From owner-freebsd-net@FreeBSD.ORG  Sat Aug  2 10:45:16 2003
Return-Path: <owner-freebsd-net@FreeBSD.ORG>
Delivered-To: freebsd-net@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 188AE37B401
	for <freebsd-net@freebsd.org>; Sat,  2 Aug 2003 10:45:16 -0700 (PDT)
Received: from relay.pair.com (relay.pair.com [209.68.1.20])
	by mx1.FreeBSD.org (Postfix) with SMTP id A85B143FEC
	for <freebsd-net@freebsd.org>; Sat,  2 Aug 2003 10:45:12 -0700 (PDT)
	(envelope-from silby@silby.com)
Received: (qmail 90247 invoked from network); 2 Aug 2003 17:45:11 -0000
Received: from niwun.pair.com (HELO localhost) (209.68.2.70)
  by relay.pair.com with SMTP; 2 Aug 2003 17:45:11 -0000
X-pair-Authenticated: 209.68.2.70
Date: Sat, 2 Aug 2003 12:43:06 -0500 (CDT)
From: Mike Silbersack <silby@silby.com>
To: Scot Loach <sloach@sandvine.com>
In-Reply-To: <FE045D4D9F7AED4CBFF1B3B813C8533701AE86BF@mail.sandvine.com>
Message-ID: <20030802123049.Y2165@odysseus.silby.com>
References: <FE045D4D9F7AED4CBFF1B3B813C8533701AE86BF@mail.sandvine.com>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
cc: "'freebsd-net@freebsd.org'" <freebsd-net@freebsd.org>
Subject: RE: TCP socket shutdown race condition
X-BeenThere: freebsd-net@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Networking and TCP/IP with FreeBSD <freebsd-net.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-net>,
	<mailto:freebsd-net-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-net>
List-Post: <mailto:freebsd-net@freebsd.org>
List-Help: <mailto:freebsd-net-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-net>,
	<mailto:freebsd-net-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sat, 02 Aug 2003 17:45:16 -0000


On Sat, 2 Aug 2003, Scot Loach wrote:

> I don't think that's the problem, although it does seem suspicious.
>
> Here's the struct ucred pointed to by the socket:
>
> (kgdb) p *so.so_cred
> $2 = {cr_ref = 3279453304, cr_uid = 3486088556, cr_ngroups = 1, cr_groups =
> {
>     0, 3276863080, 3277717504, 21162, 0, 0, 0, 0, 0, 4294967295, 4294967295,
>     0, 0, 0, 0, 3279496516}, cr_uidinfo = 0x0}
>
> This looks like garbage, but the cr_uidinfo pointer is null, and the cr_ref
> of _this_ structure is 32 bits.
>
> This doesn't look to me like a problem with the uidinfo, it looks to me like
> the ucred structure has already been freed.
>
> scot.

Well, as ui_ref is the best bet, redoing your tests with it expanded to
ui_int is where we need to start before looking further. :)

I believe that a uidinfo->ui_ref over/underflow could cause random memory
corruption, so maybe the panic you're seeing comes about after a bunch of
memory has already been trashed.

So anyway, promote ui_ref to a u_int and retest.  Tell us what happens.

Mike "Silby" Silbersack