projects/linux·blob v2.6.26 · refs

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1/*
2 * linux/kernel/capability.c
3 *
4 * Copyright (C) 1997 Andrew Main <[email protected]>
5 *
6 * Integrated into 2.1.97+, Andrew G. Morgan <[email protected]>
7 * 30 May 2002: Cleanup, Robert M. Love <[email protected]>
8 */
9
10#include <linux/capability.h>
11#include <linux/mm.h>
12#include <linux/module.h>
13#include <linux/security.h>
14#include <linux/syscalls.h>
15#include <linux/pid_namespace.h>
16#include <asm/uaccess.h>
17
18/*
19 * This lock protects task->cap_* for all tasks including current.
20 * Locking rule: acquire this prior to tasklist_lock.
21 */
22static DEFINE_SPINLOCK(task_capability_lock);
23
24/*
25 * Leveraged for setting/resetting capabilities
26 */
27
28const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
29const kernel_cap_t __cap_full_set = CAP_FULL_SET;
30const kernel_cap_t __cap_init_eff_set = CAP_INIT_EFF_SET;
31
32EXPORT_SYMBOL(__cap_empty_set);
33EXPORT_SYMBOL(__cap_full_set);
34EXPORT_SYMBOL(__cap_init_eff_set);
35
36/*
37 * More recent versions of libcap are available from:
38 *
39 * http://www.kernel.org/pub/linux/libs/security/linux-privs/
40 */
41
42static void warn_legacy_capability_use(void)
43{
44 static int warned;
45 if (!warned) {
46 char name[sizeof(current->comm)];
47
48 printk(KERN_INFO "warning: `%s' uses 32-bit capabilities"
49 " (legacy support in use)\n",
50 get_task_comm(name, current));
51 warned = 1;
52 }
53}
54
55/*
56 * Version 2 capabilities worked fine, but the linux/capability.h file
57 * that accompanied their introduction encouraged their use without
58 * the necessary user-space source code changes. As such, we have
59 * created a version 3 with equivalent functionality to version 2, but
60 * with a header change to protect legacy source code from using
61 * version 2 when it wanted to use version 1. If your system has code
62 * that trips the following warning, it is using version 2 specific
63 * capabilities and may be doing so insecurely.
64 *
65 * The remedy is to either upgrade your version of libcap (to 2.10+,
66 * if the application is linked against it), or recompile your
67 * application with modern kernel headers and this warning will go
68 * away.
69 */
70
71static void warn_deprecated_v2(void)
72{
73 static int warned;
74
75 if (!warned) {
76 char name[sizeof(current->comm)];
77
78 printk(KERN_INFO "warning: `%s' uses deprecated v2"
79 " capabilities in a way that may be insecure.\n",
80 get_task_comm(name, current));
81 warned = 1;
82 }
83}
84
85/*
86 * Version check. Return the number of u32s in each capability flag
87 * array, or a negative value on error.
88 */
89static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
90{
91 __u32 version;
92
93 if (get_user(version, &header->version))
94 return -EFAULT;
95
96 switch (version) {
97 case _LINUX_CAPABILITY_VERSION_1:
98 warn_legacy_capability_use();
99 *tocopy = _LINUX_CAPABILITY_U32S_1;
100 break;
101 case _LINUX_CAPABILITY_VERSION_2:
102 warn_deprecated_v2();
103 /*
104 * fall through - v3 is otherwise equivalent to v2.
105 */
106 case _LINUX_CAPABILITY_VERSION_3:
107 *tocopy = _LINUX_CAPABILITY_U32S_3;
108 break;
109 default:
110 if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
111 return -EFAULT;
112 return -EINVAL;
113 }
114
115 return 0;
116}
117
118/*
119 * For sys_getproccap() and sys_setproccap(), any of the three
120 * capability set pointers may be NULL -- indicating that that set is
121 * uninteresting and/or not to be changed.
122 */
123
124/*
125 * Atomically modify the effective capabilities returning the original
126 * value. No permission check is performed here - it is assumed that the
127 * caller is permitted to set the desired effective capabilities.
128 */
129kernel_cap_t cap_set_effective(const kernel_cap_t pE_new)
130{
131 kernel_cap_t pE_old;
132
133 spin_lock(&task_capability_lock);
134
135 pE_old = current->cap_effective;
136 current->cap_effective = pE_new;
137
138 spin_unlock(&task_capability_lock);
139
140 return pE_old;
141}
142
143EXPORT_SYMBOL(cap_set_effective);
144
145/**
146 * sys_capget - get the capabilities of a given process.
147 * @header: pointer to struct that contains capability version and
148 * target pid data
149 * @dataptr: pointer to struct that contains the effective, permitted,
150 * and inheritable capabilities that are returned
151 *
152 * Returns 0 on success and < 0 on error.
153 */
154asmlinkage long sys_capget(cap_user_header_t header, cap_user_data_t dataptr)
155{
156 int ret = 0;
157 pid_t pid;
158 struct task_struct *target;
159 unsigned tocopy;
160 kernel_cap_t pE, pI, pP;
161
162 ret = cap_validate_magic(header, &tocopy);
163 if (ret != 0)
164 return ret;
165
166 if (get_user(pid, &header->pid))
167 return -EFAULT;
168
169 if (pid < 0)
170 return -EINVAL;
171
172 spin_lock(&task_capability_lock);
173 read_lock(&tasklist_lock);
174
175 if (pid && pid != task_pid_vnr(current)) {
176 target = find_task_by_vpid(pid);
177 if (!target) {
178 ret = -ESRCH;
179 goto out;
180 }
181 } else
182 target = current;
183
184 ret = security_capget(target, &pE, &pI, &pP);
185
186out:
187 read_unlock(&tasklist_lock);
188 spin_unlock(&task_capability_lock);
189
190 if (!ret) {
191 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
192 unsigned i;
193
194 for (i = 0; i < tocopy; i++) {
195 kdata[i].effective = pE.cap[i];
196 kdata[i].permitted = pP.cap[i];
197 kdata[i].inheritable = pI.cap[i];
198 }
199
200 /*
201 * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
202 * we silently drop the upper capabilities here. This
203 * has the effect of making older libcap
204 * implementations implicitly drop upper capability
205 * bits when they perform a: capget/modify/capset
206 * sequence.
207 *
208 * This behavior is considered fail-safe
209 * behavior. Upgrading the application to a newer
210 * version of libcap will enable access to the newer
211 * capabilities.
212 *
213 * An alternative would be to return an error here
214 * (-ERANGE), but that causes legacy applications to
215 * unexpectidly fail; the capget/modify/capset aborts
216 * before modification is attempted and the application
217 * fails.
218 */
219
220 if (copy_to_user(dataptr, kdata, tocopy
221 * sizeof(struct __user_cap_data_struct))) {
222 return -EFAULT;
223 }
224 }
225
226 return ret;
227}
228
229/*
230 * cap_set_pg - set capabilities for all processes in a given process
231 * group. We call this holding task_capability_lock and tasklist_lock.
232 */
233static inline int cap_set_pg(int pgrp_nr, kernel_cap_t *effective,
234 kernel_cap_t *inheritable,
235 kernel_cap_t *permitted)
236{
237 struct task_struct *g, *target;
238 int ret = -EPERM;
239 int found = 0;
240 struct pid *pgrp;
241
242 pgrp = find_vpid(pgrp_nr);
243 do_each_pid_task(pgrp, PIDTYPE_PGID, g) {
244 target = g;
245 while_each_thread(g, target) {
246 if (!security_capset_check(target, effective,
247 inheritable,
248 permitted)) {
249 security_capset_set(target, effective,
250 inheritable,
251 permitted);
252 ret = 0;
253 }
254 found = 1;
255 }
256 } while_each_pid_task(pgrp, PIDTYPE_PGID, g);
257
258 if (!found)
259 ret = 0;
260 return ret;
261}
262
263/*
264 * cap_set_all - set capabilities for all processes other than init
265 * and self. We call this holding task_capability_lock and tasklist_lock.
266 */
267static inline int cap_set_all(kernel_cap_t *effective,
268 kernel_cap_t *inheritable,
269 kernel_cap_t *permitted)
270{
271 struct task_struct *g, *target;
272 int ret = -EPERM;
273 int found = 0;
274
275 do_each_thread(g, target) {
276 if (target == current || is_container_init(target->group_leader))
277 continue;
278 found = 1;
279 if (security_capset_check(target, effective, inheritable,
280 permitted))
281 continue;
282 ret = 0;
283 security_capset_set(target, effective, inheritable, permitted);
284 } while_each_thread(g, target);
285
286 if (!found)
287 ret = 0;
288 return ret;
289}
290
291/**
292 * sys_capset - set capabilities for a process or a group of processes
293 * @header: pointer to struct that contains capability version and
294 * target pid data
295 * @data: pointer to struct that contains the effective, permitted,
296 * and inheritable capabilities
297 *
298 * Set capabilities for a given process, all processes, or all
299 * processes in a given process group.
300 *
301 * The restrictions on setting capabilities are specified as:
302 *
303 * [pid is for the 'target' task. 'current' is the calling task.]
304 *
305 * I: any raised capabilities must be a subset of the (old current) permitted
306 * P: any raised capabilities must be a subset of the (old current) permitted
307 * E: must be set to a subset of (new target) permitted
308 *
309 * Returns 0 on success and < 0 on error.
310 */
311asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data)
312{
313 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
314 unsigned i, tocopy;
315 kernel_cap_t inheritable, permitted, effective;
316 struct task_struct *target;
317 int ret;
318 pid_t pid;
319
320 ret = cap_validate_magic(header, &tocopy);
321 if (ret != 0)
322 return ret;
323
324 if (get_user(pid, &header->pid))
325 return -EFAULT;
326
327 if (pid && pid != task_pid_vnr(current) && !capable(CAP_SETPCAP))
328 return -EPERM;
329
330 if (copy_from_user(&kdata, data, tocopy
331 * sizeof(struct __user_cap_data_struct))) {
332 return -EFAULT;
333 }
334
335 for (i = 0; i < tocopy; i++) {
336 effective.cap[i] = kdata[i].effective;
337 permitted.cap[i] = kdata[i].permitted;
338 inheritable.cap[i] = kdata[i].inheritable;
339 }
340 while (i < _KERNEL_CAPABILITY_U32S) {
341 effective.cap[i] = 0;
342 permitted.cap[i] = 0;
343 inheritable.cap[i] = 0;
344 i++;
345 }
346
347 spin_lock(&task_capability_lock);
348 read_lock(&tasklist_lock);
349
350 if (pid > 0 && pid != task_pid_vnr(current)) {
351 target = find_task_by_vpid(pid);
352 if (!target) {
353 ret = -ESRCH;
354 goto out;
355 }
356 } else
357 target = current;
358
359 ret = 0;
360
361 /* having verified that the proposed changes are legal,
362 we now put them into effect. */
363 if (pid < 0) {
364 if (pid == -1) /* all procs other than current and init */
365 ret = cap_set_all(&effective, &inheritable, &permitted);
366
367 else /* all procs in process group */
368 ret = cap_set_pg(-pid, &effective, &inheritable,
369 &permitted);
370 } else {
371 ret = security_capset_check(target, &effective, &inheritable,
372 &permitted);
373 if (!ret)
374 security_capset_set(target, &effective, &inheritable,
375 &permitted);
376 }
377
378out:
379 read_unlock(&tasklist_lock);
380 spin_unlock(&task_capability_lock);
381
382 return ret;
383}
384
385int __capable(struct task_struct *t, int cap)
386{
387 if (security_capable(t, cap) == 0) {
388 t->flags |= PF_SUPERPRIV;
389 return 1;
390 }
391 return 0;
392}
393
394int capable(int cap)
395{
396 return __capable(current, cap);
397}
398EXPORT_SYMBOL(capable);