kmod: unexport call_usermodehelper_freeinfo()
[linux-3.10.git] / kernel / kmod.c
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 #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/completion.h>
28 #include <linux/cred.h>
29 #include <linux/file.h>
30 #include <linux/fdtable.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 <linux/notifier.h>
38 #include <linux/suspend.h>
39 #include <linux/rwsem.h>
40 #include <asm/uaccess.h>
41
42 #include <trace/events/module.h>
43
44 extern int max_threads;
45
46 static struct workqueue_struct *khelper_wq;
47
48 #define CAP_BSET        (void *)1
49 #define CAP_PI          (void *)2
50
51 static kernel_cap_t usermodehelper_bset = CAP_FULL_SET;
52 static kernel_cap_t usermodehelper_inheritable = CAP_FULL_SET;
53 static DEFINE_SPINLOCK(umh_sysctl_lock);
54 static DECLARE_RWSEM(umhelper_sem);
55
56 #ifdef CONFIG_MODULES
57
58 /*
59         modprobe_path is set via /proc/sys.
60 */
61 char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
62
63 static void free_modprobe_argv(struct subprocess_info *info)
64 {
65         kfree(info->argv[3]); /* check call_modprobe() */
66         kfree(info->argv);
67 }
68
69 static int call_modprobe(char *module_name, int wait)
70 {
71         static char *envp[] = {
72                 "HOME=/",
73                 "TERM=linux",
74                 "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
75                 NULL
76         };
77
78         char **argv = kmalloc(sizeof(char *[5]), GFP_KERNEL);
79         if (!argv)
80                 goto out;
81
82         module_name = kstrdup(module_name, GFP_KERNEL);
83         if (!module_name)
84                 goto free_argv;
85
86         argv[0] = modprobe_path;
87         argv[1] = "-q";
88         argv[2] = "--";
89         argv[3] = module_name;  /* check free_modprobe_argv() */
90         argv[4] = NULL;
91
92         return call_usermodehelper_fns(modprobe_path, argv, envp,
93                 wait | UMH_KILLABLE, NULL, free_modprobe_argv, NULL);
94 free_argv:
95         kfree(argv);
96 out:
97         return -ENOMEM;
98 }
99
100 /**
101  * __request_module - try to load a kernel module
102  * @wait: wait (or not) for the operation to complete
103  * @fmt: printf style format string for the name of the module
104  * @...: arguments as specified in the format string
105  *
106  * Load a module using the user mode module loader. The function returns
107  * zero on success or a negative errno code on failure. Note that a
108  * successful module load does not mean the module did not then unload
109  * and exit on an error of its own. Callers must check that the service
110  * they requested is now available not blindly invoke it.
111  *
112  * If module auto-loading support is disabled then this function
113  * becomes a no-operation.
114  */
115 int __request_module(bool wait, const char *fmt, ...)
116 {
117         va_list args;
118         char module_name[MODULE_NAME_LEN];
119         unsigned int max_modprobes;
120         int ret;
121         static atomic_t kmod_concurrent = ATOMIC_INIT(0);
122 #define MAX_KMOD_CONCURRENT 50  /* Completely arbitrary value - KAO */
123         static int kmod_loop_msg;
124
125         va_start(args, fmt);
126         ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
127         va_end(args);
128         if (ret >= MODULE_NAME_LEN)
129                 return -ENAMETOOLONG;
130
131         ret = security_kernel_module_request(module_name);
132         if (ret)
133                 return ret;
134
135         /* If modprobe needs a service that is in a module, we get a recursive
136          * loop.  Limit the number of running kmod threads to max_threads/2 or
137          * MAX_KMOD_CONCURRENT, whichever is the smaller.  A cleaner method
138          * would be to run the parents of this process, counting how many times
139          * kmod was invoked.  That would mean accessing the internals of the
140          * process tables to get the command line, proc_pid_cmdline is static
141          * and it is not worth changing the proc code just to handle this case. 
142          * KAO.
143          *
144          * "trace the ppid" is simple, but will fail if someone's
145          * parent exits.  I think this is as good as it gets. --RR
146          */
147         max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
148         atomic_inc(&kmod_concurrent);
149         if (atomic_read(&kmod_concurrent) > max_modprobes) {
150                 /* We may be blaming an innocent here, but unlikely */
151                 if (kmod_loop_msg < 5) {
152                         printk(KERN_ERR
153                                "request_module: runaway loop modprobe %s\n",
154                                module_name);
155                         kmod_loop_msg++;
156                 }
157                 atomic_dec(&kmod_concurrent);
158                 return -ENOMEM;
159         }
160
161         trace_module_request(module_name, wait, _RET_IP_);
162
163         ret = call_modprobe(module_name, wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC);
164
165         atomic_dec(&kmod_concurrent);
166         return ret;
167 }
168 EXPORT_SYMBOL(__request_module);
169 #endif /* CONFIG_MODULES */
170
171 /*
172  * This is the task which runs the usermode application
173  */
174 static int ____call_usermodehelper(void *data)
175 {
176         struct subprocess_info *sub_info = data;
177         struct cred *new;
178         int retval;
179
180         spin_lock_irq(&current->sighand->siglock);
181         flush_signal_handlers(current, 1);
182         spin_unlock_irq(&current->sighand->siglock);
183
184         /* We can run anywhere, unlike our parent keventd(). */
185         set_cpus_allowed_ptr(current, cpu_all_mask);
186
187         /*
188          * Our parent is keventd, which runs with elevated scheduling priority.
189          * Avoid propagating that into the userspace child.
190          */
191         set_user_nice(current, 0);
192
193         retval = -ENOMEM;
194         new = prepare_kernel_cred(current);
195         if (!new)
196                 goto fail;
197
198         spin_lock(&umh_sysctl_lock);
199         new->cap_bset = cap_intersect(usermodehelper_bset, new->cap_bset);
200         new->cap_inheritable = cap_intersect(usermodehelper_inheritable,
201                                              new->cap_inheritable);
202         spin_unlock(&umh_sysctl_lock);
203
204         if (sub_info->init) {
205                 retval = sub_info->init(sub_info, new);
206                 if (retval) {
207                         abort_creds(new);
208                         goto fail;
209                 }
210         }
211
212         commit_creds(new);
213
214         retval = kernel_execve(sub_info->path,
215                                (const char *const *)sub_info->argv,
216                                (const char *const *)sub_info->envp);
217
218         /* Exec failed? */
219 fail:
220         sub_info->retval = retval;
221         return 0;
222 }
223
224 static void call_usermodehelper_freeinfo(struct subprocess_info *info)
225 {
226         if (info->cleanup)
227                 (*info->cleanup)(info);
228         kfree(info);
229 }
230
231 static void umh_complete(struct subprocess_info *sub_info)
232 {
233         struct completion *comp = xchg(&sub_info->complete, NULL);
234         /*
235          * See call_usermodehelper_exec(). If xchg() returns NULL
236          * we own sub_info, the UMH_KILLABLE caller has gone away.
237          */
238         if (comp)
239                 complete(comp);
240         else
241                 call_usermodehelper_freeinfo(sub_info);
242 }
243
244 /* Keventd can't block, but this (a child) can. */
245 static int wait_for_helper(void *data)
246 {
247         struct subprocess_info *sub_info = data;
248         pid_t pid;
249
250         /* If SIGCLD is ignored sys_wait4 won't populate the status. */
251         spin_lock_irq(&current->sighand->siglock);
252         current->sighand->action[SIGCHLD-1].sa.sa_handler = SIG_DFL;
253         spin_unlock_irq(&current->sighand->siglock);
254
255         pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
256         if (pid < 0) {
257                 sub_info->retval = pid;
258         } else {
259                 int ret = -ECHILD;
260                 /*
261                  * Normally it is bogus to call wait4() from in-kernel because
262                  * wait4() wants to write the exit code to a userspace address.
263                  * But wait_for_helper() always runs as keventd, and put_user()
264                  * to a kernel address works OK for kernel threads, due to their
265                  * having an mm_segment_t which spans the entire address space.
266                  *
267                  * Thus the __user pointer cast is valid here.
268                  */
269                 sys_wait4(pid, (int __user *)&ret, 0, NULL);
270
271                 /*
272                  * If ret is 0, either ____call_usermodehelper failed and the
273                  * real error code is already in sub_info->retval or
274                  * sub_info->retval is 0 anyway, so don't mess with it then.
275                  */
276                 if (ret)
277                         sub_info->retval = ret;
278         }
279
280         umh_complete(sub_info);
281         return 0;
282 }
283
284 /* This is run by khelper thread  */
285 static void __call_usermodehelper(struct work_struct *work)
286 {
287         struct subprocess_info *sub_info =
288                 container_of(work, struct subprocess_info, work);
289         int wait = sub_info->wait & ~UMH_KILLABLE;
290         pid_t pid;
291
292         /* CLONE_VFORK: wait until the usermode helper has execve'd
293          * successfully We need the data structures to stay around
294          * until that is done.  */
295         if (wait == UMH_WAIT_PROC)
296                 pid = kernel_thread(wait_for_helper, sub_info,
297                                     CLONE_FS | CLONE_FILES | SIGCHLD);
298         else
299                 pid = kernel_thread(____call_usermodehelper, sub_info,
300                                     CLONE_VFORK | SIGCHLD);
301
302         switch (wait) {
303         case UMH_NO_WAIT:
304                 call_usermodehelper_freeinfo(sub_info);
305                 break;
306
307         case UMH_WAIT_PROC:
308                 if (pid > 0)
309                         break;
310                 /* FALLTHROUGH */
311         case UMH_WAIT_EXEC:
312                 if (pid < 0)
313                         sub_info->retval = pid;
314                 umh_complete(sub_info);
315         }
316 }
317
318 /*
319  * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
320  * (used for preventing user land processes from being created after the user
321  * land has been frozen during a system-wide hibernation or suspend operation).
322  * Should always be manipulated under umhelper_sem acquired for write.
323  */
324 static enum umh_disable_depth usermodehelper_disabled = UMH_DISABLED;
325
326 /* Number of helpers running */
327 static atomic_t running_helpers = ATOMIC_INIT(0);
328
329 /*
330  * Wait queue head used by usermodehelper_disable() to wait for all running
331  * helpers to finish.
332  */
333 static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);
334
335 /*
336  * Used by usermodehelper_read_lock_wait() to wait for usermodehelper_disabled
337  * to become 'false'.
338  */
339 static DECLARE_WAIT_QUEUE_HEAD(usermodehelper_disabled_waitq);
340
341 /*
342  * Time to wait for running_helpers to become zero before the setting of
343  * usermodehelper_disabled in usermodehelper_disable() fails
344  */
345 #define RUNNING_HELPERS_TIMEOUT (5 * HZ)
346
347 int usermodehelper_read_trylock(void)
348 {
349         DEFINE_WAIT(wait);
350         int ret = 0;
351
352         down_read(&umhelper_sem);
353         for (;;) {
354                 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
355                                 TASK_INTERRUPTIBLE);
356                 if (!usermodehelper_disabled)
357                         break;
358
359                 if (usermodehelper_disabled == UMH_DISABLED)
360                         ret = -EAGAIN;
361
362                 up_read(&umhelper_sem);
363
364                 if (ret)
365                         break;
366
367                 schedule();
368                 try_to_freeze();
369
370                 down_read(&umhelper_sem);
371         }
372         finish_wait(&usermodehelper_disabled_waitq, &wait);
373         return ret;
374 }
375 EXPORT_SYMBOL_GPL(usermodehelper_read_trylock);
376
377 long usermodehelper_read_lock_wait(long timeout)
378 {
379         DEFINE_WAIT(wait);
380
381         if (timeout < 0)
382                 return -EINVAL;
383
384         down_read(&umhelper_sem);
385         for (;;) {
386                 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
387                                 TASK_UNINTERRUPTIBLE);
388                 if (!usermodehelper_disabled)
389                         break;
390
391                 up_read(&umhelper_sem);
392
393                 timeout = schedule_timeout(timeout);
394                 if (!timeout)
395                         break;
396
397                 down_read(&umhelper_sem);
398         }
399         finish_wait(&usermodehelper_disabled_waitq, &wait);
400         return timeout;
401 }
402 EXPORT_SYMBOL_GPL(usermodehelper_read_lock_wait);
403
404 void usermodehelper_read_unlock(void)
405 {
406         up_read(&umhelper_sem);
407 }
408 EXPORT_SYMBOL_GPL(usermodehelper_read_unlock);
409
410 /**
411  * __usermodehelper_set_disable_depth - Modify usermodehelper_disabled.
412  * depth: New value to assign to usermodehelper_disabled.
413  *
414  * Change the value of usermodehelper_disabled (under umhelper_sem locked for
415  * writing) and wakeup tasks waiting for it to change.
416  */
417 void __usermodehelper_set_disable_depth(enum umh_disable_depth depth)
418 {
419         down_write(&umhelper_sem);
420         usermodehelper_disabled = depth;
421         wake_up(&usermodehelper_disabled_waitq);
422         up_write(&umhelper_sem);
423 }
424
425 /**
426  * __usermodehelper_disable - Prevent new helpers from being started.
427  * @depth: New value to assign to usermodehelper_disabled.
428  *
429  * Set usermodehelper_disabled to @depth and wait for running helpers to exit.
430  */
431 int __usermodehelper_disable(enum umh_disable_depth depth)
432 {
433         long retval;
434
435         if (!depth)
436                 return -EINVAL;
437
438         down_write(&umhelper_sem);
439         usermodehelper_disabled = depth;
440         up_write(&umhelper_sem);
441
442         /*
443          * From now on call_usermodehelper_exec() won't start any new
444          * helpers, so it is sufficient if running_helpers turns out to
445          * be zero at one point (it may be increased later, but that
446          * doesn't matter).
447          */
448         retval = wait_event_timeout(running_helpers_waitq,
449                                         atomic_read(&running_helpers) == 0,
450                                         RUNNING_HELPERS_TIMEOUT);
451         if (retval)
452                 return 0;
453
454         __usermodehelper_set_disable_depth(UMH_ENABLED);
455         return -EAGAIN;
456 }
457
458 static void helper_lock(void)
459 {
460         atomic_inc(&running_helpers);
461         smp_mb__after_atomic_inc();
462 }
463
464 static void helper_unlock(void)
465 {
466         if (atomic_dec_and_test(&running_helpers))
467                 wake_up(&running_helpers_waitq);
468 }
469
470 /**
471  * call_usermodehelper_setup - prepare to call a usermode helper
472  * @path: path to usermode executable
473  * @argv: arg vector for process
474  * @envp: environment for process
475  * @gfp_mask: gfp mask for memory allocation
476  *
477  * Returns either %NULL on allocation failure, or a subprocess_info
478  * structure.  This should be passed to call_usermodehelper_exec to
479  * exec the process and free the structure.
480  */
481 struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
482                                                   char **envp, gfp_t gfp_mask)
483 {
484         struct subprocess_info *sub_info;
485         sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
486         if (!sub_info)
487                 goto out;
488
489         INIT_WORK(&sub_info->work, __call_usermodehelper);
490         sub_info->path = path;
491         sub_info->argv = argv;
492         sub_info->envp = envp;
493   out:
494         return sub_info;
495 }
496 EXPORT_SYMBOL(call_usermodehelper_setup);
497
498 /**
499  * call_usermodehelper_setfns - set a cleanup/init function
500  * @info: a subprocess_info returned by call_usermodehelper_setup
501  * @cleanup: a cleanup function
502  * @init: an init function
503  * @data: arbitrary context sensitive data
504  *
505  * The init function is used to customize the helper process prior to
506  * exec.  A non-zero return code causes the process to error out, exit,
507  * and return the failure to the calling process
508  *
509  * The cleanup function is just before ethe subprocess_info is about to
510  * be freed.  This can be used for freeing the argv and envp.  The
511  * Function must be runnable in either a process context or the
512  * context in which call_usermodehelper_exec is called.
513  */
514 void call_usermodehelper_setfns(struct subprocess_info *info,
515                     int (*init)(struct subprocess_info *info, struct cred *new),
516                     void (*cleanup)(struct subprocess_info *info),
517                     void *data)
518 {
519         info->cleanup = cleanup;
520         info->init = init;
521         info->data = data;
522 }
523 EXPORT_SYMBOL(call_usermodehelper_setfns);
524
525 /**
526  * call_usermodehelper_exec - start a usermode application
527  * @sub_info: information about the subprocessa
528  * @wait: wait for the application to finish and return status.
529  *        when -1 don't wait at all, but you get no useful error back when
530  *        the program couldn't be exec'ed. This makes it safe to call
531  *        from interrupt context.
532  *
533  * Runs a user-space application.  The application is started
534  * asynchronously if wait is not set, and runs as a child of keventd.
535  * (ie. it runs with full root capabilities).
536  */
537 int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
538 {
539         DECLARE_COMPLETION_ONSTACK(done);
540         int retval = 0;
541
542         helper_lock();
543         if (sub_info->path[0] == '\0')
544                 goto out;
545
546         if (!khelper_wq || usermodehelper_disabled) {
547                 retval = -EBUSY;
548                 goto out;
549         }
550
551         sub_info->complete = &done;
552         sub_info->wait = wait;
553
554         queue_work(khelper_wq, &sub_info->work);
555         if (wait == UMH_NO_WAIT)        /* task has freed sub_info */
556                 goto unlock;
557
558         if (wait & UMH_KILLABLE) {
559                 retval = wait_for_completion_killable(&done);
560                 if (!retval)
561                         goto wait_done;
562
563                 /* umh_complete() will see NULL and free sub_info */
564                 if (xchg(&sub_info->complete, NULL))
565                         goto unlock;
566                 /* fallthrough, umh_complete() was already called */
567         }
568
569         wait_for_completion(&done);
570 wait_done:
571         retval = sub_info->retval;
572 out:
573         call_usermodehelper_freeinfo(sub_info);
574 unlock:
575         helper_unlock();
576         return retval;
577 }
578 EXPORT_SYMBOL(call_usermodehelper_exec);
579
580 static int proc_cap_handler(struct ctl_table *table, int write,
581                          void __user *buffer, size_t *lenp, loff_t *ppos)
582 {
583         struct ctl_table t;
584         unsigned long cap_array[_KERNEL_CAPABILITY_U32S];
585         kernel_cap_t new_cap;
586         int err, i;
587
588         if (write && (!capable(CAP_SETPCAP) ||
589                       !capable(CAP_SYS_MODULE)))
590                 return -EPERM;
591
592         /*
593          * convert from the global kernel_cap_t to the ulong array to print to
594          * userspace if this is a read.
595          */
596         spin_lock(&umh_sysctl_lock);
597         for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)  {
598                 if (table->data == CAP_BSET)
599                         cap_array[i] = usermodehelper_bset.cap[i];
600                 else if (table->data == CAP_PI)
601                         cap_array[i] = usermodehelper_inheritable.cap[i];
602                 else
603                         BUG();
604         }
605         spin_unlock(&umh_sysctl_lock);
606
607         t = *table;
608         t.data = &cap_array;
609
610         /*
611          * actually read or write and array of ulongs from userspace.  Remember
612          * these are least significant 32 bits first
613          */
614         err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos);
615         if (err < 0)
616                 return err;
617
618         /*
619          * convert from the sysctl array of ulongs to the kernel_cap_t
620          * internal representation
621          */
622         for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)
623                 new_cap.cap[i] = cap_array[i];
624
625         /*
626          * Drop everything not in the new_cap (but don't add things)
627          */
628         spin_lock(&umh_sysctl_lock);
629         if (write) {
630                 if (table->data == CAP_BSET)
631                         usermodehelper_bset = cap_intersect(usermodehelper_bset, new_cap);
632                 if (table->data == CAP_PI)
633                         usermodehelper_inheritable = cap_intersect(usermodehelper_inheritable, new_cap);
634         }
635         spin_unlock(&umh_sysctl_lock);
636
637         return 0;
638 }
639
640 struct ctl_table usermodehelper_table[] = {
641         {
642                 .procname       = "bset",
643                 .data           = CAP_BSET,
644                 .maxlen         = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
645                 .mode           = 0600,
646                 .proc_handler   = proc_cap_handler,
647         },
648         {
649                 .procname       = "inheritable",
650                 .data           = CAP_PI,
651                 .maxlen         = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
652                 .mode           = 0600,
653                 .proc_handler   = proc_cap_handler,
654         },
655         { }
656 };
657
658 void __init usermodehelper_init(void)
659 {
660         khelper_wq = create_singlethread_workqueue("khelper");
661         BUG_ON(!khelper_wq);
662 }