DMARC-Filter: OpenDMARC Filter v1.4.2 delorie.com 4BIETU58470516
Authentication-Results: delorie.com; dmarc=pass (p=none dis=none) header.from=cygwin.com
Authentication-Results: delorie.com; spf=pass smtp.mailfrom=cygwin.com
DKIM-Filter: OpenDKIM Filter v2.11.0 delorie.com 4BIETU58470516
Authentication-Results: delorie.com;
	dkim=pass (1024-bit key, unprotected) header.d=cygwin.com header.i=@cygwin.com header.a=rsa-sha256 header.s=default header.b=jcax7HcZ
X-Recipient: archive-cygwin AT delorie DOT com
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org B10663858C98
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cygwin.com;
	s=default; t=1734532167;
	bh=q4ais8HYImT6cIWy6CWgnreSHwzszf+MqEe30h6qWIw=;
	h=Date:To:Subject:References:In-Reply-To:List-Id:List-Unsubscribe:
	 List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc:
	 From;
	b=jcax7HcZjZCia8JVBpJHooVBErskvOn9jQiIz7LreujAPrCouPQmOLucfgZQPdiO+
	 o8hL3WsaJpZ6S1dDZJ1UIVBkFrP2k1Vh8DcILwjkkXKpdk8jld7uSIsjarEL/jgmCl
	 8ijO5bQESC7v6hFvixi0Vkv03JB+C5CWyK/wP1oI=
X-Original-To: cygwin AT cygwin DOT com
Delivered-To: cygwin AT cygwin DOT com
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org AD5EF3858D20
Date: Wed, 18 Dec 2024 15:28:24 +0100
To: cygwin AT cygwin DOT com
Subject: Re: Atomic mmap replacement
Message-ID: <Z2LcCIToHJ8Xc0VV@calimero.vinschen.de>
Mail-Followup-To: cygwin AT cygwin DOT com
References: <66bf4f86-4618-b9a3-3e33-2c240b9204d0 AT cornell DOT edu>
 <20180219090042 DOT GC3417 AT calimero DOT vinschen DOT de>
 <e6b3bd42-f981-405e-b65b-529693598735 AT cornell DOT edu>
 <d84f7f6c-5527-4f39-83a5-1aa16d8e451f AT cornell DOT edu>
 <Z2AsCg7Oo4FyHFjG AT calimero DOT vinschen DOT de>
 <b7564609-6a87-4691-b5ec-1f56b51543df AT cornell DOT edu>
 <bb796c13-c2b7-48a0-899b-cc7485fee783 AT cornell DOT edu>
 <Z2GpCxIUDMqp6yen AT calimero DOT vinschen DOT de>
 <cbeac0c9-70a1-4be9-acbb-eceadfde2e1e AT cornell DOT edu>
MIME-Version: 1.0
Content-Disposition: inline
In-Reply-To: <cbeac0c9-70a1-4be9-acbb-eceadfde2e1e@cornell.edu>
X-BeenThere: cygwin AT cygwin DOT com
X-Mailman-Version: 2.1.30
Precedence: list
List-Id: General Cygwin discussions and problem reports <cygwin.cygwin.com>
List-Unsubscribe: <https://cygwin.com/mailman/options/cygwin>,
 <mailto:cygwin-request AT cygwin DOT com?subject=unsubscribe>
List-Archive: <https://cygwin.com/pipermail/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-request AT cygwin DOT com?subject=help>
List-Subscribe: <https://cygwin.com/mailman/listinfo/cygwin>,
 <mailto:cygwin-request AT cygwin DOT com?subject=subscribe>
From: Corinna Vinschen via Cygwin <cygwin AT cygwin DOT com>
Reply-To: cygwin AT cygwin DOT com
Cc: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Errors-To: cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com
Sender: "Cygwin" <cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com>

Hi Ken,

On Dec 17 15:23, Ken Brown via Cygwin wrote:
> Hi Corinna,
> 
> On 12/17/2024 11:38 AM, Corinna Vinschen via Cygwin wrote:
> > Ideally a separate patch.  If you see a chance to send it to cygwin-patches
> > this week, we can even merge it into 3.5.5, which I'm planning to release
> > end of this week (after that --> vacation :)))
> That should be no problem.  By the way, I think I found a second bug.
> Shouldn't mmap:649 be
> 
> (*)  if (u_addr > (caddr_t) addr || u_len < len
> 
> instead of
> 
> (**)  if (u_addr > (caddr_t) addr || u_addr + len < (caddr_t) addr + len
> 
> ?
> 
> If the first condition in (**) fails, then u_addr == addr, so the second
> condition is automatically false.  But what we want to be testing at this
> point is whether the matched region is big enough, as in (*).  Or am I
> confused?

u_addr could be < addr.  We have two areas, the free area in u_addr and
u_len, and the requested area in addr and len.

So we have to check that addr is >= u_addr and addr + len is <= u_len:

  |----------------------------------------------------|
 u_addr                                           u_addr + u_len

           |--------------------|
          addr             addr + len

Make sense?


Corinna

-- 
Problem reports:      https://cygwin.com/problems.html
FAQ:                  https://cygwin.com/faq/
Documentation:        https://cygwin.com/docs.html
Unsubscribe info:     https://cygwin.com/ml/#unsubscribe-simple