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1/*
2 * fs/kernfs/file.c - kernfs file implementation
3 *
4 * Copyright (c) 2001-3 Patrick Mochel
5 * Copyright (c) 2007 SUSE Linux Products GmbH
6 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
7 *
8 * This file is released under the GPLv2.
9 */
10
11#include <linux/fs.h>
12#include <linux/seq_file.h>
13#include <linux/slab.h>
14#include <linux/poll.h>
15#include <linux/pagemap.h>
16#include <linux/sched.h>
17#include <linux/fsnotify.h>
18
19#include "kernfs-internal.h"
20
21/*
22 * There's one kernfs_open_file for each open file and one kernfs_open_node
23 * for each kernfs_node with one or more open files.
24 *
25 * kernfs_node->attr.open points to kernfs_open_node. attr.open is
26 * protected by kernfs_open_node_lock.
27 *
28 * filp->private_data points to seq_file whose ->private points to
29 * kernfs_open_file. kernfs_open_files are chained at
30 * kernfs_open_node->files, which is protected by kernfs_open_file_mutex.
31 */
32static DEFINE_SPINLOCK(kernfs_open_node_lock);
33static DEFINE_MUTEX(kernfs_open_file_mutex);
34
35struct kernfs_open_node {
36 atomic_t refcnt;
37 atomic_t event;
38 wait_queue_head_t poll;
39 struct list_head files; /* goes through kernfs_open_file.list */
40};
41
42/*
43 * kernfs_notify() may be called from any context and bounces notifications
44 * through a work item. To minimize space overhead in kernfs_node, the
45 * pending queue is implemented as a singly linked list of kernfs_nodes.
46 * The list is terminated with the self pointer so that whether a
47 * kernfs_node is on the list or not can be determined by testing the next
48 * pointer for NULL.
49 */
50#define KERNFS_NOTIFY_EOL ((void *)&kernfs_notify_list)
51
52static DEFINE_SPINLOCK(kernfs_notify_lock);
53static struct kernfs_node *kernfs_notify_list = KERNFS_NOTIFY_EOL;
54
55static struct kernfs_open_file *kernfs_of(struct file *file)
56{
57 return ((struct seq_file *)file->private_data)->private;
58}
59
60/*
61 * Determine the kernfs_ops for the given kernfs_node. This function must
62 * be called while holding an active reference.
63 */
64static const struct kernfs_ops *kernfs_ops(struct kernfs_node *kn)
65{
66 if (kn->flags & KERNFS_LOCKDEP)
67 lockdep_assert_held(kn);
68 return kn->attr.ops;
69}
70
71/*
72 * As kernfs_seq_stop() is also called after kernfs_seq_start() or
73 * kernfs_seq_next() failure, it needs to distinguish whether it's stopping
74 * a seq_file iteration which is fully initialized with an active reference
75 * or an aborted kernfs_seq_start() due to get_active failure. The
76 * position pointer is the only context for each seq_file iteration and
77 * thus the stop condition should be encoded in it. As the return value is
78 * directly visible to userland, ERR_PTR(-ENODEV) is the only acceptable
79 * choice to indicate get_active failure.
80 *
81 * Unfortunately, this is complicated due to the optional custom seq_file
82 * operations which may return ERR_PTR(-ENODEV) too. kernfs_seq_stop()
83 * can't distinguish whether ERR_PTR(-ENODEV) is from get_active failure or
84 * custom seq_file operations and thus can't decide whether put_active
85 * should be performed or not only on ERR_PTR(-ENODEV).
86 *
87 * This is worked around by factoring out the custom seq_stop() and
88 * put_active part into kernfs_seq_stop_active(), skipping it from
89 * kernfs_seq_stop() if ERR_PTR(-ENODEV) while invoking it directly after
90 * custom seq_file operations fail with ERR_PTR(-ENODEV) - this ensures
91 * that kernfs_seq_stop_active() is skipped only after get_active failure.
92 */
93static void kernfs_seq_stop_active(struct seq_file *sf, void *v)
94{
95 struct kernfs_open_file *of = sf->private;
96 const struct kernfs_ops *ops = kernfs_ops(of->kn);
97
98 if (ops->seq_stop)
99 ops->seq_stop(sf, v);
100 kernfs_put_active(of->kn);
101}
102
103static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
104{
105 struct kernfs_open_file *of = sf->private;
106 const struct kernfs_ops *ops;
107
108 /*
109 * @of->mutex nests outside active ref and is primarily to ensure that
110 * the ops aren't called concurrently for the same open file.
111 */
112 mutex_lock(&of->mutex);
113 if (!kernfs_get_active(of->kn))
114 return ERR_PTR(-ENODEV);
115
116 ops = kernfs_ops(of->kn);
117 if (ops->seq_start) {
118 void *next = ops->seq_start(sf, ppos);
119 /* see the comment above kernfs_seq_stop_active() */
120 if (next == ERR_PTR(-ENODEV))
121 kernfs_seq_stop_active(sf, next);
122 return next;
123 } else {
124 /*
125 * The same behavior and code as single_open(). Returns
126 * !NULL if pos is at the beginning; otherwise, NULL.
127 */
128 return NULL + !*ppos;
129 }
130}
131
132static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos)
133{
134 struct kernfs_open_file *of = sf->private;
135 const struct kernfs_ops *ops = kernfs_ops(of->kn);
136
137 if (ops->seq_next) {
138 void *next = ops->seq_next(sf, v, ppos);
139 /* see the comment above kernfs_seq_stop_active() */
140 if (next == ERR_PTR(-ENODEV))
141 kernfs_seq_stop_active(sf, next);
142 return next;
143 } else {
144 /*
145 * The same behavior and code as single_open(), always
146 * terminate after the initial read.
147 */
148 ++*ppos;
149 return NULL;
150 }
151}
152
153static void kernfs_seq_stop(struct seq_file *sf, void *v)
154{
155 struct kernfs_open_file *of = sf->private;
156
157 if (v != ERR_PTR(-ENODEV))
158 kernfs_seq_stop_active(sf, v);
159 mutex_unlock(&of->mutex);
160}
161
162static int kernfs_seq_show(struct seq_file *sf, void *v)
163{
164 struct kernfs_open_file *of = sf->private;
165
166 of->event = atomic_read(&of->kn->attr.open->event);
167
168 return of->kn->attr.ops->seq_show(sf, v);
169}
170
171static const struct seq_operations kernfs_seq_ops = {
172 .start = kernfs_seq_start,
173 .next = kernfs_seq_next,
174 .stop = kernfs_seq_stop,
175 .show = kernfs_seq_show,
176};
177
178/*
179 * As reading a bin file can have side-effects, the exact offset and bytes
180 * specified in read(2) call should be passed to the read callback making
181 * it difficult to use seq_file. Implement simplistic custom buffering for
182 * bin files.
183 */
184static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
185 char __user *user_buf, size_t count,
186 loff_t *ppos)
187{
188 ssize_t len = min_t(size_t, count, PAGE_SIZE);
189 const struct kernfs_ops *ops;
190 char *buf;
191
192 buf = of->prealloc_buf;
193 if (buf)
194 mutex_lock(&of->prealloc_mutex);
195 else
196 buf = kmalloc(len, GFP_KERNEL);
197 if (!buf)
198 return -ENOMEM;
199
200 /*
201 * @of->mutex nests outside active ref and is used both to ensure that
202 * the ops aren't called concurrently for the same open file.
203 */
204 mutex_lock(&of->mutex);
205 if (!kernfs_get_active(of->kn)) {
206 len = -ENODEV;
207 mutex_unlock(&of->mutex);
208 goto out_free;
209 }
210
211 of->event = atomic_read(&of->kn->attr.open->event);
212 ops = kernfs_ops(of->kn);
213 if (ops->read)
214 len = ops->read(of, buf, len, *ppos);
215 else
216 len = -EINVAL;
217
218 kernfs_put_active(of->kn);
219 mutex_unlock(&of->mutex);
220
221 if (len < 0)
222 goto out_free;
223
224 if (copy_to_user(user_buf, buf, len)) {
225 len = -EFAULT;
226 goto out_free;
227 }
228
229 *ppos += len;
230
231 out_free:
232 if (buf == of->prealloc_buf)
233 mutex_unlock(&of->prealloc_mutex);
234 else
235 kfree(buf);
236 return len;
237}
238
239/**
240 * kernfs_fop_read - kernfs vfs read callback
241 * @file: file pointer
242 * @user_buf: data to write
243 * @count: number of bytes
244 * @ppos: starting offset
245 */
246static ssize_t kernfs_fop_read(struct file *file, char __user *user_buf,
247 size_t count, loff_t *ppos)
248{
249 struct kernfs_open_file *of = kernfs_of(file);
250
251 if (of->kn->flags & KERNFS_HAS_SEQ_SHOW)
252 return seq_read(file, user_buf, count, ppos);
253 else
254 return kernfs_file_direct_read(of, user_buf, count, ppos);
255}
256
257/**
258 * kernfs_fop_write - kernfs vfs write callback
259 * @file: file pointer
260 * @user_buf: data to write
261 * @count: number of bytes
262 * @ppos: starting offset
263 *
264 * Copy data in from userland and pass it to the matching kernfs write
265 * operation.
266 *
267 * There is no easy way for us to know if userspace is only doing a partial
268 * write, so we don't support them. We expect the entire buffer to come on
269 * the first write. Hint: if you're writing a value, first read the file,
270 * modify only the the value you're changing, then write entire buffer
271 * back.
272 */
273static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
274 size_t count, loff_t *ppos)
275{
276 struct kernfs_open_file *of = kernfs_of(file);
277 const struct kernfs_ops *ops;
278 size_t len;
279 char *buf;
280
281 if (of->atomic_write_len) {
282 len = count;
283 if (len > of->atomic_write_len)
284 return -E2BIG;
285 } else {
286 len = min_t(size_t, count, PAGE_SIZE);
287 }
288
289 buf = of->prealloc_buf;
290 if (buf)
291 mutex_lock(&of->prealloc_mutex);
292 else
293 buf = kmalloc(len + 1, GFP_KERNEL);
294 if (!buf)
295 return -ENOMEM;
296
297 if (copy_from_user(buf, user_buf, len)) {
298 len = -EFAULT;
299 goto out_free;
300 }
301 buf[len] = '\0'; /* guarantee string termination */
302
303 /*
304 * @of->mutex nests outside active ref and is used both to ensure that
305 * the ops aren't called concurrently for the same open file.
306 */
307 mutex_lock(&of->mutex);
308 if (!kernfs_get_active(of->kn)) {
309 mutex_unlock(&of->mutex);
310 len = -ENODEV;
311 goto out_free;
312 }
313
314 ops = kernfs_ops(of->kn);
315 if (ops->write)
316 len = ops->write(of, buf, len, *ppos);
317 else
318 len = -EINVAL;
319
320 kernfs_put_active(of->kn);
321 mutex_unlock(&of->mutex);
322
323 if (len > 0)
324 *ppos += len;
325
326out_free:
327 if (buf == of->prealloc_buf)
328 mutex_unlock(&of->prealloc_mutex);
329 else
330 kfree(buf);
331 return len;
332}
333
334static void kernfs_vma_open(struct vm_area_struct *vma)
335{
336 struct file *file = vma->vm_file;
337 struct kernfs_open_file *of = kernfs_of(file);
338
339 if (!of->vm_ops)
340 return;
341
342 if (!kernfs_get_active(of->kn))
343 return;
344
345 if (of->vm_ops->open)
346 of->vm_ops->open(vma);
347
348 kernfs_put_active(of->kn);
349}
350
351static int kernfs_vma_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
352{
353 struct file *file = vma->vm_file;
354 struct kernfs_open_file *of = kernfs_of(file);
355 int ret;
356
357 if (!of->vm_ops)
358 return VM_FAULT_SIGBUS;
359
360 if (!kernfs_get_active(of->kn))
361 return VM_FAULT_SIGBUS;
362
363 ret = VM_FAULT_SIGBUS;
364 if (of->vm_ops->fault)
365 ret = of->vm_ops->fault(vma, vmf);
366
367 kernfs_put_active(of->kn);
368 return ret;
369}
370
371static int kernfs_vma_page_mkwrite(struct vm_area_struct *vma,
372 struct vm_fault *vmf)
373{
374 struct file *file = vma->vm_file;
375 struct kernfs_open_file *of = kernfs_of(file);
376 int ret;
377
378 if (!of->vm_ops)
379 return VM_FAULT_SIGBUS;
380
381 if (!kernfs_get_active(of->kn))
382 return VM_FAULT_SIGBUS;
383
384 ret = 0;
385 if (of->vm_ops->page_mkwrite)
386 ret = of->vm_ops->page_mkwrite(vma, vmf);
387 else
388 file_update_time(file);
389
390 kernfs_put_active(of->kn);
391 return ret;
392}
393
394static int kernfs_vma_access(struct vm_area_struct *vma, unsigned long addr,
395 void *buf, int len, int write)
396{
397 struct file *file = vma->vm_file;
398 struct kernfs_open_file *of = kernfs_of(file);
399 int ret;
400
401 if (!of->vm_ops)
402 return -EINVAL;
403
404 if (!kernfs_get_active(of->kn))
405 return -EINVAL;
406
407 ret = -EINVAL;
408 if (of->vm_ops->access)
409 ret = of->vm_ops->access(vma, addr, buf, len, write);
410
411 kernfs_put_active(of->kn);
412 return ret;
413}
414
415#ifdef CONFIG_NUMA
416static int kernfs_vma_set_policy(struct vm_area_struct *vma,
417 struct mempolicy *new)
418{
419 struct file *file = vma->vm_file;
420 struct kernfs_open_file *of = kernfs_of(file);
421 int ret;
422
423 if (!of->vm_ops)
424 return 0;
425
426 if (!kernfs_get_active(of->kn))
427 return -EINVAL;
428
429 ret = 0;
430 if (of->vm_ops->set_policy)
431 ret = of->vm_ops->set_policy(vma, new);
432
433 kernfs_put_active(of->kn);
434 return ret;
435}
436
437static struct mempolicy *kernfs_vma_get_policy(struct vm_area_struct *vma,
438 unsigned long addr)
439{
440 struct file *file = vma->vm_file;
441 struct kernfs_open_file *of = kernfs_of(file);
442 struct mempolicy *pol;
443
444 if (!of->vm_ops)
445 return vma->vm_policy;
446
447 if (!kernfs_get_active(of->kn))
448 return vma->vm_policy;
449
450 pol = vma->vm_policy;
451 if (of->vm_ops->get_policy)
452 pol = of->vm_ops->get_policy(vma, addr);
453
454 kernfs_put_active(of->kn);
455 return pol;
456}
457
458#endif
459
460static const struct vm_operations_struct kernfs_vm_ops = {
461 .open = kernfs_vma_open,
462 .fault = kernfs_vma_fault,
463 .page_mkwrite = kernfs_vma_page_mkwrite,
464 .access = kernfs_vma_access,
465#ifdef CONFIG_NUMA
466 .set_policy = kernfs_vma_set_policy,
467 .get_policy = kernfs_vma_get_policy,
468#endif
469};
470
471static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
472{
473 struct kernfs_open_file *of = kernfs_of(file);
474 const struct kernfs_ops *ops;
475 int rc;
476
477 /*
478 * mmap path and of->mutex are prone to triggering spurious lockdep
479 * warnings and we don't want to add spurious locking dependency
480 * between the two. Check whether mmap is actually implemented
481 * without grabbing @of->mutex by testing HAS_MMAP flag. See the
482 * comment in kernfs_file_open() for more details.
483 */
484 if (!(of->kn->flags & KERNFS_HAS_MMAP))
485 return -ENODEV;
486
487 mutex_lock(&of->mutex);
488
489 rc = -ENODEV;
490 if (!kernfs_get_active(of->kn))
491 goto out_unlock;
492
493 ops = kernfs_ops(of->kn);
494 rc = ops->mmap(of, vma);
495 if (rc)
496 goto out_put;
497
498 /*
499 * PowerPC's pci_mmap of legacy_mem uses shmem_zero_setup()
500 * to satisfy versions of X which crash if the mmap fails: that
501 * substitutes a new vm_file, and we don't then want bin_vm_ops.
502 */
503 if (vma->vm_file != file)
504 goto out_put;
505
506 rc = -EINVAL;
507 if (of->mmapped && of->vm_ops != vma->vm_ops)
508 goto out_put;
509
510 /*
511 * It is not possible to successfully wrap close.
512 * So error if someone is trying to use close.
513 */
514 rc = -EINVAL;
515 if (vma->vm_ops && vma->vm_ops->close)
516 goto out_put;
517
518 rc = 0;
519 of->mmapped = 1;
520 of->vm_ops = vma->vm_ops;
521 vma->vm_ops = &kernfs_vm_ops;
522out_put:
523 kernfs_put_active(of->kn);
524out_unlock:
525 mutex_unlock(&of->mutex);
526
527 return rc;
528}
529
530/**
531 * kernfs_get_open_node - get or create kernfs_open_node
532 * @kn: target kernfs_node
533 * @of: kernfs_open_file for this instance of open
534 *
535 * If @kn->attr.open exists, increment its reference count; otherwise,
536 * create one. @of is chained to the files list.
537 *
538 * LOCKING:
539 * Kernel thread context (may sleep).
540 *
541 * RETURNS:
542 * 0 on success, -errno on failure.
543 */
544static int kernfs_get_open_node(struct kernfs_node *kn,
545 struct kernfs_open_file *of)
546{
547 struct kernfs_open_node *on, *new_on = NULL;
548
549 retry:
550 mutex_lock(&kernfs_open_file_mutex);
551 spin_lock_irq(&kernfs_open_node_lock);
552
553 if (!kn->attr.open && new_on) {
554 kn->attr.open = new_on;
555 new_on = NULL;
556 }
557
558 on = kn->attr.open;
559 if (on) {
560 atomic_inc(&on->refcnt);
561 list_add_tail(&of->list, &on->files);
562 }
563
564 spin_unlock_irq(&kernfs_open_node_lock);
565 mutex_unlock(&kernfs_open_file_mutex);
566
567 if (on) {
568 kfree(new_on);
569 return 0;
570 }
571
572 /* not there, initialize a new one and retry */
573 new_on = kmalloc(sizeof(*new_on), GFP_KERNEL);
574 if (!new_on)
575 return -ENOMEM;
576
577 atomic_set(&new_on->refcnt, 0);
578 atomic_set(&new_on->event, 1);
579 init_waitqueue_head(&new_on->poll);
580 INIT_LIST_HEAD(&new_on->files);
581 goto retry;
582}
583
584/**
585 * kernfs_put_open_node - put kernfs_open_node
586 * @kn: target kernfs_nodet
587 * @of: associated kernfs_open_file
588 *
589 * Put @kn->attr.open and unlink @of from the files list. If
590 * reference count reaches zero, disassociate and free it.
591 *
592 * LOCKING:
593 * None.
594 */
595static void kernfs_put_open_node(struct kernfs_node *kn,
596 struct kernfs_open_file *of)
597{
598 struct kernfs_open_node *on = kn->attr.open;
599 unsigned long flags;
600
601 mutex_lock(&kernfs_open_file_mutex);
602 spin_lock_irqsave(&kernfs_open_node_lock, flags);
603
604 if (of)
605 list_del(&of->list);
606
607 if (atomic_dec_and_test(&on->refcnt))
608 kn->attr.open = NULL;
609 else
610 on = NULL;
611
612 spin_unlock_irqrestore(&kernfs_open_node_lock, flags);
613 mutex_unlock(&kernfs_open_file_mutex);
614
615 kfree(on);
616}
617
618static int kernfs_fop_open(struct inode *inode, struct file *file)
619{
620 struct kernfs_node *kn = file->f_path.dentry->d_fsdata;
621 struct kernfs_root *root = kernfs_root(kn);
622 const struct kernfs_ops *ops;
623 struct kernfs_open_file *of;
624 bool has_read, has_write, has_mmap;
625 int error = -EACCES;
626
627 if (!kernfs_get_active(kn))
628 return -ENODEV;
629
630 ops = kernfs_ops(kn);
631
632 has_read = ops->seq_show || ops->read || ops->mmap;
633 has_write = ops->write || ops->mmap;
634 has_mmap = ops->mmap;
635
636 /* see the flag definition for details */
637 if (root->flags & KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK) {
638 if ((file->f_mode & FMODE_WRITE) &&
639 (!(inode->i_mode & S_IWUGO) || !has_write))
640 goto err_out;
641
642 if ((file->f_mode & FMODE_READ) &&
643 (!(inode->i_mode & S_IRUGO) || !has_read))
644 goto err_out;
645 }
646
647 /* allocate a kernfs_open_file for the file */
648 error = -ENOMEM;
649 of = kzalloc(sizeof(struct kernfs_open_file), GFP_KERNEL);
650 if (!of)
651 goto err_out;
652
653 /*
654 * The following is done to give a different lockdep key to
655 * @of->mutex for files which implement mmap. This is a rather
656 * crude way to avoid false positive lockdep warning around
657 * mm->mmap_sem - mmap nests @of->mutex under mm->mmap_sem and
658 * reading /sys/block/sda/trace/act_mask grabs sr_mutex, under
659 * which mm->mmap_sem nests, while holding @of->mutex. As each
660 * open file has a separate mutex, it's okay as long as those don't
661 * happen on the same file. At this point, we can't easily give
662 * each file a separate locking class. Let's differentiate on
663 * whether the file has mmap or not for now.
664 *
665 * Both paths of the branch look the same. They're supposed to
666 * look that way and give @of->mutex different static lockdep keys.
667 */
668 if (has_mmap)
669 mutex_init(&of->mutex);
670 else
671 mutex_init(&of->mutex);
672
673 of->kn = kn;
674 of->file = file;
675
676 /*
677 * Write path needs to atomic_write_len outside active reference.
678 * Cache it in open_file. See kernfs_fop_write() for details.
679 */
680 of->atomic_write_len = ops->atomic_write_len;
681
682 error = -EINVAL;
683 /*
684 * ->seq_show is incompatible with ->prealloc,
685 * as seq_read does its own allocation.
686 * ->read must be used instead.
687 */
688 if (ops->prealloc && ops->seq_show)
689 goto err_free;
690 if (ops->prealloc) {
691 int len = of->atomic_write_len ?: PAGE_SIZE;
692 of->prealloc_buf = kmalloc(len + 1, GFP_KERNEL);
693 error = -ENOMEM;
694 if (!of->prealloc_buf)
695 goto err_free;
696 mutex_init(&of->prealloc_mutex);
697 }
698
699 /*
700 * Always instantiate seq_file even if read access doesn't use
701 * seq_file or is not requested. This unifies private data access
702 * and readable regular files are the vast majority anyway.
703 */
704 if (ops->seq_show)
705 error = seq_open(file, &kernfs_seq_ops);
706 else
707 error = seq_open(file, NULL);
708 if (error)
709 goto err_free;
710
711 ((struct seq_file *)file->private_data)->private = of;
712
713 /* seq_file clears PWRITE unconditionally, restore it if WRITE */
714 if (file->f_mode & FMODE_WRITE)
715 file->f_mode |= FMODE_PWRITE;
716
717 /* make sure we have open node struct */
718 error = kernfs_get_open_node(kn, of);
719 if (error)
720 goto err_close;
721
722 /* open succeeded, put active references */
723 kernfs_put_active(kn);
724 return 0;
725
726err_close:
727 seq_release(inode, file);
728err_free:
729 kfree(of->prealloc_buf);
730 kfree(of);
731err_out:
732 kernfs_put_active(kn);
733 return error;
734}
735
736static int kernfs_fop_release(struct inode *inode, struct file *filp)
737{
738 struct kernfs_node *kn = filp->f_path.dentry->d_fsdata;
739 struct kernfs_open_file *of = kernfs_of(filp);
740
741 kernfs_put_open_node(kn, of);
742 seq_release(inode, filp);
743 kfree(of->prealloc_buf);
744 kfree(of);
745
746 return 0;
747}
748
749void kernfs_unmap_bin_file(struct kernfs_node *kn)
750{
751 struct kernfs_open_node *on;
752 struct kernfs_open_file *of;
753
754 if (!(kn->flags & KERNFS_HAS_MMAP))
755 return;
756
757 spin_lock_irq(&kernfs_open_node_lock);
758 on = kn->attr.open;
759 if (on)
760 atomic_inc(&on->refcnt);
761 spin_unlock_irq(&kernfs_open_node_lock);
762 if (!on)
763 return;
764
765 mutex_lock(&kernfs_open_file_mutex);
766 list_for_each_entry(of, &on->files, list) {
767 struct inode *inode = file_inode(of->file);
768 unmap_mapping_range(inode->i_mapping, 0, 0, 1);
769 }
770 mutex_unlock(&kernfs_open_file_mutex);
771
772 kernfs_put_open_node(kn, NULL);
773}
774
775/*
776 * Kernfs attribute files are pollable. The idea is that you read
777 * the content and then you use 'poll' or 'select' to wait for
778 * the content to change. When the content changes (assuming the
779 * manager for the kobject supports notification), poll will
780 * return POLLERR|POLLPRI, and select will return the fd whether
781 * it is waiting for read, write, or exceptions.
782 * Once poll/select indicates that the value has changed, you
783 * need to close and re-open the file, or seek to 0 and read again.
784 * Reminder: this only works for attributes which actively support
785 * it, and it is not possible to test an attribute from userspace
786 * to see if it supports poll (Neither 'poll' nor 'select' return
787 * an appropriate error code). When in doubt, set a suitable timeout value.
788 */
789static unsigned int kernfs_fop_poll(struct file *filp, poll_table *wait)
790{
791 struct kernfs_open_file *of = kernfs_of(filp);
792 struct kernfs_node *kn = filp->f_path.dentry->d_fsdata;
793 struct kernfs_open_node *on = kn->attr.open;
794
795 if (!kernfs_get_active(kn))
796 goto trigger;
797
798 poll_wait(filp, &on->poll, wait);
799
800 kernfs_put_active(kn);
801
802 if (of->event != atomic_read(&on->event))
803 goto trigger;
804
805 return DEFAULT_POLLMASK;
806
807 trigger:
808 return DEFAULT_POLLMASK|POLLERR|POLLPRI;
809}
810
811static void kernfs_notify_workfn(struct work_struct *work)
812{
813 struct kernfs_node *kn;
814 struct kernfs_open_node *on;
815 struct kernfs_super_info *info;
816repeat:
817 /* pop one off the notify_list */
818 spin_lock_irq(&kernfs_notify_lock);
819 kn = kernfs_notify_list;
820 if (kn == KERNFS_NOTIFY_EOL) {
821 spin_unlock_irq(&kernfs_notify_lock);
822 return;
823 }
824 kernfs_notify_list = kn->attr.notify_next;
825 kn->attr.notify_next = NULL;
826 spin_unlock_irq(&kernfs_notify_lock);
827
828 /* kick poll */
829 spin_lock_irq(&kernfs_open_node_lock);
830
831 on = kn->attr.open;
832 if (on) {
833 atomic_inc(&on->event);
834 wake_up_interruptible(&on->poll);
835 }
836
837 spin_unlock_irq(&kernfs_open_node_lock);
838
839 /* kick fsnotify */
840 mutex_lock(&kernfs_mutex);
841
842 list_for_each_entry(info, &kernfs_root(kn)->supers, node) {
843 struct kernfs_node *parent;
844 struct inode *inode;
845
846 /*
847 * We want fsnotify_modify() on @kn but as the
848 * modifications aren't originating from userland don't
849 * have the matching @file available. Look up the inodes
850 * and generate the events manually.
851 */
852 inode = ilookup(info->sb, kn->ino);
853 if (!inode)
854 continue;
855
856 parent = kernfs_get_parent(kn);
857 if (parent) {
858 struct inode *p_inode;
859
860 p_inode = ilookup(info->sb, parent->ino);
861 if (p_inode) {
862 fsnotify(p_inode, FS_MODIFY | FS_EVENT_ON_CHILD,
863 inode, FSNOTIFY_EVENT_INODE, kn->name, 0);
864 iput(p_inode);
865 }
866
867 kernfs_put(parent);
868 }
869
870 fsnotify(inode, FS_MODIFY, inode, FSNOTIFY_EVENT_INODE,
871 kn->name, 0);
872 iput(inode);
873 }
874
875 mutex_unlock(&kernfs_mutex);
876 kernfs_put(kn);
877 goto repeat;
878}
879
880/**
881 * kernfs_notify - notify a kernfs file
882 * @kn: file to notify
883 *
884 * Notify @kn such that poll(2) on @kn wakes up. Maybe be called from any
885 * context.
886 */
887void kernfs_notify(struct kernfs_node *kn)
888{
889 static DECLARE_WORK(kernfs_notify_work, kernfs_notify_workfn);
890 unsigned long flags;
891
892 if (WARN_ON(kernfs_type(kn) != KERNFS_FILE))
893 return;
894
895 spin_lock_irqsave(&kernfs_notify_lock, flags);
896 if (!kn->attr.notify_next) {
897 kernfs_get(kn);
898 kn->attr.notify_next = kernfs_notify_list;
899 kernfs_notify_list = kn;
900 schedule_work(&kernfs_notify_work);
901 }
902 spin_unlock_irqrestore(&kernfs_notify_lock, flags);
903}
904EXPORT_SYMBOL_GPL(kernfs_notify);
905
906const struct file_operations kernfs_file_fops = {
907 .read = kernfs_fop_read,
908 .write = kernfs_fop_write,
909 .llseek = generic_file_llseek,
910 .mmap = kernfs_fop_mmap,
911 .open = kernfs_fop_open,
912 .release = kernfs_fop_release,
913 .poll = kernfs_fop_poll,
914 .fsync = noop_fsync,
915};
916
917/**
918 * __kernfs_create_file - kernfs internal function to create a file
919 * @parent: directory to create the file in
920 * @name: name of the file
921 * @mode: mode of the file
922 * @size: size of the file
923 * @ops: kernfs operations for the file
924 * @priv: private data for the file
925 * @ns: optional namespace tag of the file
926 * @key: lockdep key for the file's active_ref, %NULL to disable lockdep
927 *
928 * Returns the created node on success, ERR_PTR() value on error.
929 */
930struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
931 const char *name,
932 umode_t mode, loff_t size,
933 const struct kernfs_ops *ops,
934 void *priv, const void *ns,
935 struct lock_class_key *key)
936{
937 struct kernfs_node *kn;
938 unsigned flags;
939 int rc;
940
941 flags = KERNFS_FILE;
942
943 kn = kernfs_new_node(parent, name, (mode & S_IALLUGO) | S_IFREG, flags);
944 if (!kn)
945 return ERR_PTR(-ENOMEM);
946
947 kn->attr.ops = ops;
948 kn->attr.size = size;
949 kn->ns = ns;
950 kn->priv = priv;
951
952#ifdef CONFIG_DEBUG_LOCK_ALLOC
953 if (key) {
954 lockdep_init_map(&kn->dep_map, "s_active", key, 0);
955 kn->flags |= KERNFS_LOCKDEP;
956 }
957#endif
958
959 /*
960 * kn->attr.ops is accesible only while holding active ref. We
961 * need to know whether some ops are implemented outside active
962 * ref. Cache their existence in flags.
963 */
964 if (ops->seq_show)
965 kn->flags |= KERNFS_HAS_SEQ_SHOW;
966 if (ops->mmap)
967 kn->flags |= KERNFS_HAS_MMAP;
968
969 rc = kernfs_add_one(kn);
970 if (rc) {
971 kernfs_put(kn);
972 return ERR_PTR(rc);
973 }
974 return kn;
975}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * fs/kernfs/file.c - kernfs file implementation
4 *
5 * Copyright (c) 2001-3 Patrick Mochel
6 * Copyright (c) 2007 SUSE Linux Products GmbH
7 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
8 */
9
10#include <linux/fs.h>
11#include <linux/seq_file.h>
12#include <linux/slab.h>
13#include <linux/poll.h>
14#include <linux/pagemap.h>
15#include <linux/sched/mm.h>
16#include <linux/fsnotify.h>
17#include <linux/uio.h>
18
19#include "kernfs-internal.h"
20
21/*
22 * There's one kernfs_open_file for each open file and one kernfs_open_node
23 * for each kernfs_node with one or more open files.
24 *
25 * kernfs_node->attr.open points to kernfs_open_node. attr.open is
26 * protected by kernfs_open_node_lock.
27 *
28 * filp->private_data points to seq_file whose ->private points to
29 * kernfs_open_file. kernfs_open_files are chained at
30 * kernfs_open_node->files, which is protected by kernfs_open_file_mutex.
31 */
32static DEFINE_SPINLOCK(kernfs_open_node_lock);
33static DEFINE_MUTEX(kernfs_open_file_mutex);
34
35struct kernfs_open_node {
36 atomic_t refcnt;
37 atomic_t event;
38 wait_queue_head_t poll;
39 struct list_head files; /* goes through kernfs_open_file.list */
40};
41
42/*
43 * kernfs_notify() may be called from any context and bounces notifications
44 * through a work item. To minimize space overhead in kernfs_node, the
45 * pending queue is implemented as a singly linked list of kernfs_nodes.
46 * The list is terminated with the self pointer so that whether a
47 * kernfs_node is on the list or not can be determined by testing the next
48 * pointer for NULL.
49 */
50#define KERNFS_NOTIFY_EOL ((void *)&kernfs_notify_list)
51
52static DEFINE_SPINLOCK(kernfs_notify_lock);
53static struct kernfs_node *kernfs_notify_list = KERNFS_NOTIFY_EOL;
54
55static struct kernfs_open_file *kernfs_of(struct file *file)
56{
57 return ((struct seq_file *)file->private_data)->private;
58}
59
60/*
61 * Determine the kernfs_ops for the given kernfs_node. This function must
62 * be called while holding an active reference.
63 */
64static const struct kernfs_ops *kernfs_ops(struct kernfs_node *kn)
65{
66 if (kn->flags & KERNFS_LOCKDEP)
67 lockdep_assert_held(kn);
68 return kn->attr.ops;
69}
70
71/*
72 * As kernfs_seq_stop() is also called after kernfs_seq_start() or
73 * kernfs_seq_next() failure, it needs to distinguish whether it's stopping
74 * a seq_file iteration which is fully initialized with an active reference
75 * or an aborted kernfs_seq_start() due to get_active failure. The
76 * position pointer is the only context for each seq_file iteration and
77 * thus the stop condition should be encoded in it. As the return value is
78 * directly visible to userland, ERR_PTR(-ENODEV) is the only acceptable
79 * choice to indicate get_active failure.
80 *
81 * Unfortunately, this is complicated due to the optional custom seq_file
82 * operations which may return ERR_PTR(-ENODEV) too. kernfs_seq_stop()
83 * can't distinguish whether ERR_PTR(-ENODEV) is from get_active failure or
84 * custom seq_file operations and thus can't decide whether put_active
85 * should be performed or not only on ERR_PTR(-ENODEV).
86 *
87 * This is worked around by factoring out the custom seq_stop() and
88 * put_active part into kernfs_seq_stop_active(), skipping it from
89 * kernfs_seq_stop() if ERR_PTR(-ENODEV) while invoking it directly after
90 * custom seq_file operations fail with ERR_PTR(-ENODEV) - this ensures
91 * that kernfs_seq_stop_active() is skipped only after get_active failure.
92 */
93static void kernfs_seq_stop_active(struct seq_file *sf, void *v)
94{
95 struct kernfs_open_file *of = sf->private;
96 const struct kernfs_ops *ops = kernfs_ops(of->kn);
97
98 if (ops->seq_stop)
99 ops->seq_stop(sf, v);
100 kernfs_put_active(of->kn);
101}
102
103static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
104{
105 struct kernfs_open_file *of = sf->private;
106 const struct kernfs_ops *ops;
107
108 /*
109 * @of->mutex nests outside active ref and is primarily to ensure that
110 * the ops aren't called concurrently for the same open file.
111 */
112 mutex_lock(&of->mutex);
113 if (!kernfs_get_active(of->kn))
114 return ERR_PTR(-ENODEV);
115
116 ops = kernfs_ops(of->kn);
117 if (ops->seq_start) {
118 void *next = ops->seq_start(sf, ppos);
119 /* see the comment above kernfs_seq_stop_active() */
120 if (next == ERR_PTR(-ENODEV))
121 kernfs_seq_stop_active(sf, next);
122 return next;
123 } else {
124 /*
125 * The same behavior and code as single_open(). Returns
126 * !NULL if pos is at the beginning; otherwise, NULL.
127 */
128 return NULL + !*ppos;
129 }
130}
131
132static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos)
133{
134 struct kernfs_open_file *of = sf->private;
135 const struct kernfs_ops *ops = kernfs_ops(of->kn);
136
137 if (ops->seq_next) {
138 void *next = ops->seq_next(sf, v, ppos);
139 /* see the comment above kernfs_seq_stop_active() */
140 if (next == ERR_PTR(-ENODEV))
141 kernfs_seq_stop_active(sf, next);
142 return next;
143 } else {
144 /*
145 * The same behavior and code as single_open(), always
146 * terminate after the initial read.
147 */
148 ++*ppos;
149 return NULL;
150 }
151}
152
153static void kernfs_seq_stop(struct seq_file *sf, void *v)
154{
155 struct kernfs_open_file *of = sf->private;
156
157 if (v != ERR_PTR(-ENODEV))
158 kernfs_seq_stop_active(sf, v);
159 mutex_unlock(&of->mutex);
160}
161
162static int kernfs_seq_show(struct seq_file *sf, void *v)
163{
164 struct kernfs_open_file *of = sf->private;
165
166 of->event = atomic_read(&of->kn->attr.open->event);
167
168 return of->kn->attr.ops->seq_show(sf, v);
169}
170
171static const struct seq_operations kernfs_seq_ops = {
172 .start = kernfs_seq_start,
173 .next = kernfs_seq_next,
174 .stop = kernfs_seq_stop,
175 .show = kernfs_seq_show,
176};
177
178/*
179 * As reading a bin file can have side-effects, the exact offset and bytes
180 * specified in read(2) call should be passed to the read callback making
181 * it difficult to use seq_file. Implement simplistic custom buffering for
182 * bin files.
183 */
184static ssize_t kernfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
185{
186 struct kernfs_open_file *of = kernfs_of(iocb->ki_filp);
187 ssize_t len = min_t(size_t, iov_iter_count(iter), PAGE_SIZE);
188 const struct kernfs_ops *ops;
189 char *buf;
190
191 buf = of->prealloc_buf;
192 if (buf)
193 mutex_lock(&of->prealloc_mutex);
194 else
195 buf = kmalloc(len, GFP_KERNEL);
196 if (!buf)
197 return -ENOMEM;
198
199 /*
200 * @of->mutex nests outside active ref and is used both to ensure that
201 * the ops aren't called concurrently for the same open file.
202 */
203 mutex_lock(&of->mutex);
204 if (!kernfs_get_active(of->kn)) {
205 len = -ENODEV;
206 mutex_unlock(&of->mutex);
207 goto out_free;
208 }
209
210 of->event = atomic_read(&of->kn->attr.open->event);
211 ops = kernfs_ops(of->kn);
212 if (ops->read)
213 len = ops->read(of, buf, len, iocb->ki_pos);
214 else
215 len = -EINVAL;
216
217 kernfs_put_active(of->kn);
218 mutex_unlock(&of->mutex);
219
220 if (len < 0)
221 goto out_free;
222
223 if (copy_to_iter(buf, len, iter) != len) {
224 len = -EFAULT;
225 goto out_free;
226 }
227
228 iocb->ki_pos += len;
229
230 out_free:
231 if (buf == of->prealloc_buf)
232 mutex_unlock(&of->prealloc_mutex);
233 else
234 kfree(buf);
235 return len;
236}
237
238static ssize_t kernfs_fop_read_iter(struct kiocb *iocb, struct iov_iter *iter)
239{
240 if (kernfs_of(iocb->ki_filp)->kn->flags & KERNFS_HAS_SEQ_SHOW)
241 return seq_read_iter(iocb, iter);
242 return kernfs_file_read_iter(iocb, iter);
243}
244
245/*
246 * Copy data in from userland and pass it to the matching kernfs write
247 * operation.
248 *
249 * There is no easy way for us to know if userspace is only doing a partial
250 * write, so we don't support them. We expect the entire buffer to come on
251 * the first write. Hint: if you're writing a value, first read the file,
252 * modify only the the value you're changing, then write entire buffer
253 * back.
254 */
255static ssize_t kernfs_fop_write_iter(struct kiocb *iocb, struct iov_iter *iter)
256{
257 struct kernfs_open_file *of = kernfs_of(iocb->ki_filp);
258 ssize_t len = iov_iter_count(iter);
259 const struct kernfs_ops *ops;
260 char *buf;
261
262 if (of->atomic_write_len) {
263 if (len > of->atomic_write_len)
264 return -E2BIG;
265 } else {
266 len = min_t(size_t, len, PAGE_SIZE);
267 }
268
269 buf = of->prealloc_buf;
270 if (buf)
271 mutex_lock(&of->prealloc_mutex);
272 else
273 buf = kmalloc(len + 1, GFP_KERNEL);
274 if (!buf)
275 return -ENOMEM;
276
277 if (copy_from_iter(buf, len, iter) != len) {
278 len = -EFAULT;
279 goto out_free;
280 }
281 buf[len] = '\0'; /* guarantee string termination */
282
283 /*
284 * @of->mutex nests outside active ref and is used both to ensure that
285 * the ops aren't called concurrently for the same open file.
286 */
287 mutex_lock(&of->mutex);
288 if (!kernfs_get_active(of->kn)) {
289 mutex_unlock(&of->mutex);
290 len = -ENODEV;
291 goto out_free;
292 }
293
294 ops = kernfs_ops(of->kn);
295 if (ops->write)
296 len = ops->write(of, buf, len, iocb->ki_pos);
297 else
298 len = -EINVAL;
299
300 kernfs_put_active(of->kn);
301 mutex_unlock(&of->mutex);
302
303 if (len > 0)
304 iocb->ki_pos += len;
305
306out_free:
307 if (buf == of->prealloc_buf)
308 mutex_unlock(&of->prealloc_mutex);
309 else
310 kfree(buf);
311 return len;
312}
313
314static void kernfs_vma_open(struct vm_area_struct *vma)
315{
316 struct file *file = vma->vm_file;
317 struct kernfs_open_file *of = kernfs_of(file);
318
319 if (!of->vm_ops)
320 return;
321
322 if (!kernfs_get_active(of->kn))
323 return;
324
325 if (of->vm_ops->open)
326 of->vm_ops->open(vma);
327
328 kernfs_put_active(of->kn);
329}
330
331static vm_fault_t kernfs_vma_fault(struct vm_fault *vmf)
332{
333 struct file *file = vmf->vma->vm_file;
334 struct kernfs_open_file *of = kernfs_of(file);
335 vm_fault_t ret;
336
337 if (!of->vm_ops)
338 return VM_FAULT_SIGBUS;
339
340 if (!kernfs_get_active(of->kn))
341 return VM_FAULT_SIGBUS;
342
343 ret = VM_FAULT_SIGBUS;
344 if (of->vm_ops->fault)
345 ret = of->vm_ops->fault(vmf);
346
347 kernfs_put_active(of->kn);
348 return ret;
349}
350
351static vm_fault_t kernfs_vma_page_mkwrite(struct vm_fault *vmf)
352{
353 struct file *file = vmf->vma->vm_file;
354 struct kernfs_open_file *of = kernfs_of(file);
355 vm_fault_t ret;
356
357 if (!of->vm_ops)
358 return VM_FAULT_SIGBUS;
359
360 if (!kernfs_get_active(of->kn))
361 return VM_FAULT_SIGBUS;
362
363 ret = 0;
364 if (of->vm_ops->page_mkwrite)
365 ret = of->vm_ops->page_mkwrite(vmf);
366 else
367 file_update_time(file);
368
369 kernfs_put_active(of->kn);
370 return ret;
371}
372
373static int kernfs_vma_access(struct vm_area_struct *vma, unsigned long addr,
374 void *buf, int len, int write)
375{
376 struct file *file = vma->vm_file;
377 struct kernfs_open_file *of = kernfs_of(file);
378 int ret;
379
380 if (!of->vm_ops)
381 return -EINVAL;
382
383 if (!kernfs_get_active(of->kn))
384 return -EINVAL;
385
386 ret = -EINVAL;
387 if (of->vm_ops->access)
388 ret = of->vm_ops->access(vma, addr, buf, len, write);
389
390 kernfs_put_active(of->kn);
391 return ret;
392}
393
394#ifdef CONFIG_NUMA
395static int kernfs_vma_set_policy(struct vm_area_struct *vma,
396 struct mempolicy *new)
397{
398 struct file *file = vma->vm_file;
399 struct kernfs_open_file *of = kernfs_of(file);
400 int ret;
401
402 if (!of->vm_ops)
403 return 0;
404
405 if (!kernfs_get_active(of->kn))
406 return -EINVAL;
407
408 ret = 0;
409 if (of->vm_ops->set_policy)
410 ret = of->vm_ops->set_policy(vma, new);
411
412 kernfs_put_active(of->kn);
413 return ret;
414}
415
416static struct mempolicy *kernfs_vma_get_policy(struct vm_area_struct *vma,
417 unsigned long addr)
418{
419 struct file *file = vma->vm_file;
420 struct kernfs_open_file *of = kernfs_of(file);
421 struct mempolicy *pol;
422
423 if (!of->vm_ops)
424 return vma->vm_policy;
425
426 if (!kernfs_get_active(of->kn))
427 return vma->vm_policy;
428
429 pol = vma->vm_policy;
430 if (of->vm_ops->get_policy)
431 pol = of->vm_ops->get_policy(vma, addr);
432
433 kernfs_put_active(of->kn);
434 return pol;
435}
436
437#endif
438
439static const struct vm_operations_struct kernfs_vm_ops = {
440 .open = kernfs_vma_open,
441 .fault = kernfs_vma_fault,
442 .page_mkwrite = kernfs_vma_page_mkwrite,
443 .access = kernfs_vma_access,
444#ifdef CONFIG_NUMA
445 .set_policy = kernfs_vma_set_policy,
446 .get_policy = kernfs_vma_get_policy,
447#endif
448};
449
450static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
451{
452 struct kernfs_open_file *of = kernfs_of(file);
453 const struct kernfs_ops *ops;
454 int rc;
455
456 /*
457 * mmap path and of->mutex are prone to triggering spurious lockdep
458 * warnings and we don't want to add spurious locking dependency
459 * between the two. Check whether mmap is actually implemented
460 * without grabbing @of->mutex by testing HAS_MMAP flag. See the
461 * comment in kernfs_file_open() for more details.
462 */
463 if (!(of->kn->flags & KERNFS_HAS_MMAP))
464 return -ENODEV;
465
466 mutex_lock(&of->mutex);
467
468 rc = -ENODEV;
469 if (!kernfs_get_active(of->kn))
470 goto out_unlock;
471
472 ops = kernfs_ops(of->kn);
473 rc = ops->mmap(of, vma);
474 if (rc)
475 goto out_put;
476
477 /*
478 * PowerPC's pci_mmap of legacy_mem uses shmem_zero_setup()
479 * to satisfy versions of X which crash if the mmap fails: that
480 * substitutes a new vm_file, and we don't then want bin_vm_ops.
481 */
482 if (vma->vm_file != file)
483 goto out_put;
484
485 rc = -EINVAL;
486 if (of->mmapped && of->vm_ops != vma->vm_ops)
487 goto out_put;
488
489 /*
490 * It is not possible to successfully wrap close.
491 * So error if someone is trying to use close.
492 */
493 rc = -EINVAL;
494 if (vma->vm_ops && vma->vm_ops->close)
495 goto out_put;
496
497 rc = 0;
498 of->mmapped = true;
499 of->vm_ops = vma->vm_ops;
500 vma->vm_ops = &kernfs_vm_ops;
501out_put:
502 kernfs_put_active(of->kn);
503out_unlock:
504 mutex_unlock(&of->mutex);
505
506 return rc;
507}
508
509/**
510 * kernfs_get_open_node - get or create kernfs_open_node
511 * @kn: target kernfs_node
512 * @of: kernfs_open_file for this instance of open
513 *
514 * If @kn->attr.open exists, increment its reference count; otherwise,
515 * create one. @of is chained to the files list.
516 *
517 * LOCKING:
518 * Kernel thread context (may sleep).
519 *
520 * RETURNS:
521 * 0 on success, -errno on failure.
522 */
523static int kernfs_get_open_node(struct kernfs_node *kn,
524 struct kernfs_open_file *of)
525{
526 struct kernfs_open_node *on, *new_on = NULL;
527
528 retry:
529 mutex_lock(&kernfs_open_file_mutex);
530 spin_lock_irq(&kernfs_open_node_lock);
531
532 if (!kn->attr.open && new_on) {
533 kn->attr.open = new_on;
534 new_on = NULL;
535 }
536
537 on = kn->attr.open;
538 if (on) {
539 atomic_inc(&on->refcnt);
540 list_add_tail(&of->list, &on->files);
541 }
542
543 spin_unlock_irq(&kernfs_open_node_lock);
544 mutex_unlock(&kernfs_open_file_mutex);
545
546 if (on) {
547 kfree(new_on);
548 return 0;
549 }
550
551 /* not there, initialize a new one and retry */
552 new_on = kmalloc(sizeof(*new_on), GFP_KERNEL);
553 if (!new_on)
554 return -ENOMEM;
555
556 atomic_set(&new_on->refcnt, 0);
557 atomic_set(&new_on->event, 1);
558 init_waitqueue_head(&new_on->poll);
559 INIT_LIST_HEAD(&new_on->files);
560 goto retry;
561}
562
563/**
564 * kernfs_put_open_node - put kernfs_open_node
565 * @kn: target kernfs_nodet
566 * @of: associated kernfs_open_file
567 *
568 * Put @kn->attr.open and unlink @of from the files list. If
569 * reference count reaches zero, disassociate and free it.
570 *
571 * LOCKING:
572 * None.
573 */
574static void kernfs_put_open_node(struct kernfs_node *kn,
575 struct kernfs_open_file *of)
576{
577 struct kernfs_open_node *on = kn->attr.open;
578 unsigned long flags;
579
580 mutex_lock(&kernfs_open_file_mutex);
581 spin_lock_irqsave(&kernfs_open_node_lock, flags);
582
583 if (of)
584 list_del(&of->list);
585
586 if (atomic_dec_and_test(&on->refcnt))
587 kn->attr.open = NULL;
588 else
589 on = NULL;
590
591 spin_unlock_irqrestore(&kernfs_open_node_lock, flags);
592 mutex_unlock(&kernfs_open_file_mutex);
593
594 kfree(on);
595}
596
597static int kernfs_fop_open(struct inode *inode, struct file *file)
598{
599 struct kernfs_node *kn = inode->i_private;
600 struct kernfs_root *root = kernfs_root(kn);
601 const struct kernfs_ops *ops;
602 struct kernfs_open_file *of;
603 bool has_read, has_write, has_mmap;
604 int error = -EACCES;
605
606 if (!kernfs_get_active(kn))
607 return -ENODEV;
608
609 ops = kernfs_ops(kn);
610
611 has_read = ops->seq_show || ops->read || ops->mmap;
612 has_write = ops->write || ops->mmap;
613 has_mmap = ops->mmap;
614
615 /* see the flag definition for details */
616 if (root->flags & KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK) {
617 if ((file->f_mode & FMODE_WRITE) &&
618 (!(inode->i_mode & S_IWUGO) || !has_write))
619 goto err_out;
620
621 if ((file->f_mode & FMODE_READ) &&
622 (!(inode->i_mode & S_IRUGO) || !has_read))
623 goto err_out;
624 }
625
626 /* allocate a kernfs_open_file for the file */
627 error = -ENOMEM;
628 of = kzalloc(sizeof(struct kernfs_open_file), GFP_KERNEL);
629 if (!of)
630 goto err_out;
631
632 /*
633 * The following is done to give a different lockdep key to
634 * @of->mutex for files which implement mmap. This is a rather
635 * crude way to avoid false positive lockdep warning around
636 * mm->mmap_lock - mmap nests @of->mutex under mm->mmap_lock and
637 * reading /sys/block/sda/trace/act_mask grabs sr_mutex, under
638 * which mm->mmap_lock nests, while holding @of->mutex. As each
639 * open file has a separate mutex, it's okay as long as those don't
640 * happen on the same file. At this point, we can't easily give
641 * each file a separate locking class. Let's differentiate on
642 * whether the file has mmap or not for now.
643 *
644 * Both paths of the branch look the same. They're supposed to
645 * look that way and give @of->mutex different static lockdep keys.
646 */
647 if (has_mmap)
648 mutex_init(&of->mutex);
649 else
650 mutex_init(&of->mutex);
651
652 of->kn = kn;
653 of->file = file;
654
655 /*
656 * Write path needs to atomic_write_len outside active reference.
657 * Cache it in open_file. See kernfs_fop_write_iter() for details.
658 */
659 of->atomic_write_len = ops->atomic_write_len;
660
661 error = -EINVAL;
662 /*
663 * ->seq_show is incompatible with ->prealloc,
664 * as seq_read does its own allocation.
665 * ->read must be used instead.
666 */
667 if (ops->prealloc && ops->seq_show)
668 goto err_free;
669 if (ops->prealloc) {
670 int len = of->atomic_write_len ?: PAGE_SIZE;
671 of->prealloc_buf = kmalloc(len + 1, GFP_KERNEL);
672 error = -ENOMEM;
673 if (!of->prealloc_buf)
674 goto err_free;
675 mutex_init(&of->prealloc_mutex);
676 }
677
678 /*
679 * Always instantiate seq_file even if read access doesn't use
680 * seq_file or is not requested. This unifies private data access
681 * and readable regular files are the vast majority anyway.
682 */
683 if (ops->seq_show)
684 error = seq_open(file, &kernfs_seq_ops);
685 else
686 error = seq_open(file, NULL);
687 if (error)
688 goto err_free;
689
690 of->seq_file = file->private_data;
691 of->seq_file->private = of;
692
693 /* seq_file clears PWRITE unconditionally, restore it if WRITE */
694 if (file->f_mode & FMODE_WRITE)
695 file->f_mode |= FMODE_PWRITE;
696
697 /* make sure we have open node struct */
698 error = kernfs_get_open_node(kn, of);
699 if (error)
700 goto err_seq_release;
701
702 if (ops->open) {
703 /* nobody has access to @of yet, skip @of->mutex */
704 error = ops->open(of);
705 if (error)
706 goto err_put_node;
707 }
708
709 /* open succeeded, put active references */
710 kernfs_put_active(kn);
711 return 0;
712
713err_put_node:
714 kernfs_put_open_node(kn, of);
715err_seq_release:
716 seq_release(inode, file);
717err_free:
718 kfree(of->prealloc_buf);
719 kfree(of);
720err_out:
721 kernfs_put_active(kn);
722 return error;
723}
724
725/* used from release/drain to ensure that ->release() is called exactly once */
726static void kernfs_release_file(struct kernfs_node *kn,
727 struct kernfs_open_file *of)
728{
729 /*
730 * @of is guaranteed to have no other file operations in flight and
731 * we just want to synchronize release and drain paths.
732 * @kernfs_open_file_mutex is enough. @of->mutex can't be used
733 * here because drain path may be called from places which can
734 * cause circular dependency.
735 */
736 lockdep_assert_held(&kernfs_open_file_mutex);
737
738 if (!of->released) {
739 /*
740 * A file is never detached without being released and we
741 * need to be able to release files which are deactivated
742 * and being drained. Don't use kernfs_ops().
743 */
744 kn->attr.ops->release(of);
745 of->released = true;
746 }
747}
748
749static int kernfs_fop_release(struct inode *inode, struct file *filp)
750{
751 struct kernfs_node *kn = inode->i_private;
752 struct kernfs_open_file *of = kernfs_of(filp);
753
754 if (kn->flags & KERNFS_HAS_RELEASE) {
755 mutex_lock(&kernfs_open_file_mutex);
756 kernfs_release_file(kn, of);
757 mutex_unlock(&kernfs_open_file_mutex);
758 }
759
760 kernfs_put_open_node(kn, of);
761 seq_release(inode, filp);
762 kfree(of->prealloc_buf);
763 kfree(of);
764
765 return 0;
766}
767
768void kernfs_drain_open_files(struct kernfs_node *kn)
769{
770 struct kernfs_open_node *on;
771 struct kernfs_open_file *of;
772
773 if (!(kn->flags & (KERNFS_HAS_MMAP | KERNFS_HAS_RELEASE)))
774 return;
775
776 spin_lock_irq(&kernfs_open_node_lock);
777 on = kn->attr.open;
778 if (on)
779 atomic_inc(&on->refcnt);
780 spin_unlock_irq(&kernfs_open_node_lock);
781 if (!on)
782 return;
783
784 mutex_lock(&kernfs_open_file_mutex);
785
786 list_for_each_entry(of, &on->files, list) {
787 struct inode *inode = file_inode(of->file);
788
789 if (kn->flags & KERNFS_HAS_MMAP)
790 unmap_mapping_range(inode->i_mapping, 0, 0, 1);
791
792 if (kn->flags & KERNFS_HAS_RELEASE)
793 kernfs_release_file(kn, of);
794 }
795
796 mutex_unlock(&kernfs_open_file_mutex);
797
798 kernfs_put_open_node(kn, NULL);
799}
800
801/*
802 * Kernfs attribute files are pollable. The idea is that you read
803 * the content and then you use 'poll' or 'select' to wait for
804 * the content to change. When the content changes (assuming the
805 * manager for the kobject supports notification), poll will
806 * return EPOLLERR|EPOLLPRI, and select will return the fd whether
807 * it is waiting for read, write, or exceptions.
808 * Once poll/select indicates that the value has changed, you
809 * need to close and re-open the file, or seek to 0 and read again.
810 * Reminder: this only works for attributes which actively support
811 * it, and it is not possible to test an attribute from userspace
812 * to see if it supports poll (Neither 'poll' nor 'select' return
813 * an appropriate error code). When in doubt, set a suitable timeout value.
814 */
815__poll_t kernfs_generic_poll(struct kernfs_open_file *of, poll_table *wait)
816{
817 struct kernfs_node *kn = kernfs_dentry_node(of->file->f_path.dentry);
818 struct kernfs_open_node *on = kn->attr.open;
819
820 poll_wait(of->file, &on->poll, wait);
821
822 if (of->event != atomic_read(&on->event))
823 return DEFAULT_POLLMASK|EPOLLERR|EPOLLPRI;
824
825 return DEFAULT_POLLMASK;
826}
827
828static __poll_t kernfs_fop_poll(struct file *filp, poll_table *wait)
829{
830 struct kernfs_open_file *of = kernfs_of(filp);
831 struct kernfs_node *kn = kernfs_dentry_node(filp->f_path.dentry);
832 __poll_t ret;
833
834 if (!kernfs_get_active(kn))
835 return DEFAULT_POLLMASK|EPOLLERR|EPOLLPRI;
836
837 if (kn->attr.ops->poll)
838 ret = kn->attr.ops->poll(of, wait);
839 else
840 ret = kernfs_generic_poll(of, wait);
841
842 kernfs_put_active(kn);
843 return ret;
844}
845
846static void kernfs_notify_workfn(struct work_struct *work)
847{
848 struct kernfs_node *kn;
849 struct kernfs_super_info *info;
850repeat:
851 /* pop one off the notify_list */
852 spin_lock_irq(&kernfs_notify_lock);
853 kn = kernfs_notify_list;
854 if (kn == KERNFS_NOTIFY_EOL) {
855 spin_unlock_irq(&kernfs_notify_lock);
856 return;
857 }
858 kernfs_notify_list = kn->attr.notify_next;
859 kn->attr.notify_next = NULL;
860 spin_unlock_irq(&kernfs_notify_lock);
861
862 /* kick fsnotify */
863 mutex_lock(&kernfs_mutex);
864
865 list_for_each_entry(info, &kernfs_root(kn)->supers, node) {
866 struct kernfs_node *parent;
867 struct inode *p_inode = NULL;
868 struct inode *inode;
869 struct qstr name;
870
871 /*
872 * We want fsnotify_modify() on @kn but as the
873 * modifications aren't originating from userland don't
874 * have the matching @file available. Look up the inodes
875 * and generate the events manually.
876 */
877 inode = ilookup(info->sb, kernfs_ino(kn));
878 if (!inode)
879 continue;
880
881 name = (struct qstr)QSTR_INIT(kn->name, strlen(kn->name));
882 parent = kernfs_get_parent(kn);
883 if (parent) {
884 p_inode = ilookup(info->sb, kernfs_ino(parent));
885 if (p_inode) {
886 fsnotify(FS_MODIFY | FS_EVENT_ON_CHILD,
887 inode, FSNOTIFY_EVENT_INODE,
888 p_inode, &name, inode, 0);
889 iput(p_inode);
890 }
891
892 kernfs_put(parent);
893 }
894
895 if (!p_inode)
896 fsnotify_inode(inode, FS_MODIFY);
897
898 iput(inode);
899 }
900
901 mutex_unlock(&kernfs_mutex);
902 kernfs_put(kn);
903 goto repeat;
904}
905
906/**
907 * kernfs_notify - notify a kernfs file
908 * @kn: file to notify
909 *
910 * Notify @kn such that poll(2) on @kn wakes up. Maybe be called from any
911 * context.
912 */
913void kernfs_notify(struct kernfs_node *kn)
914{
915 static DECLARE_WORK(kernfs_notify_work, kernfs_notify_workfn);
916 unsigned long flags;
917 struct kernfs_open_node *on;
918
919 if (WARN_ON(kernfs_type(kn) != KERNFS_FILE))
920 return;
921
922 /* kick poll immediately */
923 spin_lock_irqsave(&kernfs_open_node_lock, flags);
924 on = kn->attr.open;
925 if (on) {
926 atomic_inc(&on->event);
927 wake_up_interruptible(&on->poll);
928 }
929 spin_unlock_irqrestore(&kernfs_open_node_lock, flags);
930
931 /* schedule work to kick fsnotify */
932 spin_lock_irqsave(&kernfs_notify_lock, flags);
933 if (!kn->attr.notify_next) {
934 kernfs_get(kn);
935 kn->attr.notify_next = kernfs_notify_list;
936 kernfs_notify_list = kn;
937 schedule_work(&kernfs_notify_work);
938 }
939 spin_unlock_irqrestore(&kernfs_notify_lock, flags);
940}
941EXPORT_SYMBOL_GPL(kernfs_notify);
942
943const struct file_operations kernfs_file_fops = {
944 .read_iter = kernfs_fop_read_iter,
945 .write_iter = kernfs_fop_write_iter,
946 .llseek = generic_file_llseek,
947 .mmap = kernfs_fop_mmap,
948 .open = kernfs_fop_open,
949 .release = kernfs_fop_release,
950 .poll = kernfs_fop_poll,
951 .fsync = noop_fsync,
952 .splice_read = generic_file_splice_read,
953 .splice_write = iter_file_splice_write,
954};
955
956/**
957 * __kernfs_create_file - kernfs internal function to create a file
958 * @parent: directory to create the file in
959 * @name: name of the file
960 * @mode: mode of the file
961 * @uid: uid of the file
962 * @gid: gid of the file
963 * @size: size of the file
964 * @ops: kernfs operations for the file
965 * @priv: private data for the file
966 * @ns: optional namespace tag of the file
967 * @key: lockdep key for the file's active_ref, %NULL to disable lockdep
968 *
969 * Returns the created node on success, ERR_PTR() value on error.
970 */
971struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
972 const char *name,
973 umode_t mode, kuid_t uid, kgid_t gid,
974 loff_t size,
975 const struct kernfs_ops *ops,
976 void *priv, const void *ns,
977 struct lock_class_key *key)
978{
979 struct kernfs_node *kn;
980 unsigned flags;
981 int rc;
982
983 flags = KERNFS_FILE;
984
985 kn = kernfs_new_node(parent, name, (mode & S_IALLUGO) | S_IFREG,
986 uid, gid, flags);
987 if (!kn)
988 return ERR_PTR(-ENOMEM);
989
990 kn->attr.ops = ops;
991 kn->attr.size = size;
992 kn->ns = ns;
993 kn->priv = priv;
994
995#ifdef CONFIG_DEBUG_LOCK_ALLOC
996 if (key) {
997 lockdep_init_map(&kn->dep_map, "kn->active", key, 0);
998 kn->flags |= KERNFS_LOCKDEP;
999 }
1000#endif
1001
1002 /*
1003 * kn->attr.ops is accesible only while holding active ref. We
1004 * need to know whether some ops are implemented outside active
1005 * ref. Cache their existence in flags.
1006 */
1007 if (ops->seq_show)
1008 kn->flags |= KERNFS_HAS_SEQ_SHOW;
1009 if (ops->mmap)
1010 kn->flags |= KERNFS_HAS_MMAP;
1011 if (ops->release)
1012 kn->flags |= KERNFS_HAS_RELEASE;
1013
1014 rc = kernfs_add_one(kn);
1015 if (rc) {
1016 kernfs_put(kn);
1017 return ERR_PTR(rc);
1018 }
1019 return kn;
1020}