1 /*
2 * Copyright (c) 1982, 1986, 1989, 1993
3 * The Regents of the University of California. All rights reserved.
4 * (c) UNIX System Laboratories, Inc.
5 * All or some portions of this file are derived from material licensed
6 * to the University of California by American Telephone and Telegraph
7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
8 * the permission of UNIX System Laboratories, Inc.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 *
34 * @(#)vfs_lookup.c 8.4 (Berkeley) 2/16/94
35 * $FreeBSD: src/sys/kern/vfs_lookup.c,v 1.38.2.3 2001/08/31 19:36:49 dillon Exp $
36 */
37
38 #include "opt_ktrace.h"
39
40 #include <sys/param.h>
41 #include <sys/systm.h>
42 #include <sys/kernel.h>
43 #include <sys/vnode.h>
44 #include <sys/mount.h>
45 #include <sys/filedesc.h>
46 #include <sys/proc.h>
47 #include <sys/namei.h>
48 #include <sys/sysctl.h>
49
50 #ifdef KTRACE
51 #include <sys/ktrace.h>
52 #endif
53
54 #include <vm/vm_zone.h>
55
56 int varsym_enable = 0;
57 SYSCTL_INT(_vfs, OID_AUTO, varsym_enable, CTLFLAG_RW, &varsym_enable, 0,
58 "Enable Variant Symlinks");
59
60 /*
61 * OLD API FUNCTION
62 *
63 * Relookup a path name component. This function is only used by the
64 * old API *_rename() code under very specific conditions. CNP_LOCKPARENT
65 * must be set in the cnp. dvp must be unlocked on entry and will be left
66 * unlocked if an error occurs.
67 *
68 * The returned *vpp will be NULL if an error occurs. Note that no error
69 * will occur (error == 0) for CREATE requests on a non-existant target, but
70 * *vpp will be NULL in that case. Both dvp and *vpp (if not NULL) will be
71 * locked in the no-error case. No additional references are made to dvp,
72 * only the locking state changes.
73 */
74 int
relookup(struct vnode * dvp,struct vnode ** vpp,struct componentname * cnp)75 relookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp)
76 {
77 int rdonly; /* lookup read-only flag bit */
78 int error = 0;
79
80 /*
81 * Setup: break out flag bits into variables.
82 */
83 KKASSERT(cnp->cn_flags & CNP_LOCKPARENT);
84 KKASSERT(cnp->cn_flags & CNP_PDIRUNLOCK);
85 vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY);
86 cnp->cn_flags &= ~CNP_PDIRUNLOCK;
87
88 *vpp = NULL;
89 rdonly = cnp->cn_flags & CNP_RDONLY;
90
91 /*
92 * Search a new directory.
93 */
94
95 /*
96 * Degenerate lookups (e.g. "/", "..", derived from "/.", etc)
97 * are not allowed.
98 */
99 if (cnp->cn_nameptr[0] == '\0') {
100 error = EISDIR;
101 goto bad;
102 }
103 if (cnp->cn_flags & CNP_ISDOTDOT)
104 panic ("relookup: lookup on dot-dot");
105
106 /*
107 * We now have a segment name to search for, and a directory to search.
108 */
109 if ((error = VOP_OLD_LOOKUP(dvp, vpp, cnp)) != 0) {
110 KASSERT(*vpp == NULL, ("leaf should be empty"));
111 if (error != EJUSTRETURN)
112 goto bad;
113 /*
114 * If creating and at end of pathname, then can consider
115 * allowing file to be created.
116 */
117 if (rdonly) {
118 error = EROFS;
119 goto bad;
120 }
121 /*
122 * We return with ni_vp NULL to indicate that the entry
123 * doesn't currently exist, leaving a pointer to the
124 * (possibly locked) directory inode in ndp->ni_dvp.
125 */
126 return (0);
127 }
128
129 /*
130 * Check for symbolic link
131 */
132 KASSERT((*vpp)->v_type != VLNK || !(cnp->cn_flags & CNP_FOLLOW),
133 ("relookup: symlink found."));
134
135 /*
136 * Disallow directory write attempts on read-only file systems.
137 */
138 if (rdonly && (cnp->cn_nameiop == NAMEI_DELETE ||
139 cnp->cn_nameiop == NAMEI_RENAME)) {
140 error = EROFS;
141 goto bad;
142 }
143 KKASSERT((cnp->cn_flags & CNP_PDIRUNLOCK) == 0);
144 return (0);
145
146 bad:
147 if ((cnp->cn_flags & CNP_PDIRUNLOCK) == 0) {
148 cnp->cn_flags |= CNP_PDIRUNLOCK;
149 vn_unlock(dvp);
150 }
151 if (*vpp) {
152 vput(*vpp);
153 *vpp = NULL;
154 }
155 return (error);
156 }
157
158