[arch-security] [ASA-201706-31] linux: privilege escalation

[Levente Polyak]

Arch Linux Security Advisory ASA-201706-31
==========================================

Severity: High
Date    : 2017-06-23
CVE-ID  : CVE-2017-1000364
Package : linux
Type    : privilege escalation
Remote  : No
Link    : https://security.archlinux.org/AVG-313

Summary
=======

The package linux before version 4.11.6-3 is vulnerable to privilege
escalation.

Resolution
==========

Upgrade to 4.11.6-3.

# pacman -Syu "linux>=4.11.6-3"

The problem has been fixed upstream but no release is available yet.

Workaround
==========

None.

Description
===========

A flaw was found in the way memory was being allocated on the stack for
user space binaries. If heap (or different memory region) and stack
memory regions were adjacent to each other, an attacker could use this
flaw to jump over the stack guard gap, cause controlled memory
corruption on process stack or the adjacent memory region, and thus
increase their privileges on the system. This is a kernel-side
mitigation which increases the stack guard gap size from one page to 1
MiB to make successful exploitation of this issue more difficult.

Impact
======

A local attacker is able to bypass the stack guard for user space
binaries effectively leading to elevation of privileges by choosing a
suitable target application.

References
==========

https://www.qualys.com/2017/06/19/stack-clash/stack-clash.txt
https://git.kernel.org/linus/1be7107fbe18eed3e319a6c3e83c78254b693acb
https://security.archlinux.org/CVE-2017-1000364

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