Commit | Line | Data |
---|---|---|
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 | */ | |
21 | #define __KERNEL_SYSCALLS__ | |
22 | ||
23 | #include <linux/config.h> | |
24 | #include <linux/module.h> | |
25 | #include <linux/sched.h> | |
26 | #include <linux/syscalls.h> | |
27 | #include <linux/unistd.h> | |
28 | #include <linux/kmod.h> | |
29 | #include <linux/smp_lock.h> | |
30 | #include <linux/slab.h> | |
31 | #include <linux/namespace.h> | |
32 | #include <linux/completion.h> | |
33 | #include <linux/file.h> | |
34 | #include <linux/workqueue.h> | |
35 | #include <linux/security.h> | |
36 | #include <linux/mount.h> | |
37 | #include <linux/kernel.h> | |
38 | #include <linux/init.h> | |
39 | #include <asm/uaccess.h> | |
40 | ||
41 | extern int max_threads; | |
42 | ||
43 | static struct workqueue_struct *khelper_wq; | |
44 | ||
45 | #ifdef CONFIG_KMOD | |
46 | ||
47 | /* | |
48 | modprobe_path is set via /proc/sys. | |
49 | */ | |
50 | char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe"; | |
51 | ||
52 | /** | |
53 | * request_module - try to load a kernel module | |
54 | * @fmt: printf style format string for the name of the module | |
55 | * @varargs: arguements as specified in the format string | |
56 | * | |
57 | * Load a module using the user mode module loader. The function returns | |
58 | * zero on success or a negative errno code on failure. Note that a | |
59 | * successful module load does not mean the module did not then unload | |
60 | * and exit on an error of its own. Callers must check that the service | |
61 | * they requested is now available not blindly invoke it. | |
62 | * | |
63 | * If module auto-loading support is disabled then this function | |
64 | * becomes a no-operation. | |
65 | */ | |
66 | int request_module(const char *fmt, ...) | |
67 | { | |
68 | va_list args; | |
69 | char module_name[MODULE_NAME_LEN]; | |
70 | unsigned int max_modprobes; | |
71 | int ret; | |
72 | char *argv[] = { modprobe_path, "-q", "--", module_name, NULL }; | |
73 | static char *envp[] = { "HOME=/", | |
74 | "TERM=linux", | |
75 | "PATH=/sbin:/usr/sbin:/bin:/usr/bin", | |
76 | NULL }; | |
77 | static atomic_t kmod_concurrent = ATOMIC_INIT(0); | |
78 | #define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */ | |
79 | static int kmod_loop_msg; | |
80 | ||
81 | va_start(args, fmt); | |
82 | ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args); | |
83 | va_end(args); | |
84 | if (ret >= MODULE_NAME_LEN) | |
85 | return -ENAMETOOLONG; | |
86 | ||
87 | /* If modprobe needs a service that is in a module, we get a recursive | |
88 | * loop. Limit the number of running kmod threads to max_threads/2 or | |
89 | * MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method | |
90 | * would be to run the parents of this process, counting how many times | |
91 | * kmod was invoked. That would mean accessing the internals of the | |
92 | * process tables to get the command line, proc_pid_cmdline is static | |
93 | * and it is not worth changing the proc code just to handle this case. | |
94 | * KAO. | |
95 | * | |
96 | * "trace the ppid" is simple, but will fail if someone's | |
97 | * parent exits. I think this is as good as it gets. --RR | |
98 | */ | |
99 | max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT); | |
100 | atomic_inc(&kmod_concurrent); | |
101 | if (atomic_read(&kmod_concurrent) > max_modprobes) { | |
102 | /* We may be blaming an innocent here, but unlikely */ | |
103 | if (kmod_loop_msg++ < 5) | |
104 | printk(KERN_ERR | |
105 | "request_module: runaway loop modprobe %s\n", | |
106 | module_name); | |
107 | atomic_dec(&kmod_concurrent); | |
108 | return -ENOMEM; | |
109 | } | |
110 | ||
111 | ret = call_usermodehelper(modprobe_path, argv, envp, 1); | |
112 | atomic_dec(&kmod_concurrent); | |
113 | return ret; | |
114 | } | |
115 | EXPORT_SYMBOL(request_module); | |
116 | #endif /* CONFIG_KMOD */ | |
117 | ||
118 | struct subprocess_info { | |
119 | struct completion *complete; | |
120 | char *path; | |
121 | char **argv; | |
122 | char **envp; | |
123 | int wait; | |
124 | int retval; | |
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; | |
133 | int retval; | |
134 | ||
135 | /* Unblock all signals. */ | |
136 | flush_signals(current); | |
137 | spin_lock_irq(¤t->sighand->siglock); | |
138 | flush_signal_handlers(current, 1); | |
139 | sigemptyset(¤t->blocked); | |
140 | recalc_sigpending(); | |
141 | spin_unlock_irq(¤t->sighand->siglock); | |
142 | ||
143 | /* We can run anywhere, unlike our parent keventd(). */ | |
144 | set_cpus_allowed(current, CPU_MASK_ALL); | |
145 | ||
146 | retval = -EPERM; | |
147 | if (current->fs->root) | |
148 | retval = execve(sub_info->path, sub_info->argv,sub_info->envp); | |
149 | ||
150 | /* Exec failed? */ | |
151 | sub_info->retval = retval; | |
152 | do_exit(0); | |
153 | } | |
154 | ||
155 | /* Keventd can't block, but this (a child) can. */ | |
156 | static int wait_for_helper(void *data) | |
157 | { | |
158 | struct subprocess_info *sub_info = data; | |
159 | pid_t pid; | |
160 | struct k_sigaction sa; | |
161 | ||
162 | /* Install a handler: if SIGCLD isn't handled sys_wait4 won't | |
163 | * populate the status, but will return -ECHILD. */ | |
164 | sa.sa.sa_handler = SIG_IGN; | |
165 | sa.sa.sa_flags = 0; | |
166 | siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD)); | |
167 | do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0); | |
168 | allow_signal(SIGCHLD); | |
169 | ||
170 | pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD); | |
171 | if (pid < 0) { | |
172 | sub_info->retval = pid; | |
173 | } else { | |
174 | /* | |
175 | * Normally it is bogus to call wait4() from in-kernel because | |
176 | * wait4() wants to write the exit code to a userspace address. | |
177 | * But wait_for_helper() always runs as keventd, and put_user() | |
178 | * to a kernel address works OK for kernel threads, due to their | |
179 | * having an mm_segment_t which spans the entire address space. | |
180 | * | |
181 | * Thus the __user pointer cast is valid here. | |
182 | */ | |
183 | sys_wait4(pid, (int __user *) &sub_info->retval, 0, NULL); | |
184 | } | |
185 | ||
186 | complete(sub_info->complete); | |
187 | return 0; | |
188 | } | |
189 | ||
190 | /* This is run by khelper thread */ | |
191 | static void __call_usermodehelper(void *data) | |
192 | { | |
193 | struct subprocess_info *sub_info = data; | |
194 | pid_t pid; | |
195 | ||
196 | /* CLONE_VFORK: wait until the usermode helper has execve'd | |
197 | * successfully We need the data structures to stay around | |
198 | * until that is done. */ | |
199 | if (sub_info->wait) | |
200 | pid = kernel_thread(wait_for_helper, sub_info, | |
201 | CLONE_FS | CLONE_FILES | SIGCHLD); | |
202 | else | |
203 | pid = kernel_thread(____call_usermodehelper, sub_info, | |
204 | CLONE_VFORK | SIGCHLD); | |
205 | ||
206 | if (pid < 0) { | |
207 | sub_info->retval = pid; | |
208 | complete(sub_info->complete); | |
209 | } else if (!sub_info->wait) | |
210 | complete(sub_info->complete); | |
211 | } | |
212 | ||
213 | /** | |
214 | * call_usermodehelper - start a usermode application | |
215 | * @path: pathname for the application | |
216 | * @argv: null-terminated argument list | |
217 | * @envp: null-terminated environment list | |
218 | * @wait: wait for the application to finish and return status. | |
219 | * | |
220 | * Runs a user-space application. The application is started | |
221 | * asynchronously if wait is not set, and runs as a child of keventd. | |
222 | * (ie. it runs with full root capabilities). | |
223 | * | |
224 | * Must be called from process context. Returns a negative error code | |
225 | * if program was not execed successfully, or 0. | |
226 | */ | |
227 | int call_usermodehelper(char *path, char **argv, char **envp, int wait) | |
228 | { | |
229 | DECLARE_COMPLETION(done); | |
230 | struct subprocess_info sub_info = { | |
231 | .complete = &done, | |
232 | .path = path, | |
233 | .argv = argv, | |
234 | .envp = envp, | |
235 | .wait = wait, | |
236 | .retval = 0, | |
237 | }; | |
238 | DECLARE_WORK(work, __call_usermodehelper, &sub_info); | |
239 | ||
240 | if (!khelper_wq) | |
241 | return -EBUSY; | |
242 | ||
243 | if (path[0] == '\0') | |
244 | return 0; | |
245 | ||
246 | queue_work(khelper_wq, &work); | |
247 | wait_for_completion(&done); | |
248 | return sub_info.retval; | |
249 | } | |
250 | EXPORT_SYMBOL(call_usermodehelper); | |
251 | ||
252 | void __init usermodehelper_init(void) | |
253 | { | |
254 | khelper_wq = create_singlethread_workqueue("khelper"); | |
255 | BUG_ON(!khelper_wq); | |
256 | } |