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 /* 23 * Copyright 2010 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 #include <sys/types.h> 36 #include <sys/t_lock.h> 37 #include <sys/param.h> 38 #include <sys/errno.h> 39 #include <sys/fstyp.h> 40 #include <sys/kmem.h> 41 #include <sys/systm.h> 42 #include <sys/mount.h> 43 #include <sys/vfs.h> 44 #include <sys/cred.h> 45 #include <sys/vnode.h> 46 #include <sys/cmn_err.h> 47 #include <sys/debug.h> 48 #include <sys/pathname.h> 49 #include <sys/policy.h> 50 #include <sys/zone.h> 51 52 #define UMOUNT2_SET_ERRNO(e, is_syscall) ((is_syscall) ? set_errno((e)) : (e)) 53 54 /* 55 * The heart of the umount2 call - it is pulled out to allow kernel 56 * level particpation when the only reference is the vfs pointer. 57 * 58 * Note that some of the callers may not be in the context of a 59 * syscall (created by zthread_create() for example) and as such 60 * may not have an associated curthread->t_lwp. This is handled 61 * by is_syscall. 62 */ 63 int 64 umount2_engine(vfs_t *vfsp, int flag, cred_t *cr, int is_syscall) 65 { 66 int error; 67 68 /* 69 * Protect the call to vn_vfswlock() with the vfs reflock. This 70 * ensures vfs_vnodecovered will either be NULL (because someone 71 * beat us to the umount) or valid (because vfs_lock() prevents 72 * another umount from getting through here until we've called 73 * vn_vfswlock() on the covered vnode). 74 * 75 * At one point, we did the non-blocking version (vfs_lock()), 76 * and if it failed, bailed out with EBUSY. However, dounmount() 77 * calls vfs_lock_wait() and we drop the vfs lock before calling 78 * dounmount(), so there's no difference between waiting here 79 * for the lock or waiting there because grabbed it as soon as 80 * we drop it below. No returning with EBUSY at this point 81 * reduces the number of spurious unmount failures that happen 82 * as a side-effect of fsflush() and other mount and unmount 83 * operations that might be going on simultaneously. 84 */ 85 vfs_lock_wait(vfsp); 86 87 /* 88 * Call vn_vfswlock() on the covered vnode so that dounmount() 89 * can do its thing. It will call the corresponding vn_vfsunlock(). 90 * Note that vfsp->vfs_vnodecovered can be NULL here, either because 91 * someone did umount on "/" or because someone beat us to the umount 92 * before we did the vfs_lock() above. In these cases, vn_vfswlock() 93 * returns EBUSY and we just pass that up. Also note that we're 94 * looking at a vnode without doing a VN_HOLD() on it. This is 95 * safe because it can't go away while something is mounted on it 96 * and we're locking out other umounts at this point. 97 */ 98 if (vn_vfswlock(vfsp->vfs_vnodecovered)) { 99 vfs_unlock(vfsp); 100 VFS_RELE(vfsp); 101 return (UMOUNT2_SET_ERRNO(EBUSY, is_syscall)); 102 } 103 104 /* 105 * Now that the VVFSLOCK in the covered vnode is protecting this 106 * path, we don't need the vfs reflock or the hold on the vfs anymore. 107 */ 108 vfs_unlock(vfsp); 109 VFS_RELE(vfsp); 110 111 /* 112 * Perform the unmount. 113 */ 114 if ((error = dounmount(vfsp, flag, cr)) != 0) 115 return (UMOUNT2_SET_ERRNO(error, is_syscall)); 116 return (0); 117 } 118 119 /* 120 * New umount() system call (for force unmount flag and perhaps others later). 121 */ 122 int 123 umount2(char *pathp, int flag) 124 { 125 struct pathname pn; 126 struct vfs *vfsp; 127 int error; 128 129 /* 130 * Some flags are disallowed through the system call interface. 131 */ 132 flag &= MS_UMOUNT_MASK; 133 134 /* 135 * Lookup user-supplied name by trying to match it against the 136 * mount points recorded at mount time. If no match is found 137 * (which can happen if the path to the mount point is specified 138 * differently between mount & umount, or if a block device were 139 * passed to umount) then we fall back to calling lookupname() 140 * to find the vfs. Doing it this way prevents calling lookupname() 141 * in most cases and that allows forcible umount to work even if 142 * lookupname() would hang (i.e. because an NFS server is dead). 143 */ 144 145 if (error = pn_get(pathp, UIO_USERSPACE, &pn)) 146 return (set_errno(error)); 147 148 /* 149 * Only a privileged user is allowed to bypass the security 150 * checks done by lookupname() and use the results from 151 * vfs_mntpoint2vfsp() instead. It could be argued that the 152 * proper check is FILE_DAC_SEARCH but we put it all 153 * under the mount privilege. Also, make sure the caller 154 * isn't in an environment with an alternate root (to the zone's root) 155 * directory, i.e. chroot(2). 156 */ 157 if (secpolicy_fs_unmount(CRED(), NULL) != 0 || 158 (PTOU(curproc)->u_rdir != NULL && 159 PTOU(curproc)->u_rdir != curproc->p_zone->zone_rootvp) || 160 (vfsp = vfs_mntpoint2vfsp(pn.pn_path)) == NULL) { 161 vnode_t *fsrootvp; 162 163 /* fall back to lookupname() on path given to us */ 164 if (error = lookupname(pn.pn_path, UIO_SYSSPACE, FOLLOW, 165 NULLVPP, &fsrootvp)) { 166 pn_free(&pn); 167 return (set_errno(error)); 168 } 169 /* 170 * Find the vfs to be unmounted. The caller may have specified 171 * either the directory mount point (preferred) or else (for a 172 * disk-based file system) the block device which was mounted. 173 * Check to see which it is; if it's the device, search the VFS 174 * list to find the associated vfs entry. 175 */ 176 if (fsrootvp->v_flag & VROOT) { 177 vfsp = fsrootvp->v_vfsp; 178 VFS_HOLD(vfsp); 179 } else if (fsrootvp->v_type == VBLK) 180 vfsp = vfs_dev2vfsp(fsrootvp->v_rdev); 181 else 182 vfsp = NULL; 183 184 VN_RELE(fsrootvp); 185 186 if (vfsp == NULL) { 187 pn_free(&pn); 188 return (set_errno(EINVAL)); 189 } 190 } 191 pn_free(&pn); 192 193 return (umount2_engine(vfsp, flag, CRED(), 1)); 194 } 195