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 extern int max_threads;
42 static struct workqueue_struct *khelper_wq;
47 modprobe_path is set via /proc/sys.
49 char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
52 * __request_module - try to load a kernel module
53 * @wait: wait (or not) for the operation to complete
54 * @fmt: printf style format string for the name of the module
55 * @...: arguments as specified in the format string
57 * Load a module using the user mode module loader. The function returns
58 * zero on success or a negative errno code on failure. Note that a
59 * successful module load does not mean the module did not then unload
60 * and exit on an error of its own. Callers must check that the service
61 * they requested is now available not blindly invoke it.
63 * If module auto-loading support is disabled then this function
64 * becomes a no-operation.
66 int __request_module(bool wait, const char *fmt, ...)
69 char module_name[MODULE_NAME_LEN];
70 unsigned int max_modprobes;
72 char *argv[] = { modprobe_path, "-q", "--", module_name, NULL };
73 static char *envp[] = { "HOME=/",
75 "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
77 static atomic_t kmod_concurrent = ATOMIC_INIT(0);
78 #define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */
79 static int kmod_loop_msg;
81 ret = security_kernel_module_request();
86 ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
88 if (ret >= MODULE_NAME_LEN)
91 /* If modprobe needs a service that is in a module, we get a recursive
92 * loop. Limit the number of running kmod threads to max_threads/2 or
93 * MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method
94 * would be to run the parents of this process, counting how many times
95 * kmod was invoked. That would mean accessing the internals of the
96 * process tables to get the command line, proc_pid_cmdline is static
97 * and it is not worth changing the proc code just to handle this case.
100 * "trace the ppid" is simple, but will fail if someone's
101 * parent exits. I think this is as good as it gets. --RR
103 max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
104 atomic_inc(&kmod_concurrent);
105 if (atomic_read(&kmod_concurrent) > max_modprobes) {
106 /* We may be blaming an innocent here, but unlikely */
107 if (kmod_loop_msg++ < 5)
109 "request_module: runaway loop modprobe %s\n",
111 atomic_dec(&kmod_concurrent);
115 ret = call_usermodehelper(modprobe_path, argv, envp,
116 wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC);
117 atomic_dec(&kmod_concurrent);
120 EXPORT_SYMBOL(__request_module);
121 #endif /* CONFIG_MODULES */
123 struct subprocess_info {
124 struct work_struct work;
125 struct completion *complete;
133 void (*cleanup)(char **argv, char **envp);
137 * This is the task which runs the usermode application
139 static int ____call_usermodehelper(void *data)
141 struct subprocess_info *sub_info = data;
144 BUG_ON(atomic_read(&sub_info->cred->usage) != 1);
146 /* Unblock all signals */
147 spin_lock_irq(¤t->sighand->siglock);
148 flush_signal_handlers(current, 1);
149 sigemptyset(¤t->blocked);
151 spin_unlock_irq(¤t->sighand->siglock);
153 /* Install the credentials */
154 commit_creds(sub_info->cred);
155 sub_info->cred = NULL;
157 /* Install input pipe when needed */
158 if (sub_info->stdin) {
159 struct files_struct *f = current->files;
161 /* no races because files should be private here */
163 fd_install(0, sub_info->stdin);
164 spin_lock(&f->file_lock);
165 fdt = files_fdtable(f);
166 FD_SET(0, fdt->open_fds);
167 FD_CLR(0, fdt->close_on_exec);
168 spin_unlock(&f->file_lock);
170 /* and disallow core files too */
171 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){0, 0};
174 /* We can run anywhere, unlike our parent keventd(). */
175 set_cpus_allowed_ptr(current, cpu_all_mask);
178 * Our parent is keventd, which runs with elevated scheduling priority.
179 * Avoid propagating that into the userspace child.
181 set_user_nice(current, 0);
183 retval = kernel_execve(sub_info->path, sub_info->argv, sub_info->envp);
186 sub_info->retval = retval;
190 void call_usermodehelper_freeinfo(struct subprocess_info *info)
193 (*info->cleanup)(info->argv, info->envp);
195 put_cred(info->cred);
198 EXPORT_SYMBOL(call_usermodehelper_freeinfo);
200 /* Keventd can't block, but this (a child) can. */
201 static int wait_for_helper(void *data)
203 struct subprocess_info *sub_info = data;
206 /* Install a handler: if SIGCLD isn't handled sys_wait4 won't
207 * populate the status, but will return -ECHILD. */
208 allow_signal(SIGCHLD);
210 pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
212 sub_info->retval = pid;
217 * Normally it is bogus to call wait4() from in-kernel because
218 * wait4() wants to write the exit code to a userspace address.
219 * But wait_for_helper() always runs as keventd, and put_user()
220 * to a kernel address works OK for kernel threads, due to their
221 * having an mm_segment_t which spans the entire address space.
223 * Thus the __user pointer cast is valid here.
225 sys_wait4(pid, (int __user *)&ret, 0, NULL);
228 * If ret is 0, either ____call_usermodehelper failed and the
229 * real error code is already in sub_info->retval or
230 * sub_info->retval is 0 anyway, so don't mess with it then.
233 sub_info->retval = ret;
236 if (sub_info->wait == UMH_NO_WAIT)
237 call_usermodehelper_freeinfo(sub_info);
239 complete(sub_info->complete);
243 /* This is run by khelper thread */
244 static void __call_usermodehelper(struct work_struct *work)
246 struct subprocess_info *sub_info =
247 container_of(work, struct subprocess_info, work);
249 enum umh_wait wait = sub_info->wait;
251 BUG_ON(atomic_read(&sub_info->cred->usage) != 1);
253 /* CLONE_VFORK: wait until the usermode helper has execve'd
254 * successfully We need the data structures to stay around
255 * until that is done. */
256 if (wait == UMH_WAIT_PROC || wait == UMH_NO_WAIT)
257 pid = kernel_thread(wait_for_helper, sub_info,
258 CLONE_FS | CLONE_FILES | SIGCHLD);
260 pid = kernel_thread(____call_usermodehelper, sub_info,
261 CLONE_VFORK | SIGCHLD);
270 sub_info->retval = pid;
274 complete(sub_info->complete);
278 #ifdef CONFIG_PM_SLEEP
280 * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
281 * (used for preventing user land processes from being created after the user
282 * land has been frozen during a system-wide hibernation or suspend operation).
284 static int usermodehelper_disabled;
286 /* Number of helpers running */
287 static atomic_t running_helpers = ATOMIC_INIT(0);
290 * Wait queue head used by usermodehelper_pm_callback() to wait for all running
293 static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);
296 * Time to wait for running_helpers to become zero before the setting of
297 * usermodehelper_disabled in usermodehelper_pm_callback() fails
299 #define RUNNING_HELPERS_TIMEOUT (5 * HZ)
302 * usermodehelper_disable - prevent new helpers from being started
304 int usermodehelper_disable(void)
308 usermodehelper_disabled = 1;
311 * From now on call_usermodehelper_exec() won't start any new
312 * helpers, so it is sufficient if running_helpers turns out to
313 * be zero at one point (it may be increased later, but that
316 retval = wait_event_timeout(running_helpers_waitq,
317 atomic_read(&running_helpers) == 0,
318 RUNNING_HELPERS_TIMEOUT);
322 usermodehelper_disabled = 0;
327 * usermodehelper_enable - allow new helpers to be started again
329 void usermodehelper_enable(void)
331 usermodehelper_disabled = 0;
334 static void helper_lock(void)
336 atomic_inc(&running_helpers);
337 smp_mb__after_atomic_inc();
340 static void helper_unlock(void)
342 if (atomic_dec_and_test(&running_helpers))
343 wake_up(&running_helpers_waitq);
345 #else /* CONFIG_PM_SLEEP */
346 #define usermodehelper_disabled 0
348 static inline void helper_lock(void) {}
349 static inline void helper_unlock(void) {}
350 #endif /* CONFIG_PM_SLEEP */
353 * call_usermodehelper_setup - prepare to call a usermode helper
354 * @path: path to usermode executable
355 * @argv: arg vector for process
356 * @envp: environment for process
357 * @gfp_mask: gfp mask for memory allocation
359 * Returns either %NULL on allocation failure, or a subprocess_info
360 * structure. This should be passed to call_usermodehelper_exec to
361 * exec the process and free the structure.
363 struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
364 char **envp, gfp_t gfp_mask)
366 struct subprocess_info *sub_info;
367 sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
371 INIT_WORK(&sub_info->work, __call_usermodehelper);
372 sub_info->path = path;
373 sub_info->argv = argv;
374 sub_info->envp = envp;
375 sub_info->cred = prepare_usermodehelper_creds();
376 if (!sub_info->cred) {
384 EXPORT_SYMBOL(call_usermodehelper_setup);
387 * call_usermodehelper_setkeys - set the session keys for usermode helper
388 * @info: a subprocess_info returned by call_usermodehelper_setup
389 * @session_keyring: the session keyring for the process
391 void call_usermodehelper_setkeys(struct subprocess_info *info,
392 struct key *session_keyring)
395 struct thread_group_cred *tgcred = info->cred->tgcred;
396 key_put(tgcred->session_keyring);
397 tgcred->session_keyring = key_get(session_keyring);
402 EXPORT_SYMBOL(call_usermodehelper_setkeys);
405 * call_usermodehelper_setcleanup - set a cleanup function
406 * @info: a subprocess_info returned by call_usermodehelper_setup
407 * @cleanup: a cleanup function
409 * The cleanup function is just befor ethe subprocess_info is about to
410 * be freed. This can be used for freeing the argv and envp. The
411 * Function must be runnable in either a process context or the
412 * context in which call_usermodehelper_exec is called.
414 void call_usermodehelper_setcleanup(struct subprocess_info *info,
415 void (*cleanup)(char **argv, char **envp))
417 info->cleanup = cleanup;
419 EXPORT_SYMBOL(call_usermodehelper_setcleanup);
422 * call_usermodehelper_stdinpipe - set up a pipe to be used for stdin
423 * @sub_info: a subprocess_info returned by call_usermodehelper_setup
424 * @filp: set to the write-end of a pipe
426 * This constructs a pipe, and sets the read end to be the stdin of the
427 * subprocess, and returns the write-end in *@filp.
429 int call_usermodehelper_stdinpipe(struct subprocess_info *sub_info,
434 f = create_write_pipe(0);
439 f = create_read_pipe(f, 0);
441 free_write_pipe(*filp);
448 EXPORT_SYMBOL(call_usermodehelper_stdinpipe);
451 * call_usermodehelper_exec - start a usermode application
452 * @sub_info: information about the subprocessa
453 * @wait: wait for the application to finish and return status.
454 * when -1 don't wait at all, but you get no useful error back when
455 * the program couldn't be exec'ed. This makes it safe to call
456 * from interrupt context.
458 * Runs a user-space application. The application is started
459 * asynchronously if wait is not set, and runs as a child of keventd.
460 * (ie. it runs with full root capabilities).
462 int call_usermodehelper_exec(struct subprocess_info *sub_info,
465 DECLARE_COMPLETION_ONSTACK(done);
468 BUG_ON(atomic_read(&sub_info->cred->usage) != 1);
469 validate_creds(sub_info->cred);
472 if (sub_info->path[0] == '\0')
475 if (!khelper_wq || usermodehelper_disabled) {
480 sub_info->complete = &done;
481 sub_info->wait = wait;
483 queue_work(khelper_wq, &sub_info->work);
484 if (wait == UMH_NO_WAIT) /* task has freed sub_info */
486 wait_for_completion(&done);
487 retval = sub_info->retval;
490 call_usermodehelper_freeinfo(sub_info);
495 EXPORT_SYMBOL(call_usermodehelper_exec);
498 * call_usermodehelper_pipe - call a usermode helper process with a pipe stdin
499 * @path: path to usermode executable
500 * @argv: arg vector for process
501 * @envp: environment for process
502 * @filp: set to the write-end of a pipe
504 * This is a simple wrapper which executes a usermode-helper function
505 * with a pipe as stdin. It is implemented entirely in terms of
506 * lower-level call_usermodehelper_* functions.
508 int call_usermodehelper_pipe(char *path, char **argv, char **envp,
511 struct subprocess_info *sub_info;
514 sub_info = call_usermodehelper_setup(path, argv, envp, GFP_KERNEL);
515 if (sub_info == NULL)
518 ret = call_usermodehelper_stdinpipe(sub_info, filp);
522 return call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC);
525 call_usermodehelper_freeinfo(sub_info);
528 EXPORT_SYMBOL(call_usermodehelper_pipe);
530 void __init usermodehelper_init(void)
532 khelper_wq = create_singlethread_workqueue("khelper");