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Date:   Thu, 26 Jul 2018 11:22:45 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Mark Salyzyn <salyzyn@android.com>
Cc:     linux-kernel@vger.kernel.org,
        Nick Desaulniers <ndesaulniers@google.com>,
        Ingo Molnar <mingo@redhat.com>, kernel-team@android.com,
        stable@vger.kernel.org
Subject: Re: [PATCH] tracing: do not leak kernel addresses
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In-Reply-To: <11437c3e-5131-7190-c496-7b51eb7fcc2a@android.com>
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        <20180725210717.3b807191@vmware.local.home>
        <11437c3e-5131-7190-c496-7b51eb7fcc2a@android.com>
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On Thu, 26 Jul 2018 08:14:08 -0700
Mark Salyzyn <salyzyn@android.com> wrote:

> Thank you Steve, much appreciated feedback, I have asked the security 
> developers to keep this in mind and come up with a correct fix.
> 
> The correct fix that meets your guidelines would _not_ be suitable for 
> stable due to the invasiveness it sounds, only for the latest will such 
> a rework make sense. As such, the fix proposed in this patch is the only 
> one that meets the bar for stable patch simplicity, and merely(!) needs 
> to state that if the fix is taken, perf and trace are broken.
> 
> Posting this patch publicly on the lists, that may never be applied, may 
> be the limit of our responsibility for a fix to stable kernel releases, 
> to be optionally applied by vendors concerned with this CVE criteria?
>

The patch breaks the code it touches. It makes it useless. If you want
something for stable, add a command line parameter that just disables
the creation of that file. Otherwise you will break usespace and that
will be a definitely NAK from Linus, and for stable itself. This is a
very minor security issue, and does not justify breaking userspace
applications. I would be very upset if a new stable release broke both
perf and trace-cmd's ability to read certain trace events.

-- Steve