On Tue, Apr 04, 2017 at 09:45:36PM -0600, Tycho Andersen wrote: > Hi Kees, > > On Tue, Apr 04, 2017 at 03:17:57PM -0700, Kees Cook wrote: > > On Tue, Apr 4, 2017 at 3:08 PM, Tycho Andersen <ty...@docker.com> wrote: > > > The goal of this patch is to protect the JIT against an attacker with a > > > write-in-memory primitive. The JIT allocates a buffer which will > > > eventually > > > be marked +x, so we need to make sure that what was written to this buffer > > > is what was intended. > > > > > > We acheive this by building a hash of the instruction buffer as > > > instructions are emittted and then comparing that to a hash at the end of > > > the JIT compile after the buffer has been marked read-only. > > > > > > Signed-off-by: Tycho Andersen <ty...@docker.com> > > > CC: Daniel Borkmann <dan...@iogearbox.net> > > > CC: Alexei Starovoitov <a...@kernel.org> > > > CC: Kees Cook <keesc...@chromium.org> > > > CC: Mickaël Salaün <m...@digikod.net> > > > > Cool! This closes the race condition on producing the JIT vs going > > read-only. I wonder if it might be possible to make this a more > > generic interface to the BPF which would be allocate the hash, provide > > the update callback during emit, and then do the hash check itself at > > the end of bpf_jit_binary_lock_ro()? > > Yes, probably so. I can look into that for the next version.
Nack. Please stop wasting yours and our time with buggy code that pretends to fix a problem that doesn't exist. This security paranoia around JIT must stop. Make sure that CONFIG_BPF_JIT is off in your system.
