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From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Kees Cook <keescook@chromium.org>
Cc: William Cohen <wcohen@redhat.com>,
	stable@vger.kernel.org, Laura Abbott <labbott@redhat.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Russell King <rmk+kernel@armlinux.org.uk>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	lttng@reliableembeddedsystems.com,
	lttng-dev <lttng-dev@lists.lttng.org>
Subject: BUG: optimized kprobes illegal instructions in v4.19 stable kernels
Date: Mon, 4 Feb 2019 14:15:21 -0500 (EST)	[thread overview]
Message-ID: <342740659.2887.1549307721609.JavaMail.zimbra@efficios.com> (raw)

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_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

             reply	other threads:[~2019-02-04 19:15 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-04 19:15 Mathieu Desnoyers [this message]
2019-02-05 15:06 ` BUG: optimized kprobes illegal instructions in v4.19 stable kernels Kees Cook
2019-02-06  4:41   ` Masami Hiramatsu
2019-02-18 12:26     ` Greg KH
2019-02-18 14:11       ` Masami Hiramatsu
2019-02-18 14:55       ` Mathieu Desnoyers
2019-02-21 20:02         ` Mathieu Desnoyers
2019-02-22  0:10           ` Russell King - ARM Linux admin
2019-02-22  0:17             ` Mathieu Desnoyers
2019-02-22  6:25               ` Greg Kroah-Hartman
2019-02-22  8:29                 ` Greg Kroah-Hartman
2019-02-22 20:18                   ` Mathieu Desnoyers
2019-02-06 11:48 ` David Laight

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