linux-kernel - [PATCH v2 0/5] stackprotector: ascii armor the stack canary

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Message-Id: <20170524155751.424-1-riel@redhat.com>
Date:   Wed, 24 May 2017 11:57:46 -0400
From:   riel@...hat.com
To:     linux-kernel@...r.kernel.org
Cc:     danielmicay@...il.com, tytso@....edu, keescook@...omium.org,
        hpa@...or.com, luto@...capital.net, mingo@...nel.org,
        x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        catalin.marinas@....com, linux-sh@...r.kernel.org,
        ysato@...rs.sourceforge.jp, kernel-hardening@...ts.openwall.com
Subject: [PATCH v2 0/5] stackprotector: ascii armor the stack canary

Zero out the first byte of the stack canary value on 64 bit systems,
in order to mitigate unterminated C string overflows.

The null byte both prevents C string functions from reading the
canary, and from writing it if the canary value were guessed or
obtained through some other means.

Reducing the entropy by 8 bits is acceptable on 64-bit systems,
which will still have 56 bits of entropy left, but not on 32
bit systems, so the "ascii armor" canary is only implemented on
64-bit systems.

Inspired by the "ascii armor" code in execshield and Daniel Micay's
linux-hardened tree.

Also see https://github.com/thestinger/linux-hardened/

v2:
 - improve changelogs
 - address Ingo's coding style comments