1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License, Version 1.0 only 6 * (the "License"). You may not use this file except in compliance 7 * with the License. 8 * 9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 10 * or http://www.opensolaris.org/os/licensing. 11 * See the License for the specific language governing permissions 12 * and limitations under the License. 13 * 14 * When distributing Covered Code, include this CDDL HEADER in each 15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 16 * If applicable, add the following below this CDDL HEADER, with the 17 * fields enclosed by brackets "[]" replaced with your own identifying 18 * information: Portions Copyright [yyyy] [name of copyright owner] 19 * 20 * CDDL HEADER END 21 */ 22 /* 23 * Copyright 2003 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 /* Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T */ 28 /* All Rights Reserved */ 29 30 /* 31 * Portions of this source code were derived from Berkeley 4.3 BSD 32 * under license from the Regents of the University of California. 33 */ 34 35 #pragma ident "%Z%%M% %I% %E% SMI" 36 37 #include <sys/types.h> 38 #include <sys/t_lock.h> 39 #include <sys/param.h> 40 #include <sys/errno.h> 41 #include <sys/fstyp.h> 42 #include <sys/kmem.h> 43 #include <sys/systm.h> 44 #include <sys/mount.h> 45 #include <sys/vfs.h> 46 #include <sys/cred.h> 47 #include <sys/vnode.h> 48 #include <sys/cmn_err.h> 49 #include <sys/debug.h> 50 #include <sys/pathname.h> 51 #include <sys/policy.h> 52 #include <sys/zone.h> 53 54 55 /* 56 * New umount() system call (for force unmount flag and perhaps others later). 57 */ 58 int 59 umount2(char *pathp, int flag) 60 { 61 struct pathname pn; 62 struct vfs *vfsp; 63 int error; 64 65 /* 66 * Some flags are disallowed through the system call interface. 67 */ 68 flag &= MS_UMOUNT_MASK; 69 70 /* 71 * Lookup user-supplied name by trying to match it against the 72 * mount points recorded at mount time. If no match is found 73 * (which can happen if the path to the mount point is specified 74 * differently between mount & umount, or if a block device were 75 * passed to umount) then we fall back to calling lookupname() 76 * to find the vfs. Doing it this way prevents calling lookupname() 77 * in most cases and that allows forcible umount to work even if 78 * lookupname() would hang (i.e. because an NFS server is dead). 79 */ 80 81 if (error = pn_get(pathp, UIO_USERSPACE, &pn)) 82 return (set_errno(error)); 83 84 /* 85 * Only a privileged user is allowed to bypass the security 86 * checks done by lookupname() and use the results from 87 * vfs_mntpoint2vfsp() instead. It could be argued that the 88 * proper check is FILE_DAC_SEARCH but we put it all 89 * under the mount privilege. Also, make sure the caller 90 * isn't in an environment with an alternate root (to the zone's root) 91 * directory, i.e. chroot(2). 92 */ 93 if (secpolicy_fs_unmount(CRED(), NULL) != 0 || 94 (PTOU(curproc)->u_rdir != NULL && 95 PTOU(curproc)->u_rdir != curproc->p_zone->zone_rootvp) || 96 (vfsp = vfs_mntpoint2vfsp(pn.pn_path)) == NULL) { 97 vnode_t *fsrootvp; 98 99 /* fall back to lookupname() on path given to us */ 100 if (error = lookupname(pn.pn_path, UIO_SYSSPACE, FOLLOW, 101 NULLVPP, &fsrootvp)) { 102 pn_free(&pn); 103 return (set_errno(error)); 104 } 105 /* 106 * Find the vfs to be unmounted. The caller may have specified 107 * either the directory mount point (preferred) or else (for a 108 * disk-based file system) the block device which was mounted. 109 * Check to see which it is; if it's the device, search the VFS 110 * list to find the associated vfs entry. 111 */ 112 if (fsrootvp->v_flag & VROOT) { 113 vfsp = fsrootvp->v_vfsp; 114 VFS_HOLD(vfsp); 115 } else if (fsrootvp->v_type == VBLK) 116 vfsp = vfs_dev2vfsp(fsrootvp->v_rdev); 117 else 118 vfsp = NULL; 119 120 VN_RELE(fsrootvp); 121 122 if (vfsp == NULL) { 123 pn_free(&pn); 124 return (set_errno(EINVAL)); 125 } 126 } 127 pn_free(&pn); 128 129 /* 130 * Protect the call to vn_vfswlock() with the vfs reflock. This 131 * ensures vfs_vnodecovered will either be NULL (because someone 132 * beat us to the umount) or valid (because vfs_lock() prevents 133 * another umount from getting through here until we've called 134 * vn_vfswlock() on the covered vnode). 135 * 136 * At one point, we did the non-blocking version (vfs_lock()), 137 * and if it failed, bailed out with EBUSY. However, dounmount() 138 * calls vfs_lock_wait() and we drop the vfs lock before calling 139 * dounmount(), so there's no difference between waiting here 140 * for the lock or waiting there because grabbed it as soon as 141 * we drop it below. No returning with EBUSY at this point 142 * reduces the number of spurious unmount failures that happen 143 * as a side-effect of fsflush() and other mount and unmount 144 * operations that might be going on simultaneously. 145 */ 146 vfs_lock_wait(vfsp); 147 148 /* 149 * Call vn_vfswlock() on the covered vnode so that dounmount() 150 * can do its thing. It will call the corresponding vn_vfsunlock(). 151 * Note that vfsp->vfs_vnodecovered can be NULL here, either because 152 * someone did umount on "/" or because someone beat us to the umount 153 * before we did the vfs_lock() above. In these cases, vn_vfswlock() 154 * returns EBUSY and we just pass that up. Also note that we're 155 * looking at a vnode without doing a VN_HOLD() on it. This is 156 * safe because it can't go away while something is mounted on it 157 * and we're locking out other umounts at this point. 158 */ 159 if (vn_vfswlock(vfsp->vfs_vnodecovered)) { 160 vfs_unlock(vfsp); 161 VFS_RELE(vfsp); 162 return (set_errno(EBUSY)); 163 } 164 165 /* 166 * Now that the VVFSLOCK in the covered vnode is protecting this 167 * path, we don't need the vfs reflock or the hold on the vfs anymore. 168 */ 169 vfs_unlock(vfsp); 170 VFS_RELE(vfsp); 171 172 /* 173 * Perform the unmount. 174 */ 175 if ((error = dounmount(vfsp, flag, CRED())) != 0) 176 return (set_errno(error)); 177 return (0); 178 } 179 180 /* 181 * Old umount() system call for compatibility. 182 * Changes due to support for forced unmount. 183 */ 184 int 185 umount(char *pathp) 186 { 187 return (umount2(pathp, 0)); 188 } 189