On Wed, Oct 02, 2013 at 03:13:16PM +0200, Stephane Eranian wrote: > On Wed, Oct 2, 2013 at 3:01 PM, Peter Zijlstra <pet...@infradead.org> wrote: > > On Wed, Oct 02, 2013 at 02:59:32PM +0200, Stephane Eranian wrote: > >> On Wed, Oct 2, 2013 at 2:46 PM, Peter Zijlstra <pet...@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: > > > > Oh right you are.. so yes that's a very viable avenue. > > You mean simply encoding the vma->vm_mm as the ino number, for instance.
Nah.. I think Kees would very much shoot us on the spot for doing that. But with the paranoid level defaulting to 1 the PMU attack on the kernel SHA implenentation is feasible. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
