fs/ecryptfs/mmap.c - linux - Git at Google

 // 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 <mahalcro@us.ibm.com>
  */

 #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)
 {
 	struct page *page = read_mapping_page(inode->i_mapping, index, NULL);
 	if (!IS_ERR(page))
 		lock_page(page);
 	return page;
 }

 /**
  * 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)
 {
 	int rc;

 	rc = ecryptfs_encrypt_page(page);
 	if (rc) {
 		ecryptfs_printk(KERN_WARNING, "Error encrypting "
 				"page (upper index [0x%.16lx])\n", page->index);
 		ClearPageUptodate(page);
 		goto out;
 	}
 	SetPageUptodate(page);
 out:
 	unlock_page(page);
 	return rc;
 }

 static void strip_xattr_flag(char *page_virt,
 			     struct ecryptfs_crypt_stat *crypt_stat)
 {
 	if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 		size_t written;

 		crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
 		ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
 						&written);
 		crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
 	}
 }

 /*
  *   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)
 {
 	loff_t extent_num_in_page = 0;
 	loff_t num_extents_per_page = (PAGE_SIZE
 				       / crypt_stat->extent_size);
 	int rc = 0;

 	while (extent_num_in_page < num_extents_per_page) {
 		loff_t view_extent_num = ((((loff_t)page->index)
 					   * num_extents_per_page)
 					  + extent_num_in_page);
 		size_t num_header_extents_at_front =
 			(crypt_stat->metadata_size / crypt_stat->extent_size);

 		if (view_extent_num < num_header_extents_at_front) {
 			/* This is a header extent */
 			char *page_virt;

 			page_virt = kmap_atomic(page);
 			memset(page_virt, 0, PAGE_SIZE);
 			/* TODO: Support more than one header extent */
 			if (view_extent_num == 0) {
 				size_t written;

 				rc = ecryptfs_read_xattr_region(
 					page_virt, page->mapping->host);
 				strip_xattr_flag(page_virt + 16, crypt_stat);
 				ecryptfs_write_header_metadata(page_virt + 20,
 							       crypt_stat,
 							       &written);
 			}
 			kunmap_atomic(page_virt);
 			flush_dcache_page(page);
 			if (rc) {
 				printk(KERN_ERR "%s: Error reading xattr "
 				       "region; rc = [%d]\n", __func__, rc);
 				goto out;
 			}
 		} else {
 			/* This is an encrypted data extent */
 			loff_t lower_offset =
 				((view_extent_num * crypt_stat->extent_size)
 				 - crypt_stat->metadata_size);

 			rc = ecryptfs_read_lower_page_segment(
 				page, (lower_offset >> PAGE_SHIFT),
 				(lower_offset & ~PAGE_MASK),
 				crypt_stat->extent_size, page->mapping->host);
 			if (rc) {
 				printk(KERN_ERR "%s: Error attempting to read "
 				       "extent at offset [%lld] in the lower "
 				       "file; rc = [%d]\n", __func__,
 				       lower_offset, rc);
 				goto out;
 			}
 		}
 		extent_num_in_page++;
 	}
 out:
 	return rc;
 }

 /**
  * ecryptfs_readpage
  * @file: An eCryptfs file
  * @page: Page from eCryptfs inode mapping into which to stick the read data
  *
  * Read in a page, decrypting if necessary.
  *
  * Returns zero on success; non-zero on error.
  */
 static int ecryptfs_readpage(struct file *file, struct page *page)
 {
 	struct ecryptfs_crypt_stat *crypt_stat =
 		&ecryptfs_inode_to_private(page->mapping->host)->crypt_stat;
 	int rc = 0;

 	if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 		rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
 						      PAGE_SIZE,
 						      page->mapping->host);
 	} else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 		if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 			rc = ecryptfs_copy_up_encrypted_with_header(page,
 								    crypt_stat);
 			if (rc) {
 				printk(KERN_ERR "%s: Error attempting to copy "
 				       "the encrypted content from the lower "
 				       "file whilst inserting the metadata "
 				       "from the xattr into the header; rc = "
 				       "[%d]\n", __func__, rc);
 				goto out;
 			}

 		} else {
 			rc = ecryptfs_read_lower_page_segment(
 				page, page->index, 0, PAGE_SIZE,
 				page->mapping->host);
 			if (rc) {
 				printk(KERN_ERR "Error reading page; rc = "
 				       "[%d]\n", rc);
 				goto out;
 			}
 		}
 	} else {
 		rc = ecryptfs_decrypt_page(page);
 		if (rc) {
 			ecryptfs_printk(KERN_ERR, "Error decrypting page; "
 					"rc = [%d]\n", rc);
 			goto out;
 		}
 	}
 out:
 	if (rc)
 		ClearPageUptodate(page);
 	else
 		SetPageUptodate(page);
 	ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n",
 			page->index);
 	unlock_page(page);
 	return rc;
 }

 /*
  * Called with lower inode mutex held.
  */
 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
 {
 	struct inode *inode = page->mapping->host;
 	int end_byte_in_page;

 	if ((i_size_read(inode) / PAGE_SIZE) != page->index)
 		goto out;
 	end_byte_in_page = i_size_read(inode) % PAGE_SIZE;
 	if (to > end_byte_in_page)
 		end_byte_in_page = to;
 	zero_user_segment(page, end_byte_in_page, PAGE_SIZE);
 out:
 	return 0;
 }

 /**
  * 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
  * @flags: Various flags
  * @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, unsigned flags,
 			struct page **pagep, void **fsdata)
 {
 	pgoff_t index = pos >> PAGE_SHIFT;
 	struct page *page;
 	loff_t prev_page_end_size;
 	int rc = 0;

 	page = grab_cache_page_write_begin(mapping, index, flags);
 	if (!page)
 		return -ENOMEM;
 	*pagep = page;

 	prev_page_end_size = ((loff_t)index << PAGE_SHIFT);
 	if (!PageUptodate(page)) {
 		struct ecryptfs_crypt_stat *crypt_stat =
 			&ecryptfs_inode_to_private(mapping->host)->crypt_stat;

 		if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 			rc = ecryptfs_read_lower_page_segment(
 				page, index, 0, PAGE_SIZE, mapping->host);
 			if (rc) {
 				printk(KERN_ERR "%s: Error attempting to read "
 				       "lower page segment; rc = [%d]\n",
 				       __func__, rc);
 				ClearPageUptodate(page);
 				goto out;
 			} else
 				SetPageUptodate(page);
 		} else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 			if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 				rc = ecryptfs_copy_up_encrypted_with_header(
 					page, crypt_stat);
 				if (rc) {
 					printk(KERN_ERR "%s: Error attempting "
 					       "to copy the encrypted content "
 					       "from the lower file whilst "
 					       "inserting the metadata from "
 					       "the xattr into the header; rc "
 					       "= [%d]\n", __func__, rc);
 					ClearPageUptodate(page);
 					goto out;
 				}
 				SetPageUptodate(page);
 			} else {
 				rc = ecryptfs_read_lower_page_segment(
 					page, index, 0, PAGE_SIZE,
 					mapping->host);
 				if (rc) {
 					printk(KERN_ERR "%s: Error reading "
 					       "page; rc = [%d]\n",
 					       __func__, rc);
 					ClearPageUptodate(page);
 					goto out;
 				}
 				SetPageUptodate(page);
 			}
 		} else {
 			if (prev_page_end_size
 			    >= i_size_read(page->mapping->host)) {
 				zero_user(page, 0, PAGE_SIZE);
 				SetPageUptodate(page);
 			} else if (len < PAGE_SIZE) {
 				rc = ecryptfs_decrypt_page(page);
 				if (rc) {
 					printk(KERN_ERR "%s: Error decrypting "
 					       "page at index [%ld]; "
 					       "rc = [%d]\n",
 					       __func__, page->index, rc);
 					ClearPageUptodate(page);
 					goto out;
 				}
 				SetPageUptodate(page);
 			}
 		}
 	}
 	/* If creating a page or more of holes, zero them out via truncate.
 	 * Note, this will increase i_size. */
 	if (index != 0) {
 		if (prev_page_end_size > i_size_read(page->mapping->host)) {
 			rc = ecryptfs_truncate(file->f_path.dentry,
 					       prev_page_end_size);
 			if (rc) {
 				printk(KERN_ERR "%s: Error on attempt to "
 				       "truncate to (higher) offset [%lld];"
 				       " rc = [%d]\n", __func__,
 				       prev_page_end_size, rc);
 				goto out;
 			}
 		}
 	}
 	/* Writing to a new page, and creating a small hole from start
 	 * of page?  Zero it out. */
 	if ((i_size_read(mapping->host) == prev_page_end_size)
 	    && (pos != 0))
 		zero_user(page, 0, PAGE_SIZE);
 out:
 	if (unlikely(rc)) {
 		unlock_page(page);
 		put_page(page);
 		*pagep = NULL;
 	}
 	return rc;
 }

 /*
  * 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)
 {
 	char *file_size_virt;
 	int rc;

 	file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
 	if (!file_size_virt) {
 		rc = -ENOMEM;
 		goto out;
 	}
 	put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
 	rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
 				  sizeof(u64));
 	kfree(file_size_virt);
 	if (rc < 0)
 		printk(KERN_ERR "%s: Error writing file size to header; "
 		       "rc = [%d]\n", __func__, rc);
 	else
 		rc = 0;
 out:
 	return rc;
 }

 struct kmem_cache *ecryptfs_xattr_cache;

 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 {
 	ssize_t size;
 	void *xattr_virt;
 	struct dentry *lower_dentry =
 		ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry;
 	struct inode *lower_inode = d_inode(lower_dentry);
 	int rc;

 	if (!(lower_inode->i_opflags & IOP_XATTR)) {
 		printk(KERN_WARNING
 		       "No support for setting xattr in lower filesystem\n");
 		rc = -ENOSYS;
 		goto out;
 	}
 	xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
 	if (!xattr_virt) {
 		rc = -ENOMEM;
 		goto out;
 	}
 	inode_lock(lower_inode);
 	size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
 			      xattr_virt, PAGE_SIZE);
 	if (size < 0)
 		size = 8;
 	put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
 	rc = __vfs_setxattr(&init_user_ns, lower_dentry, lower_inode,
 			    ECRYPTFS_XATTR_NAME, xattr_virt, size, 0);
 	inode_unlock(lower_inode);
 	if (rc)
 		printk(KERN_ERR "Error whilst attempting to write inode size "
 		       "to lower file xattr; rc = [%d]\n", rc);
 	kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
 out:
 	return rc;
 }

 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
 {
 	struct ecryptfs_crypt_stat *crypt_stat;

 	crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 	BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
 	if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
 		return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
 	else
 		return ecryptfs_write_inode_size_to_header(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)
 {
 	pgoff_t index = pos >> PAGE_SHIFT;
 	unsigned from = pos & (PAGE_SIZE - 1);
 	unsigned to = from + copied;
 	struct inode *ecryptfs_inode = mapping->host;
 	struct ecryptfs_crypt_stat *crypt_stat =
 		&ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 	int rc;

 	ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
 			"(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
 	if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 		rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
 						       to);
 		if (!rc) {
 			rc = copied;
 			fsstack_copy_inode_size(ecryptfs_inode,
 				ecryptfs_inode_to_lower(ecryptfs_inode));
 		}
 		goto out;
 	}
 	if (!PageUptodate(page)) {
 		if (copied < PAGE_SIZE) {
 			rc = 0;
 			goto out;
 		}
 		SetPageUptodate(page);
 	}
 	/* Fills in zeros if 'to' goes beyond inode size */
 	rc = fill_zeros_to_end_of_page(page, to);
 	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)
 {
 	struct inode *lower_inode = ecryptfs_inode_to_lower(mapping->host);
 	int ret = bmap(lower_inode, &block);

 	if (ret)
 		return 0;
 	return block;
 }

 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,
 };
	// 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 <mahalcro@us.ibm.com>
	*/

	#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)
	{
	struct page *page = read_mapping_page(inode->i_mapping, index, NULL);
	if (!IS_ERR(page))
	lock_page(page);
	return page;
	}

	/**
	* 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)
	{
	int rc;

	rc = ecryptfs_encrypt_page(page);
	if (rc) {
	ecryptfs_printk(KERN_WARNING, "Error encrypting "
	"page (upper index [0x%.16lx])\n", page->index);
	ClearPageUptodate(page);
	goto out;
	}
	SetPageUptodate(page);
	out:
	unlock_page(page);
	return rc;
	}

	static void strip_xattr_flag(char *page_virt,
	struct ecryptfs_crypt_stat *crypt_stat)
	{
	if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
	size_t written;

	crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
	ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
	&written);
	crypt_stat->flags \|= ECRYPTFS_METADATA_IN_XATTR;
	}
	}

	/*
	* 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)
	{
	loff_t extent_num_in_page = 0;
	loff_t num_extents_per_page = (PAGE_SIZE
	/ crypt_stat->extent_size);
	int rc = 0;

	while (extent_num_in_page < num_extents_per_page) {
	loff_t view_extent_num = ((((loff_t)page->index)
	* num_extents_per_page)
	+ extent_num_in_page);
	size_t num_header_extents_at_front =
	(crypt_stat->metadata_size / crypt_stat->extent_size);

	if (view_extent_num < num_header_extents_at_front) {
	/* This is a header extent */
	char *page_virt;

	page_virt = kmap_atomic(page);
	memset(page_virt, 0, PAGE_SIZE);
	/* TODO: Support more than one header extent */
	if (view_extent_num == 0) {
	size_t written;

	rc = ecryptfs_read_xattr_region(
	page_virt, page->mapping->host);
	strip_xattr_flag(page_virt + 16, crypt_stat);
	ecryptfs_write_header_metadata(page_virt + 20,
	crypt_stat,
	&written);
	}
	kunmap_atomic(page_virt);
	flush_dcache_page(page);
	if (rc) {
	printk(KERN_ERR "%s: Error reading xattr "
	"region; rc = [%d]\n", __func__, rc);
	goto out;
	}
	} else {
	/* This is an encrypted data extent */
	loff_t lower_offset =
	((view_extent_num * crypt_stat->extent_size)
	- crypt_stat->metadata_size);

	rc = ecryptfs_read_lower_page_segment(
	page, (lower_offset >> PAGE_SHIFT),
	(lower_offset & ~PAGE_MASK),
	crypt_stat->extent_size, page->mapping->host);
	if (rc) {
	printk(KERN_ERR "%s: Error attempting to read "
	"extent at offset [%lld] in the lower "
	"file; rc = [%d]\n", __func__,
	lower_offset, rc);
	goto out;
	}
	}
	extent_num_in_page++;
	}
	out:
	return rc;
	}

	/**
	* ecryptfs_readpage
	* @file: An eCryptfs file
	* @page: Page from eCryptfs inode mapping into which to stick the read data
	*
	* Read in a page, decrypting if necessary.
	*
	* Returns zero on success; non-zero on error.
	*/
	static int ecryptfs_readpage(struct file file, struct page page)
	{
	struct ecryptfs_crypt_stat *crypt_stat =
	&ecryptfs_inode_to_private(page->mapping->host)->crypt_stat;
	int rc = 0;

	if (!crypt_stat \|\| !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
	rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
	PAGE_SIZE,
	page->mapping->host);
	} else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
	if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
	rc = ecryptfs_copy_up_encrypted_with_header(page,
	crypt_stat);
	if (rc) {
	printk(KERN_ERR "%s: Error attempting to copy "
	"the encrypted content from the lower "
	"file whilst inserting the metadata "
	"from the xattr into the header; rc = "
	"[%d]\n", __func__, rc);
	goto out;
	}

	} else {
	rc = ecryptfs_read_lower_page_segment(
	page, page->index, 0, PAGE_SIZE,
	page->mapping->host);
	if (rc) {
	printk(KERN_ERR "Error reading page; rc = "
	"[%d]\n", rc);
	goto out;
	}
	}
	} else {
	rc = ecryptfs_decrypt_page(page);
	if (rc) {
	ecryptfs_printk(KERN_ERR, "Error decrypting page; "
	"rc = [%d]\n", rc);
	goto out;
	}
	}
	out:
	if (rc)
	ClearPageUptodate(page);
	else
	SetPageUptodate(page);
	ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n",
	page->index);
	unlock_page(page);
	return rc;
	}

	/*
	* Called with lower inode mutex held.
	*/
	static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
	{
	struct inode *inode = page->mapping->host;
	int end_byte_in_page;

	if ((i_size_read(inode) / PAGE_SIZE) != page->index)
	goto out;
	end_byte_in_page = i_size_read(inode) % PAGE_SIZE;
	if (to > end_byte_in_page)
	end_byte_in_page = to;
	zero_user_segment(page, end_byte_in_page, PAGE_SIZE);
	out:
	return 0;
	}

	/**
	* 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
	* @flags: Various flags
	* @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, unsigned flags,
	struct page pagep, void fsdata)
	{
	pgoff_t index = pos >> PAGE_SHIFT;
	struct page *page;
	loff_t prev_page_end_size;
	int rc = 0;

	page = grab_cache_page_write_begin(mapping, index, flags);
	if (!page)
	return -ENOMEM;
	*pagep = page;

	prev_page_end_size = ((loff_t)index << PAGE_SHIFT);
	if (!PageUptodate(page)) {
	struct ecryptfs_crypt_stat *crypt_stat =
	&ecryptfs_inode_to_private(mapping->host)->crypt_stat;

	if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
	rc = ecryptfs_read_lower_page_segment(
	page, index, 0, PAGE_SIZE, mapping->host);
	if (rc) {
	printk(KERN_ERR "%s: Error attempting to read "
	"lower page segment; rc = [%d]\n",
	__func__, rc);
	ClearPageUptodate(page);
	goto out;
	} else
	SetPageUptodate(page);
	} else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
	if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
	rc = ecryptfs_copy_up_encrypted_with_header(
	page, crypt_stat);
	if (rc) {
	printk(KERN_ERR "%s: Error attempting "
	"to copy the encrypted content "
	"from the lower file whilst "
	"inserting the metadata from "
	"the xattr into the header; rc "
	"= [%d]\n", __func__, rc);
	ClearPageUptodate(page);
	goto out;
	}
	SetPageUptodate(page);
	} else {
	rc = ecryptfs_read_lower_page_segment(
	page, index, 0, PAGE_SIZE,
	mapping->host);
	if (rc) {
	printk(KERN_ERR "%s: Error reading "
	"page; rc = [%d]\n",
	__func__, rc);
	ClearPageUptodate(page);
	goto out;
	}
	SetPageUptodate(page);
	}
	} else {
	if (prev_page_end_size
	>= i_size_read(page->mapping->host)) {
	zero_user(page, 0, PAGE_SIZE);
	SetPageUptodate(page);
	} else if (len < PAGE_SIZE) {
	rc = ecryptfs_decrypt_page(page);
	if (rc) {
	printk(KERN_ERR "%s: Error decrypting "
	"page at index [%ld]; "
	"rc = [%d]\n",
	__func__, page->index, rc);
	ClearPageUptodate(page);
	goto out;
	}
	SetPageUptodate(page);
	}
	}
	}
	/* If creating a page or more of holes, zero them out via truncate.
	* Note, this will increase i_size. */
	if (index != 0) {
	if (prev_page_end_size > i_size_read(page->mapping->host)) {
	rc = ecryptfs_truncate(file->f_path.dentry,
	prev_page_end_size);
	if (rc) {
	printk(KERN_ERR "%s: Error on attempt to "
	"truncate to (higher) offset [%lld];"
	" rc = [%d]\n", __func__,
	prev_page_end_size, rc);
	goto out;
	}
	}
	}
	/* Writing to a new page, and creating a small hole from start
	* of page? Zero it out. */
	if ((i_size_read(mapping->host) == prev_page_end_size)
	&& (pos != 0))
	zero_user(page, 0, PAGE_SIZE);
	out:
	if (unlikely(rc)) {
	unlock_page(page);
	put_page(page);
	*pagep = NULL;
	}
	return rc;
	}

	/*
	* 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)
	{
	char *file_size_virt;
	int rc;

	file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
	if (!file_size_virt) {
	rc = -ENOMEM;
	goto out;
	}
	put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
	rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
	sizeof(u64));
	kfree(file_size_virt);
	if (rc < 0)
	printk(KERN_ERR "%s: Error writing file size to header; "
	"rc = [%d]\n", __func__, rc);
	else
	rc = 0;
	out:
	return rc;
	}

	struct kmem_cache *ecryptfs_xattr_cache;

	static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
	{
	ssize_t size;
	void *xattr_virt;
	struct dentry *lower_dentry =
	ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry;
	struct inode *lower_inode = d_inode(lower_dentry);
	int rc;

	if (!(lower_inode->i_opflags & IOP_XATTR)) {
	printk(KERN_WARNING
	"No support for setting xattr in lower filesystem\n");
	rc = -ENOSYS;
	goto out;
	}
	xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
	if (!xattr_virt) {
	rc = -ENOMEM;
	goto out;
	}
	inode_lock(lower_inode);
	size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
	xattr_virt, PAGE_SIZE);
	if (size < 0)
	size = 8;
	put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
	rc = __vfs_setxattr(&init_user_ns, lower_dentry, lower_inode,
	ECRYPTFS_XATTR_NAME, xattr_virt, size, 0);
	inode_unlock(lower_inode);
	if (rc)
	printk(KERN_ERR "Error whilst attempting to write inode size "
	"to lower file xattr; rc = [%d]\n", rc);
	kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
	out:
	return rc;
	}

	int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
	{
	struct ecryptfs_crypt_stat *crypt_stat;

	crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
	BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
	if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
	return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
	else
	return ecryptfs_write_inode_size_to_header(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)
	{
	pgoff_t index = pos >> PAGE_SHIFT;
	unsigned from = pos & (PAGE_SIZE - 1);
	unsigned to = from + copied;
	struct inode *ecryptfs_inode = mapping->host;
	struct ecryptfs_crypt_stat *crypt_stat =
	&ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
	int rc;

	ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
	"(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
	if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
	rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
	to);
	if (!rc) {
	rc = copied;
	fsstack_copy_inode_size(ecryptfs_inode,
	ecryptfs_inode_to_lower(ecryptfs_inode));
	}
	goto out;
	}
	if (!PageUptodate(page)) {
	if (copied < PAGE_SIZE) {
	rc = 0;
	goto out;
	}
	SetPageUptodate(page);
	}
	/* Fills in zeros if 'to' goes beyond inode size */
	rc = fill_zeros_to_end_of_page(page, to);
	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)
	{
	struct inode *lower_inode = ecryptfs_inode_to_lower(mapping->host);
	int ret = bmap(lower_inode, &block);

	if (ret)
	return 0;
	return block;
	}

	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,
	};