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/* $OpenBSD: uucplock.c,v 1.20 2019/06/28 13:32:43 deraadt Exp $ */
/*
* Copyright (c) 1988, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
*
*/
#include <sys/types.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <paths.h>
#include <string.h>
#include "util.h"
#define MAXTRIES 5
#define LOCKTMP "LCKTMP..%ld"
#define LOCKFMT "LCK..%s"
#define GORET(level, val) { err = errno; uuerr = (val); \
goto __CONCAT(ret, level); }
/* Forward declarations */
static int put_pid(int fd, pid_t pid);
static pid_t get_pid(int fd,int *err);
/*
* uucp style locking routines
*/
int
uu_lock(const char *ttyname)
{
char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN],
lcktmpname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
int fd, tmpfd, i, err, uuerr;
pid_t pid, pid_old;
pid = getpid();
(void)snprintf(lcktmpname, sizeof(lcktmpname), _PATH_UUCPLOCK LOCKTMP,
(long)pid);
(void)snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT,
ttyname);
tmpfd = open(lcktmpname, O_CREAT|O_TRUNC|O_WRONLY|O_CLOEXEC, 0664);
if (tmpfd == -1)
GORET(0, UU_LOCK_CREAT_ERR);
for (i = 0; i < MAXTRIES; i++) {
if (link(lcktmpname, lckname) == -1) {
if (errno != EEXIST)
GORET(1, UU_LOCK_LINK_ERR);
/*
* file is already locked
* check to see if the process holding the lock
* still exists
*/
if ((fd = open(lckname, O_RDONLY | O_CLOEXEC)) == -1)
GORET(1, UU_LOCK_OPEN_ERR);
if ((pid_old = get_pid(fd, &err)) == -1)
GORET(2, UU_LOCK_READ_ERR);
close(fd);
if (kill(pid_old, 0) == 0 || errno != ESRCH)
GORET(1, UU_LOCK_INUSE);
/*
* The process that locked the file isn't running, so
* we'll lock it ourselves
*/
(void)unlink(lckname);
} else {
if (!put_pid(tmpfd, pid))
GORET(3, UU_LOCK_WRITE_ERR);
break;
}
}
GORET(1, (i >= MAXTRIES) ? UU_LOCK_TRY_ERR : UU_LOCK_OK);
ret3:
(void)unlink(lckname);
goto ret1;
ret2:
(void)close(fd);
ret1:
(void)close(tmpfd);
(void)unlink(lcktmpname);
ret0:
errno = err;
return uuerr;
}
int
uu_lock_txfr(const char *ttyname, pid_t pid)
{
char lckname[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
int fd, err, ret;
snprintf(lckname, sizeof(lckname), _PATH_UUCPLOCK LOCKFMT, ttyname);
if ((fd = open(lckname, O_RDWR | O_CLOEXEC)) == -1)
return UU_LOCK_OWNER_ERR;
if (get_pid(fd, &err) != getpid())
ret = UU_LOCK_OWNER_ERR;
else {
lseek(fd, 0, SEEK_SET);
ret = put_pid(fd, pid) ? UU_LOCK_OK : UU_LOCK_WRITE_ERR;
}
close(fd);
return ret;
}
int
uu_unlock(const char *ttyname)
{
char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN];
(void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, ttyname);
return unlink(tbuf);
}
const char *
uu_lockerr(int uu_lockresult)
{
static char errbuf[128];
const char *err;
switch (uu_lockresult) {
case UU_LOCK_INUSE:
return "device in use";
case UU_LOCK_OK:
return "";
case UU_LOCK_OPEN_ERR:
err = "open error";
break;
case UU_LOCK_READ_ERR:
err = "read error";
break;
case UU_LOCK_CREAT_ERR:
err = "creat error";
break;
case UU_LOCK_WRITE_ERR:
err = "write error";
break;
case UU_LOCK_LINK_ERR:
err = "link error";
break;
case UU_LOCK_TRY_ERR:
err = "too many tries";
break;
case UU_LOCK_OWNER_ERR:
err = "not locking process";
break;
default:
err = "undefined error";
break;
}
(void)snprintf(errbuf, sizeof(errbuf), "%s: %s", err, strerror(errno));
return errbuf;
}
static int
put_pid(int fd, pid_t pid)
{
char buf[32];
int len;
len = snprintf(buf, sizeof buf, "%10ld\n", (long)pid);
if (len < sizeof buf && len != -1 && write(fd, buf, (size_t)len) == len) {
/* We don't mind too much if ftruncate() fails - see get_pid */
ftruncate(fd, (off_t)len);
return 1;
}
return 0;
}
static pid_t
get_pid(int fd, int *err)
{
ssize_t bytes_read;
char buf[32];
pid_t pid;
bytes_read = read(fd, buf, sizeof (buf) - 1);
if (bytes_read > 0) {
buf[bytes_read] = '\0';
pid = (pid_t)strtoul(buf, (char **) NULL, 10);
} else {
pid = -1;
*err = bytes_read ? errno : EINVAL;
}
return pid;
}
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