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",
115 atomic_dec(&kmod_concurrent
);
119 trace_module_request(module_name
, wait
, _RET_IP_
);
121 ret
= call_usermodehelper(modprobe_path
, argv
, envp
,
122 wait
? UMH_WAIT_PROC
: UMH_WAIT_EXEC
);
123 atomic_dec(&kmod_concurrent
);
126 EXPORT_SYMBOL(__request_module
);
127 #endif /* CONFIG_MODULES */
129 struct subprocess_info
{
130 struct work_struct work
;
131 struct completion
*complete
;
139 void (*cleanup
)(char **argv
, char **envp
);
143 * This is the task which runs the usermode application
145 static int ____call_usermodehelper(void *data
)
147 struct subprocess_info
*sub_info
= data
;
150 BUG_ON(atomic_read(&sub_info
->cred
->usage
) != 1);
152 /* Unblock all signals */
153 spin_lock_irq(¤t
->sighand
->siglock
);
154 flush_signal_handlers(current
, 1);
155 sigemptyset(¤t
->blocked
);
157 spin_unlock_irq(¤t
->sighand
->siglock
);
159 /* Install the credentials */
160 commit_creds(sub_info
->cred
);
161 sub_info
->cred
= NULL
;
163 /* Install input pipe when needed */
164 if (sub_info
->stdin
) {
165 struct files_struct
*f
= current
->files
;
167 /* no races because files should be private here */
169 fd_install(0, sub_info
->stdin
);
170 spin_lock(&f
->file_lock
);
171 fdt
= files_fdtable(f
);
172 FD_SET(0, fdt
->open_fds
);
173 FD_CLR(0, fdt
->close_on_exec
);
174 spin_unlock(&f
->file_lock
);
176 /* and disallow core files too */
177 current
->signal
->rlim
[RLIMIT_CORE
] = (struct rlimit
){0, 0};
180 /* We can run anywhere, unlike our parent keventd(). */
181 set_cpus_allowed_ptr(current
, cpu_all_mask
);
184 * Our parent is keventd, which runs with elevated scheduling priority.
185 * Avoid propagating that into the userspace child.
187 set_user_nice(current
, 0);
189 retval
= kernel_execve(sub_info
->path
, sub_info
->argv
, sub_info
->envp
);
192 sub_info
->retval
= retval
;
196 void call_usermodehelper_freeinfo(struct subprocess_info
*info
)
199 (*info
->cleanup
)(info
->argv
, info
->envp
);
201 put_cred(info
->cred
);
204 EXPORT_SYMBOL(call_usermodehelper_freeinfo
);
206 /* Keventd can't block, but this (a child) can. */
207 static int wait_for_helper(void *data
)
209 struct subprocess_info
*sub_info
= data
;
212 /* Install a handler: if SIGCLD isn't handled sys_wait4 won't
213 * populate the status, but will return -ECHILD. */
214 allow_signal(SIGCHLD
);
216 pid
= kernel_thread(____call_usermodehelper
, sub_info
, SIGCHLD
);
218 sub_info
->retval
= pid
;
223 * Normally it is bogus to call wait4() from in-kernel because
224 * wait4() wants to write the exit code to a userspace address.
225 * But wait_for_helper() always runs as keventd, and put_user()
226 * to a kernel address works OK for kernel threads, due to their
227 * having an mm_segment_t which spans the entire address space.
229 * Thus the __user pointer cast is valid here.
231 sys_wait4(pid
, (int __user
*)&ret
, 0, NULL
);
234 * If ret is 0, either ____call_usermodehelper failed and the
235 * real error code is already in sub_info->retval or
236 * sub_info->retval is 0 anyway, so don't mess with it then.
239 sub_info
->retval
= ret
;
242 if (sub_info
->wait
== UMH_NO_WAIT
)
243 call_usermodehelper_freeinfo(sub_info
);
245 complete(sub_info
->complete
);
249 /* This is run by khelper thread */
250 static void __call_usermodehelper(struct work_struct
*work
)
252 struct subprocess_info
*sub_info
=
253 container_of(work
, struct subprocess_info
, work
);
255 enum umh_wait wait
= sub_info
->wait
;
257 BUG_ON(atomic_read(&sub_info
->cred
->usage
) != 1);
259 /* CLONE_VFORK: wait until the usermode helper has execve'd
260 * successfully We need the data structures to stay around
261 * until that is done. */
262 if (wait
== UMH_WAIT_PROC
|| wait
== UMH_NO_WAIT
)
263 pid
= kernel_thread(wait_for_helper
, sub_info
,
264 CLONE_FS
| CLONE_FILES
| SIGCHLD
);
266 pid
= kernel_thread(____call_usermodehelper
, sub_info
,
267 CLONE_VFORK
| SIGCHLD
);
276 sub_info
->retval
= pid
;
280 complete(sub_info
->complete
);
284 #ifdef CONFIG_PM_SLEEP
286 * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
287 * (used for preventing user land processes from being created after the user
288 * land has been frozen during a system-wide hibernation or suspend operation).
290 static int usermodehelper_disabled
;
292 /* Number of helpers running */
293 static atomic_t running_helpers
= ATOMIC_INIT(0);
296 * Wait queue head used by usermodehelper_pm_callback() to wait for all running
299 static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq
);
302 * Time to wait for running_helpers to become zero before the setting of
303 * usermodehelper_disabled in usermodehelper_pm_callback() fails
305 #define RUNNING_HELPERS_TIMEOUT (5 * HZ)
308 * usermodehelper_disable - prevent new helpers from being started
310 int usermodehelper_disable(void)
314 usermodehelper_disabled
= 1;
317 * From now on call_usermodehelper_exec() won't start any new
318 * helpers, so it is sufficient if running_helpers turns out to
319 * be zero at one point (it may be increased later, but that
322 retval
= wait_event_timeout(running_helpers_waitq
,
323 atomic_read(&running_helpers
) == 0,
324 RUNNING_HELPERS_TIMEOUT
);
328 usermodehelper_disabled
= 0;
333 * usermodehelper_enable - allow new helpers to be started again
335 void usermodehelper_enable(void)
337 usermodehelper_disabled
= 0;
340 static void helper_lock(void)
342 atomic_inc(&running_helpers
);
343 smp_mb__after_atomic_inc();
346 static void helper_unlock(void)
348 if (atomic_dec_and_test(&running_helpers
))
349 wake_up(&running_helpers_waitq
);
351 #else /* CONFIG_PM_SLEEP */
352 #define usermodehelper_disabled 0
354 static inline void helper_lock(void) {}
355 static inline void helper_unlock(void) {}
356 #endif /* CONFIG_PM_SLEEP */
359 * call_usermodehelper_setup - prepare to call a usermode helper
360 * @path: path to usermode executable
361 * @argv: arg vector for process
362 * @envp: environment for process
363 * @gfp_mask: gfp mask for memory allocation
365 * Returns either %NULL on allocation failure, or a subprocess_info
366 * structure. This should be passed to call_usermodehelper_exec to
367 * exec the process and free the structure.
369 struct subprocess_info
*call_usermodehelper_setup(char *path
, char **argv
,
370 char **envp
, gfp_t gfp_mask
)
372 struct subprocess_info
*sub_info
;
373 sub_info
= kzalloc(sizeof(struct subprocess_info
), gfp_mask
);
377 INIT_WORK(&sub_info
->work
, __call_usermodehelper
);
378 sub_info
->path
= path
;
379 sub_info
->argv
= argv
;
380 sub_info
->envp
= envp
;
381 sub_info
->cred
= prepare_usermodehelper_creds();
382 if (!sub_info
->cred
) {
390 EXPORT_SYMBOL(call_usermodehelper_setup
);
393 * call_usermodehelper_setkeys - set the session keys for usermode helper
394 * @info: a subprocess_info returned by call_usermodehelper_setup
395 * @session_keyring: the session keyring for the process
397 void call_usermodehelper_setkeys(struct subprocess_info
*info
,
398 struct key
*session_keyring
)
401 struct thread_group_cred
*tgcred
= info
->cred
->tgcred
;
402 key_put(tgcred
->session_keyring
);
403 tgcred
->session_keyring
= key_get(session_keyring
);
408 EXPORT_SYMBOL(call_usermodehelper_setkeys
);
411 * call_usermodehelper_setcleanup - set a cleanup function
412 * @info: a subprocess_info returned by call_usermodehelper_setup
413 * @cleanup: a cleanup function
415 * The cleanup function is just befor ethe subprocess_info is about to
416 * be freed. This can be used for freeing the argv and envp. The
417 * Function must be runnable in either a process context or the
418 * context in which call_usermodehelper_exec is called.
420 void call_usermodehelper_setcleanup(struct subprocess_info
*info
,
421 void (*cleanup
)(char **argv
, char **envp
))
423 info
->cleanup
= cleanup
;
425 EXPORT_SYMBOL(call_usermodehelper_setcleanup
);
428 * call_usermodehelper_stdinpipe - set up a pipe to be used for stdin
429 * @sub_info: a subprocess_info returned by call_usermodehelper_setup
430 * @filp: set to the write-end of a pipe
432 * This constructs a pipe, and sets the read end to be the stdin of the
433 * subprocess, and returns the write-end in *@filp.
435 int call_usermodehelper_stdinpipe(struct subprocess_info
*sub_info
,
440 f
= create_write_pipe(0);
445 f
= create_read_pipe(f
, 0);
447 free_write_pipe(*filp
);
454 EXPORT_SYMBOL(call_usermodehelper_stdinpipe
);
457 * call_usermodehelper_exec - start a usermode application
458 * @sub_info: information about the subprocessa
459 * @wait: wait for the application to finish and return status.
460 * when -1 don't wait at all, but you get no useful error back when
461 * the program couldn't be exec'ed. This makes it safe to call
462 * from interrupt context.
464 * Runs a user-space application. The application is started
465 * asynchronously if wait is not set, and runs as a child of keventd.
466 * (ie. it runs with full root capabilities).
468 int call_usermodehelper_exec(struct subprocess_info
*sub_info
,
471 DECLARE_COMPLETION_ONSTACK(done
);
474 BUG_ON(atomic_read(&sub_info
->cred
->usage
) != 1);
475 validate_creds(sub_info
->cred
);
478 if (sub_info
->path
[0] == '\0')
481 if (!khelper_wq
|| usermodehelper_disabled
) {
486 sub_info
->complete
= &done
;
487 sub_info
->wait
= wait
;
489 queue_work(khelper_wq
, &sub_info
->work
);
490 if (wait
== UMH_NO_WAIT
) /* task has freed sub_info */
492 wait_for_completion(&done
);
493 retval
= sub_info
->retval
;
496 call_usermodehelper_freeinfo(sub_info
);
501 EXPORT_SYMBOL(call_usermodehelper_exec
);
504 * call_usermodehelper_pipe - call a usermode helper process with a pipe stdin
505 * @path: path to usermode executable
506 * @argv: arg vector for process
507 * @envp: environment for process
508 * @filp: set to the write-end of a pipe
510 * This is a simple wrapper which executes a usermode-helper function
511 * with a pipe as stdin. It is implemented entirely in terms of
512 * lower-level call_usermodehelper_* functions.
514 int call_usermodehelper_pipe(char *path
, char **argv
, char **envp
,
517 struct subprocess_info
*sub_info
;
520 sub_info
= call_usermodehelper_setup(path
, argv
, envp
, GFP_KERNEL
);
521 if (sub_info
== NULL
)
524 ret
= call_usermodehelper_stdinpipe(sub_info
, filp
);
526 call_usermodehelper_freeinfo(sub_info
);
530 ret
= call_usermodehelper_exec(sub_info
, UMH_WAIT_EXEC
);
531 if (ret
< 0) /* Failed to execute helper, close pipe */
532 filp_close(*filp
, NULL
);
536 EXPORT_SYMBOL(call_usermodehelper_pipe
);
538 void __init
usermodehelper_init(void)
540 khelper_wq
= create_singlethread_workqueue("khelper");