projects/linux·blob v2.6.38-rc4 · refs

425 lines · 11.8 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/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
42extern int max_threads;
43
44static struct workqueue_struct *khelper_wq;
45
46#ifdef CONFIG_MODULES
47
48/*
49 modprobe_path is set via /proc/sys.
50*/
51char 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 */
68int __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}
126EXPORT_SYMBOL(__request_module);
127#endif /* CONFIG_MODULES */
128
129/*
130 * This is the task which runs the usermode application
131 */
132static int ____call_usermodehelper(void *data)
133{
134 struct subprocess_info *sub_info = data;
135 int retval;
136
137 spin_lock_irq(&current->sighand->siglock);
138 flush_signal_handlers(current, 1);
139 spin_unlock_irq(&current->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? */
161fail:
162 sub_info->retval = retval;
163 do_exit(0);
164}
165
166void call_usermodehelper_freeinfo(struct subprocess_info *info)
167{
168 if (info->cleanup)
169 (*info->cleanup)(info);
170 kfree(info);
171}
172EXPORT_SYMBOL(call_usermodehelper_freeinfo);
173
174/* Keventd can't block, but this (a child) can. */
175static 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(&current->sighand->siglock);
182 current->sighand->action[SIGCHLD-1].sa.sa_handler = SIG_DFL;
183 spin_unlock_irq(&current->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 */
215static 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 */
254static int usermodehelper_disabled;
255
256/* Number of helpers running */
257static 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 */
263static 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 */
274int 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 */
299void usermodehelper_enable(void)
300{
301 usermodehelper_disabled = 0;
302}
303
304static void helper_lock(void)
305{
306 atomic_inc(&running_helpers);
307 smp_mb__after_atomic_inc();
308}
309
310static 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
318static inline void helper_lock(void) {}
319static 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 */
333struct 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}
348EXPORT_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 */
366void 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}
375EXPORT_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 */
389int 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
413out:
414 call_usermodehelper_freeinfo(sub_info);
415unlock:
416 helper_unlock();
417 return retval;
418}
419EXPORT_SYMBOL(call_usermodehelper_exec);
420
421void __init usermodehelper_init(void)
422{
423 khelper_wq = create_singlethread_workqueue("khelper");
424 BUG_ON(!khelper_wq);
425}