projects/linux·blob v3.4-rc3 · refs

663 lines · 17.3 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
224void call_usermodehelper_freeinfo(struct subprocess_info *info)
225{
226 if (info->cleanup)
227 (*info->cleanup)(info);
228 kfree(info);
229}
230EXPORT_SYMBOL(call_usermodehelper_freeinfo);
231
232static void umh_complete(struct subprocess_info *sub_info)
233{
234 struct completion *comp = xchg(&sub_info->complete, NULL);
235 /*
236 * See call_usermodehelper_exec(). If xchg() returns NULL
237 * we own sub_info, the UMH_KILLABLE caller has gone away.
238 */
239 if (comp)
240 complete(comp);
241 else
242 call_usermodehelper_freeinfo(sub_info);
243}
244
245/* Keventd can't block, but this (a child) can. */
246static int wait_for_helper(void *data)
247{
248 struct subprocess_info *sub_info = data;
249 pid_t pid;
250
251 /* If SIGCLD is ignored sys_wait4 won't populate the status. */
252 spin_lock_irq(&current->sighand->siglock);
253 current->sighand->action[SIGCHLD-1].sa.sa_handler = SIG_DFL;
254 spin_unlock_irq(&current->sighand->siglock);
255
256 pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
257 if (pid < 0) {
258 sub_info->retval = pid;
259 } else {
260 int ret = -ECHILD;
261 /*
262 * Normally it is bogus to call wait4() from in-kernel because
263 * wait4() wants to write the exit code to a userspace address.
264 * But wait_for_helper() always runs as keventd, and put_user()
265 * to a kernel address works OK for kernel threads, due to their
266 * having an mm_segment_t which spans the entire address space.
267 *
268 * Thus the __user pointer cast is valid here.
269 */
270 sys_wait4(pid, (int __user *)&ret, 0, NULL);
271
272 /*
273 * If ret is 0, either ____call_usermodehelper failed and the
274 * real error code is already in sub_info->retval or
275 * sub_info->retval is 0 anyway, so don't mess with it then.
276 */
277 if (ret)
278 sub_info->retval = ret;
279 }
280
281 umh_complete(sub_info);
282 return 0;
283}
284
285/* This is run by khelper thread */
286static void __call_usermodehelper(struct work_struct *work)
287{
288 struct subprocess_info *sub_info =
289 container_of(work, struct subprocess_info, work);
290 int wait = sub_info->wait & ~UMH_KILLABLE;
291 pid_t pid;
292
293 /* CLONE_VFORK: wait until the usermode helper has execve'd
294 * successfully We need the data structures to stay around
295 * until that is done. */
296 if (wait == UMH_WAIT_PROC)
297 pid = kernel_thread(wait_for_helper, sub_info,
298 CLONE_FS | CLONE_FILES | SIGCHLD);
299 else
300 pid = kernel_thread(____call_usermodehelper, sub_info,
301 CLONE_VFORK | SIGCHLD);
302
303 switch (wait) {
304 case UMH_NO_WAIT:
305 call_usermodehelper_freeinfo(sub_info);
306 break;
307
308 case UMH_WAIT_PROC:
309 if (pid > 0)
310 break;
311 /* FALLTHROUGH */
312 case UMH_WAIT_EXEC:
313 if (pid < 0)
314 sub_info->retval = pid;
315 umh_complete(sub_info);
316 }
317}
318
319/*
320 * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
321 * (used for preventing user land processes from being created after the user
322 * land has been frozen during a system-wide hibernation or suspend operation).
323 * Should always be manipulated under umhelper_sem acquired for write.
324 */
325static enum umh_disable_depth usermodehelper_disabled = UMH_DISABLED;
326
327/* Number of helpers running */
328static atomic_t running_helpers = ATOMIC_INIT(0);
329
330/*
331 * Wait queue head used by usermodehelper_disable() to wait for all running
332 * helpers to finish.
333 */
334static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);
335
336/*
337 * Used by usermodehelper_read_lock_wait() to wait for usermodehelper_disabled
338 * to become 'false'.
339 */
340static DECLARE_WAIT_QUEUE_HEAD(usermodehelper_disabled_waitq);
341
342/*
343 * Time to wait for running_helpers to become zero before the setting of
344 * usermodehelper_disabled in usermodehelper_disable() fails
345 */
346#define RUNNING_HELPERS_TIMEOUT (5 * HZ)
347
348int usermodehelper_read_trylock(void)
349{
350 DEFINE_WAIT(wait);
351 int ret = 0;
352
353 down_read(&umhelper_sem);
354 for (;;) {
355 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
356 TASK_INTERRUPTIBLE);
357 if (!usermodehelper_disabled)
358 break;
359
360 if (usermodehelper_disabled == UMH_DISABLED)
361 ret = -EAGAIN;
362
363 up_read(&umhelper_sem);
364
365 if (ret)
366 break;
367
368 schedule();
369 try_to_freeze();
370
371 down_read(&umhelper_sem);
372 }
373 finish_wait(&usermodehelper_disabled_waitq, &wait);
374 return ret;
375}
376EXPORT_SYMBOL_GPL(usermodehelper_read_trylock);
377
378long usermodehelper_read_lock_wait(long timeout)
379{
380 DEFINE_WAIT(wait);
381
382 if (timeout < 0)
383 return -EINVAL;
384
385 down_read(&umhelper_sem);
386 for (;;) {
387 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
388 TASK_UNINTERRUPTIBLE);
389 if (!usermodehelper_disabled)
390 break;
391
392 up_read(&umhelper_sem);
393
394 timeout = schedule_timeout(timeout);
395 if (!timeout)
396 break;
397
398 down_read(&umhelper_sem);
399 }
400 finish_wait(&usermodehelper_disabled_waitq, &wait);
401 return timeout;
402}
403EXPORT_SYMBOL_GPL(usermodehelper_read_lock_wait);
404
405void usermodehelper_read_unlock(void)
406{
407 up_read(&umhelper_sem);
408}
409EXPORT_SYMBOL_GPL(usermodehelper_read_unlock);
410
411/**
412 * __usermodehelper_set_disable_depth - Modify usermodehelper_disabled.
413 * depth: New value to assign to usermodehelper_disabled.
414 *
415 * Change the value of usermodehelper_disabled (under umhelper_sem locked for
416 * writing) and wakeup tasks waiting for it to change.
417 */
418void __usermodehelper_set_disable_depth(enum umh_disable_depth depth)
419{
420 down_write(&umhelper_sem);
421 usermodehelper_disabled = depth;
422 wake_up(&usermodehelper_disabled_waitq);
423 up_write(&umhelper_sem);
424}
425
426/**
427 * __usermodehelper_disable - Prevent new helpers from being started.
428 * @depth: New value to assign to usermodehelper_disabled.
429 *
430 * Set usermodehelper_disabled to @depth and wait for running helpers to exit.
431 */
432int __usermodehelper_disable(enum umh_disable_depth depth)
433{
434 long retval;
435
436 if (!depth)
437 return -EINVAL;
438
439 down_write(&umhelper_sem);
440 usermodehelper_disabled = depth;
441 up_write(&umhelper_sem);
442
443 /*
444 * From now on call_usermodehelper_exec() won't start any new
445 * helpers, so it is sufficient if running_helpers turns out to
446 * be zero at one point (it may be increased later, but that
447 * doesn't matter).
448 */
449 retval = wait_event_timeout(running_helpers_waitq,
450 atomic_read(&running_helpers) == 0,
451 RUNNING_HELPERS_TIMEOUT);
452 if (retval)
453 return 0;
454
455 __usermodehelper_set_disable_depth(UMH_ENABLED);
456 return -EAGAIN;
457}
458
459static void helper_lock(void)
460{
461 atomic_inc(&running_helpers);
462 smp_mb__after_atomic_inc();
463}
464
465static void helper_unlock(void)
466{
467 if (atomic_dec_and_test(&running_helpers))
468 wake_up(&running_helpers_waitq);
469}
470
471/**
472 * call_usermodehelper_setup - prepare to call a usermode helper
473 * @path: path to usermode executable
474 * @argv: arg vector for process
475 * @envp: environment for process
476 * @gfp_mask: gfp mask for memory allocation
477 *
478 * Returns either %NULL on allocation failure, or a subprocess_info
479 * structure. This should be passed to call_usermodehelper_exec to
480 * exec the process and free the structure.
481 */
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}
497EXPORT_SYMBOL(call_usermodehelper_setup);
498
499/**
500 * call_usermodehelper_setfns - set a cleanup/init function
501 * @info: a subprocess_info returned by call_usermodehelper_setup
502 * @cleanup: a cleanup function
503 * @init: an init function
504 * @data: arbitrary context sensitive data
505 *
506 * The init function is used to customize the helper process prior to
507 * exec. A non-zero return code causes the process to error out, exit,
508 * and return the failure to the calling process
509 *
510 * The cleanup function is just before ethe subprocess_info is about to
511 * be freed. This can be used for freeing the argv and envp. The
512 * Function must be runnable in either a process context or the
513 * context in which call_usermodehelper_exec is called.
514 */
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}
524EXPORT_SYMBOL(call_usermodehelper_setfns);
525
526/**
527 * call_usermodehelper_exec - start a usermode application
528 * @sub_info: information about the subprocessa
529 * @wait: wait for the application to finish and return status.
530 * when -1 don't wait at all, but you get no useful error back when
531 * the program couldn't be exec'ed. This makes it safe to call
532 * from interrupt context.
533 *
534 * Runs a user-space application. The application is started
535 * asynchronously if wait is not set, and runs as a child of keventd.
536 * (ie. it runs with full root capabilities).
537 */
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}
579EXPORT_SYMBOL(call_usermodehelper_exec);
580
581static int proc_cap_handler(struct ctl_table *table, int write,
582 void __user *buffer, size_t *lenp, loff_t *ppos)
583{
584 struct ctl_table t;
585 unsigned long cap_array[_KERNEL_CAPABILITY_U32S];
586 kernel_cap_t new_cap;
587 int err, i;
588
589 if (write && (!capable(CAP_SETPCAP) ||
590 !capable(CAP_SYS_MODULE)))
591 return -EPERM;
592
593 /*
594 * convert from the global kernel_cap_t to the ulong array to print to
595 * userspace if this is a read.
596 */
597 spin_lock(&umh_sysctl_lock);
598 for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++) {
599 if (table->data == CAP_BSET)
600 cap_array[i] = usermodehelper_bset.cap[i];
601 else if (table->data == CAP_PI)
602 cap_array[i] = usermodehelper_inheritable.cap[i];
603 else
604 BUG();
605 }
606 spin_unlock(&umh_sysctl_lock);
607
608 t = *table;
609 t.data = &cap_array;
610
611 /*
612 * actually read or write and array of ulongs from userspace. Remember
613 * these are least significant 32 bits first
614 */
615 err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos);
616 if (err < 0)
617 return err;
618
619 /*
620 * convert from the sysctl array of ulongs to the kernel_cap_t
621 * internal representation
622 */
623 for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)
624 new_cap.cap[i] = cap_array[i];
625
626 /*
627 * Drop everything not in the new_cap (but don't add things)
628 */
629 spin_lock(&umh_sysctl_lock);
630 if (write) {
631 if (table->data == CAP_BSET)
632 usermodehelper_bset = cap_intersect(usermodehelper_bset, new_cap);
633 if (table->data == CAP_PI)
634 usermodehelper_inheritable = cap_intersect(usermodehelper_inheritable, new_cap);
635 }
636 spin_unlock(&umh_sysctl_lock);
637
638 return 0;
639}
640
641struct ctl_table usermodehelper_table[] = {
642 {
643 .procname = "bset",
644 .data = CAP_BSET,
645 .maxlen = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
646 .mode = 0600,
647 .proc_handler = proc_cap_handler,
648 },
649 {
650 .procname = "inheritable",
651 .data = CAP_PI,
652 .maxlen = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
653 .mode = 0600,
654 .proc_handler = proc_cap_handler,
655 },
656 { }
657};
658
659void __init usermodehelper_init(void)
660{
661 khelper_wq = create_singlethread_workqueue("khelper");
662 BUG_ON(!khelper_wq);
663}