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
umount2_engine(vfs_t * vfsp,int flag,cred_t * cr,int is_syscall)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
umount2(char * pathp,int flag)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