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#include <linux/binfmts.h>
32#include <linux/personality.h>
33
34/*
35 * If a non-root user executes a setuid-root binary in
36 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
37 * However if fE is also set, then the intent is for only
38 * the file capabilities to be applied, and the setuid-root
39 * bit is left on either to change the uid (plausible) or
40 * to get full privilege on a kernel without file capabilities
41 * support. So in that case we do not raise capabilities.
42 *
43 * Warn if that happens, once per boot.
44 */
45static void warn_setuid_and_fcaps_mixed(const char *fname)
46{
47    static int warned;
48    if (!warned) {
49        printk(KERN_INFO "warning: `%s' has both setuid-root and"
50            " effective capabilities. Therefore not raising all"
51            " capabilities.\n", fname);
52        warned = 1;
53    }
54}
55
56int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
57{
58    return 0;
59}
60
61/**
62 * cap_capable - Determine whether a task has a particular effective capability
63 * @cred: The credentials to use
64 * @ns: The user namespace in which we need the capability
65 * @cap: The capability to check for
66 * @audit: Whether to write an audit message or not
67 *
68 * Determine whether the nominated task has the specified capability amongst
69 * its effective set, returning 0 if it does, -ve if it does not.
70 *
71 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
72 * and has_capability() functions. That is, it has the reverse semantics:
73 * cap_has_capability() returns 0 when a task has a capability, but the
74 * kernel's capable() and has_capability() returns 1 for this case.
75 */
76int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
77        int cap, int audit)
78{
79    for (;;) {
80        /* The creator of the user namespace has all caps. */
81        if (targ_ns != &init_user_ns && targ_ns->creator == cred->user)
82            return 0;
83
84        /* Do we have the necessary capabilities? */
85        if (targ_ns == cred->user->user_ns)
86            return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
87
88        /* Have we tried all of the parent namespaces? */
89        if (targ_ns == &init_user_ns)
90            return -EPERM;
91
92        /*
93         *If you have a capability in a parent user ns, then you have
94         * it over all children user namespaces as well.
95         */
96        targ_ns = targ_ns->creator->user_ns;
97    }
98
99    /* We never get here */
100}
101
102/**
103 * cap_settime - Determine whether the current process may set the system clock
104 * @ts: The time to set
105 * @tz: The timezone to set
106 *
107 * Determine whether the current process may set the system clock and timezone
108 * information, returning 0 if permission granted, -ve if denied.
109 */
110int cap_settime(const struct timespec *ts, const struct timezone *tz)
111{
112    if (!capable(CAP_SYS_TIME))
113        return -EPERM;
114    return 0;
115}
116
117/**
118 * cap_ptrace_access_check - Determine whether the current process may access
119 * another
120 * @child: The process to be accessed
121 * @mode: The mode of attachment.
122 *
123 * If we are in the same or an ancestor user_ns and have all the target
124 * task's capabilities, then ptrace access is allowed.
125 * If we have the ptrace capability to the target user_ns, then ptrace
126 * access is allowed.
127 * Else denied.
128 *
129 * Determine whether a process may access another, returning 0 if permission
130 * granted, -ve if denied.
131 */
132int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
133{
134    int ret = 0;
135    const struct cred *cred, *child_cred;
136
137    rcu_read_lock();
138    cred = current_cred();
139    child_cred = __task_cred(child);
140    if (cred->user->user_ns == child_cred->user->user_ns &&
141        cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
142        goto out;
143    if (ns_capable(child_cred->user->user_ns, CAP_SYS_PTRACE))
144        goto out;
145    ret = -EPERM;
146out:
147    rcu_read_unlock();
148    return ret;
149}
150
151/**
152 * cap_ptrace_traceme - Determine whether another process may trace the current
153 * @parent: The task proposed to be the tracer
154 *
155 * If parent is in the same or an ancestor user_ns and has all current's
156 * capabilities, then ptrace access is allowed.
157 * If parent has the ptrace capability to current's user_ns, then ptrace
158 * access is allowed.
159 * Else denied.
160 *
161 * Determine whether the nominated task is permitted to trace the current
162 * process, returning 0 if permission is granted, -ve if denied.
163 */
164int cap_ptrace_traceme(struct task_struct *parent)
165{
166    int ret = 0;
167    const struct cred *cred, *child_cred;
168
169    rcu_read_lock();
170    cred = __task_cred(parent);
171    child_cred = current_cred();
172    if (cred->user->user_ns == child_cred->user->user_ns &&
173        cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
174        goto out;
175    if (has_ns_capability(parent, child_cred->user->user_ns, CAP_SYS_PTRACE))
176        goto out;
177    ret = -EPERM;
178out:
179    rcu_read_unlock();
180    return ret;
181}
182
183/**
184 * cap_capget - Retrieve a task's capability sets
185 * @target: The task from which to retrieve the capability sets
186 * @effective: The place to record the effective set
187 * @inheritable: The place to record the inheritable set
188 * @permitted: The place to record the permitted set
189 *
190 * This function retrieves the capabilities of the nominated task and returns
191 * them to the caller.
192 */
193int cap_capget(struct task_struct *target, kernel_cap_t *effective,
194           kernel_cap_t *inheritable, kernel_cap_t *permitted)
195{
196    const struct cred *cred;
197
198    /* Derived from kernel/capability.c:sys_capget. */
199    rcu_read_lock();
200    cred = __task_cred(target);
201    *effective = cred->cap_effective;
202    *inheritable = cred->cap_inheritable;
203    *permitted = cred->cap_permitted;
204    rcu_read_unlock();
205    return 0;
206}
207
208/*
209 * Determine whether the inheritable capabilities are limited to the old
210 * permitted set. Returns 1 if they are limited, 0 if they are not.
211 */
212static inline int cap_inh_is_capped(void)
213{
214
215    /* they are so limited unless the current task has the CAP_SETPCAP
216     * capability
217     */
218    if (cap_capable(current_cred(), current_cred()->user->user_ns,
219            CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0)
220        return 0;
221    return 1;
222}
223
224/**
225 * cap_capset - Validate and apply proposed changes to current's capabilities
226 * @new: The proposed new credentials; alterations should be made here
227 * @old: The current task's current credentials
228 * @effective: A pointer to the proposed new effective capabilities set
229 * @inheritable: A pointer to the proposed new inheritable capabilities set
230 * @permitted: A pointer to the proposed new permitted capabilities set
231 *
232 * This function validates and applies a proposed mass change to the current
233 * process's capability sets. The changes are made to the proposed new
234 * credentials, and assuming no error, will be committed by the caller of LSM.
235 */
236int cap_capset(struct cred *new,
237           const struct cred *old,
238           const kernel_cap_t *effective,
239           const kernel_cap_t *inheritable,
240           const kernel_cap_t *permitted)
241{
242    if (cap_inh_is_capped() &&
243        !cap_issubset(*inheritable,
244              cap_combine(old->cap_inheritable,
245                      old->cap_permitted)))
246        /* incapable of using this inheritable set */
247        return -EPERM;
248
249    if (!cap_issubset(*inheritable,
250              cap_combine(old->cap_inheritable,
251                      old->cap_bset)))
252        /* no new pI capabilities outside bounding set */
253        return -EPERM;
254
255    /* verify restrictions on target's new Permitted set */
256    if (!cap_issubset(*permitted, old->cap_permitted))
257        return -EPERM;
258
259    /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
260    if (!cap_issubset(*effective, *permitted))
261        return -EPERM;
262
263    new->cap_effective = *effective;
264    new->cap_inheritable = *inheritable;
265    new->cap_permitted = *permitted;
266    return 0;
267}
268
269/*
270 * Clear proposed capability sets for execve().
271 */
272static inline void bprm_clear_caps(struct linux_binprm *bprm)
273{
274    cap_clear(bprm->cred->cap_permitted);
275    bprm->cap_effective = false;
276}
277
278/**
279 * cap_inode_need_killpriv - Determine if inode change affects privileges
280 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
281 *
282 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
283 * affects the security markings on that inode, and if it is, should
284 * inode_killpriv() be invoked or the change rejected?
285 *
286 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
287 * -ve to deny the change.
288 */
289int cap_inode_need_killpriv(struct dentry *dentry)
290{
291    struct inode *inode = dentry->d_inode;
292    int error;
293
294    if (!inode->i_op->getxattr)
295           return 0;
296
297    error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
298    if (error <= 0)
299        return 0;
300    return 1;
301}
302
303/**
304 * cap_inode_killpriv - Erase the security markings on an inode
305 * @dentry: The inode/dentry to alter
306 *
307 * Erase the privilege-enhancing security markings on an inode.
308 *
309 * Returns 0 if successful, -ve on error.
310 */
311int cap_inode_killpriv(struct dentry *dentry)
312{
313    struct inode *inode = dentry->d_inode;
314
315    if (!inode->i_op->removexattr)
316           return 0;
317
318    return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
319}
320
321/*
322 * Calculate the new process capability sets from the capability sets attached
323 * to a file.
324 */
325static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
326                      struct linux_binprm *bprm,
327                      bool *effective,
328                      bool *has_cap)
329{
330    struct cred *new = bprm->cred;
331    unsigned i;
332    int ret = 0;
333
334    if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
335        *effective = true;
336
337    if (caps->magic_etc & VFS_CAP_REVISION_MASK)
338        *has_cap = true;
339
340    CAP_FOR_EACH_U32(i) {
341        __u32 permitted = caps->permitted.cap[i];
342        __u32 inheritable = caps->inheritable.cap[i];
343
344        /*
345         * pP' = (X & fP) | (pI & fI)
346         */
347        new->cap_permitted.cap[i] =
348            (new->cap_bset.cap[i] & permitted) |
349            (new->cap_inheritable.cap[i] & inheritable);
350
351        if (permitted & ~new->cap_permitted.cap[i])
352            /* insufficient to execute correctly */
353            ret = -EPERM;
354    }
355
356    /*
357     * For legacy apps, with no internal support for recognizing they
358     * do not have enough capabilities, we return an error if they are
359     * missing some "forced" (aka file-permitted) capabilities.
360     */
361    return *effective ? ret : 0;
362}
363
364/*
365 * Extract the on-exec-apply capability sets for an executable file.
366 */
367int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
368{
369    struct inode *inode = dentry->d_inode;
370    __u32 magic_etc;
371    unsigned tocopy, i;
372    int size;
373    struct vfs_cap_data caps;
374
375    memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
376
377    if (!inode || !inode->i_op->getxattr)
378        return -ENODATA;
379
380    size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps,
381                   XATTR_CAPS_SZ);
382    if (size == -ENODATA || size == -EOPNOTSUPP)
383        /* no data, that's ok */
384        return -ENODATA;
385    if (size < 0)
386        return size;
387
388    if (size < sizeof(magic_etc))
389        return -EINVAL;
390
391    cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
392
393    switch (magic_etc & VFS_CAP_REVISION_MASK) {
394    case VFS_CAP_REVISION_1:
395        if (size != XATTR_CAPS_SZ_1)
396            return -EINVAL;
397        tocopy = VFS_CAP_U32_1;
398        break;
399    case VFS_CAP_REVISION_2:
400        if (size != XATTR_CAPS_SZ_2)
401            return -EINVAL;
402        tocopy = VFS_CAP_U32_2;
403        break;
404    default:
405        return -EINVAL;
406    }
407
408    CAP_FOR_EACH_U32(i) {
409        if (i >= tocopy)
410            break;
411        cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
412        cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
413    }
414
415    return 0;
416}
417
418/*
419 * Attempt to get the on-exec apply capability sets for an executable file from
420 * its xattrs and, if present, apply them to the proposed credentials being
421 * constructed by execve().
422 */
423static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap)
424{
425    struct dentry *dentry;
426    int rc = 0;
427    struct cpu_vfs_cap_data vcaps;
428
429    bprm_clear_caps(bprm);
430
431    if (!file_caps_enabled)
432        return 0;
433
434    if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID)
435        return 0;
436
437    dentry = dget(bprm->file->f_dentry);
438
439    rc = get_vfs_caps_from_disk(dentry, &vcaps);
440    if (rc < 0) {
441        if (rc == -EINVAL)
442            printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
443                __func__, rc, bprm->filename);
444        else if (rc == -ENODATA)
445            rc = 0;
446        goto out;
447    }
448
449    rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap);
450    if (rc == -EINVAL)
451        printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
452               __func__, rc, bprm->filename);
453
454out:
455    dput(dentry);
456    if (rc)
457        bprm_clear_caps(bprm);
458
459    return rc;
460}
461
462/**
463 * cap_bprm_set_creds - Set up the proposed credentials for execve().
464 * @bprm: The execution parameters, including the proposed creds
465 *
466 * Set up the proposed credentials for a new execution context being
467 * constructed by execve(). The proposed creds in @bprm->cred is altered,
468 * which won't take effect immediately. Returns 0 if successful, -ve on error.
469 */
470int cap_bprm_set_creds(struct linux_binprm *bprm)
471{
472    const struct cred *old = current_cred();
473    struct cred *new = bprm->cred;
474    bool effective, has_cap = false;
475    int ret;
476
477    effective = false;
478    ret = get_file_caps(bprm, &effective, &has_cap);
479    if (ret < 0)
480        return ret;
481
482    if (!issecure(SECURE_NOROOT)) {
483        /*
484         * If the legacy file capability is set, then don't set privs
485         * for a setuid root binary run by a non-root user. Do set it
486         * for a root user just to cause least surprise to an admin.
487         */
488        if (has_cap && new->uid != 0 && new->euid == 0) {
489            warn_setuid_and_fcaps_mixed(bprm->filename);
490            goto skip;
491        }
492        /*
493         * To support inheritance of root-permissions and suid-root
494         * executables under compatibility mode, we override the
495         * capability sets for the file.
496         *
497         * If only the real uid is 0, we do not set the effective bit.
498         */
499        if (new->euid == 0 || new->uid == 0) {
500            /* pP' = (cap_bset & ~0) | (pI & ~0) */
501            new->cap_permitted = cap_combine(old->cap_bset,
502                             old->cap_inheritable);
503        }
504        if (new->euid == 0)
505            effective = true;
506    }
507skip:
508
509    /* if we have fs caps, clear dangerous personality flags */
510    if (!cap_issubset(new->cap_permitted, old->cap_permitted))
511        bprm->per_clear |= PER_CLEAR_ON_SETID;
512
513
514    /* Don't let someone trace a set[ug]id/setpcap binary with the revised
515     * credentials unless they have the appropriate permit
516     */
517    if ((new->euid != old->uid ||
518         new->egid != old->gid ||
519         !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
520        bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
521        /* downgrade; they get no more than they had, and maybe less */
522        if (!capable(CAP_SETUID)) {
523            new->euid = new->uid;
524            new->egid = new->gid;
525        }
526        new->cap_permitted = cap_intersect(new->cap_permitted,
527                           old->cap_permitted);
528    }
529
530    new->suid = new->fsuid = new->euid;
531    new->sgid = new->fsgid = new->egid;
532
533    if (effective)
534        new->cap_effective = new->cap_permitted;
535    else
536        cap_clear(new->cap_effective);
537    bprm->cap_effective = effective;
538
539    /*
540     * Audit candidate if current->cap_effective is set
541     *
542     * We do not bother to audit if 3 things are true:
543     * 1) cap_effective has all caps
544     * 2) we are root
545     * 3) root is supposed to have all caps (SECURE_NOROOT)
546     * Since this is just a normal root execing a process.
547     *
548     * Number 1 above might fail if you don't have a full bset, but I think
549     * that is interesting information to audit.
550     */
551    if (!cap_isclear(new->cap_effective)) {
552        if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
553            new->euid != 0 || new->uid != 0 ||
554            issecure(SECURE_NOROOT)) {
555            ret = audit_log_bprm_fcaps(bprm, new, old);
556            if (ret < 0)
557                return ret;
558        }
559    }
560
561    new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
562    return 0;
563}
564
565/**
566 * cap_bprm_secureexec - Determine whether a secure execution is required
567 * @bprm: The execution parameters
568 *
569 * Determine whether a secure execution is required, return 1 if it is, and 0
570 * if it is not.
571 *
572 * The credentials have been committed by this point, and so are no longer
573 * available through @bprm->cred.
574 */
575int cap_bprm_secureexec(struct linux_binprm *bprm)
576{
577    const struct cred *cred = current_cred();
578
579    if (cred->uid != 0) {
580        if (bprm->cap_effective)
581            return 1;
582        if (!cap_isclear(cred->cap_permitted))
583            return 1;
584    }
585
586    return (cred->euid != cred->uid ||
587        cred->egid != cred->gid);
588}
589
590/**
591 * cap_inode_setxattr - Determine whether an xattr may be altered
592 * @dentry: The inode/dentry being altered
593 * @name: The name of the xattr to be changed
594 * @value: The value that the xattr will be changed to
595 * @size: The size of value
596 * @flags: The replacement flag
597 *
598 * Determine whether an xattr may be altered or set on an inode, returning 0 if
599 * permission is granted, -ve if denied.
600 *
601 * This is used to make sure security xattrs don't get updated or set by those
602 * who aren't privileged to do so.
603 */
604int cap_inode_setxattr(struct dentry *dentry, const char *name,
605               const void *value, size_t size, int flags)
606{
607    if (!strcmp(name, XATTR_NAME_CAPS)) {
608        if (!capable(CAP_SETFCAP))
609            return -EPERM;
610        return 0;
611    }
612
613    if (!strncmp(name, XATTR_SECURITY_PREFIX,
614             sizeof(XATTR_SECURITY_PREFIX) - 1) &&
615        !capable(CAP_SYS_ADMIN))
616        return -EPERM;
617    return 0;
618}
619
620/**
621 * cap_inode_removexattr - Determine whether an xattr may be removed
622 * @dentry: The inode/dentry being altered
623 * @name: The name of the xattr to be changed
624 *
625 * Determine whether an xattr may be removed from an inode, returning 0 if
626 * permission is granted, -ve if denied.
627 *
628 * This is used to make sure security xattrs don't get removed by those who
629 * aren't privileged to remove them.
630 */
631int cap_inode_removexattr(struct dentry *dentry, const char *name)
632{
633    if (!strcmp(name, XATTR_NAME_CAPS)) {
634        if (!capable(CAP_SETFCAP))
635            return -EPERM;
636        return 0;
637    }
638
639    if (!strncmp(name, XATTR_SECURITY_PREFIX,
640             sizeof(XATTR_SECURITY_PREFIX) - 1) &&
641        !capable(CAP_SYS_ADMIN))
642        return -EPERM;
643    return 0;
644}
645
646/*
647 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
648 * a process after a call to setuid, setreuid, or setresuid.
649 *
650 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
651 * {r,e,s}uid != 0, the permitted and effective capabilities are
652 * cleared.
653 *
654 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
655 * capabilities of the process are cleared.
656 *
657 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
658 * capabilities are set to the permitted capabilities.
659 *
660 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
661 * never happen.
662 *
663 * -astor
664 *
665 * cevans - New behaviour, Oct '99
666 * A process may, via prctl(), elect to keep its capabilities when it
667 * calls setuid() and switches away from uid==0. Both permitted and
668 * effective sets will be retained.
669 * Without this change, it was impossible for a daemon to drop only some
670 * of its privilege. The call to setuid(!=0) would drop all privileges!
671 * Keeping uid 0 is not an option because uid 0 owns too many vital
672 * files..
673 * Thanks to Olaf Kirch and Peter Benie for spotting this.
674 */
675static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
676{
677    if ((old->uid == 0 || old->euid == 0 || old->suid == 0) &&
678        (new->uid != 0 && new->euid != 0 && new->suid != 0) &&
679        !issecure(SECURE_KEEP_CAPS)) {
680        cap_clear(new->cap_permitted);
681        cap_clear(new->cap_effective);
682    }
683    if (old->euid == 0 && new->euid != 0)
684        cap_clear(new->cap_effective);
685    if (old->euid != 0 && new->euid == 0)
686        new->cap_effective = new->cap_permitted;
687}
688
689/**
690 * cap_task_fix_setuid - Fix up the results of setuid() call
691 * @new: The proposed credentials
692 * @old: The current task's current credentials
693 * @flags: Indications of what has changed
694 *
695 * Fix up the results of setuid() call before the credential changes are
696 * actually applied, returning 0 to grant the changes, -ve to deny them.
697 */
698int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
699{
700    switch (flags) {
701    case LSM_SETID_RE:
702    case LSM_SETID_ID:
703    case LSM_SETID_RES:
704        /* juggle the capabilities to follow [RES]UID changes unless
705         * otherwise suppressed */
706        if (!issecure(SECURE_NO_SETUID_FIXUP))
707            cap_emulate_setxuid(new, old);
708        break;
709
710    case LSM_SETID_FS:
711        /* juggle the capabilties to follow FSUID changes, unless
712         * otherwise suppressed
713         *
714         * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
715         * if not, we might be a bit too harsh here.
716         */
717        if (!issecure(SECURE_NO_SETUID_FIXUP)) {
718            if (old->fsuid == 0 && new->fsuid != 0)
719                new->cap_effective =
720                    cap_drop_fs_set(new->cap_effective);
721
722            if (old->fsuid != 0 && new->fsuid == 0)
723                new->cap_effective =
724                    cap_raise_fs_set(new->cap_effective,
725                             new->cap_permitted);
726        }
727        break;
728
729    default:
730        return -EINVAL;
731    }
732
733    return 0;
734}
735
736/*
737 * Rationale: code calling task_setscheduler, task_setioprio, and
738 * task_setnice, assumes that
739 * . if capable(cap_sys_nice), then those actions should be allowed
740 * . if not capable(cap_sys_nice), but acting on your own processes,
741 * then those actions should be allowed
742 * This is insufficient now since you can call code without suid, but
743 * yet with increased caps.
744 * So we check for increased caps on the target process.
745 */
746static int cap_safe_nice(struct task_struct *p)
747{
748    int is_subset;
749
750    rcu_read_lock();
751    is_subset = cap_issubset(__task_cred(p)->cap_permitted,
752                 current_cred()->cap_permitted);
753    rcu_read_unlock();
754
755    if (!is_subset && !capable(CAP_SYS_NICE))
756        return -EPERM;
757    return 0;
758}
759
760/**
761 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
762 * @p: The task to affect
763 *
764 * Detemine if the requested scheduler policy change is permitted for the
765 * specified task, returning 0 if permission is granted, -ve if denied.
766 */
767int cap_task_setscheduler(struct task_struct *p)
768{
769    return cap_safe_nice(p);
770}
771
772/**
773 * cap_task_ioprio - Detemine if I/O priority change is permitted
774 * @p: The task to affect
775 * @ioprio: The I/O priority to set
776 *
777 * Detemine if the requested I/O priority change is permitted for the specified
778 * task, returning 0 if permission is granted, -ve if denied.
779 */
780int cap_task_setioprio(struct task_struct *p, int ioprio)
781{
782    return cap_safe_nice(p);
783}
784
785/**
786 * cap_task_ioprio - Detemine if task priority change is permitted
787 * @p: The task to affect
788 * @nice: The nice value to set
789 *
790 * Detemine if the requested task priority change is permitted for the
791 * specified task, returning 0 if permission is granted, -ve if denied.
792 */
793int cap_task_setnice(struct task_struct *p, int nice)
794{
795    return cap_safe_nice(p);
796}
797
798/*
799 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
800 * the current task's bounding set. Returns 0 on success, -ve on error.
801 */
802static long cap_prctl_drop(struct cred *new, unsigned long cap)
803{
804    if (!capable(CAP_SETPCAP))
805        return -EPERM;
806    if (!cap_valid(cap))
807        return -EINVAL;
808
809    cap_lower(new->cap_bset, cap);
810    return 0;
811}
812
813/**
814 * cap_task_prctl - Implement process control functions for this security module
815 * @option: The process control function requested
816 * @arg2, @arg3, @arg4, @arg5: The argument data for this function
817 *
818 * Allow process control functions (sys_prctl()) to alter capabilities; may
819 * also deny access to other functions not otherwise implemented here.
820 *
821 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
822 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
823 * modules will consider performing the function.
824 */
825int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
826           unsigned long arg4, unsigned long arg5)
827{
828    struct cred *new;
829    long error = 0;
830
831    new = prepare_creds();
832    if (!new)
833        return -ENOMEM;
834
835    switch (option) {
836    case PR_CAPBSET_READ:
837        error = -EINVAL;
838        if (!cap_valid(arg2))
839            goto error;
840        error = !!cap_raised(new->cap_bset, arg2);
841        goto no_change;
842
843    case PR_CAPBSET_DROP:
844        error = cap_prctl_drop(new, arg2);
845        if (error < 0)
846            goto error;
847        goto changed;
848
849    /*
850     * The next four prctl's remain to assist with transitioning a
851     * system from legacy UID=0 based privilege (when filesystem
852     * capabilities are not in use) to a system using filesystem
853     * capabilities only - as the POSIX.1e draft intended.
854     *
855     * Note:
856     *
857     * PR_SET_SECUREBITS =
858     * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
859     * | issecure_mask(SECURE_NOROOT)
860     * | issecure_mask(SECURE_NOROOT_LOCKED)
861     * | issecure_mask(SECURE_NO_SETUID_FIXUP)
862     * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
863     *
864     * will ensure that the current process and all of its
865     * children will be locked into a pure
866     * capability-based-privilege environment.
867     */
868    case PR_SET_SECUREBITS:
869        error = -EPERM;
870        if ((((new->securebits & SECURE_ALL_LOCKS) >> 1)
871             & (new->securebits ^ arg2)) /*[1]*/
872            || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
873            || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
874            || (cap_capable(current_cred(),
875                    current_cred()->user->user_ns, CAP_SETPCAP,
876                    SECURITY_CAP_AUDIT) != 0) /*[4]*/
877            /*
878             * [1] no changing of bits that are locked
879             * [2] no unlocking of locks
880             * [3] no setting of unsupported bits
881             * [4] doing anything requires privilege (go read about
882             * the "sendmail capabilities bug")
883             */
884            )
885            /* cannot change a locked bit */
886            goto error;
887        new->securebits = arg2;
888        goto changed;
889
890    case PR_GET_SECUREBITS:
891        error = new->securebits;
892        goto no_change;
893
894    case PR_GET_KEEPCAPS:
895        if (issecure(SECURE_KEEP_CAPS))
896            error = 1;
897        goto no_change;
898
899    case PR_SET_KEEPCAPS:
900        error = -EINVAL;
901        if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
902            goto error;
903        error = -EPERM;
904        if (issecure(SECURE_KEEP_CAPS_LOCKED))
905            goto error;
906        if (arg2)
907            new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
908        else
909            new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
910        goto changed;
911
912    default:
913        /* No functionality available - continue with default */
914        error = -ENOSYS;
915        goto error;
916    }
917
918    /* Functionality provided */
919changed:
920    return commit_creds(new);
921
922no_change:
923error:
924    abort_creds(new);
925    return error;
926}
927
928/**
929 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
930 * @mm: The VM space in which the new mapping is to be made
931 * @pages: The size of the mapping
932 *
933 * Determine whether the allocation of a new virtual mapping by the current
934 * task is permitted, returning 0 if permission is granted, -ve if not.
935 */
936int cap_vm_enough_memory(struct mm_struct *mm, long pages)
937{
938    int cap_sys_admin = 0;
939
940    if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN,
941            SECURITY_CAP_NOAUDIT) == 0)
942        cap_sys_admin = 1;
943    return __vm_enough_memory(mm, pages, cap_sys_admin);
944}
945
946/*
947 * cap_file_mmap - check if able to map given addr
948 * @file: unused
949 * @reqprot: unused
950 * @prot: unused
951 * @flags: unused
952 * @addr: address attempting to be mapped
953 * @addr_only: unused
954 *
955 * If the process is attempting to map memory below dac_mmap_min_addr they need
956 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
957 * capability security module. Returns 0 if this mapping should be allowed
958 * -EPERM if not.
959 */
960int cap_file_mmap(struct file *file, unsigned long reqprot,
961          unsigned long prot, unsigned long flags,
962          unsigned long addr, unsigned long addr_only)
963{
964    int ret = 0;
965
966    if (addr < dac_mmap_min_addr) {
967        ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
968                  SECURITY_CAP_AUDIT);
969        /* set PF_SUPERPRIV if it turns out we allow the low mmap */
970        if (ret == 0)
971            current->flags |= PF_SUPERPRIV;
972    }
973    return ret;
974}
975

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