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
29 struct 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
49 static 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
56 static 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
80 static 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;
101 out:
102 mutex_unlock(&buffer->mutex);
103 return retval;
104 }
105
106 static 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;
175 out:
176 mutex_unlock(&buffer->mutex);
177 return retval;
178 }
179
180 /* Fill @buffer with data coming from @from. */
181 static 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
199 static int
200 flush_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 */
220 static 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
236 static 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;
285 out:
286 mutex_unlock(&buffer->mutex);
287 return len ? : -EFAULT;
288 }
289
290 static 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
370 out_put_module:
371 module_put(buffer->owner);
372 out_free_buffer:
373 up_read(&frag->frag_sem);
374 kfree(buffer);
375 out:
376 return error;
377 }
378
379 static 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
391 static int configfs_open_file(struct inode *inode, struct file *filp)
392 {
393 return __configfs_open_file(inode, filp, CONFIGFS_ITEM_ATTR);
394 }
395
396 static 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
401 static 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
425 const 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
433 const 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
447 int 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
468 int 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
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