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 old;
 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 old;
 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 old;
 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 old;
 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         return 0;
 368 }
 369
 370 int audit_send_list(void *_dest)
 371 {
 372         struct audit_netlink_list *dest = _dest;
 373         int pid = dest->pid;
 374         struct sk_buff *skb;
 375
 376         /* wait for parent to finish and send an ACK */
 377         mutex_lock(&audit_netlink_mutex);
 378         mutex_unlock(&audit_netlink_mutex);
 379
 380         while ((skb = __skb_dequeue(&dest->q)) != NULL)
 381                 netlink_unicast(audit_sock, skb, pid, 0);
 382
 383         kfree(dest);
 384
 385         return 0;
 386 }
 387
 388 struct sk_buff *audit_make_reply(int pid, int seq, int type, int done,
 389                                  int multi, void *payload, int size)
 390 {
 391         struct sk_buff  *skb;
 392         struct nlmsghdr *nlh;
 393         int             len = NLMSG_SPACE(size);
 394         void            *data;
 395         int             flags = multi ? NLM_F_MULTI : 0;
 396         int             t     = done  ? NLMSG_DONE  : type;
 397
 398         skb = alloc_skb(len, GFP_KERNEL);
 399         if (!skb)
 400                 return NULL;
 401
 402         nlh              = NLMSG_PUT(skb, pid, seq, t, size);
 403         nlh->nlmsg_flags = flags;
 404         data             = NLMSG_DATA(nlh);
 405         memcpy(data, payload, size);
 406         return skb;
 407
 408 nlmsg_failure:                  /* Used by NLMSG_PUT */
 409         if (skb)
 410                 kfree_skb(skb);
 411         return NULL;
 412 }
 413
 414 /**
 415  * audit_send_reply - send an audit reply message via netlink
 416  * @pid: process id to send reply to
 417  * @seq: sequence number
 418  * @type: audit message type
 419  * @done: done (last) flag
 420  * @multi: multi-part message flag
 421  * @payload: payload data
 422  * @size: payload size
 423  *
 424  * Allocates an skb, builds the netlink message, and sends it to the pid.
 425  * No failure notifications.
 426  */
 427 void audit_send_reply(int pid, int seq, int type, int done, int multi,
 428                       void *payload, int size)
 429 {
 430         struct sk_buff  *skb;
 431         skb = audit_make_reply(pid, seq, type, done, multi, payload, size);
 432         if (!skb)
 433                 return;
 434         /* Ignore failure. It'll only happen if the sender goes away,
 435            because our timeout is set to infinite. */
 436         netlink_unicast(audit_sock, skb, pid, 0);
 437         return;
 438 }
 439
 440 /*
 441  * Check for appropriate CAP_AUDIT_ capabilities on incoming audit
 442  * control messages.
 443  */
 444 static int audit_netlink_ok(kernel_cap_t eff_cap, u16 msg_type)
 445 {
 446         int err = 0;
 447
 448         switch (msg_type) {
 449         case AUDIT_GET:
 450         case AUDIT_LIST:
 451         case AUDIT_LIST_RULES:
 452         case AUDIT_SET:
 453         case AUDIT_ADD:
 454         case AUDIT_ADD_RULE:
 455         case AUDIT_DEL:
 456         case AUDIT_DEL_RULE:
 457         case AUDIT_SIGNAL_INFO:
 458                 if (!cap_raised(eff_cap, CAP_AUDIT_CONTROL))
 459                         err = -EPERM;
 460                 break;
 461         case AUDIT_USER:
 462         case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG:
 463         case AUDIT_FIRST_USER_MSG2...AUDIT_LAST_USER_MSG2:
 464                 if (!cap_raised(eff_cap, CAP_AUDIT_WRITE))
 465                         err = -EPERM;
 466                 break;
 467         default:  /* bad msg */
 468                 err = -EINVAL;
 469         }
 470
 471         return err;
 472 }
 473
 474 static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 475 {
 476         u32                     uid, pid, seq, sid;
 477         void                    *data;
 478         struct audit_status     *status_get, status_set;
 479         int                     err;
 480         struct audit_buffer     *ab;
 481         u16                     msg_type = nlh->nlmsg_type;
 482         uid_t                   loginuid; /* loginuid of sender */
 483         struct audit_sig_info   *sig_data;
 484         char                    *ctx;
 485         u32                     len;
 486
 487         err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
 488         if (err)
 489                 return err;
 490
 491         /* As soon as there's any sign of userspace auditd,
 492          * start kauditd to talk to it */
 493         if (!kauditd_task)
 494                 kauditd_task = kthread_run(kauditd_thread, NULL, "kauditd");
 495         if (IS_ERR(kauditd_task)) {
 496                 err = PTR_ERR(kauditd_task);
 497                 kauditd_task = NULL;
 498                 return err;
 499         }
 500
 501         pid  = NETLINK_CREDS(skb)->pid;
 502         uid  = NETLINK_CREDS(skb)->uid;
 503         loginuid = NETLINK_CB(skb).loginuid;
 504         sid  = NETLINK_CB(skb).sid;
 505         seq  = nlh->nlmsg_seq;
 506         data = NLMSG_DATA(nlh);
 507
 508         switch (msg_type) {
 509         case AUDIT_GET:
 510                 status_set.enabled       = audit_enabled;
 511                 status_set.failure       = audit_failure;
 512                 status_set.pid           = audit_pid;
 513                 status_set.rate_limit    = audit_rate_limit;
 514                 status_set.backlog_limit = audit_backlog_limit;
 515                 status_set.lost          = atomic_read(&audit_lost);
 516                 status_set.backlog       = skb_queue_len(&audit_skb_queue);
 517                 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0,
 518                                  &status_set, sizeof(status_set));
 519                 break;
 520         case AUDIT_SET:
 521                 if (nlh->nlmsg_len < sizeof(struct audit_status))
 522                         return -EINVAL;
 523                 status_get   = (struct audit_status *)data;
 524                 if (status_get->mask & AUDIT_STATUS_ENABLED) {
 525                         err = audit_set_enabled(status_get->enabled,
 526                                                         loginuid, sid);
 527                         if (err < 0) return err;
 528                 }
 529                 if (status_get->mask & AUDIT_STATUS_FAILURE) {
 530                         err = audit_set_failure(status_get->failure,
 531                                                          loginuid, sid);
 532                         if (err < 0) return err;
 533                 }
 534                 if (status_get->mask & AUDIT_STATUS_PID) {
 535                         int old   = audit_pid;
 536                         if (sid) {
 537                                 if ((err = selinux_ctxid_to_string(
 538                                                 sid, &ctx, &len)))
 539                                         return err;
 540                                 else
 541                                         audit_log(NULL, GFP_KERNEL,
 542                                                 AUDIT_CONFIG_CHANGE,
 543                                                 "audit_pid=%d old=%d by auid=%u subj=%s",
 544                                                 status_get->pid, old,
 545                                                 loginuid, ctx);
 546                                 kfree(ctx);
 547                         } else
 548                                 audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 549                                         "audit_pid=%d old=%d by auid=%u",
 550                                           status_get->pid, old, loginuid);
 551                         audit_pid = status_get->pid;
 552                 }
 553                 if (status_get->mask & AUDIT_STATUS_RATE_LIMIT)
 554                         audit_set_rate_limit(status_get->rate_limit,
 555                                                          loginuid, sid);
 556                 if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT)
 557                         audit_set_backlog_limit(status_get->backlog_limit,
 558                                                         loginuid, sid);
 559                 break;
 560         case AUDIT_USER:
 561         case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG:
 562         case AUDIT_FIRST_USER_MSG2...AUDIT_LAST_USER_MSG2:
 563                 if (!audit_enabled && msg_type != AUDIT_USER_AVC)
 564                         return 0;
 565
 566                 err = audit_filter_user(&NETLINK_CB(skb), msg_type);
 567                 if (err == 1) {
 568                         err = 0;
 569                         ab = audit_log_start(NULL, GFP_KERNEL, msg_type);
 570                         if (ab) {
 571                                 audit_log_format(ab,
 572                                                  "user pid=%d uid=%u auid=%u",
 573                                                  pid, uid, loginuid);
 574                                 if (sid) {
 575                                         if (selinux_ctxid_to_string(
 576                                                         sid, &ctx, &len)) {
 577                                                 audit_log_format(ab,
 578                                                         " ssid=%u", sid);
 579                                                 /* Maybe call audit_panic? */
 580                                         } else
 581                                                 audit_log_format(ab,
 582                                                         " subj=%s", ctx);
 583                                         kfree(ctx);
 584                                 }
 585                                 audit_log_format(ab, " msg='%.1024s'",
 586                                          (char *)data);
 587                                 audit_set_pid(ab, pid);
 588                                 audit_log_end(ab);
 589                         }
 590                 }
 591                 break;
 592         case AUDIT_ADD:
 593         case AUDIT_DEL:
 594                 if (nlmsg_len(nlh) < sizeof(struct audit_rule))
 595                         return -EINVAL;
 596                 /* fallthrough */
 597         case AUDIT_LIST:
 598                 err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
 599                                            uid, seq, data, nlmsg_len(nlh),
 600                                            loginuid, sid);
 601                 break;
 602         case AUDIT_ADD_RULE:
 603         case AUDIT_DEL_RULE:
 604                 if (nlmsg_len(nlh) < sizeof(struct audit_rule_data))
 605                         return -EINVAL;
 606                 /* fallthrough */
 607         case AUDIT_LIST_RULES:
 608                 err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
 609                                            uid, seq, data, nlmsg_len(nlh),
 610                                            loginuid, sid);
 611                 break;
 612         case AUDIT_SIGNAL_INFO:
 613                 err = selinux_ctxid_to_string(audit_sig_sid, &ctx, &len);
 614                 if (err)
 615                         return err;
 616                 sig_data = kmalloc(sizeof(*sig_data) + len, GFP_KERNEL);
 617                 if (!sig_data) {
 618                         kfree(ctx);
 619                         return -ENOMEM;
 620                 }
 621                 sig_data->uid = audit_sig_uid;
 622                 sig_data->pid = audit_sig_pid;
 623                 memcpy(sig_data->ctx, ctx, len);
 624                 kfree(ctx);
 625                 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_SIGNAL_INFO,
 626                                 0, 0, sig_data, sizeof(*sig_data) + len);
 627                 kfree(sig_data);
 628                 break;
 629         default:
 630                 err = -EINVAL;
 631                 break;
 632         }
 633
 634         return err < 0 ? err : 0;
 635 }
 636
 637 /*
 638  * Get message from skb (based on rtnetlink_rcv_skb).  Each message is
 639  * processed by audit_receive_msg.  Malformed skbs with wrong length are
 640  * discarded silently.
 641  */
 642 static void audit_receive_skb(struct sk_buff *skb)
 643 {
 644         int             err;
 645         struct nlmsghdr *nlh;
 646         u32             rlen;
 647
 648         while (skb->len >= NLMSG_SPACE(0)) {
 649                 nlh = (struct nlmsghdr *)skb->data;
 650                 if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
 651                         return;
 652                 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
 653                 if (rlen > skb->len)
 654                         rlen = skb->len;
 655                 if ((err = audit_receive_msg(skb, nlh))) {
 656                         netlink_ack(skb, nlh, err);
 657                 } else if (nlh->nlmsg_flags & NLM_F_ACK)
 658                         netlink_ack(skb, nlh, 0);
 659                 skb_pull(skb, rlen);
 660         }
 661 }
 662
 663 /* Receive messages from netlink socket. */
 664 static void audit_receive(struct sock *sk, int length)
 665 {
 666         struct sk_buff  *skb;
 667         unsigned int qlen;
 668
 669         mutex_lock(&audit_netlink_mutex);
 670
 671         for (qlen = skb_queue_len(&sk->sk_receive_queue); qlen; qlen--) {
 672                 skb = skb_dequeue(&sk->sk_receive_queue);
 673                 audit_receive_skb(skb);
 674                 kfree_skb(skb);
 675         }
 676         mutex_unlock(&audit_netlink_mutex);
 677 }
 678
 679
 680 /* Initialize audit support at boot time. */
 681 static int __init audit_init(void)
 682 {
 683         printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
 684                audit_default ? "enabled" : "disabled");
 685         audit_sock = netlink_kernel_create(NETLINK_AUDIT, 0, audit_receive,
 686                                            THIS_MODULE);
 687         if (!audit_sock)
 688                 audit_panic("cannot initialize netlink socket");
 689         else
 690                 audit_sock->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT;
 691
 692         skb_queue_head_init(&audit_skb_queue);
 693         audit_initialized = 1;
 694         audit_enabled = audit_default;
 695
 696         /* Register the callback with selinux.  This callback will be invoked
 697          * when a new policy is loaded. */
 698         selinux_audit_set_callback(&selinux_audit_rule_update);
 699
 700         audit_log(NULL, GFP_KERNEL, AUDIT_KERNEL, "initialized");
 701         return 0;
 702 }
 703 __initcall(audit_init);
 704
 705 /* Process kernel command-line parameter at boot time.  audit=0 or audit=1. */
 706 static int __init audit_enable(char *str)
 707 {
 708         audit_default = !!simple_strtol(str, NULL, 0);
 709         printk(KERN_INFO "audit: %s%s\n",
 710                audit_default ? "enabled" : "disabled",
 711                audit_initialized ? "" : " (after initialization)");
 712         if (audit_initialized)
 713                 audit_enabled = audit_default;
 714         return 1;
 715 }
 716
 717 __setup("audit=", audit_enable);
 718
 719 static void audit_buffer_free(struct audit_buffer *ab)
 720 {
 721         unsigned long flags;
 722
 723         if (!ab)
 724                 return;
 725
 726         if (ab->skb)
 727                 kfree_skb(ab->skb);
 728
 729         spin_lock_irqsave(&audit_freelist_lock, flags);
 730         if (++audit_freelist_count > AUDIT_MAXFREE)
 731                 kfree(ab);
 732         else
 733                 list_add(&ab->list, &audit_freelist);
 734         spin_unlock_irqrestore(&audit_freelist_lock, flags);
 735 }
 736
 737 static struct audit_buffer * audit_buffer_alloc(struct audit_context *ctx,
 738                                                 gfp_t gfp_mask, int type)
 739 {
 740         unsigned long flags;
 741         struct audit_buffer *ab = NULL;
 742         struct nlmsghdr *nlh;
 743
 744         spin_lock_irqsave(&audit_freelist_lock, flags);
 745         if (!list_empty(&audit_freelist)) {
 746                 ab = list_entry(audit_freelist.next,
 747                                 struct audit_buffer, list);
 748                 list_del(&ab->list);
 749                 --audit_freelist_count;
 750         }
 751         spin_unlock_irqrestore(&audit_freelist_lock, flags);
 752
 753         if (!ab) {
 754                 ab = kmalloc(sizeof(*ab), gfp_mask);
 755                 if (!ab)
 756                         goto err;
 757         }
 758
 759         ab->skb = alloc_skb(AUDIT_BUFSIZ, gfp_mask);
 760         if (!ab->skb)
 761                 goto err;
 762
 763         ab->ctx = ctx;
 764         ab->gfp_mask = gfp_mask;
 765         nlh = (struct nlmsghdr *)skb_put(ab->skb, NLMSG_SPACE(0));
 766         nlh->nlmsg_type = type;
 767         nlh->nlmsg_flags = 0;
 768         nlh->nlmsg_pid = 0;
 769         nlh->nlmsg_seq = 0;
 770         return ab;
 771 err:
 772         audit_buffer_free(ab);
 773         return NULL;
 774 }
 775
 776 /**
 777  * audit_serial - compute a serial number for the audit record
 778  *
 779  * Compute a serial number for the audit record.  Audit records are
 780  * written to user-space as soon as they are generated, so a complete
 781  * audit record may be written in several pieces.  The timestamp of the
 782  * record and this serial number are used by the user-space tools to
 783  * determine which pieces belong to the same audit record.  The
 784  * (timestamp,serial) tuple is unique for each syscall and is live from
 785  * syscall entry to syscall exit.
 786  *
 787  * NOTE: Another possibility is to store the formatted records off the
 788  * audit context (for those records that have a context), and emit them
 789  * all at syscall exit.  However, this could delay the reporting of
 790  * significant errors until syscall exit (or never, if the system
 791  * halts).
 792  */
 793 unsigned int audit_serial(void)
 794 {
 795         static spinlock_t serial_lock = SPIN_LOCK_UNLOCKED;
 796         static unsigned int serial = 0;
 797
 798         unsigned long flags;
 799         unsigned int ret;
 800
 801         spin_lock_irqsave(&serial_lock, flags);
 802         do {
 803                 ret = ++serial;
 804         } while (unlikely(!ret));
 805         spin_unlock_irqrestore(&serial_lock, flags);
 806
 807         return ret;
 808 }
 809
 810 static inline void audit_get_stamp(struct audit_context *ctx,
 811                                    struct timespec *t, unsigned int *serial)
 812 {
 813         if (ctx)
 814                 auditsc_get_stamp(ctx, t, serial);
 815         else {
 816                 *t = CURRENT_TIME;
 817                 *serial = audit_serial();
 818         }
 819 }
 820
 821 /* Obtain an audit buffer.  This routine does locking to obtain the
 822  * audit buffer, but then no locking is required for calls to
 823  * audit_log_*format.  If the tsk is a task that is currently in a
 824  * syscall, then the syscall is marked as auditable and an audit record
 825  * will be written at syscall exit.  If there is no associated task, tsk
 826  * should be NULL. */
 827
 828 /**
 829  * audit_log_start - obtain an audit buffer
 830  * @ctx: audit_context (may be NULL)
 831  * @gfp_mask: type of allocation
 832  * @type: audit message type
 833  *
 834  * Returns audit_buffer pointer on success or NULL on error.
 835  *
 836  * Obtain an audit buffer.  This routine does locking to obtain the
 837  * audit buffer, but then no locking is required for calls to
 838  * audit_log_*format.  If the task (ctx) is a task that is currently in a
 839  * syscall, then the syscall is marked as auditable and an audit record
 840  * will be written at syscall exit.  If there is no associated task, then
 841  * task context (ctx) should be NULL.
 842  */
 843 struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
 844                                      int type)
 845 {
 846         struct audit_buffer     *ab     = NULL;
 847         struct timespec         t;
 848         unsigned int            serial;
 849         int reserve;
 850         unsigned long timeout_start = jiffies;
 851
 852         if (!audit_initialized)
 853                 return NULL;
 854
 855         if (unlikely(audit_filter_type(type)))
 856                 return NULL;
 857
 858         if (gfp_mask & __GFP_WAIT)
 859                 reserve = 0;
 860         else
 861                 reserve = 5; /* Allow atomic callers to go up to five
 862                                 entries over the normal backlog limit */
 863
 864         while (audit_backlog_limit
 865                && skb_queue_len(&audit_skb_queue) > audit_backlog_limit + reserve) {
 866                 if (gfp_mask & __GFP_WAIT && audit_backlog_wait_time
 867                     && time_before(jiffies, timeout_start + audit_backlog_wait_time)) {
 868
 869                         /* Wait for auditd to drain the queue a little */
 870                         DECLARE_WAITQUEUE(wait, current);
 871                         set_current_state(TASK_INTERRUPTIBLE);
 872                         add_wait_queue(&audit_backlog_wait, &wait);
 873
 874                         if (audit_backlog_limit &&
 875                             skb_queue_len(&audit_skb_queue) > audit_backlog_limit)
 876                                 schedule_timeout(timeout_start + audit_backlog_wait_time - jiffies);
 877
 878                         __set_current_state(TASK_RUNNING);
 879                         remove_wait_queue(&audit_backlog_wait, &wait);
 880                         continue;
 881                 }
 882                 if (audit_rate_check())
 883                         printk(KERN_WARNING
 884                                "audit: audit_backlog=%d > "
 885                                "audit_backlog_limit=%d\n",
 886                                skb_queue_len(&audit_skb_queue),
 887                                audit_backlog_limit);
 888                 audit_log_lost("backlog limit exceeded");
 889                 audit_backlog_wait_time = audit_backlog_wait_overflow;
 890                 wake_up(&audit_backlog_wait);
 891                 return NULL;
 892         }
 893
 894         ab = audit_buffer_alloc(ctx, gfp_mask, type);
 895         if (!ab) {
 896                 audit_log_lost("out of memory in audit_log_start");
 897                 return NULL;
 898         }
 899
 900         audit_get_stamp(ab->ctx, &t, &serial);
 901
 902         audit_log_format(ab, "audit(%lu.%03lu:%u): ",
 903                          t.tv_sec, t.tv_nsec/1000000, serial);
 904         return ab;
 905 }
 906
 907 /**
 908  * audit_expand - expand skb in the audit buffer
 909  * @ab: audit_buffer
 910  * @extra: space to add at tail of the skb
 911  *
 912  * Returns 0 (no space) on failed expansion, or available space if
 913  * successful.
 914  */
 915 static inline int audit_expand(struct audit_buffer *ab, int extra)
 916 {
 917         struct sk_buff *skb = ab->skb;
 918         int ret = pskb_expand_head(skb, skb_headroom(skb), extra,
 919                                    ab->gfp_mask);
 920         if (ret < 0) {
 921                 audit_log_lost("out of memory in audit_expand");
 922                 return 0;
 923         }
 924         return skb_tailroom(skb);
 925 }
 926
 927 /*
 928  * Format an audit message into the audit buffer.  If there isn't enough
 929  * room in the audit buffer, more room will be allocated and vsnprint
 930  * will be called a second time.  Currently, we assume that a printk
 931  * can't format message larger than 1024 bytes, so we don't either.
 932  */
 933 static void audit_log_vformat(struct audit_buffer *ab, const char *fmt,
 934                               va_list args)
 935 {
 936         int len, avail;
 937         struct sk_buff *skb;
 938         va_list args2;
 939
 940         if (!ab)
 941                 return;
 942
 943         BUG_ON(!ab->skb);
 944         skb = ab->skb;
 945         avail = skb_tailroom(skb);
 946         if (avail == 0) {
 947                 avail = audit_expand(ab, AUDIT_BUFSIZ);
 948                 if (!avail)
 949                         goto out;
 950         }
 951         va_copy(args2, args);
 952         len = vsnprintf(skb->tail, avail, fmt, args);
 953         if (len >= avail) {
 954                 /* The printk buffer is 1024 bytes long, so if we get
 955                  * here and AUDIT_BUFSIZ is at least 1024, then we can
 956                  * log everything that printk could have logged. */
 957                 avail = audit_expand(ab,
 958                         max_t(unsigned, AUDIT_BUFSIZ, 1+len-avail));
 959                 if (!avail)
 960                         goto out;
 961                 len = vsnprintf(skb->tail, avail, fmt, args2);
 962         }
 963         if (len > 0)
 964                 skb_put(skb, len);
 965 out:
 966         return;
 967 }
 968
 969 /**
 970  * audit_log_format - format a message into the audit buffer.
 971  * @ab: audit_buffer
 972  * @fmt: format string
 973  * @...: optional parameters matching @fmt string
 974  *
 975  * All the work is done in audit_log_vformat.
 976  */
 977 void audit_log_format(struct audit_buffer *ab, const char *fmt, ...)
 978 {
 979         va_list args;
 980
 981         if (!ab)
 982                 return;
 983         va_start(args, fmt);
 984         audit_log_vformat(ab, fmt, args);
 985         va_end(args);
 986 }
 987
 988 /**
 989  * audit_log_hex - convert a buffer to hex and append it to the audit skb
 990  * @ab: the audit_buffer
 991  * @buf: buffer to convert to hex
 992  * @len: length of @buf to be converted
 993  *
 994  * No return value; failure to expand is silently ignored.
 995  *
 996  * This function will take the passed buf and convert it into a string of
 997  * ascii hex digits. The new string is placed onto the skb.
 998  */
 999 void audit_log_hex(struct audit_buffer *ab, const unsigned char *buf,
1000                 size_t len)
1001 {
1002         int i, avail, new_len;
1003         unsigned char *ptr;
1004         struct sk_buff *skb;
1005         static const unsigned char *hex = "0123456789ABCDEF";
1006
1007         BUG_ON(!ab->skb);
1008         skb = ab->skb;
1009         avail = skb_tailroom(skb);
1010         new_len = len<<1;
1011         if (new_len >= avail) {
1012                 /* Round the buffer request up to the next multiple */
1013                 new_len = AUDIT_BUFSIZ*(((new_len-avail)/AUDIT_BUFSIZ) + 1);
1014                 avail = audit_expand(ab, new_len);
1015                 if (!avail)
1016                         return;
1017         }
1018
1019         ptr = skb->tail;
1020         for (i=0; i<len; i++) {
1021                 *ptr++ = hex[(buf[i] & 0xF0)>>4]; /* Upper nibble */
1022                 *ptr++ = hex[buf[i] & 0x0F];      /* Lower nibble */
1023         }
1024         *ptr = 0;
1025         skb_put(skb, len << 1); /* new string is twice the old string */
1026 }
1027
1028 /**
1029  * audit_log_unstrustedstring - log a string that may contain random characters
1030  * @ab: audit_buffer
1031  * @string: string to be logged
1032  *
1033  * This code will escape a string that is passed to it if the string
1034  * contains a control character, unprintable character, double quote mark,
1035  * or a space. Unescaped strings will start and end with a double quote mark.
1036  * Strings that are escaped are printed in hex (2 digits per char).
1037  */
1038 const char *audit_log_untrustedstring(struct audit_buffer *ab, const char *string)
1039 {
1040         const unsigned char *p = string;
1041         size_t len = strlen(string);
1042
1043         while (*p) {
1044                 if (*p == '"' || *p < 0x21 || *p > 0x7f) {
1045                         audit_log_hex(ab, string, len);
1046                         return string + len + 1;
1047                 }
1048                 p++;
1049         }
1050         audit_log_format(ab, "\"%s\"", string);
1051         return p + 1;
1052 }
1053
1054 /* This is a helper-function to print the escaped d_path */
1055 void audit_log_d_path(struct audit_buffer *ab, const char *prefix,
1056                       struct dentry *dentry, struct vfsmount *vfsmnt)
1057 {
1058         char *p, *path;
1059
1060         if (prefix)
1061                 audit_log_format(ab, " %s", prefix);
1062
1063         /* We will allow 11 spaces for ' (deleted)' to be appended */
1064         path = kmalloc(PATH_MAX+11, ab->gfp_mask);
1065         if (!path) {
1066                 audit_log_format(ab, "<no memory>");
1067                 return;
1068         }
1069         p = d_path(dentry, vfsmnt, path, PATH_MAX+11);
1070         if (IS_ERR(p)) { /* Should never happen since we send PATH_MAX */
1071                 /* FIXME: can we save some information here? */
1072                 audit_log_format(ab, "<too long>");
1073         } else
1074                 audit_log_untrustedstring(ab, p);
1075         kfree(path);
1076 }
1077
1078 /**
1079  * audit_log_end - end one audit record
1080  * @ab: the audit_buffer
1081  *
1082  * The netlink_* functions cannot be called inside an irq context, so
1083  * the audit buffer is placed on a queue and a tasklet is scheduled to
1084  * remove them from the queue outside the irq context.  May be called in
1085  * any context.
1086  */
1087 void audit_log_end(struct audit_buffer *ab)
1088 {
1089         if (!ab)
1090                 return;
1091         if (!audit_rate_check()) {
1092                 audit_log_lost("rate limit exceeded");
1093         } else {
1094                 if (audit_pid) {
1095                         struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data;
1096                         nlh->nlmsg_len = ab->skb->len - NLMSG_SPACE(0);
1097                         skb_queue_tail(&audit_skb_queue, ab->skb);
1098                         ab->skb = NULL;
1099                         wake_up_interruptible(&kauditd_wait);
1100                 } else {
1101                         printk(KERN_NOTICE "%s\n", ab->skb->data + NLMSG_SPACE(0));
1102                 }
1103         }
1104         audit_buffer_free(ab);
1105 }
1106
1107 /**
1108  * audit_log - Log an audit record
1109  * @ctx: audit context
1110  * @gfp_mask: type of allocation
1111  * @type: audit message type
1112  * @fmt: format string to use
1113  * @...: variable parameters matching the format string
1114  *
1115  * This is a convenience function that calls audit_log_start,
1116  * audit_log_vformat, and audit_log_end.  It may be called
1117  * in any context.
1118  */
1119 void audit_log(struct audit_context *ctx, gfp_t gfp_mask, int type,
1120                const char *fmt, ...)
1121 {
1122         struct audit_buffer *ab;
1123         va_list args;
1124
1125         ab = audit_log_start(ctx, gfp_mask, type);
1126         if (ab) {
1127                 va_start(args, fmt);
1128                 audit_log_vformat(ab, fmt, args);
1129                 va_end(args);
1130                 audit_log_end(ab);
1131         }
1132 }
1133
1134 EXPORT_SYMBOL(audit_log_start);
1135 EXPORT_SYMBOL(audit_log_end);
1136 EXPORT_SYMBOL(audit_log_format);
1137 EXPORT_SYMBOL(audit_log);