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(sem: &frag->frag_sem); |
67 | if (!frag->frag_dead) |
68 | count = buffer->attr->show(buffer->item, buffer->page); |
69 | up_read(sem: &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(addr: buffer->page + iocb->ki_pos, |
97 | bytes: buffer->count - iocb->ki_pos, i: to); |
98 | iocb->ki_pos += retval; |
99 | if (retval == 0) |
100 | retval = -EFAULT; |
101 | out: |
102 | mutex_unlock(lock: &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(sem: &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(sem: &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(size: 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(sem: &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(sem: &frag->frag_sem); |
157 | if (len < 0) { |
158 | retval = len; |
159 | vfree(addr: 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(addr: buffer->bin_buffer + iocb->ki_pos, |
171 | bytes: buffer->bin_buffer_size - iocb->ki_pos, i: to); |
172 | iocb->ki_pos += retval; |
173 | if (retval == 0) |
174 | retval = -EFAULT; |
175 | out: |
176 | mutex_unlock(lock: &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, order: 0); |
188 | if (!buffer->page) |
189 | return -ENOMEM; |
190 | |
191 | copied = copy_from_iter(addr: buffer->page, SIMPLE_ATTR_SIZE - 1, i: 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(sem: &frag->frag_sem); |
206 | if (!frag->frag_dead) |
207 | res = buffer->attr->store(buffer->item, buffer->page, count); |
208 | up_read(sem: &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, count: len); |
230 | if (len > 0) |
231 | iocb->ki_pos += len; |
232 | mutex_unlock(lock: &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(i: 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(size: 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(addr: 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(addr: buffer->bin_buffer + iocb->ki_pos, |
283 | bytes: buffer->bin_buffer_size - iocb->ki_pos, i: from); |
284 | iocb->ki_pos += len; |
285 | out: |
286 | mutex_unlock(lock: &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(size: sizeof(struct configfs_buffer), GFP_KERNEL); |
300 | if (!buffer) |
301 | goto out; |
302 | |
303 | error = -ENOENT; |
304 | down_read(sem: &frag->frag_sem); |
305 | if (unlikely(frag->frag_dead)) |
306 | goto out_free_buffer; |
307 | |
308 | error = -EINVAL; |
309 | buffer->item = to_item(dentry: 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(module: 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(sem: &frag->frag_sem); |
368 | return 0; |
369 | |
370 | out_put_module: |
371 | module_put(module: buffer->owner); |
372 | out_free_buffer: |
373 | up_read(sem: &frag->frag_sem); |
374 | kfree(objp: 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(module: buffer->owner); |
384 | if (buffer->page) |
385 | free_page((unsigned long)buffer->page); |
386 | mutex_destroy(lock: &buffer->mutex); |
387 | kfree(objp: 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, file: 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, file: 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(sem: &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(sem: &frag->frag_sem); |
416 | } |
417 | |
418 | vfree(addr: buffer->bin_buffer); |
419 | |
420 | configfs_release(inode, filp: 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(inode: d_inode(dentry: dir), subclass: 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(inode: d_inode(dentry: 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(inode: dir->d_inode, subclass: 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(inode: dir->d_inode); |
480 | |
481 | return error; |
482 | } |
483 | |