linux-kernel - Re: [PATCH 4.19 095/103] bpf: prevent out of bounds speculation on pointer arithmetic

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Date:   Fri, 1 Feb 2019 15:45:31 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Jann Horn <jannh@...gle.com>
Cc:     kernel list <linux-kernel@...r.kernel.org>, stable@...r.kernel.org,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 095/103] bpf: prevent out of bounds speculation on
 pointer arithmetic

On Fri, Feb 01, 2019 at 03:08:52PM +0100, Greg Kroah-Hartman wrote:
> On Fri, Feb 01, 2019 at 03:00:18PM +0100, Jann Horn wrote:
> > On Tue, Jan 29, 2019 at 12:47 PM Greg Kroah-Hartman
> > <gregkh@...uxfoundation.org> wrote:
> > > 4.19-stable review patch.  If anyone has any objections, please let me know.
> > >
> > > ------------------
> > >
> > > [ commit 979d63d50c0c0f7bc537bf821e056cc9fe5abd38 upstream ]
> > >
> > > Jann reported that the original commit back in b2157399cc98
> > > ("bpf: prevent out-of-bounds speculation") was not sufficient
> > > to stop CPU from speculating out of bounds memory access:
> > > While b2157399cc98 only focussed on masking array map access
> > > for unprivileged users for tail calls and data access such
> > > that the user provided index gets sanitized from BPF program
> > > and syscall side, there is still a more generic form affected
> > > from BPF programs that applies to most maps that hold user
> > > data in relation to dynamic map access when dealing with
> > > unknown scalars or "slow" known scalars as access offset, for
> > > example:
> > 
> > Is this also going into 4.14 and 4.9? I don't see anything related in
> > the stable queue or in stable-rc.
> 
> Ah, the original submitter did not send backported patches, but you are
> right, it should go further back.  I'll see how hard it would be to do
> the backport, thanks for letting me know.

Ok, no, there's no way I can do this backport.  It didn't apply cleanly,
and trying to take the patches prior to this resulted in a huge mess.

So, it would be wonderful if someone who knows the bpf code stack could
do this and send it in.

thanks,

greg k-h