From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hugh Dickins Subject: Re: [PATCH] st: don't doublefree pages from scatterlist Date: Fri, 3 Feb 2006 21:16:34 +0000 (GMT) Message-ID: References: <20060104172727.GA320@tau.solarneutrino.net> <20060105201249.GB1795@tau.solarneutrino.net> <20060109033149.GC283@tau.solarneutrino.net> <20060109185350.GG283@tau.solarneutrino.net> <20060118001252.GB821@tau.solarneutrino.net> <43E3BF33.6050705@cs.wisc.edu> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Return-path: Received: from silver.veritas.com ([143.127.12.111]:21070 "EHLO silver.veritas.com") by vger.kernel.org with ESMTP id S1030245AbWBCVP4 (ORCPT ); Fri, 3 Feb 2006 16:15:56 -0500 Received: from goblin.wat.veritas.com([10.10.97.2]) (3368 bytes) by megami.veritas.com via sendmail with P:esmtp/R:smart_host/T:smtp (sender: ) id for ; Fri, 3 Feb 2006 13:15:55 -0800 (PST) (Smail-3.2.0.101 1997-Dec-17 #15 built 2001-Aug-30) In-Reply-To: <43E3BF33.6050705@cs.wisc.edu> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Mike Christie Cc: Kai Makisara , James Bottomley , Doug Gilbert , Andrew Morton , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org On Fri, 3 Feb 2006, Mike Christie wrote: > Hugh Dickins wrote: > > On some architectures, mapping the scatterlist may coalesce entries: > > if that coalesced list is then used for freeing the pages afterwards, > > there's a danger that pages may be doubly freed (and others leaked). > > > > Fix SCSI Tape's sgl_unmap_user_pages by freeing from the pagelist used > > in sgl_map_user_pages. Fixes Ryan Richter's crash on x86_64, with Bad > > page state mapcount 2 from sgl_unmap_user_pages, and consequent mayhem. > > Is this crash occuring with 2.6.16-rc1? I do believe 2.6.15 is the latest release that Ryan has tried (and, strangely, nobody else has ever reported it - identifiably, anyway). Interested in trying unpatched 2.6.16-rc2, Ryan? > I ask becuase in that kernel the scatterlist passed into scsi_execute_async > > if (scsi_execute_async(STp->device, cmd, direction, > &((STp->buffer)->sg[0]), bytes, > > is not the same one that gets send down to the device/HBA. Wow, great info, thanks. > scsi_execute_async takes the scatterlist passed to it from st or sg, uses it > as a hint to build a request + bios, then later when the request is sent to > the device a new scatterlist is sent to the device and the device does the > pci/dma operation on that scatterlist from the block/scsi layer. Very interesting. James can confirm, but I think that means everybody can ignore my drivers/scsi/st.c patch for 2.6.16-rc, and the unposted sg.c patches for the same issue that I was going to send Doug. But the Infiniband, ipr and osst patches still look to be necessary - unless maintainers can point to a similar intervening layer. Hugh