projects/linux·blob v2.6.26 · refs

518 lines · 14.1 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/mnt_namespace.h>
28#include <linux/completion.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 <asm/uaccess.h>
40
41extern int max_threads;
42
43static struct workqueue_struct *khelper_wq;
44
45#ifdef CONFIG_KMOD
46
47/*
48 modprobe_path is set via /proc/sys.
49*/
50char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
51
52/**
53 * request_module - try to load a kernel module
54 * @fmt: printf style format string for the name of the module
55 * @varargs: arguements as specified in the format string
56 *
57 * Load a module using the user mode module loader. The function returns
58 * zero on success or a negative errno code on failure. Note that a
59 * successful module load does not mean the module did not then unload
60 * and exit on an error of its own. Callers must check that the service
61 * they requested is now available not blindly invoke it.
62 *
63 * If module auto-loading support is disabled then this function
64 * becomes a no-operation.
65 */
66int request_module(const char *fmt, ...)
67{
68 va_list args;
69 char module_name[MODULE_NAME_LEN];
70 unsigned int max_modprobes;
71 int ret;
72 char *argv[] = { modprobe_path, "-q", "--", module_name, NULL };
73 static char *envp[] = { "HOME=/",
74 "TERM=linux",
75 "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
76 NULL };
77 static atomic_t kmod_concurrent = ATOMIC_INIT(0);
78#define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */
79 static int kmod_loop_msg;
80
81 va_start(args, fmt);
82 ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
83 va_end(args);
84 if (ret >= MODULE_NAME_LEN)
85 return -ENAMETOOLONG;
86
87 /* If modprobe needs a service that is in a module, we get a recursive
88 * loop. Limit the number of running kmod threads to max_threads/2 or
89 * MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method
90 * would be to run the parents of this process, counting how many times
91 * kmod was invoked. That would mean accessing the internals of the
92 * process tables to get the command line, proc_pid_cmdline is static
93 * and it is not worth changing the proc code just to handle this case.
94 * KAO.
95 *
96 * "trace the ppid" is simple, but will fail if someone's
97 * parent exits. I think this is as good as it gets. --RR
98 */
99 max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
100 atomic_inc(&kmod_concurrent);
101 if (atomic_read(&kmod_concurrent) > max_modprobes) {
102 /* We may be blaming an innocent here, but unlikely */
103 if (kmod_loop_msg++ < 5)
104 printk(KERN_ERR
105 "request_module: runaway loop modprobe %s\n",
106 module_name);
107 atomic_dec(&kmod_concurrent);
108 return -ENOMEM;
109 }
110
111 ret = call_usermodehelper(modprobe_path, argv, envp, 1);
112 atomic_dec(&kmod_concurrent);
113 return ret;
114}
115EXPORT_SYMBOL(request_module);
116#endif /* CONFIG_KMOD */
117
118struct subprocess_info {
119 struct work_struct work;
120 struct completion *complete;
121 char *path;
122 char **argv;
123 char **envp;
124 struct key *ring;
125 enum umh_wait wait;
126 int retval;
127 struct file *stdin;
128 void (*cleanup)(char **argv, char **envp);
129};
130
131/*
132 * This is the task which runs the usermode application
133 */
134static int ____call_usermodehelper(void *data)
135{
136 struct subprocess_info *sub_info = data;
137 struct key *new_session, *old_session;
138 int retval;
139
140 /* Unblock all signals and set the session keyring. */
141 new_session = key_get(sub_info->ring);
142 spin_lock_irq(&current->sighand->siglock);
143 old_session = __install_session_keyring(current, new_session);
144 flush_signal_handlers(current, 1);
145 sigemptyset(&current->blocked);
146 recalc_sigpending();
147 spin_unlock_irq(&current->sighand->siglock);
148
149 key_put(old_session);
150
151 /* Install input pipe when needed */
152 if (sub_info->stdin) {
153 struct files_struct *f = current->files;
154 struct fdtable *fdt;
155 /* no races because files should be private here */
156 sys_close(0);
157 fd_install(0, sub_info->stdin);
158 spin_lock(&f->file_lock);
159 fdt = files_fdtable(f);
160 FD_SET(0, fdt->open_fds);
161 FD_CLR(0, fdt->close_on_exec);
162 spin_unlock(&f->file_lock);
163
164 /* and disallow core files too */
165 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){0, 0};
166 }
167
168 /* We can run anywhere, unlike our parent keventd(). */
169 set_cpus_allowed_ptr(current, CPU_MASK_ALL_PTR);
170
171 /*
172 * Our parent is keventd, which runs with elevated scheduling priority.
173 * Avoid propagating that into the userspace child.
174 */
175 set_user_nice(current, 0);
176
177 retval = kernel_execve(sub_info->path, sub_info->argv, sub_info->envp);
178
179 /* Exec failed? */
180 sub_info->retval = retval;
181 do_exit(0);
182}
183
184void call_usermodehelper_freeinfo(struct subprocess_info *info)
185{
186 if (info->cleanup)
187 (*info->cleanup)(info->argv, info->envp);
188 kfree(info);
189}
190EXPORT_SYMBOL(call_usermodehelper_freeinfo);
191
192/* Keventd can't block, but this (a child) can. */
193static int wait_for_helper(void *data)
194{
195 struct subprocess_info *sub_info = data;
196 pid_t pid;
197
198 /* Install a handler: if SIGCLD isn't handled sys_wait4 won't
199 * populate the status, but will return -ECHILD. */
200 allow_signal(SIGCHLD);
201
202 pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
203 if (pid < 0) {
204 sub_info->retval = pid;
205 } else {
206 int ret;
207
208 /*
209 * Normally it is bogus to call wait4() from in-kernel because
210 * wait4() wants to write the exit code to a userspace address.
211 * But wait_for_helper() always runs as keventd, and put_user()
212 * to a kernel address works OK for kernel threads, due to their
213 * having an mm_segment_t which spans the entire address space.
214 *
215 * Thus the __user pointer cast is valid here.
216 */
217 sys_wait4(pid, (int __user *)&ret, 0, NULL);
218
219 /*
220 * If ret is 0, either ____call_usermodehelper failed and the
221 * real error code is already in sub_info->retval or
222 * sub_info->retval is 0 anyway, so don't mess with it then.
223 */
224 if (ret)
225 sub_info->retval = ret;
226 }
227
228 if (sub_info->wait == UMH_NO_WAIT)
229 call_usermodehelper_freeinfo(sub_info);
230 else
231 complete(sub_info->complete);
232 return 0;
233}
234
235/* This is run by khelper thread */
236static void __call_usermodehelper(struct work_struct *work)
237{
238 struct subprocess_info *sub_info =
239 container_of(work, struct subprocess_info, work);
240 pid_t pid;
241 enum umh_wait wait = sub_info->wait;
242
243 /* CLONE_VFORK: wait until the usermode helper has execve'd
244 * successfully We need the data structures to stay around
245 * until that is done. */
246 if (wait == UMH_WAIT_PROC || wait == UMH_NO_WAIT)
247 pid = kernel_thread(wait_for_helper, sub_info,
248 CLONE_FS | CLONE_FILES | SIGCHLD);
249 else
250 pid = kernel_thread(____call_usermodehelper, sub_info,
251 CLONE_VFORK | SIGCHLD);
252
253 switch (wait) {
254 case UMH_NO_WAIT:
255 break;
256
257 case UMH_WAIT_PROC:
258 if (pid > 0)
259 break;
260 sub_info->retval = pid;
261 /* FALLTHROUGH */
262
263 case UMH_WAIT_EXEC:
264 complete(sub_info->complete);
265 }
266}
267
268#ifdef CONFIG_PM
269/*
270 * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
271 * (used for preventing user land processes from being created after the user
272 * land has been frozen during a system-wide hibernation or suspend operation).
273 */
274static int usermodehelper_disabled;
275
276/* Number of helpers running */
277static atomic_t running_helpers = ATOMIC_INIT(0);
278
279/*
280 * Wait queue head used by usermodehelper_pm_callback() to wait for all running
281 * helpers to finish.
282 */
283static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);
284
285/*
286 * Time to wait for running_helpers to become zero before the setting of
287 * usermodehelper_disabled in usermodehelper_pm_callback() fails
288 */
289#define RUNNING_HELPERS_TIMEOUT (5 * HZ)
290
291static int usermodehelper_pm_callback(struct notifier_block *nfb,
292 unsigned long action,
293 void *ignored)
294{
295 long retval;
296
297 switch (action) {
298 case PM_HIBERNATION_PREPARE:
299 case PM_SUSPEND_PREPARE:
300 usermodehelper_disabled = 1;
301 smp_mb();
302 /*
303 * From now on call_usermodehelper_exec() won't start any new
304 * helpers, so it is sufficient if running_helpers turns out to
305 * be zero at one point (it may be increased later, but that
306 * doesn't matter).
307 */
308 retval = wait_event_timeout(running_helpers_waitq,
309 atomic_read(&running_helpers) == 0,
310 RUNNING_HELPERS_TIMEOUT);
311 if (retval) {
312 return NOTIFY_OK;
313 } else {
314 usermodehelper_disabled = 0;
315 return NOTIFY_BAD;
316 }
317 case PM_POST_HIBERNATION:
318 case PM_POST_SUSPEND:
319 usermodehelper_disabled = 0;
320 return NOTIFY_OK;
321 }
322
323 return NOTIFY_DONE;
324}
325
326static void helper_lock(void)
327{
328 atomic_inc(&running_helpers);
329 smp_mb__after_atomic_inc();
330}
331
332static void helper_unlock(void)
333{
334 if (atomic_dec_and_test(&running_helpers))
335 wake_up(&running_helpers_waitq);
336}
337
338static void register_pm_notifier_callback(void)
339{
340 pm_notifier(usermodehelper_pm_callback, 0);
341}
342#else /* CONFIG_PM */
343#define usermodehelper_disabled 0
344
345static inline void helper_lock(void) {}
346static inline void helper_unlock(void) {}
347static inline void register_pm_notifier_callback(void) {}
348#endif /* CONFIG_PM */
349
350/**
351 * call_usermodehelper_setup - prepare to call a usermode helper
352 * @path: path to usermode executable
353 * @argv: arg vector for process
354 * @envp: environment for process
355 *
356 * Returns either %NULL on allocation failure, or a subprocess_info
357 * structure. This should be passed to call_usermodehelper_exec to
358 * exec the process and free the structure.
359 */
360struct subprocess_info *call_usermodehelper_setup(char *path,
361 char **argv, char **envp)
362{
363 struct subprocess_info *sub_info;
364 sub_info = kzalloc(sizeof(struct subprocess_info), GFP_ATOMIC);
365 if (!sub_info)
366 goto out;
367
368 INIT_WORK(&sub_info->work, __call_usermodehelper);
369 sub_info->path = path;
370 sub_info->argv = argv;
371 sub_info->envp = envp;
372
373 out:
374 return sub_info;
375}
376EXPORT_SYMBOL(call_usermodehelper_setup);
377
378/**
379 * call_usermodehelper_setkeys - set the session keys for usermode helper
380 * @info: a subprocess_info returned by call_usermodehelper_setup
381 * @session_keyring: the session keyring for the process
382 */
383void call_usermodehelper_setkeys(struct subprocess_info *info,
384 struct key *session_keyring)
385{
386 info->ring = session_keyring;
387}
388EXPORT_SYMBOL(call_usermodehelper_setkeys);
389
390/**
391 * call_usermodehelper_setcleanup - set a cleanup function
392 * @info: a subprocess_info returned by call_usermodehelper_setup
393 * @cleanup: a cleanup function
394 *
395 * The cleanup function is just befor ethe subprocess_info is about to
396 * be freed. This can be used for freeing the argv and envp. The
397 * Function must be runnable in either a process context or the
398 * context in which call_usermodehelper_exec is called.
399 */
400void call_usermodehelper_setcleanup(struct subprocess_info *info,
401 void (*cleanup)(char **argv, char **envp))
402{
403 info->cleanup = cleanup;
404}
405EXPORT_SYMBOL(call_usermodehelper_setcleanup);
406
407/**
408 * call_usermodehelper_stdinpipe - set up a pipe to be used for stdin
409 * @sub_info: a subprocess_info returned by call_usermodehelper_setup
410 * @filp: set to the write-end of a pipe
411 *
412 * This constructs a pipe, and sets the read end to be the stdin of the
413 * subprocess, and returns the write-end in *@filp.
414 */
415int call_usermodehelper_stdinpipe(struct subprocess_info *sub_info,
416 struct file **filp)
417{
418 struct file *f;
419
420 f = create_write_pipe();
421 if (IS_ERR(f))
422 return PTR_ERR(f);
423 *filp = f;
424
425 f = create_read_pipe(f);
426 if (IS_ERR(f)) {
427 free_write_pipe(*filp);
428 return PTR_ERR(f);
429 }
430 sub_info->stdin = f;
431
432 return 0;
433}
434EXPORT_SYMBOL(call_usermodehelper_stdinpipe);
435
436/**
437 * call_usermodehelper_exec - start a usermode application
438 * @sub_info: information about the subprocessa
439 * @wait: wait for the application to finish and return status.
440 * when -1 don't wait at all, but you get no useful error back when
441 * the program couldn't be exec'ed. This makes it safe to call
442 * from interrupt context.
443 *
444 * Runs a user-space application. The application is started
445 * asynchronously if wait is not set, and runs as a child of keventd.
446 * (ie. it runs with full root capabilities).
447 */
448int call_usermodehelper_exec(struct subprocess_info *sub_info,
449 enum umh_wait wait)
450{
451 DECLARE_COMPLETION_ONSTACK(done);
452 int retval = 0;
453
454 helper_lock();
455 if (sub_info->path[0] == '\0')
456 goto out;
457
458 if (!khelper_wq || usermodehelper_disabled) {
459 retval = -EBUSY;
460 goto out;
461 }
462
463 sub_info->complete = &done;
464 sub_info->wait = wait;
465
466 queue_work(khelper_wq, &sub_info->work);
467 if (wait == UMH_NO_WAIT) /* task has freed sub_info */
468 goto unlock;
469 wait_for_completion(&done);
470 retval = sub_info->retval;
471
472out:
473 call_usermodehelper_freeinfo(sub_info);
474unlock:
475 helper_unlock();
476 return retval;
477}
478EXPORT_SYMBOL(call_usermodehelper_exec);
479
480/**
481 * call_usermodehelper_pipe - call a usermode helper process with a pipe stdin
482 * @path: path to usermode executable
483 * @argv: arg vector for process
484 * @envp: environment for process
485 * @filp: set to the write-end of a pipe
486 *
487 * This is a simple wrapper which executes a usermode-helper function
488 * with a pipe as stdin. It is implemented entirely in terms of
489 * lower-level call_usermodehelper_* functions.
490 */
491int call_usermodehelper_pipe(char *path, char **argv, char **envp,
492 struct file **filp)
493{
494 struct subprocess_info *sub_info;
495 int ret;
496
497 sub_info = call_usermodehelper_setup(path, argv, envp);
498 if (sub_info == NULL)
499 return -ENOMEM;
500
501 ret = call_usermodehelper_stdinpipe(sub_info, filp);
502 if (ret < 0)
503 goto out;
504
505 return call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC);
506
507 out:
508 call_usermodehelper_freeinfo(sub_info);
509 return ret;
510}
511EXPORT_SYMBOL(call_usermodehelper_pipe);
512
513void __init usermodehelper_init(void)
514{
515 khelper_wq = create_singlethread_workqueue("khelper");
516 BUG_ON(!khelper_wq);
517 register_pm_notifier_callback();
518}