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Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | kmod, the new module loader (replaces kerneld) | |
3 | Kirk Petersen | |
4 | ||
5 | Reorganized not to be a daemon by Adam Richter, with guidance | |
6 | from Greg Zornetzer. | |
7 | ||
8 | Modified to avoid chroot and file sharing problems. | |
9 | Mikael Pettersson | |
10 | ||
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 | |
14 | ||
15 | Unblock all signals when we exec a usermode process. | |
16 | Shuu Yamaguchi <shuu@wondernetworkresources.com> December 2000 | |
17 | ||
18 | call_usermodehelper wait flag, and remove exec_usermodehelper. | |
19 | Rusty Russell <rusty@rustcorp.com.au> Jan 2003 | |
20 | */ | |
1da177e4 LT |
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/smp_lock.h> | |
27 | #include <linux/slab.h> | |
28 | #include <linux/namespace.h> | |
29 | #include <linux/completion.h> | |
30 | #include <linux/file.h> | |
31 | #include <linux/workqueue.h> | |
32 | #include <linux/security.h> | |
33 | #include <linux/mount.h> | |
34 | #include <linux/kernel.h> | |
35 | #include <linux/init.h> | |
d025c9db | 36 | #include <linux/resource.h> |
1da177e4 LT |
37 | #include <asm/uaccess.h> |
38 | ||
39 | extern int max_threads; | |
40 | ||
41 | static struct workqueue_struct *khelper_wq; | |
42 | ||
43 | #ifdef CONFIG_KMOD | |
44 | ||
45 | /* | |
46 | modprobe_path is set via /proc/sys. | |
47 | */ | |
48 | char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe"; | |
49 | ||
50 | /** | |
51 | * request_module - try to load a kernel module | |
52 | * @fmt: printf style format string for the name of the module | |
53 | * @varargs: arguements as specified in the format string | |
54 | * | |
55 | * Load a module using the user mode module loader. The function returns | |
56 | * zero on success or a negative errno code on failure. Note that a | |
57 | * successful module load does not mean the module did not then unload | |
58 | * and exit on an error of its own. Callers must check that the service | |
59 | * they requested is now available not blindly invoke it. | |
60 | * | |
61 | * If module auto-loading support is disabled then this function | |
62 | * becomes a no-operation. | |
63 | */ | |
64 | int request_module(const char *fmt, ...) | |
65 | { | |
66 | va_list args; | |
67 | char module_name[MODULE_NAME_LEN]; | |
68 | unsigned int max_modprobes; | |
69 | int ret; | |
70 | char *argv[] = { modprobe_path, "-q", "--", module_name, NULL }; | |
71 | static char *envp[] = { "HOME=/", | |
72 | "TERM=linux", | |
73 | "PATH=/sbin:/usr/sbin:/bin:/usr/bin", | |
74 | NULL }; | |
75 | static atomic_t kmod_concurrent = ATOMIC_INIT(0); | |
76 | #define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */ | |
77 | static int kmod_loop_msg; | |
78 | ||
79 | va_start(args, fmt); | |
80 | ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args); | |
81 | va_end(args); | |
82 | if (ret >= MODULE_NAME_LEN) | |
83 | return -ENAMETOOLONG; | |
84 | ||
85 | /* If modprobe needs a service that is in a module, we get a recursive | |
86 | * loop. Limit the number of running kmod threads to max_threads/2 or | |
87 | * MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method | |
88 | * would be to run the parents of this process, counting how many times | |
89 | * kmod was invoked. That would mean accessing the internals of the | |
90 | * process tables to get the command line, proc_pid_cmdline is static | |
91 | * and it is not worth changing the proc code just to handle this case. | |
92 | * KAO. | |
93 | * | |
94 | * "trace the ppid" is simple, but will fail if someone's | |
95 | * parent exits. I think this is as good as it gets. --RR | |
96 | */ | |
97 | max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT); | |
98 | atomic_inc(&kmod_concurrent); | |
99 | if (atomic_read(&kmod_concurrent) > max_modprobes) { | |
100 | /* We may be blaming an innocent here, but unlikely */ | |
101 | if (kmod_loop_msg++ < 5) | |
102 | printk(KERN_ERR | |
103 | "request_module: runaway loop modprobe %s\n", | |
104 | module_name); | |
105 | atomic_dec(&kmod_concurrent); | |
106 | return -ENOMEM; | |
107 | } | |
108 | ||
109 | ret = call_usermodehelper(modprobe_path, argv, envp, 1); | |
110 | atomic_dec(&kmod_concurrent); | |
111 | return ret; | |
112 | } | |
113 | EXPORT_SYMBOL(request_module); | |
114 | #endif /* CONFIG_KMOD */ | |
115 | ||
116 | struct subprocess_info { | |
117 | struct completion *complete; | |
118 | char *path; | |
119 | char **argv; | |
120 | char **envp; | |
7888e7ff | 121 | struct key *ring; |
1da177e4 LT |
122 | int wait; |
123 | int retval; | |
e239ca54 | 124 | struct file *stdin; |
1da177e4 LT |
125 | }; |
126 | ||
127 | /* | |
128 | * This is the task which runs the usermode application | |
129 | */ | |
130 | static int ____call_usermodehelper(void *data) | |
131 | { | |
132 | struct subprocess_info *sub_info = data; | |
20e1129a | 133 | struct key *new_session, *old_session; |
1da177e4 LT |
134 | int retval; |
135 | ||
7888e7ff | 136 | /* Unblock all signals and set the session keyring. */ |
20e1129a | 137 | new_session = key_get(sub_info->ring); |
1da177e4 LT |
138 | flush_signals(current); |
139 | spin_lock_irq(¤t->sighand->siglock); | |
20e1129a | 140 | old_session = __install_session_keyring(current, new_session); |
1da177e4 LT |
141 | flush_signal_handlers(current, 1); |
142 | sigemptyset(¤t->blocked); | |
143 | recalc_sigpending(); | |
144 | spin_unlock_irq(¤t->sighand->siglock); | |
145 | ||
7888e7ff DH |
146 | key_put(old_session); |
147 | ||
e239ca54 AK |
148 | /* Install input pipe when needed */ |
149 | if (sub_info->stdin) { | |
150 | struct files_struct *f = current->files; | |
151 | struct fdtable *fdt; | |
152 | /* no races because files should be private here */ | |
153 | sys_close(0); | |
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); | |
d025c9db AK |
160 | |
161 | /* and disallow core files too */ | |
162 | current->signal->rlim[RLIMIT_CORE] = (struct rlimit){0, 0}; | |
e239ca54 AK |
163 | } |
164 | ||
1da177e4 LT |
165 | /* We can run anywhere, unlike our parent keventd(). */ |
166 | set_cpus_allowed(current, CPU_MASK_ALL); | |
167 | ||
168 | retval = -EPERM; | |
169 | if (current->fs->root) | |
67608567 AB |
170 | retval = kernel_execve(sub_info->path, |
171 | sub_info->argv, sub_info->envp); | |
1da177e4 LT |
172 | |
173 | /* Exec failed? */ | |
174 | sub_info->retval = retval; | |
175 | do_exit(0); | |
176 | } | |
177 | ||
178 | /* Keventd can't block, but this (a child) can. */ | |
179 | static int wait_for_helper(void *data) | |
180 | { | |
181 | struct subprocess_info *sub_info = data; | |
182 | pid_t pid; | |
183 | struct k_sigaction sa; | |
184 | ||
185 | /* Install a handler: if SIGCLD isn't handled sys_wait4 won't | |
186 | * populate the status, but will return -ECHILD. */ | |
187 | sa.sa.sa_handler = SIG_IGN; | |
188 | sa.sa.sa_flags = 0; | |
189 | siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD)); | |
8292d633 | 190 | do_sigaction(SIGCHLD, &sa, NULL); |
1da177e4 LT |
191 | allow_signal(SIGCHLD); |
192 | ||
193 | pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD); | |
194 | if (pid < 0) { | |
195 | sub_info->retval = pid; | |
196 | } else { | |
111dbe0c BS |
197 | int ret; |
198 | ||
1da177e4 LT |
199 | /* |
200 | * Normally it is bogus to call wait4() from in-kernel because | |
201 | * wait4() wants to write the exit code to a userspace address. | |
202 | * But wait_for_helper() always runs as keventd, and put_user() | |
203 | * to a kernel address works OK for kernel threads, due to their | |
204 | * having an mm_segment_t which spans the entire address space. | |
205 | * | |
206 | * Thus the __user pointer cast is valid here. | |
207 | */ | |
111dbe0c BS |
208 | sys_wait4(pid, (int __user *)&ret, 0, NULL); |
209 | ||
210 | /* | |
211 | * If ret is 0, either ____call_usermodehelper failed and the | |
212 | * real error code is already in sub_info->retval or | |
213 | * sub_info->retval is 0 anyway, so don't mess with it then. | |
214 | */ | |
215 | if (ret) | |
216 | sub_info->retval = ret; | |
1da177e4 LT |
217 | } |
218 | ||
219 | complete(sub_info->complete); | |
220 | return 0; | |
221 | } | |
222 | ||
223 | /* This is run by khelper thread */ | |
224 | static void __call_usermodehelper(void *data) | |
225 | { | |
226 | struct subprocess_info *sub_info = data; | |
227 | pid_t pid; | |
e4b69aa2 | 228 | int wait = sub_info->wait; |
1da177e4 LT |
229 | |
230 | /* CLONE_VFORK: wait until the usermode helper has execve'd | |
231 | * successfully We need the data structures to stay around | |
232 | * until that is done. */ | |
e4b69aa2 | 233 | if (wait) |
1da177e4 LT |
234 | pid = kernel_thread(wait_for_helper, sub_info, |
235 | CLONE_FS | CLONE_FILES | SIGCHLD); | |
236 | else | |
237 | pid = kernel_thread(____call_usermodehelper, sub_info, | |
238 | CLONE_VFORK | SIGCHLD); | |
239 | ||
240 | if (pid < 0) { | |
241 | sub_info->retval = pid; | |
242 | complete(sub_info->complete); | |
e4b69aa2 | 243 | } else if (!wait) |
1da177e4 LT |
244 | complete(sub_info->complete); |
245 | } | |
246 | ||
247 | /** | |
7888e7ff | 248 | * call_usermodehelper_keys - start a usermode application |
1da177e4 LT |
249 | * @path: pathname for the application |
250 | * @argv: null-terminated argument list | |
251 | * @envp: null-terminated environment list | |
7888e7ff | 252 | * @session_keyring: session keyring for process (NULL for an empty keyring) |
1da177e4 LT |
253 | * @wait: wait for the application to finish and return status. |
254 | * | |
255 | * Runs a user-space application. The application is started | |
256 | * asynchronously if wait is not set, and runs as a child of keventd. | |
257 | * (ie. it runs with full root capabilities). | |
258 | * | |
259 | * Must be called from process context. Returns a negative error code | |
260 | * if program was not execed successfully, or 0. | |
261 | */ | |
7888e7ff DH |
262 | int call_usermodehelper_keys(char *path, char **argv, char **envp, |
263 | struct key *session_keyring, int wait) | |
1da177e4 | 264 | { |
60be6b9a | 265 | DECLARE_COMPLETION_ONSTACK(done); |
1da177e4 LT |
266 | struct subprocess_info sub_info = { |
267 | .complete = &done, | |
268 | .path = path, | |
269 | .argv = argv, | |
270 | .envp = envp, | |
7888e7ff | 271 | .ring = session_keyring, |
1da177e4 LT |
272 | .wait = wait, |
273 | .retval = 0, | |
274 | }; | |
275 | DECLARE_WORK(work, __call_usermodehelper, &sub_info); | |
276 | ||
277 | if (!khelper_wq) | |
278 | return -EBUSY; | |
279 | ||
280 | if (path[0] == '\0') | |
281 | return 0; | |
282 | ||
283 | queue_work(khelper_wq, &work); | |
284 | wait_for_completion(&done); | |
285 | return sub_info.retval; | |
286 | } | |
7888e7ff | 287 | EXPORT_SYMBOL(call_usermodehelper_keys); |
1da177e4 | 288 | |
e239ca54 AK |
289 | int call_usermodehelper_pipe(char *path, char **argv, char **envp, |
290 | struct file **filp) | |
291 | { | |
292 | DECLARE_COMPLETION(done); | |
293 | struct subprocess_info sub_info = { | |
294 | .complete = &done, | |
295 | .path = path, | |
296 | .argv = argv, | |
297 | .envp = envp, | |
298 | .retval = 0, | |
299 | }; | |
300 | struct file *f; | |
301 | DECLARE_WORK(work, __call_usermodehelper, &sub_info); | |
302 | ||
303 | if (!khelper_wq) | |
304 | return -EBUSY; | |
305 | ||
306 | if (path[0] == '\0') | |
307 | return 0; | |
308 | ||
309 | f = create_write_pipe(); | |
310 | if (!f) | |
311 | return -ENOMEM; | |
312 | *filp = f; | |
313 | ||
314 | f = create_read_pipe(f); | |
315 | if (!f) { | |
316 | free_write_pipe(*filp); | |
317 | return -ENOMEM; | |
318 | } | |
319 | sub_info.stdin = f; | |
320 | ||
321 | queue_work(khelper_wq, &work); | |
322 | wait_for_completion(&done); | |
323 | return sub_info.retval; | |
324 | } | |
325 | EXPORT_SYMBOL(call_usermodehelper_pipe); | |
326 | ||
1da177e4 LT |
327 | void __init usermodehelper_init(void) |
328 | { | |
329 | khelper_wq = create_singlethread_workqueue("khelper"); | |
330 | BUG_ON(!khelper_wq); | |
331 | } |