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 /** 60 * cap_capable - Determine whether a task has a particular effective capability 61 * @cred: The credentials to use 62 * @ns: The user namespace in which we need the capability 63 * @cap: The capability to check for 64 * @audit: Whether to write an audit message or not 65 * 66 * Determine whether the nominated task has the specified capability amongst 67 * its effective set, returning 0 if it does, -ve if it does not. 68 * 69 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() 70 * and has_capability() functions. That is, it has the reverse semantics: 71 * cap_has_capability() returns 0 when a task has a capability, but the 72 * kernel's capable() and has_capability() returns 1 for this case. 73 */ 74 int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, 75 int cap, int audit) 76 { 77 for (;;) { 78 /* The creator of the user namespace has all caps. */ 79 if (targ_ns != &init_user_ns && targ_ns->creator == cred->user) 80 return 0; 81 82 /* Do we have the necessary capabilities? */ 83 if (targ_ns == cred->user->user_ns) 84 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; 85 86 /* Have we tried all of the parent namespaces? */ 87 if (targ_ns == &init_user_ns) 88 return -EPERM; 89 90 /* 91 *If you have a capability in a parent user ns, then you have 92 * it over all children user namespaces as well. 93 */ 94 targ_ns = targ_ns->creator->user_ns; 95 } 96 97 /* We never get here */ 98 } 99 100 /** 101 * cap_settime - Determine whether the current process may set the system clock 102 * @ts: The time to set 103 * @tz: The timezone to set 104 * 105 * Determine whether the current process may set the system clock and timezone 106 * information, returning 0 if permission granted, -ve if denied. 107 */ 108 int cap_settime(const struct timespec *ts, const struct timezone *tz) 109 { 110 if (!capable(CAP_SYS_TIME)) 111 return -EPERM; 112 return 0; 113 } 114 115 /** 116 * cap_ptrace_access_check - Determine whether the current process may access 117 * another 118 * @child: The process to be accessed 119 * @mode: The mode of attachment. 120 * 121 * If we are in the same or an ancestor user_ns and have all the target 122 * task's capabilities, then ptrace access is allowed. 123 * If we have the ptrace capability to the target user_ns, then ptrace 124 * access is allowed. 125 * Else denied. 126 * 127 * Determine whether a process may access another, returning 0 if permission 128 * granted, -ve if denied. 129 */ 130 int cap_ptrace_access_check(struct task_struct *child, unsigned int mode) 131 { 132 int ret = 0; 133 const struct cred *cred, *child_cred; 134 135 rcu_read_lock(); 136 cred = current_cred(); 137 child_cred = __task_cred(child); 138 if (cred->user->user_ns == child_cred->user->user_ns && 139 cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) 140 goto out; 141 if (ns_capable(child_cred->user->user_ns, CAP_SYS_PTRACE)) 142 goto out; 143 ret = -EPERM; 144 out: 145 rcu_read_unlock(); 146 return ret; 147 } 148 149 /** 150 * cap_ptrace_traceme - Determine whether another process may trace the current 151 * @parent: The task proposed to be the tracer 152 * 153 * If parent is in the same or an ancestor user_ns and has all current's 154 * capabilities, then ptrace access is allowed. 155 * If parent has the ptrace capability to current's user_ns, then ptrace 156 * access is allowed. 157 * Else denied. 158 * 159 * Determine whether the nominated task is permitted to trace the current 160 * process, returning 0 if permission is granted, -ve if denied. 161 */ 162 int cap_ptrace_traceme(struct task_struct *parent) 163 { 164 int ret = 0; 165 const struct cred *cred, *child_cred; 166 167 rcu_read_lock(); 168 cred = __task_cred(parent); 169 child_cred = current_cred(); 170 if (cred->user->user_ns == child_cred->user->user_ns && 171 cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) 172 goto out; 173 if (has_ns_capability(parent, child_cred->user->user_ns, CAP_SYS_PTRACE)) 174 goto out; 175 ret = -EPERM; 176 out: 177 rcu_read_unlock(); 178 return ret; 179 } 180 181 /** 182 * cap_capget - Retrieve a task's capability sets 183 * @target: The task from which to retrieve the capability sets 184 * @effective: The place to record the effective set 185 * @inheritable: The place to record the inheritable set 186 * @permitted: The place to record the permitted set 187 * 188 * This function retrieves the capabilities of the nominated task and returns 189 * them to the caller. 190 */ 191 int cap_capget(struct task_struct *target, kernel_cap_t *effective, 192 kernel_cap_t *inheritable, kernel_cap_t *permitted) 193 { 194 const struct cred *cred; 195 196 /* Derived from kernel/capability.c:sys_capget. */ 197 rcu_read_lock(); 198 cred = __task_cred(target); 199 *effective = cred->cap_effective; 200 *inheritable = cred->cap_inheritable; 201 *permitted = cred->cap_permitted; 202 rcu_read_unlock(); 203 return 0; 204 } 205 206 /* 207 * Determine whether the inheritable capabilities are limited to the old 208 * permitted set. Returns 1 if they are limited, 0 if they are not. 209 */ 210 static inline int cap_inh_is_capped(void) 211 { 212 213 /* they are so limited unless the current task has the CAP_SETPCAP 214 * capability 215 */ 216 if (cap_capable(current_cred(), current_cred()->user->user_ns, 217 CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0) 218 return 0; 219 return 1; 220 } 221 222 /** 223 * cap_capset - Validate and apply proposed changes to current's capabilities 224 * @new: The proposed new credentials; alterations should be made here 225 * @old: The current task's current credentials 226 * @effective: A pointer to the proposed new effective capabilities set 227 * @inheritable: A pointer to the proposed new inheritable capabilities set 228 * @permitted: A pointer to the proposed new permitted capabilities set 229 * 230 * This function validates and applies a proposed mass change to the current 231 * process's capability sets. The changes are made to the proposed new 232 * credentials, and assuming no error, will be committed by the caller of LSM. 233 */ 234 int cap_capset(struct cred *new, 235 const struct cred *old, 236 const kernel_cap_t *effective, 237 const kernel_cap_t *inheritable, 238 const kernel_cap_t *permitted) 239 { 240 if (cap_inh_is_capped() && 241 !cap_issubset(*inheritable, 242 cap_combine(old->cap_inheritable, 243 old->cap_permitted))) 244 /* incapable of using this inheritable set */ 245 return -EPERM; 246 247 if (!cap_issubset(*inheritable, 248 cap_combine(old->cap_inheritable, 249 old->cap_bset))) 250 /* no new pI capabilities outside bounding set */ 251 return -EPERM; 252 253 /* verify restrictions on target's new Permitted set */ 254 if (!cap_issubset(*permitted, old->cap_permitted)) 255 return -EPERM; 256 257 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ 258 if (!cap_issubset(*effective, *permitted)) 259 return -EPERM; 260 261 new->cap_effective = *effective; 262 new->cap_inheritable = *inheritable; 263 new->cap_permitted = *permitted; 264 return 0; 265 } 266 267 /* 268 * Clear proposed capability sets for execve(). 269 */ 270 static inline void bprm_clear_caps(struct linux_binprm *bprm) 271 { 272 cap_clear(bprm->cred->cap_permitted); 273 bprm->cap_effective = false; 274 } 275 276 /** 277 * cap_inode_need_killpriv - Determine if inode change affects privileges 278 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV 279 * 280 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV 281 * affects the security markings on that inode, and if it is, should 282 * inode_killpriv() be invoked or the change rejected? 283 * 284 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and 285 * -ve to deny the change. 286 */ 287 int cap_inode_need_killpriv(struct dentry *dentry) 288 { 289 struct inode *inode = dentry->d_inode; 290 int error; 291 292 if (!inode->i_op->getxattr) 293 return 0; 294 295 error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0); 296 if (error <= 0) 297 return 0; 298 return 1; 299 } 300 301 /** 302 * cap_inode_killpriv - Erase the security markings on an inode 303 * @dentry: The inode/dentry to alter 304 * 305 * Erase the privilege-enhancing security markings on an inode. 306 * 307 * Returns 0 if successful, -ve on error. 308 */ 309 int cap_inode_killpriv(struct dentry *dentry) 310 { 311 struct inode *inode = dentry->d_inode; 312 313 if (!inode->i_op->removexattr) 314 return 0; 315 316 return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS); 317 } 318 319 /* 320 * Calculate the new process capability sets from the capability sets attached 321 * to a file. 322 */ 323 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, 324 struct linux_binprm *bprm, 325 bool *effective, 326 bool *has_cap) 327 { 328 struct cred *new = bprm->cred; 329 unsigned i; 330 int ret = 0; 331 332 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) 333 *effective = true; 334 335 if (caps->magic_etc & VFS_CAP_REVISION_MASK) 336 *has_cap = true; 337 338 CAP_FOR_EACH_U32(i) { 339 __u32 permitted = caps->permitted.cap[i]; 340 __u32 inheritable = caps->inheritable.cap[i]; 341 342 /* 343 * pP' = (X & fP) | (pI & fI) 344 */ 345 new->cap_permitted.cap[i] = 346 (new->cap_bset.cap[i] & permitted) | 347 (new->cap_inheritable.cap[i] & inheritable); 348 349 if (permitted & ~new->cap_permitted.cap[i]) 350 /* insufficient to execute correctly */ 351 ret = -EPERM; 352 } 353 354 /* 355 * For legacy apps, with no internal support for recognizing they 356 * do not have enough capabilities, we return an error if they are 357 * missing some "forced" (aka file-permitted) capabilities. 358 */ 359 return *effective ? ret : 0; 360 } 361 362 /* 363 * Extract the on-exec-apply capability sets for an executable file. 364 */ 365 int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) 366 { 367 struct inode *inode = dentry->d_inode; 368 __u32 magic_etc; 369 unsigned tocopy, i; 370 int size; 371 struct vfs_cap_data caps; 372 373 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); 374 375 if (!inode || !inode->i_op->getxattr) 376 return -ENODATA; 377 378 size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps, 379 XATTR_CAPS_SZ); 380 if (size == -ENODATA || size == -EOPNOTSUPP) 381 /* no data, that's ok */ 382 return -ENODATA; 383 if (size < 0) 384 return size; 385 386 if (size < sizeof(magic_etc)) 387 return -EINVAL; 388 389 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc); 390 391 switch (magic_etc & VFS_CAP_REVISION_MASK) { 392 case VFS_CAP_REVISION_1: 393 if (size != XATTR_CAPS_SZ_1) 394 return -EINVAL; 395 tocopy = VFS_CAP_U32_1; 396 break; 397 case VFS_CAP_REVISION_2: 398 if (size != XATTR_CAPS_SZ_2) 399 return -EINVAL; 400 tocopy = VFS_CAP_U32_2; 401 break; 402 default: 403 return -EINVAL; 404 } 405 406 CAP_FOR_EACH_U32(i) { 407 if (i >= tocopy) 408 break; 409 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted); 410 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable); 411 } 412 413 return 0; 414 } 415 416 /* 417 * Attempt to get the on-exec apply capability sets for an executable file from 418 * its xattrs and, if present, apply them to the proposed credentials being 419 * constructed by execve(). 420 */ 421 static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap) 422 { 423 struct dentry *dentry; 424 int rc = 0; 425 struct cpu_vfs_cap_data vcaps; 426 427 bprm_clear_caps(bprm); 428 429 if (!file_caps_enabled) 430 return 0; 431 432 if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID) 433 return 0; 434 435 dentry = dget(bprm->file->f_dentry); 436 437 rc = get_vfs_caps_from_disk(dentry, &vcaps); 438 if (rc < 0) { 439 if (rc == -EINVAL) 440 printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n", 441 __func__, rc, bprm->filename); 442 else if (rc == -ENODATA) 443 rc = 0; 444 goto out; 445 } 446 447 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap); 448 if (rc == -EINVAL) 449 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", 450 __func__, rc, bprm->filename); 451 452 out: 453 dput(dentry); 454 if (rc) 455 bprm_clear_caps(bprm); 456 457 return rc; 458 } 459 460 /** 461 * cap_bprm_set_creds - Set up the proposed credentials for execve(). 462 * @bprm: The execution parameters, including the proposed creds 463 * 464 * Set up the proposed credentials for a new execution context being 465 * constructed by execve(). The proposed creds in @bprm->cred is altered, 466 * which won't take effect immediately. Returns 0 if successful, -ve on error. 467 */ 468 int cap_bprm_set_creds(struct linux_binprm *bprm) 469 { 470 const struct cred *old = current_cred(); 471 struct cred *new = bprm->cred; 472 bool effective, has_cap = false; 473 int ret; 474 475 effective = false; 476 ret = get_file_caps(bprm, &effective, &has_cap); 477 if (ret < 0) 478 return ret; 479 480 if (!issecure(SECURE_NOROOT)) { 481 /* 482 * If the legacy file capability is set, then don't set privs 483 * for a setuid root binary run by a non-root user. Do set it 484 * for a root user just to cause least surprise to an admin. 485 */ 486 if (has_cap && new->uid != 0 && new->euid == 0) { 487 warn_setuid_and_fcaps_mixed(bprm->filename); 488 goto skip; 489 } 490 /* 491 * To support inheritance of root-permissions and suid-root 492 * executables under compatibility mode, we override the 493 * capability sets for the file. 494 * 495 * If only the real uid is 0, we do not set the effective bit. 496 */ 497 if (new->euid == 0 || new->uid == 0) { 498 /* pP' = (cap_bset & ~0) | (pI & ~0) */ 499 new->cap_permitted = cap_combine(old->cap_bset, 500 old->cap_inheritable); 501 } 502 if (new->euid == 0) 503 effective = true; 504 } 505 skip: 506 507 /* Don't let someone trace a set[ug]id/setpcap binary with the revised 508 * credentials unless they have the appropriate permit 509 */ 510 if ((new->euid != old->uid || 511 new->egid != old->gid || 512 !cap_issubset(new->cap_permitted, old->cap_permitted)) && 513 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) { 514 /* downgrade; they get no more than they had, and maybe less */ 515 if (!capable(CAP_SETUID)) { 516 new->euid = new->uid; 517 new->egid = new->gid; 518 } 519 new->cap_permitted = cap_intersect(new->cap_permitted, 520 old->cap_permitted); 521 } 522 523 new->suid = new->fsuid = new->euid; 524 new->sgid = new->fsgid = new->egid; 525 526 if (effective) 527 new->cap_effective = new->cap_permitted; 528 else 529 cap_clear(new->cap_effective); 530 bprm->cap_effective = effective; 531 532 /* 533 * Audit candidate if current->cap_effective is set 534 * 535 * We do not bother to audit if 3 things are true: 536 * 1) cap_effective has all caps 537 * 2) we are root 538 * 3) root is supposed to have all caps (SECURE_NOROOT) 539 * Since this is just a normal root execing a process. 540 * 541 * Number 1 above might fail if you don't have a full bset, but I think 542 * that is interesting information to audit. 543 */ 544 if (!cap_isclear(new->cap_effective)) { 545 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) || 546 new->euid != 0 || new->uid != 0 || 547 issecure(SECURE_NOROOT)) { 548 ret = audit_log_bprm_fcaps(bprm, new, old); 549 if (ret < 0) 550 return ret; 551 } 552 } 553 554 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 555 return 0; 556 } 557 558 /** 559 * cap_bprm_secureexec - Determine whether a secure execution is required 560 * @bprm: The execution parameters 561 * 562 * Determine whether a secure execution is required, return 1 if it is, and 0 563 * if it is not. 564 * 565 * The credentials have been committed by this point, and so are no longer 566 * available through @bprm->cred. 567 */ 568 int cap_bprm_secureexec(struct linux_binprm *bprm) 569 { 570 const struct cred *cred = current_cred(); 571 572 if (cred->uid != 0) { 573 if (bprm->cap_effective) 574 return 1; 575 if (!cap_isclear(cred->cap_permitted)) 576 return 1; 577 } 578 579 return (cred->euid != cred->uid || 580 cred->egid != cred->gid); 581 } 582 583 /** 584 * cap_inode_setxattr - Determine whether an xattr may be altered 585 * @dentry: The inode/dentry being altered 586 * @name: The name of the xattr to be changed 587 * @value: The value that the xattr will be changed to 588 * @size: The size of value 589 * @flags: The replacement flag 590 * 591 * Determine whether an xattr may be altered or set on an inode, returning 0 if 592 * permission is granted, -ve if denied. 593 * 594 * This is used to make sure security xattrs don't get updated or set by those 595 * who aren't privileged to do so. 596 */ 597 int cap_inode_setxattr(struct dentry *dentry, const char *name, 598 const void *value, size_t size, int flags) 599 { 600 if (!strcmp(name, XATTR_NAME_CAPS)) { 601 if (!capable(CAP_SETFCAP)) 602 return -EPERM; 603 return 0; 604 } 605 606 if (!strncmp(name, XATTR_SECURITY_PREFIX, 607 sizeof(XATTR_SECURITY_PREFIX) - 1) && 608 !capable(CAP_SYS_ADMIN)) 609 return -EPERM; 610 return 0; 611 } 612 613 /** 614 * cap_inode_removexattr - Determine whether an xattr may be removed 615 * @dentry: The inode/dentry being altered 616 * @name: The name of the xattr to be changed 617 * 618 * Determine whether an xattr may be removed from an inode, returning 0 if 619 * permission is granted, -ve if denied. 620 * 621 * This is used to make sure security xattrs don't get removed by those who 622 * aren't privileged to remove them. 623 */ 624 int cap_inode_removexattr(struct dentry *dentry, const char *name) 625 { 626 if (!strcmp(name, XATTR_NAME_CAPS)) { 627 if (!capable(CAP_SETFCAP)) 628 return -EPERM; 629 return 0; 630 } 631 632 if (!strncmp(name, XATTR_SECURITY_PREFIX, 633 sizeof(XATTR_SECURITY_PREFIX) - 1) && 634 !capable(CAP_SYS_ADMIN)) 635 return -EPERM; 636 return 0; 637 } 638 639 /* 640 * cap_emulate_setxuid() fixes the effective / permitted capabilities of 641 * a process after a call to setuid, setreuid, or setresuid. 642 * 643 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of 644 * {r,e,s}uid != 0, the permitted and effective capabilities are 645 * cleared. 646 * 647 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective 648 * capabilities of the process are cleared. 649 * 650 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective 651 * capabilities are set to the permitted capabilities. 652 * 653 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 654 * never happen. 655 * 656 * -astor 657 * 658 * cevans - New behaviour, Oct '99 659 * A process may, via prctl(), elect to keep its capabilities when it 660 * calls setuid() and switches away from uid==0. Both permitted and 661 * effective sets will be retained. 662 * Without this change, it was impossible for a daemon to drop only some 663 * of its privilege. The call to setuid(!=0) would drop all privileges! 664 * Keeping uid 0 is not an option because uid 0 owns too many vital 665 * files.. 666 * Thanks to Olaf Kirch and Peter Benie for spotting this. 667 */ 668 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) 669 { 670 if ((old->uid == 0 || old->euid == 0 || old->suid == 0) && 671 (new->uid != 0 && new->euid != 0 && new->suid != 0) && 672 !issecure(SECURE_KEEP_CAPS)) { 673 cap_clear(new->cap_permitted); 674 cap_clear(new->cap_effective); 675 } 676 if (old->euid == 0 && new->euid != 0) 677 cap_clear(new->cap_effective); 678 if (old->euid != 0 && new->euid == 0) 679 new->cap_effective = new->cap_permitted; 680 } 681 682 /** 683 * cap_task_fix_setuid - Fix up the results of setuid() call 684 * @new: The proposed credentials 685 * @old: The current task's current credentials 686 * @flags: Indications of what has changed 687 * 688 * Fix up the results of setuid() call before the credential changes are 689 * actually applied, returning 0 to grant the changes, -ve to deny them. 690 */ 691 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) 692 { 693 switch (flags) { 694 case LSM_SETID_RE: 695 case LSM_SETID_ID: 696 case LSM_SETID_RES: 697 /* juggle the capabilities to follow [RES]UID changes unless 698 * otherwise suppressed */ 699 if (!issecure(SECURE_NO_SETUID_FIXUP)) 700 cap_emulate_setxuid(new, old); 701 break; 702 703 case LSM_SETID_FS: 704 /* juggle the capabilties to follow FSUID changes, unless 705 * otherwise suppressed 706 * 707 * FIXME - is fsuser used for all CAP_FS_MASK capabilities? 708 * if not, we might be a bit too harsh here. 709 */ 710 if (!issecure(SECURE_NO_SETUID_FIXUP)) { 711 if (old->fsuid == 0 && new->fsuid != 0) 712 new->cap_effective = 713 cap_drop_fs_set(new->cap_effective); 714 715 if (old->fsuid != 0 && new->fsuid == 0) 716 new->cap_effective = 717 cap_raise_fs_set(new->cap_effective, 718 new->cap_permitted); 719 } 720 break; 721 722 default: 723 return -EINVAL; 724 } 725 726 return 0; 727 } 728 729 /* 730 * Rationale: code calling task_setscheduler, task_setioprio, and 731 * task_setnice, assumes that 732 * . if capable(cap_sys_nice), then those actions should be allowed 733 * . if not capable(cap_sys_nice), but acting on your own processes, 734 * then those actions should be allowed 735 * This is insufficient now since you can call code without suid, but 736 * yet with increased caps. 737 * So we check for increased caps on the target process. 738 */ 739 static int cap_safe_nice(struct task_struct *p) 740 { 741 int is_subset; 742 743 rcu_read_lock(); 744 is_subset = cap_issubset(__task_cred(p)->cap_permitted, 745 current_cred()->cap_permitted); 746 rcu_read_unlock(); 747 748 if (!is_subset && !capable(CAP_SYS_NICE)) 749 return -EPERM; 750 return 0; 751 } 752 753 /** 754 * cap_task_setscheduler - Detemine if scheduler policy change is permitted 755 * @p: The task to affect 756 * 757 * Detemine if the requested scheduler policy change is permitted for the 758 * specified task, returning 0 if permission is granted, -ve if denied. 759 */ 760 int cap_task_setscheduler(struct task_struct *p) 761 { 762 return cap_safe_nice(p); 763 } 764 765 /** 766 * cap_task_ioprio - Detemine if I/O priority change is permitted 767 * @p: The task to affect 768 * @ioprio: The I/O priority to set 769 * 770 * Detemine if the requested I/O priority change is permitted for the specified 771 * task, returning 0 if permission is granted, -ve if denied. 772 */ 773 int cap_task_setioprio(struct task_struct *p, int ioprio) 774 { 775 return cap_safe_nice(p); 776 } 777 778 /** 779 * cap_task_ioprio - Detemine if task priority change is permitted 780 * @p: The task to affect 781 * @nice: The nice value to set 782 * 783 * Detemine if the requested task priority change is permitted for the 784 * specified task, returning 0 if permission is granted, -ve if denied. 785 */ 786 int cap_task_setnice(struct task_struct *p, int nice) 787 { 788 return cap_safe_nice(p); 789 } 790 791 /* 792 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from 793 * the current task's bounding set. Returns 0 on success, -ve on error. 794 */ 795 static long cap_prctl_drop(struct cred *new, unsigned long cap) 796 { 797 if (!capable(CAP_SETPCAP)) 798 return -EPERM; 799 if (!cap_valid(cap)) 800 return -EINVAL; 801 802 cap_lower(new->cap_bset, cap); 803 return 0; 804 } 805 806 /** 807 * cap_task_prctl - Implement process control functions for this security module 808 * @option: The process control function requested 809 * @arg2, @arg3, @arg4, @arg5: The argument data for this function 810 * 811 * Allow process control functions (sys_prctl()) to alter capabilities; may 812 * also deny access to other functions not otherwise implemented here. 813 * 814 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented 815 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM 816 * modules will consider performing the function. 817 */ 818 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, 819 unsigned long arg4, unsigned long arg5) 820 { 821 struct cred *new; 822 long error = 0; 823 824 new = prepare_creds(); 825 if (!new) 826 return -ENOMEM; 827 828 switch (option) { 829 case PR_CAPBSET_READ: 830 error = -EINVAL; 831 if (!cap_valid(arg2)) 832 goto error; 833 error = !!cap_raised(new->cap_bset, arg2); 834 goto no_change; 835 836 case PR_CAPBSET_DROP: 837 error = cap_prctl_drop(new, arg2); 838 if (error < 0) 839 goto error; 840 goto changed; 841 842 /* 843 * The next four prctl's remain to assist with transitioning a 844 * system from legacy UID=0 based privilege (when filesystem 845 * capabilities are not in use) to a system using filesystem 846 * capabilities only - as the POSIX.1e draft intended. 847 * 848 * Note: 849 * 850 * PR_SET_SECUREBITS = 851 * issecure_mask(SECURE_KEEP_CAPS_LOCKED) 852 * | issecure_mask(SECURE_NOROOT) 853 * | issecure_mask(SECURE_NOROOT_LOCKED) 854 * | issecure_mask(SECURE_NO_SETUID_FIXUP) 855 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) 856 * 857 * will ensure that the current process and all of its 858 * children will be locked into a pure 859 * capability-based-privilege environment. 860 */ 861 case PR_SET_SECUREBITS: 862 error = -EPERM; 863 if ((((new->securebits & SECURE_ALL_LOCKS) >> 1) 864 & (new->securebits ^ arg2)) /*[1]*/ 865 || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ 866 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ 867 || (cap_capable(current_cred(), 868 current_cred()->user->user_ns, CAP_SETPCAP, 869 SECURITY_CAP_AUDIT) != 0) /*[4]*/ 870 /* 871 * [1] no changing of bits that are locked 872 * [2] no unlocking of locks 873 * [3] no setting of unsupported bits 874 * [4] doing anything requires privilege (go read about 875 * the "sendmail capabilities bug") 876 */ 877 ) 878 /* cannot change a locked bit */ 879 goto error; 880 new->securebits = arg2; 881 goto changed; 882 883 case PR_GET_SECUREBITS: 884 error = new->securebits; 885 goto no_change; 886 887 case PR_GET_KEEPCAPS: 888 if (issecure(SECURE_KEEP_CAPS)) 889 error = 1; 890 goto no_change; 891 892 case PR_SET_KEEPCAPS: 893 error = -EINVAL; 894 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ 895 goto error; 896 error = -EPERM; 897 if (issecure(SECURE_KEEP_CAPS_LOCKED)) 898 goto error; 899 if (arg2) 900 new->securebits |= issecure_mask(SECURE_KEEP_CAPS); 901 else 902 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 903 goto changed; 904 905 default: 906 /* No functionality available - continue with default */ 907 error = -ENOSYS; 908 goto error; 909 } 910 911 /* Functionality provided */ 912 changed: 913 return commit_creds(new); 914 915 no_change: 916 error: 917 abort_creds(new); 918 return error; 919 } 920 921 /** 922 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted 923 * @mm: The VM space in which the new mapping is to be made 924 * @pages: The size of the mapping 925 * 926 * Determine whether the allocation of a new virtual mapping by the current 927 * task is permitted, returning 0 if permission is granted, -ve if not. 928 */ 929 int cap_vm_enough_memory(struct mm_struct *mm, long pages) 930 { 931 int cap_sys_admin = 0; 932 933 if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN, 934 SECURITY_CAP_NOAUDIT) == 0) 935 cap_sys_admin = 1; 936 return __vm_enough_memory(mm, pages, cap_sys_admin); 937 } 938 939 /* 940 * cap_file_mmap - check if able to map given addr 941 * @file: unused 942 * @reqprot: unused 943 * @prot: unused 944 * @flags: unused 945 * @addr: address attempting to be mapped 946 * @addr_only: unused 947 * 948 * If the process is attempting to map memory below dac_mmap_min_addr they need 949 * CAP_SYS_RAWIO. The other parameters to this function are unused by the 950 * capability security module. Returns 0 if this mapping should be allowed 951 * -EPERM if not. 952 */ 953 int cap_file_mmap(struct file *file, unsigned long reqprot, 954 unsigned long prot, unsigned long flags, 955 unsigned long addr, unsigned long addr_only) 956 { 957 int ret = 0; 958 959 if (addr < dac_mmap_min_addr) { 960 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO, 961 SECURITY_CAP_AUDIT); 962 /* set PF_SUPERPRIV if it turns out we allow the low mmap */ 963 if (ret == 0) 964 current->flags |= PF_SUPERPRIV; 965 } 966 return ret; 967 } 968