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1da177e4 LT |
1 | /* |
2 | * linux/kernel/capability.c | |
3 | * | |
4 | * Copyright (C) 1997 Andrew Main <zefram@fysh.org> | |
5 | * | |
72c2d582 | 6 | * Integrated into 2.1.97+, Andrew G. Morgan <morgan@kernel.org> |
1da177e4 | 7 | * 30 May 2002: Cleanup, Robert M. Love <rml@tech9.net> |
314f70fd | 8 | */ |
1da177e4 | 9 | |
c59ede7b | 10 | #include <linux/capability.h> |
1da177e4 LT |
11 | #include <linux/mm.h> |
12 | #include <linux/module.h> | |
13 | #include <linux/security.h> | |
14 | #include <linux/syscalls.h> | |
b460cbc5 | 15 | #include <linux/pid_namespace.h> |
1da177e4 LT |
16 | #include <asm/uaccess.h> |
17 | ||
1da177e4 LT |
18 | /* |
19 | * This lock protects task->cap_* for all tasks including current. | |
20 | * Locking rule: acquire this prior to tasklist_lock. | |
21 | */ | |
22 | static DEFINE_SPINLOCK(task_capability_lock); | |
23 | ||
e338d263 AM |
24 | /* |
25 | * Leveraged for setting/resetting capabilities | |
26 | */ | |
27 | ||
28 | const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET; | |
29 | const kernel_cap_t __cap_full_set = CAP_FULL_SET; | |
30 | const kernel_cap_t __cap_init_eff_set = CAP_INIT_EFF_SET; | |
31 | ||
32 | EXPORT_SYMBOL(__cap_empty_set); | |
33 | EXPORT_SYMBOL(__cap_full_set); | |
34 | EXPORT_SYMBOL(__cap_init_eff_set); | |
35 | ||
1f29fae2 SH |
36 | #ifdef CONFIG_SECURITY_FILE_CAPABILITIES |
37 | int file_caps_enabled = 1; | |
38 | ||
39 | static int __init file_caps_disable(char *str) | |
40 | { | |
41 | file_caps_enabled = 0; | |
42 | return 1; | |
43 | } | |
44 | __setup("no_file_caps", file_caps_disable); | |
45 | #endif | |
46 | ||
e338d263 AM |
47 | /* |
48 | * More recent versions of libcap are available from: | |
49 | * | |
50 | * http://www.kernel.org/pub/linux/libs/security/linux-privs/ | |
51 | */ | |
52 | ||
53 | static void warn_legacy_capability_use(void) | |
54 | { | |
55 | static int warned; | |
56 | if (!warned) { | |
57 | char name[sizeof(current->comm)]; | |
58 | ||
59 | printk(KERN_INFO "warning: `%s' uses 32-bit capabilities" | |
60 | " (legacy support in use)\n", | |
61 | get_task_comm(name, current)); | |
62 | warned = 1; | |
63 | } | |
64 | } | |
65 | ||
ca05a99a AM |
66 | /* |
67 | * Version 2 capabilities worked fine, but the linux/capability.h file | |
68 | * that accompanied their introduction encouraged their use without | |
69 | * the necessary user-space source code changes. As such, we have | |
70 | * created a version 3 with equivalent functionality to version 2, but | |
71 | * with a header change to protect legacy source code from using | |
72 | * version 2 when it wanted to use version 1. If your system has code | |
73 | * that trips the following warning, it is using version 2 specific | |
74 | * capabilities and may be doing so insecurely. | |
75 | * | |
76 | * The remedy is to either upgrade your version of libcap (to 2.10+, | |
77 | * if the application is linked against it), or recompile your | |
78 | * application with modern kernel headers and this warning will go | |
79 | * away. | |
80 | */ | |
81 | ||
82 | static void warn_deprecated_v2(void) | |
83 | { | |
84 | static int warned; | |
85 | ||
86 | if (!warned) { | |
87 | char name[sizeof(current->comm)]; | |
88 | ||
89 | printk(KERN_INFO "warning: `%s' uses deprecated v2" | |
90 | " capabilities in a way that may be insecure.\n", | |
91 | get_task_comm(name, current)); | |
92 | warned = 1; | |
93 | } | |
94 | } | |
95 | ||
96 | /* | |
97 | * Version check. Return the number of u32s in each capability flag | |
98 | * array, or a negative value on error. | |
99 | */ | |
100 | static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy) | |
101 | { | |
102 | __u32 version; | |
103 | ||
104 | if (get_user(version, &header->version)) | |
105 | return -EFAULT; | |
106 | ||
107 | switch (version) { | |
108 | case _LINUX_CAPABILITY_VERSION_1: | |
109 | warn_legacy_capability_use(); | |
110 | *tocopy = _LINUX_CAPABILITY_U32S_1; | |
111 | break; | |
112 | case _LINUX_CAPABILITY_VERSION_2: | |
113 | warn_deprecated_v2(); | |
114 | /* | |
115 | * fall through - v3 is otherwise equivalent to v2. | |
116 | */ | |
117 | case _LINUX_CAPABILITY_VERSION_3: | |
118 | *tocopy = _LINUX_CAPABILITY_U32S_3; | |
119 | break; | |
120 | default: | |
121 | if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version)) | |
122 | return -EFAULT; | |
123 | return -EINVAL; | |
124 | } | |
125 | ||
126 | return 0; | |
127 | } | |
128 | ||
ab763c71 AM |
129 | #ifndef CONFIG_SECURITY_FILE_CAPABILITIES |
130 | ||
131 | /* | |
132 | * Without filesystem capability support, we nominally support one process | |
133 | * setting the capabilities of another | |
134 | */ | |
135 | static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp, | |
136 | kernel_cap_t *pIp, kernel_cap_t *pPp) | |
137 | { | |
138 | struct task_struct *target; | |
139 | int ret; | |
140 | ||
141 | spin_lock(&task_capability_lock); | |
142 | read_lock(&tasklist_lock); | |
143 | ||
144 | if (pid && pid != task_pid_vnr(current)) { | |
145 | target = find_task_by_vpid(pid); | |
146 | if (!target) { | |
147 | ret = -ESRCH; | |
148 | goto out; | |
149 | } | |
150 | } else | |
151 | target = current; | |
152 | ||
153 | ret = security_capget(target, pEp, pIp, pPp); | |
154 | ||
155 | out: | |
156 | read_unlock(&tasklist_lock); | |
157 | spin_unlock(&task_capability_lock); | |
158 | ||
159 | return ret; | |
160 | } | |
161 | ||
162 | /* | |
163 | * cap_set_pg - set capabilities for all processes in a given process | |
164 | * group. We call this holding task_capability_lock and tasklist_lock. | |
165 | */ | |
166 | static inline int cap_set_pg(int pgrp_nr, kernel_cap_t *effective, | |
167 | kernel_cap_t *inheritable, | |
168 | kernel_cap_t *permitted) | |
169 | { | |
170 | struct task_struct *g, *target; | |
171 | int ret = -EPERM; | |
172 | int found = 0; | |
173 | struct pid *pgrp; | |
174 | ||
175 | spin_lock(&task_capability_lock); | |
176 | read_lock(&tasklist_lock); | |
177 | ||
178 | pgrp = find_vpid(pgrp_nr); | |
179 | do_each_pid_task(pgrp, PIDTYPE_PGID, g) { | |
180 | target = g; | |
181 | while_each_thread(g, target) { | |
182 | if (!security_capset_check(target, effective, | |
183 | inheritable, permitted)) { | |
184 | security_capset_set(target, effective, | |
185 | inheritable, permitted); | |
186 | ret = 0; | |
187 | } | |
188 | found = 1; | |
189 | } | |
190 | } while_each_pid_task(pgrp, PIDTYPE_PGID, g); | |
191 | ||
192 | read_unlock(&tasklist_lock); | |
193 | spin_unlock(&task_capability_lock); | |
194 | ||
195 | if (!found) | |
196 | ret = 0; | |
197 | return ret; | |
198 | } | |
199 | ||
1da177e4 | 200 | /* |
ab763c71 AM |
201 | * cap_set_all - set capabilities for all processes other than init |
202 | * and self. We call this holding task_capability_lock and tasklist_lock. | |
1da177e4 | 203 | */ |
ab763c71 AM |
204 | static inline int cap_set_all(kernel_cap_t *effective, |
205 | kernel_cap_t *inheritable, | |
206 | kernel_cap_t *permitted) | |
207 | { | |
208 | struct task_struct *g, *target; | |
209 | int ret = -EPERM; | |
210 | int found = 0; | |
211 | ||
212 | spin_lock(&task_capability_lock); | |
213 | read_lock(&tasklist_lock); | |
214 | ||
215 | do_each_thread(g, target) { | |
216 | if (target == current | |
217 | || is_container_init(target->group_leader)) | |
218 | continue; | |
219 | found = 1; | |
220 | if (security_capset_check(target, effective, inheritable, | |
221 | permitted)) | |
222 | continue; | |
223 | ret = 0; | |
224 | security_capset_set(target, effective, inheritable, permitted); | |
225 | } while_each_thread(g, target); | |
226 | ||
227 | read_unlock(&tasklist_lock); | |
228 | spin_unlock(&task_capability_lock); | |
229 | ||
230 | if (!found) | |
231 | ret = 0; | |
232 | ||
233 | return ret; | |
234 | } | |
235 | ||
236 | /* | |
237 | * Given the target pid does not refer to the current process we | |
238 | * need more elaborate support... (This support is not present when | |
239 | * filesystem capabilities are configured.) | |
240 | */ | |
241 | static inline int do_sys_capset_other_tasks(pid_t pid, kernel_cap_t *effective, | |
242 | kernel_cap_t *inheritable, | |
243 | kernel_cap_t *permitted) | |
244 | { | |
245 | struct task_struct *target; | |
246 | int ret; | |
247 | ||
248 | if (!capable(CAP_SETPCAP)) | |
249 | return -EPERM; | |
250 | ||
251 | if (pid == -1) /* all procs other than current and init */ | |
252 | return cap_set_all(effective, inheritable, permitted); | |
253 | ||
254 | else if (pid < 0) /* all procs in process group */ | |
255 | return cap_set_pg(-pid, effective, inheritable, permitted); | |
256 | ||
257 | /* target != current */ | |
258 | spin_lock(&task_capability_lock); | |
259 | read_lock(&tasklist_lock); | |
260 | ||
261 | target = find_task_by_vpid(pid); | |
262 | if (!target) | |
263 | ret = -ESRCH; | |
264 | else { | |
265 | ret = security_capset_check(target, effective, inheritable, | |
266 | permitted); | |
267 | ||
268 | /* having verified that the proposed changes are legal, | |
269 | we now put them into effect. */ | |
270 | if (!ret) | |
271 | security_capset_set(target, effective, inheritable, | |
272 | permitted); | |
273 | } | |
274 | ||
275 | read_unlock(&tasklist_lock); | |
276 | spin_unlock(&task_capability_lock); | |
277 | ||
278 | return ret; | |
279 | } | |
280 | ||
281 | #else /* ie., def CONFIG_SECURITY_FILE_CAPABILITIES */ | |
282 | ||
283 | /* | |
284 | * If we have configured with filesystem capability support, then the | |
285 | * only thing that can change the capabilities of the current process | |
286 | * is the current process. As such, we can't be in this code at the | |
287 | * same time as we are in the process of setting capabilities in this | |
288 | * process. The net result is that we can limit our use of locks to | |
289 | * when we are reading the caps of another process. | |
290 | */ | |
291 | static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp, | |
292 | kernel_cap_t *pIp, kernel_cap_t *pPp) | |
293 | { | |
294 | int ret; | |
295 | ||
296 | if (pid && (pid != task_pid_vnr(current))) { | |
297 | struct task_struct *target; | |
298 | ||
299 | spin_lock(&task_capability_lock); | |
300 | read_lock(&tasklist_lock); | |
301 | ||
302 | target = find_task_by_vpid(pid); | |
303 | if (!target) | |
304 | ret = -ESRCH; | |
305 | else | |
306 | ret = security_capget(target, pEp, pIp, pPp); | |
307 | ||
308 | read_unlock(&tasklist_lock); | |
309 | spin_unlock(&task_capability_lock); | |
310 | } else | |
311 | ret = security_capget(current, pEp, pIp, pPp); | |
312 | ||
313 | return ret; | |
314 | } | |
315 | ||
316 | /* | |
317 | * With filesystem capability support configured, the kernel does not | |
318 | * permit the changing of capabilities in one process by another | |
319 | * process. (CAP_SETPCAP has much less broad semantics when configured | |
320 | * this way.) | |
321 | */ | |
322 | static inline int do_sys_capset_other_tasks(pid_t pid, | |
323 | kernel_cap_t *effective, | |
324 | kernel_cap_t *inheritable, | |
325 | kernel_cap_t *permitted) | |
326 | { | |
327 | return -EPERM; | |
328 | } | |
329 | ||
330 | #endif /* ie., ndef CONFIG_SECURITY_FILE_CAPABILITIES */ | |
1da177e4 | 331 | |
086f7316 AM |
332 | /* |
333 | * Atomically modify the effective capabilities returning the original | |
334 | * value. No permission check is performed here - it is assumed that the | |
335 | * caller is permitted to set the desired effective capabilities. | |
336 | */ | |
337 | kernel_cap_t cap_set_effective(const kernel_cap_t pE_new) | |
338 | { | |
339 | kernel_cap_t pE_old; | |
340 | ||
341 | spin_lock(&task_capability_lock); | |
342 | ||
343 | pE_old = current->cap_effective; | |
344 | current->cap_effective = pE_new; | |
345 | ||
346 | spin_unlock(&task_capability_lock); | |
347 | ||
348 | return pE_old; | |
349 | } | |
350 | ||
351 | EXPORT_SYMBOL(cap_set_effective); | |
352 | ||
207a7ba8 | 353 | /** |
1da177e4 | 354 | * sys_capget - get the capabilities of a given process. |
207a7ba8 RD |
355 | * @header: pointer to struct that contains capability version and |
356 | * target pid data | |
357 | * @dataptr: pointer to struct that contains the effective, permitted, | |
358 | * and inheritable capabilities that are returned | |
359 | * | |
360 | * Returns 0 on success and < 0 on error. | |
1da177e4 LT |
361 | */ |
362 | asmlinkage long sys_capget(cap_user_header_t header, cap_user_data_t dataptr) | |
363 | { | |
314f70fd DW |
364 | int ret = 0; |
365 | pid_t pid; | |
e338d263 AM |
366 | unsigned tocopy; |
367 | kernel_cap_t pE, pI, pP; | |
314f70fd | 368 | |
ca05a99a AM |
369 | ret = cap_validate_magic(header, &tocopy); |
370 | if (ret != 0) | |
371 | return ret; | |
1da177e4 | 372 | |
314f70fd DW |
373 | if (get_user(pid, &header->pid)) |
374 | return -EFAULT; | |
1da177e4 | 375 | |
314f70fd DW |
376 | if (pid < 0) |
377 | return -EINVAL; | |
1da177e4 | 378 | |
ab763c71 | 379 | ret = cap_get_target_pid(pid, &pE, &pI, &pP); |
1da177e4 | 380 | |
e338d263 | 381 | if (!ret) { |
ca05a99a | 382 | struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S]; |
e338d263 AM |
383 | unsigned i; |
384 | ||
385 | for (i = 0; i < tocopy; i++) { | |
386 | kdata[i].effective = pE.cap[i]; | |
387 | kdata[i].permitted = pP.cap[i]; | |
388 | kdata[i].inheritable = pI.cap[i]; | |
389 | } | |
390 | ||
391 | /* | |
ca05a99a | 392 | * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S, |
e338d263 AM |
393 | * we silently drop the upper capabilities here. This |
394 | * has the effect of making older libcap | |
395 | * implementations implicitly drop upper capability | |
396 | * bits when they perform a: capget/modify/capset | |
397 | * sequence. | |
398 | * | |
399 | * This behavior is considered fail-safe | |
400 | * behavior. Upgrading the application to a newer | |
401 | * version of libcap will enable access to the newer | |
402 | * capabilities. | |
403 | * | |
404 | * An alternative would be to return an error here | |
405 | * (-ERANGE), but that causes legacy applications to | |
406 | * unexpectidly fail; the capget/modify/capset aborts | |
407 | * before modification is attempted and the application | |
408 | * fails. | |
409 | */ | |
e338d263 AM |
410 | if (copy_to_user(dataptr, kdata, tocopy |
411 | * sizeof(struct __user_cap_data_struct))) { | |
412 | return -EFAULT; | |
413 | } | |
414 | } | |
1da177e4 | 415 | |
314f70fd | 416 | return ret; |
1da177e4 LT |
417 | } |
418 | ||
207a7ba8 | 419 | /** |
ab763c71 | 420 | * sys_capset - set capabilities for a process or (*) a group of processes |
207a7ba8 RD |
421 | * @header: pointer to struct that contains capability version and |
422 | * target pid data | |
423 | * @data: pointer to struct that contains the effective, permitted, | |
424 | * and inheritable capabilities | |
425 | * | |
426 | * Set capabilities for a given process, all processes, or all | |
1da177e4 LT |
427 | * processes in a given process group. |
428 | * | |
429 | * The restrictions on setting capabilities are specified as: | |
430 | * | |
431 | * [pid is for the 'target' task. 'current' is the calling task.] | |
432 | * | |
433 | * I: any raised capabilities must be a subset of the (old current) permitted | |
434 | * P: any raised capabilities must be a subset of the (old current) permitted | |
435 | * E: must be set to a subset of (new target) permitted | |
207a7ba8 RD |
436 | * |
437 | * Returns 0 on success and < 0 on error. | |
1da177e4 LT |
438 | */ |
439 | asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data) | |
440 | { | |
ca05a99a | 441 | struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S]; |
e338d263 | 442 | unsigned i, tocopy; |
314f70fd | 443 | kernel_cap_t inheritable, permitted, effective; |
314f70fd DW |
444 | int ret; |
445 | pid_t pid; | |
446 | ||
ca05a99a AM |
447 | ret = cap_validate_magic(header, &tocopy); |
448 | if (ret != 0) | |
449 | return ret; | |
314f70fd DW |
450 | |
451 | if (get_user(pid, &header->pid)) | |
452 | return -EFAULT; | |
453 | ||
e338d263 AM |
454 | if (copy_from_user(&kdata, data, tocopy |
455 | * sizeof(struct __user_cap_data_struct))) { | |
314f70fd | 456 | return -EFAULT; |
e338d263 AM |
457 | } |
458 | ||
459 | for (i = 0; i < tocopy; i++) { | |
460 | effective.cap[i] = kdata[i].effective; | |
461 | permitted.cap[i] = kdata[i].permitted; | |
462 | inheritable.cap[i] = kdata[i].inheritable; | |
463 | } | |
ca05a99a | 464 | while (i < _KERNEL_CAPABILITY_U32S) { |
e338d263 AM |
465 | effective.cap[i] = 0; |
466 | permitted.cap[i] = 0; | |
467 | inheritable.cap[i] = 0; | |
468 | i++; | |
469 | } | |
314f70fd | 470 | |
ab763c71 AM |
471 | if (pid && (pid != task_pid_vnr(current))) |
472 | ret = do_sys_capset_other_tasks(pid, &effective, &inheritable, | |
473 | &permitted); | |
474 | else { | |
475 | /* | |
476 | * This lock is required even when filesystem | |
477 | * capability support is configured - it protects the | |
478 | * sys_capget() call from returning incorrect data in | |
479 | * the case that the targeted process is not the | |
480 | * current one. | |
481 | */ | |
482 | spin_lock(&task_capability_lock); | |
314f70fd | 483 | |
ab763c71 | 484 | ret = security_capset_check(current, &effective, &inheritable, |
314f70fd | 485 | &permitted); |
ab763c71 AM |
486 | /* |
487 | * Having verified that the proposed changes are | |
488 | * legal, we now put them into effect. | |
489 | */ | |
314f70fd | 490 | if (!ret) |
ab763c71 | 491 | security_capset_set(current, &effective, &inheritable, |
314f70fd | 492 | &permitted); |
ab763c71 | 493 | spin_unlock(&task_capability_lock); |
314f70fd | 494 | } |
1da177e4 | 495 | |
1da177e4 | 496 | |
314f70fd | 497 | return ret; |
1da177e4 | 498 | } |
12b5989b | 499 | |
5cd9c58f DH |
500 | /** |
501 | * capable - Determine if the current task has a superior capability in effect | |
502 | * @cap: The capability to be tested for | |
503 | * | |
504 | * Return true if the current task has the given superior capability currently | |
505 | * available for use, false if not. | |
506 | * | |
507 | * This sets PF_SUPERPRIV on the task if the capability is available on the | |
508 | * assumption that it's about to be used. | |
509 | */ | |
510 | int capable(int cap) | |
12b5989b | 511 | { |
5cd9c58f DH |
512 | if (has_capability(current, cap)) { |
513 | current->flags |= PF_SUPERPRIV; | |
12b5989b CW |
514 | return 1; |
515 | } | |
516 | return 0; | |
517 | } | |
12b5989b | 518 | EXPORT_SYMBOL(capable); |