2 kmod, the new module loader (replaces kerneld)
5 Reorganized not to be a daemon by Adam Richter, with guidance
8 Modified to avoid chroot and file sharing problems.
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
15 Unblock all signals when we exec a usermode process.
16 Shuu Yamaguchi <shuu@wondernetworkresources.com> December 2000
18 call_usermodehelper wait flag, and remove exec_usermodehelper.
19 Rusty Russell <rusty@rustcorp.com.au> Jan 2003
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>
40 #include <trace/events/module.h>
42 extern int max_threads;
44 static struct workqueue_struct *khelper_wq;
49 modprobe_path is set via /proc/sys.
51 char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
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
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.
65 * If module auto-loading support is disabled then this function
66 * becomes a no-operation.
68 int __request_module(bool wait, const char *fmt, ...)
71 char module_name[MODULE_NAME_LEN];
72 unsigned int max_modprobes;
74 char *argv[] = { modprobe_path, "-q", "--", module_name, NULL };
75 static char *envp[] = { "HOME=/",
77 "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
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;
84 ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
86 if (ret >= MODULE_NAME_LEN)
89 ret = security_kernel_module_request(module_name);
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.
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
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)
111 "request_module: runaway loop modprobe %s\n",
113 atomic_dec(&kmod_concurrent);
117 trace_module_request(module_name, wait, _RET_IP_);
119 ret = call_usermodehelper_fns(modprobe_path, argv, envp,
120 wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC,
123 atomic_dec(&kmod_concurrent);
126 EXPORT_SYMBOL(__request_module);
127 #endif /* CONFIG_MODULES */
130 * This is the task which runs the usermode application
132 static int ____call_usermodehelper(void *data)
134 struct subprocess_info *sub_info = data;
137 BUG_ON(atomic_read(&sub_info->cred->usage) != 1);
139 /* Unblock all signals */
140 spin_lock_irq(¤t->sighand->siglock);
141 flush_signal_handlers(current, 1);
142 sigemptyset(¤t->blocked);
144 spin_unlock_irq(¤t->sighand->siglock);
146 /* Install the credentials */
147 commit_creds(sub_info->cred);
148 sub_info->cred = NULL;
150 /* We can run anywhere, unlike our parent keventd(). */
151 set_cpus_allowed_ptr(current, cpu_all_mask);
154 * Our parent is keventd, which runs with elevated scheduling priority.
155 * Avoid propagating that into the userspace child.
157 set_user_nice(current, 0);
159 if (sub_info->init) {
160 retval = sub_info->init(sub_info);
165 retval = kernel_execve(sub_info->path, sub_info->argv, sub_info->envp);
169 sub_info->retval = retval;
173 void call_usermodehelper_freeinfo(struct subprocess_info *info)
176 (*info->cleanup)(info);
178 put_cred(info->cred);
181 EXPORT_SYMBOL(call_usermodehelper_freeinfo);
183 /* Keventd can't block, but this (a child) can. */
184 static int wait_for_helper(void *data)
186 struct subprocess_info *sub_info = data;
189 /* Install a handler: if SIGCLD isn't handled sys_wait4 won't
190 * populate the status, but will return -ECHILD. */
191 allow_signal(SIGCHLD);
193 pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
195 sub_info->retval = pid;
200 * Normally it is bogus to call wait4() from in-kernel because
201 * wait4() wants to write the exit code to a userspace address.
202 * But wait_for_helper() always runs as keventd, and put_user()
203 * to a kernel address works OK for kernel threads, due to their
204 * having an mm_segment_t which spans the entire address space.
206 * Thus the __user pointer cast is valid here.
208 sys_wait4(pid, (int __user *)&ret, 0, NULL);
211 * If ret is 0, either ____call_usermodehelper failed and the
212 * real error code is already in sub_info->retval or
213 * sub_info->retval is 0 anyway, so don't mess with it then.
216 sub_info->retval = ret;
219 if (sub_info->wait == UMH_NO_WAIT)
220 call_usermodehelper_freeinfo(sub_info);
222 complete(sub_info->complete);
226 /* This is run by khelper thread */
227 static void __call_usermodehelper(struct work_struct *work)
229 struct subprocess_info *sub_info =
230 container_of(work, struct subprocess_info, work);
232 enum umh_wait wait = sub_info->wait;
234 BUG_ON(atomic_read(&sub_info->cred->usage) != 1);
236 /* CLONE_VFORK: wait until the usermode helper has execve'd
237 * successfully We need the data structures to stay around
238 * until that is done. */
239 if (wait == UMH_WAIT_PROC || wait == UMH_NO_WAIT)
240 pid = kernel_thread(wait_for_helper, sub_info,
241 CLONE_FS | CLONE_FILES | SIGCHLD);
243 pid = kernel_thread(____call_usermodehelper, sub_info,
244 CLONE_VFORK | SIGCHLD);
253 sub_info->retval = pid;
257 complete(sub_info->complete);
261 #ifdef CONFIG_PM_SLEEP
263 * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
264 * (used for preventing user land processes from being created after the user
265 * land has been frozen during a system-wide hibernation or suspend operation).
267 static int usermodehelper_disabled;
269 /* Number of helpers running */
270 static atomic_t running_helpers = ATOMIC_INIT(0);
273 * Wait queue head used by usermodehelper_pm_callback() to wait for all running
276 static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);
279 * Time to wait for running_helpers to become zero before the setting of
280 * usermodehelper_disabled in usermodehelper_pm_callback() fails
282 #define RUNNING_HELPERS_TIMEOUT (5 * HZ)
285 * usermodehelper_disable - prevent new helpers from being started
287 int usermodehelper_disable(void)
291 usermodehelper_disabled = 1;
294 * From now on call_usermodehelper_exec() won't start any new
295 * helpers, so it is sufficient if running_helpers turns out to
296 * be zero at one point (it may be increased later, but that
299 retval = wait_event_timeout(running_helpers_waitq,
300 atomic_read(&running_helpers) == 0,
301 RUNNING_HELPERS_TIMEOUT);
305 usermodehelper_disabled = 0;
310 * usermodehelper_enable - allow new helpers to be started again
312 void usermodehelper_enable(void)
314 usermodehelper_disabled = 0;
317 static void helper_lock(void)
319 atomic_inc(&running_helpers);
320 smp_mb__after_atomic_inc();
323 static void helper_unlock(void)
325 if (atomic_dec_and_test(&running_helpers))
326 wake_up(&running_helpers_waitq);
328 #else /* CONFIG_PM_SLEEP */
329 #define usermodehelper_disabled 0
331 static inline void helper_lock(void) {}
332 static inline void helper_unlock(void) {}
333 #endif /* CONFIG_PM_SLEEP */
336 * call_usermodehelper_setup - prepare to call a usermode helper
337 * @path: path to usermode executable
338 * @argv: arg vector for process
339 * @envp: environment for process
340 * @gfp_mask: gfp mask for memory allocation
342 * Returns either %NULL on allocation failure, or a subprocess_info
343 * structure. This should be passed to call_usermodehelper_exec to
344 * exec the process and free the structure.
346 struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
347 char **envp, gfp_t gfp_mask)
349 struct subprocess_info *sub_info;
350 sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
354 INIT_WORK(&sub_info->work, __call_usermodehelper);
355 sub_info->path = path;
356 sub_info->argv = argv;
357 sub_info->envp = envp;
358 sub_info->cred = prepare_usermodehelper_creds();
359 if (!sub_info->cred) {
367 EXPORT_SYMBOL(call_usermodehelper_setup);
370 * call_usermodehelper_setkeys - set the session keys for usermode helper
371 * @info: a subprocess_info returned by call_usermodehelper_setup
372 * @session_keyring: the session keyring for the process
374 void call_usermodehelper_setkeys(struct subprocess_info *info,
375 struct key *session_keyring)
378 struct thread_group_cred *tgcred = info->cred->tgcred;
379 key_put(tgcred->session_keyring);
380 tgcred->session_keyring = key_get(session_keyring);
385 EXPORT_SYMBOL(call_usermodehelper_setkeys);
388 * call_usermodehelper_setfns - set a cleanup/init function
389 * @info: a subprocess_info returned by call_usermodehelper_setup
390 * @cleanup: a cleanup function
391 * @init: an init function
392 * @data: arbitrary context sensitive data
394 * The init function is used to customize the helper process prior to
395 * exec. A non-zero return code causes the process to error out, exit,
396 * and return the failure to the calling process
398 * The cleanup function is just before ethe subprocess_info is about to
399 * be freed. This can be used for freeing the argv and envp. The
400 * Function must be runnable in either a process context or the
401 * context in which call_usermodehelper_exec is called.
403 void call_usermodehelper_setfns(struct subprocess_info *info,
404 int (*init)(struct subprocess_info *info),
405 void (*cleanup)(struct subprocess_info *info),
408 info->cleanup = cleanup;
412 EXPORT_SYMBOL(call_usermodehelper_setfns);
415 * call_usermodehelper_exec - start a usermode application
416 * @sub_info: information about the subprocessa
417 * @wait: wait for the application to finish and return status.
418 * when -1 don't wait at all, but you get no useful error back when
419 * the program couldn't be exec'ed. This makes it safe to call
420 * from interrupt context.
422 * Runs a user-space application. The application is started
423 * asynchronously if wait is not set, and runs as a child of keventd.
424 * (ie. it runs with full root capabilities).
426 int call_usermodehelper_exec(struct subprocess_info *sub_info,
429 DECLARE_COMPLETION_ONSTACK(done);
432 BUG_ON(atomic_read(&sub_info->cred->usage) != 1);
433 validate_creds(sub_info->cred);
436 if (sub_info->path[0] == '\0')
439 if (!khelper_wq || usermodehelper_disabled) {
444 sub_info->complete = &done;
445 sub_info->wait = wait;
447 queue_work(khelper_wq, &sub_info->work);
448 if (wait == UMH_NO_WAIT) /* task has freed sub_info */
450 wait_for_completion(&done);
451 retval = sub_info->retval;
454 call_usermodehelper_freeinfo(sub_info);
459 EXPORT_SYMBOL(call_usermodehelper_exec);
461 void __init usermodehelper_init(void)
463 khelper_wq = create_singlethread_workqueue("khelper");