1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * file.c - operations for regular (text) files.
4 *
5 * Based on sysfs:
6 * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
7 *
8 * configfs Copyright (C) 2005 Oracle.  All rights reserved.
9 */
10
11#include <linux/fs.h>
12#include <linux/module.h>
13#include <linux/slab.h>
14#include <linux/mutex.h>
15#include <linux/vmalloc.h>
16#include <linux/uaccess.h>
17#include <linux/uio.h>
18#include <linux/configfs.h>
19#include "configfs_internal.h"
20
21/*
22 * A simple attribute can only be 4096 characters.  Why 4k?  Because the
23 * original code limited it to PAGE_SIZE.  That's a bad idea, though,
24 * because an attribute of 16k on ia64 won't work on x86.  So we limit to
25 * 4k, our minimum common page size.
26 */
27#define SIMPLE_ATTR_SIZE 4096
28
29struct configfs_buffer {
30	size_t			count;
31	loff_t			pos;
32	char			* page;
33	struct configfs_item_operations	* ops;
34	struct mutex		mutex;
35	int			needs_read_fill;
36	bool			read_in_progress;
37	bool			write_in_progress;
38	char			*bin_buffer;
39	int			bin_buffer_size;
40	int			cb_max_size;
41	struct config_item	*item;
42	struct module		*owner;
43	union {
44		struct configfs_attribute	*attr;
45		struct configfs_bin_attribute	*bin_attr;
46	};
47};
48
49static inline struct configfs_fragment *to_frag(struct file *file)
50{
51	struct configfs_dirent *sd = file->f_path.dentry->d_fsdata;
52
53	return sd->s_frag;
54}
55
56static int fill_read_buffer(struct file *file, struct configfs_buffer *buffer)
57{
58	struct configfs_fragment *frag = to_frag(file);
59	ssize_t count = -ENOENT;
60
61	if (!buffer->page)
62		buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
63	if (!buffer->page)
64		return -ENOMEM;
65
66	down_read(&frag->frag_sem);
67	if (!frag->frag_dead)
68		count = buffer->attr->show(buffer->item, buffer->page);
69	up_read(&frag->frag_sem);
70
71	if (count < 0)
72		return count;
73	if (WARN_ON_ONCE(count > (ssize_t)SIMPLE_ATTR_SIZE))
74		return -EIO;
75	buffer->needs_read_fill = 0;
76	buffer->count = count;
77	return 0;
78}
79
80static ssize_t configfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
81{
82	struct file *file = iocb->ki_filp;
83	struct configfs_buffer *buffer = file->private_data;
84	ssize_t retval = 0;
85
86	mutex_lock(&buffer->mutex);
87	if (buffer->needs_read_fill) {
88		retval = fill_read_buffer(file, buffer);
89		if (retval)
90			goto out;
91	}
92	pr_debug("%s: count = %zd, pos = %lld, buf = %s\n",
93		 __func__, iov_iter_count(to), iocb->ki_pos, buffer->page);
94	if (iocb->ki_pos >= buffer->count)
95		goto out;
96	retval = copy_to_iter(buffer->page + iocb->ki_pos,
97			      buffer->count - iocb->ki_pos, to);
98	iocb->ki_pos += retval;
99	if (retval == 0)
100		retval = -EFAULT;
101out:
102	mutex_unlock(&buffer->mutex);
103	return retval;
104}
105
106static ssize_t configfs_bin_read_iter(struct kiocb *iocb, struct iov_iter *to)
107{
108	struct file *file = iocb->ki_filp;
109	struct configfs_fragment *frag = to_frag(file);
110	struct configfs_buffer *buffer = file->private_data;
111	ssize_t retval = 0;
112	ssize_t len;
113
114	mutex_lock(&buffer->mutex);
115
116	/* we don't support switching read/write modes */
117	if (buffer->write_in_progress) {
118		retval = -ETXTBSY;
119		goto out;
120	}
121	buffer->read_in_progress = true;
122
123	if (buffer->needs_read_fill) {
124		/* perform first read with buf == NULL to get extent */
125		down_read(&frag->frag_sem);
126		if (!frag->frag_dead)
127			len = buffer->bin_attr->read(buffer->item, NULL, 0);
128		else
129			len = -ENOENT;
130		up_read(&frag->frag_sem);
131		if (len <= 0) {
132			retval = len;
133			goto out;
134		}
135
136		/* do not exceed the maximum value */
137		if (buffer->cb_max_size && len > buffer->cb_max_size) {
138			retval = -EFBIG;
139			goto out;
140		}
141
142		buffer->bin_buffer = vmalloc(len);
143		if (buffer->bin_buffer == NULL) {
144			retval = -ENOMEM;
145			goto out;
146		}
147		buffer->bin_buffer_size = len;
148
149		/* perform second read to fill buffer */
150		down_read(&frag->frag_sem);
151		if (!frag->frag_dead)
152			len = buffer->bin_attr->read(buffer->item,
153						     buffer->bin_buffer, len);
154		else
155			len = -ENOENT;
156		up_read(&frag->frag_sem);
157		if (len < 0) {
158			retval = len;
159			vfree(buffer->bin_buffer);
160			buffer->bin_buffer_size = 0;
161			buffer->bin_buffer = NULL;
162			goto out;
163		}
164
165		buffer->needs_read_fill = 0;
166	}
167
168	if (iocb->ki_pos >= buffer->bin_buffer_size)
169		goto out;
170	retval = copy_to_iter(buffer->bin_buffer + iocb->ki_pos,
171			      buffer->bin_buffer_size - iocb->ki_pos, to);
172	iocb->ki_pos += retval;
173	if (retval == 0)
174		retval = -EFAULT;
175out:
176	mutex_unlock(&buffer->mutex);
177	return retval;
178}
179
180/* Fill @buffer with data coming from @from. */
181static int fill_write_buffer(struct configfs_buffer *buffer,
182			     struct iov_iter *from)
183{
184	int copied;
185
186	if (!buffer->page)
187		buffer->page = (char *)__get_free_pages(GFP_KERNEL, 0);
188	if (!buffer->page)
189		return -ENOMEM;
190
191	copied = copy_from_iter(buffer->page, SIMPLE_ATTR_SIZE - 1, from);
192	buffer->needs_read_fill = 1;
193	/* if buf is assumed to contain a string, terminate it by \0,
194	 * so e.g. sscanf() can scan the string easily */
195	buffer->page[copied] = 0;
196	return copied ? : -EFAULT;
197}
198
199static int
200flush_write_buffer(struct file *file, struct configfs_buffer *buffer, size_t count)
201{
202	struct configfs_fragment *frag = to_frag(file);
203	int res = -ENOENT;
204
205	down_read(&frag->frag_sem);
206	if (!frag->frag_dead)
207		res = buffer->attr->store(buffer->item, buffer->page, count);
208	up_read(&frag->frag_sem);
209	return res;
210}
211
212
213/*
214 * There is no easy way for us to know if userspace is only doing a partial
215 * write, so we don't support them. We expect the entire buffer to come on the
216 * first write.
217 * Hint: if you're writing a value, first read the file, modify only the value
218 * you're changing, then write entire buffer back.
219 */
220static ssize_t configfs_write_iter(struct kiocb *iocb, struct iov_iter *from)
221{
222	struct file *file = iocb->ki_filp;
223	struct configfs_buffer *buffer = file->private_data;
224	int len;
225
226	mutex_lock(&buffer->mutex);
227	len = fill_write_buffer(buffer, from);
228	if (len > 0)
229		len = flush_write_buffer(file, buffer, len);
230	if (len > 0)
231		iocb->ki_pos += len;
232	mutex_unlock(&buffer->mutex);
233	return len;
234}
235
236static ssize_t configfs_bin_write_iter(struct kiocb *iocb,
237				       struct iov_iter *from)
238{
239	struct file *file = iocb->ki_filp;
240	struct configfs_buffer *buffer = file->private_data;
241	void *tbuf = NULL;
242	size_t end_offset;
243	ssize_t len;
244
245	mutex_lock(&buffer->mutex);
246
247	/* we don't support switching read/write modes */
248	if (buffer->read_in_progress) {
249		len = -ETXTBSY;
250		goto out;
251	}
252	buffer->write_in_progress = true;
253
254	/* buffer grows? */
255	end_offset = iocb->ki_pos + iov_iter_count(from);
256	if (end_offset > buffer->bin_buffer_size) {
257		if (buffer->cb_max_size && end_offset > buffer->cb_max_size) {
258			len = -EFBIG;
259			goto out;
260		}
261
262		tbuf = vmalloc(end_offset);
263		if (tbuf == NULL) {
264			len = -ENOMEM;
265			goto out;
266		}
267
268		/* copy old contents */
269		if (buffer->bin_buffer) {
270			memcpy(tbuf, buffer->bin_buffer,
271				buffer->bin_buffer_size);
272			vfree(buffer->bin_buffer);
273		}
274
275		/* clear the new area */
276		memset(tbuf + buffer->bin_buffer_size, 0,
277			end_offset - buffer->bin_buffer_size);
278		buffer->bin_buffer = tbuf;
279		buffer->bin_buffer_size = end_offset;
280	}
281
282	len = copy_from_iter(buffer->bin_buffer + iocb->ki_pos,
283			     buffer->bin_buffer_size - iocb->ki_pos, from);
284	iocb->ki_pos += len;
285out:
286	mutex_unlock(&buffer->mutex);
287	return len ? : -EFAULT;
288}
289
290static int __configfs_open_file(struct inode *inode, struct file *file, int type)
291{
292	struct dentry *dentry = file->f_path.dentry;
293	struct configfs_fragment *frag = to_frag(file);
294	struct configfs_attribute *attr;
295	struct configfs_buffer *buffer;
296	int error;
297
298	error = -ENOMEM;
299	buffer = kzalloc(sizeof(struct configfs_buffer), GFP_KERNEL);
300	if (!buffer)
301		goto out;
302
303	error = -ENOENT;
304	down_read(&frag->frag_sem);
305	if (unlikely(frag->frag_dead))
306		goto out_free_buffer;
307
308	error = -EINVAL;
309	buffer->item = to_item(dentry->d_parent);
310	if (!buffer->item)
311		goto out_free_buffer;
312
313	attr = to_attr(dentry);
314	if (!attr)
315		goto out_free_buffer;
316
317	if (type & CONFIGFS_ITEM_BIN_ATTR) {
318		buffer->bin_attr = to_bin_attr(dentry);
319		buffer->cb_max_size = buffer->bin_attr->cb_max_size;
320	} else {
321		buffer->attr = attr;
322	}
323
324	buffer->owner = attr->ca_owner;
325	/* Grab the module reference for this attribute if we have one */
326	error = -ENODEV;
327	if (!try_module_get(buffer->owner))
328		goto out_free_buffer;
329
330	error = -EACCES;
331	if (!buffer->item->ci_type)
332		goto out_put_module;
333
334	buffer->ops = buffer->item->ci_type->ct_item_ops;
335
336	/* File needs write support.
337	 * The inode's perms must say it's ok,
338	 * and we must have a store method.
339	 */
340	if (file->f_mode & FMODE_WRITE) {
341		if (!(inode->i_mode & S_IWUGO))
342			goto out_put_module;
343		if ((type & CONFIGFS_ITEM_ATTR) && !attr->store)
344			goto out_put_module;
345		if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->write)
346			goto out_put_module;
347	}
348
349	/* File needs read support.
350	 * The inode's perms must say it's ok, and we there
351	 * must be a show method for it.
352	 */
353	if (file->f_mode & FMODE_READ) {
354		if (!(inode->i_mode & S_IRUGO))
355			goto out_put_module;
356		if ((type & CONFIGFS_ITEM_ATTR) && !attr->show)
357			goto out_put_module;
358		if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->read)
359			goto out_put_module;
360	}
361
362	mutex_init(&buffer->mutex);
363	buffer->needs_read_fill = 1;
364	buffer->read_in_progress = false;
365	buffer->write_in_progress = false;
366	file->private_data = buffer;
367	up_read(&frag->frag_sem);
368	return 0;
369
370out_put_module:
371	module_put(buffer->owner);
372out_free_buffer:
373	up_read(&frag->frag_sem);
374	kfree(buffer);
375out:
376	return error;
377}
378
379static int configfs_release(struct inode *inode, struct file *filp)
380{
381	struct configfs_buffer *buffer = filp->private_data;
382
383	module_put(buffer->owner);
384	if (buffer->page)
385		free_page((unsigned long)buffer->page);
386	mutex_destroy(&buffer->mutex);
387	kfree(buffer);
388	return 0;
389}
390
391static int configfs_open_file(struct inode *inode, struct file *filp)
392{
393	return __configfs_open_file(inode, filp, CONFIGFS_ITEM_ATTR);
394}
395
396static int configfs_open_bin_file(struct inode *inode, struct file *filp)
397{
398	return __configfs_open_file(inode, filp, CONFIGFS_ITEM_BIN_ATTR);
399}
400
401static int configfs_release_bin_file(struct inode *inode, struct file *file)
402{
403	struct configfs_buffer *buffer = file->private_data;
404
405	if (buffer->write_in_progress) {
406		struct configfs_fragment *frag = to_frag(file);
407
408		down_read(&frag->frag_sem);
409		if (!frag->frag_dead) {
410			/* result of ->release() is ignored */
411			buffer->bin_attr->write(buffer->item,
412					buffer->bin_buffer,
413					buffer->bin_buffer_size);
414		}
415		up_read(&frag->frag_sem);
416	}
417
418	vfree(buffer->bin_buffer);
419
420	configfs_release(inode, file);
421	return 0;
422}
423
424
425const struct file_operations configfs_file_operations = {
426	.read_iter	= configfs_read_iter,
427	.write_iter	= configfs_write_iter,
428	.llseek		= generic_file_llseek,
429	.open		= configfs_open_file,
430	.release	= configfs_release,
431};
432
433const struct file_operations configfs_bin_file_operations = {
434	.read_iter	= configfs_bin_read_iter,
435	.write_iter	= configfs_bin_write_iter,
436	.llseek		= NULL,		/* bin file is not seekable */
437	.open		= configfs_open_bin_file,
438	.release	= configfs_release_bin_file,
439};
440
441/**
442 *	configfs_create_file - create an attribute file for an item.
443 *	@item:	item we're creating for.
444 *	@attr:	atrribute descriptor.
445 */
446
447int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr)
448{
449	struct dentry *dir = item->ci_dentry;
450	struct configfs_dirent *parent_sd = dir->d_fsdata;
451	umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
452	int error = 0;
453
454	inode_lock_nested(d_inode(dir), I_MUTEX_NORMAL);
455	error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode,
456				     CONFIGFS_ITEM_ATTR, parent_sd->s_frag);
457	inode_unlock(d_inode(dir));
458
459	return error;
460}
461
462/**
463 *	configfs_create_bin_file - create a binary attribute file for an item.
464 *	@item:	item we're creating for.
465 *	@bin_attr: atrribute descriptor.
466 */
467
468int configfs_create_bin_file(struct config_item *item,
469		const struct configfs_bin_attribute *bin_attr)
470{
471	struct dentry *dir = item->ci_dentry;
472	struct configfs_dirent *parent_sd = dir->d_fsdata;
473	umode_t mode = (bin_attr->cb_attr.ca_mode & S_IALLUGO) | S_IFREG;
474	int error = 0;
475
476	inode_lock_nested(dir->d_inode, I_MUTEX_NORMAL);
477	error = configfs_make_dirent(parent_sd, NULL, (void *) bin_attr, mode,
478				     CONFIGFS_ITEM_BIN_ATTR, parent_sd->s_frag);
479	inode_unlock(dir->d_inode);
480
481	return error;
482}
483