[215] in bugtraq
[8lgm]-Advisory-8.UNIX.SunOS-kernel.11-Nov-1994
daemon@ATHENA.MIT.EDU ([8LGM] Security Team)
Sun Nov 27 23:50:18 1994
Date: Mon, 28 Nov 1994 00:50:10 GMT
From: "[8LGM] Security Team" <8lgm@bagpuss.demon.co.uk>
To: 8lgm-advisories@bagpuss.demon.co.uk, bugtraq@fc.net, cert@cert.org,
security-alert@sun.com
This advisory has been sent to:
comp.security.unix
BUGTRAQ <bugtraq@fc.net>
CERT/CC <cert@cert.org>
Sun Microsystems <security-alert@sun.com>
===========================================================================
[8lgm]-Advisory-8.UNIX.SunOS-kernel.11-Nov-1994
PROGRAM:
SunOS 4.1.x kernel
VULNERABLE OS's:
SunOS 4.1.x
DESCRIPTION:
A problem was reported to bugtraq by dawagner@phoenix.princeton.edu
(David Wagner) showing that unprivileged users can panic the
SunOS 4.1.x kernel if the TMPFS filesystem is in use.
The purpose of this advisory is to provide a workaround for
this problem. This patch has been successfully tested by a number
of people on the bugtraq list.
IMPACT:
Any user can crash the system.
REPEAT BY:
Assuming /tmp is a tmpfs filesystem:
% cd /tmp
% /usr/etc/mknod fifo p
% ln fifo link
% ls -ClFg link fifo
Obviously do not do this, unless you have the authority to
install the fix below.
DISCUSSION:
The problem actually occurs with any 'special' file on the
tmpfs filesystem. tmp_link() incorrectly updates the link count
(va_nlink in struct vattr) in the snode's vnode rather than in
the real vnode.
WORKAROUND & FIX:
1. Contact your vendor for a patch.
2. In the meantime either install the workaround given
below, or avoid using TMPFS mounted filesystems.
8<------------------------- cut here -------------------------
/*
* 8lgm_tmpfs.c - SunOS 4.1.x TMPFS bugfix.
* Copyright (C) 1994 by [8LGM].
*
* This works around a fatal bug in tmpfs, reported to Bugtraq
* by dawagner@phoenix.princeton.edu (David A. Wagner) on 2/11/94.
*
* Bug:
* cd /tmp; /usr/etc/mknod fifo p; ln fifo link; ls -ClFg link fifo
* panics the kernel with a bus error.
*
* To use:
* cc -c -O -DKERNEL -D<kernel-arch> 8lgm_tmpfs.c
* modload 8lgm_tmpfs.o
*/
#include <sys/types.h>
#include <sys/conf.h>
#include <sys/buf.h>
#include <sys/param.h>
#include <sys/errno.h>
#include <sys/user.h>
#include <sys/time.h>
#include <sys/vfs.h>
#include <sys/vnode.h>
#include <sys/ucred.h>
#include <sys/syslog.h>
#include <sundev/mbvar.h>
#include <sun/autoconf.h>
#include <sun/vddrv.h>
extern struct vnodeops tmp_vnodeops;
struct vdldrv vd;
int (*real_tmp_link)();
int loaded_8lgm = 0;
int
tmp_link_8lgm(vn, dirp, name, cred)
struct vnode *vn;
struct vnode *dirp;
char *name;
struct ucred*cred;
{
struct vnode *real_vn;
if (!(VOP_REALVP(vn, &real_vn)))
vn = real_vn;
return ((real_tmp_link)(vn, dirp, name, cred));
}
int
load_8lgm_tmpfsfix()
{
int x;
x = splhigh();
real_tmp_link = tmp_vnodeops.vn_link;
tmp_vnodeops.vn_link = tmp_link_8lgm;
splx(x);
return(0);
}
int
unload_8lgm_tmpfsfix()
{
int x;
x = splhigh();
tmp_vnodeops.vn_link = real_tmp_link;
splx(x);
return(0);
}
int
xxxinit(function_code, vdp, vdi, vds)
unsigned int function_code;
struct vddrv *vdp;
addr_t vdi;
struct vdstat *vds;
{
bzero(&vd, sizeof(vd));
vd.Drv_magic = VDMAGIC_PSEUDO;
vd.Drv_name = "8lgm-tmpfs";
switch(function_code) {
case VDLOAD:
if (loaded_8lgm) {
log(LOG_INFO, "8lgm: tmpfs fix module loaded\n");
return(EEXIST);
}
vdp->vdd_vdtab = (struct vdlinkage*)&vd;
load_8lgm_tmpfsfix();
loaded_8lgm++;
log(LOG_INFO, "8lgm: tmpfs fix module loaded\n");
return(0);
case VDUNLOAD:
return (unload(vdp, vdi));
case VDSTAT:
return(0);
default:
return(EIO);
}
}
static int
unload(vdp, vdi)
struct vddrv *vdp;
struct vdioctl_unload *vdi;
{
if (loaded_8lgm == 0) {
log(LOG_INFO, "8lgm: tmpfs fix module not loaded!\n");
return(0);
}
unload_8lgm_tmpfsfix();
loaded_8lgm = 0;
log(LOG_INFO, "8lgm: tmpfs fix module unloaded\n");
return(0);
}
8<------------------------- cut here -------------------------
-----------------------------------------------------------------------
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===========================================================================
