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1da177e4 LT |
1 | /* |
2 | * linux/kernel/sys.c | |
3 | * | |
4 | * Copyright (C) 1991, 1992 Linus Torvalds | |
5 | */ | |
6 | ||
7 | #include <linux/config.h> | |
8 | #include <linux/module.h> | |
9 | #include <linux/mm.h> | |
10 | #include <linux/utsname.h> | |
11 | #include <linux/mman.h> | |
12 | #include <linux/smp_lock.h> | |
13 | #include <linux/notifier.h> | |
14 | #include <linux/reboot.h> | |
15 | #include <linux/prctl.h> | |
16 | #include <linux/init.h> | |
17 | #include <linux/highuid.h> | |
18 | #include <linux/fs.h> | |
dc009d92 EB |
19 | #include <linux/kernel.h> |
20 | #include <linux/kexec.h> | |
1da177e4 LT |
21 | #include <linux/workqueue.h> |
22 | #include <linux/device.h> | |
23 | #include <linux/key.h> | |
24 | #include <linux/times.h> | |
25 | #include <linux/posix-timers.h> | |
26 | #include <linux/security.h> | |
27 | #include <linux/dcookies.h> | |
28 | #include <linux/suspend.h> | |
29 | #include <linux/tty.h> | |
7ed20e1a | 30 | #include <linux/signal.h> |
1da177e4 LT |
31 | |
32 | #include <linux/compat.h> | |
33 | #include <linux/syscalls.h> | |
34 | ||
35 | #include <asm/uaccess.h> | |
36 | #include <asm/io.h> | |
37 | #include <asm/unistd.h> | |
38 | ||
39 | #ifndef SET_UNALIGN_CTL | |
40 | # define SET_UNALIGN_CTL(a,b) (-EINVAL) | |
41 | #endif | |
42 | #ifndef GET_UNALIGN_CTL | |
43 | # define GET_UNALIGN_CTL(a,b) (-EINVAL) | |
44 | #endif | |
45 | #ifndef SET_FPEMU_CTL | |
46 | # define SET_FPEMU_CTL(a,b) (-EINVAL) | |
47 | #endif | |
48 | #ifndef GET_FPEMU_CTL | |
49 | # define GET_FPEMU_CTL(a,b) (-EINVAL) | |
50 | #endif | |
51 | #ifndef SET_FPEXC_CTL | |
52 | # define SET_FPEXC_CTL(a,b) (-EINVAL) | |
53 | #endif | |
54 | #ifndef GET_FPEXC_CTL | |
55 | # define GET_FPEXC_CTL(a,b) (-EINVAL) | |
56 | #endif | |
57 | ||
58 | /* | |
59 | * this is where the system-wide overflow UID and GID are defined, for | |
60 | * architectures that now have 32-bit UID/GID but didn't in the past | |
61 | */ | |
62 | ||
63 | int overflowuid = DEFAULT_OVERFLOWUID; | |
64 | int overflowgid = DEFAULT_OVERFLOWGID; | |
65 | ||
66 | #ifdef CONFIG_UID16 | |
67 | EXPORT_SYMBOL(overflowuid); | |
68 | EXPORT_SYMBOL(overflowgid); | |
69 | #endif | |
70 | ||
71 | /* | |
72 | * the same as above, but for filesystems which can only store a 16-bit | |
73 | * UID and GID. as such, this is needed on all architectures | |
74 | */ | |
75 | ||
76 | int fs_overflowuid = DEFAULT_FS_OVERFLOWUID; | |
77 | int fs_overflowgid = DEFAULT_FS_OVERFLOWUID; | |
78 | ||
79 | EXPORT_SYMBOL(fs_overflowuid); | |
80 | EXPORT_SYMBOL(fs_overflowgid); | |
81 | ||
82 | /* | |
83 | * this indicates whether you can reboot with ctrl-alt-del: the default is yes | |
84 | */ | |
85 | ||
86 | int C_A_D = 1; | |
87 | int cad_pid = 1; | |
88 | ||
89 | /* | |
90 | * Notifier list for kernel code which wants to be called | |
91 | * at shutdown. This is used to stop any idling DMA operations | |
92 | * and the like. | |
93 | */ | |
94 | ||
95 | static struct notifier_block *reboot_notifier_list; | |
96 | static DEFINE_RWLOCK(notifier_lock); | |
97 | ||
98 | /** | |
99 | * notifier_chain_register - Add notifier to a notifier chain | |
100 | * @list: Pointer to root list pointer | |
101 | * @n: New entry in notifier chain | |
102 | * | |
103 | * Adds a notifier to a notifier chain. | |
104 | * | |
105 | * Currently always returns zero. | |
106 | */ | |
107 | ||
108 | int notifier_chain_register(struct notifier_block **list, struct notifier_block *n) | |
109 | { | |
110 | write_lock(¬ifier_lock); | |
111 | while(*list) | |
112 | { | |
113 | if(n->priority > (*list)->priority) | |
114 | break; | |
115 | list= &((*list)->next); | |
116 | } | |
117 | n->next = *list; | |
118 | *list=n; | |
119 | write_unlock(¬ifier_lock); | |
120 | return 0; | |
121 | } | |
122 | ||
123 | EXPORT_SYMBOL(notifier_chain_register); | |
124 | ||
125 | /** | |
126 | * notifier_chain_unregister - Remove notifier from a notifier chain | |
127 | * @nl: Pointer to root list pointer | |
128 | * @n: New entry in notifier chain | |
129 | * | |
130 | * Removes a notifier from a notifier chain. | |
131 | * | |
132 | * Returns zero on success, or %-ENOENT on failure. | |
133 | */ | |
134 | ||
135 | int notifier_chain_unregister(struct notifier_block **nl, struct notifier_block *n) | |
136 | { | |
137 | write_lock(¬ifier_lock); | |
138 | while((*nl)!=NULL) | |
139 | { | |
140 | if((*nl)==n) | |
141 | { | |
142 | *nl=n->next; | |
143 | write_unlock(¬ifier_lock); | |
144 | return 0; | |
145 | } | |
146 | nl=&((*nl)->next); | |
147 | } | |
148 | write_unlock(¬ifier_lock); | |
149 | return -ENOENT; | |
150 | } | |
151 | ||
152 | EXPORT_SYMBOL(notifier_chain_unregister); | |
153 | ||
154 | /** | |
155 | * notifier_call_chain - Call functions in a notifier chain | |
156 | * @n: Pointer to root pointer of notifier chain | |
157 | * @val: Value passed unmodified to notifier function | |
158 | * @v: Pointer passed unmodified to notifier function | |
159 | * | |
160 | * Calls each function in a notifier chain in turn. | |
161 | * | |
162 | * If the return value of the notifier can be and'd | |
163 | * with %NOTIFY_STOP_MASK, then notifier_call_chain | |
164 | * will return immediately, with the return value of | |
165 | * the notifier function which halted execution. | |
166 | * Otherwise, the return value is the return value | |
167 | * of the last notifier function called. | |
168 | */ | |
169 | ||
170 | int notifier_call_chain(struct notifier_block **n, unsigned long val, void *v) | |
171 | { | |
172 | int ret=NOTIFY_DONE; | |
173 | struct notifier_block *nb = *n; | |
174 | ||
175 | while(nb) | |
176 | { | |
177 | ret=nb->notifier_call(nb,val,v); | |
178 | if(ret&NOTIFY_STOP_MASK) | |
179 | { | |
180 | return ret; | |
181 | } | |
182 | nb=nb->next; | |
183 | } | |
184 | return ret; | |
185 | } | |
186 | ||
187 | EXPORT_SYMBOL(notifier_call_chain); | |
188 | ||
189 | /** | |
190 | * register_reboot_notifier - Register function to be called at reboot time | |
191 | * @nb: Info about notifier function to be called | |
192 | * | |
193 | * Registers a function with the list of functions | |
194 | * to be called at reboot time. | |
195 | * | |
196 | * Currently always returns zero, as notifier_chain_register | |
197 | * always returns zero. | |
198 | */ | |
199 | ||
200 | int register_reboot_notifier(struct notifier_block * nb) | |
201 | { | |
202 | return notifier_chain_register(&reboot_notifier_list, nb); | |
203 | } | |
204 | ||
205 | EXPORT_SYMBOL(register_reboot_notifier); | |
206 | ||
207 | /** | |
208 | * unregister_reboot_notifier - Unregister previously registered reboot notifier | |
209 | * @nb: Hook to be unregistered | |
210 | * | |
211 | * Unregisters a previously registered reboot | |
212 | * notifier function. | |
213 | * | |
214 | * Returns zero on success, or %-ENOENT on failure. | |
215 | */ | |
216 | ||
217 | int unregister_reboot_notifier(struct notifier_block * nb) | |
218 | { | |
219 | return notifier_chain_unregister(&reboot_notifier_list, nb); | |
220 | } | |
221 | ||
222 | EXPORT_SYMBOL(unregister_reboot_notifier); | |
223 | ||
224 | static int set_one_prio(struct task_struct *p, int niceval, int error) | |
225 | { | |
226 | int no_nice; | |
227 | ||
228 | if (p->uid != current->euid && | |
229 | p->euid != current->euid && !capable(CAP_SYS_NICE)) { | |
230 | error = -EPERM; | |
231 | goto out; | |
232 | } | |
e43379f1 | 233 | if (niceval < task_nice(p) && !can_nice(p, niceval)) { |
1da177e4 LT |
234 | error = -EACCES; |
235 | goto out; | |
236 | } | |
237 | no_nice = security_task_setnice(p, niceval); | |
238 | if (no_nice) { | |
239 | error = no_nice; | |
240 | goto out; | |
241 | } | |
242 | if (error == -ESRCH) | |
243 | error = 0; | |
244 | set_user_nice(p, niceval); | |
245 | out: | |
246 | return error; | |
247 | } | |
248 | ||
249 | asmlinkage long sys_setpriority(int which, int who, int niceval) | |
250 | { | |
251 | struct task_struct *g, *p; | |
252 | struct user_struct *user; | |
253 | int error = -EINVAL; | |
254 | ||
255 | if (which > 2 || which < 0) | |
256 | goto out; | |
257 | ||
258 | /* normalize: avoid signed division (rounding problems) */ | |
259 | error = -ESRCH; | |
260 | if (niceval < -20) | |
261 | niceval = -20; | |
262 | if (niceval > 19) | |
263 | niceval = 19; | |
264 | ||
265 | read_lock(&tasklist_lock); | |
266 | switch (which) { | |
267 | case PRIO_PROCESS: | |
268 | if (!who) | |
269 | who = current->pid; | |
270 | p = find_task_by_pid(who); | |
271 | if (p) | |
272 | error = set_one_prio(p, niceval, error); | |
273 | break; | |
274 | case PRIO_PGRP: | |
275 | if (!who) | |
276 | who = process_group(current); | |
277 | do_each_task_pid(who, PIDTYPE_PGID, p) { | |
278 | error = set_one_prio(p, niceval, error); | |
279 | } while_each_task_pid(who, PIDTYPE_PGID, p); | |
280 | break; | |
281 | case PRIO_USER: | |
282 | user = current->user; | |
283 | if (!who) | |
284 | who = current->uid; | |
285 | else | |
286 | if ((who != current->uid) && !(user = find_user(who))) | |
287 | goto out_unlock; /* No processes for this user */ | |
288 | ||
289 | do_each_thread(g, p) | |
290 | if (p->uid == who) | |
291 | error = set_one_prio(p, niceval, error); | |
292 | while_each_thread(g, p); | |
293 | if (who != current->uid) | |
294 | free_uid(user); /* For find_user() */ | |
295 | break; | |
296 | } | |
297 | out_unlock: | |
298 | read_unlock(&tasklist_lock); | |
299 | out: | |
300 | return error; | |
301 | } | |
302 | ||
303 | /* | |
304 | * Ugh. To avoid negative return values, "getpriority()" will | |
305 | * not return the normal nice-value, but a negated value that | |
306 | * has been offset by 20 (ie it returns 40..1 instead of -20..19) | |
307 | * to stay compatible. | |
308 | */ | |
309 | asmlinkage long sys_getpriority(int which, int who) | |
310 | { | |
311 | struct task_struct *g, *p; | |
312 | struct user_struct *user; | |
313 | long niceval, retval = -ESRCH; | |
314 | ||
315 | if (which > 2 || which < 0) | |
316 | return -EINVAL; | |
317 | ||
318 | read_lock(&tasklist_lock); | |
319 | switch (which) { | |
320 | case PRIO_PROCESS: | |
321 | if (!who) | |
322 | who = current->pid; | |
323 | p = find_task_by_pid(who); | |
324 | if (p) { | |
325 | niceval = 20 - task_nice(p); | |
326 | if (niceval > retval) | |
327 | retval = niceval; | |
328 | } | |
329 | break; | |
330 | case PRIO_PGRP: | |
331 | if (!who) | |
332 | who = process_group(current); | |
333 | do_each_task_pid(who, PIDTYPE_PGID, p) { | |
334 | niceval = 20 - task_nice(p); | |
335 | if (niceval > retval) | |
336 | retval = niceval; | |
337 | } while_each_task_pid(who, PIDTYPE_PGID, p); | |
338 | break; | |
339 | case PRIO_USER: | |
340 | user = current->user; | |
341 | if (!who) | |
342 | who = current->uid; | |
343 | else | |
344 | if ((who != current->uid) && !(user = find_user(who))) | |
345 | goto out_unlock; /* No processes for this user */ | |
346 | ||
347 | do_each_thread(g, p) | |
348 | if (p->uid == who) { | |
349 | niceval = 20 - task_nice(p); | |
350 | if (niceval > retval) | |
351 | retval = niceval; | |
352 | } | |
353 | while_each_thread(g, p); | |
354 | if (who != current->uid) | |
355 | free_uid(user); /* for find_user() */ | |
356 | break; | |
357 | } | |
358 | out_unlock: | |
359 | read_unlock(&tasklist_lock); | |
360 | ||
361 | return retval; | |
362 | } | |
363 | ||
364 | ||
365 | /* | |
366 | * Reboot system call: for obvious reasons only root may call it, | |
367 | * and even root needs to set up some magic numbers in the registers | |
368 | * so that some mistake won't make this reboot the whole machine. | |
369 | * You can also set the meaning of the ctrl-alt-del-key here. | |
370 | * | |
371 | * reboot doesn't sync: do that yourself before calling this. | |
372 | */ | |
373 | asmlinkage long sys_reboot(int magic1, int magic2, unsigned int cmd, void __user * arg) | |
374 | { | |
375 | char buffer[256]; | |
376 | ||
377 | /* We only trust the superuser with rebooting the system. */ | |
378 | if (!capable(CAP_SYS_BOOT)) | |
379 | return -EPERM; | |
380 | ||
381 | /* For safety, we require "magic" arguments. */ | |
382 | if (magic1 != LINUX_REBOOT_MAGIC1 || | |
383 | (magic2 != LINUX_REBOOT_MAGIC2 && | |
384 | magic2 != LINUX_REBOOT_MAGIC2A && | |
385 | magic2 != LINUX_REBOOT_MAGIC2B && | |
386 | magic2 != LINUX_REBOOT_MAGIC2C)) | |
387 | return -EINVAL; | |
388 | ||
389 | lock_kernel(); | |
390 | switch (cmd) { | |
391 | case LINUX_REBOOT_CMD_RESTART: | |
392 | notifier_call_chain(&reboot_notifier_list, SYS_RESTART, NULL); | |
393 | system_state = SYSTEM_RESTART; | |
394 | device_shutdown(); | |
395 | printk(KERN_EMERG "Restarting system.\n"); | |
396 | machine_restart(NULL); | |
397 | break; | |
398 | ||
399 | case LINUX_REBOOT_CMD_CAD_ON: | |
400 | C_A_D = 1; | |
401 | break; | |
402 | ||
403 | case LINUX_REBOOT_CMD_CAD_OFF: | |
404 | C_A_D = 0; | |
405 | break; | |
406 | ||
407 | case LINUX_REBOOT_CMD_HALT: | |
408 | notifier_call_chain(&reboot_notifier_list, SYS_HALT, NULL); | |
409 | system_state = SYSTEM_HALT; | |
620b0327 | 410 | device_suspend(PMSG_SUSPEND); |
1da177e4 LT |
411 | device_shutdown(); |
412 | printk(KERN_EMERG "System halted.\n"); | |
413 | machine_halt(); | |
414 | unlock_kernel(); | |
415 | do_exit(0); | |
416 | break; | |
417 | ||
418 | case LINUX_REBOOT_CMD_POWER_OFF: | |
419 | notifier_call_chain(&reboot_notifier_list, SYS_POWER_OFF, NULL); | |
420 | system_state = SYSTEM_POWER_OFF; | |
620b0327 | 421 | device_suspend(PMSG_SUSPEND); |
1da177e4 LT |
422 | device_shutdown(); |
423 | printk(KERN_EMERG "Power down.\n"); | |
424 | machine_power_off(); | |
425 | unlock_kernel(); | |
426 | do_exit(0); | |
427 | break; | |
428 | ||
429 | case LINUX_REBOOT_CMD_RESTART2: | |
430 | if (strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1) < 0) { | |
431 | unlock_kernel(); | |
432 | return -EFAULT; | |
433 | } | |
434 | buffer[sizeof(buffer) - 1] = '\0'; | |
435 | ||
436 | notifier_call_chain(&reboot_notifier_list, SYS_RESTART, buffer); | |
437 | system_state = SYSTEM_RESTART; | |
620b0327 | 438 | device_suspend(PMSG_FREEZE); |
1da177e4 LT |
439 | device_shutdown(); |
440 | printk(KERN_EMERG "Restarting system with command '%s'.\n", buffer); | |
441 | machine_restart(buffer); | |
442 | break; | |
443 | ||
dc009d92 EB |
444 | #ifdef CONFIG_KEXEC |
445 | case LINUX_REBOOT_CMD_KEXEC: | |
446 | { | |
447 | struct kimage *image; | |
448 | image = xchg(&kexec_image, 0); | |
449 | if (!image) { | |
450 | unlock_kernel(); | |
451 | return -EINVAL; | |
452 | } | |
453 | notifier_call_chain(&reboot_notifier_list, SYS_RESTART, NULL); | |
454 | system_state = SYSTEM_RESTART; | |
455 | device_shutdown(); | |
456 | printk(KERN_EMERG "Starting new kernel\n"); | |
457 | machine_shutdown(); | |
458 | machine_kexec(image); | |
459 | break; | |
460 | } | |
461 | #endif | |
1da177e4 LT |
462 | #ifdef CONFIG_SOFTWARE_SUSPEND |
463 | case LINUX_REBOOT_CMD_SW_SUSPEND: | |
464 | { | |
465 | int ret = software_suspend(); | |
466 | unlock_kernel(); | |
467 | return ret; | |
468 | } | |
469 | #endif | |
470 | ||
471 | default: | |
472 | unlock_kernel(); | |
473 | return -EINVAL; | |
474 | } | |
475 | unlock_kernel(); | |
476 | return 0; | |
477 | } | |
478 | ||
479 | static void deferred_cad(void *dummy) | |
480 | { | |
481 | notifier_call_chain(&reboot_notifier_list, SYS_RESTART, NULL); | |
482 | machine_restart(NULL); | |
483 | } | |
484 | ||
485 | /* | |
486 | * This function gets called by ctrl-alt-del - ie the keyboard interrupt. | |
487 | * As it's called within an interrupt, it may NOT sync: the only choice | |
488 | * is whether to reboot at once, or just ignore the ctrl-alt-del. | |
489 | */ | |
490 | void ctrl_alt_del(void) | |
491 | { | |
492 | static DECLARE_WORK(cad_work, deferred_cad, NULL); | |
493 | ||
494 | if (C_A_D) | |
495 | schedule_work(&cad_work); | |
496 | else | |
497 | kill_proc(cad_pid, SIGINT, 1); | |
498 | } | |
499 | ||
500 | ||
501 | /* | |
502 | * Unprivileged users may change the real gid to the effective gid | |
503 | * or vice versa. (BSD-style) | |
504 | * | |
505 | * If you set the real gid at all, or set the effective gid to a value not | |
506 | * equal to the real gid, then the saved gid is set to the new effective gid. | |
507 | * | |
508 | * This makes it possible for a setgid program to completely drop its | |
509 | * privileges, which is often a useful assertion to make when you are doing | |
510 | * a security audit over a program. | |
511 | * | |
512 | * The general idea is that a program which uses just setregid() will be | |
513 | * 100% compatible with BSD. A program which uses just setgid() will be | |
514 | * 100% compatible with POSIX with saved IDs. | |
515 | * | |
516 | * SMP: There are not races, the GIDs are checked only by filesystem | |
517 | * operations (as far as semantic preservation is concerned). | |
518 | */ | |
519 | asmlinkage long sys_setregid(gid_t rgid, gid_t egid) | |
520 | { | |
521 | int old_rgid = current->gid; | |
522 | int old_egid = current->egid; | |
523 | int new_rgid = old_rgid; | |
524 | int new_egid = old_egid; | |
525 | int retval; | |
526 | ||
527 | retval = security_task_setgid(rgid, egid, (gid_t)-1, LSM_SETID_RE); | |
528 | if (retval) | |
529 | return retval; | |
530 | ||
531 | if (rgid != (gid_t) -1) { | |
532 | if ((old_rgid == rgid) || | |
533 | (current->egid==rgid) || | |
534 | capable(CAP_SETGID)) | |
535 | new_rgid = rgid; | |
536 | else | |
537 | return -EPERM; | |
538 | } | |
539 | if (egid != (gid_t) -1) { | |
540 | if ((old_rgid == egid) || | |
541 | (current->egid == egid) || | |
542 | (current->sgid == egid) || | |
543 | capable(CAP_SETGID)) | |
544 | new_egid = egid; | |
545 | else { | |
546 | return -EPERM; | |
547 | } | |
548 | } | |
549 | if (new_egid != old_egid) | |
550 | { | |
d6e71144 | 551 | current->mm->dumpable = suid_dumpable; |
d59dd462 | 552 | smp_wmb(); |
1da177e4 LT |
553 | } |
554 | if (rgid != (gid_t) -1 || | |
555 | (egid != (gid_t) -1 && egid != old_rgid)) | |
556 | current->sgid = new_egid; | |
557 | current->fsgid = new_egid; | |
558 | current->egid = new_egid; | |
559 | current->gid = new_rgid; | |
560 | key_fsgid_changed(current); | |
561 | return 0; | |
562 | } | |
563 | ||
564 | /* | |
565 | * setgid() is implemented like SysV w/ SAVED_IDS | |
566 | * | |
567 | * SMP: Same implicit races as above. | |
568 | */ | |
569 | asmlinkage long sys_setgid(gid_t gid) | |
570 | { | |
571 | int old_egid = current->egid; | |
572 | int retval; | |
573 | ||
574 | retval = security_task_setgid(gid, (gid_t)-1, (gid_t)-1, LSM_SETID_ID); | |
575 | if (retval) | |
576 | return retval; | |
577 | ||
578 | if (capable(CAP_SETGID)) | |
579 | { | |
580 | if(old_egid != gid) | |
581 | { | |
d6e71144 | 582 | current->mm->dumpable = suid_dumpable; |
d59dd462 | 583 | smp_wmb(); |
1da177e4 LT |
584 | } |
585 | current->gid = current->egid = current->sgid = current->fsgid = gid; | |
586 | } | |
587 | else if ((gid == current->gid) || (gid == current->sgid)) | |
588 | { | |
589 | if(old_egid != gid) | |
590 | { | |
d6e71144 | 591 | current->mm->dumpable = suid_dumpable; |
d59dd462 | 592 | smp_wmb(); |
1da177e4 LT |
593 | } |
594 | current->egid = current->fsgid = gid; | |
595 | } | |
596 | else | |
597 | return -EPERM; | |
598 | ||
599 | key_fsgid_changed(current); | |
600 | return 0; | |
601 | } | |
602 | ||
603 | static int set_user(uid_t new_ruid, int dumpclear) | |
604 | { | |
605 | struct user_struct *new_user; | |
606 | ||
607 | new_user = alloc_uid(new_ruid); | |
608 | if (!new_user) | |
609 | return -EAGAIN; | |
610 | ||
611 | if (atomic_read(&new_user->processes) >= | |
612 | current->signal->rlim[RLIMIT_NPROC].rlim_cur && | |
613 | new_user != &root_user) { | |
614 | free_uid(new_user); | |
615 | return -EAGAIN; | |
616 | } | |
617 | ||
618 | switch_uid(new_user); | |
619 | ||
620 | if(dumpclear) | |
621 | { | |
d6e71144 | 622 | current->mm->dumpable = suid_dumpable; |
d59dd462 | 623 | smp_wmb(); |
1da177e4 LT |
624 | } |
625 | current->uid = new_ruid; | |
626 | return 0; | |
627 | } | |
628 | ||
629 | /* | |
630 | * Unprivileged users may change the real uid to the effective uid | |
631 | * or vice versa. (BSD-style) | |
632 | * | |
633 | * If you set the real uid at all, or set the effective uid to a value not | |
634 | * equal to the real uid, then the saved uid is set to the new effective uid. | |
635 | * | |
636 | * This makes it possible for a setuid program to completely drop its | |
637 | * privileges, which is often a useful assertion to make when you are doing | |
638 | * a security audit over a program. | |
639 | * | |
640 | * The general idea is that a program which uses just setreuid() will be | |
641 | * 100% compatible with BSD. A program which uses just setuid() will be | |
642 | * 100% compatible with POSIX with saved IDs. | |
643 | */ | |
644 | asmlinkage long sys_setreuid(uid_t ruid, uid_t euid) | |
645 | { | |
646 | int old_ruid, old_euid, old_suid, new_ruid, new_euid; | |
647 | int retval; | |
648 | ||
649 | retval = security_task_setuid(ruid, euid, (uid_t)-1, LSM_SETID_RE); | |
650 | if (retval) | |
651 | return retval; | |
652 | ||
653 | new_ruid = old_ruid = current->uid; | |
654 | new_euid = old_euid = current->euid; | |
655 | old_suid = current->suid; | |
656 | ||
657 | if (ruid != (uid_t) -1) { | |
658 | new_ruid = ruid; | |
659 | if ((old_ruid != ruid) && | |
660 | (current->euid != ruid) && | |
661 | !capable(CAP_SETUID)) | |
662 | return -EPERM; | |
663 | } | |
664 | ||
665 | if (euid != (uid_t) -1) { | |
666 | new_euid = euid; | |
667 | if ((old_ruid != euid) && | |
668 | (current->euid != euid) && | |
669 | (current->suid != euid) && | |
670 | !capable(CAP_SETUID)) | |
671 | return -EPERM; | |
672 | } | |
673 | ||
674 | if (new_ruid != old_ruid && set_user(new_ruid, new_euid != old_euid) < 0) | |
675 | return -EAGAIN; | |
676 | ||
677 | if (new_euid != old_euid) | |
678 | { | |
d6e71144 | 679 | current->mm->dumpable = suid_dumpable; |
d59dd462 | 680 | smp_wmb(); |
1da177e4 LT |
681 | } |
682 | current->fsuid = current->euid = new_euid; | |
683 | if (ruid != (uid_t) -1 || | |
684 | (euid != (uid_t) -1 && euid != old_ruid)) | |
685 | current->suid = current->euid; | |
686 | current->fsuid = current->euid; | |
687 | ||
688 | key_fsuid_changed(current); | |
689 | ||
690 | return security_task_post_setuid(old_ruid, old_euid, old_suid, LSM_SETID_RE); | |
691 | } | |
692 | ||
693 | ||
694 | ||
695 | /* | |
696 | * setuid() is implemented like SysV with SAVED_IDS | |
697 | * | |
698 | * Note that SAVED_ID's is deficient in that a setuid root program | |
699 | * like sendmail, for example, cannot set its uid to be a normal | |
700 | * user and then switch back, because if you're root, setuid() sets | |
701 | * the saved uid too. If you don't like this, blame the bright people | |
702 | * in the POSIX committee and/or USG. Note that the BSD-style setreuid() | |
703 | * will allow a root program to temporarily drop privileges and be able to | |
704 | * regain them by swapping the real and effective uid. | |
705 | */ | |
706 | asmlinkage long sys_setuid(uid_t uid) | |
707 | { | |
708 | int old_euid = current->euid; | |
709 | int old_ruid, old_suid, new_ruid, new_suid; | |
710 | int retval; | |
711 | ||
712 | retval = security_task_setuid(uid, (uid_t)-1, (uid_t)-1, LSM_SETID_ID); | |
713 | if (retval) | |
714 | return retval; | |
715 | ||
716 | old_ruid = new_ruid = current->uid; | |
717 | old_suid = current->suid; | |
718 | new_suid = old_suid; | |
719 | ||
720 | if (capable(CAP_SETUID)) { | |
721 | if (uid != old_ruid && set_user(uid, old_euid != uid) < 0) | |
722 | return -EAGAIN; | |
723 | new_suid = uid; | |
724 | } else if ((uid != current->uid) && (uid != new_suid)) | |
725 | return -EPERM; | |
726 | ||
727 | if (old_euid != uid) | |
728 | { | |
d6e71144 | 729 | current->mm->dumpable = suid_dumpable; |
d59dd462 | 730 | smp_wmb(); |
1da177e4 LT |
731 | } |
732 | current->fsuid = current->euid = uid; | |
733 | current->suid = new_suid; | |
734 | ||
735 | key_fsuid_changed(current); | |
736 | ||
737 | return security_task_post_setuid(old_ruid, old_euid, old_suid, LSM_SETID_ID); | |
738 | } | |
739 | ||
740 | ||
741 | /* | |
742 | * This function implements a generic ability to update ruid, euid, | |
743 | * and suid. This allows you to implement the 4.4 compatible seteuid(). | |
744 | */ | |
745 | asmlinkage long sys_setresuid(uid_t ruid, uid_t euid, uid_t suid) | |
746 | { | |
747 | int old_ruid = current->uid; | |
748 | int old_euid = current->euid; | |
749 | int old_suid = current->suid; | |
750 | int retval; | |
751 | ||
752 | retval = security_task_setuid(ruid, euid, suid, LSM_SETID_RES); | |
753 | if (retval) | |
754 | return retval; | |
755 | ||
756 | if (!capable(CAP_SETUID)) { | |
757 | if ((ruid != (uid_t) -1) && (ruid != current->uid) && | |
758 | (ruid != current->euid) && (ruid != current->suid)) | |
759 | return -EPERM; | |
760 | if ((euid != (uid_t) -1) && (euid != current->uid) && | |
761 | (euid != current->euid) && (euid != current->suid)) | |
762 | return -EPERM; | |
763 | if ((suid != (uid_t) -1) && (suid != current->uid) && | |
764 | (suid != current->euid) && (suid != current->suid)) | |
765 | return -EPERM; | |
766 | } | |
767 | if (ruid != (uid_t) -1) { | |
768 | if (ruid != current->uid && set_user(ruid, euid != current->euid) < 0) | |
769 | return -EAGAIN; | |
770 | } | |
771 | if (euid != (uid_t) -1) { | |
772 | if (euid != current->euid) | |
773 | { | |
d6e71144 | 774 | current->mm->dumpable = suid_dumpable; |
d59dd462 | 775 | smp_wmb(); |
1da177e4 LT |
776 | } |
777 | current->euid = euid; | |
778 | } | |
779 | current->fsuid = current->euid; | |
780 | if (suid != (uid_t) -1) | |
781 | current->suid = suid; | |
782 | ||
783 | key_fsuid_changed(current); | |
784 | ||
785 | return security_task_post_setuid(old_ruid, old_euid, old_suid, LSM_SETID_RES); | |
786 | } | |
787 | ||
788 | asmlinkage long sys_getresuid(uid_t __user *ruid, uid_t __user *euid, uid_t __user *suid) | |
789 | { | |
790 | int retval; | |
791 | ||
792 | if (!(retval = put_user(current->uid, ruid)) && | |
793 | !(retval = put_user(current->euid, euid))) | |
794 | retval = put_user(current->suid, suid); | |
795 | ||
796 | return retval; | |
797 | } | |
798 | ||
799 | /* | |
800 | * Same as above, but for rgid, egid, sgid. | |
801 | */ | |
802 | asmlinkage long sys_setresgid(gid_t rgid, gid_t egid, gid_t sgid) | |
803 | { | |
804 | int retval; | |
805 | ||
806 | retval = security_task_setgid(rgid, egid, sgid, LSM_SETID_RES); | |
807 | if (retval) | |
808 | return retval; | |
809 | ||
810 | if (!capable(CAP_SETGID)) { | |
811 | if ((rgid != (gid_t) -1) && (rgid != current->gid) && | |
812 | (rgid != current->egid) && (rgid != current->sgid)) | |
813 | return -EPERM; | |
814 | if ((egid != (gid_t) -1) && (egid != current->gid) && | |
815 | (egid != current->egid) && (egid != current->sgid)) | |
816 | return -EPERM; | |
817 | if ((sgid != (gid_t) -1) && (sgid != current->gid) && | |
818 | (sgid != current->egid) && (sgid != current->sgid)) | |
819 | return -EPERM; | |
820 | } | |
821 | if (egid != (gid_t) -1) { | |
822 | if (egid != current->egid) | |
823 | { | |
d6e71144 | 824 | current->mm->dumpable = suid_dumpable; |
d59dd462 | 825 | smp_wmb(); |
1da177e4 LT |
826 | } |
827 | current->egid = egid; | |
828 | } | |
829 | current->fsgid = current->egid; | |
830 | if (rgid != (gid_t) -1) | |
831 | current->gid = rgid; | |
832 | if (sgid != (gid_t) -1) | |
833 | current->sgid = sgid; | |
834 | ||
835 | key_fsgid_changed(current); | |
836 | return 0; | |
837 | } | |
838 | ||
839 | asmlinkage long sys_getresgid(gid_t __user *rgid, gid_t __user *egid, gid_t __user *sgid) | |
840 | { | |
841 | int retval; | |
842 | ||
843 | if (!(retval = put_user(current->gid, rgid)) && | |
844 | !(retval = put_user(current->egid, egid))) | |
845 | retval = put_user(current->sgid, sgid); | |
846 | ||
847 | return retval; | |
848 | } | |
849 | ||
850 | ||
851 | /* | |
852 | * "setfsuid()" sets the fsuid - the uid used for filesystem checks. This | |
853 | * is used for "access()" and for the NFS daemon (letting nfsd stay at | |
854 | * whatever uid it wants to). It normally shadows "euid", except when | |
855 | * explicitly set by setfsuid() or for access.. | |
856 | */ | |
857 | asmlinkage long sys_setfsuid(uid_t uid) | |
858 | { | |
859 | int old_fsuid; | |
860 | ||
861 | old_fsuid = current->fsuid; | |
862 | if (security_task_setuid(uid, (uid_t)-1, (uid_t)-1, LSM_SETID_FS)) | |
863 | return old_fsuid; | |
864 | ||
865 | if (uid == current->uid || uid == current->euid || | |
866 | uid == current->suid || uid == current->fsuid || | |
867 | capable(CAP_SETUID)) | |
868 | { | |
869 | if (uid != old_fsuid) | |
870 | { | |
d6e71144 | 871 | current->mm->dumpable = suid_dumpable; |
d59dd462 | 872 | smp_wmb(); |
1da177e4 LT |
873 | } |
874 | current->fsuid = uid; | |
875 | } | |
876 | ||
877 | key_fsuid_changed(current); | |
878 | ||
879 | security_task_post_setuid(old_fsuid, (uid_t)-1, (uid_t)-1, LSM_SETID_FS); | |
880 | ||
881 | return old_fsuid; | |
882 | } | |
883 | ||
884 | /* | |
885 |