Re: [security-advisories@freebsd.org: FreeBSD Security Advisory FreeBSD-SA-02:44.filedesc]

From: horcy (apehaar@text-only.demon.nl)
Date: 01/08/03 

From: "horcy" <apehaar@text-only.demon.nl>
To: "budsz" <budsz@kumprang.or.id>
Date: Wed, 8 Jan 2003 17:25:20 +0100

II. Problem Description

A programming error in the fpathconf system call can result in the
given file descriptor's reference count being erroneously incremented.

A similar problem exists in the developer preview versions of FreeBSD
5.0, affecting the lseek(2), dup(2), and other system calls.

III. Impact

A local attacker may cause the operating system to crash by repeatedly
calling fpathconf on a file descriptor until the reference count wraps
to a negative value, and then calling close on that file descriptor.

Similarly, it may be possible to cause a file descriptor to reference
unallocated kernel memory, but remain valid. If a new file is later
opened and the kernel allocates the new file structure at the same
memory location, then an attacker may be able to gain read or write
access to that file. This may in turn lead to privilege escalation.

IV. Workaround

There is no workaround.

V. Solution

The following patch has been verified to apply to FreeBSD 4.4, 4.5,
4.6, and 4.7 systems.

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

# fetch
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-02:44/filedesc.patch
# fetch
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-02:44/filedesc.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.

The question:

If I periodicly upgrade with cvsup stable and compile kernel it's will fix
that problem, or I must patch only. does cvsup will replace all of
source?
---------------------------
Answer:

if you cvsup to stable it will fix it and of course the patch will fix it.
But you still have to recompile you kernel, so to if it was time for your
cvsup stable then i sould suggest you do that. Both will take some time.
So i would go for the cvsup.

l8r

horcy 

--
budsz
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