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
;
128 * This is the task which runs the usermode application
130 static int ____call_usermodehelper(void *data
)
132 struct subprocess_info
*sub_info
= data
;
133 struct key
*new_session
, *old_session
;
136 /* Unblock all signals and set the session keyring. */
137 new_session
= key_get(sub_info
->ring
);
138 flush_signals(current
);
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 /* Keventd can't block, but this (a child) can. */
185 static int wait_for_helper(void *data
)
187 struct subprocess_info
*sub_info
= data
;
189 struct k_sigaction sa
;
191 /* Install a handler: if SIGCLD isn't handled sys_wait4 won't
192 * populate the status, but will return -ECHILD. */
193 sa
.sa
.sa_handler
= SIG_IGN
;
195 siginitset(&sa
.sa
.sa_mask
, sigmask(SIGCHLD
));
196 do_sigaction(SIGCHLD
, &sa
, NULL
);
197 allow_signal(SIGCHLD
);
199 pid
= kernel_thread(____call_usermodehelper
, sub_info
, SIGCHLD
);
201 sub_info
->retval
= pid
;
206 * Normally it is bogus to call wait4() from in-kernel because
207 * wait4() wants to write the exit code to a userspace address.
208 * But wait_for_helper() always runs as keventd, and put_user()
209 * to a kernel address works OK for kernel threads, due to their
210 * having an mm_segment_t which spans the entire address space.
212 * Thus the __user pointer cast is valid here.
214 sys_wait4(pid
, (int __user
*)&ret
, 0, NULL
);
217 * If ret is 0, either ____call_usermodehelper failed and the
218 * real error code is already in sub_info->retval or
219 * sub_info->retval is 0 anyway, so don't mess with it then.
222 sub_info
->retval
= ret
;
225 if (sub_info
->wait
< 0)
228 complete(sub_info
->complete
);
232 /* This is run by khelper thread */
233 static void __call_usermodehelper(struct work_struct
*work
)
235 struct subprocess_info
*sub_info
=
236 container_of(work
, struct subprocess_info
, work
);
238 int wait
= sub_info
->wait
;
240 /* CLONE_VFORK: wait until the usermode helper has execve'd
241 * successfully We need the data structures to stay around
242 * until that is done. */
244 pid
= kernel_thread(wait_for_helper
, sub_info
,
245 CLONE_FS
| CLONE_FILES
| SIGCHLD
);
247 pid
= kernel_thread(____call_usermodehelper
, sub_info
,
248 CLONE_VFORK
| SIGCHLD
);
254 sub_info
->retval
= pid
;
255 complete(sub_info
->complete
);
257 complete(sub_info
->complete
);
261 * call_usermodehelper_keys - start a usermode application
262 * @path: pathname for the application
263 * @argv: null-terminated argument list
264 * @envp: null-terminated environment list
265 * @session_keyring: session keyring for process (NULL for an empty keyring)
266 * @wait: wait for the application to finish and return status.
267 * when -1 don't wait at all, but you get no useful error back when
268 * the program couldn't be exec'ed. This makes it safe to call
269 * from interrupt context.
271 * Runs a user-space application. The application is started
272 * asynchronously if wait is not set, and runs as a child of keventd.
273 * (ie. it runs with full root capabilities).
275 * Must be called from process context. Returns a negative error code
276 * if program was not execed successfully, or 0.
278 int call_usermodehelper_keys(char *path
, char **argv
, char **envp
,
279 struct key
*session_keyring
, int wait
)
281 DECLARE_COMPLETION_ONSTACK(done
);
282 struct subprocess_info
*sub_info
;
291 sub_info
= kzalloc(sizeof(struct subprocess_info
), GFP_ATOMIC
);
295 INIT_WORK(&sub_info
->work
, __call_usermodehelper
);
296 sub_info
->complete
= &done
;
297 sub_info
->path
= path
;
298 sub_info
->argv
= argv
;
299 sub_info
->envp
= envp
;
300 sub_info
->ring
= session_keyring
;
301 sub_info
->wait
= wait
;
303 queue_work(khelper_wq
, &sub_info
->work
);
304 if (wait
< 0) /* task has freed sub_info */
306 wait_for_completion(&done
);
307 retval
= sub_info
->retval
;
311 EXPORT_SYMBOL(call_usermodehelper_keys
);
313 int call_usermodehelper_pipe(char *path
, char **argv
, char **envp
,
316 DECLARE_COMPLETION(done
);
317 struct subprocess_info sub_info
= {
318 .work
= __WORK_INITIALIZER(sub_info
.work
,
319 __call_usermodehelper
),
334 f
= create_write_pipe();
339 f
= create_read_pipe(f
);
341 free_write_pipe(*filp
);
346 queue_work(khelper_wq
, &sub_info
.work
);
347 wait_for_completion(&done
);
348 return sub_info
.retval
;
350 EXPORT_SYMBOL(call_usermodehelper_pipe
);
352 void __init
usermodehelper_init(void)
354 khelper_wq
= create_singlethread_workqueue("khelper");