356 lines
11 KiB
C
356 lines
11 KiB
C
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/**
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* eCryptfs: Linux filesystem encryption layer
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*
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* Copyright (C) 2007 International Business Machines Corp.
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* Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
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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 License as
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* published by the Free Software Foundation; either version 2 of the
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* 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, but
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* 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 License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
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* 02111-1307, USA.
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*/
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#include <linux/fs.h>
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#include <linux/pagemap.h>
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#include "ecryptfs_kernel.h"
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/**
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* ecryptfs_write_lower
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* @ecryptfs_inode: The eCryptfs inode
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* @data: Data to write
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* @offset: Byte offset in the lower file to which to write the data
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* @size: Number of bytes from @data to write at @offset in the lower
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* file
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*
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* Write data to the lower file.
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*
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* Returns bytes written on success; less than zero on error
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*/
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int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
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loff_t offset, size_t size)
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{
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struct ecryptfs_inode_info *inode_info;
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mm_segment_t fs_save;
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ssize_t rc;
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inode_info = ecryptfs_inode_to_private(ecryptfs_inode);
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mutex_lock(&inode_info->lower_file_mutex);
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BUG_ON(!inode_info->lower_file);
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inode_info->lower_file->f_pos = offset;
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fs_save = get_fs();
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set_fs(get_ds());
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rc = vfs_write(inode_info->lower_file, data, size,
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&inode_info->lower_file->f_pos);
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set_fs(fs_save);
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mutex_unlock(&inode_info->lower_file_mutex);
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mark_inode_dirty_sync(ecryptfs_inode);
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return rc;
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}
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/**
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* ecryptfs_write_lower_page_segment
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* @ecryptfs_inode: The eCryptfs inode
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* @page_for_lower: The page containing the data to be written to the
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* lower file
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* @offset_in_page: The offset in the @page_for_lower from which to
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* start writing the data
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* @size: The amount of data from @page_for_lower to write to the
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* lower file
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*
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* Determines the byte offset in the file for the given page and
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* offset within the page, maps the page, and makes the call to write
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* the contents of @page_for_lower to the lower inode.
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*
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* Returns zero on success; non-zero otherwise
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*/
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int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
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struct page *page_for_lower,
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size_t offset_in_page, size_t size)
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{
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char *virt;
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loff_t offset;
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int rc;
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offset = ((((loff_t)page_for_lower->index) << PAGE_CACHE_SHIFT)
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+ offset_in_page);
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virt = kmap(page_for_lower);
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rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
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if (rc > 0)
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rc = 0;
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kunmap(page_for_lower);
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return rc;
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}
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/**
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* ecryptfs_write
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* @ecryptfs_file: The eCryptfs file into which to write
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* @data: Virtual address where data to write is located
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* @offset: Offset in the eCryptfs file at which to begin writing the
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* data from @data
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* @size: The number of bytes to write from @data
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*
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* Write an arbitrary amount of data to an arbitrary location in the
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* eCryptfs inode page cache. This is done on a page-by-page, and then
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* by an extent-by-extent, basis; individual extents are encrypted and
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* written to the lower page cache (via VFS writes). This function
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* takes care of all the address translation to locations in the lower
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* filesystem; it also handles truncate events, writing out zeros
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* where necessary.
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*
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* Returns zero on success; non-zero otherwise
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*/
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int ecryptfs_write(struct file *ecryptfs_file, char *data, loff_t offset,
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size_t size)
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{
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struct page *ecryptfs_page;
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struct ecryptfs_crypt_stat *crypt_stat;
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struct inode *ecryptfs_inode = ecryptfs_file->f_dentry->d_inode;
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char *ecryptfs_page_virt;
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loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode);
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loff_t data_offset = 0;
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loff_t pos;
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int rc = 0;
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crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
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/*
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* if we are writing beyond current size, then start pos
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* at the current size - we'll fill in zeros from there.
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*/
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if (offset > ecryptfs_file_size)
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pos = ecryptfs_file_size;
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else
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pos = offset;
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while (pos < (offset + size)) {
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pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
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size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
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size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
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size_t total_remaining_bytes = ((offset + size) - pos);
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if (num_bytes > total_remaining_bytes)
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num_bytes = total_remaining_bytes;
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if (pos < offset) {
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/* remaining zeros to write, up to destination offset */
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size_t total_remaining_zeros = (offset - pos);
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if (num_bytes > total_remaining_zeros)
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num_bytes = total_remaining_zeros;
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}
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ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file,
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ecryptfs_page_idx);
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if (IS_ERR(ecryptfs_page)) {
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rc = PTR_ERR(ecryptfs_page);
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printk(KERN_ERR "%s: Error getting page at "
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"index [%ld] from eCryptfs inode "
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"mapping; rc = [%d]\n", __func__,
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ecryptfs_page_idx, rc);
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goto out;
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}
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ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0);
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/*
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* pos: where we're now writing, offset: where the request was
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* If current pos is before request, we are filling zeros
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* If we are at or beyond request, we are writing the *data*
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* If we're in a fresh page beyond eof, zero it in either case
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*/
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if (pos < offset || !start_offset_in_page) {
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/* We are extending past the previous end of the file.
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* Fill in zero values to the end of the page */
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memset(((char *)ecryptfs_page_virt
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+ start_offset_in_page), 0,
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PAGE_CACHE_SIZE - start_offset_in_page);
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}
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/* pos >= offset, we are now writing the data request */
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if (pos >= offset) {
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memcpy(((char *)ecryptfs_page_virt
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+ start_offset_in_page),
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(data + data_offset), num_bytes);
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data_offset += num_bytes;
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}
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kunmap_atomic(ecryptfs_page_virt, KM_USER0);
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flush_dcache_page(ecryptfs_page);
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SetPageUptodate(ecryptfs_page);
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unlock_page(ecryptfs_page);
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if (crypt_stat->flags & ECRYPTFS_ENCRYPTED)
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rc = ecryptfs_encrypt_page(ecryptfs_page);
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else
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rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
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ecryptfs_page,
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start_offset_in_page,
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data_offset);
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page_cache_release(ecryptfs_page);
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if (rc) {
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printk(KERN_ERR "%s: Error encrypting "
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"page; rc = [%d]\n", __func__, rc);
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goto out;
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}
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pos += num_bytes;
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}
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if ((offset + size) > ecryptfs_file_size) {
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i_size_write(ecryptfs_inode, (offset + size));
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if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
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rc = ecryptfs_write_inode_size_to_metadata(
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ecryptfs_inode);
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if (rc) {
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printk(KERN_ERR "Problem with "
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"ecryptfs_write_inode_size_to_metadata; "
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"rc = [%d]\n", rc);
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goto out;
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}
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}
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}
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out:
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return rc;
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}
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/**
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* ecryptfs_read_lower
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* @data: The read data is stored here by this function
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* @offset: Byte offset in the lower file from which to read the data
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* @size: Number of bytes to read from @offset of the lower file and
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* store into @data
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* @ecryptfs_inode: The eCryptfs inode
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*
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* Read @size bytes of data at byte offset @offset from the lower
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* inode into memory location @data.
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*
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* Returns bytes read on success; 0 on EOF; less than zero on error
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*/
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int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
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struct inode *ecryptfs_inode)
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{
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struct ecryptfs_inode_info *inode_info =
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ecryptfs_inode_to_private(ecryptfs_inode);
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mm_segment_t fs_save;
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ssize_t rc;
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mutex_lock(&inode_info->lower_file_mutex);
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BUG_ON(!inode_info->lower_file);
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inode_info->lower_file->f_pos = offset;
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fs_save = get_fs();
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set_fs(get_ds());
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rc = vfs_read(inode_info->lower_file, data, size,
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&inode_info->lower_file->f_pos);
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set_fs(fs_save);
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mutex_unlock(&inode_info->lower_file_mutex);
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return rc;
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}
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/**
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* ecryptfs_read_lower_page_segment
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* @page_for_ecryptfs: The page into which data for eCryptfs will be
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* written
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* @offset_in_page: Offset in @page_for_ecryptfs from which to start
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* writing
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* @size: The number of bytes to write into @page_for_ecryptfs
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* @ecryptfs_inode: The eCryptfs inode
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*
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* Determines the byte offset in the file for the given page and
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* offset within the page, maps the page, and makes the call to read
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* the contents of @page_for_ecryptfs from the lower inode.
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*
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* Returns zero on success; non-zero otherwise
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*/
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int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
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pgoff_t page_index,
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size_t offset_in_page, size_t size,
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struct inode *ecryptfs_inode)
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{
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char *virt;
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loff_t offset;
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int rc;
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offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page);
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virt = kmap(page_for_ecryptfs);
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rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
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if (rc > 0)
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rc = 0;
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kunmap(page_for_ecryptfs);
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flush_dcache_page(page_for_ecryptfs);
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return rc;
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}
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#if 0
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/**
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* ecryptfs_read
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* @data: The virtual address into which to write the data read (and
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* possibly decrypted) from the lower file
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* @offset: The offset in the decrypted view of the file from which to
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* read into @data
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* @size: The number of bytes to read into @data
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* @ecryptfs_file: The eCryptfs file from which to read
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*
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* Read an arbitrary amount of data from an arbitrary location in the
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* eCryptfs page cache. This is done on an extent-by-extent basis;
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* individual extents are decrypted and read from the lower page
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* cache (via VFS reads). This function takes care of all the
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* address translation to locations in the lower filesystem.
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*
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* Returns zero on success; non-zero otherwise
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*/
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int ecryptfs_read(char *data, loff_t offset, size_t size,
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struct file *ecryptfs_file)
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{
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struct page *ecryptfs_page;
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char *ecryptfs_page_virt;
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loff_t ecryptfs_file_size =
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i_size_read(ecryptfs_file->f_dentry->d_inode);
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loff_t data_offset = 0;
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loff_t pos;
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int rc = 0;
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if ((offset + size) > ecryptfs_file_size) {
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rc = -EINVAL;
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printk(KERN_ERR "%s: Attempt to read data past the end of the "
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"file; offset = [%lld]; size = [%td]; "
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"ecryptfs_file_size = [%lld]\n",
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__func__, offset, size, ecryptfs_file_size);
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goto out;
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}
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pos = offset;
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while (pos < (offset + size)) {
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pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
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size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
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size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
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size_t total_remaining_bytes = ((offset + size) - pos);
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if (num_bytes > total_remaining_bytes)
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num_bytes = total_remaining_bytes;
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ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file,
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ecryptfs_page_idx);
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if (IS_ERR(ecryptfs_page)) {
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rc = PTR_ERR(ecryptfs_page);
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printk(KERN_ERR "%s: Error getting page at "
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"index [%ld] from eCryptfs inode "
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"mapping; rc = [%d]\n", __func__,
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ecryptfs_page_idx, rc);
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goto out;
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}
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ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0);
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memcpy((data + data_offset),
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((char *)ecryptfs_page_virt + start_offset_in_page),
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num_bytes);
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kunmap_atomic(ecryptfs_page_virt, KM_USER0);
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flush_dcache_page(ecryptfs_page);
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|
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SetPageUptodate(ecryptfs_page);
|
||
|
|
unlock_page(ecryptfs_page);
|
||
|
|
page_cache_release(ecryptfs_page);
|
||
|
|
pos += num_bytes;
|
||
|
|
data_offset += num_bytes;
|
||
|
|
}
|
||
|
|
out:
|
||
|
|
return rc;
|
||
|
|
}
|
||
|
|
#endif /* 0 */
|