483 lines · c
1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * file.c - operations for regular (text) files.4 *5 * Based on sysfs:6 * sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel7 *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 the23 * 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 to25 * 4k, our minimum common page size.26 */27#define SIMPLE_ATTR_SIZE 409628 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 else129 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 else155 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 int200flush_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 partial215 * write, so we don't support them. We expect the entire buffer to come on the216 * first write.217 * Hint: if you're writing a value, first read the file, modify only the value218 * 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 there351 * 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