linux-kernel - Re: Please pull my perf.git urgent branch

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Date:	Wed, 28 Jul 2010 14:47:31 +1000
From:	Paul Mackerras <paulus@...ba.org>
To:	Scott Wood <scottwood@...escale.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Kumar Gala <kumar.gala@...escale.com>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
	Ingo Molnar <mingo@...e.hu>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: Please pull my perf.git urgent branch

On Tue, Jul 27, 2010 at 11:28:54AM -0500, Scott Wood wrote:

> Doesn't the setting of .period need to be maintained (it is in the other
> powerpc perf_event implementation that this is derived from)?

Gah, yes it does.

> I don't see how this is a security fix -- the existing initializer above
> should zero-fill the fields that are not explicitly initialized.  In fact,
> it's taking other fields that were previously initialized to zero and is
> making them uninitialized, since perf_sample_data_init only sets addr and
> raw.

So I misunderstood how an initializer for an automatic struct works.
Brown paper bag time for me... :(

Regarding the other fields, I assume Peter et al. have checked that
they don't need to be cleared, so it's a microoptimization to not
clear them.

> CCing linuxppc-dev on the original patch would have been nice...

True, but at least I can blame Peter Z. for that. :)

Kumar and Ben, how do you want to proceed on this one?

Paul.
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