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
  29/*
  30 * If a non-root user executes a setuid-root binary in
  31 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
  32 * However if fE is also set, then the intent is for only
  33 * the file capabilities to be applied, and the setuid-root
  34 * bit is left on either to change the uid (plausible) or
  35 * to get full privilege on a kernel without file capabilities
  36 * support.  So in that case we do not raise capabilities.
  37 *
  38 * Warn if that happens, once per boot.
  39 */
  40static void warn_setuid_and_fcaps_mixed(const char *fname)
  41{
  42	static int warned;
  43	if (!warned) {
  44		printk(KERN_INFO "warning: `%s' has both setuid-root and"
  45			" effective capabilities. Therefore not raising all"
  46			" capabilities.\n", fname);
  47		warned = 1;
  48	}
  49}
  50
  51/**
  52 * cap_capable - Determine whether a task has a particular effective capability
  53 * @cred: The credentials to use
  54 * @targ_ns:  The user namespace in which we need the capability
  55 * @cap: The capability to check for
  56 * @opts: Bitmask of options defined in include/linux/security.h
  57 *
  58 * Determine whether the nominated task has the specified capability amongst
  59 * its effective set, returning 0 if it does, -ve if it does not.
  60 *
  61 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
  62 * and has_capability() functions.  That is, it has the reverse semantics:
  63 * cap_has_capability() returns 0 when a task has a capability, but the
  64 * kernel's capable() and has_capability() returns 1 for this case.
  65 */
  66int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
  67		int cap, unsigned int opts)
  68{
  69	struct user_namespace *ns = targ_ns;
  70
  71	/* See if cred has the capability in the target user namespace
  72	 * by examining the target user namespace and all of the target
  73	 * user namespace's parents.
  74	 */
  75	for (;;) {
  76		/* Do we have the necessary capabilities? */
  77		if (ns == cred->user_ns)
  78			return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
  79
  80		/*
  81		 * If we're already at a lower level than we're looking for,
  82		 * we're done searching.
  83		 */
  84		if (ns->level <= cred->user_ns->level)
  85			return -EPERM;
  86
  87		/* 
  88		 * The owner of the user namespace in the parent of the
  89		 * user namespace has all caps.
  90		 */
  91		if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
  92			return 0;
  93
  94		/*
  95		 * If you have a capability in a parent user ns, then you have
  96		 * it over all children user namespaces as well.
  97		 */
  98		ns = ns->parent;
  99	}
 100
 101	/* We never get here */
 102}
 103
 104/**
 105 * cap_settime - Determine whether the current process may set the system clock
 106 * @ts: The time to set
 107 * @tz: The timezone to set
 108 *
 109 * Determine whether the current process may set the system clock and timezone
 110 * information, returning 0 if permission granted, -ve if denied.
 111 */
 112int cap_settime(const struct timespec64 *ts, const struct timezone *tz)
 113{
 114	if (!capable(CAP_SYS_TIME))
 115		return -EPERM;
 116	return 0;
 117}
 118
 119/**
 120 * cap_ptrace_access_check - Determine whether the current process may access
 121 *			   another
 122 * @child: The process to be accessed
 123 * @mode: The mode of attachment.
 124 *
 125 * If we are in the same or an ancestor user_ns and have all the target
 126 * task's capabilities, then ptrace access is allowed.
 127 * If we have the ptrace capability to the target user_ns, then ptrace
 128 * access is allowed.
 129 * Else denied.
 130 *
 131 * Determine whether a process may access another, returning 0 if permission
 132 * granted, -ve if denied.
 133 */
 134int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
 135{
 136	int ret = 0;
 137	const struct cred *cred, *child_cred;
 138	const kernel_cap_t *caller_caps;
 139
 140	rcu_read_lock();
 141	cred = current_cred();
 142	child_cred = __task_cred(child);
 143	if (mode & PTRACE_MODE_FSCREDS)
 144		caller_caps = &cred->cap_effective;
 145	else
 146		caller_caps = &cred->cap_permitted;
 147	if (cred->user_ns == child_cred->user_ns &&
 148	    cap_issubset(child_cred->cap_permitted, *caller_caps))
 149		goto out;
 150	if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
 151		goto out;
 152	ret = -EPERM;
 153out:
 154	rcu_read_unlock();
 155	return ret;
 156}
 157
 158/**
 159 * cap_ptrace_traceme - Determine whether another process may trace the current
 160 * @parent: The task proposed to be the tracer
 161 *
 162 * If parent is in the same or an ancestor user_ns and has all current's
 163 * capabilities, then ptrace access is allowed.
 164 * If parent has the ptrace capability to current's user_ns, then ptrace
 165 * access is allowed.
 166 * Else denied.
 167 *
 168 * Determine whether the nominated task is permitted to trace the current
 169 * process, returning 0 if permission is granted, -ve if denied.
 170 */
 171int cap_ptrace_traceme(struct task_struct *parent)
 172{
 173	int ret = 0;
 174	const struct cred *cred, *child_cred;
 175
 176	rcu_read_lock();
 177	cred = __task_cred(parent);
 178	child_cred = current_cred();
 179	if (cred->user_ns == child_cred->user_ns &&
 180	    cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
 181		goto out;
 182	if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
 183		goto out;
 184	ret = -EPERM;
 185out:
 186	rcu_read_unlock();
 187	return ret;
 188}
 189
 190/**
 191 * cap_capget - Retrieve a task's capability sets
 192 * @target: The task from which to retrieve the capability sets
 193 * @effective: The place to record the effective set
 194 * @inheritable: The place to record the inheritable set
 195 * @permitted: The place to record the permitted set
 196 *
 197 * This function retrieves the capabilities of the nominated task and returns
 198 * them to the caller.
 199 */
 200int cap_capget(struct task_struct *target, kernel_cap_t *effective,
 201	       kernel_cap_t *inheritable, kernel_cap_t *permitted)
 202{
 203	const struct cred *cred;
 204
 205	/* Derived from kernel/capability.c:sys_capget. */
 206	rcu_read_lock();
 207	cred = __task_cred(target);
 208	*effective   = cred->cap_effective;
 209	*inheritable = cred->cap_inheritable;
 210	*permitted   = cred->cap_permitted;
 211	rcu_read_unlock();
 212	return 0;
 213}
 214
 215/*
 216 * Determine whether the inheritable capabilities are limited to the old
 217 * permitted set.  Returns 1 if they are limited, 0 if they are not.
 218 */
 219static inline int cap_inh_is_capped(void)
 220{
 
 221	/* they are so limited unless the current task has the CAP_SETPCAP
 222	 * capability
 223	 */
 224	if (cap_capable(current_cred(), current_cred()->user_ns,
 225			CAP_SETPCAP, CAP_OPT_NONE) == 0)
 226		return 0;
 227	return 1;
 228}
 229
 230/**
 231 * cap_capset - Validate and apply proposed changes to current's capabilities
 232 * @new: The proposed new credentials; alterations should be made here
 233 * @old: The current task's current credentials
 234 * @effective: A pointer to the proposed new effective capabilities set
 235 * @inheritable: A pointer to the proposed new inheritable capabilities set
 236 * @permitted: A pointer to the proposed new permitted capabilities set
 237 *
 238 * This function validates and applies a proposed mass change to the current
 239 * process's capability sets.  The changes are made to the proposed new
 240 * credentials, and assuming no error, will be committed by the caller of LSM.
 241 */
 242int cap_capset(struct cred *new,
 243	       const struct cred *old,
 244	       const kernel_cap_t *effective,
 245	       const kernel_cap_t *inheritable,
 246	       const kernel_cap_t *permitted)
 247{
 248	if (cap_inh_is_capped() &&
 249	    !cap_issubset(*inheritable,
 250			  cap_combine(old->cap_inheritable,
 251				      old->cap_permitted)))
 252		/* incapable of using this inheritable set */
 253		return -EPERM;
 254
 255	if (!cap_issubset(*inheritable,
 256			  cap_combine(old->cap_inheritable,
 257				      old->cap_bset)))
 258		/* no new pI capabilities outside bounding set */
 259		return -EPERM;
 260
 261	/* verify restrictions on target's new Permitted set */
 262	if (!cap_issubset(*permitted, old->cap_permitted))
 263		return -EPERM;
 264
 265	/* verify the _new_Effective_ is a subset of the _new_Permitted_ */
 266	if (!cap_issubset(*effective, *permitted))
 267		return -EPERM;
 268
 269	new->cap_effective   = *effective;
 270	new->cap_inheritable = *inheritable;
 271	new->cap_permitted   = *permitted;
 272
 273	/*
 274	 * Mask off ambient bits that are no longer both permitted and
 275	 * inheritable.
 276	 */
 277	new->cap_ambient = cap_intersect(new->cap_ambient,
 278					 cap_intersect(*permitted,
 279						       *inheritable));
 280	if (WARN_ON(!cap_ambient_invariant_ok(new)))
 281		return -EINVAL;
 282	return 0;
 283}
 284
 
 
 
 
 
 
 
 
 
 285/**
 286 * cap_inode_need_killpriv - Determine if inode change affects privileges
 287 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
 288 *
 289 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
 290 * affects the security markings on that inode, and if it is, should
 291 * inode_killpriv() be invoked or the change rejected.
 292 *
 293 * Return: 1 if security.capability has a value, meaning inode_killpriv()
 294 * is required, 0 otherwise, meaning inode_killpriv() is not required.
 295 */
 296int cap_inode_need_killpriv(struct dentry *dentry)
 297{
 298	struct inode *inode = d_backing_inode(dentry);
 299	int error;
 300
 301	error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0);
 302	return error > 0;
 303}
 304
 305/**
 306 * cap_inode_killpriv - Erase the security markings on an inode
 307 *
 308 * @mnt_userns:	user namespace of the mount the inode was found from
 309 * @dentry:	The inode/dentry to alter
 310 *
 311 * Erase the privilege-enhancing security markings on an inode.
 312 *
 313 * If the inode has been found through an idmapped mount the user namespace of
 314 * the vfsmount must be passed through @mnt_userns. This function will then
 315 * take care to map the inode according to @mnt_userns before checking
 316 * permissions. On non-idmapped mounts or if permission checking is to be
 317 * performed on the raw inode simply passs init_user_ns.
 318 *
 319 * Return: 0 if successful, -ve on error.
 320 */
 321int cap_inode_killpriv(struct user_namespace *mnt_userns, struct dentry *dentry)
 322{
 323	int error;
 324
 325	error = __vfs_removexattr(mnt_userns, dentry, XATTR_NAME_CAPS);
 326	if (error == -EOPNOTSUPP)
 327		error = 0;
 328	return error;
 329}
 330
 331static bool rootid_owns_currentns(vfsuid_t rootvfsuid)
 332{
 333	struct user_namespace *ns;
 334	kuid_t kroot;
 335
 336	if (!vfsuid_valid(rootvfsuid))
 337		return false;
 338
 339	kroot = vfsuid_into_kuid(rootvfsuid);
 340	for (ns = current_user_ns();; ns = ns->parent) {
 341		if (from_kuid(ns, kroot) == 0)
 342			return true;
 343		if (ns == &init_user_ns)
 344			break;
 345	}
 346
 347	return false;
 348}
 349
 350static __u32 sansflags(__u32 m)
 351{
 352	return m & ~VFS_CAP_FLAGS_EFFECTIVE;
 353}
 354
 355static bool is_v2header(int size, const struct vfs_cap_data *cap)
 356{
 357	if (size != XATTR_CAPS_SZ_2)
 358		return false;
 359	return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_2;
 360}
 361
 362static bool is_v3header(int size, const struct vfs_cap_data *cap)
 363{
 364	if (size != XATTR_CAPS_SZ_3)
 365		return false;
 366	return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_3;
 367}
 368
 369/*
 370 * getsecurity: We are called for security.* before any attempt to read the
 371 * xattr from the inode itself.
 372 *
 373 * This gives us a chance to read the on-disk value and convert it.  If we
 374 * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler.
 375 *
 376 * Note we are not called by vfs_getxattr_alloc(), but that is only called
 377 * by the integrity subsystem, which really wants the unconverted values -
 378 * so that's good.
 379 */
 380int cap_inode_getsecurity(struct user_namespace *mnt_userns,
 381			  struct inode *inode, const char *name, void **buffer,
 382			  bool alloc)
 383{
 384	int size;
 385	kuid_t kroot;
 386	vfsuid_t vfsroot;
 387	u32 nsmagic, magic;
 388	uid_t root, mappedroot;
 389	char *tmpbuf = NULL;
 390	struct vfs_cap_data *cap;
 391	struct vfs_ns_cap_data *nscap = NULL;
 392	struct dentry *dentry;
 393	struct user_namespace *fs_ns;
 394
 395	if (strcmp(name, "capability") != 0)
 396		return -EOPNOTSUPP;
 397
 398	dentry = d_find_any_alias(inode);
 399	if (!dentry)
 400		return -EINVAL;
 401	size = vfs_getxattr_alloc(mnt_userns, dentry, XATTR_NAME_CAPS, &tmpbuf,
 402				  sizeof(struct vfs_ns_cap_data), GFP_NOFS);
 403	dput(dentry);
 404	/* gcc11 complains if we don't check for !tmpbuf */
 405	if (size < 0 || !tmpbuf)
 406		goto out_free;
 407
 408	fs_ns = inode->i_sb->s_user_ns;
 409	cap = (struct vfs_cap_data *) tmpbuf;
 410	if (is_v2header(size, cap)) {
 411		root = 0;
 412	} else if (is_v3header(size, cap)) {
 413		nscap = (struct vfs_ns_cap_data *) tmpbuf;
 414		root = le32_to_cpu(nscap->rootid);
 415	} else {
 416		size = -EINVAL;
 417		goto out_free;
 418	}
 419
 420	kroot = make_kuid(fs_ns, root);
 421
 422	/* If this is an idmapped mount shift the kuid. */
 423	vfsroot = make_vfsuid(mnt_userns, fs_ns, kroot);
 424
 425	/* If the root kuid maps to a valid uid in current ns, then return
 426	 * this as a nscap. */
 427	mappedroot = from_kuid(current_user_ns(), vfsuid_into_kuid(vfsroot));
 428	if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) {
 429		size = sizeof(struct vfs_ns_cap_data);
 430		if (alloc) {
 431			if (!nscap) {
 432				/* v2 -> v3 conversion */
 433				nscap = kzalloc(size, GFP_ATOMIC);
 434				if (!nscap) {
 435					size = -ENOMEM;
 436					goto out_free;
 437				}
 438				nsmagic = VFS_CAP_REVISION_3;
 439				magic = le32_to_cpu(cap->magic_etc);
 440				if (magic & VFS_CAP_FLAGS_EFFECTIVE)
 441					nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
 442				memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
 443				nscap->magic_etc = cpu_to_le32(nsmagic);
 444			} else {
 445				/* use allocated v3 buffer */
 446				tmpbuf = NULL;
 447			}
 448			nscap->rootid = cpu_to_le32(mappedroot);
 449			*buffer = nscap;
 450		}
 451		goto out_free;
 452	}
 453
 454	if (!rootid_owns_currentns(vfsroot)) {
 455		size = -EOVERFLOW;
 456		goto out_free;
 457	}
 458
 459	/* This comes from a parent namespace.  Return as a v2 capability */
 460	size = sizeof(struct vfs_cap_data);
 461	if (alloc) {
 462		if (nscap) {
 463			/* v3 -> v2 conversion */
 464			cap = kzalloc(size, GFP_ATOMIC);
 465			if (!cap) {
 466				size = -ENOMEM;
 467				goto out_free;
 468			}
 469			magic = VFS_CAP_REVISION_2;
 470			nsmagic = le32_to_cpu(nscap->magic_etc);
 471			if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE)
 472				magic |= VFS_CAP_FLAGS_EFFECTIVE;
 473			memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
 474			cap->magic_etc = cpu_to_le32(magic);
 475		} else {
 476			/* use unconverted v2 */
 477			tmpbuf = NULL;
 478		}
 479		*buffer = cap;
 480	}
 481out_free:
 482	kfree(tmpbuf);
 483	return size;
 484}
 485
 486/**
 487 * rootid_from_xattr - translate root uid of vfs caps
 488 *
 489 * @value:	vfs caps value which may be modified by this function
 490 * @size:	size of @ivalue
 491 * @task_ns:	user namespace of the caller
 492 */
 493static vfsuid_t rootid_from_xattr(const void *value, size_t size,
 494				  struct user_namespace *task_ns)
 495{
 496	const struct vfs_ns_cap_data *nscap = value;
 497	uid_t rootid = 0;
 498
 499	if (size == XATTR_CAPS_SZ_3)
 500		rootid = le32_to_cpu(nscap->rootid);
 501
 502	return VFSUIDT_INIT(make_kuid(task_ns, rootid));
 503}
 504
 505static bool validheader(size_t size, const struct vfs_cap_data *cap)
 506{
 507	return is_v2header(size, cap) || is_v3header(size, cap);
 508}
 509
 510/**
 511 * cap_convert_nscap - check vfs caps
 512 *
 513 * @mnt_userns:	user namespace of the mount the inode was found from
 514 * @dentry:	used to retrieve inode to check permissions on
 515 * @ivalue:	vfs caps value which may be modified by this function
 516 * @size:	size of @ivalue
 517 *
 518 * User requested a write of security.capability.  If needed, update the
 519 * xattr to change from v2 to v3, or to fixup the v3 rootid.
 520 *
 521 * If the inode has been found through an idmapped mount the user namespace of
 522 * the vfsmount must be passed through @mnt_userns. This function will then
 523 * take care to map the inode according to @mnt_userns before checking
 524 * permissions. On non-idmapped mounts or if permission checking is to be
 525 * performed on the raw inode simply passs init_user_ns.
 526 *
 527 * Return: On success, return the new size; on error, return < 0.
 528 */
 529int cap_convert_nscap(struct user_namespace *mnt_userns, struct dentry *dentry,
 530		      const void **ivalue, size_t size)
 531{
 532	struct vfs_ns_cap_data *nscap;
 533	uid_t nsrootid;
 534	const struct vfs_cap_data *cap = *ivalue;
 535	__u32 magic, nsmagic;
 536	struct inode *inode = d_backing_inode(dentry);
 537	struct user_namespace *task_ns = current_user_ns(),
 538		*fs_ns = inode->i_sb->s_user_ns;
 539	kuid_t rootid;
 540	vfsuid_t vfsrootid;
 541	size_t newsize;
 542
 543	if (!*ivalue)
 544		return -EINVAL;
 545	if (!validheader(size, cap))
 546		return -EINVAL;
 547	if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP))
 548		return -EPERM;
 549	if (size == XATTR_CAPS_SZ_2 && (mnt_userns == fs_ns))
 550		if (ns_capable(inode->i_sb->s_user_ns, CAP_SETFCAP))
 551			/* user is privileged, just write the v2 */
 552			return size;
 553
 554	vfsrootid = rootid_from_xattr(*ivalue, size, task_ns);
 555	if (!vfsuid_valid(vfsrootid))
 556		return -EINVAL;
 557
 558	rootid = from_vfsuid(mnt_userns, fs_ns, vfsrootid);
 559	if (!uid_valid(rootid))
 560		return -EINVAL;
 561
 562	nsrootid = from_kuid(fs_ns, rootid);
 563	if (nsrootid == -1)
 564		return -EINVAL;
 565
 566	newsize = sizeof(struct vfs_ns_cap_data);
 567	nscap = kmalloc(newsize, GFP_ATOMIC);
 568	if (!nscap)
 569		return -ENOMEM;
 570	nscap->rootid = cpu_to_le32(nsrootid);
 571	nsmagic = VFS_CAP_REVISION_3;
 572	magic = le32_to_cpu(cap->magic_etc);
 573	if (magic & VFS_CAP_FLAGS_EFFECTIVE)
 574		nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
 575	nscap->magic_etc = cpu_to_le32(nsmagic);
 576	memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
 577
 578	*ivalue = nscap;
 579	return newsize;
 580}
 581
 582/*
 583 * Calculate the new process capability sets from the capability sets attached
 584 * to a file.
 585 */
 586static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
 587					  struct linux_binprm *bprm,
 588					  bool *effective,
 589					  bool *has_fcap)
 590{
 591	struct cred *new = bprm->cred;
 592	unsigned i;
 593	int ret = 0;
 594
 595	if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
 596		*effective = true;
 597
 598	if (caps->magic_etc & VFS_CAP_REVISION_MASK)
 599		*has_fcap = true;
 600
 601	CAP_FOR_EACH_U32(i) {
 602		__u32 permitted = caps->permitted.cap[i];
 603		__u32 inheritable = caps->inheritable.cap[i];
 604
 605		/*
 606		 * pP' = (X & fP) | (pI & fI)
 607		 * The addition of pA' is handled later.
 608		 */
 609		new->cap_permitted.cap[i] =
 610			(new->cap_bset.cap[i] & permitted) |
 611			(new->cap_inheritable.cap[i] & inheritable);
 612
 613		if (permitted & ~new->cap_permitted.cap[i])
 614			/* insufficient to execute correctly */
 615			ret = -EPERM;
 616	}
 617
 618	/*
 619	 * For legacy apps, with no internal support for recognizing they
 620	 * do not have enough capabilities, we return an error if they are
 621	 * missing some "forced" (aka file-permitted) capabilities.
 622	 */
 623	return *effective ? ret : 0;
 624}
 625
 626/**
 627 * get_vfs_caps_from_disk - retrieve vfs caps from disk
 628 *
 629 * @mnt_userns:	user namespace of the mount the inode was found from
 630 * @dentry:	dentry from which @inode is retrieved
 631 * @cpu_caps:	vfs capabilities
 632 *
 633 * Extract the on-exec-apply capability sets for an executable file.
 634 *
 635 * If the inode has been found through an idmapped mount the user namespace of
 636 * the vfsmount must be passed through @mnt_userns. This function will then
 637 * take care to map the inode according to @mnt_userns before checking
 638 * permissions. On non-idmapped mounts or if permission checking is to be
 639 * performed on the raw inode simply passs init_user_ns.
 640 */
 641int get_vfs_caps_from_disk(struct user_namespace *mnt_userns,
 642			   const struct dentry *dentry,
 643			   struct cpu_vfs_cap_data *cpu_caps)
 644{
 645	struct inode *inode = d_backing_inode(dentry);
 646	__u32 magic_etc;
 647	unsigned tocopy, i;
 648	int size;
 649	struct vfs_ns_cap_data data, *nscaps = &data;
 650	struct vfs_cap_data *caps = (struct vfs_cap_data *) &data;
 651	kuid_t rootkuid;
 652	vfsuid_t rootvfsuid;
 653	struct user_namespace *fs_ns;
 654
 655	memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
 656
 657	if (!inode)
 658		return -ENODATA;
 659
 660	fs_ns = inode->i_sb->s_user_ns;
 661	size = __vfs_getxattr((struct dentry *)dentry, inode,
 662			      XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ);
 663	if (size == -ENODATA || size == -EOPNOTSUPP)
 664		/* no data, that's ok */
 665		return -ENODATA;
 666
 667	if (size < 0)
 668		return size;
 669
 670	if (size < sizeof(magic_etc))
 671		return -EINVAL;
 672
 673	cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps->magic_etc);
 674
 675	rootkuid = make_kuid(fs_ns, 0);
 676	switch (magic_etc & VFS_CAP_REVISION_MASK) {
 677	case VFS_CAP_REVISION_1:
 678		if (size != XATTR_CAPS_SZ_1)
 679			return -EINVAL;
 680		tocopy = VFS_CAP_U32_1;
 681		break;
 682	case VFS_CAP_REVISION_2:
 683		if (size != XATTR_CAPS_SZ_2)
 684			return -EINVAL;
 685		tocopy = VFS_CAP_U32_2;
 686		break;
 687	case VFS_CAP_REVISION_3:
 688		if (size != XATTR_CAPS_SZ_3)
 689			return -EINVAL;
 690		tocopy = VFS_CAP_U32_3;
 691		rootkuid = make_kuid(fs_ns, le32_to_cpu(nscaps->rootid));
 692		break;
 693
 694	default:
 695		return -EINVAL;
 696	}
 697
 698	rootvfsuid = make_vfsuid(mnt_userns, fs_ns, rootkuid);
 699	if (!vfsuid_valid(rootvfsuid))
 700		return -ENODATA;
 701
 702	/* Limit the caps to the mounter of the filesystem
 703	 * or the more limited uid specified in the xattr.
 704	 */
 705	if (!rootid_owns_currentns(rootvfsuid))
 706		return -ENODATA;
 707
 708	CAP_FOR_EACH_U32(i) {
 709		if (i >= tocopy)
 710			break;
 711		cpu_caps->permitted.cap[i] = le32_to_cpu(caps->data[i].permitted);
 712		cpu_caps->inheritable.cap[i] = le32_to_cpu(caps->data[i].inheritable);
 713	}
 714
 715	cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
 716	cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
 717
 718	cpu_caps->rootid = vfsuid_into_kuid(rootvfsuid);
 719
 720	return 0;
 721}
 722
 723/*
 724 * Attempt to get the on-exec apply capability sets for an executable file from
 725 * its xattrs and, if present, apply them to the proposed credentials being
 726 * constructed by execve().
 727 */
 728static int get_file_caps(struct linux_binprm *bprm, struct file *file,
 729			 bool *effective, bool *has_fcap)
 730{
 731	int rc = 0;
 732	struct cpu_vfs_cap_data vcaps;
 733
 734	cap_clear(bprm->cred->cap_permitted);
 735
 736	if (!file_caps_enabled)
 737		return 0;
 738
 739	if (!mnt_may_suid(file->f_path.mnt))
 740		return 0;
 741
 742	/*
 743	 * This check is redundant with mnt_may_suid() but is kept to make
 744	 * explicit that capability bits are limited to s_user_ns and its
 745	 * descendants.
 746	 */
 747	if (!current_in_userns(file->f_path.mnt->mnt_sb->s_user_ns))
 748		return 0;
 749
 750	rc = get_vfs_caps_from_disk(file_mnt_user_ns(file),
 751				    file->f_path.dentry, &vcaps);
 752	if (rc < 0) {
 753		if (rc == -EINVAL)
 754			printk(KERN_NOTICE "Invalid argument reading file caps for %s\n",
 755					bprm->filename);
 756		else if (rc == -ENODATA)
 757			rc = 0;
 758		goto out;
 759	}
 760
 761	rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_fcap);
 
 
 
 762
 763out:
 764	if (rc)
 765		cap_clear(bprm->cred->cap_permitted);
 766
 767	return rc;
 768}
 769
 770static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); }
 771
 772static inline bool __is_real(kuid_t uid, struct cred *cred)
 773{ return uid_eq(cred->uid, uid); }
 774
 775static inline bool __is_eff(kuid_t uid, struct cred *cred)
 776{ return uid_eq(cred->euid, uid); }
 777
 778static inline bool __is_suid(kuid_t uid, struct cred *cred)
 779{ return !__is_real(uid, cred) && __is_eff(uid, cred); }
 780
 781/*
 782 * handle_privileged_root - Handle case of privileged root
 783 * @bprm: The execution parameters, including the proposed creds
 784 * @has_fcap: Are any file capabilities set?
 785 * @effective: Do we have effective root privilege?
 786 * @root_uid: This namespace' root UID WRT initial USER namespace
 787 *
 788 * Handle the case where root is privileged and hasn't been neutered by
 789 * SECURE_NOROOT.  If file capabilities are set, they won't be combined with
 790 * set UID root and nothing is changed.  If we are root, cap_permitted is
 791 * updated.  If we have become set UID root, the effective bit is set.
 792 */
 793static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap,
 794				   bool *effective, kuid_t root_uid)
 795{
 796	const struct cred *old = current_cred();
 797	struct cred *new = bprm->cred;
 798
 799	if (!root_privileged())
 800		return;
 801	/*
 802	 * If the legacy file capability is set, then don't set privs
 803	 * for a setuid root binary run by a non-root user.  Do set it
 804	 * for a root user just to cause least surprise to an admin.
 805	 */
 806	if (has_fcap && __is_suid(root_uid, new)) {
 807		warn_setuid_and_fcaps_mixed(bprm->filename);
 808		return;
 809	}
 810	/*
 811	 * To support inheritance of root-permissions and suid-root
 812	 * executables under compatibility mode, we override the
 813	 * capability sets for the file.
 814	 */
 815	if (__is_eff(root_uid, new) || __is_real(root_uid, new)) {
 816		/* pP' = (cap_bset & ~0) | (pI & ~0) */
 817		new->cap_permitted = cap_combine(old->cap_bset,
 818						 old->cap_inheritable);
 819	}
 820	/*
 821	 * If only the real uid is 0, we do not set the effective bit.
 822	 */
 823	if (__is_eff(root_uid, new))
 824		*effective = true;
 825}
 826
 827#define __cap_gained(field, target, source) \
 828	!cap_issubset(target->cap_##field, source->cap_##field)
 829#define __cap_grew(target, source, cred) \
 830	!cap_issubset(cred->cap_##target, cred->cap_##source)
 831#define __cap_full(field, cred) \
 832	cap_issubset(CAP_FULL_SET, cred->cap_##field)
 833
 834static inline bool __is_setuid(struct cred *new, const struct cred *old)
 835{ return !uid_eq(new->euid, old->uid); }
 836
 837static inline bool __is_setgid(struct cred *new, const struct cred *old)
 838{ return !gid_eq(new->egid, old->gid); }
 839
 840/*
 841 * 1) Audit candidate if current->cap_effective is set
 842 *
 843 * We do not bother to audit if 3 things are true:
 844 *   1) cap_effective has all caps
 845 *   2) we became root *OR* are were already root
 846 *   3) root is supposed to have all caps (SECURE_NOROOT)
 847 * Since this is just a normal root execing a process.
 848 *
 849 * Number 1 above might fail if you don't have a full bset, but I think
 850 * that is interesting information to audit.
 851 *
 852 * A number of other conditions require logging:
 853 * 2) something prevented setuid root getting all caps
 854 * 3) non-setuid root gets fcaps
 855 * 4) non-setuid root gets ambient
 856 */
 857static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old,
 858				     kuid_t root, bool has_fcap)
 859{
 860	bool ret = false;
 861
 862	if ((__cap_grew(effective, ambient, new) &&
 863	     !(__cap_full(effective, new) &&
 864	       (__is_eff(root, new) || __is_real(root, new)) &&
 865	       root_privileged())) ||
 866	    (root_privileged() &&
 867	     __is_suid(root, new) &&
 868	     !__cap_full(effective, new)) ||
 869	    (!__is_setuid(new, old) &&
 870	     ((has_fcap &&
 871	       __cap_gained(permitted, new, old)) ||
 872	      __cap_gained(ambient, new, old))))
 873
 874		ret = true;
 875
 876	return ret;
 877}
 878
 879/**
 880 * cap_bprm_creds_from_file - Set up the proposed credentials for execve().
 881 * @bprm: The execution parameters, including the proposed creds
 882 * @file: The file to pull the credentials from
 883 *
 884 * Set up the proposed credentials for a new execution context being
 885 * constructed by execve().  The proposed creds in @bprm->cred is altered,
 886 * which won't take effect immediately.
 887 *
 888 * Return: 0 if successful, -ve on error.
 889 */
 890int cap_bprm_creds_from_file(struct linux_binprm *bprm, struct file *file)
 891{
 892	/* Process setpcap binaries and capabilities for uid 0 */
 893	const struct cred *old = current_cred();
 894	struct cred *new = bprm->cred;
 895	bool effective = false, has_fcap = false, is_setid;
 896	int ret;
 897	kuid_t root_uid;
 898
 899	if (WARN_ON(!cap_ambient_invariant_ok(old)))
 900		return -EPERM;
 901
 902	ret = get_file_caps(bprm, file, &effective, &has_fcap);
 
 903	if (ret < 0)
 904		return ret;
 905
 906	root_uid = make_kuid(new->user_ns, 0);
 907
 908	handle_privileged_root(bprm, has_fcap, &effective, root_uid);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 909
 910	/* if we have fs caps, clear dangerous personality flags */
 911	if (__cap_gained(permitted, new, old))
 912		bprm->per_clear |= PER_CLEAR_ON_SETID;
 913
 
 914	/* Don't let someone trace a set[ug]id/setpcap binary with the revised
 915	 * credentials unless they have the appropriate permit.
 916	 *
 917	 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
 918	 */
 919	is_setid = __is_setuid(new, old) || __is_setgid(new, old);
 920
 921	if ((is_setid || __cap_gained(permitted, new, old)) &&
 922	    ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) ||
 923	     !ptracer_capable(current, new->user_ns))) {
 924		/* downgrade; they get no more than they had, and maybe less */
 925		if (!ns_capable(new->user_ns, CAP_SETUID) ||
 926		    (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
 927			new->euid = new->uid;
 928			new->egid = new->gid;
 929		}
 930		new->cap_permitted = cap_intersect(new->cap_permitted,
 931						   old->cap_permitted);
 932	}
 933
 934	new->suid = new->fsuid = new->euid;
 935	new->sgid = new->fsgid = new->egid;
 936
 937	/* File caps or setid cancels ambient. */
 938	if (has_fcap || is_setid)
 939		cap_clear(new->cap_ambient);
 940
 941	/*
 942	 * Now that we've computed pA', update pP' to give:
 943	 *   pP' = (X & fP) | (pI & fI) | pA'
 944	 */
 945	new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
 946
 947	/*
 948	 * Set pE' = (fE ? pP' : pA').  Because pA' is zero if fE is set,
 949	 * this is the same as pE' = (fE ? pP' : 0) | pA'.
 950	 */
 951	if (effective)
 952		new->cap_effective = new->cap_permitted;
 953	else
 954		new->cap_effective = new->cap_ambient;
 955
 956	if (WARN_ON(!cap_ambient_invariant_ok(new)))
 957		return -EPERM;
 958
 959	if (nonroot_raised_pE(new, old, root_uid, has_fcap)) {
 960		ret = audit_log_bprm_fcaps(bprm, new, old);
 961		if (ret < 0)
 962			return ret;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 963	}
 964
 965	new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
 966
 967	if (WARN_ON(!cap_ambient_invariant_ok(new)))
 968		return -EPERM;
 969
 970	/* Check for privilege-elevated exec. */
 971	if (is_setid ||
 972	    (!__is_real(root_uid, new) &&
 973	     (effective ||
 974	      __cap_grew(permitted, ambient, new))))
 975		bprm->secureexec = 1;
 976
 977	return 0;
 978}
 979
 980/**
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 981 * cap_inode_setxattr - Determine whether an xattr may be altered
 982 * @dentry: The inode/dentry being altered
 983 * @name: The name of the xattr to be changed
 984 * @value: The value that the xattr will be changed to
 985 * @size: The size of value
 986 * @flags: The replacement flag
 987 *
 988 * Determine whether an xattr may be altered or set on an inode, returning 0 if
 989 * permission is granted, -ve if denied.
 990 *
 991 * This is used to make sure security xattrs don't get updated or set by those
 992 * who aren't privileged to do so.
 993 */
 994int cap_inode_setxattr(struct dentry *dentry, const char *name,
 995		       const void *value, size_t size, int flags)
 996{
 997	struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
 998
 999	/* Ignore non-security xattrs */
1000	if (strncmp(name, XATTR_SECURITY_PREFIX,
1001			XATTR_SECURITY_PREFIX_LEN) != 0)
1002		return 0;
1003
1004	/*
1005	 * For XATTR_NAME_CAPS the check will be done in
1006	 * cap_convert_nscap(), called by setxattr()
1007	 */
1008	if (strcmp(name, XATTR_NAME_CAPS) == 0)
1009		return 0;
 
1010
1011	if (!ns_capable(user_ns, CAP_SYS_ADMIN))
 
 
1012		return -EPERM;
1013	return 0;
1014}
1015
1016/**
1017 * cap_inode_removexattr - Determine whether an xattr may be removed
1018 *
1019 * @mnt_userns:	User namespace of the mount the inode was found from
1020 * @dentry:	The inode/dentry being altered
1021 * @name:	The name of the xattr to be changed
1022 *
1023 * Determine whether an xattr may be removed from an inode, returning 0 if
1024 * permission is granted, -ve if denied.
1025 *
1026 * If the inode has been found through an idmapped mount the user namespace of
1027 * the vfsmount must be passed through @mnt_userns. This function will then
1028 * take care to map the inode according to @mnt_userns before checking
1029 * permissions. On non-idmapped mounts or if permission checking is to be
1030 * performed on the raw inode simply passs init_user_ns.
1031 *
1032 * This is used to make sure security xattrs don't get removed by those who
1033 * aren't privileged to remove them.
1034 */
1035int cap_inode_removexattr(struct user_namespace *mnt_userns,
1036			  struct dentry *dentry, const char *name)
1037{
1038	struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
1039
1040	/* Ignore non-security xattrs */
1041	if (strncmp(name, XATTR_SECURITY_PREFIX,
1042			XATTR_SECURITY_PREFIX_LEN) != 0)
1043		return 0;
1044
1045	if (strcmp(name, XATTR_NAME_CAPS) == 0) {
1046		/* security.capability gets namespaced */
1047		struct inode *inode = d_backing_inode(dentry);
1048		if (!inode)
1049			return -EINVAL;
1050		if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP))
1051			return -EPERM;
1052		return 0;
1053	}
1054
1055	if (!ns_capable(user_ns, CAP_SYS_ADMIN))
 
 
1056		return -EPERM;
1057	return 0;
1058}
1059
1060/*
1061 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
1062 * a process after a call to setuid, setreuid, or setresuid.
1063 *
1064 *  1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
1065 *  {r,e,s}uid != 0, the permitted and effective capabilities are
1066 *  cleared.
1067 *
1068 *  2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
1069 *  capabilities of the process are cleared.
1070 *
1071 *  3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
1072 *  capabilities are set to the permitted capabilities.
1073 *
1074 *  fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
1075 *  never happen.
1076 *
1077 *  -astor
1078 *
1079 * cevans - New behaviour, Oct '99
1080 * A process may, via prctl(), elect to keep its capabilities when it
1081 * calls setuid() and switches away from uid==0. Both permitted and
1082 * effective sets will be retained.
1083 * Without this change, it was impossible for a daemon to drop only some
1084 * of its privilege. The call to setuid(!=0) would drop all privileges!
1085 * Keeping uid 0 is not an option because uid 0 owns too many vital
1086 * files..
1087 * Thanks to Olaf Kirch and Peter Benie for spotting this.
1088 */
1089static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
1090{
1091	kuid_t root_uid = make_kuid(old->user_ns, 0);
1092
1093	if ((uid_eq(old->uid, root_uid) ||
1094	     uid_eq(old->euid, root_uid) ||
1095	     uid_eq(old->suid, root_uid)) &&
1096	    (!uid_eq(new->uid, root_uid) &&
1097	     !uid_eq(new->euid, root_uid) &&
1098	     !uid_eq(new->suid, root_uid))) {
1099		if (!issecure(SECURE_KEEP_CAPS)) {
1100			cap_clear(new->cap_permitted);
1101			cap_clear(new->cap_effective);
1102		}
1103
1104		/*
1105		 * Pre-ambient programs expect setresuid to nonroot followed
1106		 * by exec to drop capabilities.  We should make sure that
1107		 * this remains the case.
1108		 */
1109		cap_clear(new->cap_ambient);
1110	}
1111	if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
1112		cap_clear(new->cap_effective);
1113	if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
1114		new->cap_effective = new->cap_permitted;
1115}
1116
1117/**
1118 * cap_task_fix_setuid - Fix up the results of setuid() call
1119 * @new: The proposed credentials
1120 * @old: The current task's current credentials
1121 * @flags: Indications of what has changed
1122 *
1123 * Fix up the results of setuid() call before the credential changes are
1124 * actually applied.
1125 *
1126 * Return: 0 to grant the changes, -ve to deny them.
1127 */
1128int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
1129{
1130	switch (flags) {
1131	case LSM_SETID_RE:
1132	case LSM_SETID_ID:
1133	case LSM_SETID_RES:
1134		/* juggle the capabilities to follow [RES]UID changes unless
1135		 * otherwise suppressed */
1136		if (!issecure(SECURE_NO_SETUID_FIXUP))
1137			cap_emulate_setxuid(new, old);
1138		break;
1139
1140	case LSM_SETID_FS:
1141		/* juggle the capabilties to follow FSUID changes, unless
1142		 * otherwise suppressed
1143		 *
1144		 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
1145		 *          if not, we might be a bit too harsh here.
1146		 */
1147		if (!issecure(SECURE_NO_SETUID_FIXUP)) {
1148			kuid_t root_uid = make_kuid(old->user_ns, 0);
1149			if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
1150				new->cap_effective =
1151					cap_drop_fs_set(new->cap_effective);
1152
1153			if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
1154				new->cap_effective =
1155					cap_raise_fs_set(new->cap_effective,
1156							 new->cap_permitted);
1157		}
1158		break;
1159
1160	default:
1161		return -EINVAL;
1162	}
1163
1164	return 0;
1165}
1166
1167/*
1168 * Rationale: code calling task_setscheduler, task_setioprio, and
1169 * task_setnice, assumes that
1170 *   . if capable(cap_sys_nice), then those actions should be allowed
1171 *   . if not capable(cap_sys_nice), but acting on your own processes,
1172 *   	then those actions should be allowed
1173 * This is insufficient now since you can call code without suid, but
1174 * yet with increased caps.
1175 * So we check for increased caps on the target process.
1176 */
1177static int cap_safe_nice(struct task_struct *p)
1178{
1179	int is_subset, ret = 0;
1180
1181	rcu_read_lock();
1182	is_subset = cap_issubset(__task_cred(p)->cap_permitted,
1183				 current_cred()->cap_permitted);
1184	if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
1185		ret = -EPERM;
1186	rcu_read_unlock();
1187
1188	return ret;
1189}
1190
1191/**
1192 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
1193 * @p: The task to affect
1194 *
1195 * Detemine if the requested scheduler policy change is permitted for the
1196 * specified task.
1197 *
1198 * Return: 0 if permission is granted, -ve if denied.
1199 */
1200int cap_task_setscheduler(struct task_struct *p)
1201{
1202	return cap_safe_nice(p);
1203}
1204
1205/**
1206 * cap_task_setioprio - Detemine if I/O priority change is permitted
1207 * @p: The task to affect
1208 * @ioprio: The I/O priority to set
1209 *
1210 * Detemine if the requested I/O priority change is permitted for the specified
1211 * task.
1212 *
1213 * Return: 0 if permission is granted, -ve if denied.
1214 */
1215int cap_task_setioprio(struct task_struct *p, int ioprio)
1216{
1217	return cap_safe_nice(p);
1218}
1219
1220/**
1221 * cap_task_setnice - Detemine if task priority change is permitted
1222 * @p: The task to affect
1223 * @nice: The nice value to set
1224 *
1225 * Detemine if the requested task priority change is permitted for the
1226 * specified task.
1227 *
1228 * Return: 0 if permission is granted, -ve if denied.
1229 */
1230int cap_task_setnice(struct task_struct *p, int nice)
1231{
1232	return cap_safe_nice(p);
1233}
1234
1235/*
1236 * Implement PR_CAPBSET_DROP.  Attempt to remove the specified capability from
1237 * the current task's bounding set.  Returns 0 on success, -ve on error.
1238 */
1239static int cap_prctl_drop(unsigned long cap)
1240{
1241	struct cred *new;
1242
1243	if (!ns_capable(current_user_ns(), CAP_SETPCAP))
1244		return -EPERM;
1245	if (!cap_valid(cap))
1246		return -EINVAL;
1247
1248	new = prepare_creds();
1249	if (!new)
1250		return -ENOMEM;
1251	cap_lower(new->cap_bset, cap);
1252	return commit_creds(new);
1253}
1254
1255/**
1256 * cap_task_prctl - Implement process control functions for this security module
1257 * @option: The process control function requested
1258 * @arg2: The argument data for this function
1259 * @arg3: The argument data for this function
1260 * @arg4: The argument data for this function
1261 * @arg5: The argument data for this function
1262 *
1263 * Allow process control functions (sys_prctl()) to alter capabilities; may
1264 * also deny access to other functions not otherwise implemented here.
1265 *
1266 * Return: 0 or +ve on success, -ENOSYS if this function is not implemented
1267 * here, other -ve on error.  If -ENOSYS is returned, sys_prctl() and other LSM
1268 * modules will consider performing the function.
1269 */
1270int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
1271		   unsigned long arg4, unsigned long arg5)
1272{
1273	const struct cred *old = current_cred();
1274	struct cred *new;
1275
1276	switch (option) {
1277	case PR_CAPBSET_READ:
1278		if (!cap_valid(arg2))
1279			return -EINVAL;
1280		return !!cap_raised(old->cap_bset, arg2);
1281
1282	case PR_CAPBSET_DROP:
1283		return cap_prctl_drop(arg2);
1284
1285	/*
1286	 * The next four prctl's remain to assist with transitioning a
1287	 * system from legacy UID=0 based privilege (when filesystem
1288	 * capabilities are not in use) to a system using filesystem
1289	 * capabilities only - as the POSIX.1e draft intended.
1290	 *
1291	 * Note:
1292	 *
1293	 *  PR_SET_SECUREBITS =
1294	 *      issecure_mask(SECURE_KEEP_CAPS_LOCKED)
1295	 *    | issecure_mask(SECURE_NOROOT)
1296	 *    | issecure_mask(SECURE_NOROOT_LOCKED)
1297	 *    | issecure_mask(SECURE_NO_SETUID_FIXUP)
1298	 *    | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
1299	 *
1300	 * will ensure that the current process and all of its
1301	 * children will be locked into a pure
1302	 * capability-based-privilege environment.
1303	 */
1304	case PR_SET_SECUREBITS:
1305		if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
1306		     & (old->securebits ^ arg2))			/*[1]*/
1307		    || ((old->securebits & SECURE_ALL_LOCKS & ~arg2))	/*[2]*/
1308		    || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS))	/*[3]*/
1309		    || (cap_capable(current_cred(),
1310				    current_cred()->user_ns,
1311				    CAP_SETPCAP,
1312				    CAP_OPT_NONE) != 0)			/*[4]*/
1313			/*
1314			 * [1] no changing of bits that are locked
1315			 * [2] no unlocking of locks
1316			 * [3] no setting of unsupported bits
1317			 * [4] doing anything requires privilege (go read about
1318			 *     the "sendmail capabilities bug")
1319			 */
1320		    )
1321			/* cannot change a locked bit */
1322			return -EPERM;
1323
1324		new = prepare_creds();
1325		if (!new)
1326			return -ENOMEM;
1327		new->securebits = arg2;
1328		return commit_creds(new);
1329
1330	case PR_GET_SECUREBITS:
1331		return old->securebits;
1332
1333	case PR_GET_KEEPCAPS:
1334		return !!issecure(SECURE_KEEP_CAPS);
1335
1336	case PR_SET_KEEPCAPS:
1337		if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
1338			return -EINVAL;
1339		if (issecure(SECURE_KEEP_CAPS_LOCKED))
1340			return -EPERM;
1341
1342		new = prepare_creds();
1343		if (!new)
1344			return -ENOMEM;
1345		if (arg2)
1346			new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
1347		else
1348			new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
1349		return commit_creds(new);
1350
1351	case PR_CAP_AMBIENT:
1352		if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
1353			if (arg3 | arg4 | arg5)
1354				return -EINVAL;
1355
1356			new = prepare_creds();
1357			if (!new)
1358				return -ENOMEM;
1359			cap_clear(new->cap_ambient);
1360			return commit_creds(new);
1361		}
1362
1363		if (((!cap_valid(arg3)) | arg4 | arg5))
1364			return -EINVAL;
1365
1366		if (arg2 == PR_CAP_AMBIENT_IS_SET) {
1367			return !!cap_raised(current_cred()->cap_ambient, arg3);
1368		} else if (arg2 != PR_CAP_AMBIENT_RAISE &&
1369			   arg2 != PR_CAP_AMBIENT_LOWER) {
1370			return -EINVAL;
1371		} else {
1372			if (arg2 == PR_CAP_AMBIENT_RAISE &&
1373			    (!cap_raised(current_cred()->cap_permitted, arg3) ||
1374			     !cap_raised(current_cred()->cap_inheritable,
1375					 arg3) ||
1376			     issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
1377				return -EPERM;
1378
1379			new = prepare_creds();
1380			if (!new)
1381				return -ENOMEM;
1382			if (arg2 == PR_CAP_AMBIENT_RAISE)
1383				cap_raise(new->cap_ambient, arg3);
1384			else
1385				cap_lower(new->cap_ambient, arg3);
1386			return commit_creds(new);
1387		}
1388
1389	default:
1390		/* No functionality available - continue with default */
1391		return -ENOSYS;
1392	}
1393}
1394
1395/**
1396 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
1397 * @mm: The VM space in which the new mapping is to be made
1398 * @pages: The size of the mapping
1399 *
1400 * Determine whether the allocation of a new virtual mapping by the current
1401 * task is permitted.
1402 *
1403 * Return: 1 if permission is granted, 0 if not.
1404 */
1405int cap_vm_enough_memory(struct mm_struct *mm, long pages)
1406{
1407	int cap_sys_admin = 0;
1408
1409	if (cap_capable(current_cred(), &init_user_ns,
1410				CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) == 0)
1411		cap_sys_admin = 1;
1412
1413	return cap_sys_admin;
1414}
1415
1416/**
1417 * cap_mmap_addr - check if able to map given addr
1418 * @addr: address attempting to be mapped
1419 *
1420 * If the process is attempting to map memory below dac_mmap_min_addr they need
1421 * CAP_SYS_RAWIO.  The other parameters to this function are unused by the
1422 * capability security module.
1423 *
1424 * Return: 0 if this mapping should be allowed or -EPERM if not.
1425 */
1426int cap_mmap_addr(unsigned long addr)
1427{
1428	int ret = 0;
1429
1430	if (addr < dac_mmap_min_addr) {
1431		ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
1432				  CAP_OPT_NONE);
1433		/* set PF_SUPERPRIV if it turns out we allow the low mmap */
1434		if (ret == 0)
1435			current->flags |= PF_SUPERPRIV;
1436	}
1437	return ret;
1438}
1439
1440int cap_mmap_file(struct file *file, unsigned long reqprot,
1441		  unsigned long prot, unsigned long flags)
1442{
1443	return 0;
1444}
1445
1446#ifdef CONFIG_SECURITY
1447
1448static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
1449	LSM_HOOK_INIT(capable, cap_capable),
1450	LSM_HOOK_INIT(settime, cap_settime),
1451	LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
1452	LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
1453	LSM_HOOK_INIT(capget, cap_capget),
1454	LSM_HOOK_INIT(capset, cap_capset),
1455	LSM_HOOK_INIT(bprm_creds_from_file, cap_bprm_creds_from_file),
 
1456	LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
1457	LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
1458	LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity),
1459	LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
1460	LSM_HOOK_INIT(mmap_file, cap_mmap_file),
1461	LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
1462	LSM_HOOK_INIT(task_prctl, cap_task_prctl),
1463	LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
1464	LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
1465	LSM_HOOK_INIT(task_setnice, cap_task_setnice),
1466	LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
1467};
1468
1469static int __init capability_init(void)
1470{
1471	security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
1472				"capability");
1473	return 0;
1474}
1475
1476DEFINE_LSM(capability) = {
1477	.name = "capability",
1478	.order = LSM_ORDER_FIRST,
1479	.init = capability_init,
1480};
1481
1482#endif /* CONFIG_SECURITY */