![Tal Shorer](/assets/img/avatar_default.png)
A confgifs attribute's show() callback is called once the first time the user attempts to read from it. If it returns an error, that error is returned to the user. However, the open file's buffer_needs_fill is still set to zero and consecutive read() calls will find an empty buffer that doesn't need filling and return 0 to the user. This could give the user the wrong impression that the attribute was read successfully. Fix this by not setting buffer_needs_fill if show() returns an error, making consecutive read() calls call show() again and either get an error again or get data. Signed-off-by: Tal Shorer <tal.shorer@gmail.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
570 lines
15 KiB
C
570 lines
15 KiB
C
/* -*- mode: c; c-basic-offset: 8; -*-
|
|
* vim: noexpandtab sw=8 ts=8 sts=0:
|
|
*
|
|
* file.c - operations for regular (text) files.
|
|
*
|
|
* This program is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU General Public
|
|
* License as published by the Free Software Foundation; either
|
|
* version 2 of the License, or (at your option) any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
* General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public
|
|
* License along with this program; if not, write to the
|
|
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
|
|
* Boston, MA 021110-1307, USA.
|
|
*
|
|
* 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 <asm/uaccess.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;
|
|
};
|
|
|
|
|
|
/**
|
|
* fill_read_buffer - allocate and fill buffer from item.
|
|
* @dentry: dentry pointer.
|
|
* @buffer: data buffer for file.
|
|
*
|
|
* Allocate @buffer->page, if it hasn't been already, then call the
|
|
* config_item's show() method to fill the buffer with this attribute's
|
|
* data.
|
|
* This is called only once, on the file's first read.
|
|
*/
|
|
static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buffer)
|
|
{
|
|
struct configfs_attribute * attr = to_attr(dentry);
|
|
struct config_item * item = to_item(dentry->d_parent);
|
|
int ret = 0;
|
|
ssize_t count;
|
|
|
|
if (!buffer->page)
|
|
buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
|
|
if (!buffer->page)
|
|
return -ENOMEM;
|
|
|
|
count = attr->show(item, buffer->page);
|
|
|
|
BUG_ON(count > (ssize_t)SIMPLE_ATTR_SIZE);
|
|
if (count >= 0) {
|
|
buffer->needs_read_fill = 0;
|
|
buffer->count = count;
|
|
} else
|
|
ret = count;
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* configfs_read_file - read an attribute.
|
|
* @file: file pointer.
|
|
* @buf: buffer to fill.
|
|
* @count: number of bytes to read.
|
|
* @ppos: starting offset in file.
|
|
*
|
|
* Userspace wants to read an attribute file. The attribute descriptor
|
|
* is in the file's ->d_fsdata. The target item is in the directory's
|
|
* ->d_fsdata.
|
|
*
|
|
* We call fill_read_buffer() to allocate and fill the buffer from the
|
|
* item's show() method exactly once (if the read is happening from
|
|
* the beginning of the file). That should fill the entire buffer with
|
|
* all the data the item has to offer for that attribute.
|
|
* We then call flush_read_buffer() to copy the buffer to userspace
|
|
* in the increments specified.
|
|
*/
|
|
|
|
static ssize_t
|
|
configfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
|
|
{
|
|
struct configfs_buffer * buffer = file->private_data;
|
|
ssize_t retval = 0;
|
|
|
|
mutex_lock(&buffer->mutex);
|
|
if (buffer->needs_read_fill) {
|
|
if ((retval = fill_read_buffer(file->f_path.dentry,buffer)))
|
|
goto out;
|
|
}
|
|
pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
|
|
__func__, count, *ppos, buffer->page);
|
|
retval = simple_read_from_buffer(buf, count, ppos, buffer->page,
|
|
buffer->count);
|
|
out:
|
|
mutex_unlock(&buffer->mutex);
|
|
return retval;
|
|
}
|
|
|
|
/**
|
|
* configfs_read_bin_file - read a binary attribute.
|
|
* @file: file pointer.
|
|
* @buf: buffer to fill.
|
|
* @count: number of bytes to read.
|
|
* @ppos: starting offset in file.
|
|
*
|
|
* Userspace wants to read a binary attribute file. The attribute
|
|
* descriptor is in the file's ->d_fsdata. The target item is in the
|
|
* directory's ->d_fsdata.
|
|
*
|
|
* We check whether we need to refill the buffer. If so we will
|
|
* call the attributes' attr->read() twice. The first time we
|
|
* will pass a NULL as a buffer pointer, which the attributes' method
|
|
* will use to return the size of the buffer required. If no error
|
|
* occurs we will allocate the buffer using vmalloc and call
|
|
* attr->read() again passing that buffer as an argument.
|
|
* Then we just copy to user-space using simple_read_from_buffer.
|
|
*/
|
|
|
|
static ssize_t
|
|
configfs_read_bin_file(struct file *file, char __user *buf,
|
|
size_t count, loff_t *ppos)
|
|
{
|
|
struct configfs_buffer *buffer = file->private_data;
|
|
struct dentry *dentry = file->f_path.dentry;
|
|
struct config_item *item = to_item(dentry->d_parent);
|
|
struct configfs_bin_attribute *bin_attr = to_bin_attr(dentry);
|
|
ssize_t retval = 0;
|
|
ssize_t len = min_t(size_t, count, PAGE_SIZE);
|
|
|
|
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 = 1;
|
|
|
|
if (buffer->needs_read_fill) {
|
|
/* perform first read with buf == NULL to get extent */
|
|
len = bin_attr->read(item, NULL, 0);
|
|
if (len <= 0) {
|
|
retval = len;
|
|
goto out;
|
|
}
|
|
|
|
/* do not exceed the maximum value */
|
|
if (bin_attr->cb_max_size && len > bin_attr->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 */
|
|
len = bin_attr->read(item, buffer->bin_buffer, len);
|
|
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;
|
|
}
|
|
|
|
retval = simple_read_from_buffer(buf, count, ppos, buffer->bin_buffer,
|
|
buffer->bin_buffer_size);
|
|
out:
|
|
mutex_unlock(&buffer->mutex);
|
|
return retval;
|
|
}
|
|
|
|
|
|
/**
|
|
* fill_write_buffer - copy buffer from userspace.
|
|
* @buffer: data buffer for file.
|
|
* @buf: data from user.
|
|
* @count: number of bytes in @userbuf.
|
|
*
|
|
* Allocate @buffer->page if it hasn't been already, then
|
|
* copy the user-supplied buffer into it.
|
|
*/
|
|
|
|
static int
|
|
fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size_t count)
|
|
{
|
|
int error;
|
|
|
|
if (!buffer->page)
|
|
buffer->page = (char *)__get_free_pages(GFP_KERNEL, 0);
|
|
if (!buffer->page)
|
|
return -ENOMEM;
|
|
|
|
if (count >= SIMPLE_ATTR_SIZE)
|
|
count = SIMPLE_ATTR_SIZE - 1;
|
|
error = copy_from_user(buffer->page,buf,count);
|
|
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[count] = 0;
|
|
return error ? -EFAULT : count;
|
|
}
|
|
|
|
|
|
/**
|
|
* flush_write_buffer - push buffer to config_item.
|
|
* @dentry: dentry to the attribute
|
|
* @buffer: data buffer for file.
|
|
* @count: number of bytes
|
|
*
|
|
* Get the correct pointers for the config_item and the attribute we're
|
|
* dealing with, then call the store() method for the attribute,
|
|
* passing the buffer that we acquired in fill_write_buffer().
|
|
*/
|
|
|
|
static int
|
|
flush_write_buffer(struct dentry * dentry, struct configfs_buffer * buffer, size_t count)
|
|
{
|
|
struct configfs_attribute * attr = to_attr(dentry);
|
|
struct config_item * item = to_item(dentry->d_parent);
|
|
|
|
return attr->store(item, buffer->page, count);
|
|
}
|
|
|
|
|
|
/**
|
|
* configfs_write_file - write an attribute.
|
|
* @file: file pointer
|
|
* @buf: data to write
|
|
* @count: number of bytes
|
|
* @ppos: starting offset
|
|
*
|
|
* Similar to configfs_read_file(), though working in the opposite direction.
|
|
* We allocate and fill the data from the user in fill_write_buffer(),
|
|
* then push it to the config_item in flush_write_buffer().
|
|
* 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
|
|
* the value you're changing, then write entire buffer back.
|
|
*/
|
|
|
|
static ssize_t
|
|
configfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
|
|
{
|
|
struct configfs_buffer * buffer = file->private_data;
|
|
ssize_t len;
|
|
|
|
mutex_lock(&buffer->mutex);
|
|
len = fill_write_buffer(buffer, buf, count);
|
|
if (len > 0)
|
|
len = flush_write_buffer(file->f_path.dentry, buffer, len);
|
|
if (len > 0)
|
|
*ppos += len;
|
|
mutex_unlock(&buffer->mutex);
|
|
return len;
|
|
}
|
|
|
|
/**
|
|
* configfs_write_bin_file - write a binary attribute.
|
|
* @file: file pointer
|
|
* @buf: data to write
|
|
* @count: number of bytes
|
|
* @ppos: starting offset
|
|
*
|
|
* Writing to a binary attribute file is similar to a normal read.
|
|
* We buffer the consecutive writes (binary attribute files do not
|
|
* support lseek) in a continuously growing buffer, but we don't
|
|
* commit until the close of the file.
|
|
*/
|
|
|
|
static ssize_t
|
|
configfs_write_bin_file(struct file *file, const char __user *buf,
|
|
size_t count, loff_t *ppos)
|
|
{
|
|
struct configfs_buffer *buffer = file->private_data;
|
|
struct dentry *dentry = file->f_path.dentry;
|
|
struct configfs_bin_attribute *bin_attr = to_bin_attr(dentry);
|
|
void *tbuf = NULL;
|
|
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 = 1;
|
|
|
|
/* buffer grows? */
|
|
if (*ppos + count > buffer->bin_buffer_size) {
|
|
|
|
if (bin_attr->cb_max_size &&
|
|
*ppos + count > bin_attr->cb_max_size) {
|
|
len = -EFBIG;
|
|
}
|
|
|
|
tbuf = vmalloc(*ppos + count);
|
|
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,
|
|
*ppos + count - buffer->bin_buffer_size);
|
|
buffer->bin_buffer = tbuf;
|
|
buffer->bin_buffer_size = *ppos + count;
|
|
}
|
|
|
|
len = simple_write_to_buffer(buffer->bin_buffer,
|
|
buffer->bin_buffer_size, ppos, buf, count);
|
|
out:
|
|
mutex_unlock(&buffer->mutex);
|
|
return len;
|
|
}
|
|
|
|
static int check_perm(struct inode * inode, struct file * file, int type)
|
|
{
|
|
struct config_item *item = configfs_get_config_item(file->f_path.dentry->d_parent);
|
|
struct configfs_attribute * attr = to_attr(file->f_path.dentry);
|
|
struct configfs_bin_attribute *bin_attr = NULL;
|
|
struct configfs_buffer * buffer;
|
|
struct configfs_item_operations * ops = NULL;
|
|
int error = 0;
|
|
|
|
if (!item || !attr)
|
|
goto Einval;
|
|
|
|
if (type & CONFIGFS_ITEM_BIN_ATTR)
|
|
bin_attr = to_bin_attr(file->f_path.dentry);
|
|
|
|
/* Grab the module reference for this attribute if we have one */
|
|
if (!try_module_get(attr->ca_owner)) {
|
|
error = -ENODEV;
|
|
goto Done;
|
|
}
|
|
|
|
if (item->ci_type)
|
|
ops = item->ci_type->ct_item_ops;
|
|
else
|
|
goto Eaccess;
|
|
|
|
/* 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 Eaccess;
|
|
|
|
if ((type & CONFIGFS_ITEM_ATTR) && !attr->store)
|
|
goto Eaccess;
|
|
|
|
if ((type & CONFIGFS_ITEM_BIN_ATTR) && !bin_attr->write)
|
|
goto Eaccess;
|
|
}
|
|
|
|
/* 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 Eaccess;
|
|
|
|
if ((type & CONFIGFS_ITEM_ATTR) && !attr->show)
|
|
goto Eaccess;
|
|
|
|
if ((type & CONFIGFS_ITEM_BIN_ATTR) && !bin_attr->read)
|
|
goto Eaccess;
|
|
}
|
|
|
|
/* No error? Great, allocate a buffer for the file, and store it
|
|
* it in file->private_data for easy access.
|
|
*/
|
|
buffer = kzalloc(sizeof(struct configfs_buffer),GFP_KERNEL);
|
|
if (!buffer) {
|
|
error = -ENOMEM;
|
|
goto Enomem;
|
|
}
|
|
mutex_init(&buffer->mutex);
|
|
buffer->needs_read_fill = 1;
|
|
buffer->read_in_progress = 0;
|
|
buffer->write_in_progress = 0;
|
|
buffer->ops = ops;
|
|
file->private_data = buffer;
|
|
goto Done;
|
|
|
|
Einval:
|
|
error = -EINVAL;
|
|
goto Done;
|
|
Eaccess:
|
|
error = -EACCES;
|
|
Enomem:
|
|
module_put(attr->ca_owner);
|
|
Done:
|
|
if (error && item)
|
|
config_item_put(item);
|
|
return error;
|
|
}
|
|
|
|
static int configfs_release(struct inode *inode, struct file *filp)
|
|
{
|
|
struct config_item * item = to_item(filp->f_path.dentry->d_parent);
|
|
struct configfs_attribute * attr = to_attr(filp->f_path.dentry);
|
|
struct module * owner = attr->ca_owner;
|
|
struct configfs_buffer * buffer = filp->private_data;
|
|
|
|
if (item)
|
|
config_item_put(item);
|
|
/* After this point, attr should not be accessed. */
|
|
module_put(owner);
|
|
|
|
if (buffer) {
|
|
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 check_perm(inode, filp, CONFIGFS_ITEM_ATTR);
|
|
}
|
|
|
|
static int configfs_open_bin_file(struct inode *inode, struct file *filp)
|
|
{
|
|
return check_perm(inode, filp, CONFIGFS_ITEM_BIN_ATTR);
|
|
}
|
|
|
|
static int configfs_release_bin_file(struct inode *inode, struct file *filp)
|
|
{
|
|
struct configfs_buffer *buffer = filp->private_data;
|
|
struct dentry *dentry = filp->f_path.dentry;
|
|
struct config_item *item = to_item(dentry->d_parent);
|
|
struct configfs_bin_attribute *bin_attr = to_bin_attr(dentry);
|
|
ssize_t len = 0;
|
|
int ret;
|
|
|
|
buffer->read_in_progress = 0;
|
|
|
|
if (buffer->write_in_progress) {
|
|
buffer->write_in_progress = 0;
|
|
|
|
len = bin_attr->write(item, buffer->bin_buffer,
|
|
buffer->bin_buffer_size);
|
|
|
|
/* vfree on NULL is safe */
|
|
vfree(buffer->bin_buffer);
|
|
buffer->bin_buffer = NULL;
|
|
buffer->bin_buffer_size = 0;
|
|
buffer->needs_read_fill = 1;
|
|
}
|
|
|
|
ret = configfs_release(inode, filp);
|
|
if (len < 0)
|
|
return len;
|
|
return ret;
|
|
}
|
|
|
|
|
|
const struct file_operations configfs_file_operations = {
|
|
.read = configfs_read_file,
|
|
.write = configfs_write_file,
|
|
.llseek = generic_file_llseek,
|
|
.open = configfs_open_file,
|
|
.release = configfs_release,
|
|
};
|
|
|
|
const struct file_operations configfs_bin_file_operations = {
|
|
.read = configfs_read_bin_file,
|
|
.write = configfs_write_bin_file,
|
|
.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);
|
|
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.
|
|
* @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);
|
|
inode_unlock(dir->d_inode);
|
|
|
|
return error;
|
|
}
|