linux/fs/ecryptfs/read_write.c
Tyler Hicks 96a7b9c2f5 eCryptfs: Propagate vfs_read and vfs_write return codes
Errors returned from vfs_read() and vfs_write() calls to the lower
filesystem were being masked as -EINVAL.  This caused some confusion to
users who saw EINVAL instead of ENOSPC when the disk was full, for
instance.

Also, the actual bytes read or written were not accessible by callers to
ecryptfs_read_lower() and ecryptfs_write_lower(), which may be useful in
some cases.  This patch updates the error handling logic where those
functions are called in order to accept positive return codes indicating
success.

Cc: Eric Sandeen <esandeen@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: ecryptfs-devel@lists.launchpad.net
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>
2009-09-23 09:10:34 -05:00

356 lines
11 KiB
C

/**
* 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 ecryptfs_inode_info *inode_info;
mm_segment_t fs_save;
ssize_t rc;
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());
rc = vfs_write(inode_info->lower_file, data, size,
&inode_info->lower_file->f_pos);
set_fs(fs_save);
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 = ((((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_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;
struct ecryptfs_crypt_stat *crypt_stat;
struct inode *ecryptfs_inode = ecryptfs_file->f_dentry->d_inode;
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);
size_t total_remaining_bytes = ((offset + size) - pos);
if (num_bytes > total_remaining_bytes)
num_bytes = total_remaining_bytes;
if (pos < offset) {
/* remaining zeros to write, up to destination 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", __func__,
ecryptfs_page_idx, rc);
goto out;
}
ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0);
/*
* 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, KM_USER0);
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 ((offset + size) > ecryptfs_file_size) {
i_size_write(ecryptfs_inode, (offset + size));
if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
rc = ecryptfs_write_inode_size_to_metadata(
ecryptfs_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 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 ecryptfs_inode_info *inode_info =
ecryptfs_inode_to_private(ecryptfs_inode);
mm_segment_t fs_save;
ssize_t rc;
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());
rc = vfs_read(inode_info->lower_file, data, size,
&inode_info->lower_file->f_pos);
set_fs(fs_save);
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);
if (rc > 0)
rc = 0;
kunmap(page_for_ecryptfs);
flush_dcache_page(page_for_ecryptfs);
return rc;
}
#if 0
/**
* 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",
__func__, 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", __func__,
ecryptfs_page_idx, rc);
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;
}
#endif /* 0 */