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SubjectRe: [RFC] perf: mmap2 not covering VM_CLONE regions
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On Wed, Oct 2, 2013 at 2:46 PM, Peter Zijlstra <peterz@infradead.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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