freebsd-dev/sys/fs/fuse/fuse_file.h
Alan Somers f067b60946 fusefs: implement VOP_ADVLOCK
PR:		234581
Sponsored by:	The FreeBSD Foundation
2019-04-12 23:22:27 +00:00

173 lines
7.6 KiB
C

/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 2007-2009 Google Inc. and Amit Singh
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Copyright (C) 2005 Csaba Henk.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#ifndef _FUSE_FILE_H_
#define _FUSE_FILE_H_
#include <sys/types.h>
#include <sys/fcntl.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/vnode.h>
/*
* The fufh type is the access mode of the fuse file handle. It's the portion
* of the open(2) flags related to permission.
*/
typedef enum fufh_type {
FUFH_INVALID = -1,
FUFH_RDONLY = O_RDONLY,
FUFH_WRONLY = O_WRONLY,
FUFH_RDWR = O_RDWR,
FUFH_EXEC = O_EXEC,
} fufh_type_t;
/*
* FUSE File Handles
*
* The FUSE protocol says that a server may assign a unique 64-bit file handle
* every time that a file is opened. Effectively, that's once for each file
* descriptor.
*
* Unfortunately, the VFS doesn't help us here. VOPs don't have a
* struct file* argument. fileops do, but many syscalls bypass the fileops
* layer and go straight to a vnode. Some, like writing from cache, can't
* track a file handle even in theory. The entire concept of the file handle
* is a product of FUSE's Linux origins; Linux lacks vnodes and almost every
* file system operation takes a struct file* argument.
*
* Since FreeBSD's VFS is more file descriptor-agnostic, we must store FUSE
* filehandles in the vnode. One option would be to only store a single file
* handle and never open FUSE files concurrently. That's what NetBSD does.
* But that violates FUSE's security model. FUSE expects the server to do all
* authorization (except when mounted with -o default_permissions). In order
* to do that, the server needs us to send FUSE_OPEN every time somebody opens
* a new file descriptor.
*
* Another option would be to never open FUSE files concurrently, but send a
* FUSE_ACCESS prior to every open after the first. That would give the server
* the opportunity to authorize the access. Unfortunately, the FUSE protocol
* makes ACCESS optional. File systems that don't implement it are assumed to
* authorize everything. A survey of 32 fuse file systems showed that only 14
* implemented access. Among the laggards were a few that really ought to be
* doing server-side authorization.
*
* So we do something hacky, similar to what OpenBSD, Illumos, and OSXFuse do.
* we store a list of file handles, one for each combination of vnode, uid,
* gid, pid, and access mode. When opening a file, we first check whether
* there's already a matching file handle. If so, we reuse it. If not, we
* send FUSE_OPEN and create a new file handle. That minimizes the number of
* open file handles while still allowing the server to authorize stuff.
*
* VOPs that need a file handle search through the list for a close match.
* They can't be guaranteed of finding an exact match because, for example, a
* process may have changed its UID since opening the file. Also, most VOPs
* don't know exactly what permission they need. Is O_RDWR required or is
* O_RDONLY good enough? So the file handle we end up using may not be exactly
* the one we're supposed to use with that file descriptor. But if the FUSE
* file system isn't too picky, it will work. (FWIW even Linux sometimes
* guesses the file handle, during writes from cache or most SETATTR
* operations).
*
* I suspect this mess is part of the reason why neither NFS nor 9P have an
* equivalent of FUSE file handles.
*/
struct fuse_filehandle {
LIST_ENTRY(fuse_filehandle) next;
/* The filehandle returned by FUSE_OPEN */
uint64_t fh_id;
/* flags returned by FUSE_OPEN */
uint32_t fuse_open_flags;
/* The access mode of the file handle */
fufh_type_t fufh_type;
/* Credentials used to open the file */
gid_t gid;
pid_t pid;
uid_t uid;
};
#define FUFH_IS_VALID(f) ((f)->fufh_type != FUFH_INVALID)
bool fuse_filehandle_validrw(struct vnode *vp, int mode,
struct ucred *cred, pid_t pid);
int fuse_filehandle_get(struct vnode *vp, int fflag,
struct fuse_filehandle **fufhp, struct ucred *cred,
pid_t pid);
int fuse_filehandle_get_anyflags(struct vnode *vp,
struct fuse_filehandle **fufhp, struct ucred *cred,
pid_t pid);
int fuse_filehandle_getrw(struct vnode *vp, int fflag,
struct fuse_filehandle **fufhp, struct ucred *cred,
pid_t pid);
void fuse_filehandle_init(struct vnode *vp, fufh_type_t fufh_type,
struct fuse_filehandle **fufhp, struct thread *td,
struct ucred *cred, struct fuse_open_out *foo);
int fuse_filehandle_open(struct vnode *vp, int mode,
struct fuse_filehandle **fufhp, struct thread *td,
struct ucred *cred);
int fuse_filehandle_close(struct vnode *vp, struct fuse_filehandle *fufh,
struct thread *td, struct ucred *cred);
#endif /* _FUSE_FILE_H_ */