linux/fs/ecryptfs/mmap.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * eCryptfs: Linux filesystem encryption layer
 * This is where eCryptfs coordinates the symmetric encryption and
 * decryption of the file data as it passes between the lower
 * encrypted file and the upper decrypted file.
 *
 * Copyright (C) 1997-2003 Erez Zadok
 * Copyright (C) 2001-2003 Stony Brook University
 * Copyright (C) 2004-2007 International Business Machines Corp.
 *   Author(s): Michael A. Halcrow <[email protected]>
 */

#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/page-flags.h>
#include <linux/mount.h>
#include <linux/file.h>
#include <linux/scatterlist.h>
#include <linux/slab.h>
#include <linux/xattr.h>
#include <asm/unaligned.h>
#include "ecryptfs_kernel.h"

/*
 * ecryptfs_get_locked_page
 *
 * Get one page from cache or lower f/s, return error otherwise.
 *
 * Returns locked and up-to-date page (if ok), with increased
 * refcnt.
 */
struct page *ecryptfs_get_locked_page(struct inode *inode, loff_t index)
{ … }

/**
 * ecryptfs_writepage
 * @page: Page that is locked before this call is made
 * @wbc: Write-back control structure
 *
 * Returns zero on success; non-zero otherwise
 *
 * This is where we encrypt the data and pass the encrypted data to
 * the lower filesystem.  In OpenPGP-compatible mode, we operate on
 * entire underlying packets.
 */
static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
{ … }

static void strip_xattr_flag(char *page_virt,
			     struct ecryptfs_crypt_stat *crypt_stat)
{ … }

/*
 *   Header Extent:
 *     Octets 0-7:        Unencrypted file size (big-endian)
 *     Octets 8-15:       eCryptfs special marker
 *     Octets 16-19:      Flags
 *      Octet 16:         File format version number (between 0 and 255)
 *      Octets 17-18:     Reserved
 *      Octet 19:         Bit 1 (lsb): Reserved
 *                        Bit 2: Encrypted?
 *                        Bits 3-8: Reserved
 *     Octets 20-23:      Header extent size (big-endian)
 *     Octets 24-25:      Number of header extents at front of file
 *                        (big-endian)
 *     Octet  26:         Begin RFC 2440 authentication token packet set
 */

/**
 * ecryptfs_copy_up_encrypted_with_header
 * @page: Sort of a ``virtual'' representation of the encrypted lower
 *        file. The actual lower file does not have the metadata in
 *        the header. This is locked.
 * @crypt_stat: The eCryptfs inode's cryptographic context
 *
 * The ``view'' is the version of the file that userspace winds up
 * seeing, with the header information inserted.
 */
static int
ecryptfs_copy_up_encrypted_with_header(struct page *page,
				       struct ecryptfs_crypt_stat *crypt_stat)
{ … }

/**
 * ecryptfs_read_folio
 * @file: An eCryptfs file
 * @folio: Folio from eCryptfs inode mapping into which to stick the read data
 *
 * Read in a folio, decrypting if necessary.
 *
 * Returns zero on success; non-zero on error.
 */
static int ecryptfs_read_folio(struct file *file, struct folio *folio)
{ … }

/*
 * Called with lower inode mutex held.
 */
static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
{ … }

/**
 * ecryptfs_write_begin
 * @file: The eCryptfs file
 * @mapping: The eCryptfs object
 * @pos: The file offset at which to start writing
 * @len: Length of the write
 * @pagep: Pointer to return the page
 * @fsdata: Pointer to return fs data (unused)
 *
 * This function must zero any hole we create
 *
 * Returns zero on success; non-zero otherwise
 */
static int ecryptfs_write_begin(struct file *file,
			struct address_space *mapping,
			loff_t pos, unsigned len,
			struct page **pagep, void **fsdata)
{ … }

/*
 * ecryptfs_write_inode_size_to_header
 *
 * Writes the lower file size to the first 8 bytes of the header.
 *
 * Returns zero on success; non-zero on error.
 */
static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
{ … }

struct kmem_cache *ecryptfs_xattr_cache;

static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
{ … }

int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
{ … }

/**
 * ecryptfs_write_end
 * @file: The eCryptfs file object
 * @mapping: The eCryptfs object
 * @pos: The file position
 * @len: The length of the data (unused)
 * @copied: The amount of data copied
 * @page: The eCryptfs page
 * @fsdata: The fsdata (unused)
 */
static int ecryptfs_write_end(struct file *file,
			struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *page, void *fsdata)
{ … }

static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
{ … }

#include <linux/buffer_head.h>

const struct address_space_operations ecryptfs_aops = …;