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/mnt_namespace.h>
28 #include <linux/completion.h>
29 #include <linux/file.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 <asm/uaccess.h>
38 extern int max_threads;
40 static struct workqueue_struct *khelper_wq;
45 modprobe_path is set via /proc/sys.
47 char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
50 * request_module - try to load a kernel module
51 * @fmt: printf style format string for the name of the module
52 * @varargs: arguements as specified in the format string
54 * Load a module using the user mode module loader. The function returns
55 * zero on success or a negative errno code on failure. Note that a
56 * successful module load does not mean the module did not then unload
57 * and exit on an error of its own. Callers must check that the service
58 * they requested is now available not blindly invoke it.
60 * If module auto-loading support is disabled then this function
61 * becomes a no-operation.
63 int request_module(const char *fmt, ...)
66 char module_name[MODULE_NAME_LEN];
67 unsigned int max_modprobes;
69 char *argv[] = { modprobe_path, "-q", "--", module_name, NULL };
70 static char *envp[] = { "HOME=/",
72 "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
74 static atomic_t kmod_concurrent = ATOMIC_INIT(0);
75 #define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */
76 static int kmod_loop_msg;
79 ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
81 if (ret >= MODULE_NAME_LEN)
84 /* If modprobe needs a service that is in a module, we get a recursive
85 * loop. Limit the number of running kmod threads to max_threads/2 or
86 * MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method
87 * would be to run the parents of this process, counting how many times
88 * kmod was invoked. That would mean accessing the internals of the
89 * process tables to get the command line, proc_pid_cmdline is static
90 * and it is not worth changing the proc code just to handle this case.
93 * "trace the ppid" is simple, but will fail if someone's
94 * parent exits. I think this is as good as it gets. --RR
96 max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
97 atomic_inc(&kmod_concurrent);
98 if (atomic_read(&kmod_concurrent) > max_modprobes) {
99 /* We may be blaming an innocent here, but unlikely */
100 if (kmod_loop_msg++ < 5)
102 "request_module: runaway loop modprobe %s\n",
104 atomic_dec(&kmod_concurrent);
108 ret = call_usermodehelper(modprobe_path, argv, envp, 1);
109 atomic_dec(&kmod_concurrent);
112 EXPORT_SYMBOL(request_module);
113 #endif /* CONFIG_KMOD */
115 struct subprocess_info {
116 struct work_struct work;
117 struct completion *complete;
125 void (*cleanup)(char **argv, char **envp);
129 * This is the task which runs the usermode application
131 static int ____call_usermodehelper(void *data)
133 struct subprocess_info *sub_info = data;
134 struct key *new_session, *old_session;
137 /* Unblock all signals and set the session keyring. */
138 new_session = key_get(sub_info->ring);
139 spin_lock_irq(¤t->sighand->siglock);
140 old_session = __install_session_keyring(current, new_session);
141 flush_signal_handlers(current, 1);
142 sigemptyset(¤t->blocked);
144 spin_unlock_irq(¤t->sighand->siglock);
146 key_put(old_session);
148 /* Install input pipe when needed */
149 if (sub_info->stdin) {
150 struct files_struct *f = current->files;
152 /* no races because files should be private here */
154 fd_install(0, sub_info->stdin);
155 spin_lock(&f->file_lock);
156 fdt = files_fdtable(f);
157 FD_SET(0, fdt->open_fds);
158 FD_CLR(0, fdt->close_on_exec);
159 spin_unlock(&f->file_lock);
161 /* and disallow core files too */
162 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){0, 0};
165 /* We can run anywhere, unlike our parent keventd(). */
166 set_cpus_allowed(current, CPU_MASK_ALL);
169 * Our parent is keventd, which runs with elevated scheduling priority.
170 * Avoid propagating that into the userspace child.
172 set_user_nice(current, 0);
175 if (current->fs->root)
176 retval = kernel_execve(sub_info->path,
177 sub_info->argv, sub_info->envp);
180 sub_info->retval = retval;
184 void call_usermodehelper_freeinfo(struct subprocess_info *info)
187 (*info->cleanup)(info->argv, info->envp);
190 EXPORT_SYMBOL(call_usermodehelper_freeinfo);
192 /* Keventd can't block, but this (a child) can. */
193 static int wait_for_helper(void *data)
195 struct subprocess_info *sub_info = data;
198 /* Install a handler: if SIGCLD isn't handled sys_wait4 won't
199 * populate the status, but will return -ECHILD. */
200 allow_signal(SIGCHLD);
202 pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
204 sub_info->retval = pid;
209 * Normally it is bogus to call wait4() from in-kernel because
210 * wait4() wants to write the exit code to a userspace address.
211 * But wait_for_helper() always runs as keventd, and put_user()
212 * to a kernel address works OK for kernel threads, due to their
213 * having an mm_segment_t which spans the entire address space.
215 * Thus the __user pointer cast is valid here.
217 sys_wait4(pid, (int __user *)&ret, 0, NULL);
220 * If ret is 0, either ____call_usermodehelper failed and the
221 * real error code is already in sub_info->retval or
222 * sub_info->retval is 0 anyway, so don't mess with it then.
225 sub_info->retval = ret;
228 if (sub_info->wait == UMH_NO_WAIT)
229 call_usermodehelper_freeinfo(sub_info);
231 complete(sub_info->complete);
235 /* This is run by khelper thread */
236 static void __call_usermodehelper(struct work_struct *work)
238 struct subprocess_info *sub_info =
239 container_of(work, struct subprocess_info, work);
241 enum umh_wait wait = sub_info->wait;
243 /* CLONE_VFORK: wait until the usermode helper has execve'd
244 * successfully We need the data structures to stay around
245 * until that is done. */
246 if (wait == UMH_WAIT_PROC || wait == UMH_NO_WAIT)
247 pid = kernel_thread(wait_for_helper, sub_info,
248 CLONE_FS | CLONE_FILES | SIGCHLD);
250 pid = kernel_thread(____call_usermodehelper, sub_info,
251 CLONE_VFORK | SIGCHLD);
260 sub_info->retval = pid;
264 complete(sub_info->complete);
269 * call_usermodehelper_setup - prepare to call a usermode helper
270 * @path - path to usermode executable
271 * @argv - arg vector for process
272 * @envp - environment for process
274 * Returns either NULL on allocation failure, or a subprocess_info
275 * structure. This should be passed to call_usermodehelper_exec to
276 * exec the process and free the structure.
278 struct subprocess_info *call_usermodehelper_setup(char *path,
279 char **argv, char **envp)
281 struct subprocess_info *sub_info;
282 sub_info = kzalloc(sizeof(struct subprocess_info), GFP_ATOMIC);
286 INIT_WORK(&sub_info->work, __call_usermodehelper);
287 sub_info->path = path;
288 sub_info->argv = argv;
289 sub_info->envp = envp;
294 EXPORT_SYMBOL(call_usermodehelper_setup);
297 * call_usermodehelper_setkeys - set the session keys for usermode helper
298 * @info: a subprocess_info returned by call_usermodehelper_setup
299 * @session_keyring: the session keyring for the process
301 void call_usermodehelper_setkeys(struct subprocess_info *info,
302 struct key *session_keyring)
304 info->ring = session_keyring;
306 EXPORT_SYMBOL(call_usermodehelper_setkeys);
309 * call_usermodehelper_setcleanup - set a cleanup function
310 * @info: a subprocess_info returned by call_usermodehelper_setup
311 * @cleanup: a cleanup function
313 * The cleanup function is just befor ethe subprocess_info is about to
314 * be freed. This can be used for freeing the argv and envp. The
315 * Function must be runnable in either a process context or the
316 * context in which call_usermodehelper_exec is called.
318 void call_usermodehelper_setcleanup(struct subprocess_info *info,
319 void (*cleanup)(char **argv, char **envp))
321 info->cleanup = cleanup;
323 EXPORT_SYMBOL(call_usermodehelper_setcleanup);
326 * call_usermodehelper_stdinpipe - set up a pipe to be used for stdin
327 * @sub_info: a subprocess_info returned by call_usermodehelper_setup
328 * @filp: set to the write-end of a pipe
330 * This constructs a pipe, and sets the read end to be the stdin of the
331 * subprocess, and returns the write-end in *@filp.
333 int call_usermodehelper_stdinpipe(struct subprocess_info *sub_info,
338 f = create_write_pipe();
343 f = create_read_pipe(f);
345 free_write_pipe(*filp);
352 EXPORT_SYMBOL(call_usermodehelper_stdinpipe);
355 * call_usermodehelper_exec - start a usermode application
356 * @sub_info: information about the subprocessa
357 * @wait: wait for the application to finish and return status.
358 * when -1 don't wait at all, but you get no useful error back when
359 * the program couldn't be exec'ed. This makes it safe to call
360 * from interrupt context.
362 * Runs a user-space application. The application is started
363 * asynchronously if wait is not set, and runs as a child of keventd.
364 * (ie. it runs with full root capabilities).
366 int call_usermodehelper_exec(struct subprocess_info *sub_info,
369 DECLARE_COMPLETION_ONSTACK(done);
372 if (sub_info->path[0] == '\0') {
382 sub_info->complete = &done;
383 sub_info->wait = wait;
385 queue_work(khelper_wq, &sub_info->work);
386 if (wait == UMH_NO_WAIT) /* task has freed sub_info */
388 wait_for_completion(&done);
389 retval = sub_info->retval;
392 call_usermodehelper_freeinfo(sub_info);
395 EXPORT_SYMBOL(call_usermodehelper_exec);
398 * call_usermodehelper_pipe - call a usermode helper process with a pipe stdin
399 * @path: path to usermode executable
400 * @argv: arg vector for process
401 * @envp: environment for process
402 * @filp: set to the write-end of a pipe
404 * This is a simple wrapper which executes a usermode-helper function
405 * with a pipe as stdin. It is implemented entirely in terms of
406 * lower-level call_usermodehelper_* functions.
408 int call_usermodehelper_pipe(char *path, char **argv, char **envp,
411 struct subprocess_info *sub_info;
414 sub_info = call_usermodehelper_setup(path, argv, envp);
415 if (sub_info == NULL)
418 ret = call_usermodehelper_stdinpipe(sub_info, filp);
422 return call_usermodehelper_exec(sub_info, 1);
425 call_usermodehelper_freeinfo(sub_info);
428 EXPORT_SYMBOL(call_usermodehelper_pipe);
430 void __init usermodehelper_init(void)
432 khelper_wq = create_singlethread_workqueue("khelper");