inode.c

linux 内核源代码

/**
 * 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 <[e-mail]>
 *              Michael C. Thompsion <[e-mail]>
 *
 * 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/vmalloc.h>
#include <linux/pagemap.h>
#include <linux/dcache.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/crypto.h>
#include <linux/fs_stack.h>
#include "ecryptfs_kernel.h"

static struct dentry *lock_parent(struct dentry *dentry)
{
	struct dentry *dir;

	dir = dget(dentry->d_parent);
	mutex_lock_nested(&(dir->d_inode->i_mutex), I_MUTEX_PARENT);
	return dir;
}

static void unlock_parent(struct dentry *dentry)
{
	mutex_unlock(&(dentry->d_parent->d_inode->i_mutex));
	dput(dentry->d_parent);
}

static void unlock_dir(struct dentry *dir)
{
	mutex_unlock(&dir->d_inode->i_mutex);
	dput(dir);
}

/**
 * ecryptfs_create_underlying_file
 * @lower_dir_inode: inode of the parent in the lower fs of the new file
 * @lower_dentry: New file's dentry in the lower fs
 * @ecryptfs_dentry: New file's dentry in ecryptfs
 * @mode: The mode of the new file
 * @nd: nameidata of ecryptfs' parent's dentry & vfsmount
 *
 * Creates the file in the lower file system.
 *
 * Returns zero on success; non-zero on error condition
 */
static int
ecryptfs_create_underlying_file(struct inode *lower_dir_inode,
				struct dentry *dentry, int mode,
				struct nameidata *nd)
{
	struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry);
	struct vfsmount *lower_mnt = ecryptfs_dentry_to_lower_mnt(dentry);
	struct dentry *dentry_save;
	struct vfsmount *vfsmount_save;
	int rc;

	dentry_save = nd->dentry;
	vfsmount_save = nd->mnt;
	nd->dentry = lower_dentry;
	nd->mnt = lower_mnt;
	rc = vfs_create(lower_dir_inode, lower_dentry, mode, nd);
	nd->dentry = dentry_save;
	nd->mnt = vfsmount_save;
	return rc;
}

/**
 * ecryptfs_do_create
 * @directory_inode: inode of the new file's dentry's parent in ecryptfs
 * @ecryptfs_dentry: New file's dentry in ecryptfs
 * @mode: The mode of the new file
 * @nd: nameidata of ecryptfs' parent's dentry & vfsmount
 *
 * Creates the underlying file and the eCryptfs inode which will link to
 * it. It will also update the eCryptfs directory inode to mimic the
 * stat of the lower directory inode.
 *
 * Returns zero on success; non-zero on error condition
 */
static int
ecryptfs_do_create(struct inode *directory_inode,
		   struct dentry *ecryptfs_dentry, int mode,
		   struct nameidata *nd)
{
	int rc;
	struct dentry *lower_dentry;
	struct dentry *lower_dir_dentry;

	lower_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry);
	lower_dir_dentry = lock_parent(lower_dentry);
	if (unlikely(IS_ERR(lower_dir_dentry))) {
		ecryptfs_printk(KERN_ERR, "Error locking directory of "
				"dentry\n");
		rc = PTR_ERR(lower_dir_dentry);
		goto out;
	}
	rc = ecryptfs_create_underlying_file(lower_dir_dentry->d_inode,
					     ecryptfs_dentry, mode, nd);
	if (rc) {
		printk(KERN_ERR "%s: Failure to create dentry in lower fs; "
		       "rc = [%d]\n", __FUNCTION__, rc);
		goto out_lock;
	}
	rc = ecryptfs_interpose(lower_dentry, ecryptfs_dentry,
				directory_inode->i_sb, 0);
	if (rc) {
		ecryptfs_printk(KERN_ERR, "Failure in ecryptfs_interpose\n");
		goto out_lock;
	}
	fsstack_copy_attr_times(directory_inode, lower_dir_dentry->d_inode);
	fsstack_copy_inode_size(directory_inode, lower_dir_dentry->d_inode);
out_lock:
	unlock_dir(lower_dir_dentry);
out:
	return rc;
}

/**
 * grow_file
 * @ecryptfs_dentry: the eCryptfs dentry
 *
 * This is the code which will grow the file to its correct size.
 */
static int grow_file(struct dentry *ecryptfs_dentry)
{
	struct inode *ecryptfs_inode = ecryptfs_dentry->d_inode;
	struct file fake_file;
	struct ecryptfs_file_info tmp_file_info;
	char zero_virt[] = { 0x00 };
	int rc = 0;

	memset(&fake_file, 0, sizeof(fake_file));
	fake_file.f_path.dentry = ecryptfs_dentry;
	memset(&tmp_file_info, 0, sizeof(tmp_file_info));
	ecryptfs_set_file_private(&fake_file, &tmp_file_info);
	ecryptfs_set_file_lower(
		&fake_file,
		ecryptfs_inode_to_private(ecryptfs_inode)->lower_file);
	rc = ecryptfs_write(&fake_file, zero_virt, 0, 1);
	i_size_write(ecryptfs_inode, 0);
	rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
	ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat.flags |=
		ECRYPTFS_NEW_FILE;
	return rc;
}

/**
 * ecryptfs_initialize_file
 *
 * Cause the file to be changed from a basic empty file to an ecryptfs
 * file with a header and first data page.
 *
 * Returns zero on success
 */
static int ecryptfs_initialize_file(struct dentry *ecryptfs_dentry)
{
	struct ecryptfs_crypt_stat *crypt_stat =
		&ecryptfs_inode_to_private(ecryptfs_dentry->d_inode)->crypt_stat;
	int rc = 0;

	if (S_ISDIR(ecryptfs_dentry->d_inode->i_mode)) {
		ecryptfs_printk(KERN_DEBUG, "This is a directory\n");
		crypt_stat->flags &= ~(ECRYPTFS_ENCRYPTED);
		goto out;
	}
	crypt_stat->flags |= ECRYPTFS_NEW_FILE;
	ecryptfs_printk(KERN_DEBUG, "Initializing crypto context\n");
	rc = ecryptfs_new_file_context(ecryptfs_dentry);
	if (rc) {
		ecryptfs_printk(KERN_ERR, "Error creating new file "
				"context; rc = [%d]\n", rc);
		goto out;
	}
	rc = ecryptfs_write_metadata(ecryptfs_dentry);
	if (rc) {
		printk(KERN_ERR "Error writing headers; rc = [%d]\n", rc);
		goto out;
	}
	rc = grow_file(ecryptfs_dentry);
	if (rc)
		printk(KERN_ERR "Error growing file; rc = [%d]\n", rc);
out:
	return rc;
}

/**
 * ecryptfs_create
 * @dir: The inode of the directory in which to create the file.
 * @dentry: The eCryptfs dentry
 * @mode: The mode of the new file.
 * @nd: nameidata
 *
 * Creates a new file.
 *
 * Returns zero on success; non-zero on error condition
 */
static int
ecryptfs_create(struct inode *directory_inode, struct dentry *ecryptfs_dentry,
		int mode, struct nameidata *nd)
{
	int rc;

	/* ecryptfs_do_create() calls ecryptfs_interpose(), which opens
	 * the crypt_stat->lower_file (persistent file) */
	rc = ecryptfs_do_create(directory_inode, ecryptfs_dentry, mode, nd);
	if (unlikely(rc)) {
		ecryptfs_printk(KERN_WARNING, "Failed to create file in"
				"lower filesystem\n");
		goto out;
	}
	/* At this point, a file exists on "disk"; we need to make sure
	 * that this on disk file is prepared to be an ecryptfs file */
	rc = ecryptfs_initialize_file(ecryptfs_dentry);
out:
	return rc;
}

/**
 * ecryptfs_lookup
 * @dir: inode
 * @dentry: The dentry
 * @nd: nameidata, may be NULL
 *
 * Find a file on disk. If the file does not exist, then we'll add it to the
 * dentry cache and continue on to read it from the disk.
 */
static struct dentry *ecryptfs_lookup(struct inode *dir, struct dentry *dentry,
				      struct nameidata *nd)
{
	int rc = 0;
	struct dentry *lower_dir_dentry;
	struct dentry *lower_dentry;
	struct vfsmount *lower_mnt;
	char *encoded_name;
	int encoded_namelen;
	struct ecryptfs_crypt_stat *crypt_stat = NULL;
	struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
	char *page_virt = NULL;
	struct inode *lower_inode;
	u64 file_size;

	lower_dir_dentry = ecryptfs_dentry_to_lower(dentry->d_parent);
	dentry->d_op = &ecryptfs_dops;
	if ((dentry->d_name.len == 1 && !strcmp(dentry->d_name.name, "."))
	    || (dentry->d_name.len == 2
		&& !strcmp(dentry->d_name.name, ".."))) {
		d_drop(dentry);
		goto out;
	}
	encoded_namelen = ecryptfs_encode_filename(crypt_stat,
						   dentry->d_name.name,
						   dentry->d_name.len,
						   &encoded_name);
	if (encoded_namelen < 0) {
		rc = encoded_namelen;
		d_drop(dentry);
		goto out;
	}
	ecryptfs_printk(KERN_DEBUG, "encoded_name = [%s]; encoded_namelen "
			"= [%d]\n", encoded_name, encoded_namelen);
	lower_dentry = lookup_one_len(encoded_name, lower_dir_dentry,
				      encoded_namelen - 1);
	kfree(encoded_name);
	if (IS_ERR(lower_dentry)) {
		ecryptfs_printk(KERN_ERR, "ERR from lower_dentry\n");
		rc = PTR_ERR(lower_dentry);
		d_drop(dentry);
		goto out;
	}
	lower_mnt = mntget(ecryptfs_dentry_to_lower_mnt(dentry->d_parent));
	ecryptfs_printk(KERN_DEBUG, "lower_dentry = [%p]; lower_dentry->"
       		"d_name.name = [%s]\n", lower_dentry,
		lower_dentry->d_name.name);
	lower_inode = lower_dentry->d_inode;
	fsstack_copy_attr_atime(dir, lower_dir_dentry->d_inode);
	BUG_ON(!atomic_read(&lower_dentry->d_count));
	ecryptfs_set_dentry_private(dentry,
				    kmem_cache_alloc(ecryptfs_dentry_info_cache,
						     GFP_KERNEL));
	if (!ecryptfs_dentry_to_private(dentry)) {
		rc = -ENOMEM;
		ecryptfs_printk(KERN_ERR, "Out of memory whilst attempting "
				"to allocate ecryptfs_dentry_info struct\n");
		goto out_dput;
	}
	ecryptfs_set_dentry_lower(dentry, lower_dentry);
	ecryptfs_set_dentry_lower_mnt(dentry, lower_mnt);
	if (!lower_dentry->d_inode) {
		/* We want to add because we couldn't find in lower */
		d_add(dentry, NULL);
		goto out;
	}
	rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb, 1);
	if (rc) {
		ecryptfs_printk(KERN_ERR, "Error interposing\n");
		goto out_dput;
	}
	if (S_ISDIR(lower_inode->i_mode)) {
		ecryptfs_printk(KERN_DEBUG, "Is a directory; returning\n");
		goto out;
	}
	if (S_ISLNK(lower_inode->i_mode)) {
		ecryptfs_printk(KERN_DEBUG, "Is a symlink; returning\n");
		goto out;
	}
	if (special_file(lower_inode->i_mode)) {
		ecryptfs_printk(KERN_DEBUG, "Is a special file; returning\n");
		goto out;
	}
	if (!nd) {
		ecryptfs_printk(KERN_DEBUG, "We have a NULL nd, just leave"
				"as we *think* we are about to unlink\n");
		goto out;
	}
	/* Released in this function */
	page_virt = kmem_cache_zalloc(ecryptfs_header_cache_2,
				      GFP_USER);
	if (!page_virt) {
		rc = -ENOMEM;
		ecryptfs_printk(KERN_ERR,
				"Cannot ecryptfs_kmalloc a page\n");
		goto out_dput;
	}
	crypt_stat = &ecryptfs_inode_to_private(dentry->d_inode)->crypt_stat;
	if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED))
		ecryptfs_set_default_sizes(crypt_stat);
	rc = ecryptfs_read_and_validate_header_region(page_virt,
						      dentry->d_inode);