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Vigil@nce - Linux kernel: information disclosure via set_thread_area espfix
December 2014 by Vigil@nce
This bulletin was written by Vigil@nce : http://vigilance.fr/offer
SYNTHESIS OF THE VULNERABILITY
An attacker can use set_thread_area() on the Linux kernel, in
order to obtain information about the memory layout to bypass ASLR.
Impacted products: Linux
Severity: 1/4
Creation date: 16/12/2014
DESCRIPTION OF THE VULNERABILITY
The Linux kernel implements "espfix" which fixes a processor bug
related to 16 bit addresses.
However, an attacker can create a 16 bit stack with
set_thread_area(), and then return in 32 bits, to obtain the 16
top bits of the kernel stack pointer address.
An attacker can therefore use set_thread_area() on the Linux
kernel, in order to obtain information about the memory layout to
bypass ASLR.
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