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 <kaos@ocs.com.au> December 1999
14
15 Unblock all signals when we exec a usermode process.
16 Shuu Yamaguchi <shuu@wondernetworkresources.com> December 2000
17
18 call_usermodehelper wait flag, and remove exec_usermodehelper.
19 Rusty Russell <rusty@rustcorp.com.au> 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
41 extern int max_threads;
42
43 static struct workqueue_struct *khelper_wq;
44
45 #ifdef CONFIG_MODULES
46
47 /*
48 modprobe_path is set via /proc/sys.
49 */
50 char 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 * @...: arguments 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 */
request_module(const char * fmt,...)66 int 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 }
115 EXPORT_SYMBOL(request_module);
116 #endif /* CONFIG_MODULES */
117
118 struct subprocess_info {
119 struct work_struct work;
120 struct completion *complete;
121 struct cred *cred;
122 char *path;
123 char **argv;
124 char **envp;
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 */
____call_usermodehelper(void * data)134 static int ____call_usermodehelper(void *data)
135 {
136 struct subprocess_info *sub_info = data;
137 int retval;
138
139 BUG_ON(atomic_read(&sub_info->cred->usage) != 1);
140
141 /* Unblock all signals */
142 spin_lock_irq(¤t->sighand->siglock);
143 flush_signal_handlers(current, 1);
144 sigemptyset(¤t->blocked);
145 recalc_sigpending();
146 spin_unlock_irq(¤t->sighand->siglock);
147
148 /* Install the credentials */
149 commit_creds(sub_info->cred);
150 sub_info->cred = NULL;
151
152 /* Install input pipe when needed */
153 if (sub_info->stdin) {
154 struct files_struct *f = current->files;
155 struct fdtable *fdt;
156 /* no races because files should be private here */
157 sys_close(0);
158 fd_install(0, sub_info->stdin);
159 spin_lock(&f->file_lock);
160 fdt = files_fdtable(f);
161 FD_SET(0, fdt->open_fds);
162 FD_CLR(0, fdt->close_on_exec);
163 spin_unlock(&f->file_lock);
164
165 /* and disallow core files too */
166 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){0, 0};
167 }
168
169 /* We can run anywhere, unlike our parent keventd(). */
170 set_cpus_allowed_ptr(current, CPU_MASK_ALL_PTR);
171
172 /*
173 * Our parent is keventd, which runs with elevated scheduling priority.
174 * Avoid propagating that into the userspace child.
175 */
176 set_user_nice(current, 0);
177
178 retval = kernel_execve(sub_info->path, sub_info->argv, sub_info->envp);
179
180 /* Exec failed? */
181 sub_info->retval = retval;
182 do_exit(0);
183 }
184
call_usermodehelper_freeinfo(struct subprocess_info * info)185 void call_usermodehelper_freeinfo(struct subprocess_info *info)
186 {
187 if (info->cleanup)
188 (*info->cleanup)(info->argv, info->envp);
189 if (info->cred)
190 put_cred(info->cred);
191 kfree(info);
192 }
193 EXPORT_SYMBOL(call_usermodehelper_freeinfo);
194
195 /* Keventd can't block, but this (a child) can. */
wait_for_helper(void * data)196 static int wait_for_helper(void *data)
197 {
198 struct subprocess_info *sub_info = data;
199 pid_t pid;
200
201 /* Install a handler: if SIGCLD isn't handled sys_wait4 won't
202 * populate the status, but will return -ECHILD. */
203 allow_signal(SIGCHLD);
204
205 pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
206 if (pid < 0) {
207 sub_info->retval = pid;
208 } else {
209 int ret;
210
211 /*
212 * Normally it is bogus to call wait4() from in-kernel because
213 * wait4() wants to write the exit code to a userspace address.
214 * But wait_for_helper() always runs as keventd, and put_user()
215 * to a kernel address works OK for kernel threads, due to their
216 * having an mm_segment_t which spans the entire address space.
217 *
218 * Thus the __user pointer cast is valid here.
219 */
220 sys_wait4(pid, (int __user *)&ret, 0, NULL);
221
222 /*
223 * If ret is 0, either ____call_usermodehelper failed and the
224 * real error code is already in sub_info->retval or
225 * sub_info->retval is 0 anyway, so don't mess with it then.
226 */
227 if (ret)
228 sub_info->retval = ret;
229 }
230
231 if (sub_info->wait == UMH_NO_WAIT)
232 call_usermodehelper_freeinfo(sub_info);
233 else
234 complete(sub_info->complete);
235 return 0;
236 }
237
238 /* This is run by khelper thread */
__call_usermodehelper(struct work_struct * work)239 static void __call_usermodehelper(struct work_struct *work)
240 {
241 struct subprocess_info *sub_info =
242 container_of(work, struct subprocess_info, work);
243 pid_t pid;
244 enum umh_wait wait = sub_info->wait;
245
246 BUG_ON(atomic_read(&sub_info->cred->usage) != 1);
247
248 /* CLONE_VFORK: wait until the usermode helper has execve'd
249 * successfully We need the data structures to stay around
250 * until that is done. */
251 if (wait == UMH_WAIT_PROC || wait == UMH_NO_WAIT)
252 pid = kernel_thread(wait_for_helper, sub_info,
253 CLONE_FS | CLONE_FILES | SIGCHLD);
254 else
255 pid = kernel_thread(____call_usermodehelper, sub_info,
256 CLONE_VFORK | SIGCHLD);
257
258 switch (wait) {
259 case UMH_NO_WAIT:
260 break;
261
262 case UMH_WAIT_PROC:
263 if (pid > 0)
264 break;
265 sub_info->retval = pid;
266 /* FALLTHROUGH */
267
268 case UMH_WAIT_EXEC:
269 complete(sub_info->complete);
270 }
271 }
272
273 #ifdef CONFIG_PM_SLEEP
274 /*
275 * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
276 * (used for preventing user land processes from being created after the user
277 * land has been frozen during a system-wide hibernation or suspend operation).
278 */
279 static int usermodehelper_disabled;
280
281 /* Number of helpers running */
282 static atomic_t running_helpers = ATOMIC_INIT(0);
283
284 /*
285 * Wait queue head used by usermodehelper_pm_callback() to wait for all running
286 * helpers to finish.
287 */
288 static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);
289
290 /*
291 * Time to wait for running_helpers to become zero before the setting of
292 * usermodehelper_disabled in usermodehelper_pm_callback() fails
293 */
294 #define RUNNING_HELPERS_TIMEOUT (5 * HZ)
295
296 /**
297 * usermodehelper_disable - prevent new helpers from being started
298 */
usermodehelper_disable(void)299 int usermodehelper_disable(void)
300 {
301 long retval;
302
303 usermodehelper_disabled = 1;
304 smp_mb();
305 /*
306 * From now on call_usermodehelper_exec() won't start any new
307 * helpers, so it is sufficient if running_helpers turns out to
308 * be zero at one point (it may be increased later, but that
309 * doesn't matter).
310 */
311 retval = wait_event_timeout(running_helpers_waitq,
312 atomic_read(&running_helpers) == 0,
313 RUNNING_HELPERS_TIMEOUT);
314 if (retval)
315 return 0;
316
317 usermodehelper_disabled = 0;
318 return -EAGAIN;
319 }
320
321 /**
322 * usermodehelper_enable - allow new helpers to be started again
323 */
usermodehelper_enable(void)324 void usermodehelper_enable(void)
325 {
326 usermodehelper_disabled = 0;
327 }
328
helper_lock(void)329 static void helper_lock(void)
330 {
331 atomic_inc(&running_helpers);
332 smp_mb__after_atomic_inc();
333 }
334
helper_unlock(void)335 static void helper_unlock(void)
336 {
337 if (atomic_dec_and_test(&running_helpers))
338 wake_up(&running_helpers_waitq);
339 }
340 #else /* CONFIG_PM_SLEEP */
341 #define usermodehelper_disabled 0
342
helper_lock(void)343 static inline void helper_lock(void) {}
helper_unlock(void)344 static inline void helper_unlock(void) {}
345 #endif /* CONFIG_PM_SLEEP */
346
347 /**
348 * call_usermodehelper_setup - prepare to call a usermode helper
349 * @path: path to usermode executable
350 * @argv: arg vector for process
351 * @envp: environment for process
352 * @gfp_mask: gfp mask for memory allocation
353 *
354 * Returns either %NULL on allocation failure, or a subprocess_info
355 * structure. This should be passed to call_usermodehelper_exec to
356 * exec the process and free the structure.
357 */
call_usermodehelper_setup(char * path,char ** argv,char ** envp,gfp_t gfp_mask)358 struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
359 char **envp, gfp_t gfp_mask)
360 {
361 struct subprocess_info *sub_info;
362 sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
363 if (!sub_info)
364 goto out;
365
366 INIT_WORK(&sub_info->work, __call_usermodehelper);
367 sub_info->path = path;
368 sub_info->argv = argv;
369 sub_info->envp = envp;
370 sub_info->cred = prepare_usermodehelper_creds();
371 if (!sub_info->cred)
372 return NULL;
373
374 out:
375 return sub_info;
376 }
377 EXPORT_SYMBOL(call_usermodehelper_setup);
378
379 /**
380 * call_usermodehelper_setkeys - set the session keys for usermode helper
381 * @info: a subprocess_info returned by call_usermodehelper_setup
382 * @session_keyring: the session keyring for the process
383 */
call_usermodehelper_setkeys(struct subprocess_info * info,struct key * session_keyring)384 void call_usermodehelper_setkeys(struct subprocess_info *info,
385 struct key *session_keyring)
386 {
387 #ifdef CONFIG_KEYS
388 struct thread_group_cred *tgcred = info->cred->tgcred;
389 key_put(tgcred->session_keyring);
390 tgcred->session_keyring = key_get(session_keyring);
391 #else
392 BUG();
393 #endif
394 }
395 EXPORT_SYMBOL(call_usermodehelper_setkeys);
396
397 /**
398 * call_usermodehelper_setcleanup - set a cleanup function
399 * @info: a subprocess_info returned by call_usermodehelper_setup
400 * @cleanup: a cleanup function
401 *
402 * The cleanup function is just befor ethe subprocess_info is about to
403 * be freed. This can be used for freeing the argv and envp. The
404 * Function must be runnable in either a process context or the
405 * context in which call_usermodehelper_exec is called.
406 */
call_usermodehelper_setcleanup(struct subprocess_info * info,void (* cleanup)(char ** argv,char ** envp))407 void call_usermodehelper_setcleanup(struct subprocess_info *info,
408 void (*cleanup)(char **argv, char **envp))
409 {
410 info->cleanup = cleanup;
411 }
412 EXPORT_SYMBOL(call_usermodehelper_setcleanup);
413
414 /**
415 * call_usermodehelper_stdinpipe - set up a pipe to be used for stdin
416 * @sub_info: a subprocess_info returned by call_usermodehelper_setup
417 * @filp: set to the write-end of a pipe
418 *
419 * This constructs a pipe, and sets the read end to be the stdin of the
420 * subprocess, and returns the write-end in *@filp.
421 */
call_usermodehelper_stdinpipe(struct subprocess_info * sub_info,struct file ** filp)422 int call_usermodehelper_stdinpipe(struct subprocess_info *sub_info,
423 struct file **filp)
424 {
425 struct file *f;
426
427 f = create_write_pipe(0);
428 if (IS_ERR(f))
429 return PTR_ERR(f);
430 *filp = f;
431
432 f = create_read_pipe(f, 0);
433 if (IS_ERR(f)) {
434 free_write_pipe(*filp);
435 return PTR_ERR(f);
436 }
437 sub_info->stdin = f;
438
439 return 0;
440 }
441 EXPORT_SYMBOL(call_usermodehelper_stdinpipe);
442
443 /**
444 * call_usermodehelper_exec - start a usermode application
445 * @sub_info: information about the subprocessa
446 * @wait: wait for the application to finish and return status.
447 * when -1 don't wait at all, but you get no useful error back when
448 * the program couldn't be exec'ed. This makes it safe to call
449 * from interrupt context.
450 *
451 * Runs a user-space application. The application is started
452 * asynchronously if wait is not set, and runs as a child of keventd.
453 * (ie. it runs with full root capabilities).
454 */
call_usermodehelper_exec(struct subprocess_info * sub_info,enum umh_wait wait)455 int call_usermodehelper_exec(struct subprocess_info *sub_info,
456 enum umh_wait wait)
457 {
458 DECLARE_COMPLETION_ONSTACK(done);
459 int retval = 0;
460
461 BUG_ON(atomic_read(&sub_info->cred->usage) != 1);
462
463 helper_lock();
464 if (sub_info->path[0] == '\0')
465 goto out;
466
467 if (!khelper_wq || usermodehelper_disabled) {
468 retval = -EBUSY;
469 goto out;
470 }
471
472 sub_info->complete = &done;
473 sub_info->wait = wait;
474
475 queue_work(khelper_wq, &sub_info->work);
476 if (wait == UMH_NO_WAIT) /* task has freed sub_info */
477 goto unlock;
478 wait_for_completion(&done);
479 retval = sub_info->retval;
480
481 out:
482 call_usermodehelper_freeinfo(sub_info);
483 unlock:
484 helper_unlock();
485 return retval;
486 }
487 EXPORT_SYMBOL(call_usermodehelper_exec);
488
489 /**
490 * call_usermodehelper_pipe - call a usermode helper process with a pipe stdin
491 * @path: path to usermode executable
492 * @argv: arg vector for process
493 * @envp: environment for process
494 * @filp: set to the write-end of a pipe
495 *
496 * This is a simple wrapper which executes a usermode-helper function
497 * with a pipe as stdin. It is implemented entirely in terms of
498 * lower-level call_usermodehelper_* functions.
499 */
call_usermodehelper_pipe(char * path,char ** argv,char ** envp,struct file ** filp)500 int call_usermodehelper_pipe(char *path, char **argv, char **envp,
501 struct file **filp)
502 {
503 struct subprocess_info *sub_info;
504 int ret;
505
506 sub_info = call_usermodehelper_setup(path, argv, envp, GFP_KERNEL);
507 if (sub_info == NULL)
508 return -ENOMEM;
509
510 ret = call_usermodehelper_stdinpipe(sub_info, filp);
511 if (ret < 0)
512 goto out;
513
514 return call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC);
515
516 out:
517 call_usermodehelper_freeinfo(sub_info);
518 return ret;
519 }
520 EXPORT_SYMBOL(call_usermodehelper_pipe);
521
usermodehelper_init(void)522 void __init usermodehelper_init(void)
523 {
524 khelper_wq = create_singlethread_workqueue("khelper");
525 BUG_ON(!khelper_wq);
526 }
527