1 /* Common capabilities, needed by capability.o and root_plug.o 2 * 3 * This program is free software; you can redistribute it and/or modify 4 * it under the terms of the GNU General Public License as published by 5 * the Free Software Foundation; either version 2 of the License, or 6 * (at your option) any later version. 7 * 8 */ 9 10 #include <linux/capability.h> 11 #include <linux/audit.h> 12 #include <linux/module.h> 13 #include <linux/init.h> 14 #include <linux/kernel.h> 15 #include <linux/security.h> 16 #include <linux/file.h> 17 #include <linux/mm.h> 18 #include <linux/mman.h> 19 #include <linux/pagemap.h> 20 #include <linux/swap.h> 21 #include <linux/skbuff.h> 22 #include <linux/netlink.h> 23 #include <linux/ptrace.h> 24 #include <linux/xattr.h> 25 #include <linux/hugetlb.h> 26 #include <linux/mount.h> 27 #include <linux/sched.h> 28 #include <linux/prctl.h> 29 #include <linux/securebits.h> 30 31 int cap_netlink_send(struct sock *sk, struct sk_buff *skb) 32 { 33 NETLINK_CB(skb).eff_cap = current_cap(); 34 return 0; 35 } 36 37 int cap_netlink_recv(struct sk_buff *skb, int cap) 38 { 39 if (!cap_raised(NETLINK_CB(skb).eff_cap, cap)) 40 return -EPERM; 41 return 0; 42 } 43 EXPORT_SYMBOL(cap_netlink_recv); 44 45 /** 46 * cap_capable - Determine whether a task has a particular effective capability 47 * @tsk: The task to query 48 * @cred: The credentials to use 49 * @cap: The capability to check for 50 * @audit: Whether to write an audit message or not 51 * 52 * Determine whether the nominated task has the specified capability amongst 53 * its effective set, returning 0 if it does, -ve if it does not. 54 * 55 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() 56 * and has_capability() functions. That is, it has the reverse semantics: 57 * cap_has_capability() returns 0 when a task has a capability, but the 58 * kernel's capable() and has_capability() returns 1 for this case. 59 */ 60 int cap_capable(struct task_struct *tsk, const struct cred *cred, int cap, 61 int audit) 62 { 63 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; 64 } 65 66 /** 67 * cap_settime - Determine whether the current process may set the system clock 68 * @ts: The time to set 69 * @tz: The timezone to set 70 * 71 * Determine whether the current process may set the system clock and timezone 72 * information, returning 0 if permission granted, -ve if denied. 73 */ 74 int cap_settime(struct timespec *ts, struct timezone *tz) 75 { 76 if (!capable(CAP_SYS_TIME)) 77 return -EPERM; 78 return 0; 79 } 80 81 /** 82 * cap_ptrace_may_access - Determine whether the current process may access 83 * another 84 * @child: The process to be accessed 85 * @mode: The mode of attachment. 86 * 87 * Determine whether a process may access another, returning 0 if permission 88 * granted, -ve if denied. 89 */ 90 int cap_ptrace_may_access(struct task_struct *child, unsigned int mode) 91 { 92 int ret = 0; 93 94 rcu_read_lock(); 95 if (!cap_issubset(__task_cred(child)->cap_permitted, 96 current_cred()->cap_permitted) && 97 !capable(CAP_SYS_PTRACE)) 98 ret = -EPERM; 99 rcu_read_unlock(); 100 return ret; 101 } 102 103 /** 104 * cap_ptrace_traceme - Determine whether another process may trace the current 105 * @parent: The task proposed to be the tracer 106 * 107 * Determine whether the nominated task is permitted to trace the current 108 * process, returning 0 if permission is granted, -ve if denied. 109 */ 110 int cap_ptrace_traceme(struct task_struct *parent) 111 { 112 int ret = 0; 113 114 rcu_read_lock(); 115 if (!cap_issubset(current_cred()->cap_permitted, 116 __task_cred(parent)->cap_permitted) && 117 !has_capability(parent, CAP_SYS_PTRACE)) 118 ret = -EPERM; 119 rcu_read_unlock(); 120 return ret; 121 } 122 123 /** 124 * cap_capget - Retrieve a task's capability sets 125 * @target: The task from which to retrieve the capability sets 126 * @effective: The place to record the effective set 127 * @inheritable: The place to record the inheritable set 128 * @permitted: The place to record the permitted set 129 * 130 * This function retrieves the capabilities of the nominated task and returns 131 * them to the caller. 132 */ 133 int cap_capget(struct task_struct *target, kernel_cap_t *effective, 134 kernel_cap_t *inheritable, kernel_cap_t *permitted) 135 { 136 const struct cred *cred; 137 138 /* Derived from kernel/capability.c:sys_capget. */ 139 rcu_read_lock(); 140 cred = __task_cred(target); 141 *effective = cred->cap_effective; 142 *inheritable = cred->cap_inheritable; 143 *permitted = cred->cap_permitted; 144 rcu_read_unlock(); 145 return 0; 146 } 147 148 /* 149 * Determine whether the inheritable capabilities are limited to the old 150 * permitted set. Returns 1 if they are limited, 0 if they are not. 151 */ 152 static inline int cap_inh_is_capped(void) 153 { 154 #ifdef CONFIG_SECURITY_FILE_CAPABILITIES 155 156 /* they are so limited unless the current task has the CAP_SETPCAP 157 * capability 158 */ 159 if (cap_capable(current, current_cred(), CAP_SETPCAP, 160 SECURITY_CAP_AUDIT) == 0) 161 return 0; 162 #endif 163 return 1; 164 } 165 166 /** 167 * cap_capset - Validate and apply proposed changes to current's capabilities 168 * @new: The proposed new credentials; alterations should be made here 169 * @old: The current task's current credentials 170 * @effective: A pointer to the proposed new effective capabilities set 171 * @inheritable: A pointer to the proposed new inheritable capabilities set 172 * @permitted: A pointer to the proposed new permitted capabilities set 173 * 174 * This function validates and applies a proposed mass change to the current 175 * process's capability sets. The changes are made to the proposed new 176 * credentials, and assuming no error, will be committed by the caller of LSM. 177 */ 178 int cap_capset(struct cred *new, 179 const struct cred *old, 180 const kernel_cap_t *effective, 181 const kernel_cap_t *inheritable, 182 const kernel_cap_t *permitted) 183 { 184 if (cap_inh_is_capped() && 185 !cap_issubset(*inheritable, 186 cap_combine(old->cap_inheritable, 187 old->cap_permitted))) 188 /* incapable of using this inheritable set */ 189 return -EPERM; 190 191 if (!cap_issubset(*inheritable, 192 cap_combine(old->cap_inheritable, 193 old->cap_bset))) 194 /* no new pI capabilities outside bounding set */ 195 return -EPERM; 196 197 /* verify restrictions on target's new Permitted set */ 198 if (!cap_issubset(*permitted, old->cap_permitted)) 199 return -EPERM; 200 201 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ 202 if (!cap_issubset(*effective, *permitted)) 203 return -EPERM; 204 205 new->cap_effective = *effective; 206 new->cap_inheritable = *inheritable; 207 new->cap_permitted = *permitted; 208 return 0; 209 } 210 211 /* 212 * Clear proposed capability sets for execve(). 213 */ 214 static inline void bprm_clear_caps(struct linux_binprm *bprm) 215 { 216 cap_clear(bprm->cred->cap_permitted); 217 bprm->cap_effective = false; 218 } 219 220 #ifdef CONFIG_SECURITY_FILE_CAPABILITIES 221 222 /** 223 * cap_inode_need_killpriv - Determine if inode change affects privileges 224 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV 225 * 226 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV 227 * affects the security markings on that inode, and if it is, should 228 * inode_killpriv() be invoked or the change rejected? 229 * 230 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and 231 * -ve to deny the change. 232 */ 233 int cap_inode_need_killpriv(struct dentry *dentry) 234 { 235 struct inode *inode = dentry->d_inode; 236 int error; 237 238 if (!inode->i_op->getxattr) 239 return 0; 240 241 error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0); 242 if (error <= 0) 243 return 0; 244 return 1; 245 } 246 247 /** 248 * cap_inode_killpriv - Erase the security markings on an inode 249 * @dentry: The inode/dentry to alter 250 * 251 * Erase the privilege-enhancing security markings on an inode. 252 * 253 * Returns 0 if successful, -ve on error. 254 */ 255 int cap_inode_killpriv(struct dentry *dentry) 256 { 257 struct inode *inode = dentry->d_inode; 258 259 if (!inode->i_op->removexattr) 260 return 0; 261 262 return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS); 263 } 264 265 /* 266 * Calculate the new process capability sets from the capability sets attached 267 * to a file. 268 */ 269 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, 270 struct linux_binprm *bprm, 271 bool *effective) 272 { 273 struct cred *new = bprm->cred; 274 unsigned i; 275 int ret = 0; 276 277 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) 278 *effective = true; 279 280 CAP_FOR_EACH_U32(i) { 281 __u32 permitted = caps->permitted.cap[i]; 282 __u32 inheritable = caps->inheritable.cap[i]; 283 284 /* 285 * pP' = (X & fP) | (pI & fI) 286 */ 287 new->cap_permitted.cap[i] = 288 (new->cap_bset.cap[i] & permitted) | 289 (new->cap_inheritable.cap[i] & inheritable); 290 291 if (permitted & ~new->cap_permitted.cap[i]) 292 /* insufficient to execute correctly */ 293 ret = -EPERM; 294 } 295 296 /* 297 * For legacy apps, with no internal support for recognizing they 298 * do not have enough capabilities, we return an error if they are 299 * missing some "forced" (aka file-permitted) capabilities. 300 */ 301 return *effective ? ret : 0; 302 } 303 304 /* 305 * Extract the on-exec-apply capability sets for an executable file. 306 */ 307 int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) 308 { 309 struct inode *inode = dentry->d_inode; 310 __u32 magic_etc; 311 unsigned tocopy, i; 312 int size; 313 struct vfs_cap_data caps; 314 315 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); 316 317 if (!inode || !inode->i_op->getxattr) 318 return -ENODATA; 319 320 size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps, 321 XATTR_CAPS_SZ); 322 if (size == -ENODATA || size == -EOPNOTSUPP) 323 /* no data, that's ok */ 324 return -ENODATA; 325 if (size < 0) 326 return size; 327 328 if (size < sizeof(magic_etc)) 329 return -EINVAL; 330 331 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc); 332 333 switch (magic_etc & VFS_CAP_REVISION_MASK) { 334 case VFS_CAP_REVISION_1: 335 if (size != XATTR_CAPS_SZ_1) 336 return -EINVAL; 337 tocopy = VFS_CAP_U32_1; 338 break; 339 case VFS_CAP_REVISION_2: 340 if (size != XATTR_CAPS_SZ_2) 341 return -EINVAL; 342 tocopy = VFS_CAP_U32_2; 343 break; 344 default: 345 return -EINVAL; 346 } 347 348 CAP_FOR_EACH_U32(i) { 349 if (i >= tocopy) 350 break; 351 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted); 352 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable); 353 } 354 355 return 0; 356 } 357 358 /* 359 * Attempt to get the on-exec apply capability sets for an executable file from 360 * its xattrs and, if present, apply them to the proposed credentials being 361 * constructed by execve(). 362 */ 363 static int get_file_caps(struct linux_binprm *bprm, bool *effective) 364 { 365 struct dentry *dentry; 366 int rc = 0; 367 struct cpu_vfs_cap_data vcaps; 368 369 bprm_clear_caps(bprm); 370 371 if (!file_caps_enabled) 372 return 0; 373 374 if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID) 375 return 0; 376 377 dentry = dget(bprm->file->f_dentry); 378 379 rc = get_vfs_caps_from_disk(dentry, &vcaps); 380 if (rc < 0) { 381 if (rc == -EINVAL) 382 printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n", 383 __func__, rc, bprm->filename); 384 else if (rc == -ENODATA) 385 rc = 0; 386 goto out; 387 } 388 389 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective); 390 if (rc == -EINVAL) 391 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", 392 __func__, rc, bprm->filename); 393 394 out: 395 dput(dentry); 396 if (rc) 397 bprm_clear_caps(bprm); 398 399 return rc; 400 } 401 402 #else 403 int cap_inode_need_killpriv(struct dentry *dentry) 404 { 405 return 0; 406 } 407 408 int cap_inode_killpriv(struct dentry *dentry) 409 { 410 return 0; 411 } 412 413 int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) 414 { 415 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); 416 return -ENODATA; 417 } 418 419 static inline int get_file_caps(struct linux_binprm *bprm, bool *effective) 420 { 421 bprm_clear_caps(bprm); 422 return 0; 423 } 424 #endif 425 426 /* 427 * Determine whether a exec'ing process's new permitted capabilities should be 428 * limited to just what it already has. 429 * 430 * This prevents processes that are being ptraced from gaining access to 431 * CAP_SETPCAP, unless the process they're tracing already has it, and the 432 * binary they're executing has filecaps that elevate it. 433 * 434 * Returns 1 if they should be limited, 0 if they are not. 435 */ 436 static inline int cap_limit_ptraced_target(void) 437 { 438 #ifndef CONFIG_SECURITY_FILE_CAPABILITIES 439 if (capable(CAP_SETPCAP)) 440 return 0; 441 #endif 442 return 1; 443 } 444 445 /** 446 * cap_bprm_set_creds - Set up the proposed credentials for execve(). 447 * @bprm: The execution parameters, including the proposed creds 448 * 449 * Set up the proposed credentials for a new execution context being 450 * constructed by execve(). The proposed creds in @bprm->cred is altered, 451 * which won't take effect immediately. Returns 0 if successful, -ve on error. 452 */ 453 int cap_bprm_set_creds(struct linux_binprm *bprm) 454 { 455 const struct cred *old = current_cred(); 456 struct cred *new = bprm->cred; 457 bool effective; 458 int ret; 459 460 effective = false; 461 ret = get_file_caps(bprm, &effective); 462 if (ret < 0) 463 return ret; 464 465 if (!issecure(SECURE_NOROOT)) { 466 /* 467 * To support inheritance of root-permissions and suid-root 468 * executables under compatibility mode, we override the 469 * capability sets for the file. 470 * 471 * If only the real uid is 0, we do not set the effective bit. 472 */ 473 if (new->euid == 0 || new->uid == 0) { 474 /* pP' = (cap_bset & ~0) | (pI & ~0) */ 475 new->cap_permitted = cap_combine(old->cap_bset, 476 old->cap_inheritable); 477 } 478 if (new->euid == 0) 479 effective = true; 480 } 481 482 /* Don't let someone trace a set[ug]id/setpcap binary with the revised 483 * credentials unless they have the appropriate permit 484 */ 485 if ((new->euid != old->uid || 486 new->egid != old->gid || 487 !cap_issubset(new->cap_permitted, old->cap_permitted)) && 488 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) { 489 /* downgrade; they get no more than they had, and maybe less */ 490 if (!capable(CAP_SETUID)) { 491 new->euid = new->uid; 492 new->egid = new->gid; 493 } 494 if (cap_limit_ptraced_target()) 495 new->cap_permitted = cap_intersect(new->cap_permitted, 496 old->cap_permitted); 497 } 498 499 new->suid = new->fsuid = new->euid; 500 new->sgid = new->fsgid = new->egid; 501 502 /* For init, we want to retain the capabilities set in the initial 503 * task. Thus we skip the usual capability rules 504 */ 505 if (!is_global_init(current)) { 506 if (effective) 507 new->cap_effective = new->cap_permitted; 508 else 509 cap_clear(new->cap_effective); 510 } 511 bprm->cap_effective = effective; 512 513 /* 514 * Audit candidate if current->cap_effective is set 515 * 516 * We do not bother to audit if 3 things are true: 517 * 1) cap_effective has all caps 518 * 2) we are root 519 * 3) root is supposed to have all caps (SECURE_NOROOT) 520 * Since this is just a normal root execing a process. 521 * 522 * Number 1 above might fail if you don't have a full bset, but I think 523 * that is interesting information to audit. 524 */ 525 if (!cap_isclear(new->cap_effective)) { 526 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) || 527 new->euid != 0 || new->uid != 0 || 528 issecure(SECURE_NOROOT)) { 529 ret = audit_log_bprm_fcaps(bprm, new, old); 530 if (ret < 0) 531 return ret; 532 } 533 } 534 535 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 536 return 0; 537 } 538 539 /** 540 * cap_bprm_secureexec - Determine whether a secure execution is required 541 * @bprm: The execution parameters 542 * 543 * Determine whether a secure execution is required, return 1 if it is, and 0 544 * if it is not. 545 * 546 * The credentials have been committed by this point, and so are no longer 547 * available through @bprm->cred. 548 */ 549 int cap_bprm_secureexec(struct linux_binprm *bprm) 550 { 551 const struct cred *cred = current_cred(); 552 553 if (cred->uid != 0) { 554 if (bprm->cap_effective) 555 return 1; 556 if (!cap_isclear(cred->cap_permitted)) 557 return 1; 558 } 559 560 return (cred->euid != cred->uid || 561 cred->egid != cred->gid); 562 } 563 564 /** 565 * cap_inode_setxattr - Determine whether an xattr may be altered 566 * @dentry: The inode/dentry being altered 567 * @name: The name of the xattr to be changed 568 * @value: The value that the xattr will be changed to 569 * @size: The size of value 570 * @flags: The replacement flag 571 * 572 * Determine whether an xattr may be altered or set on an inode, returning 0 if 573 * permission is granted, -ve if denied. 574 * 575 * This is used to make sure security xattrs don't get updated or set by those 576 * who aren't privileged to do so. 577 */ 578 int cap_inode_setxattr(struct dentry *dentry, const char *name, 579 const void *value, size_t size, int flags) 580 { 581 if (!strcmp(name, XATTR_NAME_CAPS)) { 582 if (!capable(CAP_SETFCAP)) 583 return -EPERM; 584 return 0; 585 } 586 587 if (!strncmp(name, XATTR_SECURITY_PREFIX, 588 sizeof(XATTR_SECURITY_PREFIX) - 1) && 589 !capable(CAP_SYS_ADMIN)) 590 return -EPERM; 591 return 0; 592 } 593 594 /** 595 * cap_inode_removexattr - Determine whether an xattr may be removed 596 * @dentry: The inode/dentry being altered 597 * @name: The name of the xattr to be changed 598 * 599 * Determine whether an xattr may be removed from an inode, returning 0 if 600 * permission is granted, -ve if denied. 601 * 602 * This is used to make sure security xattrs don't get removed by those who 603 * aren't privileged to remove them. 604 */ 605 int cap_inode_removexattr(struct dentry *dentry, const char *name) 606 { 607 if (!strcmp(name, XATTR_NAME_CAPS)) { 608 if (!capable(CAP_SETFCAP)) 609 return -EPERM; 610 return 0; 611 } 612 613 if (!strncmp(name, XATTR_SECURITY_PREFIX, 614 sizeof(XATTR_SECURITY_PREFIX) - 1) && 615 !capable(CAP_SYS_ADMIN)) 616 return -EPERM; 617 return 0; 618 } 619 620 /* 621 * cap_emulate_setxuid() fixes the effective / permitted capabilities of 622 * a process after a call to setuid, setreuid, or setresuid. 623 * 624 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of 625 * {r,e,s}uid != 0, the permitted and effective capabilities are 626 * cleared. 627 * 628 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective 629 * capabilities of the process are cleared. 630 * 631 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective 632 * capabilities are set to the permitted capabilities. 633 * 634 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 635 * never happen. 636 * 637 * -astor 638 * 639 * cevans - New behaviour, Oct '99 640 * A process may, via prctl(), elect to keep its capabilities when it 641 * calls setuid() and switches away from uid==0. Both permitted and 642 * effective sets will be retained. 643 * Without this change, it was impossible for a daemon to drop only some 644 * of its privilege. The call to setuid(!=0) would drop all privileges! 645 * Keeping uid 0 is not an option because uid 0 owns too many vital 646 * files.. 647 * Thanks to Olaf Kirch and Peter Benie for spotting this. 648 */ 649 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) 650 { 651 if ((old->uid == 0 || old->euid == 0 || old->suid == 0) && 652 (new->uid != 0 && new->euid != 0 && new->suid != 0) && 653 !issecure(SECURE_KEEP_CAPS)) { 654 cap_clear(new->cap_permitted); 655 cap_clear(new->cap_effective); 656 } 657 if (old->euid == 0 && new->euid != 0) 658 cap_clear(new->cap_effective); 659 if (old->euid != 0 && new->euid == 0) 660 new->cap_effective = new->cap_permitted; 661 } 662 663 /** 664 * cap_task_fix_setuid - Fix up the results of setuid() call 665 * @new: The proposed credentials 666 * @old: The current task's current credentials 667 * @flags: Indications of what has changed 668 * 669 * Fix up the results of setuid() call before the credential changes are 670 * actually applied, returning 0 to grant the changes, -ve to deny them. 671 */ 672 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) 673 { 674 switch (flags) { 675 case LSM_SETID_RE: 676 case LSM_SETID_ID: 677 case LSM_SETID_RES: 678 /* juggle the capabilities to follow [RES]UID changes unless 679 * otherwise suppressed */ 680 if (!issecure(SECURE_NO_SETUID_FIXUP)) 681 cap_emulate_setxuid(new, old); 682 break; 683 684 case LSM_SETID_FS: 685 /* juggle the capabilties to follow FSUID changes, unless 686 * otherwise suppressed 687 * 688 * FIXME - is fsuser used for all CAP_FS_MASK capabilities? 689 * if not, we might be a bit too harsh here. 690 */ 691 if (!issecure(SECURE_NO_SETUID_FIXUP)) { 692 if (old->fsuid == 0 && new->fsuid != 0) 693 new->cap_effective = 694 cap_drop_fs_set(new->cap_effective); 695 696 if (old->fsuid != 0 && new->fsuid == 0) 697 new->cap_effective = 698 cap_raise_fs_set(new->cap_effective, 699 new->cap_permitted); 700 } 701 break; 702 703 default: 704 return -EINVAL; 705 } 706 707 return 0; 708 } 709 710 #ifdef CONFIG_SECURITY_FILE_CAPABILITIES 711 /* 712 * Rationale: code calling task_setscheduler, task_setioprio, and 713 * task_setnice, assumes that 714 * . if capable(cap_sys_nice), then those actions should be allowed 715 * . if not capable(cap_sys_nice), but acting on your own processes, 716 * then those actions should be allowed 717 * This is insufficient now since you can call code without suid, but 718 * yet with increased caps. 719 * So we check for increased caps on the target process. 720 */ 721 static int cap_safe_nice(struct task_struct *p) 722 { 723 int is_subset; 724 725 rcu_read_lock(); 726 is_subset = cap_issubset(__task_cred(p)->cap_permitted, 727 current_cred()->cap_permitted); 728 rcu_read_unlock(); 729 730 if (!is_subset && !capable(CAP_SYS_NICE)) 731 return -EPERM; 732 return 0; 733 } 734 735 /** 736 * cap_task_setscheduler - Detemine if scheduler policy change is permitted 737 * @p: The task to affect 738 * @policy: The policy to effect 739 * @lp: The parameters to the scheduling policy 740 * 741 * Detemine if the requested scheduler policy change is permitted for the 742 * specified task, returning 0 if permission is granted, -ve if denied. 743 */ 744 int cap_task_setscheduler(struct task_struct *p, int policy, 745 struct sched_param *lp) 746 { 747 return cap_safe_nice(p); 748 } 749 750 /** 751 * cap_task_ioprio - Detemine if I/O priority change is permitted 752 * @p: The task to affect 753 * @ioprio: The I/O priority to set 754 * 755 * Detemine if the requested I/O priority change is permitted for the specified 756 * task, returning 0 if permission is granted, -ve if denied. 757 */ 758 int cap_task_setioprio(struct task_struct *p, int ioprio) 759 { 760 return cap_safe_nice(p); 761 } 762 763 /** 764 * cap_task_ioprio - Detemine if task priority change is permitted 765 * @p: The task to affect 766 * @nice: The nice value to set 767 * 768 * Detemine if the requested task priority change is permitted for the 769 * specified task, returning 0 if permission is granted, -ve if denied. 770 */ 771 int cap_task_setnice(struct task_struct *p, int nice) 772 { 773 return cap_safe_nice(p); 774 } 775 776 /* 777 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from 778 * the current task's bounding set. Returns 0 on success, -ve on error. 779 */ 780 static long cap_prctl_drop(struct cred *new, unsigned long cap) 781 { 782 if (!capable(CAP_SETPCAP)) 783 return -EPERM; 784 if (!cap_valid(cap)) 785 return -EINVAL; 786 787 cap_lower(new->cap_bset, cap); 788 return 0; 789 } 790 791 #else 792 int cap_task_setscheduler (struct task_struct *p, int policy, 793 struct sched_param *lp) 794 { 795 return 0; 796 } 797 int cap_task_setioprio (struct task_struct *p, int ioprio) 798 { 799 return 0; 800 } 801 int cap_task_setnice (struct task_struct *p, int nice) 802 { 803 return 0; 804 } 805 #endif 806 807 /** 808 * cap_task_prctl - Implement process control functions for this security module 809 * @option: The process control function requested 810 * @arg2, @arg3, @arg4, @arg5: The argument data for this function 811 * 812 * Allow process control functions (sys_prctl()) to alter capabilities; may 813 * also deny access to other functions not otherwise implemented here. 814 * 815 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented 816 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM 817 * modules will consider performing the function. 818 */ 819 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, 820 unsigned long arg4, unsigned long arg5) 821 { 822 struct cred *new; 823 long error = 0; 824 825 new = prepare_creds(); 826 if (!new) 827 return -ENOMEM; 828 829 switch (option) { 830 case PR_CAPBSET_READ: 831 error = -EINVAL; 832 if (!cap_valid(arg2)) 833 goto error; 834 error = !!cap_raised(new->cap_bset, arg2); 835 goto no_change; 836 837 #ifdef CONFIG_SECURITY_FILE_CAPABILITIES 838 case PR_CAPBSET_DROP: 839 error = cap_prctl_drop(new, arg2); 840 if (error < 0) 841 goto error; 842 goto changed; 843 844 /* 845 * The next four prctl's remain to assist with transitioning a 846 * system from legacy UID=0 based privilege (when filesystem 847 * capabilities are not in use) to a system using filesystem 848 * capabilities only - as the POSIX.1e draft intended. 849 * 850 * Note: 851 * 852 * PR_SET_SECUREBITS = 853 * issecure_mask(SECURE_KEEP_CAPS_LOCKED) 854 * | issecure_mask(SECURE_NOROOT) 855 * | issecure_mask(SECURE_NOROOT_LOCKED) 856 * | issecure_mask(SECURE_NO_SETUID_FIXUP) 857 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) 858 * 859 * will ensure that the current process and all of its 860 * children will be locked into a pure 861 * capability-based-privilege environment. 862 */ 863 case PR_SET_SECUREBITS: 864 error = -EPERM; 865 if ((((new->securebits & SECURE_ALL_LOCKS) >> 1) 866 & (new->securebits ^ arg2)) /*[1]*/ 867 || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ 868 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ 869 || (cap_capable(current, current_cred(), CAP_SETPCAP, 870 SECURITY_CAP_AUDIT) != 0) /*[4]*/ 871 /* 872 * [1] no changing of bits that are locked 873 * [2] no unlocking of locks 874 * [3] no setting of unsupported bits 875 * [4] doing anything requires privilege (go read about 876 * the "sendmail capabilities bug") 877 */ 878 ) 879 /* cannot change a locked bit */ 880 goto error; 881 new->securebits = arg2; 882 goto changed; 883 884 case PR_GET_SECUREBITS: 885 error = new->securebits; 886 goto no_change; 887 888 #endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */ 889 890 case PR_GET_KEEPCAPS: 891 if (issecure(SECURE_KEEP_CAPS)) 892 error = 1; 893 goto no_change; 894 895 case PR_SET_KEEPCAPS: 896 error = -EINVAL; 897 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ 898 goto error; 899 error = -EPERM; 900 if (issecure(SECURE_KEEP_CAPS_LOCKED)) 901 goto error; 902 if (arg2) 903 new->securebits |= issecure_mask(SECURE_KEEP_CAPS); 904 else 905 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 906 goto changed; 907 908 default: 909 /* No functionality available - continue with default */ 910 error = -ENOSYS; 911 goto error; 912 } 913 914 /* Functionality provided */ 915 changed: 916 return commit_creds(new); 917 918 no_change: 919 error: 920 abort_creds(new); 921 return error; 922 } 923 924 /** 925 * cap_syslog - Determine whether syslog function is permitted 926 * @type: Function requested 927 * 928 * Determine whether the current process is permitted to use a particular 929 * syslog function, returning 0 if permission is granted, -ve if not. 930 */ 931 int cap_syslog(int type) 932 { 933 if ((type != 3 && type != 10) && !capable(CAP_SYS_ADMIN)) 934 return -EPERM; 935 return 0; 936 } 937 938 /** 939 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted 940 * @mm: The VM space in which the new mapping is to be made 941 * @pages: The size of the mapping 942 * 943 * Determine whether the allocation of a new virtual mapping by the current 944 * task is permitted, returning 0 if permission is granted, -ve if not. 945 */ 946 int cap_vm_enough_memory(struct mm_struct *mm, long pages) 947 { 948 int cap_sys_admin = 0; 949 950 if (cap_capable(current, current_cred(), CAP_SYS_ADMIN, 951 SECURITY_CAP_NOAUDIT) == 0) 952 cap_sys_admin = 1; 953 return __vm_enough_memory(mm, pages, cap_sys_admin); 954 } 955