1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1988, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32
33 #include <sys/types.h>
34 #include <sys/file.h>
35 #include <dirent.h>
36 #include <errno.h>
37 #include <paths.h>
38 #include <signal.h>
39 #include <stdio.h>
40 #include <stdlib.h>
41 #include <string.h>
42 #include <unistd.h>
43 #include "libutil.h"
44
45 #define MAXTRIES 5
46
47 #define LOCKTMP "LCKTMP..%d"
48 #define LOCKFMT "LCK..%s"
49
50 #define GORET(level, val) { err = errno; uuerr = (val); \
51 goto __CONCAT(ret, level); }
52
53 /* Forward declarations */
54 static int put_pid (int fd, pid_t pid);
55 static pid_t get_pid (int fd,int *err);
56
57 /*
58 * uucp style locking routines
59 */
60
61 int
uu_lock(const char * tty_name)62 uu_lock(const char *tty_name)
63 {
64 int fd, tmpfd, i;
65 pid_t pid, pid_old;
66 char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN],
67 lcktmpname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
68 int err, uuerr;
69
70 pid = getpid();
71 (void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP,
72 pid);
73 (void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT,
74 tty_name);
75 if ((tmpfd = open(lcktmpname, O_CREAT | O_TRUNC | O_WRONLY | O_CLOEXEC,
76 0664)) < 0)
77 GORET(0, UU_LOCK_CREAT_ERR);
78
79 for (i = 0; i < MAXTRIES; i++) {
80 if (link (lcktmpname, lckname) < 0) {
81 if (errno != EEXIST)
82 GORET(1, UU_LOCK_LINK_ERR);
83 /*
84 * file is already locked
85 * check to see if the process holding the lock
86 * still exists
87 */
88 if ((fd = open(lckname, O_RDONLY | O_CLOEXEC)) < 0)
89 GORET(1, UU_LOCK_OPEN_ERR);
90
91 if ((pid_old = get_pid (fd, &err)) == -1)
92 GORET(2, UU_LOCK_READ_ERR);
93
94 close(fd);
95
96 if (kill(pid_old, 0) == 0 || errno != ESRCH)
97 GORET(1, UU_LOCK_INUSE);
98 /*
99 * The process that locked the file isn't running, so
100 * we'll lock it ourselves
101 */
102 (void)unlink(lckname);
103 } else {
104 if (!put_pid (tmpfd, pid))
105 GORET(3, UU_LOCK_WRITE_ERR);
106 break;
107 }
108 }
109 GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK);
110
111 ret3:
112 (void)unlink(lckname);
113 goto ret1;
114 ret2:
115 (void)close(fd);
116 ret1:
117 (void)close(tmpfd);
118 (void)unlink(lcktmpname);
119 ret0:
120 errno = err;
121 return uuerr;
122 }
123
124 int
uu_lock_txfr(const char * tty_name,pid_t pid)125 uu_lock_txfr(const char *tty_name, pid_t pid)
126 {
127 int fd, err;
128 char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
129
130 snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, tty_name);
131
132 if ((fd = open(lckname, O_RDWR | O_CLOEXEC)) < 0)
133 return UU_LOCK_OWNER_ERR;
134 if (get_pid(fd, &err) != getpid())
135 err = UU_LOCK_OWNER_ERR;
136 else {
137 lseek(fd, (off_t)0, SEEK_SET);
138 err = put_pid(fd, pid) ? 0 : UU_LOCK_WRITE_ERR;
139 }
140 close(fd);
141
142 return err;
143 }
144
145 int
uu_unlock(const char * tty_name)146 uu_unlock(const char *tty_name)
147 {
148 char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
149
150 (void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, tty_name);
151 return unlink(tbuf);
152 }
153
154 const char *
uu_lockerr(int uu_lockresult)155 uu_lockerr(int uu_lockresult)
156 {
157 static char errbuf[128];
158 const char *fmt;
159
160 switch (uu_lockresult) {
161 case UU_LOCK_INUSE:
162 return "device in use";
163 case UU_LOCK_OK:
164 return "";
165 case UU_LOCK_OPEN_ERR:
166 fmt = "open error: %s";
167 break;
168 case UU_LOCK_READ_ERR:
169 fmt = "read error: %s";
170 break;
171 case UU_LOCK_CREAT_ERR:
172 fmt = "creat error: %s";
173 break;
174 case UU_LOCK_WRITE_ERR:
175 fmt = "write error: %s";
176 break;
177 case UU_LOCK_LINK_ERR:
178 fmt = "link error: %s";
179 break;
180 case UU_LOCK_TRY_ERR:
181 fmt = "too many tries: %s";
182 break;
183 case UU_LOCK_OWNER_ERR:
184 fmt = "not locking process: %s";
185 break;
186 default:
187 fmt = "undefined error: %s";
188 break;
189 }
190
191 (void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno));
192 return errbuf;
193 }
194
195 static int
put_pid(int fd,pid_t pid)196 put_pid(int fd, pid_t pid)
197 {
198 char buf[32];
199 int len;
200
201 len = sprintf (buf, "%10d\n", (int)pid);
202 return write (fd, buf, (size_t)len) == len;
203 }
204
205 static pid_t
get_pid(int fd,int * err)206 get_pid(int fd, int *err)
207 {
208 int bytes_read;
209 char buf[32];
210 pid_t pid;
211
212 bytes_read = read (fd, buf, sizeof (buf) - 1);
213 if (bytes_read > 0) {
214 buf[bytes_read] = '\0';
215 pid = (pid_t)strtol (buf, (char **) NULL, 10);
216 } else {
217 pid = -1;
218 *err = bytes_read ? errno : EINVAL;
219 }
220 return pid;
221 }
222
223 /* end of uucplock.c */
224