path: root/fs/xfs/xfs_handle.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * Copyright (c) 2022-2024 Oracle.
 * All rights reserved.
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_shared.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_inode.h"
#include "xfs_error.h"
#include "xfs_trace.h"
#include "xfs_trans.h"
#include "xfs_da_format.h"
#include "xfs_da_btree.h"
#include "xfs_attr.h"
#include "xfs_ioctl.h"
#include "xfs_parent.h"
#include "xfs_handle.h"
#include "xfs_health.h"
#include "xfs_icache.h"
#include "xfs_export.h"
#include "xfs_xattr.h"
#include "xfs_acl.h"

#include <linux/namei.h>

static inline size_t
xfs_filehandle_fid_len(void)
{
	struct xfs_handle	*handle = NULL;

	return sizeof(struct xfs_fid) - sizeof(handle->ha_fid.fid_len);
}

static inline size_t
xfs_filehandle_init(
	struct xfs_mount	*mp,
	xfs_ino_t		ino,
	uint32_t		gen,
	struct xfs_handle	*handle)
{
	memcpy(&handle->ha_fsid, mp->m_fixedfsid, sizeof(struct xfs_fsid));

	handle->ha_fid.fid_len = xfs_filehandle_fid_len();
	handle->ha_fid.fid_pad = 0;
	handle->ha_fid.fid_gen = gen;
	handle->ha_fid.fid_ino = ino;

	return sizeof(struct xfs_handle);
}

static inline size_t
xfs_fshandle_init(
	struct xfs_mount	*mp,
	struct xfs_handle	*handle)
{
	memcpy(&handle->ha_fsid, mp->m_fixedfsid, sizeof(struct xfs_fsid));
	memset(&handle->ha_fid, 0, sizeof(handle->ha_fid));

	return sizeof(struct xfs_fsid);
}

/*
 * xfs_find_handle maps from userspace xfs_fsop_handlereq structure to
 * a file or fs handle.
 *
 * XFS_IOC_PATH_TO_FSHANDLE
 *    returns fs handle for a mount point or path within that mount point
 * XFS_IOC_FD_TO_HANDLE
 *    returns full handle for a FD opened in user space
 * XFS_IOC_PATH_TO_HANDLE
 *    returns full handle for a path
 */
int
xfs_find_handle(
	unsigned int		cmd,
	xfs_fsop_handlereq_t	*hreq)
{
	int			hsize;
	xfs_handle_t		handle;
	struct inode		*inode;
	struct path		path;
	int			error;
	struct xfs_inode	*ip;

	if (cmd == XFS_IOC_FD_TO_HANDLE) {
		CLASS(fd, f)(hreq->fd);

		if (fd_empty(f))
			return -EBADF;
		path = fd_file(f)->f_path;
		path_get(&path);
	} else {
		error = user_path_at(AT_FDCWD, hreq->path, 0, &path);
		if (error)
			return error;
	}
	inode = d_inode(path.dentry);
	ip = XFS_I(inode);

	/*
	 * We can only generate handles for inodes residing on a XFS filesystem,
	 * and only for regular files, directories or symbolic links.
	 */
	error = -EINVAL;
	if (inode->i_sb->s_magic != XFS_SB_MAGIC)
		goto out_put;

	error = -EBADF;
	if (!S_ISREG(inode->i_mode) &&
	    !S_ISDIR(inode->i_mode) &&
	    !S_ISLNK(inode->i_mode))
		goto out_put;


	memcpy(&handle.ha_fsid, ip->i_mount->m_fixedfsid, sizeof(xfs_fsid_t));

	if (cmd == XFS_IOC_PATH_TO_FSHANDLE)
		hsize = xfs_fshandle_init(ip->i_mount, &handle);
	else
		hsize = xfs_filehandle_init(ip->i_mount, ip->i_ino,
				inode->i_generation, &handle);

	error = -EFAULT;
	if (copy_to_user(hreq->ohandle, &handle, hsize) ||
	    copy_to_user(hreq->ohandlen, &hsize, sizeof(__s32)))
		goto out_put;

	error = 0;

 out_put:
	path_put(&path);
	return error;
}

/*
 * No need to do permission checks on the various pathname components
 * as the handle operations are privileged.
 */
STATIC int
xfs_handle_acceptable(
	void			*context,
	struct dentry		*dentry)
{
	return 1;
}

/* Convert handle already copied to kernel space into a dentry. */
static struct dentry *
xfs_khandle_to_dentry(
	struct file		*file,
	struct xfs_handle	*handle)
{
	struct xfs_fid64        fid = {
		.ino		= handle->ha_fid.fid_ino,
		.gen		= handle->ha_fid.fid_gen,
	};

	/*
	 * Only allow handle opens under a directory.
	 */
	if (!S_ISDIR(file_inode(file)->i_mode))
		return ERR_PTR(-ENOTDIR);

	if (handle->ha_fid.fid_len != xfs_filehandle_fid_len())
		return ERR_PTR(-EINVAL);

	return exportfs_decode_fh(file->f_path.mnt, (struct fid *)&fid, 3,
			FILEID_INO32_GEN | XFS_FILEID_TYPE_64FLAG,
			xfs_handle_acceptable, NULL);
}

/* Convert handle already copied to kernel space into an xfs_inode. */
static struct xfs_inode *
xfs_khandle_to_inode