From owner-freebsd-current@FreeBSD.ORG Tue Mar 8 14:50:34 2005 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 70D8216A4CE; Tue, 8 Mar 2005 14:50:34 +0000 (GMT) Received: from www.cryptography.com (li-22.members.linode.com [64.5.53.22]) by mx1.FreeBSD.org (Postfix) with ESMTP id 1FFE543D1F; Tue, 8 Mar 2005 14:50:34 +0000 (GMT) (envelope-from nate@root.org) Received: from [10.0.1.4] ([218.149.156.148]) by www.cryptography.com (8.12.8/8.12.8) with ESMTP id j28EoQZj003323 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Tue, 8 Mar 2005 06:50:28 -0800 Message-ID: <422DBBA5.1000903@root.org> Date: Tue, 08 Mar 2005 06:50:13 -0800 From: Nate Lawson User-Agent: Mozilla Thunderbird 1.0 (Windows/20041206) X-Accept-Language: en-us, en MIME-Version: 1.0 To: =?ISO-8859-1?Q?S=F8ren_Schmidt?= References: <422225D6.5020009@root.org> <422D84FF.1010707@DeepCore.dk> In-Reply-To: <422D84FF.1010707@DeepCore.dk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit cc: stable@freebsd.org cc: current@freebsd.org Subject: Re: patch: fix ata panic with Thinkpad CD and DVD drives X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 08 Mar 2005 14:50:34 -0000 Søren Schmidt wrote: > Nate Lawson wrote: > >> If you've been having "memory modified after free" panics on -current >> and have a Thinkpad, the attached patch should fix things for you. A >> quick check of RELENG_5 indicates that the bug is probably there also >> but I haven't tested for it there. >> >> The bug is triggered by timeouts in the ata_getparam() probe path. >> The ata_timeout() fires and ata_end_transaction() is called to get the >> status. However, it continues down into ata_pio_read() even though >> there is no data available since we had a timeout, not read >> completion. ata_pio_read() reads 512 bytes of probably bogus data. >> The important problem is that it also advances donecount. On >> subsequent timeouts (note there are 4 below), donecount advances into >> unallocated memory and so subsequent ata_pio_read() calls overwrite >> 512 bytes of someone else's memory. >> >> The fix is to exit immediately if ATA_R_TIMEOUT is set after reading >> the status in ata_end_transaction(). It shouldn't go into >> ata_pio_read() if there was a timeout. The patch does this. >> >> However, it only handles PIO timeouts since I wasn't sure the best way >> to proceed for unwinding DMA state and the like for the other cases. >> This is enough to fix the overwrite and subsequent panic on my >> systems. I've run heavy IO stress and DVD accesses for a while and no >> further panics. >> >> While looking into this, I found another potential problem. In one >> reinjection case, donecount wasn't reset to 0. The patch for >> ata-queue.c does this and I think it's necessary but don't hit this >> case in testing so I can't be sure. Finally, there's one whitespace >> nit that helps with clarity. >> >> These are similar bugs to one found back in August that had the same >> effect. Here's the closest reference I could find in the mail >> archives for this: >> http://lists.freebsd.org/mailman/htdig/freebsd-current/2004-August/033033.html > > > Just a note from here, these bugs are fixed in ATA mkIII so you could > just have gleaned the solution from there (or maybe you did :)) Nope, but I'm glad you can corroborate these fixes are correct. -- Nate