FreeBSD: core:sys Buffer cache invalidation vulnerability
Posted by LinuxSecurity.com Team   
FreeBSD In some situations, a user with read access to a file may be able to prevent changes to that file from being committed to disk.

FreeBSD-SA-04:11.msync                                      Security Advisory
                                                          The FreeBSD Project

Topic:          buffer cache invalidation implementation issues

Category:       core
Module:         sys
Announced:      2004-05-26
Credits:        Stephan Uphoff <ups@tree.com>
                Matt Dillon <dillon@apollo.backplane.com>
Affects:        All FreeBSD versions prior to the correction date
Corrected:      2004-05-25 22:46:38 UTC (RELENG_4, 4.10-STABLE)
                2004-05-25 23:07:55 UTC (RELENG_5_2, 5.2.1-RELEASE-p8)
                2004-05-22 23:09:19 UTC (RELENG_4_10, 4.10-RELEASE)
                2004-05-25 23:01:21 UTC (RELENG_4_9, 4.9-RELEASE-p9)
                2004-05-25 23:01:19 UTC (RELENG_4_8, 4.8-RELEASE-p22)
CVE Name:       CAN-2004-0435
FreeBSD only:   YES

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit
http://www.freebsd.org/security/>.

I.   Background

The msync(2) system call is used by applications to request that
modified memory pages are written to permanent storage.

II.  Problem Description

Programming errors in the implementation of the msync(2) system call
involving the MS_INVALIDATE operation lead to cache consistency
problems between the virtual memory system and on-disk contents.

III. Impact

In some situations, a user with read access to a file may be able to
prevent changes to that file from being committed to disk.

IV.  Workaround

There is no workaround.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to 4-STABLE; or to the RELENG_5_2,
RELENG_4_10, RELENG_4_9, or RELENG_4_8 security branch dated after the
correction date.

2) To patch your present system:

The following patches have been verified to apply to FreeBSD 4.8, 4.9,
4.10 and 5.2 systems.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

[FreeBSD 5.2]
# fetch  ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:11/msync5.patch
# fetch  ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:11/msync5.patch.asc

[FreeBSD 4.8, 4.9, 4.10]
# fetch  ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:11/msync4.patch
# fetch  ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:11/msync4.patch.asc

b) Apply the patch.

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel as described in
http://www.freebsd.org/handbook/kernelconfig.html> and reboot the
system.

VI.  Correction details

The following list contains the revision numbers of each file that was
corrected in FreeBSD.

Branch                                                           Revision
  Path
- -------------------------------------------------------------------------
RELENG_4
  src/sys/ufs/ufs/ufs_readwrite.c                               1.65.2.16
  src/sys/vm/vm_map.c                                          1.187.2.30
RELENG_4_10
  src/sys/ufs/ufs/ufs_readwrite.c                           1.65.2.14.4.1
  src/sys/vm/vm_map.c                                      1.187.2.24.2.4
RELENG_4_9
  src/UPDATING                                             1.73.2.89.2.10
  src/sys/conf/newvers.sh                                  1.44.2.32.2.10
  src/sys/ufs/ufs/ufs_readwrite.c                           1.65.2.14.2.1
  src/sys/vm/vm_map.c                                      1.187.2.23.2.1
RELENG_4_8
  src/UPDATING                                             1.73.2.80.2.25
  src/sys/conf/newvers.sh                                  1.44.2.29.2.23
  src/sys/ufs/ufs/ufs_readwrite.c                           1.65.2.13.2.1
  src/sys/vm/vm_map.c                                      1.187.2.17.2.1
RELENG_5_2
  src/UPDATING                                                 1.282.2.16
  src/sys/conf/newvers.sh                                       1.56.2.15
  src/sys/ufs/ffs/ffs_vnops.c                                   1.119.2.1
  src/sys/vm/vm_object.c                                        1.317.2.1