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 /* If modprobe needs a service that is in a module, we get a recursive
90 * loop. Limit the number of running kmod threads to max_threads/2 or
91 * MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method
92 * would be to run the parents of this process, counting how many times
93 * kmod was invoked. That would mean accessing the internals of the
94 * process tables to get the command line, proc_pid_cmdline is static
95 * and it is not worth changing the proc code just to handle this case.
98 * "trace the ppid" is simple, but will fail if someone's
99 * parent exits. I think this is as good as it gets. --RR
101 max_modprobes
= min(max_threads
/2, MAX_KMOD_CONCURRENT
);
102 atomic_inc(&kmod_concurrent
);
103 if (atomic_read(&kmod_concurrent
) > max_modprobes
) {
104 /* We may be blaming an innocent here, but unlikely */
105 if (kmod_loop_msg
++ < 5)
107 "request_module: runaway loop modprobe %s\n",
109 atomic_dec(&kmod_concurrent
);
113 trace_module_request(module_name
, wait
, _RET_IP_
);
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);
471 if (sub_info
->path
[0] == '\0')
474 if (!khelper_wq
|| usermodehelper_disabled
) {
479 sub_info
->complete
= &done
;
480 sub_info
->wait
= wait
;
482 queue_work(khelper_wq
, &sub_info
->work
);
483 if (wait
== UMH_NO_WAIT
) /* task has freed sub_info */
485 wait_for_completion(&done
);
486 retval
= sub_info
->retval
;
489 call_usermodehelper_freeinfo(sub_info
);
494 EXPORT_SYMBOL(call_usermodehelper_exec
);
497 * call_usermodehelper_pipe - call a usermode helper process with a pipe stdin
498 * @path: path to usermode executable
499 * @argv: arg vector for process
500 * @envp: environment for process
501 * @filp: set to the write-end of a pipe
503 * This is a simple wrapper which executes a usermode-helper function
504 * with a pipe as stdin. It is implemented entirely in terms of
505 * lower-level call_usermodehelper_* functions.
507 int call_usermodehelper_pipe(char *path
, char **argv
, char **envp
,
510 struct subprocess_info
*sub_info
;
513 sub_info
= call_usermodehelper_setup(path
, argv
, envp
, GFP_KERNEL
);
514 if (sub_info
== NULL
)
517 ret
= call_usermodehelper_stdinpipe(sub_info
, filp
);
521 return call_usermodehelper_exec(sub_info
, UMH_WAIT_EXEC
);
524 call_usermodehelper_freeinfo(sub_info
);
527 EXPORT_SYMBOL(call_usermodehelper_pipe
);
529 void __init
usermodehelper_init(void)
531 khelper_wq
= create_singlethread_workqueue("khelper");