The system must limit the ability of processes to have simultaneous write and execute access to memory.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-38597	RHEL-06-000079	SV-50398r2_rule		Medium

Description
ExecShield uses the segmentation feature on all x86 systems to prevent execution in memory higher than a certain address. It writes an address as a limit in the code segment descriptor, to control where code can be executed, on a per-process basis. When the kernel places a process's memory regions such as the stack and heap higher than this address, the hardware prevents execution in that address range.

Description

ExecShield uses the segmentation feature on all x86 systems to prevent execution in memory higher than a certain address. It writes an address as a limit in the code segment descriptor, to control where code can be executed, on a per-process basis. When the kernel places a process's memory regions such as the stack and heap higher than this address, the hardware prevents execution in that address range.

STIG	Date
Red Hat Enterprise Linux 6 Security Technical Implementation Guide	2015-03-06

Details

Check Text ( C-46155r3_chk )
The status of the "kernel.exec-shield" kernel parameter can be queried by running the following command: $ sysctl kernel.exec-shield $ grep kernel.exec-shield /etc/sysctl.conf The output of the command should indicate a value of "1". If this value is not the default value, investigate how it could have been adjusted at runtime, and verify it is not set improperly in "/etc/sysctl.conf". If the correct value is not returned, this is a finding.

Check Text ( C-46155r3_chk )

The status of the "kernel.exec-shield" kernel parameter can be queried by running the following command:

$ sysctl kernel.exec-shield
$ grep kernel.exec-shield /etc/sysctl.conf

The output of the command should indicate a value of "1". If this value is not the default value, investigate how it could have been adjusted at runtime, and verify it is not set improperly in "/etc/sysctl.conf".
If the correct value is not returned, this is a finding.

Fix Text (F-43545r1_fix)
To set the runtime status of the "kernel.exec-shield" kernel parameter, run the following command: # sysctl -w kernel.exec-shield=1 If this is not the system's default value, add the following line to "/etc/sysctl.conf": kernel.exec-shield = 1