Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933086AbcLUXTf (ORCPT ); Wed, 21 Dec 2016 18:19:35 -0500 Received: from mail-io0-f195.google.com ([209.85.223.195]:33408 "EHLO mail-io0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758958AbcLUXTR (ORCPT ); Wed, 21 Dec 2016 18:19:17 -0500 MIME-Version: 1.0 In-Reply-To: <20161221221638.GD4758@dastard> References: <20161214222411.GH4326@dastard> <20161214222953.GI4326@dastard> <20161216185906.t2wmrr6wqjdsrduw@straylight.hirudinean.org> <20161221221638.GD4758@dastard> From: Linus Torvalds Date: Wed, 21 Dec 2016 15:19:15 -0800 X-Google-Sender-Auth: 9pa6SnH5CyyWnsBahLNZb0GioTo Message-ID: Subject: Re: [4.10, panic, regression] iscsi: null pointer deref at iscsi_tcp_segment_done+0x20d/0x2e0 To: Dave Chinner Cc: Chris Leech , Linux Kernel Mailing List , Lee Duncan , open-iscsi@googlegroups.com, Linux SCSI List , linux-block@vger.kernel.org, Christoph Hellwig Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1919 Lines: 52 Hi, On Wed, Dec 21, 2016 at 2:16 PM, Dave Chinner wrote: > On Fri, Dec 16, 2016 at 10:59:06AM -0800, Chris Leech wrote: >> Thanks Dave, >> >> I'm hitting a bug at scatterlist.h:140 before I even get any iSCSI >> modules loaded (virtio block) so there's something else going on in the >> current merge window. I'll keep an eye on it and make sure there's >> nothing iSCSI needs fixing for. > > OK, so before this slips through the cracks..... > > Linus - your tree as of a few minutes ago still panics immediately > when starting xfstests on iscsi devices. It appears to be a > scatterlist corruption and not an iscsi problem, so the iscsi guys > seem to have bounced it and no-one is looking at it. Hmm. There's not much to go by. Can somebody in iscsi-land please try to just bisect it - I'm not seeing a lot of clues to where this comes from otherwise. There clearly hasn't been anything done to drivers/scsi/*iscsi* since 4.9, so it's coming from elsewhere, presumably the block layer changes as you say. But I think we need iscsi people to pinpoint it a bit more, since nobody else seems to be complaining. Looking around a bit, the only even halfway suspicious scatterlist initialization thing I see is commit f9d03f96b988 ("block: improve handling of the magic discard payload") which used to have a magic hack wrt !bio->bi_vcnt, and that got removed. See __blk_bios_map_sg(), now it does __blk_bvec_map_sg() instead. Maybe __blk_bvec_map_sg() would want that same if (!bio->bi_vcnt) return 0; adding Christoph explicitly so that he can tell me why I'm a clueless weenie. Although I suspect he's already on the scsi and block lists and would have done so anyway. > I'm disappearing for several months at the end of tomorrow, so I > thought I better make sure you know about it. I've also added > linux-scsi, linux-block to the cc list.... Thanks, Linus