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 #include <linux/syslog.h> 31 32 /* 33 * If a non-root user executes a setuid-root binary in 34 * !secure(SECURE_NOROOT) mode, then we raise capabilities. 35 * However if fE is also set, then the intent is for only 36 * the file capabilities to be applied, and the setuid-root 37 * bit is left on either to change the uid (plausible) or 38 * to get full privilege on a kernel without file capabilities 39 * support. So in that case we do not raise capabilities. 40 * 41 * Warn if that happens, once per boot. 42 */ 43 static void warn_setuid_and_fcaps_mixed(const char *fname) 44 { 45 static int warned; 46 if (!warned) { 47 printk(KERN_INFO "warning: `%s' has both setuid-root and" 48 " effective capabilities. Therefore not raising all" 49 " capabilities.\n", fname); 50 warned = 1; 51 } 52 } 53 54 int cap_netlink_send(struct sock *sk, struct sk_buff *skb) 55 { 56 NETLINK_CB(skb).eff_cap = current_cap(); 57 return 0; 58 } 59 60 int cap_netlink_recv(struct sk_buff *skb, int cap) 61 { 62 if (!cap_raised(NETLINK_CB(skb).eff_cap, cap)) 63 return -EPERM; 64 return 0; 65 } 66 EXPORT_SYMBOL(cap_netlink_recv); 67 68 /** 69 * cap_capable - Determine whether a task has a particular effective capability 70 * @tsk: The task to query 71 * @cred: The credentials to use 72 * @cap: The capability to check for 73 * @audit: Whether to write an audit message or not 74 * 75 * Determine whether the nominated task has the specified capability amongst 76 * its effective set, returning 0 if it does, -ve if it does not. 77 * 78 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() 79 * and has_capability() functions. That is, it has the reverse semantics: 80 * cap_has_capability() returns 0 when a task has a capability, but the 81 * kernel's capable() and has_capability() returns 1 for this case. 82 */ 83 int cap_capable(struct task_struct *tsk, const struct cred *cred, int cap, 84 int audit) 85 { 86 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; 87 } 88 89 /** 90 * cap_settime - Determine whether the current process may set the system clock 91 * @ts: The time to set 92 * @tz: The timezone to set 93 * 94 * Determine whether the current process may set the system clock and timezone 95 * information, returning 0 if permission granted, -ve if denied. 96 */ 97 int cap_settime(struct timespec *ts, struct timezone *tz) 98 { 99 if (!capable(CAP_SYS_TIME)) 100 return -EPERM; 101 return 0; 102 } 103 104 /** 105 * cap_ptrace_access_check - Determine whether the current process may access 106 * another 107 * @child: The process to be accessed 108 * @mode: The mode of attachment. 109 * 110 * Determine whether a process may access another, returning 0 if permission 111 * granted, -ve if denied. 112 */ 113 int cap_ptrace_access_check(struct task_struct *child, unsigned int mode) 114 { 115 int ret = 0; 116 117 rcu_read_lock(); 118 if (!cap_issubset(__task_cred(child)->cap_permitted, 119 current_cred()->cap_permitted) && 120 !capable(CAP_SYS_PTRACE)) 121 ret = -EPERM; 122 rcu_read_unlock(); 123 return ret; 124 } 125 126 /** 127 * cap_ptrace_traceme - Determine whether another process may trace the current 128 * @parent: The task proposed to be the tracer 129 * 130 * Determine whether the nominated task is permitted to trace the current 131 * process, returning 0 if permission is granted, -ve if denied. 132 */ 133 int cap_ptrace_traceme(struct task_struct *parent) 134 { 135 int ret = 0; 136 137 rcu_read_lock(); 138 if (!cap_issubset(current_cred()->cap_permitted, 139 __task_cred(parent)->cap_permitted) && 140 !has_capability(parent, CAP_SYS_PTRACE)) 141 ret = -EPERM; 142 rcu_read_unlock(); 143 return ret; 144 } 145 146 /** 147 * cap_capget - Retrieve a task's capability sets 148 * @target: The task from which to retrieve the capability sets 149 * @effective: The place to record the effective set 150 * @inheritable: The place to record the inheritable set 151 * @permitted: The place to record the permitted set 152 * 153 * This function retrieves the capabilities of the nominated task and returns 154 * them to the caller. 155 */ 156 int cap_capget(struct task_struct *target, kernel_cap_t *effective, 157 kernel_cap_t *inheritable, kernel_cap_t *permitted) 158 { 159 const struct cred *cred; 160 161 /* Derived from kernel/capability.c:sys_capget. */ 162 rcu_read_lock(); 163 cred = __task_cred(target); 164 *effective = cred->cap_effective; 165 *inheritable = cred->cap_inheritable; 166 *permitted = cred->cap_permitted; 167 rcu_read_unlock(); 168 return 0; 169 } 170 171 /* 172 * Determine whether the inheritable capabilities are limited to the old 173 * permitted set. Returns 1 if they are limited, 0 if they are not. 174 */ 175 static inline int cap_inh_is_capped(void) 176 { 177 178 /* they are so limited unless the current task has the CAP_SETPCAP 179 * capability 180 */ 181 if (cap_capable(current, current_cred(), CAP_SETPCAP, 182 SECURITY_CAP_AUDIT) == 0) 183 return 0; 184 return 1; 185 } 186 187 /** 188 * cap_capset - Validate and apply proposed changes to current's capabilities 189 * @new: The proposed new credentials; alterations should be made here 190 * @old: The current task's current credentials 191 * @effective: A pointer to the proposed new effective capabilities set 192 * @inheritable: A pointer to the proposed new inheritable capabilities set 193 * @permitted: A pointer to the proposed new permitted capabilities set 194 * 195 * This function validates and applies a proposed mass change to the current 196 * process's capability sets. The changes are made to the proposed new 197 * credentials, and assuming no error, will be committed by the caller of LSM. 198 */ 199 int cap_capset(struct cred *new, 200 const struct cred *old, 201 const kernel_cap_t *effective, 202 const kernel_cap_t *inheritable, 203 const kernel_cap_t *permitted) 204 { 205 if (cap_inh_is_capped() && 206 !cap_issubset(*inheritable, 207 cap_combine(old->cap_inheritable, 208 old->cap_permitted))) 209 /* incapable of using this inheritable set */ 210 return -EPERM; 211 212 if (!cap_issubset(*inheritable, 213 cap_combine(old->cap_inheritable, 214 old->cap_bset))) 215 /* no new pI capabilities outside bounding set */ 216 return -EPERM; 217 218 /* verify restrictions on target's new Permitted set */ 219 if (!cap_issubset(*permitted, old->cap_permitted)) 220 return -EPERM; 221 222 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ 223 if (!cap_issubset(*effective, *permitted)) 224 return -EPERM; 225 226 new->cap_effective = *effective; 227 new->cap_inheritable = *inheritable; 228 new->cap_permitted = *permitted; 229 return 0; 230 } 231 232 /* 233 * Clear proposed capability sets for execve(). 234 */ 235 static inline void bprm_clear_caps(struct linux_binprm *bprm) 236 { 237 cap_clear(bprm->cred->cap_permitted); 238 bprm->cap_effective = false; 239 } 240 241 /** 242 * cap_inode_need_killpriv - Determine if inode change affects privileges 243 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV 244 * 245 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV 246 * affects the security markings on that inode, and if it is, should 247 * inode_killpriv() be invoked or the change rejected? 248 * 249 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and 250 * -ve to deny the change. 251 */ 252 int cap_inode_need_killpriv(struct dentry *dentry) 253 { 254 struct inode *inode = dentry->d_inode; 255 int error; 256 257 if (!inode->i_op->getxattr) 258 return 0; 259 260 error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0); 261 if (error <= 0) 262 return 0; 263 return 1; 264 } 265 266 /** 267 * cap_inode_killpriv - Erase the security markings on an inode 268 * @dentry: The inode/dentry to alter 269 * 270 * Erase the privilege-enhancing security markings on an inode. 271 * 272 * Returns 0 if successful, -ve on error. 273 */ 274 int cap_inode_killpriv(struct dentry *dentry) 275 { 276 struct inode *inode = dentry->d_inode; 277 278 if (!inode->i_op->removexattr) 279 return 0; 280 281 return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS); 282 } 283 284 /* 285 * Calculate the new process capability sets from the capability sets attached 286 * to a file. 287 */ 288 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, 289 struct linux_binprm *bprm, 290 bool *effective) 291 { 292 struct cred *new = bprm->cred; 293 unsigned i; 294 int ret = 0; 295 296 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) 297 *effective = true; 298 299 CAP_FOR_EACH_U32(i) { 300 __u32 permitted = caps->permitted.cap[i]; 301 __u32 inheritable = caps->inheritable.cap[i]; 302 303 /* 304 * pP' = (X & fP) | (pI & fI) 305 */ 306 new->cap_permitted.cap[i] = 307 (new->cap_bset.cap[i] & permitted) | 308 (new->cap_inheritable.cap[i] & inheritable); 309 310 if (permitted & ~new->cap_permitted.cap[i]) 311 /* insufficient to execute correctly */ 312 ret = -EPERM; 313 } 314 315 /* 316 * For legacy apps, with no internal support for recognizing they 317 * do not have enough capabilities, we return an error if they are 318 * missing some "forced" (aka file-permitted) capabilities. 319 */ 320 return *effective ? ret : 0; 321 } 322 323 /* 324 * Extract the on-exec-apply capability sets for an executable file. 325 */ 326 int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) 327 { 328 struct inode *inode = dentry->d_inode; 329 __u32 magic_etc; 330 unsigned tocopy, i; 331 int size; 332 struct vfs_cap_data caps; 333 334 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); 335 336 if (!inode || !inode->i_op->getxattr) 337 return -ENODATA; 338 339 size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps, 340 XATTR_CAPS_SZ); 341 if (size == -ENODATA || size == -EOPNOTSUPP) 342 /* no data, that's ok */ 343 return -ENODATA; 344 if (size < 0) 345 return size; 346 347 if (size < sizeof(magic_etc)) 348 return -EINVAL; 349 350 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc); 351 352 switch (magic_etc & VFS_CAP_REVISION_MASK) { 353 case VFS_CAP_REVISION_1: 354 if (size != XATTR_CAPS_SZ_1) 355 return -EINVAL; 356 tocopy = VFS_CAP_U32_1; 357 break; 358 case VFS_CAP_REVISION_2: 359 if (size != XATTR_CAPS_SZ_2) 360 return -EINVAL; 361 tocopy = VFS_CAP_U32_2; 362 break; 363 default: 364 return -EINVAL; 365 } 366 367 CAP_FOR_EACH_U32(i) { 368 if (i >= tocopy) 369 break; 370 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted); 371 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable); 372 } 373 374 return 0; 375 } 376 377 /* 378 * Attempt to get the on-exec apply capability sets for an executable file from 379 * its xattrs and, if present, apply them to the proposed credentials being 380 * constructed by execve(). 381 */ 382 static int get_file_caps(struct linux_binprm *bprm, bool *effective) 383 { 384 struct dentry *dentry; 385 int rc = 0; 386 struct cpu_vfs_cap_data vcaps; 387 388 bprm_clear_caps(bprm); 389 390 if (!file_caps_enabled) 391 return 0; 392 393 if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID) 394 return 0; 395 396 dentry = dget(bprm->file->f_dentry); 397 398 rc = get_vfs_caps_from_disk(dentry, &vcaps); 399 if (rc < 0) { 400 if (rc == -EINVAL) 401 printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n", 402 __func__, rc, bprm->filename); 403 else if (rc == -ENODATA) 404 rc = 0; 405 goto out; 406 } 407 408 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective); 409 if (rc == -EINVAL) 410 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", 411 __func__, rc, bprm->filename); 412 413 out: 414 dput(dentry); 415 if (rc) 416 bprm_clear_caps(bprm); 417 418 return rc; 419 } 420 421 /** 422 * cap_bprm_set_creds - Set up the proposed credentials for execve(). 423 * @bprm: The execution parameters, including the proposed creds 424 * 425 * Set up the proposed credentials for a new execution context being 426 * constructed by execve(). The proposed creds in @bprm->cred is altered, 427 * which won't take effect immediately. Returns 0 if successful, -ve on error. 428 */ 429 int cap_bprm_set_creds(struct linux_binprm *bprm) 430 { 431 const struct cred *old = current_cred(); 432 struct cred *new = bprm->cred; 433 bool effective; 434 int ret; 435 436 effective = false; 437 ret = get_file_caps(bprm, &effective); 438 if (ret < 0) 439 return ret; 440 441 if (!issecure(SECURE_NOROOT)) { 442 /* 443 * If the legacy file capability is set, then don't set privs 444 * for a setuid root binary run by a non-root user. Do set it 445 * for a root user just to cause least surprise to an admin. 446 */ 447 if (effective && new->uid != 0 && new->euid == 0) { 448 warn_setuid_and_fcaps_mixed(bprm->filename); 449 goto skip; 450 } 451 /* 452 * To support inheritance of root-permissions and suid-root 453 * executables under compatibility mode, we override the 454 * capability sets for the file. 455 * 456 * If only the real uid is 0, we do not set the effective bit. 457 */ 458 if (new->euid == 0 || new->uid == 0) { 459 /* pP' = (cap_bset & ~0) | (pI & ~0) */ 460 new->cap_permitted = cap_combine(old->cap_bset, 461 old->cap_inheritable); 462 } 463 if (new->euid == 0) 464 effective = true; 465 } 466 skip: 467 468 /* Don't let someone trace a set[ug]id/setpcap binary with the revised 469 * credentials unless they have the appropriate permit 470 */ 471 if ((new->euid != old->uid || 472 new->egid != old->gid || 473 !cap_issubset(new->cap_permitted, old->cap_permitted)) && 474 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) { 475 /* downgrade; they get no more than they had, and maybe less */ 476 if (!capable(CAP_SETUID)) { 477 new->euid = new->uid; 478 new->egid = new->gid; 479 } 480 new->cap_permitted = cap_intersect(new->cap_permitted, 481 old->cap_permitted); 482 } 483 484 new->suid = new->fsuid = new->euid; 485 new->sgid = new->fsgid = new->egid; 486 487 /* For init, we want to retain the capabilities set in the initial 488 * task. Thus we skip the usual capability rules 489 */ 490 if (!is_global_init(current)) { 491 if (effective) 492 new->cap_effective = new->cap_permitted; 493 else 494 cap_clear(new->cap_effective); 495 } 496 bprm->cap_effective = effective; 497 498 /* 499 * Audit candidate if current->cap_effective is set 500 * 501 * We do not bother to audit if 3 things are true: 502 * 1) cap_effective has all caps 503 * 2) we are root 504 * 3) root is supposed to have all caps (SECURE_NOROOT) 505 * Since this is just a normal root execing a process. 506 * 507 * Number 1 above might fail if you don't have a full bset, but I think 508 * that is interesting information to audit. 509 */ 510 if (!cap_isclear(new->cap_effective)) { 511 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) || 512 new->euid != 0 || new->uid != 0 || 513 issecure(SECURE_NOROOT)) { 514 ret = audit_log_bprm_fcaps(bprm, new, old); 515 if (ret < 0) 516 return ret; 517 } 518 } 519 520 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 521 return 0; 522 } 523 524 /** 525 * cap_bprm_secureexec - Determine whether a secure execution is required 526 * @bprm: The execution parameters 527 * 528 * Determine whether a secure execution is required, return 1 if it is, and 0 529 * if it is not. 530 * 531 * The credentials have been committed by this point, and so are no longer 532 * available through @bprm->cred. 533 */ 534 int cap_bprm_secureexec(struct linux_binprm *bprm) 535 { 536 const struct cred *cred = current_cred(); 537 538 if (cred->uid != 0) { 539 if (bprm->cap_effective) 540 return 1; 541 if (!cap_isclear(cred->cap_permitted)) 542 return 1; 543 } 544 545 return (cred->euid != cred->uid || 546 cred->egid != cred->gid); 547 } 548 549 /** 550 * cap_inode_setxattr - Determine whether an xattr may be altered 551 * @dentry: The inode/dentry being altered 552 * @name: The name of the xattr to be changed 553 * @value: The value that the xattr will be changed to 554 * @size: The size of value 555 * @flags: The replacement flag 556 * 557 * Determine whether an xattr may be altered or set on an inode, returning 0 if 558 * permission is granted, -ve if denied. 559 * 560 * This is used to make sure security xattrs don't get updated or set by those 561 * who aren't privileged to do so. 562 */ 563 int cap_inode_setxattr(struct dentry *dentry, const char *name, 564 const void *value, size_t size, int flags) 565 { 566 if (!strcmp(name, XATTR_NAME_CAPS)) { 567 if (!capable(CAP_SETFCAP)) 568 return -EPERM; 569 return 0; 570 } 571 572 if (!strncmp(name, XATTR_SECURITY_PREFIX, 573 sizeof(XATTR_SECURITY_PREFIX) - 1) && 574 !capable(CAP_SYS_ADMIN)) 575 return -EPERM; 576 return 0; 577 } 578 579 /** 580 * cap_inode_removexattr - Determine whether an xattr may be removed 581 * @dentry: The inode/dentry being altered 582 * @name: The name of the xattr to be changed 583 * 584 * Determine whether an xattr may be removed from an inode, returning 0 if 585 * permission is granted, -ve if denied. 586 * 587 * This is used to make sure security xattrs don't get removed by those who 588 * aren't privileged to remove them. 589 */ 590 int cap_inode_removexattr(struct dentry *dentry, const char *name) 591 { 592 if (!strcmp(name, XATTR_NAME_CAPS)) { 593 if (!capable(CAP_SETFCAP)) 594 return -EPERM; 595 return 0; 596 } 597 598 if (!strncmp(name, XATTR_SECURITY_PREFIX, 599 sizeof(XATTR_SECURITY_PREFIX) - 1) && 600 !capable(CAP_SYS_ADMIN)) 601 return -EPERM; 602 return 0; 603 } 604 605 /* 606 * cap_emulate_setxuid() fixes the effective / permitted capabilities of 607 * a process after a call to setuid, setreuid, or setresuid. 608 * 609 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of 610 * {r,e,s}uid != 0, the permitted and effective capabilities are 611 * cleared. 612 * 613 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective 614 * capabilities of the process are cleared. 615 * 616 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective 617 * capabilities are set to the permitted capabilities. 618 * 619 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 620 * never happen. 621 * 622 * -astor 623 * 624 * cevans - New behaviour, Oct '99 625 * A process may, via prctl(), elect to keep its capabilities when it 626 * calls setuid() and switches away from uid==0. Both permitted and 627 * effective sets will be retained. 628 * Without this change, it was impossible for a daemon to drop only some 629 * of its privilege. The call to setuid(!=0) would drop all privileges! 630 * Keeping uid 0 is not an option because uid 0 owns too many vital 631 * files.. 632 * Thanks to Olaf Kirch and Peter Benie for spotting this. 633 */ 634 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) 635 { 636 if ((old->uid == 0 || old->euid == 0 || old->suid == 0) && 637 (new->uid != 0 && new->euid != 0 && new->suid != 0) && 638 !issecure(SECURE_KEEP_CAPS)) { 639 cap_clear(new->cap_permitted); 640 cap_clear(new->cap_effective); 641 } 642 if (old->euid == 0 && new->euid != 0) 643 cap_clear(new->cap_effective); 644 if (old->euid != 0 && new->euid == 0) 645 new->cap_effective = new->cap_permitted; 646 } 647 648 /** 649 * cap_task_fix_setuid - Fix up the results of setuid() call 650 * @new: The proposed credentials 651 * @old: The current task's current credentials 652 * @flags: Indications of what has changed 653 * 654 * Fix up the results of setuid() call before the credential changes are 655 * actually applied, returning 0 to grant the changes, -ve to deny them. 656 */ 657 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) 658 { 659 switch (flags) { 660 case LSM_SETID_RE: 661 case LSM_SETID_ID: 662 case LSM_SETID_RES: 663 /* juggle the capabilities to follow [RES]UID changes unless 664 * otherwise suppressed */ 665 if (!issecure(SECURE_NO_SETUID_FIXUP)) 666 cap_emulate_setxuid(new, old); 667 break; 668 669 case LSM_SETID_FS: 670 /* juggle the capabilties to follow FSUID changes, unless 671 * otherwise suppressed 672 * 673 * FIXME - is fsuser used for all CAP_FS_MASK capabilities? 674 * if not, we might be a bit too harsh here. 675 */ 676 if (!issecure(SECURE_NO_SETUID_FIXUP)) { 677 if (old->fsuid == 0 && new->fsuid != 0) 678 new->cap_effective = 679 cap_drop_fs_set(new->cap_effective); 680 681 if (old->fsuid != 0 && new->fsuid == 0) 682 new->cap_effective = 683 cap_raise_fs_set(new->cap_effective, 684 new->cap_permitted); 685 } 686 break; 687 688 default: 689 return -EINVAL; 690 } 691 692 return 0; 693 } 694 695 /* 696 * Rationale: code calling task_setscheduler, task_setioprio, and 697 * task_setnice, assumes that 698 * . if capable(cap_sys_nice), then those actions should be allowed 699 * . if not capable(cap_sys_nice), but acting on your own processes, 700 * then those actions should be allowed 701 * This is insufficient now since you can call code without suid, but 702 * yet with increased caps. 703 * So we check for increased caps on the target process. 704 */ 705 static int cap_safe_nice(struct task_struct *p) 706 { 707 int is_subset; 708 709 rcu_read_lock(); 710 is_subset = cap_issubset(__task_cred(p)->cap_permitted, 711 current_cred()->cap_permitted); 712 rcu_read_unlock(); 713 714 if (!is_subset && !capable(CAP_SYS_NICE)) 715 return -EPERM; 716 return 0; 717 } 718 719 /** 720 * cap_task_setscheduler - Detemine if scheduler policy change is permitted 721 * @p: The task to affect 722 * 723 * Detemine if the requested scheduler policy change is permitted for the 724 * specified task, returning 0 if permission is granted, -ve if denied. 725 */ 726 int cap_task_setscheduler(struct task_struct *p) 727 { 728 return cap_safe_nice(p); 729 } 730 731 /** 732 * cap_task_ioprio - Detemine if I/O priority change is permitted 733 * @p: The task to affect 734 * @ioprio: The I/O priority to set 735 * 736 * Detemine if the requested I/O priority change is permitted for the specified 737 * task, returning 0 if permission is granted, -ve if denied. 738 */ 739 int cap_task_setioprio(struct task_struct *p, int ioprio) 740 { 741 return cap_safe_nice(p); 742 } 743 744 /** 745 * cap_task_ioprio - Detemine if task priority change is permitted 746 * @p: The task to affect 747 * @nice: The nice value to set 748 * 749 * Detemine if the requested task priority change is permitted for the 750 * specified task, returning 0 if permission is granted, -ve if denied. 751 */ 752 int cap_task_setnice(struct task_struct *p, int nice) 753 { 754 return cap_safe_nice(p); 755 } 756 757 /* 758 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from 759 * the current task's bounding set. Returns 0 on success, -ve on error. 760 */ 761 static long cap_prctl_drop(struct cred *new, unsigned long cap) 762 { 763 if (!capable(CAP_SETPCAP)) 764 return -EPERM; 765 if (!cap_valid(cap)) 766 return -EINVAL; 767 768 cap_lower(new->cap_bset, cap); 769 return 0; 770 } 771 772 /** 773 * cap_task_prctl - Implement process control functions for this security module 774 * @option: The process control function requested 775 * @arg2, @arg3, @arg4, @arg5: The argument data for this function 776 * 777 * Allow process control functions (sys_prctl()) to alter capabilities; may 778 * also deny access to other functions not otherwise implemented here. 779 * 780 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented 781 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM 782 * modules will consider performing the function. 783 */ 784 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, 785 unsigned long arg4, unsigned long arg5) 786 { 787 struct cred *new; 788 long error = 0; 789 790 new = prepare_creds(); 791 if (!new) 792 return -ENOMEM; 793 794 switch (option) { 795 case PR_CAPBSET_READ: 796 error = -EINVAL; 797 if (!cap_valid(arg2)) 798 goto error; 799 error = !!cap_raised(new->cap_bset, arg2); 800 goto no_change; 801 802 case PR_CAPBSET_DROP: 803 error = cap_prctl_drop(new, arg2); 804 if (error < 0) 805 goto error; 806 goto changed; 807 808 /* 809 * The next four prctl's remain to assist with transitioning a 810 * system from legacy UID=0 based privilege (when filesystem 811 * capabilities are not in use) to a system using filesystem 812 * capabilities only - as the POSIX.1e draft intended. 813 * 814 * Note: 815 * 816 * PR_SET_SECUREBITS = 817 * issecure_mask(SECURE_KEEP_CAPS_LOCKED) 818 * | issecure_mask(SECURE_NOROOT) 819 * | issecure_mask(SECURE_NOROOT_LOCKED) 820 * | issecure_mask(SECURE_NO_SETUID_FIXUP) 821 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) 822 * 823 * will ensure that the current process and all of its 824 * children will be locked into a pure 825 * capability-based-privilege environment. 826 */ 827 case PR_SET_SECUREBITS: 828 error = -EPERM; 829 if ((((new->securebits & SECURE_ALL_LOCKS) >> 1) 830 & (new->securebits ^ arg2)) /*[1]*/ 831 || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ 832 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ 833 || (cap_capable(current, current_cred(), CAP_SETPCAP, 834 SECURITY_CAP_AUDIT) != 0) /*[4]*/ 835 /* 836 * [1] no changing of bits that are locked 837 * [2] no unlocking of locks 838 * [3] no setting of unsupported bits 839 * [4] doing anything requires privilege (go read about 840 * the "sendmail capabilities bug") 841 */ 842 ) 843 /* cannot change a locked bit */ 844 goto error; 845 new->securebits = arg2; 846 goto changed; 847 848 case PR_GET_SECUREBITS: 849 error = new->securebits; 850 goto no_change; 851 852 case PR_GET_KEEPCAPS: 853 if (issecure(SECURE_KEEP_CAPS)) 854 error = 1; 855 goto no_change; 856 857 case PR_SET_KEEPCAPS: 858 error = -EINVAL; 859 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ 860 goto error; 861 error = -EPERM; 862 if (issecure(SECURE_KEEP_CAPS_LOCKED)) 863 goto error; 864 if (arg2) 865 new->securebits |= issecure_mask(SECURE_KEEP_CAPS); 866 else 867 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 868 goto changed; 869 870 default: 871 /* No functionality available - continue with default */ 872 error = -ENOSYS; 873 goto error; 874 } 875 876 /* Functionality provided */ 877 changed: 878 return commit_creds(new); 879 880 no_change: 881 error: 882 abort_creds(new); 883 return error; 884 } 885 886 /** 887 * cap_syslog - Determine whether syslog function is permitted 888 * @type: Function requested 889 * @from_file: Whether this request came from an open file (i.e. /proc) 890 * 891 * Determine whether the current process is permitted to use a particular 892 * syslog function, returning 0 if permission is granted, -ve if not. 893 */ 894 int cap_syslog(int type, bool from_file) 895 { 896 if (type != SYSLOG_ACTION_OPEN && from_file) 897 return 0; 898 if ((type != SYSLOG_ACTION_READ_ALL && 899 type != SYSLOG_ACTION_SIZE_BUFFER) && !capable(CAP_SYS_ADMIN)) 900 return -EPERM; 901 return 0; 902 } 903 904 /** 905 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted 906 * @mm: The VM space in which the new mapping is to be made 907 * @pages: The size of the mapping 908 * 909 * Determine whether the allocation of a new virtual mapping by the current 910 * task is permitted, returning 0 if permission is granted, -ve if not. 911 */ 912 int cap_vm_enough_memory(struct mm_struct *mm, long pages) 913 { 914 int cap_sys_admin = 0; 915 916 if (cap_capable(current, current_cred(), CAP_SYS_ADMIN, 917 SECURITY_CAP_NOAUDIT) == 0) 918 cap_sys_admin = 1; 919 return __vm_enough_memory(mm, pages, cap_sys_admin); 920 } 921 922 /* 923 * cap_file_mmap - check if able to map given addr 924 * @file: unused 925 * @reqprot: unused 926 * @prot: unused 927 * @flags: unused 928 * @addr: address attempting to be mapped 929 * @addr_only: unused 930 * 931 * If the process is attempting to map memory below dac_mmap_min_addr they need 932 * CAP_SYS_RAWIO. The other parameters to this function are unused by the 933 * capability security module. Returns 0 if this mapping should be allowed 934 * -EPERM if not. 935 */ 936 int cap_file_mmap(struct file *file, unsigned long reqprot, 937 unsigned long prot, unsigned long flags, 938 unsigned long addr, unsigned long addr_only) 939 { 940 int ret = 0; 941 942 if (addr < dac_mmap_min_addr) { 943 ret = cap_capable(current, current_cred(), CAP_SYS_RAWIO, 944 SECURITY_CAP_AUDIT); 945 /* set PF_SUPERPRIV if it turns out we allow the low mmap */ 946 if (ret == 0) 947 current->flags |= PF_SUPERPRIV; 948 } 949 return ret; 950 } 951