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
  28/*
  29 * If a non-root user executes a setuid-root binary in
  30 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
  31 * However if fE is also set, then the intent is for only
  32 * the file capabilities to be applied, and the setuid-root
  33 * bit is left on either to change the uid (plausible) or
  34 * to get full privilege on a kernel without file capabilities
  35 * support.  So in that case we do not raise capabilities.
  36 *
  37 * Warn if that happens, once per boot.
  38 */
  39static void warn_setuid_and_fcaps_mixed(const char *fname)
  40{
  41	static int warned;
  42	if (!warned) {
  43		printk(KERN_INFO "warning: `%s' has both setuid-root and"
  44			" effective capabilities. Therefore not raising all"
  45			" capabilities.\n", fname);
  46		warned = 1;
  47	}
  48}
  49
 
 
 
 
 
  50/**
  51 * cap_capable - Determine whether a task has a particular effective capability
  52 * @cred: The credentials to use
  53 * @targ_ns:  The user namespace in which we need the capability
  54 * @cap: The capability to check for
  55 * @opts: Bitmask of options defined in include/linux/security.h
  56 *
  57 * Determine whether the nominated task has the specified capability amongst
  58 * its effective set, returning 0 if it does, -ve if it does not.
  59 *
  60 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
  61 * and has_capability() functions.  That is, it has the reverse semantics:
  62 * cap_has_capability() returns 0 when a task has a capability, but the
  63 * kernel's capable() and has_capability() returns 1 for this case.
  64 */
  65int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
  66		int cap, unsigned int opts)
  67{
  68	struct user_namespace *ns = targ_ns;
  69
  70	/* See if cred has the capability in the target user namespace
  71	 * by examining the target user namespace and all of the target
  72	 * user namespace's parents.
  73	 */
  74	for (;;) {
  75		/* Do we have the necessary capabilities? */
  76		if (ns == cred->user_ns)
  77			return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
  78
  79		/*
  80		 * If we're already at a lower level than we're looking for,
  81		 * we're done searching.
  82		 */
  83		if (ns->level <= cred->user_ns->level)
  84			return -EPERM;
  85
  86		/* 
  87		 * The owner of the user namespace in the parent of the
  88		 * user namespace has all caps.
  89		 */
  90		if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
  91			return 0;
  92
  93		/*
  94		 * If you have a capability in a parent user ns, then you have
  95		 * it over all children user namespaces as well.
  96		 */
  97		ns = ns->parent;
  98	}
  99
 100	/* We never get here */
 101}
 102
 103/**
 104 * cap_settime - Determine whether the current process may set the system clock
 105 * @ts: The time to set
 106 * @tz: The timezone to set
 107 *
 108 * Determine whether the current process may set the system clock and timezone
 109 * information, returning 0 if permission granted, -ve if denied.
 110 */
 111int cap_settime(const struct timespec64 *ts, const struct timezone *tz)
 112{
 113	if (!capable(CAP_SYS_TIME))
 114		return -EPERM;
 115	return 0;
 116}
 117
 118/**
 119 * cap_ptrace_access_check - Determine whether the current process may access
 120 *			   another
 121 * @child: The process to be accessed
 122 * @mode: The mode of attachment.
 123 *
 124 * If we are in the same or an ancestor user_ns and have all the target
 125 * task's capabilities, then ptrace access is allowed.
 126 * If we have the ptrace capability to the target user_ns, then ptrace
 127 * access is allowed.
 128 * Else denied.
 129 *
 130 * Determine whether a process may access another, returning 0 if permission
 131 * granted, -ve if denied.
 132 */
 133int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
 134{
 135	int ret = 0;
 136	const struct cred *cred, *child_cred;
 137	const kernel_cap_t *caller_caps;
 138
 139	rcu_read_lock();
 140	cred = current_cred();
 141	child_cred = __task_cred(child);
 142	if (mode & PTRACE_MODE_FSCREDS)
 143		caller_caps = &cred->cap_effective;
 144	else
 145		caller_caps = &cred->cap_permitted;
 146	if (cred->user_ns == child_cred->user_ns &&
 147	    cap_issubset(child_cred->cap_permitted, *caller_caps))
 148		goto out;
 149	if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
 150		goto out;
 151	ret = -EPERM;
 152out:
 153	rcu_read_unlock();
 154	return ret;
 155}
 156
 157/**
 158 * cap_ptrace_traceme - Determine whether another process may trace the current
 159 * @parent: The task proposed to be the tracer
 160 *
 161 * If parent is in the same or an ancestor user_ns and has all current's
 162 * capabilities, then ptrace access is allowed.
 163 * If parent has the ptrace capability to current's user_ns, then ptrace
 164 * access is allowed.
 165 * Else denied.
 166 *
 167 * Determine whether the nominated task is permitted to trace the current
 168 * process, returning 0 if permission is granted, -ve if denied.
 169 */
 170int cap_ptrace_traceme(struct task_struct *parent)
 171{
 172	int ret = 0;
 173	const struct cred *cred, *child_cred;
 174
 175	rcu_read_lock();
 176	cred = __task_cred(parent);
 177	child_cred = current_cred();
 178	if (cred->user_ns == child_cred->user_ns &&
 179	    cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
 180		goto out;
 181	if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
 182		goto out;
 183	ret = -EPERM;
 184out:
 185	rcu_read_unlock();
 186	return ret;
 187}
 188
 189/**
 190 * cap_capget - Retrieve a task's capability sets
 191 * @target: The task from which to retrieve the capability sets
 192 * @effective: The place to record the effective set
 193 * @inheritable: The place to record the inheritable set
 194 * @permitted: The place to record the permitted set
 195 *
 196 * This function retrieves the capabilities of the nominated task and returns
 197 * them to the caller.
 198 */
 199int cap_capget(struct task_struct *target, kernel_cap_t *effective,
 200	       kernel_cap_t *inheritable, kernel_cap_t *permitted)
 201{
 202	const struct cred *cred;
 203
 204	/* Derived from kernel/capability.c:sys_capget. */
 205	rcu_read_lock();
 206	cred = __task_cred(target);
 207	*effective   = cred->cap_effective;
 208	*inheritable = cred->cap_inheritable;
 209	*permitted   = cred->cap_permitted;
 210	rcu_read_unlock();
 211	return 0;
 212}
 213
 214/*
 215 * Determine whether the inheritable capabilities are limited to the old
 216 * permitted set.  Returns 1 if they are limited, 0 if they are not.
 217 */
 218static inline int cap_inh_is_capped(void)
 219{
 
 220	/* they are so limited unless the current task has the CAP_SETPCAP
 221	 * capability
 222	 */
 223	if (cap_capable(current_cred(), current_cred()->user_ns,
 224			CAP_SETPCAP, CAP_OPT_NONE) == 0)
 225		return 0;
 226	return 1;
 227}
 228
 229/**
 230 * cap_capset - Validate and apply proposed changes to current's capabilities
 231 * @new: The proposed new credentials; alterations should be made here
 232 * @old: The current task's current credentials
 233 * @effective: A pointer to the proposed new effective capabilities set
 234 * @inheritable: A pointer to the proposed new inheritable capabilities set
 235 * @permitted: A pointer to the proposed new permitted capabilities set
 236 *
 237 * This function validates and applies a proposed mass change to the current
 238 * process's capability sets.  The changes are made to the proposed new
 239 * credentials, and assuming no error, will be committed by the caller of LSM.
 240 */
 241int cap_capset(struct cred *new,
 242	       const struct cred *old,
 243	       const kernel_cap_t *effective,
 244	       const kernel_cap_t *inheritable,
 245	       const kernel_cap_t *permitted)
 246{
 247	if (cap_inh_is_capped() &&
 248	    !cap_issubset(*inheritable,
 249			  cap_combine(old->cap_inheritable,
 250				      old->cap_permitted)))
 251		/* incapable of using this inheritable set */
 252		return -EPERM;
 253
 254	if (!cap_issubset(*inheritable,
 255			  cap_combine(old->cap_inheritable,
 256				      old->cap_bset)))
 257		/* no new pI capabilities outside bounding set */
 258		return -EPERM;
 259
 260	/* verify restrictions on target's new Permitted set */
 261	if (!cap_issubset(*permitted, old->cap_permitted))
 262		return -EPERM;
 263
 264	/* verify the _new_Effective_ is a subset of the _new_Permitted_ */
 265	if (!cap_issubset(*effective, *permitted))
 266		return -EPERM;
 267
 268	new->cap_effective   = *effective;
 269	new->cap_inheritable = *inheritable;
 270	new->cap_permitted   = *permitted;
 271
 272	/*
 273	 * Mask off ambient bits that are no longer both permitted and
 274	 * inheritable.
 275	 */
 276	new->cap_ambient = cap_intersect(new->cap_ambient,
 277					 cap_intersect(*permitted,
 278						       *inheritable));
 279	if (WARN_ON(!cap_ambient_invariant_ok(new)))
 280		return -EINVAL;
 281	return 0;
 282}
 283
 
 
 
 
 
 
 
 
 
 284/**
 285 * cap_inode_need_killpriv - Determine if inode change affects privileges
 286 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
 287 *
 288 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
 289 * affects the security markings on that inode, and if it is, should
 290 * inode_killpriv() be invoked or the change rejected.
 291 *
 292 * Return: 1 if security.capability has a value, meaning inode_killpriv()
 293 * is required, 0 otherwise, meaning inode_killpriv() is not required.
 294 */
 295int cap_inode_need_killpriv(struct dentry *dentry)
 296{
 297	struct inode *inode = d_backing_inode(dentry);
 298	int error;
 299
 300	error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0);
 301	return error > 0;
 
 
 
 
 
 302}
 303
 304/**
 305 * cap_inode_killpriv - Erase the security markings on an inode
 306 *
 307 * @mnt_userns:	user namespace of the mount the inode was found from
 308 * @dentry:	The inode/dentry to alter
 309 *
 310 * Erase the privilege-enhancing security markings on an inode.
 311 *
 312 * If the inode has been found through an idmapped mount the user namespace of
 313 * the vfsmount must be passed through @mnt_userns. This function will then
 314 * take care to map the inode according to @mnt_userns before checking
 315 * permissions. On non-idmapped mounts or if permission checking is to be
 316 * performed on the raw inode simply passs init_user_ns.
 317 *
 318 * Return: 0 if successful, -ve on error.
 319 */
 320int cap_inode_killpriv(struct user_namespace *mnt_userns, struct dentry *dentry)
 321{
 322	int error;
 323
 324	error = __vfs_removexattr(mnt_userns, dentry, XATTR_NAME_CAPS);
 325	if (error == -EOPNOTSUPP)
 326		error = 0;
 327	return error;
 328}
 329
 330static bool rootid_owns_currentns(kuid_t kroot)
 331{
 332	struct user_namespace *ns;
 333
 334	if (!uid_valid(kroot))
 335		return false;
 336
 337	for (ns = current_user_ns(); ; ns = ns->parent) {
 338		if (from_kuid(ns, kroot) == 0)
 339			return true;
 340		if (ns == &init_user_ns)
 341			break;
 342	}
 343
 344	return false;
 345}
 346
 347static __u32 sansflags(__u32 m)
 348{
 349	return m & ~VFS_CAP_FLAGS_EFFECTIVE;
 350}
 351
 352static bool is_v2header(size_t size, const struct vfs_cap_data *cap)
 353{
 354	if (size != XATTR_CAPS_SZ_2)
 355		return false;
 356	return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_2;
 357}
 358
 359static bool is_v3header(size_t size, const struct vfs_cap_data *cap)
 360{
 361	if (size != XATTR_CAPS_SZ_3)
 362		return false;
 363	return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_3;
 364}
 365
 366/*
 367 * getsecurity: We are called for security.* before any attempt to read the
 368 * xattr from the inode itself.
 369 *
 370 * This gives us a chance to read the on-disk value and convert it.  If we
 371 * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler.
 372 *
 373 * Note we are not called by vfs_getxattr_alloc(), but that is only called
 374 * by the integrity subsystem, which really wants the unconverted values -
 375 * so that's good.
 376 */
 377int cap_inode_getsecurity(struct user_namespace *mnt_userns,
 378			  struct inode *inode, const char *name, void **buffer,
 379			  bool alloc)
 380{
 381	int size, ret;
 382	kuid_t kroot;
 383	u32 nsmagic, magic;
 384	uid_t root, mappedroot;
 385	char *tmpbuf = NULL;
 386	struct vfs_cap_data *cap;
 387	struct vfs_ns_cap_data *nscap = NULL;
 388	struct dentry *dentry;
 389	struct user_namespace *fs_ns;
 390
 391	if (strcmp(name, "capability") != 0)
 392		return -EOPNOTSUPP;
 393
 394	dentry = d_find_any_alias(inode);
 395	if (!dentry)
 396		return -EINVAL;
 397
 398	size = sizeof(struct vfs_ns_cap_data);
 399	ret = (int)vfs_getxattr_alloc(mnt_userns, dentry, XATTR_NAME_CAPS,
 400				      &tmpbuf, size, GFP_NOFS);
 401	dput(dentry);
 402
 403	if (ret < 0 || !tmpbuf)
 404		return ret;
 405
 406	fs_ns = inode->i_sb->s_user_ns;
 407	cap = (struct vfs_cap_data *) tmpbuf;
 408	if (is_v2header((size_t) ret, cap)) {
 409		root = 0;
 410	} else if (is_v3header((size_t) ret, cap)) {
 411		nscap = (struct vfs_ns_cap_data *) tmpbuf;
 412		root = le32_to_cpu(nscap->rootid);
 413	} else {
 414		size = -EINVAL;
 415		goto out_free;
 416	}
 417
 418	kroot = make_kuid(fs_ns, root);
 419
 420	/* If this is an idmapped mount shift the kuid. */
 421	kroot = kuid_into_mnt(mnt_userns, kroot);
 422
 423	/* If the root kuid maps to a valid uid in current ns, then return
 424	 * this as a nscap. */
 425	mappedroot = from_kuid(current_user_ns(), kroot);
 426	if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) {
 427		size = sizeof(struct vfs_ns_cap_data);
 428		if (alloc) {
 429			if (!nscap) {
 430				/* v2 -> v3 conversion */
 431				nscap = kzalloc(size, GFP_ATOMIC);
 432				if (!nscap) {
 433					size = -ENOMEM;
 434					goto out_free;
 435				}
 436				nsmagic = VFS_CAP_REVISION_3;
 437				magic = le32_to_cpu(cap->magic_etc);
 438				if (magic & VFS_CAP_FLAGS_EFFECTIVE)
 439					nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
 440				memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
 441				nscap->magic_etc = cpu_to_le32(nsmagic);
 442			} else {
 443				/* use allocated v3 buffer */
 444				tmpbuf = NULL;
 445			}
 446			nscap->rootid = cpu_to_le32(mappedroot);
 447			*buffer = nscap;
 448		}
 449		goto out_free;
 450	}
 451
 452	if (!rootid_owns_currentns(kroot)) {
 453		size = -EOVERFLOW;
 454		goto out_free;
 455	}
 456
 457	/* This comes from a parent namespace.  Return as a v2 capability */
 458	size = sizeof(struct vfs_cap_data);
 459	if (alloc) {
 460		if (nscap) {
 461			/* v3 -> v2 conversion */
 462			cap = kzalloc(size, GFP_ATOMIC);
 463			if (!cap) {
 464				size = -ENOMEM;
 465				goto out_free;
 466			}
 467			magic = VFS_CAP_REVISION_2;
 468			nsmagic = le32_to_cpu(nscap->magic_etc);
 469			if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE)
 470				magic |= VFS_CAP_FLAGS_EFFECTIVE;
 471			memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
 472			cap->magic_etc = cpu_to_le32(magic);
 473		} else {
 474			/* use unconverted v2 */
 475			tmpbuf = NULL;
 476		}
 477		*buffer = cap;
 478	}
 479out_free:
 480	kfree(tmpbuf);
 481	return size;
 482}
 483
 484/**
 485 * rootid_from_xattr - translate root uid of vfs caps
 486 *
 487 * @value:	vfs caps value which may be modified by this function
 488 * @size:	size of @ivalue
 489 * @task_ns:	user namespace of the caller
 490 * @mnt_userns:	user namespace of the mount the inode was found from
 491 *
 492 * If the inode has been found through an idmapped mount the user namespace of
 493 * the vfsmount must be passed through @mnt_userns. This function will then
 494 * take care to map the inode according to @mnt_userns before checking
 495 * permissions. On non-idmapped mounts or if permission checking is to be
 496 * performed on the raw inode simply passs init_user_ns.
 497 */
 498static kuid_t rootid_from_xattr(const void *value, size_t size,
 499				struct user_namespace *task_ns,
 500				struct user_namespace *mnt_userns)
 501{
 502	const struct vfs_ns_cap_data *nscap = value;
 503	kuid_t rootkid;
 504	uid_t rootid = 0;
 505
 506	if (size == XATTR_CAPS_SZ_3)
 507		rootid = le32_to_cpu(nscap->rootid);
 508
 509	rootkid = make_kuid(task_ns, rootid);
 510	return kuid_from_mnt(mnt_userns, rootkid);
 511}
 512
 513static bool validheader(size_t size, const struct vfs_cap_data *cap)
 514{
 515	return is_v2header(size, cap) || is_v3header(size, cap);
 516}
 517
 518/**
 519 * cap_convert_nscap - check vfs caps
 520 *
 521 * @mnt_userns:	user namespace of the mount the inode was found from
 522 * @dentry:	used to retrieve inode to check permissions on
 523 * @ivalue:	vfs caps value which may be modified by this function
 524 * @size:	size of @ivalue
 525 *
 526 * User requested a write of security.capability.  If needed, update the
 527 * xattr to change from v2 to v3, or to fixup the v3 rootid.
 528 *
 529 * If the inode has been found through an idmapped mount the user namespace of
 530 * the vfsmount must be passed through @mnt_userns. This function will then
 531 * take care to map the inode according to @mnt_userns before checking
 532 * permissions. On non-idmapped mounts or if permission checking is to be
 533 * performed on the raw inode simply passs init_user_ns.
 534 *
 535 * Return: On success, return the new size; on error, return < 0.
 536 */
 537int cap_convert_nscap(struct user_namespace *mnt_userns, struct dentry *dentry,
 538		      const void **ivalue, size_t size)
 539{
 540	struct vfs_ns_cap_data *nscap;
 541	uid_t nsrootid;
 542	const struct vfs_cap_data *cap = *ivalue;
 543	__u32 magic, nsmagic;
 544	struct inode *inode = d_backing_inode(dentry);
 545	struct user_namespace *task_ns = current_user_ns(),
 546		*fs_ns = inode->i_sb->s_user_ns;
 547	kuid_t rootid;
 548	size_t newsize;
 549
 550	if (!*ivalue)
 551		return -EINVAL;
 552	if (!validheader(size, cap))
 553		return -EINVAL;
 554	if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP))
 555		return -EPERM;
 556	if (size == XATTR_CAPS_SZ_2 && (mnt_userns == &init_user_ns))
 557		if (ns_capable(inode->i_sb->s_user_ns, CAP_SETFCAP))
 558			/* user is privileged, just write the v2 */
 559			return size;
 560
 561	rootid = rootid_from_xattr(*ivalue, size, task_ns, mnt_userns);
 562	if (!uid_valid(rootid))
 563		return -EINVAL;
 564
 565	nsrootid = from_kuid(fs_ns, rootid);
 566	if (nsrootid == -1)
 567		return -EINVAL;
 568
 569	newsize = sizeof(struct vfs_ns_cap_data);
 570	nscap = kmalloc(newsize, GFP_ATOMIC);
 571	if (!nscap)
 572		return -ENOMEM;
 573	nscap->rootid = cpu_to_le32(nsrootid);
 574	nsmagic = VFS_CAP_REVISION_3;
 575	magic = le32_to_cpu(cap->magic_etc);
 576	if (magic & VFS_CAP_FLAGS_EFFECTIVE)
 577		nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
 578	nscap->magic_etc = cpu_to_le32(nsmagic);
 579	memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
 580
 581	*ivalue = nscap;
 582	return newsize;
 583}
 584
 585/*
 586 * Calculate the new process capability sets from the capability sets attached
 587 * to a file.
 588 */
 589static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
 590					  struct linux_binprm *bprm,
 591					  bool *effective,
 592					  bool *has_fcap)
 593{
 594	struct cred *new = bprm->cred;
 595	unsigned i;
 596	int ret = 0;
 597
 598	if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
 599		*effective = true;
 600
 601	if (caps->magic_etc & VFS_CAP_REVISION_MASK)
 602		*has_fcap = true;
 603
 604	CAP_FOR_EACH_U32(i) {
 605		__u32 permitted = caps->permitted.cap[i];
 606		__u32 inheritable = caps->inheritable.cap[i];
 607
 608		/*
 609		 * pP' = (X & fP) | (pI & fI)
 610		 * The addition of pA' is handled later.
 611		 */
 612		new->cap_permitted.cap[i] =
 613			(new->cap_bset.cap[i] & permitted) |
 614			(new->cap_inheritable.cap[i] & inheritable);
 615
 616		if (permitted & ~new->cap_permitted.cap[i])
 617			/* insufficient to execute correctly */
 618			ret = -EPERM;
 619	}
 620
 621	/*
 622	 * For legacy apps, with no internal support for recognizing they
 623	 * do not have enough capabilities, we return an error if they are
 624	 * missing some "forced" (aka file-permitted) capabilities.
 625	 */
 626	return *effective ? ret : 0;
 627}
 628
 629/**
 630 * get_vfs_caps_from_disk - retrieve vfs caps from disk
 631 *
 632 * @mnt_userns:	user namespace of the mount the inode was found from
 633 * @dentry:	dentry from which @inode is retrieved
 634 * @cpu_caps:	vfs capabilities
 635 *
 636 * Extract the on-exec-apply capability sets for an executable file.
 637 *
 638 * If the inode has been found through an idmapped mount the user namespace of
 639 * the vfsmount must be passed through @mnt_userns. This function will then
 640 * take care to map the inode according to @mnt_userns before checking
 641 * permissions. On non-idmapped mounts or if permission checking is to be
 642 * performed on the raw inode simply passs init_user_ns.
 643 */
 644int get_vfs_caps_from_disk(struct user_namespace *mnt_userns,
 645			   const struct dentry *dentry,
 646			   struct cpu_vfs_cap_data *cpu_caps)
 647{
 648	struct inode *inode = d_backing_inode(dentry);
 649	__u32 magic_etc;
 650	unsigned tocopy, i;
 651	int size;
 652	struct vfs_ns_cap_data data, *nscaps = &data;
 653	struct vfs_cap_data *caps = (struct vfs_cap_data *) &data;
 654	kuid_t rootkuid;
 655	struct user_namespace *fs_ns;
 656
 657	memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
 658
 659	if (!inode)
 660		return -ENODATA;
 661
 662	fs_ns = inode->i_sb->s_user_ns;
 663	size = __vfs_getxattr((struct dentry *)dentry, inode,
 664			      XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ);
 665	if (size == -ENODATA || size == -EOPNOTSUPP)
 666		/* no data, that's ok */
 667		return -ENODATA;
 668
 669	if (size < 0)
 670		return size;
 671
 672	if (size < sizeof(magic_etc))
 673		return -EINVAL;
 674
 675	cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps->magic_etc);
 676
 677	rootkuid = make_kuid(fs_ns, 0);
 678	switch (magic_etc & VFS_CAP_REVISION_MASK) {
 679	case VFS_CAP_REVISION_1:
 680		if (size != XATTR_CAPS_SZ_1)
 681			return -EINVAL;
 682		tocopy = VFS_CAP_U32_1;
 683		break;
 684	case VFS_CAP_REVISION_2:
 685		if (size != XATTR_CAPS_SZ_2)
 686			return -EINVAL;
 687		tocopy = VFS_CAP_U32_2;
 688		break;
 689	case VFS_CAP_REVISION_3:
 690		if (size != XATTR_CAPS_SZ_3)
 691			return -EINVAL;
 692		tocopy = VFS_CAP_U32_3;
 693		rootkuid = make_kuid(fs_ns, le32_to_cpu(nscaps->rootid));
 694		break;
 695
 696	default:
 697		return -EINVAL;
 698	}
 699	/* Limit the caps to the mounter of the filesystem
 700	 * or the more limited uid specified in the xattr.
 701	 */
 702	rootkuid = kuid_into_mnt(mnt_userns, rootkuid);
 703	if (!rootid_owns_currentns(rootkuid))
 704		return -ENODATA;
 705
 706	CAP_FOR_EACH_U32(i) {
 707		if (i >= tocopy)
 708			break;
 709		cpu_caps->permitted.cap[i] = le32_to_cpu(caps->data[i].permitted);
 710		cpu_caps->inheritable.cap[i] = le32_to_cpu(caps->data[i].inheritable);
 711	}
 712
 713	cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
 714	cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
 715
 716	cpu_caps->rootid = rootkuid;
 717
 718	return 0;
 719}
 720
 721/*
 722 * Attempt to get the on-exec apply capability sets for an executable file from
 723 * its xattrs and, if present, apply them to the proposed credentials being
 724 * constructed by execve().
 725 */
 726static int get_file_caps(struct linux_binprm *bprm, struct file *file,
 727			 bool *effective, bool *has_fcap)
 728{
 
 729	int rc = 0;
 730	struct cpu_vfs_cap_data vcaps;
 731
 732	cap_clear(bprm->cred->cap_permitted);
 733
 734	if (!file_caps_enabled)
 735		return 0;
 736
 737	if (!mnt_may_suid(file->f_path.mnt))
 738		return 0;
 739
 740	/*
 741	 * This check is redundant with mnt_may_suid() but is kept to make
 742	 * explicit that capability bits are limited to s_user_ns and its
 743	 * descendants.
 744	 */
 745	if (!current_in_userns(file->f_path.mnt->mnt_sb->s_user_ns))
 746		return 0;
 747
 748	rc = get_vfs_caps_from_disk(file_mnt_user_ns(file),
 749				    file->f_path.dentry, &vcaps);
 750	if (rc < 0) {
 751		if (rc == -EINVAL)
 752			printk(KERN_NOTICE "Invalid argument reading file caps for %s\n",
 753					bprm->filename);
 754		else if (rc == -ENODATA)
 755			rc = 0;
 756		goto out;
 757	}
 758
 759	rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_fcap);
 
 
 
 760
 761out:
 
 762	if (rc)
 763		cap_clear(bprm->cred->cap_permitted);
 764
 765	return rc;
 766}
 767
 768static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); }
 769
 770static inline bool __is_real(kuid_t uid, struct cred *cred)
 771{ return uid_eq(cred->uid, uid); }
 772
 773static inline bool __is_eff(kuid_t uid, struct cred *cred)
 774{ return uid_eq(cred->euid, uid); }
 775
 776static inline bool __is_suid(kuid_t uid, struct cred *cred)
 777{ return !__is_real(uid, cred) && __is_eff(uid, cred); }
 778
 779/*
 780 * handle_privileged_root - Handle case of privileged root
 781 * @bprm: The execution parameters, including the proposed creds
 782 * @has_fcap: Are any file capabilities set?
 783 * @effective: Do we have effective root privilege?
 784 * @root_uid: This namespace' root UID WRT initial USER namespace
 785 *
 786 * Handle the case where root is privileged and hasn't been neutered by
 787 * SECURE_NOROOT.  If file capabilities are set, they won't be combined with
 788 * set UID root and nothing is changed.  If we are root, cap_permitted is
 789 * updated.  If we have become set UID root, the effective bit is set.
 790 */
 791static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap,
 792				   bool *effective, kuid_t root_uid)
 793{
 794	const struct cred *old = current_cred();
 795	struct cred *new = bprm->cred;
 796
 797	if (!root_privileged())
 798		return;
 799	/*
 800	 * If the legacy file capability is set, then don't set privs
 801	 * for a setuid root binary run by a non-root user.  Do set it
 802	 * for a root user just to cause least surprise to an admin.
 803	 */
 804	if (has_fcap && __is_suid(root_uid, new)) {
 805		warn_setuid_and_fcaps_mixed(bprm->filename);
 806		return;
 807	}
 808	/*
 809	 * To support inheritance of root-permissions and suid-root
 810	 * executables under compatibility mode, we override the
 811	 * capability sets for the file.
 812	 */
 813	if (__is_eff(root_uid, new) || __is_real(root_uid, new)) {
 814		/* pP' = (cap_bset & ~0) | (pI & ~0) */
 815		new->cap_permitted = cap_combine(old->cap_bset,
 816						 old->cap_inheritable);
 817	}
 818	/*
 819	 * If only the real uid is 0, we do not set the effective bit.
 820	 */
 821	if (__is_eff(root_uid, new))
 822		*effective = true;
 823}
 824
 825#define __cap_gained(field, target, source) \
 826	!cap_issubset(target->cap_##field, source->cap_##field)
 827#define __cap_grew(target, source, cred) \
 828	!cap_issubset(cred->cap_##target, cred->cap_##source)
 829#define __cap_full(field, cred) \
 830	cap_issubset(CAP_FULL_SET, cred->cap_##field)
 831
 832static inline bool __is_setuid(struct cred *new, const struct cred *old)
 833{ return !uid_eq(new->euid, old->uid); }
 834
 835static inline bool __is_setgid(struct cred *new, const struct cred *old)
 836{ return !gid_eq(new->egid, old->gid); }
 837
 838/*
 839 * 1) Audit candidate if current->cap_effective is set
 840 *
 841 * We do not bother to audit if 3 things are true:
 842 *   1) cap_effective has all caps
 843 *   2) we became root *OR* are were already root
 844 *   3) root is supposed to have all caps (SECURE_NOROOT)
 845 * Since this is just a normal root execing a process.
 846 *
 847 * Number 1 above might fail if you don't have a full bset, but I think
 848 * that is interesting information to audit.
 849 *
 850 * A number of other conditions require logging:
 851 * 2) something prevented setuid root getting all caps
 852 * 3) non-setuid root gets fcaps
 853 * 4) non-setuid root gets ambient
 854 */
 855static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old,
 856				     kuid_t root, bool has_fcap)
 857{
 858	bool ret = false;
 859
 860	if ((__cap_grew(effective, ambient, new) &&
 861	     !(__cap_full(effective, new) &&
 862	       (__is_eff(root, new) || __is_real(root, new)) &&
 863	       root_privileged())) ||
 864	    (root_privileged() &&
 865	     __is_suid(root, new) &&
 866	     !__cap_full(effective, new)) ||
 867	    (!__is_setuid(new, old) &&
 868	     ((has_fcap &&
 869	       __cap_gained(permitted, new, old)) ||
 870	      __cap_gained(ambient, new, old))))
 871
 872		ret = true;
 873
 874	return ret;
 875}
 876
 877/**
 878 * cap_bprm_creds_from_file - Set up the proposed credentials for execve().
 879 * @bprm: The execution parameters, including the proposed creds
 880 * @file: The file to pull the credentials from
 881 *
 882 * Set up the proposed credentials for a new execution context being
 883 * constructed by execve().  The proposed creds in @bprm->cred is altered,
 884 * which won't take effect immediately.
 885 *
 886 * Return: 0 if successful, -ve on error.
 887 */
 888int cap_bprm_creds_from_file(struct linux_binprm *bprm, struct file *file)
 889{
 890	/* Process setpcap binaries and capabilities for uid 0 */
 891	const struct cred *old = current_cred();
 892	struct cred *new = bprm->cred;
 893	bool effective = false, has_fcap = false, is_setid;
 894	int ret;
 895	kuid_t root_uid;
 896
 897	if (WARN_ON(!cap_ambient_invariant_ok(old)))
 898		return -EPERM;
 899
 900	ret = get_file_caps(bprm, file, &effective, &has_fcap);
 901	if (ret < 0)
 902		return ret;
 903
 904	root_uid = make_kuid(new->user_ns, 0);
 905
 906	handle_privileged_root(bprm, has_fcap, &effective, root_uid);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 907
 908	/* if we have fs caps, clear dangerous personality flags */
 909	if (__cap_gained(permitted, new, old))
 910		bprm->per_clear |= PER_CLEAR_ON_SETID;
 911
 
 912	/* Don't let someone trace a set[ug]id/setpcap binary with the revised
 913	 * credentials unless they have the appropriate permit.
 914	 *
 915	 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
 916	 */
 917	is_setid = __is_setuid(new, old) || __is_setgid(new, old);
 918
 919	if ((is_setid || __cap_gained(permitted, new, old)) &&
 920	    ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) ||
 921	     !ptracer_capable(current, new->user_ns))) {
 922		/* downgrade; they get no more than they had, and maybe less */
 923		if (!ns_capable(new->user_ns, CAP_SETUID) ||
 924		    (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
 925			new->euid = new->uid;
 926			new->egid = new->gid;
 927		}
 928		new->cap_permitted = cap_intersect(new->cap_permitted,
 929						   old->cap_permitted);
 930	}
 931
 932	new->suid = new->fsuid = new->euid;
 933	new->sgid = new->fsgid = new->egid;
 934
 935	/* File caps or setid cancels ambient. */
 936	if (has_fcap || is_setid)
 937		cap_clear(new->cap_ambient);
 938
 939	/*
 940	 * Now that we've computed pA', update pP' to give:
 941	 *   pP' = (X & fP) | (pI & fI) | pA'
 942	 */
 943	new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
 944
 945	/*
 946	 * Set pE' = (fE ? pP' : pA').  Because pA' is zero if fE is set,
 947	 * this is the same as pE' = (fE ? pP' : 0) | pA'.
 948	 */
 949	if (effective)
 950		new->cap_effective = new->cap_permitted;
 951	else
 952		new->cap_effective = new->cap_ambient;
 953
 954	if (WARN_ON(!cap_ambient_invariant_ok(new)))
 955		return -EPERM;
 956
 957	if (nonroot_raised_pE(new, old, root_uid, has_fcap)) {
 958		ret = audit_log_bprm_fcaps(bprm, new, old);
 959		if (ret < 0)
 960			return ret;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 961	}
 962
 963	new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
 
 
 964
 965	if (WARN_ON(!cap_ambient_invariant_ok(new)))
 966		return -EPERM;
 
 
 
 
 
 
 
 
 
 
 
 
 967
 968	/* Check for privilege-elevated exec. */
 969	if (is_setid ||
 970	    (!__is_real(root_uid, new) &&
 971	     (effective ||
 972	      __cap_grew(permitted, ambient, new))))
 973		bprm->secureexec = 1;
 974
 975	return 0;
 
 976}
 977
 978/**
 979 * cap_inode_setxattr - Determine whether an xattr may be altered
 980 * @dentry: The inode/dentry being altered
 981 * @name: The name of the xattr to be changed
 982 * @value: The value that the xattr will be changed to
 983 * @size: The size of value
 984 * @flags: The replacement flag
 985 *
 986 * Determine whether an xattr may be altered or set on an inode, returning 0 if
 987 * permission is granted, -ve if denied.
 988 *
 989 * This is used to make sure security xattrs don't get updated or set by those
 990 * who aren't privileged to do so.
 991 */
 992int cap_inode_setxattr(struct dentry *dentry, const char *name,
 993		       const void *value, size_t size, int flags)
 994{
 995	struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
 996
 997	/* Ignore non-security xattrs */
 998	if (strncmp(name, XATTR_SECURITY_PREFIX,
 999			XATTR_SECURITY_PREFIX_LEN) != 0)
1000		return 0;
1001
1002	/*
1003	 * For XATTR_NAME_CAPS the check will be done in
1004	 * cap_convert_nscap(), called by setxattr()
1005	 */
1006	if (strcmp(name, XATTR_NAME_CAPS) == 0)
1007		return 0;
 
1008
1009	if (!ns_capable(user_ns, CAP_SYS_ADMIN))
 
 
1010		return -EPERM;
1011	return 0;
1012}
1013
1014/**
1015 * cap_inode_removexattr - Determine whether an xattr may be removed
1016 *
1017 * @mnt_userns:	User namespace of the mount the inode was found from
1018 * @dentry:	The inode/dentry being altered
1019 * @name:	The name of the xattr to be changed
1020 *
1021 * Determine whether an xattr may be removed from an inode, returning 0 if
1022 * permission is granted, -ve if denied.
1023 *
1024 * If the inode has been found through an idmapped mount the user namespace of
1025 * the vfsmount must be passed through @mnt_userns. This function will then
1026 * take care to map the inode according to @mnt_userns before checking
1027 * permissions. On non-idmapped mounts or if permission checking is to be
1028 * performed on the raw inode simply passs init_user_ns.
1029 *
1030 * This is used to make sure security xattrs don't get removed by those who
1031 * aren't privileged to remove them.
1032 */
1033int cap_inode_removexattr(struct user_namespace *mnt_userns,
1034			  struct dentry *dentry, const char *name)
1035{
1036	struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
1037
1038	/* Ignore non-security xattrs */
1039	if (strncmp(name, XATTR_SECURITY_PREFIX,
1040			XATTR_SECURITY_PREFIX_LEN) != 0)
1041		return 0;
1042
1043	if (strcmp(name, XATTR_NAME_CAPS) == 0) {
1044		/* security.capability gets namespaced */
1045		struct inode *inode = d_backing_inode(dentry);
1046		if (!inode)
1047			return -EINVAL;
1048		if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP))
1049			return -EPERM;
1050		return 0;
1051	}
1052
1053	if (!ns_capable(user_ns, CAP_SYS_ADMIN))
 
 
1054		return -EPERM;
1055	return 0;
1056}
1057
1058/*
1059 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
1060 * a process after a call to setuid, setreuid, or setresuid.
1061 *
1062 *  1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
1063 *  {r,e,s}uid != 0, the permitted and effective capabilities are
1064 *  cleared.
1065 *
1066 *  2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
1067 *  capabilities of the process are cleared.
1068 *
1069 *  3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
1070 *  capabilities are set to the permitted capabilities.
1071 *
1072 *  fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
1073 *  never happen.
1074 *
1075 *  -astor
1076 *
1077 * cevans - New behaviour, Oct '99
1078 * A process may, via prctl(), elect to keep its capabilities when it
1079 * calls setuid() and switches away from uid==0. Both permitted and
1080 * effective sets will be retained.
1081 * Without this change, it was impossible for a daemon to drop only some
1082 * of its privilege. The call to setuid(!=0) would drop all privileges!
1083 * Keeping uid 0 is not an option because uid 0 owns too many vital
1084 * files..
1085 * Thanks to Olaf Kirch and Peter Benie for spotting this.
1086 */
1087static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
1088{
1089	kuid_t root_uid = make_kuid(old->user_ns, 0);
1090
1091	if ((uid_eq(old->uid, root_uid) ||
1092	     uid_eq(old->euid, root_uid) ||
1093	     uid_eq(old->suid, root_uid)) &&
1094	    (!uid_eq(new->uid, root_uid) &&
1095	     !uid_eq(new->euid, root_uid) &&
1096	     !uid_eq(new->suid, root_uid))) {
1097		if (!issecure(SECURE_KEEP_CAPS)) {
1098			cap_clear(new->cap_permitted);
1099			cap_clear(new->cap_effective);
1100		}
1101
1102		/*
1103		 * Pre-ambient programs expect setresuid to nonroot followed
1104		 * by exec to drop capabilities.  We should make sure that
1105		 * this remains the case.
1106		 */
1107		cap_clear(new->cap_ambient);
1108	}
1109	if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
1110		cap_clear(new->cap_effective);
1111	if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
1112		new->cap_effective = new->cap_permitted;
1113}
1114
1115/**
1116 * cap_task_fix_setuid - Fix up the results of setuid() call
1117 * @new: The proposed credentials
1118 * @old: The current task's current credentials
1119 * @flags: Indications of what has changed
1120 *
1121 * Fix up the results of setuid() call before the credential changes are
1122 * actually applied.
1123 *
1124 * Return: 0 to grant the changes, -ve to deny them.
1125 */
1126int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
1127{
1128	switch (flags) {
1129	case LSM_SETID_RE:
1130	case LSM_SETID_ID:
1131	case LSM_SETID_RES:
1132		/* juggle the capabilities to follow [RES]UID changes unless
1133		 * otherwise suppressed */
1134		if (!issecure(SECURE_NO_SETUID_FIXUP))
1135			cap_emulate_setxuid(new, old);
1136		break;
1137
1138	case LSM_SETID_FS:
1139		/* juggle the capabilties to follow FSUID changes, unless
1140		 * otherwise suppressed
1141		 *
1142		 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
1143		 *          if not, we might be a bit too harsh here.
1144		 */
1145		if (!issecure(SECURE_NO_SETUID_FIXUP)) {
1146			kuid_t root_uid = make_kuid(old->user_ns, 0);
1147			if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
1148				new->cap_effective =
1149					cap_drop_fs_set(new->cap_effective);
1150
1151			if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
1152				new->cap_effective =
1153					cap_raise_fs_set(new->cap_effective,
1154							 new->cap_permitted);
1155		}
1156		break;
1157
1158	default:
1159		return -EINVAL;
1160	}
1161
1162	return 0;
1163}
1164
1165/*
1166 * Rationale: code calling task_setscheduler, task_setioprio, and
1167 * task_setnice, assumes that
1168 *   . if capable(cap_sys_nice), then those actions should be allowed
1169 *   . if not capable(cap_sys_nice), but acting on your own processes,
1170 *   	then those actions should be allowed
1171 * This is insufficient now since you can call code without suid, but
1172 * yet with increased caps.
1173 * So we check for increased caps on the target process.
1174 */
1175static int cap_safe_nice(struct task_struct *p)
1176{
1177	int is_subset, ret = 0;
1178
1179	rcu_read_lock();
1180	is_subset = cap_issubset(__task_cred(p)->cap_permitted,
1181				 current_cred()->cap_permitted);
1182	if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
1183		ret = -EPERM;
1184	rcu_read_unlock();
1185
1186	return ret;
1187}
1188
1189/**
1190 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
1191 * @p: The task to affect
1192 *
1193 * Detemine if the requested scheduler policy change is permitted for the
1194 * specified task.
1195 *
1196 * Return: 0 if permission is granted, -ve if denied.
1197 */
1198int cap_task_setscheduler(struct task_struct *p)
1199{
1200	return cap_safe_nice(p);
1201}
1202
1203/**
1204 * cap_task_setioprio - Detemine if I/O priority change is permitted
1205 * @p: The task to affect
1206 * @ioprio: The I/O priority to set
1207 *
1208 * Detemine if the requested I/O priority change is permitted for the specified
1209 * task.
1210 *
1211 * Return: 0 if permission is granted, -ve if denied.
1212 */
1213int cap_task_setioprio(struct task_struct *p, int ioprio)
1214{
1215	return cap_safe_nice(p);
1216}
1217
1218/**
1219 * cap_task_setnice - Detemine if task priority change is permitted
1220 * @p: The task to affect
1221 * @nice: The nice value to set
1222 *
1223 * Detemine if the requested task priority change is permitted for the
1224 * specified task.
1225 *
1226 * Return: 0 if permission is granted, -ve if denied.
1227 */
1228int cap_task_setnice(struct task_struct *p, int nice)
1229{
1230	return cap_safe_nice(p);
1231}
1232
1233/*
1234 * Implement PR_CAPBSET_DROP.  Attempt to remove the specified capability from
1235 * the current task's bounding set.  Returns 0 on success, -ve on error.
1236 */
1237static int cap_prctl_drop(unsigned long cap)
1238{
1239	struct cred *new;
1240
1241	if (!ns_capable(current_user_ns(), CAP_SETPCAP))
1242		return -EPERM;
1243	if (!cap_valid(cap))
1244		return -EINVAL;
1245
1246	new = prepare_creds();
1247	if (!new)
1248		return -ENOMEM;
1249	cap_lower(new->cap_bset, cap);
1250	return commit_creds(new);
1251}
1252
1253/**
1254 * cap_task_prctl - Implement process control functions for this security module
1255 * @option: The process control function requested
1256 * @arg2: The argument data for this function
1257 * @arg3: The argument data for this function
1258 * @arg4: The argument data for this function
1259 * @arg5: The argument data for this function
1260 *
1261 * Allow process control functions (sys_prctl()) to alter capabilities; may
1262 * also deny access to other functions not otherwise implemented here.
1263 *
1264 * Return: 0 or +ve on success, -ENOSYS if this function is not implemented
1265 * here, other -ve on error.  If -ENOSYS is returned, sys_prctl() and other LSM
1266 * modules will consider performing the function.
1267 */
1268int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
1269		   unsigned long arg4, unsigned long arg5)
1270{
1271	const struct cred *old = current_cred();
1272	struct cred *new;
 
 
 
 
 
1273
1274	switch (option) {
1275	case PR_CAPBSET_READ:
 
1276		if (!cap_valid(arg2))
1277			return -EINVAL;
1278		return !!cap_raised(old->cap_bset, arg2);
 
1279
1280	case PR_CAPBSET_DROP:
1281		return cap_prctl_drop(arg2);
 
 
 
1282
1283	/*
1284	 * The next four prctl's remain to assist with transitioning a
1285	 * system from legacy UID=0 based privilege (when filesystem
1286	 * capabilities are not in use) to a system using filesystem
1287	 * capabilities only - as the POSIX.1e draft intended.
1288	 *
1289	 * Note:
1290	 *
1291	 *  PR_SET_SECUREBITS =
1292	 *      issecure_mask(SECURE_KEEP_CAPS_LOCKED)
1293	 *    | issecure_mask(SECURE_NOROOT)
1294	 *    | issecure_mask(SECURE_NOROOT_LOCKED)
1295	 *    | issecure_mask(SECURE_NO_SETUID_FIXUP)
1296	 *    | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
1297	 *
1298	 * will ensure that the current process and all of its
1299	 * children will be locked into a pure
1300	 * capability-based-privilege environment.
1301	 */
1302	case PR_SET_SECUREBITS:
1303		if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
1304		     & (old->securebits ^ arg2))			/*[1]*/
1305		    || ((old->securebits & SECURE_ALL_LOCKS & ~arg2))	/*[2]*/
 
1306		    || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS))	/*[3]*/
1307		    || (cap_capable(current_cred(),
1308				    current_cred()->user_ns,
1309				    CAP_SETPCAP,
1310				    CAP_OPT_NONE) != 0)			/*[4]*/
1311			/*
1312			 * [1] no changing of bits that are locked
1313			 * [2] no unlocking of locks
1314			 * [3] no setting of unsupported bits
1315			 * [4] doing anything requires privilege (go read about
1316			 *     the "sendmail capabilities bug")
1317			 */
1318		    )
1319			/* cannot change a locked bit */
1320			return -EPERM;
1321
1322		new = prepare_creds();
1323		if (!new)
1324			return -ENOMEM;
1325		new->securebits = arg2;
1326		return commit_creds(new);
1327
1328	case PR_GET_SECUREBITS:
1329		return old->securebits;
 
1330
1331	case PR_GET_KEEPCAPS:
1332		return !!issecure(SECURE_KEEP_CAPS);
 
 
1333
1334	case PR_SET_KEEPCAPS:
 
1335		if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
1336			return -EINVAL;
 
1337		if (issecure(SECURE_KEEP_CAPS_LOCKED))
1338			return -EPERM;
1339
1340		new = prepare_creds();
1341		if (!new)
1342			return -ENOMEM;
1343		if (arg2)
1344			new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
1345		else
1346			new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
1347		return commit_creds(new);
1348
1349	case PR_CAP_AMBIENT:
1350		if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
1351			if (arg3 | arg4 | arg5)
1352				return -EINVAL;
1353
1354			new = prepare_creds();
1355			if (!new)
1356				return -ENOMEM;
1357			cap_clear(new->cap_ambient);
1358			return commit_creds(new);
1359		}
1360
1361		if (((!cap_valid(arg3)) | arg4 | arg5))
1362			return -EINVAL;
1363
1364		if (arg2 == PR_CAP_AMBIENT_IS_SET) {
1365			return !!cap_raised(current_cred()->cap_ambient, arg3);
1366		} else if (arg2 != PR_CAP_AMBIENT_RAISE &&
1367			   arg2 != PR_CAP_AMBIENT_LOWER) {
1368			return -EINVAL;
1369		} else {
1370			if (arg2 == PR_CAP_AMBIENT_RAISE &&
1371			    (!cap_raised(current_cred()->cap_permitted, arg3) ||
1372			     !cap_raised(current_cred()->cap_inheritable,
1373					 arg3) ||
1374			     issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
1375				return -EPERM;
1376
1377			new = prepare_creds();
1378			if (!new)
1379				return -ENOMEM;
1380			if (arg2 == PR_CAP_AMBIENT_RAISE)
1381				cap_raise(new->cap_ambient, arg3);
1382			else
1383				cap_lower(new->cap_ambient, arg3);
1384			return commit_creds(new);
1385		}
1386
1387	default:
1388		/* No functionality available - continue with default */
1389		return -ENOSYS;
 
1390	}
 
 
 
 
 
 
 
 
 
1391}
1392
1393/**
1394 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
1395 * @mm: The VM space in which the new mapping is to be made
1396 * @pages: The size of the mapping
1397 *
1398 * Determine whether the allocation of a new virtual mapping by the current
1399 * task is permitted.
1400 *
1401 * Return: 1 if permission is granted, 0 if not.
1402 */
1403int cap_vm_enough_memory(struct mm_struct *mm, long pages)
1404{
1405	int cap_sys_admin = 0;
1406
1407	if (cap_capable(current_cred(), &init_user_ns,
1408				CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) == 0)
1409		cap_sys_admin = 1;
1410
1411	return cap_sys_admin;
1412}
1413
1414/**
1415 * cap_mmap_addr - check if able to map given addr
1416 * @addr: address attempting to be mapped
1417 *
1418 * If the process is attempting to map memory below dac_mmap_min_addr they need
1419 * CAP_SYS_RAWIO.  The other parameters to this function are unused by the
1420 * capability security module.
1421 *
1422 * Return: 0 if this mapping should be allowed or -EPERM if not.
1423 */
1424int cap_mmap_addr(unsigned long addr)
1425{
1426	int ret = 0;
1427
1428	if (addr < dac_mmap_min_addr) {
1429		ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
1430				  CAP_OPT_NONE);
1431		/* set PF_SUPERPRIV if it turns out we allow the low mmap */
1432		if (ret == 0)
1433			current->flags |= PF_SUPERPRIV;
1434	}
1435	return ret;
1436}
1437
1438int cap_mmap_file(struct file *file, unsigned long reqprot,
1439		  unsigned long prot, unsigned long flags)
1440{
1441	return 0;
1442}
1443
1444#ifdef CONFIG_SECURITY
1445
1446static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
1447	LSM_HOOK_INIT(capable, cap_capable),
1448	LSM_HOOK_INIT(settime, cap_settime),
1449	LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
1450	LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
1451	LSM_HOOK_INIT(capget, cap_capget),
1452	LSM_HOOK_INIT(capset, cap_capset),
1453	LSM_HOOK_INIT(bprm_creds_from_file, cap_bprm_creds_from_file),
1454	LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
1455	LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
1456	LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity),
1457	LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
1458	LSM_HOOK_INIT(mmap_file, cap_mmap_file),
1459	LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
1460	LSM_HOOK_INIT(task_prctl, cap_task_prctl),
1461	LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
1462	LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
1463	LSM_HOOK_INIT(task_setnice, cap_task_setnice),
1464	LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
1465};
1466
1467static int __init capability_init(void)
1468{
1469	security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
1470				"capability");
1471	return 0;
1472}
1473
1474DEFINE_LSM(capability) = {
1475	.name = "capability",
1476	.order = LSM_ORDER_FIRST,
1477	.init = capability_init,
1478};
1479
1480#endif /* CONFIG_SECURITY */