From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S935704AbdAKFts (ORCPT <rfc822;w@1wt.eu>);
        Wed, 11 Jan 2017 00:49:48 -0500
Received: from mail3-relais-sop.national.inria.fr ([192.134.164.104]:52639
        "EHLO mail3-relais-sop.national.inria.fr" rhost-flags-OK-OK-OK-OK)
        by vger.kernel.org with ESMTP id S932505AbdAKFtr (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Wed, 11 Jan 2017 00:49:47 -0500
X-IronPort-AV: E=Sophos;i="5.33,345,1477954800"; 
   d="scan'208";a="208703113"
Date: Wed, 11 Jan 2017 06:49:43 +0100 (CET)
From: Julia Lawall <julia.lawall@lip6.fr>
X-X-Sender: jll@hadrien
To: Kees Cook <keescook@chromium.org>
cc: cocci@systeme.lip6.fr, Pengfei Wang <wpengfeinudt@gmail.com>,
        Vaishali Thakkar <vthakkar1994@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] coccicheck: add a test for repeat memory fetches
In-Reply-To: <CAGXu5jJ55j1r3H2NP8P4Tv4kqu+DZbj+Q6eor6mUcX8eRj4NTQ@mail.gmail.com>
Message-ID: <alpine.DEB.2.20.1701110646550.2396@hadrien>
References: <20170109231323.GA89642@beast> <alpine.DEB.2.20.1701101927070.1981@hadrien> <CAGXu5j+Nk9r7K=FJe4v5b8mX_Fn411JMGks2sueyOFS2aTo1Ow@mail.gmail.com> <alpine.DEB.2.20.1701102028300.1981@hadrien> <CAGXu5jLT8w6bK8SC4=Wne1BtfPsALiBSeyr6OK_jsCfaiJ+KRg@mail.gmail.com>
 <alpine.DEB.2.20.1701102207590.1981@hadrien> <CAGXu5jJ55j1r3H2NP8P4Tv4kqu+DZbj+Q6eor6mUcX8eRj4NTQ@mail.gmail.com>
User-Agent: Alpine 2.20 (DEB 67 2015-01-07)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org



On Tue, 10 Jan 2017, Kees Cook wrote:

> On Tue, Jan 10, 2017 at 1:14 PM, Julia Lawall <julia.lawall@lip6.fr> wrote:
> > OK, I have the impression that what you are looking for is the following,
> > that currently does not seem to work well. Still maybe it gives an idea.
> >
> > The basic pattern is the following sequence:
> >
> > 1. copy_from_user
> > 2. test on a field of the copied value
> > 3. another copy_from_user
> > 4. a use of the same field as tested in step 2 from the structure obtained
> > by the second copy_from_user or a function call with the structure as an
> > argument
>
> This looks pretty good!
>
> > In the case where the second copy_from_user stores the result in a
> > pointer, then a return with no reference of the tested field is also a
> > concern, unless, the pointer was already kfreed.
>
> I think sequence "2" above missing just looking at a direct value,
> like if instead of a field it was a u32. Also, should binop include
> "=="?

I wasn't sure what to do with a direct value, because one wouldn't know
what field it would correspond to.  A solution could be to pull the first
field out of the structure declaration.

I'll add == and !=.

> And we need to add back in get_user() too... hmmm

OK.

julia