// SPDX-License-Identifier: GPL-2.0-or-later
/*
* file.c - operations for regular (text) files.
*
* Based on sysfs:
* sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
*
* configfs Copyright (C) 2005 Oracle. All rights reserved.
*/
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/vmalloc.h>
#include <linux/uaccess.h>
#include <linux/uio.h>
#include <linux/configfs.h>
#include "configfs_internal.h"
/*
* A simple attribute can only be 4096 characters. Why 4k? Because the
* original code limited it to PAGE_SIZE. That's a bad idea, though,
* because an attribute of 16k on ia64 won't work on x86. So we limit to
* 4k, our minimum common page size.
*/
#define SIMPLE_ATTR_SIZE 4096
struct configfs_buffer {
size_t count;
loff_t pos;
char * page;
struct configfs_item_operations * ops;
struct mutex mutex;
int needs_read_fill;
bool read_in_progress;
bool write_in_progress;
char *bin_buffer;
int bin_buffer_size;
int cb_max_size;
struct config_item *item;
struct module *owner;
union {
struct configfs_attribute *attr;
struct configfs_bin_attribute *bin_attr;
};
};
static inline struct configfs_fragment *to_frag(struct file *file)
{
struct configfs_dirent *sd = file->f_path.dentry->d_fsdata;
return sd->s_frag;
}
static int fill_read_buffer(struct file *file, struct configfs_buffer *buffer)
{
struct configfs_fragment *frag = to_frag(file);
ssize_t count = -ENOENT;
if (!buffer->page)
buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
if (!buffer->page)
return -ENOMEM;
down_read(&frag->frag_sem);
if (!frag->frag_dead)
count = buffer->attr->show(buffer->item, buffer->page);
up_read(&frag->frag_sem);
if (count < 0)
return count;
if (WARN_ON_ONCE(count > (ssize_t)SIMPLE_ATTR_SIZE))
return -EIO;
buffer->needs_read_fill = 0;
buffer->count = count;
return 0;
}
static ssize_t configfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
struct file *file = iocb->ki_filp;
struct configfs_buffer *buffer = file->private_data;
ssize_t retval = 0;
mutex_lock(&buffer->mutex);
if (buffer->needs_read_fill) {
retval = fill_read_buffer(file, buffer);
if (retval)
goto out;
}
pr_debug("%s: count = %zd, pos = %lld, buf = %s\n",
__func__, iov_iter_count(to), iocb->ki_pos, buffer->page);
if (iocb->ki_pos >= buffer->count)
goto out;
retval = copy_to_iter(buffer->page + iocb->ki_pos,
buffer->count - iocb->ki_pos, to);
iocb->ki_pos += retval;
if (retval == 0)
retval = -EFAULT;
out:
mutex_unlock(&buffer->mutex);
return retval;
}
static ssize_t configfs_bin_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
struct file *file = iocb->ki_filp;
struct configfs_fragment *frag = to_frag(file);
struct configfs_buffer *buffer = file->private_data;
ssize_t retval = 0;
ssize_t len;
mutex_lock(&buffer->mutex);
/* we don't support switching read/write modes */
if (buffer->write_in_progress) {
retval = -ETXTBSY;
goto out;
}
buffer->read_in_progress = true;
if (buffer->needs_read_fill) {
/* perform first read with buf == NULL to get extent */
down_read(&frag->frag_sem);
if (!frag->frag_dead)
len = buffer->bin_attr->read(buffer->item, NULL, 0);
else
len = -ENOENT;
up_read(&frag->frag_sem);
if (len <= 0) {
retval = len;
goto out;
}
/* do not exceed the maximum value */
if (buffer->cb_max_size && len > buffer->cb_max_size) {
retval = -EFBIG;
goto out;
}
buffer->bin_buffer = vmalloc(len);
if (buffer->bin_buffer == NULL) {
retval = -ENOMEM;
goto out;
}
buffer->bin_buffer_size = len;
/* perform second read to fill buffer */
down_read(&frag->frag_sem);
if (!frag->frag_dead)
len = buffer->bin_attr->read(buffer->item,
buffer->bin_buffer, len);
else
len = -ENOENT;
up_read(&frag->frag_sem);
if (len < 0) {
retval = len;
vfree(buffer->bin_buffer);
buffer->bin_buffer_size = 0;
buffer->bin_buffer = NULL;
goto out;
}
buffer->needs_read_fill = 0;
}
if (iocb->ki_pos >= buffer->bin_buffer_size)
goto out;
retval = copy_to_iter(buffer->bin_buffer + iocb->ki_pos,
buffer->bin_buffer_size - iocb->ki_pos, to);
iocb->ki_pos += retval;
if (retval == 0)
retval = -EFAULT;
out:
mutex_unlock(&buffer->mutex);
return retval;
}
/* Fill @buffer with data coming from @from. */
static int fill_write_buffer(struct configfs_buffer *buffer,
struct iov_iter *from)
{
int copied;
if (!buffer->page)
buffer->page = (char *)__get_free_pages(GFP_KERNEL, 0);
if (!buffer->page)
return -ENOMEM;
copied = copy_from_iter(buffer->page, SIMPLE_ATTR_SIZE - 1, from);
buffer->needs_read_fill = 1;
/* if buf is assumed to contain a string, terminate it by \0,
* so e.g. sscanf() can scan the string easily */
buffer->page[copied] = 0;
return copied ? : -EFAULT;
}
static int
flush_write_buffer(struct file *file, struct configfs_buffer *buffer, size_t count)
{
struct configfs_fragment *frag = to_frag(file);
int res = -ENOENT;
down_read(&frag->frag_sem);
if (!frag->frag_dead)
res = buffer->attr->store(buffer->item, buffer->page, count);
up_read(&frag->frag_sem);
return res;
}
/*
* There is no easy way for us to know if userspace is only doing a partial
* write, so we don't support them. We expect the entire buffer to come on the
* first write.
* Hint: if you're writing a value, first read the file, modify only the value
* you're changing, then write entire buffer back.
*/
static ssize_t configfs_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
struct file *file = iocb->ki_filp;
struct configfs_buffer *buffer = file->private_data;
int len;
mutex_lock(&buffer->mutex);
len = fill_write_buffer(buffer, from);
if (len > 0)
len = flush_write_buffer(file, buffer, len);
if (len > 0)
iocb->ki_pos += len;
mutex_unlock(&buffer->mutex);
return len;
}
static ssize_t configfs_bin_write_iter(struct kiocb *iocb,
struct iov_iter *from)
{
struct file *file = iocb->ki_filp;
struct configfs_buffer *buffer = file->private_data;
void *tbuf = NULL;
size_t end_offset;
ssize_t len;
mutex_lock(&buffer->mutex);
/* we don't support switching read/write modes */
if (buffer->read_in_progress) {
len = -ETXTBSY;
goto out;
}
buffer->write_in_progress = true;
/* buffer grows? */
end_offset = iocb->ki_pos + iov_iter_count(from);
if (end_offset > buffer->bin_buffer_size) {
if (buffer->cb_max_size && end_offset > buffer->cb_max_size) {
len = -EFBIG;
goto out;
}
tbuf = vmalloc(end_offset);
if (tbuf == NULL) {
len = -ENOMEM;
goto out;
}
/* copy old contents */
if (buffer->bin_buffer) {
memcpy(tbuf, buffer->bin_buffer,
buffer->bin_buffer_size);
vfree(buffer->bin_buffer);
}
/* clear the new area */
memset(tbuf + buffer->bin_buffer_size, 0,
end_offset - buffer->bin_buffer_size);
buffer->bin_buffer = tbuf;
buffer->bin_buffer_size = end_offset;
}
len = copy_from_iter(buffer->bin_buffer + iocb->ki_pos,
buffer->bin_buffer_size - iocb->ki_pos, from);
iocb->ki_pos += len;
out:
mutex_unlock(&buffer->mutex);
return len ? : -EFAULT;
}
static int __configfs_open_file(struct inode *inode, struct file *file, int type)
{
struct dentry *dentry = file->f_path.dentry;
struct configfs_fragment *frag = to_frag(file);
struct configfs_attribute *attr;
struct configfs_buffer *buffer;
int error;
error = -ENOMEM;
buffer = kzalloc(sizeof(struct configfs_buffer), GFP_KERNEL);
if (!buffer)
goto out;
error = -ENOENT;
down_read(&frag->frag_sem);
if (unlikely(frag->frag_dead))
goto out_free_buffer;
error = -EINVAL;
buffer->item = to_item(dentry->d_parent);
if (!buffer->item)
goto out_free_buffer;
attr = to_attr(dentry);
if (!attr)
goto out_free_buffer;
if (type & CONFIGFS_ITEM_BIN_ATTR) {
buffer->bin_attr = to_bin_attr(dentry);
buffer->cb_max_size = buffer->bin_attr->cb_max_size;
} else {
buffer->attr = attr;
}
buffer->owner = attr->ca_owner;
/* Grab the module reference for this attribute if we have one */
error = -ENODEV;
if (!try_module_get(buffer->owner))
goto out_free_buffer;
error = -EACCES;
if (!buffer->item->ci_type)
goto out_put_module;
buffer->ops = buffer->item->ci_type->ct_item_ops;
/* File needs write support.
* The inode's perms must say it's ok,
* and we must have a store method.
*/
if (file->f_mode & FMODE_WRITE) {
if (!(inode->i_mode & S_IWUGO))
goto out_put_module;
if ((type & CONFIGFS_ITEM_ATTR) && !attr->store)
goto out_put_module;
if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->write)
goto out_put_module;
}
/* File needs read support.
* The inode's perms must say it's ok, and we there
* must be a show method for it.
*/
if (file->f_mode & FMODE_READ) {
if (!(inode->i_mode & S_IRUGO))
goto out_put_module;
if ((type & CONFIGFS_ITEM_ATTR) && !attr->show)
goto out_put_module;
if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->read)
goto out_put_module;
}
mutex_init(&buffer->mutex);
buffer->needs_read_fill = 1;
buffer->read_in_progress = false;
buffer->write_in_progress = false;
file->private_data = buffer;
up_read(&frag->frag_sem);
return 0;
out_put_module:
module_put(buffer->owner);
out_free_buffer:
up_read(&frag->frag_sem);
kfree(buffer);
out:
return error;
}
static int configfs_release(struct inode *inode, struct file *filp)
{
struct configfs_buffer *buffer = filp->private_data;
module_put(buffer->owner);
if (buffer->page)
free_page((unsigned long)buffer->page);
mutex_destroy(&buffer->mutex);
kfree(buffer);
return 0;
}
static int configfs_open_file(struct inode *inode, struct file *filp)
{
return __configfs_open_file(inode, filp, CONFIGFS_ITEM_ATTR);
}
static int configfs_open_bin_file(struct inode *inode, struct file *filp)
{
return __configfs_open_file(inode, filp, CONFIGFS_ITEM_BIN_ATTR);
}
static int configfs_release_bin_file(struct inode *inode, struct file *file)
{
struct configfs_buffer *buffer = file->private_data;
if (buffer->write_in_progress) {
struct configfs_fragment *frag = to_frag(file);
down_read(&frag->frag_sem);
if (!frag->frag_dead) {
/* result of ->release() is ignored */
buffer->bin_attr->write(buffer->item,
buffer->bin_buffer,
buffer->bin_buffer_size);
}
up_read(&frag->frag_sem);
}
vfree(buffer->bin_buffer);
configfs_release(inode, file);
return 0;
}
const struct file_operations configfs_file_operations = {
.read_iter = configfs_read_iter,
.write_iter = configfs_write_iter,
.llseek = generic_file_llseek,
.open = configfs_open_file,
.release = configfs_release,
};
const struct file_operations configfs_bin_file_operations = {
.read_iter = configfs_bin_read_iter,
.write_iter = configfs_bin_write_iter,
.llseek = NULL, /* bin file is not seekable */
.open = configfs_open_bin_file,
.release = configfs_release_bin_file,
};
/**
* configfs_create_file - create an attribute file for an item.
* @item: item we're creating for.
* @attr: atrribute descriptor.
*/
int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr)
{
struct dentry *dir = item->ci_dentry;
struct configfs_dirent *parent_sd = dir->d_fsdata;
umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
int error = 0;
inode_lock_nested(d_inode(dir), I_MUTEX_NORMAL);
error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode,
CONFIGFS_ITEM_ATTR, parent_sd->s_frag);
inode_unlock(d_inode(dir));
return error;
}
/**
* configfs_create_bin_file - create a binary attribute file for an item.
* @item: item we're creating for.
* @bin_attr: atrribute descriptor.
*/
int configfs_create_bin_file(struct config_item *item,
const struct configfs_bin_attribute *bin_attr)
{
struct dentry *dir = item->ci_dentry;
struct configfs_dirent *parent_sd = dir->d_fsdata;
umode_t mode = (bin_attr->cb_attr.ca_mode & S_IALLUGO) | S_IFREG;
int error = 0;
inode_lock_nested(dir->d_inode, I_MUTEX_NORMAL);
error = configfs_make_dirent(parent_sd, NULL, (void *) bin_attr, mode,
CONFIGFS_ITEM_BIN_ATTR, parent_sd->s_frag);
inode_unlock(dir->d_inode);
return error;
}
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