linux-stable/fs/configfs/file.c
Bart Van Assche 769f526767 configfs: restore the kernel v5.13 text attribute write behavior
Instead of appending new text attribute data at the offset specified by the
write() system call, only pass the newly written data to the .store()
callback.

Reported-by: Bodo Stroesser <bostroesser@gmail.com>
Tested-by: Bodo Stroesser <bostroesser@gmail.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
2021-08-09 16:56:00 +02:00

482 lines
12 KiB
C

// 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;
}