[mirror_ubuntu-zesty-kernel.git] / fs / overlayfs / inode.c

/*
 *
 * 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"

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;

	err = ovl_copy_up(dentry);
	if (!err) {
		upperdentry = ovl_dentry_upper(dentry);

		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);
	}
	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) {
			err = ovl_copy_up_flags(dentry, file_flags);
			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,
	.getattr	= ovl_getattr,
	.listxattr	= ovl_listxattr,
	.update_time	= ovl_update_time,
};

static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev)
{
	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

	switch (mode & S_IFMT) {
	case S_IFREG:
		inode->i_op = &ovl_file_inode_operations;
		break;

	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:
		inode->i_op = &ovl_file_inode_operations;
		init_special_inode(inode, mode, rdev);
		break;
	}
}

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

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

	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, realinode->i_rdev);
		set_nlink(inode, realinode->i_nlink);
		unlock_new_inode(inode);
	}

	return inode;
}
Commit	Line	Data
	1	/*
	2	*
	3	* Copyright (C) 2011 Novell Inc.
	4	*
	5	* This program is free software; you can redistribute it and/or modify it
	6	* under the terms of the GNU General Public License version 2 as published by
	7	* the Free Software Foundation.
	8	*/
	9
	10	#include <linux/fs.h>
	11	#include <linux/slab.h>
	12	#include <linux/xattr.h>
	13	#include <linux/posix_acl.h>
	14	#include "overlayfs.h"
	15
	16	int ovl_setattr(struct dentry dentry, struct iattr attr)
	17	{
	18	int err;
	19	struct dentry *upperdentry;
	20	const struct cred *old_cred;
	21
	22	/*
	23	* Check for permissions before trying to copy-up. This is redundant
	24	* since it will be rechecked later by ->setattr() on upper dentry. But
	25	* without this, copy-up can be triggered by just about anybody.
	26	*
	27	* We don't initialize inode->size, which just means that
	28	* inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
	29	* check for a swapfile (which this won't be anyway).
	30	*/
	31	err = setattr_prepare(dentry, attr);
	32	if (err)
	33	return err;
	34
	35	err = ovl_want_write(dentry);
	36	if (err)
	37	goto out;
	38
	39	err = ovl_copy_up(dentry);
	40	if (!err) {
	41	upperdentry = ovl_dentry_upper(dentry);
	42
	43	if (attr->ia_valid & (ATTR_KILL_SUID\|ATTR_KILL_SGID))
	44	attr->ia_valid &= ~ATTR_MODE;
	45
	46	inode_lock(upperdentry->d_inode);
	47	old_cred = ovl_override_creds(dentry->d_sb);
	48	err = notify_change(upperdentry, attr, NULL);
	49	revert_creds(old_cred);
	50	if (!err)
	51	ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
	52	inode_unlock(upperdentry->d_inode);
	53	}
	54	ovl_drop_write(dentry);
	55	out:
	56	return err;
	57	}
	58
	59	static int ovl_getattr(struct vfsmount mnt, struct dentry dentry,
	60	struct kstat *stat)
	61	{
	62	struct path realpath;
	63	const struct cred *old_cred;
	64	int err;
	65
	66	ovl_path_real(dentry, &realpath);
	67	old_cred = ovl_override_creds(dentry->d_sb);
	68	err = vfs_getattr(&realpath, stat);
	69	revert_creds(old_cred);
	70	return err;
	71	}
	72
	73	int ovl_permission(struct inode *inode, int mask)
	74	{
	75	bool is_upper;
	76	struct inode *realinode = ovl_inode_real(inode, &is_upper);
	77	const struct cred *old_cred;
	78	int err;
	79
	80	/* Careful in RCU walk mode */
	81	if (!realinode) {
	82	WARN_ON(!(mask & MAY_NOT_BLOCK));
	83	return -ECHILD;
	84	}
	85
	86	/*
	87	* Check overlay inode with the creds of task and underlying inode
	88	* with creds of mounter
	89	*/
	90	err = generic_permission(inode, mask);
	91	if (err)
	92	return err;
	93
	94	old_cred = ovl_override_creds(inode->i_sb);
	95	if (!is_upper && !special_file(realinode->i_mode) && mask & MAY_WRITE) {
	96	mask &= ~(MAY_WRITE \| MAY_APPEND);
	97	/* Make sure mounter can read file for copy up later */
	98	mask \|= MAY_READ;
	99	}
	100	err = inode_permission(realinode, mask);
	101	revert_creds(old_cred);
	102
	103	return err;
	104	}
	105
	106	static const char ovl_get_link(struct dentry dentry,
	107	struct inode *inode,
	108	struct delayed_call *done)
	109	{
	110	const struct cred *old_cred;
	111	const char *p;
	112
	113	if (!dentry)
	114	return ERR_PTR(-ECHILD);
	115
	116	old_cred = ovl_override_creds(dentry->d_sb);
	117	p = vfs_get_link(ovl_dentry_real(dentry), done);
	118	revert_creds(old_cred);
	119	return p;
	120	}
	121
	122	bool ovl_is_private_xattr(const char *name)
	123	{
	124	return strncmp(name, OVL_XATTR_PREFIX,
	125	sizeof(OVL_XATTR_PREFIX) - 1) == 0;
	126	}
	127
	128	int ovl_xattr_set(struct dentry dentry, const char name, const void *value,
	129	size_t size, int flags)
	130	{
	131	int err;
	132	struct path realpath;
	133	enum ovl_path_type type = ovl_path_real(dentry, &realpath);
	134	const struct cred *old_cred;
	135
	136	err = ovl_want_write(dentry);
	137	if (err)
	138	goto out;
	139
	140	if (!value && !OVL_TYPE_UPPER(type)) {
	141	err = vfs_getxattr(realpath.dentry, name, NULL, 0);
	142	if (err < 0)
	143	goto out_drop_write;
	144	}
	145
	146	err = ovl_copy_up(dentry);
	147	if (err)
	148	goto out_drop_write;
	149
	150	if (!OVL_TYPE_UPPER(type))
	151	ovl_path_upper(dentry, &realpath);
	152
	153	old_cred = ovl_override_creds(dentry->d_sb);
	154	if (value)
	155	err = vfs_setxattr(realpath.dentry, name, value, size, flags);
	156	else {
	157	WARN_ON(flags != XATTR_REPLACE);
	158	err = vfs_removexattr(realpath.dentry, name);
	159	}
	160	revert_creds(old_cred);
	161
	162	out_drop_write:
	163	ovl_drop_write(dentry);
	164	out:
	165	return err;
	166	}
	167
	168	int ovl_xattr_get(struct dentry dentry, const char name,
	169	void *value, size_t size)
	170	{
	171	struct dentry *realdentry = ovl_dentry_real(dentry);
	172	ssize_t res;
	173	const struct cred *old_cred;
	174
	175	old_cred = ovl_override_creds(dentry->d_sb);
	176	res = vfs_getxattr(realdentry, name, value, size);
	177	revert_creds(old_cred);
	178	return res;
	179	}
	180
	181	ssize_t ovl_listxattr(struct dentry dentry, char list, size_t size)
	182	{
	183	struct dentry *realdentry = ovl_dentry_real(dentry);
	184	ssize_t res;
	185	size_t len;
	186	char *s;
	187	const struct cred *old_cred;
	188
	189	old_cred = ovl_override_creds(dentry->d_sb);
	190	res = vfs_listxattr(realdentry, list, size);
	191	revert_creds(old_cred);
	192	if (res <= 0 \|\| size == 0)
	193	return res;
	194
	195	/* filter out private xattrs */
	196	for (s = list, len = res; len;) {
	197	size_t slen = strnlen(s, len) + 1;
	198
	199	/* underlying fs providing us with an broken xattr list? */
	200	if (WARN_ON(slen > len))
	201	return -EIO;
	202
	203	len -= slen;
	204	if (ovl_is_private_xattr(s)) {
	205	res -= slen;
	206	memmove(s, s + slen, len);
	207	} else {
	208	s += slen;
	209	}
	210	}
	211
	212	return res;
	213	}
	214
	215	struct posix_acl ovl_get_acl(struct inode inode, int type)
	216	{
	217	struct inode *realinode = ovl_inode_real(inode, NULL);
	218	const struct cred *old_cred;
	219	struct posix_acl *acl;
	220
	221	if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) \|\| !IS_POSIXACL(realinode))
	222	return NULL;
	223
	224	old_cred = ovl_override_creds(inode->i_sb);
	225	acl = get_acl(realinode, type);
	226	revert_creds(old_cred);
	227
	228	return acl;
	229	}
	230
	231	static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
	232	struct dentry *realdentry)
	233	{
	234	if (OVL_TYPE_UPPER(type))
	235	return false;
	236
	237	if (special_file(realdentry->d_inode->i_mode))
	238	return false;
	239
	240	if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
	241	return false;
	242
	243	return true;
	244	}
	245
	246	int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags)
	247	{
	248	int err = 0;
	249	struct path realpath;
	250	enum ovl_path_type type;
	251
	252	type = ovl_path_real(dentry, &realpath);
	253	if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) {
	254	err = ovl_want_write(dentry);
	255	if (!err) {
	256	err = ovl_copy_up_flags(dentry, file_flags);
	257	ovl_drop_write(dentry);
	258	}
	259	}
	260
	261	return err;
	262	}
	263
	264	int ovl_update_time(struct inode inode, struct timespec ts, int flags)
	265	{
	266	struct dentry *alias;
	267	struct path upperpath;
	268
	269	if (!(flags & S_ATIME))
	270	return 0;
	271
	272	alias = d_find_any_alias(inode);
	273	if (!alias)
	274	return 0;
	275
	276	ovl_path_upper(alias, &upperpath);
	277	if (upperpath.dentry) {
	278	touch_atime(&upperpath);
	279	inode->i_atime = d_inode(upperpath.dentry)->i_atime;
	280	}
	281
	282	dput(alias);
	283
	284	return 0;
	285	}
	286
	287	static const struct inode_operations ovl_file_inode_operations = {
	288	.setattr = ovl_setattr,
	289	.permission = ovl_permission,
	290	.getattr = ovl_getattr,
	291	.listxattr = ovl_listxattr,
	292	.get_acl = ovl_get_acl,
	293	.update_time = ovl_update_time,
	294	};
	295
	296	static const struct inode_operations ovl_symlink_inode_operations = {
	297	.setattr = ovl_setattr,
	298	.get_link = ovl_get_link,
	299	.getattr = ovl_getattr,
	300	.listxattr = ovl_listxattr,
	301	.update_time = ovl_update_time,
	302	};
	303
	304	static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev)
	305	{
	306	inode->i_ino = get_next_ino();
	307	inode->i_mode = mode;
	308	inode->i_flags \|= S_NOCMTIME;
	309	#ifdef CONFIG_FS_POSIX_ACL
	310	inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE;
	311	#endif
	312
	313	switch (mode & S_IFMT) {
	314	case S_IFREG:
	315	inode->i_op = &ovl_file_inode_operations;
	316	break;
	317
	318	case S_IFDIR:
	319	inode->i_op = &ovl_dir_inode_operations;
	320	inode->i_fop = &ovl_dir_operations;
	321	break;
	322
	323	case S_IFLNK:
	324	inode->i_op = &ovl_symlink_inode_operations;
	325	break;
	326
	327	default:
	328	inode->i_op = &ovl_file_inode_operations;
	329	init_special_inode(inode, mode, rdev);
	330	break;
	331	}
	332	}
	333
	334	struct inode ovl_new_inode(struct super_block sb, umode_t mode, dev_t rdev)
	335	{
	336	struct inode *inode;
	337
	338	inode = new_inode(sb);
	339	if (inode)
	340	ovl_fill_inode(inode, mode, rdev);
	341
	342	return inode;
	343	}
	344
	345	static int ovl_inode_test(struct inode inode, void data)
	346	{
	347	return ovl_inode_real(inode, NULL) == data;
	348	}
	349
	350	static int ovl_inode_set(struct inode inode, void data)
	351	{
	352	inode->i_private = (void *) (((unsigned long) data) \| OVL_ISUPPER_MASK);
	353	return 0;
	354	}
	355
	356	struct inode ovl_get_inode(struct super_block sb, struct inode *realinode)
	357
	358	{
	359	struct inode *inode;
	360
	361	inode = iget5_locked(sb, (unsigned long) realinode,
	362	ovl_inode_test, ovl_inode_set, realinode);
	363	if (inode && inode->i_state & I_NEW) {
	364	ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev);
	365	set_nlink(inode, realinode->i_nlink);
	366	unlock_new_inode(inode);
	367	}
	368
	369	return inode;
	370	}