xref: /linux-6.15/security/commoncap.c (revision f6fbd8cb)
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  */
40 static 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  */
66 int 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  */
112 int 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  */
134 int 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;
153 out:
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  */
171 int 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;
185 out:
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  */
200 int 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  */
219 static 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  */
242 int 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  */
296 int 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  */
321 int 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 
331 static bool rootid_owns_currentns(kuid_t kroot)
332 {
333 	struct user_namespace *ns;
334 
335 	if (!uid_valid(kroot))
336 		return false;
337 
338 	for (ns = current_user_ns(); ; ns = ns->parent) {
339 		if (from_kuid(ns, kroot) == 0)
340 			return true;
341 		if (ns == &init_user_ns)
342 			break;
343 	}
344 
345 	return false;
346 }
347 
348 static __u32 sansflags(__u32 m)
349 {
350 	return m & ~VFS_CAP_FLAGS_EFFECTIVE;
351 }
352 
353 static bool is_v2header(int size, const struct vfs_cap_data *cap)
354 {
355 	if (size != XATTR_CAPS_SZ_2)
356 		return false;
357 	return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_2;
358 }
359 
360 static bool is_v3header(int size, const struct vfs_cap_data *cap)
361 {
362 	if (size != XATTR_CAPS_SZ_3)
363 		return false;
364 	return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_3;
365 }
366 
367 /*
368  * getsecurity: We are called for security.* before any attempt to read the
369  * xattr from the inode itself.
370  *
371  * This gives us a chance to read the on-disk value and convert it.  If we
372  * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler.
373  *
374  * Note we are not called by vfs_getxattr_alloc(), but that is only called
375  * by the integrity subsystem, which really wants the unconverted values -
376  * so that's good.
377  */
378 int cap_inode_getsecurity(struct user_namespace *mnt_userns,
379 			  struct inode *inode, const char *name, void **buffer,
380 			  bool alloc)
381 {
382 	int size;
383 	kuid_t kroot;
384 	u32 nsmagic, magic;
385 	uid_t root, mappedroot;
386 	char *tmpbuf = NULL;
387 	struct vfs_cap_data *cap;
388 	struct vfs_ns_cap_data *nscap = NULL;
389 	struct dentry *dentry;
390 	struct user_namespace *fs_ns;
391 
392 	if (strcmp(name, "capability") != 0)
393 		return -EOPNOTSUPP;
394 
395 	dentry = d_find_any_alias(inode);
396 	if (!dentry)
397 		return -EINVAL;
398 	size = vfs_getxattr_alloc(mnt_userns, dentry, XATTR_NAME_CAPS, &tmpbuf,
399 				  sizeof(struct vfs_ns_cap_data), GFP_NOFS);
400 	dput(dentry);
401 	/* gcc11 complains if we don't check for !tmpbuf */
402 	if (size < 0 || !tmpbuf)
403 		goto out_free;
404 
405 	fs_ns = inode->i_sb->s_user_ns;
406 	cap = (struct vfs_cap_data *) tmpbuf;
407 	if (is_v2header(size, cap)) {
408 		root = 0;
409 	} else if (is_v3header(size, cap)) {
410 		nscap = (struct vfs_ns_cap_data *) tmpbuf;
411 		root = le32_to_cpu(nscap->rootid);
412 	} else {
413 		size = -EINVAL;
414 		goto out_free;
415 	}
416 
417 	kroot = make_kuid(fs_ns, root);
418 
419 	/* If this is an idmapped mount shift the kuid. */
420 	kroot = mapped_kuid_fs(mnt_userns, fs_ns, kroot);
421 
422 	/* If the root kuid maps to a valid uid in current ns, then return
423 	 * this as a nscap. */
424 	mappedroot = from_kuid(current_user_ns(), kroot);
425 	if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) {
426 		size = sizeof(struct vfs_ns_cap_data);
427 		if (alloc) {
428 			if (!nscap) {
429 				/* v2 -> v3 conversion */
430 				nscap = kzalloc(size, GFP_ATOMIC);
431 				if (!nscap) {
432 					size = -ENOMEM;
433 					goto out_free;
434 				}
435 				nsmagic = VFS_CAP_REVISION_3;
436 				magic = le32_to_cpu(cap->magic_etc);
437 				if (magic & VFS_CAP_FLAGS_EFFECTIVE)
438 					nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
439 				memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
440 				nscap->magic_etc = cpu_to_le32(nsmagic);
441 			} else {
442 				/* use allocated v3 buffer */
443 				tmpbuf = NULL;
444 			}
445 			nscap->rootid = cpu_to_le32(mappedroot);
446 			*buffer = nscap;
447 		}
448 		goto out_free;
449 	}
450 
451 	if (!rootid_owns_currentns(kroot)) {
452 		size = -EOVERFLOW;
453 		goto out_free;
454 	}
455 
456 	/* This comes from a parent namespace.  Return as a v2 capability */
457 	size = sizeof(struct vfs_cap_data);
458 	if (alloc) {
459 		if (nscap) {
460 			/* v3 -> v2 conversion */
461 			cap = kzalloc(size, GFP_ATOMIC);
462 			if (!cap) {
463 				size = -ENOMEM;
464 				goto out_free;
465 			}
466 			magic = VFS_CAP_REVISION_2;
467 			nsmagic = le32_to_cpu(nscap->magic_etc);
468 			if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE)
469 				magic |= VFS_CAP_FLAGS_EFFECTIVE;
470 			memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
471 			cap->magic_etc = cpu_to_le32(magic);
472 		} else {
473 			/* use unconverted v2 */
474 			tmpbuf = NULL;
475 		}
476 		*buffer = cap;
477 	}
478 out_free:
479 	kfree(tmpbuf);
480 	return size;
481 }
482 
483 /**
484  * rootid_from_xattr - translate root uid of vfs caps
485  *
486  * @value:	vfs caps value which may be modified by this function
487  * @size:	size of @ivalue
488  * @task_ns:	user namespace of the caller
489  * @mnt_userns:	user namespace of the mount the inode was found from
490  * @fs_userns:	user namespace of the filesystem
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  */
498 static kuid_t rootid_from_xattr(const void *value, size_t size,
499 				struct user_namespace *task_ns,
500 				struct user_namespace *mnt_userns,
501 				struct user_namespace *fs_userns)
502 {
503 	const struct vfs_ns_cap_data *nscap = value;
504 	kuid_t rootkid;
505 	uid_t rootid = 0;
506 
507 	if (size == XATTR_CAPS_SZ_3)
508 		rootid = le32_to_cpu(nscap->rootid);
509 
510 	rootkid = make_kuid(task_ns, rootid);
511 	return mapped_kuid_user(mnt_userns, fs_userns, rootkid);
512 }
513 
514 static bool validheader(size_t size, const struct vfs_cap_data *cap)
515 {
516 	return is_v2header(size, cap) || is_v3header(size, cap);
517 }
518 
519 /**
520  * cap_convert_nscap - check vfs caps
521  *
522  * @mnt_userns:	user namespace of the mount the inode was found from
523  * @dentry:	used to retrieve inode to check permissions on
524  * @ivalue:	vfs caps value which may be modified by this function
525  * @size:	size of @ivalue
526  *
527  * User requested a write of security.capability.  If needed, update the
528  * xattr to change from v2 to v3, or to fixup the v3 rootid.
529  *
530  * If the inode has been found through an idmapped mount the user namespace of
531  * the vfsmount must be passed through @mnt_userns. This function will then
532  * take care to map the inode according to @mnt_userns before checking
533  * permissions. On non-idmapped mounts or if permission checking is to be
534  * performed on the raw inode simply passs init_user_ns.
535  *
536  * Return: On success, return the new size; on error, return < 0.
537  */
538 int cap_convert_nscap(struct user_namespace *mnt_userns, struct dentry *dentry,
539 		      const void **ivalue, size_t size)
540 {
541 	struct vfs_ns_cap_data *nscap;
542 	uid_t nsrootid;
543 	const struct vfs_cap_data *cap = *ivalue;
544 	__u32 magic, nsmagic;
545 	struct inode *inode = d_backing_inode(dentry);
546 	struct user_namespace *task_ns = current_user_ns(),
547 		*fs_ns = inode->i_sb->s_user_ns;
548 	kuid_t rootid;
549 	size_t newsize;
550 
551 	if (!*ivalue)
552 		return -EINVAL;
553 	if (!validheader(size, cap))
554 		return -EINVAL;
555 	if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP))
556 		return -EPERM;
557 	if (size == XATTR_CAPS_SZ_2 && (mnt_userns == fs_ns))
558 		if (ns_capable(inode->i_sb->s_user_ns, CAP_SETFCAP))
559 			/* user is privileged, just write the v2 */
560 			return size;
561 
562 	rootid = rootid_from_xattr(*ivalue, size, task_ns, mnt_userns, fs_ns);
563 	if (!uid_valid(rootid))
564 		return -EINVAL;
565 
566 	nsrootid = from_kuid(fs_ns, rootid);
567 	if (nsrootid == -1)
568 		return -EINVAL;
569 
570 	newsize = sizeof(struct vfs_ns_cap_data);
571 	nscap = kmalloc(newsize, GFP_ATOMIC);
572 	if (!nscap)
573 		return -ENOMEM;
574 	nscap->rootid = cpu_to_le32(nsrootid);
575 	nsmagic = VFS_CAP_REVISION_3;
576 	magic = le32_to_cpu(cap->magic_etc);
577 	if (magic & VFS_CAP_FLAGS_EFFECTIVE)
578 		nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
579 	nscap->magic_etc = cpu_to_le32(nsmagic);
580 	memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
581 
582 	*ivalue = nscap;
583 	return newsize;
584 }
585 
586 /*
587  * Calculate the new process capability sets from the capability sets attached
588  * to a file.
589  */
590 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
591 					  struct linux_binprm *bprm,
592 					  bool *effective,
593 					  bool *has_fcap)
594 {
595 	struct cred *new = bprm->cred;
596 	unsigned i;
597 	int ret = 0;
598 
599 	if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
600 		*effective = true;
601 
602 	if (caps->magic_etc & VFS_CAP_REVISION_MASK)
603 		*has_fcap = true;
604 
605 	CAP_FOR_EACH_U32(i) {
606 		__u32 permitted = caps->permitted.cap[i];
607 		__u32 inheritable = caps->inheritable.cap[i];
608 
609 		/*
610 		 * pP' = (X & fP) | (pI & fI)
611 		 * The addition of pA' is handled later.
612 		 */
613 		new->cap_permitted.cap[i] =
614 			(new->cap_bset.cap[i] & permitted) |
615 			(new->cap_inheritable.cap[i] & inheritable);
616 
617 		if (permitted & ~new->cap_permitted.cap[i])
618 			/* insufficient to execute correctly */
619 			ret = -EPERM;
620 	}
621 
622 	/*
623 	 * For legacy apps, with no internal support for recognizing they
624 	 * do not have enough capabilities, we return an error if they are
625 	 * missing some "forced" (aka file-permitted) capabilities.
626 	 */
627 	return *effective ? ret : 0;
628 }
629 
630 /**
631  * get_vfs_caps_from_disk - retrieve vfs caps from disk
632  *
633  * @mnt_userns:	user namespace of the mount the inode was found from
634  * @dentry:	dentry from which @inode is retrieved
635  * @cpu_caps:	vfs capabilities
636  *
637  * Extract the on-exec-apply capability sets for an executable file.
638  *
639  * If the inode has been found through an idmapped mount the user namespace of
640  * the vfsmount must be passed through @mnt_userns. This function will then
641  * take care to map the inode according to @mnt_userns before checking
642  * permissions. On non-idmapped mounts or if permission checking is to be
643  * performed on the raw inode simply passs init_user_ns.
644  */
645 int get_vfs_caps_from_disk(struct user_namespace *mnt_userns,
646 			   const struct dentry *dentry,
647 			   struct cpu_vfs_cap_data *cpu_caps)
648 {
649 	struct inode *inode = d_backing_inode(dentry);
650 	__u32 magic_etc;
651 	unsigned tocopy, i;
652 	int size;
653 	struct vfs_ns_cap_data data, *nscaps = &data;
654 	struct vfs_cap_data *caps = (struct vfs_cap_data *) &data;
655 	kuid_t rootkuid;
656 	struct user_namespace *fs_ns;
657 
658 	memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
659 
660 	if (!inode)
661 		return -ENODATA;
662 
663 	fs_ns = inode->i_sb->s_user_ns;
664 	size = __vfs_getxattr((struct dentry *)dentry, inode,
665 			      XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ);
666 	if (size == -ENODATA || size == -EOPNOTSUPP)
667 		/* no data, that's ok */
668 		return -ENODATA;
669 
670 	if (size < 0)
671 		return size;
672 
673 	if (size < sizeof(magic_etc))
674 		return -EINVAL;
675 
676 	cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps->magic_etc);
677 
678 	rootkuid = make_kuid(fs_ns, 0);
679 	switch (magic_etc & VFS_CAP_REVISION_MASK) {
680 	case VFS_CAP_REVISION_1:
681 		if (size != XATTR_CAPS_SZ_1)
682 			return -EINVAL;
683 		tocopy = VFS_CAP_U32_1;
684 		break;
685 	case VFS_CAP_REVISION_2:
686 		if (size != XATTR_CAPS_SZ_2)
687 			return -EINVAL;
688 		tocopy = VFS_CAP_U32_2;
689 		break;
690 	case VFS_CAP_REVISION_3:
691 		if (size != XATTR_CAPS_SZ_3)
692 			return -EINVAL;
693 		tocopy = VFS_CAP_U32_3;
694 		rootkuid = make_kuid(fs_ns, le32_to_cpu(nscaps->rootid));
695 		break;
696 
697 	default:
698 		return -EINVAL;
699 	}
700 	/* Limit the caps to the mounter of the filesystem
701 	 * or the more limited uid specified in the xattr.
702 	 */
703 	rootkuid = mapped_kuid_fs(mnt_userns, fs_ns, rootkuid);
704 	if (!rootid_owns_currentns(rootkuid))
705 		return -ENODATA;
706 
707 	CAP_FOR_EACH_U32(i) {
708 		if (i >= tocopy)
709 			break;
710 		cpu_caps->permitted.cap[i] = le32_to_cpu(caps->data[i].permitted);
711 		cpu_caps->inheritable.cap[i] = le32_to_cpu(caps->data[i].inheritable);
712 	}
713 
714 	cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
715 	cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
716 
717 	cpu_caps->rootid = rootkuid;
718 
719 	return 0;
720 }
721 
722 /*
723  * Attempt to get the on-exec apply capability sets for an executable file from
724  * its xattrs and, if present, apply them to the proposed credentials being
725  * constructed by execve().
726  */
727 static int get_file_caps(struct linux_binprm *bprm, struct file *file,
728 			 bool *effective, bool *has_fcap)
729 {
730 	int rc = 0;
731 	struct cpu_vfs_cap_data vcaps;
732 
733 	cap_clear(bprm->cred->cap_permitted);
734 
735 	if (!file_caps_enabled)
736 		return 0;
737 
738 	if (!mnt_may_suid(file->f_path.mnt))
739 		return 0;
740 
741 	/*
742 	 * This check is redundant with mnt_may_suid() but is kept to make
743 	 * explicit that capability bits are limited to s_user_ns and its
744 	 * descendants.
745 	 */
746 	if (!current_in_userns(file->f_path.mnt->mnt_sb->s_user_ns))
747 		return 0;
748 
749 	rc = get_vfs_caps_from_disk(file_mnt_user_ns(file),
750 				    file->f_path.dentry, &vcaps);
751 	if (rc < 0) {
752 		if (rc == -EINVAL)
753 			printk(KERN_NOTICE "Invalid argument reading file caps for %s\n",
754 					bprm->filename);
755 		else if (rc == -ENODATA)
756 			rc = 0;
757 		goto out;
758 	}
759 
760 	rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_fcap);
761 
762 out:
763 	if (rc)
764 		cap_clear(bprm->cred->cap_permitted);
765 
766 	return rc;
767 }
768 
769 static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); }
770 
771 static inline bool __is_real(kuid_t uid, struct cred *cred)
772 { return uid_eq(cred->uid, uid); }
773 
774 static inline bool __is_eff(kuid_t uid, struct cred *cred)
775 { return uid_eq(cred->euid, uid); }
776 
777 static inline bool __is_suid(kuid_t uid, struct cred *cred)
778 { return !__is_real(uid, cred) && __is_eff(uid, cred); }
779 
780 /*
781  * handle_privileged_root - Handle case of privileged root
782  * @bprm: The execution parameters, including the proposed creds
783  * @has_fcap: Are any file capabilities set?
784  * @effective: Do we have effective root privilege?
785  * @root_uid: This namespace' root UID WRT initial USER namespace
786  *
787  * Handle the case where root is privileged and hasn't been neutered by
788  * SECURE_NOROOT.  If file capabilities are set, they won't be combined with
789  * set UID root and nothing is changed.  If we are root, cap_permitted is
790  * updated.  If we have become set UID root, the effective bit is set.
791  */
792 static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap,
793 				   bool *effective, kuid_t root_uid)
794 {
795 	const struct cred *old = current_cred();
796 	struct cred *new = bprm->cred;
797 
798 	if (!root_privileged())
799 		return;
800 	/*
801 	 * If the legacy file capability is set, then don't set privs
802 	 * for a setuid root binary run by a non-root user.  Do set it
803 	 * for a root user just to cause least surprise to an admin.
804 	 */
805 	if (has_fcap && __is_suid(root_uid, new)) {
806 		warn_setuid_and_fcaps_mixed(bprm->filename);
807 		return;
808 	}
809 	/*
810 	 * To support inheritance of root-permissions and suid-root
811 	 * executables under compatibility mode, we override the
812 	 * capability sets for the file.
813 	 */
814 	if (__is_eff(root_uid, new) || __is_real(root_uid, new)) {
815 		/* pP' = (cap_bset & ~0) | (pI & ~0) */
816 		new->cap_permitted = cap_combine(old->cap_bset,
817 						 old->cap_inheritable);
818 	}
819 	/*
820 	 * If only the real uid is 0, we do not set the effective bit.
821 	 */
822 	if (__is_eff(root_uid, new))
823 		*effective = true;
824 }
825 
826 #define __cap_gained(field, target, source) \
827 	!cap_issubset(target->cap_##field, source->cap_##field)
828 #define __cap_grew(target, source, cred) \
829 	!cap_issubset(cred->cap_##target, cred->cap_##source)
830 #define __cap_full(field, cred) \
831 	cap_issubset(CAP_FULL_SET, cred->cap_##field)
832 
833 static inline bool __is_setuid(struct cred *new, const struct cred *old)
834 { return !uid_eq(new->euid, old->uid); }
835 
836 static inline bool __is_setgid(struct cred *new, const struct cred *old)
837 { return !gid_eq(new->egid, old->gid); }
838 
839 /*
840  * 1) Audit candidate if current->cap_effective is set
841  *
842  * We do not bother to audit if 3 things are true:
843  *   1) cap_effective has all caps
844  *   2) we became root *OR* are were already root
845  *   3) root is supposed to have all caps (SECURE_NOROOT)
846  * Since this is just a normal root execing a process.
847  *
848  * Number 1 above might fail if you don't have a full bset, but I think
849  * that is interesting information to audit.
850  *
851  * A number of other conditions require logging:
852  * 2) something prevented setuid root getting all caps
853  * 3) non-setuid root gets fcaps
854  * 4) non-setuid root gets ambient
855  */
856 static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old,
857 				     kuid_t root, bool has_fcap)
858 {
859 	bool ret = false;
860 
861 	if ((__cap_grew(effective, ambient, new) &&
862 	     !(__cap_full(effective, new) &&
863 	       (__is_eff(root, new) || __is_real(root, new)) &&
864 	       root_privileged())) ||
865 	    (root_privileged() &&
866 	     __is_suid(root, new) &&
867 	     !__cap_full(effective, new)) ||
868 	    (!__is_setuid(new, old) &&
869 	     ((has_fcap &&
870 	       __cap_gained(permitted, new, old)) ||
871 	      __cap_gained(ambient, new, old))))
872 
873 		ret = true;
874 
875 	return ret;
876 }
877 
878 /**
879  * cap_bprm_creds_from_file - Set up the proposed credentials for execve().
880  * @bprm: The execution parameters, including the proposed creds
881  * @file: The file to pull the credentials from
882  *
883  * Set up the proposed credentials for a new execution context being
884  * constructed by execve().  The proposed creds in @bprm->cred is altered,
885  * which won't take effect immediately.
886  *
887  * Return: 0 if successful, -ve on error.
888  */
889 int cap_bprm_creds_from_file(struct linux_binprm *bprm, struct file *file)
890 {
891 	/* Process setpcap binaries and capabilities for uid 0 */
892 	const struct cred *old = current_cred();
893 	struct cred *new = bprm->cred;
894 	bool effective = false, has_fcap = false, is_setid;
895 	int ret;
896 	kuid_t root_uid;
897 
898 	if (WARN_ON(!cap_ambient_invariant_ok(old)))
899 		return -EPERM;
900 
901 	ret = get_file_caps(bprm, file, &effective, &has_fcap);
902 	if (ret < 0)
903 		return ret;
904 
905 	root_uid = make_kuid(new->user_ns, 0);
906 
907 	handle_privileged_root(bprm, has_fcap, &effective, root_uid);
908 
909 	/* if we have fs caps, clear dangerous personality flags */
910 	if (__cap_gained(permitted, new, old))
911 		bprm->per_clear |= PER_CLEAR_ON_SETID;
912 
913 	/* Don't let someone trace a set[ug]id/setpcap binary with the revised
914 	 * credentials unless they have the appropriate permit.
915 	 *
916 	 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
917 	 */
918 	is_setid = __is_setuid(new, old) || __is_setgid(new, old);
919 
920 	if ((is_setid || __cap_gained(permitted, new, old)) &&
921 	    ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) ||
922 	     !ptracer_capable(current, new->user_ns))) {
923 		/* downgrade; they get no more than they had, and maybe less */
924 		if (!ns_capable(new->user_ns, CAP_SETUID) ||
925 		    (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
926 			new->euid = new->uid;
927 			new->egid = new->gid;
928 		}
929 		new->cap_permitted = cap_intersect(new->cap_permitted,
930 						   old->cap_permitted);
931 	}
932 
933 	new->suid = new->fsuid = new->euid;
934 	new->sgid = new->fsgid = new->egid;
935 
936 	/* File caps or setid cancels ambient. */
937 	if (has_fcap || is_setid)
938 		cap_clear(new->cap_ambient);
939 
940 	/*
941 	 * Now that we've computed pA', update pP' to give:
942 	 *   pP' = (X & fP) | (pI & fI) | pA'
943 	 */
944 	new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
945 
946 	/*
947 	 * Set pE' = (fE ? pP' : pA').  Because pA' is zero if fE is set,
948 	 * this is the same as pE' = (fE ? pP' : 0) | pA'.
949 	 */
950 	if (effective)
951 		new->cap_effective = new->cap_permitted;
952 	else
953 		new->cap_effective = new->cap_ambient;
954 
955 	if (WARN_ON(!cap_ambient_invariant_ok(new)))
956 		return -EPERM;
957 
958 	if (nonroot_raised_pE(new, old, root_uid, has_fcap)) {
959 		ret = audit_log_bprm_fcaps(bprm, new, old);
960 		if (ret < 0)
961 			return ret;
962 	}
963 
964 	new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
965 
966 	if (WARN_ON(!cap_ambient_invariant_ok(new)))
967 		return -EPERM;
968 
969 	/* Check for privilege-elevated exec. */
970 	if (is_setid ||
971 	    (!__is_real(root_uid, new) &&
972 	     (effective ||
973 	      __cap_grew(permitted, ambient, new))))
974 		bprm->secureexec = 1;
975 
976 	return 0;
977 }
978 
979 /**
980  * cap_inode_setxattr - Determine whether an xattr may be altered
981  * @dentry: The inode/dentry being altered
982  * @name: The name of the xattr to be changed
983  * @value: The value that the xattr will be changed to
984  * @size: The size of value
985  * @flags: The replacement flag
986  *
987  * Determine whether an xattr may be altered or set on an inode, returning 0 if
988  * permission is granted, -ve if denied.
989  *
990  * This is used to make sure security xattrs don't get updated or set by those
991  * who aren't privileged to do so.
992  */
993 int cap_inode_setxattr(struct dentry *dentry, const char *name,
994 		       const void *value, size_t size, int flags)
995 {
996 	struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
997 
998 	/* Ignore non-security xattrs */
999 	if (strncmp(name, XATTR_SECURITY_PREFIX,
1000 			XATTR_SECURITY_PREFIX_LEN) != 0)
1001 		return 0;
1002 
1003 	/*
1004 	 * For XATTR_NAME_CAPS the check will be done in
1005 	 * cap_convert_nscap(), called by setxattr()
1006 	 */
1007 	if (strcmp(name, XATTR_NAME_CAPS) == 0)
1008 		return 0;
1009 
1010 	if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1011 		return -EPERM;
1012 	return 0;
1013 }
1014 
1015 /**
1016  * cap_inode_removexattr - Determine whether an xattr may be removed
1017  *
1018  * @mnt_userns:	User namespace of the mount the inode was found from
1019  * @dentry:	The inode/dentry being altered
1020  * @name:	The name of the xattr to be changed
1021  *
1022  * Determine whether an xattr may be removed from an inode, returning 0 if
1023  * permission is granted, -ve if denied.
1024  *
1025  * If the inode has been found through an idmapped mount the user namespace of
1026  * the vfsmount must be passed through @mnt_userns. This function will then
1027  * take care to map the inode according to @mnt_userns before checking
1028  * permissions. On non-idmapped mounts or if permission checking is to be
1029  * performed on the raw inode simply passs init_user_ns.
1030  *
1031  * This is used to make sure security xattrs don't get removed by those who
1032  * aren't privileged to remove them.
1033  */
1034 int cap_inode_removexattr(struct user_namespace *mnt_userns,
1035 			  struct dentry *dentry, const char *name)
1036 {
1037 	struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
1038 
1039 	/* Ignore non-security xattrs */
1040 	if (strncmp(name, XATTR_SECURITY_PREFIX,
1041 			XATTR_SECURITY_PREFIX_LEN) != 0)
1042 		return 0;
1043 
1044 	if (strcmp(name, XATTR_NAME_CAPS) == 0) {
1045 		/* security.capability gets namespaced */
1046 		struct inode *inode = d_backing_inode(dentry);
1047 		if (!inode)
1048 			return -EINVAL;
1049 		if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP))
1050 			return -EPERM;
1051 		return 0;
1052 	}
1053 
1054 	if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1055 		return -EPERM;
1056 	return 0;
1057 }
1058 
1059 /*
1060  * cap_emulate_setxuid() fixes the effective / permitted capabilities of
1061  * a process after a call to setuid, setreuid, or setresuid.
1062  *
1063  *  1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
1064  *  {r,e,s}uid != 0, the permitted and effective capabilities are
1065  *  cleared.
1066  *
1067  *  2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
1068  *  capabilities of the process are cleared.
1069  *
1070  *  3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
1071  *  capabilities are set to the permitted capabilities.
1072  *
1073  *  fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
1074  *  never happen.
1075  *
1076  *  -astor
1077  *
1078  * cevans - New behaviour, Oct '99
1079  * A process may, via prctl(), elect to keep its capabilities when it
1080  * calls setuid() and switches away from uid==0. Both permitted and
1081  * effective sets will be retained.
1082  * Without this change, it was impossible for a daemon to drop only some
1083  * of its privilege. The call to setuid(!=0) would drop all privileges!
1084  * Keeping uid 0 is not an option because uid 0 owns too many vital
1085  * files..
1086  * Thanks to Olaf Kirch and Peter Benie for spotting this.
1087  */
1088 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
1089 {
1090 	kuid_t root_uid = make_kuid(old->user_ns, 0);
1091 
1092 	if ((uid_eq(old->uid, root_uid) ||
1093 	     uid_eq(old->euid, root_uid) ||
1094 	     uid_eq(old->suid, root_uid)) &&
1095 	    (!uid_eq(new->uid, root_uid) &&
1096 	     !uid_eq(new->euid, root_uid) &&
1097 	     !uid_eq(new->suid, root_uid))) {
1098 		if (!issecure(SECURE_KEEP_CAPS)) {
1099 			cap_clear(new->cap_permitted);
1100 			cap_clear(new->cap_effective);
1101 		}
1102 
1103 		/*
1104 		 * Pre-ambient programs expect setresuid to nonroot followed
1105 		 * by exec to drop capabilities.  We should make sure that
1106 		 * this remains the case.
1107 		 */
1108 		cap_clear(new->cap_ambient);
1109 	}
1110 	if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
1111 		cap_clear(new->cap_effective);
1112 	if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
1113 		new->cap_effective = new->cap_permitted;
1114 }
1115 
1116 /**
1117  * cap_task_fix_setuid - Fix up the results of setuid() call
1118  * @new: The proposed credentials
1119  * @old: The current task's current credentials
1120  * @flags: Indications of what has changed
1121  *
1122  * Fix up the results of setuid() call before the credential changes are
1123  * actually applied.
1124  *
1125  * Return: 0 to grant the changes, -ve to deny them.
1126  */
1127 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
1128 {
1129 	switch (flags) {
1130 	case LSM_SETID_RE:
1131 	case LSM_SETID_ID:
1132 	case LSM_SETID_RES:
1133 		/* juggle the capabilities to follow [RES]UID changes unless
1134 		 * otherwise suppressed */
1135 		if (!issecure(SECURE_NO_SETUID_FIXUP))
1136 			cap_emulate_setxuid(new, old);
1137 		break;
1138 
1139 	case LSM_SETID_FS:
1140 		/* juggle the capabilties to follow FSUID changes, unless
1141 		 * otherwise suppressed
1142 		 *
1143 		 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
1144 		 *          if not, we might be a bit too harsh here.
1145 		 */
1146 		if (!issecure(SECURE_NO_SETUID_FIXUP)) {
1147 			kuid_t root_uid = make_kuid(old->user_ns, 0);
1148 			if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
1149 				new->cap_effective =
1150 					cap_drop_fs_set(new->cap_effective);
1151 
1152 			if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
1153 				new->cap_effective =
1154 					cap_raise_fs_set(new->cap_effective,
1155 							 new->cap_permitted);
1156 		}
1157 		break;
1158 
1159 	default:
1160 		return -EINVAL;
1161 	}
1162 
1163 	return 0;
1164 }
1165 
1166 /*
1167  * Rationale: code calling task_setscheduler, task_setioprio, and
1168  * task_setnice, assumes that
1169  *   . if capable(cap_sys_nice), then those actions should be allowed
1170  *   . if not capable(cap_sys_nice), but acting on your own processes,
1171  *   	then those actions should be allowed
1172  * This is insufficient now since you can call code without suid, but
1173  * yet with increased caps.
1174  * So we check for increased caps on the target process.
1175  */
1176 static int cap_safe_nice(struct task_struct *p)
1177 {
1178 	int is_subset, ret = 0;
1179 
1180 	rcu_read_lock();
1181 	is_subset = cap_issubset(__task_cred(p)->cap_permitted,
1182 				 current_cred()->cap_permitted);
1183 	if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
1184 		ret = -EPERM;
1185 	rcu_read_unlock();
1186 
1187 	return ret;
1188 }
1189 
1190 /**
1191  * cap_task_setscheduler - Detemine if scheduler policy change is permitted
1192  * @p: The task to affect
1193  *
1194  * Detemine if the requested scheduler policy change is permitted for the
1195  * specified task.
1196  *
1197  * Return: 0 if permission is granted, -ve if denied.
1198  */
1199 int cap_task_setscheduler(struct task_struct *p)
1200 {
1201 	return cap_safe_nice(p);
1202 }
1203 
1204 /**
1205  * cap_task_setioprio - Detemine if I/O priority change is permitted
1206  * @p: The task to affect
1207  * @ioprio: The I/O priority to set
1208  *
1209  * Detemine if the requested I/O priority change is permitted for the specified
1210  * task.
1211  *
1212  * Return: 0 if permission is granted, -ve if denied.
1213  */
1214 int cap_task_setioprio(struct task_struct *p, int ioprio)
1215 {
1216 	return cap_safe_nice(p);
1217 }
1218 
1219 /**
1220  * cap_task_setnice - Detemine if task priority change is permitted
1221  * @p: The task to affect
1222  * @nice: The nice value to set
1223  *
1224  * Detemine if the requested task priority change is permitted for the
1225  * specified task.
1226  *
1227  * Return: 0 if permission is granted, -ve if denied.
1228  */
1229 int cap_task_setnice(struct task_struct *p, int nice)
1230 {
1231 	return cap_safe_nice(p);
1232 }
1233 
1234 /*
1235  * Implement PR_CAPBSET_DROP.  Attempt to remove the specified capability from
1236  * the current task's bounding set.  Returns 0 on success, -ve on error.
1237  */
1238 static int cap_prctl_drop(unsigned long cap)
1239 {
1240 	struct cred *new;
1241 
1242 	if (!ns_capable(current_user_ns(), CAP_SETPCAP))
1243 		return -EPERM;
1244 	if (!cap_valid(cap))
1245 		return -EINVAL;
1246 
1247 	new = prepare_creds();
1248 	if (!new)
1249 		return -ENOMEM;
1250 	cap_lower(new->cap_bset, cap);
1251 	return commit_creds(new);
1252 }
1253 
1254 /**
1255  * cap_task_prctl - Implement process control functions for this security module
1256  * @option: The process control function requested
1257  * @arg2: The argument data for this function
1258  * @arg3: The argument data for this function
1259  * @arg4: The argument data for this function
1260  * @arg5: The argument data for this function
1261  *
1262  * Allow process control functions (sys_prctl()) to alter capabilities; may
1263  * also deny access to other functions not otherwise implemented here.
1264  *
1265  * Return: 0 or +ve on success, -ENOSYS if this function is not implemented
1266  * here, other -ve on error.  If -ENOSYS is returned, sys_prctl() and other LSM
1267  * modules will consider performing the function.
1268  */
1269 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
1270 		   unsigned long arg4, unsigned long arg5)
1271 {
1272 	const struct cred *old = current_cred();
1273 	struct cred *new;
1274 
1275 	switch (option) {
1276 	case PR_CAPBSET_READ:
1277 		if (!cap_valid(arg2))
1278 			return -EINVAL;
1279 		return !!cap_raised(old->cap_bset, arg2);
1280 
1281 	case PR_CAPBSET_DROP:
1282 		return cap_prctl_drop(arg2);
1283 
1284 	/*
1285 	 * The next four prctl's remain to assist with transitioning a
1286 	 * system from legacy UID=0 based privilege (when filesystem
1287 	 * capabilities are not in use) to a system using filesystem
1288 	 * capabilities only - as the POSIX.1e draft intended.
1289 	 *
1290 	 * Note:
1291 	 *
1292 	 *  PR_SET_SECUREBITS =
1293 	 *      issecure_mask(SECURE_KEEP_CAPS_LOCKED)
1294 	 *    | issecure_mask(SECURE_NOROOT)
1295 	 *    | issecure_mask(SECURE_NOROOT_LOCKED)
1296 	 *    | issecure_mask(SECURE_NO_SETUID_FIXUP)
1297 	 *    | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
1298 	 *
1299 	 * will ensure that the current process and all of its
1300 	 * children will be locked into a pure
1301 	 * capability-based-privilege environment.
1302 	 */
1303 	case PR_SET_SECUREBITS:
1304 		if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
1305 		     & (old->securebits ^ arg2))			/*[1]*/
1306 		    || ((old->securebits & SECURE_ALL_LOCKS & ~arg2))	/*[2]*/
1307 		    || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS))	/*[3]*/
1308 		    || (cap_capable(current_cred(),
1309 				    current_cred()->user_ns,
1310 				    CAP_SETPCAP,
1311 				    CAP_OPT_NONE) != 0)			/*[4]*/
1312 			/*
1313 			 * [1] no changing of bits that are locked
1314 			 * [2] no unlocking of locks
1315 			 * [3] no setting of unsupported bits
1316 			 * [4] doing anything requires privilege (go read about
1317 			 *     the "sendmail capabilities bug")
1318 			 */
1319 		    )
1320 			/* cannot change a locked bit */
1321 			return -EPERM;
1322 
1323 		new = prepare_creds();
1324 		if (!new)
1325 			return -ENOMEM;
1326 		new->securebits = arg2;
1327 		return commit_creds(new);
1328 
1329 	case PR_GET_SECUREBITS:
1330 		return old->securebits;
1331 
1332 	case PR_GET_KEEPCAPS:
1333 		return !!issecure(SECURE_KEEP_CAPS);
1334 
1335 	case PR_SET_KEEPCAPS:
1336 		if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
1337 			return -EINVAL;
1338 		if (issecure(SECURE_KEEP_CAPS_LOCKED))
1339 			return -EPERM;
1340 
1341 		new = prepare_creds();
1342 		if (!new)
1343 			return -ENOMEM;
1344 		if (arg2)
1345 			new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
1346 		else
1347 			new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
1348 		return commit_creds(new);
1349 
1350 	case PR_CAP_AMBIENT:
1351 		if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
1352 			if (arg3 | arg4 | arg5)
1353 				return -EINVAL;
1354 
1355 			new = prepare_creds();
1356 			if (!new)
1357 				return -ENOMEM;
1358 			cap_clear(new->cap_ambient);
1359 			return commit_creds(new);
1360 		}
1361 
1362 		if (((!cap_valid(arg3)) | arg4 | arg5))
1363 			return -EINVAL;
1364 
1365 		if (arg2 == PR_CAP_AMBIENT_IS_SET) {
1366 			return !!cap_raised(current_cred()->cap_ambient, arg3);
1367 		} else if (arg2 != PR_CAP_AMBIENT_RAISE &&
1368 			   arg2 != PR_CAP_AMBIENT_LOWER) {
1369 			return -EINVAL;
1370 		} else {
1371 			if (arg2 == PR_CAP_AMBIENT_RAISE &&
1372 			    (!cap_raised(current_cred()->cap_permitted, arg3) ||
1373 			     !cap_raised(current_cred()->cap_inheritable,
1374 					 arg3) ||
1375 			     issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
1376 				return -EPERM;
1377 
1378 			new = prepare_creds();
1379 			if (!new)
1380 				return -ENOMEM;
1381 			if (arg2 == PR_CAP_AMBIENT_RAISE)
1382 				cap_raise(new->cap_ambient, arg3);
1383 			else
1384 				cap_lower(new->cap_ambient, arg3);
1385 			return commit_creds(new);
1386 		}
1387 
1388 	default:
1389 		/* No functionality available - continue with default */
1390 		return -ENOSYS;
1391 	}
1392 }
1393 
1394 /**
1395  * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
1396  * @mm: The VM space in which the new mapping is to be made
1397  * @pages: The size of the mapping
1398  *
1399  * Determine whether the allocation of a new virtual mapping by the current
1400  * task is permitted.
1401  *
1402  * Return: 1 if permission is granted, 0 if not.
1403  */
1404 int cap_vm_enough_memory(struct mm_struct *mm, long pages)
1405 {
1406 	int cap_sys_admin = 0;
1407 
1408 	if (cap_capable(current_cred(), &init_user_ns,
1409 				CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) == 0)
1410 		cap_sys_admin = 1;
1411 
1412 	return cap_sys_admin;
1413 }
1414 
1415 /**
1416  * cap_mmap_addr - check if able to map given addr
1417  * @addr: address attempting to be mapped
1418  *
1419  * If the process is attempting to map memory below dac_mmap_min_addr they need
1420  * CAP_SYS_RAWIO.  The other parameters to this function are unused by the
1421  * capability security module.
1422  *
1423  * Return: 0 if this mapping should be allowed or -EPERM if not.
1424  */
1425 int cap_mmap_addr(unsigned long addr)
1426 {
1427 	int ret = 0;
1428 
1429 	if (addr < dac_mmap_min_addr) {
1430 		ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
1431 				  CAP_OPT_NONE);
1432 		/* set PF_SUPERPRIV if it turns out we allow the low mmap */
1433 		if (ret == 0)
1434 			current->flags |= PF_SUPERPRIV;
1435 	}
1436 	return ret;
1437 }
1438 
1439 int cap_mmap_file(struct file *file, unsigned long reqprot,
1440 		  unsigned long prot, unsigned long flags)
1441 {
1442 	return 0;
1443 }
1444 
1445 #ifdef CONFIG_SECURITY
1446 
1447 static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
1448 	LSM_HOOK_INIT(capable, cap_capable),
1449 	LSM_HOOK_INIT(settime, cap_settime),
1450 	LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
1451 	LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
1452 	LSM_HOOK_INIT(capget, cap_capget),
1453 	LSM_HOOK_INIT(capset, cap_capset),
1454 	LSM_HOOK_INIT(bprm_creds_from_file, cap_bprm_creds_from_file),
1455 	LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
1456 	LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
1457 	LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity),
1458 	LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
1459 	LSM_HOOK_INIT(mmap_file, cap_mmap_file),
1460 	LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
1461 	LSM_HOOK_INIT(task_prctl, cap_task_prctl),
1462 	LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
1463 	LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
1464 	LSM_HOOK_INIT(task_setnice, cap_task_setnice),
1465 	LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
1466 };
1467 
1468 static int __init capability_init(void)
1469 {
1470 	security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
1471 				"capability");
1472 	return 0;
1473 }
1474 
1475 DEFINE_LSM(capability) = {
1476 	.name = "capability",
1477 	.order = LSM_ORDER_FIRST,
1478 	.init = capability_init,
1479 };
1480 
1481 #endif /* CONFIG_SECURITY */
1482