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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
18#include "kernfs-internal.h"
19
20/*
21 * There's one kernfs_open_file for each open file and one kernfs_open_node
22 * for each kernfs_node with one or more open files.
23 *
24 * kernfs_node->attr.open points to kernfs_open_node. attr.open is
25 * protected by kernfs_open_node_lock.
26 *
27 * filp->private_data points to seq_file whose ->private points to
28 * kernfs_open_file. kernfs_open_files are chained at
29 * kernfs_open_node->files, which is protected by kernfs_open_file_mutex.
30 */
31static DEFINE_SPINLOCK(kernfs_open_node_lock);
32static DEFINE_MUTEX(kernfs_open_file_mutex);
33
34struct kernfs_open_node {
35 atomic_t refcnt;
36 atomic_t event;
37 wait_queue_head_t poll;
38 struct list_head files; /* goes through kernfs_open_file.list */
39};
40
41/*
42 * kernfs_notify() may be called from any context and bounces notifications
43 * through a work item. To minimize space overhead in kernfs_node, the
44 * pending queue is implemented as a singly linked list of kernfs_nodes.
45 * The list is terminated with the self pointer so that whether a
46 * kernfs_node is on the list or not can be determined by testing the next
47 * pointer for NULL.
48 */
49#define KERNFS_NOTIFY_EOL ((void *)&kernfs_notify_list)
50
51static DEFINE_SPINLOCK(kernfs_notify_lock);
52static struct kernfs_node *kernfs_notify_list = KERNFS_NOTIFY_EOL;
53
54static struct kernfs_open_file *kernfs_of(struct file *file)
55{
56 return ((struct seq_file *)file->private_data)->private;
57}
58
59/*
60 * Determine the kernfs_ops for the given kernfs_node. This function must
61 * be called while holding an active reference.
62 */
63static const struct kernfs_ops *kernfs_ops(struct kernfs_node *kn)
64{
65 if (kn->flags & KERNFS_LOCKDEP)
66 lockdep_assert_held(kn);
67 return kn->attr.ops;
68}
69
70/*
71 * As kernfs_seq_stop() is also called after kernfs_seq_start() or
72 * kernfs_seq_next() failure, it needs to distinguish whether it's stopping
73 * a seq_file iteration which is fully initialized with an active reference
74 * or an aborted kernfs_seq_start() due to get_active failure. The
75 * position pointer is the only context for each seq_file iteration and
76 * thus the stop condition should be encoded in it. As the return value is
77 * directly visible to userland, ERR_PTR(-ENODEV) is the only acceptable
78 * choice to indicate get_active failure.
79 *
80 * Unfortunately, this is complicated due to the optional custom seq_file
81 * operations which may return ERR_PTR(-ENODEV) too. kernfs_seq_stop()
82 * can't distinguish whether ERR_PTR(-ENODEV) is from get_active failure or
83 * custom seq_file operations and thus can't decide whether put_active
84 * should be performed or not only on ERR_PTR(-ENODEV).
85 *
86 * This is worked around by factoring out the custom seq_stop() and
87 * put_active part into kernfs_seq_stop_active(), skipping it from
88 * kernfs_seq_stop() if ERR_PTR(-ENODEV) while invoking it directly after
89 * custom seq_file operations fail with ERR_PTR(-ENODEV) - this ensures
90 * that kernfs_seq_stop_active() is skipped only after get_active failure.
91 */
92static void kernfs_seq_stop_active(struct seq_file *sf, void *v)
93{
94 struct kernfs_open_file *of = sf->private;
95 const struct kernfs_ops *ops = kernfs_ops(of->kn);
96
97 if (ops->seq_stop)
98 ops->seq_stop(sf, v);
99 kernfs_put_active(of->kn);
100}
101
102static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
103{
104 struct kernfs_open_file *of = sf->private;
105 const struct kernfs_ops *ops;
106
107 /*
108 * @of->mutex nests outside active ref and is primarily to ensure that
109 * the ops aren't called concurrently for the same open file.
110 */
111 mutex_lock(&of->mutex);
112 if (!kernfs_get_active(of->kn))
113 return ERR_PTR(-ENODEV);
114
115 ops = kernfs_ops(of->kn);
116 if (ops->seq_start) {
117 void *next = ops->seq_start(sf, ppos);
118 /* see the comment above kernfs_seq_stop_active() */
119 if (next == ERR_PTR(-ENODEV))
120 kernfs_seq_stop_active(sf, next);
121 return next;
122 } else {
123 /*
124 * The same behavior and code as single_open(). Returns
125 * !NULL if pos is at the beginning; otherwise, NULL.
126 */
127 return NULL + !*ppos;
128 }
129}
130
131static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos)
132{
133 struct kernfs_open_file *of = sf->private;
134 const struct kernfs_ops *ops = kernfs_ops(of->kn);
135
136 if (ops->seq_next) {
137 void *next = ops->seq_next(sf, v, ppos);
138 /* see the comment above kernfs_seq_stop_active() */
139 if (next == ERR_PTR(-ENODEV))
140 kernfs_seq_stop_active(sf, next);
141 return next;
142 } else {
143 /*
144 * The same behavior and code as single_open(), always
145 * terminate after the initial read.
146 */
147 ++*ppos;
148 return NULL;
149 }
150}
151
152static void kernfs_seq_stop(struct seq_file *sf, void *v)
153{
154 struct kernfs_open_file *of = sf->private;
155
156 if (v != ERR_PTR(-ENODEV))
157 kernfs_seq_stop_active(sf, v);
158 mutex_unlock(&of->mutex);
159}
160
161static int kernfs_seq_show(struct seq_file *sf, void *v)
162{
163 struct kernfs_open_file *of = sf->private;
164
165 of->event = atomic_read(&of->kn->attr.open->event);
166
167 return of->kn->attr.ops->seq_show(sf, v);
168}
169
170static const struct seq_operations kernfs_seq_ops = {
171 .start = kernfs_seq_start,
172 .next = kernfs_seq_next,
173 .stop = kernfs_seq_stop,
174 .show = kernfs_seq_show,
175};
176
177/*
178 * As reading a bin file can have side-effects, the exact offset and bytes
179 * specified in read(2) call should be passed to the read callback making
180 * it difficult to use seq_file. Implement simplistic custom buffering for
181 * bin files.
182 */
183static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
184 char __user *user_buf, size_t count,
185 loff_t *ppos)
186{
187 ssize_t len = min_t(size_t, count, 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, *ppos);
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_user(user_buf, buf, len)) {
224 len = -EFAULT;
225 goto out_free;
226 }
227
228 *ppos += 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
238/**
239 * kernfs_fop_read - kernfs vfs read callback
240 * @file: file pointer
241 * @user_buf: data to write
242 * @count: number of bytes
243 * @ppos: starting offset
244 */
245static ssize_t kernfs_fop_read(struct file *file, char __user *user_buf,
246 size_t count, loff_t *ppos)
247{
248 struct kernfs_open_file *of = kernfs_of(file);
249
250 if (of->kn->flags & KERNFS_HAS_SEQ_SHOW)
251 return seq_read(file, user_buf, count, ppos);
252 else
253 return kernfs_file_direct_read(of, user_buf, count, ppos);
254}
255
256/**
257 * kernfs_fop_write - kernfs vfs write callback
258 * @file: file pointer
259 * @user_buf: data to write
260 * @count: number of bytes
261 * @ppos: starting offset
262 *
263 * Copy data in from userland and pass it to the matching kernfs write
264 * operation.
265 *
266 * There is no easy way for us to know if userspace is only doing a partial
267 * write, so we don't support them. We expect the entire buffer to come on
268 * the first write. Hint: if you're writing a value, first read the file,
269 * modify only the the value you're changing, then write entire buffer
270 * back.
271 */
272static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
273 size_t count, loff_t *ppos)
274{
275 struct kernfs_open_file *of = kernfs_of(file);
276 const struct kernfs_ops *ops;
277 ssize_t len;
278 char *buf;
279
280 if (of->atomic_write_len) {
281 len = count;
282 if (len > of->atomic_write_len)
283 return -E2BIG;
284 } else {
285 len = min_t(size_t, count, PAGE_SIZE);
286 }
287
288 buf = of->prealloc_buf;
289 if (buf)
290 mutex_lock(&of->prealloc_mutex);
291 else
292 buf = kmalloc(len + 1, GFP_KERNEL);
293 if (!buf)
294 return -ENOMEM;
295
296 if (copy_from_user(buf, user_buf, len)) {
297 len = -EFAULT;
298 goto out_free;
299 }
300 buf[len] = '\0'; /* guarantee string termination */
301
302 /*
303 * @of->mutex nests outside active ref and is used both to ensure that
304 * the ops aren't called concurrently for the same open file.
305 */
306 mutex_lock(&of->mutex);
307 if (!kernfs_get_active(of->kn)) {
308 mutex_unlock(&of->mutex);
309 len = -ENODEV;
310 goto out_free;
311 }
312
313 ops = kernfs_ops(of->kn);
314 if (ops->write)
315 len = ops->write(of, buf, len, *ppos);
316 else
317 len = -EINVAL;
318
319 kernfs_put_active(of->kn);
320 mutex_unlock(&of->mutex);
321
322 if (len > 0)
323 *ppos += len;
324
325out_free:
326 if (buf == of->prealloc_buf)
327 mutex_unlock(&of->prealloc_mutex);
328 else
329 kfree(buf);
330 return len;
331}
332
333static void kernfs_vma_open(struct vm_area_struct *vma)
334{
335 struct file *file = vma->vm_file;
336 struct kernfs_open_file *of = kernfs_of(file);
337
338 if (!of->vm_ops)
339 return;
340
341 if (!kernfs_get_active(of->kn))
342 return;
343
344 if (of->vm_ops->open)
345 of->vm_ops->open(vma);
346
347 kernfs_put_active(of->kn);
348}
349
350static vm_fault_t kernfs_vma_fault(struct vm_fault *vmf)
351{
352 struct file *file = vmf->vma->vm_file;
353 struct kernfs_open_file *of = kernfs_of(file);
354 vm_fault_t ret;
355
356 if (!of->vm_ops)
357 return VM_FAULT_SIGBUS;
358
359 if (!kernfs_get_active(of->kn))
360 return VM_FAULT_SIGBUS;
361
362 ret = VM_FAULT_SIGBUS;
363 if (of->vm_ops->fault)
364 ret = of->vm_ops->fault(vmf);
365
366 kernfs_put_active(of->kn);
367 return ret;
368}
369
370static vm_fault_t kernfs_vma_page_mkwrite(struct vm_fault *vmf)
371{
372 struct file *file = vmf->vma->vm_file;
373 struct kernfs_open_file *of = kernfs_of(file);
374 vm_fault_t ret;
375
376 if (!of->vm_ops)
377 return VM_FAULT_SIGBUS;
378
379 if (!kernfs_get_active(of->kn))
380 return VM_FAULT_SIGBUS;
381
382 ret = 0;
383 if (of->vm_ops->page_mkwrite)
384 ret = of->vm_ops->page_mkwrite(vmf);
385 else
386 file_update_time(file);
387
388 kernfs_put_active(of->kn);
389 return ret;
390}
391
392static int kernfs_vma_access(struct vm_area_struct *vma, unsigned long addr,
393 void *buf, int len, int write)
394{
395 struct file *file = vma->vm_file;
396 struct kernfs_open_file *of = kernfs_of(file);
397 int ret;
398
399 if (!of->vm_ops)
400 return -EINVAL;
401
402 if (!kernfs_get_active(of->kn))
403 return -EINVAL;
404
405 ret = -EINVAL;
406 if (of->vm_ops->access)
407 ret = of->vm_ops->access(vma, addr, buf, len, write);
408
409 kernfs_put_active(of->kn);
410 return ret;
411}
412
413#ifdef CONFIG_NUMA
414static int kernfs_vma_set_policy(struct vm_area_struct *vma,
415 struct mempolicy *new)
416{
417 struct file *file = vma->vm_file;
418 struct kernfs_open_file *of = kernfs_of(file);
419 int ret;
420
421 if (!of->vm_ops)
422 return 0;
423
424 if (!kernfs_get_active(of->kn))
425 return -EINVAL;
426
427 ret = 0;
428 if (of->vm_ops->set_policy)
429 ret = of->vm_ops->set_policy(vma, new);
430
431 kernfs_put_active(of->kn);
432 return ret;
433}
434
435static struct mempolicy *kernfs_vma_get_policy(struct vm_area_struct *vma,
436 unsigned long addr)
437{
438 struct file *file = vma->vm_file;
439 struct kernfs_open_file *of = kernfs_of(file);
440 struct mempolicy *pol;
441
442 if (!of->vm_ops)
443 return vma->vm_policy;
444
445 if (!kernfs_get_active(of->kn))
446 return vma->vm_policy;
447
448 pol = vma->vm_policy;
449 if (of->vm_ops->get_policy)
450 pol = of->vm_ops->get_policy(vma, addr);
451
452 kernfs_put_active(of->kn);
453 return pol;
454}
455
456#endif
457
458static const struct vm_operations_struct kernfs_vm_ops = {
459 .open = kernfs_vma_open,
460 .fault = kernfs_vma_fault,
461 .page_mkwrite = kernfs_vma_page_mkwrite,
462 .access = kernfs_vma_access,
463#ifdef CONFIG_NUMA
464 .set_policy = kernfs_vma_set_policy,
465 .get_policy = kernfs_vma_get_policy,
466#endif
467};
468
469static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
470{
471 struct kernfs_open_file *of = kernfs_of(file);
472 const struct kernfs_ops *ops;
473 int rc;
474
475 /*
476 * mmap path and of->mutex are prone to triggering spurious lockdep
477 * warnings and we don't want to add spurious locking dependency
478 * between the two. Check whether mmap is actually implemented
479 * without grabbing @of->mutex by testing HAS_MMAP flag. See the
480 * comment in kernfs_file_open() for more details.
481 */
482 if (!(of->kn->flags & KERNFS_HAS_MMAP))
483 return -ENODEV;
484
485 mutex_lock(&of->mutex);
486
487 rc = -ENODEV;
488 if (!kernfs_get_active(of->kn))
489 goto out_unlock;
490
491 ops = kernfs_ops(of->kn);
492 rc = ops->mmap(of, vma);
493 if (rc)
494 goto out_put;
495
496 /*
497 * PowerPC's pci_mmap of legacy_mem uses shmem_zero_setup()
498 * to satisfy versions of X which crash if the mmap fails: that
499 * substitutes a new vm_file, and we don't then want bin_vm_ops.
500 */
501 if (vma->vm_file != file)
502 goto out_put;
503
504 rc = -EINVAL;
505 if (of->mmapped && of->vm_ops != vma->vm_ops)
506 goto out_put;
507
508 /*
509 * It is not possible to successfully wrap close.
510 * So error if someone is trying to use close.
511 */
512 rc = -EINVAL;
513 if (vma->vm_ops && vma->vm_ops->close)
514 goto out_put;
515
516 rc = 0;
517 of->mmapped = true;
518 of->vm_ops = vma->vm_ops;
519 vma->vm_ops = &kernfs_vm_ops;
520out_put:
521 kernfs_put_active(of->kn);
522out_unlock:
523 mutex_unlock(&of->mutex);
524
525 return rc;
526}
527
528/**
529 * kernfs_get_open_node - get or create kernfs_open_node
530 * @kn: target kernfs_node
531 * @of: kernfs_open_file for this instance of open
532 *
533 * If @kn->attr.open exists, increment its reference count; otherwise,
534 * create one. @of is chained to the files list.
535 *
536 * LOCKING:
537 * Kernel thread context (may sleep).
538 *
539 * RETURNS:
540 * 0 on success, -errno on failure.
541 */
542static int kernfs_get_open_node(struct kernfs_node *kn,
543 struct kernfs_open_file *of)
544{
545 struct kernfs_open_node *on, *new_on = NULL;
546
547 retry:
548 mutex_lock(&kernfs_open_file_mutex);
549 spin_lock_irq(&kernfs_open_node_lock);
550
551 if (!kn->attr.open && new_on) {
552 kn->attr.open = new_on;
553 new_on = NULL;
554 }
555
556 on = kn->attr.open;
557 if (on) {
558 atomic_inc(&on->refcnt);
559 list_add_tail(&of->list, &on->files);
560 }
561
562 spin_unlock_irq(&kernfs_open_node_lock);
563 mutex_unlock(&kernfs_open_file_mutex);
564
565 if (on) {
566 kfree(new_on);
567 return 0;
568 }
569
570 /* not there, initialize a new one and retry */
571 new_on = kmalloc(sizeof(*new_on), GFP_KERNEL);
572 if (!new_on)
573 return -ENOMEM;
574
575 atomic_set(&new_on->refcnt, 0);
576 atomic_set(&new_on->event, 1);
577 init_waitqueue_head(&new_on->poll);
578 INIT_LIST_HEAD(&new_on->files);
579 goto retry;
580}
581
582/**
583 * kernfs_put_open_node - put kernfs_open_node
584 * @kn: target kernfs_nodet
585 * @of: associated kernfs_open_file
586 *
587 * Put @kn->attr.open and unlink @of from the files list. If
588 * reference count reaches zero, disassociate and free it.
589 *
590 * LOCKING:
591 * None.
592 */
593static void kernfs_put_open_node(struct kernfs_node *kn,
594 struct kernfs_open_file *of)
595{
596 struct kernfs_open_node *on = kn->attr.open;
597 unsigned long flags;
598
599 mutex_lock(&kernfs_open_file_mutex);
600 spin_lock_irqsave(&kernfs_open_node_lock, flags);
601
602 if (of)
603 list_del(&of->list);
604
605 if (atomic_dec_and_test(&on->refcnt))
606 kn->attr.open = NULL;
607 else
608 on = NULL;
609
610 spin_unlock_irqrestore(&kernfs_open_node_lock, flags);
611 mutex_unlock(&kernfs_open_file_mutex);
612
613 kfree(on);
614}
615
616static int kernfs_fop_open(struct inode *inode, struct file *file)
617{
618 struct kernfs_node *kn = inode->i_private;
619 struct kernfs_root *root = kernfs_root(kn);
620 const struct kernfs_ops *ops;
621 struct kernfs_open_file *of;
622 bool has_read, has_write, has_mmap;
623 int error = -EACCES;
624
625 if (!kernfs_get_active(kn))
626 return -ENODEV;
627
628 ops = kernfs_ops(kn);
629
630 has_read = ops->seq_show || ops->read || ops->mmap;
631 has_write = ops->write || ops->mmap;
632 has_mmap = ops->mmap;
633
634 /* see the flag definition for details */
635 if (root->flags & KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK) {
636 if ((file->f_mode & FMODE_WRITE) &&
637 (!(inode->i_mode & S_IWUGO) || !has_write))
638 goto err_out;
639
640 if ((file->f_mode & FMODE_READ) &&
641 (!(inode->i_mode & S_IRUGO) || !has_read))
642 goto err_out;
643 }
644
645 /* allocate a kernfs_open_file for the file */
646 error = -ENOMEM;
647 of = kzalloc(sizeof(struct kernfs_open_file), GFP_KERNEL);
648 if (!of)
649 goto err_out;
650
651 /*
652 * The following is done to give a different lockdep key to
653 * @of->mutex for files which implement mmap. This is a rather
654 * crude way to avoid false positive lockdep warning around
655 * mm->mmap_sem - mmap nests @of->mutex under mm->mmap_sem and
656 * reading /sys/block/sda/trace/act_mask grabs sr_mutex, under
657 * which mm->mmap_sem nests, while holding @of->mutex. As each
658 * open file has a separate mutex, it's okay as long as those don't
659 * happen on the same file. At this point, we can't easily give
660 * each file a separate locking class. Let's differentiate on
661 * whether the file has mmap or not for now.
662 *
663 * Both paths of the branch look the same. They're supposed to
664 * look that way and give @of->mutex different static lockdep keys.
665 */
666 if (has_mmap)
667 mutex_init(&of->mutex);
668 else
669 mutex_init(&of->mutex);
670
671 of->kn = kn;
672 of->file = file;
673
674 /*
675 * Write path needs to atomic_write_len outside active reference.
676 * Cache it in open_file. See kernfs_fop_write() for details.
677 */
678 of->atomic_write_len = ops->atomic_write_len;
679
680 error = -EINVAL;
681 /*
682 * ->seq_show is incompatible with ->prealloc,
683 * as seq_read does its own allocation.
684 * ->read must be used instead.
685 */
686 if (ops->prealloc && ops->seq_show)
687 goto err_free;
688 if (ops->prealloc) {
689 int len = of->atomic_write_len ?: PAGE_SIZE;
690 of->prealloc_buf = kmalloc(len + 1, GFP_KERNEL);
691 error = -ENOMEM;
692 if (!of->prealloc_buf)
693 goto err_free;
694 mutex_init(&of->prealloc_mutex);
695 }
696
697 /*
698 * Always instantiate seq_file even if read access doesn't use
699 * seq_file or is not requested. This unifies private data access
700 * and readable regular files are the vast majority anyway.
701 */
702 if (ops->seq_show)
703 error = seq_open(file, &kernfs_seq_ops);
704 else
705 error = seq_open(file, NULL);
706 if (error)
707 goto err_free;
708
709 of->seq_file = file->private_data;
710 of->seq_file->private = of;
711
712 /* seq_file clears PWRITE unconditionally, restore it if WRITE */
713 if (file->f_mode & FMODE_WRITE)
714 file->f_mode |= FMODE_PWRITE;
715
716 /* make sure we have open node struct */
717 error = kernfs_get_open_node(kn, of);
718 if (error)
719 goto err_seq_release;
720
721 if (ops->open) {
722 /* nobody has access to @of yet, skip @of->mutex */
723 error = ops->open(of);
724 if (error)
725 goto err_put_node;
726 }
727
728 /* open succeeded, put active references */
729 kernfs_put_active(kn);
730 return 0;
731
732err_put_node:
733 kernfs_put_open_node(kn, of);
734err_seq_release:
735 seq_release(inode, file);
736err_free:
737 kfree(of->prealloc_buf);
738 kfree(of);
739err_out:
740 kernfs_put_active(kn);
741 return error;
742}
743
744/* used from release/drain to ensure that ->release() is called exactly once */
745static void kernfs_release_file(struct kernfs_node *kn,
746 struct kernfs_open_file *of)
747{
748 /*
749 * @of is guaranteed to have no other file operations in flight and
750 * we just want to synchronize release and drain paths.
751 * @kernfs_open_file_mutex is enough. @of->mutex can't be used
752 * here because drain path may be called from places which can
753 * cause circular dependency.
754 */
755 lockdep_assert_held(&kernfs_open_file_mutex);
756
757 if (!of->released) {
758 /*
759 * A file is never detached without being released and we
760 * need to be able to release files which are deactivated
761 * and being drained. Don't use kernfs_ops().
762 */
763 kn->attr.ops->release(of);
764 of->released = true;
765 }
766}
767
768static int kernfs_fop_release(struct inode *inode, struct file *filp)
769{
770 struct kernfs_node *kn = inode->i_private;
771 struct kernfs_open_file *of = kernfs_of(filp);
772
773 if (kn->flags & KERNFS_HAS_RELEASE) {
774 mutex_lock(&kernfs_open_file_mutex);
775 kernfs_release_file(kn, of);
776 mutex_unlock(&kernfs_open_file_mutex);
777 }
778
779 kernfs_put_open_node(kn, of);
780 seq_release(inode, filp);
781 kfree(of->prealloc_buf);
782 kfree(of);
783
784 return 0;
785}
786
787void kernfs_drain_open_files(struct kernfs_node *kn)
788{
789 struct kernfs_open_node *on;
790 struct kernfs_open_file *of;
791
792 if (!(kn->flags & (KERNFS_HAS_MMAP | KERNFS_HAS_RELEASE)))
793 return;
794
795 spin_lock_irq(&kernfs_open_node_lock);
796 on = kn->attr.open;
797 if (on)
798 atomic_inc(&on->refcnt);
799 spin_unlock_irq(&kernfs_open_node_lock);
800 if (!on)
801 return;
802
803 mutex_lock(&kernfs_open_file_mutex);
804
805 list_for_each_entry(of, &on->files, list) {
806 struct inode *inode = file_inode(of->file);
807
808 if (kn->flags & KERNFS_HAS_MMAP)
809 unmap_mapping_range(inode->i_mapping, 0, 0, 1);
810
811 if (kn->flags & KERNFS_HAS_RELEASE)
812 kernfs_release_file(kn, of);
813 }
814
815 mutex_unlock(&kernfs_open_file_mutex);
816
817 kernfs_put_open_node(kn, NULL);
818}
819
820/*
821 * Kernfs attribute files are pollable. The idea is that you read
822 * the content and then you use 'poll' or 'select' to wait for
823 * the content to change. When the content changes (assuming the
824 * manager for the kobject supports notification), poll will
825 * return EPOLLERR|EPOLLPRI, and select will return the fd whether
826 * it is waiting for read, write, or exceptions.
827 * Once poll/select indicates that the value has changed, you
828 * need to close and re-open the file, or seek to 0 and read again.
829 * Reminder: this only works for attributes which actively support
830 * it, and it is not possible to test an attribute from userspace
831 * to see if it supports poll (Neither 'poll' nor 'select' return
832 * an appropriate error code). When in doubt, set a suitable timeout value.
833 */
834__poll_t kernfs_generic_poll(struct kernfs_open_file *of, poll_table *wait)
835{
836 struct kernfs_node *kn = kernfs_dentry_node(of->file->f_path.dentry);
837 struct kernfs_open_node *on = kn->attr.open;
838
839 poll_wait(of->file, &on->poll, wait);
840
841 if (of->event != atomic_read(&on->event))
842 return DEFAULT_POLLMASK|EPOLLERR|EPOLLPRI;
843
844 return DEFAULT_POLLMASK;
845}
846
847static __poll_t kernfs_fop_poll(struct file *filp, poll_table *wait)
848{
849 struct kernfs_open_file *of = kernfs_of(filp);
850 struct kernfs_node *kn = kernfs_dentry_node(filp->f_path.dentry);
851 __poll_t ret;
852
853 if (!kernfs_get_active(kn))
854 return DEFAULT_POLLMASK|EPOLLERR|EPOLLPRI;
855
856 if (kn->attr.ops->poll)
857 ret = kn->attr.ops->poll(of, wait);
858 else
859 ret = kernfs_generic_poll(of, wait);
860
861 kernfs_put_active(kn);
862 return ret;
863}
864
865static void kernfs_notify_workfn(struct work_struct *work)
866{
867 struct kernfs_node *kn;
868 struct kernfs_super_info *info;
869repeat:
870 /* pop one off the notify_list */
871 spin_lock_irq(&kernfs_notify_lock);
872 kn = kernfs_notify_list;
873 if (kn == KERNFS_NOTIFY_EOL) {
874 spin_unlock_irq(&kernfs_notify_lock);
875 return;
876 }
877 kernfs_notify_list = kn->attr.notify_next;
878 kn->attr.notify_next = NULL;
879 spin_unlock_irq(&kernfs_notify_lock);
880
881 /* kick fsnotify */
882 mutex_lock(&kernfs_mutex);
883
884 list_for_each_entry(info, &kernfs_root(kn)->supers, node) {
885 struct kernfs_node *parent;
886 struct inode *inode;
887 struct qstr name;
888
889 /*
890 * We want fsnotify_modify() on @kn but as the
891 * modifications aren't originating from userland don't
892 * have the matching @file available. Look up the inodes
893 * and generate the events manually.
894 */
895 inode = ilookup(info->sb, kn->id.ino);
896 if (!inode)
897 continue;
898
899 name = (struct qstr)QSTR_INIT(kn->name, strlen(kn->name));
900 parent = kernfs_get_parent(kn);
901 if (parent) {
902 struct inode *p_inode;
903
904 p_inode = ilookup(info->sb, parent->id.ino);
905 if (p_inode) {
906 fsnotify(p_inode, FS_MODIFY | FS_EVENT_ON_CHILD,
907 inode, FSNOTIFY_EVENT_INODE, &name, 0);
908 iput(p_inode);
909 }
910
911 kernfs_put(parent);
912 }
913
914 fsnotify(inode, FS_MODIFY, inode, FSNOTIFY_EVENT_INODE,
915 &name, 0);
916 iput(inode);
917 }
918
919 mutex_unlock(&kernfs_mutex);
920 kernfs_put(kn);
921 goto repeat;
922}
923
924/**
925 * kernfs_notify - notify a kernfs file
926 * @kn: file to notify
927 *
928 * Notify @kn such that poll(2) on @kn wakes up. Maybe be called from any
929 * context.
930 */
931void kernfs_notify(struct kernfs_node *kn)
932{
933 static DECLARE_WORK(kernfs_notify_work, kernfs_notify_workfn);
934 unsigned long flags;
935 struct kernfs_open_node *on;
936
937 if (WARN_ON(kernfs_type(kn) != KERNFS_FILE))
938 return;
939
940 /* kick poll immediately */
941 spin_lock_irqsave(&kernfs_open_node_lock, flags);
942 on = kn->attr.open;
943 if (on) {
944 atomic_inc(&on->event);
945 wake_up_interruptible(&on->poll);
946 }
947 spin_unlock_irqrestore(&kernfs_open_node_lock, flags);
948
949 /* schedule work to kick fsnotify */
950 spin_lock_irqsave(&kernfs_notify_lock, flags);
951 if (!kn->attr.notify_next) {
952 kernfs_get(kn);
953 kn->attr.notify_next = kernfs_notify_list;
954 kernfs_notify_list = kn;
955 schedule_work(&kernfs_notify_work);
956 }
957 spin_unlock_irqrestore(&kernfs_notify_lock, flags);
958}
959EXPORT_SYMBOL_GPL(kernfs_notify);
960
961const struct file_operations kernfs_file_fops = {
962 .read = kernfs_fop_read,
963 .write = kernfs_fop_write,
964 .llseek = generic_file_llseek,
965 .mmap = kernfs_fop_mmap,
966 .open = kernfs_fop_open,
967 .release = kernfs_fop_release,
968 .poll = kernfs_fop_poll,
969 .fsync = noop_fsync,
970};
971
972/**
973 * __kernfs_create_file - kernfs internal function to create a file
974 * @parent: directory to create the file in
975 * @name: name of the file
976 * @mode: mode of the file
977 * @uid: uid of the file
978 * @gid: gid of the file
979 * @size: size of the file
980 * @ops: kernfs operations for the file
981 * @priv: private data for the file
982 * @ns: optional namespace tag of the file
983 * @key: lockdep key for the file's active_ref, %NULL to disable lockdep
984 *
985 * Returns the created node on success, ERR_PTR() value on error.
986 */
987struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
988 const char *name,
989 umode_t mode, kuid_t uid, kgid_t gid,
990 loff_t size,
991 const struct kernfs_ops *ops,
992 void *priv, const void *ns,
993 struct lock_class_key *key)
994{
995 struct kernfs_node *kn;
996 unsigned flags;
997 int rc;
998
999 flags = KERNFS_FILE;
1000
1001 kn = kernfs_new_node(parent, name, (mode & S_IALLUGO) | S_IFREG,
1002 uid, gid, flags);
1003 if (!kn)
1004 return ERR_PTR(-ENOMEM);
1005
1006 kn->attr.ops = ops;
1007 kn->attr.size = size;
1008 kn->ns = ns;
1009 kn->priv = priv;
1010
1011#ifdef CONFIG_DEBUG_LOCK_ALLOC
1012 if (key) {
1013 lockdep_init_map(&kn->dep_map, "kn->count", key, 0);
1014 kn->flags |= KERNFS_LOCKDEP;
1015 }
1016#endif
1017
1018 /*
1019 * kn->attr.ops is accesible only while holding active ref. We
1020 * need to know whether some ops are implemented outside active
1021 * ref. Cache their existence in flags.
1022 */
1023 if (ops->seq_show)
1024 kn->flags |= KERNFS_HAS_SEQ_SHOW;
1025 if (ops->mmap)
1026 kn->flags |= KERNFS_HAS_MMAP;
1027 if (ops->release)
1028 kn->flags |= KERNFS_HAS_RELEASE;
1029
1030 rc = kernfs_add_one(kn);
1031 if (rc) {
1032 kernfs_put(kn);
1033 return ERR_PTR(rc);
1034 }
1035 return kn;
1036}
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
18#include "kernfs-internal.h"
19
20/*
21 * There's one kernfs_open_file for each open file and one kernfs_open_node
22 * for each kernfs_node with one or more open files.
23 *
24 * kernfs_node->attr.open points to kernfs_open_node. attr.open is
25 * protected by kernfs_open_node_lock.
26 *
27 * filp->private_data points to seq_file whose ->private points to
28 * kernfs_open_file. kernfs_open_files are chained at
29 * kernfs_open_node->files, which is protected by kernfs_open_file_mutex.
30 */
31static DEFINE_SPINLOCK(kernfs_open_node_lock);
32static DEFINE_MUTEX(kernfs_open_file_mutex);
33
34struct kernfs_open_node {
35 atomic_t refcnt;
36 atomic_t event;
37 wait_queue_head_t poll;
38 struct list_head files; /* goes through kernfs_open_file.list */
39};
40
41static struct kernfs_open_file *kernfs_of(struct file *file)
42{
43 return ((struct seq_file *)file->private_data)->private;
44}
45
46/*
47 * Determine the kernfs_ops for the given kernfs_node. This function must
48 * be called while holding an active reference.
49 */
50static const struct kernfs_ops *kernfs_ops(struct kernfs_node *kn)
51{
52 if (kn->flags & KERNFS_LOCKDEP)
53 lockdep_assert_held(kn);
54 return kn->attr.ops;
55}
56
57/*
58 * As kernfs_seq_stop() is also called after kernfs_seq_start() or
59 * kernfs_seq_next() failure, it needs to distinguish whether it's stopping
60 * a seq_file iteration which is fully initialized with an active reference
61 * or an aborted kernfs_seq_start() due to get_active failure. The
62 * position pointer is the only context for each seq_file iteration and
63 * thus the stop condition should be encoded in it. As the return value is
64 * directly visible to userland, ERR_PTR(-ENODEV) is the only acceptable
65 * choice to indicate get_active failure.
66 *
67 * Unfortunately, this is complicated due to the optional custom seq_file
68 * operations which may return ERR_PTR(-ENODEV) too. kernfs_seq_stop()
69 * can't distinguish whether ERR_PTR(-ENODEV) is from get_active failure or
70 * custom seq_file operations and thus can't decide whether put_active
71 * should be performed or not only on ERR_PTR(-ENODEV).
72 *
73 * This is worked around by factoring out the custom seq_stop() and
74 * put_active part into kernfs_seq_stop_active(), skipping it from
75 * kernfs_seq_stop() if ERR_PTR(-ENODEV) while invoking it directly after
76 * custom seq_file operations fail with ERR_PTR(-ENODEV) - this ensures
77 * that kernfs_seq_stop_active() is skipped only after get_active failure.
78 */
79static void kernfs_seq_stop_active(struct seq_file *sf, void *v)
80{
81 struct kernfs_open_file *of = sf->private;
82 const struct kernfs_ops *ops = kernfs_ops(of->kn);
83
84 if (ops->seq_stop)
85 ops->seq_stop(sf, v);
86 kernfs_put_active(of->kn);
87}
88
89static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
90{
91 struct kernfs_open_file *of = sf->private;
92 const struct kernfs_ops *ops;
93
94 /*
95 * @of->mutex nests outside active ref and is just to ensure that
96 * the ops aren't called concurrently for the same open file.
97 */
98 mutex_lock(&of->mutex);
99 if (!kernfs_get_active(of->kn))
100 return ERR_PTR(-ENODEV);
101
102 ops = kernfs_ops(of->kn);
103 if (ops->seq_start) {
104 void *next = ops->seq_start(sf, ppos);
105 /* see the comment above kernfs_seq_stop_active() */
106 if (next == ERR_PTR(-ENODEV))
107 kernfs_seq_stop_active(sf, next);
108 return next;
109 } else {
110 /*
111 * The same behavior and code as single_open(). Returns
112 * !NULL if pos is at the beginning; otherwise, NULL.
113 */
114 return NULL + !*ppos;
115 }
116}
117
118static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos)
119{
120 struct kernfs_open_file *of = sf->private;
121 const struct kernfs_ops *ops = kernfs_ops(of->kn);
122
123 if (ops->seq_next) {
124 void *next = ops->seq_next(sf, v, ppos);
125 /* see the comment above kernfs_seq_stop_active() */
126 if (next == ERR_PTR(-ENODEV))
127 kernfs_seq_stop_active(sf, next);
128 return next;
129 } else {
130 /*
131 * The same behavior and code as single_open(), always
132 * terminate after the initial read.
133 */
134 ++*ppos;
135 return NULL;
136 }
137}
138
139static void kernfs_seq_stop(struct seq_file *sf, void *v)
140{
141 struct kernfs_open_file *of = sf->private;
142
143 if (v != ERR_PTR(-ENODEV))
144 kernfs_seq_stop_active(sf, v);
145 mutex_unlock(&of->mutex);
146}
147
148static int kernfs_seq_show(struct seq_file *sf, void *v)
149{
150 struct kernfs_open_file *of = sf->private;
151
152 of->event = atomic_read(&of->kn->attr.open->event);
153
154 return of->kn->attr.ops->seq_show(sf, v);
155}
156
157static const struct seq_operations kernfs_seq_ops = {
158 .start = kernfs_seq_start,
159 .next = kernfs_seq_next,
160 .stop = kernfs_seq_stop,
161 .show = kernfs_seq_show,
162};
163
164/*
165 * As reading a bin file can have side-effects, the exact offset and bytes
166 * specified in read(2) call should be passed to the read callback making
167 * it difficult to use seq_file. Implement simplistic custom buffering for
168 * bin files.
169 */
170static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
171 char __user *user_buf, size_t count,
172 loff_t *ppos)
173{
174 ssize_t len = min_t(size_t, count, PAGE_SIZE);
175 const struct kernfs_ops *ops;
176 char *buf;
177
178 buf = kmalloc(len, GFP_KERNEL);
179 if (!buf)
180 return -ENOMEM;
181
182 /*
183 * @of->mutex nests outside active ref and is just to ensure that
184 * the ops aren't called concurrently for the same open file.
185 */
186 mutex_lock(&of->mutex);
187 if (!kernfs_get_active(of->kn)) {
188 len = -ENODEV;
189 mutex_unlock(&of->mutex);
190 goto out_free;
191 }
192
193 ops = kernfs_ops(of->kn);
194 if (ops->read)
195 len = ops->read(of, buf, len, *ppos);
196 else
197 len = -EINVAL;
198
199 kernfs_put_active(of->kn);
200 mutex_unlock(&of->mutex);
201
202 if (len < 0)
203 goto out_free;
204
205 if (copy_to_user(user_buf, buf, len)) {
206 len = -EFAULT;
207 goto out_free;
208 }
209
210 *ppos += len;
211
212 out_free:
213 kfree(buf);
214 return len;
215}
216
217/**
218 * kernfs_fop_read - kernfs vfs read callback
219 * @file: file pointer
220 * @user_buf: data to write
221 * @count: number of bytes
222 * @ppos: starting offset
223 */
224static ssize_t kernfs_fop_read(struct file *file, char __user *user_buf,
225 size_t count, loff_t *ppos)
226{
227 struct kernfs_open_file *of = kernfs_of(file);
228
229 if (of->kn->flags & KERNFS_HAS_SEQ_SHOW)
230 return seq_read(file, user_buf, count, ppos);
231 else
232 return kernfs_file_direct_read(of, user_buf, count, ppos);
233}
234
235/**
236 * kernfs_fop_write - kernfs vfs write callback
237 * @file: file pointer
238 * @user_buf: data to write
239 * @count: number of bytes
240 * @ppos: starting offset
241 *
242 * Copy data in from userland and pass it to the matching kernfs write
243 * operation.
244 *
245 * There is no easy way for us to know if userspace is only doing a partial
246 * write, so we don't support them. We expect the entire buffer to come on
247 * the first write. Hint: if you're writing a value, first read the file,
248 * modify only the the value you're changing, then write entire buffer
249 * back.
250 */
251static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
252 size_t count, loff_t *ppos)
253{
254 struct kernfs_open_file *of = kernfs_of(file);
255 const struct kernfs_ops *ops;
256 size_t len;
257 char *buf;
258
259 if (of->atomic_write_len) {
260 len = count;
261 if (len > of->atomic_write_len)
262 return -E2BIG;
263 } else {
264 len = min_t(size_t, count, PAGE_SIZE);
265 }
266
267 buf = kmalloc(len + 1, GFP_KERNEL);
268 if (!buf)
269 return -ENOMEM;
270
271 if (copy_from_user(buf, user_buf, len)) {
272 len = -EFAULT;
273 goto out_free;
274 }
275 buf[len] = '\0'; /* guarantee string termination */
276
277 /*
278 * @of->mutex nests outside active ref and is just to ensure that
279 * the ops aren't called concurrently for the same open file.
280 */
281 mutex_lock(&of->mutex);
282 if (!kernfs_get_active(of->kn)) {
283 mutex_unlock(&of->mutex);
284 len = -ENODEV;
285 goto out_free;
286 }
287
288 ops = kernfs_ops(of->kn);
289 if (ops->write)
290 len = ops->write(of, buf, len, *ppos);
291 else
292 len = -EINVAL;
293
294 kernfs_put_active(of->kn);
295 mutex_unlock(&of->mutex);
296
297 if (len > 0)
298 *ppos += len;
299out_free:
300 kfree(buf);
301 return len;
302}
303
304static void kernfs_vma_open(struct vm_area_struct *vma)
305{
306 struct file *file = vma->vm_file;
307 struct kernfs_open_file *of = kernfs_of(file);
308
309 if (!of->vm_ops)
310 return;
311
312 if (!kernfs_get_active(of->kn))
313 return;
314
315 if (of->vm_ops->open)
316 of->vm_ops->open(vma);
317
318 kernfs_put_active(of->kn);
319}
320
321static int kernfs_vma_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
322{
323 struct file *file = vma->vm_file;
324 struct kernfs_open_file *of = kernfs_of(file);
325 int ret;
326
327 if (!of->vm_ops)
328 return VM_FAULT_SIGBUS;
329
330 if (!kernfs_get_active(of->kn))
331 return VM_FAULT_SIGBUS;
332
333 ret = VM_FAULT_SIGBUS;
334 if (of->vm_ops->fault)
335 ret = of->vm_ops->fault(vma, vmf);
336
337 kernfs_put_active(of->kn);
338 return ret;
339}
340
341static int kernfs_vma_page_mkwrite(struct vm_area_struct *vma,
342 struct vm_fault *vmf)
343{
344 struct file *file = vma->vm_file;
345 struct kernfs_open_file *of = kernfs_of(file);
346 int ret;
347
348 if (!of->vm_ops)
349 return VM_FAULT_SIGBUS;
350
351 if (!kernfs_get_active(of->kn))
352 return VM_FAULT_SIGBUS;
353
354 ret = 0;
355 if (of->vm_ops->page_mkwrite)
356 ret = of->vm_ops->page_mkwrite(vma, vmf);
357 else
358 file_update_time(file);
359
360 kernfs_put_active(of->kn);
361 return ret;
362}
363
364static int kernfs_vma_access(struct vm_area_struct *vma, unsigned long addr,
365 void *buf, int len, int write)
366{
367 struct file *file = vma->vm_file;
368 struct kernfs_open_file *of = kernfs_of(file);
369 int ret;
370
371 if (!of->vm_ops)
372 return -EINVAL;
373
374 if (!kernfs_get_active(of->kn))
375 return -EINVAL;
376
377 ret = -EINVAL;
378 if (of->vm_ops->access)
379 ret = of->vm_ops->access(vma, addr, buf, len, write);
380
381 kernfs_put_active(of->kn);
382 return ret;
383}
384
385#ifdef CONFIG_NUMA
386static int kernfs_vma_set_policy(struct vm_area_struct *vma,
387 struct mempolicy *new)
388{
389 struct file *file = vma->vm_file;
390 struct kernfs_open_file *of = kernfs_of(file);
391 int ret;
392
393 if (!of->vm_ops)
394 return 0;
395
396 if (!kernfs_get_active(of->kn))
397 return -EINVAL;
398
399 ret = 0;
400 if (of->vm_ops->set_policy)
401 ret = of->vm_ops->set_policy(vma, new);
402
403 kernfs_put_active(of->kn);
404 return ret;
405}
406
407static struct mempolicy *kernfs_vma_get_policy(struct vm_area_struct *vma,
408 unsigned long addr)
409{
410 struct file *file = vma->vm_file;
411 struct kernfs_open_file *of = kernfs_of(file);
412 struct mempolicy *pol;
413
414 if (!of->vm_ops)
415 return vma->vm_policy;
416
417 if (!kernfs_get_active(of->kn))
418 return vma->vm_policy;
419
420 pol = vma->vm_policy;
421 if (of->vm_ops->get_policy)
422 pol = of->vm_ops->get_policy(vma, addr);
423
424 kernfs_put_active(of->kn);
425 return pol;
426}
427
428static int kernfs_vma_migrate(struct vm_area_struct *vma,
429 const nodemask_t *from, const nodemask_t *to,
430 unsigned long flags)
431{
432 struct file *file = vma->vm_file;
433 struct kernfs_open_file *of = kernfs_of(file);
434 int ret;
435
436 if (!of->vm_ops)
437 return 0;
438
439 if (!kernfs_get_active(of->kn))
440 return 0;
441
442 ret = 0;
443 if (of->vm_ops->migrate)
444 ret = of->vm_ops->migrate(vma, from, to, flags);
445
446 kernfs_put_active(of->kn);
447 return ret;
448}
449#endif
450
451static const struct vm_operations_struct kernfs_vm_ops = {
452 .open = kernfs_vma_open,
453 .fault = kernfs_vma_fault,
454 .page_mkwrite = kernfs_vma_page_mkwrite,
455 .access = kernfs_vma_access,
456#ifdef CONFIG_NUMA
457 .set_policy = kernfs_vma_set_policy,
458 .get_policy = kernfs_vma_get_policy,
459 .migrate = kernfs_vma_migrate,
460#endif
461};
462
463static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
464{
465 struct kernfs_open_file *of = kernfs_of(file);
466 const struct kernfs_ops *ops;
467 int rc;
468
469 /*
470 * mmap path and of->mutex are prone to triggering spurious lockdep
471 * warnings and we don't want to add spurious locking dependency
472 * between the two. Check whether mmap is actually implemented
473 * without grabbing @of->mutex by testing HAS_MMAP flag. See the
474 * comment in kernfs_file_open() for more details.
475 */
476 if (!(of->kn->flags & KERNFS_HAS_MMAP))
477 return -ENODEV;
478
479 mutex_lock(&of->mutex);
480
481 rc = -ENODEV;
482 if (!kernfs_get_active(of->kn))
483 goto out_unlock;
484
485 ops = kernfs_ops(of->kn);
486 rc = ops->mmap(of, vma);
487 if (rc)
488 goto out_put;
489
490 /*
491 * PowerPC's pci_mmap of legacy_mem uses shmem_zero_setup()
492 * to satisfy versions of X which crash if the mmap fails: that
493 * substitutes a new vm_file, and we don't then want bin_vm_ops.
494 */
495 if (vma->vm_file != file)
496 goto out_put;
497
498 rc = -EINVAL;
499 if (of->mmapped && of->vm_ops != vma->vm_ops)
500 goto out_put;
501
502 /*
503 * It is not possible to successfully wrap close.
504 * So error if someone is trying to use close.
505 */
506 rc = -EINVAL;
507 if (vma->vm_ops && vma->vm_ops->close)
508 goto out_put;
509
510 rc = 0;
511 of->mmapped = 1;
512 of->vm_ops = vma->vm_ops;
513 vma->vm_ops = &kernfs_vm_ops;
514out_put:
515 kernfs_put_active(of->kn);
516out_unlock:
517 mutex_unlock(&of->mutex);
518
519 return rc;
520}
521
522/**
523 * kernfs_get_open_node - get or create kernfs_open_node
524 * @kn: target kernfs_node
525 * @of: kernfs_open_file for this instance of open
526 *
527 * If @kn->attr.open exists, increment its reference count; otherwise,
528 * create one. @of is chained to the files list.
529 *
530 * LOCKING:
531 * Kernel thread context (may sleep).
532 *
533 * RETURNS:
534 * 0 on success, -errno on failure.
535 */
536static int kernfs_get_open_node(struct kernfs_node *kn,
537 struct kernfs_open_file *of)
538{
539 struct kernfs_open_node *on, *new_on = NULL;
540
541 retry:
542 mutex_lock(&kernfs_open_file_mutex);
543 spin_lock_irq(&kernfs_open_node_lock);
544
545 if (!kn->attr.open && new_on) {
546 kn->attr.open = new_on;
547 new_on = NULL;
548 }
549
550 on = kn->attr.open;
551 if (on) {
552 atomic_inc(&on->refcnt);
553 list_add_tail(&of->list, &on->files);
554 }
555
556 spin_unlock_irq(&kernfs_open_node_lock);
557 mutex_unlock(&kernfs_open_file_mutex);
558
559 if (on) {
560 kfree(new_on);
561 return 0;
562 }
563
564 /* not there, initialize a new one and retry */
565 new_on = kmalloc(sizeof(*new_on), GFP_KERNEL);
566 if (!new_on)
567 return -ENOMEM;
568
569 atomic_set(&new_on->refcnt, 0);
570 atomic_set(&new_on->event, 1);
571 init_waitqueue_head(&new_on->poll);
572 INIT_LIST_HEAD(&new_on->files);
573 goto retry;
574}
575
576/**
577 * kernfs_put_open_node - put kernfs_open_node
578 * @kn: target kernfs_nodet
579 * @of: associated kernfs_open_file
580 *
581 * Put @kn->attr.open and unlink @of from the files list. If
582 * reference count reaches zero, disassociate and free it.
583 *
584 * LOCKING:
585 * None.
586 */
587static void kernfs_put_open_node(struct kernfs_node *kn,
588 struct kernfs_open_file *of)
589{
590 struct kernfs_open_node *on = kn->attr.open;
591 unsigned long flags;
592
593 mutex_lock(&kernfs_open_file_mutex);
594 spin_lock_irqsave(&kernfs_open_node_lock, flags);
595
596 if (of)
597 list_del(&of->list);
598
599 if (atomic_dec_and_test(&on->refcnt))
600 kn->attr.open = NULL;
601 else
602 on = NULL;
603
604 spin_unlock_irqrestore(&kernfs_open_node_lock, flags);
605 mutex_unlock(&kernfs_open_file_mutex);
606
607 kfree(on);
608}
609
610static int kernfs_fop_open(struct inode *inode, struct file *file)
611{
612 struct kernfs_node *kn = file->f_path.dentry->d_fsdata;
613 struct kernfs_root *root = kernfs_root(kn);
614 const struct kernfs_ops *ops;
615 struct kernfs_open_file *of;
616 bool has_read, has_write, has_mmap;
617 int error = -EACCES;
618
619 if (!kernfs_get_active(kn))
620 return -ENODEV;
621
622 ops = kernfs_ops(kn);
623
624 has_read = ops->seq_show || ops->read || ops->mmap;
625 has_write = ops->write || ops->mmap;
626 has_mmap = ops->mmap;
627
628 /* see the flag definition for details */
629 if (root->flags & KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK) {
630 if ((file->f_mode & FMODE_WRITE) &&
631 (!(inode->i_mode & S_IWUGO) || !has_write))
632 goto err_out;
633
634 if ((file->f_mode & FMODE_READ) &&
635 (!(inode->i_mode & S_IRUGO) || !has_read))
636 goto err_out;
637 }
638
639 /* allocate a kernfs_open_file for the file */
640 error = -ENOMEM;
641 of = kzalloc(sizeof(struct kernfs_open_file), GFP_KERNEL);
642 if (!of)
643 goto err_out;
644
645 /*
646 * The following is done to give a different lockdep key to
647 * @of->mutex for files which implement mmap. This is a rather
648 * crude way to avoid false positive lockdep warning around
649 * mm->mmap_sem - mmap nests @of->mutex under mm->mmap_sem and
650 * reading /sys/block/sda/trace/act_mask grabs sr_mutex, under
651 * which mm->mmap_sem nests, while holding @of->mutex. As each
652 * open file has a separate mutex, it's okay as long as those don't
653 * happen on the same file. At this point, we can't easily give
654 * each file a separate locking class. Let's differentiate on
655 * whether the file has mmap or not for now.
656 *
657 * Both paths of the branch look the same. They're supposed to
658 * look that way and give @of->mutex different static lockdep keys.
659 */
660 if (has_mmap)
661 mutex_init(&of->mutex);
662 else
663 mutex_init(&of->mutex);
664
665 of->kn = kn;
666 of->file = file;
667
668 /*
669 * Write path needs to atomic_write_len outside active reference.
670 * Cache it in open_file. See kernfs_fop_write() for details.
671 */
672 of->atomic_write_len = ops->atomic_write_len;
673
674 /*
675 * Always instantiate seq_file even if read access doesn't use
676 * seq_file or is not requested. This unifies private data access
677 * and readable regular files are the vast majority anyway.
678 */
679 if (ops->seq_show)
680 error = seq_open(file, &kernfs_seq_ops);
681 else
682 error = seq_open(file, NULL);
683 if (error)
684 goto err_free;
685
686 ((struct seq_file *)file->private_data)->private = of;
687
688 /* seq_file clears PWRITE unconditionally, restore it if WRITE */
689 if (file->f_mode & FMODE_WRITE)
690 file->f_mode |= FMODE_PWRITE;
691
692 /* make sure we have open node struct */
693 error = kernfs_get_open_node(kn, of);
694 if (error)
695 goto err_close;
696
697 /* open succeeded, put active references */
698 kernfs_put_active(kn);
699 return 0;
700
701err_close:
702 seq_release(inode, file);
703err_free:
704 kfree(of);
705err_out:
706 kernfs_put_active(kn);
707 return error;
708}
709
710static int kernfs_fop_release(struct inode *inode, struct file *filp)
711{
712 struct kernfs_node *kn = filp->f_path.dentry->d_fsdata;
713 struct kernfs_open_file *of = kernfs_of(filp);
714
715 kernfs_put_open_node(kn, of);
716 seq_release(inode, filp);
717 kfree(of);
718
719 return 0;
720}
721
722void kernfs_unmap_bin_file(struct kernfs_node *kn)
723{
724 struct kernfs_open_node *on;
725 struct kernfs_open_file *of;
726
727 if (!(kn->flags & KERNFS_HAS_MMAP))
728 return;
729
730 spin_lock_irq(&kernfs_open_node_lock);
731 on = kn->attr.open;
732 if (on)
733 atomic_inc(&on->refcnt);
734 spin_unlock_irq(&kernfs_open_node_lock);
735 if (!on)
736 return;
737
738 mutex_lock(&kernfs_open_file_mutex);
739 list_for_each_entry(of, &on->files, list) {
740 struct inode *inode = file_inode(of->file);
741 unmap_mapping_range(inode->i_mapping, 0, 0, 1);
742 }
743 mutex_unlock(&kernfs_open_file_mutex);
744
745 kernfs_put_open_node(kn, NULL);
746}
747
748/*
749 * Kernfs attribute files are pollable. The idea is that you read
750 * the content and then you use 'poll' or 'select' to wait for
751 * the content to change. When the content changes (assuming the
752 * manager for the kobject supports notification), poll will
753 * return POLLERR|POLLPRI, and select will return the fd whether
754 * it is waiting for read, write, or exceptions.
755 * Once poll/select indicates that the value has changed, you
756 * need to close and re-open the file, or seek to 0 and read again.
757 * Reminder: this only works for attributes which actively support
758 * it, and it is not possible to test an attribute from userspace
759 * to see if it supports poll (Neither 'poll' nor 'select' return
760 * an appropriate error code). When in doubt, set a suitable timeout value.
761 */
762static unsigned int kernfs_fop_poll(struct file *filp, poll_table *wait)
763{
764 struct kernfs_open_file *of = kernfs_of(filp);
765 struct kernfs_node *kn = filp->f_path.dentry->d_fsdata;
766 struct kernfs_open_node *on = kn->attr.open;
767
768 /* need parent for the kobj, grab both */
769 if (!kernfs_get_active(kn))
770 goto trigger;
771
772 poll_wait(filp, &on->poll, wait);
773
774 kernfs_put_active(kn);
775
776 if (of->event != atomic_read(&on->event))
777 goto trigger;
778
779 return DEFAULT_POLLMASK;
780
781 trigger:
782 return DEFAULT_POLLMASK|POLLERR|POLLPRI;
783}
784
785/**
786 * kernfs_notify - notify a kernfs file
787 * @kn: file to notify
788 *
789 * Notify @kn such that poll(2) on @kn wakes up.
790 */
791void kernfs_notify(struct kernfs_node *kn)
792{
793 struct kernfs_open_node *on;
794 unsigned long flags;
795
796 spin_lock_irqsave(&kernfs_open_node_lock, flags);
797
798 if (!WARN_ON(kernfs_type(kn) != KERNFS_FILE)) {
799 on = kn->attr.open;
800 if (on) {
801 atomic_inc(&on->event);
802 wake_up_interruptible(&on->poll);
803 }
804 }
805
806 spin_unlock_irqrestore(&kernfs_open_node_lock, flags);
807}
808EXPORT_SYMBOL_GPL(kernfs_notify);
809
810const struct file_operations kernfs_file_fops = {
811 .read = kernfs_fop_read,
812 .write = kernfs_fop_write,
813 .llseek = generic_file_llseek,
814 .mmap = kernfs_fop_mmap,
815 .open = kernfs_fop_open,
816 .release = kernfs_fop_release,
817 .poll = kernfs_fop_poll,
818};
819
820/**
821 * __kernfs_create_file - kernfs internal function to create a file
822 * @parent: directory to create the file in
823 * @name: name of the file
824 * @mode: mode of the file
825 * @size: size of the file
826 * @ops: kernfs operations for the file
827 * @priv: private data for the file
828 * @ns: optional namespace tag of the file
829 * @static_name: don't copy file name
830 * @key: lockdep key for the file's active_ref, %NULL to disable lockdep
831 *
832 * Returns the created node on success, ERR_PTR() value on error.
833 */
834struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
835 const char *name,
836 umode_t mode, loff_t size,
837 const struct kernfs_ops *ops,
838 void *priv, const void *ns,
839 bool name_is_static,
840 struct lock_class_key *key)
841{
842 struct kernfs_node *kn;
843 unsigned flags;
844 int rc;
845
846 flags = KERNFS_FILE;
847 if (name_is_static)
848 flags |= KERNFS_STATIC_NAME;
849
850 kn = kernfs_new_node(parent, name, (mode & S_IALLUGO) | S_IFREG, flags);
851 if (!kn)
852 return ERR_PTR(-ENOMEM);
853
854 kn->attr.ops = ops;
855 kn->attr.size = size;
856 kn->ns = ns;
857 kn->priv = priv;
858
859#ifdef CONFIG_DEBUG_LOCK_ALLOC
860 if (key) {
861 lockdep_init_map(&kn->dep_map, "s_active", key, 0);
862 kn->flags |= KERNFS_LOCKDEP;
863 }
864#endif
865
866 /*
867 * kn->attr.ops is accesible only while holding active ref. We
868 * need to know whether some ops are implemented outside active
869 * ref. Cache their existence in flags.
870 */
871 if (ops->seq_show)
872 kn->flags |= KERNFS_HAS_SEQ_SHOW;
873 if (ops->mmap)
874 kn->flags |= KERNFS_HAS_MMAP;
875
876 rc = kernfs_add_one(kn);
877 if (rc) {
878 kernfs_put(kn);
879 return ERR_PTR(rc);
880 }
881 return kn;
882}