Date: Wed, 2 Oct 2013 15:01:44 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Stephane Eranian <eranian@google.com>
Cc: Ingo Molnar <mingo@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        "mingo@elte.hu" <mingo@elte.hu>,
        "ak@linux.intel.com" <ak@linux.intel.com>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        David Ahern <dsahern@gmail.com>, Jiri Olsa <jolsa@redhat.com>,
        Hugh Dickins <hughd@google.com>, Kees Cook <keescook@chromium.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC] perf: mmap2 not covering VM_CLONE regions
Message-ID: <20131002130143.GF28601@twins.programming.kicks-ass.net>
References: <CABPqkBQrTzMKnL-f5iCe4jhM1mHXNE6aZ=OwVmpsezOLaRLntA@mail.gmail.com>
 <20130930161546.GG3081@twins.programming.kicks-ass.net>
 <CABPqkBSRV651SynNHpAo7-B+8aX2hsMXKJNeTkimBoWo91TvFQ@mail.gmail.com>
 <20130930165420.GI3081@twins.programming.kicks-ass.net>
 <CABPqkBS_zDkgX4NioducZ+H9VEt1jb7gQDbZ_zB6ui5Tf=UR5A@mail.gmail.com>
 <20131002112316.GP3081@twins.programming.kicks-ass.net>
 <20131002115826.GM26785@twins.programming.kicks-ass.net>
 <20131002123953.GB27811@gmail.com>
 <20131002124610.GD28601@twins.programming.kicks-ass.net>
 <CABPqkBQyCfz5d+SQxDwPD5m52ofE6y5HKur+s-F0s=hN00cxkw@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CABPqkBQyCfz5d+SQxDwPD5m52ofE6y5HKur+s-F0s=hN00cxkw@mail.gmail.com>
User-Agent: Mutt/1.5.21 (2012-12-30)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1312
Lines: 25

On Wed, Oct 02, 2013 at 02:59:32PM +0200, Stephane Eranian wrote:
> 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:

Oh right you are.. so yes that's a very viable avenue.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/