Date: Mon, 8 Jun 1998 13:10:18 -0700 (PDT) From: Craig Spannring <cts@internetcds.com> To: nate@mt.sri.com, phk@FreeBSD.ORG Cc: freebsd-bugs@FreeBSD.ORG Subject: Re: bin/6787: race condition in pw command Message-ID: <199806082010.NAA21530@bangkok.office.cdsnet.net> In-Reply-To: <199806011822.MAA10429@mt.sri.com> References: <199805291844.LAA07680@hub.freebsd.org> <199805300220.UAA28867@mt.sri.com> <199806011818.LAA28408@bangkok.office.cdsnet.net> <199806011822.MAA10429@mt.sri.com>
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Here are the patches for -current. I have compiled them, but I don't
have a 3.0 machine available for testing so I haven't run them.
Sorry.
>---cut here---<
diff -c -r pw-cur.original/edgroup.c pw-cur/edgroup.c
*** pw-cur.original/edgroup.c Mon Jun 8 10:39:32 1998
--- pw-cur/edgroup.c Mon Jun 8 12:13:39 1998
***************
*** 64,70 ****
int rc = 0;
int infd;
! if ((infd = open(groupfile, O_RDWR | O_CREAT | O_EXLOCK, 0644)) != -1) {
FILE *infp;
if ((infp = fdopen(infd, "r+")) == NULL)
--- 64,70 ----
int rc = 0;
int infd;
! if ((infd = open(groupfile, O_RDWR | O_CREAT, 0644)) != -1) {
FILE *infp;
if ((infp = fdopen(infd, "r+")) == NULL)
diff -c -r pw-cur.original/fileupd.c pw-cur/fileupd.c
*** pw-cur.original/fileupd.c Mon Jun 8 10:39:32 1998
--- pw-cur/fileupd.c Mon Jun 8 12:32:27 1998
***************
*** 76,82 ****
if (pfxlen <= 1)
errno = EINVAL;
else {
! int infd = open(filename, O_RDWR | O_CREAT | O_EXLOCK, fmode);
if (infd != -1) {
FILE *infp = fdopen(infd, "r+");
--- 76,82 ----
if (pfxlen <= 1)
errno = EINVAL;
else {
! int infd = open(filename, O_RDWR | O_CREAT, fmode);
if (infd != -1) {
FILE *infp = fdopen(infd, "r+");
***************
*** 168,176 ****
fputs(line, infp);
/*
* This is a gross hack, but we may have
* corrupted the original file
! * Unfortunately, it will lose the inode.
*/
if (fflush(infp) == EOF || ferror(infp))
rc = rename(file, filename) == 0;
--- 168,187 ----
fputs(line, infp);
/*
+ * If there was a problem with copying
+ * we will just rename 'file.new'
+ * to 'file'.
* This is a gross hack, but we may have
* corrupted the original file
! * Unfortunately, it will lose the inode
! * and hence the lock.
! *
! * The implications of this is that this invocation of pw
! * won't have the file locked and concurrent copies
! * of pw, vipw etc could clobber what this one is doing.
! *
! * It should probably just return an error instead
! * of going on like nothing is wrong.
*/
if (fflush(infp) == EOF || ferror(infp))
rc = rename(file, filename) == 0;
diff -c -r pw-cur.original/pw.c pw-cur/pw.c
*** pw-cur.original/pw.c Mon Jun 8 10:39:33 1998
--- pw-cur/pw.c Mon Jun 8 12:30:05 1998
***************
*** 31,36 ****
--- 31,37 ----
#include "pw.h"
#include <err.h>
+ #include <fcntl.h>
#include <paths.h>
#include <sys/wait.h>
***************
*** 49,54 ****
--- 50,56 ----
static int getindex(const char *words[], const char *word);
static void cmdhelp(int mode, int which);
+ static int filelock(const char *filename);
int
***************
*** 147,153 ****
* Now, let's do the common initialisation
*/
cnf = read_userconfig(getarg(&arglist, 'C') ? getarg(&arglist, 'C')->val : NULL);
! ch = funcs[which] (cnf, mode, &arglist);
/*
* If everything went ok, and we've been asked to update
--- 149,168 ----
* Now, let's do the common initialisation
*/
cnf = read_userconfig(getarg(&arglist, 'C') ? getarg(&arglist, 'C')->val : NULL);
!
!
! /*
! * Be pessimistic and lock the master passowrd and group
! * files right away. Keep it locked for the duration.
! */
! if (-1 == filelock(_PATH_GROUP) || -1 == filelock(_PATH_MASTERPASSWD))
! {
! ch = EX_IOERR;
! }
! else
! {
! ch = funcs[which] (cnf, mode, &arglist);
! }
/*
* If everything went ok, and we've been asked to update
***************
*** 175,180 ****
--- 190,201 ----
}
}
return ch;
+ }
+
+ static int
+ filelock(const char *filename)
+ {
+ return open(filename, O_RDONLY | O_EXLOCK, 0);
}
static int
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