projects/linux·blob v2.6.22 · refs

350 lines · 9.5 KiB

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 <[email protected]> December 1999
14
15 Unblock all signals when we exec a usermode process.
16 Shuu Yamaguchi <[email protected]> December 2000
17
18 call_usermodehelper wait flag, and remove exec_usermodehelper.
19 Rusty Russell <[email protected]> Jan 2003
20*/
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>
37
38extern int max_threads;
39
40static struct workqueue_struct *khelper_wq;
41
42#ifdef CONFIG_KMOD
43
44/*
45 modprobe_path is set via /proc/sys.
46*/
47char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
48
49/**
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
53 *
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.
59 *
60 * If module auto-loading support is disabled then this function
61 * becomes a no-operation.
62 */
63int request_module(const char *fmt, ...)
64{
65 va_list args;
66 char module_name[MODULE_NAME_LEN];
67 unsigned int max_modprobes;
68 int ret;
69 char *argv[] = { modprobe_path, "-q", "--", module_name, NULL };
70 static char *envp[] = { "HOME=/",
71 "TERM=linux",
72 "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
73 NULL };
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;
77
78 va_start(args, fmt);
79 ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
80 va_end(args);
81 if (ret >= MODULE_NAME_LEN)
82 return -ENAMETOOLONG;
83
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.
91 * KAO.
92 *
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
95 */
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)
101 printk(KERN_ERR
102 "request_module: runaway loop modprobe %s\n",
103 module_name);
104 atomic_dec(&kmod_concurrent);
105 return -ENOMEM;
106 }
107
108 ret = call_usermodehelper(modprobe_path, argv, envp, 1);
109 atomic_dec(&kmod_concurrent);
110 return ret;
111}
112EXPORT_SYMBOL(request_module);
113#endif /* CONFIG_KMOD */
114
115struct subprocess_info {
116 struct work_struct work;
117 struct completion *complete;
118 char *path;
119 char **argv;
120 char **envp;
121 struct key *ring;
122 int wait;
123 int retval;
124 struct file *stdin;
125};
126
127/*
128 * This is the task which runs the usermode application
129 */
130static int ____call_usermodehelper(void *data)
131{
132 struct subprocess_info *sub_info = data;
133 struct key *new_session, *old_session;
134 int retval;
135
136 /* Unblock all signals and set the session keyring. */
137 new_session = key_get(sub_info->ring);
138 spin_lock_irq(&current->sighand->siglock);
139 old_session = __install_session_keyring(current, new_session);
140 flush_signal_handlers(current, 1);
141 sigemptyset(&current->blocked);
142 recalc_sigpending();
143 spin_unlock_irq(&current->sighand->siglock);
144
145 key_put(old_session);
146
147 /* Install input pipe when needed */
148 if (sub_info->stdin) {
149 struct files_struct *f = current->files;
150 struct fdtable *fdt;
151 /* no races because files should be private here */
152 sys_close(0);
153 fd_install(0, sub_info->stdin);
154 spin_lock(&f->file_lock);
155 fdt = files_fdtable(f);
156 FD_SET(0, fdt->open_fds);
157 FD_CLR(0, fdt->close_on_exec);
158 spin_unlock(&f->file_lock);
159
160 /* and disallow core files too */
161 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){0, 0};
162 }
163
164 /* We can run anywhere, unlike our parent keventd(). */
165 set_cpus_allowed(current, CPU_MASK_ALL);
166
167 /*
168 * Our parent is keventd, which runs with elevated scheduling priority.
169 * Avoid propagating that into the userspace child.
170 */
171 set_user_nice(current, 0);
172
173 retval = -EPERM;
174 if (current->fs->root)
175 retval = kernel_execve(sub_info->path,
176 sub_info->argv, sub_info->envp);
177
178 /* Exec failed? */
179 sub_info->retval = retval;
180 do_exit(0);
181}
182
183/* Keventd can't block, but this (a child) can. */
184static int wait_for_helper(void *data)
185{
186 struct subprocess_info *sub_info = data;
187 pid_t pid;
188
189 /* Install a handler: if SIGCLD isn't handled sys_wait4 won't
190 * populate the status, but will return -ECHILD. */
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 {
197 int ret;
198
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 */
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;
217 }
218
219 if (sub_info->wait < 0)
220 kfree(sub_info);
221 else
222 complete(sub_info->complete);
223 return 0;
224}
225
226/* This is run by khelper thread */
227static void __call_usermodehelper(struct work_struct *work)
228{
229 struct subprocess_info *sub_info =
230 container_of(work, struct subprocess_info, work);
231 pid_t pid;
232 int wait = sub_info->wait;
233
234 /* CLONE_VFORK: wait until the usermode helper has execve'd
235 * successfully We need the data structures to stay around
236 * until that is done. */
237 if (wait)
238 pid = kernel_thread(wait_for_helper, sub_info,
239 CLONE_FS | CLONE_FILES | SIGCHLD);
240 else
241 pid = kernel_thread(____call_usermodehelper, sub_info,
242 CLONE_VFORK | SIGCHLD);
243
244 if (wait < 0)
245 return;
246
247 if (pid < 0) {
248 sub_info->retval = pid;
249 complete(sub_info->complete);
250 } else if (!wait)
251 complete(sub_info->complete);
252}
253
254/**
255 * call_usermodehelper_keys - start a usermode application
256 * @path: pathname for the application
257 * @argv: null-terminated argument list
258 * @envp: null-terminated environment list
259 * @session_keyring: session keyring for process (NULL for an empty keyring)
260 * @wait: wait for the application to finish and return status.
261 * when -1 don't wait at all, but you get no useful error back when
262 * the program couldn't be exec'ed. This makes it safe to call
263 * from interrupt context.
264 *
265 * Runs a user-space application. The application is started
266 * asynchronously if wait is not set, and runs as a child of keventd.
267 * (ie. it runs with full root capabilities).
268 *
269 * Must be called from process context. Returns a negative error code
270 * if program was not execed successfully, or 0.
271 */
272int call_usermodehelper_keys(char *path, char **argv, char **envp,
273 struct key *session_keyring, int wait)
274{
275 DECLARE_COMPLETION_ONSTACK(done);
276 struct subprocess_info *sub_info;
277 int retval;
278
279 if (!khelper_wq)
280 return -EBUSY;
281
282 if (path[0] == '\0')
283 return 0;
284
285 sub_info = kzalloc(sizeof(struct subprocess_info), GFP_ATOMIC);
286 if (!sub_info)
287 return -ENOMEM;
288
289 INIT_WORK(&sub_info->work, __call_usermodehelper);
290 sub_info->complete = &done;
291 sub_info->path = path;
292 sub_info->argv = argv;
293 sub_info->envp = envp;
294 sub_info->ring = session_keyring;
295 sub_info->wait = wait;
296
297 queue_work(khelper_wq, &sub_info->work);
298 if (wait < 0) /* task has freed sub_info */
299 return 0;
300 wait_for_completion(&done);
301 retval = sub_info->retval;
302 kfree(sub_info);
303 return retval;
304}
305EXPORT_SYMBOL(call_usermodehelper_keys);
306
307int call_usermodehelper_pipe(char *path, char **argv, char **envp,
308 struct file **filp)
309{
310 DECLARE_COMPLETION(done);
311 struct subprocess_info sub_info = {
312 .work = __WORK_INITIALIZER(sub_info.work,
313 __call_usermodehelper),
314 .complete = &done,
315 .path = path,
316 .argv = argv,
317 .envp = envp,
318 .retval = 0,
319 };
320 struct file *f;
321
322 if (!khelper_wq)
323 return -EBUSY;
324
325 if (path[0] == '\0')
326 return 0;
327
328 f = create_write_pipe();
329 if (IS_ERR(f))
330 return PTR_ERR(f);
331 *filp = f;
332
333 f = create_read_pipe(f);
334 if (IS_ERR(f)) {
335 free_write_pipe(*filp);
336 return PTR_ERR(f);
337 }
338 sub_info.stdin = f;
339
340 queue_work(khelper_wq, &sub_info.work);
341 wait_for_completion(&done);
342 return sub_info.retval;
343}
344EXPORT_SYMBOL(call_usermodehelper_pipe);
345
346void __init usermodehelper_init(void)
347{
348 khelper_wq = create_singlethread_workqueue("khelper");
349 BUG_ON(!khelper_wq);
350}