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/types.h>
  46 #include <asm/atomic.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 <net/netlink.h>
  56 #include <linux/skbuff.h>
  57 #include <linux/netlink.h>
  58 #include <linux/selinux.h>
  59
  60 #include "audit.h"
  61
  62 /* No auditing will take place until audit_initialized != 0.
  63  * (Initialization happens after skb_init is called.) */
  64 static int      audit_initialized;
  65
  66 /* No syscall auditing will take place unless audit_enabled != 0. */
  67 int             audit_enabled;
  68
  69 /* Default state when kernel boots without any parameters. */
  70 static int      audit_default;
  71
  72 /* If auditing cannot proceed, audit_failure selects what happens. */
  73 static int      audit_failure = AUDIT_FAIL_PRINTK;
  74
  75 /* If audit records are to be written to the netlink socket, audit_pid
  76  * contains the (non-zero) pid. */
  77 int             audit_pid;
  78
  79 /* If audit_rate_limit is non-zero, limit the rate of sending audit records
  80  * to that number per second.  This prevents DoS attacks, but results in
  81  * audit records being dropped. */
  82 static int      audit_rate_limit;
  83
  84 /* Number of outstanding audit_buffers allowed. */
  85 static int      audit_backlog_limit = 64;
  86 static int      audit_backlog_wait_time = 60 * HZ;
  87 static int      audit_backlog_wait_overflow = 0;
  88
  89 /* The identity of the user shutting down the audit system. */
  90 uid_t           audit_sig_uid = -1;
  91 pid_t           audit_sig_pid = -1;
  92 u32             audit_sig_sid = 0;
  93
  94 /* Records can be lost in several ways:
  95    0) [suppressed in audit_alloc]
  96    1) out of memory in audit_log_start [kmalloc of struct audit_buffer]
  97    2) out of memory in audit_log_move [alloc_skb]
  98    3) suppressed due to audit_rate_limit
  99    4) suppressed due to audit_backlog_limit
 100 */
 101 static atomic_t    audit_lost = ATOMIC_INIT(0);
 102
 103 /* The netlink socket. */
 104 static struct sock *audit_sock;
 105
 106 /* The audit_freelist is a list of pre-allocated audit buffers (if more
 107  * than AUDIT_MAXFREE are in use, the audit buffer is freed instead of
 108  * being placed on the freelist). */
 109 static DEFINE_SPINLOCK(audit_freelist_lock);
 110 static int         audit_freelist_count;
 111 static LIST_HEAD(audit_freelist);
 112
 113 static struct sk_buff_head audit_skb_queue;
 114 static struct task_struct *kauditd_task;
 115 static DECLARE_WAIT_QUEUE_HEAD(kauditd_wait);
 116 static DECLARE_WAIT_QUEUE_HEAD(audit_backlog_wait);
 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 simultaneously in
 120  * auditsc.c */
 121 DEFINE_MUTEX(audit_netlink_mutex);
 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         gfp_t                gfp_mask;
 142 };
 143
 144 static void audit_set_pid(struct audit_buffer *ab, pid_t pid)
 145 {
 146         struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data;
 147         nlh->nlmsg_pid = pid;
 148 }
 149
 150 void audit_panic(const char *message)
 151 {
 152         switch (audit_failure)
 153         {
 154         case AUDIT_FAIL_SILENT:
 155                 break;
 156         case AUDIT_FAIL_PRINTK:
 157                 printk(KERN_ERR "audit: %s\n", message);
 158                 break;
 159         case AUDIT_FAIL_PANIC:
 160                 panic("audit: %s\n", message);
 161                 break;
 162         }
 163 }
 164
 165 static inline int audit_rate_check(void)
 166 {
 167         static unsigned long    last_check = 0;
 168         static int              messages   = 0;
 169         static DEFINE_SPINLOCK(lock);
 170         unsigned long           flags;
 171         unsigned long           now;
 172         unsigned long           elapsed;
 173         int                     retval     = 0;
 174
 175         if (!audit_rate_limit) return 1;
 176
 177         spin_lock_irqsave(&lock, flags);
 178         if (++messages < audit_rate_limit) {
 179                 retval = 1;
 180         } else {
 181                 now     = jiffies;
 182                 elapsed = now - last_check;
 183                 if (elapsed > HZ) {
 184                         last_check = now;
 185                         messages   = 0;
 186                         retval     = 1;
 187                 }
 188         }
 189         spin_unlock_irqrestore(&lock, flags);
 190
 191         return retval;
 192 }
 193
 194 /**
 195  * audit_log_lost - conditionally log lost audit message event
 196  * @message: the message stating reason for lost audit message
 197  *
 198  * Emit at least 1 message per second, even if audit_rate_check is
 199  * throttling.
 200  * Always increment the lost messages counter.
 201 */
 202 void audit_log_lost(const char *message)
 203 {
 204         static unsigned long    last_msg = 0;
 205         static DEFINE_SPINLOCK(lock);
 206         unsigned long           flags;
 207         unsigned long           now;
 208         int                     print;
 209
 210         atomic_inc(&audit_lost);
 211
 212         print = (audit_failure == AUDIT_FAIL_PANIC || !audit_rate_limit);
 213
 214         if (!print) {
 215                 spin_lock_irqsave(&lock, flags);
 216                 now = jiffies;
 217                 if (now - last_msg > HZ) {
 218                         print = 1;
 219                         last_msg = now;
 220                 }
 221                 spin_unlock_irqrestore(&lock, flags);
 222         }
 223
 224         if (print) {
 225                 printk(KERN_WARNING
 226                        "audit: audit_lost=%d audit_rate_limit=%d audit_backlog_limit=%d\n",
 227                        atomic_read(&audit_lost),
 228                        audit_rate_limit,
 229                        audit_backlog_limit);
 230                 audit_panic(message);
 231         }
 232 }
 233
 234 static int audit_set_rate_limit(int limit, uid_t loginuid, u32 sid)
 235 {
 236         int old = audit_rate_limit;
 237
 238         if (sid) {
 239                 char *ctx = NULL;
 240                 u32 len;
 241                 int rc;
 242                 if ((rc = selinux_ctxid_to_string(sid, &ctx, &len)))
 243                         return rc;
 244                 else
 245                         audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 246                                 "audit_rate_limit=%d old=%d by auid=%u subj=%s",
 247                                 limit, old, loginuid, ctx);
 248                 kfree(ctx);
 249         } else
 250                 audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 251                         "audit_rate_limit=%d old=%d by auid=%u",
 252                         limit, old, loginuid);
 253         audit_rate_limit = limit;
 254         return 0;
 255 }
 256
 257 static int audit_set_backlog_limit(int limit, uid_t loginuid, u32 sid)
 258 {
 259         int old = audit_backlog_limit;
 260
 261         if (sid) {
 262                 char *ctx = NULL;
 263                 u32 len;
 264                 int rc;
 265                 if ((rc = selinux_ctxid_to_string(sid, &ctx, &len)))
 266                         return rc;
 267                 else
 268                         audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 269                             "audit_backlog_limit=%d old=%d by auid=%u subj=%s",
 270                                 limit, old, loginuid, ctx);
 271                 kfree(ctx);
 272         } else
 273                 audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 274                         "audit_backlog_limit=%d old=%d by auid=%u",
 275                         limit, old, loginuid);
 276         audit_backlog_limit = limit;
 277         return 0;
 278 }
 279
 280 static int audit_set_enabled(int state, uid_t loginuid, u32 sid)
 281 {
 282         int old = audit_enabled;
 283
 284         if (state != 0 && state != 1)
 285                 return -EINVAL;
 286
 287         if (sid) {
 288                 char *ctx = NULL;
 289                 u32 len;
 290                 int rc;
 291                 if ((rc = selinux_ctxid_to_string(sid, &ctx, &len)))
 292                         return rc;
 293                 else
 294                         audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 295                                 "audit_enabled=%d old=%d by auid=%u subj=%s",
 296                                 state, old, loginuid, ctx);
 297                 kfree(ctx);
 298         } else
 299                 audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 300                         "audit_enabled=%d old=%d by auid=%u",
 301                         state, old, loginuid);
 302         audit_enabled = state;
 303         return 0;
 304 }
 305
 306 static int audit_set_failure(int state, uid_t loginuid, u32 sid)
 307 {
 308         int old = audit_failure;
 309
 310         if (state != AUDIT_FAIL_SILENT
 311             && state != AUDIT_FAIL_PRINTK
 312             && state != AUDIT_FAIL_PANIC)
 313                 return -EINVAL;
 314
 315         if (sid) {
 316                 char *ctx = NULL;
 317                 u32 len;
 318                 int rc;
 319                 if ((rc = selinux_ctxid_to_string(sid, &ctx, &len)))
 320                         return rc;
 321                 else
 322                         audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 323                                 "audit_failure=%d old=%d by auid=%u subj=%s",
 324                                 state, old, loginuid, ctx);
 325                 kfree(ctx);
 326         } else
 327                 audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 328                         "audit_failure=%d old=%d by auid=%u",
 329                         state, old, loginuid);
 330         audit_failure = state;
 331         return 0;
 332 }
 333
 334 static int kauditd_thread(void *dummy)
 335 {
 336         struct sk_buff *skb;
 337
 338         while (1) {
 339                 skb = skb_dequeue(&audit_skb_queue);
 340                 wake_up(&audit_backlog_wait);
 341                 if (skb) {
 342                         if (audit_pid) {
 343                                 int err = netlink_unicast(audit_sock, skb, audit_pid, 0);
 344                                 if (err < 0) {
 345                                         BUG_ON(err != -ECONNREFUSED); /* Shoudn't happen */
 346                                         printk(KERN_ERR "audit: *NO* daemon at audit_pid=%d\n", audit_pid);
 347                                         audit_pid = 0;
 348                                 }
 349                         } else {
 350                                 printk(KERN_NOTICE "%s\n", skb->data + NLMSG_SPACE(0));
 351                                 kfree_skb(skb);
 352                         }
 353                 } else {
 354                         DECLARE_WAITQUEUE(wait, current);
 355                         set_current_state(TASK_INTERRUPTIBLE);
 356                         add_wait_queue(&kauditd_wait, &wait);
 357
 358                         if (!skb_queue_len(&audit_skb_queue)) {
 359                                 try_to_freeze();
 360                                 schedule();
 361                         }
 362
 363                         __set_current_state(TASK_RUNNING);
 364                         remove_wait_queue(&kauditd_wait, &wait);
 365                 }
 366         }
 367 }
 368
 369 int audit_send_list(void *_dest)
 370 {
 371         struct audit_netlink_list *dest = _dest;
 372         int pid = dest->pid;
 373         struct sk_buff *skb;
 374
 375         /* wait for parent to finish and send an ACK */
 376         mutex_lock(&audit_netlink_mutex);
 377         mutex_unlock(&audit_netlink_mutex);
 378
 379         while ((skb = __skb_dequeue(&dest->q)) != NULL)
 380                 netlink_unicast(audit_sock, skb, pid, 0);
 381
 382         kfree(dest);
 383
 384         return 0;
 385 }
 386
 387 struct sk_buff *audit_make_reply(int pid, int seq, int type, int done,
 388                                  int multi, void *payload, int size)
 389 {
 390         struct sk_buff  *skb;
 391         struct nlmsghdr *nlh;
 392         int             len = NLMSG_SPACE(size);
 393         void            *data;
 394         int             flags = multi ? NLM_F_MULTI : 0;
 395         int             t     = done  ? NLMSG_DONE  : type;
 396
 397         skb = alloc_skb(len, GFP_KERNEL);
 398         if (!skb)
 399                 return NULL;
 400
 401         nlh              = NLMSG_PUT(skb, pid, seq, t, size);
 402         nlh->nlmsg_flags = flags;
 403         data             = NLMSG_DATA(nlh);
 404         memcpy(data, payload, size);
 405         return skb;
 406
 407 nlmsg_failure:                  /* Used by NLMSG_PUT */
 408         if (skb)
 409                 kfree_skb(skb);
 410         return NULL;
 411 }
 412
 413 /**
 414  * audit_send_reply - send an audit reply message via netlink
 415  * @pid: process id to send reply to
 416  * @seq: sequence number
 417  * @type: audit message type
 418  * @done: done (last) flag
 419  * @multi: multi-part message flag
 420  * @payload: payload data
 421  * @size: payload size
 422  *
 423  * Allocates an skb, builds the netlink message, and sends it to the pid.
 424  * No failure notifications.
 425  */
 426 void audit_send_reply(int pid, int seq, int type, int done, int multi,
 427                       void *payload, int size)
 428 {
 429         struct sk_buff  *skb;
 430         skb = audit_make_reply(pid, seq, type, done, multi, payload, size);
 431         if (!skb)
 432                 return;
 433         /* Ignore failure. It'll only happen if the sender goes away,
 434            because our timeout is set to infinite. */
 435         netlink_unicast(audit_sock, skb, pid, 0);
 436         return;
 437 }
 438
 439 /*
 440  * Check for appropriate CAP_AUDIT_ capabilities on incoming audit
 441  * control messages.
 442  */
 443 static int audit_netlink_ok(kernel_cap_t eff_cap, u16 msg_type)
 444 {
 445         int err = 0;
 446
 447         switch (msg_type) {
 448         case AUDIT_GET:
 449         case AUDIT_LIST:
 450         case AUDIT_LIST_RULES:
 451         case AUDIT_SET:
 452         case AUDIT_ADD:
 453         case AUDIT_ADD_RULE:
 454         case AUDIT_DEL:
 455         case AUDIT_DEL_RULE:
 456         case AUDIT_SIGNAL_INFO:
 457                 if (!cap_raised(eff_cap, CAP_AUDIT_CONTROL))
 458                         err = -EPERM;
 459                 break;
 460         case AUDIT_USER:
 461         case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG:
 462         case AUDIT_FIRST_USER_MSG2...AUDIT_LAST_USER_MSG2:
 463                 if (!cap_raised(eff_cap, CAP_AUDIT_WRITE))
 464                         err = -EPERM;
 465                 break;
 466         default:  /* bad msg */
 467                 err = -EINVAL;
 468         }
 469
 470         return err;
 471 }
 472
 473 static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 474 {
 475         u32                     uid, pid, seq, sid;
 476         void                    *data;
 477         struct audit_status     *status_get, status_set;
 478         int                     err;
 479         struct audit_buffer     *ab;
 480         u16                     msg_type = nlh->nlmsg_type;
 481         uid_t                   loginuid; /* loginuid of sender */
 482         struct audit_sig_info   *sig_data;
 483         char                    *ctx;
 484         u32                     len;
 485
 486         err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
 487         if (err)
 488                 return err;
 489
 490         /* As soon as there's any sign of userspace auditd,
 491          * start kauditd to talk to it */
 492         if (!kauditd_task)
 493                 kauditd_task = kthread_run(kauditd_thread, NULL, "kauditd");
 494         if (IS_ERR(kauditd_task)) {
 495                 err = PTR_ERR(kauditd_task);
 496                 kauditd_task = NULL;
 497                 return err;
 498         }
 499
 500         pid  = NETLINK_CREDS(skb)->pid;
 501         uid  = NETLINK_CREDS(skb)->uid;
 502         loginuid = NETLINK_CB(skb).loginuid;
 503         sid  = NETLINK_CB(skb).sid;
 504         seq  = nlh->nlmsg_seq;
 505         data = NLMSG_DATA(nlh);
 506
 507         switch (msg_type) {
 508         case AUDIT_GET:
 509                 status_set.enabled       = audit_enabled;
 510                 status_set.failure       = audit_failure;
 511                 status_set.pid           = audit_pid;
 512                 status_set.rate_limit    = audit_rate_limit;
 513                 status_set.backlog_limit = audit_backlog_limit;
 514                 status_set.lost          = atomic_read(&audit_lost);
 515                 status_set.backlog       = skb_queue_len(&audit_skb_queue);
 516                 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0,
 517                                  &status_set, sizeof(status_set));
 518                 break;
 519         case AUDIT_SET:
 520                 if (nlh->nlmsg_len < sizeof(struct audit_status))
 521                         return -EINVAL;
 522                 status_get   = (struct audit_status *)data;
 523                 if (status_get->mask & AUDIT_STATUS_ENABLED) {
 524                         err = audit_set_enabled(status_get->enabled,
 525                                                         loginuid, sid);
 526                         if (err < 0) return err;
 527                 }
 528                 if (status_get->mask & AUDIT_STATUS_FAILURE) {
 529                         err = audit_set_failure(status_get->failure,
 530                                                          loginuid, sid);
 531                         if (err < 0) return err;
 532                 }
 533                 if (status_get->mask & AUDIT_STATUS_PID) {
 534                         int old   = audit_pid;
 535                         if (sid) {
 536                                 if ((err = selinux_ctxid_to_string(
 537                                                 sid, &ctx, &len)))
 538                                         return err;
 539                                 else
 540                                         audit_log(NULL, GFP_KERNEL,
 541                                                 AUDIT_CONFIG_CHANGE,
 542                                                 "audit_pid=%d old=%d by auid=%u subj=%s",
 543                                                 status_get->pid, old,
 544                                                 loginuid, ctx);
 545                                 kfree(ctx);
 546                         } else
 547                                 audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 548                                         "audit_pid=%d old=%d by auid=%u",
 549                                           status_get->pid, old, loginuid);
 550                         audit_pid = status_get->pid;
 551                 }
 552                 if (status_get->mask & AUDIT_STATUS_RATE_LIMIT)
 553                         err = audit_set_rate_limit(status_get->rate_limit,
 554                                                          loginuid, sid);
 555                 if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT)
 556                         err = audit_set_backlog_limit(status_get->backlog_limit,
 557                                                         loginuid, sid);
 558                 break;
 559         case AUDIT_USER:
 560         case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG:
 561         case AUDIT_FIRST_USER_MSG2...AUDIT_LAST_USER_MSG2:
 562                 if (!audit_enabled && msg_type != AUDIT_USER_AVC)
 563                         return 0;
 564
 565                 err = audit_filter_user(&NETLINK_CB(skb), msg_type);
 566                 if (err == 1) {
 567                         err = 0;
 568                         ab = audit_log_start(NULL, GFP_KERNEL, msg_type);
 569                         if (ab) {
 570                                 audit_log_format(ab,
 571                                                  "user pid=%d uid=%u auid=%u",
 572                                                  pid, uid, loginuid);
 573                                 if (sid) {
 574                                         if (selinux_ctxid_to_string(
 575                                                         sid, &ctx, &len)) {
 576                                                 audit_log_format(ab,
 577                                                         " ssid=%u", sid);
 578                                                 /* Maybe call audit_panic? */
 579                                         } else
 580                                                 audit_log_format(ab,
 581                                                         " subj=%s", ctx);
 582                                         kfree(ctx);
 583                                 }
 584                                 audit_log_format(ab, " msg='%.1024s'",
 585                                          (char *)data);
 586                                 audit_set_pid(ab, pid);
 587                                 audit_log_end(ab);
 588                         }
 589                 }
 590                 break;
 591         case AUDIT_ADD:
 592         case AUDIT_DEL:
 593                 if (nlmsg_len(nlh) < sizeof(struct audit_rule))
 594                         return -EINVAL;
 595                 /* fallthrough */
 596         case AUDIT_LIST:
 597                 err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
 598                                            uid, seq, data, nlmsg_len(nlh),
 599                                            loginuid, sid);
 600                 break;
 601         case AUDIT_ADD_RULE:
 602         case AUDIT_DEL_RULE:
 603                 if (nlmsg_len(nlh) < sizeof(struct audit_rule_data))
 604                         return -EINVAL;
 605                 /* fallthrough */
 606         case AUDIT_LIST_RULES:
 607                 err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
 608                                            uid, seq, data, nlmsg_len(nlh),
 609                                            loginuid, sid);
 610                 break;
 611         case AUDIT_SIGNAL_INFO:
 612                 err = selinux_ctxid_to_string(audit_sig_sid, &ctx, &len);
 613                 if (err)
 614                         return err;
 615                 sig_data = kmalloc(sizeof(*sig_data) + len, GFP_KERNEL);
 616                 if (!sig_data) {
 617                         kfree(ctx);
 618                         return -ENOMEM;
 619                 }
 620                 sig_data->uid = audit_sig_uid;
 621                 sig_data->pid = audit_sig_pid;
 622                 memcpy(sig_data->ctx, ctx, len);
 623                 kfree(ctx);
 624                 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_SIGNAL_INFO,
 625                                 0, 0, sig_data, sizeof(*sig_data) + len);
 626                 kfree(sig_data);
 627                 break;
 628         default:
 629                 err = -EINVAL;
 630                 break;
 631         }
 632
 633         return err < 0 ? err : 0;
 634 }
 635
 636 /*
 637  * Get message from skb (based on rtnetlink_rcv_skb).  Each message is
 638  * processed by audit_receive_msg.  Malformed skbs with wrong length are
 639  * discarded silently.
 640  */
 641 static void audit_receive_skb(struct sk_buff *skb)
 642 {
 643         int             err;
 644         struct nlmsghdr *nlh;
 645         u32             rlen;
 646
 647         while (skb->len >= NLMSG_SPACE(0)) {
 648                 nlh = (struct nlmsghdr *)skb->data;
 649                 if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
 650                         return;
 651                 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
 652                 if (rlen > skb->len)
 653                         rlen = skb->len;
 654                 if ((err = audit_receive_msg(skb, nlh))) {
 655                         netlink_ack(skb, nlh, err);
 656                 } else if (nlh->nlmsg_flags & NLM_F_ACK)
 657                         netlink_ack(skb, nlh, 0);
 658                 skb_pull(skb, rlen);
 659         }
 660 }
 661
 662 /* Receive messages from netlink socket. */
 663 static void audit_receive(struct sock *sk, int length)
 664 {
 665         struct sk_buff  *skb;
 666         unsigned int qlen;
 667
 668         mutex_lock(&audit_netlink_mutex);
 669
 670         for (qlen = skb_queue_len(&sk->sk_receive_queue); qlen; qlen--) {
 671                 skb = skb_dequeue(&sk->sk_receive_queue);
 672                 audit_receive_skb(skb);
 673                 kfree_skb(skb);
 674         }
 675         mutex_unlock(&audit_netlink_mutex);
 676 }
 677
 678
 679 /* Initialize audit support at boot time. */
 680 static int __init audit_init(void)
 681 {
 682         printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
 683                audit_default ? "enabled" : "disabled");
 684         audit_sock = netlink_kernel_create(NETLINK_AUDIT, 0, audit_receive,
 685                                            THIS_MODULE);
 686         if (!audit_sock)
 687                 audit_panic("cannot initialize netlink socket");
 688         else
 689                 audit_sock->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT;
 690
 691         skb_queue_head_init(&audit_skb_queue);
 692         audit_initialized = 1;
 693         audit_enabled = audit_default;
 694
 695         /* Register the callback with selinux.  This callback will be invoked
 696          * when a new policy is loaded. */
 697         selinux_audit_set_callback(&selinux_audit_rule_update);
 698
 699         audit_log(NULL, GFP_KERNEL, AUDIT_KERNEL, "initialized");
 700         return 0;
 701 }
 702 __initcall(audit_init);
 703
 704 /* Process kernel command-line parameter at boot time.  audit=0 or audit=1. */
 705 static int __init audit_enable(char *str)
 706 {
 707         audit_default = !!simple_strtol(str, NULL, 0);
 708         printk(KERN_INFO "audit: %s%s\n",
 709                audit_default ? "enabled" : "disabled",
 710                audit_initialized ? "" : " (after initialization)");
 711         if (audit_initialized)
 712                 audit_enabled = audit_default;
 713         return 1;
 714 }
 715
 716 __setup("audit=", audit_enable);
 717
 718 static void audit_buffer_free(struct audit_buffer *ab)
 719 {
 720         unsigned long flags;
 721
 722         if (!ab)
 723                 return;
 724
 725         if (ab->skb)
 726                 kfree_skb(ab->skb);
 727
 728         spin_lock_irqsave(&audit_freelist_lock, flags);
 729         if (audit_freelist_count > AUDIT_MAXFREE)
 730                 kfree(ab);
 731         else {
 732                 audit_freelist_count++;
 733                 list_add(&ab->list, &audit_freelist);
 734         }
 735         spin_unlock_irqrestore(&audit_freelist_lock, flags);
 736 }
 737
 738 static struct audit_buffer * audit_buffer_alloc(struct audit_context *ctx,
 739                                                 gfp_t gfp_mask, int type)
 740 {
 741         unsigned long flags;
 742         struct audit_buffer *ab = NULL;
 743         struct nlmsghdr *nlh;
 744
 745         spin_lock_irqsave(&audit_freelist_lock, flags);
 746         if (!list_empty(&audit_freelist)) {
 747                 ab = list_entry(audit_freelist.next,
 748                                 struct audit_buffer, list);
 749                 list_del(&ab->list);
 750                 --audit_freelist_count;
 751         }
 752         spin_unlock_irqrestore(&audit_freelist_lock, flags);
 753
 754         if (!ab) {
 755                 ab = kmalloc(sizeof(*ab), gfp_mask);
 756                 if (!ab)
 757                         goto err;
 758         }
 759
 760         ab->skb = alloc_skb(AUDIT_BUFSIZ, gfp_mask);
 761         if (!ab->skb)
 762                 goto err;
 763
 764         ab->ctx = ctx;
 765         ab->gfp_mask = gfp_mask;
 766         nlh = (struct nlmsghdr *)skb_put(ab->skb, NLMSG_SPACE(0));
 767         nlh->nlmsg_type = type;
 768         nlh->nlmsg_flags = 0;
 769         nlh->nlmsg_pid = 0;
 770         nlh->nlmsg_seq = 0;
 771         return ab;
 772 err:
 773         audit_buffer_free(ab);
 774         return NULL;
 775 }
 776
 777 /**
 778  * audit_serial - compute a serial number for the audit record
 779  *
 780  * Compute a serial number for the audit record.  Audit records are
 781  * written to user-space as soon as they are generated, so a complete
 782  * audit record may be written in several pieces.  The timestamp of the
 783  * record and this serial number are used by the user-space tools to
 784  * determine which pieces belong to the same audit record.  The
 785  * (timestamp,serial) tuple is unique for each syscall and is live from
 786  * syscall entry to syscall exit.
 787  *
 788  * NOTE: Another possibility is to store the formatted records off the
 789  * audit context (for those records that have a context), and emit them
 790  * all at syscall exit.  However, this could delay the reporting of
 791  * significant errors until syscall exit (or never, if the system
 792  * halts).
 793  */
 794 unsigned int audit_serial(void)
 795 {
 796         static spinlock_t serial_lock = SPIN_LOCK_UNLOCKED;
 797         static unsigned int serial = 0;
 798
 799         unsigned long flags;
 800         unsigned int ret;
 801
 802         spin_lock_irqsave(&serial_lock, flags);
 803         do {
 804                 ret = ++serial;
 805         } while (unlikely(!ret));
 806         spin_unlock_irqrestore(&serial_lock, flags);
 807
 808         return ret;
 809 }
 810
 811 static inline void audit_get_stamp(struct audit_context *ctx,
 812                                    struct timespec *t, unsigned int *serial)
 813 {
 814         if (ctx)
 815                 auditsc_get_stamp(ctx, t, serial);
 816         else {
 817                 *t = CURRENT_TIME;
 818                 *serial = audit_serial();
 819         }
 820 }
 821
 822 /* Obtain an audit buffer.  This routine does locking to obtain the
 823  * audit buffer, but then no locking is required for calls to
 824  * audit_log_*format.  If the tsk is a task that is currently in a
 825  * syscall, then the syscall is marked as auditable and an audit record
 826  * will be written at syscall exit.  If there is no associated task, tsk
 827  * should be NULL. */
 828
 829 /**
 830  * audit_log_start - obtain an audit buffer
 831  * @ctx: audit_context (may be NULL)
 832  * @gfp_mask: type of allocation
 833  * @type: audit message type
 834  *
 835  * Returns audit_buffer pointer on success or NULL on error.
 836  *
 837  * Obtain an audit buffer.  This routine does locking to obtain the
 838  * audit buffer, but then no locking is required for calls to
 839  * audit_log_*format.  If the task (ctx) is a task that is currently in a
 840  * syscall, then the syscall is marked as auditable and an audit record
 841  * will be written at syscall exit.  If there is no associated task, then
 842  * task context (ctx) should be NULL.
 843  */
 844 struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
 845                                      int type)
 846 {
 847         struct audit_buffer     *ab     = NULL;
 848         struct timespec         t;
 849         unsigned int            serial;
 850         int reserve;
 851         unsigned long timeout_start = jiffies;
 852
 853         if (!audit_initialized)
 854                 return NULL;
 855
 856         if (unlikely(audit_filter_type(type)))
 857                 return NULL;
 858
 859         if (gfp_mask & __GFP_WAIT)
 860                 reserve = 0;
 861         else
 862                 reserve = 5; /* Allow atomic callers to go up to five
 863                                 entries over the normal backlog limit */
 864
 865         while (audit_backlog_limit
 866                && skb_queue_len(&audit_skb_queue) > audit_backlog_limit + reserve) {
 867                 if (gfp_mask & __GFP_WAIT && audit_backlog_wait_time
 868                     && time_before(jiffies, timeout_start + audit_backlog_wait_time)) {
 869
 870                         /* Wait for auditd to drain the queue a little */
 871                         DECLARE_WAITQUEUE(wait, current);
 872                         set_current_state(TASK_INTERRUPTIBLE);
 873                         add_wait_queue(&audit_backlog_wait, &wait);
 874
 875                         if (audit_backlog_limit &&
 876                             skb_queue_len(&audit_skb_queue) > audit_backlog_limit)
 877                                 schedule_timeout(timeout_start + audit_backlog_wait_time - jiffies);
 878
 879                         __set_current_state(TASK_RUNNING);
 880                         remove_wait_queue(&audit_backlog_wait, &wait);
 881                         continue;
 882                 }
 883                 if (audit_rate_check())
 884                         printk(KERN_WARNING
 885                                "audit: audit_backlog=%d > "
 886                                "audit_backlog_limit=%d\n",
 887                                skb_queue_len(&audit_skb_queue),
 888                                audit_backlog_limit);
 889                 audit_log_lost("backlog limit exceeded");
 890                 audit_backlog_wait_time = audit_backlog_wait_overflow;
 891                 wake_up(&audit_backlog_wait);
 892                 return NULL;
 893         }
 894
 895         ab = audit_buffer_alloc(ctx, gfp_mask, type);
 896         if (!ab) {
 897                 audit_log_lost("out of memory in audit_log_start");
 898                 return NULL;
 899         }
 900
 901         audit_get_stamp(ab->ctx, &t, &serial);
 902
 903         audit_log_format(ab, "audit(%lu.%03lu:%u): ",
 904                          t.tv_sec, t.tv_nsec/1000000, serial);
 905         return ab;
 906 }
 907
 908 /**
 909  * audit_expand - expand skb in the audit buffer
 910  * @ab: audit_buffer
 911  * @extra: space to add at tail of the skb
 912  *
 913  * Returns 0 (no space) on failed expansion, or available space if
 914  * successful.
 915  */
 916 static inline int audit_expand(struct audit_buffer *ab, int extra)
 917 {
 918         struct sk_buff *skb = ab->skb;
 919         int ret = pskb_expand_head(skb, skb_headroom(skb), extra,
 920                                    ab->gfp_mask);
 921         if (ret < 0) {
 922                 audit_log_lost("out of memory in audit_expand");
 923                 return 0;
 924         }
 925         return skb_tailroom(skb);
 926 }
 927
 928 /*
 929  * Format an audit message into the audit buffer.  If there isn't enough
 930  * room in the audit buffer, more room will be allocated and vsnprint
 931  * will be called a second time.  Currently, we assume that a printk
 932  * can't format message larger than 1024 bytes, so we don't either.
 933  */
 934 static void audit_log_vformat(struct audit_buffer *ab, const char *fmt,
 935                               va_list args)
 936 {
 937         int len, avail;
 938         struct sk_buff *skb;
 939         va_list args2;
 940
 941         if (!ab)
 942                 return;
 943
 944         BUG_ON(!ab->skb);
 945         skb = ab->skb;
 946         avail = skb_tailroom(skb);
 947         if (avail == 0) {
 948                 avail = audit_expand(ab, AUDIT_BUFSIZ);
 949                 if (!avail)
 950                         goto out;
 951         }
 952         va_copy(args2, args);
 953         len = vsnprintf(skb->tail, avail, fmt, args);
 954         if (len >= avail) {
 955                 /* The printk buffer is 1024 bytes long, so if we get
 956                  * here and AUDIT_BUFSIZ is at least 1024, then we can
 957                  * log everything that printk could have logged. */
 958                 avail = audit_expand(ab,
 959                         max_t(unsigned, AUDIT_BUFSIZ, 1+len-avail));
 960                 if (!avail)
 961                         goto out;
 962                 len = vsnprintf(skb->tail, avail, fmt, args2);
 963         }
 964         if (len > 0)
 965                 skb_put(skb, len);
 966 out:
 967         return;
 968 }
 969
 970 /**
 971  * audit_log_format - format a message into the audit buffer.
 972  * @ab: audit_buffer
 973  * @fmt: format string
 974  * @...: optional parameters matching @fmt string
 975  *
 976  * All the work is done in audit_log_vformat.
 977  */
 978 void audit_log_format(struct audit_buffer *ab, const char *fmt, ...)
 979 {
 980         va_list args;
 981
 982         if (!ab)
 983                 return;
 984         va_start(args, fmt);
 985         audit_log_vformat(ab, fmt, args);
 986         va_end(args);
 987 }
 988
 989 /**
 990  * audit_log_hex - convert a buffer to hex and append it to the audit skb
 991  * @ab: the audit_buffer
 992  * @buf: buffer to convert to hex
 993  * @len: length of @buf to be converted
 994  *
 995  * No return value; failure to expand is silently ignored.
 996  *
 997  * This function will take the passed buf and convert it into a string of
 998  * ascii hex digits. The new string is placed onto the skb.
 999  */
1000 void audit_log_hex(struct audit_buffer *ab, const unsigned char *buf,
1001                 size_t len)
1002 {
1003         int i, avail, new_len;
1004         unsigned char *ptr;
1005         struct sk_buff *skb;
1006         static const unsigned char *hex = "0123456789ABCDEF";
1007
1008         BUG_ON(!ab->skb);
1009         skb = ab->skb;
1010         avail = skb_tailroom(skb);
1011         new_len = len<<1;
1012         if (new_len >= avail) {
1013                 /* Round the buffer request up to the next multiple */
1014                 new_len = AUDIT_BUFSIZ*(((new_len-avail)/AUDIT_BUFSIZ) + 1);
1015                 avail = audit_expand(ab, new_len);
1016                 if (!avail)
1017                         return;
1018         }
1019
1020         ptr = skb->tail;
1021         for (i=0; i<len; i++) {
1022                 *ptr++ = hex[(buf[i] & 0xF0)>>4]; /* Upper nibble */
1023                 *ptr++ = hex[buf[i] & 0x0F];      /* Lower nibble */
1024         }
1025         *ptr = 0;
1026         skb_put(skb, len << 1); /* new string is twice the old string */
1027 }
1028
1029 /**
1030  * audit_log_unstrustedstring - log a string that may contain random characters
1031  * @ab: audit_buffer
1032  * @string: string to be logged
1033  *
1034  * This code will escape a string that is passed to it if the string
1035  * contains a control character, unprintable character, double quote mark,
1036  * or a space. Unescaped strings will start and end with a double quote mark.
1037  * Strings that are escaped are printed in hex (2 digits per char).
1038  */
1039 const char *audit_log_untrustedstring(struct audit_buffer *ab, const char *string)
1040 {
1041         const unsigned char *p = string;
1042         size_t len = strlen(string);
1043
1044         while (*p) {
1045                 if (*p == '"' || *p < 0x21 || *p > 0x7f) {
1046                         audit_log_hex(ab, string, len);
1047                         return string + len + 1;
1048                 }
1049                 p++;
1050         }
1051         audit_log_format(ab, "\"%s\"", string);
1052         return p + 1;
1053 }
1054
1055 /* This is a helper-function to print the escaped d_path */
1056 void audit_log_d_path(struct audit_buffer *ab, const char *prefix,
1057                       struct dentry *dentry, struct vfsmount *vfsmnt)
1058 {
1059         char *p, *path;
1060
1061         if (prefix)
1062                 audit_log_format(ab, " %s", prefix);
1063
1064         /* We will allow 11 spaces for ' (deleted)' to be appended */
1065         path = kmalloc(PATH_MAX+11, ab->gfp_mask);
1066         if (!path) {
1067                 audit_log_format(ab, "<no memory>");
1068                 return;
1069         }
1070         p = d_path(dentry, vfsmnt, path, PATH_MAX+11);
1071         if (IS_ERR(p)) { /* Should never happen since we send PATH_MAX */
1072                 /* FIXME: can we save some information here? */
1073                 audit_log_format(ab, "<too long>");
1074         } else
1075                 audit_log_untrustedstring(ab, p);
1076         kfree(path);
1077 }
1078
1079 /**
1080  * audit_log_end - end one audit record
1081  * @ab: the audit_buffer
1082  *
1083  * The netlink_* functions cannot be called inside an irq context, so
1084  * the audit buffer is placed on a queue and a tasklet is scheduled to
1085  * remove them from the queue outside the irq context.  May be called in
1086  * any context.
1087  */
1088 void audit_log_end(struct audit_buffer *ab)
1089 {
1090         if (!ab)
1091                 return;
1092         if (!audit_rate_check()) {
1093                 audit_log_lost("rate limit exceeded");
1094         } else {
1095                 if (audit_pid) {
1096                         struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data;
1097                         nlh->nlmsg_len = ab->skb->len - NLMSG_SPACE(0);
1098                         skb_queue_tail(&audit_skb_queue, ab->skb);
1099                         ab->skb = NULL;
1100                         wake_up_interruptible(&kauditd_wait);
1101                 } else {
1102                         printk(KERN_NOTICE "%s\n", ab->skb->data + NLMSG_SPACE(0));
1103                 }
1104         }
1105         audit_buffer_free(ab);
1106 }
1107
1108 /**
1109  * audit_log - Log an audit record
1110  * @ctx: audit context
1111  * @gfp_mask: type of allocation
1112  * @type: audit message type
1113  * @fmt: format string to use
1114  * @...: variable parameters matching the format string
1115  *
1116  * This is a convenience function that calls audit_log_start,
1117  * audit_log_vformat, and audit_log_end.  It may be called
1118  * in any context.
1119  */
1120 void audit_log(struct audit_context *ctx, gfp_t gfp_mask, int type,
1121                const char *fmt, ...)
1122 {
1123         struct audit_buffer *ab;
1124         va_list args;
1125
1126         ab = audit_log_start(ctx, gfp_mask, type);
1127         if (ab) {
1128                 va_start(args, fmt);
1129                 audit_log_vformat(ab, fmt, args);
1130                 va_end(args);
1131                 audit_log_end(ab);
1132         }
1133 }
1134
1135 EXPORT_SYMBOL(audit_log_start);
1136 EXPORT_SYMBOL(audit_log_end);
1137 EXPORT_SYMBOL(audit_log_format);
1138 EXPORT_SYMBOL(audit_log);