fs/overlayfs/inode.c - linux-imx - 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 <linux/posix_acl.h>
 #include "overlayfs.h"

 static int ovl_copy_up_truncate(struct dentry *dentry)
 {
 	int err;
 	struct dentry *parent;
 	struct kstat stat;
 	struct path lowerpath;
 	const struct cred *old_cred;

 	parent = dget_parent(dentry);
 	err = ovl_copy_up(parent);
 	if (err)
 		goto out_dput_parent;

 	ovl_path_lower(dentry, &lowerpath);

 	old_cred = ovl_override_creds(dentry->d_sb);
 	err = vfs_getattr(&lowerpath, &stat);
 	if (!err) {
 		stat.size = 0;
 		err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);
 	}
 	revert_creds(old_cred);

 out_dput_parent:
 	dput(parent);
 	return err;
 }

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

 	/*
 	 * Check for permissions before trying to copy-up.  This is redundant
 	 * since it will be rechecked later by ->setattr() on upper dentry.  But
 	 * without this, copy-up can be triggered by just about anybody.
 	 *
 	 * We don't initialize inode->size, which just means that
 	 * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
 	 * check for a swapfile (which this won't be anyway).
 	 */
 	err = setattr_prepare(dentry, attr);
 	if (err)
 		return err;

 	err = ovl_want_write(dentry);
 	if (err)
 		goto out;

 	if (attr->ia_valid & ATTR_SIZE) {
 		struct inode *realinode = d_inode(ovl_dentry_real(dentry));

 		err = -ETXTBSY;
 		if (atomic_read(&realinode->i_writecount) < 0)
 			goto out_drop_write;
 	}

 	err = ovl_copy_up(dentry);
 	if (!err) {
 		struct inode *winode = NULL;

 		upperdentry = ovl_dentry_upper(dentry);

 		if (attr->ia_valid & ATTR_SIZE) {
 			winode = d_inode(upperdentry);
 			err = get_write_access(winode);
 			if (err)
 				goto out_drop_write;
 		}

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

 		inode_lock(upperdentry->d_inode);
 		old_cred = ovl_override_creds(dentry->d_sb);
 		err = notify_change(upperdentry, attr, NULL);
 		revert_creds(old_cred);
 		if (!err)
 			ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
 		inode_unlock(upperdentry->d_inode);

 		if (winode)
 			put_write_access(winode);
 	}
 out_drop_write:
 	ovl_drop_write(dentry);
 out:
 	return err;
 }

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

 	ovl_path_real(dentry, &realpath);
 	old_cred = ovl_override_creds(dentry->d_sb);
 	err = vfs_getattr(&realpath, stat);
 	revert_creds(old_cred);
 	return err;
 }

 int ovl_permission(struct inode *inode, int mask)
 {
 	bool is_upper;
 	struct inode *realinode = ovl_inode_real(inode, &is_upper);
 	const struct cred *old_cred;
 	int err;

 	/* Careful in RCU walk mode */
 	if (!realinode) {
 		WARN_ON(!(mask & MAY_NOT_BLOCK));
 		return -ECHILD;
 	}

 	/*
 	 * Check overlay inode with the creds of task and underlying inode
 	 * with creds of mounter
 	 */
 	err = generic_permission(inode, mask);
 	if (err)
 		return err;

 	old_cred = ovl_override_creds(inode->i_sb);
 	if (!is_upper && !special_file(realinode->i_mode) && mask & MAY_WRITE) {
 		mask &= ~(MAY_WRITE | MAY_APPEND);
 		/* Make sure mounter can read file for copy up later */
 		mask |= MAY_READ;
 	}
 	err = inode_permission(realinode, mask);
 	revert_creds(old_cred);

 	return err;
 }

 static const char *ovl_get_link(struct dentry *dentry,
 				struct inode *inode,
 				struct delayed_call *done)
 {
 	const struct cred *old_cred;
 	const char *p;

 	if (!dentry)
 		return ERR_PTR(-ECHILD);

 	old_cred = ovl_override_creds(dentry->d_sb);
 	p = vfs_get_link(ovl_dentry_real(dentry), done);
 	revert_creds(old_cred);
 	return p;
 }

 bool ovl_is_private_xattr(const char *name)
 {
 	return strncmp(name, OVL_XATTR_PREFIX,
 		       sizeof(OVL_XATTR_PREFIX) - 1) == 0;
 }

 int ovl_xattr_set(struct dentry *dentry, const char *name, const void *value,
 		  size_t size, int flags)
 {
 	int err;
 	struct path realpath;
 	enum ovl_path_type type = ovl_path_real(dentry, &realpath);
 	const struct cred *old_cred;

 	err = ovl_want_write(dentry);
 	if (err)
 		goto out;

 	if (!value && !OVL_TYPE_UPPER(type)) {
 		err = vfs_getxattr(realpath.dentry, name, NULL, 0);
 		if (err < 0)
 			goto out_drop_write;
 	}

 	err = ovl_copy_up(dentry);
 	if (err)
 		goto out_drop_write;

 	if (!OVL_TYPE_UPPER(type))
 		ovl_path_upper(dentry, &realpath);

 	old_cred = ovl_override_creds(dentry->d_sb);
 	if (value)
 		err = vfs_setxattr(realpath.dentry, name, value, size, flags);
 	else {
 		WARN_ON(flags != XATTR_REPLACE);
 		err = vfs_removexattr(realpath.dentry, name);
 	}
 	revert_creds(old_cred);

 out_drop_write:
 	ovl_drop_write(dentry);
 out:
 	return err;
 }

 int ovl_xattr_get(struct dentry *dentry, const char *name,
 		  void *value, size_t size)
 {
 	struct dentry *realdentry = ovl_dentry_real(dentry);
 	ssize_t res;
 	const struct cred *old_cred;

 	old_cred = ovl_override_creds(dentry->d_sb);
 	res = vfs_getxattr(realdentry, name, value, size);
 	revert_creds(old_cred);
 	return res;
 }

 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
 {
 	struct dentry *realdentry = ovl_dentry_real(dentry);
 	ssize_t res;
 	size_t len;
 	char *s;
 	const struct cred *old_cred;

 	old_cred = ovl_override_creds(dentry->d_sb);
 	res = vfs_listxattr(realdentry, list, size);
 	revert_creds(old_cred);
 	if (res <= 0 || size == 0)
 		return res;

 	/* filter out private xattrs */
 	for (s = list, len = res; len;) {
 		size_t slen = strnlen(s, len) + 1;

 		/* underlying fs providing us with an broken xattr list? */
 		if (WARN_ON(slen > len))
 			return -EIO;

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

 	return res;
 }

 struct posix_acl *ovl_get_acl(struct inode *inode, int type)
 {
 	struct inode *realinode = ovl_inode_real(inode, NULL);
 	const struct cred *old_cred;
 	struct posix_acl *acl;

 	if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode))
 		return NULL;

 	old_cred = ovl_override_creds(inode->i_sb);
 	acl = get_acl(realinode, type);
 	revert_creds(old_cred);

 	return acl;
 }

 static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
 				  struct dentry *realdentry)
 {
 	if (OVL_TYPE_UPPER(type))
 		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;
 }

 int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags)
 {
 	int err = 0;
 	struct path realpath;
 	enum ovl_path_type type;

 	type = ovl_path_real(dentry, &realpath);
 	if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) {
 		err = ovl_want_write(dentry);
 		if (!err) {
 			if (file_flags & O_TRUNC)
 				err = ovl_copy_up_truncate(dentry);
 			else
 				err = ovl_copy_up(dentry);
 			ovl_drop_write(dentry);
 		}
 	}

 	return err;
 }

 int ovl_update_time(struct inode *inode, struct timespec *ts, int flags)
 {
 	struct dentry *alias;
 	struct path upperpath;

 	if (!(flags & S_ATIME))
 		return 0;

 	alias = d_find_any_alias(inode);
 	if (!alias)
 		return 0;

 	ovl_path_upper(alias, &upperpath);
 	if (upperpath.dentry) {
 		touch_atime(&upperpath);
 		inode->i_atime = d_inode(upperpath.dentry)->i_atime;
 	}

 	dput(alias);

 	return 0;
 }

 static const struct inode_operations ovl_file_inode_operations = {
 	.setattr	= ovl_setattr,
 	.permission	= ovl_permission,
 	.getattr	= ovl_getattr,
 	.listxattr	= ovl_listxattr,
 	.get_acl	= ovl_get_acl,
 	.update_time	= ovl_update_time,
 };

 static const struct inode_operations ovl_symlink_inode_operations = {
 	.setattr	= ovl_setattr,
 	.get_link	= ovl_get_link,
 	.readlink	= generic_readlink,
 	.getattr	= ovl_getattr,
 	.listxattr	= ovl_listxattr,
 	.update_time	= ovl_update_time,
 };

 static void ovl_fill_inode(struct inode *inode, umode_t mode)
 {
 	inode->i_ino = get_next_ino();
 	inode->i_mode = mode;
 	inode->i_flags |= S_NOCMTIME;
 #ifdef CONFIG_FS_POSIX_ACL
 	inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE;
 #endif

 	mode &= S_IFMT;
 	switch (mode) {
 	case S_IFDIR:
 		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;

 	default:
 		WARN(1, "illegal file type: %i\n", mode);
 		/* Fall through */

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

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

 	inode = new_inode(sb);
 	if (inode)
 		ovl_fill_inode(inode, mode);

 	return inode;
 }

 static int ovl_inode_test(struct inode *inode, void *data)
 {
 	return ovl_inode_real(inode, NULL) == data;
 }

 static int ovl_inode_set(struct inode *inode, void *data)
 {
 	inode->i_private = (void *) (((unsigned long) data) | OVL_ISUPPER_MASK);
 	return 0;
 }

 struct inode *ovl_get_inode(struct super_block *sb, struct inode *realinode)

 {
 	struct inode *inode;

 	inode = iget5_locked(sb, (unsigned long) realinode,
 			     ovl_inode_test, ovl_inode_set, realinode);
 	if (inode && inode->i_state & I_NEW) {
 		ovl_fill_inode(inode, realinode->i_mode);
 		set_nlink(inode, realinode->i_nlink);
 		unlock_new_inode(inode);
 	}

 	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 <linux/posix_acl.h>
	#include "overlayfs.h"

	static int ovl_copy_up_truncate(struct dentry *dentry)
	{
	int err;
	struct dentry *parent;
	struct kstat stat;
	struct path lowerpath;
	const struct cred *old_cred;

	parent = dget_parent(dentry);
	err = ovl_copy_up(parent);
	if (err)
	goto out_dput_parent;

	ovl_path_lower(dentry, &lowerpath);

	old_cred = ovl_override_creds(dentry->d_sb);
	err = vfs_getattr(&lowerpath, &stat);
	if (!err) {
	stat.size = 0;
	err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);
	}
	revert_creds(old_cred);

	out_dput_parent:
	dput(parent);
	return err;
	}

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

	/*
	* Check for permissions before trying to copy-up. This is redundant
	* since it will be rechecked later by ->setattr() on upper dentry. But
	* without this, copy-up can be triggered by just about anybody.
	*
	* We don't initialize inode->size, which just means that
	* inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
	* check for a swapfile (which this won't be anyway).
	*/
	err = setattr_prepare(dentry, attr);
	if (err)
	return err;

	err = ovl_want_write(dentry);
	if (err)
	goto out;

	if (attr->ia_valid & ATTR_SIZE) {
	struct inode *realinode = d_inode(ovl_dentry_real(dentry));

	err = -ETXTBSY;
	if (atomic_read(&realinode->i_writecount) < 0)
	goto out_drop_write;
	}

	err = ovl_copy_up(dentry);
	if (!err) {
	struct inode *winode = NULL;

	upperdentry = ovl_dentry_upper(dentry);

	if (attr->ia_valid & ATTR_SIZE) {
	winode = d_inode(upperdentry);
	err = get_write_access(winode);
	if (err)
	goto out_drop_write;
	}

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

	inode_lock(upperdentry->d_inode);
	old_cred = ovl_override_creds(dentry->d_sb);
	err = notify_change(upperdentry, attr, NULL);
	revert_creds(old_cred);
	if (!err)
	ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
	inode_unlock(upperdentry->d_inode);

	if (winode)
	put_write_access(winode);
	}
	out_drop_write:
	ovl_drop_write(dentry);
	out:
	return err;
	}

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

	ovl_path_real(dentry, &realpath);
	old_cred = ovl_override_creds(dentry->d_sb);
	err = vfs_getattr(&realpath, stat);
	revert_creds(old_cred);
	return err;
	}

	int ovl_permission(struct inode *inode, int mask)
	{
	bool is_upper;
	struct inode *realinode = ovl_inode_real(inode, &is_upper);
	const struct cred *old_cred;
	int err;

	/* Careful in RCU walk mode */
	if (!realinode) {
	WARN_ON(!(mask & MAY_NOT_BLOCK));
	return -ECHILD;
	}

	/*
	* Check overlay inode with the creds of task and underlying inode
	* with creds of mounter
	*/
	err = generic_permission(inode, mask);
	if (err)
	return err;

	old_cred = ovl_override_creds(inode->i_sb);
	if (!is_upper && !special_file(realinode->i_mode) && mask & MAY_WRITE) {
	mask &= ~(MAY_WRITE \| MAY_APPEND);
	/* Make sure mounter can read file for copy up later */
	mask \|= MAY_READ;
	}
	err = inode_permission(realinode, mask);
	revert_creds(old_cred);

	return err;
	}

	static const char ovl_get_link(struct dentry dentry,
	struct inode *inode,
	struct delayed_call *done)
	{
	const struct cred *old_cred;
	const char *p;

	if (!dentry)
	return ERR_PTR(-ECHILD);

	old_cred = ovl_override_creds(dentry->d_sb);
	p = vfs_get_link(ovl_dentry_real(dentry), done);
	revert_creds(old_cred);
	return p;
	}

	bool ovl_is_private_xattr(const char *name)
	{
	return strncmp(name, OVL_XATTR_PREFIX,
	sizeof(OVL_XATTR_PREFIX) - 1) == 0;
	}

	int ovl_xattr_set(struct dentry dentry, const char name, const void *value,
	size_t size, int flags)
	{
	int err;
	struct path realpath;
	enum ovl_path_type type = ovl_path_real(dentry, &realpath);
	const struct cred *old_cred;

	err = ovl_want_write(dentry);
	if (err)
	goto out;

	if (!value && !OVL_TYPE_UPPER(type)) {
	err = vfs_getxattr(realpath.dentry, name, NULL, 0);
	if (err < 0)
	goto out_drop_write;
	}

	err = ovl_copy_up(dentry);
	if (err)
	goto out_drop_write;

	if (!OVL_TYPE_UPPER(type))
	ovl_path_upper(dentry, &realpath);

	old_cred = ovl_override_creds(dentry->d_sb);
	if (value)
	err = vfs_setxattr(realpath.dentry, name, value, size, flags);
	else {
	WARN_ON(flags != XATTR_REPLACE);
	err = vfs_removexattr(realpath.dentry, name);
	}
	revert_creds(old_cred);

	out_drop_write:
	ovl_drop_write(dentry);
	out:
	return err;
	}

	int ovl_xattr_get(struct dentry dentry, const char name,
	void *value, size_t size)
	{
	struct dentry *realdentry = ovl_dentry_real(dentry);
	ssize_t res;
	const struct cred *old_cred;

	old_cred = ovl_override_creds(dentry->d_sb);
	res = vfs_getxattr(realdentry, name, value, size);
	revert_creds(old_cred);
	return res;
	}

	ssize_t ovl_listxattr(struct dentry dentry, char list, size_t size)
	{
	struct dentry *realdentry = ovl_dentry_real(dentry);
	ssize_t res;
	size_t len;
	char *s;
	const struct cred *old_cred;

	old_cred = ovl_override_creds(dentry->d_sb);
	res = vfs_listxattr(realdentry, list, size);
	revert_creds(old_cred);
	if (res <= 0 \|\| size == 0)
	return res;

	/* filter out private xattrs */
	for (s = list, len = res; len;) {
	size_t slen = strnlen(s, len) + 1;

	/* underlying fs providing us with an broken xattr list? */
	if (WARN_ON(slen > len))
	return -EIO;

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

	return res;
	}

	struct posix_acl ovl_get_acl(struct inode inode, int type)
	{
	struct inode *realinode = ovl_inode_real(inode, NULL);
	const struct cred *old_cred;
	struct posix_acl *acl;

	if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) \|\| !IS_POSIXACL(realinode))
	return NULL;

	old_cred = ovl_override_creds(inode->i_sb);
	acl = get_acl(realinode, type);
	revert_creds(old_cred);

	return acl;
	}

	static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
	struct dentry *realdentry)
	{
	if (OVL_TYPE_UPPER(type))
	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;
	}

	int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags)
	{
	int err = 0;
	struct path realpath;
	enum ovl_path_type type;

	type = ovl_path_real(dentry, &realpath);
	if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) {
	err = ovl_want_write(dentry);
	if (!err) {
	if (file_flags & O_TRUNC)
	err = ovl_copy_up_truncate(dentry);
	else
	err = ovl_copy_up(dentry);
	ovl_drop_write(dentry);
	}
	}

	return err;
	}

	int ovl_update_time(struct inode inode, struct timespec ts, int flags)
	{
	struct dentry *alias;
	struct path upperpath;

	if (!(flags & S_ATIME))
	return 0;

	alias = d_find_any_alias(inode);
	if (!alias)
	return 0;

	ovl_path_upper(alias, &upperpath);
	if (upperpath.dentry) {
	touch_atime(&upperpath);
	inode->i_atime = d_inode(upperpath.dentry)->i_atime;
	}

	dput(alias);

	return 0;
	}

	static const struct inode_operations ovl_file_inode_operations = {
	.setattr = ovl_setattr,
	.permission = ovl_permission,
	.getattr = ovl_getattr,
	.listxattr = ovl_listxattr,
	.get_acl = ovl_get_acl,
	.update_time = ovl_update_time,
	};

	static const struct inode_operations ovl_symlink_inode_operations = {
	.setattr = ovl_setattr,
	.get_link = ovl_get_link,
	.readlink = generic_readlink,
	.getattr = ovl_getattr,
	.listxattr = ovl_listxattr,
	.update_time = ovl_update_time,
	};

	static void ovl_fill_inode(struct inode *inode, umode_t mode)
	{
	inode->i_ino = get_next_ino();
	inode->i_mode = mode;
	inode->i_flags \|= S_NOCMTIME;
	#ifdef CONFIG_FS_POSIX_ACL
	inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE;
	#endif

	mode &= S_IFMT;
	switch (mode) {
	case S_IFDIR:
	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;

	default:
	WARN(1, "illegal file type: %i\n", mode);
	/* Fall through */

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

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

	inode = new_inode(sb);
	if (inode)
	ovl_fill_inode(inode, mode);

	return inode;
	}

	static int ovl_inode_test(struct inode inode, void data)
	{
	return ovl_inode_real(inode, NULL) == data;
	}

	static int ovl_inode_set(struct inode inode, void data)
	{
	inode->i_private = (void *) (((unsigned long) data) \| OVL_ISUPPER_MASK);
	return 0;
	}

	struct inode ovl_get_inode(struct super_block sb, struct inode *realinode)

	{
	struct inode *inode;

	inode = iget5_locked(sb, (unsigned long) realinode,
	ovl_inode_test, ovl_inode_set, realinode);
	if (inode && inode->i_state & I_NEW) {
	ovl_fill_inode(inode, realinode->i_mode);
	set_nlink(inode, realinode->i_nlink);
	unlock_new_inode(inode);
	}

	return inode;
	}