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 <linux/unaligned.h>
 #include "ecryptfs_kernel.h"

 /*
  * 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_writepages(struct address_space *mapping,
 		struct writeback_control *wbc)
 {
 	struct folio *folio = NULL;
 	int error;

 	while ((folio = writeback_iter(mapping, wbc, folio, &error))) {
 		error = ecryptfs_encrypt_page(folio);
 		if (error) {
 			ecryptfs_printk(KERN_WARNING,
 				"Error encrypting folio (index [0x%.16lx])\n",
 				folio->index);
 			folio_clear_uptodate(folio);
 			mapping_set_error(mapping, error);
 		}
 		folio_unlock(folio);
 	}

 	return error;
 }

 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
  * @folio: 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 folio *folio,
 				       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)folio->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_local_folio(folio, 0);
 			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, folio->mapping->host);
 				strip_xattr_flag(page_virt + 16, crypt_stat);
 				ecryptfs_write_header_metadata(page_virt + 20,
 							       crypt_stat,
 							       &written);
 			}
 			kunmap_local(page_virt);
 			flush_dcache_folio(folio);
 			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(
 				folio, (lower_offset >> PAGE_SHIFT),
 				(lower_offset & ~PAGE_MASK),
 				crypt_stat->extent_size, folio->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_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)
 {
 	struct inode *inode = folio->mapping->host;
 	struct ecryptfs_crypt_stat *crypt_stat =
 		&ecryptfs_inode_to_private(inode)->crypt_stat;
 	int err = 0;

 	if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 		err = ecryptfs_read_lower_page_segment(folio, folio->index, 0,
 				folio_size(folio), inode);
 	} else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 		if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 			err = ecryptfs_copy_up_encrypted_with_header(folio,
 					crypt_stat);
 			if (err) {
 				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; err = "
 				       "[%d]\n", __func__, err);
 				goto out;
 			}

 		} else {
 			err = ecryptfs_read_lower_page_segment(folio,
 					folio->index, 0, folio_size(folio),
 					inode);
 			if (err) {
 				printk(KERN_ERR "Error reading page; err = "
 				       "[%d]\n", err);
 				goto out;
 			}
 		}
 	} else {
 		err = ecryptfs_decrypt_page(folio);
 		if (err) {
 			ecryptfs_printk(KERN_ERR, "Error decrypting page; "
 					"err = [%d]\n", err);
 			goto out;
 		}
 	}
 out:
 	ecryptfs_printk(KERN_DEBUG, "Unlocking folio with index = [0x%.16lx]\n",
 			folio->index);
 	folio_end_read(folio, err == 0);
 	return err;
 }

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

 	if ((i_size_read(inode) / PAGE_SIZE) != folio->index)
 		goto out;
 	end_byte_in_page = i_size_read(inode) % PAGE_SIZE;
 	if (to > end_byte_in_page)
 		end_byte_in_page = to;
 	folio_zero_segment(folio, 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
  * @foliop: Pointer to return the folio
  * @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 folio **foliop, void **fsdata)
 {
 	pgoff_t index = pos >> PAGE_SHIFT;
 	struct folio *folio;
 	loff_t prev_page_end_size;
 	int rc = 0;

 	folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
 			mapping_gfp_mask(mapping));
 	if (IS_ERR(folio))
 		return PTR_ERR(folio);
 	*foliop = folio;

 	prev_page_end_size = ((loff_t)index << PAGE_SHIFT);
 	if (!folio_test_uptodate(folio)) {
 		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(
 				folio, index, 0, PAGE_SIZE, mapping->host);
 			if (rc) {
 				printk(KERN_ERR "%s: Error attempting to read "
 				       "lower page segment; rc = [%d]\n",
 				       __func__, rc);
 				folio_clear_uptodate(folio);
 				goto out;
 			} else
 				folio_mark_uptodate(folio);
 		} else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 			if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 				rc = ecryptfs_copy_up_encrypted_with_header(
 					folio, 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);
 					folio_clear_uptodate(folio);
 					goto out;
 				}
 				folio_mark_uptodate(folio);
 			} else {
 				rc = ecryptfs_read_lower_page_segment(
 					folio, index, 0, PAGE_SIZE,
 					mapping->host);
 				if (rc) {
 					printk(KERN_ERR "%s: Error reading "
 					       "page; rc = [%d]\n",
 					       __func__, rc);
 					folio_clear_uptodate(folio);
 					goto out;
 				}
 				folio_mark_uptodate(folio);
 			}
 		} else {
 			if (prev_page_end_size
 			    >= i_size_read(mapping->host)) {
 				folio_zero_range(folio, 0, PAGE_SIZE);
 				folio_mark_uptodate(folio);
 			} else if (len < PAGE_SIZE) {
 				rc = ecryptfs_decrypt_page(folio);
 				if (rc) {
 					printk(KERN_ERR "%s: Error decrypting "
 					       "page at index [%ld]; "
 					       "rc = [%d]\n",
 					       __func__, folio->index, rc);
 					folio_clear_uptodate(folio);
 					goto out;
 				}
 				folio_mark_uptodate(folio);
 			}
 		}
 	}
 	/* 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(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))
 		folio_zero_range(folio, 0, PAGE_SIZE);
 out:
 	if (unlikely(rc)) {
 		folio_unlock(folio);
 		folio_put(folio);
 	}
 	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(&nop_mnt_idmap, 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
  * @folio: The eCryptfs folio
  * @fsdata: The fsdata (unused)
  */
 static int ecryptfs_write_end(struct file *file,
 			struct address_space *mapping,
 			loff_t pos, unsigned len, unsigned copied,
 			struct folio *folio, 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,
 				folio, 0, to);
 		if (!rc) {
 			rc = copied;
 			fsstack_copy_inode_size(ecryptfs_inode,
 				ecryptfs_inode_to_lower(ecryptfs_inode));
 		}
 		goto out;
 	}
 	if (!folio_test_uptodate(folio)) {
 		if (copied < PAGE_SIZE) {
 			rc = 0;
 			goto out;
 		}
 		folio_mark_uptodate(folio);
 	}
 	/* Fills in zeros if 'to' goes beyond inode size */
 	rc = fill_zeros_to_end_of_page(folio, 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(folio);
 	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:
 	folio_unlock(folio);
 	folio_put(folio);
 	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;
 }

 #include <linux/buffer_head.h>

 const struct address_space_operations ecryptfs_aops = {
 	/*
 	 * XXX: This is pretty broken for multiple reasons: ecryptfs does not
 	 * actually use buffer_heads, and ecryptfs will crash without
 	 * CONFIG_BLOCK.  But it matches the behavior before the default for
 	 * address_space_operations without the ->dirty_folio method was
 	 * cleaned up, so this is the best we can do without maintainer
 	 * feedback.
 	 */
 #ifdef CONFIG_BLOCK
 	.dirty_folio	= block_dirty_folio,
 	.invalidate_folio = block_invalidate_folio,
 #endif
 	.writepages = ecryptfs_writepages,
 	.read_folio = ecryptfs_read_folio,
 	.write_begin = ecryptfs_write_begin,
 	.write_end = ecryptfs_write_end,
 	.migrate_folio = filemap_migrate_folio,
 	.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 <linux/unaligned.h>
	#include "ecryptfs_kernel.h"

	/*
	* 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_writepages(struct address_space *mapping,
	struct writeback_control *wbc)
	{
	struct folio *folio = NULL;
	int error;

	while ((folio = writeback_iter(mapping, wbc, folio, &error))) {
	error = ecryptfs_encrypt_page(folio);
	if (error) {
	ecryptfs_printk(KERN_WARNING,
	"Error encrypting folio (index [0x%.16lx])\n",
	folio->index);
	folio_clear_uptodate(folio);
	mapping_set_error(mapping, error);
	}
	folio_unlock(folio);
	}

	return error;
	}

	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
	* @folio: 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 folio *folio,
	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)folio->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_local_folio(folio, 0);
	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, folio->mapping->host);
	strip_xattr_flag(page_virt + 16, crypt_stat);
	ecryptfs_write_header_metadata(page_virt + 20,
	crypt_stat,
	&written);
	}
	kunmap_local(page_virt);
	flush_dcache_folio(folio);
	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(
	folio, (lower_offset >> PAGE_SHIFT),
	(lower_offset & ~PAGE_MASK),
	crypt_stat->extent_size, folio->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_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)
	{
	struct inode *inode = folio->mapping->host;
	struct ecryptfs_crypt_stat *crypt_stat =
	&ecryptfs_inode_to_private(inode)->crypt_stat;
	int err = 0;

	if (!crypt_stat \|\| !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
	err = ecryptfs_read_lower_page_segment(folio, folio->index, 0,
	folio_size(folio), inode);
	} else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
	if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
	err = ecryptfs_copy_up_encrypted_with_header(folio,
	crypt_stat);
	if (err) {
	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; err = "
	"[%d]\n", __func__, err);
	goto out;
	}

	} else {
	err = ecryptfs_read_lower_page_segment(folio,
	folio->index, 0, folio_size(folio),
	inode);
	if (err) {
	printk(KERN_ERR "Error reading page; err = "
	"[%d]\n", err);
	goto out;
	}
	}
	} else {
	err = ecryptfs_decrypt_page(folio);
	if (err) {
	ecryptfs_printk(KERN_ERR, "Error decrypting page; "
	"err = [%d]\n", err);
	goto out;
	}
	}
	out:
	ecryptfs_printk(KERN_DEBUG, "Unlocking folio with index = [0x%.16lx]\n",
	folio->index);
	folio_end_read(folio, err == 0);
	return err;
	}

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

	if ((i_size_read(inode) / PAGE_SIZE) != folio->index)
	goto out;
	end_byte_in_page = i_size_read(inode) % PAGE_SIZE;
	if (to > end_byte_in_page)
	end_byte_in_page = to;
	folio_zero_segment(folio, 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
	* @foliop: Pointer to return the folio
	* @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 folio foliop, void fsdata)
	{
	pgoff_t index = pos >> PAGE_SHIFT;
	struct folio *folio;
	loff_t prev_page_end_size;
	int rc = 0;

	folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
	mapping_gfp_mask(mapping));
	if (IS_ERR(folio))
	return PTR_ERR(folio);
	*foliop = folio;

	prev_page_end_size = ((loff_t)index << PAGE_SHIFT);
	if (!folio_test_uptodate(folio)) {
	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(
	folio, index, 0, PAGE_SIZE, mapping->host);
	if (rc) {
	printk(KERN_ERR "%s: Error attempting to read "
	"lower page segment; rc = [%d]\n",
	__func__, rc);
	folio_clear_uptodate(folio);
	goto out;
	} else
	folio_mark_uptodate(folio);
	} else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
	if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
	rc = ecryptfs_copy_up_encrypted_with_header(
	folio, 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);
	folio_clear_uptodate(folio);
	goto out;
	}
	folio_mark_uptodate(folio);
	} else {
	rc = ecryptfs_read_lower_page_segment(
	folio, index, 0, PAGE_SIZE,
	mapping->host);
	if (rc) {
	printk(KERN_ERR "%s: Error reading "
	"page; rc = [%d]\n",
	__func__, rc);
	folio_clear_uptodate(folio);
	goto out;
	}
	folio_mark_uptodate(folio);
	}
	} else {
	if (prev_page_end_size
	>= i_size_read(mapping->host)) {
	folio_zero_range(folio, 0, PAGE_SIZE);
	folio_mark_uptodate(folio);
	} else if (len < PAGE_SIZE) {
	rc = ecryptfs_decrypt_page(folio);
	if (rc) {
	printk(KERN_ERR "%s: Error decrypting "
	"page at index [%ld]; "
	"rc = [%d]\n",
	__func__, folio->index, rc);
	folio_clear_uptodate(folio);
	goto out;
	}
	folio_mark_uptodate(folio);
	}
	}
	}
	/* 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(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))
	folio_zero_range(folio, 0, PAGE_SIZE);
	out:
	if (unlikely(rc)) {
	folio_unlock(folio);
	folio_put(folio);
	}
	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(&nop_mnt_idmap, 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
	* @folio: The eCryptfs folio
	* @fsdata: The fsdata (unused)
	*/
	static int ecryptfs_write_end(struct file *file,
	struct address_space *mapping,
	loff_t pos, unsigned len, unsigned copied,
	struct folio folio, 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,
	folio, 0, to);
	if (!rc) {
	rc = copied;
	fsstack_copy_inode_size(ecryptfs_inode,
	ecryptfs_inode_to_lower(ecryptfs_inode));
	}
	goto out;
	}
	if (!folio_test_uptodate(folio)) {
	if (copied < PAGE_SIZE) {
	rc = 0;
	goto out;
	}
	folio_mark_uptodate(folio);
	}
	/* Fills in zeros if 'to' goes beyond inode size */
	rc = fill_zeros_to_end_of_page(folio, 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(folio);
	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:
	folio_unlock(folio);
	folio_put(folio);
	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;
	}

	#include <linux/buffer_head.h>

	const struct address_space_operations ecryptfs_aops = {
	/*
	* XXX: This is pretty broken for multiple reasons: ecryptfs does not
	* actually use buffer_heads, and ecryptfs will crash without
	* CONFIG_BLOCK. But it matches the behavior before the default for
	* address_space_operations without the ->dirty_folio method was
	* cleaned up, so this is the best we can do without maintainer
	* feedback.
	*/
	#ifdef CONFIG_BLOCK
	.dirty_folio = block_dirty_folio,
	.invalidate_folio = block_invalidate_folio,
	#endif
	.writepages = ecryptfs_writepages,
	.read_folio = ecryptfs_read_folio,
	.write_begin = ecryptfs_write_begin,
	.write_end = ecryptfs_write_end,
	.migrate_folio = filemap_migrate_folio,
	.bmap = ecryptfs_bmap,
	};