Date: Tue, 4 Apr 2017 21:45:36 -0600 From: Tycho Andersen <tycho@...ker.com> To: Kees Cook <keescook@...omium.org> Cc: Daniel Borkmann <daniel@...earbox.net>, Alexei Starovoitov <ast@...nel.org>, LKML <linux-kernel@...r.kernel.org>, Network Development <netdev@...r.kernel.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Mickaël Salaün <mic@...ikod.net> Subject: Re: [PATCH] ebpf: verify the output of the JIT 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 <tycho@...ker.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 <tycho@...ker.com> > > CC: Daniel Borkmann <daniel@...earbox.net> > > CC: Alexei Starovoitov <ast@...nel.org> > > CC: Kees Cook <keescook@...omium.org> > > CC: Mickaël Salaün <mic@...ikod.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. Tycho
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