }
 154
 155 struct audit_entry {
 156         struct list_head  list;
 157         struct audit_rule rule;
 158 };
 159
 160 static void audit_log_end_irq(struct audit_buffer *ab);
 161 static void audit_log_end_fast(struct audit_buffer *ab);
 162
 163 static void audit_panic(const char *message)
 164 {
 165         switch (audit_failure)
 166         {
 167         case AUDIT_FAIL_SILENT:
 168                 break;
 169         case AUDIT_FAIL_PRINTK:
 170                 printk(KERN_ERR "audit: %s\n", message);
 171                 break;
 172         case AUDIT_FAIL_PANIC:
 173                 panic("audit: %s\n", message);
 174                 break;
 175         }
 176 }
 177
 178 static inline int audit_rate_check(void)
 179 {
 180         static unsigned long    last_check = 0;
 181         static int              messages   = 0;
 182         static DEFINE_SPINLOCK(lock);
 183         unsigned long           flags;
 184         unsigned long           now;
 185         unsigned long           elapsed;
 186         int                     retval     = 0;
 187
 188         if (!audit_rate_limit) return 1;
 189
 190         spin_lock_irqsave(&lock, flags);
 191         if (++messages < audit_rate_limit) {
 192                 retval = 1;
 193         } else {
 194                 now     = jiffies;
 195                 elapsed = now - last_check;
 196                 if (elapsed > HZ) {
 197                         last_check = now;
 198                         messages   = 0;
 199                         retval     = 1;
 200                 }
 201         }
 202         spin_unlock_irqrestore(&lock, flags);
 203
 204         return retval;
 205 }
 206
 207 /* Emit at least 1 message per second, even if audit_rate_check is
 208  * throttling. */
 209 void audit_log_lost(const char *message)
 210 {
 211         static unsigned long    last_msg = 0;
 212         static DEFINE_SPINLOCK(lock);
 213         unsigned long           flags;
 214         unsigned long           now;
 215         int                     print;
 216
 217         atomic_inc(&audit_lost);
 218
 219         print = (audit_failure == AUDIT_FAIL_PANIC || !audit_rate_limit);
 220
 221         if (!print) {
 222                 spin_lock_irqsave(&lock, flags);
 223                 now = jiffies;
 224                 if (now - last_msg > HZ) {
 225                         print = 1;
 226                         last_msg = now;
 227                 }
 228                 spin_unlock_irqrestore(&lock, flags);
 229         }
 230
 231         if (print) {
 232                 printk(KERN_WARNING
 233                        "audit: audit_lost=%d audit_backlog=%d"
 234                        " audit_rate_limit=%d audit_backlog_limit=%d\n",
 235                        atomic_read(&audit_lost),
 236                        atomic_read(&audit_backlog),
 237                        audit_rate_limit,
 238                        audit_backlog_limit);
 239                 audit_panic(message);
 240         }
 241
 242 }
 243
 244 static int audit_set_rate_limit(int limit, uid_t loginuid)
 245 {
 246         int old          = audit_rate_limit;
 247         audit_rate_limit = limit;
 248         audit_log(NULL, "audit_rate_limit=%d old=%d by auid %u",
 249                         audit_rate_limit, old, loginuid);
 250         return old;
 251 }
 252
 253 static int audit_set_backlog_limit(int limit, uid_t loginuid)
 254 {
 255         int old          = audit_backlog_limit;
 256         audit_backlog_limit = limit;
 257         audit_log(NULL, "audit_backlog_limit=%d old=%d by auid %u",
 258                         audit_backlog_limit, old, loginuid);
 259         return old;
 260 }
 261
 262 static int audit_set_enabled(int state, uid_t loginuid)
 263 {
 264         int old          = audit_enabled;
 265         if (state != 0 && state != 1)
 266                 return -EINVAL;
 267         audit_enabled = state;
 268         audit_log(NULL, "audit_enabled=%d old=%d by auid %u",
 269                   audit_enabled, old, loginuid);
 270         return old;
 271 }
 272
 273 static int audit_set_failure(int state, uid_t loginuid)
 274 {
 275         int old          = audit_failure;
 276         if (state != AUDIT_FAIL_SILENT
 277             && state != AUDIT_FAIL_PRINTK
 278             && state != AUDIT_FAIL_PANIC)
 279                 return -EINVAL;
 280         audit_failure = state;
 281         audit_log(NULL, "audit_failure=%d old=%d by auid %u",
 282                   audit_failure, old, loginuid);
 283         return old;
 284 }
 285
 286 void audit_send_reply(int pid, int seq, int type, int done, int multi,
 287                       void *payload, int size)
 288 {
 289         struct sk_buff  *skb;
 290         struct nlmsghdr *nlh;
 291         int             len = NLMSG_SPACE(size);
 292         void            *data;
 293         int             flags = multi ? NLM_F_MULTI : 0;
 294         int             t     = done  ? NLMSG_DONE  : type;
 295
 296         skb = alloc_skb(len, GFP_KERNEL);
 297         if (!skb)
 298                 goto nlmsg_failure;
 299
 300         nlh              = NLMSG_PUT(skb, pid, seq, t, len - sizeof(*nlh));
 301         nlh->nlmsg_flags = flags;
 302         data             = NLMSG_DATA(nlh);
 303         memcpy(data, payload, size);
 304         netlink_unicast(audit_sock, skb, pid, MSG_DONTWAIT);
 305         return;
 306
 307 nlmsg_failure:                  /* Used by NLMSG_PUT */
 308         if (skb)
 309                 kfree_skb(skb);
 310 }
 311
 312 /*
 313  * Check for appropriate CAP_AUDIT_ capabilities on incoming audit
 314  * control messages.
 315  */
 316 static int audit_netlink_ok(kernel_cap_t eff_cap, u16 msg_type)
 317 {
 318         int err = 0;
 319
 320         switch (msg_type) {
 321         case AUDIT_GET:
 322         case AUDIT_LIST:
 323         case AUDIT_SET:
 324         case AUDIT_ADD:
 325         case AUDIT_DEL:
 326         case AUDIT_SIGNAL_INFO:
 327                 if (!cap_raised(eff_cap, CAP_AUDIT_CONTROL))
 328                         err = -EPERM;
 329                 break;
 330         case AUDIT_USER:
 331                 if (!cap_raised(eff_cap, CAP_AUDIT_WRITE))
 332                         err = -EPERM;
 333                 break;
 334         default:  /* bad msg */
 335                 err = -EINVAL;
 336         }
 337
 338         return err;
 339 }
 340
 341 static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 342 {
 343         u32                     uid, pid, seq;
 344         void                    *data;
 345         struct audit_status     *status_get, status_set;
 346         int                     err;
 347         struct audit_buffer     *ab;
 348         u16                     msg_type = nlh->nlmsg_type;
 349         uid_t                   loginuid; /* loginuid of sender */
 350         struct audit_sig_info   sig_data;
 351
 352         err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
 353         if (err)
 354                 return err;
 355
 356         pid  = NETLINK_CREDS(skb)->pid;
 357         uid  = NETLINK_CREDS(skb)->uid;
 358         loginuid = NETLINK_CB(skb).loginuid;
 359         seq  = nlh->nlmsg_seq;
 360         data = NLMSG_DATA(nlh);
 361
 362         switch (msg_type) {
 363         case AUDIT_GET:
 364                 status_set.enabled       = audit_enabled;
 365                 status_set.failure       = audit_failure;
 366                 status_set.pid           = audit_pid;
 367                 status_set.rate_limit    = audit_rate_limit;
 368                 status_set.backlog_limit = audit_backlog_limit;
 369                 status_set.lost          = atomic_read(&audit_lost);
 370                 status_set.backlog       = atomic_read(&audit_backlog);
 371                 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0,
 372                                  &status_set, sizeof(status_set));
 373                 break;
 374         case AUDIT_SET:
 375                 if (nlh->nlmsg_len < sizeof(struct audit_status))
 376                         return -EINVAL;
 377                 status_get   = (struct audit_status *)data;
 378                 if (status_get->mask & AUDIT_STATUS_ENABLED) {
 379                         err = audit_set_enabled(status_get->enabled, loginuid);
 380                         if (err < 0) return err;
 381                 }
 382                 if (status_get->mask & AUDIT_STATUS_FAILURE) {
 383                         err = audit_set_failure(status_get->failure, loginuid);
 384                         if (err < 0) return err;
 385                 }
 386                 if (status_get->mask & AUDIT_STATUS_PID) {
 387                         int old   = audit_pid;
 388                         audit_pid = status_get->pid;
 389                         audit_log(NULL, "audit_pid=%d old=%d by auid %u",
 390                                   audit_pid, old, loginuid);
 391                 }
 392                 if (status_get->mask & AUDIT_STATUS_RATE_LIMIT)
 393                         audit_set_rate_limit(status_get->rate_limit, loginuid);
 394                 if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT)
 395                         audit_set_backlog_limit(status_get->backlog_limit,
 396                                                         loginuid);
 397                 break;
 398         case AUDIT_USER:
 399                 ab = audit_log_start(NULL);
 400                 if (!ab)
 401                         break;  /* audit_panic has been called */
 402                 audit_log_format(ab,
 403                                  "user pid=%d uid=%d length=%d loginuid=%u"
 404                                  " msg='%.1024s'",
 405                                  pid, uid,
 406                                  (int)(nlh->nlmsg_len
 407                                        - ((char *)data - (char *)nlh)),
 408                                  loginuid, (char *)data);
 409                 audit_set_type(ab, AUDIT_USER);
 410                 audit_set_pid(ab, pid);
 411                 audit_log_end(ab);
 412                 break;
 413         case AUDIT_ADD:
 414         case AUDIT_DEL:
 415                 if (nlh->nlmsg_len < sizeof(struct audit_rule))
 416                         return -EINVAL;
 417                 /* fallthrough */
 418         case AUDIT_LIST:
 419 #ifdef CONFIG_AUDITSYSCALL
 420                 err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
 421                                            uid, seq, data, loginuid);
 422 #else
 423                 err = -EOPNOTSUPP;
 424 #endif
 425                 break;
 426         case AUDIT_SIGNAL_INFO:
 427                 sig_data.uid = audit_sig_uid;
 428                 sig_data.pid = audit_sig_pid;
 429                 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_SIGNAL_INFO,
 430                                 0, 0, &sig_data, sizeof(sig_data));
 431                 break;
 432         default:
 433                 err = -EINVAL;
 434                 break;
 435         }
 436
 437         return err < 0 ? err : 0;
 438 }
 439
 440 /* Get message from skb (based on rtnetlink_rcv_skb).  Each message is
 441  * processed by audit_receive_msg.  Malformed skbs with wrong length are
 442  * discarded silently.  */
 443 static void audit_receive_skb(struct sk_buff *skb)
 444 {
 445         int             err;
 446         struct nlmsghdr *nlh;
 447         u32             rlen;
 448
 449         while (skb->len >= NLMSG_SPACE(0)) {
 450                 nlh = (struct nlmsghdr *)skb->data;
 451                 if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
 452                         return;
 453                 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
 454                 if (rlen > skb->len)
 455                         rlen = skb->len;
 456                 if ((err = audit_receive_msg(skb, nlh))) {
 457                         netlink_ack(skb, nlh, err);
 458                 } else if (nlh->nlmsg_flags & NLM_F_ACK)
 459                         netlink_ack(skb, nlh, 0);
 460                 skb_pull(skb, rlen);
 461         }
 462 }
 463
 464 /* Receive messages from netlink socket. */
 465 static void audit_receive(struct sock *sk, int length)
 466 {
 467         struct sk_buff  *skb;
 468         unsigned int qlen;
 469
 470         down(&audit_netlink_sem);
 471
 472         for (qlen = skb_queue_len(&sk->sk_receive_queue); qlen; qlen--) {
 473                 skb = skb_dequeue(&sk->sk_receive_queue);
 474                 audit_receive_skb(skb);
 475                 kfree_skb(skb);
 476         }
 477         up(&audit_netlink_sem);
 478 }
 479
 480 /* Grab skbuff from the audit_buffer and send to user space. */
 481 static inline int audit_log_drain(struct audit_buffer *ab)
 482 {
 483         struct sk_buff *skb = ab->skb;
 484
 485         if (skb) {
 486                 int retval = 0;
 487
 488                 if (audit_pid) {
 489                         struct nlmsghdr *nlh = (struct nlmsghdr *)skb->data;
 490                         nlh->nlmsg_len = skb->len - NLMSG_SPACE(0);
 491                         skb_get(skb); /* because netlink_* frees */
 492                         retval = netlink_unicast(audit_sock, skb, audit_pid,
 493                                                  MSG_DONTWAIT);
 494                 }
 495                 if (retval == -EAGAIN &&
 496                     (atomic_read(&audit_backlog)) < audit_backlog_limit) {
 497                         audit_log_end_irq(ab);
 498                         return 1;
 499                 }
 500                 if (retval < 0) {
 501                         if (retval == -ECONNREFUSED) {
 502                                 printk(KERN_ERR
 503                                        "audit: *NO* daemon at audit_pid=%d\n",
 504                                        audit_pid);
 505                                 audit_pid = 0;
 506                         } else
 507                                 audit_log_lost("netlink socket too busy");
 508                 }
 509                 if (!audit_pid) { /* No daemon */
 510                         int offset = NLMSG_SPACE(0);
 511                         int len    = skb->len - offset;
 512                         skb->data[offset + len] = '\0';
 513                         printk(KERN_ERR "%s\n", skb->data + offset);
 514                 }
 515         }
 516         return 0;
 517 }
 518
 519 /* Initialize audit support at boot time. */
 520 static int __init audit_init(void)
 521 {
 522         printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
 523                audit_default ? "enabled" : "disabled");
 524         audit_sock = netlink_kernel_create(NETLINK_AUDIT, audit_receive);
 525         if (!audit_sock)
 526                 audit_panic("cannot initialize netlink socket");
 527
 528         audit_initialized = 1;
 529         audit_enabled = audit_default;
 530         audit_log(NULL, "initialized");
 531         return 0;
 532 }
 533 __initcall(audit_init);
 534
 535 /* Process kernel command-line parameter at boot time.  audit=0 or audit=1. */
 536 static int __init audit_enable(char *str)
 537 {
 538         audit_default = !!simple_strtol(str, NULL, 0);
 539         printk(KERN_INFO "audit: %s%s\n",
 540                audit_default ? "enabled" : "disabled",
 541                audit_initialized ? "" : " (after initialization)");
 542         if (audit_initialized)
 543                 audit_enabled = audit_default;
 544         return 0;
 545 }
 546
 547 __setup("audit=", audit_enable);
 548
 549 static void audit_buffer_free(struct audit_buffer *ab)
 550 {
 551         unsigned long flags;
 552
 553         if (!ab)
 554                 return;
 555
 556         if (ab->skb)
 557                 kfree_skb(ab->skb);
 558         atomic_dec(&audit_backlog);
 559         spin_lock_irqsave(&audit_freelist_lock, flags);
 560         if (++audit_freelist_count > AUDIT_MAXFREE)
 561                 kfree(ab);
 562         else
 563                 list_add(&ab->list, &audit_freelist);
 564         spin_unlock_irqrestore(&audit_freelist_lock, flags);
 565 }
 566
 567 static struct audit_buffer * audit_buffer_alloc(struct audit_context *ctx,
 568                                                 int gfp_mask)
 569 {
 570         unsigned long flags;
 571         struct audit_buffer *ab = NULL;
 572         struct nlmsghdr *nlh;
 573
 574         spin_lock_irqsave(&audit_freelist_lock, flags);
 575         if (!list_empty(&audit_freelist)) {
 576                 ab = list_entry(audit_freelist.next,
 577                                 struct audit_buffer, list);
 578                 list_del(&ab->list);
 579                 --audit_freelist_count;
 580         }
 581         spin_unlock_irqrestore(&audit_freelist_lock, flags);
 582
 583         if (!ab) {
 584                 ab = kmalloc(sizeof(*ab), gfp_mask);
 585                 if (!ab)
 586                         goto err;
 587         }
 588         atomic_inc(&audit_backlog);
 589
 590         ab->skb = alloc_skb(AUDIT_BUFSIZ, gfp_mask);
 591         if (!ab->skb)
 592                 goto err;
 593
 594         ab->ctx   = ctx;
 595         nlh = (struct nlmsghdr *)skb_put(ab->skb, NLMSG_SPACE(0));
 596         nlh->nlmsg_type = AUDIT_KERNEL;
 597         nlh->nlmsg_flags = 0;
 598         nlh->nlmsg_pid = 0;
 599         nlh->nlmsg_seq = 0;
 600         return ab;
 601 err:
 602         audit_buffer_free(ab);
 603         return NULL;
 604 }
 605
 606 /* Obtain an audit buffer.  This routine does locking to obtain the
 607  * audit buffer, but then no locking is required for calls to
 608  * audit_log_*format.  If the tsk is a task that is currently in a
 609  * syscall, then the syscall is marked as auditable and an audit record
 610  * will be written at syscall exit.  If there is no associated task, tsk
 611  * should be NULL. */
 612 struct audit_buffer *audit_log_start(struct audit_context *ctx)
 613 {
 614         struct audit_buffer     *ab     = NULL;
 615         struct timespec         t;
 616         unsigned int            serial;
 617
 618         if (!audit_initialized)
 619                 return NULL;
 620
 621         if (audit_backlog_limit
 622             && atomic_read(&audit_backlog) > audit_backlog_limit) {
 623                 if (audit_rate_check())
 624                         printk(KERN_WARNING
 625                                "audit: audit_backlog=%d > "
 626                                "audit_backlog_limit=%d\n",
 627                                atomic_read(&audit_backlog),
 628                                audit_backlog_limit);
 629                 audit_log_lost("backlog limit exceeded");
 630                 return NULL;
 631         }
 632
 633         ab = audit_buffer_alloc(ctx, GFP_ATOMIC);
 634         if (!ab) {
 635                 audit_log_lost("out of memory in audit_log_start");
 636                 return NULL;
 637         }
 638
 639 #ifdef CONFIG_AUDITSYSCALL
 640         if (ab->ctx)
 641                 audit_get_stamp(ab->ctx, &t, &serial);
 642         else
 643 #endif
 644         {
 645                 t = CURRENT_TIME;
 646                 serial = 0;
 647         }
 648         audit_log_format(ab, "audit(%lu.%03lu:%u): ",
 649                          t.tv_sec, t.tv_nsec/1000000, serial);
 650         return ab;
 651 }
 652
 653 /**
 654  * audit_expand - expand skb in the audit buffer
 655  * @ab: audit_buffer
 656  *
 657  * Returns 0 (no space) on failed expansion, or available space if
 658  * successful.
 659  */
 660 static inline int audit_expand(struct audit_buffer *ab, int extra)
 661 {
 662         struct sk_buff *skb = ab->skb;
 663         int ret = pskb_expand_head(skb, skb_headroom(skb), extra,
 664                                    GFP_ATOMIC);
 665         if (ret < 0) {
 666                 audit_log_lost("out of memory in audit_expand");
 667                 return 0;
 668         }
 669         return skb_tailroom(skb);
 670 }
 671
 672 /* Format an audit message into the audit buffer.  If there isn't enough
 673  * room in the audit buffer, more room will be allocated and vsnprint
 674  * will be called a second time.  Currently, we assume that a printk
 675  * can't format message larger than 1024 bytes, so we don't either. */
 676 static void audit_log_vformat(struct audit_buffer *ab, const char *fmt,
 677                               va_list args)
 678 {
 679         int len, avail;
 680         struct sk_buff *skb;
 681         va_list args2;
 682
 683         if (!ab)
 684                 return;
 685
 686         BUG_ON(!ab->skb);
 687         skb = ab->skb;
 688         avail = skb_tailroom(skb);
 689         if (avail == 0) {
 690                 avail = audit_expand(ab, AUDIT_BUFSIZ);
 691                 if (!avail)
 692                         goto out;
 693         }
 694         va_copy(args2, args);
 695         len = vsnprintf(skb->tail, avail, fmt, args);
 696         if (len >= avail) {
 697                 /* The printk buffer is 1024 bytes long, so if we get
 698                  * here and AUDIT_BUFSIZ is at least 1024, then we can
 699                  * log everything that printk could have logged. */
 700                 avail = audit_expand(ab, 1+len-avail);
 701                 if (!avail)
 702                         goto out;
 703                 len = vsnprintf(skb->tail, avail, fmt, args2);
 704         }
 705         skb_put(skb, (len < avail) ? len : avail);
 706 out:
 707         return;
 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 void audit_log_hex(struct audit_buffer *ab, const unsigned char *buf, size_t len)
 724 {
 725         int i;
 726
 727         for (i=0; i<len; i++)
 728                 audit_log_format(ab, "%02x", buf[i]);
 729 }
 730
 731 void audit_log_untrustedstring(struct audit_buffer *ab, const char *string)
 732 {
 733         const unsigned char *p = string;
 734
 735         while (*p) {
 736                 if (*p == '"' || *p == ' ' || *p < 0x20 || *p > 0x7f) {
 737                         audit_log_hex(ab, string, strlen(string));
 738                         return;
 739                 }
 740                 p++;
 741         }
 742         audit_log_format(ab, "\"%s\"", string);
 743 }
 744
 745
 746 /* This is a helper-function to print the d_path without using a static
 747  * buffer or allocating another buffer in addition to the one in
 748  * audit_buffer. */
 749 void audit_log_d_path(struct audit_buffer *ab, const char *prefix,
 750                       struct dentry *dentry, struct vfsmount *vfsmnt)
 751 {
 752         char *p;
 753         struct sk_buff *skb = ab->skb;
 754         int  len, avail;
 755
 756         if (prefix)
 757                 audit_log_format(ab, " %s", prefix);
 758
 759         avail = skb_tailroom(skb);
 760         p = d_path(dentry, vfsmnt, skb->tail, avail);
 761         if (IS_ERR(p)) {
 762                 /* FIXME: can we save some information here? */
 763                 audit_log_format(ab, "<toolong>");
 764         } else {
 765                 /* path isn't at start of buffer */
 766                 len = ((char *)skb->tail + avail - 1) - p;
 767                 memmove(skb->tail, p, len);
 768                 skb_put(skb, len);
 769         }
 770 }
 771
 772 /* Remove queued messages from the audit_txlist and send them to userspace. */
 773 static void audit_tasklet_handler(unsigned long arg)
 774 {
 775         LIST_HEAD(list);
 776         struct audit_buffer *ab;
 777         unsigned long       flags;
 778
 779         spin_lock_irqsave(&audit_txlist_lock, flags);
 780         list_splice_init(&audit_txlist, &list);
 781         spin_unlock_irqrestore(&audit_txlist_lock, flags);
 782
 783         while (!list_empty(&list)) {
 784                 ab = list_entry(list.next, struct audit_buffer, list);
 785                 list_del(&ab->list);
 786                 audit_log_end_fast(ab);
 787         }
 788 }
 789
 790 static DECLARE_TASKLET(audit_tasklet, audit_tasklet_handler, 0);
 791
 792 /* The netlink_* functions cannot be called inside an irq context, so
 793  * the audit buffer is places on a queue and a tasklet is scheduled to
 794  * remove them from the queue outside the irq context.  May be called in
 795  * any context. */
 796 static void audit_log_end_irq(struct audit_buffer *ab)
 797 {
 798         unsigned long flags;
 799
 800         if (!ab)
 801                 return;
 802         spin_lock_irqsave(&audit_txlist_lock, flags);
 803         list_add_tail(&ab->list, &audit_txlist);
 804         spin_unlock_irqrestore(&audit_txlist_lock, flags);
 805
 806         tasklet_schedule(&audit_tasklet);
 807 }
 808
 809 /* Send the message in the audit buffer directly to user space.  May not
 810  * be called in an irq context. */
 811 static void audit_log_end_fast(struct audit_buffer *ab)
 812 {
 813         BUG_ON(in_irq());
 814         if (!ab)
 815                 return;
 816         if (!audit_rate_check()) {
 817                 audit_log_lost("rate limit exceeded");
 818         } else {
 819                 if (audit_log_drain(ab))
 820                         return;
 821         }
 822         audit_buffer_free(ab);
 823 }
 824
 825 /* Send or queue the message in the audit buffer, depending on the
 826  * current context.  (A convenience function that may be called in any
 827  * context.) */
 828 void audit_log_end(struct audit_buffer *ab)
 829 {
 830         if (in_irq())
 831                 audit_log_end_irq(ab);
 832         else
 833                 audit_log_end_fast(ab);
 834 }
 835
 836 /* Log an audit record.  This is a convenience function that calls
 837  * audit_log_start, audit_log_vformat, and audit_log_end.  It may be
 838  * called in any context. */
 839 void audit_log(struct audit_context *ctx, const char *fmt, ...)
 840 {
 841         struct audit_buffer *ab;
 842         va_list args;
 843
 844         ab = audit_log_start(ctx);
 845         if (ab) {
 846                 va_start(args, fmt);
 847                 audit_log_vformat(ab, fmt, args);
 848                 va_end(args);
 849                 audit_log_end(ab);
 850         }
 851 }