From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <netdev-owner@vger.kernel.org>
Date: Fri, 22 Dec 2017 19:51:42 -0800
From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Ben Hutchings <ben@decadent.org.uk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, netdev@vger.kernel.org,
        Edward Cree <ecree@solarflare.com>,
        Jann Horn <jannh@google.com>,
        Alexei Starovoitov <ast@kernel.org>
Subject: Re: [PATCH 4.9] bpf/verifier: Fix states_equal() comparison of
 pointer and UNKNOWN
Message-ID: <20171223035140.mcv34grauxixvxsi@ast-mbp>
References: <20171223022617.GO2971@decadent.org.uk>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20171223022617.GO2971@decadent.org.uk>
Sender: netdev-owner@vger.kernel.org
List-ID: <stable.vger.kernel.org>

On Sat, Dec 23, 2017 at 02:26:17AM +0000, Ben Hutchings wrote:
> An UNKNOWN_VALUE is not supposed to be derived from a pointer, unless
> pointer leaks are allowed.  Therefore, states_equal() must not treat
> a state with a pointer in a register as "equal" to a state with an
> UNKNOWN_VALUE in that register.
> 
> This was fixed differently upstream, but the code around here was
> largely rewritten in 4.14 by commit f1174f77b50c "bpf/verifier: rework
> value tracking".  The bug can be detected by the bpf/verifier sub-test
> "pointer/scalar confusion in state equality check (way 1)".
> 
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> Cc: Edward Cree <ecree@solarflare.com>
> Cc: Jann Horn <jannh@google.com>
> Cc: Alexei Starovoitov <ast@kernel.org>

Acked-by: Alexei Starovoitov <ast@kernel.org>