fs/ecryptfs/read_write.c - kernel/bruno - Git at Google

 /**
  * eCryptfs: Linux filesystem encryption layer
  *
  * Copyright (C) 2007 International Business Machines Corp.
  *   Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
  * published by the Free Software Foundation; either version 2 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful, but
  * WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  * 02111-1307, USA.
  */

 #include <linux/fs.h>
 #include <linux/pagemap.h>
 #include "ecryptfs_kernel.h"

 /**
  * ecryptfs_write_lower
  * @ecryptfs_inode: The eCryptfs inode
  * @data: Data to write
  * @offset: Byte offset in the lower file to which to write the data
  * @size: Number of bytes from @data to write at @offset in the lower
  *        file
  *
  * Write data to the lower file.
  *
  * Returns bytes written on success; less than zero on error
  */
 int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
 			 loff_t offset, size_t size)
 {
 	struct file *lower_file;
 	ssize_t rc;

 	lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
 	if (!lower_file)
 		return -EIO;
 	rc = kernel_write(lower_file, data, size, offset);
 	mark_inode_dirty_sync(ecryptfs_inode);
 	return rc;
 }

 /**
  * ecryptfs_write_lower_page_segment
  * @ecryptfs_inode: The eCryptfs inode
  * @page_for_lower: The page containing the data to be written to the
  *                  lower file
  * @offset_in_page: The offset in the @page_for_lower from which to
  *                  start writing the data
  * @size: The amount of data from @page_for_lower to write to the
  *        lower file
  *
  * Determines the byte offset in the file for the given page and
  * offset within the page, maps the page, and makes the call to write
  * the contents of @page_for_lower to the lower inode.
  *
  * Returns zero on success; non-zero otherwise
  */
 int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
 				      struct page *page_for_lower,
 				      size_t offset_in_page, size_t size)
 {
 	char *virt;
 	loff_t offset;
 	int rc;

 	offset = ((((loff_t)page_for_lower->index) << PAGE_CACHE_SHIFT)
 		  + offset_in_page);
 	virt = kmap(page_for_lower);
 	rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
 	if (rc > 0)
 		rc = 0;
 	kunmap(page_for_lower);
 	return rc;
 }

 /**
  * ecryptfs_write
  * @ecryptfs_inode: The eCryptfs file into which to write
  * @data: Virtual address where data to write is located
  * @offset: Offset in the eCryptfs file at which to begin writing the
  *          data from @data
  * @size: The number of bytes to write from @data
  *
  * Write an arbitrary amount of data to an arbitrary location in the
  * eCryptfs inode page cache. This is done on a page-by-page, and then
  * by an extent-by-extent, basis; individual extents are encrypted and
  * written to the lower page cache (via VFS writes). This function
  * takes care of all the address translation to locations in the lower
  * filesystem; it also handles truncate events, writing out zeros
  * where necessary.
  *
  * Returns zero on success; non-zero otherwise
  */
 int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset,
 		   size_t size)
 {
 	struct page *ecryptfs_page;
 	struct ecryptfs_crypt_stat *crypt_stat;
 	char *ecryptfs_page_virt;
 	loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode);
 	loff_t data_offset = 0;
 	loff_t pos;
 	int rc = 0;

 	crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 	/*
 	 * if we are writing beyond current size, then start pos
 	 * at the current size - we'll fill in zeros from there.
 	 */
 	if (offset > ecryptfs_file_size)
 		pos = ecryptfs_file_size;
 	else
 		pos = offset;
 	while (pos < (offset + size)) {
 		pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
 		size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
 		size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
 		loff_t total_remaining_bytes = ((offset + size) - pos);

 		if (fatal_signal_pending(current)) {
 			rc = -EINTR;
 			break;
 		}

 		if (num_bytes > total_remaining_bytes)
 			num_bytes = total_remaining_bytes;
 		if (pos < offset) {
 			/* remaining zeros to write, up to destination offset */
 			loff_t total_remaining_zeros = (offset - pos);

 			if (num_bytes > total_remaining_zeros)
 				num_bytes = total_remaining_zeros;
 		}
 		ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_inode,
 							 ecryptfs_page_idx);
 		if (IS_ERR(ecryptfs_page)) {
 			rc = PTR_ERR(ecryptfs_page);
 			printk(KERN_ERR "%s: Error getting page at "
 			       "index [%ld] from eCryptfs inode "
 			       "mapping; rc = [%d]\n", __func__,
 			       ecryptfs_page_idx, rc);
 			goto out;
 		}
 		ecryptfs_page_virt = kmap_atomic(ecryptfs_page);

 		/*
 		 * pos: where we're now writing, offset: where the request was
 		 * If current pos is before request, we are filling zeros
 		 * If we are at or beyond request, we are writing the *data*
 		 * If we're in a fresh page beyond eof, zero it in either case
 		 */
 		if (pos < offset || !start_offset_in_page) {
 			/* We are extending past the previous end of the file.
 			 * Fill in zero values to the end of the page */
 			memset(((char *)ecryptfs_page_virt
 				+ start_offset_in_page), 0,
 				PAGE_CACHE_SIZE - start_offset_in_page);
 		}

 		/* pos >= offset, we are now writing the data request */
 		if (pos >= offset) {
 			memcpy(((char *)ecryptfs_page_virt
 				+ start_offset_in_page),
 			       (data + data_offset), num_bytes);
 			data_offset += num_bytes;
 		}
 		kunmap_atomic(ecryptfs_page_virt);
 		flush_dcache_page(ecryptfs_page);
 		SetPageUptodate(ecryptfs_page);
 		unlock_page(ecryptfs_page);
 		if (crypt_stat->flags & ECRYPTFS_ENCRYPTED)
 			rc = ecryptfs_encrypt_page(ecryptfs_page);
 		else
 			rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
 						ecryptfs_page,
 						start_offset_in_page,
 						data_offset);
 		page_cache_release(ecryptfs_page);
 		if (rc) {
 			printk(KERN_ERR "%s: Error encrypting "
 			       "page; rc = [%d]\n", __func__, rc);
 			goto out;
 		}
 		pos += num_bytes;
 	}
 	if (pos > ecryptfs_file_size) {
 		i_size_write(ecryptfs_inode, pos);
 		if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
 			int rc2;

 			rc2 = ecryptfs_write_inode_size_to_metadata(
 								ecryptfs_inode);
 			if (rc2) {
 				printk(KERN_ERR	"Problem with "
 				       "ecryptfs_write_inode_size_to_metadata; "
 				       "rc = [%d]\n", rc2);
 				if (!rc)
 					rc = rc2;
 				goto out;
 			}
 		}
 	}
 out:
 	return rc;
 }

 /**
  * ecryptfs_read_lower
  * @data: The read data is stored here by this function
  * @offset: Byte offset in the lower file from which to read the data
  * @size: Number of bytes to read from @offset of the lower file and
  *        store into @data
  * @ecryptfs_inode: The eCryptfs inode
  *
  * Read @size bytes of data at byte offset @offset from the lower
  * inode into memory location @data.
  *
  * Returns bytes read on success; 0 on EOF; less than zero on error
  */
 int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
 			struct inode *ecryptfs_inode)
 {
 	struct file *lower_file;
 	lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
 	if (!lower_file)
 		return -EIO;
 	return kernel_read(lower_file, offset, data, size);
 }

 /**
  * ecryptfs_read_lower_page_segment
  * @page_for_ecryptfs: The page into which data for eCryptfs will be
  *                     written
  * @offset_in_page: Offset in @page_for_ecryptfs from which to start
  *                  writing
  * @size: The number of bytes to write into @page_for_ecryptfs
  * @ecryptfs_inode: The eCryptfs inode
  *
  * Determines the byte offset in the file for the given page and
  * offset within the page, maps the page, and makes the call to read
  * the contents of @page_for_ecryptfs from the lower inode.
  *
  * Returns zero on success; non-zero otherwise
  */
 int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
 				     pgoff_t page_index,
 				     size_t offset_in_page, size_t size,
 				     struct inode *ecryptfs_inode)
 {
 	char *virt;
 	loff_t offset;
 	int rc;

 	offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page);
 	virt = kmap(page_for_ecryptfs);
 	rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
 	if (rc > 0)
 		rc = 0;
 	kunmap(page_for_ecryptfs);
 	flush_dcache_page(page_for_ecryptfs);
 	return rc;
 }
	/**
	* eCryptfs: Linux filesystem encryption layer
	*
	* Copyright (C) 2007 International Business Machines Corp.
	* Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License as
	* published by the Free Software Foundation; either version 2 of the
	* License, or (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful, but
	* WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
	* 02111-1307, USA.
	*/

	#include <linux/fs.h>
	#include <linux/pagemap.h>
	#include "ecryptfs_kernel.h"

	/**
	* ecryptfs_write_lower
	* @ecryptfs_inode: The eCryptfs inode
	* @data: Data to write
	* @offset: Byte offset in the lower file to which to write the data
	* @size: Number of bytes from @data to write at @offset in the lower
	* file
	*
	* Write data to the lower file.
	*
	* Returns bytes written on success; less than zero on error
	*/
	int ecryptfs_write_lower(struct inode ecryptfs_inode, char data,
	loff_t offset, size_t size)
	{
	struct file *lower_file;
	ssize_t rc;

	lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
	if (!lower_file)
	return -EIO;
	rc = kernel_write(lower_file, data, size, offset);
	mark_inode_dirty_sync(ecryptfs_inode);
	return rc;
	}

	/**
	* ecryptfs_write_lower_page_segment
	* @ecryptfs_inode: The eCryptfs inode
	* @page_for_lower: The page containing the data to be written to the
	* lower file
	* @offset_in_page: The offset in the @page_for_lower from which to
	* start writing the data
	* @size: The amount of data from @page_for_lower to write to the
	* lower file
	*
	* Determines the byte offset in the file for the given page and
	* offset within the page, maps the page, and makes the call to write
	* the contents of @page_for_lower to the lower inode.
	*
	* Returns zero on success; non-zero otherwise
	*/
	int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
	struct page *page_for_lower,
	size_t offset_in_page, size_t size)
	{
	char *virt;
	loff_t offset;
	int rc;

	offset = ((((loff_t)page_for_lower->index) << PAGE_CACHE_SHIFT)
	+ offset_in_page);
	virt = kmap(page_for_lower);
	rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
	if (rc > 0)
	rc = 0;
	kunmap(page_for_lower);
	return rc;
	}

	/**
	* ecryptfs_write
	* @ecryptfs_inode: The eCryptfs file into which to write
	* @data: Virtual address where data to write is located
	* @offset: Offset in the eCryptfs file at which to begin writing the
	* data from @data
	* @size: The number of bytes to write from @data
	*
	* Write an arbitrary amount of data to an arbitrary location in the
	* eCryptfs inode page cache. This is done on a page-by-page, and then
	* by an extent-by-extent, basis; individual extents are encrypted and
	* written to the lower page cache (via VFS writes). This function
	* takes care of all the address translation to locations in the lower
	* filesystem; it also handles truncate events, writing out zeros
	* where necessary.
	*
	* Returns zero on success; non-zero otherwise
	*/
	int ecryptfs_write(struct inode ecryptfs_inode, char data, loff_t offset,
	size_t size)
	{
	struct page *ecryptfs_page;
	struct ecryptfs_crypt_stat *crypt_stat;
	char *ecryptfs_page_virt;
	loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode);
	loff_t data_offset = 0;
	loff_t pos;
	int rc = 0;

	crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
	/*
	* if we are writing beyond current size, then start pos
	* at the current size - we'll fill in zeros from there.
	*/
	if (offset > ecryptfs_file_size)
	pos = ecryptfs_file_size;
	else
	pos = offset;
	while (pos < (offset + size)) {
	pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
	size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
	size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
	loff_t total_remaining_bytes = ((offset + size) - pos);

	if (fatal_signal_pending(current)) {
	rc = -EINTR;
	break;
	}

	if (num_bytes > total_remaining_bytes)
	num_bytes = total_remaining_bytes;
	if (pos < offset) {
	/* remaining zeros to write, up to destination offset */
	loff_t total_remaining_zeros = (offset - pos);

	if (num_bytes > total_remaining_zeros)
	num_bytes = total_remaining_zeros;
	}
	ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_inode,
	ecryptfs_page_idx);
	if (IS_ERR(ecryptfs_page)) {
	rc = PTR_ERR(ecryptfs_page);
	printk(KERN_ERR "%s: Error getting page at "
	"index [%ld] from eCryptfs inode "
	"mapping; rc = [%d]\n", __func__,
	ecryptfs_page_idx, rc);
	goto out;
	}
	ecryptfs_page_virt = kmap_atomic(ecryptfs_page);

	/*
	* pos: where we're now writing, offset: where the request was
	* If current pos is before request, we are filling zeros
	* If we are at or beyond request, we are writing the data
	* If we're in a fresh page beyond eof, zero it in either case
	*/
	if (pos < offset \|\| !start_offset_in_page) {
	/* We are extending past the previous end of the file.
	* Fill in zero values to the end of the page */
	memset(((char *)ecryptfs_page_virt
	+ start_offset_in_page), 0,
	PAGE_CACHE_SIZE - start_offset_in_page);
	}

	/* pos >= offset, we are now writing the data request */
	if (pos >= offset) {
	memcpy(((char *)ecryptfs_page_virt
	+ start_offset_in_page),
	(data + data_offset), num_bytes);
	data_offset += num_bytes;
	}
	kunmap_atomic(ecryptfs_page_virt);
	flush_dcache_page(ecryptfs_page);
	SetPageUptodate(ecryptfs_page);
	unlock_page(ecryptfs_page);
	if (crypt_stat->flags & ECRYPTFS_ENCRYPTED)
	rc = ecryptfs_encrypt_page(ecryptfs_page);
	else
	rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
	ecryptfs_page,
	start_offset_in_page,
	data_offset);
	page_cache_release(ecryptfs_page);
	if (rc) {
	printk(KERN_ERR "%s: Error encrypting "
	"page; rc = [%d]\n", __func__, rc);
	goto out;
	}
	pos += num_bytes;
	}
	if (pos > ecryptfs_file_size) {
	i_size_write(ecryptfs_inode, pos);
	if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
	int rc2;

	rc2 = ecryptfs_write_inode_size_to_metadata(
	ecryptfs_inode);
	if (rc2) {
	printk(KERN_ERR "Problem with "
	"ecryptfs_write_inode_size_to_metadata; "
	"rc = [%d]\n", rc2);
	if (!rc)
	rc = rc2;
	goto out;
	}
	}
	}
	out:
	return rc;
	}

	/**
	* ecryptfs_read_lower
	* @data: The read data is stored here by this function
	* @offset: Byte offset in the lower file from which to read the data
	* @size: Number of bytes to read from @offset of the lower file and
	* store into @data
	* @ecryptfs_inode: The eCryptfs inode
	*
	* Read @size bytes of data at byte offset @offset from the lower
	* inode into memory location @data.
	*
	* Returns bytes read on success; 0 on EOF; less than zero on error
	*/
	int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
	struct inode *ecryptfs_inode)
	{
	struct file *lower_file;
	lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
	if (!lower_file)
	return -EIO;
	return kernel_read(lower_file, offset, data, size);
	}

	/**
	* ecryptfs_read_lower_page_segment
	* @page_for_ecryptfs: The page into which data for eCryptfs will be
	* written
	* @offset_in_page: Offset in @page_for_ecryptfs from which to start
	* writing
	* @size: The number of bytes to write into @page_for_ecryptfs
	* @ecryptfs_inode: The eCryptfs inode
	*
	* Determines the byte offset in the file for the given page and
	* offset within the page, maps the page, and makes the call to read
	* the contents of @page_for_ecryptfs from the lower inode.
	*
	* Returns zero on success; non-zero otherwise
	*/
	int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
	pgoff_t page_index,
	size_t offset_in_page, size_t size,
	struct inode *ecryptfs_inode)
	{
	char *virt;
	loff_t offset;
	int rc;

	offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page);
	virt = kmap(page_for_ecryptfs);
	rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
	if (rc > 0)
	rc = 0;
	kunmap(page_for_ecryptfs);
	flush_dcache_page(page_for_ecryptfs);
	return rc;
	}