fs/sdcardfs/derived_perm.c - kernel/common.git - Git at Google

 /*
  * fs/sdcardfs/derived_perm.c
  *
  * Copyright (c) 2013 Samsung Electronics Co. Ltd
  *   Authors: Daeho Jeong, Woojoong Lee, Seunghwan Hyun,
  *               Sunghwan Yun, Sungjong Seo
  *
  * This program has been developed as a stackable file system based on
  * the WrapFS which written by
  *
  * Copyright (c) 1998-2011 Erez Zadok
  * Copyright (c) 2009     Shrikar Archak
  * Copyright (c) 2003-2011 Stony Brook University
  * Copyright (c) 2003-2011 The Research Foundation of SUNY
  *
  * This file is dual licensed.  It may be redistributed and/or modified
  * under the terms of the Apache 2.0 License OR version 2 of the GNU
  * General Public License.
  */

 #include "sdcardfs.h"

 /* copy derived state from parent inode */
 static void inherit_derived_state(struct inode *parent, struct inode *child)
 {
 	struct sdcardfs_inode_info *pi = SDCARDFS_I(parent);
 	struct sdcardfs_inode_info *ci = SDCARDFS_I(child);

 	ci->data->perm = PERM_INHERIT;
 	ci->data->userid = pi->data->userid;
 	ci->data->d_uid = pi->data->d_uid;
 	ci->data->under_android = pi->data->under_android;
 	ci->data->under_cache = pi->data->under_cache;
 	ci->data->under_obb = pi->data->under_obb;
 	set_top(ci, pi->top_data);
 }

 /* helper function for derived state */
 void setup_derived_state(struct inode *inode, perm_t perm, userid_t userid,
 					uid_t uid, bool under_android,
 					struct sdcardfs_inode_data *top)
 {
 	struct sdcardfs_inode_info *info = SDCARDFS_I(inode);

 	info->data->perm = perm;
 	info->data->userid = userid;
 	info->data->d_uid = uid;
 	info->data->under_android = under_android;
 	info->data->under_cache = false;
 	info->data->under_obb = false;
 	set_top(info, top);
 }

 /* While renaming, there is a point where we want the path from dentry,
  * but the name from newdentry
  */
 void get_derived_permission_new(struct dentry *parent, struct dentry *dentry,
 				const struct qstr *name)
 {
 	struct sdcardfs_inode_info *info = SDCARDFS_I(d_inode(dentry));
 	struct sdcardfs_inode_data *parent_data =
 			SDCARDFS_I(d_inode(parent))->data;
 	appid_t appid;
 	unsigned long user_num;
 	int err;
 	struct qstr q_Android = QSTR_LITERAL("Android");
 	struct qstr q_data = QSTR_LITERAL("data");
 	struct qstr q_obb = QSTR_LITERAL("obb");
 	struct qstr q_media = QSTR_LITERAL("media");
 	struct qstr q_cache = QSTR_LITERAL("cache");

 	/* By default, each inode inherits from its parent.
 	 * the properties are maintained on its private fields
 	 * because the inode attributes will be modified with that of
 	 * its lower inode.
 	 * These values are used by our custom permission call instead
 	 * of using the inode permissions.
 	 */

 	inherit_derived_state(d_inode(parent), d_inode(dentry));

 	/* Files don't get special labels */
 	if (!S_ISDIR(d_inode(dentry)->i_mode))
 		return;
 	/* Derive custom permissions based on parent and current node */
 	switch (parent_data->perm) {
 	case PERM_INHERIT:
 	case PERM_ANDROID_PACKAGE_CACHE:
 		/* Already inherited above */
 		break;
 	case PERM_PRE_ROOT:
 		/* Legacy internal layout places users at top level */
 		info->data->perm = PERM_ROOT;
 		err = kstrtoul(name->name, 10, &user_num);
 		if (err)
 			info->data->userid = 0;
 		else
 			info->data->userid = user_num;
 		set_top(info, info->data);
 		break;
 	case PERM_ROOT:
 		/* Assume masked off by default. */
 		if (qstr_case_eq(name, &q_Android)) {
 			/* App-specific directories inside; let anyone traverse */
 			info->data->perm = PERM_ANDROID;
 			info->data->under_android = true;
 			set_top(info, info->data);
 		}
 		break;
 	case PERM_ANDROID:
 		if (qstr_case_eq(name, &q_data)) {
 			/* App-specific directories inside; let anyone traverse */
 			info->data->perm = PERM_ANDROID_DATA;
 			set_top(info, info->data);
 		} else if (qstr_case_eq(name, &q_obb)) {
 			/* App-specific directories inside; let anyone traverse */
 			info->data->perm = PERM_ANDROID_OBB;
 			info->data->under_obb = true;
 			set_top(info, info->data);
 			/* Single OBB directory is always shared */
 		} else if (qstr_case_eq(name, &q_media)) {
 			/* App-specific directories inside; let anyone traverse */
 			info->data->perm = PERM_ANDROID_MEDIA;
 			set_top(info, info->data);
 		}
 		break;
 	case PERM_ANDROID_OBB:
 	case PERM_ANDROID_DATA:
 	case PERM_ANDROID_MEDIA:
 		info->data->perm = PERM_ANDROID_PACKAGE;
 		appid = get_appid(name->name);
 		if (appid != 0 && !is_excluded(name->name, parent_data->userid))
 			info->data->d_uid =
 				multiuser_get_uid(parent_data->userid, appid);
 		set_top(info, info->data);
 		break;
 	case PERM_ANDROID_PACKAGE:
 		if (qstr_case_eq(name, &q_cache)) {
 			info->data->perm = PERM_ANDROID_PACKAGE_CACHE;
 			info->data->under_cache = true;
 		}
 		break;
 	}
 }

 void get_derived_permission(struct dentry *parent, struct dentry *dentry)
 {
 	get_derived_permission_new(parent, dentry, &dentry->d_name);
 }

 static appid_t get_type(const char *name)
 {
 	const char *ext = strrchr(name, '.');
 	appid_t id;

 	if (ext && ext[0]) {
 		ext = &ext[1];
 		id = get_ext_gid(ext);
 		return id?:AID_MEDIA_RW;
 	}
 	return AID_MEDIA_RW;
 }

 void fixup_lower_ownership(struct dentry *dentry, const char *name)
 {
 	struct path path;
 	struct inode *inode;
 	struct inode *delegated_inode = NULL;
 	int error;
 	struct sdcardfs_inode_info *info;
 	struct sdcardfs_inode_data *info_d;
 	struct sdcardfs_inode_data *info_top;
 	perm_t perm;
 	struct sdcardfs_sb_info *sbi = SDCARDFS_SB(dentry->d_sb);
 	uid_t uid = sbi->options.fs_low_uid;
 	gid_t gid = sbi->options.fs_low_gid;
 	struct iattr newattrs;

 	info = SDCARDFS_I(d_inode(dentry));
 	info_d = info->data;
 	perm = info_d->perm;
 	if (info_d->under_obb) {
 		perm = PERM_ANDROID_OBB;
 	} else if (info_d->under_cache) {
 		perm = PERM_ANDROID_PACKAGE_CACHE;
 	} else if (perm == PERM_INHERIT) {
 		info_top = top_data_get(info);
 		perm = info_top->perm;
 		data_put(info_top);
 	}

 	switch (perm) {
 	case PERM_ROOT:
 	case PERM_ANDROID:
 	case PERM_ANDROID_DATA:
 	case PERM_ANDROID_MEDIA:
 	case PERM_ANDROID_PACKAGE:
 	case PERM_ANDROID_PACKAGE_CACHE:
 		uid = multiuser_get_uid(info_d->userid, uid);
 		break;
 	case PERM_ANDROID_OBB:
 		uid = AID_MEDIA_OBB;
 		break;
 	case PERM_PRE_ROOT:
 	default:
 		break;
 	}
 	switch (perm) {
 	case PERM_ROOT:
 	case PERM_ANDROID:
 	case PERM_ANDROID_DATA:
 	case PERM_ANDROID_MEDIA:
 		if (S_ISDIR(d_inode(dentry)->i_mode))
 			gid = multiuser_get_uid(info_d->userid, AID_MEDIA_RW);
 		else
 			gid = multiuser_get_uid(info_d->userid, get_type(name));
 		break;
 	case PERM_ANDROID_OBB:
 		gid = AID_MEDIA_OBB;
 		break;
 	case PERM_ANDROID_PACKAGE:
 		if (uid_is_app(info_d->d_uid))
 			gid = multiuser_get_ext_gid(info_d->d_uid);
 		else
 			gid = multiuser_get_uid(info_d->userid, AID_MEDIA_RW);
 		break;
 	case PERM_ANDROID_PACKAGE_CACHE:
 		if (uid_is_app(info_d->d_uid))
 			gid = multiuser_get_ext_cache_gid(info_d->d_uid);
 		else
 			gid = multiuser_get_uid(info_d->userid, AID_MEDIA_RW);
 		break;
 	case PERM_PRE_ROOT:
 	default:
 		break;
 	}

 	sdcardfs_get_lower_path(dentry, &path);
 	inode = d_inode(path.dentry);
 	if (d_inode(path.dentry)->i_gid.val != gid || d_inode(path.dentry)->i_uid.val != uid) {
 retry_deleg:
 		newattrs.ia_valid = ATTR_GID | ATTR_UID | ATTR_FORCE;
 		newattrs.ia_uid = make_kuid(current_user_ns(), uid);
 		newattrs.ia_gid = make_kgid(current_user_ns(), gid);
 		if (!S_ISDIR(inode->i_mode))
 			newattrs.ia_valid |=
 				ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
 		mutex_lock(&inode->i_mutex);
 		error = security_path_chown(&path, newattrs.ia_uid, newattrs.ia_gid);
 		if (!error)
 			error = notify_change2(path.mnt, path.dentry, &newattrs, &delegated_inode);
 		mutex_unlock(&inode->i_mutex);
 		if (delegated_inode) {
 			error = break_deleg_wait(&delegated_inode);
 			if (!error)
 				goto retry_deleg;
 		}
 		if (error)
 			pr_debug("sdcardfs: Failed to touch up lower fs gid/uid for %s\n", name);
 	}
 	sdcardfs_put_lower_path(dentry, &path);
 }

 static int descendant_may_need_fixup(struct sdcardfs_inode_data *data,
 		struct limit_search *limit)
 {
 	if (data->perm == PERM_ROOT)
 		return (limit->flags & BY_USERID) ?
 				data->userid == limit->userid : 1;
 	if (data->perm == PERM_PRE_ROOT || data->perm == PERM_ANDROID)
 		return 1;
 	return 0;
 }

 static int needs_fixup(perm_t perm)
 {
 	if (perm == PERM_ANDROID_DATA || perm == PERM_ANDROID_OBB
 			|| perm == PERM_ANDROID_MEDIA)
 		return 1;
 	return 0;
 }

 static void __fixup_perms_recursive(struct dentry *dentry, struct limit_search *limit, int depth)
 {
 	struct dentry *child;
 	struct sdcardfs_inode_info *info;

 	/*
 	 * All paths will terminate their recursion on hitting PERM_ANDROID_OBB,
 	 * PERM_ANDROID_MEDIA, or PERM_ANDROID_DATA. This happens at a depth of
 	 * at most 3.
 	 */
 	WARN(depth > 3, "%s: Max expected depth exceeded!\n", __func__);
 	spin_lock_nested(&dentry->d_lock, depth);
 	if (!d_inode(dentry)) {
 		spin_unlock(&dentry->d_lock);
 		return;
 	}
 	info = SDCARDFS_I(d_inode(dentry));

 	if (needs_fixup(info->data->perm)) {
 		list_for_each_entry(child, &dentry->d_subdirs, d_child) {
 			spin_lock_nested(&child->d_lock, depth + 1);
 			if (!(limit->flags & BY_NAME) || qstr_case_eq(&child->d_name, &limit->name)) {
 				if (d_inode(child)) {
 					get_derived_permission(dentry, child);
 					fixup_tmp_permissions(d_inode(child));
 					spin_unlock(&child->d_lock);
 					break;
 				}
 			}
 			spin_unlock(&child->d_lock);
 		}
 	} else if (descendant_may_need_fixup(info->data, limit)) {
 		list_for_each_entry(child, &dentry->d_subdirs, d_child) {
 			__fixup_perms_recursive(child, limit, depth + 1);
 		}
 	}
 	spin_unlock(&dentry->d_lock);
 }

 void fixup_perms_recursive(struct dentry *dentry, struct limit_search *limit)
 {
 	__fixup_perms_recursive(dentry, limit, 0);
 }

 /* main function for updating derived permission */
 inline void update_derived_permission_lock(struct dentry *dentry)
 {
 	struct dentry *parent;

 	if (!dentry || !d_inode(dentry)) {
 		pr_err("sdcardfs: %s: invalid dentry\n", __func__);
 		return;
 	}
 	/* FIXME:
 	 * 1. need to check whether the dentry is updated or not
 	 * 2. remove the root dentry update
 	 */
 	if (!IS_ROOT(dentry)) {
 		parent = dget_parent(dentry);
 		if (parent) {
 			get_derived_permission(parent, dentry);
 			dput(parent);
 		}
 	}
 	fixup_tmp_permissions(d_inode(dentry));
 }

 int need_graft_path(struct dentry *dentry)
 {
 	int ret = 0;
 	struct dentry *parent = dget_parent(dentry);
 	struct sdcardfs_inode_info *parent_info = SDCARDFS_I(d_inode(parent));
 	struct sdcardfs_sb_info *sbi = SDCARDFS_SB(dentry->d_sb);
 	struct qstr obb = QSTR_LITERAL("obb");

 	if (parent_info->data->perm == PERM_ANDROID &&
 			qstr_case_eq(&dentry->d_name, &obb)) {

 		/* /Android/obb is the base obbpath of DERIVED_UNIFIED */
 		if (!(sbi->options.multiuser == false
 				&& parent_info->data->userid == 0)) {
 			ret = 1;
 		}
 	}
 	dput(parent);
 	return ret;
 }

 int is_obbpath_invalid(struct dentry *dent)
 {
 	int ret = 0;
 	struct sdcardfs_dentry_info *di = SDCARDFS_D(dent);
 	struct sdcardfs_sb_info *sbi = SDCARDFS_SB(dent->d_sb);
 	char *path_buf, *obbpath_s;
 	int need_put = 0;
 	struct path lower_path;

 	/* check the base obbpath has been changed.
 	 * this routine can check an uninitialized obb dentry as well.
 	 * regarding the uninitialized obb, refer to the sdcardfs_mkdir()
 	 */
 	spin_lock(&di->lock);
 	if (di->orig_path.dentry) {
 		if (!di->lower_path.dentry) {
 			ret = 1;
 		} else {
 			path_get(&di->lower_path);

 			path_buf = kmalloc(PATH_MAX, GFP_ATOMIC);
 			if (!path_buf) {
 				ret = 1;
 				pr_err("sdcardfs: fail to allocate path_buf in %s.\n", __func__);
 			} else {
 				obbpath_s = d_path(&di->lower_path, path_buf, PATH_MAX);
 				if (d_unhashed(di->lower_path.dentry) ||
 					!str_case_eq(sbi->obbpath_s, obbpath_s)) {
 					ret = 1;
 				}
 				kfree(path_buf);
 			}

 			pathcpy(&lower_path, &di->lower_path);
 			need_put = 1;
 		}
 	}
 	spin_unlock(&di->lock);
 	if (need_put)
 		path_put(&lower_path);
 	return ret;
 }

 int is_base_obbpath(struct dentry *dentry)
 {
 	int ret = 0;
 	struct dentry *parent = dget_parent(dentry);
 	struct sdcardfs_inode_info *parent_info = SDCARDFS_I(d_inode(parent));
 	struct sdcardfs_sb_info *sbi = SDCARDFS_SB(dentry->d_sb);
 	struct qstr q_obb = QSTR_LITERAL("obb");

 	spin_lock(&SDCARDFS_D(dentry)->lock);
 	if (sbi->options.multiuser) {
 		if (parent_info->data->perm == PERM_PRE_ROOT &&
 				qstr_case_eq(&dentry->d_name, &q_obb)) {
 			ret = 1;
 		}
 	} else  if (parent_info->data->perm == PERM_ANDROID &&
 			qstr_case_eq(&dentry->d_name, &q_obb)) {
 		ret = 1;
 	}
 	spin_unlock(&SDCARDFS_D(dentry)->lock);
 	return ret;
 }

 /* The lower_path will be stored to the dentry's orig_path
  * and the base obbpath will be copyed to the lower_path variable.
  * if an error returned, there's no change in the lower_path
  * returns: -ERRNO if error (0: no error)
  */
 int setup_obb_dentry(struct dentry *dentry, struct path *lower_path)
 {
 	int err = 0;
 	struct sdcardfs_sb_info *sbi = SDCARDFS_SB(dentry->d_sb);
 	struct path obbpath;

 	/* A local obb dentry must have its own orig_path to support rmdir
 	 * and mkdir of itself. Usually, we expect that the sbi->obbpath
 	 * is avaiable on this stage.
 	 */
 	sdcardfs_set_orig_path(dentry, lower_path);

 	err = kern_path(sbi->obbpath_s,
 			LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &obbpath);

 	if (!err) {
 		/* the obbpath base has been found */
 		pathcpy(lower_path, &obbpath);
 	} else {
 		/* if the sbi->obbpath is not available, we can optionally
 		 * setup the lower_path with its orig_path.
 		 * but, the current implementation just returns an error
 		 * because the sdcard daemon also regards this case as
 		 * a lookup fail.
 		 */
 		pr_info("sdcardfs: the sbi->obbpath is not available\n");
 	}
 	return err;
 }
	/*
	* fs/sdcardfs/derived_perm.c
	*
	* Copyright (c) 2013 Samsung Electronics Co. Ltd
	* Authors: Daeho Jeong, Woojoong Lee, Seunghwan Hyun,
	* Sunghwan Yun, Sungjong Seo
	*
	* This program has been developed as a stackable file system based on
	* the WrapFS which written by
	*
	* Copyright (c) 1998-2011 Erez Zadok
	* Copyright (c) 2009 Shrikar Archak
	* Copyright (c) 2003-2011 Stony Brook University
	* Copyright (c) 2003-2011 The Research Foundation of SUNY
	*
	* This file is dual licensed. It may be redistributed and/or modified
	* under the terms of the Apache 2.0 License OR version 2 of the GNU
	* General Public License.
	*/

	#include "sdcardfs.h"

	/* copy derived state from parent inode */
	static void inherit_derived_state(struct inode parent, struct inode child)
	{
	struct sdcardfs_inode_info *pi = SDCARDFS_I(parent);
	struct sdcardfs_inode_info *ci = SDCARDFS_I(child);

	ci->data->perm = PERM_INHERIT;
	ci->data->userid = pi->data->userid;
	ci->data->d_uid = pi->data->d_uid;
	ci->data->under_android = pi->data->under_android;
	ci->data->under_cache = pi->data->under_cache;
	ci->data->under_obb = pi->data->under_obb;
	set_top(ci, pi->top_data);
	}

	/* helper function for derived state */
	void setup_derived_state(struct inode *inode, perm_t perm, userid_t userid,
	uid_t uid, bool under_android,
	struct sdcardfs_inode_data *top)
	{
	struct sdcardfs_inode_info *info = SDCARDFS_I(inode);

	info->data->perm = perm;
	info->data->userid = userid;
	info->data->d_uid = uid;
	info->data->under_android = under_android;
	info->data->under_cache = false;
	info->data->under_obb = false;
	set_top(info, top);
	}

	/* While renaming, there is a point where we want the path from dentry,
	* but the name from newdentry
	*/
	void get_derived_permission_new(struct dentry parent, struct dentry dentry,
	const struct qstr *name)
	{
	struct sdcardfs_inode_info *info = SDCARDFS_I(d_inode(dentry));
	struct sdcardfs_inode_data *parent_data =
	SDCARDFS_I(d_inode(parent))->data;
	appid_t appid;
	unsigned long user_num;
	int err;
	struct qstr q_Android = QSTR_LITERAL("Android");
	struct qstr q_data = QSTR_LITERAL("data");
	struct qstr q_obb = QSTR_LITERAL("obb");
	struct qstr q_media = QSTR_LITERAL("media");
	struct qstr q_cache = QSTR_LITERAL("cache");

	/* By default, each inode inherits from its parent.
	* the properties are maintained on its private fields
	* because the inode attributes will be modified with that of
	* its lower inode.
	* These values are used by our custom permission call instead
	* of using the inode permissions.
	*/

	inherit_derived_state(d_inode(parent), d_inode(dentry));

	/* Files don't get special labels */
	if (!S_ISDIR(d_inode(dentry)->i_mode))
	return;
	/* Derive custom permissions based on parent and current node */
	switch (parent_data->perm) {
	case PERM_INHERIT:
	case PERM_ANDROID_PACKAGE_CACHE:
	/* Already inherited above */
	break;
	case PERM_PRE_ROOT:
	/* Legacy internal layout places users at top level */
	info->data->perm = PERM_ROOT;
	err = kstrtoul(name->name, 10, &user_num);
	if (err)
	info->data->userid = 0;
	else
	info->data->userid = user_num;
	set_top(info, info->data);
	break;
	case PERM_ROOT:
	/* Assume masked off by default. */
	if (qstr_case_eq(name, &q_Android)) {
	/* App-specific directories inside; let anyone traverse */
	info->data->perm = PERM_ANDROID;
	info->data->under_android = true;
	set_top(info, info->data);
	}
	break;
	case PERM_ANDROID:
	if (qstr_case_eq(name, &q_data)) {
	/* App-specific directories inside; let anyone traverse */
	info->data->perm = PERM_ANDROID_DATA;
	set_top(info, info->data);
	} else if (qstr_case_eq(name, &q_obb)) {
	/* App-specific directories inside; let anyone traverse */
	info->data->perm = PERM_ANDROID_OBB;
	info->data->under_obb = true;
	set_top(info, info->data);
	/* Single OBB directory is always shared */
	} else if (qstr_case_eq(name, &q_media)) {
	/* App-specific directories inside; let anyone traverse */
	info->data->perm = PERM_ANDROID_MEDIA;
	set_top(info, info->data);
	}
	break;
	case PERM_ANDROID_OBB:
	case PERM_ANDROID_DATA:
	case PERM_ANDROID_MEDIA:
	info->data->perm = PERM_ANDROID_PACKAGE;
	appid = get_appid(name->name);
	if (appid != 0 && !is_excluded(name->name, parent_data->userid))
	info->data->d_uid =
	multiuser_get_uid(parent_data->userid, appid);
	set_top(info, info->data);
	break;
	case PERM_ANDROID_PACKAGE:
	if (qstr_case_eq(name, &q_cache)) {
	info->data->perm = PERM_ANDROID_PACKAGE_CACHE;
	info->data->under_cache = true;
	}
	break;
	}
	}

	void get_derived_permission(struct dentry parent, struct dentry dentry)
	{
	get_derived_permission_new(parent, dentry, &dentry->d_name);
	}

	static appid_t get_type(const char *name)
	{
	const char *ext = strrchr(name, '.');
	appid_t id;

	if (ext && ext[0]) {
	ext = &ext[1];
	id = get_ext_gid(ext);
	return id?:AID_MEDIA_RW;
	}
	return AID_MEDIA_RW;
	}

	void fixup_lower_ownership(struct dentry dentry, const char name)
	{
	struct path path;
	struct inode *inode;
	struct inode *delegated_inode = NULL;
	int error;
	struct sdcardfs_inode_info *info;
	struct sdcardfs_inode_data *info_d;
	struct sdcardfs_inode_data *info_top;
	perm_t perm;
	struct sdcardfs_sb_info *sbi = SDCARDFS_SB(dentry->d_sb);
	uid_t uid = sbi->options.fs_low_uid;
	gid_t gid = sbi->options.fs_low_gid;
	struct iattr newattrs;

	info = SDCARDFS_I(d_inode(dentry));
	info_d = info->data;
	perm = info_d->perm;
	if (info_d->under_obb) {
	perm = PERM_ANDROID_OBB;
	} else if (info_d->under_cache) {
	perm = PERM_ANDROID_PACKAGE_CACHE;
	} else if (perm == PERM_INHERIT) {
	info_top = top_data_get(info);
	perm = info_top->perm;
	data_put(info_top);
	}

	switch (perm) {
	case PERM_ROOT:
	case PERM_ANDROID:
	case PERM_ANDROID_DATA:
	case PERM_ANDROID_MEDIA:
	case PERM_ANDROID_PACKAGE:
	case PERM_ANDROID_PACKAGE_CACHE:
	uid = multiuser_get_uid(info_d->userid, uid);
	break;
	case PERM_ANDROID_OBB:
	uid = AID_MEDIA_OBB;
	break;
	case PERM_PRE_ROOT:
	default:
	break;
	}
	switch (perm) {
	case PERM_ROOT:
	case PERM_ANDROID:
	case PERM_ANDROID_DATA:
	case PERM_ANDROID_MEDIA:
	if (S_ISDIR(d_inode(dentry)->i_mode))
	gid = multiuser_get_uid(info_d->userid, AID_MEDIA_RW);
	else
	gid = multiuser_get_uid(info_d->userid, get_type(name));
	break;
	case PERM_ANDROID_OBB:
	gid = AID_MEDIA_OBB;
	break;
	case PERM_ANDROID_PACKAGE:
	if (uid_is_app(info_d->d_uid))
	gid = multiuser_get_ext_gid(info_d->d_uid);
	else
	gid = multiuser_get_uid(info_d->userid, AID_MEDIA_RW);
	break;
	case PERM_ANDROID_PACKAGE_CACHE:
	if (uid_is_app(info_d->d_uid))
	gid = multiuser_get_ext_cache_gid(info_d->d_uid);
	else
	gid = multiuser_get_uid(info_d->userid, AID_MEDIA_RW);
	break;
	case PERM_PRE_ROOT:
	default:
	break;
	}

	sdcardfs_get_lower_path(dentry, &path);
	inode = d_inode(path.dentry);
	if (d_inode(path.dentry)->i_gid.val != gid \|\| d_inode(path.dentry)->i_uid.val != uid) {
	retry_deleg:
	newattrs.ia_valid = ATTR_GID \| ATTR_UID \| ATTR_FORCE;
	newattrs.ia_uid = make_kuid(current_user_ns(), uid);
	newattrs.ia_gid = make_kgid(current_user_ns(), gid);
	if (!S_ISDIR(inode->i_mode))
	newattrs.ia_valid \|=
	ATTR_KILL_SUID \| ATTR_KILL_SGID \| ATTR_KILL_PRIV;
	mutex_lock(&inode->i_mutex);
	error = security_path_chown(&path, newattrs.ia_uid, newattrs.ia_gid);
	if (!error)
	error = notify_change2(path.mnt, path.dentry, &newattrs, &delegated_inode);
	mutex_unlock(&inode->i_mutex);
	if (delegated_inode) {
	error = break_deleg_wait(&delegated_inode);
	if (!error)
	goto retry_deleg;
	}
	if (error)
	pr_debug("sdcardfs: Failed to touch up lower fs gid/uid for %s\n", name);
	}
	sdcardfs_put_lower_path(dentry, &path);
	}

	static int descendant_may_need_fixup(struct sdcardfs_inode_data *data,
	struct limit_search *limit)
	{
	if (data->perm == PERM_ROOT)
	return (limit->flags & BY_USERID) ?
	data->userid == limit->userid : 1;
	if (data->perm == PERM_PRE_ROOT \|\| data->perm == PERM_ANDROID)
	return 1;
	return 0;
	}

	static int needs_fixup(perm_t perm)
	{
	if (perm == PERM_ANDROID_DATA \|\| perm == PERM_ANDROID_OBB
	\|\| perm == PERM_ANDROID_MEDIA)
	return 1;
	return 0;
	}

	static void __fixup_perms_recursive(struct dentry dentry, struct limit_search limit, int depth)
	{
	struct dentry *child;
	struct sdcardfs_inode_info *info;

	/*
	* All paths will terminate their recursion on hitting PERM_ANDROID_OBB,
	* PERM_ANDROID_MEDIA, or PERM_ANDROID_DATA. This happens at a depth of
	* at most 3.
	*/
	WARN(depth > 3, "%s: Max expected depth exceeded!\n", __func__);
	spin_lock_nested(&dentry->d_lock, depth);
	if (!d_inode(dentry)) {
	spin_unlock(&dentry->d_lock);
	return;
	}
	info = SDCARDFS_I(d_inode(dentry));

	if (needs_fixup(info->data->perm)) {
	list_for_each_entry(child, &dentry->d_subdirs, d_child) {
	spin_lock_nested(&child->d_lock, depth + 1);
	if (!(limit->flags & BY_NAME) \|\| qstr_case_eq(&child->d_name, &limit->name)) {
	if (d_inode(child)) {
	get_derived_permission(dentry, child);
	fixup_tmp_permissions(d_inode(child));
	spin_unlock(&child->d_lock);
	break;
	}
	}
	spin_unlock(&child->d_lock);
	}
	} else if (descendant_may_need_fixup(info->data, limit)) {
	list_for_each_entry(child, &dentry->d_subdirs, d_child) {
	__fixup_perms_recursive(child, limit, depth + 1);
	}
	}
	spin_unlock(&dentry->d_lock);
	}

	void fixup_perms_recursive(struct dentry dentry, struct limit_search limit)
	{
	__fixup_perms_recursive(dentry, limit, 0);
	}

	/* main function for updating derived permission */
	inline void update_derived_permission_lock(struct dentry *dentry)
	{
	struct dentry *parent;

	if (!dentry \|\| !d_inode(dentry)) {
	pr_err("sdcardfs: %s: invalid dentry\n", __func__);
	return;
	}
	/* FIXME:
	* 1. need to check whether the dentry is updated or not
	* 2. remove the root dentry update
	*/
	if (!IS_ROOT(dentry)) {
	parent = dget_parent(dentry);
	if (parent) {
	get_derived_permission(parent, dentry);
	dput(parent);
	}
	}
	fixup_tmp_permissions(d_inode(dentry));
	}

	int need_graft_path(struct dentry *dentry)
	{
	int ret = 0;
	struct dentry *parent = dget_parent(dentry);
	struct sdcardfs_inode_info *parent_info = SDCARDFS_I(d_inode(parent));
	struct sdcardfs_sb_info *sbi = SDCARDFS_SB(dentry->d_sb);
	struct qstr obb = QSTR_LITERAL("obb");

	if (parent_info->data->perm == PERM_ANDROID &&
	qstr_case_eq(&dentry->d_name, &obb)) {

	/* /Android/obb is the base obbpath of DERIVED_UNIFIED */
	if (!(sbi->options.multiuser == false
	&& parent_info->data->userid == 0)) {
	ret = 1;
	}
	}
	dput(parent);
	return ret;
	}

	int is_obbpath_invalid(struct dentry *dent)
	{
	int ret = 0;
	struct sdcardfs_dentry_info *di = SDCARDFS_D(dent);
	struct sdcardfs_sb_info *sbi = SDCARDFS_SB(dent->d_sb);
	char path_buf, obbpath_s;
	int need_put = 0;
	struct path lower_path;

	/* check the base obbpath has been changed.
	* this routine can check an uninitialized obb dentry as well.
	* regarding the uninitialized obb, refer to the sdcardfs_mkdir()
	*/
	spin_lock(&di->lock);
	if (di->orig_path.dentry) {
	if (!di->lower_path.dentry) {
	ret = 1;
	} else {
	path_get(&di->lower_path);

	path_buf = kmalloc(PATH_MAX, GFP_ATOMIC);
	if (!path_buf) {
	ret = 1;
	pr_err("sdcardfs: fail to allocate path_buf in %s.\n", __func__);
	} else {
	obbpath_s = d_path(&di->lower_path, path_buf, PATH_MAX);
	if (d_unhashed(di->lower_path.dentry) \|\|
	!str_case_eq(sbi->obbpath_s, obbpath_s)) {
	ret = 1;
	}
	kfree(path_buf);
	}

	pathcpy(&lower_path, &di->lower_path);
	need_put = 1;
	}
	}
	spin_unlock(&di->lock);
	if (need_put)
	path_put(&lower_path);
	return ret;
	}

	int is_base_obbpath(struct dentry *dentry)
	{
	int ret = 0;
	struct dentry *parent = dget_parent(dentry);
	struct sdcardfs_inode_info *parent_info = SDCARDFS_I(d_inode(parent));
	struct sdcardfs_sb_info *sbi = SDCARDFS_SB(dentry->d_sb);
	struct qstr q_obb = QSTR_LITERAL("obb");

	spin_lock(&SDCARDFS_D(dentry)->lock);
	if (sbi->options.multiuser) {
	if (parent_info->data->perm == PERM_PRE_ROOT &&
	qstr_case_eq(&dentry->d_name, &q_obb)) {
	ret = 1;
	}
	} else if (parent_info->data->perm == PERM_ANDROID &&
	qstr_case_eq(&dentry->d_name, &q_obb)) {
	ret = 1;
	}
	spin_unlock(&SDCARDFS_D(dentry)->lock);
	return ret;
	}

	/* The lower_path will be stored to the dentry's orig_path
	* and the base obbpath will be copyed to the lower_path variable.
	* if an error returned, there's no change in the lower_path
	* returns: -ERRNO if error (0: no error)
	*/
	int setup_obb_dentry(struct dentry dentry, struct path lower_path)
	{
	int err = 0;
	struct sdcardfs_sb_info *sbi = SDCARDFS_SB(dentry->d_sb);
	struct path obbpath;

	/* A local obb dentry must have its own orig_path to support rmdir
	* and mkdir of itself. Usually, we expect that the sbi->obbpath
	* is avaiable on this stage.
	*/
	sdcardfs_set_orig_path(dentry, lower_path);

	err = kern_path(sbi->obbpath_s,
	LOOKUP_FOLLOW \| LOOKUP_DIRECTORY, &obbpath);

	if (!err) {
	/* the obbpath base has been found */
	pathcpy(lower_path, &obbpath);
	} else {
	/* if the sbi->obbpath is not available, we can optionally
	* setup the lower_path with its orig_path.
	* but, the current implementation just returns an error
	* because the sdcard daemon also regards this case as
	* a lookup fail.
	*/
	pr_info("sdcardfs: the sbi->obbpath is not available\n");
	}
	return err;
	}