path: root/fs/overlayfs/util.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2011 Novell Inc.
 * Copyright (C) 2016 Red Hat, Inc.
 */

#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/xattr.h>
#include <linux/exportfs.h>
#include <linux/fileattr.h>
#include <linux/uuid.h>
#include <linux/namei.h>
#include <linux/ratelimit.h>
#include "overlayfs.h"

int ovl_want_write(struct dentry *dentry)
{
	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
	return mnt_want_write(ovl_upper_mnt(ofs));
}

void ovl_drop_write(struct dentry *dentry)
{
	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
	mnt_drop_write(ovl_upper_mnt(ofs));
}

struct dentry *ovl_workdir(struct dentry *dentry)
{
	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
	return ofs->workdir;
}

const struct cred *ovl_override_creds(struct super_block *sb)
{
	struct ovl_fs *ofs = sb->s_fs_info;

	return override_creds(ofs->creator_cred);
}

/*
 * Check if underlying fs supports file handles and try to determine encoding
 * type, in order to deduce maximum inode number used by fs.
 *
 * Return 0 if file handles are not supported.
 * Return 1 (FILEID_INO32_GEN) if fs uses the default 32bit inode encoding.
 * Return -1 if fs uses a non default encoding with unknown inode size.
 */
int ovl_can_decode_fh(struct super_block *sb)
{
	if (!capable(CAP_DAC_READ_SEARCH))
		return 0;

	if (!sb->s_export_op || !sb->s_export_op->fh_to_dentry)
		return 0;

	return sb->s_export_op->encode_fh ? -1 : FILEID_INO32_GEN;
}

struct dentry *ovl_indexdir(struct super_block *sb)
{
	struct ovl_fs *ofs = sb->s_fs_info;

	return ofs->indexdir;
}

/* Index all files on copy up. For now only enabled for NFS export */
bool ovl_index_all(struct super_block *sb)
{
	struct ovl_fs *ofs = sb->s_fs_info;

	return ofs->config.nfs_export && ofs->config.index;
}

/* Verify lower origin on lookup. For now only enabled for NFS export */
bool ovl_verify_lower(struct super_block *sb)
{
	struct ovl_fs *ofs = sb->s_fs_info;

	return ofs->config.nfs_export && ofs->config.index;
}

struct ovl_path *ovl_stack_alloc(unsigned int n)
{
	return kcalloc(n, sizeof(struct ovl_path), GFP_KERNEL);
}

void ovl_stack_cpy(struct ovl_path *dst, struct ovl_path *src, unsigned int n)
{
	unsigned int i;

	memcpy(dst, src, sizeof(struct ovl_path) * n);
	for (i = 0; i < n; i++)
		dget(src[i].dentry);
}

void ovl_stack_put(struct ovl_path *stack, unsigned int n)
{
	unsigned int i;

	for (i = 0; stack && i < n; i++)
		dput(stack[i].dentry);
}

void ovl_stack_free(struct ovl_path *stack, unsigned int n)
{
	ovl_stack_put(stack, n);
	kfree(stack);
}

struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
{
	size_t size = offsetof(struct ovl_entry, __lowerstack[numlower]);
	struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);

	if (oe)
		oe->__numlower = numlower;

	return oe;
}

void ovl_free_entry(struct ovl_entry *oe)
{
	ovl_stack_put(ovl_lowerstack(oe), ovl_numlower(oe));
	kfree(oe);
}

#define OVL_D_REVALIDATE (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE)

bool