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Vulnerability of Linux kernel: integer overflow via kvm_dev_ioctl_get_supported_cpuid

Synthesis of the vulnerability 

On a 32 bits processor, a local attacker can generate an overflow in the kvm_dev_ioctl_get_supported_cpuid() function, in order to create a denial of service, or possibly to execute code.
Vulnerable systems: Debian, Fedora, Linux, Mandriva Linux.
Severity of this threat: 2/4.
Creation date: 23/10/2009.
Références of this weakness: BID-36803, CERTA-2002-AVI-244, CVE-2009-3638, DSA-1927-1, DSA-1962-1, FEDORA-2009-11032, FEDORA-2009-11038, FEDORA-2009-13098, MDVSA-2009:301, MDVSA-2009:329, VIGILANCE-VUL-9116.

Description of the vulnerability 

The KVM_GET_SUPPORTED_CPUID ioctl is used by a KVM guest system, in order to obtain information about the processor.

This ioctl calls the kvm_dev_ioctl_get_supported_cpuid() function of the arch/x86/kvm/x86.c file. However, when the user requests too many information, a multiplication overflows, and a short memory area is allocated. Information about the processor thus corrupt the memory.

A local attacker can therefore generate an overflow in the kvm_dev_ioctl_get_supported_cpuid() function, in order to create a denial of service, or possibly to execute code.
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This computer vulnerability impacts software or systems such as Debian, Fedora, Linux, Mandriva Linux.

Our Vigil@nce team determined that the severity of this weakness bulletin is medium.

The trust level is of type confirmed by the editor, with an origin of user shell.

An attacker with a expert ability can exploit this weakness.

Solutions for this threat 

Linux kernel: version 2.6.27.39.
Version 2.6.27.39 is corrected:
  http://www.kernel.org/pub/linux/kernel/v2.6/

Linux kernel: patch for kvm_dev_ioctl_get_supported_cpuid.
A patch is available in information sources.

Debian: new kvm packages.
New packages are available:
http://security.debian.org/pool/updates/main/k/kvm/kvm_72+dfsg-5~lenny4_*.deb

Debian: new linux-2.6.26 packages.
New packages are available:
  http://security.debian.org/pool/updates/main/l/linux-2.6/linux-*_2.6.26-19lenny2_*.deb

Fedora 10: new kernel-2.6.27.38 packages.
New packages are available:
  kernel-2.6.27.38-170.2.113.fc10

Fedora 10: new kernel packages.
New packages are available:
  kernel-2.6.27.41-170.2.117.fc10

Fedora 11: new kernel-2.6.30.9 packages.
New packages are available:
  Fedora 11: kernel-2.6.30.9 96.fc11

Mandriva ES 5: new kernel packages.
New packages are available:
  kernel-2.6.27.39-1mnb-1-1mnb2

Mandriva: new kernel packages.
New packages are available:
Mandriva Linux 2009.1:
  kernel-2.6.29.6-3mnb2
Mandriva Linux 2010.0:
  kernel-2.6.31.6-1mnb2
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