projects/linux·blob v3.5-rc1 · refs

681 lines · 17.7 KiB

1/*
2 kmod, the new module loader (replaces kerneld)
3 Kirk Petersen
4
5 Reorganized not to be a daemon by Adam Richter, with guidance
6 from Greg Zornetzer.
7
8 Modified to avoid chroot and file sharing problems.
9 Mikael Pettersson
10
11 Limit the concurrent number of kmod modprobes to catch loops from
12 "modprobe needs a service that is in a module".
13 Keith Owens <[email protected]> December 1999
14
15 Unblock all signals when we exec a usermode process.
16 Shuu Yamaguchi <[email protected]> December 2000
17
18 call_usermodehelper wait flag, and remove exec_usermodehelper.
19 Rusty Russell <[email protected]> Jan 2003
20*/
21#include <linux/module.h>
22#include <linux/sched.h>
23#include <linux/syscalls.h>
24#include <linux/unistd.h>
25#include <linux/kmod.h>
26#include <linux/slab.h>
27#include <linux/completion.h>
28#include <linux/cred.h>
29#include <linux/file.h>
30#include <linux/fdtable.h>
31#include <linux/workqueue.h>
32#include <linux/security.h>
33#include <linux/mount.h>
34#include <linux/kernel.h>
35#include <linux/init.h>
36#include <linux/resource.h>
37#include <linux/notifier.h>
38#include <linux/suspend.h>
39#include <linux/rwsem.h>
40#include <asm/uaccess.h>
41
42#include <trace/events/module.h>
43
44extern int max_threads;
45
46static struct workqueue_struct *khelper_wq;
47
48#define CAP_BSET (void *)1
49#define CAP_PI (void *)2
50
51static kernel_cap_t usermodehelper_bset = CAP_FULL_SET;
52static kernel_cap_t usermodehelper_inheritable = CAP_FULL_SET;
53static DEFINE_SPINLOCK(umh_sysctl_lock);
54static DECLARE_RWSEM(umhelper_sem);
55
56#ifdef CONFIG_MODULES
57
58/*
59 modprobe_path is set via /proc/sys.
60*/
61char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
62
63static void free_modprobe_argv(struct subprocess_info *info)
64{
65 kfree(info->argv[3]); /* check call_modprobe() */
66 kfree(info->argv);
67}
68
69static int call_modprobe(char *module_name, int wait)
70{
71 static char *envp[] = {
72 "HOME=/",
73 "TERM=linux",
74 "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
75 NULL
76 };
77
78 char **argv = kmalloc(sizeof(char *[5]), GFP_KERNEL);
79 if (!argv)
80 goto out;
81
82 module_name = kstrdup(module_name, GFP_KERNEL);
83 if (!module_name)
84 goto free_argv;
85
86 argv[0] = modprobe_path;
87 argv[1] = "-q";
88 argv[2] = "--";
89 argv[3] = module_name; /* check free_modprobe_argv() */
90 argv[4] = NULL;
91
92 return call_usermodehelper_fns(modprobe_path, argv, envp,
93 wait | UMH_KILLABLE, NULL, free_modprobe_argv, NULL);
94free_argv:
95 kfree(argv);
96out:
97 return -ENOMEM;
98}
99
100/**
101 * __request_module - try to load a kernel module
102 * @wait: wait (or not) for the operation to complete
103 * @fmt: printf style format string for the name of the module
104 * @...: arguments as specified in the format string
105 *
106 * Load a module using the user mode module loader. The function returns
107 * zero on success or a negative errno code on failure. Note that a
108 * successful module load does not mean the module did not then unload
109 * and exit on an error of its own. Callers must check that the service
110 * they requested is now available not blindly invoke it.
111 *
112 * If module auto-loading support is disabled then this function
113 * becomes a no-operation.
114 */
115int __request_module(bool wait, const char *fmt, ...)
116{
117 va_list args;
118 char module_name[MODULE_NAME_LEN];
119 unsigned int max_modprobes;
120 int ret;
121 static atomic_t kmod_concurrent = ATOMIC_INIT(0);
122#define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */
123 static int kmod_loop_msg;
124
125 va_start(args, fmt);
126 ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
127 va_end(args);
128 if (ret >= MODULE_NAME_LEN)
129 return -ENAMETOOLONG;
130
131 ret = security_kernel_module_request(module_name);
132 if (ret)
133 return ret;
134
135 /* If modprobe needs a service that is in a module, we get a recursive
136 * loop. Limit the number of running kmod threads to max_threads/2 or
137 * MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method
138 * would be to run the parents of this process, counting how many times
139 * kmod was invoked. That would mean accessing the internals of the
140 * process tables to get the command line, proc_pid_cmdline is static
141 * and it is not worth changing the proc code just to handle this case.
142 * KAO.
143 *
144 * "trace the ppid" is simple, but will fail if someone's
145 * parent exits. I think this is as good as it gets. --RR
146 */
147 max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
148 atomic_inc(&kmod_concurrent);
149 if (atomic_read(&kmod_concurrent) > max_modprobes) {
150 /* We may be blaming an innocent here, but unlikely */
151 if (kmod_loop_msg < 5) {
152 printk(KERN_ERR
153 "request_module: runaway loop modprobe %s\n",
154 module_name);
155 kmod_loop_msg++;
156 }
157 atomic_dec(&kmod_concurrent);
158 return -ENOMEM;
159 }
160
161 trace_module_request(module_name, wait, _RET_IP_);
162
163 ret = call_modprobe(module_name, wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC);
164
165 atomic_dec(&kmod_concurrent);
166 return ret;
167}
168EXPORT_SYMBOL(__request_module);
169#endif /* CONFIG_MODULES */
170
171/*
172 * This is the task which runs the usermode application
173 */
174static int ____call_usermodehelper(void *data)
175{
176 struct subprocess_info *sub_info = data;
177 struct cred *new;
178 int retval;
179
180 spin_lock_irq(&current->sighand->siglock);
181 flush_signal_handlers(current, 1);
182 spin_unlock_irq(&current->sighand->siglock);
183
184 /* We can run anywhere, unlike our parent keventd(). */
185 set_cpus_allowed_ptr(current, cpu_all_mask);
186
187 /*
188 * Our parent is keventd, which runs with elevated scheduling priority.
189 * Avoid propagating that into the userspace child.
190 */
191 set_user_nice(current, 0);
192
193 retval = -ENOMEM;
194 new = prepare_kernel_cred(current);
195 if (!new)
196 goto fail;
197
198 spin_lock(&umh_sysctl_lock);
199 new->cap_bset = cap_intersect(usermodehelper_bset, new->cap_bset);
200 new->cap_inheritable = cap_intersect(usermodehelper_inheritable,
201 new->cap_inheritable);
202 spin_unlock(&umh_sysctl_lock);
203
204 if (sub_info->init) {
205 retval = sub_info->init(sub_info, new);
206 if (retval) {
207 abort_creds(new);
208 goto fail;
209 }
210 }
211
212 commit_creds(new);
213
214 retval = kernel_execve(sub_info->path,
215 (const char *const *)sub_info->argv,
216 (const char *const *)sub_info->envp);
217
218 /* Exec failed? */
219fail:
220 sub_info->retval = retval;
221 return 0;
222}
223
224static void call_usermodehelper_freeinfo(struct subprocess_info *info)
225{
226 if (info->cleanup)
227 (*info->cleanup)(info);
228 kfree(info);
229}
230
231static void umh_complete(struct subprocess_info *sub_info)
232{
233 struct completion *comp = xchg(&sub_info->complete, NULL);
234 /*
235 * See call_usermodehelper_exec(). If xchg() returns NULL
236 * we own sub_info, the UMH_KILLABLE caller has gone away.
237 */
238 if (comp)
239 complete(comp);
240 else
241 call_usermodehelper_freeinfo(sub_info);
242}
243
244/* Keventd can't block, but this (a child) can. */
245static int wait_for_helper(void *data)
246{
247 struct subprocess_info *sub_info = data;
248 pid_t pid;
249
250 /* If SIGCLD is ignored sys_wait4 won't populate the status. */
251 spin_lock_irq(&current->sighand->siglock);
252 current->sighand->action[SIGCHLD-1].sa.sa_handler = SIG_DFL;
253 spin_unlock_irq(&current->sighand->siglock);
254
255 pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
256 if (pid < 0) {
257 sub_info->retval = pid;
258 } else {
259 int ret = -ECHILD;
260 /*
261 * Normally it is bogus to call wait4() from in-kernel because
262 * wait4() wants to write the exit code to a userspace address.
263 * But wait_for_helper() always runs as keventd, and put_user()
264 * to a kernel address works OK for kernel threads, due to their
265 * having an mm_segment_t which spans the entire address space.
266 *
267 * Thus the __user pointer cast is valid here.
268 */
269 sys_wait4(pid, (int __user *)&ret, 0, NULL);
270
271 /*
272 * If ret is 0, either ____call_usermodehelper failed and the
273 * real error code is already in sub_info->retval or
274 * sub_info->retval is 0 anyway, so don't mess with it then.
275 */
276 if (ret)
277 sub_info->retval = ret;
278 }
279
280 umh_complete(sub_info);
281 return 0;
282}
283
284/* This is run by khelper thread */
285static void __call_usermodehelper(struct work_struct *work)
286{
287 struct subprocess_info *sub_info =
288 container_of(work, struct subprocess_info, work);
289 int wait = sub_info->wait & ~UMH_KILLABLE;
290 pid_t pid;
291
292 /* CLONE_VFORK: wait until the usermode helper has execve'd
293 * successfully We need the data structures to stay around
294 * until that is done. */
295 if (wait == UMH_WAIT_PROC)
296 pid = kernel_thread(wait_for_helper, sub_info,
297 CLONE_FS | CLONE_FILES | SIGCHLD);
298 else
299 pid = kernel_thread(____call_usermodehelper, sub_info,
300 CLONE_VFORK | SIGCHLD);
301
302 switch (wait) {
303 case UMH_NO_WAIT:
304 call_usermodehelper_freeinfo(sub_info);
305 break;
306
307 case UMH_WAIT_PROC:
308 if (pid > 0)
309 break;
310 /* FALLTHROUGH */
311 case UMH_WAIT_EXEC:
312 if (pid < 0)
313 sub_info->retval = pid;
314 umh_complete(sub_info);
315 }
316}
317
318/*
319 * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
320 * (used for preventing user land processes from being created after the user
321 * land has been frozen during a system-wide hibernation or suspend operation).
322 * Should always be manipulated under umhelper_sem acquired for write.
323 */
324static enum umh_disable_depth usermodehelper_disabled = UMH_DISABLED;
325
326/* Number of helpers running */
327static atomic_t running_helpers = ATOMIC_INIT(0);
328
329/*
330 * Wait queue head used by usermodehelper_disable() to wait for all running
331 * helpers to finish.
332 */
333static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);
334
335/*
336 * Used by usermodehelper_read_lock_wait() to wait for usermodehelper_disabled
337 * to become 'false'.
338 */
339static DECLARE_WAIT_QUEUE_HEAD(usermodehelper_disabled_waitq);
340
341/*
342 * Time to wait for running_helpers to become zero before the setting of
343 * usermodehelper_disabled in usermodehelper_disable() fails
344 */
345#define RUNNING_HELPERS_TIMEOUT (5 * HZ)
346
347int usermodehelper_read_trylock(void)
348{
349 DEFINE_WAIT(wait);
350 int ret = 0;
351
352 down_read(&umhelper_sem);
353 for (;;) {
354 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
355 TASK_INTERRUPTIBLE);
356 if (!usermodehelper_disabled)
357 break;
358
359 if (usermodehelper_disabled == UMH_DISABLED)
360 ret = -EAGAIN;
361
362 up_read(&umhelper_sem);
363
364 if (ret)
365 break;
366
367 schedule();
368 try_to_freeze();
369
370 down_read(&umhelper_sem);
371 }
372 finish_wait(&usermodehelper_disabled_waitq, &wait);
373 return ret;
374}
375EXPORT_SYMBOL_GPL(usermodehelper_read_trylock);
376
377long usermodehelper_read_lock_wait(long timeout)
378{
379 DEFINE_WAIT(wait);
380
381 if (timeout < 0)
382 return -EINVAL;
383
384 down_read(&umhelper_sem);
385 for (;;) {
386 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
387 TASK_UNINTERRUPTIBLE);
388 if (!usermodehelper_disabled)
389 break;
390
391 up_read(&umhelper_sem);
392
393 timeout = schedule_timeout(timeout);
394 if (!timeout)
395 break;
396
397 down_read(&umhelper_sem);
398 }
399 finish_wait(&usermodehelper_disabled_waitq, &wait);
400 return timeout;
401}
402EXPORT_SYMBOL_GPL(usermodehelper_read_lock_wait);
403
404void usermodehelper_read_unlock(void)
405{
406 up_read(&umhelper_sem);
407}
408EXPORT_SYMBOL_GPL(usermodehelper_read_unlock);
409
410/**
411 * __usermodehelper_set_disable_depth - Modify usermodehelper_disabled.
412 * @depth: New value to assign to usermodehelper_disabled.
413 *
414 * Change the value of usermodehelper_disabled (under umhelper_sem locked for
415 * writing) and wakeup tasks waiting for it to change.
416 */
417void __usermodehelper_set_disable_depth(enum umh_disable_depth depth)
418{
419 down_write(&umhelper_sem);
420 usermodehelper_disabled = depth;
421 wake_up(&usermodehelper_disabled_waitq);
422 up_write(&umhelper_sem);
423}
424
425/**
426 * __usermodehelper_disable - Prevent new helpers from being started.
427 * @depth: New value to assign to usermodehelper_disabled.
428 *
429 * Set usermodehelper_disabled to @depth and wait for running helpers to exit.
430 */
431int __usermodehelper_disable(enum umh_disable_depth depth)
432{
433 long retval;
434
435 if (!depth)
436 return -EINVAL;
437
438 down_write(&umhelper_sem);
439 usermodehelper_disabled = depth;
440 up_write(&umhelper_sem);
441
442 /*
443 * From now on call_usermodehelper_exec() won't start any new
444 * helpers, so it is sufficient if running_helpers turns out to
445 * be zero at one point (it may be increased later, but that
446 * doesn't matter).
447 */
448 retval = wait_event_timeout(running_helpers_waitq,
449 atomic_read(&running_helpers) == 0,
450 RUNNING_HELPERS_TIMEOUT);
451 if (retval)
452 return 0;
453
454 __usermodehelper_set_disable_depth(UMH_ENABLED);
455 return -EAGAIN;
456}
457
458static void helper_lock(void)
459{
460 atomic_inc(&running_helpers);
461 smp_mb__after_atomic_inc();
462}
463
464static void helper_unlock(void)
465{
466 if (atomic_dec_and_test(&running_helpers))
467 wake_up(&running_helpers_waitq);
468}
469
470/**
471 * call_usermodehelper_setup - prepare to call a usermode helper
472 * @path: path to usermode executable
473 * @argv: arg vector for process
474 * @envp: environment for process
475 * @gfp_mask: gfp mask for memory allocation
476 *
477 * Returns either %NULL on allocation failure, or a subprocess_info
478 * structure. This should be passed to call_usermodehelper_exec to
479 * exec the process and free the structure.
480 */
481static
482struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
483 char **envp, gfp_t gfp_mask)
484{
485 struct subprocess_info *sub_info;
486 sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
487 if (!sub_info)
488 goto out;
489
490 INIT_WORK(&sub_info->work, __call_usermodehelper);
491 sub_info->path = path;
492 sub_info->argv = argv;
493 sub_info->envp = envp;
494 out:
495 return sub_info;
496}
497
498/**
499 * call_usermodehelper_setfns - set a cleanup/init function
500 * @info: a subprocess_info returned by call_usermodehelper_setup
501 * @cleanup: a cleanup function
502 * @init: an init function
503 * @data: arbitrary context sensitive data
504 *
505 * The init function is used to customize the helper process prior to
506 * exec. A non-zero return code causes the process to error out, exit,
507 * and return the failure to the calling process
508 *
509 * The cleanup function is just before ethe subprocess_info is about to
510 * be freed. This can be used for freeing the argv and envp. The
511 * Function must be runnable in either a process context or the
512 * context in which call_usermodehelper_exec is called.
513 */
514static
515void call_usermodehelper_setfns(struct subprocess_info *info,
516 int (*init)(struct subprocess_info *info, struct cred *new),
517 void (*cleanup)(struct subprocess_info *info),
518 void *data)
519{
520 info->cleanup = cleanup;
521 info->init = init;
522 info->data = data;
523}
524
525/**
526 * call_usermodehelper_exec - start a usermode application
527 * @sub_info: information about the subprocessa
528 * @wait: wait for the application to finish and return status.
529 * when -1 don't wait at all, but you get no useful error back when
530 * the program couldn't be exec'ed. This makes it safe to call
531 * from interrupt context.
532 *
533 * Runs a user-space application. The application is started
534 * asynchronously if wait is not set, and runs as a child of keventd.
535 * (ie. it runs with full root capabilities).
536 */
537static
538int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
539{
540 DECLARE_COMPLETION_ONSTACK(done);
541 int retval = 0;
542
543 helper_lock();
544 if (sub_info->path[0] == '\0')
545 goto out;
546
547 if (!khelper_wq || usermodehelper_disabled) {
548 retval = -EBUSY;
549 goto out;
550 }
551
552 sub_info->complete = &done;
553 sub_info->wait = wait;
554
555 queue_work(khelper_wq, &sub_info->work);
556 if (wait == UMH_NO_WAIT) /* task has freed sub_info */
557 goto unlock;
558
559 if (wait & UMH_KILLABLE) {
560 retval = wait_for_completion_killable(&done);
561 if (!retval)
562 goto wait_done;
563
564 /* umh_complete() will see NULL and free sub_info */
565 if (xchg(&sub_info->complete, NULL))
566 goto unlock;
567 /* fallthrough, umh_complete() was already called */
568 }
569
570 wait_for_completion(&done);
571wait_done:
572 retval = sub_info->retval;
573out:
574 call_usermodehelper_freeinfo(sub_info);
575unlock:
576 helper_unlock();
577 return retval;
578}
579
580int call_usermodehelper_fns(
581 char *path, char **argv, char **envp, int wait,
582 int (*init)(struct subprocess_info *info, struct cred *new),
583 void (*cleanup)(struct subprocess_info *), void *data)
584{
585 struct subprocess_info *info;
586 gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
587
588 info = call_usermodehelper_setup(path, argv, envp, gfp_mask);
589
590 if (info == NULL)
591 return -ENOMEM;
592
593 call_usermodehelper_setfns(info, init, cleanup, data);
594
595 return call_usermodehelper_exec(info, wait);
596}
597EXPORT_SYMBOL(call_usermodehelper_fns);
598
599static int proc_cap_handler(struct ctl_table *table, int write,
600 void __user *buffer, size_t *lenp, loff_t *ppos)
601{
602 struct ctl_table t;
603 unsigned long cap_array[_KERNEL_CAPABILITY_U32S];
604 kernel_cap_t new_cap;
605 int err, i;
606
607 if (write && (!capable(CAP_SETPCAP) ||
608 !capable(CAP_SYS_MODULE)))
609 return -EPERM;
610
611 /*
612 * convert from the global kernel_cap_t to the ulong array to print to
613 * userspace if this is a read.
614 */
615 spin_lock(&umh_sysctl_lock);
616 for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++) {
617 if (table->data == CAP_BSET)
618 cap_array[i] = usermodehelper_bset.cap[i];
619 else if (table->data == CAP_PI)
620 cap_array[i] = usermodehelper_inheritable.cap[i];
621 else
622 BUG();
623 }
624 spin_unlock(&umh_sysctl_lock);
625
626 t = *table;
627 t.data = &cap_array;
628
629 /*
630 * actually read or write and array of ulongs from userspace. Remember
631 * these are least significant 32 bits first
632 */
633 err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos);
634 if (err < 0)
635 return err;
636
637 /*
638 * convert from the sysctl array of ulongs to the kernel_cap_t
639 * internal representation
640 */
641 for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)
642 new_cap.cap[i] = cap_array[i];
643
644 /*
645 * Drop everything not in the new_cap (but don't add things)
646 */
647 spin_lock(&umh_sysctl_lock);
648 if (write) {
649 if (table->data == CAP_BSET)
650 usermodehelper_bset = cap_intersect(usermodehelper_bset, new_cap);
651 if (table->data == CAP_PI)
652 usermodehelper_inheritable = cap_intersect(usermodehelper_inheritable, new_cap);
653 }
654 spin_unlock(&umh_sysctl_lock);
655
656 return 0;
657}
658
659struct ctl_table usermodehelper_table[] = {
660 {
661 .procname = "bset",
662 .data = CAP_BSET,
663 .maxlen = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
664 .mode = 0600,
665 .proc_handler = proc_cap_handler,
666 },
667 {
668 .procname = "inheritable",
669 .data = CAP_PI,
670 .maxlen = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
671 .mode = 0600,
672 .proc_handler = proc_cap_handler,
673 },
674 { }
675};
676
677void __init usermodehelper_init(void)
678{
679 khelper_wq = create_singlethread_workqueue("khelper");
680 BUG_ON(!khelper_wq);
681}