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/user_namespace.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 return 0; 57 } 58 59 int cap_netlink_recv(struct sk_buff *skb, int cap) 60 { 61 if (!cap_raised(current_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 * @ns: The user namespace in which we need the capability 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, 84 struct user_namespace *targ_ns, int cap, int audit) 85 { 86 for (;;) { 87 /* The creator of the user namespace has all caps. */ 88 if (targ_ns != &init_user_ns && targ_ns->creator == cred->user) 89 return 0; 90 91 /* Do we have the necessary capabilities? */ 92 if (targ_ns == cred->user->user_ns) 93 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; 94 95 /* Have we tried all of the parent namespaces? */ 96 if (targ_ns == &init_user_ns) 97 return -EPERM; 98 99 /* 100 *If you have a capability in a parent user ns, then you have 101 * it over all children user namespaces as well. 102 */ 103 targ_ns = targ_ns->creator->user_ns; 104 } 105 106 /* We never get here */ 107 } 108 109 /** 110 * cap_settime - Determine whether the current process may set the system clock 111 * @ts: The time to set 112 * @tz: The timezone to set 113 * 114 * Determine whether the current process may set the system clock and timezone 115 * information, returning 0 if permission granted, -ve if denied. 116 */ 117 int cap_settime(const struct timespec *ts, const struct timezone *tz) 118 { 119 if (!capable(CAP_SYS_TIME)) 120 return -EPERM; 121 return 0; 122 } 123 124 /** 125 * cap_ptrace_access_check - Determine whether the current process may access 126 * another 127 * @child: The process to be accessed 128 * @mode: The mode of attachment. 129 * 130 * If we are in the same or an ancestor user_ns and have all the target 131 * task's capabilities, then ptrace access is allowed. 132 * If we have the ptrace capability to the target user_ns, then ptrace 133 * access is allowed. 134 * Else denied. 135 * 136 * Determine whether a process may access another, returning 0 if permission 137 * granted, -ve if denied. 138 */ 139 int cap_ptrace_access_check(struct task_struct *child, unsigned int mode) 140 { 141 int ret = 0; 142 const struct cred *cred, *child_cred; 143 144 rcu_read_lock(); 145 cred = current_cred(); 146 child_cred = __task_cred(child); 147 if (cred->user->user_ns == child_cred->user->user_ns && 148 cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) 149 goto out; 150 if (ns_capable(child_cred->user->user_ns, CAP_SYS_PTRACE)) 151 goto out; 152 ret = -EPERM; 153 out: 154 rcu_read_unlock(); 155 return ret; 156 } 157 158 /** 159 * cap_ptrace_traceme - Determine whether another process may trace the current 160 * @parent: The task proposed to be the tracer 161 * 162 * If parent is in the same or an ancestor user_ns and has all current's 163 * capabilities, then ptrace access is allowed. 164 * If parent has the ptrace capability to current's user_ns, then ptrace 165 * access is allowed. 166 * Else denied. 167 * 168 * Determine whether the nominated task is permitted to trace the current 169 * process, returning 0 if permission is granted, -ve if denied. 170 */ 171 int cap_ptrace_traceme(struct task_struct *parent) 172 { 173 int ret = 0; 174 const struct cred *cred, *child_cred; 175 176 rcu_read_lock(); 177 cred = __task_cred(parent); 178 child_cred = current_cred(); 179 if (cred->user->user_ns == child_cred->user->user_ns && 180 cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) 181 goto out; 182 if (has_ns_capability(parent, child_cred->user->user_ns, CAP_SYS_PTRACE)) 183 goto out; 184 ret = -EPERM; 185 out: 186 rcu_read_unlock(); 187 return ret; 188 } 189 190 /** 191 * cap_capget - Retrieve a task's capability sets 192 * @target: The task from which to retrieve the capability sets 193 * @effective: The place to record the effective set 194 * @inheritable: The place to record the inheritable set 195 * @permitted: The place to record the permitted set 196 * 197 * This function retrieves the capabilities of the nominated task and returns 198 * them to the caller. 199 */ 200 int cap_capget(struct task_struct *target, kernel_cap_t *effective, 201 kernel_cap_t *inheritable, kernel_cap_t *permitted) 202 { 203 const struct cred *cred; 204 205 /* Derived from kernel/capability.c:sys_capget. */ 206 rcu_read_lock(); 207 cred = __task_cred(target); 208 *effective = cred->cap_effective; 209 *inheritable = cred->cap_inheritable; 210 *permitted = cred->cap_permitted; 211 rcu_read_unlock(); 212 return 0; 213 } 214 215 /* 216 * Determine whether the inheritable capabilities are limited to the old 217 * permitted set. Returns 1 if they are limited, 0 if they are not. 218 */ 219 static inline int cap_inh_is_capped(void) 220 { 221 222 /* they are so limited unless the current task has the CAP_SETPCAP 223 * capability 224 */ 225 if (cap_capable(current, current_cred(), 226 current_cred()->user->user_ns, CAP_SETPCAP, 227 SECURITY_CAP_AUDIT) == 0) 228 return 0; 229 return 1; 230 } 231 232 /** 233 * cap_capset - Validate and apply proposed changes to current's capabilities 234 * @new: The proposed new credentials; alterations should be made here 235 * @old: The current task's current credentials 236 * @effective: A pointer to the proposed new effective capabilities set 237 * @inheritable: A pointer to the proposed new inheritable capabilities set 238 * @permitted: A pointer to the proposed new permitted capabilities set 239 * 240 * This function validates and applies a proposed mass change to the current 241 * process's capability sets. The changes are made to the proposed new 242 * credentials, and assuming no error, will be committed by the caller of LSM. 243 */ 244 int cap_capset(struct cred *new, 245 const struct cred *old, 246 const kernel_cap_t *effective, 247 const kernel_cap_t *inheritable, 248 const kernel_cap_t *permitted) 249 { 250 if (cap_inh_is_capped() && 251 !cap_issubset(*inheritable, 252 cap_combine(old->cap_inheritable, 253 old->cap_permitted))) 254 /* incapable of using this inheritable set */ 255 return -EPERM; 256 257 if (!cap_issubset(*inheritable, 258 cap_combine(old->cap_inheritable, 259 old->cap_bset))) 260 /* no new pI capabilities outside bounding set */ 261 return -EPERM; 262 263 /* verify restrictions on target's new Permitted set */ 264 if (!cap_issubset(*permitted, old->cap_permitted)) 265 return -EPERM; 266 267 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ 268 if (!cap_issubset(*effective, *permitted)) 269 return -EPERM; 270 271 new->cap_effective = *effective; 272 new->cap_inheritable = *inheritable; 273 new->cap_permitted = *permitted; 274 return 0; 275 } 276 277 /* 278 * Clear proposed capability sets for execve(). 279 */ 280 static inline void bprm_clear_caps(struct linux_binprm *bprm) 281 { 282 cap_clear(bprm->cred->cap_permitted); 283 bprm->cap_effective = false; 284 } 285 286 /** 287 * cap_inode_need_killpriv - Determine if inode change affects privileges 288 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV 289 * 290 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV 291 * affects the security markings on that inode, and if it is, should 292 * inode_killpriv() be invoked or the change rejected? 293 * 294 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and 295 * -ve to deny the change. 296 */ 297 int cap_inode_need_killpriv(struct dentry *dentry) 298 { 299 struct inode *inode = dentry->d_inode; 300 int error; 301 302 if (!inode->i_op->getxattr) 303 return 0; 304 305 error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0); 306 if (error <= 0) 307 return 0; 308 return 1; 309 } 310 311 /** 312 * cap_inode_killpriv - Erase the security markings on an inode 313 * @dentry: The inode/dentry to alter 314 * 315 * Erase the privilege-enhancing security markings on an inode. 316 * 317 * Returns 0 if successful, -ve on error. 318 */ 319 int cap_inode_killpriv(struct dentry *dentry) 320 { 321 struct inode *inode = dentry->d_inode; 322 323 if (!inode->i_op->removexattr) 324 return 0; 325 326 return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS); 327 } 328 329 /* 330 * Calculate the new process capability sets from the capability sets attached 331 * to a file. 332 */ 333 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, 334 struct linux_binprm *bprm, 335 bool *effective, 336 bool *has_cap) 337 { 338 struct cred *new = bprm->cred; 339 unsigned i; 340 int ret = 0; 341 342 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) 343 *effective = true; 344 345 if (caps->magic_etc & VFS_CAP_REVISION_MASK) 346 *has_cap = true; 347 348 CAP_FOR_EACH_U32(i) { 349 __u32 permitted = caps->permitted.cap[i]; 350 __u32 inheritable = caps->inheritable.cap[i]; 351 352 /* 353 * pP' = (X & fP) | (pI & fI) 354 */ 355 new->cap_permitted.cap[i] = 356 (new->cap_bset.cap[i] & permitted) | 357 (new->cap_inheritable.cap[i] & inheritable); 358 359 if (permitted & ~new->cap_permitted.cap[i]) 360 /* insufficient to execute correctly */ 361 ret = -EPERM; 362 } 363 364 /* 365 * For legacy apps, with no internal support for recognizing they 366 * do not have enough capabilities, we return an error if they are 367 * missing some "forced" (aka file-permitted) capabilities. 368 */ 369 return *effective ? ret : 0; 370 } 371 372 /* 373 * Extract the on-exec-apply capability sets for an executable file. 374 */ 375 int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) 376 { 377 struct inode *inode = dentry->d_inode; 378 __u32 magic_etc; 379 unsigned tocopy, i; 380 int size; 381 struct vfs_cap_data caps; 382 383 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); 384 385 if (!inode || !inode->i_op->getxattr) 386 return -ENODATA; 387 388 size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps, 389 XATTR_CAPS_SZ); 390 if (size == -ENODATA || size == -EOPNOTSUPP) 391 /* no data, that's ok */ 392 return -ENODATA; 393 if (size < 0) 394 return size; 395 396 if (size < sizeof(magic_etc)) 397 return -EINVAL; 398 399 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc); 400 401 switch (magic_etc & VFS_CAP_REVISION_MASK) { 402 case VFS_CAP_REVISION_1: 403 if (size != XATTR_CAPS_SZ_1) 404 return -EINVAL; 405 tocopy = VFS_CAP_U32_1; 406 break; 407 case VFS_CAP_REVISION_2: 408 if (size != XATTR_CAPS_SZ_2) 409 return -EINVAL; 410 tocopy = VFS_CAP_U32_2; 411 break; 412 default: 413 return -EINVAL; 414 } 415 416 CAP_FOR_EACH_U32(i) { 417 if (i >= tocopy) 418 break; 419 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted); 420 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable); 421 } 422 423 return 0; 424 } 425 426 /* 427 * Attempt to get the on-exec apply capability sets for an executable file from 428 * its xattrs and, if present, apply them to the proposed credentials being 429 * constructed by execve(). 430 */ 431 static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap) 432 { 433 struct dentry *dentry; 434 int rc = 0; 435 struct cpu_vfs_cap_data vcaps; 436 437 bprm_clear_caps(bprm); 438 439 if (!file_caps_enabled) 440 return 0; 441 442 if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID) 443 return 0; 444 445 dentry = dget(bprm->file->f_dentry); 446 447 rc = get_vfs_caps_from_disk(dentry, &vcaps); 448 if (rc < 0) { 449 if (rc == -EINVAL) 450 printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n", 451 __func__, rc, bprm->filename); 452 else if (rc == -ENODATA) 453 rc = 0; 454 goto out; 455 } 456 457 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap); 458 if (rc == -EINVAL) 459 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", 460 __func__, rc, bprm->filename); 461 462 out: 463 dput(dentry); 464 if (rc) 465 bprm_clear_caps(bprm); 466 467 return rc; 468 } 469 470 /** 471 * cap_bprm_set_creds - Set up the proposed credentials for execve(). 472 * @bprm: The execution parameters, including the proposed creds 473 * 474 * Set up the proposed credentials for a new execution context being 475 * constructed by execve(). The proposed creds in @bprm->cred is altered, 476 * which won't take effect immediately. Returns 0 if successful, -ve on error. 477 */ 478 int cap_bprm_set_creds(struct linux_binprm *bprm) 479 { 480 const struct cred *old = current_cred(); 481 struct cred *new = bprm->cred; 482 bool effective, has_cap = false; 483 int ret; 484 485 effective = false; 486 ret = get_file_caps(bprm, &effective, &has_cap); 487 if (ret < 0) 488 return ret; 489 490 if (!issecure(SECURE_NOROOT)) { 491 /* 492 * If the legacy file capability is set, then don't set privs 493 * for a setuid root binary run by a non-root user. Do set it 494 * for a root user just to cause least surprise to an admin. 495 */ 496 if (has_cap && new->uid != 0 && new->euid == 0) { 497 warn_setuid_and_fcaps_mixed(bprm->filename); 498 goto skip; 499 } 500 /* 501 * To support inheritance of root-permissions and suid-root 502 * executables under compatibility mode, we override the 503 * capability sets for the file. 504 * 505 * If only the real uid is 0, we do not set the effective bit. 506 */ 507 if (new->euid == 0 || new->uid == 0) { 508 /* pP' = (cap_bset & ~0) | (pI & ~0) */ 509 new->cap_permitted = cap_combine(old->cap_bset, 510 old->cap_inheritable); 511 } 512 if (new->euid == 0) 513 effective = true; 514 } 515 skip: 516 517 /* Don't let someone trace a set[ug]id/setpcap binary with the revised 518 * credentials unless they have the appropriate permit 519 */ 520 if ((new->euid != old->uid || 521 new->egid != old->gid || 522 !cap_issubset(new->cap_permitted, old->cap_permitted)) && 523 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) { 524 /* downgrade; they get no more than they had, and maybe less */ 525 if (!capable(CAP_SETUID)) { 526 new->euid = new->uid; 527 new->egid = new->gid; 528 } 529 new->cap_permitted = cap_intersect(new->cap_permitted, 530 old->cap_permitted); 531 } 532 533 new->suid = new->fsuid = new->euid; 534 new->sgid = new->fsgid = new->egid; 535 536 if (effective) 537 new->cap_effective = new->cap_permitted; 538 else 539 cap_clear(new->cap_effective); 540 bprm->cap_effective = effective; 541 542 /* 543 * Audit candidate if current->cap_effective is set 544 * 545 * We do not bother to audit if 3 things are true: 546 * 1) cap_effective has all caps 547 * 2) we are root 548 * 3) root is supposed to have all caps (SECURE_NOROOT) 549 * Since this is just a normal root execing a process. 550 * 551 * Number 1 above might fail if you don't have a full bset, but I think 552 * that is interesting information to audit. 553 */ 554 if (!cap_isclear(new->cap_effective)) { 555 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) || 556 new->euid != 0 || new->uid != 0 || 557 issecure(SECURE_NOROOT)) { 558 ret = audit_log_bprm_fcaps(bprm, new, old); 559 if (ret < 0) 560 return ret; 561 } 562 } 563 564 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 565 return 0; 566 } 567 568 /** 569 * cap_bprm_secureexec - Determine whether a secure execution is required 570 * @bprm: The execution parameters 571 * 572 * Determine whether a secure execution is required, return 1 if it is, and 0 573 * if it is not. 574 * 575 * The credentials have been committed by this point, and so are no longer 576 * available through @bprm->cred. 577 */ 578 int cap_bprm_secureexec(struct linux_binprm *bprm) 579 { 580 const struct cred *cred = current_cred(); 581 582 if (cred->uid != 0) { 583 if (bprm->cap_effective) 584 return 1; 585 if (!cap_isclear(cred->cap_permitted)) 586 return 1; 587 } 588 589 return (cred->euid != cred->uid || 590 cred->egid != cred->gid); 591 } 592 593 /** 594 * cap_inode_setxattr - Determine whether an xattr may be altered 595 * @dentry: The inode/dentry being altered 596 * @name: The name of the xattr to be changed 597 * @value: The value that the xattr will be changed to 598 * @size: The size of value 599 * @flags: The replacement flag 600 * 601 * Determine whether an xattr may be altered or set on an inode, returning 0 if 602 * permission is granted, -ve if denied. 603 * 604 * This is used to make sure security xattrs don't get updated or set by those 605 * who aren't privileged to do so. 606 */ 607 int cap_inode_setxattr(struct dentry *dentry, const char *name, 608 const void *value, size_t size, int flags) 609 { 610 if (!strcmp(name, XATTR_NAME_CAPS)) { 611 if (!capable(CAP_SETFCAP)) 612 return -EPERM; 613 return 0; 614 } 615 616 if (!strncmp(name, XATTR_SECURITY_PREFIX, 617 sizeof(XATTR_SECURITY_PREFIX) - 1) && 618 !capable(CAP_SYS_ADMIN)) 619 return -EPERM; 620 return 0; 621 } 622 623 /** 624 * cap_inode_removexattr - Determine whether an xattr may be removed 625 * @dentry: The inode/dentry being altered 626 * @name: The name of the xattr to be changed 627 * 628 * Determine whether an xattr may be removed from an inode, returning 0 if 629 * permission is granted, -ve if denied. 630 * 631 * This is used to make sure security xattrs don't get removed by those who 632 * aren't privileged to remove them. 633 */ 634 int cap_inode_removexattr(struct dentry *dentry, const char *name) 635 { 636 if (!strcmp(name, XATTR_NAME_CAPS)) { 637 if (!capable(CAP_SETFCAP)) 638 return -EPERM; 639 return 0; 640 } 641 642 if (!strncmp(name, XATTR_SECURITY_PREFIX, 643 sizeof(XATTR_SECURITY_PREFIX) - 1) && 644 !capable(CAP_SYS_ADMIN)) 645 return -EPERM; 646 return 0; 647 } 648 649 /* 650 * cap_emulate_setxuid() fixes the effective / permitted capabilities of 651 * a process after a call to setuid, setreuid, or setresuid. 652 * 653 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of 654 * {r,e,s}uid != 0, the permitted and effective capabilities are 655 * cleared. 656 * 657 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective 658 * capabilities of the process are cleared. 659 * 660 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective 661 * capabilities are set to the permitted capabilities. 662 * 663 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 664 * never happen. 665 * 666 * -astor 667 * 668 * cevans - New behaviour, Oct '99 669 * A process may, via prctl(), elect to keep its capabilities when it 670 * calls setuid() and switches away from uid==0. Both permitted and 671 * effective sets will be retained. 672 * Without this change, it was impossible for a daemon to drop only some 673 * of its privilege. The call to setuid(!=0) would drop all privileges! 674 * Keeping uid 0 is not an option because uid 0 owns too many vital 675 * files.. 676 * Thanks to Olaf Kirch and Peter Benie for spotting this. 677 */ 678 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) 679 { 680 if ((old->uid == 0 || old->euid == 0 || old->suid == 0) && 681 (new->uid != 0 && new->euid != 0 && new->suid != 0) && 682 !issecure(SECURE_KEEP_CAPS)) { 683 cap_clear(new->cap_permitted); 684 cap_clear(new->cap_effective); 685 } 686 if (old->euid == 0 && new->euid != 0) 687 cap_clear(new->cap_effective); 688 if (old->euid != 0 && new->euid == 0) 689 new->cap_effective = new->cap_permitted; 690 } 691 692 /** 693 * cap_task_fix_setuid - Fix up the results of setuid() call 694 * @new: The proposed credentials 695 * @old: The current task's current credentials 696 * @flags: Indications of what has changed 697 * 698 * Fix up the results of setuid() call before the credential changes are 699 * actually applied, returning 0 to grant the changes, -ve to deny them. 700 */ 701 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) 702 { 703 switch (flags) { 704 case LSM_SETID_RE: 705 case LSM_SETID_ID: 706 case LSM_SETID_RES: 707 /* juggle the capabilities to follow [RES]UID changes unless 708 * otherwise suppressed */ 709 if (!issecure(SECURE_NO_SETUID_FIXUP)) 710 cap_emulate_setxuid(new, old); 711 break; 712 713 case LSM_SETID_FS: 714 /* juggle the capabilties to follow FSUID changes, unless 715 * otherwise suppressed 716 * 717 * FIXME - is fsuser used for all CAP_FS_MASK capabilities? 718 * if not, we might be a bit too harsh here. 719 */ 720 if (!issecure(SECURE_NO_SETUID_FIXUP)) { 721 if (old->fsuid == 0 && new->fsuid != 0) 722 new->cap_effective = 723 cap_drop_fs_set(new->cap_effective); 724 725 if (old->fsuid != 0 && new->fsuid == 0) 726 new->cap_effective = 727 cap_raise_fs_set(new->cap_effective, 728 new->cap_permitted); 729 } 730 break; 731 732 default: 733 return -EINVAL; 734 } 735 736 return 0; 737 } 738 739 /* 740 * Rationale: code calling task_setscheduler, task_setioprio, and 741 * task_setnice, assumes that 742 * . if capable(cap_sys_nice), then those actions should be allowed 743 * . if not capable(cap_sys_nice), but acting on your own processes, 744 * then those actions should be allowed 745 * This is insufficient now since you can call code without suid, but 746 * yet with increased caps. 747 * So we check for increased caps on the target process. 748 */ 749 static int cap_safe_nice(struct task_struct *p) 750 { 751 int is_subset; 752 753 rcu_read_lock(); 754 is_subset = cap_issubset(__task_cred(p)->cap_permitted, 755 current_cred()->cap_permitted); 756 rcu_read_unlock(); 757 758 if (!is_subset && !capable(CAP_SYS_NICE)) 759 return -EPERM; 760 return 0; 761 } 762 763 /** 764 * cap_task_setscheduler - Detemine if scheduler policy change is permitted 765 * @p: The task to affect 766 * 767 * Detemine if the requested scheduler policy change is permitted for the 768 * specified task, returning 0 if permission is granted, -ve if denied. 769 */ 770 int cap_task_setscheduler(struct task_struct *p) 771 { 772 return cap_safe_nice(p); 773 } 774 775 /** 776 * cap_task_ioprio - Detemine if I/O priority change is permitted 777 * @p: The task to affect 778 * @ioprio: The I/O priority to set 779 * 780 * Detemine if the requested I/O priority change is permitted for the specified 781 * task, returning 0 if permission is granted, -ve if denied. 782 */ 783 int cap_task_setioprio(struct task_struct *p, int ioprio) 784 { 785 return cap_safe_nice(p); 786 } 787 788 /** 789 * cap_task_ioprio - Detemine if task priority change is permitted 790 * @p: The task to affect 791 * @nice: The nice value to set 792 * 793 * Detemine if the requested task priority change is permitted for the 794 * specified task, returning 0 if permission is granted, -ve if denied. 795 */ 796 int cap_task_setnice(struct task_struct *p, int nice) 797 { 798 return cap_safe_nice(p); 799 } 800 801 /* 802 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from 803 * the current task's bounding set. Returns 0 on success, -ve on error. 804 */ 805 static long cap_prctl_drop(struct cred *new, unsigned long cap) 806 { 807 if (!capable(CAP_SETPCAP)) 808 return -EPERM; 809 if (!cap_valid(cap)) 810 return -EINVAL; 811 812 cap_lower(new->cap_bset, cap); 813 return 0; 814 } 815 816 /** 817 * cap_task_prctl - Implement process control functions for this security module 818 * @option: The process control function requested 819 * @arg2, @arg3, @arg4, @arg5: The argument data for this function 820 * 821 * Allow process control functions (sys_prctl()) to alter capabilities; may 822 * also deny access to other functions not otherwise implemented here. 823 * 824 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented 825 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM 826 * modules will consider performing the function. 827 */ 828 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, 829 unsigned long arg4, unsigned long arg5) 830 { 831 struct cred *new; 832 long error = 0; 833 834 new = prepare_creds(); 835 if (!new) 836 return -ENOMEM; 837 838 switch (option) { 839 case PR_CAPBSET_READ: 840 error = -EINVAL; 841 if (!cap_valid(arg2)) 842 goto error; 843 error = !!cap_raised(new->cap_bset, arg2); 844 goto no_change; 845 846 case PR_CAPBSET_DROP: 847 error = cap_prctl_drop(new, arg2); 848 if (error < 0) 849 goto error; 850 goto changed; 851 852 /* 853 * The next four prctl's remain to assist with transitioning a 854 * system from legacy UID=0 based privilege (when filesystem 855 * capabilities are not in use) to a system using filesystem 856 * capabilities only - as the POSIX.1e draft intended. 857 * 858 * Note: 859 * 860 * PR_SET_SECUREBITS = 861 * issecure_mask(SECURE_KEEP_CAPS_LOCKED) 862 * | issecure_mask(SECURE_NOROOT) 863 * | issecure_mask(SECURE_NOROOT_LOCKED) 864 * | issecure_mask(SECURE_NO_SETUID_FIXUP) 865 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) 866 * 867 * will ensure that the current process and all of its 868 * children will be locked into a pure 869 * capability-based-privilege environment. 870 */ 871 case PR_SET_SECUREBITS: 872 error = -EPERM; 873 if ((((new->securebits & SECURE_ALL_LOCKS) >> 1) 874 & (new->securebits ^ arg2)) /*[1]*/ 875 || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ 876 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ 877 || (cap_capable(current, current_cred(), 878 current_cred()->user->user_ns, CAP_SETPCAP, 879 SECURITY_CAP_AUDIT) != 0) /*[4]*/ 880 /* 881 * [1] no changing of bits that are locked 882 * [2] no unlocking of locks 883 * [3] no setting of unsupported bits 884 * [4] doing anything requires privilege (go read about 885 * the "sendmail capabilities bug") 886 */ 887 ) 888 /* cannot change a locked bit */ 889 goto error; 890 new->securebits = arg2; 891 goto changed; 892 893 case PR_GET_SECUREBITS: 894 error = new->securebits; 895 goto no_change; 896 897 case PR_GET_KEEPCAPS: 898 if (issecure(SECURE_KEEP_CAPS)) 899 error = 1; 900 goto no_change; 901 902 case PR_SET_KEEPCAPS: 903 error = -EINVAL; 904 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ 905 goto error; 906 error = -EPERM; 907 if (issecure(SECURE_KEEP_CAPS_LOCKED)) 908 goto error; 909 if (arg2) 910 new->securebits |= issecure_mask(SECURE_KEEP_CAPS); 911 else 912 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 913 goto changed; 914 915 default: 916 /* No functionality available - continue with default */ 917 error = -ENOSYS; 918 goto error; 919 } 920 921 /* Functionality provided */ 922 changed: 923 return commit_creds(new); 924 925 no_change: 926 error: 927 abort_creds(new); 928 return error; 929 } 930 931 /** 932 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted 933 * @mm: The VM space in which the new mapping is to be made 934 * @pages: The size of the mapping 935 * 936 * Determine whether the allocation of a new virtual mapping by the current 937 * task is permitted, returning 0 if permission is granted, -ve if not. 938 */ 939 int cap_vm_enough_memory(struct mm_struct *mm, long pages) 940 { 941 int cap_sys_admin = 0; 942 943 if (cap_capable(current, current_cred(), &init_user_ns, CAP_SYS_ADMIN, 944 SECURITY_CAP_NOAUDIT) == 0) 945 cap_sys_admin = 1; 946 return __vm_enough_memory(mm, pages, cap_sys_admin); 947 } 948 949 /* 950 * cap_file_mmap - check if able to map given addr 951 * @file: unused 952 * @reqprot: unused 953 * @prot: unused 954 * @flags: unused 955 * @addr: address attempting to be mapped 956 * @addr_only: unused 957 * 958 * If the process is attempting to map memory below dac_mmap_min_addr they need 959 * CAP_SYS_RAWIO. The other parameters to this function are unused by the 960 * capability security module. Returns 0 if this mapping should be allowed 961 * -EPERM if not. 962 */ 963 int cap_file_mmap(struct file *file, unsigned long reqprot, 964 unsigned long prot, unsigned long flags, 965 unsigned long addr, unsigned long addr_only) 966 { 967 int ret = 0; 968 969 if (addr < dac_mmap_min_addr) { 970 ret = cap_capable(current, current_cred(), &init_user_ns, CAP_SYS_RAWIO, 971 SECURITY_CAP_AUDIT); 972 /* set PF_SUPERPRIV if it turns out we allow the low mmap */ 973 if (ret == 0) 974 current->flags |= PF_SUPERPRIV; 975 } 976 return ret; 977 } 978