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Vigil@nce: Linux kernel, denial of service via EFER

April 2009 by Vigil@nce

On an x86 virtualized computer, a local attacker can use EFER to stop the system.

- Severity: 1/4
- Consequences: denial of service of computer
- Provenance: user shell
- Means of attack: no proof of concept, no attack
- Ability of attacker: expert (4/4)
- Confidence: confirmed by the editor (5/5)
- Diffusion of the vulnerable configuration: high (3/3)
- Creation date: 01/04/2009

IMPACTED PRODUCTS

- Linux kernel

DESCRIPTION OF THE VULNERABILITY

An x86 processor supports VMX (Virtual Machine Extensions).

The vmx_set_msr() function of the arch/x86/kvm/vmx.c file sets MSR (Model Specific Registers):
- MSR_EFER : extended feature
- MSR_STAR : legacy mode syscall target
- etc.

The EFER MSR is specific to x64 processors. However, in a i386 virtual machine, the vmx_set_msr() function tries to set it, which panics the kernel.

On an x86 virtualized computer, a local attacker can therefore use EFER to stop the system.

CHARACTERISTICS

- Identifiers: VIGILANCE-VUL-8585
- Url: http://vigilance.fr/vulnerability/Linux-kernel-denial-of-service-via-EFER-8585




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