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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/completion.h> |
28 | #include <linux/file.h> |
29 | #include <linux/fdtable.h> |
30 | #include <linux/workqueue.h> |
31 | #include <linux/security.h> |
32 | #include <linux/mount.h> |
33 | #include <linux/kernel.h> |
34 | #include <linux/init.h> |
35 | #include <linux/resource.h> |
36 | #include <linux/notifier.h> |
37 | #include <linux/suspend.h> |
38 | #include <asm/uaccess.h> |
39 | |
40 | #include <trace/events/module.h> |
41 | |
42 | extern int max_threads; |
43 | |
44 | static struct workqueue_struct *khelper_wq; |
45 | |
46 | #ifdef CONFIG_MODULES |
47 | |
48 | /* |
49 | modprobe_path is set via /proc/sys. |
50 | */ |
51 | char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe"; |
52 | |
53 | /** |
54 | * __request_module - try to load a kernel module |
55 | * @wait: wait (or not) for the operation to complete |
56 | * @fmt: printf style format string for the name of the module |
57 | * @...: arguments as specified in the format string |
58 | * |
59 | * Load a module using the user mode module loader. The function returns |
60 | * zero on success or a negative errno code on failure. Note that a |
61 | * successful module load does not mean the module did not then unload |
62 | * and exit on an error of its own. Callers must check that the service |
63 | * they requested is now available not blindly invoke it. |
64 | * |
65 | * If module auto-loading support is disabled then this function |
66 | * becomes a no-operation. |
67 | */ |
68 | int __request_module(bool wait, const char *fmt, ...) |
69 | { |
70 | va_list args; |
71 | char module_name[MODULE_NAME_LEN]; |
72 | unsigned int max_modprobes; |
73 | int ret; |
74 | char *argv[] = { modprobe_path, "-q", "--", module_name, NULL }; |
75 | static char *envp[] = { "HOME=/", |
76 | "TERM=linux", |
77 | "PATH=/sbin:/usr/sbin:/bin:/usr/bin", |
78 | NULL }; |
79 | static atomic_t kmod_concurrent = ATOMIC_INIT(0); |
80 | #define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */ |
81 | static int kmod_loop_msg; |
82 | |
83 | va_start(args, fmt); |
84 | ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args); |
85 | va_end(args); |
86 | if (ret >= MODULE_NAME_LEN) |
87 | return -ENAMETOOLONG; |
88 | |
89 | ret = security_kernel_module_request(module_name); |
90 | if (ret) |
91 | return ret; |
92 | |
93 | /* If modprobe needs a service that is in a module, we get a recursive |
94 | * loop. Limit the number of running kmod threads to max_threads/2 or |
95 | * MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method |
96 | * would be to run the parents of this process, counting how many times |
97 | * kmod was invoked. That would mean accessing the internals of the |
98 | * process tables to get the command line, proc_pid_cmdline is static |
99 | * and it is not worth changing the proc code just to handle this case. |
100 | * KAO. |
101 | * |
102 | * "trace the ppid" is simple, but will fail if someone's |
103 | * parent exits. I think this is as good as it gets. --RR |
104 | */ |
105 | max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT); |
106 | atomic_inc(&kmod_concurrent); |
107 | if (atomic_read(&kmod_concurrent) > max_modprobes) { |
108 | /* We may be blaming an innocent here, but unlikely */ |
109 | if (kmod_loop_msg++ < 5) |
110 | printk(KERN_ERR |
111 | "request_module: runaway loop modprobe %s\n", |
112 | module_name); |
113 | atomic_dec(&kmod_concurrent); |
114 | return -ENOMEM; |
115 | } |
116 | |
117 | trace_module_request(module_name, wait, _RET_IP_); |
118 | |
119 | ret = call_usermodehelper(modprobe_path, argv, envp, |
120 | wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC); |
121 | atomic_dec(&kmod_concurrent); |
122 | return ret; |
123 | } |
124 | EXPORT_SYMBOL(__request_module); |
125 | #endif /* CONFIG_MODULES */ |
126 | |
127 | struct subprocess_info { |
128 | struct work_struct work; |
129 | struct completion *complete; |
130 | struct cred *cred; |
131 | char *path; |
132 | char **argv; |
133 | char **envp; |
134 | enum umh_wait wait; |
135 | int retval; |
136 | struct file *stdin; |
137 | void (*cleanup)(char **argv, char **envp); |
138 | }; |
139 | |
140 | /* |
141 | * This is the task which runs the usermode application |
142 | */ |
143 | static int ____call_usermodehelper(void *data) |
144 | { |
145 | struct subprocess_info *sub_info = data; |
146 | int retval; |
147 | |
148 | BUG_ON(atomic_read(&sub_info->cred->usage) != 1); |
149 | |
150 | /* Unblock all signals */ |
151 | spin_lock_irq(¤t->sighand->siglock); |
152 | flush_signal_handlers(current, 1); |
153 | sigemptyset(¤t->blocked); |
154 | recalc_sigpending(); |
155 | spin_unlock_irq(¤t->sighand->siglock); |
156 | |
157 | /* Install the credentials */ |
158 | commit_creds(sub_info->cred); |
159 | sub_info->cred = NULL; |
160 | |
161 | /* Install input pipe when needed */ |
162 | if (sub_info->stdin) { |
163 | struct files_struct *f = current->files; |
164 | struct fdtable *fdt; |
165 | /* no races because files should be private here */ |
166 | sys_close(0); |
167 | fd_install(0, sub_info->stdin); |
168 | spin_lock(&f->file_lock); |
169 | fdt = files_fdtable(f); |
170 | FD_SET(0, fdt->open_fds); |
171 | FD_CLR(0, fdt->close_on_exec); |
172 | spin_unlock(&f->file_lock); |
173 | |
174 | /* and disallow core files too */ |
175 | current->signal->rlim[RLIMIT_CORE] = (struct rlimit){0, 0}; |
176 | } |
177 | |
178 | /* We can run anywhere, unlike our parent keventd(). */ |
179 | set_cpus_allowed_ptr(current, cpu_all_mask); |
180 | |
181 | /* |
182 | * Our parent is keventd, which runs with elevated scheduling priority. |
183 | * Avoid propagating that into the userspace child. |
184 | */ |
185 | set_user_nice(current, 0); |
186 | |
187 | retval = kernel_execve(sub_info->path, sub_info->argv, sub_info->envp); |
188 | |
189 | /* Exec failed? */ |
190 | sub_info->retval = retval; |
191 | do_exit(0); |
192 | } |
193 | |
194 | void call_usermodehelper_freeinfo(struct subprocess_info *info) |
195 | { |
196 | if (info->cleanup) |
197 | (*info->cleanup)(info->argv, info->envp); |
198 | if (info->cred) |
199 | put_cred(info->cred); |
200 | kfree(info); |
201 | } |
202 | EXPORT_SYMBOL(call_usermodehelper_freeinfo); |
203 | |
204 | /* Keventd can't block, but this (a child) can. */ |
205 | static int wait_for_helper(void *data) |
206 | { |
207 | struct subprocess_info *sub_info = data; |
208 | pid_t pid; |
209 | |
210 | /* Install a handler: if SIGCLD isn't handled sys_wait4 won't |
211 | * populate the status, but will return -ECHILD. */ |
212 | allow_signal(SIGCHLD); |
213 | |
214 | pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD); |
215 | if (pid < 0) { |
216 | sub_info->retval = pid; |
217 | } else { |
218 | int ret; |
219 | |
220 | /* |
221 | * Normally it is bogus to call wait4() from in-kernel because |
222 | * wait4() wants to write the exit code to a userspace address. |
223 | * But wait_for_helper() always runs as keventd, and put_user() |
224 | * to a kernel address works OK for kernel threads, due to their |
225 | * having an mm_segment_t which spans the entire address space. |
226 | * |
227 | * Thus the __user pointer cast is valid here. |
228 | */ |
229 | sys_wait4(pid, (int __user *)&ret, 0, NULL); |
230 | |
231 | /* |
232 | * If ret is 0, either ____call_usermodehelper failed and the |
233 | * real error code is already in sub_info->retval or |
234 | * sub_info->retval is 0 anyway, so don't mess with it then. |
235 | */ |
236 | if (ret) |
237 | sub_info->retval = ret; |
238 | } |
239 | |
240 | if (sub_info->wait == UMH_NO_WAIT) |
241 | call_usermodehelper_freeinfo(sub_info); |
242 | else |
243 | complete(sub_info->complete); |
244 | return 0; |
245 | } |
246 | |
247 | /* This is run by khelper thread */ |
248 | static void __call_usermodehelper(struct work_struct *work) |
249 | { |
250 | struct subprocess_info *sub_info = |
251 | container_of(work, struct subprocess_info, work); |
252 | pid_t pid; |
253 | enum umh_wait wait = sub_info->wait; |
254 | |
255 | BUG_ON(atomic_read(&sub_info->cred->usage) != 1); |
256 | |
257 | /* CLONE_VFORK: wait until the usermode helper has execve'd |
258 | * successfully We need the data structures to stay around |
259 | * until that is done. */ |
260 | if (wait == UMH_WAIT_PROC || wait == UMH_NO_WAIT) |
261 | pid = kernel_thread(wait_for_helper, sub_info, |
262 | CLONE_FS | CLONE_FILES | SIGCHLD); |
263 | else |
264 | pid = kernel_thread(____call_usermodehelper, sub_info, |
265 | CLONE_VFORK | SIGCHLD); |
266 | |
267 | switch (wait) { |
268 | case UMH_NO_WAIT: |
269 | break; |
270 | |
271 | case UMH_WAIT_PROC: |
272 | if (pid > 0) |
273 | break; |
274 | sub_info->retval = pid; |
275 | /* FALLTHROUGH */ |
276 | |
277 | case UMH_WAIT_EXEC: |
278 | complete(sub_info->complete); |
279 | } |
280 | } |
281 | |
282 | #ifdef CONFIG_PM_SLEEP |
283 | /* |
284 | * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY |
285 | * (used for preventing user land processes from being created after the user |
286 | * land has been frozen during a system-wide hibernation or suspend operation). |
287 | */ |
288 | static int usermodehelper_disabled; |
289 | |
290 | /* Number of helpers running */ |
291 | static atomic_t running_helpers = ATOMIC_INIT(0); |
292 | |
293 | /* |
294 | * Wait queue head used by usermodehelper_pm_callback() to wait for all running |
295 | * helpers to finish. |
296 | */ |
297 | static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq); |
298 | |
299 | /* |
300 | * Time to wait for running_helpers to become zero before the setting of |
301 | * usermodehelper_disabled in usermodehelper_pm_callback() fails |
302 | */ |
303 | #define RUNNING_HELPERS_TIMEOUT (5 * HZ) |
304 | |
305 | /** |
306 | * usermodehelper_disable - prevent new helpers from being started |
307 | */ |
308 | int usermodehelper_disable(void) |
309 | { |
310 | long retval; |
311 | |
312 | usermodehelper_disabled = 1; |
313 | smp_mb(); |
314 | /* |
315 | * From now on call_usermodehelper_exec() won't start any new |
316 | * helpers, so it is sufficient if running_helpers turns out to |
317 | * be zero at one point (it may be increased later, but that |
318 | * doesn't matter). |
319 | */ |
320 | retval = wait_event_timeout(running_helpers_waitq, |
321 | atomic_read(&running_helpers) == 0, |
322 | RUNNING_HELPERS_TIMEOUT); |
323 | if (retval) |
324 | return 0; |
325 | |
326 | usermodehelper_disabled = 0; |
327 | return -EAGAIN; |
328 | } |
329 | |
330 | /** |
331 | * usermodehelper_enable - allow new helpers to be started again |
332 | */ |
333 | void usermodehelper_enable(void) |
334 | { |
335 | usermodehelper_disabled = 0; |
336 | } |
337 | |
338 | static void helper_lock(void) |
339 | { |
340 | atomic_inc(&running_helpers); |
341 | smp_mb__after_atomic_inc(); |
342 | } |
343 | |
344 | static void helper_unlock(void) |
345 | { |
346 | if (atomic_dec_and_test(&running_helpers)) |
347 | wake_up(&running_helpers_waitq); |
348 | } |
349 | #else /* CONFIG_PM_SLEEP */ |
350 | #define usermodehelper_disabled 0 |
351 | |
352 | static inline void helper_lock(void) {} |
353 | static inline void helper_unlock(void) {} |
354 | #endif /* CONFIG_PM_SLEEP */ |
355 | |
356 | /** |
357 | * call_usermodehelper_setup - prepare to call a usermode helper |
358 | * @path: path to usermode executable |
359 | * @argv: arg vector for process |
360 | * @envp: environment for process |
361 | * @gfp_mask: gfp mask for memory allocation |
362 | * |
363 | * Returns either %NULL on allocation failure, or a subprocess_info |
364 | * structure. This should be passed to call_usermodehelper_exec to |
365 | * exec the process and free the structure. |
366 | */ |
367 | struct subprocess_info *call_usermodehelper_setup(char *path, char **argv, |
368 | char **envp, gfp_t gfp_mask) |
369 | { |
370 | struct subprocess_info *sub_info; |
371 | sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask); |
372 | if (!sub_info) |
373 | goto out; |
374 | |
375 | INIT_WORK(&sub_info->work, __call_usermodehelper); |
376 | sub_info->path = path; |
377 | sub_info->argv = argv; |
378 | sub_info->envp = envp; |
379 | sub_info->cred = prepare_usermodehelper_creds(); |
380 | if (!sub_info->cred) { |
381 | kfree(sub_info); |
382 | return NULL; |
383 | } |
384 | |
385 | out: |
386 | return sub_info; |
387 | } |
388 | EXPORT_SYMBOL(call_usermodehelper_setup); |
389 | |
390 | /** |
391 | * call_usermodehelper_setkeys - set the session keys for usermode helper |
392 | * @info: a subprocess_info returned by call_usermodehelper_setup |
393 | * @session_keyring: the session keyring for the process |
394 | */ |
395 | void call_usermodehelper_setkeys(struct subprocess_info *info, |
396 | struct key *session_keyring) |
397 | { |
398 | #ifdef CONFIG_KEYS |
399 | struct thread_group_cred *tgcred = info->cred->tgcred; |
400 | key_put(tgcred->session_keyring); |
401 | tgcred->session_keyring = key_get(session_keyring); |
402 | #else |
403 | BUG(); |
404 | #endif |
405 | } |
406 | EXPORT_SYMBOL(call_usermodehelper_setkeys); |
407 | |
408 | /** |
409 | * call_usermodehelper_setcleanup - set a cleanup function |
410 | * @info: a subprocess_info returned by call_usermodehelper_setup |
411 | * @cleanup: a cleanup function |
412 | * |
413 | * The cleanup function is just befor ethe subprocess_info is about to |
414 | * be freed. This can be used for freeing the argv and envp. The |
415 | * Function must be runnable in either a process context or the |
416 | * context in which call_usermodehelper_exec is called. |
417 | */ |
418 | void call_usermodehelper_setcleanup(struct subprocess_info *info, |
419 | void (*cleanup)(char **argv, char **envp)) |
420 | { |
421 | info->cleanup = cleanup; |
422 | } |
423 | EXPORT_SYMBOL(call_usermodehelper_setcleanup); |
424 | |
425 | /** |
426 | * call_usermodehelper_stdinpipe - set up a pipe to be used for stdin |
427 | * @sub_info: a subprocess_info returned by call_usermodehelper_setup |
428 | * @filp: set to the write-end of a pipe |
429 | * |
430 | * This constructs a pipe, and sets the read end to be the stdin of the |
431 | * subprocess, and returns the write-end in *@filp. |
432 | */ |
433 | int call_usermodehelper_stdinpipe(struct subprocess_info *sub_info, |
434 | struct file **filp) |
435 | { |
436 | struct file *f; |
437 | |
438 | f = create_write_pipe(0); |
439 | if (IS_ERR(f)) |
440 | return PTR_ERR(f); |
441 | *filp = f; |
442 | |
443 | f = create_read_pipe(f, 0); |
444 | if (IS_ERR(f)) { |
445 | free_write_pipe(*filp); |
446 | return PTR_ERR(f); |
447 | } |
448 | sub_info->stdin = f; |
449 | |
450 | return 0; |
451 | } |
452 | EXPORT_SYMBOL(call_usermodehelper_stdinpipe); |
453 | |
454 | /** |
455 | * call_usermodehelper_exec - start a usermode application |
456 | * @sub_info: information about the subprocessa |
457 | * @wait: wait for the application to finish and return status. |
458 | * when -1 don't wait at all, but you get no useful error back when |
459 | * the program couldn't be exec'ed. This makes it safe to call |
460 | * from interrupt context. |
461 | * |
462 | * Runs a user-space application. The application is started |
463 | * asynchronously if wait is not set, and runs as a child of keventd. |
464 | * (ie. it runs with full root capabilities). |
465 | */ |
466 | int call_usermodehelper_exec(struct subprocess_info *sub_info, |
467 | enum umh_wait wait) |
468 | { |
469 | DECLARE_COMPLETION_ONSTACK(done); |
470 | int retval = 0; |
471 | |
472 | BUG_ON(atomic_read(&sub_info->cred->usage) != 1); |
473 | validate_creds(sub_info->cred); |
474 | |
475 | helper_lock(); |
476 | if (sub_info->path[0] == '\0') |
477 | goto out; |
478 | |
479 | if (!khelper_wq || usermodehelper_disabled) { |
480 | retval = -EBUSY; |
481 | goto out; |
482 | } |
483 | |
484 | sub_info->complete = &done; |
485 | sub_info->wait = wait; |
486 | |
487 | queue_work(khelper_wq, &sub_info->work); |
488 | if (wait == UMH_NO_WAIT) /* task has freed sub_info */ |
489 | goto unlock; |
490 | wait_for_completion(&done); |
491 | retval = sub_info->retval; |
492 | |
493 | out: |
494 | call_usermodehelper_freeinfo(sub_info); |
495 | unlock: |
496 | helper_unlock(); |
497 | return retval; |
498 | } |
499 | EXPORT_SYMBOL(call_usermodehelper_exec); |
500 | |
501 | /** |
502 | * call_usermodehelper_pipe - call a usermode helper process with a pipe stdin |
503 | * @path: path to usermode executable |
504 | * @argv: arg vector for process |
505 | * @envp: environment for process |
506 | * @filp: set to the write-end of a pipe |
507 | * |
508 | * This is a simple wrapper which executes a usermode-helper function |
509 | * with a pipe as stdin. It is implemented entirely in terms of |
510 | * lower-level call_usermodehelper_* functions. |
511 | */ |
512 | int call_usermodehelper_pipe(char *path, char **argv, char **envp, |
513 | struct file **filp) |
514 | { |
515 | struct subprocess_info *sub_info; |
516 | int ret; |
517 | |
518 | sub_info = call_usermodehelper_setup(path, argv, envp, GFP_KERNEL); |
519 | if (sub_info == NULL) |
520 | return -ENOMEM; |
521 | |
522 | ret = call_usermodehelper_stdinpipe(sub_info, filp); |
523 | if (ret < 0) { |
524 | call_usermodehelper_freeinfo(sub_info); |
525 | return ret; |
526 | } |
527 | |
528 | ret = call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC); |
529 | if (ret < 0) /* Failed to execute helper, close pipe */ |
530 | filp_close(*filp, NULL); |
531 | |
532 | return ret; |
533 | } |
534 | EXPORT_SYMBOL(call_usermodehelper_pipe); |
535 | |
536 | void __init usermodehelper_init(void) |
537 | { |
538 | khelper_wq = create_singlethread_workqueue("khelper"); |
539 | BUG_ON(!khelper_wq); |
540 | } |
541 |
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