1 /* $OpenBSD: uucplock.c,v 1.11 2006/03/16 19:32:46 deraadt Exp $ */
2 /* $NetBSD: uucplock.c,v 1.7 1997/02/11 09:24:08 mrg Exp $ */
3
4 /*-
5 * SPDX-License-Identifier: BSD-3-Clause
6 *
7 * Copyright (c) 1988, 1993
8 * The Regents of the University of California. All rights reserved.
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
35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD$");
37
38 #ifndef lint
39 #if 0
40 static char sccsid[] = "@(#)uucplock.c 8.1 (Berkeley) 6/6/93";
41 static const char rcsid[] = "$OpenBSD: uucplock.c,v 1.11 2006/03/16 19:32:46 deraadt Exp $";
42 #endif
43 #endif /* not lint */
44
45 #include <sys/types.h>
46 #include <sys/file.h>
47 #include <sys/dirent.h>
48 #include <stdio.h>
49 #include <string.h>
50 #include <signal.h>
51 #include <unistd.h>
52 #include <stdlib.h>
53 #include <errno.h>
54 #include "tip.h"
55 #include "pathnames.h"
56
57 /*
58 * uucp style locking routines
59 * return: 0 - success
60 * -1 - failure
61 */
62
63 int
uu_lock(char * ttyname)64 uu_lock(char *ttyname)
65 {
66 int fd, len;
67 char tbuf[sizeof(_PATH_LOCKDIRNAME) + MAXNAMLEN];
68 char text_pid[81];
69 pid_t pid;
70
71 (void)snprintf(tbuf, sizeof tbuf, _PATH_LOCKDIRNAME, ttyname);
72 fd = open(tbuf, O_RDWR|O_CREAT|O_EXCL, 0660);
73 if (fd < 0) {
74 /*
75 * file is already locked
76 * check to see if the process holding the lock still exists
77 */
78 fd = open(tbuf, O_RDWR, 0);
79 if (fd < 0) {
80 perror(tbuf);
81 fprintf(stderr, "Can't open lock file.\n");
82 return(-1);
83 }
84 len = read(fd, text_pid, sizeof(text_pid)-1);
85 if (len<=0) {
86 perror(tbuf);
87 (void)close(fd);
88 fprintf(stderr, "Can't read lock file.\n");
89 return(-1);
90 }
91 text_pid[len] = 0;
92 pid = atol(text_pid);
93
94 if (kill(pid, 0) == 0 || errno != ESRCH) {
95 (void)close(fd); /* process is still running */
96 return(-1);
97 }
98 /*
99 * The process that locked the file isn't running, so
100 * we'll lock it ourselves
101 */
102 fprintf(stderr, "Stale lock on %s PID=%ld... overriding.\n",
103 ttyname, (long)pid);
104 if (lseek(fd, (off_t)0, SEEK_SET) < 0) {
105 perror(tbuf);
106 (void)close(fd);
107 fprintf(stderr, "Can't seek lock file.\n");
108 return(-1);
109 }
110 /* fall out and finish the locking process */
111 }
112 pid = getpid();
113 (void)snprintf(text_pid, sizeof text_pid, "%10ld\n", (long)pid);
114 len = strlen(text_pid);
115 if (write(fd, text_pid, len) != len) {
116 (void)close(fd);
117 (void)unlink(tbuf);
118 perror("lock write");
119 return(-1);
120 }
121 (void)close(fd);
122 return(0);
123 }
124
125 int
uu_unlock(char * ttyname)126 uu_unlock(char *ttyname)
127 {
128 char tbuf[sizeof(_PATH_LOCKDIRNAME) + MAXNAMLEN];
129
130 (void)snprintf(tbuf, sizeof tbuf, _PATH_LOCKDIRNAME, ttyname);
131 unexcl();
132 return(unlink(tbuf));
133 }
134