546 lines
15 KiB
C
546 lines
15 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/**
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* eCryptfs: Linux filesystem encryption layer
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* This is where eCryptfs coordinates the symmetric encryption and
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* decryption of the file data as it passes between the lower
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* encrypted file and the upper decrypted file.
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*
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* Copyright (C) 1997-2003 Erez Zadok
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* Copyright (C) 2001-2003 Stony Brook University
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* Copyright (C) 2004-2007 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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#include <linux/pagemap.h>
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#include <linux/writeback.h>
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#include <linux/page-flags.h>
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#include <linux/mount.h>
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#include <linux/file.h>
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#include <linux/scatterlist.h>
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#include <linux/slab.h>
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#include <linux/xattr.h>
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#include <asm/unaligned.h>
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#include "ecryptfs_kernel.h"
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/**
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* ecryptfs_get_locked_page
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*
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* Get one page from cache or lower f/s, return error otherwise.
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*
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* Returns locked and up-to-date page (if ok), with increased
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* refcnt.
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*/
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struct page *ecryptfs_get_locked_page(struct inode *inode, loff_t index)
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{
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struct page *page = read_mapping_page(inode->i_mapping, index, NULL);
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if (!IS_ERR(page))
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lock_page(page);
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return page;
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}
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/**
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* ecryptfs_writepage
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* @page: Page that is locked before this call is made
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*
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* Returns zero on success; non-zero otherwise
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*
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* This is where we encrypt the data and pass the encrypted data to
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* the lower filesystem. In OpenPGP-compatible mode, we operate on
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* entire underlying packets.
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*/
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static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
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{
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int rc;
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rc = ecryptfs_encrypt_page(page);
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if (rc) {
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ecryptfs_printk(KERN_WARNING, "Error encrypting "
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"page (upper index [0x%.16lx])\n", page->index);
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ClearPageUptodate(page);
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goto out;
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}
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SetPageUptodate(page);
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out:
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unlock_page(page);
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return rc;
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}
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static void strip_xattr_flag(char *page_virt,
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struct ecryptfs_crypt_stat *crypt_stat)
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{
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if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
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size_t written;
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crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
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ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
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&written);
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crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
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}
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}
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/**
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* Header Extent:
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* Octets 0-7: Unencrypted file size (big-endian)
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* Octets 8-15: eCryptfs special marker
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* Octets 16-19: Flags
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* Octet 16: File format version number (between 0 and 255)
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* Octets 17-18: Reserved
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* Octet 19: Bit 1 (lsb): Reserved
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* Bit 2: Encrypted?
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* Bits 3-8: Reserved
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* Octets 20-23: Header extent size (big-endian)
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* Octets 24-25: Number of header extents at front of file
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* (big-endian)
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* Octet 26: Begin RFC 2440 authentication token packet set
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*/
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/**
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* ecryptfs_copy_up_encrypted_with_header
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* @page: Sort of a ``virtual'' representation of the encrypted lower
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* file. The actual lower file does not have the metadata in
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* the header. This is locked.
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* @crypt_stat: The eCryptfs inode's cryptographic context
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*
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* The ``view'' is the version of the file that userspace winds up
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* seeing, with the header information inserted.
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*/
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static int
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ecryptfs_copy_up_encrypted_with_header(struct page *page,
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struct ecryptfs_crypt_stat *crypt_stat)
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{
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loff_t extent_num_in_page = 0;
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loff_t num_extents_per_page = (PAGE_SIZE
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/ crypt_stat->extent_size);
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int rc = 0;
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while (extent_num_in_page < num_extents_per_page) {
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loff_t view_extent_num = ((((loff_t)page->index)
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* num_extents_per_page)
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+ extent_num_in_page);
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size_t num_header_extents_at_front =
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(crypt_stat->metadata_size / crypt_stat->extent_size);
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if (view_extent_num < num_header_extents_at_front) {
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/* This is a header extent */
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char *page_virt;
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page_virt = kmap_atomic(page);
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memset(page_virt, 0, PAGE_SIZE);
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/* TODO: Support more than one header extent */
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if (view_extent_num == 0) {
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size_t written;
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rc = ecryptfs_read_xattr_region(
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page_virt, page->mapping->host);
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strip_xattr_flag(page_virt + 16, crypt_stat);
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ecryptfs_write_header_metadata(page_virt + 20,
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crypt_stat,
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&written);
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}
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kunmap_atomic(page_virt);
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flush_dcache_page(page);
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if (rc) {
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printk(KERN_ERR "%s: Error reading xattr "
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"region; rc = [%d]\n", __func__, rc);
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goto out;
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}
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} else {
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/* This is an encrypted data extent */
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loff_t lower_offset =
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((view_extent_num * crypt_stat->extent_size)
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- crypt_stat->metadata_size);
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rc = ecryptfs_read_lower_page_segment(
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page, (lower_offset >> PAGE_SHIFT),
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(lower_offset & ~PAGE_MASK),
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crypt_stat->extent_size, page->mapping->host);
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if (rc) {
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printk(KERN_ERR "%s: Error attempting to read "
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"extent at offset [%lld] in the lower "
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"file; rc = [%d]\n", __func__,
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lower_offset, rc);
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goto out;
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}
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}
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extent_num_in_page++;
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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_readpage
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* @file: An eCryptfs file
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* @page: Page from eCryptfs inode mapping into which to stick the read data
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*
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* Read in a page, decrypting if necessary.
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*
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* Returns zero on success; non-zero on error.
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*/
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static int ecryptfs_readpage(struct file *file, struct page *page)
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{
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struct ecryptfs_crypt_stat *crypt_stat =
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&ecryptfs_inode_to_private(page->mapping->host)->crypt_stat;
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int rc = 0;
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if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
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rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
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PAGE_SIZE,
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page->mapping->host);
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} else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
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if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
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rc = ecryptfs_copy_up_encrypted_with_header(page,
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crypt_stat);
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if (rc) {
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printk(KERN_ERR "%s: Error attempting to copy "
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"the encrypted content from the lower "
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"file whilst inserting the metadata "
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"from the xattr into the header; rc = "
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"[%d]\n", __func__, rc);
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goto out;
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}
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} else {
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rc = ecryptfs_read_lower_page_segment(
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page, page->index, 0, PAGE_SIZE,
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page->mapping->host);
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if (rc) {
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printk(KERN_ERR "Error reading page; rc = "
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"[%d]\n", rc);
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goto out;
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}
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}
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} else {
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rc = ecryptfs_decrypt_page(page);
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if (rc) {
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ecryptfs_printk(KERN_ERR, "Error decrypting page; "
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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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out:
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if (rc)
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ClearPageUptodate(page);
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else
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SetPageUptodate(page);
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ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n",
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page->index);
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unlock_page(page);
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return rc;
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}
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/**
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* Called with lower inode mutex held.
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*/
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static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
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{
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struct inode *inode = page->mapping->host;
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int end_byte_in_page;
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if ((i_size_read(inode) / PAGE_SIZE) != page->index)
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goto out;
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end_byte_in_page = i_size_read(inode) % PAGE_SIZE;
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if (to > end_byte_in_page)
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end_byte_in_page = to;
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zero_user_segment(page, end_byte_in_page, PAGE_SIZE);
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out:
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return 0;
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}
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/**
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* ecryptfs_write_begin
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* @file: The eCryptfs file
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* @mapping: The eCryptfs object
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* @pos: The file offset at which to start writing
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* @len: Length of the write
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* @flags: Various flags
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* @pagep: Pointer to return the page
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* @fsdata: Pointer to return fs data (unused)
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*
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* This function must zero any hole we create
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*
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* Returns zero on success; non-zero otherwise
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*/
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static int ecryptfs_write_begin(struct file *file,
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struct address_space *mapping,
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loff_t pos, unsigned len, unsigned flags,
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struct page **pagep, void **fsdata)
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{
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pgoff_t index = pos >> PAGE_SHIFT;
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struct page *page;
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loff_t prev_page_end_size;
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int rc = 0;
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page = grab_cache_page_write_begin(mapping, index, flags);
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if (!page)
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return -ENOMEM;
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*pagep = page;
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prev_page_end_size = ((loff_t)index << PAGE_SHIFT);
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if (!PageUptodate(page)) {
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struct ecryptfs_crypt_stat *crypt_stat =
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&ecryptfs_inode_to_private(mapping->host)->crypt_stat;
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if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
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rc = ecryptfs_read_lower_page_segment(
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page, index, 0, PAGE_SIZE, mapping->host);
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if (rc) {
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printk(KERN_ERR "%s: Error attempting to read "
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"lower page segment; rc = [%d]\n",
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__func__, rc);
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ClearPageUptodate(page);
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goto out;
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} else
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SetPageUptodate(page);
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} else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
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if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
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rc = ecryptfs_copy_up_encrypted_with_header(
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page, crypt_stat);
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if (rc) {
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printk(KERN_ERR "%s: Error attempting "
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"to copy the encrypted content "
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"from the lower file whilst "
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"inserting the metadata from "
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"the xattr into the header; rc "
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"= [%d]\n", __func__, rc);
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ClearPageUptodate(page);
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goto out;
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}
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SetPageUptodate(page);
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} else {
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rc = ecryptfs_read_lower_page_segment(
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page, index, 0, PAGE_SIZE,
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mapping->host);
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if (rc) {
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printk(KERN_ERR "%s: Error reading "
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"page; rc = [%d]\n",
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__func__, rc);
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ClearPageUptodate(page);
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goto out;
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}
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SetPageUptodate(page);
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}
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} else {
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if (prev_page_end_size
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>= i_size_read(page->mapping->host)) {
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zero_user(page, 0, PAGE_SIZE);
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SetPageUptodate(page);
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} else if (len < PAGE_SIZE) {
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rc = ecryptfs_decrypt_page(page);
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if (rc) {
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printk(KERN_ERR "%s: Error decrypting "
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"page at index [%ld]; "
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"rc = [%d]\n",
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__func__, page->index, rc);
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ClearPageUptodate(page);
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goto out;
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}
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SetPageUptodate(page);
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}
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}
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}
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/* If creating a page or more of holes, zero them out via truncate.
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* Note, this will increase i_size. */
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if (index != 0) {
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if (prev_page_end_size > i_size_read(page->mapping->host)) {
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rc = ecryptfs_truncate(file->f_path.dentry,
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prev_page_end_size);
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if (rc) {
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printk(KERN_ERR "%s: Error on attempt to "
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"truncate to (higher) offset [%lld];"
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" rc = [%d]\n", __func__,
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prev_page_end_size, rc);
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goto out;
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}
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}
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}
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/* Writing to a new page, and creating a small hole from start
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* of page? Zero it out. */
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if ((i_size_read(mapping->host) == prev_page_end_size)
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&& (pos != 0))
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zero_user(page, 0, PAGE_SIZE);
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out:
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if (unlikely(rc)) {
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unlock_page(page);
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put_page(page);
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*pagep = NULL;
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}
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return rc;
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}
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/**
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* ecryptfs_write_inode_size_to_header
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*
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* Writes the lower file size to the first 8 bytes of the header.
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*
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* Returns zero on success; non-zero on error.
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*/
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static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
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{
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char *file_size_virt;
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int rc;
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file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
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if (!file_size_virt) {
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rc = -ENOMEM;
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goto out;
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}
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put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
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rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
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sizeof(u64));
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kfree(file_size_virt);
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if (rc < 0)
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printk(KERN_ERR "%s: Error writing file size to header; "
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"rc = [%d]\n", __func__, rc);
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else
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rc = 0;
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out:
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return rc;
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}
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struct kmem_cache *ecryptfs_xattr_cache;
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static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
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{
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ssize_t size;
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void *xattr_virt;
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struct dentry *lower_dentry =
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ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry;
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struct inode *lower_inode = d_inode(lower_dentry);
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int rc;
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if (!(lower_inode->i_opflags & IOP_XATTR)) {
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printk(KERN_WARNING
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"No support for setting xattr in lower filesystem\n");
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rc = -ENOSYS;
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goto out;
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}
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xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
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if (!xattr_virt) {
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rc = -ENOMEM;
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goto out;
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}
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inode_lock(lower_inode);
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size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
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xattr_virt, PAGE_SIZE);
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if (size < 0)
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size = 8;
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put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
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rc = __vfs_setxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
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xattr_virt, size, 0);
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inode_unlock(lower_inode);
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if (rc)
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printk(KERN_ERR "Error whilst attempting to write inode size "
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"to lower file xattr; rc = [%d]\n", rc);
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kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
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out:
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return rc;
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}
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int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
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{
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struct ecryptfs_crypt_stat *crypt_stat;
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crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
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BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
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if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
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return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
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else
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return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
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}
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/**
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* ecryptfs_write_end
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* @file: The eCryptfs file object
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* @mapping: The eCryptfs object
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* @pos: The file position
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* @len: The length of the data (unused)
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* @copied: The amount of data copied
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* @page: The eCryptfs page
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* @fsdata: The fsdata (unused)
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*/
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static int ecryptfs_write_end(struct file *file,
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struct address_space *mapping,
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loff_t pos, unsigned len, unsigned copied,
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struct page *page, void *fsdata)
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{
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pgoff_t index = pos >> PAGE_SHIFT;
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unsigned from = pos & (PAGE_SIZE - 1);
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unsigned to = from + copied;
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struct inode *ecryptfs_inode = mapping->host;
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struct ecryptfs_crypt_stat *crypt_stat =
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&ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
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int rc;
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ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
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"(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
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if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
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rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
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to);
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if (!rc) {
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rc = copied;
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fsstack_copy_inode_size(ecryptfs_inode,
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ecryptfs_inode_to_lower(ecryptfs_inode));
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}
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goto out;
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}
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if (!PageUptodate(page)) {
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if (copied < PAGE_SIZE) {
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rc = 0;
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goto out;
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}
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SetPageUptodate(page);
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}
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/* Fills in zeros if 'to' goes beyond inode size */
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rc = fill_zeros_to_end_of_page(page, to);
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if (rc) {
|
|
ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
|
|
"zeros in page with index = [0x%.16lx]\n", index);
|
|
goto out;
|
|
}
|
|
rc = ecryptfs_encrypt_page(page);
|
|
if (rc) {
|
|
ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
|
|
"index [0x%.16lx])\n", index);
|
|
goto out;
|
|
}
|
|
if (pos + copied > i_size_read(ecryptfs_inode)) {
|
|
i_size_write(ecryptfs_inode, pos + copied);
|
|
ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
|
|
"[0x%.16llx]\n",
|
|
(unsigned long long)i_size_read(ecryptfs_inode));
|
|
}
|
|
rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
|
|
if (rc)
|
|
printk(KERN_ERR "Error writing inode size to metadata; "
|
|
"rc = [%d]\n", rc);
|
|
else
|
|
rc = copied;
|
|
out:
|
|
unlock_page(page);
|
|
put_page(page);
|
|
return rc;
|
|
}
|
|
|
|
static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
|
|
{
|
|
int rc = 0;
|
|
struct inode *inode;
|
|
struct inode *lower_inode;
|
|
|
|
inode = (struct inode *)mapping->host;
|
|
lower_inode = ecryptfs_inode_to_lower(inode);
|
|
if (lower_inode->i_mapping->a_ops->bmap)
|
|
rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
|
|
block);
|
|
return rc;
|
|
}
|
|
|
|
const struct address_space_operations ecryptfs_aops = {
|
|
.writepage = ecryptfs_writepage,
|
|
.readpage = ecryptfs_readpage,
|
|
.write_begin = ecryptfs_write_begin,
|
|
.write_end = ecryptfs_write_end,
|
|
.bmap = ecryptfs_bmap,
|
|
};
|