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
<URL: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
<URL: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
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