[14047] in Athena Bugs
cleanup locking is somewhat broken
daemon@ATHENA.MIT.EDU (Greg Hudson)
Sun Dec 10 16:22:56 1995
Date: Sun, 10 Dec 1995 16:22:47 -0500
From: Greg Hudson <ghudson@MIT.EDU>
To: bugs@MIT.EDU
Here is the function in cleanup.c for locking /etc/ptmp or /etc/gtmp:
int
lock_file(fn)
char *fn;
{
int i, fd;
for (i = 0; i < 10; i++)
if ((fd = open(fn, O_RDWR | O_CREAT | O_EXCL, 0644)) == -1 &&
errno == EEXIST)
sleep(1);
else
break;
if (fd == -1) {
if (i < 10)
fprintf(stderr, "cleanup: unable to lock passwd file: %s\n",
sys_errlist[errno]);
else
(void) unlink(fn);
}
close(fd);
}
There are two problems with this, neither of them extremely serious:
1. In the case where the loop exits with fd == -1 and i == 10,
it unlinks the lock file and doesn't acquire it again;
thus, it exits without the file locked. Since /etc/nologin
exists at this point, this isn't critical.
2. In the case where the loop exits with fd == -1, it runs
close(-1).
