debugfs: fix debugfs_rename parameter checking
[linux/fpc-iii.git] / kernel / umh.c
blobc449858946afc23706e06ab1e893ba0cef4c4f99
1 /*
2 * umh - the kernel usermode helper
3 */
4 #include <linux/module.h>
5 #include <linux/sched.h>
6 #include <linux/sched/task.h>
7 #include <linux/binfmts.h>
8 #include <linux/syscalls.h>
9 #include <linux/unistd.h>
10 #include <linux/kmod.h>
11 #include <linux/slab.h>
12 #include <linux/completion.h>
13 #include <linux/cred.h>
14 #include <linux/file.h>
15 #include <linux/fdtable.h>
16 #include <linux/workqueue.h>
17 #include <linux/security.h>
18 #include <linux/mount.h>
19 #include <linux/kernel.h>
20 #include <linux/init.h>
21 #include <linux/resource.h>
22 #include <linux/notifier.h>
23 #include <linux/suspend.h>
24 #include <linux/rwsem.h>
25 #include <linux/ptrace.h>
26 #include <linux/async.h>
27 #include <linux/uaccess.h>
28 #include <linux/shmem_fs.h>
29 #include <linux/pipe_fs_i.h>
31 #include <trace/events/module.h>
33 #define CAP_BSET (void *)1
34 #define CAP_PI (void *)2
36 static kernel_cap_t usermodehelper_bset = CAP_FULL_SET;
37 static kernel_cap_t usermodehelper_inheritable = CAP_FULL_SET;
38 static DEFINE_SPINLOCK(umh_sysctl_lock);
39 static DECLARE_RWSEM(umhelper_sem);
41 static void call_usermodehelper_freeinfo(struct subprocess_info *info)
43 if (info->cleanup)
44 (*info->cleanup)(info);
45 kfree(info);
48 static void umh_complete(struct subprocess_info *sub_info)
50 struct completion *comp = xchg(&sub_info->complete, NULL);
52 * See call_usermodehelper_exec(). If xchg() returns NULL
53 * we own sub_info, the UMH_KILLABLE caller has gone away
54 * or the caller used UMH_NO_WAIT.
56 if (comp)
57 complete(comp);
58 else
59 call_usermodehelper_freeinfo(sub_info);
63 * This is the task which runs the usermode application
65 static int call_usermodehelper_exec_async(void *data)
67 struct subprocess_info *sub_info = data;
68 struct cred *new;
69 int retval;
71 spin_lock_irq(&current->sighand->siglock);
72 flush_signal_handlers(current, 1);
73 spin_unlock_irq(&current->sighand->siglock);
76 * Our parent (unbound workqueue) runs with elevated scheduling
77 * priority. Avoid propagating that into the userspace child.
79 set_user_nice(current, 0);
81 retval = -ENOMEM;
82 new = prepare_kernel_cred(current);
83 if (!new)
84 goto out;
86 spin_lock(&umh_sysctl_lock);
87 new->cap_bset = cap_intersect(usermodehelper_bset, new->cap_bset);
88 new->cap_inheritable = cap_intersect(usermodehelper_inheritable,
89 new->cap_inheritable);
90 spin_unlock(&umh_sysctl_lock);
92 if (sub_info->init) {
93 retval = sub_info->init(sub_info, new);
94 if (retval) {
95 abort_creds(new);
96 goto out;
100 commit_creds(new);
102 sub_info->pid = task_pid_nr(current);
103 if (sub_info->file)
104 retval = do_execve_file(sub_info->file,
105 sub_info->argv, sub_info->envp);
106 else
107 retval = do_execve(getname_kernel(sub_info->path),
108 (const char __user *const __user *)sub_info->argv,
109 (const char __user *const __user *)sub_info->envp);
110 out:
111 sub_info->retval = retval;
113 * call_usermodehelper_exec_sync() will call umh_complete
114 * if UHM_WAIT_PROC.
116 if (!(sub_info->wait & UMH_WAIT_PROC))
117 umh_complete(sub_info);
118 if (!retval)
119 return 0;
120 do_exit(0);
123 /* Handles UMH_WAIT_PROC. */
124 static void call_usermodehelper_exec_sync(struct subprocess_info *sub_info)
126 pid_t pid;
128 /* If SIGCLD is ignored kernel_wait4 won't populate the status. */
129 kernel_sigaction(SIGCHLD, SIG_DFL);
130 pid = kernel_thread(call_usermodehelper_exec_async, sub_info, SIGCHLD);
131 if (pid < 0) {
132 sub_info->retval = pid;
133 } else {
134 int ret = -ECHILD;
136 * Normally it is bogus to call wait4() from in-kernel because
137 * wait4() wants to write the exit code to a userspace address.
138 * But call_usermodehelper_exec_sync() always runs as kernel
139 * thread (workqueue) and put_user() to a kernel address works
140 * OK for kernel threads, due to their having an mm_segment_t
141 * which spans the entire address space.
143 * Thus the __user pointer cast is valid here.
145 kernel_wait4(pid, (int __user *)&ret, 0, NULL);
148 * If ret is 0, either call_usermodehelper_exec_async failed and
149 * the real error code is already in sub_info->retval or
150 * sub_info->retval is 0 anyway, so don't mess with it then.
152 if (ret)
153 sub_info->retval = ret;
156 /* Restore default kernel sig handler */
157 kernel_sigaction(SIGCHLD, SIG_IGN);
159 umh_complete(sub_info);
163 * We need to create the usermodehelper kernel thread from a task that is affine
164 * to an optimized set of CPUs (or nohz housekeeping ones) such that they
165 * inherit a widest affinity irrespective of call_usermodehelper() callers with
166 * possibly reduced affinity (eg: per-cpu workqueues). We don't want
167 * usermodehelper targets to contend a busy CPU.
169 * Unbound workqueues provide such wide affinity and allow to block on
170 * UMH_WAIT_PROC requests without blocking pending request (up to some limit).
172 * Besides, workqueues provide the privilege level that caller might not have
173 * to perform the usermodehelper request.
176 static void call_usermodehelper_exec_work(struct work_struct *work)
178 struct subprocess_info *sub_info =
179 container_of(work, struct subprocess_info, work);
181 if (sub_info->wait & UMH_WAIT_PROC) {
182 call_usermodehelper_exec_sync(sub_info);
183 } else {
184 pid_t pid;
186 * Use CLONE_PARENT to reparent it to kthreadd; we do not
187 * want to pollute current->children, and we need a parent
188 * that always ignores SIGCHLD to ensure auto-reaping.
190 pid = kernel_thread(call_usermodehelper_exec_async, sub_info,
191 CLONE_PARENT | SIGCHLD);
192 if (pid < 0) {
193 sub_info->retval = pid;
194 umh_complete(sub_info);
200 * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
201 * (used for preventing user land processes from being created after the user
202 * land has been frozen during a system-wide hibernation or suspend operation).
203 * Should always be manipulated under umhelper_sem acquired for write.
205 static enum umh_disable_depth usermodehelper_disabled = UMH_DISABLED;
207 /* Number of helpers running */
208 static atomic_t running_helpers = ATOMIC_INIT(0);
211 * Wait queue head used by usermodehelper_disable() to wait for all running
212 * helpers to finish.
214 static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);
217 * Used by usermodehelper_read_lock_wait() to wait for usermodehelper_disabled
218 * to become 'false'.
220 static DECLARE_WAIT_QUEUE_HEAD(usermodehelper_disabled_waitq);
223 * Time to wait for running_helpers to become zero before the setting of
224 * usermodehelper_disabled in usermodehelper_disable() fails
226 #define RUNNING_HELPERS_TIMEOUT (5 * HZ)
228 int usermodehelper_read_trylock(void)
230 DEFINE_WAIT(wait);
231 int ret = 0;
233 down_read(&umhelper_sem);
234 for (;;) {
235 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
236 TASK_INTERRUPTIBLE);
237 if (!usermodehelper_disabled)
238 break;
240 if (usermodehelper_disabled == UMH_DISABLED)
241 ret = -EAGAIN;
243 up_read(&umhelper_sem);
245 if (ret)
246 break;
248 schedule();
249 try_to_freeze();
251 down_read(&umhelper_sem);
253 finish_wait(&usermodehelper_disabled_waitq, &wait);
254 return ret;
256 EXPORT_SYMBOL_GPL(usermodehelper_read_trylock);
258 long usermodehelper_read_lock_wait(long timeout)
260 DEFINE_WAIT(wait);
262 if (timeout < 0)
263 return -EINVAL;
265 down_read(&umhelper_sem);
266 for (;;) {
267 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
268 TASK_UNINTERRUPTIBLE);
269 if (!usermodehelper_disabled)
270 break;
272 up_read(&umhelper_sem);
274 timeout = schedule_timeout(timeout);
275 if (!timeout)
276 break;
278 down_read(&umhelper_sem);
280 finish_wait(&usermodehelper_disabled_waitq, &wait);
281 return timeout;
283 EXPORT_SYMBOL_GPL(usermodehelper_read_lock_wait);
285 void usermodehelper_read_unlock(void)
287 up_read(&umhelper_sem);
289 EXPORT_SYMBOL_GPL(usermodehelper_read_unlock);
292 * __usermodehelper_set_disable_depth - Modify usermodehelper_disabled.
293 * @depth: New value to assign to usermodehelper_disabled.
295 * Change the value of usermodehelper_disabled (under umhelper_sem locked for
296 * writing) and wakeup tasks waiting for it to change.
298 void __usermodehelper_set_disable_depth(enum umh_disable_depth depth)
300 down_write(&umhelper_sem);
301 usermodehelper_disabled = depth;
302 wake_up(&usermodehelper_disabled_waitq);
303 up_write(&umhelper_sem);
307 * __usermodehelper_disable - Prevent new helpers from being started.
308 * @depth: New value to assign to usermodehelper_disabled.
310 * Set usermodehelper_disabled to @depth and wait for running helpers to exit.
312 int __usermodehelper_disable(enum umh_disable_depth depth)
314 long retval;
316 if (!depth)
317 return -EINVAL;
319 down_write(&umhelper_sem);
320 usermodehelper_disabled = depth;
321 up_write(&umhelper_sem);
324 * From now on call_usermodehelper_exec() won't start any new
325 * helpers, so it is sufficient if running_helpers turns out to
326 * be zero at one point (it may be increased later, but that
327 * doesn't matter).
329 retval = wait_event_timeout(running_helpers_waitq,
330 atomic_read(&running_helpers) == 0,
331 RUNNING_HELPERS_TIMEOUT);
332 if (retval)
333 return 0;
335 __usermodehelper_set_disable_depth(UMH_ENABLED);
336 return -EAGAIN;
339 static void helper_lock(void)
341 atomic_inc(&running_helpers);
342 smp_mb__after_atomic();
345 static void helper_unlock(void)
347 if (atomic_dec_and_test(&running_helpers))
348 wake_up(&running_helpers_waitq);
352 * call_usermodehelper_setup - prepare to call a usermode helper
353 * @path: path to usermode executable
354 * @argv: arg vector for process
355 * @envp: environment for process
356 * @gfp_mask: gfp mask for memory allocation
357 * @cleanup: a cleanup function
358 * @init: an init function
359 * @data: arbitrary context sensitive data
361 * Returns either %NULL on allocation failure, or a subprocess_info
362 * structure. This should be passed to call_usermodehelper_exec to
363 * exec the process and free the structure.
365 * The init function is used to customize the helper process prior to
366 * exec. A non-zero return code causes the process to error out, exit,
367 * and return the failure to the calling process
369 * The cleanup function is just before ethe subprocess_info is about to
370 * be freed. This can be used for freeing the argv and envp. The
371 * Function must be runnable in either a process context or the
372 * context in which call_usermodehelper_exec is called.
374 struct subprocess_info *call_usermodehelper_setup(const char *path, char **argv,
375 char **envp, gfp_t gfp_mask,
376 int (*init)(struct subprocess_info *info, struct cred *new),
377 void (*cleanup)(struct subprocess_info *info),
378 void *data)
380 struct subprocess_info *sub_info;
381 sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
382 if (!sub_info)
383 goto out;
385 INIT_WORK(&sub_info->work, call_usermodehelper_exec_work);
387 #ifdef CONFIG_STATIC_USERMODEHELPER
388 sub_info->path = CONFIG_STATIC_USERMODEHELPER_PATH;
389 #else
390 sub_info->path = path;
391 #endif
392 sub_info->argv = argv;
393 sub_info->envp = envp;
395 sub_info->cleanup = cleanup;
396 sub_info->init = init;
397 sub_info->data = data;
398 out:
399 return sub_info;
401 EXPORT_SYMBOL(call_usermodehelper_setup);
403 struct subprocess_info *call_usermodehelper_setup_file(struct file *file,
404 int (*init)(struct subprocess_info *info, struct cred *new),
405 void (*cleanup)(struct subprocess_info *info), void *data)
407 struct subprocess_info *sub_info;
409 sub_info = kzalloc(sizeof(struct subprocess_info), GFP_KERNEL);
410 if (!sub_info)
411 return NULL;
413 INIT_WORK(&sub_info->work, call_usermodehelper_exec_work);
414 sub_info->path = "none";
415 sub_info->file = file;
416 sub_info->init = init;
417 sub_info->cleanup = cleanup;
418 sub_info->data = data;
419 return sub_info;
422 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
424 struct umh_info *umh_info = info->data;
425 struct file *from_umh[2];
426 struct file *to_umh[2];
427 int err;
429 /* create pipe to send data to umh */
430 err = create_pipe_files(to_umh, 0);
431 if (err)
432 return err;
433 err = replace_fd(0, to_umh[0], 0);
434 fput(to_umh[0]);
435 if (err < 0) {
436 fput(to_umh[1]);
437 return err;
440 /* create pipe to receive data from umh */
441 err = create_pipe_files(from_umh, 0);
442 if (err) {
443 fput(to_umh[1]);
444 replace_fd(0, NULL, 0);
445 return err;
447 err = replace_fd(1, from_umh[1], 0);
448 fput(from_umh[1]);
449 if (err < 0) {
450 fput(to_umh[1]);
451 replace_fd(0, NULL, 0);
452 fput(from_umh[0]);
453 return err;
456 umh_info->pipe_to_umh = to_umh[1];
457 umh_info->pipe_from_umh = from_umh[0];
458 return 0;
461 static void umh_save_pid(struct subprocess_info *info)
463 struct umh_info *umh_info = info->data;
465 umh_info->pid = info->pid;
469 * fork_usermode_blob - fork a blob of bytes as a usermode process
470 * @data: a blob of bytes that can be do_execv-ed as a file
471 * @len: length of the blob
472 * @info: information about usermode process (shouldn't be NULL)
474 * Returns either negative error or zero which indicates success
475 * in executing a blob of bytes as a usermode process. In such
476 * case 'struct umh_info *info' is populated with two pipes
477 * and a pid of the process. The caller is responsible for health
478 * check of the user process, killing it via pid, and closing the
479 * pipes when user process is no longer needed.
481 int fork_usermode_blob(void *data, size_t len, struct umh_info *info)
483 struct subprocess_info *sub_info;
484 struct file *file;
485 ssize_t written;
486 loff_t pos = 0;
487 int err;
489 file = shmem_kernel_file_setup("", len, 0);
490 if (IS_ERR(file))
491 return PTR_ERR(file);
493 written = kernel_write(file, data, len, &pos);
494 if (written != len) {
495 err = written;
496 if (err >= 0)
497 err = -ENOMEM;
498 goto out;
501 err = -ENOMEM;
502 sub_info = call_usermodehelper_setup_file(file, umh_pipe_setup,
503 umh_save_pid, info);
504 if (!sub_info)
505 goto out;
507 err = call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC);
508 out:
509 fput(file);
510 return err;
512 EXPORT_SYMBOL_GPL(fork_usermode_blob);
515 * call_usermodehelper_exec - start a usermode application
516 * @sub_info: information about the subprocessa
517 * @wait: wait for the application to finish and return status.
518 * when UMH_NO_WAIT don't wait at all, but you get no useful error back
519 * when the program couldn't be exec'ed. This makes it safe to call
520 * from interrupt context.
522 * Runs a user-space application. The application is started
523 * asynchronously if wait is not set, and runs as a child of system workqueues.
524 * (ie. it runs with full root capabilities and optimized affinity).
526 int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
528 DECLARE_COMPLETION_ONSTACK(done);
529 int retval = 0;
531 if (!sub_info->path) {
532 call_usermodehelper_freeinfo(sub_info);
533 return -EINVAL;
535 helper_lock();
536 if (usermodehelper_disabled) {
537 retval = -EBUSY;
538 goto out;
542 * If there is no binary for us to call, then just return and get out of
543 * here. This allows us to set STATIC_USERMODEHELPER_PATH to "" and
544 * disable all call_usermodehelper() calls.
546 if (strlen(sub_info->path) == 0)
547 goto out;
550 * Set the completion pointer only if there is a waiter.
551 * This makes it possible to use umh_complete to free
552 * the data structure in case of UMH_NO_WAIT.
554 sub_info->complete = (wait == UMH_NO_WAIT) ? NULL : &done;
555 sub_info->wait = wait;
557 queue_work(system_unbound_wq, &sub_info->work);
558 if (wait == UMH_NO_WAIT) /* task has freed sub_info */
559 goto unlock;
561 if (wait & UMH_KILLABLE) {
562 retval = wait_for_completion_killable(&done);
563 if (!retval)
564 goto wait_done;
566 /* umh_complete() will see NULL and free sub_info */
567 if (xchg(&sub_info->complete, NULL))
568 goto unlock;
569 /* fallthrough, umh_complete() was already called */
572 wait_for_completion(&done);
573 wait_done:
574 retval = sub_info->retval;
575 out:
576 call_usermodehelper_freeinfo(sub_info);
577 unlock:
578 helper_unlock();
579 return retval;
581 EXPORT_SYMBOL(call_usermodehelper_exec);
584 * call_usermodehelper() - prepare and start a usermode application
585 * @path: path to usermode executable
586 * @argv: arg vector for process
587 * @envp: environment for process
588 * @wait: wait for the application to finish and return status.
589 * when UMH_NO_WAIT don't wait at all, but you get no useful error back
590 * when the program couldn't be exec'ed. This makes it safe to call
591 * from interrupt context.
593 * This function is the equivalent to use call_usermodehelper_setup() and
594 * call_usermodehelper_exec().
596 int call_usermodehelper(const char *path, char **argv, char **envp, int wait)
598 struct subprocess_info *info;
599 gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
601 info = call_usermodehelper_setup(path, argv, envp, gfp_mask,
602 NULL, NULL, NULL);
603 if (info == NULL)
604 return -ENOMEM;
606 return call_usermodehelper_exec(info, wait);
608 EXPORT_SYMBOL(call_usermodehelper);
610 static int proc_cap_handler(struct ctl_table *table, int write,
611 void __user *buffer, size_t *lenp, loff_t *ppos)
613 struct ctl_table t;
614 unsigned long cap_array[_KERNEL_CAPABILITY_U32S];
615 kernel_cap_t new_cap;
616 int err, i;
618 if (write && (!capable(CAP_SETPCAP) ||
619 !capable(CAP_SYS_MODULE)))
620 return -EPERM;
623 * convert from the global kernel_cap_t to the ulong array to print to
624 * userspace if this is a read.
626 spin_lock(&umh_sysctl_lock);
627 for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++) {
628 if (table->data == CAP_BSET)
629 cap_array[i] = usermodehelper_bset.cap[i];
630 else if (table->data == CAP_PI)
631 cap_array[i] = usermodehelper_inheritable.cap[i];
632 else
633 BUG();
635 spin_unlock(&umh_sysctl_lock);
637 t = *table;
638 t.data = &cap_array;
641 * actually read or write and array of ulongs from userspace. Remember
642 * these are least significant 32 bits first
644 err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos);
645 if (err < 0)
646 return err;
649 * convert from the sysctl array of ulongs to the kernel_cap_t
650 * internal representation
652 for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)
653 new_cap.cap[i] = cap_array[i];
656 * Drop everything not in the new_cap (but don't add things)
658 if (write) {
659 spin_lock(&umh_sysctl_lock);
660 if (table->data == CAP_BSET)
661 usermodehelper_bset = cap_intersect(usermodehelper_bset, new_cap);
662 if (table->data == CAP_PI)
663 usermodehelper_inheritable = cap_intersect(usermodehelper_inheritable, new_cap);
664 spin_unlock(&umh_sysctl_lock);
667 return 0;
670 struct ctl_table usermodehelper_table[] = {
672 .procname = "bset",
673 .data = CAP_BSET,
674 .maxlen = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
675 .mode = 0600,
676 .proc_handler = proc_cap_handler,
679 .procname = "inheritable",
680 .data = CAP_PI,
681 .maxlen = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
682 .mode = 0600,
683 .proc_handler = proc_cap_handler,