| 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. All advertising materials mentioning features or use of this software |
| 19 | * must display the following acknowledgement: |
| 20 | * This product includes software developed by the University of |
| 21 | * California, Berkeley and its contributors. |
| 22 | * 4. Neither the name of the University nor the names of its contributors |
| 23 | * may be used to endorse or promote products derived from this software |
| 24 | * without specific prior written permission. |
| 25 | * |
| 26 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
| 27 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 28 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 29 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
| 30 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| 31 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| 32 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 33 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| 34 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| 35 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| 36 | * SUCH DAMAGE. |
| 37 | * |
| 38 | * @(#)vfs_lookup.c 8.4 (Berkeley) 2/16/94 |
| 39 | * $FreeBSD: src/sys/kern/vfs_lookup.c,v 1.38.2.3 2001/08/31 19:36:49 dillon Exp $ |
| 40 | * $DragonFly: src/sys/kern/vfs_lookup.c,v 1.22 2006/05/05 21:15:09 dillon Exp $ |
| 41 | */ |
| 42 | |
| 43 | #include "opt_ktrace.h" |
| 44 | |
| 45 | #include <sys/param.h> |
| 46 | #include <sys/systm.h> |
| 47 | #include <sys/kernel.h> |
| 48 | #include <sys/vnode.h> |
| 49 | #include <sys/mount.h> |
| 50 | #include <sys/filedesc.h> |
| 51 | #include <sys/proc.h> |
| 52 | #include <sys/namei.h> |
| 53 | #include <sys/sysctl.h> |
| 54 | |
| 55 | #ifdef KTRACE |
| 56 | #include <sys/ktrace.h> |
| 57 | #endif |
| 58 | |
| 59 | #include <vm/vm_zone.h> |
| 60 | |
| 61 | int varsym_enable = 0; |
| 62 | SYSCTL_INT(_vfs, OID_AUTO, varsym_enable, CTLFLAG_RW, &varsym_enable, 0, |
| 63 | "Enable Variant Symlinks"); |
| 64 | |
| 65 | /* |
| 66 | * OLD API FUNCTION |
| 67 | * |
| 68 | * Relookup a path name component. This function is only used by the |
| 69 | * old API *_rename() code under very specific conditions. CNP_LOCKPARENT |
| 70 | * must be set in the cnp. dvp must be unlocked on entry and will be left |
| 71 | * unlocked if an error occurs. |
| 72 | * |
| 73 | * The returned *vpp will be NULL if an error occurs. Note that no error |
| 74 | * will occur (error == 0) for CREATE requests on a non-existant target, but |
| 75 | * *vpp will be NULL in that case. Both dvp and *vpp (if not NULL) will be |
| 76 | * locked in the no-error case. No additional references are made to dvp, |
| 77 | * only the locking state changes. |
| 78 | */ |
| 79 | int |
| 80 | relookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp) |
| 81 | { |
| 82 | int rdonly; /* lookup read-only flag bit */ |
| 83 | int error = 0; |
| 84 | |
| 85 | /* |
| 86 | * Setup: break out flag bits into variables. |
| 87 | */ |
| 88 | KKASSERT(cnp->cn_flags & CNP_LOCKPARENT); |
| 89 | KKASSERT(cnp->cn_flags & CNP_PDIRUNLOCK); |
| 90 | vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY); |
| 91 | cnp->cn_flags &= ~CNP_PDIRUNLOCK; |
| 92 | |
| 93 | *vpp = NULL; |
| 94 | rdonly = cnp->cn_flags & CNP_RDONLY; |
| 95 | |
| 96 | /* |
| 97 | * Search a new directory. |
| 98 | */ |
| 99 | |
| 100 | /* |
| 101 | * Degenerate lookups (e.g. "/", "..", derived from "/.", etc) |
| 102 | * are not allowed. |
| 103 | */ |
| 104 | if (cnp->cn_nameptr[0] == '\0') { |
| 105 | error = EISDIR; |
| 106 | goto bad; |
| 107 | } |
| 108 | if (cnp->cn_flags & CNP_ISDOTDOT) |
| 109 | panic ("relookup: lookup on dot-dot"); |
| 110 | |
| 111 | /* |
| 112 | * We now have a segment name to search for, and a directory to search. |
| 113 | */ |
| 114 | if ((error = VOP_OLD_LOOKUP(dvp, vpp, cnp)) != 0) { |
| 115 | KASSERT(*vpp == NULL, ("leaf should be empty")); |
| 116 | if (error != EJUSTRETURN) |
| 117 | goto bad; |
| 118 | /* |
| 119 | * If creating and at end of pathname, then can consider |
| 120 | * allowing file to be created. |
| 121 | */ |
| 122 | if (rdonly) { |
| 123 | error = EROFS; |
| 124 | goto bad; |
| 125 | } |
| 126 | /* |
| 127 | * We return with ni_vp NULL to indicate that the entry |
| 128 | * doesn't currently exist, leaving a pointer to the |
| 129 | * (possibly locked) directory inode in ndp->ni_dvp. |
| 130 | */ |
| 131 | return (0); |
| 132 | } |
| 133 | |
| 134 | /* |
| 135 | * Check for symbolic link |
| 136 | */ |
| 137 | KASSERT((*vpp)->v_type != VLNK || !(cnp->cn_flags & CNP_FOLLOW), |
| 138 | ("relookup: symlink found.\n")); |
| 139 | |
| 140 | /* |
| 141 | * Disallow directory write attempts on read-only file systems. |
| 142 | */ |
| 143 | if (rdonly && (cnp->cn_nameiop == NAMEI_DELETE || |
| 144 | cnp->cn_nameiop == NAMEI_RENAME)) { |
| 145 | error = EROFS; |
| 146 | goto bad; |
| 147 | } |
| 148 | KKASSERT((cnp->cn_flags & CNP_PDIRUNLOCK) == 0); |
| 149 | return (0); |
| 150 | |
| 151 | bad: |
| 152 | if ((cnp->cn_flags & CNP_PDIRUNLOCK) == 0) { |
| 153 | cnp->cn_flags |= CNP_PDIRUNLOCK; |
| 154 | VOP_UNLOCK(dvp, 0); |
| 155 | } |
| 156 | if (*vpp) { |
| 157 | vput(*vpp); |
| 158 | *vpp = NULL; |
| 159 | } |
| 160 | return (error); |
| 161 | } |
| 162 | |