projects/linux·blob v2.6.21 · refs

351 lines · 9.6 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/smp_lock.h>
27#include <linux/slab.h>
28#include <linux/mnt_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>
36#include <linux/resource.h>
37#include <asm/uaccess.h>
38
39extern int max_threads;
40
41static struct workqueue_struct *khelper_wq;
42
43#ifdef CONFIG_KMOD
44
45/*
46 modprobe_path is set via /proc/sys.
47*/
48char 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 */
64int 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}
113EXPORT_SYMBOL(request_module);
114#endif /* CONFIG_KMOD */
115
116struct subprocess_info {
117 struct work_struct work;
118 struct completion *complete;
119 char *path;
120 char **argv;
121 char **envp;
122 struct key *ring;
123 int wait;
124 int retval;
125 struct file *stdin;
126};
127
128/*
129 * This is the task which runs the usermode application
130 */
131static int ____call_usermodehelper(void *data)
132{
133 struct subprocess_info *sub_info = data;
134 struct key *new_session, *old_session;
135 int retval;
136
137 /* Unblock all signals and set the session keyring. */
138 new_session = key_get(sub_info->ring);
139 flush_signals(current);
140 spin_lock_irq(&current->sighand->siglock);
141 old_session = __install_session_keyring(current, new_session);
142 flush_signal_handlers(current, 1);
143 sigemptyset(&current->blocked);
144 recalc_sigpending();
145 spin_unlock_irq(&current->sighand->siglock);
146
147 key_put(old_session);
148
149 /* Install input pipe when needed */
150 if (sub_info->stdin) {
151 struct files_struct *f = current->files;
152 struct fdtable *fdt;
153 /* no races because files should be private here */
154 sys_close(0);
155 fd_install(0, sub_info->stdin);
156 spin_lock(&f->file_lock);
157 fdt = files_fdtable(f);
158 FD_SET(0, fdt->open_fds);
159 FD_CLR(0, fdt->close_on_exec);
160 spin_unlock(&f->file_lock);
161
162 /* and disallow core files too */
163 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){0, 0};
164 }
165
166 /* We can run anywhere, unlike our parent keventd(). */
167 set_cpus_allowed(current, CPU_MASK_ALL);
168
169 retval = -EPERM;
170 if (current->fs->root)
171 retval = kernel_execve(sub_info->path,
172 sub_info->argv, sub_info->envp);
173
174 /* Exec failed? */
175 sub_info->retval = retval;
176 do_exit(0);
177}
178
179/* Keventd can't block, but this (a child) can. */
180static int wait_for_helper(void *data)
181{
182 struct subprocess_info *sub_info = data;
183 pid_t pid;
184 struct k_sigaction sa;
185
186 /* Install a handler: if SIGCLD isn't handled sys_wait4 won't
187 * populate the status, but will return -ECHILD. */
188 sa.sa.sa_handler = SIG_IGN;
189 sa.sa.sa_flags = 0;
190 siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
191 do_sigaction(SIGCHLD, &sa, NULL);
192 allow_signal(SIGCHLD);
193
194 pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
195 if (pid < 0) {
196 sub_info->retval = pid;
197 } else {
198 int ret;
199
200 /*
201 * Normally it is bogus to call wait4() from in-kernel because
202 * wait4() wants to write the exit code to a userspace address.
203 * But wait_for_helper() always runs as keventd, and put_user()
204 * to a kernel address works OK for kernel threads, due to their
205 * having an mm_segment_t which spans the entire address space.
206 *
207 * Thus the __user pointer cast is valid here.
208 */
209 sys_wait4(pid, (int __user *)&ret, 0, NULL);
210
211 /*
212 * If ret is 0, either ____call_usermodehelper failed and the
213 * real error code is already in sub_info->retval or
214 * sub_info->retval is 0 anyway, so don't mess with it then.
215 */
216 if (ret)
217 sub_info->retval = ret;
218 }
219
220 if (sub_info->wait < 0)
221 kfree(sub_info);
222 else
223 complete(sub_info->complete);
224 return 0;
225}
226
227/* This is run by khelper thread */
228static void __call_usermodehelper(struct work_struct *work)
229{
230 struct subprocess_info *sub_info =
231 container_of(work, struct subprocess_info, work);
232 pid_t pid;
233 int wait = sub_info->wait;
234
235 /* CLONE_VFORK: wait until the usermode helper has execve'd
236 * successfully We need the data structures to stay around
237 * until that is done. */
238 if (wait)
239 pid = kernel_thread(wait_for_helper, sub_info,
240 CLONE_FS | CLONE_FILES | SIGCHLD);
241 else
242 pid = kernel_thread(____call_usermodehelper, sub_info,
243 CLONE_VFORK | SIGCHLD);
244
245 if (wait < 0)
246 return;
247
248 if (pid < 0) {
249 sub_info->retval = pid;
250 complete(sub_info->complete);
251 } else if (!wait)
252 complete(sub_info->complete);
253}
254
255/**
256 * call_usermodehelper_keys - start a usermode application
257 * @path: pathname for the application
258 * @argv: null-terminated argument list
259 * @envp: null-terminated environment list
260 * @session_keyring: session keyring for process (NULL for an empty keyring)
261 * @wait: wait for the application to finish and return status.
262 * when -1 don't wait at all, but you get no useful error back when
263 * the program couldn't be exec'ed. This makes it safe to call
264 * from interrupt context.
265 *
266 * Runs a user-space application. The application is started
267 * asynchronously if wait is not set, and runs as a child of keventd.
268 * (ie. it runs with full root capabilities).
269 *
270 * Must be called from process context. Returns a negative error code
271 * if program was not execed successfully, or 0.
272 */
273int call_usermodehelper_keys(char *path, char **argv, char **envp,
274 struct key *session_keyring, int wait)
275{
276 DECLARE_COMPLETION_ONSTACK(done);
277 struct subprocess_info *sub_info;
278 int retval;
279
280 if (!khelper_wq)
281 return -EBUSY;
282
283 if (path[0] == '\0')
284 return 0;
285
286 sub_info = kzalloc(sizeof(struct subprocess_info), GFP_ATOMIC);
287 if (!sub_info)
288 return -ENOMEM;
289
290 INIT_WORK(&sub_info->work, __call_usermodehelper);
291 sub_info->complete = &done;
292 sub_info->path = path;
293 sub_info->argv = argv;
294 sub_info->envp = envp;
295 sub_info->ring = session_keyring;
296 sub_info->wait = wait;
297
298 queue_work(khelper_wq, &sub_info->work);
299 if (wait < 0) /* task has freed sub_info */
300 return 0;
301 wait_for_completion(&done);
302 retval = sub_info->retval;
303 kfree(sub_info);
304 return retval;
305}
306EXPORT_SYMBOL(call_usermodehelper_keys);
307
308int call_usermodehelper_pipe(char *path, char **argv, char **envp,
309 struct file **filp)
310{
311 DECLARE_COMPLETION(done);
312 struct subprocess_info sub_info = {
313 .work = __WORK_INITIALIZER(sub_info.work,
314 __call_usermodehelper),
315 .complete = &done,
316 .path = path,
317 .argv = argv,
318 .envp = envp,
319 .retval = 0,
320 };
321 struct file *f;
322
323 if (!khelper_wq)
324 return -EBUSY;
325
326 if (path[0] == '\0')
327 return 0;
328
329 f = create_write_pipe();
330 if (IS_ERR(f))
331 return PTR_ERR(f);
332 *filp = f;
333
334 f = create_read_pipe(f);
335 if (IS_ERR(f)) {
336 free_write_pipe(*filp);
337 return PTR_ERR(f);
338 }
339 sub_info.stdin = f;
340
341 queue_work(khelper_wq, &sub_info.work);
342 wait_for_completion(&done);
343 return sub_info.retval;
344}
345EXPORT_SYMBOL(call_usermodehelper_pipe);
346
347void __init usermodehelper_init(void)
348{
349 khelper_wq = create_singlethread_workqueue("khelper");
350 BUG_ON(!khelper_wq);
351}