Scientific Linux Security Update : kvm on SL5.4 x86_64

This script is Copyright (C) 2012 Tenable Network Security, Inc.

Synopsis :

The remote Scientific Linux host is missing one or more security

Description :

CVE-2009-4031 kernel: KVM: x86 emulator: limit instructions to 15

On x86 platforms, the do_insn_fetch() function did not limit the
amount of instruction bytes fetched per instruction. Users in guest
operating systems could leverage this flaw to cause large latencies on
SMP hosts that could lead to a local denial of service on the host
operating system. This update fixes this issue by imposing the
architecturally-defined 15 byte length limit for instructions.

This update also fixes the following bugs :

- performance problems occurred when using the qcow2 image
format with the qemu-kvm -drive 'cache=none' option (the
default setting when not specified otherwise). This
could cause guest operating system installations to take
hours. With this update, performance patches have been
backported so that using the qcow2 image format with the
'cache=none' option no longer causes performance issues.

- when using the virtual vm8086 mode, bugs in the emulated
hardware task switching implementation may have, in some
situations, caused older guest operating systems to
malfunction. (BZ#532031)

- Windows Server 2003 guests (32-bit) with more than 4GB
of memory may have crashed during reboot when using the
default qemu-kvm CPU settings. (BZ#532043)

- with Scientific Linux Virtualization, guests continued
to run after encountering disk read errors. This could
have led to their file systems becoming corrupted (but
not the host's), notably in environments that use
networked storage. With this update, the qemu-kvm -drive
'werror=stop' option now applies not only to write
errors but also to read errors: When using this option,
guests will pause on disk read and write errors.

By default, guests managed by Scientific Linux Virtualization use the
'werror=stop' option. This option is not used by default for guests
managed by libvirt. (BZ#537334, BZ#540406)

- the para-virtualized block driver (virtio-blk) silently
ignored read errors when accessing disk images. With
this update, the driver correctly signals the read error
to the guest. (BZ#537334)

See also :

Solution :

Update the affected packages.

Risk factor :

High / CVSS Base Score : 7.8

Family: Scientific Linux Local Security Checks

Nessus Plugin ID: 60704 ()

Bugtraq ID:

CVE ID: CVE-2009-4031

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