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 #include <linux/audit.h>
11 #include <linux/capability.h>
13 #include <linux/module.h>
14 #include <linux/security.h>
15 #include <linux/syscalls.h>
16 #include <linux/pid_namespace.h>
17 #include <asm/uaccess.h>
20 * Leveraged for setting/resetting capabilities
23 const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
24 const kernel_cap_t __cap_full_set = CAP_FULL_SET;
25 const kernel_cap_t __cap_init_eff_set = CAP_INIT_EFF_SET;
27 EXPORT_SYMBOL(__cap_empty_set);
28 EXPORT_SYMBOL(__cap_full_set);
29 EXPORT_SYMBOL(__cap_init_eff_set);
31 #ifdef CONFIG_SECURITY_FILE_CAPABILITIES
32 int file_caps_enabled = 1;
34 static int __init file_caps_disable(char *str)
36 file_caps_enabled = 0;
39 __setup("no_file_caps", file_caps_disable);
43 * More recent versions of libcap are available from:
45 * http://www.kernel.org/pub/linux/libs/security/linux-privs/
48 static void warn_legacy_capability_use(void)
52 char name[sizeof(current->comm)];
54 printk(KERN_INFO "warning: `%s' uses 32-bit capabilities"
55 " (legacy support in use)\n",
56 get_task_comm(name, current));
62 * Version 2 capabilities worked fine, but the linux/capability.h file
63 * that accompanied their introduction encouraged their use without
64 * the necessary user-space source code changes. As such, we have
65 * created a version 3 with equivalent functionality to version 2, but
66 * with a header change to protect legacy source code from using
67 * version 2 when it wanted to use version 1. If your system has code
68 * that trips the following warning, it is using version 2 specific
69 * capabilities and may be doing so insecurely.
71 * The remedy is to either upgrade your version of libcap (to 2.10+,
72 * if the application is linked against it), or recompile your
73 * application with modern kernel headers and this warning will go
77 static void warn_deprecated_v2(void)
82 char name[sizeof(current->comm)];
84 printk(KERN_INFO "warning: `%s' uses deprecated v2"
85 " capabilities in a way that may be insecure.\n",
86 get_task_comm(name, current));
92 * Version check. Return the number of u32s in each capability flag
93 * array, or a negative value on error.
95 static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
99 if (get_user(version, &header->version))
103 case _LINUX_CAPABILITY_VERSION_1:
104 warn_legacy_capability_use();
105 *tocopy = _LINUX_CAPABILITY_U32S_1;
107 case _LINUX_CAPABILITY_VERSION_2:
108 warn_deprecated_v2();
110 * fall through - v3 is otherwise equivalent to v2.
112 case _LINUX_CAPABILITY_VERSION_3:
113 *tocopy = _LINUX_CAPABILITY_U32S_3;
116 if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
125 * The only thing that can change the capabilities of the current
126 * process is the current process. As such, we can't be in this code
127 * at the same time as we are in the process of setting capabilities
128 * in this process. The net result is that we can limit our use of
129 * locks to when we are reading the caps of another process.
131 static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
132 kernel_cap_t *pIp, kernel_cap_t *pPp)
136 if (pid && (pid != task_pid_vnr(current))) {
137 struct task_struct *target;
139 read_lock(&tasklist_lock);
141 target = find_task_by_vpid(pid);
145 ret = security_capget(target, pEp, pIp, pPp);
147 read_unlock(&tasklist_lock);
149 ret = security_capget(current, pEp, pIp, pPp);
155 * sys_capget - get the capabilities of a given process.
156 * @header: pointer to struct that contains capability version and
158 * @dataptr: pointer to struct that contains the effective, permitted,
159 * and inheritable capabilities that are returned
161 * Returns 0 on success and < 0 on error.
163 SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
168 kernel_cap_t pE, pI, pP;
170 ret = cap_validate_magic(header, &tocopy);
174 if (get_user(pid, &header->pid))
180 ret = cap_get_target_pid(pid, &pE, &pI, &pP);
182 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
185 for (i = 0; i < tocopy; i++) {
186 kdata[i].effective = pE.cap[i];
187 kdata[i].permitted = pP.cap[i];
188 kdata[i].inheritable = pI.cap[i];
192 * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
193 * we silently drop the upper capabilities here. This
194 * has the effect of making older libcap
195 * implementations implicitly drop upper capability
196 * bits when they perform a: capget/modify/capset
199 * This behavior is considered fail-safe
200 * behavior. Upgrading the application to a newer
201 * version of libcap will enable access to the newer
204 * An alternative would be to return an error here
205 * (-ERANGE), but that causes legacy applications to
206 * unexpectidly fail; the capget/modify/capset aborts
207 * before modification is attempted and the application
210 if (copy_to_user(dataptr, kdata, tocopy
211 * sizeof(struct __user_cap_data_struct))) {
220 * sys_capset - set capabilities for a process or (*) a group of processes
221 * @header: pointer to struct that contains capability version and
223 * @data: pointer to struct that contains the effective, permitted,
224 * and inheritable capabilities
226 * Set capabilities for the current process only. The ability to any other
227 * process(es) has been deprecated and removed.
229 * The restrictions on setting capabilities are specified as:
231 * I: any raised capabilities must be a subset of the old permitted
232 * P: any raised capabilities must be a subset of the old permitted
233 * E: must be set to a subset of new permitted
235 * Returns 0 on success and < 0 on error.
237 SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
239 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
241 kernel_cap_t inheritable, permitted, effective;
246 ret = cap_validate_magic(header, &tocopy);
250 if (get_user(pid, &header->pid))
253 /* may only affect current now */
254 if (pid != 0 && pid != task_pid_vnr(current))
257 if (copy_from_user(&kdata, data,
258 tocopy * sizeof(struct __user_cap_data_struct)))
261 for (i = 0; i < tocopy; i++) {
262 effective.cap[i] = kdata[i].effective;
263 permitted.cap[i] = kdata[i].permitted;
264 inheritable.cap[i] = kdata[i].inheritable;
266 while (i < _KERNEL_CAPABILITY_U32S) {
267 effective.cap[i] = 0;
268 permitted.cap[i] = 0;
269 inheritable.cap[i] = 0;
273 new = prepare_creds();
277 ret = security_capset(new, current_cred(),
278 &effective, &inheritable, &permitted);
282 audit_log_capset(pid, new, current_cred());
284 return commit_creds(new);
292 * capable - Determine if the current task has a superior capability in effect
293 * @cap: The capability to be tested for
295 * Return true if the current task has the given superior capability currently
296 * available for use, false if not.
298 * This sets PF_SUPERPRIV on the task if the capability is available on the
299 * assumption that it's about to be used.
303 if (unlikely(!cap_valid(cap))) {
304 printk(KERN_CRIT "capable() called with invalid cap=%u\n", cap);
308 if (security_capable(cap) == 0) {
309 current->flags |= PF_SUPERPRIV;
314 EXPORT_SYMBOL(capable);