On Tue, 5 Feb 2019 15:06:10 +0000 Kees Cook keescook@chromium.org wrote:
On Mon, Feb 4, 2019 at 7:15 PM Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:
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 keescook@chromium.org Date: Tue Oct 30 22:12:56 2018 +0100
ARM: 8806/1: kprobes: Fix false positive with FORTIFY_SOURCEI *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.
Yeah, this was a typo on my part. :(
Ah, I thought it had been fixed as same as x86. On x86, all optprobe_template_* are defined as kprobe_opcode_t [], but on arm, it still be kprobe_opcode_t.
Hmm, but I think we should use kprobe_opcode_t [] or char[] as asm/sections.h does. OK, I'll prepare for the change.
Thank you,
Has this change ever been runtime-tested ?
I thought I had, given the details from the original bug report, but clearly it didn't exercise it.
Thanks for fixing this!
-Kees
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
-- Kees Cook