security/commoncap.c

   1 /* Common capabilities, needed by capability.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 /*
  32  * If a non-root user executes a setuid-root binary in
  33  * !secure(SECURE_NOROOT) mode, then we raise capabilities.
  34  * However if fE is also set, then the intent is for only
  35  * the file capabilities to be applied, and the setuid-root
  36  * bit is left on either to change the uid (plausible) or
  37  * to get full privilege on a kernel without file capabilities
  38  * support.  So in that case we do not raise capabilities.
  39  *
  40  * Warn if that happens, once per boot.
  41  */
  42 static void warn_setuid_and_fcaps_mixed(const char *fname)
  43 {
  44         static int warned;
  45         if (!warned) {
  46                 printk(KERN_INFO "warning: `%s' has both setuid-root and"
  47                         " effective capabilities. Therefore not raising all"
  48                         " capabilities.\n", fname);
  49                 warned = 1;
  50         }
  51 }
  52
  53 int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
  54 {
  55         NETLINK_CB(skb).eff_cap = current_cap();
  56         return 0;
  57 }
  58
  59 int cap_netlink_recv(struct sk_buff *skb, int cap)
  60 {
  61         if (!cap_raised(NETLINK_CB(skb).eff_cap, cap))
  62                 return -EPERM;
  63         return 0;
  64 }
  65 EXPORT_SYMBOL(cap_netlink_recv);
  66
  67 /**
  68  * cap_capable - Determine whether a task has a particular effective capability
  69  * @tsk: The task to query
  70  * @cred: The credentials to use
  71  * @cap: The capability to check for
  72  * @audit: Whether to write an audit message or not
  73  *
  74  * Determine whether the nominated task has the specified capability amongst
  75  * its effective set, returning 0 if it does, -ve if it does not.
  76  *
  77  * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
  78  * and has_capability() functions.  That is, it has the reverse semantics:
  79  * cap_has_capability() returns 0 when a task has a capability, but the
  80  * kernel's capable() and has_capability() returns 1 for this case.
  81  */
  82 int cap_capable(struct task_struct *tsk, const struct cred *cred, int cap,
  83                 int audit)
  84 {
  85         return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
  86 }
  87
  88 /**
  89  * cap_settime - Determine whether the current process may set the system clock
  90  * @ts: The time to set
  91  * @tz: The timezone to set
  92  *
  93  * Determine whether the current process may set the system clock and timezone
  94  * information, returning 0 if permission granted, -ve if denied.
  95  */
  96 int cap_settime(struct timespec *ts, struct timezone *tz)
  97 {
  98         if (!capable(CAP_SYS_TIME))
  99                 return -EPERM;
 100         return 0;
 101 }
 102
 103 /**
 104  * cap_ptrace_access_check - Determine whether the current process may access
 105  *                         another
 106  * @child: The process to be accessed
 107  * @mode: The mode of attachment.
 108  *
 109  * Determine whether a process may access another, returning 0 if permission
 110  * granted, -ve if denied.
 111  */
 112 int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
 113 {
 114         int ret = 0;
 115
 116         rcu_read_lock();
 117         if (!cap_issubset(__task_cred(child)->cap_permitted,
 118                           current_cred()->cap_permitted) &&
 119             !capable(CAP_SYS_PTRACE))
 120                 ret = -EPERM;
 121         rcu_read_unlock();
 122         return ret;
 123 }
 124
 125 /**
 126  * cap_ptrace_traceme - Determine whether another process may trace the current
 127  * @parent: The task proposed to be the tracer
 128  *
 129  * Determine whether the nominated task is permitted to trace the current
 130  * process, returning 0 if permission is granted, -ve if denied.
 131  */
 132 int cap_ptrace_traceme(struct task_struct *parent)
 133 {
 134         int ret = 0;
 135
 136         rcu_read_lock();
 137         if (!cap_issubset(current_cred()->cap_permitted,
 138                           __task_cred(parent)->cap_permitted) &&
 139             !has_capability(parent, CAP_SYS_PTRACE))
 140                 ret = -EPERM;
 141         rcu_read_unlock();
 142         return ret;
 143 }
 144
 145 /**
 146  * cap_capget - Retrieve a task's capability sets
 147  * @target: The task from which to retrieve the capability sets
 148  * @effective: The place to record the effective set
 149  * @inheritable: The place to record the inheritable set
 150  * @permitted: The place to record the permitted set
 151  *
 152  * This function retrieves the capabilities of the nominated task and returns
 153  * them to the caller.
 154  */
 155 int cap_capget(struct task_struct *target, kernel_cap_t *effective,
 156                kernel_cap_t *inheritable, kernel_cap_t *permitted)
 157 {
 158         const struct cred *cred;
 159
 160         /* Derived from kernel/capability.c:sys_capget. */
 161         rcu_read_lock();
 162         cred = __task_cred(target);
 163         *effective   = cred->cap_effective;
 164         *inheritable = cred->cap_inheritable;
 165         *permitted   = cred->cap_permitted;
 166         rcu_read_unlock();
 167         return 0;
 168 }
 169
 170 /*
 171  * Determine whether the inheritable capabilities are limited to the old
 172  * permitted set.  Returns 1 if they are limited, 0 if they are not.
 173  */
 174 static inline int cap_inh_is_capped(void)
 175 {
 176
 177         /* they are so limited unless the current task has the CAP_SETPCAP
 178          * capability
 179          */
 180         if (cap_capable(current, current_cred(), CAP_SETPCAP,
 181                         SECURITY_CAP_AUDIT) == 0)
 182                 return 0;
 183         return 1;
 184 }
 185
 186 /**
 187  * cap_capset - Validate and apply proposed changes to current's capabilities
 188  * @new: The proposed new credentials; alterations should be made here
 189  * @old: The current task's current credentials
 190  * @effective: A pointer to the proposed new effective capabilities set
 191  * @inheritable: A pointer to the proposed new inheritable capabilities set
 192  * @permitted: A pointer to the proposed new permitted capabilities set
 193  *
 194  * This function validates and applies a proposed mass change to the current
 195  * process's capability sets.  The changes are made to the proposed new
 196  * credentials, and assuming no error, will be committed by the caller of LSM.
 197  */
 198 int cap_capset(struct cred *new,
 199                const struct cred *old,
 200                const kernel_cap_t *effective,
 201                const kernel_cap_t *inheritable,
 202                const kernel_cap_t *permitted)
 203 {
 204         if (cap_inh_is_capped() &&
 205             !cap_issubset(*inheritable,
 206                           cap_combine(old->cap_inheritable,
 207                                       old->cap_permitted)))
 208                 /* incapable of using this inheritable set */
 209                 return -EPERM;
 210
 211         if (!cap_issubset(*inheritable,
 212                           cap_combine(old->cap_inheritable,
 213                                       old->cap_bset)))
 214                 /* no new pI capabilities outside bounding set */
 215                 return -EPERM;
 216
 217         /* verify restrictions on target's new Permitted set */
 218         if (!cap_issubset(*permitted, old->cap_permitted))
 219                 return -EPERM;
 220
 221         /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
 222         if (!cap_issubset(*effective, *permitted))
 223                 return -EPERM;
 224
 225         new->cap_effective   = *effective;
 226         new->cap_inheritable = *inheritable;
 227         new->cap_permitted   = *permitted;
 228         return 0;
 229 }
 230
 231 /*
 232  * Clear proposed capability sets for execve().
 233  */
 234 static inline void bprm_clear_caps(struct linux_binprm *bprm)
 235 {
 236         cap_clear(bprm->cred->cap_permitted);
 237         bprm->cap_effective = false;
 238 }
 239
 240 /**
 241  * cap_inode_need_killpriv - Determine if inode change affects privileges
 242  * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
 243  *
 244  * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
 245  * affects the security markings on that inode, and if it is, should
 246  * inode_killpriv() be invoked or the change rejected?
 247  *
 248  * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
 249  * -ve to deny the change.
 250  */
 251 int cap_inode_need_killpriv(struct dentry *dentry)
 252 {
 253         struct inode *inode = dentry->d_inode;
 254         int error;
 255
 256         if (!inode->i_op->getxattr)
 257                return 0;
 258
 259         error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
 260         if (error <= 0)
 261                 return 0;
 262         return 1;
 263 }
 264
 265 /**
 266  * cap_inode_killpriv - Erase the security markings on an inode
 267  * @dentry: The inode/dentry to alter
 268  *
 269  * Erase the privilege-enhancing security markings on an inode.
 270  *
 271  * Returns 0 if successful, -ve on error.
 272  */
 273 int cap_inode_killpriv(struct dentry *dentry)
 274 {
 275         struct inode *inode = dentry->d_inode;
 276
 277         if (!inode->i_op->removexattr)
 278                return 0;
 279
 280         return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
 281 }
 282
 283 /*
 284  * Calculate the new process capability sets from the capability sets attached
 285  * to a file.
 286  */
 287 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
 288                                           struct linux_binprm *bprm,
 289                                           bool *effective)
 290 {
 291         struct cred *new = bprm->cred;
 292         unsigned i;
 293         int ret = 0;
 294
 295         if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
 296                 *effective = true;
 297
 298         CAP_FOR_EACH_U32(i) {
 299                 __u32 permitted = caps->permitted.cap[i];
 300                 __u32 inheritable = caps->inheritable.cap[i];
 301
 302                 /*
 303                  * pP' = (X & fP) | (pI & fI)
 304                  */
 305                 new->cap_permitted.cap[i] =
 306                         (new->cap_bset.cap[i] & permitted) |
 307                         (new->cap_inheritable.cap[i] & inheritable);
 308
 309                 if (permitted & ~new->cap_permitted.cap[i])
 310                         /* insufficient to execute correctly */
 311                         ret = -EPERM;
 312         }
 313
 314         /*
 315          * For legacy apps, with no internal support for recognizing they
 316          * do not have enough capabilities, we return an error if they are
 317          * missing some "forced" (aka file-permitted) capabilities.
 318          */
 319         return *effective ? ret : 0;
 320 }
 321
 322 /*
 323  * Extract the on-exec-apply capability sets for an executable file.
 324  */
 325 int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
 326 {
 327         struct inode *inode = dentry->d_inode;
 328         __u32 magic_etc;
 329         unsigned tocopy, i;
 330         int size;
 331         struct vfs_cap_data caps;
 332
 333         memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
 334
 335         if (!inode || !inode->i_op->getxattr)
 336                 return -ENODATA;
 337
 338         size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps,
 339                                    XATTR_CAPS_SZ);
 340         if (size == -ENODATA || size == -EOPNOTSUPP)
 341                 /* no data, that's ok */
 342                 return -ENODATA;
 343         if (size < 0)
 344                 return size;
 345
 346         if (size < sizeof(magic_etc))
 347                 return -EINVAL;
 348
 349         cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
 350
 351         switch (magic_etc & VFS_CAP_REVISION_MASK) {
 352         case VFS_CAP_REVISION_1:
 353                 if (size != XATTR_CAPS_SZ_1)
 354                         return -EINVAL;
 355                 tocopy = VFS_CAP_U32_1;
 356                 break;
 357         case VFS_CAP_REVISION_2:
 358                 if (size != XATTR_CAPS_SZ_2)
 359                         return -EINVAL;
 360                 tocopy = VFS_CAP_U32_2;
 361                 break;
 362         default:
 363                 return -EINVAL;
 364         }
 365
 366         CAP_FOR_EACH_U32(i) {
 367                 if (i >= tocopy)
 368                         break;
 369                 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
 370                 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
 371         }
 372
 373         return 0;
 374 }
 375
 376 /*
 377  * Attempt to get the on-exec apply capability sets for an executable file from
 378  * its xattrs and, if present, apply them to the proposed credentials being
 379  * constructed by execve().
 380  */
 381 static int get_file_caps(struct linux_binprm *bprm, bool *effective)
 382 {
 383         struct dentry *dentry;
 384         int rc = 0;
 385         struct cpu_vfs_cap_data vcaps;
 386
 387         bprm_clear_caps(bprm);
 388
 389         if (!file_caps_enabled)
 390                 return 0;
 391
 392         if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID)
 393                 return 0;
 394
 395         dentry = dget(bprm->file->f_dentry);
 396
 397         rc = get_vfs_caps_from_disk(dentry, &vcaps);
 398         if (rc < 0) {
 399                 if (rc == -EINVAL)
 400                         printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
 401                                 __func__, rc, bprm->filename);
 402                 else if (rc == -ENODATA)
 403                         rc = 0;
 404                 goto out;
 405         }
 406
 407         rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective);
 408         if (rc == -EINVAL)
 409                 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
 410                        __func__, rc, bprm->filename);
 411
 412 out:
 413         dput(dentry);
 414         if (rc)
 415                 bprm_clear_caps(bprm);
 416
 417         return rc;
 418 }
 419
 420 /**
 421  * cap_bprm_set_creds - Set up the proposed credentials for execve().
 422  * @bprm: The execution parameters, including the proposed creds
 423  *
 424  * Set up the proposed credentials for a new execution context being
 425  * constructed by execve().  The proposed creds in @bprm->cred is altered,
 426  * which won't take effect immediately.  Returns 0 if successful, -ve on error.
 427  */
 428 int cap_bprm_set_creds(struct linux_binprm *bprm)
 429 {
 430         const struct cred *old = current_cred();
 431         struct cred *new = bprm->cred;
 432         bool effective;
 433         int ret;
 434
 435         effective = false;
 436         ret = get_file_caps(bprm, &effective);
 437         if (ret < 0)
 438                 return ret;
 439
 440         if (!issecure(SECURE_NOROOT)) {
 441                 /*
 442                  * If the legacy file capability is set, then don't set privs
 443                  * for a setuid root binary run by a non-root user.  Do set it
 444                  * for a root user just to cause least surprise to an admin.
 445                  */
 446                 if (effective && new->uid != 0 && new->euid == 0) {
 447                         warn_setuid_and_fcaps_mixed(bprm->filename);
 448                         goto skip;
 449                 }
 450                 /*
 451                  * To support inheritance of root-permissions and suid-root
 452                  * executables under compatibility mode, we override the
 453                  * capability sets for the file.
 454                  *
 455                  * If only the real uid is 0, we do not set the effective bit.
 456                  */
 457                 if (new->euid == 0 || new->uid == 0) {
 458                         /* pP' = (cap_bset & ~0) | (pI & ~0) */
 459                         new->cap_permitted = cap_combine(old->cap_bset,
 460                                                          old->cap_inheritable);
 461                 }
 462                 if (new->euid == 0)
 463                         effective = true;
 464         }
 465 skip:
 466
 467         /* Don't let someone trace a set[ug]id/setpcap binary with the revised
 468          * credentials unless they have the appropriate permit
 469          */
 470         if ((new->euid != old->uid ||
 471              new->egid != old->gid ||
 472              !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
 473             bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
 474                 /* downgrade; they get no more than they had, and maybe less */
 475                 if (!capable(CAP_SETUID)) {
 476                         new->euid = new->uid;
 477                         new->egid = new->gid;
 478                 }
 479                 new->cap_permitted = cap_intersect(new->cap_permitted,
 480                                                    old->cap_permitted);
 481         }
 482
 483         new->suid = new->fsuid = new->euid;
 484         new->sgid = new->fsgid = new->egid;
 485
 486         /* For init, we want to retain the capabilities set in the initial
 487          * task.  Thus we skip the usual capability rules
 488          */
 489         if (!is_global_init(current)) {
 490                 if (effective)
 491                         new->cap_effective = new->cap_permitted;
 492                 else
 493                         cap_clear(new->cap_effective);
 494         }
 495         bprm->cap_effective = effective;
 496
 497         /*
 498          * Audit candidate if current->cap_effective is set
 499          *
 500          * We do not bother to audit if 3 things are true:
 501          *   1) cap_effective has all caps
 502          *   2) we are root
 503          *   3) root is supposed to have all caps (SECURE_NOROOT)
 504          * Since this is just a normal root execing a process.
 505          *
 506          * Number 1 above might fail if you don't have a full bset, but I think
 507          * that is interesting information to audit.
 508          */
 509         if (!cap_isclear(new->cap_effective)) {
 510                 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
 511                     new->euid != 0 || new->uid != 0 ||
 512                     issecure(SECURE_NOROOT)) {
 513                         ret = audit_log_bprm_fcaps(bprm, new, old);
 514                         if (ret < 0)
 515                                 return ret;
 516                 }
 517         }
 518
 519         new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
 520         return 0;
 521 }
 522
 523 /**
 524  * cap_bprm_secureexec - Determine whether a secure execution is required
 525  * @bprm: The execution parameters
 526  *
 527  * Determine whether a secure execution is required, return 1 if it is, and 0
 528  * if it is not.
 529  *
 530  * The credentials have been committed by this point, and so are no longer
 531  * available through @bprm->cred.
 532  */
 533 int cap_bprm_secureexec(struct linux_binprm *bprm)
 534 {
 535         const struct cred *cred = current_cred();
 536
 537         if (cred->uid != 0) {
 538                 if (bprm->cap_effective)
 539                         return 1;
 540                 if (!cap_isclear(cred->cap_permitted))
 541                         return 1;
 542         }
 543
 544         return (cred->euid != cred->uid ||
 545                 cred->egid != cred->gid);
 546 }
 547
 548 /**
 549  * cap_inode_setxattr - Determine whether an xattr may be altered
 550  * @dentry: The inode/dentry being altered
 551  * @name: The name of the xattr to be changed
 552  * @value: The value that the xattr will be changed to
 553  * @size: The size of value
 554  * @flags: The replacement flag
 555  *
 556  * Determine whether an xattr may be altered or set on an inode, returning 0 if
 557  * permission is granted, -ve if denied.
 558  *
 559  * This is used to make sure security xattrs don't get updated or set by those
 560  * who aren't privileged to do so.
 561  */
 562 int cap_inode_setxattr(struct dentry *dentry, const char *name,
 563                        const void *value, size_t size, int flags)
 564 {
 565         if (!strcmp(name, XATTR_NAME_CAPS)) {
 566                 if (!capable(CAP_SETFCAP))
 567                         return -EPERM;
 568                 return 0;
 569         }
 570
 571         if (!strncmp(name, XATTR_SECURITY_PREFIX,
 572                      sizeof(XATTR_SECURITY_PREFIX) - 1) &&
 573             !capable(CAP_SYS_ADMIN))
 574                 return -EPERM;
 575         return 0;
 576 }
 577
 578 /**
 579  * cap_inode_removexattr - Determine whether an xattr may be removed
 580  * @dentry: The inode/dentry being altered
 581  * @name: The name of the xattr to be changed
 582  *
 583  * Determine whether an xattr may be removed from an inode, returning 0 if
 584  * permission is granted, -ve if denied.
 585  *
 586  * This is used to make sure security xattrs don't get removed by those who
 587  * aren't privileged to remove them.
 588  */
 589 int cap_inode_removexattr(struct dentry *dentry, const char *name)
 590 {
 591         if (!strcmp(name, XATTR_NAME_CAPS)) {
 592                 if (!capable(CAP_SETFCAP))
 593                         return -EPERM;
 594                 return 0;
 595         }
 596
 597         if (!strncmp(name, XATTR_SECURITY_PREFIX,
 598                      sizeof(XATTR_SECURITY_PREFIX) - 1) &&
 599             !capable(CAP_SYS_ADMIN))
 600                 return -EPERM;
 601         return 0;
 602 }
 603
 604 /*
 605  * cap_emulate_setxuid() fixes the effective / permitted capabilities of
 606  * a process after a call to setuid, setreuid, or setresuid.
 607  *
 608  *  1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
 609  *  {r,e,s}uid != 0, the permitted and effective capabilities are
 610  *  cleared.
 611  *
 612  *  2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
 613  *  capabilities of the process are cleared.
 614  *
 615  *  3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
 616  *  capabilities are set to the permitted capabilities.
 617  *
 618  *  fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
 619  *  never happen.
 620  *
 621  *  -astor
 622  *
 623  * cevans - New behaviour, Oct '99
 624  * A process may, via prctl(), elect to keep its capabilities when it
 625  * calls setuid() and switches away from uid==0. Both permitted and
 626  * effective sets will be retained.
 627  * Without this change, it was impossible for a daemon to drop only some
 628  * of its privilege. The call to setuid(!=0) would drop all privileges!
 629  * Keeping uid 0 is not an option because uid 0 owns too many vital
 630  * files..
 631  * Thanks to Olaf Kirch and Peter Benie for spotting this.
 632  */
 633 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
 634 {
 635         if ((old->uid == 0 || old->euid == 0 || old->suid == 0) &&
 636             (new->uid != 0 && new->euid != 0 && new->suid != 0) &&
 637             !issecure(SECURE_KEEP_CAPS)) {
 638                 cap_clear(new->cap_permitted);
 639                 cap_clear(new->cap_effective);
 640         }
 641         if (old->euid == 0 && new->euid != 0)
 642                 cap_clear(new->cap_effective);
 643         if (old->euid != 0 && new->euid == 0)
 644                 new->cap_effective = new->cap_permitted;
 645 }
 646
 647 /**
 648  * cap_task_fix_setuid - Fix up the results of setuid() call
 649  * @new: The proposed credentials
 650  * @old: The current task's current credentials
 651  * @flags: Indications of what has changed
 652  *
 653  * Fix up the results of setuid() call before the credential changes are
 654  * actually applied, returning 0 to grant the changes, -ve to deny them.
 655  */
 656 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
 657 {
 658         switch (flags) {
 659         case LSM_SETID_RE:
 660         case LSM_SETID_ID:
 661         case LSM_SETID_RES:
 662                 /* juggle the capabilities to follow [RES]UID changes unless
 663                  * otherwise suppressed */
 664                 if (!issecure(SECURE_NO_SETUID_FIXUP))
 665                         cap_emulate_setxuid(new, old);
 666                 break;
 667
 668         case LSM_SETID_FS:
 669                 /* juggle the capabilties to follow FSUID changes, unless
 670                  * otherwise suppressed
 671                  *
 672                  * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
 673                  *          if not, we might be a bit too harsh here.
 674                  */
 675                 if (!issecure(SECURE_NO_SETUID_FIXUP)) {
 676                         if (old->fsuid == 0 && new->fsuid != 0)
 677                                 new->cap_effective =
 678                                         cap_drop_fs_set(new->cap_effective);
 679
 680                         if (old->fsuid != 0 && new->fsuid == 0)
 681                                 new->cap_effective =
 682                                         cap_raise_fs_set(new->cap_effective,
 683                                                          new->cap_permitted);
 684                 }
 685                 break;
 686
 687         default:
 688                 return -EINVAL;
 689         }
 690
 691         return 0;
 692 }
 693
 694 /*
 695  * Rationale: code calling task_setscheduler, task_setioprio, and
 696  * task_setnice, assumes that
 697  *   . if capable(cap_sys_nice), then those actions should be allowed
 698  *   . if not capable(cap_sys_nice), but acting on your own processes,
 699  *      then those actions should be allowed
 700  * This is insufficient now since you can call code without suid, but
 701  * yet with increased caps.
 702  * So we check for increased caps on the target process.
 703  */
 704 static int cap_safe_nice(struct task_struct *p)
 705 {
 706         int is_subset;
 707
 708         rcu_read_lock();
 709         is_subset = cap_issubset(__task_cred(p)->cap_permitted,
 710                                  current_cred()->cap_permitted);
 711         rcu_read_unlock();
 712
 713         if (!is_subset && !capable(CAP_SYS_NICE))
 714                 return -EPERM;
 715         return 0;
 716 }
 717
 718 /**
 719  * cap_task_setscheduler - Detemine if scheduler policy change is permitted
 720  * @p: The task to affect
 721  *
 722  * Detemine if the requested scheduler policy change is permitted for the
 723  * specified task, returning 0 if permission is granted, -ve if denied.
 724  */
 725 int cap_task_setscheduler(struct task_struct *p)
 726 {
 727         return cap_safe_nice(p);
 728 }
 729
 730 /**
 731  * cap_task_ioprio - Detemine if I/O priority change is permitted
 732  * @p: The task to affect
 733  * @ioprio: The I/O priority to set
 734  *
 735  * Detemine if the requested I/O priority change is permitted for the specified
 736  * task, returning 0 if permission is granted, -ve if denied.
 737  */
 738 int cap_task_setioprio(struct task_struct *p, int ioprio)
 739 {
 740         return cap_safe_nice(p);
 741 }
 742
 743 /**
 744  * cap_task_ioprio - Detemine if task priority change is permitted
 745  * @p: The task to affect
 746  * @nice: The nice value to set
 747  *
 748  * Detemine if the requested task priority change is permitted for the
 749  * specified task, returning 0 if permission is granted, -ve if denied.
 750  */
 751 int cap_task_setnice(struct task_struct *p, int nice)
 752 {
 753         return cap_safe_nice(p);
 754 }
 755
 756 /*
 757  * Implement PR_CAPBSET_DROP.  Attempt to remove the specified capability from
 758  * the current task's bounding set.  Returns 0 on success, -ve on error.
 759  */
 760 static long cap_prctl_drop(struct cred *new, unsigned long cap)
 761 {
 762         if (!capable(CAP_SETPCAP))
 763                 return -EPERM;
 764         if (!cap_valid(cap))
 765                 return -EINVAL;
 766
 767         cap_lower(new->cap_bset, cap);
 768         return 0;
 769 }
 770
 771 /**
 772  * cap_task_prctl - Implement process control functions for this security module
 773  * @option: The process control function requested
 774  * @arg2, @arg3, @arg4, @arg5: The argument data for this function
 775  *
 776  * Allow process control functions (sys_prctl()) to alter capabilities; may
 777  * also deny access to other functions not otherwise implemented here.
 778  *
 779  * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
 780  * here, other -ve on error.  If -ENOSYS is returned, sys_prctl() and other LSM
 781  * modules will consider performing the function.
 782  */
 783 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
 784                    unsigned long arg4, unsigned long arg5)
 785 {
 786         struct cred *new;
 787         long error = 0;
 788
 789         new = prepare_creds();
 790         if (!new)
 791                 return -ENOMEM;
 792
 793         switch (option) {
 794         case PR_CAPBSET_READ:
 795                 error = -EINVAL;
 796                 if (!cap_valid(arg2))
 797                         goto error;
 798                 error = !!cap_raised(new->cap_bset, arg2);
 799                 goto no_change;
 800
 801         case PR_CAPBSET_DROP:
 802                 error = cap_prctl_drop(new, arg2);
 803                 if (error < 0)
 804                         goto error;
 805                 goto changed;
 806
 807         /*
 808          * The next four prctl's remain to assist with transitioning a
 809          * system from legacy UID=0 based privilege (when filesystem
 810          * capabilities are not in use) to a system using filesystem
 811          * capabilities only - as the POSIX.1e draft intended.
 812          *
 813          * Note:
 814          *
 815          *  PR_SET_SECUREBITS =
 816          *      issecure_mask(SECURE_KEEP_CAPS_LOCKED)
 817          *    | issecure_mask(SECURE_NOROOT)
 818          *    | issecure_mask(SECURE_NOROOT_LOCKED)
 819          *    | issecure_mask(SECURE_NO_SETUID_FIXUP)
 820          *    | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
 821          *
 822          * will ensure that the current process and all of its
 823          * children will be locked into a pure
 824          * capability-based-privilege environment.
 825          */
 826         case PR_SET_SECUREBITS:
 827                 error = -EPERM;
 828                 if ((((new->securebits & SECURE_ALL_LOCKS) >> 1)
 829                      & (new->securebits ^ arg2))                        /*[1]*/
 830                     || ((new->securebits & SECURE_ALL_LOCKS & ~arg2))   /*[2]*/
 831                     || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS))   /*[3]*/
 832                     || (cap_capable(current, current_cred(), CAP_SETPCAP,
 833                                     SECURITY_CAP_AUDIT) != 0)           /*[4]*/
 834                         /*
 835                          * [1] no changing of bits that are locked
 836                          * [2] no unlocking of locks
 837                          * [3] no setting of unsupported bits
 838                          * [4] doing anything requires privilege (go read about
 839                          *     the "sendmail capabilities bug")
 840                          */
 841                     )
 842                         /* cannot change a locked bit */
 843                         goto error;
 844                 new->securebits = arg2;
 845                 goto changed;
 846
 847         case PR_GET_SECUREBITS:
 848                 error = new->securebits;
 849                 goto no_change;
 850
 851         case PR_GET_KEEPCAPS:
 852                 if (issecure(SECURE_KEEP_CAPS))
 853                         error = 1;
 854                 goto no_change;
 855
 856         case PR_SET_KEEPCAPS:
 857                 error = -EINVAL;
 858                 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
 859                         goto error;
 860                 error = -EPERM;
 861                 if (issecure(SECURE_KEEP_CAPS_LOCKED))
 862                         goto error;
 863                 if (arg2)
 864                         new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
 865                 else
 866                         new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
 867                 goto changed;
 868
 869         default:
 870                 /* No functionality available - continue with default */
 871                 error = -ENOSYS;
 872                 goto error;
 873         }
 874
 875         /* Functionality provided */
 876 changed:
 877         return commit_creds(new);
 878
 879 no_change:
 880 error:
 881         abort_creds(new);
 882         return error;
 883 }
 884
 885 /**
 886  * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
 887  * @mm: The VM space in which the new mapping is to be made
 888  * @pages: The size of the mapping
 889  *
 890  * Determine whether the allocation of a new virtual mapping by the current
 891  * task is permitted, returning 0 if permission is granted, -ve if not.
 892  */
 893 int cap_vm_enough_memory(struct mm_struct *mm, long pages)
 894 {
 895         int cap_sys_admin = 0;
 896
 897         if (cap_capable(current, current_cred(), CAP_SYS_ADMIN,
 898                         SECURITY_CAP_NOAUDIT) == 0)
 899                 cap_sys_admin = 1;
 900         return __vm_enough_memory(mm, pages, cap_sys_admin);
 901 }
 902
 903 /*
 904  * cap_file_mmap - check if able to map given addr
 905  * @file: unused
 906  * @reqprot: unused
 907  * @prot: unused
 908  * @flags: unused
 909  * @addr: address attempting to be mapped
 910  * @addr_only: unused
 911  *
 912  * If the process is attempting to map memory below dac_mmap_min_addr they need
 913  * CAP_SYS_RAWIO.  The other parameters to this function are unused by the
 914  * capability security module.  Returns 0 if this mapping should be allowed
 915  * -EPERM if not.
 916  */
 917 int cap_file_mmap(struct file *file, unsigned long reqprot,
 918                   unsigned long prot, unsigned long flags,
 919                   unsigned long addr, unsigned long addr_only)
 920 {
 921         int ret = 0;
 922
 923         if (addr < dac_mmap_min_addr) {
 924                 ret = cap_capable(current, current_cred(), CAP_SYS_RAWIO,
 925                                   SECURITY_CAP_AUDIT);
 926                 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
 927                 if (ret == 0)
 928                         current->flags |= PF_SUPERPRIV;
 929         }
 930         return ret;
 931 }