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redhatRedHatRHSA-2009:1659
HistoryDec 09, 2009 - 12:00 a.m.

(RHSA-2009:1659) Moderate: kvm security and bug fix update

2009-12-0900:00:00
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13

7.8 High

CVSS2

Access Vector

NETWORK

Access Complexity

LOW

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

COMPLETE

AV:N/AC:L/Au:N/C:N/I:N/A:C

0.002 Low

EPSS

Percentile

60.9%

KVM (Kernel-based Virtual Machine) is a full virtualization solution for
Linux on AMD64 and Intel 64 systems. KVM is a Linux kernel module built for
the standard Red Hat Enterprise Linux kernel.

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. (CVE-2009-4031)

This update also fixes the following bugs:

  • performance problems occurred when using the qcow2 image format with the
    qemu-kvm -drive β€œcache=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 β€œcache=none” option no longer causes
    performance issues. (BZ#520693)

  • 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 Red Hat Enterprise 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 β€œwerror=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 Red Hat Enterprise Virtualization use the
β€œwerror=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)

All KVM users should upgrade to these updated packages, which contain
backported patches to resolve these issues. Note: The procedure in the
Solution section must be performed before this update will take effect.

7.8 High

CVSS2

Access Vector

NETWORK

Access Complexity

LOW

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

COMPLETE

AV:N/AC:L/Au:N/C:N/I:N/A:C

0.002 Low

EPSS

Percentile

60.9%