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 /* Unblock all signals */
138 spin_lock_irq(¤t
->sighand
->siglock
);
139 flush_signal_handlers(current
, 1);
140 sigemptyset(¤t
->blocked
);
142 spin_unlock_irq(¤t
->sighand
->siglock
);
144 /* We can run anywhere, unlike our parent keventd(). */
145 set_cpus_allowed_ptr(current
, cpu_all_mask
);
148 * Our parent is keventd, which runs with elevated scheduling priority.
149 * Avoid propagating that into the userspace child.
151 set_user_nice(current
, 0);
153 if (sub_info
->init
) {
154 retval
= sub_info
->init(sub_info
);
159 retval
= kernel_execve(sub_info
->path
, sub_info
->argv
, sub_info
->envp
);
163 sub_info
->retval
= retval
;
167 void call_usermodehelper_freeinfo(struct subprocess_info
*info
)
170 (*info
->cleanup
)(info
);
173 EXPORT_SYMBOL(call_usermodehelper_freeinfo
);
175 /* Keventd can't block, but this (a child) can. */
176 static int wait_for_helper(void *data
)
178 struct subprocess_info
*sub_info
= data
;
181 /* Install a handler: if SIGCLD isn't handled sys_wait4 won't
182 * populate the status, but will return -ECHILD. */
183 allow_signal(SIGCHLD
);
185 pid
= kernel_thread(____call_usermodehelper
, sub_info
, SIGCHLD
);
187 sub_info
->retval
= pid
;
192 * Normally it is bogus to call wait4() from in-kernel because
193 * wait4() wants to write the exit code to a userspace address.
194 * But wait_for_helper() always runs as keventd, and put_user()
195 * to a kernel address works OK for kernel threads, due to their
196 * having an mm_segment_t which spans the entire address space.
198 * Thus the __user pointer cast is valid here.
200 sys_wait4(pid
, (int __user
*)&ret
, 0, NULL
);
203 * If ret is 0, either ____call_usermodehelper failed and the
204 * real error code is already in sub_info->retval or
205 * sub_info->retval is 0 anyway, so don't mess with it then.
208 sub_info
->retval
= ret
;
211 if (sub_info
->wait
== UMH_NO_WAIT
)
212 call_usermodehelper_freeinfo(sub_info
);
214 complete(sub_info
->complete
);
218 /* This is run by khelper thread */
219 static void __call_usermodehelper(struct work_struct
*work
)
221 struct subprocess_info
*sub_info
=
222 container_of(work
, struct subprocess_info
, work
);
224 enum umh_wait wait
= sub_info
->wait
;
226 /* CLONE_VFORK: wait until the usermode helper has execve'd
227 * successfully We need the data structures to stay around
228 * until that is done. */
229 if (wait
== UMH_WAIT_PROC
|| wait
== UMH_NO_WAIT
)
230 pid
= kernel_thread(wait_for_helper
, sub_info
,
231 CLONE_FS
| CLONE_FILES
| SIGCHLD
);
233 pid
= kernel_thread(____call_usermodehelper
, sub_info
,
234 CLONE_VFORK
| SIGCHLD
);
243 sub_info
->retval
= pid
;
247 complete(sub_info
->complete
);
251 #ifdef CONFIG_PM_SLEEP
253 * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
254 * (used for preventing user land processes from being created after the user
255 * land has been frozen during a system-wide hibernation or suspend operation).
257 static int usermodehelper_disabled
;
259 /* Number of helpers running */
260 static atomic_t running_helpers
= ATOMIC_INIT(0);
263 * Wait queue head used by usermodehelper_pm_callback() to wait for all running
266 static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq
);
269 * Time to wait for running_helpers to become zero before the setting of
270 * usermodehelper_disabled in usermodehelper_pm_callback() fails
272 #define RUNNING_HELPERS_TIMEOUT (5 * HZ)
275 * usermodehelper_disable - prevent new helpers from being started
277 int usermodehelper_disable(void)
281 usermodehelper_disabled
= 1;
284 * From now on call_usermodehelper_exec() won't start any new
285 * helpers, so it is sufficient if running_helpers turns out to
286 * be zero at one point (it may be increased later, but that
289 retval
= wait_event_timeout(running_helpers_waitq
,
290 atomic_read(&running_helpers
) == 0,
291 RUNNING_HELPERS_TIMEOUT
);
295 usermodehelper_disabled
= 0;
300 * usermodehelper_enable - allow new helpers to be started again
302 void usermodehelper_enable(void)
304 usermodehelper_disabled
= 0;
307 static void helper_lock(void)
309 atomic_inc(&running_helpers
);
310 smp_mb__after_atomic_inc();
313 static void helper_unlock(void)
315 if (atomic_dec_and_test(&running_helpers
))
316 wake_up(&running_helpers_waitq
);
318 #else /* CONFIG_PM_SLEEP */
319 #define usermodehelper_disabled 0
321 static inline void helper_lock(void) {}
322 static inline void helper_unlock(void) {}
323 #endif /* CONFIG_PM_SLEEP */
326 * call_usermodehelper_setup - prepare to call a usermode helper
327 * @path: path to usermode executable
328 * @argv: arg vector for process
329 * @envp: environment for process
330 * @gfp_mask: gfp mask for memory allocation
332 * Returns either %NULL on allocation failure, or a subprocess_info
333 * structure. This should be passed to call_usermodehelper_exec to
334 * exec the process and free the structure.
336 struct subprocess_info
*call_usermodehelper_setup(char *path
, char **argv
,
337 char **envp
, gfp_t gfp_mask
)
339 struct subprocess_info
*sub_info
;
340 sub_info
= kzalloc(sizeof(struct subprocess_info
), gfp_mask
);
344 INIT_WORK(&sub_info
->work
, __call_usermodehelper
);
345 sub_info
->path
= path
;
346 sub_info
->argv
= argv
;
347 sub_info
->envp
= envp
;
351 EXPORT_SYMBOL(call_usermodehelper_setup
);
354 * call_usermodehelper_setfns - set a cleanup/init function
355 * @info: a subprocess_info returned by call_usermodehelper_setup
356 * @cleanup: a cleanup function
357 * @init: an init function
358 * @data: arbitrary context sensitive data
360 * The init function is used to customize the helper process prior to
361 * exec. A non-zero return code causes the process to error out, exit,
362 * and return the failure to the calling process
364 * The cleanup function is just before ethe subprocess_info is about to
365 * be freed. This can be used for freeing the argv and envp. The
366 * Function must be runnable in either a process context or the
367 * context in which call_usermodehelper_exec is called.
369 void call_usermodehelper_setfns(struct subprocess_info
*info
,
370 int (*init
)(struct subprocess_info
*info
),
371 void (*cleanup
)(struct subprocess_info
*info
),
374 info
->cleanup
= cleanup
;
378 EXPORT_SYMBOL(call_usermodehelper_setfns
);
381 * call_usermodehelper_exec - start a usermode application
382 * @sub_info: information about the subprocessa
383 * @wait: wait for the application to finish and return status.
384 * when -1 don't wait at all, but you get no useful error back when
385 * the program couldn't be exec'ed. This makes it safe to call
386 * from interrupt context.
388 * Runs a user-space application. The application is started
389 * asynchronously if wait is not set, and runs as a child of keventd.
390 * (ie. it runs with full root capabilities).
392 int call_usermodehelper_exec(struct subprocess_info
*sub_info
,
395 DECLARE_COMPLETION_ONSTACK(done
);
399 if (sub_info
->path
[0] == '\0')
402 if (!khelper_wq
|| usermodehelper_disabled
) {
407 sub_info
->complete
= &done
;
408 sub_info
->wait
= wait
;
410 queue_work(khelper_wq
, &sub_info
->work
);
411 if (wait
== UMH_NO_WAIT
) /* task has freed sub_info */
413 wait_for_completion(&done
);
414 retval
= sub_info
->retval
;
417 call_usermodehelper_freeinfo(sub_info
);
422 EXPORT_SYMBOL(call_usermodehelper_exec
);
424 void __init
usermodehelper_init(void)
426 khelper_wq
= create_singlethread_workqueue("khelper");