SAFE public projects git trees. - safe/jmp/linux-2.6/blob - security/commoncap.c

   1 /* Common capabilities, needed by capability.o and root_plug.o
   2  *
   3  *      This program is free software; you can redistribute it and/or modify
   4  *      it under the terms of the GNU General Public License as published by
   5  *      the Free Software Foundation; either version 2 of the License, or
   6  *      (at your option) any later version.
   7  *
   8  */
   9
  10 #include <linux/capability.h>
  11 #include <linux/audit.h>
  12 #include <linux/module.h>
  13 #include <linux/init.h>
  14 #include <linux/kernel.h>
  15 #include <linux/security.h>
  16 #include <linux/file.h>
  17 #include <linux/mm.h>
  18 #include <linux/mman.h>
  19 #include <linux/pagemap.h>
  20 #include <linux/swap.h>
  21 #include <linux/skbuff.h>
  22 #include <linux/netlink.h>
  23 #include <linux/ptrace.h>
  24 #include <linux/xattr.h>
  25 #include <linux/hugetlb.h>
  26 #include <linux/mount.h>
  27 #include <linux/sched.h>
  28 #include <linux/prctl.h>
  29 #include <linux/securebits.h>
  30
  31 int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
  32 {
  33         NETLINK_CB(skb).eff_cap = current_cap();
  34         return 0;
  35 }
  36
  37 int cap_netlink_recv(struct sk_buff *skb, int cap)
  38 {
  39         if (!cap_raised(NETLINK_CB(skb).eff_cap, cap))
  40                 return -EPERM;
  41         return 0;
  42 }
  43
  44 EXPORT_SYMBOL(cap_netlink_recv);
  45
  46 /*
  47  * NOTE WELL: cap_capable() cannot be used like the kernel's capable()
  48  * function.  That is, it has the reverse semantics: cap_capable()
  49  * returns 0 when a task has a capability, but the kernel's capable()
  50  * returns 1 for this case.
  51  */
  52 int cap_capable(struct task_struct *tsk, int cap, int audit)
  53 {
  54         __u32 cap_raised;
  55
  56         /* Derived from include/linux/sched.h:capable. */
  57         rcu_read_lock();
  58         cap_raised = cap_raised(__task_cred(tsk)->cap_effective, cap);
  59         rcu_read_unlock();
  60         return cap_raised ? 0 : -EPERM;
  61 }
  62
  63 int cap_settime(struct timespec *ts, struct timezone *tz)
  64 {
  65         if (!capable(CAP_SYS_TIME))
  66                 return -EPERM;
  67         return 0;
  68 }
  69
  70 int cap_ptrace_may_access(struct task_struct *child, unsigned int mode)
  71 {
  72         int ret = 0;
  73
  74         rcu_read_lock();
  75         if (!cap_issubset(child->cred->cap_permitted,
  76                           current->cred->cap_permitted) &&
  77             !capable(CAP_SYS_PTRACE))
  78                 ret = -EPERM;
  79         rcu_read_unlock();
  80         return ret;
  81 }
  82
  83 int cap_ptrace_traceme(struct task_struct *parent)
  84 {
  85         int ret = 0;
  86
  87         rcu_read_lock();
  88         if (!cap_issubset(current->cred->cap_permitted,
  89                          parent->cred->cap_permitted) &&
  90             !has_capability(parent, CAP_SYS_PTRACE))
  91                 ret = -EPERM;
  92         rcu_read_unlock();
  93         return ret;
  94 }
  95
  96 int cap_capget (struct task_struct *target, kernel_cap_t *effective,
  97                 kernel_cap_t *inheritable, kernel_cap_t *permitted)
  98 {
  99         const struct cred *cred;
 100
 101         /* Derived from kernel/capability.c:sys_capget. */
 102         rcu_read_lock();
 103         cred = __task_cred(target);
 104         *effective   = cred->cap_effective;
 105         *inheritable = cred->cap_inheritable;
 106         *permitted   = cred->cap_permitted;
 107         rcu_read_unlock();
 108         return 0;
 109 }
 110
 111 #ifdef CONFIG_SECURITY_FILE_CAPABILITIES
 112
 113 static inline int cap_inh_is_capped(void)
 114 {
 115         /*
 116          * Return 1 if changes to the inheritable set are limited
 117          * to the old permitted set. That is, if the current task
 118          * does *not* possess the CAP_SETPCAP capability.
 119          */
 120         return (cap_capable(current, CAP_SETPCAP, SECURITY_CAP_AUDIT) != 0);
 121 }
 122
 123 static inline int cap_limit_ptraced_target(void) { return 1; }
 124
 125 #else /* ie., ndef CONFIG_SECURITY_FILE_CAPABILITIES */
 126
 127 static inline int cap_inh_is_capped(void) { return 1; }
 128 static inline int cap_limit_ptraced_target(void)
 129 {
 130         return !capable(CAP_SETPCAP);
 131 }
 132
 133 #endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */
 134
 135 int cap_capset_check(const kernel_cap_t *effective,
 136                      const kernel_cap_t *inheritable,
 137                      const kernel_cap_t *permitted)
 138 {
 139         const struct cred *cred = current->cred;
 140
 141         if (cap_inh_is_capped()
 142             && !cap_issubset(*inheritable,
 143                              cap_combine(cred->cap_inheritable,
 144                                          cred->cap_permitted))) {
 145                 /* incapable of using this inheritable set */
 146                 return -EPERM;
 147         }
 148         if (!cap_issubset(*inheritable,
 149                            cap_combine(cred->cap_inheritable,
 150                                        cred->cap_bset))) {
 151                 /* no new pI capabilities outside bounding set */
 152                 return -EPERM;
 153         }
 154
 155         /* verify restrictions on target's new Permitted set */
 156         if (!cap_issubset (*permitted,
 157                            cap_combine (cred->cap_permitted,
 158                                         cred->cap_permitted))) {
 159                 return -EPERM;
 160         }
 161
 162         /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
 163         if (!cap_issubset (*effective, *permitted)) {
 164                 return -EPERM;
 165         }
 166
 167         return 0;
 168 }
 169
 170 void cap_capset_set(const kernel_cap_t *effective,
 171                     const kernel_cap_t *inheritable,
 172                     const kernel_cap_t *permitted)
 173 {
 174         struct cred *cred = current->cred;
 175
 176         cred->cap_effective   = *effective;
 177         cred->cap_inheritable = *inheritable;
 178         cred->cap_permitted   = *permitted;
 179 }
 180
 181 static inline void bprm_clear_caps(struct linux_binprm *bprm)
 182 {
 183         cap_clear(bprm->cap_post_exec_permitted);
 184         bprm->cap_effective = false;
 185 }
 186
 187 #ifdef CONFIG_SECURITY_FILE_CAPABILITIES
 188
 189 int cap_inode_need_killpriv(struct dentry *dentry)
 190 {
 191         struct inode *inode = dentry->d_inode;
 192         int error;
 193
 194         if (!inode->i_op || !inode->i_op->getxattr)
 195                return 0;
 196
 197         error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
 198         if (error <= 0)
 199                 return 0;
 200         return 1;
 201 }
 202
 203 int cap_inode_killpriv(struct dentry *dentry)
 204 {
 205         struct inode *inode = dentry->d_inode;
 206
 207         if (!inode->i_op || !inode->i_op->removexattr)
 208                return 0;
 209
 210         return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
 211 }
 212
 213 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
 214                                           struct linux_binprm *bprm)
 215 {
 216         unsigned i;
 217         int ret = 0;
 218
 219         if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
 220                 bprm->cap_effective = true;
 221         else
 222                 bprm->cap_effective = false;
 223
 224         CAP_FOR_EACH_U32(i) {
 225                 __u32 permitted = caps->permitted.cap[i];
 226                 __u32 inheritable = caps->inheritable.cap[i];
 227
 228                 /*
 229                  * pP' = (X & fP) | (pI & fI)
 230                  */
 231                 bprm->cap_post_exec_permitted.cap[i] =
 232                         (current->cred->cap_bset.cap[i] & permitted) |
 233                         (current->cred->cap_inheritable.cap[i] & inheritable);
 234
 235                 if (permitted & ~bprm->cap_post_exec_permitted.cap[i]) {
 236                         /*
 237                          * insufficient to execute correctly
 238                          */
 239                         ret = -EPERM;
 240                 }
 241         }
 242
 243         /*
 244          * For legacy apps, with no internal support for recognizing they
 245          * do not have enough capabilities, we return an error if they are
 246          * missing some "forced" (aka file-permitted) capabilities.
 247          */
 248         return bprm->cap_effective ? ret : 0;
 249 }
 250
 251 int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
 252 {
 253         struct inode *inode = dentry->d_inode;
 254         __u32 magic_etc;
 255         unsigned tocopy, i;
 256         int size;
 257         struct vfs_cap_data caps;
 258
 259         memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
 260
 261         if (!inode || !inode->i_op || !inode->i_op->getxattr)
 262                 return -ENODATA;
 263
 264         size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps,
 265                                    XATTR_CAPS_SZ);
 266         if (size == -ENODATA || size == -EOPNOTSUPP) {
 267                 /* no data, that's ok */
 268                 return -ENODATA;
 269         }
 270         if (size < 0)
 271                 return size;
 272
 273         if (size < sizeof(magic_etc))
 274                 return -EINVAL;
 275
 276         cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
 277
 278         switch ((magic_etc & VFS_CAP_REVISION_MASK)) {
 279         case VFS_CAP_REVISION_1:
 280                 if (size != XATTR_CAPS_SZ_1)
 281                         return -EINVAL;
 282                 tocopy = VFS_CAP_U32_1;
 283                 break;
 284         case VFS_CAP_REVISION_2:
 285                 if (size != XATTR_CAPS_SZ_2)
 286                         return -EINVAL;
 287                 tocopy = VFS_CAP_U32_2;
 288                 break;
 289         default:
 290                 return -EINVAL;
 291         }
 292
 293         CAP_FOR_EACH_U32(i) {
 294                 if (i >= tocopy)
 295                         break;
 296                 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
 297                 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
 298         }
 299         return 0;
 300 }
 301
 302 /* Locate any VFS capabilities: */
 303 static int get_file_caps(struct linux_binprm *bprm)
 304 {
 305         struct dentry *dentry;
 306         int rc = 0;
 307         struct cpu_vfs_cap_data vcaps;
 308
 309         bprm_clear_caps(bprm);
 310
 311         if (!file_caps_enabled)
 312                 return 0;
 313
 314         if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID)
 315                 return 0;
 316
 317         dentry = dget(bprm->file->f_dentry);
 318
 319         rc = get_vfs_caps_from_disk(dentry, &vcaps);
 320         if (rc < 0) {
 321                 if (rc == -EINVAL)
 322                         printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
 323                                 __func__, rc, bprm->filename);
 324                 else if (rc == -ENODATA)
 325                         rc = 0;
 326                 goto out;
 327         }
 328
 329         rc = bprm_caps_from_vfs_caps(&vcaps, bprm);
 330
 331 out:
 332         dput(dentry);
 333         if (rc)
 334                 bprm_clear_caps(bprm);
 335
 336         return rc;
 337 }
 338
 339 #else
 340 int cap_inode_need_killpriv(struct dentry *dentry)
 341 {
 342         return 0;
 343 }
 344
 345 int cap_inode_killpriv(struct dentry *dentry)
 346 {
 347         return 0;
 348 }
 349
 350 static inline int get_file_caps(struct linux_binprm *bprm)
 351 {
 352         bprm_clear_caps(bprm);
 353         return 0;
 354 }
 355 #endif
 356
 357 int cap_bprm_set_security (struct linux_binprm *bprm)
 358 {
 359         int ret;
 360
 361         ret = get_file_caps(bprm);
 362
 363         if (!issecure(SECURE_NOROOT)) {
 364                 /*
 365                  * To support inheritance of root-permissions and suid-root
 366                  * executables under compatibility mode, we override the
 367                  * capability sets for the file.
 368                  *
 369                  * If only the real uid is 0, we do not set the effective
 370                  * bit.
 371                  */
 372                 if (bprm->e_uid == 0 || current_uid() == 0) {
 373                         /* pP' = (cap_bset & ~0) | (pI & ~0) */
 374                         bprm->cap_post_exec_permitted = cap_combine(
 375                                 current->cred->cap_bset,
 376                                 current->cred->cap_inheritable);
 377                         bprm->cap_effective = (bprm->e_uid == 0);
 378                         ret = 0;
 379                 }
 380         }
 381
 382         return ret;
 383 }
 384
 385 void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
 386 {
 387         struct cred *cred = current->cred;
 388
 389         if (bprm->e_uid != cred->uid || bprm->e_gid != cred->gid ||
 390             !cap_issubset(bprm->cap_post_exec_permitted,
 391                           cred->cap_permitted)) {
 392                 set_dumpable(current->mm, suid_dumpable);
 393                 current->pdeath_signal = 0;
 394
 395                 if (unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
 396                         if (!capable(CAP_SETUID)) {
 397                                 bprm->e_uid = cred->uid;
 398                                 bprm->e_gid = cred->gid;
 399                         }
 400                         if (cap_limit_ptraced_target()) {
 401                                 bprm->cap_post_exec_permitted = cap_intersect(
 402                                         bprm->cap_post_exec_permitted,
 403                                         cred->cap_permitted);
 404                         }
 405                 }
 406         }
 407
 408         cred->suid = cred->euid = cred->fsuid = bprm->e_uid;
 409         cred->sgid = cred->egid = cred->fsgid = bprm->e_gid;
 410
 411         /* For init, we want to retain the capabilities set
 412          * in the init_task struct. Thus we skip the usual
 413          * capability rules */
 414         if (!is_global_init(current)) {
 415                 cred->cap_permitted = bprm->cap_post_exec_permitted;
 416                 if (bprm->cap_effective)
 417                         cred->cap_effective = bprm->cap_post_exec_permitted;
 418                 else
 419                         cap_clear(cred->cap_effective);
 420         }
 421
 422         /*
 423          * Audit candidate if current->cap_effective is set
 424          *
 425          * We do not bother to audit if 3 things are true:
 426          *   1) cap_effective has all caps
 427          *   2) we are root
 428          *   3) root is supposed to have all caps (SECURE_NOROOT)
 429          * Since this is just a normal root execing a process.
 430          *
 431          * Number 1 above might fail if you don't have a full bset, but I think
 432          * that is interesting information to audit.
 433          */
 434         if (!cap_isclear(cred->cap_effective)) {
 435                 if (!cap_issubset(CAP_FULL_SET, cred->cap_effective) ||
 436                     (bprm->e_uid != 0) || (cred->uid != 0) ||
 437                     issecure(SECURE_NOROOT))
 438                         audit_log_bprm_fcaps(bprm, &cred->cap_permitted,
 439                                              &cred->cap_effective);
 440         }
 441
 442         cred->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
 443 }
 444
 445 int cap_bprm_secureexec (struct linux_binprm *bprm)
 446 {
 447         const struct cred *cred = current_cred();
 448
 449         if (cred->uid != 0) {
 450                 if (bprm->cap_effective)
 451                         return 1;
 452                 if (!cap_isclear(bprm->cap_post_exec_permitted))
 453                         return 1;
 454         }
 455
 456         return (cred->euid != cred->uid ||
 457                 cred->egid != cred->gid);
 458 }
 459
 460 int cap_inode_setxattr(struct dentry *dentry, const char *name,
 461                        const void *value, size_t size, int flags)
 462 {
 463         if (!strcmp(name, XATTR_NAME_CAPS)) {
 464                 if (!capable(CAP_SETFCAP))
 465                         return -EPERM;
 466                 return 0;
 467         } else if (!strncmp(name, XATTR_SECURITY_PREFIX,
 468                      sizeof(XATTR_SECURITY_PREFIX) - 1)  &&
 469             !capable(CAP_SYS_ADMIN))
 470                 return -EPERM;
 471         return 0;
 472 }
 473
 474 int cap_inode_removexattr(struct dentry *dentry, const char *name)
 475 {
 476         if (!strcmp(name, XATTR_NAME_CAPS)) {
 477                 if (!capable(CAP_SETFCAP))
 478                         return -EPERM;
 479                 return 0;
 480         } else if (!strncmp(name, XATTR_SECURITY_PREFIX,
 481                      sizeof(XATTR_SECURITY_PREFIX) - 1)  &&
 482             !capable(CAP_SYS_ADMIN))
 483                 return -EPERM;
 484         return 0;
 485 }
 486
 487 /* moved from kernel/sys.c. */
 488 /*
 489  * cap_emulate_setxuid() fixes the effective / permitted capabilities of
 490  * a process after a call to setuid, setreuid, or setresuid.
 491  *
 492  *  1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
 493  *  {r,e,s}uid != 0, the permitted and effective capabilities are
 494  *  cleared.
 495  *
 496  *  2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
 497  *  capabilities of the process are cleared.
 498  *
 499  *  3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
 500  *  capabilities are set to the permitted capabilities.
 501  *
 502  *  fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
 503  *  never happen.
 504  *
 505  *  -astor
 506  *
 507  * cevans - New behaviour, Oct '99
 508  * A process may, via prctl(), elect to keep its capabilities when it
 509  * calls setuid() and switches away from uid==0. Both permitted and
 510  * effective sets will be retained.
 511  * Without this change, it was impossible for a daemon to drop only some
 512  * of its privilege. The call to setuid(!=0) would drop all privileges!
 513  * Keeping uid 0 is not an option because uid 0 owns too many vital
 514  * files..
 515  * Thanks to Olaf Kirch and Peter Benie for spotting this.
 516  */
 517 static inline void cap_emulate_setxuid (int old_ruid, int old_euid,
 518                                         int old_suid)
 519 {
 520         struct cred *cred = current->cred;
 521
 522         if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
 523             (cred->uid != 0 && cred->euid != 0 && cred->suid != 0) &&
 524             !issecure(SECURE_KEEP_CAPS)) {
 525                 cap_clear(cred->cap_permitted);
 526                 cap_clear(cred->cap_effective);
 527         }
 528         if (old_euid == 0 && cred->euid != 0) {
 529                 cap_clear(cred->cap_effective);
 530         }
 531         if (old_euid != 0 && cred->euid == 0) {
 532                 cred->cap_effective = cred->cap_permitted;
 533         }
 534 }
 535
 536 int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid,
 537                           int flags)
 538 {
 539         struct cred *cred = current->cred;
 540
 541         switch (flags) {
 542         case LSM_SETID_RE:
 543         case LSM_SETID_ID:
 544         case LSM_SETID_RES:
 545                 /* Copied from kernel/sys.c:setreuid/setuid/setresuid. */
 546                 if (!issecure (SECURE_NO_SETUID_FIXUP)) {
 547                         cap_emulate_setxuid (old_ruid, old_euid, old_suid);
 548                 }
 549                 break;
 550         case LSM_SETID_FS:
 551                 {
 552                         uid_t old_fsuid = old_ruid;
 553
 554                         /* Copied from kernel/sys.c:setfsuid. */
 555
 556                         /*
 557                          * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
 558                          *          if not, we might be a bit too harsh here.
 559                          */
 560
 561                         if (!issecure (SECURE_NO_SETUID_FIXUP)) {
 562                                 if (old_fsuid == 0 && cred->fsuid != 0) {
 563                                         cred->cap_effective =
 564                                                 cap_drop_fs_set(
 565                                                         cred->cap_effective);
 566                                 }
 567                                 if (old_fsuid != 0 && cred->fsuid == 0) {
 568                                         cred->cap_effective =
 569                                                 cap_raise_fs_set(
 570                                                     cred->cap_effective,
 571                                                     cred->cap_permitted);
 572                                 }
 573                         }
 574                         break;
 575                 }
 576         default:
 577                 return -EINVAL;
 578         }
 579
 580         return 0;
 581 }
 582
 583 #ifdef CONFIG_SECURITY_FILE_CAPABILITIES
 584 /*
 585  * Rationale: code calling task_setscheduler, task_setioprio, and
 586  * task_setnice, assumes that
 587  *   . if capable(cap_sys_nice), then those actions should be allowed
 588  *   . if not capable(cap_sys_nice), but acting on your own processes,
 589  *      then those actions should be allowed
 590  * This is insufficient now since you can call code without suid, but
 591  * yet with increased caps.
 592  * So we check for increased caps on the target process.
 593  */
 594 static int cap_safe_nice(struct task_struct *p)
 595 {
 596         int is_subset;
 597
 598         rcu_read_lock();
 599         is_subset = cap_issubset(__task_cred(p)->cap_permitted,
 600                                  current_cred()->cap_permitted);
 601         rcu_read_unlock();
 602
 603         if (!is_subset && !capable(CAP_SYS_NICE))
 604                 return -EPERM;
 605         return 0;
 606 }
 607
 608 int cap_task_setscheduler (struct task_struct *p, int policy,
 609                            struct sched_param *lp)
 610 {
 611         return cap_safe_nice(p);
 612 }
 613
 614 int cap_task_setioprio (struct task_struct *p, int ioprio)
 615 {
 616         return cap_safe_nice(p);
 617 }
 618
 619 int cap_task_setnice (struct task_struct *p, int nice)
 620 {
 621         return cap_safe_nice(p);
 622 }
 623
 624 /*
 625  * called from kernel/sys.c for prctl(PR_CABSET_DROP)
 626  * done without task_capability_lock() because it introduces
 627  * no new races - i.e. only another task doing capget() on
 628  * this task could get inconsistent info.  There can be no
 629  * racing writer bc a task can only change its own caps.
 630  */
 631 static long cap_prctl_drop(unsigned long cap)
 632 {
 633         if (!capable(CAP_SETPCAP))
 634                 return -EPERM;
 635         if (!cap_valid(cap))
 636                 return -EINVAL;
 637         cap_lower(current->cred->cap_bset, cap);
 638         return 0;
 639 }
 640
 641 #else
 642 int cap_task_setscheduler (struct task_struct *p, int policy,
 643                            struct sched_param *lp)
 644 {
 645         return 0;
 646 }
 647 int cap_task_setioprio (struct task_struct *p, int ioprio)
 648 {
 649         return 0;
 650 }
 651 int cap_task_setnice (struct task_struct *p, int nice)
 652 {
 653         return 0;
 654 }
 655 #endif
 656
 657 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
 658                    unsigned long arg4, unsigned long arg5, long *rc_p)
 659 {
 660         struct cred *cred = current_cred();
 661         long error = 0;
 662
 663         switch (option) {
 664         case PR_CAPBSET_READ:
 665                 if (!cap_valid(arg2))
 666                         error = -EINVAL;
 667                 else
 668                         error = !!cap_raised(cred->cap_bset, arg2);
 669                 break;
 670 #ifdef CONFIG_SECURITY_FILE_CAPABILITIES
 671         case PR_CAPBSET_DROP:
 672                 error = cap_prctl_drop(arg2);
 673                 break;
 674
 675         /*
 676          * The next four prctl's remain to assist with transitioning a
 677          * system from legacy UID=0 based privilege (when filesystem
 678          * capabilities are not in use) to a system using filesystem
 679          * capabilities only - as the POSIX.1e draft intended.
 680          *
 681          * Note:
 682          *
 683          *  PR_SET_SECUREBITS =
 684          *      issecure_mask(SECURE_KEEP_CAPS_LOCKED)
 685          *    | issecure_mask(SECURE_NOROOT)
 686          *    | issecure_mask(SECURE_NOROOT_LOCKED)
 687          *    | issecure_mask(SECURE_NO_SETUID_FIXUP)
 688          *    | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
 689          *
 690          * will ensure that the current process and all of its
 691          * children will be locked into a pure
 692          * capability-based-privilege environment.
 693          */
 694         case PR_SET_SECUREBITS:
 695                 if ((((cred->securebits & SECURE_ALL_LOCKS) >> 1)
 696                      & (cred->securebits ^ arg2))                  /*[1]*/
 697                     || ((cred->securebits & SECURE_ALL_LOCKS
 698                          & ~arg2))                                    /*[2]*/
 699                     || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
 700                     || (cap_capable(current, CAP_SETPCAP, SECURITY_CAP_AUDIT) != 0)) { /*[4]*/
 701                         /*
 702                          * [1] no changing of bits that are locked
 703                          * [2] no unlocking of locks
 704                          * [3] no setting of unsupported bits
 705                          * [4] doing anything requires privilege (go read about
 706                          *     the "sendmail capabilities bug")
 707                          */
 708                         error = -EPERM;  /* cannot change a locked bit */
 709                 } else {
 710                         cred->securebits = arg2;
 711                 }
 712                 break;
 713         case PR_GET_SECUREBITS:
 714                 error = cred->securebits;
 715                 break;
 716
 717 #endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */
 718
 719         case PR_GET_KEEPCAPS:
 720                 if (issecure(SECURE_KEEP_CAPS))
 721                         error = 1;
 722                 break;
 723         case PR_SET_KEEPCAPS:
 724                 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
 725                         error = -EINVAL;
 726                 else if (issecure(SECURE_KEEP_CAPS_LOCKED))
 727                         error = -EPERM;
 728                 else if (arg2)
 729                         cred->securebits |= issecure_mask(SECURE_KEEP_CAPS);
 730                 else
 731                         cred->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
 732                 break;
 733
 734         default:
 735                 /* No functionality available - continue with default */
 736                 return 0;
 737         }
 738
 739         /* Functionality provided */
 740         *rc_p = error;
 741         return 1;
 742 }
 743
 744 void cap_task_reparent_to_init (struct task_struct *p)
 745 {
 746         struct cred *cred = p->cred;
 747
 748         cap_set_init_eff(cred->cap_effective);
 749         cap_clear(cred->cap_inheritable);
 750         cap_set_full(cred->cap_permitted);
 751         p->cred->securebits = SECUREBITS_DEFAULT;
 752 }
 753
 754 int cap_syslog (int type)
 755 {
 756         if ((type != 3 && type != 10) && !capable(CAP_SYS_ADMIN))
 757                 return -EPERM;
 758         return 0;
 759 }
 760
 761 int cap_vm_enough_memory(struct mm_struct *mm, long pages)
 762 {
 763         int cap_sys_admin = 0;
 764
 765         if (cap_capable(current, CAP_SYS_ADMIN, SECURITY_CAP_NOAUDIT) == 0)
 766                 cap_sys_admin = 1;
 767         return __vm_enough_memory(mm, pages, cap_sys_admin);
 768 }
 769