projects/linux·blob v6.11-rc3 · refs

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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/kernel/capability.c
4 *
5 * Copyright (C) 1997 Andrew Main <[email protected]>
6 *
7 * Integrated into 2.1.97+, Andrew G. Morgan <[email protected]>
8 * 30 May 2002: Cleanup, Robert M. Love <[email protected]>
9 */
10
11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12
13#include <linux/audit.h>
14#include <linux/capability.h>
15#include <linux/mm.h>
16#include <linux/export.h>
17#include <linux/security.h>
18#include <linux/syscalls.h>
19#include <linux/pid_namespace.h>
20#include <linux/user_namespace.h>
21#include <linux/uaccess.h>
22
23int file_caps_enabled = 1;
24
25static int __init file_caps_disable(char *str)
26{
27 file_caps_enabled = 0;
28 return 1;
29}
30__setup("no_file_caps", file_caps_disable);
31
32#ifdef CONFIG_MULTIUSER
33/*
34 * More recent versions of libcap are available from:
35 *
36 * http://www.kernel.org/pub/linux/libs/security/linux-privs/
37 */
38
39static void warn_legacy_capability_use(void)
40{
41 char name[sizeof(current->comm)];
42
43 pr_info_once("warning: `%s' uses 32-bit capabilities (legacy support in use)\n",
44 get_task_comm(name, current));
45}
46
47/*
48 * Version 2 capabilities worked fine, but the linux/capability.h file
49 * that accompanied their introduction encouraged their use without
50 * the necessary user-space source code changes. As such, we have
51 * created a version 3 with equivalent functionality to version 2, but
52 * with a header change to protect legacy source code from using
53 * version 2 when it wanted to use version 1. If your system has code
54 * that trips the following warning, it is using version 2 specific
55 * capabilities and may be doing so insecurely.
56 *
57 * The remedy is to either upgrade your version of libcap (to 2.10+,
58 * if the application is linked against it), or recompile your
59 * application with modern kernel headers and this warning will go
60 * away.
61 */
62
63static void warn_deprecated_v2(void)
64{
65 char name[sizeof(current->comm)];
66
67 pr_info_once("warning: `%s' uses deprecated v2 capabilities in a way that may be insecure\n",
68 get_task_comm(name, current));
69}
70
71/*
72 * Version check. Return the number of u32s in each capability flag
73 * array, or a negative value on error.
74 */
75static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
76{
77 __u32 version;
78
79 if (get_user(version, &header->version))
80 return -EFAULT;
81
82 switch (version) {
83 case _LINUX_CAPABILITY_VERSION_1:
84 warn_legacy_capability_use();
85 *tocopy = _LINUX_CAPABILITY_U32S_1;
86 break;
87 case _LINUX_CAPABILITY_VERSION_2:
88 warn_deprecated_v2();
89 fallthrough; /* v3 is otherwise equivalent to v2 */
90 case _LINUX_CAPABILITY_VERSION_3:
91 *tocopy = _LINUX_CAPABILITY_U32S_3;
92 break;
93 default:
94 if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
95 return -EFAULT;
96 return -EINVAL;
97 }
98
99 return 0;
100}
101
102/*
103 * The only thing that can change the capabilities of the current
104 * process is the current process. As such, we can't be in this code
105 * at the same time as we are in the process of setting capabilities
106 * in this process. The net result is that we can limit our use of
107 * locks to when we are reading the caps of another process.
108 */
109static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
110 kernel_cap_t *pIp, kernel_cap_t *pPp)
111{
112 int ret;
113
114 if (pid && (pid != task_pid_vnr(current))) {
115 const struct task_struct *target;
116
117 rcu_read_lock();
118
119 target = find_task_by_vpid(pid);
120 if (!target)
121 ret = -ESRCH;
122 else
123 ret = security_capget(target, pEp, pIp, pPp);
124
125 rcu_read_unlock();
126 } else
127 ret = security_capget(current, pEp, pIp, pPp);
128
129 return ret;
130}
131
132/**
133 * sys_capget - get the capabilities of a given process.
134 * @header: pointer to struct that contains capability version and
135 * target pid data
136 * @dataptr: pointer to struct that contains the effective, permitted,
137 * and inheritable capabilities that are returned
138 *
139 * Returns 0 on success and < 0 on error.
140 */
141SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
142{
143 int ret = 0;
144 pid_t pid;
145 unsigned tocopy;
146 kernel_cap_t pE, pI, pP;
147 struct __user_cap_data_struct kdata[2];
148
149 ret = cap_validate_magic(header, &tocopy);
150 if ((dataptr == NULL) || (ret != 0))
151 return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;
152
153 if (get_user(pid, &header->pid))
154 return -EFAULT;
155
156 if (pid < 0)
157 return -EINVAL;
158
159 ret = cap_get_target_pid(pid, &pE, &pI, &pP);
160 if (ret)
161 return ret;
162
163 /*
164 * Annoying legacy format with 64-bit capabilities exposed
165 * as two sets of 32-bit fields, so we need to split the
166 * capability values up.
167 */
168 kdata[0].effective = pE.val; kdata[1].effective = pE.val >> 32;
169 kdata[0].permitted = pP.val; kdata[1].permitted = pP.val >> 32;
170 kdata[0].inheritable = pI.val; kdata[1].inheritable = pI.val >> 32;
171
172 /*
173 * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
174 * we silently drop the upper capabilities here. This
175 * has the effect of making older libcap
176 * implementations implicitly drop upper capability
177 * bits when they perform a: capget/modify/capset
178 * sequence.
179 *
180 * This behavior is considered fail-safe
181 * behavior. Upgrading the application to a newer
182 * version of libcap will enable access to the newer
183 * capabilities.
184 *
185 * An alternative would be to return an error here
186 * (-ERANGE), but that causes legacy applications to
187 * unexpectedly fail; the capget/modify/capset aborts
188 * before modification is attempted and the application
189 * fails.
190 */
191 if (copy_to_user(dataptr, kdata, tocopy * sizeof(kdata[0])))
192 return -EFAULT;
193
194 return 0;
195}
196
197static kernel_cap_t mk_kernel_cap(u32 low, u32 high)
198{
199 return (kernel_cap_t) { (low | ((u64)high << 32)) & CAP_VALID_MASK };
200}
201
202/**
203 * sys_capset - set capabilities for a process or (*) a group of processes
204 * @header: pointer to struct that contains capability version and
205 * target pid data
206 * @data: pointer to struct that contains the effective, permitted,
207 * and inheritable capabilities
208 *
209 * Set capabilities for the current process only. The ability to any other
210 * process(es) has been deprecated and removed.
211 *
212 * The restrictions on setting capabilities are specified as:
213 *
214 * I: any raised capabilities must be a subset of the old permitted
215 * P: any raised capabilities must be a subset of the old permitted
216 * E: must be set to a subset of new permitted
217 *
218 * Returns 0 on success and < 0 on error.
219 */
220SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
221{
222 struct __user_cap_data_struct kdata[2] = { { 0, }, };
223 unsigned tocopy, copybytes;
224 kernel_cap_t inheritable, permitted, effective;
225 struct cred *new;
226 int ret;
227 pid_t pid;
228
229 ret = cap_validate_magic(header, &tocopy);
230 if (ret != 0)
231 return ret;
232
233 if (get_user(pid, &header->pid))
234 return -EFAULT;
235
236 /* may only affect current now */
237 if (pid != 0 && pid != task_pid_vnr(current))
238 return -EPERM;
239
240 copybytes = tocopy * sizeof(struct __user_cap_data_struct);
241 if (copybytes > sizeof(kdata))
242 return -EFAULT;
243
244 if (copy_from_user(&kdata, data, copybytes))
245 return -EFAULT;
246
247 effective = mk_kernel_cap(kdata[0].effective, kdata[1].effective);
248 permitted = mk_kernel_cap(kdata[0].permitted, kdata[1].permitted);
249 inheritable = mk_kernel_cap(kdata[0].inheritable, kdata[1].inheritable);
250
251 new = prepare_creds();
252 if (!new)
253 return -ENOMEM;
254
255 ret = security_capset(new, current_cred(),
256 &effective, &inheritable, &permitted);
257 if (ret < 0)
258 goto error;
259
260 audit_log_capset(new, current_cred());
261
262 return commit_creds(new);
263
264error:
265 abort_creds(new);
266 return ret;
267}
268
269/**
270 * has_ns_capability - Does a task have a capability in a specific user ns
271 * @t: The task in question
272 * @ns: target user namespace
273 * @cap: The capability to be tested for
274 *
275 * Return true if the specified task has the given superior capability
276 * currently in effect to the specified user namespace, false if not.
277 *
278 * Note that this does not set PF_SUPERPRIV on the task.
279 */
280bool has_ns_capability(struct task_struct *t,
281 struct user_namespace *ns, int cap)
282{
283 int ret;
284
285 rcu_read_lock();
286 ret = security_capable(__task_cred(t), ns, cap, CAP_OPT_NONE);
287 rcu_read_unlock();
288
289 return (ret == 0);
290}
291
292/**
293 * has_capability - Does a task have a capability in init_user_ns
294 * @t: The task in question
295 * @cap: The capability to be tested for
296 *
297 * Return true if the specified task has the given superior capability
298 * currently in effect to the initial user namespace, false if not.
299 *
300 * Note that this does not set PF_SUPERPRIV on the task.
301 */
302bool has_capability(struct task_struct *t, int cap)
303{
304 return has_ns_capability(t, &init_user_ns, cap);
305}
306EXPORT_SYMBOL(has_capability);
307
308/**
309 * has_ns_capability_noaudit - Does a task have a capability (unaudited)
310 * in a specific user ns.
311 * @t: The task in question
312 * @ns: target user namespace
313 * @cap: The capability to be tested for
314 *
315 * Return true if the specified task has the given superior capability
316 * currently in effect to the specified user namespace, false if not.
317 * Do not write an audit message for the check.
318 *
319 * Note that this does not set PF_SUPERPRIV on the task.
320 */
321bool has_ns_capability_noaudit(struct task_struct *t,
322 struct user_namespace *ns, int cap)
323{
324 int ret;
325
326 rcu_read_lock();
327 ret = security_capable(__task_cred(t), ns, cap, CAP_OPT_NOAUDIT);
328 rcu_read_unlock();
329
330 return (ret == 0);
331}
332
333/**
334 * has_capability_noaudit - Does a task have a capability (unaudited) in the
335 * initial user ns
336 * @t: The task in question
337 * @cap: The capability to be tested for
338 *
339 * Return true if the specified task has the given superior capability
340 * currently in effect to init_user_ns, false if not. Don't write an
341 * audit message for the check.
342 *
343 * Note that this does not set PF_SUPERPRIV on the task.
344 */
345bool has_capability_noaudit(struct task_struct *t, int cap)
346{
347 return has_ns_capability_noaudit(t, &init_user_ns, cap);
348}
349EXPORT_SYMBOL(has_capability_noaudit);
350
351static bool ns_capable_common(struct user_namespace *ns,
352 int cap,
353 unsigned int opts)
354{
355 int capable;
356
357 if (unlikely(!cap_valid(cap))) {
358 pr_crit("capable() called with invalid cap=%u\n", cap);
359 BUG();
360 }
361
362 capable = security_capable(current_cred(), ns, cap, opts);
363 if (capable == 0) {
364 current->flags |= PF_SUPERPRIV;
365 return true;
366 }
367 return false;
368}
369
370/**
371 * ns_capable - Determine if the current task has a superior capability in effect
372 * @ns: The usernamespace we want the capability in
373 * @cap: The capability to be tested for
374 *
375 * Return true if the current task has the given superior capability currently
376 * available for use, false if not.
377 *
378 * This sets PF_SUPERPRIV on the task if the capability is available on the
379 * assumption that it's about to be used.
380 */
381bool ns_capable(struct user_namespace *ns, int cap)
382{
383 return ns_capable_common(ns, cap, CAP_OPT_NONE);
384}
385EXPORT_SYMBOL(ns_capable);
386
387/**
388 * ns_capable_noaudit - Determine if the current task has a superior capability
389 * (unaudited) in effect
390 * @ns: The usernamespace we want the capability in
391 * @cap: The capability to be tested for
392 *
393 * Return true if the current task has the given superior capability currently
394 * available for use, false if not.
395 *
396 * This sets PF_SUPERPRIV on the task if the capability is available on the
397 * assumption that it's about to be used.
398 */
399bool ns_capable_noaudit(struct user_namespace *ns, int cap)
400{
401 return ns_capable_common(ns, cap, CAP_OPT_NOAUDIT);
402}
403EXPORT_SYMBOL(ns_capable_noaudit);
404
405/**
406 * ns_capable_setid - Determine if the current task has a superior capability
407 * in effect, while signalling that this check is being done from within a
408 * setid or setgroups syscall.
409 * @ns: The usernamespace we want the capability in
410 * @cap: The capability to be tested for
411 *
412 * Return true if the current task has the given superior capability currently
413 * available for use, false if not.
414 *
415 * This sets PF_SUPERPRIV on the task if the capability is available on the
416 * assumption that it's about to be used.
417 */
418bool ns_capable_setid(struct user_namespace *ns, int cap)
419{
420 return ns_capable_common(ns, cap, CAP_OPT_INSETID);
421}
422EXPORT_SYMBOL(ns_capable_setid);
423
424/**
425 * capable - Determine if the current task has a superior capability in effect
426 * @cap: The capability to be tested for
427 *
428 * Return true if the current task has the given superior capability currently
429 * available for use, false if not.
430 *
431 * This sets PF_SUPERPRIV on the task if the capability is available on the
432 * assumption that it's about to be used.
433 */
434bool capable(int cap)
435{
436 return ns_capable(&init_user_ns, cap);
437}
438EXPORT_SYMBOL(capable);
439#endif /* CONFIG_MULTIUSER */
440
441/**
442 * file_ns_capable - Determine if the file's opener had a capability in effect
443 * @file: The file we want to check
444 * @ns: The usernamespace we want the capability in
445 * @cap: The capability to be tested for
446 *
447 * Return true if task that opened the file had a capability in effect
448 * when the file was opened.
449 *
450 * This does not set PF_SUPERPRIV because the caller may not
451 * actually be privileged.
452 */
453bool file_ns_capable(const struct file *file, struct user_namespace *ns,
454 int cap)
455{
456
457 if (WARN_ON_ONCE(!cap_valid(cap)))
458 return false;
459
460 if (security_capable(file->f_cred, ns, cap, CAP_OPT_NONE) == 0)
461 return true;
462
463 return false;
464}
465EXPORT_SYMBOL(file_ns_capable);
466
467/**
468 * privileged_wrt_inode_uidgid - Do capabilities in the namespace work over the inode?
469 * @ns: The user namespace in question
470 * @idmap: idmap of the mount @inode was found from
471 * @inode: The inode in question
472 *
473 * Return true if the inode uid and gid are within the namespace.
474 */
475bool privileged_wrt_inode_uidgid(struct user_namespace *ns,
476 struct mnt_idmap *idmap,
477 const struct inode *inode)
478{
479 return vfsuid_has_mapping(ns, i_uid_into_vfsuid(idmap, inode)) &&
480 vfsgid_has_mapping(ns, i_gid_into_vfsgid(idmap, inode));
481}
482
483/**
484 * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped
485 * @idmap: idmap of the mount @inode was found from
486 * @inode: The inode in question
487 * @cap: The capability in question
488 *
489 * Return true if the current task has the given capability targeted at
490 * its own user namespace and that the given inode's uid and gid are
491 * mapped into the current user namespace.
492 */
493bool capable_wrt_inode_uidgid(struct mnt_idmap *idmap,
494 const struct inode *inode, int cap)
495{
496 struct user_namespace *ns = current_user_ns();
497
498 return ns_capable(ns, cap) &&
499 privileged_wrt_inode_uidgid(ns, idmap, inode);
500}
501EXPORT_SYMBOL(capable_wrt_inode_uidgid);
502
503/**
504 * ptracer_capable - Determine if the ptracer holds CAP_SYS_PTRACE in the namespace
505 * @tsk: The task that may be ptraced
506 * @ns: The user namespace to search for CAP_SYS_PTRACE in
507 *
508 * Return true if the task that is ptracing the current task had CAP_SYS_PTRACE
509 * in the specified user namespace.
510 */
511bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns)
512{
513 int ret = 0; /* An absent tracer adds no restrictions */
514 const struct cred *cred;
515
516 rcu_read_lock();
517 cred = rcu_dereference(tsk->ptracer_cred);
518 if (cred)
519 ret = security_capable(cred, ns, CAP_SYS_PTRACE,
520 CAP_OPT_NOAUDIT);
521 rcu_read_unlock();
522 return (ret == 0);
523}