1 // SPDX-License-Identifier: GPL-2.0
3 * linux/kernel/capability.c
5 * Copyright (C) 1997 Andrew Main <zefram@fysh.org>
7 * Integrated into 2.1.97+, Andrew G. Morgan <morgan@kernel.org>
8 * 30 May 2002: Cleanup, Robert M. Love <rml@tech9.net>
11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13 #include <linux/audit.h>
14 #include <linux/capability.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>
24 * Leveraged for setting/resetting capabilities
27 const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
28 EXPORT_SYMBOL(__cap_empty_set);
30 int file_caps_enabled = 1;
32 static int __init file_caps_disable(char *str)
34 file_caps_enabled = 0;
37 __setup("no_file_caps", file_caps_disable);
39 #ifdef CONFIG_MULTIUSER
41 * More recent versions of libcap are available from:
43 * http://www.kernel.org/pub/linux/libs/security/linux-privs/
46 static void warn_legacy_capability_use(void)
48 char name[sizeof(current->comm)];
50 pr_info_once("warning: `%s' uses 32-bit capabilities (legacy support in use)\n",
51 get_task_comm(name, current));
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.
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
70 static void warn_deprecated_v2(void)
72 char name[sizeof(current->comm)];
74 pr_info_once("warning: `%s' uses deprecated v2 capabilities in a way that may be insecure\n",
75 get_task_comm(name, current));
79 * Version check. Return the number of u32s in each capability flag
80 * array, or a negative value on error.
82 static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
86 if (get_user(version, &header->version))
90 case _LINUX_CAPABILITY_VERSION_1:
91 warn_legacy_capability_use();
92 *tocopy = _LINUX_CAPABILITY_U32S_1;
94 case _LINUX_CAPABILITY_VERSION_2:
97 * fall through - v3 is otherwise equivalent to v2.
99 case _LINUX_CAPABILITY_VERSION_3:
100 *tocopy = _LINUX_CAPABILITY_U32S_3;
103 if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
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.
118 static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
119 kernel_cap_t *pIp, kernel_cap_t *pPp)
123 if (pid && (pid != task_pid_vnr(current))) {
124 struct task_struct *target;
128 target = find_task_by_vpid(pid);
132 ret = security_capget(target, pEp, pIp, pPp);
136 ret = security_capget(current, pEp, pIp, pPp);
142 * sys_capget - get the capabilities of a given process.
143 * @header: pointer to struct that contains capability version and
145 * @dataptr: pointer to struct that contains the effective, permitted,
146 * and inheritable capabilities that are returned
148 * Returns 0 on success and < 0 on error.
150 SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
155 kernel_cap_t pE, pI, pP;
157 ret = cap_validate_magic(header, &tocopy);
158 if ((dataptr == NULL) || (ret != 0))
159 return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;
161 if (get_user(pid, &header->pid))
167 ret = cap_get_target_pid(pid, &pE, &pI, &pP);
169 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
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];
179 * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
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
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
191 * An alternative would be to return an error here
192 * (-ERANGE), but that causes legacy applications to
193 * unexpectedly fail; the capget/modify/capset aborts
194 * before modification is attempted and the application
197 if (copy_to_user(dataptr, kdata, tocopy
198 * sizeof(struct __user_cap_data_struct))) {
207 * sys_capset - set capabilities for a process or (*) a group of processes
208 * @header: pointer to struct that contains capability version and
210 * @data: pointer to struct that contains the effective, permitted,
211 * and inheritable capabilities
213 * Set capabilities for the current process only. The ability to any other
214 * process(es) has been deprecated and removed.
216 * The restrictions on setting capabilities are specified as:
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
222 * Returns 0 on success and < 0 on error.
224 SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
226 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
227 unsigned i, tocopy, copybytes;
228 kernel_cap_t inheritable, permitted, effective;
233 ret = cap_validate_magic(header, &tocopy);
237 if (get_user(pid, &header->pid))
240 /* may only affect current now */
241 if (pid != 0 && pid != task_pid_vnr(current))
244 copybytes = tocopy * sizeof(struct __user_cap_data_struct);
245 if (copybytes > sizeof(kdata))
248 if (copy_from_user(&kdata, data, copybytes))
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;
256 while (i < _KERNEL_CAPABILITY_U32S) {
257 effective.cap[i] = 0;
258 permitted.cap[i] = 0;
259 inheritable.cap[i] = 0;
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;
267 new = prepare_creds();
271 ret = security_capset(new, current_cred(),
272 &effective, &inheritable, &permitted);
276 audit_log_capset(new, current_cred());
278 return commit_creds(new);
286 * has_ns_capability - Does a task have a capability in a specific user ns
287 * @t: The task in question
288 * @ns: target user namespace
289 * @cap: The capability to be tested for
291 * Return true if the specified task has the given superior capability
292 * currently in effect to the specified user namespace, false if not.
294 * Note that this does not set PF_SUPERPRIV on the task.
296 bool has_ns_capability(struct task_struct *t,
297 struct user_namespace *ns, int cap)
302 ret = security_capable(__task_cred(t), ns, cap);
309 * has_capability - Does a task have a capability in init_user_ns
310 * @t: The task in question
311 * @cap: The capability to be tested for
313 * Return true if the specified task has the given superior capability
314 * currently in effect to the initial user namespace, false if not.
316 * Note that this does not set PF_SUPERPRIV on the task.
318 bool has_capability(struct task_struct *t, int cap)
320 return has_ns_capability(t, &init_user_ns, cap);
322 EXPORT_SYMBOL(has_capability);
325 * has_ns_capability_noaudit - Does a task have a capability (unaudited)
326 * in a specific user ns.
327 * @t: The task in question
328 * @ns: target user namespace
329 * @cap: The capability to be tested for
331 * Return true if the specified task has the given superior capability
332 * currently in effect to the specified user namespace, false if not.
333 * Do not write an audit message for the check.
335 * Note that this does not set PF_SUPERPRIV on the task.
337 bool has_ns_capability_noaudit(struct task_struct *t,
338 struct user_namespace *ns, int cap)
343 ret = security_capable_noaudit(__task_cred(t), ns, cap);
350 * has_capability_noaudit - Does a task have a capability (unaudited) in the
352 * @t: The task in question
353 * @cap: The capability to be tested for
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.
359 * Note that this does not set PF_SUPERPRIV on the task.
361 bool has_capability_noaudit(struct task_struct *t, int cap)
363 return has_ns_capability_noaudit(t, &init_user_ns, cap);
366 static bool ns_capable_common(struct user_namespace *ns, int cap, bool audit)
370 if (unlikely(!cap_valid(cap))) {
371 pr_crit("capable() called with invalid cap=%u\n", cap);
375 capable = audit ? security_capable(current_cred(), ns, cap) :
376 security_capable_noaudit(current_cred(), ns, cap);
378 current->flags |= PF_SUPERPRIV;
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
389 * Return true if the current task has the given superior capability currently
390 * available for use, false if not.
392 * This sets PF_SUPERPRIV on the task if the capability is available on the
393 * assumption that it's about to be used.
395 bool ns_capable(struct user_namespace *ns, int cap)
397 return ns_capable_common(ns, cap, true);
399 EXPORT_SYMBOL(ns_capable);
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
407 * Return true if the current task has the given superior capability currently
408 * available for use, false if not.
410 * This sets PF_SUPERPRIV on the task if the capability is available on the
411 * assumption that it's about to be used.
413 bool ns_capable_noaudit(struct user_namespace *ns, int cap)
415 return ns_capable_common(ns, cap, false);
417 EXPORT_SYMBOL(ns_capable_noaudit);
420 * capable - Determine if the current task has a superior capability in effect
421 * @cap: The capability to be tested for
423 * Return true if the current task has the given superior capability currently
424 * available for use, false if not.
426 * This sets PF_SUPERPRIV on the task if the capability is available on the
427 * assumption that it's about to be used.
429 bool capable(int cap)
431 return ns_capable(&init_user_ns, cap);
433 EXPORT_SYMBOL(capable);
434 #endif /* CONFIG_MULTIUSER */
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
442 * Return true if task that opened the file had a capability in effect
443 * when the file was opened.
445 * This does not set PF_SUPERPRIV because the caller may not
446 * actually be privileged.
448 bool file_ns_capable(const struct file *file, struct user_namespace *ns,
451 if (WARN_ON_ONCE(!cap_valid(cap)))
454 if (security_capable(file->f_cred, ns, cap) == 0)
459 EXPORT_SYMBOL(file_ns_capable);
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
466 * Return true if the inode uid and gid are within the namespace.
468 bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct inode *inode)
470 return kuid_has_mapping(ns, inode->i_uid) &&
471 kgid_has_mapping(ns, inode->i_gid);
475 * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped
476 * @inode: The inode in question
477 * @cap: The capability in question
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.
483 bool capable_wrt_inode_uidgid(const struct inode *inode, int cap)
485 struct user_namespace *ns = current_user_ns();
487 return ns_capable(ns, cap) && privileged_wrt_inode_uidgid(ns, inode);
489 EXPORT_SYMBOL(capable_wrt_inode_uidgid);
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
496 * Return true if the task that is ptracing the current task had CAP_SYS_PTRACE
497 * in the specified user namespace.
499 bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns)
501 int ret = 0; /* An absent tracer adds no restrictions */
502 const struct cred *cred;
504 cred = rcu_dereference(tsk->ptracer_cred);
506 ret = security_capable_noaudit(cred, ns, CAP_SYS_PTRACE);