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![Chandra Seetharaman](/assets/img/avatar_default.png)
check_perm() does not drop the reference to the module when kzalloc() failure occurs. Signed-Off-By: Chandra Seetharaman <sekharan@us.ibm.com> Signed-off-by: Joel Becker <joel.becker@oracle.com> Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
362 lines
9.6 KiB
C
362 lines
9.6 KiB
C
/* -*- mode: c; c-basic-offset: 8; -*-
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* vim: noexpandtab sw=8 ts=8 sts=0:
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*
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* file.c - operations for regular (text) files.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this program; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 021110-1307, USA.
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*
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* Based on sysfs:
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* sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
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*
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* configfs Copyright (C) 2005 Oracle. All rights reserved.
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*/
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#include <linux/fs.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <asm/uaccess.h>
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#include <asm/semaphore.h>
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#include <linux/configfs.h>
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#include "configfs_internal.h"
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struct configfs_buffer {
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size_t count;
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loff_t pos;
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char * page;
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struct configfs_item_operations * ops;
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struct semaphore sem;
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int needs_read_fill;
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};
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/**
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* fill_read_buffer - allocate and fill buffer from item.
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* @dentry: dentry pointer.
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* @buffer: data buffer for file.
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*
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* Allocate @buffer->page, if it hasn't been already, then call the
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* config_item's show() method to fill the buffer with this attribute's
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* data.
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* This is called only once, on the file's first read.
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*/
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static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buffer)
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{
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struct configfs_attribute * attr = to_attr(dentry);
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struct config_item * item = to_item(dentry->d_parent);
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struct configfs_item_operations * ops = buffer->ops;
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int ret = 0;
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ssize_t count;
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if (!buffer->page)
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buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
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if (!buffer->page)
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return -ENOMEM;
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count = ops->show_attribute(item,attr,buffer->page);
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buffer->needs_read_fill = 0;
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BUG_ON(count > (ssize_t)PAGE_SIZE);
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if (count >= 0)
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buffer->count = count;
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else
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ret = count;
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return ret;
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}
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/**
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* flush_read_buffer - push buffer to userspace.
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* @buffer: data buffer for file.
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* @userbuf: user-passed buffer.
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* @count: number of bytes requested.
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* @ppos: file position.
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*
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* Copy the buffer we filled in fill_read_buffer() to userspace.
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* This is done at the reader's leisure, copying and advancing
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* the amount they specify each time.
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* This may be called continuously until the buffer is empty.
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*/
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static int flush_read_buffer(struct configfs_buffer * buffer, char __user * buf,
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size_t count, loff_t * ppos)
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{
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int error;
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if (*ppos > buffer->count)
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return 0;
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if (count > (buffer->count - *ppos))
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count = buffer->count - *ppos;
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error = copy_to_user(buf,buffer->page + *ppos,count);
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if (!error)
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*ppos += count;
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return error ? -EFAULT : count;
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}
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/**
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* configfs_read_file - read an attribute.
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* @file: file pointer.
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* @buf: buffer to fill.
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* @count: number of bytes to read.
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* @ppos: starting offset in file.
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*
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* Userspace wants to read an attribute file. The attribute descriptor
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* is in the file's ->d_fsdata. The target item is in the directory's
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* ->d_fsdata.
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*
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* We call fill_read_buffer() to allocate and fill the buffer from the
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* item's show() method exactly once (if the read is happening from
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* the beginning of the file). That should fill the entire buffer with
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* all the data the item has to offer for that attribute.
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* We then call flush_read_buffer() to copy the buffer to userspace
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* in the increments specified.
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*/
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static ssize_t
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configfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
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{
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struct configfs_buffer * buffer = file->private_data;
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ssize_t retval = 0;
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down(&buffer->sem);
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if (buffer->needs_read_fill) {
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if ((retval = fill_read_buffer(file->f_dentry,buffer)))
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goto out;
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}
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pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
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__FUNCTION__, count, *ppos, buffer->page);
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retval = flush_read_buffer(buffer,buf,count,ppos);
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out:
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up(&buffer->sem);
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return retval;
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}
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/**
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* fill_write_buffer - copy buffer from userspace.
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* @buffer: data buffer for file.
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* @buf: data from user.
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* @count: number of bytes in @userbuf.
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*
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* Allocate @buffer->page if it hasn't been already, then
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* copy the user-supplied buffer into it.
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*/
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static int
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fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size_t count)
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{
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int error;
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if (!buffer->page)
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buffer->page = (char *)get_zeroed_page(GFP_KERNEL);
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if (!buffer->page)
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return -ENOMEM;
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if (count > PAGE_SIZE)
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count = PAGE_SIZE;
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error = copy_from_user(buffer->page,buf,count);
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buffer->needs_read_fill = 1;
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return error ? -EFAULT : count;
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}
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/**
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* flush_write_buffer - push buffer to config_item.
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* @dentry: dentry to the attribute
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* @buffer: data buffer for file.
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* @count: number of bytes
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*
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* Get the correct pointers for the config_item and the attribute we're
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* dealing with, then call the store() method for the attribute,
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* passing the buffer that we acquired in fill_write_buffer().
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*/
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static int
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flush_write_buffer(struct dentry * dentry, struct configfs_buffer * buffer, size_t count)
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{
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struct configfs_attribute * attr = to_attr(dentry);
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struct config_item * item = to_item(dentry->d_parent);
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struct configfs_item_operations * ops = buffer->ops;
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return ops->store_attribute(item,attr,buffer->page,count);
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}
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/**
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* configfs_write_file - write an attribute.
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* @file: file pointer
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* @buf: data to write
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* @count: number of bytes
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* @ppos: starting offset
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*
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* Similar to configfs_read_file(), though working in the opposite direction.
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* We allocate and fill the data from the user in fill_write_buffer(),
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* then push it to the config_item in flush_write_buffer().
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* There is no easy way for us to know if userspace is only doing a partial
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* write, so we don't support them. We expect the entire buffer to come
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* on the first write.
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* Hint: if you're writing a value, first read the file, modify only the
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* the value you're changing, then write entire buffer back.
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*/
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static ssize_t
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configfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
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{
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struct configfs_buffer * buffer = file->private_data;
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ssize_t len;
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down(&buffer->sem);
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len = fill_write_buffer(buffer, buf, count);
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if (len > 0)
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len = flush_write_buffer(file->f_dentry, buffer, count);
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if (len > 0)
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*ppos += len;
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up(&buffer->sem);
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return len;
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}
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static int check_perm(struct inode * inode, struct file * file)
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{
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struct config_item *item = configfs_get_config_item(file->f_dentry->d_parent);
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struct configfs_attribute * attr = to_attr(file->f_dentry);
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struct configfs_buffer * buffer;
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struct configfs_item_operations * ops = NULL;
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int error = 0;
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if (!item || !attr)
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goto Einval;
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/* Grab the module reference for this attribute if we have one */
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if (!try_module_get(attr->ca_owner)) {
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error = -ENODEV;
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goto Done;
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}
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if (item->ci_type)
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ops = item->ci_type->ct_item_ops;
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else
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goto Eaccess;
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/* File needs write support.
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* The inode's perms must say it's ok,
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* and we must have a store method.
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*/
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if (file->f_mode & FMODE_WRITE) {
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if (!(inode->i_mode & S_IWUGO) || !ops->store_attribute)
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goto Eaccess;
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}
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/* File needs read support.
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* The inode's perms must say it's ok, and we there
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* must be a show method for it.
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*/
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if (file->f_mode & FMODE_READ) {
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if (!(inode->i_mode & S_IRUGO) || !ops->show_attribute)
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goto Eaccess;
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}
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/* No error? Great, allocate a buffer for the file, and store it
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* it in file->private_data for easy access.
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*/
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buffer = kzalloc(sizeof(struct configfs_buffer),GFP_KERNEL);
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if (!buffer) {
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error = -ENOMEM;
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goto Enomem;
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}
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init_MUTEX(&buffer->sem);
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buffer->needs_read_fill = 1;
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buffer->ops = ops;
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file->private_data = buffer;
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goto Done;
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Einval:
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error = -EINVAL;
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goto Done;
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Eaccess:
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error = -EACCES;
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Enomem:
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module_put(attr->ca_owner);
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Done:
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if (error && item)
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config_item_put(item);
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return error;
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}
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static int configfs_open_file(struct inode * inode, struct file * filp)
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{
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return check_perm(inode,filp);
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}
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static int configfs_release(struct inode * inode, struct file * filp)
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{
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struct config_item * item = to_item(filp->f_dentry->d_parent);
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struct configfs_attribute * attr = to_attr(filp->f_dentry);
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struct module * owner = attr->ca_owner;
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struct configfs_buffer * buffer = filp->private_data;
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if (item)
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config_item_put(item);
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/* After this point, attr should not be accessed. */
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module_put(owner);
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if (buffer) {
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if (buffer->page)
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free_page((unsigned long)buffer->page);
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kfree(buffer);
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}
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return 0;
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}
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const struct file_operations configfs_file_operations = {
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.read = configfs_read_file,
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.write = configfs_write_file,
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.llseek = generic_file_llseek,
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.open = configfs_open_file,
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.release = configfs_release,
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};
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int configfs_add_file(struct dentry * dir, const struct configfs_attribute * attr, int type)
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{
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struct configfs_dirent * parent_sd = dir->d_fsdata;
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umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
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int error = 0;
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mutex_lock(&dir->d_inode->i_mutex);
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error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode, type);
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mutex_unlock(&dir->d_inode->i_mutex);
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return error;
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}
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/**
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* configfs_create_file - create an attribute file for an item.
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* @item: item we're creating for.
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* @attr: atrribute descriptor.
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*/
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int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr)
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{
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BUG_ON(!item || !item->ci_dentry || !attr);
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return configfs_add_file(item->ci_dentry, attr,
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CONFIGFS_ITEM_ATTR);
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}
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