linux-kernel - Re: [PATCH] ARM: kprobes: Avoid fortify_panic() when copying optprobe template

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Message-Id: <8a30fb45-779d-4459-984b-f7792858c92e@www.fastmail.com>
Date:   Mon, 18 May 2020 10:19:45 +0930
From:   "Andrew Jeffery" <andrew@...id.au>
To:     "Kees Cook" <keescook@...omium.org>
Cc:     linux-arm-kernel@...ts.infradead.org,
        "Russell King" <linux@...linux.org.uk>, mhiramat@...nel.org,
        labbott@...hat.com, mathieu.desnoyers@...icios.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: kprobes: Avoid fortify_panic() when copying optprobe template



On Mon, 18 May 2020, at 07:18, Kees Cook wrote:
> On Mon, May 18, 2020 at 01:09:59AM +0930, Andrew Jeffery wrote:
> > As mentioned, a couple of attempts have been made to address the issue
> > by casting a pointer to optprobe_template_entry before providing it to
> > memcpy(), however gccs such as Ubuntu 20.04's arm-linux-gnueabi-gcc
> > 9.3.0 (Ubuntu 9.3.0-10ubuntu1) see through these efforts.
> 
> Ah, dang. :P
> 
> How about converting them all to unsized arrays, which would also allow
> the code to drop the "&" everywhere, I think. This is untested:

Looks better than my hack. Took it for a spin under qemu and it works for me.

Reviewed-by: Andrew Jeffery <andrew@...id.au>
Tested-by: Andrew Jeffery <andrew@...id.au>

Thanks Kees!

Andrew