Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Date: Mon, 22 Jun 2015 23:06:52 -0400 (EDT)
From: cve-assign@...re.org
To: wmealing@...hat.com
Cc: cve-assign@...re.org, oss-security@...ts.openwall.com
Subject: Re: CVE request: Linux kernel - bpf jit optimization flaw can panic kenrel.

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

> In the problematic case, the compiler fails to optimise a set
> of specially crafted instructions. This creates a problem when this faulty
> instruction list is used during filtering and the CPU can execute an invalid
> instruction (in receive_pkt).
> 
> This can be triggered as an non-root user, as they can start a server on a
> ephemeral port and the packet filter with a specially crafted filter.
> 
> These incorrect instructions will run when the server receives a packet and execute
> the buggy instructions.

> https://git.kernel.org/cgit/linux/kernel/git/davem/net.git/commit/?id=3f7352bf21f8fd7ba3e2fcef9488756f188e12be

> x86: bpf_jit: fix compilation of large bpf programs
>
> x86 has variable length encoding. x86 JIT compiler is trying to pick
> the shortest encoding for given bpf instruction. While doing so the
> jump targets are changing, so JIT is doing multiple passes over the
> program. Typical program needs 3 passes. Some very short programs
> converge with 2 passes. Large programs may need 4 or 5. But specially
> crafted bpf programs may hit the pass limit and if the program
> converges on the last iteration the JIT compiler will be producing an
> image full of 'int 3' insns. Fix this corner case by doing final
> iteration over bpf program.
> 
> - for (pass = 0; pass < 10; pass++) {
> + for (pass = 0; pass < 10 || image; pass++) {

Use CVE-2015-4700.

- -- 
CVE assignment team, MITRE CVE Numbering Authority
M/S M300
202 Burlington Road, Bedford, MA 01730 USA
[ PGP key available through http://cve.mitre.org/cve/request_id.html ]
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.14 (SunOS)

iQEcBAEBAgAGBQJViMx/AAoJEKllVAevmvmszzcH/1ohdtc1XTzmN0ZMTkRXLPT3
N2RFIEzSfUNtr3rwG28gUd7mfddN/1ANJ3d634LT0fS7Nw/OZIeaZEdQI89TZYwJ
tNhg+JvCLBLtCmqExFaG7Et3PiYSRGETfDUIYQFAZgcgXfu7nhLnvoJPkx6UMl+7
MY07c84T7pFYaJif8frMTzjQ9DQxcpacIUOA7dyyvBxKnoI0eJX8OtGeMffjmwtl
5UWnZrIYrmeYrlnacIaPUha7qOrjVn118dBUSm5ZvZsk83meHcogka9V5fI7lUPp
ORHq7GwiuCiaYv9B52TxrH845z2+C/FmT8zWPXsVamPHgFC+OgrhyN0uNweVN8Y=
=7y5J
-----END PGP SIGNATURE-----

Powered by blists - more mailing lists

Your e-mail address:

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.