freebsd-nq/sys/fs/nullfs/null.h
Konstantin Belousov 5fc9e11c42 Save lower root vnode in nullfs mnt data instead of upper.
Nullfs needs to know the root vnode of the lower fs during the
operation.  Currently it caches the upper vnode of it, which is also
the root of the nullfs mount.  On unmount, nullfs calls vflush() with
rootrefs == 1, and aborts non-forced unmount if there are any more
vnodes instantiated during vflush().  This means that the reference to
the root vnode after failed non-forced unmount could be lost and
nullm_rootvp points to the freed memory.

Fix it by storing the reference for lower vnode instead, which is kept
intact during vflush().  nullfs_root() now instantiates the upper
vnode of lower root.  Care about VV_ROOT flag in null_nodeget().

Reported and tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
2020-01-28 11:29:06 +00:00

97 lines
3.2 KiB
C

/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 1992, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software donated to Berkeley by
* Jan-Simon Pendry.
*
* 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.
* 3. Neither the name of the University 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 REGENTS 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 REGENTS 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.
*
* @(#)null.h 8.3 (Berkeley) 8/20/94
*
* $FreeBSD$
*/
#ifndef FS_NULL_H
#define FS_NULL_H
#define NULLM_CACHE 0x0001
struct null_mount {
struct mount *nullm_vfs;
struct vnode *nullm_lowerrootvp; /* Ref to lower root vnode */
uint64_t nullm_flags;
};
#ifdef _KERNEL
/*
* A cache of vnode references
*/
struct null_node {
LIST_ENTRY(null_node) null_hash; /* Hash list */
struct vnode *null_lowervp; /* VREFed once */
struct vnode *null_vnode; /* Back pointer */
u_int null_flags;
};
#define NULLV_NOUNLOCK 0x0001
#define NULLV_DROP 0x0002
#define MOUNTTONULLMOUNT(mp) ((struct null_mount *)((mp)->mnt_data))
#define VTONULL(vp) ((struct null_node *)(vp)->v_data)
#define NULLTOV(xp) ((xp)->null_vnode)
int nullfs_init(struct vfsconf *vfsp);
int nullfs_uninit(struct vfsconf *vfsp);
int null_nodeget(struct mount *mp, struct vnode *target, struct vnode **vpp);
struct vnode *null_hashget(struct mount *mp, struct vnode *lowervp);
void null_hashrem(struct null_node *xp);
int null_bypass(struct vop_generic_args *ap);
#ifdef DIAGNOSTIC
struct vnode *null_checkvp(struct vnode *vp, char *fil, int lno);
#define NULLVPTOLOWERVP(vp) null_checkvp((vp), __FILE__, __LINE__)
#else
#define NULLVPTOLOWERVP(vp) (VTONULL(vp)->null_lowervp)
#endif
extern struct vop_vector null_vnodeops;
#ifdef MALLOC_DECLARE
MALLOC_DECLARE(M_NULLFSNODE);
#endif
#ifdef NULLFS_DEBUG
#define NULLFSDEBUG(format, args...) printf(format ,## args)
#else
#define NULLFSDEBUG(format, args...)
#endif /* NULLFS_DEBUG */
#endif /* _KERNEL */
#endif