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 2008 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 */
26
27 /* Copyright (c) 1988 AT&T */
28 /* All Rights Reserved */
29
30 #pragma ident "%Z%%M% %I% %E% SMI"
31
32 #include "lint.h"
33 #include <sys/types.h>
34 #include <stdio.h>
35 #include <signal.h>
36 #include <fcntl.h>
37 #include <unistd.h>
38 #include <shadow.h>
39 #include <errno.h>
40 #include <thread.h>
41 #include "mtlib.h"
42
43 #define LOCKFILE "/etc/.pwd.lock"
44 #define S_WAITTIME 15
45
46 static struct flock flock = {
47 0, /* l_type */
48 0, /* l_whence */
49 0, /* l_start */
50 0, /* l_len */
51 0, /* l_sysid */
52 0 /* l_pid */
53 };
54
55 /*
56 * lckpwdf() returns a 0 for a successful lock within W_WAITTIME
57 * seconds and -1 otherwise. We stand on our head to make it MT-safe.
58 */
59
60 static pid_t lck_pid = 0; /* process's pid at last lock */
61 static thread_t lck_tid = 0; /* thread that holds the lock */
62 static int fildes = -1;
63 static mutex_t lck_lock = DEFAULTMUTEX;
64
65 int
lckpwdf(void)66 lckpwdf(void)
67 {
68 int seconds = 0;
69
70 lmutex_lock(&lck_lock);
71 for (;;) {
72 if (lck_pid != 0 && lck_pid != getpid()) {
73 /* somebody forked */
74 lck_pid = 0;
75 lck_tid = 0;
76 }
77 if (lck_tid == 0) {
78 if ((fildes = creat(LOCKFILE, 0600)) == -1)
79 break;
80 flock.l_type = F_WRLCK;
81 if (fcntl(fildes, F_SETLK, &flock) != -1) {
82 lck_pid = getpid();
83 lck_tid = thr_self();
84 lmutex_unlock(&lck_lock);
85 return (0);
86 }
87 (void) close(fildes);
88 fildes = -1;
89 }
90 if (seconds++ >= S_WAITTIME) {
91 /*
92 * For compatibility with the past, pretend
93 * that we were interrupted by SIGALRM.
94 */
95 errno = EINTR;
96 break;
97 }
98 lmutex_unlock(&lck_lock);
99 (void) sleep(1);
100 lmutex_lock(&lck_lock);
101 }
102 lmutex_unlock(&lck_lock);
103 return (-1);
104 }
105
106 /*
107 * ulckpwdf() returns 0 for a successful unlock and -1 otherwise
108 */
109 int
ulckpwdf(void)110 ulckpwdf(void)
111 {
112 lmutex_lock(&lck_lock);
113 if (lck_tid == thr_self() && fildes >= 0) {
114 flock.l_type = F_UNLCK;
115 (void) fcntl(fildes, F_SETLK, &flock);
116 (void) close(fildes);
117 fildes = -1;
118 lck_pid = 0;
119 lck_tid = 0;
120 lmutex_unlock(&lck_lock);
121 return (0);
122 }
123 lmutex_unlock(&lck_lock);
124 return (-1);
125 }
126