1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* Common capabilities, needed by capability.o. 3 */ 4 5 #include <linux/capability.h> 6 #include <linux/audit.h> 7 #include <linux/init.h> 8 #include <linux/kernel.h> 9 #include <linux/lsm_hooks.h> 10 #include <linux/file.h> 11 #include <linux/mm.h> 12 #include <linux/mman.h> 13 #include <linux/pagemap.h> 14 #include <linux/swap.h> 15 #include <linux/skbuff.h> 16 #include <linux/netlink.h> 17 #include <linux/ptrace.h> 18 #include <linux/xattr.h> 19 #include <linux/hugetlb.h> 20 #include <linux/mount.h> 21 #include <linux/sched.h> 22 #include <linux/prctl.h> 23 #include <linux/securebits.h> 24 #include <linux/user_namespace.h> 25 #include <linux/binfmts.h> 26 #include <linux/personality.h> 27 #include <linux/mnt_idmapping.h> 28 #include <uapi/linux/lsm.h> 29 30 #define CREATE_TRACE_POINTS 31 #include <trace/events/capability.h> 32 33 /* 34 * If a non-root user executes a setuid-root binary in 35 * !secure(SECURE_NOROOT) mode, then we raise capabilities. 36 * However if fE is also set, then the intent is for only 37 * the file capabilities to be applied, and the setuid-root 38 * bit is left on either to change the uid (plausible) or 39 * to get full privilege on a kernel without file capabilities 40 * support. So in that case we do not raise capabilities. 41 * 42 * Warn if that happens, once per boot. 43 */ 44 static void warn_setuid_and_fcaps_mixed(const char *fname) 45 { 46 static int warned; 47 if (!warned) { 48 printk(KERN_INFO "warning: `%s' has both setuid-root and" 49 " effective capabilities. Therefore not raising all" 50 " capabilities.\n", fname); 51 warned = 1; 52 } 53 } 54 55 /** 56 * cap_capable_helper - Determine whether a task has a particular effective 57 * capability. 58 * @cred: The credentials to use 59 * @target_ns: The user namespace of the resource being accessed 60 * @cred_ns: The user namespace of the credentials 61 * @cap: The capability to check for 62 * 63 * Determine whether the nominated task has the specified capability amongst 64 * its effective set, returning 0 if it does, -ve if it does not. 65 * 66 * See cap_capable for more details. 67 */ 68 static inline int cap_capable_helper(const struct cred *cred, 69 struct user_namespace *target_ns, 70 const struct user_namespace *cred_ns, 71 int cap) 72 { 73 struct user_namespace *ns = target_ns; 74 75 /* See if cred has the capability in the target user namespace 76 * by examining the target user namespace and all of the target 77 * user namespace's parents. 78 */ 79 for (;;) { 80 /* Do we have the necessary capabilities? */ 81 if (likely(ns == cred_ns)) 82 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; 83 84 /* 85 * If we're already at a lower level than we're looking for, 86 * we're done searching. 87 */ 88 if (ns->level <= cred_ns->level) 89 return -EPERM; 90 91 /* 92 * The owner of the user namespace in the parent of the 93 * user namespace has all caps. 94 */ 95 if ((ns->parent == cred_ns) && uid_eq(ns->owner, cred->euid)) 96 return 0; 97 98 /* 99 * If you have a capability in a parent user ns, then you have 100 * it over all children user namespaces as well. 101 */ 102 ns = ns->parent; 103 } 104 105 /* We never get here */ 106 } 107 108 /** 109 * cap_capable - Determine whether a task has a particular effective capability 110 * @cred: The credentials to use 111 * @target_ns: The user namespace of the resource being accessed 112 * @cap: The capability to check for 113 * @opts: Bitmask of options defined in include/linux/security.h (unused) 114 * 115 * Determine whether the nominated task has the specified capability amongst 116 * its effective set, returning 0 if it does, -ve if it does not. 117 * 118 * NOTE WELL: cap_capable() has reverse semantics to the capable() call 119 * and friends. That is cap_capable() returns an int 0 when a task has 120 * a capability, while the kernel's capable(), has_ns_capability(), 121 * has_ns_capability_noaudit(), and has_capability_noaudit() return a 122 * bool true (1) for this case. 123 */ 124 int cap_capable(const struct cred *cred, struct user_namespace *target_ns, 125 int cap, unsigned int opts) 126 { 127 const struct user_namespace *cred_ns = cred->user_ns; 128 int ret = cap_capable_helper(cred, target_ns, cred_ns, cap); 129 130 trace_cap_capable(cred, target_ns, cred_ns, cap, ret); 131 return ret; 132 } 133 134 /** 135 * cap_settime - Determine whether the current process may set the system clock 136 * @ts: The time to set 137 * @tz: The timezone to set 138 * 139 * Determine whether the current process may set the system clock and timezone 140 * information, returning 0 if permission granted, -ve if denied. 141 */ 142 int cap_settime(const struct timespec64 *ts, const struct timezone *tz) 143 { 144 if (!capable(CAP_SYS_TIME)) 145 return -EPERM; 146 return 0; 147 } 148 149 /** 150 * cap_ptrace_access_check - Determine whether the current process may access 151 * another 152 * @child: The process to be accessed 153 * @mode: The mode of attachment. 154 * 155 * If we are in the same or an ancestor user_ns and have all the target 156 * task's capabilities, then ptrace access is allowed. 157 * If we have the ptrace capability to the target user_ns, then ptrace 158 * access is allowed. 159 * Else denied. 160 * 161 * Determine whether a process may access another, returning 0 if permission 162 * granted, -ve if denied. 163 */ 164 int cap_ptrace_access_check(struct task_struct *child, unsigned int mode) 165 { 166 int ret = 0; 167 const struct cred *cred, *child_cred; 168 const kernel_cap_t *caller_caps; 169 170 rcu_read_lock(); 171 cred = current_cred(); 172 child_cred = __task_cred(child); 173 if (mode & PTRACE_MODE_FSCREDS) 174 caller_caps = &cred->cap_effective; 175 else 176 caller_caps = &cred->cap_permitted; 177 if (cred->user_ns == child_cred->user_ns && 178 cap_issubset(child_cred->cap_permitted, *caller_caps)) 179 goto out; 180 if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE)) 181 goto out; 182 ret = -EPERM; 183 out: 184 rcu_read_unlock(); 185 return ret; 186 } 187 188 /** 189 * cap_ptrace_traceme - Determine whether another process may trace the current 190 * @parent: The task proposed to be the tracer 191 * 192 * If parent is in the same or an ancestor user_ns and has all current's 193 * capabilities, then ptrace access is allowed. 194 * If parent has the ptrace capability to current's user_ns, then ptrace 195 * access is allowed. 196 * Else denied. 197 * 198 * Determine whether the nominated task is permitted to trace the current 199 * process, returning 0 if permission is granted, -ve if denied. 200 */ 201 int cap_ptrace_traceme(struct task_struct *parent) 202 { 203 int ret = 0; 204 const struct cred *cred, *child_cred; 205 206 rcu_read_lock(); 207 cred = __task_cred(parent); 208 child_cred = current_cred(); 209 if (cred->user_ns == child_cred->user_ns && 210 cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) 211 goto out; 212 if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE)) 213 goto out; 214 ret = -EPERM; 215 out: 216 rcu_read_unlock(); 217 return ret; 218 } 219 220 /** 221 * cap_capget - Retrieve a task's capability sets 222 * @target: The task from which to retrieve the capability sets 223 * @effective: The place to record the effective set 224 * @inheritable: The place to record the inheritable set 225 * @permitted: The place to record the permitted set 226 * 227 * This function retrieves the capabilities of the nominated task and returns 228 * them to the caller. 229 */ 230 int cap_capget(const struct task_struct *target, kernel_cap_t *effective, 231 kernel_cap_t *inheritable, kernel_cap_t *permitted) 232 { 233 const struct cred *cred; 234 235 /* Derived from kernel/capability.c:sys_capget. */ 236 rcu_read_lock(); 237 cred = __task_cred(target); 238 *effective = cred->cap_effective; 239 *inheritable = cred->cap_inheritable; 240 *permitted = cred->cap_permitted; 241 rcu_read_unlock(); 242 return 0; 243 } 244 245 /* 246 * Determine whether the inheritable capabilities are limited to the old 247 * permitted set. Returns 1 if they are limited, 0 if they are not. 248 */ 249 static inline int cap_inh_is_capped(void) 250 { 251 /* they are so limited unless the current task has the CAP_SETPCAP 252 * capability 253 */ 254 if (cap_capable(current_cred(), current_cred()->user_ns, 255 CAP_SETPCAP, CAP_OPT_NONE) == 0) 256 return 0; 257 return 1; 258 } 259 260 /** 261 * cap_capset - Validate and apply proposed changes to current's capabilities 262 * @new: The proposed new credentials; alterations should be made here 263 * @old: The current task's current credentials 264 * @effective: A pointer to the proposed new effective capabilities set 265 * @inheritable: A pointer to the proposed new inheritable capabilities set 266 * @permitted: A pointer to the proposed new permitted capabilities set 267 * 268 * This function validates and applies a proposed mass change to the current 269 * process's capability sets. The changes are made to the proposed new 270 * credentials, and assuming no error, will be committed by the caller of LSM. 271 */ 272 int cap_capset(struct cred *new, 273 const struct cred *old, 274 const kernel_cap_t *effective, 275 const kernel_cap_t *inheritable, 276 const kernel_cap_t *permitted) 277 { 278 if (cap_inh_is_capped() && 279 !cap_issubset(*inheritable, 280 cap_combine(old->cap_inheritable, 281 old->cap_permitted))) 282 /* incapable of using this inheritable set */ 283 return -EPERM; 284 285 if (!cap_issubset(*inheritable, 286 cap_combine(old->cap_inheritable, 287 old->cap_bset))) 288 /* no new pI capabilities outside bounding set */ 289 return -EPERM; 290 291 /* verify restrictions on target's new Permitted set */ 292 if (!cap_issubset(*permitted, old->cap_permitted)) 293 return -EPERM; 294 295 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ 296 if (!cap_issubset(*effective, *permitted)) 297 return -EPERM; 298 299 new->cap_effective = *effective; 300 new->cap_inheritable = *inheritable; 301 new->cap_permitted = *permitted; 302 303 /* 304 * Mask off ambient bits that are no longer both permitted and 305 * inheritable. 306 */ 307 new->cap_ambient = cap_intersect(new->cap_ambient, 308 cap_intersect(*permitted, 309 *inheritable)); 310 if (WARN_ON(!cap_ambient_invariant_ok(new))) 311 return -EINVAL; 312 return 0; 313 } 314 315 /** 316 * cap_inode_need_killpriv - Determine if inode change affects privileges 317 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV 318 * 319 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV 320 * affects the security markings on that inode, and if it is, should 321 * inode_killpriv() be invoked or the change rejected. 322 * 323 * Return: 1 if security.capability has a value, meaning inode_killpriv() 324 * is required, 0 otherwise, meaning inode_killpriv() is not required. 325 */ 326 int cap_inode_need_killpriv(struct dentry *dentry) 327 { 328 struct inode *inode = d_backing_inode(dentry); 329 int error; 330 331 error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0); 332 return error > 0; 333 } 334 335 /** 336 * cap_inode_killpriv - Erase the security markings on an inode 337 * 338 * @idmap: idmap of the mount the inode was found from 339 * @dentry: The inode/dentry to alter 340 * 341 * Erase the privilege-enhancing security markings on an inode. 342 * 343 * If the inode has been found through an idmapped mount the idmap of 344 * the vfsmount must be passed through @idmap. This function will then 345 * take care to map the inode according to @idmap before checking 346 * permissions. On non-idmapped mounts or if permission checking is to be 347 * performed on the raw inode simply pass @nop_mnt_idmap. 348 * 349 * Return: 0 if successful, -ve on error. 350 */ 351 int cap_inode_killpriv(struct mnt_idmap *idmap, struct dentry *dentry) 352 { 353 int error; 354 355 error = __vfs_removexattr(idmap, dentry, XATTR_NAME_CAPS); 356 if (error == -EOPNOTSUPP) 357 error = 0; 358 return error; 359 } 360 361 static bool rootid_owns_currentns(vfsuid_t rootvfsuid) 362 { 363 struct user_namespace *ns; 364 kuid_t kroot; 365 366 if (!vfsuid_valid(rootvfsuid)) 367 return false; 368 369 kroot = vfsuid_into_kuid(rootvfsuid); 370 for (ns = current_user_ns();; ns = ns->parent) { 371 if (from_kuid(ns, kroot) == 0) 372 return true; 373 if (ns == &init_user_ns) 374 break; 375 } 376 377 return false; 378 } 379 380 static __u32 sansflags(__u32 m) 381 { 382 return m & ~VFS_CAP_FLAGS_EFFECTIVE; 383 } 384 385 static bool is_v2header(int size, const struct vfs_cap_data *cap) 386 { 387 if (size != XATTR_CAPS_SZ_2) 388 return false; 389 return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_2; 390 } 391 392 static bool is_v3header(int size, const struct vfs_cap_data *cap) 393 { 394 if (size != XATTR_CAPS_SZ_3) 395 return false; 396 return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_3; 397 } 398 399 /* 400 * getsecurity: We are called for security.* before any attempt to read the 401 * xattr from the inode itself. 402 * 403 * This gives us a chance to read the on-disk value and convert it. If we 404 * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler. 405 * 406 * Note we are not called by vfs_getxattr_alloc(), but that is only called 407 * by the integrity subsystem, which really wants the unconverted values - 408 * so that's good. 409 */ 410 int cap_inode_getsecurity(struct mnt_idmap *idmap, 411 struct inode *inode, const char *name, void **buffer, 412 bool alloc) 413 { 414 int size; 415 kuid_t kroot; 416 vfsuid_t vfsroot; 417 u32 nsmagic, magic; 418 uid_t root, mappedroot; 419 char *tmpbuf = NULL; 420 struct vfs_cap_data *cap; 421 struct vfs_ns_cap_data *nscap = NULL; 422 struct dentry *dentry; 423 struct user_namespace *fs_ns; 424 425 if (strcmp(name, "capability") != 0) 426 return -EOPNOTSUPP; 427 428 dentry = d_find_any_alias(inode); 429 if (!dentry) 430 return -EINVAL; 431 size = vfs_getxattr_alloc(idmap, dentry, XATTR_NAME_CAPS, &tmpbuf, 432 sizeof(struct vfs_ns_cap_data), GFP_NOFS); 433 dput(dentry); 434 /* gcc11 complains if we don't check for !tmpbuf */ 435 if (size < 0 || !tmpbuf) 436 goto out_free; 437 438 fs_ns = inode->i_sb->s_user_ns; 439 cap = (struct vfs_cap_data *) tmpbuf; 440 if (is_v2header(size, cap)) { 441 root = 0; 442 } else if (is_v3header(size, cap)) { 443 nscap = (struct vfs_ns_cap_data *) tmpbuf; 444 root = le32_to_cpu(nscap->rootid); 445 } else { 446 size = -EINVAL; 447 goto out_free; 448 } 449 450 kroot = make_kuid(fs_ns, root); 451 452 /* If this is an idmapped mount shift the kuid. */ 453 vfsroot = make_vfsuid(idmap, fs_ns, kroot); 454 455 /* If the root kuid maps to a valid uid in current ns, then return 456 * this as a nscap. */ 457 mappedroot = from_kuid(current_user_ns(), vfsuid_into_kuid(vfsroot)); 458 if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) { 459 size = sizeof(struct vfs_ns_cap_data); 460 if (alloc) { 461 if (!nscap) { 462 /* v2 -> v3 conversion */ 463 nscap = kzalloc(size, GFP_ATOMIC); 464 if (!nscap) { 465 size = -ENOMEM; 466 goto out_free; 467 } 468 nsmagic = VFS_CAP_REVISION_3; 469 magic = le32_to_cpu(cap->magic_etc); 470 if (magic & VFS_CAP_FLAGS_EFFECTIVE) 471 nsmagic |= VFS_CAP_FLAGS_EFFECTIVE; 472 memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32); 473 nscap->magic_etc = cpu_to_le32(nsmagic); 474 } else { 475 /* use allocated v3 buffer */ 476 tmpbuf = NULL; 477 } 478 nscap->rootid = cpu_to_le32(mappedroot); 479 *buffer = nscap; 480 } 481 goto out_free; 482 } 483 484 if (!rootid_owns_currentns(vfsroot)) { 485 size = -EOVERFLOW; 486 goto out_free; 487 } 488 489 /* This comes from a parent namespace. Return as a v2 capability */ 490 size = sizeof(struct vfs_cap_data); 491 if (alloc) { 492 if (nscap) { 493 /* v3 -> v2 conversion */ 494 cap = kzalloc(size, GFP_ATOMIC); 495 if (!cap) { 496 size = -ENOMEM; 497 goto out_free; 498 } 499 magic = VFS_CAP_REVISION_2; 500 nsmagic = le32_to_cpu(nscap->magic_etc); 501 if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE) 502 magic |= VFS_CAP_FLAGS_EFFECTIVE; 503 memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32); 504 cap->magic_etc = cpu_to_le32(magic); 505 } else { 506 /* use unconverted v2 */ 507 tmpbuf = NULL; 508 } 509 *buffer = cap; 510 } 511 out_free: 512 kfree(tmpbuf); 513 return size; 514 } 515 516 /** 517 * rootid_from_xattr - translate root uid of vfs caps 518 * 519 * @value: vfs caps value which may be modified by this function 520 * @size: size of @ivalue 521 * @task_ns: user namespace of the caller 522 */ 523 static vfsuid_t rootid_from_xattr(const void *value, size_t size, 524 struct user_namespace *task_ns) 525 { 526 const struct vfs_ns_cap_data *nscap = value; 527 uid_t rootid = 0; 528 529 if (size == XATTR_CAPS_SZ_3) 530 rootid = le32_to_cpu(nscap->rootid); 531 532 return VFSUIDT_INIT(make_kuid(task_ns, rootid)); 533 } 534 535 static bool validheader(size_t size, const struct vfs_cap_data *cap) 536 { 537 return is_v2header(size, cap) || is_v3header(size, cap); 538 } 539 540 /** 541 * cap_convert_nscap - check vfs caps 542 * 543 * @idmap: idmap of the mount the inode was found from 544 * @dentry: used to retrieve inode to check permissions on 545 * @ivalue: vfs caps value which may be modified by this function 546 * @size: size of @ivalue 547 * 548 * User requested a write of security.capability. If needed, update the 549 * xattr to change from v2 to v3, or to fixup the v3 rootid. 550 * 551 * If the inode has been found through an idmapped mount the idmap of 552 * the vfsmount must be passed through @idmap. This function will then 553 * take care to map the inode according to @idmap before checking 554 * permissions. On non-idmapped mounts or if permission checking is to be 555 * performed on the raw inode simply pass @nop_mnt_idmap. 556 * 557 * Return: On success, return the new size; on error, return < 0. 558 */ 559 int cap_convert_nscap(struct mnt_idmap *idmap, struct dentry *dentry, 560 const void **ivalue, size_t size) 561 { 562 struct vfs_ns_cap_data *nscap; 563 uid_t nsrootid; 564 const struct vfs_cap_data *cap = *ivalue; 565 __u32 magic, nsmagic; 566 struct inode *inode = d_backing_inode(dentry); 567 struct user_namespace *task_ns = current_user_ns(), 568 *fs_ns = inode->i_sb->s_user_ns; 569 kuid_t rootid; 570 vfsuid_t vfsrootid; 571 size_t newsize; 572 573 if (!*ivalue) 574 return -EINVAL; 575 if (!validheader(size, cap)) 576 return -EINVAL; 577 if (!capable_wrt_inode_uidgid(idmap, inode, CAP_SETFCAP)) 578 return -EPERM; 579 if (size == XATTR_CAPS_SZ_2 && (idmap == &nop_mnt_idmap)) 580 if (ns_capable(inode->i_sb->s_user_ns, CAP_SETFCAP)) 581 /* user is privileged, just write the v2 */ 582 return size; 583 584 vfsrootid = rootid_from_xattr(*ivalue, size, task_ns); 585 if (!vfsuid_valid(vfsrootid)) 586 return -EINVAL; 587 588 rootid = from_vfsuid(idmap, fs_ns, vfsrootid); 589 if (!uid_valid(rootid)) 590 return -EINVAL; 591 592 nsrootid = from_kuid(fs_ns, rootid); 593 if (nsrootid == -1) 594 return -EINVAL; 595 596 newsize = sizeof(struct vfs_ns_cap_data); 597 nscap = kmalloc(newsize, GFP_ATOMIC); 598 if (!nscap) 599 return -ENOMEM; 600 nscap->rootid = cpu_to_le32(nsrootid); 601 nsmagic = VFS_CAP_REVISION_3; 602 magic = le32_to_cpu(cap->magic_etc); 603 if (magic & VFS_CAP_FLAGS_EFFECTIVE) 604 nsmagic |= VFS_CAP_FLAGS_EFFECTIVE; 605 nscap->magic_etc = cpu_to_le32(nsmagic); 606 memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32); 607 608 *ivalue = nscap; 609 return newsize; 610 } 611 612 /* 613 * Calculate the new process capability sets from the capability sets attached 614 * to a file. 615 */ 616 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, 617 struct linux_binprm *bprm, 618 bool *effective, 619 bool *has_fcap) 620 { 621 struct cred *new = bprm->cred; 622 int ret = 0; 623 624 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) 625 *effective = true; 626 627 if (caps->magic_etc & VFS_CAP_REVISION_MASK) 628 *has_fcap = true; 629 630 /* 631 * pP' = (X & fP) | (pI & fI) 632 * The addition of pA' is handled later. 633 */ 634 new->cap_permitted.val = 635 (new->cap_bset.val & caps->permitted.val) | 636 (new->cap_inheritable.val & caps->inheritable.val); 637 638 if (caps->permitted.val & ~new->cap_permitted.val) 639 /* insufficient to execute correctly */ 640 ret = -EPERM; 641 642 /* 643 * For legacy apps, with no internal support for recognizing they 644 * do not have enough capabilities, we return an error if they are 645 * missing some "forced" (aka file-permitted) capabilities. 646 */ 647 return *effective ? ret : 0; 648 } 649 650 /** 651 * get_vfs_caps_from_disk - retrieve vfs caps from disk 652 * 653 * @idmap: idmap of the mount the inode was found from 654 * @dentry: dentry from which @inode is retrieved 655 * @cpu_caps: vfs capabilities 656 * 657 * Extract the on-exec-apply capability sets for an executable file. 658 * 659 * If the inode has been found through an idmapped mount the idmap of 660 * the vfsmount must be passed through @idmap. This function will then 661 * take care to map the inode according to @idmap before checking 662 * permissions. On non-idmapped mounts or if permission checking is to be 663 * performed on the raw inode simply pass @nop_mnt_idmap. 664 */ 665 int get_vfs_caps_from_disk(struct mnt_idmap *idmap, 666 const struct dentry *dentry, 667 struct cpu_vfs_cap_data *cpu_caps) 668 { 669 struct inode *inode = d_backing_inode(dentry); 670 __u32 magic_etc; 671 int size; 672 struct vfs_ns_cap_data data, *nscaps = &data; 673 struct vfs_cap_data *caps = (struct vfs_cap_data *) &data; 674 kuid_t rootkuid; 675 vfsuid_t rootvfsuid; 676 struct user_namespace *fs_ns; 677 678 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); 679 680 if (!inode) 681 return -ENODATA; 682 683 fs_ns = inode->i_sb->s_user_ns; 684 size = __vfs_getxattr((struct dentry *)dentry, inode, 685 XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ); 686 if (size == -ENODATA || size == -EOPNOTSUPP) 687 /* no data, that's ok */ 688 return -ENODATA; 689 690 if (size < 0) 691 return size; 692 693 if (size < sizeof(magic_etc)) 694 return -EINVAL; 695 696 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps->magic_etc); 697 698 rootkuid = make_kuid(fs_ns, 0); 699 switch (magic_etc & VFS_CAP_REVISION_MASK) { 700 case VFS_CAP_REVISION_1: 701 if (size != XATTR_CAPS_SZ_1) 702 return -EINVAL; 703 break; 704 case VFS_CAP_REVISION_2: 705 if (size != XATTR_CAPS_SZ_2) 706 return -EINVAL; 707 break; 708 case VFS_CAP_REVISION_3: 709 if (size != XATTR_CAPS_SZ_3) 710 return -EINVAL; 711 rootkuid = make_kuid(fs_ns, le32_to_cpu(nscaps->rootid)); 712 break; 713 714 default: 715 return -EINVAL; 716 } 717 718 rootvfsuid = make_vfsuid(idmap, fs_ns, rootkuid); 719 if (!vfsuid_valid(rootvfsuid)) 720 return -ENODATA; 721 722 /* Limit the caps to the mounter of the filesystem 723 * or the more limited uid specified in the xattr. 724 */ 725 if (!rootid_owns_currentns(rootvfsuid)) 726 return -ENODATA; 727 728 cpu_caps->permitted.val = le32_to_cpu(caps->data[0].permitted); 729 cpu_caps->inheritable.val = le32_to_cpu(caps->data[0].inheritable); 730 731 /* 732 * Rev1 had just a single 32-bit word, later expanded 733 * to a second one for the high bits 734 */ 735 if ((magic_etc & VFS_CAP_REVISION_MASK) != VFS_CAP_REVISION_1) { 736 cpu_caps->permitted.val += (u64)le32_to_cpu(caps->data[1].permitted) << 32; 737 cpu_caps->inheritable.val += (u64)le32_to_cpu(caps->data[1].inheritable) << 32; 738 } 739 740 cpu_caps->permitted.val &= CAP_VALID_MASK; 741 cpu_caps->inheritable.val &= CAP_VALID_MASK; 742 743 cpu_caps->rootid = vfsuid_into_kuid(rootvfsuid); 744 745 return 0; 746 } 747 748 /* 749 * Attempt to get the on-exec apply capability sets for an executable file from 750 * its xattrs and, if present, apply them to the proposed credentials being 751 * constructed by execve(). 752 */ 753 static int get_file_caps(struct linux_binprm *bprm, const struct file *file, 754 bool *effective, bool *has_fcap) 755 { 756 int rc = 0; 757 struct cpu_vfs_cap_data vcaps; 758 759 cap_clear(bprm->cred->cap_permitted); 760 761 if (!file_caps_enabled) 762 return 0; 763 764 if (!mnt_may_suid(file->f_path.mnt)) 765 return 0; 766 767 /* 768 * This check is redundant with mnt_may_suid() but is kept to make 769 * explicit that capability bits are limited to s_user_ns and its 770 * descendants. 771 */ 772 if (!current_in_userns(file->f_path.mnt->mnt_sb->s_user_ns)) 773 return 0; 774 775 rc = get_vfs_caps_from_disk(file_mnt_idmap(file), 776 file->f_path.dentry, &vcaps); 777 if (rc < 0) { 778 if (rc == -EINVAL) 779 printk(KERN_NOTICE "Invalid argument reading file caps for %s\n", 780 bprm->filename); 781 else if (rc == -ENODATA) 782 rc = 0; 783 goto out; 784 } 785 786 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_fcap); 787 788 out: 789 if (rc) 790 cap_clear(bprm->cred->cap_permitted); 791 792 return rc; 793 } 794 795 static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); } 796 797 static inline bool __is_real(kuid_t uid, struct cred *cred) 798 { return uid_eq(cred->uid, uid); } 799 800 static inline bool __is_eff(kuid_t uid, struct cred *cred) 801 { return uid_eq(cred->euid, uid); } 802 803 static inline bool __is_suid(kuid_t uid, struct cred *cred) 804 { return !__is_real(uid, cred) && __is_eff(uid, cred); } 805 806 /* 807 * handle_privileged_root - Handle case of privileged root 808 * @bprm: The execution parameters, including the proposed creds 809 * @has_fcap: Are any file capabilities set? 810 * @effective: Do we have effective root privilege? 811 * @root_uid: This namespace' root UID WRT initial USER namespace 812 * 813 * Handle the case where root is privileged and hasn't been neutered by 814 * SECURE_NOROOT. If file capabilities are set, they won't be combined with 815 * set UID root and nothing is changed. If we are root, cap_permitted is 816 * updated. If we have become set UID root, the effective bit is set. 817 */ 818 static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap, 819 bool *effective, kuid_t root_uid) 820 { 821 const struct cred *old = current_cred(); 822 struct cred *new = bprm->cred; 823 824 if (!root_privileged()) 825 return; 826 /* 827 * If the legacy file capability is set, then don't set privs 828 * for a setuid root binary run by a non-root user. Do set it 829 * for a root user just to cause least surprise to an admin. 830 */ 831 if (has_fcap && __is_suid(root_uid, new)) { 832 warn_setuid_and_fcaps_mixed(bprm->filename); 833 return; 834 } 835 /* 836 * To support inheritance of root-permissions and suid-root 837 * executables under compatibility mode, we override the 838 * capability sets for the file. 839 */ 840 if (__is_eff(root_uid, new) || __is_real(root_uid, new)) { 841 /* pP' = (cap_bset & ~0) | (pI & ~0) */ 842 new->cap_permitted = cap_combine(old->cap_bset, 843 old->cap_inheritable); 844 } 845 /* 846 * If only the real uid is 0, we do not set the effective bit. 847 */ 848 if (__is_eff(root_uid, new)) 849 *effective = true; 850 } 851 852 #define __cap_gained(field, target, source) \ 853 !cap_issubset(target->cap_##field, source->cap_##field) 854 #define __cap_grew(target, source, cred) \ 855 !cap_issubset(cred->cap_##target, cred->cap_##source) 856 #define __cap_full(field, cred) \ 857 cap_issubset(CAP_FULL_SET, cred->cap_##field) 858 859 static inline bool __is_setuid(struct cred *new, const struct cred *old) 860 { return !uid_eq(new->euid, old->uid); } 861 862 static inline bool __is_setgid(struct cred *new, const struct cred *old) 863 { return !gid_eq(new->egid, old->gid); } 864 865 /* 866 * 1) Audit candidate if current->cap_effective is set 867 * 868 * We do not bother to audit if 3 things are true: 869 * 1) cap_effective has all caps 870 * 2) we became root *OR* are were already root 871 * 3) root is supposed to have all caps (SECURE_NOROOT) 872 * Since this is just a normal root execing a process. 873 * 874 * Number 1 above might fail if you don't have a full bset, but I think 875 * that is interesting information to audit. 876 * 877 * A number of other conditions require logging: 878 * 2) something prevented setuid root getting all caps 879 * 3) non-setuid root gets fcaps 880 * 4) non-setuid root gets ambient 881 */ 882 static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old, 883 kuid_t root, bool has_fcap) 884 { 885 bool ret = false; 886 887 if ((__cap_grew(effective, ambient, new) && 888 !(__cap_full(effective, new) && 889 (__is_eff(root, new) || __is_real(root, new)) && 890 root_privileged())) || 891 (root_privileged() && 892 __is_suid(root, new) && 893 !__cap_full(effective, new)) || 894 (!__is_setuid(new, old) && 895 ((has_fcap && 896 __cap_gained(permitted, new, old)) || 897 __cap_gained(ambient, new, old)))) 898 899 ret = true; 900 901 return ret; 902 } 903 904 /** 905 * cap_bprm_creds_from_file - Set up the proposed credentials for execve(). 906 * @bprm: The execution parameters, including the proposed creds 907 * @file: The file to pull the credentials from 908 * 909 * Set up the proposed credentials for a new execution context being 910 * constructed by execve(). The proposed creds in @bprm->cred is altered, 911 * which won't take effect immediately. 912 * 913 * Return: 0 if successful, -ve on error. 914 */ 915 int cap_bprm_creds_from_file(struct linux_binprm *bprm, const struct file *file) 916 { 917 /* Process setpcap binaries and capabilities for uid 0 */ 918 const struct cred *old = current_cred(); 919 struct cred *new = bprm->cred; 920 bool effective = false, has_fcap = false, is_setid; 921 int ret; 922 kuid_t root_uid; 923 924 if (WARN_ON(!cap_ambient_invariant_ok(old))) 925 return -EPERM; 926 927 ret = get_file_caps(bprm, file, &effective, &has_fcap); 928 if (ret < 0) 929 return ret; 930 931 root_uid = make_kuid(new->user_ns, 0); 932 933 handle_privileged_root(bprm, has_fcap, &effective, root_uid); 934 935 /* if we have fs caps, clear dangerous personality flags */ 936 if (__cap_gained(permitted, new, old)) 937 bprm->per_clear |= PER_CLEAR_ON_SETID; 938 939 /* Don't let someone trace a set[ug]id/setpcap binary with the revised 940 * credentials unless they have the appropriate permit. 941 * 942 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs. 943 */ 944 is_setid = __is_setuid(new, old) || __is_setgid(new, old); 945 946 if ((is_setid || __cap_gained(permitted, new, old)) && 947 ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) || 948 !ptracer_capable(current, new->user_ns))) { 949 /* downgrade; they get no more than they had, and maybe less */ 950 if (!ns_capable(new->user_ns, CAP_SETUID) || 951 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) { 952 new->euid = new->uid; 953 new->egid = new->gid; 954 } 955 new->cap_permitted = cap_intersect(new->cap_permitted, 956 old->cap_permitted); 957 } 958 959 new->suid = new->fsuid = new->euid; 960 new->sgid = new->fsgid = new->egid; 961 962 /* File caps or setid cancels ambient. */ 963 if (has_fcap || is_setid) 964 cap_clear(new->cap_ambient); 965 966 /* 967 * Now that we've computed pA', update pP' to give: 968 * pP' = (X & fP) | (pI & fI) | pA' 969 */ 970 new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient); 971 972 /* 973 * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set, 974 * this is the same as pE' = (fE ? pP' : 0) | pA'. 975 */ 976 if (effective) 977 new->cap_effective = new->cap_permitted; 978 else 979 new->cap_effective = new->cap_ambient; 980 981 if (WARN_ON(!cap_ambient_invariant_ok(new))) 982 return -EPERM; 983 984 if (nonroot_raised_pE(new, old, root_uid, has_fcap)) { 985 ret = audit_log_bprm_fcaps(bprm, new, old); 986 if (ret < 0) 987 return ret; 988 } 989 990 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 991 992 if (WARN_ON(!cap_ambient_invariant_ok(new))) 993 return -EPERM; 994 995 /* Check for privilege-elevated exec. */ 996 if (is_setid || 997 (!__is_real(root_uid, new) && 998 (effective || 999 __cap_grew(permitted, ambient, new)))) 1000 bprm->secureexec = 1; 1001 1002 return 0; 1003 } 1004 1005 /** 1006 * cap_inode_setxattr - Determine whether an xattr may be altered 1007 * @dentry: The inode/dentry being altered 1008 * @name: The name of the xattr to be changed 1009 * @value: The value that the xattr will be changed to 1010 * @size: The size of value 1011 * @flags: The replacement flag 1012 * 1013 * Determine whether an xattr may be altered or set on an inode, returning 0 if 1014 * permission is granted, -ve if denied. 1015 * 1016 * This is used to make sure security xattrs don't get updated or set by those 1017 * who aren't privileged to do so. 1018 */ 1019 int cap_inode_setxattr(struct dentry *dentry, const char *name, 1020 const void *value, size_t size, int flags) 1021 { 1022 struct user_namespace *user_ns = dentry->d_sb->s_user_ns; 1023 1024 /* Ignore non-security xattrs */ 1025 if (strncmp(name, XATTR_SECURITY_PREFIX, 1026 XATTR_SECURITY_PREFIX_LEN) != 0) 1027 return 0; 1028 1029 /* 1030 * For XATTR_NAME_CAPS the check will be done in 1031 * cap_convert_nscap(), called by setxattr() 1032 */ 1033 if (strcmp(name, XATTR_NAME_CAPS) == 0) 1034 return 0; 1035 1036 if (!ns_capable(user_ns, CAP_SYS_ADMIN)) 1037 return -EPERM; 1038 return 0; 1039 } 1040 1041 /** 1042 * cap_inode_removexattr - Determine whether an xattr may be removed 1043 * 1044 * @idmap: idmap of the mount the inode was found from 1045 * @dentry: The inode/dentry being altered 1046 * @name: The name of the xattr to be changed 1047 * 1048 * Determine whether an xattr may be removed from an inode, returning 0 if 1049 * permission is granted, -ve if denied. 1050 * 1051 * If the inode has been found through an idmapped mount the idmap of 1052 * the vfsmount must be passed through @idmap. This function will then 1053 * take care to map the inode according to @idmap before checking 1054 * permissions. On non-idmapped mounts or if permission checking is to be 1055 * performed on the raw inode simply pass @nop_mnt_idmap. 1056 * 1057 * This is used to make sure security xattrs don't get removed by those who 1058 * aren't privileged to remove them. 1059 */ 1060 int cap_inode_removexattr(struct mnt_idmap *idmap, 1061 struct dentry *dentry, const char *name) 1062 { 1063 struct user_namespace *user_ns = dentry->d_sb->s_user_ns; 1064 1065 /* Ignore non-security xattrs */ 1066 if (strncmp(name, XATTR_SECURITY_PREFIX, 1067 XATTR_SECURITY_PREFIX_LEN) != 0) 1068 return 0; 1069 1070 if (strcmp(name, XATTR_NAME_CAPS) == 0) { 1071 /* security.capability gets namespaced */ 1072 struct inode *inode = d_backing_inode(dentry); 1073 if (!inode) 1074 return -EINVAL; 1075 if (!capable_wrt_inode_uidgid(idmap, inode, CAP_SETFCAP)) 1076 return -EPERM; 1077 return 0; 1078 } 1079 1080 if (!ns_capable(user_ns, CAP_SYS_ADMIN)) 1081 return -EPERM; 1082 return 0; 1083 } 1084 1085 /* 1086 * cap_emulate_setxuid() fixes the effective / permitted capabilities of 1087 * a process after a call to setuid, setreuid, or setresuid. 1088 * 1089 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of 1090 * {r,e,s}uid != 0, the permitted and effective capabilities are 1091 * cleared. 1092 * 1093 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective 1094 * capabilities of the process are cleared. 1095 * 1096 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective 1097 * capabilities are set to the permitted capabilities. 1098 * 1099 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 1100 * never happen. 1101 * 1102 * -astor 1103 * 1104 * cevans - New behaviour, Oct '99 1105 * A process may, via prctl(), elect to keep its capabilities when it 1106 * calls setuid() and switches away from uid==0. Both permitted and 1107 * effective sets will be retained. 1108 * Without this change, it was impossible for a daemon to drop only some 1109 * of its privilege. The call to setuid(!=0) would drop all privileges! 1110 * Keeping uid 0 is not an option because uid 0 owns too many vital 1111 * files.. 1112 * Thanks to Olaf Kirch and Peter Benie for spotting this. 1113 */ 1114 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) 1115 { 1116 kuid_t root_uid = make_kuid(old->user_ns, 0); 1117 1118 if ((uid_eq(old->uid, root_uid) || 1119 uid_eq(old->euid, root_uid) || 1120 uid_eq(old->suid, root_uid)) && 1121 (!uid_eq(new->uid, root_uid) && 1122 !uid_eq(new->euid, root_uid) && 1123 !uid_eq(new->suid, root_uid))) { 1124 if (!issecure(SECURE_KEEP_CAPS)) { 1125 cap_clear(new->cap_permitted); 1126 cap_clear(new->cap_effective); 1127 } 1128 1129 /* 1130 * Pre-ambient programs expect setresuid to nonroot followed 1131 * by exec to drop capabilities. We should make sure that 1132 * this remains the case. 1133 */ 1134 cap_clear(new->cap_ambient); 1135 } 1136 if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid)) 1137 cap_clear(new->cap_effective); 1138 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid)) 1139 new->cap_effective = new->cap_permitted; 1140 } 1141 1142 /** 1143 * cap_task_fix_setuid - Fix up the results of setuid() call 1144 * @new: The proposed credentials 1145 * @old: The current task's current credentials 1146 * @flags: Indications of what has changed 1147 * 1148 * Fix up the results of setuid() call before the credential changes are 1149 * actually applied. 1150 * 1151 * Return: 0 to grant the changes, -ve to deny them. 1152 */ 1153 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) 1154 { 1155 switch (flags) { 1156 case LSM_SETID_RE: 1157 case LSM_SETID_ID: 1158 case LSM_SETID_RES: 1159 /* juggle the capabilities to follow [RES]UID changes unless 1160 * otherwise suppressed */ 1161 if (!issecure(SECURE_NO_SETUID_FIXUP)) 1162 cap_emulate_setxuid(new, old); 1163 break; 1164 1165 case LSM_SETID_FS: 1166 /* juggle the capabilities to follow FSUID changes, unless 1167 * otherwise suppressed 1168 * 1169 * FIXME - is fsuser used for all CAP_FS_MASK capabilities? 1170 * if not, we might be a bit too harsh here. 1171 */ 1172 if (!issecure(SECURE_NO_SETUID_FIXUP)) { 1173 kuid_t root_uid = make_kuid(old->user_ns, 0); 1174 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid)) 1175 new->cap_effective = 1176 cap_drop_fs_set(new->cap_effective); 1177 1178 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid)) 1179 new->cap_effective = 1180 cap_raise_fs_set(new->cap_effective, 1181 new->cap_permitted); 1182 } 1183 break; 1184 1185 default: 1186 return -EINVAL; 1187 } 1188 1189 return 0; 1190 } 1191 1192 /* 1193 * Rationale: code calling task_setscheduler, task_setioprio, and 1194 * task_setnice, assumes that 1195 * . if capable(cap_sys_nice), then those actions should be allowed 1196 * . if not capable(cap_sys_nice), but acting on your own processes, 1197 * then those actions should be allowed 1198 * This is insufficient now since you can call code without suid, but 1199 * yet with increased caps. 1200 * So we check for increased caps on the target process. 1201 */ 1202 static int cap_safe_nice(struct task_struct *p) 1203 { 1204 int is_subset, ret = 0; 1205 1206 rcu_read_lock(); 1207 is_subset = cap_issubset(__task_cred(p)->cap_permitted, 1208 current_cred()->cap_permitted); 1209 if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) 1210 ret = -EPERM; 1211 rcu_read_unlock(); 1212 1213 return ret; 1214 } 1215 1216 /** 1217 * cap_task_setscheduler - Determine if scheduler policy change is permitted 1218 * @p: The task to affect 1219 * 1220 * Determine if the requested scheduler policy change is permitted for the 1221 * specified task. 1222 * 1223 * Return: 0 if permission is granted, -ve if denied. 1224 */ 1225 int cap_task_setscheduler(struct task_struct *p) 1226 { 1227 return cap_safe_nice(p); 1228 } 1229 1230 /** 1231 * cap_task_setioprio - Determine if I/O priority change is permitted 1232 * @p: The task to affect 1233 * @ioprio: The I/O priority to set 1234 * 1235 * Determine if the requested I/O priority change is permitted for the specified 1236 * task. 1237 * 1238 * Return: 0 if permission is granted, -ve if denied. 1239 */ 1240 int cap_task_setioprio(struct task_struct *p, int ioprio) 1241 { 1242 return cap_safe_nice(p); 1243 } 1244 1245 /** 1246 * cap_task_setnice - Determine if task priority change is permitted 1247 * @p: The task to affect 1248 * @nice: The nice value to set 1249 * 1250 * Determine if the requested task priority change is permitted for the 1251 * specified task. 1252 * 1253 * Return: 0 if permission is granted, -ve if denied. 1254 */ 1255 int cap_task_setnice(struct task_struct *p, int nice) 1256 { 1257 return cap_safe_nice(p); 1258 } 1259 1260 /* 1261 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from 1262 * the current task's bounding set. Returns 0 on success, -ve on error. 1263 */ 1264 static int cap_prctl_drop(unsigned long cap) 1265 { 1266 struct cred *new; 1267 1268 if (!ns_capable(current_user_ns(), CAP_SETPCAP)) 1269 return -EPERM; 1270 if (!cap_valid(cap)) 1271 return -EINVAL; 1272 1273 new = prepare_creds(); 1274 if (!new) 1275 return -ENOMEM; 1276 cap_lower(new->cap_bset, cap); 1277 return commit_creds(new); 1278 } 1279 1280 /** 1281 * cap_task_prctl - Implement process control functions for this security module 1282 * @option: The process control function requested 1283 * @arg2: The argument data for this function 1284 * @arg3: The argument data for this function 1285 * @arg4: The argument data for this function 1286 * @arg5: The argument data for this function 1287 * 1288 * Allow process control functions (sys_prctl()) to alter capabilities; may 1289 * also deny access to other functions not otherwise implemented here. 1290 * 1291 * Return: 0 or +ve on success, -ENOSYS if this function is not implemented 1292 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM 1293 * modules will consider performing the function. 1294 */ 1295 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, 1296 unsigned long arg4, unsigned long arg5) 1297 { 1298 const struct cred *old = current_cred(); 1299 struct cred *new; 1300 1301 switch (option) { 1302 case PR_CAPBSET_READ: 1303 if (!cap_valid(arg2)) 1304 return -EINVAL; 1305 return !!cap_raised(old->cap_bset, arg2); 1306 1307 case PR_CAPBSET_DROP: 1308 return cap_prctl_drop(arg2); 1309 1310 /* 1311 * The next four prctl's remain to assist with transitioning a 1312 * system from legacy UID=0 based privilege (when filesystem 1313 * capabilities are not in use) to a system using filesystem 1314 * capabilities only - as the POSIX.1e draft intended. 1315 * 1316 * Note: 1317 * 1318 * PR_SET_SECUREBITS = 1319 * issecure_mask(SECURE_KEEP_CAPS_LOCKED) 1320 * | issecure_mask(SECURE_NOROOT) 1321 * | issecure_mask(SECURE_NOROOT_LOCKED) 1322 * | issecure_mask(SECURE_NO_SETUID_FIXUP) 1323 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) 1324 * 1325 * will ensure that the current process and all of its 1326 * children will be locked into a pure 1327 * capability-based-privilege environment. 1328 */ 1329 case PR_SET_SECUREBITS: 1330 if ((((old->securebits & SECURE_ALL_LOCKS) >> 1) 1331 & (old->securebits ^ arg2)) /*[1]*/ 1332 || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ 1333 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ 1334 /* 1335 * [1] no changing of bits that are locked 1336 * [2] no unlocking of locks 1337 * [3] no setting of unsupported bits 1338 */ 1339 ) 1340 /* cannot change a locked bit */ 1341 return -EPERM; 1342 1343 /* 1344 * Doing anything requires privilege (go read about the 1345 * "sendmail capabilities bug"), except for unprivileged bits. 1346 * Indeed, the SECURE_ALL_UNPRIVILEGED bits are not 1347 * restrictions enforced by the kernel but by user space on 1348 * itself. 1349 */ 1350 if (cap_capable(current_cred(), current_cred()->user_ns, 1351 CAP_SETPCAP, CAP_OPT_NONE) != 0) { 1352 const unsigned long unpriv_and_locks = 1353 SECURE_ALL_UNPRIVILEGED | 1354 SECURE_ALL_UNPRIVILEGED << 1; 1355 const unsigned long changed = old->securebits ^ arg2; 1356 1357 /* For legacy reason, denies non-change. */ 1358 if (!changed) 1359 return -EPERM; 1360 1361 /* Denies privileged changes. */ 1362 if (changed & ~unpriv_and_locks) 1363 return -EPERM; 1364 } 1365 1366 new = prepare_creds(); 1367 if (!new) 1368 return -ENOMEM; 1369 new->securebits = arg2; 1370 return commit_creds(new); 1371 1372 case PR_GET_SECUREBITS: 1373 return old->securebits; 1374 1375 case PR_GET_KEEPCAPS: 1376 return !!issecure(SECURE_KEEP_CAPS); 1377 1378 case PR_SET_KEEPCAPS: 1379 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ 1380 return -EINVAL; 1381 if (issecure(SECURE_KEEP_CAPS_LOCKED)) 1382 return -EPERM; 1383 1384 new = prepare_creds(); 1385 if (!new) 1386 return -ENOMEM; 1387 if (arg2) 1388 new->securebits |= issecure_mask(SECURE_KEEP_CAPS); 1389 else 1390 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 1391 return commit_creds(new); 1392 1393 case PR_CAP_AMBIENT: 1394 if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) { 1395 if (arg3 | arg4 | arg5) 1396 return -EINVAL; 1397 1398 new = prepare_creds(); 1399 if (!new) 1400 return -ENOMEM; 1401 cap_clear(new->cap_ambient); 1402 return commit_creds(new); 1403 } 1404 1405 if (((!cap_valid(arg3)) | arg4 | arg5)) 1406 return -EINVAL; 1407 1408 if (arg2 == PR_CAP_AMBIENT_IS_SET) { 1409 return !!cap_raised(current_cred()->cap_ambient, arg3); 1410 } else if (arg2 != PR_CAP_AMBIENT_RAISE && 1411 arg2 != PR_CAP_AMBIENT_LOWER) { 1412 return -EINVAL; 1413 } else { 1414 if (arg2 == PR_CAP_AMBIENT_RAISE && 1415 (!cap_raised(current_cred()->cap_permitted, arg3) || 1416 !cap_raised(current_cred()->cap_inheritable, 1417 arg3) || 1418 issecure(SECURE_NO_CAP_AMBIENT_RAISE))) 1419 return -EPERM; 1420 1421 new = prepare_creds(); 1422 if (!new) 1423 return -ENOMEM; 1424 if (arg2 == PR_CAP_AMBIENT_RAISE) 1425 cap_raise(new->cap_ambient, arg3); 1426 else 1427 cap_lower(new->cap_ambient, arg3); 1428 return commit_creds(new); 1429 } 1430 1431 default: 1432 /* No functionality available - continue with default */ 1433 return -ENOSYS; 1434 } 1435 } 1436 1437 /** 1438 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted 1439 * @mm: The VM space in which the new mapping is to be made 1440 * @pages: The size of the mapping 1441 * 1442 * Determine whether the allocation of a new virtual mapping by the current 1443 * task is permitted. 1444 * 1445 * Return: 0 if permission granted, negative error code if not. 1446 */ 1447 int cap_vm_enough_memory(struct mm_struct *mm, long pages) 1448 { 1449 return cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN, 1450 CAP_OPT_NOAUDIT); 1451 } 1452 1453 /** 1454 * cap_mmap_addr - check if able to map given addr 1455 * @addr: address attempting to be mapped 1456 * 1457 * If the process is attempting to map memory below dac_mmap_min_addr they need 1458 * CAP_SYS_RAWIO. The other parameters to this function are unused by the 1459 * capability security module. 1460 * 1461 * Return: 0 if this mapping should be allowed or -EPERM if not. 1462 */ 1463 int cap_mmap_addr(unsigned long addr) 1464 { 1465 int ret = 0; 1466 1467 if (addr < dac_mmap_min_addr) { 1468 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO, 1469 CAP_OPT_NONE); 1470 /* set PF_SUPERPRIV if it turns out we allow the low mmap */ 1471 if (ret == 0) 1472 current->flags |= PF_SUPERPRIV; 1473 } 1474 return ret; 1475 } 1476 1477 #ifdef CONFIG_SECURITY 1478 1479 static const struct lsm_id capability_lsmid = { 1480 .name = "capability", 1481 .id = LSM_ID_CAPABILITY, 1482 }; 1483 1484 static struct security_hook_list capability_hooks[] __ro_after_init = { 1485 LSM_HOOK_INIT(capable, cap_capable), 1486 LSM_HOOK_INIT(settime, cap_settime), 1487 LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check), 1488 LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme), 1489 LSM_HOOK_INIT(capget, cap_capget), 1490 LSM_HOOK_INIT(capset, cap_capset), 1491 LSM_HOOK_INIT(bprm_creds_from_file, cap_bprm_creds_from_file), 1492 LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv), 1493 LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv), 1494 LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity), 1495 LSM_HOOK_INIT(mmap_addr, cap_mmap_addr), 1496 LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid), 1497 LSM_HOOK_INIT(task_prctl, cap_task_prctl), 1498 LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler), 1499 LSM_HOOK_INIT(task_setioprio, cap_task_setioprio), 1500 LSM_HOOK_INIT(task_setnice, cap_task_setnice), 1501 LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory), 1502 }; 1503 1504 static int __init capability_init(void) 1505 { 1506 security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks), 1507 &capability_lsmid); 1508 return 0; 1509 } 1510 1511 DEFINE_LSM(capability) = { 1512 .name = "capability", 1513 .order = LSM_ORDER_FIRST, 1514 .init = capability_init, 1515 }; 1516 1517 #endif /* CONFIG_SECURITY */ 1518