linux/fs/ecryptfs/file.c
Tyler Hicks 821f7494a7 eCryptfs: Revert to a writethrough cache model
A change was made about a year ago to get eCryptfs to better utilize its
page cache during writes. The idea was to do the page encryption
operations during page writeback, rather than doing them when initially
writing into the page cache, to reduce the number of page encryption
operations during sequential writes. This meant that the encrypted page
would only be written to the lower filesystem during page writeback,
which was a change from how eCryptfs had previously wrote to the lower
filesystem in ecryptfs_write_end().

The change caused a few eCryptfs-internal bugs that were shook out.
Unfortunately, more grave side effects have been identified that will
force changes outside of eCryptfs. Because the lower filesystem isn't
consulted until page writeback, eCryptfs has no way to pass lower write
errors (ENOSPC, mainly) back to userspace. Additionaly, it was reported
that quotas could be bypassed because of the way eCryptfs may sometimes
open the lower filesystem using a privileged kthread.

It would be nice to resolve the latest issues, but it is best if the
eCryptfs commits be reverted to the old behavior in the meantime.

This reverts:
32001d6f "eCryptfs: Flush file in vma close"
5be79de2 "eCryptfs: Flush dirty pages in setattr"
57db4e8d "ecryptfs: modify write path to encrypt page in writepage"

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Tested-by: Colin King <colin.king@canonical.com>
Cc: Colin King <colin.king@canonical.com>
Cc: Thieu Le <thieule@google.com>
2012-07-13 16:46:06 -07:00

369 lines
11 KiB
C

/**
* eCryptfs: Linux filesystem encryption layer
*
* Copyright (C) 1997-2004 Erez Zadok
* Copyright (C) 2001-2004 Stony Brook University
* Copyright (C) 2004-2007 International Business Machines Corp.
* Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
* Michael C. Thompson <mcthomps@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/file.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/security.h>
#include <linux/compat.h>
#include <linux/fs_stack.h>
#include "ecryptfs_kernel.h"
/**
* ecryptfs_read_update_atime
*
* generic_file_read updates the atime of upper layer inode. But, it
* doesn't give us a chance to update the atime of the lower layer
* inode. This function is a wrapper to generic_file_read. It
* updates the atime of the lower level inode if generic_file_read
* returns without any errors. This is to be used only for file reads.
* The function to be used for directory reads is ecryptfs_read.
*/
static ssize_t ecryptfs_read_update_atime(struct kiocb *iocb,
const struct iovec *iov,
unsigned long nr_segs, loff_t pos)
{
ssize_t rc;
struct path lower;
struct file *file = iocb->ki_filp;
rc = generic_file_aio_read(iocb, iov, nr_segs, pos);
/*
* Even though this is a async interface, we need to wait
* for IO to finish to update atime
*/
if (-EIOCBQUEUED == rc)
rc = wait_on_sync_kiocb(iocb);
if (rc >= 0) {
lower.dentry = ecryptfs_dentry_to_lower(file->f_path.dentry);
lower.mnt = ecryptfs_dentry_to_lower_mnt(file->f_path.dentry);
touch_atime(&lower);
}
return rc;
}
struct ecryptfs_getdents_callback {
void *dirent;
struct dentry *dentry;
filldir_t filldir;
int filldir_called;
int entries_written;
};
/* Inspired by generic filldir in fs/readdir.c */
static int
ecryptfs_filldir(void *dirent, const char *lower_name, int lower_namelen,
loff_t offset, u64 ino, unsigned int d_type)
{
struct ecryptfs_getdents_callback *buf =
(struct ecryptfs_getdents_callback *)dirent;
size_t name_size;
char *name;
int rc;
buf->filldir_called++;
rc = ecryptfs_decode_and_decrypt_filename(&name, &name_size,
buf->dentry, lower_name,
lower_namelen);
if (rc) {
printk(KERN_ERR "%s: Error attempting to decode and decrypt "
"filename [%s]; rc = [%d]\n", __func__, lower_name,
rc);
goto out;
}
rc = buf->filldir(buf->dirent, name, name_size, offset, ino, d_type);
kfree(name);
if (rc >= 0)
buf->entries_written++;
out:
return rc;
}
/**
* ecryptfs_readdir
* @file: The eCryptfs directory file
* @dirent: Directory entry handle
* @filldir: The filldir callback function
*/
static int ecryptfs_readdir(struct file *file, void *dirent, filldir_t filldir)
{
int rc;
struct file *lower_file;
struct inode *inode;
struct ecryptfs_getdents_callback buf;
lower_file = ecryptfs_file_to_lower(file);
lower_file->f_pos = file->f_pos;
inode = file->f_path.dentry->d_inode;
memset(&buf, 0, sizeof(buf));
buf.dirent = dirent;
buf.dentry = file->f_path.dentry;
buf.filldir = filldir;
buf.filldir_called = 0;
buf.entries_written = 0;
rc = vfs_readdir(lower_file, ecryptfs_filldir, (void *)&buf);
file->f_pos = lower_file->f_pos;
if (rc < 0)
goto out;
if (buf.filldir_called && !buf.entries_written)
goto out;
if (rc >= 0)
fsstack_copy_attr_atime(inode,
lower_file->f_path.dentry->d_inode);
out:
return rc;
}
struct kmem_cache *ecryptfs_file_info_cache;
static int read_or_initialize_metadata(struct dentry *dentry)
{
struct inode *inode = dentry->d_inode;
struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
struct ecryptfs_crypt_stat *crypt_stat;
int rc;
crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
mount_crypt_stat = &ecryptfs_superblock_to_private(
inode->i_sb)->mount_crypt_stat;
mutex_lock(&crypt_stat->cs_mutex);
if (crypt_stat->flags & ECRYPTFS_POLICY_APPLIED &&
crypt_stat->flags & ECRYPTFS_KEY_VALID) {
rc = 0;
goto out;
}
rc = ecryptfs_read_metadata(dentry);
if (!rc)
goto out;
if (mount_crypt_stat->flags & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED) {
crypt_stat->flags &= ~(ECRYPTFS_I_SIZE_INITIALIZED
| ECRYPTFS_ENCRYPTED);
rc = 0;
goto out;
}
if (!(mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED) &&
!i_size_read(ecryptfs_inode_to_lower(inode))) {
rc = ecryptfs_initialize_file(dentry, inode);
if (!rc)
goto out;
}
rc = -EIO;
out:
mutex_unlock(&crypt_stat->cs_mutex);
return rc;
}
/**
* ecryptfs_open
* @inode: inode speciying file to open
* @file: Structure to return filled in
*
* Opens the file specified by inode.
*
* Returns zero on success; non-zero otherwise
*/
static int ecryptfs_open(struct inode *inode, struct file *file)
{
int rc = 0;
struct ecryptfs_crypt_stat *crypt_stat = NULL;
struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
struct dentry *ecryptfs_dentry = file->f_path.dentry;
/* Private value of ecryptfs_dentry allocated in
* ecryptfs_lookup() */
struct dentry *lower_dentry;
struct ecryptfs_file_info *file_info;
mount_crypt_stat = &ecryptfs_superblock_to_private(
ecryptfs_dentry->d_sb)->mount_crypt_stat;
if ((mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
&& ((file->f_flags & O_WRONLY) || (file->f_flags & O_RDWR)
|| (file->f_flags & O_CREAT) || (file->f_flags & O_TRUNC)
|| (file->f_flags & O_APPEND))) {
printk(KERN_WARNING "Mount has encrypted view enabled; "
"files may only be read\n");
rc = -EPERM;
goto out;
}
/* Released in ecryptfs_release or end of function if failure */
file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
ecryptfs_set_file_private(file, file_info);
if (!file_info) {
ecryptfs_printk(KERN_ERR,
"Error attempting to allocate memory\n");
rc = -ENOMEM;
goto out;
}
lower_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry);
crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
mutex_lock(&crypt_stat->cs_mutex);
if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED)) {
ecryptfs_printk(KERN_DEBUG, "Setting flags for stat...\n");
/* Policy code enabled in future release */
crypt_stat->flags |= (ECRYPTFS_POLICY_APPLIED
| ECRYPTFS_ENCRYPTED);
}
mutex_unlock(&crypt_stat->cs_mutex);
rc = ecryptfs_get_lower_file(ecryptfs_dentry, inode);
if (rc) {
printk(KERN_ERR "%s: Error attempting to initialize "
"the lower file for the dentry with name "
"[%s]; rc = [%d]\n", __func__,
ecryptfs_dentry->d_name.name, rc);
goto out_free;
}
if ((ecryptfs_inode_to_private(inode)->lower_file->f_flags & O_ACCMODE)
== O_RDONLY && (file->f_flags & O_ACCMODE) != O_RDONLY) {
rc = -EPERM;
printk(KERN_WARNING "%s: Lower file is RO; eCryptfs "
"file must hence be opened RO\n", __func__);
goto out_put;
}
ecryptfs_set_file_lower(
file, ecryptfs_inode_to_private(inode)->lower_file);
if (S_ISDIR(ecryptfs_dentry->d_inode->i_mode)) {
ecryptfs_printk(KERN_DEBUG, "This is a directory\n");
mutex_lock(&crypt_stat->cs_mutex);
crypt_stat->flags &= ~(ECRYPTFS_ENCRYPTED);
mutex_unlock(&crypt_stat->cs_mutex);
rc = 0;
goto out;
}
rc = read_or_initialize_metadata(ecryptfs_dentry);
if (rc)
goto out_put;
ecryptfs_printk(KERN_DEBUG, "inode w/ addr = [0x%p], i_ino = "
"[0x%.16lx] size: [0x%.16llx]\n", inode, inode->i_ino,
(unsigned long long)i_size_read(inode));
goto out;
out_put:
ecryptfs_put_lower_file(inode);
out_free:
kmem_cache_free(ecryptfs_file_info_cache,
ecryptfs_file_to_private(file));
out:
return rc;
}
static int ecryptfs_flush(struct file *file, fl_owner_t td)
{
return file->f_mode & FMODE_WRITE
? filemap_write_and_wait(file->f_mapping) : 0;
}
static int ecryptfs_release(struct inode *inode, struct file *file)
{
ecryptfs_put_lower_file(inode);
kmem_cache_free(ecryptfs_file_info_cache,
ecryptfs_file_to_private(file));
return 0;
}
static int
ecryptfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
{
return vfs_fsync(ecryptfs_file_to_lower(file), datasync);
}
static int ecryptfs_fasync(int fd, struct file *file, int flag)
{
int rc = 0;
struct file *lower_file = NULL;
lower_file = ecryptfs_file_to_lower(file);
if (lower_file->f_op && lower_file->f_op->fasync)
rc = lower_file->f_op->fasync(fd, lower_file, flag);
return rc;
}
static long
ecryptfs_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct file *lower_file = NULL;
long rc = -ENOTTY;
if (ecryptfs_file_to_private(file))
lower_file = ecryptfs_file_to_lower(file);
if (lower_file && lower_file->f_op && lower_file->f_op->unlocked_ioctl)
rc = lower_file->f_op->unlocked_ioctl(lower_file, cmd, arg);
return rc;
}
#ifdef CONFIG_COMPAT
static long
ecryptfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct file *lower_file = NULL;
long rc = -ENOIOCTLCMD;
if (ecryptfs_file_to_private(file))
lower_file = ecryptfs_file_to_lower(file);
if (lower_file && lower_file->f_op && lower_file->f_op->compat_ioctl)
rc = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);
return rc;
}
#endif
const struct file_operations ecryptfs_dir_fops = {
.readdir = ecryptfs_readdir,
.read = generic_read_dir,
.unlocked_ioctl = ecryptfs_unlocked_ioctl,
#ifdef CONFIG_COMPAT
.compat_ioctl = ecryptfs_compat_ioctl,
#endif
.open = ecryptfs_open,
.flush = ecryptfs_flush,
.release = ecryptfs_release,
.fsync = ecryptfs_fsync,
.fasync = ecryptfs_fasync,
.splice_read = generic_file_splice_read,
.llseek = default_llseek,
};
const struct file_operations ecryptfs_main_fops = {
.llseek = generic_file_llseek,
.read = do_sync_read,
.aio_read = ecryptfs_read_update_atime,
.write = do_sync_write,
.aio_write = generic_file_aio_write,
.readdir = ecryptfs_readdir,
.unlocked_ioctl = ecryptfs_unlocked_ioctl,
#ifdef CONFIG_COMPAT
.compat_ioctl = ecryptfs_compat_ioctl,
#endif
.mmap = generic_file_mmap,
.open = ecryptfs_open,
.flush = ecryptfs_flush,
.release = ecryptfs_release,
.fsync = ecryptfs_fsync,
.fasync = ecryptfs_fasync,
.splice_read = generic_file_splice_read,
};