Merge tag 'drm-misc-fixes-2023-02-23' of git://anongit.freedesktop.org/drm/drm-misc...
[platform/kernel/linux-starfive.git] / kernel / umh.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * umh - the kernel usermode helper
4  */
5 #include <linux/module.h>
6 #include <linux/sched.h>
7 #include <linux/sched/task.h>
8 #include <linux/binfmts.h>
9 #include <linux/syscalls.h>
10 #include <linux/unistd.h>
11 #include <linux/kmod.h>
12 #include <linux/slab.h>
13 #include <linux/completion.h>
14 #include <linux/cred.h>
15 #include <linux/file.h>
16 #include <linux/fdtable.h>
17 #include <linux/fs_struct.h>
18 #include <linux/workqueue.h>
19 #include <linux/security.h>
20 #include <linux/mount.h>
21 #include <linux/kernel.h>
22 #include <linux/init.h>
23 #include <linux/resource.h>
24 #include <linux/notifier.h>
25 #include <linux/suspend.h>
26 #include <linux/rwsem.h>
27 #include <linux/ptrace.h>
28 #include <linux/async.h>
29 #include <linux/uaccess.h>
30 #include <linux/initrd.h>
31 #include <linux/freezer.h>
32
33 #include <trace/events/module.h>
34
35 static kernel_cap_t usermodehelper_bset = CAP_FULL_SET;
36 static kernel_cap_t usermodehelper_inheritable = CAP_FULL_SET;
37 static DEFINE_SPINLOCK(umh_sysctl_lock);
38 static DECLARE_RWSEM(umhelper_sem);
39
40 static void call_usermodehelper_freeinfo(struct subprocess_info *info)
41 {
42         if (info->cleanup)
43                 (*info->cleanup)(info);
44         kfree(info);
45 }
46
47 static void umh_complete(struct subprocess_info *sub_info)
48 {
49         struct completion *comp = xchg(&sub_info->complete, NULL);
50         /*
51          * See call_usermodehelper_exec(). If xchg() returns NULL
52          * we own sub_info, the UMH_KILLABLE caller has gone away
53          * or the caller used UMH_NO_WAIT.
54          */
55         if (comp)
56                 complete(comp);
57         else
58                 call_usermodehelper_freeinfo(sub_info);
59 }
60
61 /*
62  * This is the task which runs the usermode application
63  */
64 static int call_usermodehelper_exec_async(void *data)
65 {
66         struct subprocess_info *sub_info = data;
67         struct cred *new;
68         int retval;
69
70         spin_lock_irq(&current->sighand->siglock);
71         flush_signal_handlers(current, 1);
72         spin_unlock_irq(&current->sighand->siglock);
73
74         /*
75          * Initial kernel threads share ther FS with init, in order to
76          * get the init root directory. But we've now created a new
77          * thread that is going to execve a user process and has its own
78          * 'struct fs_struct'. Reset umask to the default.
79          */
80         current->fs->umask = 0022;
81
82         /*
83          * Our parent (unbound workqueue) runs with elevated scheduling
84          * priority. Avoid propagating that into the userspace child.
85          */
86         set_user_nice(current, 0);
87
88         retval = -ENOMEM;
89         new = prepare_kernel_cred(current);
90         if (!new)
91                 goto out;
92
93         spin_lock(&umh_sysctl_lock);
94         new->cap_bset = cap_intersect(usermodehelper_bset, new->cap_bset);
95         new->cap_inheritable = cap_intersect(usermodehelper_inheritable,
96                                              new->cap_inheritable);
97         spin_unlock(&umh_sysctl_lock);
98
99         if (sub_info->init) {
100                 retval = sub_info->init(sub_info, new);
101                 if (retval) {
102                         abort_creds(new);
103                         goto out;
104                 }
105         }
106
107         commit_creds(new);
108
109         wait_for_initramfs();
110         retval = kernel_execve(sub_info->path,
111                                (const char *const *)sub_info->argv,
112                                (const char *const *)sub_info->envp);
113 out:
114         sub_info->retval = retval;
115         /*
116          * call_usermodehelper_exec_sync() will call umh_complete
117          * if UHM_WAIT_PROC.
118          */
119         if (!(sub_info->wait & UMH_WAIT_PROC))
120                 umh_complete(sub_info);
121         if (!retval)
122                 return 0;
123         do_exit(0);
124 }
125
126 /* Handles UMH_WAIT_PROC.  */
127 static void call_usermodehelper_exec_sync(struct subprocess_info *sub_info)
128 {
129         pid_t pid;
130
131         /* If SIGCLD is ignored do_wait won't populate the status. */
132         kernel_sigaction(SIGCHLD, SIG_DFL);
133         pid = user_mode_thread(call_usermodehelper_exec_async, sub_info, SIGCHLD);
134         if (pid < 0)
135                 sub_info->retval = pid;
136         else
137                 kernel_wait(pid, &sub_info->retval);
138
139         /* Restore default kernel sig handler */
140         kernel_sigaction(SIGCHLD, SIG_IGN);
141         umh_complete(sub_info);
142 }
143
144 /*
145  * We need to create the usermodehelper kernel thread from a task that is affine
146  * to an optimized set of CPUs (or nohz housekeeping ones) such that they
147  * inherit a widest affinity irrespective of call_usermodehelper() callers with
148  * possibly reduced affinity (eg: per-cpu workqueues). We don't want
149  * usermodehelper targets to contend a busy CPU.
150  *
151  * Unbound workqueues provide such wide affinity and allow to block on
152  * UMH_WAIT_PROC requests without blocking pending request (up to some limit).
153  *
154  * Besides, workqueues provide the privilege level that caller might not have
155  * to perform the usermodehelper request.
156  *
157  */
158 static void call_usermodehelper_exec_work(struct work_struct *work)
159 {
160         struct subprocess_info *sub_info =
161                 container_of(work, struct subprocess_info, work);
162
163         if (sub_info->wait & UMH_WAIT_PROC) {
164                 call_usermodehelper_exec_sync(sub_info);
165         } else {
166                 pid_t pid;
167                 /*
168                  * Use CLONE_PARENT to reparent it to kthreadd; we do not
169                  * want to pollute current->children, and we need a parent
170                  * that always ignores SIGCHLD to ensure auto-reaping.
171                  */
172                 pid = user_mode_thread(call_usermodehelper_exec_async, sub_info,
173                                        CLONE_PARENT | SIGCHLD);
174                 if (pid < 0) {
175                         sub_info->retval = pid;
176                         umh_complete(sub_info);
177                 }
178         }
179 }
180
181 /*
182  * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
183  * (used for preventing user land processes from being created after the user
184  * land has been frozen during a system-wide hibernation or suspend operation).
185  * Should always be manipulated under umhelper_sem acquired for write.
186  */
187 static enum umh_disable_depth usermodehelper_disabled = UMH_DISABLED;
188
189 /* Number of helpers running */
190 static atomic_t running_helpers = ATOMIC_INIT(0);
191
192 /*
193  * Wait queue head used by usermodehelper_disable() to wait for all running
194  * helpers to finish.
195  */
196 static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);
197
198 /*
199  * Used by usermodehelper_read_lock_wait() to wait for usermodehelper_disabled
200  * to become 'false'.
201  */
202 static DECLARE_WAIT_QUEUE_HEAD(usermodehelper_disabled_waitq);
203
204 /*
205  * Time to wait for running_helpers to become zero before the setting of
206  * usermodehelper_disabled in usermodehelper_disable() fails
207  */
208 #define RUNNING_HELPERS_TIMEOUT (5 * HZ)
209
210 int usermodehelper_read_trylock(void)
211 {
212         DEFINE_WAIT(wait);
213         int ret = 0;
214
215         down_read(&umhelper_sem);
216         for (;;) {
217                 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
218                                 TASK_INTERRUPTIBLE);
219                 if (!usermodehelper_disabled)
220                         break;
221
222                 if (usermodehelper_disabled == UMH_DISABLED)
223                         ret = -EAGAIN;
224
225                 up_read(&umhelper_sem);
226
227                 if (ret)
228                         break;
229
230                 schedule();
231                 try_to_freeze();
232
233                 down_read(&umhelper_sem);
234         }
235         finish_wait(&usermodehelper_disabled_waitq, &wait);
236         return ret;
237 }
238 EXPORT_SYMBOL_GPL(usermodehelper_read_trylock);
239
240 long usermodehelper_read_lock_wait(long timeout)
241 {
242         DEFINE_WAIT(wait);
243
244         if (timeout < 0)
245                 return -EINVAL;
246
247         down_read(&umhelper_sem);
248         for (;;) {
249                 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
250                                 TASK_UNINTERRUPTIBLE);
251                 if (!usermodehelper_disabled)
252                         break;
253
254                 up_read(&umhelper_sem);
255
256                 timeout = schedule_timeout(timeout);
257                 if (!timeout)
258                         break;
259
260                 down_read(&umhelper_sem);
261         }
262         finish_wait(&usermodehelper_disabled_waitq, &wait);
263         return timeout;
264 }
265 EXPORT_SYMBOL_GPL(usermodehelper_read_lock_wait);
266
267 void usermodehelper_read_unlock(void)
268 {
269         up_read(&umhelper_sem);
270 }
271 EXPORT_SYMBOL_GPL(usermodehelper_read_unlock);
272
273 /**
274  * __usermodehelper_set_disable_depth - Modify usermodehelper_disabled.
275  * @depth: New value to assign to usermodehelper_disabled.
276  *
277  * Change the value of usermodehelper_disabled (under umhelper_sem locked for
278  * writing) and wakeup tasks waiting for it to change.
279  */
280 void __usermodehelper_set_disable_depth(enum umh_disable_depth depth)
281 {
282         down_write(&umhelper_sem);
283         usermodehelper_disabled = depth;
284         wake_up(&usermodehelper_disabled_waitq);
285         up_write(&umhelper_sem);
286 }
287
288 /**
289  * __usermodehelper_disable - Prevent new helpers from being started.
290  * @depth: New value to assign to usermodehelper_disabled.
291  *
292  * Set usermodehelper_disabled to @depth and wait for running helpers to exit.
293  */
294 int __usermodehelper_disable(enum umh_disable_depth depth)
295 {
296         long retval;
297
298         if (!depth)
299                 return -EINVAL;
300
301         down_write(&umhelper_sem);
302         usermodehelper_disabled = depth;
303         up_write(&umhelper_sem);
304
305         /*
306          * From now on call_usermodehelper_exec() won't start any new
307          * helpers, so it is sufficient if running_helpers turns out to
308          * be zero at one point (it may be increased later, but that
309          * doesn't matter).
310          */
311         retval = wait_event_timeout(running_helpers_waitq,
312                                         atomic_read(&running_helpers) == 0,
313                                         RUNNING_HELPERS_TIMEOUT);
314         if (retval)
315                 return 0;
316
317         __usermodehelper_set_disable_depth(UMH_ENABLED);
318         return -EAGAIN;
319 }
320
321 static void helper_lock(void)
322 {
323         atomic_inc(&running_helpers);
324         smp_mb__after_atomic();
325 }
326
327 static void helper_unlock(void)
328 {
329         if (atomic_dec_and_test(&running_helpers))
330                 wake_up(&running_helpers_waitq);
331 }
332
333 /**
334  * call_usermodehelper_setup - prepare to call a usermode helper
335  * @path: path to usermode executable
336  * @argv: arg vector for process
337  * @envp: environment for process
338  * @gfp_mask: gfp mask for memory allocation
339  * @init: an init function
340  * @cleanup: a cleanup function
341  * @data: arbitrary context sensitive data
342  *
343  * Returns either %NULL on allocation failure, or a subprocess_info
344  * structure.  This should be passed to call_usermodehelper_exec to
345  * exec the process and free the structure.
346  *
347  * The init function is used to customize the helper process prior to
348  * exec.  A non-zero return code causes the process to error out, exit,
349  * and return the failure to the calling process
350  *
351  * The cleanup function is just before the subprocess_info is about to
352  * be freed.  This can be used for freeing the argv and envp.  The
353  * Function must be runnable in either a process context or the
354  * context in which call_usermodehelper_exec is called.
355  */
356 struct subprocess_info *call_usermodehelper_setup(const char *path, char **argv,
357                 char **envp, gfp_t gfp_mask,
358                 int (*init)(struct subprocess_info *info, struct cred *new),
359                 void (*cleanup)(struct subprocess_info *info),
360                 void *data)
361 {
362         struct subprocess_info *sub_info;
363         sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
364         if (!sub_info)
365                 goto out;
366
367         INIT_WORK(&sub_info->work, call_usermodehelper_exec_work);
368
369 #ifdef CONFIG_STATIC_USERMODEHELPER
370         sub_info->path = CONFIG_STATIC_USERMODEHELPER_PATH;
371 #else
372         sub_info->path = path;
373 #endif
374         sub_info->argv = argv;
375         sub_info->envp = envp;
376
377         sub_info->cleanup = cleanup;
378         sub_info->init = init;
379         sub_info->data = data;
380   out:
381         return sub_info;
382 }
383 EXPORT_SYMBOL(call_usermodehelper_setup);
384
385 /**
386  * call_usermodehelper_exec - start a usermode application
387  * @sub_info: information about the subprocess
388  * @wait: wait for the application to finish and return status.
389  *        when UMH_NO_WAIT don't wait at all, but you get no useful error back
390  *        when the program couldn't be exec'ed. This makes it safe to call
391  *        from interrupt context.
392  *
393  * Runs a user-space application.  The application is started
394  * asynchronously if wait is not set, and runs as a child of system workqueues.
395  * (ie. it runs with full root capabilities and optimized affinity).
396  *
397  * Note: successful return value does not guarantee the helper was called at
398  * all. You can't rely on sub_info->{init,cleanup} being called even for
399  * UMH_WAIT_* wait modes as STATIC_USERMODEHELPER_PATH="" turns all helpers
400  * into a successful no-op.
401  */
402 int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
403 {
404         unsigned int state = TASK_UNINTERRUPTIBLE;
405         DECLARE_COMPLETION_ONSTACK(done);
406         int retval = 0;
407
408         if (!sub_info->path) {
409                 call_usermodehelper_freeinfo(sub_info);
410                 return -EINVAL;
411         }
412         helper_lock();
413         if (usermodehelper_disabled) {
414                 retval = -EBUSY;
415                 goto out;
416         }
417
418         /*
419          * If there is no binary for us to call, then just return and get out of
420          * here.  This allows us to set STATIC_USERMODEHELPER_PATH to "" and
421          * disable all call_usermodehelper() calls.
422          */
423         if (strlen(sub_info->path) == 0)
424                 goto out;
425
426         /*
427          * Set the completion pointer only if there is a waiter.
428          * This makes it possible to use umh_complete to free
429          * the data structure in case of UMH_NO_WAIT.
430          */
431         sub_info->complete = (wait == UMH_NO_WAIT) ? NULL : &done;
432         sub_info->wait = wait;
433
434         queue_work(system_unbound_wq, &sub_info->work);
435         if (wait == UMH_NO_WAIT)        /* task has freed sub_info */
436                 goto unlock;
437
438         if (wait & UMH_FREEZABLE)
439                 state |= TASK_FREEZABLE;
440
441         if (wait & UMH_KILLABLE) {
442                 retval = wait_for_completion_state(&done, state | TASK_KILLABLE);
443                 if (!retval)
444                         goto wait_done;
445
446                 /* umh_complete() will see NULL and free sub_info */
447                 if (xchg(&sub_info->complete, NULL))
448                         goto unlock;
449
450                 /*
451                  * fallthrough; in case of -ERESTARTSYS now do uninterruptible
452                  * wait_for_completion_state(). Since umh_complete() shall call
453                  * complete() in a moment if xchg() above returned NULL, this
454                  * uninterruptible wait_for_completion_state() will not block
455                  * SIGKILL'ed processes for long.
456                  */
457         }
458         wait_for_completion_state(&done, state);
459
460 wait_done:
461         retval = sub_info->retval;
462 out:
463         call_usermodehelper_freeinfo(sub_info);
464 unlock:
465         helper_unlock();
466         return retval;
467 }
468 EXPORT_SYMBOL(call_usermodehelper_exec);
469
470 /**
471  * call_usermodehelper() - prepare and start a usermode application
472  * @path: path to usermode executable
473  * @argv: arg vector for process
474  * @envp: environment for process
475  * @wait: wait for the application to finish and return status.
476  *        when UMH_NO_WAIT don't wait at all, but you get no useful error back
477  *        when the program couldn't be exec'ed. This makes it safe to call
478  *        from interrupt context.
479  *
480  * This function is the equivalent to use call_usermodehelper_setup() and
481  * call_usermodehelper_exec().
482  */
483 int call_usermodehelper(const char *path, char **argv, char **envp, int wait)
484 {
485         struct subprocess_info *info;
486         gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
487
488         info = call_usermodehelper_setup(path, argv, envp, gfp_mask,
489                                          NULL, NULL, NULL);
490         if (info == NULL)
491                 return -ENOMEM;
492
493         return call_usermodehelper_exec(info, wait);
494 }
495 EXPORT_SYMBOL(call_usermodehelper);
496
497 static int proc_cap_handler(struct ctl_table *table, int write,
498                          void *buffer, size_t *lenp, loff_t *ppos)
499 {
500         struct ctl_table t;
501         unsigned long cap_array[2];
502         kernel_cap_t new_cap, *cap;
503         int err;
504
505         if (write && (!capable(CAP_SETPCAP) ||
506                       !capable(CAP_SYS_MODULE)))
507                 return -EPERM;
508
509         /*
510          * convert from the global kernel_cap_t to the ulong array to print to
511          * userspace if this is a read.
512          *
513          * Legacy format: capabilities are exposed as two 32-bit values
514          */
515         cap = table->data;
516         spin_lock(&umh_sysctl_lock);
517         cap_array[0] = (u32) cap->val;
518         cap_array[1] = cap->val >> 32;
519         spin_unlock(&umh_sysctl_lock);
520
521         t = *table;
522         t.data = &cap_array;
523
524         /*
525          * actually read or write and array of ulongs from userspace.  Remember
526          * these are least significant 32 bits first
527          */
528         err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos);
529         if (err < 0)
530                 return err;
531
532         new_cap.val = (u32)cap_array[0];
533         new_cap.val += (u64)cap_array[1] << 32;
534
535         /*
536          * Drop everything not in the new_cap (but don't add things)
537          */
538         if (write) {
539                 spin_lock(&umh_sysctl_lock);
540                 *cap = cap_intersect(*cap, new_cap);
541                 spin_unlock(&umh_sysctl_lock);
542         }
543
544         return 0;
545 }
546
547 struct ctl_table usermodehelper_table[] = {
548         {
549                 .procname       = "bset",
550                 .data           = &usermodehelper_bset,
551                 .maxlen         = 2 * sizeof(unsigned long),
552                 .mode           = 0600,
553                 .proc_handler   = proc_cap_handler,
554         },
555         {
556                 .procname       = "inheritable",
557                 .data           = &usermodehelper_inheritable,
558                 .maxlen         = 2 * sizeof(unsigned long),
559                 .mode           = 0600,
560                 .proc_handler   = proc_cap_handler,
561         },
562         { }
563 };