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Source at commit b13e7eb172b6f08e5fc22da162bdde5fcde201b5 created 11 years 11 months ago. By Maarten ter Huurne, fbcon: Add 6x10 font | |
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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/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 | |
44 | extern int max_threads; |
45 | |
46 | static struct workqueue_struct *khelper_wq; |
47 | |
48 | #define CAP_BSET (void *)1 |
49 | #define CAP_PI (void *)2 |
50 | |
51 | static kernel_cap_t usermodehelper_bset = CAP_FULL_SET; |
52 | static kernel_cap_t usermodehelper_inheritable = CAP_FULL_SET; |
53 | static DEFINE_SPINLOCK(umh_sysctl_lock); |
54 | static DECLARE_RWSEM(umhelper_sem); |
55 | |
56 | #ifdef CONFIG_MODULES |
57 | |
58 | /* |
59 | modprobe_path is set via /proc/sys. |
60 | */ |
61 | char 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 | */ |
78 | int __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 | } |
138 | EXPORT_SYMBOL(__request_module); |
139 | #endif /* CONFIG_MODULES */ |
140 | |
141 | /* |
142 | * This is the task which runs the usermode application |
143 | */ |
144 | static 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(¤t->sighand->siglock); |
151 | flush_signal_handlers(current, 1); |
152 | spin_unlock_irq(¤t->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? */ |
189 | fail: |
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); |
198 | kfree(info); |
199 | } |
200 | EXPORT_SYMBOL(call_usermodehelper_freeinfo); |
201 | |
202 | /* Keventd can't block, but this (a child) can. */ |
203 | static 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(¤t->sighand->siglock); |
210 | current->sighand->action[SIGCHLD-1].sa.sa_handler = SIG_DFL; |
211 | spin_unlock_irq(¤t->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 */ |
243 | static 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 | */ |
282 | static int usermodehelper_disabled = 1; |
283 | |
284 | /* Number of helpers running */ |
285 | static 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 | */ |
291 | static 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 | |
299 | void read_lock_usermodehelper(void) |
300 | { |
301 | down_read(&umhelper_sem); |
302 | } |
303 | EXPORT_SYMBOL_GPL(read_lock_usermodehelper); |
304 | |
305 | void read_unlock_usermodehelper(void) |
306 | { |
307 | up_read(&umhelper_sem); |
308 | } |
309 | EXPORT_SYMBOL_GPL(read_unlock_usermodehelper); |
310 | |
311 | /** |
312 | * usermodehelper_disable - prevent new helpers from being started |
313 | */ |
314 | int 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 | */ |
343 | void 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 | */ |
353 | bool usermodehelper_is_disabled(void) |
354 | { |
355 | return usermodehelper_disabled; |
356 | } |
357 | EXPORT_SYMBOL_GPL(usermodehelper_is_disabled); |
358 | |
359 | static void helper_lock(void) |
360 | { |
361 | atomic_inc(&running_helpers); |
362 | smp_mb__after_atomic_inc(); |
363 | } |
364 | |
365 | static 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 | */ |
382 | struct 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 | } |
397 | EXPORT_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 | */ |
415 | void 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 | } |
424 | EXPORT_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 | */ |
438 | int 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 | |
462 | out: |
463 | call_usermodehelper_freeinfo(sub_info); |
464 | unlock: |
465 | helper_unlock(); |
466 | return retval; |
467 | } |
468 | EXPORT_SYMBOL(call_usermodehelper_exec); |
469 | |
470 | static 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 | |
530 | struct 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 | |
548 | void __init usermodehelper_init(void) |
549 | { |
550 | khelper_wq = create_singlethread_workqueue("khelper"); |
551 | BUG_ON(!khelper_wq); |
552 | } |
553 |
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