From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mathieu Desnoyers Subject: BUG: optimized kprobes illegal instructions in v4.19 stable kernels Date: Mon, 4 Feb 2019 14:15:21 -0500 (EST) Message-ID: <342740659.2887.1549307721609.JavaMail.zimbra@efficios.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: Sender: stable-owner@vger.kernel.org To: Kees Cook Cc: William Cohen , stable@vger.kernel.org, Laura Abbott , Masami Hiramatsu , Russell King , linux-kernel , lttng@reliableembeddedsystems.com, lttng-dev List-Id: lttng-dev@lists.lttng.org Hi, I notice this commit as a possible culprit of the illegal instructions my lttng users are noticing on arm32 when using kprobes on a v4.19.13 Linux kernel in a Yocto environment [1]. They were able to reproduce the issue with perf as well. commit e46daee53bb50bde38805f1823a182979724c229 Author: Kees Cook Date: Tue Oct 30 22:12:56 2018 +0100 ARM: 8806/1: kprobes: Fix false positive with FORTIFY_SOURCE I *think* the intent there was to do - memcpy(code, &optprobe_template_entry, + memcpy(code, (unsigned long *)&optprobe_template_entry, But if you look at the commit, the "&" seems to have been stripped away, which happens to change the behavior significantly. Has this change ever been runtime-tested ? It has been backported to: - 4.19 stable as commit 3fe0c68aea21 - 4.14 stable as commit f9e0bc710347 Thanks, Mathieu [1] https://bugs.lttng.org/issues/1174 -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com