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 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 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 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 * 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 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 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