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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2010 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
* Copyright 2016 Joyent, Inc.
*/
/* Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T */
/* All Rights Reserved */
/*
* Portions of this source code were derived from Berkeley 4.3 BSD
* under license from the Regents of the University of California.
*/
#include <sys/types.h>
#include <sys/t_lock.h>
#include <sys/param.h>
#include <sys/errno.h>
#include <sys/fstyp.h>
#include <sys/kmem.h>
#include <sys/systm.h>
#include <sys/mount.h>
#include <sys/vfs.h>
#include <sys/cred.h>
#include <sys/vnode.h>
#include <sys/cmn_err.h>
#include <sys/debug.h>
#include <sys/pathname.h>
#include <sys/policy.h>
#include <sys/zone.h>
#define UMOUNT2_SET_ERRNO(e, is_syscall) ((is_syscall) ? set_errno((e)) : (e))
/*
* The heart of the umount2 call - it is pulled out to allow kernel
* level particpation when the only reference is the vfs pointer.
*
* Note that some of the callers may not be in the context of a
* syscall (created by zthread_create() for example) and as such
* may not have an associated curthread->t_lwp. This is handled
* by is_syscall.
*/
int
umount2_engine(vfs_t *vfsp, int flag, cred_t *cr, int is_syscall)
{
int error;
/*
* Protect the call to vn_vfswlock() with the vfs reflock. This
* ensures vfs_vnodecovered will either be NULL (because someone
* beat us to the umount) or valid (because vfs_lock() prevents
* another umount from getting through here until we've called
* vn_vfswlock() on the covered vnode).
*
* At one point, we did the non-blocking version (vfs_lock()),
* and if it failed, bailed out with EBUSY. However, dounmount()
* calls vfs_lock_wait() and we drop the vfs lock before calling
* dounmount(), so there's no difference between waiting here
* for the lock or waiting there because grabbed it as soon as
* we drop it below. No returning with EBUSY at this point
* reduces the number of spurious unmount failures that happen
* as a side-effect of fsflush() and other mount and unmount
* operations that might be going on simultaneously.
*/
vfs_lock_wait(vfsp);
/*
* Call vn_vfswlock() on the covered vnode so that dounmount()
* can do its thing. It will call the corresponding vn_vfsunlock().
* Note that vfsp->vfs_vnodecovered can be NULL here, either because
* someone did umount on "/" or because someone beat us to the umount
* before we did the vfs_lock() above. In these cases, vn_vfswlock()
* returns EBUSY and we just pass that up. Also note that we're
* looking at a vnode without doing a VN_HOLD() on it. This is
* safe because it can't go away while something is mounted on it
* and we're locking out other umounts at this point.
*/
if (vn_vfswlock(vfsp->vfs_vnodecovered)) {
vfs_unlock(vfsp);
VFS_RELE(vfsp);
return (UMOUNT2_SET_ERRNO(EBUSY, is_syscall));
}
/*
* Now that the VVFSLOCK in the covered vnode is protecting this
* path, we don't need the vfs reflock or the hold on the vfs anymore.
*/
vfs_unlock(vfsp);
VFS_RELE(vfsp);
/*
* Perform the unmount.
*/
if ((error = dounmount(vfsp, flag, cr)) != 0)
return (UMOUNT2_SET_ERRNO(error, is_syscall));
return (0);
}
/*
* New umount() system call (for force unmount flag and perhaps others later).
*/
int
umount2(char *pathp, int flag)
{
struct pathname pn;
struct vfs *vfsp;
int error;
boolean_t altroot;
/*
* Some flags are disallowed through the system call interface.
*/
flag &= MS_UMOUNT_MASK;
/*
* Lookup user-supplied name by trying to match it against the
* mount points recorded at mount time. If no match is found
* (which can happen if the path to the mount point is specified
* differently between mount & umount, or if a block device were
* passed to umount) then we fall back to calling lookupname()
* to find the vfs. Doing it this way prevents calling lookupname()
* in most cases and that allows forcible umount to work even if
* lookupname() would hang (i.e. because an NFS server is dead).
*/
if (error = pn_get(pathp, UIO_USERSPACE, &pn))
return (set_errno(error));
/*
* Only a privileged user is allowed to bypass the security
* checks done by lookupname() and use the results from
* vfs_mntpoint2vfsp() instead. It could be argued that the
* proper check is FILE_DAC_SEARCH but we put it all
* under the mount privilege. Also, make sure the caller
* isn't in an environment with an alternate root (to the zone's root)
* directory, i.e. chroot(2).
*/
mutex_enter(&curproc->p_lock);
altroot = (PTOU(curproc)->u_rdir != NULL &&
PTOU(curproc)->u_rdir != curproc->p_zone->zone_rootvp);
mutex_exit(&curproc->p_lock);
if (secpolicy_fs_unmount(CRED(), NULL) != 0 || altroot ||
(vfsp = vfs_mntpoint2vfsp(pn.pn_path)) == NULL) {
vnode_t *fsrootvp;
/* fall back to lookupname() on path given to us */
if (error = lookupname(pn.pn_path, UIO_SYSSPACE, FOLLOW,
NULLVPP, &fsrootvp)) {
pn_free(&pn);
return (set_errno(error));
}
/*
* Find the vfs to be unmounted. The caller may have specified
* either the directory mount point (preferred) or else (for a
* disk-based file system) the block device which was mounted.
* Check to see which it is; if it's the device, search the VFS
* list to find the associated vfs entry.
*/
if (fsrootvp->v_flag & VROOT) {
vfsp = fsrootvp->v_vfsp;
VFS_HOLD(vfsp);
} else if (fsrootvp->v_type == VBLK)
vfsp = vfs_dev2vfsp(fsrootvp->v_rdev);
else
vfsp = NULL;
VN_RELE(fsrootvp);
if (vfsp == NULL) {
pn_free(&pn);
return (set_errno(EINVAL));
}
}
pn_free(&pn);
return (umount2_engine(vfsp, flag, CRED(), 1));
}
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