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freebsd-dev/sys/fs/tmpfs/tmpfs_vfsops.c
Ryan Moeller 693d10a291 tmpfs: Preserve alignment of struct fid fields 
On 64-bit platforms, the two short fields in `struct tmpfs_fid` are padded to
the 64-bit alignment of the long field.  This pushes the offsets of the
subsequent fields by 4 bytes and makes `struct tmpfs_fid` bigger than
`struct fid`.  `tmpfs_vptofh()` casts a `struct fid *` to `struct tmpfs_fid *`,
causing 4 bytes of adjacent memory to be overwritten when the struct fields are
set.  Through several layers of indirection and embedded structs, the adjacent
memory for one particular call to `tmpfs_vptofh()` happens to be the stack
canary for `nfsrvd_compound()`.  Half of the canary ends up being clobbered,
going unnoticed until eventually the stack check fails when `nfsrvd_compound()`
returns and a panic is triggered.

Instead of duplicating fields of `struct fid` in `struct tmpfs_fid`, narrow the
struct to cover only the unique fields for tmpfs and assert at compile time
that the struct fits in the allotted space.  This way we don't have to
replicate the offsets of `struct fid` fields, we just use them directly.

Reviewed by:	kib, mav, rmacklem
Approved by:	mav (mentor)
MFC after:	1 week
Sponsored by:	iXsystems, Inc.
Differential Revision:	https://reviews.freebsd.org/D25077
2020-06-03 09:38:51 +00:00

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/* $NetBSD: tmpfs_vfsops.c,v 1.10 2005/12/11 12:24:29 christos Exp $ */
/*-
* SPDX-License-Identifier: BSD-2-Clause-NetBSD
*
* Copyright (c) 2005 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Julio M. Merino Vidal, developed as part of Google's Summer of Code
* 2005 program.
*
* 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 THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
*/
/*
* Efficient memory file system.
*
* tmpfs is a file system that uses FreeBSD's virtual memory
* sub-system to store file data and metadata in an efficient way.
* This means that it does not follow the structure of an on-disk file
* system because it simply does not need to. Instead, it uses
* memory-specific data structures and algorithms to automatically
* allocate and release resources.
*/
#include "opt_tmpfs.h"
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/dirent.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/rwlock.h>
#include <sys/stat.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/vnode.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_extern.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_param.h>
#include <fs/tmpfs/tmpfs.h>
/*
* Default permission for root node
*/
#define TMPFS_DEFAULT_ROOT_MODE (S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH)
MALLOC_DEFINE(M_TMPFSMNT, "tmpfs mount", "tmpfs mount structures");
MALLOC_DEFINE(M_TMPFSNAME, "tmpfs name", "tmpfs file names");
static int tmpfs_mount(struct mount *);
static int tmpfs_unmount(struct mount *, int);
static int tmpfs_root(struct mount *, int flags, struct vnode **);
static int tmpfs_fhtovp(struct mount *, struct fid *, int,
struct vnode **);
static int tmpfs_statfs(struct mount *, struct statfs *);
static const char *tmpfs_opts[] = {
"from", "size", "maxfilesize", "inodes", "uid", "gid", "mode", "export",
"union", "nonc", "nomtime", NULL
};
static const char *tmpfs_updateopts[] = {
"from", "export", "nomtime", "size", NULL
};
/*
* Handle updates of time from writes to mmaped regions, if allowed.
* Use MNT_VNODE_FOREACH_ALL instead of MNT_VNODE_FOREACH_LAZY, since
* unmap of the tmpfs-backed vnode does not call vinactive(), due to
* vm object type is OBJT_SWAP. If lazy, only handle delayed update
* of mtime due to the writes to mapped files.
*/
static void
tmpfs_update_mtime(struct mount *mp, bool lazy)
{
struct vnode *vp, *mvp;
struct vm_object *obj;
if (VFS_TO_TMPFS(mp)->tm_nomtime)
return;
MNT_VNODE_FOREACH_ALL(vp, mp, mvp) {
if (vp->v_type != VREG) {
VI_UNLOCK(vp);
continue;
}
obj = vp->v_object;
KASSERT((obj->flags & (OBJ_TMPFS_NODE | OBJ_TMPFS)) ==
(OBJ_TMPFS_NODE | OBJ_TMPFS), ("non-tmpfs obj"));
/*
* In lazy case, do unlocked read, avoid taking vnode
* lock if not needed. Lost update will be handled on
* the next call.
* For non-lazy case, we must flush all pending
* metadata changes now.
*/
if (!lazy || obj->generation != obj->cleangeneration) {
if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK,
curthread) != 0)
continue;
tmpfs_check_mtime(vp);
if (!lazy)
tmpfs_update(vp);
vput(vp);
} else {
VI_UNLOCK(vp);
continue;
}
}
}
struct tmpfs_check_rw_maps_arg {
bool found;
};
static bool
tmpfs_check_rw_maps_cb(struct mount *mp __unused, vm_map_t map __unused,
vm_map_entry_t entry __unused, void *arg)
{
struct tmpfs_check_rw_maps_arg *a;
a = arg;
a->found = true;
return (true);
}
/*
* Revoke write permissions from all mappings of regular files
* belonging to the specified tmpfs mount.
*/
static bool
tmpfs_revoke_rw_maps_cb(struct mount *mp __unused, vm_map_t map,
vm_map_entry_t entry, void *arg __unused)
{
/*
* XXXKIB: might be invalidate the mapping
* instead ? The process is not going to be
* happy in any case.
*/
entry->max_protection &= ~VM_PROT_WRITE;
if ((entry->protection & VM_PROT_WRITE) != 0) {
entry->protection &= ~VM_PROT_WRITE;
pmap_protect(map->pmap, entry->start, entry->end,
entry->protection);
}
return (false);
}
static void
tmpfs_all_rw_maps(struct mount *mp, bool (*cb)(struct mount *mp, vm_map_t,
vm_map_entry_t, void *), void *cb_arg)
{
struct proc *p;
struct vmspace *vm;
vm_map_t map;
vm_map_entry_t entry;
vm_object_t object;
struct vnode *vp;
int gen;
bool terminate;
terminate = false;
sx_slock(&allproc_lock);
again:
gen = allproc_gen;
FOREACH_PROC_IN_SYSTEM(p) {
PROC_LOCK(p);
if (p->p_state != PRS_NORMAL || (p->p_flag & (P_INEXEC |
P_SYSTEM | P_WEXIT)) != 0) {
PROC_UNLOCK(p);
continue;
}
vm = vmspace_acquire_ref(p);
_PHOLD_LITE(p);
PROC_UNLOCK(p);
if (vm == NULL) {
PRELE(p);
continue;
}
sx_sunlock(&allproc_lock);
map = &vm->vm_map;
vm_map_lock(map);
if (map->busy)
vm_map_wait_busy(map);
VM_MAP_ENTRY_FOREACH(entry, map) {
if ((entry->eflags & (MAP_ENTRY_GUARD |
MAP_ENTRY_IS_SUB_MAP | MAP_ENTRY_COW)) != 0 ||
(entry->max_protection & VM_PROT_WRITE) == 0)
continue;
object = entry->object.vm_object;
if (object == NULL || object->type != OBJT_SWAP ||
(object->flags & OBJ_TMPFS_NODE) == 0)
continue;
/*
* No need to dig into shadow chain, mapping
* of the object not at top is readonly.
*/
VM_OBJECT_RLOCK(object);
if (object->type == OBJT_DEAD) {
VM_OBJECT_RUNLOCK(object);
continue;
}
MPASS(object->ref_count > 1);
if ((object->flags & (OBJ_TMPFS_NODE | OBJ_TMPFS)) !=
(OBJ_TMPFS_NODE | OBJ_TMPFS)) {
VM_OBJECT_RUNLOCK(object);
continue;
}
vp = object->un_pager.swp.swp_tmpfs;
if (vp->v_mount != mp) {
VM_OBJECT_RUNLOCK(object);
continue;
}
terminate = cb(mp, map, entry, cb_arg);
VM_OBJECT_RUNLOCK(object);
if (terminate)
break;
}
vm_map_unlock(map);
vmspace_free(vm);
sx_slock(&allproc_lock);
PRELE(p);
if (terminate)
break;
}
if (!terminate && gen != allproc_gen)
goto again;
sx_sunlock(&allproc_lock);
}
static bool
tmpfs_check_rw_maps(struct mount *mp)
{
struct tmpfs_check_rw_maps_arg ca;
ca.found = false;
tmpfs_all_rw_maps(mp, tmpfs_check_rw_maps_cb, &ca);
return (ca.found);
}
static int
tmpfs_rw_to_ro(struct mount *mp)
{
int error, flags;
bool forced;
forced = (mp->mnt_flag & MNT_FORCE) != 0;
flags = WRITECLOSE | (forced ? FORCECLOSE : 0);
if ((error = vn_start_write(NULL, &mp, V_WAIT)) != 0)
return (error);
error = vfs_write_suspend_umnt(mp);
if (error != 0)
return (error);
if (!forced && tmpfs_check_rw_maps(mp)) {
error = EBUSY;
goto out;
}
VFS_TO_TMPFS(mp)->tm_ronly = 1;
MNT_ILOCK(mp);
mp->mnt_flag |= MNT_RDONLY;
MNT_IUNLOCK(mp);
for (;;) {
tmpfs_all_rw_maps(mp, tmpfs_revoke_rw_maps_cb, NULL);
tmpfs_update_mtime(mp, false);
error = vflush(mp, 0, flags, curthread);
if (error != 0) {
VFS_TO_TMPFS(mp)->tm_ronly = 0;
MNT_ILOCK(mp);
mp->mnt_flag &= ~MNT_RDONLY;
MNT_IUNLOCK(mp);
goto out;
}
if (!tmpfs_check_rw_maps(mp))
break;
}
out:
vfs_write_resume(mp, 0);
return (error);
}
static int
tmpfs_mount(struct mount *mp)
{
const size_t nodes_per_page = howmany(PAGE_SIZE,
sizeof(struct tmpfs_dirent) + sizeof(struct tmpfs_node));
struct tmpfs_mount *tmp;
struct tmpfs_node *root;
int error;
bool nomtime, nonc;
/* Size counters. */
u_quad_t pages;
off_t nodes_max, size_max, maxfilesize;
/* Root node attributes. */
uid_t root_uid;
gid_t root_gid;
mode_t root_mode;
struct vattr va;
if (vfs_filteropt(mp->mnt_optnew, tmpfs_opts))
return (EINVAL);
if (mp->mnt_flag & MNT_UPDATE) {
/* Only support update mounts for certain options. */
if (vfs_filteropt(mp->mnt_optnew, tmpfs_updateopts) != 0)
return (EOPNOTSUPP);
tmp = VFS_TO_TMPFS(mp);
if (vfs_getopt_size(mp->mnt_optnew, "size", &size_max) == 0) {
/*
* On-the-fly resizing is not supported (yet). We still
* need to have "size" listed as "supported", otherwise
* trying to update fs that is listed in fstab with size
* parameter, say trying to change rw to ro or vice
* versa, would cause vfs_filteropt() to bail.
*/
if (size_max != tmp->tm_size_max)
return (EOPNOTSUPP);
}
if (vfs_flagopt(mp->mnt_optnew, "ro", NULL, 0) &&
!tmp->tm_ronly) {
/* RW -> RO */
return (tmpfs_rw_to_ro(mp));
} else if (!vfs_flagopt(mp->mnt_optnew, "ro", NULL, 0) &&
tmp->tm_ronly) {
/* RO -> RW */
tmp->tm_ronly = 0;
MNT_ILOCK(mp);
mp->mnt_flag &= ~MNT_RDONLY;
MNT_IUNLOCK(mp);
}
tmp->tm_nomtime = vfs_getopt(mp->mnt_optnew, "nomtime", NULL,
0) == 0;
return (0);
}
vn_lock(mp->mnt_vnodecovered, LK_SHARED | LK_RETRY);
error = VOP_GETATTR(mp->mnt_vnodecovered, &va, mp->mnt_cred);
VOP_UNLOCK(mp->mnt_vnodecovered);
if (error)
return (error);
if (mp->mnt_cred->cr_ruid != 0 ||
vfs_scanopt(mp->mnt_optnew, "gid", "%d", &root_gid) != 1)
root_gid = va.va_gid;
if (mp->mnt_cred->cr_ruid != 0 ||
vfs_scanopt(mp->mnt_optnew, "uid", "%d", &root_uid) != 1)
root_uid = va.va_uid;
if (mp->mnt_cred->cr_ruid != 0 ||
vfs_scanopt(mp->mnt_optnew, "mode", "%ho", &root_mode) != 1)
root_mode = va.va_mode;
if (vfs_getopt_size(mp->mnt_optnew, "inodes", &nodes_max) != 0)
nodes_max = 0;
if (vfs_getopt_size(mp->mnt_optnew, "size", &size_max) != 0)
size_max = 0;
if (vfs_getopt_size(mp->mnt_optnew, "maxfilesize", &maxfilesize) != 0)
maxfilesize = 0;
nonc = vfs_getopt(mp->mnt_optnew, "nonc", NULL, NULL) == 0;
nomtime = vfs_getopt(mp->mnt_optnew, "nomtime", NULL, NULL) == 0;
/* Do not allow mounts if we do not have enough memory to preserve
* the minimum reserved pages. */
if (tmpfs_mem_avail() < TMPFS_PAGES_MINRESERVED)
return (ENOSPC);
/* Get the maximum number of memory pages this file system is
* allowed to use, based on the maximum size the user passed in
* the mount structure. A value of zero is treated as if the
* maximum available space was requested. */
if (size_max == 0 || size_max > OFF_MAX - PAGE_SIZE ||
(SIZE_MAX < OFF_MAX && size_max / PAGE_SIZE >= SIZE_MAX))
pages = SIZE_MAX;
else {
size_max = roundup(size_max, PAGE_SIZE);
pages = howmany(size_max, PAGE_SIZE);
}
MPASS(pages > 0);
if (nodes_max <= 3) {
if (pages < INT_MAX / nodes_per_page)
nodes_max = pages * nodes_per_page;
else
nodes_max = INT_MAX;
}
if (nodes_max > INT_MAX)
nodes_max = INT_MAX;
MPASS(nodes_max >= 3);
/* Allocate the tmpfs mount structure and fill it. */
tmp = (struct tmpfs_mount *)malloc(sizeof(struct tmpfs_mount),
M_TMPFSMNT, M_WAITOK | M_ZERO);
mtx_init(&tmp->tm_allnode_lock, "tmpfs allnode lock", NULL, MTX_DEF);
tmp->tm_nodes_max = nodes_max;
tmp->tm_nodes_inuse = 0;
tmp->tm_refcount = 1;
tmp->tm_maxfilesize = maxfilesize > 0 ? maxfilesize : OFF_MAX;
LIST_INIT(&tmp->tm_nodes_used);
tmp->tm_size_max = size_max;
tmp->tm_pages_max = pages;
tmp->tm_pages_used = 0;
new_unrhdr64(&tmp->tm_ino_unr, 2);
tmp->tm_ronly = (mp->mnt_flag & MNT_RDONLY) != 0;
tmp->tm_nonc = nonc;
tmp->tm_nomtime = nomtime;
/* Allocate the root node. */
error = tmpfs_alloc_node(mp, tmp, VDIR, root_uid, root_gid,
root_mode & ALLPERMS, NULL, NULL, VNOVAL, &root);
if (error != 0 || root == NULL) {
free(tmp, M_TMPFSMNT);
return (error);
}
KASSERT(root->tn_id == 2,
("tmpfs root with invalid ino: %ju", (uintmax_t)root->tn_id));
tmp->tm_root = root;
MNT_ILOCK(mp);
mp->mnt_flag |= MNT_LOCAL;
mp->mnt_kern_flag |= MNTK_LOOKUP_SHARED | MNTK_EXTENDED_SHARED |
MNTK_TEXT_REFS | MNTK_NOMSYNC;
MNT_IUNLOCK(mp);
mp->mnt_data = tmp;
mp->mnt_stat.f_namemax = MAXNAMLEN;
vfs_getnewfsid(mp);
vfs_mountedfrom(mp, "tmpfs");
return 0;
}
/* ARGSUSED2 */
static int
tmpfs_unmount(struct mount *mp, int mntflags)
{
struct tmpfs_mount *tmp;
struct tmpfs_node *node;
int error, flags;
flags = (mntflags & MNT_FORCE) != 0 ? FORCECLOSE : 0;
tmp = VFS_TO_TMPFS(mp);
/* Stop writers */
error = vfs_write_suspend_umnt(mp);
if (error != 0)
return (error);
/*
* At this point, nodes cannot be destroyed by any other
* thread because write suspension is started.
*/
for (;;) {
error = vflush(mp, 0, flags, curthread);
if (error != 0) {
vfs_write_resume(mp, VR_START_WRITE);
return (error);
}
MNT_ILOCK(mp);
if (mp->mnt_nvnodelistsize == 0) {
MNT_IUNLOCK(mp);
break;
}
MNT_IUNLOCK(mp);
if ((mntflags & MNT_FORCE) == 0) {
vfs_write_resume(mp, VR_START_WRITE);
return (EBUSY);
}
}
TMPFS_LOCK(tmp);
while ((node = LIST_FIRST(&tmp->tm_nodes_used)) != NULL) {
TMPFS_NODE_LOCK(node);
if (node->tn_type == VDIR)
tmpfs_dir_destroy(tmp, node);
if (tmpfs_free_node_locked(tmp, node, true))
TMPFS_LOCK(tmp);
else
TMPFS_NODE_UNLOCK(node);
}
mp->mnt_data = NULL;
tmpfs_free_tmp(tmp);
vfs_write_resume(mp, VR_START_WRITE);
MNT_ILOCK(mp);
mp->mnt_flag &= ~MNT_LOCAL;
MNT_IUNLOCK(mp);
return (0);
}
void
tmpfs_free_tmp(struct tmpfs_mount *tmp)
{
MPASS(tmp->tm_refcount > 0);
tmp->tm_refcount--;
if (tmp->tm_refcount > 0) {
TMPFS_UNLOCK(tmp);
return;
}
TMPFS_UNLOCK(tmp);
mtx_destroy(&tmp->tm_allnode_lock);
MPASS(tmp->tm_pages_used == 0);
MPASS(tmp->tm_nodes_inuse == 0);
free(tmp, M_TMPFSMNT);
}
static int
tmpfs_root(struct mount *mp, int flags, struct vnode **vpp)
{
int error;
error = tmpfs_alloc_vp(mp, VFS_TO_TMPFS(mp)->tm_root, flags, vpp);
if (error == 0)
(*vpp)->v_vflag |= VV_ROOT;
return (error);
}
static int
tmpfs_fhtovp(struct mount *mp, struct fid *fhp, int flags,
struct vnode **vpp)
{
struct tmpfs_fid_data tfd;
struct tmpfs_mount *tmp;
struct tmpfs_node *node;
int error;
if (fhp->fid_len != sizeof(tfd))
return (EINVAL);
/*
* Copy from fid_data onto the stack to avoid unaligned pointer use.
* See the comment in sys/mount.h on struct fid for details.
*/
memcpy(&tfd, fhp->fid_data, fhp->fid_len);
tmp = VFS_TO_TMPFS(mp);
if (tfd.tfd_id >= tmp->tm_nodes_max)
return (EINVAL);
TMPFS_LOCK(tmp);
LIST_FOREACH(node, &tmp->tm_nodes_used, tn_entries) {
if (node->tn_id == tfd.tfd_id &&
node->tn_gen == tfd.tfd_gen) {
tmpfs_ref_node(node);
break;
}
}
TMPFS_UNLOCK(tmp);
if (node != NULL) {
error = tmpfs_alloc_vp(mp, node, LK_EXCLUSIVE, vpp);
tmpfs_free_node(tmp, node);
} else
error = EINVAL;
return (error);
}
/* ARGSUSED2 */
static int
tmpfs_statfs(struct mount *mp, struct statfs *sbp)
{
struct tmpfs_mount *tmp;
size_t used;
tmp = VFS_TO_TMPFS(mp);
sbp->f_iosize = PAGE_SIZE;
sbp->f_bsize = PAGE_SIZE;
used = tmpfs_pages_used(tmp);
if (tmp->tm_pages_max != ULONG_MAX)
sbp->f_blocks = tmp->tm_pages_max;
else
sbp->f_blocks = used + tmpfs_mem_avail();
if (sbp->f_blocks <= used)
sbp->f_bavail = 0;
else
sbp->f_bavail = sbp->f_blocks - used;
sbp->f_bfree = sbp->f_bavail;
used = tmp->tm_nodes_inuse;
sbp->f_files = tmp->tm_nodes_max;
if (sbp->f_files <= used)
sbp->f_ffree = 0;
else
sbp->f_ffree = sbp->f_files - used;
/* sbp->f_owner = tmp->tn_uid; */
return 0;
}
static int
tmpfs_sync(struct mount *mp, int waitfor)
{
if (waitfor == MNT_SUSPEND) {
MNT_ILOCK(mp);
mp->mnt_kern_flag |= MNTK_SUSPEND2 | MNTK_SUSPENDED;
MNT_IUNLOCK(mp);
} else if (waitfor == MNT_LAZY) {
tmpfs_update_mtime(mp, true);
}
return (0);
}
static int
tmpfs_init(struct vfsconf *conf)
{
tmpfs_subr_init();
return (0);
}
static int
tmpfs_uninit(struct vfsconf *conf)
{
tmpfs_subr_uninit();
return (0);
}
/*
* tmpfs vfs operations.
*/
struct vfsops tmpfs_vfsops = {
.vfs_mount = tmpfs_mount,
.vfs_unmount = tmpfs_unmount,
.vfs_root = vfs_cache_root,
.vfs_cachedroot = tmpfs_root,
.vfs_statfs = tmpfs_statfs,
.vfs_fhtovp = tmpfs_fhtovp,
.vfs_sync = tmpfs_sync,
.vfs_init = tmpfs_init,
.vfs_uninit = tmpfs_uninit,
};
VFS_SET(tmpfs_vfsops, tmpfs, VFCF_JAIL);
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