Root/security/commoncap.c

1/* Common capabilities, needed by capability.o.
2 *
3 * This program is free software; you can redistribute it and/or modify
4 * it under the terms of the GNU General Public License as published by
5 * the Free Software Foundation; either version 2 of the License, or
6 * (at your option) any later version.
7 *
8 */
9
10#include <linux/capability.h>
11#include <linux/audit.h>
12#include <linux/module.h>
13#include <linux/init.h>
14#include <linux/kernel.h>
15#include <linux/security.h>
16#include <linux/file.h>
17#include <linux/mm.h>
18#include <linux/mman.h>
19#include <linux/pagemap.h>
20#include <linux/swap.h>
21#include <linux/skbuff.h>
22#include <linux/netlink.h>
23#include <linux/ptrace.h>
24#include <linux/xattr.h>
25#include <linux/hugetlb.h>
26#include <linux/mount.h>
27#include <linux/sched.h>
28#include <linux/prctl.h>
29#include <linux/securebits.h>
30#include <linux/user_namespace.h>
31
32/*
33 * If a non-root user executes a setuid-root binary in
34 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
35 * However if fE is also set, then the intent is for only
36 * the file capabilities to be applied, and the setuid-root
37 * bit is left on either to change the uid (plausible) or
38 * to get full privilege on a kernel without file capabilities
39 * support. So in that case we do not raise capabilities.
40 *
41 * Warn if that happens, once per boot.
42 */
43static void warn_setuid_and_fcaps_mixed(const char *fname)
44{
45    static int warned;
46    if (!warned) {
47        printk(KERN_INFO "warning: `%s' has both setuid-root and"
48            " effective capabilities. Therefore not raising all"
49            " capabilities.\n", fname);
50        warned = 1;
51    }
52}
53
54int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
55{
56    return 0;
57}
58
59int cap_netlink_recv(struct sk_buff *skb, int cap)
60{
61    if (!cap_raised(current_cap(), cap))
62        return -EPERM;
63    return 0;
64}
65EXPORT_SYMBOL(cap_netlink_recv);
66
67/**
68 * cap_capable - Determine whether a task has a particular effective capability
69 * @tsk: The task to query
70 * @cred: The credentials to use
71 * @ns: The user namespace in which we need the capability
72 * @cap: The capability to check for
73 * @audit: Whether to write an audit message or not
74 *
75 * Determine whether the nominated task has the specified capability amongst
76 * its effective set, returning 0 if it does, -ve if it does not.
77 *
78 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
79 * and has_capability() functions. That is, it has the reverse semantics:
80 * cap_has_capability() returns 0 when a task has a capability, but the
81 * kernel's capable() and has_capability() returns 1 for this case.
82 */
83int cap_capable(struct task_struct *tsk, const struct cred *cred,
84        struct user_namespace *targ_ns, int cap, int audit)
85{
86    for (;;) {
87        /* The creator of the user namespace has all caps. */
88        if (targ_ns != &init_user_ns && targ_ns->creator == cred->user)
89            return 0;
90
91        /* Do we have the necessary capabilities? */
92        if (targ_ns == cred->user->user_ns)
93            return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
94
95        /* Have we tried all of the parent namespaces? */
96        if (targ_ns == &init_user_ns)
97            return -EPERM;
98
99        /*
100         *If you have a capability in a parent user ns, then you have
101         * it over all children user namespaces as well.
102         */
103        targ_ns = targ_ns->creator->user_ns;
104    }
105
106    /* We never get here */
107}
108
109/**
110 * cap_settime - Determine whether the current process may set the system clock
111 * @ts: The time to set
112 * @tz: The timezone to set
113 *
114 * Determine whether the current process may set the system clock and timezone
115 * information, returning 0 if permission granted, -ve if denied.
116 */
117int cap_settime(const struct timespec *ts, const struct timezone *tz)
118{
119    if (!capable(CAP_SYS_TIME))
120        return -EPERM;
121    return 0;
122}
123
124/**
125 * cap_ptrace_access_check - Determine whether the current process may access
126 * another
127 * @child: The process to be accessed
128 * @mode: The mode of attachment.
129 *
130 * If we are in the same or an ancestor user_ns and have all the target
131 * task's capabilities, then ptrace access is allowed.
132 * If we have the ptrace capability to the target user_ns, then ptrace
133 * access is allowed.
134 * Else denied.
135 *
136 * Determine whether a process may access another, returning 0 if permission
137 * granted, -ve if denied.
138 */
139int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
140{
141    int ret = 0;
142    const struct cred *cred, *child_cred;
143
144    rcu_read_lock();
145    cred = current_cred();
146    child_cred = __task_cred(child);
147    if (cred->user->user_ns == child_cred->user->user_ns &&
148        cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
149        goto out;
150    if (ns_capable(child_cred->user->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->user_ns == child_cred->user->user_ns &&
180        cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
181        goto out;
182    if (has_ns_capability(parent, child_cred->user->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
222    /* they are so limited unless the current task has the CAP_SETPCAP
223     * capability
224     */
225    if (cap_capable(current, current_cred(),
226            current_cred()->user->user_ns, CAP_SETPCAP,
227            SECURITY_CAP_AUDIT) == 0)
228        return 0;
229    return 1;
230}
231
232/**
233 * cap_capset - Validate and apply proposed changes to current's capabilities
234 * @new: The proposed new credentials; alterations should be made here
235 * @old: The current task's current credentials
236 * @effective: A pointer to the proposed new effective capabilities set
237 * @inheritable: A pointer to the proposed new inheritable capabilities set
238 * @permitted: A pointer to the proposed new permitted capabilities set
239 *
240 * This function validates and applies a proposed mass change to the current
241 * process's capability sets. The changes are made to the proposed new
242 * credentials, and assuming no error, will be committed by the caller of LSM.
243 */
244int cap_capset(struct cred *new,
245           const struct cred *old,
246           const kernel_cap_t *effective,
247           const kernel_cap_t *inheritable,
248           const kernel_cap_t *permitted)
249{
250    if (cap_inh_is_capped() &&
251        !cap_issubset(*inheritable,
252              cap_combine(old->cap_inheritable,
253                      old->cap_permitted)))
254        /* incapable of using this inheritable set */
255        return -EPERM;
256
257    if (!cap_issubset(*inheritable,
258              cap_combine(old->cap_inheritable,
259                      old->cap_bset)))
260        /* no new pI capabilities outside bounding set */
261        return -EPERM;
262
263    /* verify restrictions on target's new Permitted set */
264    if (!cap_issubset(*permitted, old->cap_permitted))
265        return -EPERM;
266
267    /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
268    if (!cap_issubset(*effective, *permitted))
269        return -EPERM;
270
271    new->cap_effective = *effective;
272    new->cap_inheritable = *inheritable;
273    new->cap_permitted = *permitted;
274    return 0;
275}
276
277/*
278 * Clear proposed capability sets for execve().
279 */
280static inline void bprm_clear_caps(struct linux_binprm *bprm)
281{
282    cap_clear(bprm->cred->cap_permitted);
283    bprm->cap_effective = false;
284}
285
286/**
287 * cap_inode_need_killpriv - Determine if inode change affects privileges
288 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
289 *
290 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
291 * affects the security markings on that inode, and if it is, should
292 * inode_killpriv() be invoked or the change rejected?
293 *
294 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
295 * -ve to deny the change.
296 */
297int cap_inode_need_killpriv(struct dentry *dentry)
298{
299    struct inode *inode = dentry->d_inode;
300    int error;
301
302    if (!inode->i_op->getxattr)
303           return 0;
304
305    error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
306    if (error <= 0)
307        return 0;
308    return 1;
309}
310
311/**
312 * cap_inode_killpriv - Erase the security markings on an inode
313 * @dentry: The inode/dentry to alter
314 *
315 * Erase the privilege-enhancing security markings on an inode.
316 *
317 * Returns 0 if successful, -ve on error.
318 */
319int cap_inode_killpriv(struct dentry *dentry)
320{
321    struct inode *inode = dentry->d_inode;
322
323    if (!inode->i_op->removexattr)
324           return 0;
325
326    return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
327}
328
329/*
330 * Calculate the new process capability sets from the capability sets attached
331 * to a file.
332 */
333static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
334                      struct linux_binprm *bprm,
335                      bool *effective)
336{
337    struct cred *new = bprm->cred;
338    unsigned i;
339    int ret = 0;
340
341    if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
342        *effective = true;
343
344    CAP_FOR_EACH_U32(i) {
345        __u32 permitted = caps->permitted.cap[i];
346        __u32 inheritable = caps->inheritable.cap[i];
347
348        /*
349         * pP' = (X & fP) | (pI & fI)
350         */
351        new->cap_permitted.cap[i] =
352            (new->cap_bset.cap[i] & permitted) |
353            (new->cap_inheritable.cap[i] & inheritable);
354
355        if (permitted & ~new->cap_permitted.cap[i])
356            /* insufficient to execute correctly */
357            ret = -EPERM;
358    }
359
360    /*
361     * For legacy apps, with no internal support for recognizing they
362     * do not have enough capabilities, we return an error if they are
363     * missing some "forced" (aka file-permitted) capabilities.
364     */
365    return *effective ? ret : 0;
366}
367
368/*
369 * Extract the on-exec-apply capability sets for an executable file.
370 */
371int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
372{
373    struct inode *inode = dentry->d_inode;
374    __u32 magic_etc;
375    unsigned tocopy, i;
376    int size;
377    struct vfs_cap_data caps;
378
379    memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
380
381    if (!inode || !inode->i_op->getxattr)
382        return -ENODATA;
383
384    size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps,
385                   XATTR_CAPS_SZ);
386    if (size == -ENODATA || size == -EOPNOTSUPP)
387        /* no data, that's ok */
388        return -ENODATA;
389    if (size < 0)
390        return size;
391
392    if (size < sizeof(magic_etc))
393        return -EINVAL;
394
395    cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
396
397    switch (magic_etc & VFS_CAP_REVISION_MASK) {
398    case VFS_CAP_REVISION_1:
399        if (size != XATTR_CAPS_SZ_1)
400            return -EINVAL;
401        tocopy = VFS_CAP_U32_1;
402        break;
403    case VFS_CAP_REVISION_2:
404        if (size != XATTR_CAPS_SZ_2)
405            return -EINVAL;
406        tocopy = VFS_CAP_U32_2;
407        break;
408    default:
409        return -EINVAL;
410    }
411
412    CAP_FOR_EACH_U32(i) {
413        if (i >= tocopy)
414            break;
415        cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
416        cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
417    }
418
419    return 0;
420}
421
422/*
423 * Attempt to get the on-exec apply capability sets for an executable file from
424 * its xattrs and, if present, apply them to the proposed credentials being
425 * constructed by execve().
426 */
427static int get_file_caps(struct linux_binprm *bprm, bool *effective)
428{
429    struct dentry *dentry;
430    int rc = 0;
431    struct cpu_vfs_cap_data vcaps;
432
433    bprm_clear_caps(bprm);
434
435    if (!file_caps_enabled)
436        return 0;
437
438    if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID)
439        return 0;
440
441    dentry = dget(bprm->file->f_dentry);
442
443    rc = get_vfs_caps_from_disk(dentry, &vcaps);
444    if (rc < 0) {
445        if (rc == -EINVAL)
446            printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
447                __func__, rc, bprm->filename);
448        else if (rc == -ENODATA)
449            rc = 0;
450        goto out;
451    }
452
453    rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective);
454    if (rc == -EINVAL)
455        printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
456               __func__, rc, bprm->filename);
457
458out:
459    dput(dentry);
460    if (rc)
461        bprm_clear_caps(bprm);
462
463    return rc;
464}
465
466/**
467 * cap_bprm_set_creds - Set up the proposed credentials for execve().
468 * @bprm: The execution parameters, including the proposed creds
469 *
470 * Set up the proposed credentials for a new execution context being
471 * constructed by execve(). The proposed creds in @bprm->cred is altered,
472 * which won't take effect immediately. Returns 0 if successful, -ve on error.
473 */
474int cap_bprm_set_creds(struct linux_binprm *bprm)
475{
476    const struct cred *old = current_cred();
477    struct cred *new = bprm->cred;
478    bool effective;
479    int ret;
480
481    effective = false;
482    ret = get_file_caps(bprm, &effective);
483    if (ret < 0)
484        return ret;
485
486    if (!issecure(SECURE_NOROOT)) {
487        /*
488         * If the legacy file capability is set, then don't set privs
489         * for a setuid root binary run by a non-root user. Do set it
490         * for a root user just to cause least surprise to an admin.
491         */
492        if (effective && new->uid != 0 && new->euid == 0) {
493            warn_setuid_and_fcaps_mixed(bprm->filename);
494            goto skip;
495        }
496        /*
497         * To support inheritance of root-permissions and suid-root
498         * executables under compatibility mode, we override the
499         * capability sets for the file.
500         *
501         * If only the real uid is 0, we do not set the effective bit.
502         */
503        if (new->euid == 0 || new->uid == 0) {
504            /* pP' = (cap_bset & ~0) | (pI & ~0) */
505            new->cap_permitted = cap_combine(old->cap_bset,
506                             old->cap_inheritable);
507        }
508        if (new->euid == 0)
509            effective = true;
510    }
511skip:
512
513    /* Don't let someone trace a set[ug]id/setpcap binary with the revised
514     * credentials unless they have the appropriate permit
515     */
516    if ((new->euid != old->uid ||
517         new->egid != old->gid ||
518         !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
519        bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
520        /* downgrade; they get no more than they had, and maybe less */
521        if (!capable(CAP_SETUID)) {
522            new->euid = new->uid;
523            new->egid = new->gid;
524        }
525        new->cap_permitted = cap_intersect(new->cap_permitted,
526                           old->cap_permitted);
527    }
528
529    new->suid = new->fsuid = new->euid;
530    new->sgid = new->fsgid = new->egid;
531
532    if (effective)
533        new->cap_effective = new->cap_permitted;
534    else
535        cap_clear(new->cap_effective);
536    bprm->cap_effective = effective;
537
538    /*
539     * Audit candidate if current->cap_effective is set
540     *
541     * We do not bother to audit if 3 things are true:
542     * 1) cap_effective has all caps
543     * 2) we are root
544     * 3) root is supposed to have all caps (SECURE_NOROOT)
545     * Since this is just a normal root execing a process.
546     *
547     * Number 1 above might fail if you don't have a full bset, but I think
548     * that is interesting information to audit.
549     */
550    if (!cap_isclear(new->cap_effective)) {
551        if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
552            new->euid != 0 || new->uid != 0 ||
553            issecure(SECURE_NOROOT)) {
554            ret = audit_log_bprm_fcaps(bprm, new, old);
555            if (ret < 0)
556                return ret;
557        }
558    }
559
560    new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
561    return 0;
562}
563
564/**
565 * cap_bprm_secureexec - Determine whether a secure execution is required
566 * @bprm: The execution parameters
567 *
568 * Determine whether a secure execution is required, return 1 if it is, and 0
569 * if it is not.
570 *
571 * The credentials have been committed by this point, and so are no longer
572 * available through @bprm->cred.
573 */
574int cap_bprm_secureexec(struct linux_binprm *bprm)
575{
576    const struct cred *cred = current_cred();
577
578    if (cred->uid != 0) {
579        if (bprm->cap_effective)
580            return 1;
581        if (!cap_isclear(cred->cap_permitted))
582            return 1;
583    }
584
585    return (cred->euid != cred->uid ||
586        cred->egid != cred->gid);
587}
588
589/**
590 * cap_inode_setxattr - Determine whether an xattr may be altered
591 * @dentry: The inode/dentry being altered
592 * @name: The name of the xattr to be changed
593 * @value: The value that the xattr will be changed to
594 * @size: The size of value
595 * @flags: The replacement flag
596 *
597 * Determine whether an xattr may be altered or set on an inode, returning 0 if
598 * permission is granted, -ve if denied.
599 *
600 * This is used to make sure security xattrs don't get updated or set by those
601 * who aren't privileged to do so.
602 */
603int cap_inode_setxattr(struct dentry *dentry, const char *name,
604               const void *value, size_t size, int flags)
605{
606    if (!strcmp(name, XATTR_NAME_CAPS)) {
607        if (!capable(CAP_SETFCAP))
608            return -EPERM;
609        return 0;
610    }
611
612    if (!strncmp(name, XATTR_SECURITY_PREFIX,
613             sizeof(XATTR_SECURITY_PREFIX) - 1) &&
614        !capable(CAP_SYS_ADMIN))
615        return -EPERM;
616    return 0;
617}
618
619/**
620 * cap_inode_removexattr - Determine whether an xattr may be removed
621 * @dentry: The inode/dentry being altered
622 * @name: The name of the xattr to be changed
623 *
624 * Determine whether an xattr may be removed from an inode, returning 0 if
625 * permission is granted, -ve if denied.
626 *
627 * This is used to make sure security xattrs don't get removed by those who
628 * aren't privileged to remove them.
629 */
630int cap_inode_removexattr(struct dentry *dentry, const char *name)
631{
632    if (!strcmp(name, XATTR_NAME_CAPS)) {
633        if (!capable(CAP_SETFCAP))
634            return -EPERM;
635        return 0;
636    }
637
638    if (!strncmp(name, XATTR_SECURITY_PREFIX,
639             sizeof(XATTR_SECURITY_PREFIX) - 1) &&
640        !capable(CAP_SYS_ADMIN))
641        return -EPERM;
642    return 0;
643}
644
645/*
646 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
647 * a process after a call to setuid, setreuid, or setresuid.
648 *
649 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
650 * {r,e,s}uid != 0, the permitted and effective capabilities are
651 * cleared.
652 *
653 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
654 * capabilities of the process are cleared.
655 *
656 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
657 * capabilities are set to the permitted capabilities.
658 *
659 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
660 * never happen.
661 *
662 * -astor
663 *
664 * cevans - New behaviour, Oct '99
665 * A process may, via prctl(), elect to keep its capabilities when it
666 * calls setuid() and switches away from uid==0. Both permitted and
667 * effective sets will be retained.
668 * Without this change, it was impossible for a daemon to drop only some
669 * of its privilege. The call to setuid(!=0) would drop all privileges!
670 * Keeping uid 0 is not an option because uid 0 owns too many vital
671 * files..
672 * Thanks to Olaf Kirch and Peter Benie for spotting this.
673 */
674static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
675{
676    if ((old->uid == 0 || old->euid == 0 || old->suid == 0) &&
677        (new->uid != 0 && new->euid != 0 && new->suid != 0) &&
678        !issecure(SECURE_KEEP_CAPS)) {
679        cap_clear(new->cap_permitted);
680        cap_clear(new->cap_effective);
681    }
682    if (old->euid == 0 && new->euid != 0)
683        cap_clear(new->cap_effective);
684    if (old->euid != 0 && new->euid == 0)
685        new->cap_effective = new->cap_permitted;
686}
687
688/**
689 * cap_task_fix_setuid - Fix up the results of setuid() call
690 * @new: The proposed credentials
691 * @old: The current task's current credentials
692 * @flags: Indications of what has changed
693 *
694 * Fix up the results of setuid() call before the credential changes are
695 * actually applied, returning 0 to grant the changes, -ve to deny them.
696 */
697int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
698{
699    switch (flags) {
700    case LSM_SETID_RE:
701    case LSM_SETID_ID:
702    case LSM_SETID_RES:
703        /* juggle the capabilities to follow [RES]UID changes unless
704         * otherwise suppressed */
705        if (!issecure(SECURE_NO_SETUID_FIXUP))
706            cap_emulate_setxuid(new, old);
707        break;
708
709    case LSM_SETID_FS:
710        /* juggle the capabilties to follow FSUID changes, unless
711         * otherwise suppressed
712         *
713         * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
714         * if not, we might be a bit too harsh here.
715         */
716        if (!issecure(SECURE_NO_SETUID_FIXUP)) {
717            if (old->fsuid == 0 && new->fsuid != 0)
718                new->cap_effective =
719                    cap_drop_fs_set(new->cap_effective);
720
721            if (old->fsuid != 0 && new->fsuid == 0)
722                new->cap_effective =
723                    cap_raise_fs_set(new->cap_effective,
724                             new->cap_permitted);
725        }
726        break;
727
728    default:
729        return -EINVAL;
730    }
731
732    return 0;
733}
734
735/*
736 * Rationale: code calling task_setscheduler, task_setioprio, and
737 * task_setnice, assumes that
738 * . if capable(cap_sys_nice), then those actions should be allowed
739 * . if not capable(cap_sys_nice), but acting on your own processes,
740 * then those actions should be allowed
741 * This is insufficient now since you can call code without suid, but
742 * yet with increased caps.
743 * So we check for increased caps on the target process.
744 */
745static int cap_safe_nice(struct task_struct *p)
746{
747    int is_subset;
748
749    rcu_read_lock();
750    is_subset = cap_issubset(__task_cred(p)->cap_permitted,
751                 current_cred()->cap_permitted);
752    rcu_read_unlock();
753
754    if (!is_subset && !capable(CAP_SYS_NICE))
755        return -EPERM;
756    return 0;
757}
758
759/**
760 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
761 * @p: The task to affect
762 *
763 * Detemine if the requested scheduler policy change is permitted for the
764 * specified task, returning 0 if permission is granted, -ve if denied.
765 */
766int cap_task_setscheduler(struct task_struct *p)
767{
768    return cap_safe_nice(p);
769}
770
771/**
772 * cap_task_ioprio - Detemine if I/O priority change is permitted
773 * @p: The task to affect
774 * @ioprio: The I/O priority to set
775 *
776 * Detemine if the requested I/O priority change is permitted for the specified
777 * task, returning 0 if permission is granted, -ve if denied.
778 */
779int cap_task_setioprio(struct task_struct *p, int ioprio)
780{
781    return cap_safe_nice(p);
782}
783
784/**
785 * cap_task_ioprio - Detemine if task priority change is permitted
786 * @p: The task to affect
787 * @nice: The nice value to set
788 *
789 * Detemine if the requested task priority change is permitted for the
790 * specified task, returning 0 if permission is granted, -ve if denied.
791 */
792int cap_task_setnice(struct task_struct *p, int nice)
793{
794    return cap_safe_nice(p);
795}
796
797/*
798 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
799 * the current task's bounding set. Returns 0 on success, -ve on error.
800 */
801static long cap_prctl_drop(struct cred *new, unsigned long cap)
802{
803    if (!capable(CAP_SETPCAP))
804        return -EPERM;
805    if (!cap_valid(cap))
806        return -EINVAL;
807
808    cap_lower(new->cap_bset, cap);
809    return 0;
810}
811
812/**
813 * cap_task_prctl - Implement process control functions for this security module
814 * @option: The process control function requested
815 * @arg2, @arg3, @arg4, @arg5: The argument data for this function
816 *
817 * Allow process control functions (sys_prctl()) to alter capabilities; may
818 * also deny access to other functions not otherwise implemented here.
819 *
820 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
821 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
822 * modules will consider performing the function.
823 */
824int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
825           unsigned long arg4, unsigned long arg5)
826{
827    struct cred *new;
828    long error = 0;
829
830    new = prepare_creds();
831    if (!new)
832        return -ENOMEM;
833
834    switch (option) {
835    case PR_CAPBSET_READ:
836        error = -EINVAL;
837        if (!cap_valid(arg2))
838            goto error;
839        error = !!cap_raised(new->cap_bset, arg2);
840        goto no_change;
841
842    case PR_CAPBSET_DROP:
843        error = cap_prctl_drop(new, arg2);
844        if (error < 0)
845            goto error;
846        goto changed;
847
848    /*
849     * The next four prctl's remain to assist with transitioning a
850     * system from legacy UID=0 based privilege (when filesystem
851     * capabilities are not in use) to a system using filesystem
852     * capabilities only - as the POSIX.1e draft intended.
853     *
854     * Note:
855     *
856     * PR_SET_SECUREBITS =
857     * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
858     * | issecure_mask(SECURE_NOROOT)
859     * | issecure_mask(SECURE_NOROOT_LOCKED)
860     * | issecure_mask(SECURE_NO_SETUID_FIXUP)
861     * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
862     *
863     * will ensure that the current process and all of its
864     * children will be locked into a pure
865     * capability-based-privilege environment.
866     */
867    case PR_SET_SECUREBITS:
868        error = -EPERM;
869        if ((((new->securebits & SECURE_ALL_LOCKS) >> 1)
870             & (new->securebits ^ arg2)) /*[1]*/
871            || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
872            || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
873            || (cap_capable(current, current_cred(),
874                    current_cred()->user->user_ns, CAP_SETPCAP,
875                    SECURITY_CAP_AUDIT) != 0) /*[4]*/
876            /*
877             * [1] no changing of bits that are locked
878             * [2] no unlocking of locks
879             * [3] no setting of unsupported bits
880             * [4] doing anything requires privilege (go read about
881             * the "sendmail capabilities bug")
882             */
883            )
884            /* cannot change a locked bit */
885            goto error;
886        new->securebits = arg2;
887        goto changed;
888
889    case PR_GET_SECUREBITS:
890        error = new->securebits;
891        goto no_change;
892
893    case PR_GET_KEEPCAPS:
894        if (issecure(SECURE_KEEP_CAPS))
895            error = 1;
896        goto no_change;
897
898    case PR_SET_KEEPCAPS:
899        error = -EINVAL;
900        if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
901            goto error;
902        error = -EPERM;
903        if (issecure(SECURE_KEEP_CAPS_LOCKED))
904            goto error;
905        if (arg2)
906            new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
907        else
908            new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
909        goto changed;
910
911    default:
912        /* No functionality available - continue with default */
913        error = -ENOSYS;
914        goto error;
915    }
916
917    /* Functionality provided */
918changed:
919    return commit_creds(new);
920
921no_change:
922error:
923    abort_creds(new);
924    return error;
925}
926
927/**
928 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
929 * @mm: The VM space in which the new mapping is to be made
930 * @pages: The size of the mapping
931 *
932 * Determine whether the allocation of a new virtual mapping by the current
933 * task is permitted, returning 0 if permission is granted, -ve if not.
934 */
935int cap_vm_enough_memory(struct mm_struct *mm, long pages)
936{
937    int cap_sys_admin = 0;
938
939    if (cap_capable(current, current_cred(), &init_user_ns, CAP_SYS_ADMIN,
940            SECURITY_CAP_NOAUDIT) == 0)
941        cap_sys_admin = 1;
942    return __vm_enough_memory(mm, pages, cap_sys_admin);
943}
944
945/*
946 * cap_file_mmap - check if able to map given addr
947 * @file: unused
948 * @reqprot: unused
949 * @prot: unused
950 * @flags: unused
951 * @addr: address attempting to be mapped
952 * @addr_only: unused
953 *
954 * If the process is attempting to map memory below dac_mmap_min_addr they need
955 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
956 * capability security module. Returns 0 if this mapping should be allowed
957 * -EPERM if not.
958 */
959int cap_file_mmap(struct file *file, unsigned long reqprot,
960          unsigned long prot, unsigned long flags,
961          unsigned long addr, unsigned long addr_only)
962{
963    int ret = 0;
964
965    if (addr < dac_mmap_min_addr) {
966        ret = cap_capable(current, current_cred(), &init_user_ns, CAP_SYS_RAWIO,
967                  SECURITY_CAP_AUDIT);
968        /* set PF_SUPERPRIV if it turns out we allow the low mmap */
969        if (ret == 0)
970            current->flags |= PF_SUPERPRIV;
971    }
972    return ret;
973}
974

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