fs/overlayfs/inode.c - kernel/windcharger - Git at Google

 /*
  *
  * Copyright (C) 2011 Novell Inc.
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 as published by
  * the Free Software Foundation.
  */

 #include <linux/fs.h>
 #include <linux/slab.h>
 #include <linux/xattr.h>
 #include "overlayfs.h"

 int ovl_setattr(struct dentry *dentry, struct iattr *attr)
 {
 	struct dentry *upperdentry;
 	int err;

 	if ((attr->ia_valid & ATTR_SIZE) && !ovl_dentry_upper(dentry))
 		err = ovl_copy_up_truncate(dentry, attr->ia_size);
 	else
 		err = ovl_copy_up(dentry);
 	if (err)
 		return err;

 	upperdentry = ovl_dentry_upper(dentry);

 	if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
 		attr->ia_valid &= ~ATTR_MODE;

 	mutex_lock(&upperdentry->d_inode->i_mutex);
 	err = notify_change(upperdentry, attr);
 	mutex_unlock(&upperdentry->d_inode->i_mutex);

 	return err;
 }

 static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
 			 struct kstat *stat)
 {
 	struct path realpath;

 	ovl_path_real(dentry, &realpath);
 	return vfs_getattr(realpath.mnt, realpath.dentry, stat);
 }

 int ovl_permission(struct inode *inode, int mask)
 {
 	struct ovl_entry *oe;
 	struct dentry *alias = NULL;
 	struct inode *realinode;
 	struct dentry *realdentry;
 	bool is_upper;
 	int err;

 	if (S_ISDIR(inode->i_mode)) {
 		oe = inode->i_private;
 	} else if (mask & MAY_NOT_BLOCK) {
 		return -ECHILD;
 	} else {
 		/*
 		 * For non-directories find an alias and get the info
 		 * from there.
 		 */
 		spin_lock(&inode->i_lock);
 		if (WARN_ON(list_empty(&inode->i_dentry))) {
 			spin_unlock(&inode->i_lock);
 			return -ENOENT;
 		}
 		alias = list_entry(inode->i_dentry.next,
 				   struct dentry, d_alias);
 		dget(alias);
 		spin_unlock(&inode->i_lock);
 		oe = alias->d_fsdata;
 	}

 	realdentry = ovl_entry_real(oe, &is_upper);

 	/* Careful in RCU walk mode */
 	realinode = ACCESS_ONCE(realdentry->d_inode);
 	if (!realinode) {
 		WARN_ON(!(mask & MAY_NOT_BLOCK));
 		err = -ENOENT;
 		goto out_dput;
 	}

 	if (mask & MAY_WRITE) {
 		umode_t mode = realinode->i_mode;

 		/*
 		 * Writes will always be redirected to upper layer, so
 		 * ignore lower layer being read-only.
 		 *
 		 * If the overlay itself is read-only then proceed
 		 * with the permission check, don't return EROFS.
 		 * This will only happen if this is the lower layer of
 		 * another overlayfs.
 		 *
 		 * If upper fs becomes read-only after the overlay was
 		 * constructed return EROFS to prevent modification of
 		 * upper layer.
 		 */
 		err = -EROFS;
 		if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
 		    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
 			goto out_dput;

 		/*
 		 * Nobody gets write access to an immutable file.
 		 */
 		err = -EACCES;
 		if (IS_IMMUTABLE(realinode))
 			goto out_dput;
 	}

 	if (realinode->i_op->permission)
 		err = realinode->i_op->permission(realinode, mask);
 	else
 		err = generic_permission(realinode, mask);
 out_dput:
 	dput(alias);
 	return err;
 }


 struct ovl_link_data {
 	struct dentry *realdentry;
 	void *cookie;
 };

 static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
 	void *ret;
 	struct dentry *realdentry;
 	struct inode *realinode;

 	realdentry = ovl_dentry_real(dentry);
 	realinode = realdentry->d_inode;

 	if (WARN_ON(!realinode->i_op->follow_link))
 		return ERR_PTR(-EPERM);

 	ret = realinode->i_op->follow_link(realdentry, nd);
 	if (IS_ERR(ret))
 		return ret;

 	if (realinode->i_op->put_link) {
 		struct ovl_link_data *data;

 		data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL);
 		if (!data) {
 			realinode->i_op->put_link(realdentry, nd, ret);
 			return ERR_PTR(-ENOMEM);
 		}
 		data->realdentry = realdentry;
 		data->cookie = ret;

 		return data;
 	} else {
 		return NULL;
 	}
 }

 static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c)
 {
 	struct inode *realinode;
 	struct ovl_link_data *data = c;

 	if (!data)
 		return;

 	realinode = data->realdentry->d_inode;
 	realinode->i_op->put_link(data->realdentry, nd, data->cookie);
 	kfree(data);
 }

 static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
 {
 	struct path realpath;
 	struct inode *realinode;

 	ovl_path_real(dentry, &realpath);
 	realinode = realpath.dentry->d_inode;

 	if (!realinode->i_op->readlink)
 		return -EINVAL;

 	touch_atime(realpath.mnt, realpath.dentry);

 	return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
 }


 static bool ovl_is_private_xattr(const char *name)
 {
 	return strncmp(name, "trusted.overlay.", 14) == 0;
 }

 int ovl_setxattr(struct dentry *dentry, const char *name,
 		 const void *value, size_t size, int flags)
 {
 	int err;
 	struct dentry *upperdentry;

 	if (ovl_is_private_xattr(name))
 		return -EPERM;

 	err = ovl_copy_up(dentry);
 	if (err)
 		return err;

 	upperdentry = ovl_dentry_upper(dentry);
 	return  vfs_setxattr(upperdentry, name, value, size, flags);
 }

 ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
 		     void *value, size_t size)
 {
 	if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
 	    ovl_is_private_xattr(name))
 		return -ENODATA;

 	return vfs_getxattr(ovl_dentry_real(dentry), name, value, size);
 }

 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
 {
 	ssize_t res;
 	int off;

 	res = vfs_listxattr(ovl_dentry_real(dentry), list, size);
 	if (res <= 0 || size == 0)
 		return res;

 	if (ovl_path_type(dentry->d_parent) != OVL_PATH_MERGE)
 		return res;

 	/* filter out private xattrs */
 	for (off = 0; off < res;) {
 		char *s = list + off;
 		size_t slen = strlen(s) + 1;

 		BUG_ON(off + slen > res);

 		if (ovl_is_private_xattr(s)) {
 			res -= slen;
 			memmove(s, s + slen, res - off);
 		} else {
 			off += slen;
 		}
 	}

 	return res;
 }

 int ovl_removexattr(struct dentry *dentry, const char *name)
 {
 	int err;
 	struct path realpath;
 	enum ovl_path_type type;

 	if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
 	    ovl_is_private_xattr(name))
 		return -ENODATA;

 	type = ovl_path_real(dentry, &realpath);
 	if (type == OVL_PATH_LOWER) {
 		err = vfs_getxattr(realpath.dentry, name, NULL, 0);
 		if (err < 0)
 			return err;

 		err = ovl_copy_up(dentry);
 		if (err)
 			return err;

 		ovl_path_upper(dentry, &realpath);
 	}

 	return vfs_removexattr(realpath.dentry, name);
 }

 static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
 				  struct dentry *realdentry)
 {
 	if (type != OVL_PATH_LOWER)
 		return false;

 	if (special_file(realdentry->d_inode->i_mode))
 		return false;

 	if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
 		return false;

 	return true;
 }

 static struct file *ovl_open(struct dentry *dentry, struct file *file,
 			     const struct cred *cred)
 {
 	int err;
 	struct path realpath;
 	enum ovl_path_type type;

 	type = ovl_path_real(dentry, &realpath);
 	if (ovl_open_need_copy_up(file->f_flags, type, realpath.dentry)) {
 		if (file->f_flags & O_TRUNC)
 			err = ovl_copy_up_truncate(dentry, 0);
 		else
 			err = ovl_copy_up(dentry);
 		if (err)
 			return ERR_PTR(err);

 		ovl_path_upper(dentry, &realpath);
 	}

 	return vfs_open(&realpath, file, cred);
 }

 static const struct inode_operations ovl_file_inode_operations = {
 	.setattr	= ovl_setattr,
 	.permission	= ovl_permission,
 	.getattr	= ovl_getattr,
 	.setxattr	= ovl_setxattr,
 	.getxattr	= ovl_getxattr,
 	.listxattr	= ovl_listxattr,
 	.removexattr	= ovl_removexattr,
 	.open		= ovl_open,
 };

 static const struct inode_operations ovl_symlink_inode_operations = {
 	.setattr	= ovl_setattr,
 	.follow_link	= ovl_follow_link,
 	.put_link	= ovl_put_link,
 	.readlink	= ovl_readlink,
 	.getattr	= ovl_getattr,
 	.setxattr	= ovl_setxattr,
 	.getxattr	= ovl_getxattr,
 	.listxattr	= ovl_listxattr,
 	.removexattr	= ovl_removexattr,
 };

 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
 			    struct ovl_entry *oe)
 {
 	struct inode *inode;

 	inode = new_inode(sb);
 	if (!inode)
 		return NULL;

 	mode &= S_IFMT;

 	inode->i_ino = get_next_ino();
 	inode->i_mode = mode;
 	inode->i_flags |= S_NOATIME | S_NOCMTIME;

 	switch (mode) {
 	case S_IFDIR:
 		inode->i_private = oe;
 		inode->i_op = &ovl_dir_inode_operations;
 		inode->i_fop = &ovl_dir_operations;
 		break;

 	case S_IFLNK:
 		inode->i_op = &ovl_symlink_inode_operations;
 		break;

 	case S_IFREG:
 	case S_IFSOCK:
 	case S_IFBLK:
 	case S_IFCHR:
 	case S_IFIFO:
 		inode->i_op = &ovl_file_inode_operations;
 		break;

 	default:
 		WARN(1, "illegal file type: %i\n", mode);
 		inode = NULL;
 	}

 	return inode;

 }
	/*
	*
	* Copyright (C) 2011 Novell Inc.
	*
	* This program is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 as published by
	* the Free Software Foundation.
	*/

	#include <linux/fs.h>
	#include <linux/slab.h>
	#include <linux/xattr.h>
	#include "overlayfs.h"

	int ovl_setattr(struct dentry dentry, struct iattr attr)
	{
	struct dentry *upperdentry;
	int err;

	if ((attr->ia_valid & ATTR_SIZE) && !ovl_dentry_upper(dentry))
	err = ovl_copy_up_truncate(dentry, attr->ia_size);
	else
	err = ovl_copy_up(dentry);
	if (err)
	return err;

	upperdentry = ovl_dentry_upper(dentry);

	if (attr->ia_valid & (ATTR_KILL_SUID\|ATTR_KILL_SGID))
	attr->ia_valid &= ~ATTR_MODE;

	mutex_lock(&upperdentry->d_inode->i_mutex);
	err = notify_change(upperdentry, attr);
	mutex_unlock(&upperdentry->d_inode->i_mutex);

	return err;
	}

	static int ovl_getattr(struct vfsmount mnt, struct dentry dentry,
	struct kstat *stat)
	{
	struct path realpath;

	ovl_path_real(dentry, &realpath);
	return vfs_getattr(realpath.mnt, realpath.dentry, stat);
	}

	int ovl_permission(struct inode *inode, int mask)
	{
	struct ovl_entry *oe;
	struct dentry *alias = NULL;
	struct inode *realinode;
	struct dentry *realdentry;
	bool is_upper;
	int err;

	if (S_ISDIR(inode->i_mode)) {
	oe = inode->i_private;
	} else if (mask & MAY_NOT_BLOCK) {
	return -ECHILD;
	} else {
	/*
	* For non-directories find an alias and get the info
	* from there.
	*/
	spin_lock(&inode->i_lock);
	if (WARN_ON(list_empty(&inode->i_dentry))) {
	spin_unlock(&inode->i_lock);
	return -ENOENT;
	}
	alias = list_entry(inode->i_dentry.next,
	struct dentry, d_alias);
	dget(alias);
	spin_unlock(&inode->i_lock);
	oe = alias->d_fsdata;
	}

	realdentry = ovl_entry_real(oe, &is_upper);

	/* Careful in RCU walk mode */
	realinode = ACCESS_ONCE(realdentry->d_inode);
	if (!realinode) {
	WARN_ON(!(mask & MAY_NOT_BLOCK));
	err = -ENOENT;
	goto out_dput;
	}

	if (mask & MAY_WRITE) {
	umode_t mode = realinode->i_mode;

	/*
	* Writes will always be redirected to upper layer, so
	* ignore lower layer being read-only.
	*
	* If the overlay itself is read-only then proceed
	* with the permission check, don't return EROFS.
	* This will only happen if this is the lower layer of
	* another overlayfs.
	*
	* If upper fs becomes read-only after the overlay was
	* constructed return EROFS to prevent modification of
	* upper layer.
	*/
	err = -EROFS;
	if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
	(S_ISREG(mode) \|\| S_ISDIR(mode) \|\| S_ISLNK(mode)))
	goto out_dput;

	/*
	* Nobody gets write access to an immutable file.
	*/
	err = -EACCES;
	if (IS_IMMUTABLE(realinode))
	goto out_dput;
	}

	if (realinode->i_op->permission)
	err = realinode->i_op->permission(realinode, mask);
	else
	err = generic_permission(realinode, mask);
	out_dput:
	dput(alias);
	return err;
	}


	struct ovl_link_data {
	struct dentry *realdentry;
	void *cookie;
	};

	static void ovl_follow_link(struct dentry dentry, struct nameidata *nd)
	{
	void *ret;
	struct dentry *realdentry;
	struct inode *realinode;

	realdentry = ovl_dentry_real(dentry);
	realinode = realdentry->d_inode;

	if (WARN_ON(!realinode->i_op->follow_link))
	return ERR_PTR(-EPERM);

	ret = realinode->i_op->follow_link(realdentry, nd);
	if (IS_ERR(ret))
	return ret;

	if (realinode->i_op->put_link) {
	struct ovl_link_data *data;

	data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL);
	if (!data) {
	realinode->i_op->put_link(realdentry, nd, ret);
	return ERR_PTR(-ENOMEM);
	}
	data->realdentry = realdentry;
	data->cookie = ret;

	return data;
	} else {
	return NULL;
	}
	}

	static void ovl_put_link(struct dentry dentry, struct nameidata nd, void *c)
	{
	struct inode *realinode;
	struct ovl_link_data *data = c;

	if (!data)
	return;

	realinode = data->realdentry->d_inode;
	realinode->i_op->put_link(data->realdentry, nd, data->cookie);
	kfree(data);
	}

	static int ovl_readlink(struct dentry dentry, char __user buf, int bufsiz)
	{
	struct path realpath;
	struct inode *realinode;

	ovl_path_real(dentry, &realpath);
	realinode = realpath.dentry->d_inode;

	if (!realinode->i_op->readlink)
	return -EINVAL;

	touch_atime(realpath.mnt, realpath.dentry);

	return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
	}


	static bool ovl_is_private_xattr(const char *name)
	{
	return strncmp(name, "trusted.overlay.", 14) == 0;
	}

	int ovl_setxattr(struct dentry dentry, const char name,
	const void *value, size_t size, int flags)
	{
	int err;
	struct dentry *upperdentry;

	if (ovl_is_private_xattr(name))
	return -EPERM;

	err = ovl_copy_up(dentry);
	if (err)
	return err;

	upperdentry = ovl_dentry_upper(dentry);
	return vfs_setxattr(upperdentry, name, value, size, flags);
	}

	ssize_t ovl_getxattr(struct dentry dentry, const char name,
	void *value, size_t size)
	{
	if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
	ovl_is_private_xattr(name))
	return -ENODATA;

	return vfs_getxattr(ovl_dentry_real(dentry), name, value, size);
	}

	ssize_t ovl_listxattr(struct dentry dentry, char list, size_t size)
	{
	ssize_t res;
	int off;

	res = vfs_listxattr(ovl_dentry_real(dentry), list, size);
	if (res <= 0 \|\| size == 0)
	return res;

	if (ovl_path_type(dentry->d_parent) != OVL_PATH_MERGE)
	return res;

	/* filter out private xattrs */
	for (off = 0; off < res;) {
	char *s = list + off;
	size_t slen = strlen(s) + 1;

	BUG_ON(off + slen > res);

	if (ovl_is_private_xattr(s)) {
	res -= slen;
	memmove(s, s + slen, res - off);
	} else {
	off += slen;
	}
	}

	return res;
	}

	int ovl_removexattr(struct dentry dentry, const char name)
	{
	int err;
	struct path realpath;
	enum ovl_path_type type;

	if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
	ovl_is_private_xattr(name))
	return -ENODATA;

	type = ovl_path_real(dentry, &realpath);
	if (type == OVL_PATH_LOWER) {
	err = vfs_getxattr(realpath.dentry, name, NULL, 0);
	if (err < 0)
	return err;

	err = ovl_copy_up(dentry);
	if (err)
	return err;

	ovl_path_upper(dentry, &realpath);
	}

	return vfs_removexattr(realpath.dentry, name);
	}

	static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
	struct dentry *realdentry)
	{
	if (type != OVL_PATH_LOWER)
	return false;

	if (special_file(realdentry->d_inode->i_mode))
	return false;

	if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
	return false;

	return true;
	}

	static struct file ovl_open(struct dentry dentry, struct file *file,
	const struct cred *cred)
	{
	int err;
	struct path realpath;
	enum ovl_path_type type;

	type = ovl_path_real(dentry, &realpath);
	if (ovl_open_need_copy_up(file->f_flags, type, realpath.dentry)) {
	if (file->f_flags & O_TRUNC)
	err = ovl_copy_up_truncate(dentry, 0);
	else
	err = ovl_copy_up(dentry);
	if (err)
	return ERR_PTR(err);

	ovl_path_upper(dentry, &realpath);
	}

	return vfs_open(&realpath, file, cred);
	}

	static const struct inode_operations ovl_file_inode_operations = {
	.setattr = ovl_setattr,
	.permission = ovl_permission,
	.getattr = ovl_getattr,
	.setxattr = ovl_setxattr,
	.getxattr = ovl_getxattr,
	.listxattr = ovl_listxattr,
	.removexattr = ovl_removexattr,
	.open = ovl_open,
	};

	static const struct inode_operations ovl_symlink_inode_operations = {
	.setattr = ovl_setattr,
	.follow_link = ovl_follow_link,
	.put_link = ovl_put_link,
	.readlink = ovl_readlink,
	.getattr = ovl_getattr,
	.setxattr = ovl_setxattr,
	.getxattr = ovl_getxattr,
	.listxattr = ovl_listxattr,
	.removexattr = ovl_removexattr,
	};

	struct inode ovl_new_inode(struct super_block sb, umode_t mode,
	struct ovl_entry *oe)
	{
	struct inode *inode;

	inode = new_inode(sb);
	if (!inode)
	return NULL;

	mode &= S_IFMT;

	inode->i_ino = get_next_ino();
	inode->i_mode = mode;
	inode->i_flags \|= S_NOATIME \| S_NOCMTIME;

	switch (mode) {
	case S_IFDIR:
	inode->i_private = oe;
	inode->i_op = &ovl_dir_inode_operations;
	inode->i_fop = &ovl_dir_operations;
	break;

	case S_IFLNK:
	inode->i_op = &ovl_symlink_inode_operations;
	break;

	case S_IFREG:
	case S_IFSOCK:
	case S_IFBLK:
	case S_IFCHR:
	case S_IFIFO:
	inode->i_op = &ovl_file_inode_operations;
	break;

	default:
	WARN(1, "illegal file type: %i\n", mode);
	inode = NULL;
	}

	return inode;

	}