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Handle the race condition where vipw may lock a password file which has

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just been replaced.  After our lock succeeds we check if st_nlink is 0
    and if it is we close the descriptor and retry our open/lock sequence.
This commit is contained in:
Matthew Dillon 1998-12-13 01:36:45 +00:00
parent 0aae7eb02e
commit f16d2ab2d3
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=41710
2 changed files with 44 additions and 12 deletions
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28
lib/libutil/pw_util.c
View File

@ -36,7 +36,7 @@
static const char sccsid[] = "@(#)pw_util.c 8.3 (Berkeley) 4/2/94";
#endif
static const char rcsid[] =
"$Id: pw_util.c,v 1.10 1998/10/13 14:52:33 des Exp $";
"$Id: pw_util.c,v 1.11 1998/10/20 11:34:11 des Exp $";
#endif /* not lint */
/*
@ -115,11 +115,27 @@ pw_lock()
* that users can't get at the encrypted passwords while editing.
* Open should allow flock'ing the file; see 4.4BSD. XXX
*/
lockfd = open(_PATH_MASTERPASSWD, O_RDONLY, 0);
if (lockfd < 0 || fcntl(lockfd, F_SETFD, 1) == -1)
err(1, "%s", _PATH_MASTERPASSWD);
if (flock(lockfd, LOCK_EX|LOCK_NB))
errx(1, "the password db file is busy");
for (;;) {
struct stat st;
lockfd = open(_PATH_MASTERPASSWD, O_RDONLY, 0);
if (lockfd < 0 || fcntl(lockfd, F_SETFD, 1) == -1)
err(1, "%s", _PATH_MASTERPASSWD);
if (flock(lockfd, LOCK_EX|LOCK_NB))
errx(1, "the password db file is busy");
/*
* If the password file was replaced while we were trying to
* get the lock, our hardlink count will be 0 and we have to
* close and retry.
*/
if (fstat(lockfd, &st) < 0)
errx(1, "fstat() failed");
if (st.st_nlink != 0)
break;
close(lockfd);
lockfd = -1;
}
return (lockfd);
}

28
usr.sbin/vipw/pw_util.c
View File

@ -36,7 +36,7 @@
static const char sccsid[] = "@(#)pw_util.c 8.3 (Berkeley) 4/2/94";
#endif
static const char rcsid[] =
"$Id: pw_util.c,v 1.10 1998/10/13 14:52:33 des Exp $";
"$Id: pw_util.c,v 1.11 1998/10/20 11:34:11 des Exp $";
#endif /* not lint */
/*
@ -115,11 +115,27 @@ pw_lock()
* that users can't get at the encrypted passwords while editing.
* Open should allow flock'ing the file; see 4.4BSD. XXX
*/
lockfd = open(_PATH_MASTERPASSWD, O_RDONLY, 0);
if (lockfd < 0 || fcntl(lockfd, F_SETFD, 1) == -1)
err(1, "%s", _PATH_MASTERPASSWD);
if (flock(lockfd, LOCK_EX|LOCK_NB))
errx(1, "the password db file is busy");
for (;;) {
struct stat st;
lockfd = open(_PATH_MASTERPASSWD, O_RDONLY, 0);
if (lockfd < 0 || fcntl(lockfd, F_SETFD, 1) == -1)
err(1, "%s", _PATH_MASTERPASSWD);
if (flock(lockfd, LOCK_EX|LOCK_NB))
errx(1, "the password db file is busy");
/*
* If the password file was replaced while we were trying to
* get the lock, our hardlink count will be 0 and we have to
* close and retry.
*/
if (fstat(lockfd, &st) < 0)
errx(1, "fstat() failed");
if (st.st_nlink != 0)
break;
close(lockfd);
lockfd = -1;
}
return (lockfd);
}