Re: [RFC] perf: mmap2 not covering VM_CLONE regions

[Ingo Molnar]

* Peter Zijlstra <peterz@xxxxxxxxxxxxx> 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 didn't mean profiling - that's not a 'timing attack'.

A simple RDTSC done around repeated calls to sha_transform() using kernel 
functionality is.

Thanks,

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/