ANDROID: sdcardfs: Added top to sdcardfs_inode_info

Adding packages to the package list and moving files
takes a large amount of locks, and is currently a
heavy operation. This adds a 'top' field to the
inode_info, which points to the inode for the top
most directory whose owner you would like to match.

On permission checks and get_attr, we look up the
owner based on the information at top. When we change
a package mapping, we need only modify the information
in the corresponding top inode_info's. When renaming,
we must ensure top is set correctly in all children.
This happens when an app specific folder gets moved
outside of the folder for that app.

Change-Id: Ib749c60b568e9a45a46f8ceed985c1338246ec6c
Signed-off-by: Daniel Rosenberg <drosen@google.com>

fs/sdcardfs/derived_perm.c

@@ -30,11 +30,12 @@ static void inherit_derived_state(struct inode *parent, struct inode *child)
 	ci->userid = pi->userid;
 	ci->d_uid = pi->d_uid;
 	ci->under_android = pi->under_android;
+	set_top(ci, pi->top);
 }
 
 /* helper function for derived state */
-void setup_derived_state(struct inode *inode, perm_t perm,
-                        userid_t userid, uid_t uid, bool under_android)
+void setup_derived_state(struct inode *inode, perm_t perm, userid_t userid,
+                        uid_t uid, bool under_android, struct inode *top)
 {
 	struct sdcardfs_inode_info *info = SDCARDFS_I(inode);
 
@@ -42,6 +43,7 @@ void setup_derived_state(struct inode *inode, perm_t perm,
 	info->userid = userid;
 	info->d_uid = uid;
 	info->under_android = under_android;
+	set_top(info, top);
 }
 
 /* While renaming, there is a point where we want the path from dentry, but the name from newdentry */
@@ -70,6 +72,7 @@ void get_derived_permission_new(struct dentry *parent, struct dentry *dentry, st
 			/* Legacy internal layout places users at top level */
 			info->perm = PERM_ROOT;
 			info->userid = simple_strtoul(newdentry->d_name.name, NULL, 10);
+			set_top(info, &info->vfs_inode);
 			break;
 		case PERM_ROOT:
 			/* Assume masked off by default. */
@@ -77,19 +80,23 @@ void get_derived_permission_new(struct dentry *parent, struct dentry *dentry, st
 				/* App-specific directories inside; let anyone traverse */
 				info->perm = PERM_ANDROID;
 				info->under_android = true;
+				set_top(info, &info->vfs_inode);
 			}
 			break;
 		case PERM_ANDROID:
 			if (!strcasecmp(newdentry->d_name.name, "data")) {
 				/* App-specific directories inside; let anyone traverse */
 				info->perm = PERM_ANDROID_DATA;
+				set_top(info, &info->vfs_inode);
 			} else if (!strcasecmp(newdentry->d_name.name, "obb")) {
 				/* App-specific directories inside; let anyone traverse */
 				info->perm = PERM_ANDROID_OBB;
+				set_top(info, &info->vfs_inode);
 				/* Single OBB directory is always shared */
 			} else if (!strcasecmp(newdentry->d_name.name, "media")) {
 				/* App-specific directories inside; let anyone traverse */
 				info->perm = PERM_ANDROID_MEDIA;
+				set_top(info, &info->vfs_inode);
 			}
 			break;
 		case PERM_ANDROID_DATA:
@@ -99,6 +106,7 @@ void get_derived_permission_new(struct dentry *parent, struct dentry *dentry, st
 			if (appid != 0) {
 				info->d_uid = multiuser_get_uid(parent_info->userid, appid);
 			}
+			set_top(info, &info->vfs_inode);
 			break;
 	}
 }
@@ -108,14 +116,65 @@ void get_derived_permission(struct dentry *parent, struct dentry *dentry)
 	get_derived_permission_new(parent, dentry, dentry);
 }
 
-void get_derive_permissions_recursive(struct dentry *parent) {
+static int descendant_may_need_fixup(perm_t perm) {
+	if (perm == PERM_PRE_ROOT || perm == PERM_ROOT || 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;
+}
+
+void fixup_perms_recursive(struct dentry *dentry, const char* name, size_t len) {
+	struct dentry *child;
+	struct sdcardfs_inode_info *info;
+	if (!dget(dentry))
+		return;
+	if (!dentry->d_inode) {
+		dput(dentry);
+		return;
+	}
+	info = SDCARDFS_I(d_inode(dentry));
+
+	if (needs_fixup(info->perm)) {
+		mutex_lock(&d_inode(dentry)->i_mutex);
+		child = lookup_one_len(name, dentry, len);
+		mutex_unlock(&d_inode(dentry)->i_mutex);
+		if (!IS_ERR(child)) {
+			if (child->d_inode) {
+				get_derived_permission(dentry, child);
+				fix_derived_permission(d_inode(child));
+			}
+			dput(child);
+		}
+	} else 	if (descendant_may_need_fixup(info->perm)) {
+		mutex_lock(&d_inode(dentry)->i_mutex);
+		list_for_each_entry(child, &dentry->d_subdirs, d_child) {
+				fixup_perms_recursive(child, name, len);
+		}
+		mutex_unlock(&d_inode(dentry)->i_mutex);
+	}
+	dput(dentry);
+}
+
+void fixup_top_recursive(struct dentry *parent) {
 	struct dentry *dentry;
+	struct sdcardfs_inode_info *info;
+	if (!d_inode(parent))
+		return;
+	info = SDCARDFS_I(d_inode(parent));
 	spin_lock(&parent->d_lock);
 	list_for_each_entry(dentry, &parent->d_subdirs, d_child) {
-		if (dentry->d_inode) {
+		if (d_inode(dentry)) {
+			if (SDCARDFS_I(d_inode(parent))->top != SDCARDFS_I(d_inode(dentry))->top) {
 				get_derived_permission(parent, dentry);
-			fix_derived_permission(dentry->d_inode);
-			get_derive_permissions_recursive(dentry);
+				fix_derived_permission(d_inode(dentry));
+				fixup_top_recursive(dentry);
+			}
 		}
 	}
 	spin_unlock(&parent->d_lock);

fs/sdcardfs/inode.c

@@ -515,7 +515,7 @@ static int sdcardfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 	 * we pass along new_dentry for the name.*/
 	get_derived_permission_new(new_dentry->d_parent, old_dentry, new_dentry);
 	fix_derived_permission(d_inode(old_dentry));
-	get_derive_permissions_recursive(old_dentry);
+	fixup_top_recursive(old_dentry);
 out:
 	unlock_rename(lower_old_dir_dentry, lower_new_dir_dentry);
 	dput(lower_old_dir_dentry);
@@ -587,6 +587,16 @@ static const char *sdcardfs_follow_link(struct dentry *dentry, void **cookie)
 static int sdcardfs_permission(struct inode *inode, int mask)
 {
 	int err;
+	struct inode *top = grab_top(SDCARDFS_I(inode));
+
+	if (!top)
+		return -EINVAL;
+	/* Ensure owner is up to date */
+	if (!uid_eq(inode->i_uid, top->i_uid)) {
+		SDCARDFS_I(inode)->d_uid = SDCARDFS_I(top)->d_uid;
+		fix_derived_permission(inode);
+	}
+	release_top(SDCARDFS_I(inode));
 
 	/*
 	 * Permission check on sdcardfs inode.
@@ -725,6 +735,30 @@ out_err:
 	return err;
 }
 
+static int sdcardfs_fillattr(struct inode *inode, struct kstat *stat)
+{
+	struct sdcardfs_inode_info *info = SDCARDFS_I(inode);
+	struct inode *top = grab_top(info);
+	if (!top)
+		return -EINVAL;
+
+	stat->dev = inode->i_sb->s_dev;
+	stat->ino = inode->i_ino;
+	stat->mode = (inode->i_mode  & S_IFMT) | get_mode(SDCARDFS_I(top));
+	stat->nlink = inode->i_nlink;
+	stat->uid = make_kuid(&init_user_ns, SDCARDFS_I(top)->d_uid);
+	stat->gid = make_kgid(&init_user_ns, get_gid(SDCARDFS_I(top)));
+	stat->rdev = inode->i_rdev;
+	stat->size = i_size_read(inode);
+	stat->atime = inode->i_atime;
+	stat->mtime = inode->i_mtime;
+	stat->ctime = inode->i_ctime;
+	stat->blksize = (1 << inode->i_blkbits);
+	stat->blocks = inode->i_blocks;
+	release_top(info);
+	return 0;
+}
+
 static int sdcardfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
 		 struct kstat *stat)
 {
@@ -733,6 +767,7 @@ static int sdcardfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
 	struct inode *lower_inode;
 	struct path lower_path;
 	struct dentry *parent;
+	int err;
 
 	parent = dget_parent(dentry);
 	if(!check_caller_access_to_name(d_inode(parent), dentry->d_name.name)) {
@@ -750,14 +785,12 @@ static int sdcardfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
 	lower_dentry = lower_path.dentry;
 	lower_inode = sdcardfs_lower_inode(inode);
 
-
 	sdcardfs_copy_and_fix_attrs(inode, lower_inode);
 	fsstack_copy_inode_size(inode, lower_inode);
 
-
-	generic_fillattr(inode, stat);
+	err = sdcardfs_fillattr(inode, stat);
 	sdcardfs_put_lower_path(dentry, &lower_path);
-	return 0;
+	return err;
 }
 
 const struct inode_operations sdcardfs_symlink_iops = {
@@ -775,9 +808,7 @@ const struct inode_operations sdcardfs_symlink_iops = {
 const struct inode_operations sdcardfs_dir_iops = {
 	.create		= sdcardfs_create,
 	.lookup		= sdcardfs_lookup,
-#if 0
 	.permission	= sdcardfs_permission,
-#endif
 	.unlink		= sdcardfs_unlink,
 	.mkdir		= sdcardfs_mkdir,
 	.rmdir		= sdcardfs_rmdir,

fs/sdcardfs/main.c

@@ -268,13 +268,13 @@ static int sdcardfs_read_super(struct super_block *sb, const char *dev_name,
 	sb_info->obbpath_s = kzalloc(PATH_MAX, GFP_KERNEL);
 	mutex_lock(&sdcardfs_super_list_lock);
 	if(sb_info->options.multiuser) {
-		setup_derived_state(sb->s_root->d_inode, PERM_PRE_ROOT, sb_info->options.fs_user_id, AID_ROOT, false);
+		setup_derived_state(d_inode(sb->s_root), PERM_PRE_ROOT, sb_info->options.fs_user_id, AID_ROOT, false, d_inode(sb->s_root));
 		snprintf(sb_info->obbpath_s, PATH_MAX, "%s/obb", dev_name);
 		/*err =  prepare_dir(sb_info->obbpath_s,
 					sb_info->options.fs_low_uid,
 					sb_info->options.fs_low_gid, 00755);*/
 	} else {
-		setup_derived_state(sb->s_root->d_inode, PERM_ROOT, sb_info->options.fs_low_uid, AID_ROOT, false);
+		setup_derived_state(sb->s_root->d_inode, PERM_ROOT, sb_info->options.fs_low_uid, AID_ROOT, false, sb->s_root->d_inode);
 		snprintf(sb_info->obbpath_s, PATH_MAX, "%s/Android/obb", dev_name);
 	}
 	fix_derived_permission(sb->s_root->d_inode);

fs/sdcardfs/packagelist.c

@@ -143,18 +143,18 @@ static int insert_packagelist_entry_locked(const char *key, appid_t value)
 	return 0;
 }
 
-static void fixup_perms(struct super_block *sb) {
+static void fixup_perms(struct super_block *sb, const char *key) {
 	if (sb && sb->s_magic == SDCARDFS_SUPER_MAGIC) {
-		get_derive_permissions_recursive(sb->s_root);
+		fixup_perms_recursive(sb->s_root, key, strlen(key));
 	}
 }
 
-static void fixup_all_perms(void)
+static void fixup_all_perms(const char *key)
 {
 	struct sdcardfs_sb_info *sbinfo;
 	list_for_each_entry(sbinfo, &sdcardfs_super_list, list)
 		if (sbinfo)
-			fixup_perms(sbinfo->sb);
+			fixup_perms(sbinfo->sb, key);
 }
 
 static int insert_packagelist_entry(const char *key, appid_t value)
@@ -164,7 +164,7 @@ static int insert_packagelist_entry(const char *key, appid_t value)
 	mutex_lock(&sdcardfs_super_list_lock);
 	err = insert_packagelist_entry_locked(key, value);
 	if (!err)
-		fixup_all_perms();
+		fixup_all_perms(key);
 	mutex_unlock(&sdcardfs_super_list_lock);
 
 	return err;
@@ -196,7 +196,7 @@ static void remove_packagelist_entry(const char *key)
 {
 	mutex_lock(&sdcardfs_super_list_lock);
 	remove_packagelist_entry_locked(key);
-	fixup_all_perms();
+	fixup_all_perms(key);
 	mutex_unlock(&sdcardfs_super_list_lock);
 	return;
 }

fs/sdcardfs/sdcardfs.h

@@ -169,6 +169,8 @@ struct sdcardfs_inode_info {
 	userid_t userid;
 	uid_t d_uid;
 	bool under_android;
+	/* top folder for ownership */
+	struct inode *top;
 
 	struct inode vfs_inode;
 };
@@ -321,6 +323,35 @@ static inline void sdcardfs_put_reset_##pname(const struct dentry *dent) \
 SDCARDFS_DENT_FUNC(lower_path)
 SDCARDFS_DENT_FUNC(orig_path)
 
+/* grab a refererence if we aren't linking to ourself */
+static inline void set_top(struct sdcardfs_inode_info *info, struct inode *top)
+{
+	struct inode *old_top = NULL;
+	BUG_ON(IS_ERR_OR_NULL(top));
+	if (info->top && info->top != &info->vfs_inode) {
+		old_top = info->top;
+	}
+	if (top != &info->vfs_inode)
+		igrab(top);
+	info->top = top;
+	iput(old_top);
+}
+
+static inline struct inode *grab_top(struct sdcardfs_inode_info *info)
+{
+	struct inode *top = info->top;
+	if (top) {
+		return igrab(top);
+	} else {
+		return NULL;
+	}
+}
+
+static inline void release_top(struct sdcardfs_inode_info *info)
+{
+	iput(info->top);
+}
+
 static inline int get_gid(struct sdcardfs_inode_info *info) {
 	struct sdcardfs_sb_info *sb_info = SDCARDFS_SB(info->vfs_inode.i_sb);
 	if (sb_info->options.gid == AID_SDCARD_RW) {
@@ -337,7 +368,7 @@ static inline int get_gid(struct sdcardfs_inode_info *info) {
 static inline int get_mode(struct sdcardfs_inode_info *info) {
 	int owner_mode;
 	int filtered_mode;
-	struct sdcardfs_sb_info *sb_info = SDCARDFS_SB(info->vfs_inode.i_sb);
+	struct sdcardfs_sb_info * sb_info = SDCARDFS_SB(info->vfs_inode.i_sb);
 	int visible_mode = 0775 & ~sb_info->options.mask;
 
 	if (info->perm == PERM_PRE_ROOT) {
@@ -403,11 +434,12 @@ extern int packagelist_init(void);
 extern void packagelist_exit(void);
 
 /* for derived_perm.c */
-extern void setup_derived_state(struct inode *inode, perm_t perm,
-			userid_t userid, uid_t uid, bool under_android);
+extern void setup_derived_state(struct inode *inode, perm_t perm, userid_t userid,
+			uid_t uid, bool under_android, struct inode *top);
 extern void get_derived_permission(struct dentry *parent, struct dentry *dentry);
 extern void get_derived_permission_new(struct dentry *parent, struct dentry *dentry, struct dentry *newdentry);
-extern void get_derive_permissions_recursive(struct dentry *parent);
+extern void fixup_top_recursive(struct dentry *parent);
+extern void fixup_perms_recursive(struct dentry *dentry, const char *name, size_t len);
 
 extern void update_derived_permission_lock(struct dentry *dentry);
 extern int need_graft_path(struct dentry *dentry);

fs/sdcardfs/super.c

@@ -126,6 +126,7 @@ static void sdcardfs_evict_inode(struct inode *inode)
 	 */
 	lower_inode = sdcardfs_lower_inode(inode);
 	sdcardfs_set_lower_inode(inode, NULL);
+	set_top(SDCARDFS_I(inode), inode);
 	iput(lower_inode);
 }