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 #include "lint.h"
31 #include <sys/types.h>
32 #include <stdio.h>
33 #include <signal.h>
34 #include <fcntl.h>
35 #include <unistd.h>
36 #include <shadow.h>
37 #include <errno.h>
38 #include <thread.h>
39 #include "mtlib.h"
40
41 #define LOCKFILE "/etc/.pwd.lock"
42 #define S_WAITTIME 15
43
44 static struct flock flock = {
45 0, /* l_type */
46 0, /* l_whence */
47 0, /* l_start */
48 0, /* l_len */
49 0, /* l_sysid */
50 0 /* l_pid */
51 };
52
53 /*
54 * lckpwdf() returns a 0 for a successful lock within W_WAITTIME
55 * seconds and -1 otherwise. We stand on our head to make it MT-safe.
56 */
57
58 static pid_t lck_pid = 0; /* process's pid at last lock */
59 static thread_t lck_tid = 0; /* thread that holds the lock */
60 static int fildes = -1;
61 static mutex_t lck_lock = DEFAULTMUTEX;
62
63 int
lckpwdf(void)64 lckpwdf(void)
65 {
66 int seconds = 0;
67
68 lmutex_lock(&lck_lock);
69 for (;;) {
70 if (lck_pid != 0 && lck_pid != getpid()) {
71 /* somebody forked */
72 lck_pid = 0;
73 lck_tid = 0;
74 }
75 if (lck_tid == 0) {
76 if ((fildes = creat(LOCKFILE, 0600)) == -1)
77 break;
78 flock.l_type = F_WRLCK;
79 if (fcntl(fildes, F_SETLK, &flock) != -1) {
80 lck_pid = getpid();
81 lck_tid = thr_self();
82 lmutex_unlock(&lck_lock);
83 return (0);
84 }
85 (void) close(fildes);
86 fildes = -1;
87 }
88 if (seconds++ >= S_WAITTIME) {
89 /*
90 * For compatibility with the past, pretend
91 * that we were interrupted by SIGALRM.
92 */
93 errno = EINTR;
94 break;
95 }
96 lmutex_unlock(&lck_lock);
97 (void) sleep(1);
98 lmutex_lock(&lck_lock);
99 }
100 lmutex_unlock(&lck_lock);
101 return (-1);
102 }
103
104 /*
105 * ulckpwdf() returns 0 for a successful unlock and -1 otherwise
106 */
107 int
ulckpwdf(void)108 ulckpwdf(void)
109 {
110 lmutex_lock(&lck_lock);
111 if (lck_tid == thr_self() && fildes >= 0) {
112 flock.l_type = F_UNLCK;
113 (void) fcntl(fildes, F_SETLK, &flock);
114 (void) close(fildes);
115 fildes = -1;
116 lck_pid = 0;
117 lck_tid = 0;
118 lmutex_unlock(&lck_lock);
119 return (0);
120 }
121 lmutex_unlock(&lck_lock);
122 return (-1);
123 }
124