1 /* $OpenBSD: uucplock.c,v 1.16 2009/10/27 23:59:30 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 #include <sys/types.h> 34 #include <dirent.h> 35 #include <errno.h> 36 #include <fcntl.h> 37 #include <unistd.h> 38 #include <signal.h> 39 #include <stdio.h> 40 #include <stdlib.h> 41 #include <paths.h> 42 #include <string.h> 43 #include "util.h" 44 45 #define MAXTRIES 5 46 47 #define LOCKTMP "LCKTMP..%ld" 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 int 61 uu_lock(const char *ttyname) 62 { 63 char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN], 64 lcktmpname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN]; 65 int fd, tmpfd, i, err, uuerr; 66 pid_t pid, pid_old; 67 68 pid = getpid(); 69 (void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP, 70 (long)pid); 71 (void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, 72 ttyname); 73 if ((tmpfd = creat(lcktmpname, 0664)) < 0) 74 GORET(0, UU_LOCK_CREAT_ERR); 75 76 for (i = 0; i < MAXTRIES; i++) { 77 if (link(lcktmpname, lckname) < 0) { 78 if (errno != EEXIST) 79 GORET(1, UU_LOCK_LINK_ERR); 80 /* 81 * file is already locked 82 * check to see if the process holding the lock 83 * still exists 84 */ 85 if ((fd = open(lckname, O_RDONLY)) < 0) 86 GORET(1, UU_LOCK_OPEN_ERR); 87 88 if ((pid_old = get_pid(fd, &err)) == -1) 89 GORET(2, UU_LOCK_READ_ERR); 90 91 close(fd); 92 93 if (kill(pid_old, 0) == 0 || errno != ESRCH) 94 GORET(1, UU_LOCK_INUSE); 95 /* 96 * The process that locked the file isn't running, so 97 * we'll lock it ourselves 98 */ 99 (void)unlink(lckname); 100 } else { 101 if (!put_pid(tmpfd, pid)) 102 GORET(3, UU_LOCK_WRITE_ERR); 103 break; 104 } 105 } 106 GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK); 107 108 ret3: 109 (void)unlink(lckname); 110 goto ret1; 111 ret2: 112 (void)close(fd); 113 ret1: 114 (void)close(tmpfd); 115 (void)unlink(lcktmpname); 116 ret0: 117 errno = err; 118 return uuerr; 119 } 120 121 int 122 uu_lock_txfr(const char *ttyname, pid_t pid) 123 { 124 char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN]; 125 int fd, err, ret; 126 127 snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, ttyname); 128 129 if ((fd = open(lckname, O_RDWR)) < 0) 130 return UU_LOCK_OWNER_ERR; 131 if (get_pid(fd, &err) != getpid()) 132 ret = UU_LOCK_OWNER_ERR; 133 else { 134 lseek(fd, 0, SEEK_SET); 135 ret = put_pid(fd, pid) ? UU_LOCK_OK : UU_LOCK_WRITE_ERR; 136 } 137 138 close(fd); 139 return ret; 140 } 141 142 int 143 uu_unlock(const char *ttyname) 144 { 145 char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN]; 146 147 (void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, ttyname); 148 return unlink(tbuf); 149 } 150 151 const char * 152 uu_lockerr(int uu_lockresult) 153 { 154 static char errbuf[128]; 155 char *fmt; 156 157 switch (uu_lockresult) { 158 case UU_LOCK_INUSE: 159 return "device in use"; 160 case UU_LOCK_OK: 161 return ""; 162 case UU_LOCK_OPEN_ERR: 163 fmt = "open error: %s"; 164 break; 165 case UU_LOCK_READ_ERR: 166 fmt = "read error: %s"; 167 break; 168 case UU_LOCK_CREAT_ERR: 169 fmt = "creat error: %s"; 170 break; 171 case UU_LOCK_WRITE_ERR: 172 fmt = "write error: %s"; 173 break; 174 case UU_LOCK_LINK_ERR: 175 fmt = "link error: %s"; 176 break; 177 case UU_LOCK_TRY_ERR: 178 fmt = "too many tries: %s"; 179 break; 180 case UU_LOCK_OWNER_ERR: 181 fmt = "not locking process: %s"; 182 break; 183 default: 184 fmt = "undefined error: %s"; 185 break; 186 } 187 188 (void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno)); 189 return errbuf; 190 } 191 192 static int 193 put_pid(int fd, pid_t pid) 194 { 195 char buf[32]; 196 int len; 197 198 len = snprintf(buf, sizeof buf, "%10ld\n", (long)pid); 199 200 if (len < sizeof buf && len != -1 && write(fd, buf, (size_t)len) == len) { 201 /* We don't mind too much if ftruncate() fails - see get_pid */ 202 ftruncate(fd, (off_t)len); 203 return 1; 204 } 205 return 0; 206 } 207 208 static pid_t 209 get_pid(int fd, int *err) 210 { 211 ssize_t bytes_read; 212 char buf[32]; 213 pid_t pid; 214 215 bytes_read = read(fd, buf, sizeof (buf) - 1); 216 if (bytes_read > 0) { 217 buf[bytes_read] = '\0'; 218 pid = (pid_t)strtoul(buf, (char **) NULL, 10); 219 } else { 220 pid = -1; 221 *err = bytes_read ? errno : EINVAL; 222 } 223 return pid; 224 } 225