linux-kernel - Re: [RFC] perf: mmap2 not covering VM

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Message-ID: <CABPqkBQyCfz5d+SQxDwPD5m52ofE6y5HKur+s-F0s=hN00cxkw@mail.gmail.com>
Date:	Wed, 2 Oct 2013 14:59:32 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	Kees Cook <keescook@...omium.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC] perf: mmap2 not covering VM_CLONE regions

On Wed, Oct 2, 2013 at 2:46 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Wed, Oct 02, 2013 at 02:39:53PM +0200, Ingo Molnar wrote:
>>  - then there are timing attacks, and someone having access to a PMU
>>    context and who can trigger this SHA1 computation arbitrarily in task
>>    local context can run very accurate and low noise timing attacks...
>>
>>    I don't think the kernel's sha_transform() is hardened against timing
>>    attacks, it's performance optimized so it has variable execution time
>>    highly dependent on plaintext input - which leaks information about the
>>    plaintext.
>
> Typical user doesn't have enough priv to profile kernel space; once you
> do you also have enough priv to see kernel addresses outright (ie.
> kallsyms etc..).
>
I was going to say just that. But that's not the default, paranoid level
is at 1 by default and not 2. So I supposedly can still do:

$ perf record -e cycles ......

In per-thread mode and collect kernel level addresses.
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