projects/linux·blob v3.3 · refs

552 lines · 14.9 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
63/**
64 * __request_module - try to load a kernel module
65 * @wait: wait (or not) for the operation to complete
66 * @fmt: printf style format string for the name of the module
67 * @...: arguments as specified in the format string
68 *
69 * Load a module using the user mode module loader. The function returns
70 * zero on success or a negative errno code on failure. Note that a
71 * successful module load does not mean the module did not then unload
72 * and exit on an error of its own. Callers must check that the service
73 * they requested is now available not blindly invoke it.
74 *
75 * If module auto-loading support is disabled then this function
76 * becomes a no-operation.
77 */
78int __request_module(bool wait, const char *fmt, ...)
79{
80 va_list args;
81 char module_name[MODULE_NAME_LEN];
82 unsigned int max_modprobes;
83 int ret;
84 char *argv[] = { modprobe_path, "-q", "--", module_name, NULL };
85 static char *envp[] = { "HOME=/",
86 "TERM=linux",
87 "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
88 NULL };
89 static atomic_t kmod_concurrent = ATOMIC_INIT(0);
90#define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */
91 static int kmod_loop_msg;
92
93 va_start(args, fmt);
94 ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
95 va_end(args);
96 if (ret >= MODULE_NAME_LEN)
97 return -ENAMETOOLONG;
98
99 ret = security_kernel_module_request(module_name);
100 if (ret)
101 return ret;
102
103 /* If modprobe needs a service that is in a module, we get a recursive
104 * loop. Limit the number of running kmod threads to max_threads/2 or
105 * MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method
106 * would be to run the parents of this process, counting how many times
107 * kmod was invoked. That would mean accessing the internals of the
108 * process tables to get the command line, proc_pid_cmdline is static
109 * and it is not worth changing the proc code just to handle this case.
110 * KAO.
111 *
112 * "trace the ppid" is simple, but will fail if someone's
113 * parent exits. I think this is as good as it gets. --RR
114 */
115 max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
116 atomic_inc(&kmod_concurrent);
117 if (atomic_read(&kmod_concurrent) > max_modprobes) {
118 /* We may be blaming an innocent here, but unlikely */
119 if (kmod_loop_msg < 5) {
120 printk(KERN_ERR
121 "request_module: runaway loop modprobe %s\n",
122 module_name);
123 kmod_loop_msg++;
124 }
125 atomic_dec(&kmod_concurrent);
126 return -ENOMEM;
127 }
128
129 trace_module_request(module_name, wait, _RET_IP_);
130
131 ret = call_usermodehelper_fns(modprobe_path, argv, envp,
132 wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC,
133 NULL, NULL, NULL);
134
135 atomic_dec(&kmod_concurrent);
136 return ret;
137}
138EXPORT_SYMBOL(__request_module);
139#endif /* CONFIG_MODULES */
140
141/*
142 * This is the task which runs the usermode application
143 */
144static int ____call_usermodehelper(void *data)
145{
146 struct subprocess_info *sub_info = data;
147 struct cred *new;
148 int retval;
149
150 spin_lock_irq(&current->sighand->siglock);
151 flush_signal_handlers(current, 1);
152 spin_unlock_irq(&current->sighand->siglock);
153
154 /* We can run anywhere, unlike our parent keventd(). */
155 set_cpus_allowed_ptr(current, cpu_all_mask);
156
157 /*
158 * Our parent is keventd, which runs with elevated scheduling priority.
159 * Avoid propagating that into the userspace child.
160 */
161 set_user_nice(current, 0);
162
163 retval = -ENOMEM;
164 new = prepare_kernel_cred(current);
165 if (!new)
166 goto fail;
167
168 spin_lock(&umh_sysctl_lock);
169 new->cap_bset = cap_intersect(usermodehelper_bset, new->cap_bset);
170 new->cap_inheritable = cap_intersect(usermodehelper_inheritable,
171 new->cap_inheritable);
172 spin_unlock(&umh_sysctl_lock);
173
174 if (sub_info->init) {
175 retval = sub_info->init(sub_info, new);
176 if (retval) {
177 abort_creds(new);
178 goto fail;
179 }
180 }
181
182 commit_creds(new);
183
184 retval = kernel_execve(sub_info->path,
185 (const char *const *)sub_info->argv,
186 (const char *const *)sub_info->envp);
187
188 /* Exec failed? */
189fail:
190 sub_info->retval = retval;
191 do_exit(0);
192}
193
194void call_usermodehelper_freeinfo(struct subprocess_info *info)
195{
196 if (info->cleanup)
197 (*info->cleanup)(info);
198 kfree(info);
199}
200EXPORT_SYMBOL(call_usermodehelper_freeinfo);
201
202/* Keventd can't block, but this (a child) can. */
203static int wait_for_helper(void *data)
204{
205 struct subprocess_info *sub_info = data;
206 pid_t pid;
207
208 /* If SIGCLD is ignored sys_wait4 won't populate the status. */
209 spin_lock_irq(&current->sighand->siglock);
210 current->sighand->action[SIGCHLD-1].sa.sa_handler = SIG_DFL;
211 spin_unlock_irq(&current->sighand->siglock);
212
213 pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
214 if (pid < 0) {
215 sub_info->retval = pid;
216 } else {
217 int ret = -ECHILD;
218 /*
219 * Normally it is bogus to call wait4() from in-kernel because
220 * wait4() wants to write the exit code to a userspace address.
221 * But wait_for_helper() always runs as keventd, and put_user()
222 * to a kernel address works OK for kernel threads, due to their
223 * having an mm_segment_t which spans the entire address space.
224 *
225 * Thus the __user pointer cast is valid here.
226 */
227 sys_wait4(pid, (int __user *)&ret, 0, NULL);
228
229 /*
230 * If ret is 0, either ____call_usermodehelper failed and the
231 * real error code is already in sub_info->retval or
232 * sub_info->retval is 0 anyway, so don't mess with it then.
233 */
234 if (ret)
235 sub_info->retval = ret;
236 }
237
238 complete(sub_info->complete);
239 return 0;
240}
241
242/* This is run by khelper thread */
243static void __call_usermodehelper(struct work_struct *work)
244{
245 struct subprocess_info *sub_info =
246 container_of(work, struct subprocess_info, work);
247 enum umh_wait wait = sub_info->wait;
248 pid_t pid;
249
250 /* CLONE_VFORK: wait until the usermode helper has execve'd
251 * successfully We need the data structures to stay around
252 * until that is done. */
253 if (wait == UMH_WAIT_PROC)
254 pid = kernel_thread(wait_for_helper, sub_info,
255 CLONE_FS | CLONE_FILES | SIGCHLD);
256 else
257 pid = kernel_thread(____call_usermodehelper, sub_info,
258 CLONE_VFORK | SIGCHLD);
259
260 switch (wait) {
261 case UMH_NO_WAIT:
262 call_usermodehelper_freeinfo(sub_info);
263 break;
264
265 case UMH_WAIT_PROC:
266 if (pid > 0)
267 break;
268 /* FALLTHROUGH */
269 case UMH_WAIT_EXEC:
270 if (pid < 0)
271 sub_info->retval = pid;
272 complete(sub_info->complete);
273 }
274}
275
276/*
277 * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
278 * (used for preventing user land processes from being created after the user
279 * land has been frozen during a system-wide hibernation or suspend operation).
280 * Should always be manipulated under umhelper_sem acquired for write.
281 */
282static int usermodehelper_disabled = 1;
283
284/* Number of helpers running */
285static atomic_t running_helpers = ATOMIC_INIT(0);
286
287/*
288 * Wait queue head used by usermodehelper_disable() to wait for all running
289 * helpers to finish.
290 */
291static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);
292
293/*
294 * Time to wait for running_helpers to become zero before the setting of
295 * usermodehelper_disabled in usermodehelper_disable() fails
296 */
297#define RUNNING_HELPERS_TIMEOUT (5 * HZ)
298
299void read_lock_usermodehelper(void)
300{
301 down_read(&umhelper_sem);
302}
303EXPORT_SYMBOL_GPL(read_lock_usermodehelper);
304
305void read_unlock_usermodehelper(void)
306{
307 up_read(&umhelper_sem);
308}
309EXPORT_SYMBOL_GPL(read_unlock_usermodehelper);
310
311/**
312 * usermodehelper_disable - prevent new helpers from being started
313 */
314int usermodehelper_disable(void)
315{
316 long retval;
317
318 down_write(&umhelper_sem);
319 usermodehelper_disabled = 1;
320 up_write(&umhelper_sem);
321
322 /*
323 * From now on call_usermodehelper_exec() won't start any new
324 * helpers, so it is sufficient if running_helpers turns out to
325 * be zero at one point (it may be increased later, but that
326 * doesn't matter).
327 */
328 retval = wait_event_timeout(running_helpers_waitq,
329 atomic_read(&running_helpers) == 0,
330 RUNNING_HELPERS_TIMEOUT);
331 if (retval)
332 return 0;
333
334 down_write(&umhelper_sem);
335 usermodehelper_disabled = 0;
336 up_write(&umhelper_sem);
337 return -EAGAIN;
338}
339
340/**
341 * usermodehelper_enable - allow new helpers to be started again
342 */
343void usermodehelper_enable(void)
344{
345 down_write(&umhelper_sem);
346 usermodehelper_disabled = 0;
347 up_write(&umhelper_sem);
348}
349
350/**
351 * usermodehelper_is_disabled - check if new helpers are allowed to be started
352 */
353bool usermodehelper_is_disabled(void)
354{
355 return usermodehelper_disabled;
356}
357EXPORT_SYMBOL_GPL(usermodehelper_is_disabled);
358
359static void helper_lock(void)
360{
361 atomic_inc(&running_helpers);
362 smp_mb__after_atomic_inc();
363}
364
365static void helper_unlock(void)
366{
367 if (atomic_dec_and_test(&running_helpers))
368 wake_up(&running_helpers_waitq);
369}
370
371/**
372 * call_usermodehelper_setup - prepare to call a usermode helper
373 * @path: path to usermode executable
374 * @argv: arg vector for process
375 * @envp: environment for process
376 * @gfp_mask: gfp mask for memory allocation
377 *
378 * Returns either %NULL on allocation failure, or a subprocess_info
379 * structure. This should be passed to call_usermodehelper_exec to
380 * exec the process and free the structure.
381 */
382struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
383 char **envp, gfp_t gfp_mask)
384{
385 struct subprocess_info *sub_info;
386 sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
387 if (!sub_info)
388 goto out;
389
390 INIT_WORK(&sub_info->work, __call_usermodehelper);
391 sub_info->path = path;
392 sub_info->argv = argv;
393 sub_info->envp = envp;
394 out:
395 return sub_info;
396}
397EXPORT_SYMBOL(call_usermodehelper_setup);
398
399/**
400 * call_usermodehelper_setfns - set a cleanup/init function
401 * @info: a subprocess_info returned by call_usermodehelper_setup
402 * @cleanup: a cleanup function
403 * @init: an init function
404 * @data: arbitrary context sensitive data
405 *
406 * The init function is used to customize the helper process prior to
407 * exec. A non-zero return code causes the process to error out, exit,
408 * and return the failure to the calling process
409 *
410 * The cleanup function is just before ethe subprocess_info is about to
411 * be freed. This can be used for freeing the argv and envp. The
412 * Function must be runnable in either a process context or the
413 * context in which call_usermodehelper_exec is called.
414 */
415void call_usermodehelper_setfns(struct subprocess_info *info,
416 int (*init)(struct subprocess_info *info, struct cred *new),
417 void (*cleanup)(struct subprocess_info *info),
418 void *data)
419{
420 info->cleanup = cleanup;
421 info->init = init;
422 info->data = data;
423}
424EXPORT_SYMBOL(call_usermodehelper_setfns);
425
426/**
427 * call_usermodehelper_exec - start a usermode application
428 * @sub_info: information about the subprocessa
429 * @wait: wait for the application to finish and return status.
430 * when -1 don't wait at all, but you get no useful error back when
431 * the program couldn't be exec'ed. This makes it safe to call
432 * from interrupt context.
433 *
434 * Runs a user-space application. The application is started
435 * asynchronously if wait is not set, and runs as a child of keventd.
436 * (ie. it runs with full root capabilities).
437 */
438int call_usermodehelper_exec(struct subprocess_info *sub_info,
439 enum umh_wait wait)
440{
441 DECLARE_COMPLETION_ONSTACK(done);
442 int retval = 0;
443
444 helper_lock();
445 if (sub_info->path[0] == '\0')
446 goto out;
447
448 if (!khelper_wq || usermodehelper_disabled) {
449 retval = -EBUSY;
450 goto out;
451 }
452
453 sub_info->complete = &done;
454 sub_info->wait = wait;
455
456 queue_work(khelper_wq, &sub_info->work);
457 if (wait == UMH_NO_WAIT) /* task has freed sub_info */
458 goto unlock;
459 wait_for_completion(&done);
460 retval = sub_info->retval;
461
462out:
463 call_usermodehelper_freeinfo(sub_info);
464unlock:
465 helper_unlock();
466 return retval;
467}
468EXPORT_SYMBOL(call_usermodehelper_exec);
469
470static int proc_cap_handler(struct ctl_table *table, int write,
471 void __user *buffer, size_t *lenp, loff_t *ppos)
472{
473 struct ctl_table t;
474 unsigned long cap_array[_KERNEL_CAPABILITY_U32S];
475 kernel_cap_t new_cap;
476 int err, i;
477
478 if (write && (!capable(CAP_SETPCAP) ||
479 !capable(CAP_SYS_MODULE)))
480 return -EPERM;
481
482 /*
483 * convert from the global kernel_cap_t to the ulong array to print to
484 * userspace if this is a read.
485 */
486 spin_lock(&umh_sysctl_lock);
487 for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++) {
488 if (table->data == CAP_BSET)
489 cap_array[i] = usermodehelper_bset.cap[i];
490 else if (table->data == CAP_PI)
491 cap_array[i] = usermodehelper_inheritable.cap[i];
492 else
493 BUG();
494 }
495 spin_unlock(&umh_sysctl_lock);
496
497 t = *table;
498 t.data = &cap_array;
499
500 /*
501 * actually read or write and array of ulongs from userspace. Remember
502 * these are least significant 32 bits first
503 */
504 err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos);
505 if (err < 0)
506 return err;
507
508 /*
509 * convert from the sysctl array of ulongs to the kernel_cap_t
510 * internal representation
511 */
512 for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)
513 new_cap.cap[i] = cap_array[i];
514
515 /*
516 * Drop everything not in the new_cap (but don't add things)
517 */
518 spin_lock(&umh_sysctl_lock);
519 if (write) {
520 if (table->data == CAP_BSET)
521 usermodehelper_bset = cap_intersect(usermodehelper_bset, new_cap);
522 if (table->data == CAP_PI)
523 usermodehelper_inheritable = cap_intersect(usermodehelper_inheritable, new_cap);
524 }
525 spin_unlock(&umh_sysctl_lock);
526
527 return 0;
528}
529
530struct ctl_table usermodehelper_table[] = {
531 {
532 .procname = "bset",
533 .data = CAP_BSET,
534 .maxlen = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
535 .mode = 0600,
536 .proc_handler = proc_cap_handler,
537 },
538 {
539 .procname = "inheritable",
540 .data = CAP_PI,
541 .maxlen = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
542 .mode = 0600,
543 .proc_handler = proc_cap_handler,
544 },
545 { }
546};
547
548void __init usermodehelper_init(void)
549{
550 khelper_wq = create_singlethread_workqueue("khelper");
551 BUG_ON(!khelper_wq);
552}