1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Common capabilities, needed by capability.o.
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>
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>
29 * If a non-root user executes a setuid-root binary in
30 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
31 * However if fE is also set, then the intent is for only
32 * the file capabilities to be applied, and the setuid-root
33 * bit is left on either to change the uid (plausible) or
34 * to get full privilege on a kernel without file capabilities
35 * support. So in that case we do not raise capabilities.
37 * Warn if that happens, once per boot.
39 static void warn_setuid_and_fcaps_mixed(const char *fname)
43 printk(KERN_INFO "warning: `%s' has both setuid-root and"
44 " effective capabilities. Therefore not raising all"
45 " capabilities.\n", fname);
51 * cap_capable - Determine whether a task has a particular effective capability
52 * @cred: The credentials to use
53 * @ns: The user namespace in which we need the capability
54 * @cap: The capability to check for
55 * @opts: Bitmask of options defined in include/linux/security.h
57 * Determine whether the nominated task has the specified capability amongst
58 * its effective set, returning 0 if it does, -ve if it does not.
60 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
61 * and has_capability() functions. That is, it has the reverse semantics:
62 * cap_has_capability() returns 0 when a task has a capability, but the
63 * kernel's capable() and has_capability() returns 1 for this case.
65 int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
66 int cap, unsigned int opts)
68 struct user_namespace *ns = targ_ns;
70 /* See if cred has the capability in the target user namespace
71 * by examining the target user namespace and all of the target
72 * user namespace's parents.
75 /* Do we have the necessary capabilities? */
76 if (ns == cred->user_ns)
77 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
80 * If we're already at a lower level than we're looking for,
81 * we're done searching.
83 if (ns->level <= cred->user_ns->level)
87 * The owner of the user namespace in the parent of the
88 * user namespace has all caps.
90 if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
94 * If you have a capability in a parent user ns, then you have
95 * it over all children user namespaces as well.
100 /* We never get here */
104 * cap_settime - Determine whether the current process may set the system clock
105 * @ts: The time to set
106 * @tz: The timezone to set
108 * Determine whether the current process may set the system clock and timezone
109 * information, returning 0 if permission granted, -ve if denied.
111 int cap_settime(const struct timespec64 *ts, const struct timezone *tz)
113 if (!capable(CAP_SYS_TIME))
119 * cap_ptrace_access_check - Determine whether the current process may access
121 * @child: The process to be accessed
122 * @mode: The mode of attachment.
124 * If we are in the same or an ancestor user_ns and have all the target
125 * task's capabilities, then ptrace access is allowed.
126 * If we have the ptrace capability to the target user_ns, then ptrace
130 * Determine whether a process may access another, returning 0 if permission
131 * granted, -ve if denied.
133 int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
136 const struct cred *cred, *child_cred;
137 const kernel_cap_t *caller_caps;
140 cred = current_cred();
141 child_cred = __task_cred(child);
142 if (mode & PTRACE_MODE_FSCREDS)
143 caller_caps = &cred->cap_effective;
145 caller_caps = &cred->cap_permitted;
146 if (cred->user_ns == child_cred->user_ns &&
147 cap_issubset(child_cred->cap_permitted, *caller_caps))
149 if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
158 * cap_ptrace_traceme - Determine whether another process may trace the current
159 * @parent: The task proposed to be the tracer
161 * If parent is in the same or an ancestor user_ns and has all current's
162 * capabilities, then ptrace access is allowed.
163 * If parent has the ptrace capability to current's user_ns, then ptrace
167 * Determine whether the nominated task is permitted to trace the current
168 * process, returning 0 if permission is granted, -ve if denied.
170 int cap_ptrace_traceme(struct task_struct *parent)
173 const struct cred *cred, *child_cred;
176 cred = __task_cred(parent);
177 child_cred = current_cred();
178 if (cred->user_ns == child_cred->user_ns &&
179 cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
181 if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
190 * cap_capget - Retrieve a task's capability sets
191 * @target: The task from which to retrieve the capability sets
192 * @effective: The place to record the effective set
193 * @inheritable: The place to record the inheritable set
194 * @permitted: The place to record the permitted set
196 * This function retrieves the capabilities of the nominated task and returns
197 * them to the caller.
199 int cap_capget(struct task_struct *target, kernel_cap_t *effective,
200 kernel_cap_t *inheritable, kernel_cap_t *permitted)
202 const struct cred *cred;
204 /* Derived from kernel/capability.c:sys_capget. */
206 cred = __task_cred(target);
207 *effective = cred->cap_effective;
208 *inheritable = cred->cap_inheritable;
209 *permitted = cred->cap_permitted;
215 * Determine whether the inheritable capabilities are limited to the old
216 * permitted set. Returns 1 if they are limited, 0 if they are not.
218 static inline int cap_inh_is_capped(void)
220 /* they are so limited unless the current task has the CAP_SETPCAP
223 if (cap_capable(current_cred(), current_cred()->user_ns,
224 CAP_SETPCAP, CAP_OPT_NONE) == 0)
230 * cap_capset - Validate and apply proposed changes to current's capabilities
231 * @new: The proposed new credentials; alterations should be made here
232 * @old: The current task's current credentials
233 * @effective: A pointer to the proposed new effective capabilities set
234 * @inheritable: A pointer to the proposed new inheritable capabilities set
235 * @permitted: A pointer to the proposed new permitted capabilities set
237 * This function validates and applies a proposed mass change to the current
238 * process's capability sets. The changes are made to the proposed new
239 * credentials, and assuming no error, will be committed by the caller of LSM.
241 int cap_capset(struct cred *new,
242 const struct cred *old,
243 const kernel_cap_t *effective,
244 const kernel_cap_t *inheritable,
245 const kernel_cap_t *permitted)
247 if (cap_inh_is_capped() &&
248 !cap_issubset(*inheritable,
249 cap_combine(old->cap_inheritable,
250 old->cap_permitted)))
251 /* incapable of using this inheritable set */
254 if (!cap_issubset(*inheritable,
255 cap_combine(old->cap_inheritable,
257 /* no new pI capabilities outside bounding set */
260 /* verify restrictions on target's new Permitted set */
261 if (!cap_issubset(*permitted, old->cap_permitted))
264 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
265 if (!cap_issubset(*effective, *permitted))
268 new->cap_effective = *effective;
269 new->cap_inheritable = *inheritable;
270 new->cap_permitted = *permitted;
273 * Mask off ambient bits that are no longer both permitted and
276 new->cap_ambient = cap_intersect(new->cap_ambient,
277 cap_intersect(*permitted,
279 if (WARN_ON(!cap_ambient_invariant_ok(new)))
285 * cap_inode_need_killpriv - Determine if inode change affects privileges
286 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
288 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
289 * affects the security markings on that inode, and if it is, should
290 * inode_killpriv() be invoked or the change rejected.
292 * Returns 1 if security.capability has a value, meaning inode_killpriv()
293 * is required, 0 otherwise, meaning inode_killpriv() is not required.
295 int cap_inode_need_killpriv(struct dentry *dentry)
297 struct inode *inode = d_backing_inode(dentry);
300 error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0);
305 * cap_inode_killpriv - Erase the security markings on an inode
306 * @dentry: The inode/dentry to alter
308 * Erase the privilege-enhancing security markings on an inode.
310 * Returns 0 if successful, -ve on error.
312 int cap_inode_killpriv(struct dentry *dentry)
316 error = __vfs_removexattr(dentry, XATTR_NAME_CAPS);
317 if (error == -EOPNOTSUPP)
322 static bool rootid_owns_currentns(kuid_t kroot)
324 struct user_namespace *ns;
326 if (!uid_valid(kroot))
329 for (ns = current_user_ns(); ; ns = ns->parent) {
330 if (from_kuid(ns, kroot) == 0)
332 if (ns == &init_user_ns)
339 static __u32 sansflags(__u32 m)
341 return m & ~VFS_CAP_FLAGS_EFFECTIVE;
344 static bool is_v2header(size_t size, const struct vfs_cap_data *cap)
346 if (size != XATTR_CAPS_SZ_2)
348 return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_2;
351 static bool is_v3header(size_t size, const struct vfs_cap_data *cap)
353 if (size != XATTR_CAPS_SZ_3)
355 return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_3;
359 * getsecurity: We are called for security.* before any attempt to read the
360 * xattr from the inode itself.
362 * This gives us a chance to read the on-disk value and convert it. If we
363 * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler.
365 * Note we are not called by vfs_getxattr_alloc(), but that is only called
366 * by the integrity subsystem, which really wants the unconverted values -
369 int cap_inode_getsecurity(struct inode *inode, const char *name, void **buffer,
375 uid_t root, mappedroot;
377 struct vfs_cap_data *cap;
378 struct vfs_ns_cap_data *nscap = NULL;
379 struct dentry *dentry;
380 struct user_namespace *fs_ns;
382 if (strcmp(name, "capability") != 0)
385 dentry = d_find_any_alias(inode);
389 size = sizeof(struct vfs_ns_cap_data);
390 ret = (int) vfs_getxattr_alloc(dentry, XATTR_NAME_CAPS,
391 &tmpbuf, size, GFP_NOFS);
397 fs_ns = inode->i_sb->s_user_ns;
398 cap = (struct vfs_cap_data *) tmpbuf;
399 if (is_v2header((size_t) ret, cap)) {
401 } else if (is_v3header((size_t) ret, cap)) {
402 nscap = (struct vfs_ns_cap_data *) tmpbuf;
403 root = le32_to_cpu(nscap->rootid);
409 kroot = make_kuid(fs_ns, root);
411 /* If the root kuid maps to a valid uid in current ns, then return
412 * this as a nscap. */
413 mappedroot = from_kuid(current_user_ns(), kroot);
414 if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) {
415 size = sizeof(struct vfs_ns_cap_data);
418 /* v2 -> v3 conversion */
419 nscap = kzalloc(size, GFP_ATOMIC);
424 nsmagic = VFS_CAP_REVISION_3;
425 magic = le32_to_cpu(cap->magic_etc);
426 if (magic & VFS_CAP_FLAGS_EFFECTIVE)
427 nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
428 memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
429 nscap->magic_etc = cpu_to_le32(nsmagic);
431 /* use allocated v3 buffer */
434 nscap->rootid = cpu_to_le32(mappedroot);
440 if (!rootid_owns_currentns(kroot)) {
445 /* This comes from a parent namespace. Return as a v2 capability */
446 size = sizeof(struct vfs_cap_data);
449 /* v3 -> v2 conversion */
450 cap = kzalloc(size, GFP_ATOMIC);
455 magic = VFS_CAP_REVISION_2;
456 nsmagic = le32_to_cpu(nscap->magic_etc);
457 if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE)
458 magic |= VFS_CAP_FLAGS_EFFECTIVE;
459 memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
460 cap->magic_etc = cpu_to_le32(magic);
462 /* use unconverted v2 */
472 static kuid_t rootid_from_xattr(const void *value, size_t size,
473 struct user_namespace *task_ns)
475 const struct vfs_ns_cap_data *nscap = value;
478 if (size == XATTR_CAPS_SZ_3)
479 rootid = le32_to_cpu(nscap->rootid);
481 return make_kuid(task_ns, rootid);
484 static bool validheader(size_t size, const struct vfs_cap_data *cap)
486 return is_v2header(size, cap) || is_v3header(size, cap);
490 * User requested a write of security.capability. If needed, update the
491 * xattr to change from v2 to v3, or to fixup the v3 rootid.
493 * If all is ok, we return the new size, on error return < 0.
495 int cap_convert_nscap(struct dentry *dentry, const void **ivalue, size_t size)
497 struct vfs_ns_cap_data *nscap;
499 const struct vfs_cap_data *cap = *ivalue;
500 __u32 magic, nsmagic;
501 struct inode *inode = d_backing_inode(dentry);
502 struct user_namespace *task_ns = current_user_ns(),
503 *fs_ns = inode->i_sb->s_user_ns;
509 if (!validheader(size, cap))
511 if (!capable_wrt_inode_uidgid(inode, CAP_SETFCAP))
513 if (size == XATTR_CAPS_SZ_2)
514 if (ns_capable(inode->i_sb->s_user_ns, CAP_SETFCAP))
515 /* user is privileged, just write the v2 */
518 rootid = rootid_from_xattr(*ivalue, size, task_ns);
519 if (!uid_valid(rootid))
522 nsrootid = from_kuid(fs_ns, rootid);
526 newsize = sizeof(struct vfs_ns_cap_data);
527 nscap = kmalloc(newsize, GFP_ATOMIC);
530 nscap->rootid = cpu_to_le32(nsrootid);
531 nsmagic = VFS_CAP_REVISION_3;
532 magic = le32_to_cpu(cap->magic_etc);
533 if (magic & VFS_CAP_FLAGS_EFFECTIVE)
534 nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
535 nscap->magic_etc = cpu_to_le32(nsmagic);
536 memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
543 * Calculate the new process capability sets from the capability sets attached
546 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
547 struct linux_binprm *bprm,
551 struct cred *new = bprm->cred;
555 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
558 if (caps->magic_etc & VFS_CAP_REVISION_MASK)
561 CAP_FOR_EACH_U32(i) {
562 __u32 permitted = caps->permitted.cap[i];
563 __u32 inheritable = caps->inheritable.cap[i];
566 * pP' = (X & fP) | (pI & fI)
567 * The addition of pA' is handled later.
569 new->cap_permitted.cap[i] =
570 (new->cap_bset.cap[i] & permitted) |
571 (new->cap_inheritable.cap[i] & inheritable);
573 if (permitted & ~new->cap_permitted.cap[i])
574 /* insufficient to execute correctly */
579 * For legacy apps, with no internal support for recognizing they
580 * do not have enough capabilities, we return an error if they are
581 * missing some "forced" (aka file-permitted) capabilities.
583 return *effective ? ret : 0;
587 * Extract the on-exec-apply capability sets for an executable file.
589 int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
591 struct inode *inode = d_backing_inode(dentry);
595 struct vfs_ns_cap_data data, *nscaps = &data;
596 struct vfs_cap_data *caps = (struct vfs_cap_data *) &data;
598 struct user_namespace *fs_ns;
600 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
605 fs_ns = inode->i_sb->s_user_ns;
606 size = __vfs_getxattr((struct dentry *)dentry, inode,
607 XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ);
608 if (size == -ENODATA || size == -EOPNOTSUPP)
609 /* no data, that's ok */
615 if (size < sizeof(magic_etc))
618 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps->magic_etc);
620 rootkuid = make_kuid(fs_ns, 0);
621 switch (magic_etc & VFS_CAP_REVISION_MASK) {
622 case VFS_CAP_REVISION_1:
623 if (size != XATTR_CAPS_SZ_1)
625 tocopy = VFS_CAP_U32_1;
627 case VFS_CAP_REVISION_2:
628 if (size != XATTR_CAPS_SZ_2)
630 tocopy = VFS_CAP_U32_2;
632 case VFS_CAP_REVISION_3:
633 if (size != XATTR_CAPS_SZ_3)
635 tocopy = VFS_CAP_U32_3;
636 rootkuid = make_kuid(fs_ns, le32_to_cpu(nscaps->rootid));
642 /* Limit the caps to the mounter of the filesystem
643 * or the more limited uid specified in the xattr.
645 if (!rootid_owns_currentns(rootkuid))
648 CAP_FOR_EACH_U32(i) {
651 cpu_caps->permitted.cap[i] = le32_to_cpu(caps->data[i].permitted);
652 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps->data[i].inheritable);
655 cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
656 cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
658 cpu_caps->rootid = rootkuid;
664 * Attempt to get the on-exec apply capability sets for an executable file from
665 * its xattrs and, if present, apply them to the proposed credentials being
666 * constructed by execve().
668 static int get_file_caps(struct linux_binprm *bprm, struct file *file,
669 bool *effective, bool *has_fcap)
672 struct cpu_vfs_cap_data vcaps;
674 cap_clear(bprm->cred->cap_permitted);
676 if (!file_caps_enabled)
679 if (!mnt_may_suid(file->f_path.mnt))
683 * This check is redundant with mnt_may_suid() but is kept to make
684 * explicit that capability bits are limited to s_user_ns and its
687 if (!current_in_userns(file->f_path.mnt->mnt_sb->s_user_ns))
690 rc = get_vfs_caps_from_disk(file->f_path.dentry, &vcaps);
693 printk(KERN_NOTICE "Invalid argument reading file caps for %s\n",
695 else if (rc == -ENODATA)
700 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_fcap);
704 cap_clear(bprm->cred->cap_permitted);
709 static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); }
711 static inline bool __is_real(kuid_t uid, struct cred *cred)
712 { return uid_eq(cred->uid, uid); }
714 static inline bool __is_eff(kuid_t uid, struct cred *cred)
715 { return uid_eq(cred->euid, uid); }
717 static inline bool __is_suid(kuid_t uid, struct cred *cred)
718 { return !__is_real(uid, cred) && __is_eff(uid, cred); }
721 * handle_privileged_root - Handle case of privileged root
722 * @bprm: The execution parameters, including the proposed creds
723 * @has_fcap: Are any file capabilities set?
724 * @effective: Do we have effective root privilege?
725 * @root_uid: This namespace' root UID WRT initial USER namespace
727 * Handle the case where root is privileged and hasn't been neutered by
728 * SECURE_NOROOT. If file capabilities are set, they won't be combined with
729 * set UID root and nothing is changed. If we are root, cap_permitted is
730 * updated. If we have become set UID root, the effective bit is set.
732 static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap,
733 bool *effective, kuid_t root_uid)
735 const struct cred *old = current_cred();
736 struct cred *new = bprm->cred;
738 if (!root_privileged())
741 * If the legacy file capability is set, then don't set privs
742 * for a setuid root binary run by a non-root user. Do set it
743 * for a root user just to cause least surprise to an admin.
745 if (has_fcap && __is_suid(root_uid, new)) {
746 warn_setuid_and_fcaps_mixed(bprm->filename);
750 * To support inheritance of root-permissions and suid-root
751 * executables under compatibility mode, we override the
752 * capability sets for the file.
754 if (__is_eff(root_uid, new) || __is_real(root_uid, new)) {
755 /* pP' = (cap_bset & ~0) | (pI & ~0) */
756 new->cap_permitted = cap_combine(old->cap_bset,
757 old->cap_inheritable);
760 * If only the real uid is 0, we do not set the effective bit.
762 if (__is_eff(root_uid, new))
766 #define __cap_gained(field, target, source) \
767 !cap_issubset(target->cap_##field, source->cap_##field)
768 #define __cap_grew(target, source, cred) \
769 !cap_issubset(cred->cap_##target, cred->cap_##source)
770 #define __cap_full(field, cred) \
771 cap_issubset(CAP_FULL_SET, cred->cap_##field)
773 static inline bool __is_setuid(struct cred *new, const struct cred *old)
774 { return !uid_eq(new->euid, old->uid); }
776 static inline bool __is_setgid(struct cred *new, const struct cred *old)
777 { return !gid_eq(new->egid, old->gid); }
780 * 1) Audit candidate if current->cap_effective is set
782 * We do not bother to audit if 3 things are true:
783 * 1) cap_effective has all caps
784 * 2) we became root *OR* are were already root
785 * 3) root is supposed to have all caps (SECURE_NOROOT)
786 * Since this is just a normal root execing a process.
788 * Number 1 above might fail if you don't have a full bset, but I think
789 * that is interesting information to audit.
791 * A number of other conditions require logging:
792 * 2) something prevented setuid root getting all caps
793 * 3) non-setuid root gets fcaps
794 * 4) non-setuid root gets ambient
796 static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old,
797 kuid_t root, bool has_fcap)
801 if ((__cap_grew(effective, ambient, new) &&
802 !(__cap_full(effective, new) &&
803 (__is_eff(root, new) || __is_real(root, new)) &&
804 root_privileged())) ||
805 (root_privileged() &&
806 __is_suid(root, new) &&
807 !__cap_full(effective, new)) ||
808 (!__is_setuid(new, old) &&
810 __cap_gained(permitted, new, old)) ||
811 __cap_gained(ambient, new, old))))
819 * cap_bprm_creds_from_file - Set up the proposed credentials for execve().
820 * @bprm: The execution parameters, including the proposed creds
821 * @file: The file to pull the credentials from
823 * Set up the proposed credentials for a new execution context being
824 * constructed by execve(). The proposed creds in @bprm->cred is altered,
825 * which won't take effect immediately. Returns 0 if successful, -ve on error.
827 int cap_bprm_creds_from_file(struct linux_binprm *bprm, struct file *file)
829 /* Process setpcap binaries and capabilities for uid 0 */
830 const struct cred *old = current_cred();
831 struct cred *new = bprm->cred;
832 bool effective = false, has_fcap = false, is_setid;
836 if (WARN_ON(!cap_ambient_invariant_ok(old)))
839 ret = get_file_caps(bprm, file, &effective, &has_fcap);
843 root_uid = make_kuid(new->user_ns, 0);
845 handle_privileged_root(bprm, has_fcap, &effective, root_uid);
847 /* if we have fs caps, clear dangerous personality flags */
848 if (__cap_gained(permitted, new, old))
849 bprm->per_clear |= PER_CLEAR_ON_SETID;
851 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
852 * credentials unless they have the appropriate permit.
854 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
856 is_setid = __is_setuid(new, old) || __is_setgid(new, old);
858 if ((is_setid || __cap_gained(permitted, new, old)) &&
859 ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) ||
860 !ptracer_capable(current, new->user_ns))) {
861 /* downgrade; they get no more than they had, and maybe less */
862 if (!ns_capable(new->user_ns, CAP_SETUID) ||
863 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
864 new->euid = new->uid;
865 new->egid = new->gid;
867 new->cap_permitted = cap_intersect(new->cap_permitted,
871 new->suid = new->fsuid = new->euid;
872 new->sgid = new->fsgid = new->egid;
874 /* File caps or setid cancels ambient. */
875 if (has_fcap || is_setid)
876 cap_clear(new->cap_ambient);
879 * Now that we've computed pA', update pP' to give:
880 * pP' = (X & fP) | (pI & fI) | pA'
882 new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
885 * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set,
886 * this is the same as pE' = (fE ? pP' : 0) | pA'.
889 new->cap_effective = new->cap_permitted;
891 new->cap_effective = new->cap_ambient;
893 if (WARN_ON(!cap_ambient_invariant_ok(new)))
896 if (nonroot_raised_pE(new, old, root_uid, has_fcap)) {
897 ret = audit_log_bprm_fcaps(bprm, new, old);
902 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
904 if (WARN_ON(!cap_ambient_invariant_ok(new)))
907 /* Check for privilege-elevated exec. */
909 (!__is_real(root_uid, new) &&
911 __cap_grew(permitted, ambient, new))))
912 bprm->secureexec = 1;
918 * cap_inode_setxattr - Determine whether an xattr may be altered
919 * @dentry: The inode/dentry being altered
920 * @name: The name of the xattr to be changed
921 * @value: The value that the xattr will be changed to
922 * @size: The size of value
923 * @flags: The replacement flag
925 * Determine whether an xattr may be altered or set on an inode, returning 0 if
926 * permission is granted, -ve if denied.
928 * This is used to make sure security xattrs don't get updated or set by those
929 * who aren't privileged to do so.
931 int cap_inode_setxattr(struct dentry *dentry, const char *name,
932 const void *value, size_t size, int flags)
934 struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
936 /* Ignore non-security xattrs */
937 if (strncmp(name, XATTR_SECURITY_PREFIX,
938 XATTR_SECURITY_PREFIX_LEN) != 0)
942 * For XATTR_NAME_CAPS the check will be done in
943 * cap_convert_nscap(), called by setxattr()
945 if (strcmp(name, XATTR_NAME_CAPS) == 0)
948 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
954 * cap_inode_removexattr - Determine whether an xattr may be removed
955 * @dentry: The inode/dentry being altered
956 * @name: The name of the xattr to be changed
958 * Determine whether an xattr may be removed from an inode, returning 0 if
959 * permission is granted, -ve if denied.
961 * This is used to make sure security xattrs don't get removed by those who
962 * aren't privileged to remove them.
964 int cap_inode_removexattr(struct dentry *dentry, const char *name)
966 struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
968 /* Ignore non-security xattrs */
969 if (strncmp(name, XATTR_SECURITY_PREFIX,
970 XATTR_SECURITY_PREFIX_LEN) != 0)
973 if (strcmp(name, XATTR_NAME_CAPS) == 0) {
974 /* security.capability gets namespaced */
975 struct inode *inode = d_backing_inode(dentry);
978 if (!capable_wrt_inode_uidgid(inode, CAP_SETFCAP))
983 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
989 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
990 * a process after a call to setuid, setreuid, or setresuid.
992 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
993 * {r,e,s}uid != 0, the permitted and effective capabilities are
996 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
997 * capabilities of the process are cleared.
999 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
1000 * capabilities are set to the permitted capabilities.
1002 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
1007 * cevans - New behaviour, Oct '99
1008 * A process may, via prctl(), elect to keep its capabilities when it
1009 * calls setuid() and switches away from uid==0. Both permitted and
1010 * effective sets will be retained.
1011 * Without this change, it was impossible for a daemon to drop only some
1012 * of its privilege. The call to setuid(!=0) would drop all privileges!
1013 * Keeping uid 0 is not an option because uid 0 owns too many vital
1015 * Thanks to Olaf Kirch and Peter Benie for spotting this.
1017 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
1019 kuid_t root_uid = make_kuid(old->user_ns, 0);
1021 if ((uid_eq(old->uid, root_uid) ||
1022 uid_eq(old->euid, root_uid) ||
1023 uid_eq(old->suid, root_uid)) &&
1024 (!uid_eq(new->uid, root_uid) &&
1025 !uid_eq(new->euid, root_uid) &&
1026 !uid_eq(new->suid, root_uid))) {
1027 if (!issecure(SECURE_KEEP_CAPS)) {
1028 cap_clear(new->cap_permitted);
1029 cap_clear(new->cap_effective);
1033 * Pre-ambient programs expect setresuid to nonroot followed
1034 * by exec to drop capabilities. We should make sure that
1035 * this remains the case.
1037 cap_clear(new->cap_ambient);
1039 if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
1040 cap_clear(new->cap_effective);
1041 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
1042 new->cap_effective = new->cap_permitted;
1046 * cap_task_fix_setuid - Fix up the results of setuid() call
1047 * @new: The proposed credentials
1048 * @old: The current task's current credentials
1049 * @flags: Indications of what has changed
1051 * Fix up the results of setuid() call before the credential changes are
1052 * actually applied, returning 0 to grant the changes, -ve to deny them.
1054 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
1060 /* juggle the capabilities to follow [RES]UID changes unless
1061 * otherwise suppressed */
1062 if (!issecure(SECURE_NO_SETUID_FIXUP))
1063 cap_emulate_setxuid(new, old);
1067 /* juggle the capabilties to follow FSUID changes, unless
1068 * otherwise suppressed
1070 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
1071 * if not, we might be a bit too harsh here.
1073 if (!issecure(SECURE_NO_SETUID_FIXUP)) {
1074 kuid_t root_uid = make_kuid(old->user_ns, 0);
1075 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
1076 new->cap_effective =
1077 cap_drop_fs_set(new->cap_effective);
1079 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
1080 new->cap_effective =
1081 cap_raise_fs_set(new->cap_effective,
1082 new->cap_permitted);
1094 * Rationale: code calling task_setscheduler, task_setioprio, and
1095 * task_setnice, assumes that
1096 * . if capable(cap_sys_nice), then those actions should be allowed
1097 * . if not capable(cap_sys_nice), but acting on your own processes,
1098 * then those actions should be allowed
1099 * This is insufficient now since you can call code without suid, but
1100 * yet with increased caps.
1101 * So we check for increased caps on the target process.
1103 static int cap_safe_nice(struct task_struct *p)
1105 int is_subset, ret = 0;
1108 is_subset = cap_issubset(__task_cred(p)->cap_permitted,
1109 current_cred()->cap_permitted);
1110 if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
1118 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
1119 * @p: The task to affect
1121 * Detemine if the requested scheduler policy change is permitted for the
1122 * specified task, returning 0 if permission is granted, -ve if denied.
1124 int cap_task_setscheduler(struct task_struct *p)
1126 return cap_safe_nice(p);
1130 * cap_task_ioprio - Detemine if I/O priority change is permitted
1131 * @p: The task to affect
1132 * @ioprio: The I/O priority to set
1134 * Detemine if the requested I/O priority change is permitted for the specified
1135 * task, returning 0 if permission is granted, -ve if denied.
1137 int cap_task_setioprio(struct task_struct *p, int ioprio)
1139 return cap_safe_nice(p);
1143 * cap_task_ioprio - Detemine if task priority change is permitted
1144 * @p: The task to affect
1145 * @nice: The nice value to set
1147 * Detemine if the requested task priority change is permitted for the
1148 * specified task, returning 0 if permission is granted, -ve if denied.
1150 int cap_task_setnice(struct task_struct *p, int nice)
1152 return cap_safe_nice(p);
1156 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
1157 * the current task's bounding set. Returns 0 on success, -ve on error.
1159 static int cap_prctl_drop(unsigned long cap)
1163 if (!ns_capable(current_user_ns(), CAP_SETPCAP))
1165 if (!cap_valid(cap))
1168 new = prepare_creds();
1171 cap_lower(new->cap_bset, cap);
1172 return commit_creds(new);
1176 * cap_task_prctl - Implement process control functions for this security module
1177 * @option: The process control function requested
1178 * @arg2, @arg3, @arg4, @arg5: The argument data for this function
1180 * Allow process control functions (sys_prctl()) to alter capabilities; may
1181 * also deny access to other functions not otherwise implemented here.
1183 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
1184 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
1185 * modules will consider performing the function.
1187 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
1188 unsigned long arg4, unsigned long arg5)
1190 const struct cred *old = current_cred();
1194 case PR_CAPBSET_READ:
1195 if (!cap_valid(arg2))
1197 return !!cap_raised(old->cap_bset, arg2);
1199 case PR_CAPBSET_DROP:
1200 return cap_prctl_drop(arg2);
1203 * The next four prctl's remain to assist with transitioning a
1204 * system from legacy UID=0 based privilege (when filesystem
1205 * capabilities are not in use) to a system using filesystem
1206 * capabilities only - as the POSIX.1e draft intended.
1210 * PR_SET_SECUREBITS =
1211 * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
1212 * | issecure_mask(SECURE_NOROOT)
1213 * | issecure_mask(SECURE_NOROOT_LOCKED)
1214 * | issecure_mask(SECURE_NO_SETUID_FIXUP)
1215 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
1217 * will ensure that the current process and all of its
1218 * children will be locked into a pure
1219 * capability-based-privilege environment.
1221 case PR_SET_SECUREBITS:
1222 if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
1223 & (old->securebits ^ arg2)) /*[1]*/
1224 || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
1225 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
1226 || (cap_capable(current_cred(),
1227 current_cred()->user_ns,
1229 CAP_OPT_NONE) != 0) /*[4]*/
1231 * [1] no changing of bits that are locked
1232 * [2] no unlocking of locks
1233 * [3] no setting of unsupported bits
1234 * [4] doing anything requires privilege (go read about
1235 * the "sendmail capabilities bug")
1238 /* cannot change a locked bit */
1241 new = prepare_creds();
1244 new->securebits = arg2;
1245 return commit_creds(new);
1247 case PR_GET_SECUREBITS:
1248 return old->securebits;
1250 case PR_GET_KEEPCAPS:
1251 return !!issecure(SECURE_KEEP_CAPS);
1253 case PR_SET_KEEPCAPS:
1254 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
1256 if (issecure(SECURE_KEEP_CAPS_LOCKED))
1259 new = prepare_creds();
1263 new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
1265 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
1266 return commit_creds(new);
1268 case PR_CAP_AMBIENT:
1269 if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
1270 if (arg3 | arg4 | arg5)
1273 new = prepare_creds();
1276 cap_clear(new->cap_ambient);
1277 return commit_creds(new);
1280 if (((!cap_valid(arg3)) | arg4 | arg5))
1283 if (arg2 == PR_CAP_AMBIENT_IS_SET) {
1284 return !!cap_raised(current_cred()->cap_ambient, arg3);
1285 } else if (arg2 != PR_CAP_AMBIENT_RAISE &&
1286 arg2 != PR_CAP_AMBIENT_LOWER) {
1289 if (arg2 == PR_CAP_AMBIENT_RAISE &&
1290 (!cap_raised(current_cred()->cap_permitted, arg3) ||
1291 !cap_raised(current_cred()->cap_inheritable,
1293 issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
1296 new = prepare_creds();
1299 if (arg2 == PR_CAP_AMBIENT_RAISE)
1300 cap_raise(new->cap_ambient, arg3);
1302 cap_lower(new->cap_ambient, arg3);
1303 return commit_creds(new);
1307 /* No functionality available - continue with default */
1313 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
1314 * @mm: The VM space in which the new mapping is to be made
1315 * @pages: The size of the mapping
1317 * Determine whether the allocation of a new virtual mapping by the current
1318 * task is permitted, returning 1 if permission is granted, 0 if not.
1320 int cap_vm_enough_memory(struct mm_struct *mm, long pages)
1322 int cap_sys_admin = 0;
1324 if (cap_capable(current_cred(), &init_user_ns,
1325 CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) == 0)
1328 return cap_sys_admin;
1332 * cap_mmap_addr - check if able to map given addr
1333 * @addr: address attempting to be mapped
1335 * If the process is attempting to map memory below dac_mmap_min_addr they need
1336 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
1337 * capability security module. Returns 0 if this mapping should be allowed
1340 int cap_mmap_addr(unsigned long addr)
1344 if (addr < dac_mmap_min_addr) {
1345 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
1347 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
1349 current->flags |= PF_SUPERPRIV;
1354 int cap_mmap_file(struct file *file, unsigned long reqprot,
1355 unsigned long prot, unsigned long flags)
1360 #ifdef CONFIG_SECURITY
1362 static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
1363 LSM_HOOK_INIT(capable, cap_capable),
1364 LSM_HOOK_INIT(settime, cap_settime),
1365 LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
1366 LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
1367 LSM_HOOK_INIT(capget, cap_capget),
1368 LSM_HOOK_INIT(capset, cap_capset),
1369 LSM_HOOK_INIT(bprm_creds_from_file, cap_bprm_creds_from_file),
1370 LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
1371 LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
1372 LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity),
1373 LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
1374 LSM_HOOK_INIT(mmap_file, cap_mmap_file),
1375 LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
1376 LSM_HOOK_INIT(task_prctl, cap_task_prctl),
1377 LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
1378 LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
1379 LSM_HOOK_INIT(task_setnice, cap_task_setnice),
1380 LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
1383 static int __init capability_init(void)
1385 security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
1390 DEFINE_LSM(capability) = {
1391 .name = "capability",
1392 .order = LSM_ORDER_FIRST,
1393 .init = capability_init,
1396 #endif /* CONFIG_SECURITY */