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 (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 /* 22 * Copyright 2007 Sun Microsystems, Inc. All rights reserved. 23 * Use is subject to license terms. 24 */ 25 26 /* Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T */ 27 /* All Rights Reserved */ 28 29 /* 30 * Portions of this source code were derived from Berkeley 4.3 BSD 31 * under license from the Regents of the University of California. 32 */ 33 34 #pragma ident "%Z%%M% %I% %E% SMI" 35 36 #include <sys/types.h> 37 #include <sys/t_lock.h> 38 #include <sys/param.h> 39 #include <sys/errno.h> 40 #include <sys/fstyp.h> 41 #include <sys/kmem.h> 42 #include <sys/systm.h> 43 #include <sys/mount.h> 44 #include <sys/vfs.h> 45 #include <sys/cred.h> 46 #include <sys/vnode.h> 47 #include <sys/cmn_err.h> 48 #include <sys/debug.h> 49 #include <sys/pathname.h> 50 #include <sys/policy.h> 51 #include <sys/zone.h> 52 53 #define UMOUNT2_SET_ERRNO(e, is_syscall) ((is_syscall) ? set_errno((e)) : (e)) 54 55 /* 56 * The heart of the umount2 call - it is pulled out to allow kernel 57 * level particpation when the only reference is the vfs pointer. 58 * 59 * Note that some of the callers may not be in the context of a 60 * syscall (created by zthread_create() for example) and as such 61 * may not have an associated curthread->t_lwp. This is handled 62 * by is_syscall. 63 */ 64 int 65 umount2_engine(vfs_t *vfsp, int flag, cred_t *cr, int is_syscall) 66 { 67 int error; 68 69 /* 70 * Protect the call to vn_vfswlock() with the vfs reflock. This 71 * ensures vfs_vnodecovered will either be NULL (because someone 72 * beat us to the umount) or valid (because vfs_lock() prevents 73 * another umount from getting through here until we've called 74 * vn_vfswlock() on the covered vnode). 75 * 76 * At one point, we did the non-blocking version (vfs_lock()), 77 * and if it failed, bailed out with EBUSY. However, dounmount() 78 * calls vfs_lock_wait() and we drop the vfs lock before calling 79 * dounmount(), so there's no difference between waiting here 80 * for the lock or waiting there because grabbed it as soon as 81 * we drop it below. No returning with EBUSY at this point 82 * reduces the number of spurious unmount failures that happen 83 * as a side-effect of fsflush() and other mount and unmount 84 * operations that might be going on simultaneously. 85 */ 86 vfs_lock_wait(vfsp); 87 88 /* 89 * Call vn_vfswlock() on the covered vnode so that dounmount() 90 * can do its thing. It will call the corresponding vn_vfsunlock(). 91 * Note that vfsp->vfs_vnodecovered can be NULL here, either because 92 * someone did umount on "/" or because someone beat us to the umount 93 * before we did the vfs_lock() above. In these cases, vn_vfswlock() 94 * returns EBUSY and we just pass that up. Also note that we're 95 * looking at a vnode without doing a VN_HOLD() on it. This is 96 * safe because it can't go away while something is mounted on it 97 * and we're locking out other umounts at this point. 98 */ 99 if (vn_vfswlock(vfsp->vfs_vnodecovered)) { 100 vfs_unlock(vfsp); 101 VFS_RELE(vfsp); 102 return (UMOUNT2_SET_ERRNO(EBUSY, is_syscall)); 103 } 104 105 /* 106 * Now that the VVFSLOCK in the covered vnode is protecting this 107 * path, we don't need the vfs reflock or the hold on the vfs anymore. 108 */ 109 vfs_unlock(vfsp); 110 VFS_RELE(vfsp); 111 112 /* 113 * Perform the unmount. 114 */ 115 if ((error = dounmount(vfsp, flag, cr)) != 0) 116 return (UMOUNT2_SET_ERRNO(error, is_syscall)); 117 return (0); 118 } 119 120 /* 121 * New umount() system call (for force unmount flag and perhaps others later). 122 */ 123 int 124 umount2(char *pathp, int flag) 125 { 126 struct pathname pn; 127 struct vfs *vfsp; 128 int error; 129 130 /* 131 * Some flags are disallowed through the system call interface. 132 */ 133 flag &= MS_UMOUNT_MASK; 134 135 /* 136 * Lookup user-supplied name by trying to match it against the 137 * mount points recorded at mount time. If no match is found 138 * (which can happen if the path to the mount point is specified 139 * differently between mount & umount, or if a block device were 140 * passed to umount) then we fall back to calling lookupname() 141 * to find the vfs. Doing it this way prevents calling lookupname() 142 * in most cases and that allows forcible umount to work even if 143 * lookupname() would hang (i.e. because an NFS server is dead). 144 */ 145 146 if (error = pn_get(pathp, UIO_USERSPACE, &pn)) 147 return (set_errno(error)); 148 149 /* 150 * Only a privileged user is allowed to bypass the security 151 * checks done by lookupname() and use the results from 152 * vfs_mntpoint2vfsp() instead. It could be argued that the 153 * proper check is FILE_DAC_SEARCH but we put it all 154 * under the mount privilege. Also, make sure the caller 155 * isn't in an environment with an alternate root (to the zone's root) 156 * directory, i.e. chroot(2). 157 */ 158 if (secpolicy_fs_unmount(CRED(), NULL) != 0 || 159 (PTOU(curproc)->u_rdir != NULL && 160 PTOU(curproc)->u_rdir != curproc->p_zone->zone_rootvp) || 161 (vfsp = vfs_mntpoint2vfsp(pn.pn_path)) == NULL) { 162 vnode_t *fsrootvp; 163 164 /* fall back to lookupname() on path given to us */ 165 if (error = lookupname(pn.pn_path, UIO_SYSSPACE, FOLLOW, 166 NULLVPP, &fsrootvp)) { 167 pn_free(&pn); 168 return (set_errno(error)); 169 } 170 /* 171 * Find the vfs to be unmounted. The caller may have specified 172 * either the directory mount point (preferred) or else (for a 173 * disk-based file system) the block device which was mounted. 174 * Check to see which it is; if it's the device, search the VFS 175 * list to find the associated vfs entry. 176 */ 177 if (fsrootvp->v_flag & VROOT) { 178 vfsp = fsrootvp->v_vfsp; 179 VFS_HOLD(vfsp); 180 } else if (fsrootvp->v_type == VBLK) 181 vfsp = vfs_dev2vfsp(fsrootvp->v_rdev); 182 else 183 vfsp = NULL; 184 185 VN_RELE(fsrootvp); 186 187 if (vfsp == NULL) { 188 pn_free(&pn); 189 return (set_errno(EINVAL)); 190 } 191 } 192 pn_free(&pn); 193 194 return (umount2_engine(vfsp, flag, CRED(), 1)); 195 } 196 197 /* 198 * Old umount() system call for compatibility. 199 * Changes due to support for forced unmount. 200 */ 201 int 202 umount(char *pathp) 203 { 204 return (umount2(pathp, 0)); 205 } 206