1 /* $OpenBSD: uucplock.c,v 1.15 2006/03/30 20:56:54 deraadt Exp $ */ 2 /* 3 * Copyright (c) 1988, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. Neither the name of the University nor the names of its contributors 15 * may be used to endorse or promote products derived from this software 16 * without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 * 30 * 31 */ 32 33 #ifndef lint 34 static const char sccsid[] = "@(#)uucplock.c 8.1 (Berkeley) 6/6/93"; 35 #endif /* not lint */ 36 37 #include <sys/types.h> 38 #include <dirent.h> 39 #include <errno.h> 40 #include <fcntl.h> 41 #include <unistd.h> 42 #include <signal.h> 43 #include <stdio.h> 44 #include <stdlib.h> 45 #include <paths.h> 46 #include <string.h> 47 #include "util.h" 48 49 #define MAXTRIES 5 50 51 #define LOCKTMP "LCKTMP..%ld" 52 #define LOCKFMT "LCK..%s" 53 54 #define GORET(level, val) { err = errno; uuerr = (val); \ 55 goto __CONCAT(ret, level); } 56 57 /* Forward declarations */ 58 static int put_pid(int fd, pid_t pid); 59 static pid_t get_pid(int fd,int *err); 60 61 /* 62 * uucp style locking routines 63 */ 64 int 65 uu_lock(const char *ttyname) 66 { 67 char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN], 68 lcktmpname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN]; 69 int fd, tmpfd, i, err, uuerr; 70 pid_t pid, pid_old; 71 72 pid = getpid(); 73 (void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP, 74 (long)pid); 75 (void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, 76 ttyname); 77 if ((tmpfd = creat(lcktmpname, 0664)) < 0) 78 GORET(0, UU_LOCK_CREAT_ERR); 79 80 for (i = 0; i < MAXTRIES; i++) { 81 if (link(lcktmpname, lckname) < 0) { 82 if (errno != EEXIST) 83 GORET(1, UU_LOCK_LINK_ERR); 84 /* 85 * file is already locked 86 * check to see if the process holding the lock 87 * still exists 88 */ 89 if ((fd = open(lckname, O_RDONLY)) < 0) 90 GORET(1, UU_LOCK_OPEN_ERR); 91 92 if ((pid_old = get_pid(fd, &err)) == -1) 93 GORET(2, UU_LOCK_READ_ERR); 94 95 close(fd); 96 97 if (kill(pid_old, 0) == 0 || errno != ESRCH) 98 GORET(1, UU_LOCK_INUSE); 99 /* 100 * The process that locked the file isn't running, so 101 * we'll lock it ourselves 102 */ 103 (void)unlink(lckname); 104 } else { 105 if (!put_pid(tmpfd, pid)) 106 GORET(3, UU_LOCK_WRITE_ERR); 107 break; 108 } 109 } 110 GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK); 111 112 ret3: 113 (void)unlink(lckname); 114 goto ret1; 115 ret2: 116 (void)close(fd); 117 ret1: 118 (void)close(tmpfd); 119 (void)unlink(lcktmpname); 120 ret0: 121 errno = err; 122 return uuerr; 123 } 124 125 int 126 uu_lock_txfr(const char *ttyname, pid_t pid) 127 { 128 char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN]; 129 int fd, err, ret; 130 131 snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, ttyname); 132 133 if ((fd = open(lckname, O_RDWR)) < 0) 134 return UU_LOCK_OWNER_ERR; 135 if (get_pid(fd, &err) != getpid()) 136 ret = UU_LOCK_OWNER_ERR; 137 else { 138 lseek(fd, 0, SEEK_SET); 139 ret = put_pid(fd, pid) ? UU_LOCK_OK : UU_LOCK_WRITE_ERR; 140 } 141 142 close(fd); 143 return ret; 144 } 145 146 int 147 uu_unlock(const char *ttyname) 148 { 149 char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN]; 150 151 (void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, ttyname); 152 return unlink(tbuf); 153 } 154 155 const char * 156 uu_lockerr(int uu_lockresult) 157 { 158 static char errbuf[128]; 159 char *fmt; 160 161 switch (uu_lockresult) { 162 case UU_LOCK_INUSE: 163 return "device in use"; 164 case UU_LOCK_OK: 165 return ""; 166 case UU_LOCK_OPEN_ERR: 167 fmt = "open error: %s"; 168 break; 169 case UU_LOCK_READ_ERR: 170 fmt = "read error: %s"; 171 break; 172 case UU_LOCK_CREAT_ERR: 173 fmt = "creat error: %s"; 174 break; 175 case UU_LOCK_WRITE_ERR: 176 fmt = "write error: %s"; 177 break; 178 case UU_LOCK_LINK_ERR: 179 fmt = "link error: %s"; 180 break; 181 case UU_LOCK_TRY_ERR: 182 fmt = "too many tries: %s"; 183 break; 184 case UU_LOCK_OWNER_ERR: 185 fmt = "not locking process: %s"; 186 break; 187 default: 188 fmt = "undefined error: %s"; 189 break; 190 } 191 192 (void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno)); 193 return errbuf; 194 } 195 196 static int 197 put_pid(int fd, pid_t pid) 198 { 199 char buf[32]; 200 int len; 201 202 len = snprintf(buf, sizeof buf, "%10ld\n", (long)pid); 203 204 if (len < sizeof buf && len != -1 && write(fd, buf, (size_t)len) == len) { 205 /* We don't mind too much if ftruncate() fails - see get_pid */ 206 ftruncate(fd, (off_t)len); 207 return 1; 208 } 209 return 0; 210 } 211 212 static pid_t 213 get_pid(int fd, int *err) 214 { 215 ssize_t bytes_read; 216 char buf[32]; 217 pid_t pid; 218 219 bytes_read = read(fd, buf, sizeof (buf) - 1); 220 if (bytes_read > 0) { 221 buf[bytes_read] = '\0'; 222 pid = (pid_t)strtoul(buf, (char **) NULL, 10); 223 } else { 224 pid = -1; 225 *err = bytes_read ? errno : EINVAL; 226 } 227 return pid; 228 } 229