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
31/*
32 * If a non-root user executes a setuid-root binary in
33 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
34 * However if fE is also set, then the intent is for only
35 * the file capabilities to be applied, and the setuid-root
36 * bit is left on either to change the uid (plausible) or
37 * to get full privilege on a kernel without file capabilities
38 * support. So in that case we do not raise capabilities.
39 *
40 * Warn if that happens, once per boot.
41 */
42static void warn_setuid_and_fcaps_mixed(const char *fname)
43{
44    static int warned;
45    if (!warned) {
46        printk(KERN_INFO "warning: `%s' has both setuid-root and"
47            " effective capabilities. Therefore not raising all"
48            " capabilities.\n", fname);
49        warned = 1;
50    }
51}
52
53int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
54{
55    NETLINK_CB(skb).eff_cap = current_cap();
56    return 0;
57}
58
59int cap_netlink_recv(struct sk_buff *skb, int cap)
60{
61    if (!cap_raised(NETLINK_CB(skb).eff_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 * @cap: The capability to check for
72 * @audit: Whether to write an audit message or not
73 *
74 * Determine whether the nominated task has the specified capability amongst
75 * its effective set, returning 0 if it does, -ve if it does not.
76 *
77 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
78 * and has_capability() functions. That is, it has the reverse semantics:
79 * cap_has_capability() returns 0 when a task has a capability, but the
80 * kernel's capable() and has_capability() returns 1 for this case.
81 */
82int cap_capable(struct task_struct *tsk, const struct cred *cred, int cap,
83        int audit)
84{
85    return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
86}
87
88/**
89 * cap_settime - Determine whether the current process may set the system clock
90 * @ts: The time to set
91 * @tz: The timezone to set
92 *
93 * Determine whether the current process may set the system clock and timezone
94 * information, returning 0 if permission granted, -ve if denied.
95 */
96int cap_settime(struct timespec *ts, struct timezone *tz)
97{
98    if (!capable(CAP_SYS_TIME))
99        return -EPERM;
100    return 0;
101}
102
103/**
104 * cap_ptrace_access_check - Determine whether the current process may access
105 * another
106 * @child: The process to be accessed
107 * @mode: The mode of attachment.
108 *
109 * Determine whether a process may access another, returning 0 if permission
110 * granted, -ve if denied.
111 */
112int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
113{
114    int ret = 0;
115
116    rcu_read_lock();
117    if (!cap_issubset(__task_cred(child)->cap_permitted,
118              current_cred()->cap_permitted) &&
119        !capable(CAP_SYS_PTRACE))
120        ret = -EPERM;
121    rcu_read_unlock();
122    return ret;
123}
124
125/**
126 * cap_ptrace_traceme - Determine whether another process may trace the current
127 * @parent: The task proposed to be the tracer
128 *
129 * Determine whether the nominated task is permitted to trace the current
130 * process, returning 0 if permission is granted, -ve if denied.
131 */
132int cap_ptrace_traceme(struct task_struct *parent)
133{
134    int ret = 0;
135
136    rcu_read_lock();
137    if (!cap_issubset(current_cred()->cap_permitted,
138              __task_cred(parent)->cap_permitted) &&
139        !has_capability(parent, CAP_SYS_PTRACE))
140        ret = -EPERM;
141    rcu_read_unlock();
142    return ret;
143}
144
145/**
146 * cap_capget - Retrieve a task's capability sets
147 * @target: The task from which to retrieve the capability sets
148 * @effective: The place to record the effective set
149 * @inheritable: The place to record the inheritable set
150 * @permitted: The place to record the permitted set
151 *
152 * This function retrieves the capabilities of the nominated task and returns
153 * them to the caller.
154 */
155int cap_capget(struct task_struct *target, kernel_cap_t *effective,
156           kernel_cap_t *inheritable, kernel_cap_t *permitted)
157{
158    const struct cred *cred;
159
160    /* Derived from kernel/capability.c:sys_capget. */
161    rcu_read_lock();
162    cred = __task_cred(target);
163    *effective = cred->cap_effective;
164    *inheritable = cred->cap_inheritable;
165    *permitted = cred->cap_permitted;
166    rcu_read_unlock();
167    return 0;
168}
169
170/*
171 * Determine whether the inheritable capabilities are limited to the old
172 * permitted set. Returns 1 if they are limited, 0 if they are not.
173 */
174static inline int cap_inh_is_capped(void)
175{
176
177    /* they are so limited unless the current task has the CAP_SETPCAP
178     * capability
179     */
180    if (cap_capable(current, current_cred(), CAP_SETPCAP,
181            SECURITY_CAP_AUDIT) == 0)
182        return 0;
183    return 1;
184}
185
186/**
187 * cap_capset - Validate and apply proposed changes to current's capabilities
188 * @new: The proposed new credentials; alterations should be made here
189 * @old: The current task's current credentials
190 * @effective: A pointer to the proposed new effective capabilities set
191 * @inheritable: A pointer to the proposed new inheritable capabilities set
192 * @permitted: A pointer to the proposed new permitted capabilities set
193 *
194 * This function validates and applies a proposed mass change to the current
195 * process's capability sets. The changes are made to the proposed new
196 * credentials, and assuming no error, will be committed by the caller of LSM.
197 */
198int cap_capset(struct cred *new,
199           const struct cred *old,
200           const kernel_cap_t *effective,
201           const kernel_cap_t *inheritable,
202           const kernel_cap_t *permitted)
203{
204    if (cap_inh_is_capped() &&
205        !cap_issubset(*inheritable,
206              cap_combine(old->cap_inheritable,
207                      old->cap_permitted)))
208        /* incapable of using this inheritable set */
209        return -EPERM;
210
211    if (!cap_issubset(*inheritable,
212              cap_combine(old->cap_inheritable,
213                      old->cap_bset)))
214        /* no new pI capabilities outside bounding set */
215        return -EPERM;
216
217    /* verify restrictions on target's new Permitted set */
218    if (!cap_issubset(*permitted, old->cap_permitted))
219        return -EPERM;
220
221    /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
222    if (!cap_issubset(*effective, *permitted))
223        return -EPERM;
224
225    new->cap_effective = *effective;
226    new->cap_inheritable = *inheritable;
227    new->cap_permitted = *permitted;
228    return 0;
229}
230
231/*
232 * Clear proposed capability sets for execve().
233 */
234static inline void bprm_clear_caps(struct linux_binprm *bprm)
235{
236    cap_clear(bprm->cred->cap_permitted);
237    bprm->cap_effective = false;
238}
239
240/**
241 * cap_inode_need_killpriv - Determine if inode change affects privileges
242 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
243 *
244 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
245 * affects the security markings on that inode, and if it is, should
246 * inode_killpriv() be invoked or the change rejected?
247 *
248 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
249 * -ve to deny the change.
250 */
251int cap_inode_need_killpriv(struct dentry *dentry)
252{
253    struct inode *inode = dentry->d_inode;
254    int error;
255
256    if (!inode->i_op->getxattr)
257           return 0;
258
259    error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
260    if (error <= 0)
261        return 0;
262    return 1;
263}
264
265/**
266 * cap_inode_killpriv - Erase the security markings on an inode
267 * @dentry: The inode/dentry to alter
268 *
269 * Erase the privilege-enhancing security markings on an inode.
270 *
271 * Returns 0 if successful, -ve on error.
272 */
273int cap_inode_killpriv(struct dentry *dentry)
274{
275    struct inode *inode = dentry->d_inode;
276
277    if (!inode->i_op->removexattr)
278           return 0;
279
280    return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
281}
282
283/*
284 * Calculate the new process capability sets from the capability sets attached
285 * to a file.
286 */
287static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
288                      struct linux_binprm *bprm,
289                      bool *effective)
290{
291    struct cred *new = bprm->cred;
292    unsigned i;
293    int ret = 0;
294
295    if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
296        *effective = true;
297
298    CAP_FOR_EACH_U32(i) {
299        __u32 permitted = caps->permitted.cap[i];
300        __u32 inheritable = caps->inheritable.cap[i];
301
302        /*
303         * pP' = (X & fP) | (pI & fI)
304         */
305        new->cap_permitted.cap[i] =
306            (new->cap_bset.cap[i] & permitted) |
307            (new->cap_inheritable.cap[i] & inheritable);
308
309        if (permitted & ~new->cap_permitted.cap[i])
310            /* insufficient to execute correctly */
311            ret = -EPERM;
312    }
313
314    /*
315     * For legacy apps, with no internal support for recognizing they
316     * do not have enough capabilities, we return an error if they are
317     * missing some "forced" (aka file-permitted) capabilities.
318     */
319    return *effective ? ret : 0;
320}
321
322/*
323 * Extract the on-exec-apply capability sets for an executable file.
324 */
325int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
326{
327    struct inode *inode = dentry->d_inode;
328    __u32 magic_etc;
329    unsigned tocopy, i;
330    int size;
331    struct vfs_cap_data caps;
332
333    memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
334
335    if (!inode || !inode->i_op->getxattr)
336        return -ENODATA;
337
338    size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps,
339                   XATTR_CAPS_SZ);
340    if (size == -ENODATA || size == -EOPNOTSUPP)
341        /* no data, that's ok */
342        return -ENODATA;
343    if (size < 0)
344        return size;
345
346    if (size < sizeof(magic_etc))
347        return -EINVAL;
348
349    cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
350
351    switch (magic_etc & VFS_CAP_REVISION_MASK) {
352    case VFS_CAP_REVISION_1:
353        if (size != XATTR_CAPS_SZ_1)
354            return -EINVAL;
355        tocopy = VFS_CAP_U32_1;
356        break;
357    case VFS_CAP_REVISION_2:
358        if (size != XATTR_CAPS_SZ_2)
359            return -EINVAL;
360        tocopy = VFS_CAP_U32_2;
361        break;
362    default:
363        return -EINVAL;
364    }
365
366    CAP_FOR_EACH_U32(i) {
367        if (i >= tocopy)
368            break;
369        cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
370        cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
371    }
372
373    return 0;
374}
375
376/*
377 * Attempt to get the on-exec apply capability sets for an executable file from
378 * its xattrs and, if present, apply them to the proposed credentials being
379 * constructed by execve().
380 */
381static int get_file_caps(struct linux_binprm *bprm, bool *effective)
382{
383    struct dentry *dentry;
384    int rc = 0;
385    struct cpu_vfs_cap_data vcaps;
386
387    bprm_clear_caps(bprm);
388
389    if (!file_caps_enabled)
390        return 0;
391
392    if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID)
393        return 0;
394
395    dentry = dget(bprm->file->f_dentry);
396
397    rc = get_vfs_caps_from_disk(dentry, &vcaps);
398    if (rc < 0) {
399        if (rc == -EINVAL)
400            printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
401                __func__, rc, bprm->filename);
402        else if (rc == -ENODATA)
403            rc = 0;
404        goto out;
405    }
406
407    rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective);
408    if (rc == -EINVAL)
409        printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
410               __func__, rc, bprm->filename);
411
412out:
413    dput(dentry);
414    if (rc)
415        bprm_clear_caps(bprm);
416
417    return rc;
418}
419
420/**
421 * cap_bprm_set_creds - Set up the proposed credentials for execve().
422 * @bprm: The execution parameters, including the proposed creds
423 *
424 * Set up the proposed credentials for a new execution context being
425 * constructed by execve(). The proposed creds in @bprm->cred is altered,
426 * which won't take effect immediately. Returns 0 if successful, -ve on error.
427 */
428int cap_bprm_set_creds(struct linux_binprm *bprm)
429{
430    const struct cred *old = current_cred();
431    struct cred *new = bprm->cred;
432    bool effective;
433    int ret;
434
435    effective = false;
436    ret = get_file_caps(bprm, &effective);
437    if (ret < 0)
438        return ret;
439
440    if (!issecure(SECURE_NOROOT)) {
441        /*
442         * If the legacy file capability is set, then don't set privs
443         * for a setuid root binary run by a non-root user. Do set it
444         * for a root user just to cause least surprise to an admin.
445         */
446        if (effective && new->uid != 0 && new->euid == 0) {
447            warn_setuid_and_fcaps_mixed(bprm->filename);
448            goto skip;
449        }
450        /*
451         * To support inheritance of root-permissions and suid-root
452         * executables under compatibility mode, we override the
453         * capability sets for the file.
454         *
455         * If only the real uid is 0, we do not set the effective bit.
456         */
457        if (new->euid == 0 || new->uid == 0) {
458            /* pP' = (cap_bset & ~0) | (pI & ~0) */
459            new->cap_permitted = cap_combine(old->cap_bset,
460                             old->cap_inheritable);
461        }
462        if (new->euid == 0)
463            effective = true;
464    }
465skip:
466
467    /* Don't let someone trace a set[ug]id/setpcap binary with the revised
468     * credentials unless they have the appropriate permit
469     */
470    if ((new->euid != old->uid ||
471         new->egid != old->gid ||
472         !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
473        bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
474        /* downgrade; they get no more than they had, and maybe less */
475        if (!capable(CAP_SETUID)) {
476            new->euid = new->uid;
477            new->egid = new->gid;
478        }
479        new->cap_permitted = cap_intersect(new->cap_permitted,
480                           old->cap_permitted);
481    }
482
483    new->suid = new->fsuid = new->euid;
484    new->sgid = new->fsgid = new->egid;
485
486    /* For init, we want to retain the capabilities set in the initial
487     * task. Thus we skip the usual capability rules
488     */
489    if (!is_global_init(current)) {
490        if (effective)
491            new->cap_effective = new->cap_permitted;
492        else
493            cap_clear(new->cap_effective);
494    }
495    bprm->cap_effective = effective;
496
497    /*
498     * Audit candidate if current->cap_effective is set
499     *
500     * We do not bother to audit if 3 things are true:
501     * 1) cap_effective has all caps
502     * 2) we are root
503     * 3) root is supposed to have all caps (SECURE_NOROOT)
504     * Since this is just a normal root execing a process.
505     *
506     * Number 1 above might fail if you don't have a full bset, but I think
507     * that is interesting information to audit.
508     */
509    if (!cap_isclear(new->cap_effective)) {
510        if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
511            new->euid != 0 || new->uid != 0 ||
512            issecure(SECURE_NOROOT)) {
513            ret = audit_log_bprm_fcaps(bprm, new, old);
514            if (ret < 0)
515                return ret;
516        }
517    }
518
519    new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
520    return 0;
521}
522
523/**
524 * cap_bprm_secureexec - Determine whether a secure execution is required
525 * @bprm: The execution parameters
526 *
527 * Determine whether a secure execution is required, return 1 if it is, and 0
528 * if it is not.
529 *
530 * The credentials have been committed by this point, and so are no longer
531 * available through @bprm->cred.
532 */
533int cap_bprm_secureexec(struct linux_binprm *bprm)
534{
535    const struct cred *cred = current_cred();
536
537    if (cred->uid != 0) {
538        if (bprm->cap_effective)
539            return 1;
540        if (!cap_isclear(cred->cap_permitted))
541            return 1;
542    }
543
544    return (cred->euid != cred->uid ||
545        cred->egid != cred->gid);
546}
547
548/**
549 * cap_inode_setxattr - Determine whether an xattr may be altered
550 * @dentry: The inode/dentry being altered
551 * @name: The name of the xattr to be changed
552 * @value: The value that the xattr will be changed to
553 * @size: The size of value
554 * @flags: The replacement flag
555 *
556 * Determine whether an xattr may be altered or set on an inode, returning 0 if
557 * permission is granted, -ve if denied.
558 *
559 * This is used to make sure security xattrs don't get updated or set by those
560 * who aren't privileged to do so.
561 */
562int cap_inode_setxattr(struct dentry *dentry, const char *name,
563               const void *value, size_t size, int flags)
564{
565    if (!strcmp(name, XATTR_NAME_CAPS)) {
566        if (!capable(CAP_SETFCAP))
567            return -EPERM;
568        return 0;
569    }
570
571    if (!strncmp(name, XATTR_SECURITY_PREFIX,
572             sizeof(XATTR_SECURITY_PREFIX) - 1) &&
573        !capable(CAP_SYS_ADMIN))
574        return -EPERM;
575    return 0;
576}
577
578/**
579 * cap_inode_removexattr - Determine whether an xattr may be removed
580 * @dentry: The inode/dentry being altered
581 * @name: The name of the xattr to be changed
582 *
583 * Determine whether an xattr may be removed from an inode, returning 0 if
584 * permission is granted, -ve if denied.
585 *
586 * This is used to make sure security xattrs don't get removed by those who
587 * aren't privileged to remove them.
588 */
589int cap_inode_removexattr(struct dentry *dentry, const char *name)
590{
591    if (!strcmp(name, XATTR_NAME_CAPS)) {
592        if (!capable(CAP_SETFCAP))
593            return -EPERM;
594        return 0;
595    }
596
597    if (!strncmp(name, XATTR_SECURITY_PREFIX,
598             sizeof(XATTR_SECURITY_PREFIX) - 1) &&
599        !capable(CAP_SYS_ADMIN))
600        return -EPERM;
601    return 0;
602}
603
604/*
605 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
606 * a process after a call to setuid, setreuid, or setresuid.
607 *
608 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
609 * {r,e,s}uid != 0, the permitted and effective capabilities are
610 * cleared.
611 *
612 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
613 * capabilities of the process are cleared.
614 *
615 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
616 * capabilities are set to the permitted capabilities.
617 *
618 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
619 * never happen.
620 *
621 * -astor
622 *
623 * cevans - New behaviour, Oct '99
624 * A process may, via prctl(), elect to keep its capabilities when it
625 * calls setuid() and switches away from uid==0. Both permitted and
626 * effective sets will be retained.
627 * Without this change, it was impossible for a daemon to drop only some
628 * of its privilege. The call to setuid(!=0) would drop all privileges!
629 * Keeping uid 0 is not an option because uid 0 owns too many vital
630 * files..
631 * Thanks to Olaf Kirch and Peter Benie for spotting this.
632 */
633static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
634{
635    if ((old->uid == 0 || old->euid == 0 || old->suid == 0) &&
636        (new->uid != 0 && new->euid != 0 && new->suid != 0) &&
637        !issecure(SECURE_KEEP_CAPS)) {
638        cap_clear(new->cap_permitted);
639        cap_clear(new->cap_effective);
640    }
641    if (old->euid == 0 && new->euid != 0)
642        cap_clear(new->cap_effective);
643    if (old->euid != 0 && new->euid == 0)
644        new->cap_effective = new->cap_permitted;
645}
646
647/**
648 * cap_task_fix_setuid - Fix up the results of setuid() call
649 * @new: The proposed credentials
650 * @old: The current task's current credentials
651 * @flags: Indications of what has changed
652 *
653 * Fix up the results of setuid() call before the credential changes are
654 * actually applied, returning 0 to grant the changes, -ve to deny them.
655 */
656int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
657{
658    switch (flags) {
659    case LSM_SETID_RE:
660    case LSM_SETID_ID:
661    case LSM_SETID_RES:
662        /* juggle the capabilities to follow [RES]UID changes unless
663         * otherwise suppressed */
664        if (!issecure(SECURE_NO_SETUID_FIXUP))
665            cap_emulate_setxuid(new, old);
666        break;
667
668    case LSM_SETID_FS:
669        /* juggle the capabilties to follow FSUID changes, unless
670         * otherwise suppressed
671         *
672         * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
673         * if not, we might be a bit too harsh here.
674         */
675        if (!issecure(SECURE_NO_SETUID_FIXUP)) {
676            if (old->fsuid == 0 && new->fsuid != 0)
677                new->cap_effective =
678                    cap_drop_fs_set(new->cap_effective);
679
680            if (old->fsuid != 0 && new->fsuid == 0)
681                new->cap_effective =
682                    cap_raise_fs_set(new->cap_effective,
683                             new->cap_permitted);
684        }
685        break;
686
687    default:
688        return -EINVAL;
689    }
690
691    return 0;
692}
693
694/*
695 * Rationale: code calling task_setscheduler, task_setioprio, and
696 * task_setnice, assumes that
697 * . if capable(cap_sys_nice), then those actions should be allowed
698 * . if not capable(cap_sys_nice), but acting on your own processes,
699 * then those actions should be allowed
700 * This is insufficient now since you can call code without suid, but
701 * yet with increased caps.
702 * So we check for increased caps on the target process.
703 */
704static int cap_safe_nice(struct task_struct *p)
705{
706    int is_subset;
707
708    rcu_read_lock();
709    is_subset = cap_issubset(__task_cred(p)->cap_permitted,
710                 current_cred()->cap_permitted);
711    rcu_read_unlock();
712
713    if (!is_subset && !capable(CAP_SYS_NICE))
714        return -EPERM;
715    return 0;
716}
717
718/**
719 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
720 * @p: The task to affect
721 *
722 * Detemine if the requested scheduler policy change is permitted for the
723 * specified task, returning 0 if permission is granted, -ve if denied.
724 */
725int cap_task_setscheduler(struct task_struct *p)
726{
727    return cap_safe_nice(p);
728}
729
730/**
731 * cap_task_ioprio - Detemine if I/O priority change is permitted
732 * @p: The task to affect
733 * @ioprio: The I/O priority to set
734 *
735 * Detemine if the requested I/O priority change is permitted for the specified
736 * task, returning 0 if permission is granted, -ve if denied.
737 */
738int cap_task_setioprio(struct task_struct *p, int ioprio)
739{
740    return cap_safe_nice(p);
741}
742
743/**
744 * cap_task_ioprio - Detemine if task priority change is permitted
745 * @p: The task to affect
746 * @nice: The nice value to set
747 *
748 * Detemine if the requested task priority change is permitted for the
749 * specified task, returning 0 if permission is granted, -ve if denied.
750 */
751int cap_task_setnice(struct task_struct *p, int nice)
752{
753    return cap_safe_nice(p);
754}
755
756/*
757 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
758 * the current task's bounding set. Returns 0 on success, -ve on error.
759 */
760static long cap_prctl_drop(struct cred *new, unsigned long cap)
761{
762    if (!capable(CAP_SETPCAP))
763        return -EPERM;
764    if (!cap_valid(cap))
765        return -EINVAL;
766
767    cap_lower(new->cap_bset, cap);
768    return 0;
769}
770
771/**
772 * cap_task_prctl - Implement process control functions for this security module
773 * @option: The process control function requested
774 * @arg2, @arg3, @arg4, @arg5: The argument data for this function
775 *
776 * Allow process control functions (sys_prctl()) to alter capabilities; may
777 * also deny access to other functions not otherwise implemented here.
778 *
779 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
780 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
781 * modules will consider performing the function.
782 */
783int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
784           unsigned long arg4, unsigned long arg5)
785{
786    struct cred *new;
787    long error = 0;
788
789    new = prepare_creds();
790    if (!new)
791        return -ENOMEM;
792
793    switch (option) {
794    case PR_CAPBSET_READ:
795        error = -EINVAL;
796        if (!cap_valid(arg2))
797            goto error;
798        error = !!cap_raised(new->cap_bset, arg2);
799        goto no_change;
800
801    case PR_CAPBSET_DROP:
802        error = cap_prctl_drop(new, arg2);
803        if (error < 0)
804            goto error;
805        goto changed;
806
807    /*
808     * The next four prctl's remain to assist with transitioning a
809     * system from legacy UID=0 based privilege (when filesystem
810     * capabilities are not in use) to a system using filesystem
811     * capabilities only - as the POSIX.1e draft intended.
812     *
813     * Note:
814     *
815     * PR_SET_SECUREBITS =
816     * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
817     * | issecure_mask(SECURE_NOROOT)
818     * | issecure_mask(SECURE_NOROOT_LOCKED)
819     * | issecure_mask(SECURE_NO_SETUID_FIXUP)
820     * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
821     *
822     * will ensure that the current process and all of its
823     * children will be locked into a pure
824     * capability-based-privilege environment.
825     */
826    case PR_SET_SECUREBITS:
827        error = -EPERM;
828        if ((((new->securebits & SECURE_ALL_LOCKS) >> 1)
829             & (new->securebits ^ arg2)) /*[1]*/
830            || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
831            || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
832            || (cap_capable(current, current_cred(), CAP_SETPCAP,
833                    SECURITY_CAP_AUDIT) != 0) /*[4]*/
834            /*
835             * [1] no changing of bits that are locked
836             * [2] no unlocking of locks
837             * [3] no setting of unsupported bits
838             * [4] doing anything requires privilege (go read about
839             * the "sendmail capabilities bug")
840             */
841            )
842            /* cannot change a locked bit */
843            goto error;
844        new->securebits = arg2;
845        goto changed;
846
847    case PR_GET_SECUREBITS:
848        error = new->securebits;
849        goto no_change;
850
851    case PR_GET_KEEPCAPS:
852        if (issecure(SECURE_KEEP_CAPS))
853            error = 1;
854        goto no_change;
855
856    case PR_SET_KEEPCAPS:
857        error = -EINVAL;
858        if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
859            goto error;
860        error = -EPERM;
861        if (issecure(SECURE_KEEP_CAPS_LOCKED))
862            goto error;
863        if (arg2)
864            new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
865        else
866            new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
867        goto changed;
868
869    default:
870        /* No functionality available - continue with default */
871        error = -ENOSYS;
872        goto error;
873    }
874
875    /* Functionality provided */
876changed:
877    return commit_creds(new);
878
879no_change:
880error:
881    abort_creds(new);
882    return error;
883}
884
885/**
886 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
887 * @mm: The VM space in which the new mapping is to be made
888 * @pages: The size of the mapping
889 *
890 * Determine whether the allocation of a new virtual mapping by the current
891 * task is permitted, returning 0 if permission is granted, -ve if not.
892 */
893int cap_vm_enough_memory(struct mm_struct *mm, long pages)
894{
895    int cap_sys_admin = 0;
896
897    if (cap_capable(current, current_cred(), CAP_SYS_ADMIN,
898            SECURITY_CAP_NOAUDIT) == 0)
899        cap_sys_admin = 1;
900    return __vm_enough_memory(mm, pages, cap_sys_admin);
901}
902
903/*
904 * cap_file_mmap - check if able to map given addr
905 * @file: unused
906 * @reqprot: unused
907 * @prot: unused
908 * @flags: unused
909 * @addr: address attempting to be mapped
910 * @addr_only: unused
911 *
912 * If the process is attempting to map memory below dac_mmap_min_addr they need
913 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
914 * capability security module. Returns 0 if this mapping should be allowed
915 * -EPERM if not.
916 */
917int cap_file_mmap(struct file *file, unsigned long reqprot,
918          unsigned long prot, unsigned long flags,
919          unsigned long addr, unsigned long addr_only)
920{
921    int ret = 0;
922
923    if (addr < dac_mmap_min_addr) {
924        ret = cap_capable(current, current_cred(), CAP_SYS_RAWIO,
925                  SECURITY_CAP_AUDIT);
926        /* set PF_SUPERPRIV if it turns out we allow the low mmap */
927        if (ret == 0)
928            current->flags |= PF_SUPERPRIV;
929    }
930    return ret;
931}
932

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