2 * linux/kernel/capability.c
4 * Copyright (C) 1997 Andrew Main <zefram@fysh.org>
6 * Integrated into 2.1.97+, Andrew G. Morgan <morgan@kernel.org>
7 * 30 May 2002: Cleanup, Robert M. Love <rml@tech9.net>
10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12 #include <linux/audit.h>
13 #include <linux/capability.h>
15 #include <linux/export.h>
16 #include <linux/security.h>
17 #include <linux/syscalls.h>
18 #include <linux/pid_namespace.h>
19 #include <linux/user_namespace.h>
20 #include <asm/uaccess.h>
23 * Leveraged for setting/resetting capabilities
26 const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
27 EXPORT_SYMBOL(__cap_empty_set);
29 int file_caps_enabled = 1;
31 static int __init file_caps_disable(char *str)
33 file_caps_enabled = 0;
36 __setup("no_file_caps", file_caps_disable);
38 #ifdef CONFIG_MULTIUSER
40 * More recent versions of libcap are available from:
42 * http://www.kernel.org/pub/linux/libs/security/linux-privs/
45 static void warn_legacy_capability_use(void)
47 char name[sizeof(current->comm)];
49 pr_info_once("warning: `%s' uses 32-bit capabilities (legacy support in use)\n",
50 get_task_comm(name, current));
54 * Version 2 capabilities worked fine, but the linux/capability.h file
55 * that accompanied their introduction encouraged their use without
56 * the necessary user-space source code changes. As such, we have
57 * created a version 3 with equivalent functionality to version 2, but
58 * with a header change to protect legacy source code from using
59 * version 2 when it wanted to use version 1. If your system has code
60 * that trips the following warning, it is using version 2 specific
61 * capabilities and may be doing so insecurely.
63 * The remedy is to either upgrade your version of libcap (to 2.10+,
64 * if the application is linked against it), or recompile your
65 * application with modern kernel headers and this warning will go
69 static void warn_deprecated_v2(void)
71 char name[sizeof(current->comm)];
73 pr_info_once("warning: `%s' uses deprecated v2 capabilities in a way that may be insecure\n",
74 get_task_comm(name, current));
78 * Version check. Return the number of u32s in each capability flag
79 * array, or a negative value on error.
81 static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
85 if (get_user(version, &header->version))
89 case _LINUX_CAPABILITY_VERSION_1:
90 warn_legacy_capability_use();
91 *tocopy = _LINUX_CAPABILITY_U32S_1;
93 case _LINUX_CAPABILITY_VERSION_2:
96 * fall through - v3 is otherwise equivalent to v2.
98 case _LINUX_CAPABILITY_VERSION_3:
99 *tocopy = _LINUX_CAPABILITY_U32S_3;
102 if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
111 * The only thing that can change the capabilities of the current
112 * process is the current process. As such, we can't be in this code
113 * at the same time as we are in the process of setting capabilities
114 * in this process. The net result is that we can limit our use of
115 * locks to when we are reading the caps of another process.
117 static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
118 kernel_cap_t *pIp, kernel_cap_t *pPp)
122 if (pid && (pid != task_pid_vnr(current))) {
123 struct task_struct *target;
127 target = find_task_by_vpid(pid);
131 ret = security_capget(target, pEp, pIp, pPp);
135 ret = security_capget(current, pEp, pIp, pPp);
141 * sys_capget - get the capabilities of a given process.
142 * @header: pointer to struct that contains capability version and
144 * @dataptr: pointer to struct that contains the effective, permitted,
145 * and inheritable capabilities that are returned
147 * Returns 0 on success and < 0 on error.
149 SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
154 kernel_cap_t pE, pI, pP;
156 ret = cap_validate_magic(header, &tocopy);
157 if ((dataptr == NULL) || (ret != 0))
158 return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;
160 if (get_user(pid, &header->pid))
166 ret = cap_get_target_pid(pid, &pE, &pI, &pP);
168 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
171 for (i = 0; i < tocopy; i++) {
172 kdata[i].effective = pE.cap[i];
173 kdata[i].permitted = pP.cap[i];
174 kdata[i].inheritable = pI.cap[i];
178 * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
179 * we silently drop the upper capabilities here. This
180 * has the effect of making older libcap
181 * implementations implicitly drop upper capability
182 * bits when they perform a: capget/modify/capset
185 * This behavior is considered fail-safe
186 * behavior. Upgrading the application to a newer
187 * version of libcap will enable access to the newer
190 * An alternative would be to return an error here
191 * (-ERANGE), but that causes legacy applications to
192 * unexpectedly fail; the capget/modify/capset aborts
193 * before modification is attempted and the application
196 if (copy_to_user(dataptr, kdata, tocopy
197 * sizeof(struct __user_cap_data_struct))) {
206 * sys_capset - set capabilities for a process or (*) a group of processes
207 * @header: pointer to struct that contains capability version and
209 * @data: pointer to struct that contains the effective, permitted,
210 * and inheritable capabilities
212 * Set capabilities for the current process only. The ability to any other
213 * process(es) has been deprecated and removed.
215 * The restrictions on setting capabilities are specified as:
217 * I: any raised capabilities must be a subset of the old permitted
218 * P: any raised capabilities must be a subset of the old permitted
219 * E: must be set to a subset of new permitted
221 * Returns 0 on success and < 0 on error.
223 SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
225 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
226 unsigned i, tocopy, copybytes;
227 kernel_cap_t inheritable, permitted, effective;
232 ret = cap_validate_magic(header, &tocopy);
236 if (get_user(pid, &header->pid))
239 /* may only affect current now */
240 if (pid != 0 && pid != task_pid_vnr(current))
243 copybytes = tocopy * sizeof(struct __user_cap_data_struct);
244 if (copybytes > sizeof(kdata))
247 if (copy_from_user(&kdata, data, copybytes))
250 for (i = 0; i < tocopy; i++) {
251 effective.cap[i] = kdata[i].effective;
252 permitted.cap[i] = kdata[i].permitted;
253 inheritable.cap[i] = kdata[i].inheritable;
255 while (i < _KERNEL_CAPABILITY_U32S) {
256 effective.cap[i] = 0;
257 permitted.cap[i] = 0;
258 inheritable.cap[i] = 0;
262 effective.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
263 permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
264 inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
266 new = prepare_creds();
270 ret = security_capset(new, current_cred(),
271 &effective, &inheritable, &permitted);
275 audit_log_capset(new, current_cred());
277 return commit_creds(new);
285 * has_ns_capability - Does a task have a capability in a specific user ns
286 * @t: The task in question
287 * @ns: target user namespace
288 * @cap: The capability to be tested for
290 * Return true if the specified task has the given superior capability
291 * currently in effect to the specified user namespace, false if not.
293 * Note that this does not set PF_SUPERPRIV on the task.
295 bool has_ns_capability(struct task_struct *t,
296 struct user_namespace *ns, int cap)
301 ret = security_capable(__task_cred(t), ns, cap);
308 * has_capability - Does a task have a capability in init_user_ns
309 * @t: The task in question
310 * @cap: The capability to be tested for
312 * Return true if the specified task has the given superior capability
313 * currently in effect to the initial user namespace, false if not.
315 * Note that this does not set PF_SUPERPRIV on the task.
317 bool has_capability(struct task_struct *t, int cap)
319 return has_ns_capability(t, &init_user_ns, cap);
323 * has_ns_capability_noaudit - Does a task have a capability (unaudited)
324 * in a specific user ns.
325 * @t: The task in question
326 * @ns: target user namespace
327 * @cap: The capability to be tested for
329 * Return true if the specified task has the given superior capability
330 * currently in effect to the specified user namespace, false if not.
331 * Do not write an audit message for the check.
333 * Note that this does not set PF_SUPERPRIV on the task.
335 bool has_ns_capability_noaudit(struct task_struct *t,
336 struct user_namespace *ns, int cap)
341 ret = security_capable_noaudit(__task_cred(t), ns, cap);
348 * has_capability_noaudit - Does a task have a capability (unaudited) in the
350 * @t: The task in question
351 * @cap: The capability to be tested for
353 * Return true if the specified task has the given superior capability
354 * currently in effect to init_user_ns, false if not. Don't write an
355 * audit message for the check.
357 * Note that this does not set PF_SUPERPRIV on the task.
359 bool has_capability_noaudit(struct task_struct *t, int cap)
361 return has_ns_capability_noaudit(t, &init_user_ns, cap);
364 static bool ns_capable_common(struct user_namespace *ns, int cap, bool audit)
368 if (unlikely(!cap_valid(cap))) {
369 pr_crit("capable() called with invalid cap=%u\n", cap);
373 capable = audit ? security_capable(current_cred(), ns, cap) :
374 security_capable_noaudit(current_cred(), ns, cap);
376 current->flags |= PF_SUPERPRIV;
383 * ns_capable - Determine if the current task has a superior capability in effect
384 * @ns: The usernamespace we want the capability in
385 * @cap: The capability to be tested for
387 * Return true if the current task has the given superior capability currently
388 * available for use, false if not.
390 * This sets PF_SUPERPRIV on the task if the capability is available on the
391 * assumption that it's about to be used.
393 bool ns_capable(struct user_namespace *ns, int cap)
395 return ns_capable_common(ns, cap, true);
397 EXPORT_SYMBOL(ns_capable);
400 * ns_capable_noaudit - Determine if the current task has a superior capability
401 * (unaudited) in effect
402 * @ns: The usernamespace we want the capability in
403 * @cap: The capability to be tested for
405 * Return true if the current task has the given superior capability currently
406 * available for use, false if not.
408 * This sets PF_SUPERPRIV on the task if the capability is available on the
409 * assumption that it's about to be used.
411 bool ns_capable_noaudit(struct user_namespace *ns, int cap)
413 return ns_capable_common(ns, cap, false);
415 EXPORT_SYMBOL(ns_capable_noaudit);
418 * capable - Determine if the current task has a superior capability in effect
419 * @cap: The capability to be tested for
421 * Return true if the current task has the given superior capability currently
422 * available for use, false if not.
424 * This sets PF_SUPERPRIV on the task if the capability is available on the
425 * assumption that it's about to be used.
427 bool capable(int cap)
429 return ns_capable(&init_user_ns, cap);
431 EXPORT_SYMBOL(capable);
432 #endif /* CONFIG_MULTIUSER */
435 * file_ns_capable - Determine if the file's opener had a capability in effect
436 * @file: The file we want to check
437 * @ns: The usernamespace we want the capability in
438 * @cap: The capability to be tested for
440 * Return true if task that opened the file had a capability in effect
441 * when the file was opened.
443 * This does not set PF_SUPERPRIV because the caller may not
444 * actually be privileged.
446 bool file_ns_capable(const struct file *file, struct user_namespace *ns,
449 if (WARN_ON_ONCE(!cap_valid(cap)))
452 if (security_capable(file->f_cred, ns, cap) == 0)
457 EXPORT_SYMBOL(file_ns_capable);
460 * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped
461 * @inode: The inode in question
462 * @cap: The capability in question
464 * Return true if the current task has the given capability targeted at
465 * its own user namespace and that the given inode's uid and gid are
466 * mapped into the current user namespace.
468 bool capable_wrt_inode_uidgid(const struct inode *inode, int cap)
470 struct user_namespace *ns = current_user_ns();
472 return ns_capable(ns, cap) && kuid_has_mapping(ns, inode->i_uid) &&
473 kgid_has_mapping(ns, inode->i_gid);
475 EXPORT_SYMBOL(capable_wrt_inode_uidgid);