diff options
Diffstat (limited to 'fs/ecryptfs/read_write.c')
| -rw-r--r-- | fs/ecryptfs/read_write.c | 358 |
1 files changed, 358 insertions, 0 deletions
diff --git a/fs/ecryptfs/read_write.c b/fs/ecryptfs/read_write.c new file mode 100644 index 00000000000..2150edf9a58 --- /dev/null +++ b/fs/ecryptfs/read_write.c @@ -0,0 +1,358 @@ +/** + * 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 zero on success; non-zero on error + */ +int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data, + loff_t offset, size_t size) +{ + struct ecryptfs_inode_info *inode_info; + ssize_t octets_written; + mm_segment_t fs_save; + int rc = 0; + + inode_info = ecryptfs_inode_to_private(ecryptfs_inode); + mutex_lock(&inode_info->lower_file_mutex); + BUG_ON(!inode_info->lower_file); + inode_info->lower_file->f_pos = offset; + fs_save = get_fs(); + set_fs(get_ds()); + octets_written = vfs_write(inode_info->lower_file, data, size, + &inode_info->lower_file->f_pos); + set_fs(fs_save); + if (octets_written < 0) { + printk(KERN_ERR "%s: octets_written = [%td]; " + "expected [%td]\n", __FUNCTION__, octets_written, size); + rc = -EINVAL; + } + mutex_unlock(&inode_info->lower_file_mutex); + 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 = ((((off_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); + kunmap(page_for_lower); + return rc; +} + +/** + * ecryptfs_write + * @ecryptfs_file: 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 file *ecryptfs_file, char *data, loff_t offset, + size_t size) +{ + struct page *ecryptfs_page; + char *ecryptfs_page_virt; + loff_t ecryptfs_file_size = + i_size_read(ecryptfs_file->f_dentry->d_inode); + loff_t data_offset = 0; + loff_t pos; + int rc = 0; + + 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); + size_t total_remaining_bytes = ((offset + size) - pos); + + if (num_bytes > total_remaining_bytes) + num_bytes = total_remaining_bytes; + if (pos < offset) { + size_t total_remaining_zeros = (offset - pos); + + if (num_bytes > total_remaining_zeros) + num_bytes = total_remaining_zeros; + } + ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file, + 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", __FUNCTION__, + ecryptfs_page_idx, rc); + goto out; + } + if (start_offset_in_page) { + /* Read in the page from the lower + * into the eCryptfs inode page cache, + * decrypting */ + rc = ecryptfs_decrypt_page(ecryptfs_page); + if (rc) { + printk(KERN_ERR "%s: Error decrypting " + "page; rc = [%d]\n", + __FUNCTION__, rc); + ClearPageUptodate(ecryptfs_page); + page_cache_release(ecryptfs_page); + goto out; + } + } + ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0); + if (pos >= offset) { + memcpy(((char *)ecryptfs_page_virt + + start_offset_in_page), + (data + data_offset), num_bytes); + data_offset += num_bytes; + } else { + /* We are extending past the previous end of the file. + * Fill in zero values up to the start of where we + * will be writing data. */ + memset(((char *)ecryptfs_page_virt + + start_offset_in_page), 0, num_bytes); + } + kunmap_atomic(ecryptfs_page_virt, KM_USER0); + flush_dcache_page(ecryptfs_page); + SetPageUptodate(ecryptfs_page); + unlock_page(ecryptfs_page); + rc = ecryptfs_encrypt_page(ecryptfs_page); + page_cache_release(ecryptfs_page); + if (rc) { + printk(KERN_ERR "%s: Error encrypting " + "page; rc = [%d]\n", __FUNCTION__, rc); + goto out; + } + pos += num_bytes; + } + if ((offset + size) > ecryptfs_file_size) { + i_size_write(ecryptfs_file->f_dentry->d_inode, (offset + size)); + rc = ecryptfs_write_inode_size_to_metadata( + ecryptfs_file->f_dentry->d_inode); + if (rc) { + printk(KERN_ERR "Problem with " + "ecryptfs_write_inode_size_to_metadata; " + "rc = [%d]\n", rc); + 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 zero on success; non-zero on error + */ +int ecryptfs_read_lower(char *data, loff_t offset, size_t size, + struct inode *ecryptfs_inode) +{ + struct ecryptfs_inode_info *inode_info = + ecryptfs_inode_to_private(ecryptfs_inode); + ssize_t octets_read; + mm_segment_t fs_save; + int rc = 0; + + mutex_lock(&inode_info->lower_file_mutex); + BUG_ON(!inode_info->lower_file); + inode_info->lower_file->f_pos = offset; + fs_save = get_fs(); + set_fs(get_ds()); + octets_read = vfs_read(inode_info->lower_file, data, size, + &inode_info->lower_file->f_pos); + set_fs(fs_save); + if (octets_read < 0) { + printk(KERN_ERR "%s: octets_read = [%td]; " + "expected [%td]\n", __FUNCTION__, octets_read, size); + rc = -EINVAL; + } + mutex_unlock(&inode_info->lower_file_mutex); + return rc; +} + +/** + * 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); + kunmap(page_for_ecryptfs); + flush_dcache_page(page_for_ecryptfs); + return rc; +} + +/** + * ecryptfs_read + * @data: The virtual address into which to write the data read (and + * possibly decrypted) from the lower file + * @offset: The offset in the decrypted view of the file from which to + * read into @data + * @size: The number of bytes to read into @data + * @ecryptfs_file: The eCryptfs file from which to read + * + * Read an arbitrary amount of data from an arbitrary location in the + * eCryptfs page cache. This is done on an extent-by-extent basis; + * individual extents are decrypted and read from the lower page + * cache (via VFS reads). This function takes care of all the + * address translation to locations in the lower filesystem. + * + * Returns zero on success; non-zero otherwise + */ +int ecryptfs_read(char *data, loff_t offset, size_t size, + struct file *ecryptfs_file) +{ + struct page *ecryptfs_page; + char *ecryptfs_page_virt; + loff_t ecryptfs_file_size = + i_size_read(ecryptfs_file->f_dentry->d_inode); + loff_t data_offset = 0; + loff_t pos; + int rc = 0; + + if ((offset + size) > ecryptfs_file_size) { + rc = -EINVAL; + printk(KERN_ERR "%s: Attempt to read data past the end of the " + "file; offset = [%lld]; size = [%td]; " + "ecryptfs_file_size = [%lld]\n", + __FUNCTION__, offset, size, ecryptfs_file_size); + goto out; + } + 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); + size_t total_remaining_bytes = ((offset + size) - pos); + + if (num_bytes > total_remaining_bytes) + num_bytes = total_remaining_bytes; + ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file, + 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", __FUNCTION__, + ecryptfs_page_idx, rc); + goto out; + } + rc = ecryptfs_decrypt_page(ecryptfs_page); + if (rc) { + printk(KERN_ERR "%s: Error decrypting " + "page; rc = [%d]\n", __FUNCTION__, rc); + ClearPageUptodate(ecryptfs_page); + page_cache_release(ecryptfs_page); + goto out; + } + ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0); + memcpy((data + data_offset), + ((char *)ecryptfs_page_virt + start_offset_in_page), + num_bytes); + kunmap_atomic(ecryptfs_page_virt, KM_USER0); + flush_dcache_page(ecryptfs_page); + SetPageUptodate(ecryptfs_page); + unlock_page(ecryptfs_page); + page_cache_release(ecryptfs_page); + pos += num_bytes; + data_offset += num_bytes; + } +out: + return rc; +} |