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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_fns(modprobe_path, argv, envp, |
120 | wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC, |
121 | NULL, NULL, NULL); |
122 | |
123 | atomic_dec(&kmod_concurrent); |
124 | return ret; |
125 | } |
126 | EXPORT_SYMBOL(__request_module); |
127 | #endif /* CONFIG_MODULES */ |
128 | |
129 | /* |
130 | * This is the task which runs the usermode application |
131 | */ |
132 | static int ____call_usermodehelper(void *data) |
133 | { |
134 | struct subprocess_info *sub_info = data; |
135 | int retval; |
136 | |
137 | spin_lock_irq(¤t->sighand->siglock); |
138 | flush_signal_handlers(current, 1); |
139 | spin_unlock_irq(¤t->sighand->siglock); |
140 | |
141 | /* We can run anywhere, unlike our parent keventd(). */ |
142 | set_cpus_allowed_ptr(current, cpu_all_mask); |
143 | |
144 | /* |
145 | * Our parent is keventd, which runs with elevated scheduling priority. |
146 | * Avoid propagating that into the userspace child. |
147 | */ |
148 | set_user_nice(current, 0); |
149 | |
150 | if (sub_info->init) { |
151 | retval = sub_info->init(sub_info); |
152 | if (retval) |
153 | goto fail; |
154 | } |
155 | |
156 | retval = kernel_execve(sub_info->path, |
157 | (const char *const *)sub_info->argv, |
158 | (const char *const *)sub_info->envp); |
159 | |
160 | /* Exec failed? */ |
161 | fail: |
162 | sub_info->retval = retval; |
163 | do_exit(0); |
164 | } |
165 | |
166 | void call_usermodehelper_freeinfo(struct subprocess_info *info) |
167 | { |
168 | if (info->cleanup) |
169 | (*info->cleanup)(info); |
170 | kfree(info); |
171 | } |
172 | EXPORT_SYMBOL(call_usermodehelper_freeinfo); |
173 | |
174 | /* Keventd can't block, but this (a child) can. */ |
175 | static int wait_for_helper(void *data) |
176 | { |
177 | struct subprocess_info *sub_info = data; |
178 | pid_t pid; |
179 | |
180 | /* If SIGCLD is ignored sys_wait4 won't populate the status. */ |
181 | spin_lock_irq(¤t->sighand->siglock); |
182 | current->sighand->action[SIGCHLD-1].sa.sa_handler = SIG_DFL; |
183 | spin_unlock_irq(¤t->sighand->siglock); |
184 | |
185 | pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD); |
186 | if (pid < 0) { |
187 | sub_info->retval = pid; |
188 | } else { |
189 | int ret = -ECHILD; |
190 | /* |
191 | * Normally it is bogus to call wait4() from in-kernel because |
192 | * wait4() wants to write the exit code to a userspace address. |
193 | * But wait_for_helper() always runs as keventd, and put_user() |
194 | * to a kernel address works OK for kernel threads, due to their |
195 | * having an mm_segment_t which spans the entire address space. |
196 | * |
197 | * Thus the __user pointer cast is valid here. |
198 | */ |
199 | sys_wait4(pid, (int __user *)&ret, 0, NULL); |
200 | |
201 | /* |
202 | * If ret is 0, either ____call_usermodehelper failed and the |
203 | * real error code is already in sub_info->retval or |
204 | * sub_info->retval is 0 anyway, so don't mess with it then. |
205 | */ |
206 | if (ret) |
207 | sub_info->retval = ret; |
208 | } |
209 | |
210 | complete(sub_info->complete); |
211 | return 0; |
212 | } |
213 | |
214 | /* This is run by khelper thread */ |
215 | static void __call_usermodehelper(struct work_struct *work) |
216 | { |
217 | struct subprocess_info *sub_info = |
218 | container_of(work, struct subprocess_info, work); |
219 | enum umh_wait wait = sub_info->wait; |
220 | pid_t pid; |
221 | |
222 | /* CLONE_VFORK: wait until the usermode helper has execve'd |
223 | * successfully We need the data structures to stay around |
224 | * until that is done. */ |
225 | if (wait == UMH_WAIT_PROC) |
226 | pid = kernel_thread(wait_for_helper, sub_info, |
227 | CLONE_FS | CLONE_FILES | SIGCHLD); |
228 | else |
229 | pid = kernel_thread(____call_usermodehelper, sub_info, |
230 | CLONE_VFORK | SIGCHLD); |
231 | |
232 | switch (wait) { |
233 | case UMH_NO_WAIT: |
234 | call_usermodehelper_freeinfo(sub_info); |
235 | break; |
236 | |
237 | case UMH_WAIT_PROC: |
238 | if (pid > 0) |
239 | break; |
240 | /* FALLTHROUGH */ |
241 | case UMH_WAIT_EXEC: |
242 | if (pid < 0) |
243 | sub_info->retval = pid; |
244 | complete(sub_info->complete); |
245 | } |
246 | } |
247 | |
248 | #ifdef CONFIG_PM_SLEEP |
249 | /* |
250 | * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY |
251 | * (used for preventing user land processes from being created after the user |
252 | * land has been frozen during a system-wide hibernation or suspend operation). |
253 | */ |
254 | static int usermodehelper_disabled; |
255 | |
256 | /* Number of helpers running */ |
257 | static atomic_t running_helpers = ATOMIC_INIT(0); |
258 | |
259 | /* |
260 | * Wait queue head used by usermodehelper_pm_callback() to wait for all running |
261 | * helpers to finish. |
262 | */ |
263 | static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq); |
264 | |
265 | /* |
266 | * Time to wait for running_helpers to become zero before the setting of |
267 | * usermodehelper_disabled in usermodehelper_pm_callback() fails |
268 | */ |
269 | #define RUNNING_HELPERS_TIMEOUT (5 * HZ) |
270 | |
271 | /** |
272 | * usermodehelper_disable - prevent new helpers from being started |
273 | */ |
274 | int usermodehelper_disable(void) |
275 | { |
276 | long retval; |
277 | |
278 | usermodehelper_disabled = 1; |
279 | smp_mb(); |
280 | /* |
281 | * From now on call_usermodehelper_exec() won't start any new |
282 | * helpers, so it is sufficient if running_helpers turns out to |
283 | * be zero at one point (it may be increased later, but that |
284 | * doesn't matter). |
285 | */ |
286 | retval = wait_event_timeout(running_helpers_waitq, |
287 | atomic_read(&running_helpers) == 0, |
288 | RUNNING_HELPERS_TIMEOUT); |
289 | if (retval) |
290 | return 0; |
291 | |
292 | usermodehelper_disabled = 0; |
293 | return -EAGAIN; |
294 | } |
295 | |
296 | /** |
297 | * usermodehelper_enable - allow new helpers to be started again |
298 | */ |
299 | void usermodehelper_enable(void) |
300 | { |
301 | usermodehelper_disabled = 0; |
302 | } |
303 | |
304 | static void helper_lock(void) |
305 | { |
306 | atomic_inc(&running_helpers); |
307 | smp_mb__after_atomic_inc(); |
308 | } |
309 | |
310 | static void helper_unlock(void) |
311 | { |
312 | if (atomic_dec_and_test(&running_helpers)) |
313 | wake_up(&running_helpers_waitq); |
314 | } |
315 | #else /* CONFIG_PM_SLEEP */ |
316 | #define usermodehelper_disabled 0 |
317 | |
318 | static inline void helper_lock(void) {} |
319 | static inline void helper_unlock(void) {} |
320 | #endif /* CONFIG_PM_SLEEP */ |
321 | |
322 | /** |
323 | * call_usermodehelper_setup - prepare to call a usermode helper |
324 | * @path: path to usermode executable |
325 | * @argv: arg vector for process |
326 | * @envp: environment for process |
327 | * @gfp_mask: gfp mask for memory allocation |
328 | * |
329 | * Returns either %NULL on allocation failure, or a subprocess_info |
330 | * structure. This should be passed to call_usermodehelper_exec to |
331 | * exec the process and free the structure. |
332 | */ |
333 | struct subprocess_info *call_usermodehelper_setup(char *path, char **argv, |
334 | char **envp, gfp_t gfp_mask) |
335 | { |
336 | struct subprocess_info *sub_info; |
337 | sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask); |
338 | if (!sub_info) |
339 | goto out; |
340 | |
341 | INIT_WORK(&sub_info->work, __call_usermodehelper); |
342 | sub_info->path = path; |
343 | sub_info->argv = argv; |
344 | sub_info->envp = envp; |
345 | out: |
346 | return sub_info; |
347 | } |
348 | EXPORT_SYMBOL(call_usermodehelper_setup); |
349 | |
350 | /** |
351 | * call_usermodehelper_setfns - set a cleanup/init function |
352 | * @info: a subprocess_info returned by call_usermodehelper_setup |
353 | * @cleanup: a cleanup function |
354 | * @init: an init function |
355 | * @data: arbitrary context sensitive data |
356 | * |
357 | * The init function is used to customize the helper process prior to |
358 | * exec. A non-zero return code causes the process to error out, exit, |
359 | * and return the failure to the calling process |
360 | * |
361 | * The cleanup function is just before ethe subprocess_info is about to |
362 | * be freed. This can be used for freeing the argv and envp. The |
363 | * Function must be runnable in either a process context or the |
364 | * context in which call_usermodehelper_exec is called. |
365 | */ |
366 | void call_usermodehelper_setfns(struct subprocess_info *info, |
367 | int (*init)(struct subprocess_info *info), |
368 | void (*cleanup)(struct subprocess_info *info), |
369 | void *data) |
370 | { |
371 | info->cleanup = cleanup; |
372 | info->init = init; |
373 | info->data = data; |
374 | } |
375 | EXPORT_SYMBOL(call_usermodehelper_setfns); |
376 | |
377 | /** |
378 | * call_usermodehelper_exec - start a usermode application |
379 | * @sub_info: information about the subprocessa |
380 | * @wait: wait for the application to finish and return status. |
381 | * when -1 don't wait at all, but you get no useful error back when |
382 | * the program couldn't be exec'ed. This makes it safe to call |
383 | * from interrupt context. |
384 | * |
385 | * Runs a user-space application. The application is started |
386 | * asynchronously if wait is not set, and runs as a child of keventd. |
387 | * (ie. it runs with full root capabilities). |
388 | */ |
389 | int call_usermodehelper_exec(struct subprocess_info *sub_info, |
390 | enum umh_wait wait) |
391 | { |
392 | DECLARE_COMPLETION_ONSTACK(done); |
393 | int retval = 0; |
394 | |
395 | helper_lock(); |
396 | if (sub_info->path[0] == '\0') |
397 | goto out; |
398 | |
399 | if (!khelper_wq || usermodehelper_disabled) { |
400 | retval = -EBUSY; |
401 | goto out; |
402 | } |
403 | |
404 | sub_info->complete = &done; |
405 | sub_info->wait = wait; |
406 | |
407 | queue_work(khelper_wq, &sub_info->work); |
408 | if (wait == UMH_NO_WAIT) /* task has freed sub_info */ |
409 | goto unlock; |
410 | wait_for_completion(&done); |
411 | retval = sub_info->retval; |
412 | |
413 | out: |
414 | call_usermodehelper_freeinfo(sub_info); |
415 | unlock: |
416 | helper_unlock(); |
417 | return retval; |
418 | } |
419 | EXPORT_SYMBOL(call_usermodehelper_exec); |
420 | |
421 | void __init usermodehelper_init(void) |
422 | { |
423 | khelper_wq = create_singlethread_workqueue("khelper"); |
424 | BUG_ON(!khelper_wq); |
425 | } |
426 |
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