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b2441318 1// SPDX-License-Identifier: GPL-2.0
1da177e4
LT
2/*
3 * linux/kernel/capability.c
4 *
5 * Copyright (C) 1997 Andrew Main <zefram@fysh.org>
6 *
72c2d582 7 * Integrated into 2.1.97+, Andrew G. Morgan <morgan@kernel.org>
1da177e4 8 * 30 May 2002: Cleanup, Robert M. Love <rml@tech9.net>
314f70fd 9 */
1da177e4 10
f5645d35
JP
11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12
e68b75a0 13#include <linux/audit.h>
c59ede7b 14#include <linux/capability.h>
1da177e4 15#include <linux/mm.h>
9984de1a 16#include <linux/export.h>
1da177e4
LT
17#include <linux/security.h>
18#include <linux/syscalls.h>
b460cbc5 19#include <linux/pid_namespace.h>
3486740a 20#include <linux/user_namespace.h>
7c0f6ba6 21#include <linux/uaccess.h>
1da177e4 22
e338d263
AM
23/*
24 * Leveraged for setting/resetting capabilities
25 */
26
27const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
e338d263 28EXPORT_SYMBOL(__cap_empty_set);
e338d263 29
1f29fae2
SH
30int file_caps_enabled = 1;
31
32static int __init file_caps_disable(char *str)
33{
34 file_caps_enabled = 0;
35 return 1;
36}
37__setup("no_file_caps", file_caps_disable);
1f29fae2 38
2813893f 39#ifdef CONFIG_MULTIUSER
e338d263
AM
40/*
41 * More recent versions of libcap are available from:
42 *
43 * http://www.kernel.org/pub/linux/libs/security/linux-privs/
44 */
45
46static void warn_legacy_capability_use(void)
47{
f5645d35
JP
48 char name[sizeof(current->comm)];
49
50 pr_info_once("warning: `%s' uses 32-bit capabilities (legacy support in use)\n",
51 get_task_comm(name, current));
e338d263
AM
52}
53
ca05a99a
AM
54/*
55 * Version 2 capabilities worked fine, but the linux/capability.h file
56 * that accompanied their introduction encouraged their use without
57 * the necessary user-space source code changes. As such, we have
58 * created a version 3 with equivalent functionality to version 2, but
59 * with a header change to protect legacy source code from using
60 * version 2 when it wanted to use version 1. If your system has code
61 * that trips the following warning, it is using version 2 specific
62 * capabilities and may be doing so insecurely.
63 *
64 * The remedy is to either upgrade your version of libcap (to 2.10+,
65 * if the application is linked against it), or recompile your
66 * application with modern kernel headers and this warning will go
67 * away.
68 */
69
70static void warn_deprecated_v2(void)
71{
f5645d35 72 char name[sizeof(current->comm)];
ca05a99a 73
f5645d35
JP
74 pr_info_once("warning: `%s' uses deprecated v2 capabilities in a way that may be insecure\n",
75 get_task_comm(name, current));
ca05a99a
AM
76}
77
78/*
79 * Version check. Return the number of u32s in each capability flag
80 * array, or a negative value on error.
81 */
82static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
83{
84 __u32 version;
85
86 if (get_user(version, &header->version))
87 return -EFAULT;
88
89 switch (version) {
90 case _LINUX_CAPABILITY_VERSION_1:
91 warn_legacy_capability_use();
92 *tocopy = _LINUX_CAPABILITY_U32S_1;
93 break;
94 case _LINUX_CAPABILITY_VERSION_2:
95 warn_deprecated_v2();
96 /*
97 * fall through - v3 is otherwise equivalent to v2.
98 */
99 case _LINUX_CAPABILITY_VERSION_3:
100 *tocopy = _LINUX_CAPABILITY_U32S_3;
101 break;
102 default:
103 if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
104 return -EFAULT;
105 return -EINVAL;
106 }
107
108 return 0;
109}
110
ab763c71 111/*
d84f4f99
DH
112 * The only thing that can change the capabilities of the current
113 * process is the current process. As such, we can't be in this code
114 * at the same time as we are in the process of setting capabilities
115 * in this process. The net result is that we can limit our use of
116 * locks to when we are reading the caps of another process.
ab763c71
AM
117 */
118static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
119 kernel_cap_t *pIp, kernel_cap_t *pPp)
120{
121 int ret;
122
123 if (pid && (pid != task_pid_vnr(current))) {
124 struct task_struct *target;
125
86fc80f1 126 rcu_read_lock();
ab763c71
AM
127
128 target = find_task_by_vpid(pid);
129 if (!target)
130 ret = -ESRCH;
131 else
132 ret = security_capget(target, pEp, pIp, pPp);
133
86fc80f1 134 rcu_read_unlock();
ab763c71
AM
135 } else
136 ret = security_capget(current, pEp, pIp, pPp);
137
138 return ret;
139}
140
207a7ba8 141/**
1da177e4 142 * sys_capget - get the capabilities of a given process.
207a7ba8
RD
143 * @header: pointer to struct that contains capability version and
144 * target pid data
145 * @dataptr: pointer to struct that contains the effective, permitted,
146 * and inheritable capabilities that are returned
147 *
148 * Returns 0 on success and < 0 on error.
1da177e4 149 */
b290ebe2 150SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
1da177e4 151{
314f70fd
DW
152 int ret = 0;
153 pid_t pid;
e338d263
AM
154 unsigned tocopy;
155 kernel_cap_t pE, pI, pP;
314f70fd 156
ca05a99a 157 ret = cap_validate_magic(header, &tocopy);
c4a5af54
AM
158 if ((dataptr == NULL) || (ret != 0))
159 return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;
1da177e4 160
314f70fd
DW
161 if (get_user(pid, &header->pid))
162 return -EFAULT;
1da177e4 163
314f70fd
DW
164 if (pid < 0)
165 return -EINVAL;
1da177e4 166
ab763c71 167 ret = cap_get_target_pid(pid, &pE, &pI, &pP);
e338d263 168 if (!ret) {
ca05a99a 169 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
e338d263
AM
170 unsigned i;
171
172 for (i = 0; i < tocopy; i++) {
173 kdata[i].effective = pE.cap[i];
174 kdata[i].permitted = pP.cap[i];
175 kdata[i].inheritable = pI.cap[i];
176 }
177
178 /*
ca05a99a 179 * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
e338d263
AM
180 * we silently drop the upper capabilities here. This
181 * has the effect of making older libcap
182 * implementations implicitly drop upper capability
183 * bits when they perform a: capget/modify/capset
184 * sequence.
185 *
186 * This behavior is considered fail-safe
187 * behavior. Upgrading the application to a newer
188 * version of libcap will enable access to the newer
189 * capabilities.
190 *
191 * An alternative would be to return an error here
192 * (-ERANGE), but that causes legacy applications to
a6c8c690 193 * unexpectedly fail; the capget/modify/capset aborts
e338d263
AM
194 * before modification is attempted and the application
195 * fails.
196 */
e338d263
AM
197 if (copy_to_user(dataptr, kdata, tocopy
198 * sizeof(struct __user_cap_data_struct))) {
199 return -EFAULT;
200 }
201 }
1da177e4 202
314f70fd 203 return ret;
1da177e4
LT
204}
205
207a7ba8 206/**
ab763c71 207 * sys_capset - set capabilities for a process or (*) a group of processes
207a7ba8
RD
208 * @header: pointer to struct that contains capability version and
209 * target pid data
210 * @data: pointer to struct that contains the effective, permitted,
211 * and inheritable capabilities
212 *
1cdcbec1
DH
213 * Set capabilities for the current process only. The ability to any other
214 * process(es) has been deprecated and removed.
1da177e4
LT
215 *
216 * The restrictions on setting capabilities are specified as:
217 *
1cdcbec1
DH
218 * I: any raised capabilities must be a subset of the old permitted
219 * P: any raised capabilities must be a subset of the old permitted
220 * E: must be set to a subset of new permitted
207a7ba8
RD
221 *
222 * Returns 0 on success and < 0 on error.
1da177e4 223 */
b290ebe2 224SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
1da177e4 225{
ca05a99a 226 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
825332e4 227 unsigned i, tocopy, copybytes;
314f70fd 228 kernel_cap_t inheritable, permitted, effective;
d84f4f99 229 struct cred *new;
314f70fd
DW
230 int ret;
231 pid_t pid;
232
ca05a99a
AM
233 ret = cap_validate_magic(header, &tocopy);
234 if (ret != 0)
235 return ret;
314f70fd
DW
236
237 if (get_user(pid, &header->pid))
238 return -EFAULT;
239
1cdcbec1
DH
240 /* may only affect current now */
241 if (pid != 0 && pid != task_pid_vnr(current))
242 return -EPERM;
243
825332e4
AV
244 copybytes = tocopy * sizeof(struct __user_cap_data_struct);
245 if (copybytes > sizeof(kdata))
246 return -EFAULT;
247
248 if (copy_from_user(&kdata, data, copybytes))
314f70fd 249 return -EFAULT;
e338d263
AM
250
251 for (i = 0; i < tocopy; i++) {
252 effective.cap[i] = kdata[i].effective;
253 permitted.cap[i] = kdata[i].permitted;
254 inheritable.cap[i] = kdata[i].inheritable;
255 }
ca05a99a 256 while (i < _KERNEL_CAPABILITY_U32S) {
e338d263
AM
257 effective.cap[i] = 0;
258 permitted.cap[i] = 0;
259 inheritable.cap[i] = 0;
260 i++;
261 }
314f70fd 262
7d8b6c63
EP
263 effective.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
264 permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
265 inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
266
d84f4f99
DH
267 new = prepare_creds();
268 if (!new)
269 return -ENOMEM;
270
271 ret = security_capset(new, current_cred(),
272 &effective, &inheritable, &permitted);
273 if (ret < 0)
274 goto error;
275
ca24a23e 276 audit_log_capset(new, current_cred());
e68b75a0 277
d84f4f99
DH
278 return commit_creds(new);
279
280error:
281 abort_creds(new);
314f70fd 282 return ret;
1da177e4 283}
12b5989b 284
3263245d 285/**
25e75703 286 * has_ns_capability - Does a task have a capability in a specific user ns
3263245d 287 * @t: The task in question
25e75703 288 * @ns: target user namespace
3263245d
SH
289 * @cap: The capability to be tested for
290 *
291 * Return true if the specified task has the given superior capability
25e75703 292 * currently in effect to the specified user namespace, false if not.
3263245d
SH
293 *
294 * Note that this does not set PF_SUPERPRIV on the task.
295 */
25e75703
EP
296bool has_ns_capability(struct task_struct *t,
297 struct user_namespace *ns, int cap)
3263245d 298{
2920a840
EP
299 int ret;
300
301 rcu_read_lock();
25e75703 302 ret = security_capable(__task_cred(t), ns, cap);
2920a840 303 rcu_read_unlock();
3263245d
SH
304
305 return (ret == 0);
306}
307
308/**
25e75703 309 * has_capability - Does a task have a capability in init_user_ns
3263245d 310 * @t: The task in question
3263245d
SH
311 * @cap: The capability to be tested for
312 *
313 * Return true if the specified task has the given superior capability
25e75703 314 * currently in effect to the initial user namespace, false if not.
3263245d
SH
315 *
316 * Note that this does not set PF_SUPERPRIV on the task.
317 */
25e75703 318bool has_capability(struct task_struct *t, int cap)
3263245d 319{
25e75703 320 return has_ns_capability(t, &init_user_ns, cap);
3263245d 321}
19c816e8 322EXPORT_SYMBOL(has_capability);
3263245d
SH
323
324/**
7b61d648
EP
325 * has_ns_capability_noaudit - Does a task have a capability (unaudited)
326 * in a specific user ns.
3263245d 327 * @t: The task in question
7b61d648 328 * @ns: target user namespace
3263245d
SH
329 * @cap: The capability to be tested for
330 *
331 * Return true if the specified task has the given superior capability
7b61d648
EP
332 * currently in effect to the specified user namespace, false if not.
333 * Do not write an audit message for the check.
3263245d
SH
334 *
335 * Note that this does not set PF_SUPERPRIV on the task.
336 */
7b61d648
EP
337bool has_ns_capability_noaudit(struct task_struct *t,
338 struct user_namespace *ns, int cap)
3263245d 339{
2920a840
EP
340 int ret;
341
342 rcu_read_lock();
7b61d648 343 ret = security_capable_noaudit(__task_cred(t), ns, cap);
2920a840 344 rcu_read_unlock();
3263245d
SH
345
346 return (ret == 0);
347}
348
5cd9c58f 349/**
7b61d648
EP
350 * has_capability_noaudit - Does a task have a capability (unaudited) in the
351 * initial user ns
352 * @t: The task in question
5cd9c58f
DH
353 * @cap: The capability to be tested for
354 *
7b61d648
EP
355 * Return true if the specified task has the given superior capability
356 * currently in effect to init_user_ns, false if not. Don't write an
357 * audit message for the check.
5cd9c58f 358 *
7b61d648 359 * Note that this does not set PF_SUPERPRIV on the task.
5cd9c58f 360 */
7b61d648 361bool has_capability_noaudit(struct task_struct *t, int cap)
3486740a 362{
7b61d648 363 return has_ns_capability_noaudit(t, &init_user_ns, cap);
3486740a 364}
3486740a 365
98f368e9
TH
366static bool ns_capable_common(struct user_namespace *ns, int cap, bool audit)
367{
368 int capable;
369
370 if (unlikely(!cap_valid(cap))) {
371 pr_crit("capable() called with invalid cap=%u\n", cap);
372 BUG();
373 }
374
375 capable = audit ? security_capable(current_cred(), ns, cap) :
376 security_capable_noaudit(current_cred(), ns, cap);
377 if (capable == 0) {
378 current->flags |= PF_SUPERPRIV;
379 return true;
380 }
381 return false;
382}
383
3486740a
SH
384/**
385 * ns_capable - Determine if the current task has a superior capability in effect
386 * @ns: The usernamespace we want the capability in
387 * @cap: The capability to be tested for
388 *
389 * Return true if the current task has the given superior capability currently
390 * available for use, false if not.
391 *
392 * This sets PF_SUPERPRIV on the task if the capability is available on the
393 * assumption that it's about to be used.
394 */
395bool ns_capable(struct user_namespace *ns, int cap)
12b5989b 396{
98f368e9 397 return ns_capable_common(ns, cap, true);
12b5989b 398}
3486740a
SH
399EXPORT_SYMBOL(ns_capable);
400
98f368e9
TH
401/**
402 * ns_capable_noaudit - Determine if the current task has a superior capability
403 * (unaudited) in effect
404 * @ns: The usernamespace we want the capability in
405 * @cap: The capability to be tested for
406 *
407 * Return true if the current task has the given superior capability currently
408 * available for use, false if not.
409 *
410 * This sets PF_SUPERPRIV on the task if the capability is available on the
411 * assumption that it's about to be used.
412 */
413bool ns_capable_noaudit(struct user_namespace *ns, int cap)
414{
415 return ns_capable_common(ns, cap, false);
416}
417EXPORT_SYMBOL(ns_capable_noaudit);
2813893f
IM
418
419/**
420 * capable - Determine if the current task has a superior capability in effect
421 * @cap: The capability to be tested for
422 *
423 * Return true if the current task has the given superior capability currently
424 * available for use, false if not.
425 *
426 * This sets PF_SUPERPRIV on the task if the capability is available on the
427 * assumption that it's about to be used.
428 */
429bool capable(int cap)
430{
431 return ns_capable(&init_user_ns, cap);
432}
433EXPORT_SYMBOL(capable);
434#endif /* CONFIG_MULTIUSER */
435
935d8aab
LT
436/**
437 * file_ns_capable - Determine if the file's opener had a capability in effect
438 * @file: The file we want to check
439 * @ns: The usernamespace we want the capability in
440 * @cap: The capability to be tested for
441 *
442 * Return true if task that opened the file had a capability in effect
443 * when the file was opened.
444 *
445 * This does not set PF_SUPERPRIV because the caller may not
446 * actually be privileged.
447 */
a6c8c690
FF
448bool file_ns_capable(const struct file *file, struct user_namespace *ns,
449 int cap)
935d8aab
LT
450{
451 if (WARN_ON_ONCE(!cap_valid(cap)))
452 return false;
453
454 if (security_capable(file->f_cred, ns, cap) == 0)
455 return true;
456
457 return false;
458}
459EXPORT_SYMBOL(file_ns_capable);
460
f84df2a6
EB
461/**
462 * privileged_wrt_inode_uidgid - Do capabilities in the namespace work over the inode?
463 * @ns: The user namespace in question
464 * @inode: The inode in question
465 *
466 * Return true if the inode uid and gid are within the namespace.
467 */
468bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct inode *inode)
469{
470 return kuid_has_mapping(ns, inode->i_uid) &&
471 kgid_has_mapping(ns, inode->i_gid);
472}
473
1a48e2ac 474/**
23adbe12 475 * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped
1a48e2ac
EB
476 * @inode: The inode in question
477 * @cap: The capability in question
478 *
23adbe12
AL
479 * Return true if the current task has the given capability targeted at
480 * its own user namespace and that the given inode's uid and gid are
481 * mapped into the current user namespace.
1a48e2ac 482 */
23adbe12 483bool capable_wrt_inode_uidgid(const struct inode *inode, int cap)
1a48e2ac
EB
484{
485 struct user_namespace *ns = current_user_ns();
486
f84df2a6 487 return ns_capable(ns, cap) && privileged_wrt_inode_uidgid(ns, inode);
1a48e2ac 488}
23adbe12 489EXPORT_SYMBOL(capable_wrt_inode_uidgid);
64b875f7
EB
490
491/**
492 * ptracer_capable - Determine if the ptracer holds CAP_SYS_PTRACE in the namespace
493 * @tsk: The task that may be ptraced
494 * @ns: The user namespace to search for CAP_SYS_PTRACE in
495 *
496 * Return true if the task that is ptracing the current task had CAP_SYS_PTRACE
497 * in the specified user namespace.
498 */
499bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns)
500{
501 int ret = 0; /* An absent tracer adds no restrictions */
502 const struct cred *cred;
503 rcu_read_lock();
504 cred = rcu_dereference(tsk->ptracer_cred);
505 if (cred)
506 ret = security_capable_noaudit(cred, ns, CAP_SYS_PTRACE);
507 rcu_read_unlock();
508 return (ret == 0);
509}