Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Tue, 4 Apr 2017 21:45:36 -0600
From: Tycho Andersen <>
To: Kees Cook <>
Cc: Daniel Borkmann <>,
	Alexei Starovoitov <>,
	LKML <>,
	Network Development <>,
	"" <>,
	Mickaël Salaün <>
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 <> 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 <>
> > CC: Daniel Borkmann <>
> > CC: Alexei Starovoitov <>
> > CC: Kees Cook <>
> > CC: Mickaël Salaün <>
> 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.


Powered by blists - more mailing lists

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.