From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: multipart/mixed; boundary="===============8230784282573207855==" MIME-Version: 1.0 From: Byungchul Park To: lkp@lists.01.org Subject: Re: [lockdep] b09be676e0 BUG: unable to handle kernel NULL pointer dereference at 000001f2 Date: Tue, 10 Oct 2017 14:08:42 +0900 Message-ID: <20171010050842.GB3323@X58A-UD3R> In-Reply-To: List-Id: --===============8230784282573207855== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable On Tue, Oct 03, 2017 at 09:54:31AM -0700, Linus Torvalds wrote: > On Tue, Oct 3, 2017 at 7:06 AM, Fengguang Wu w= rote: > > > > This patch triggers a NULL-dereference bug at update_stack_state(). > > Although its parent commit also has a NULL-dereference bug, however > > the call stack looks rather different. Both dmesg files are attached. > > > > It also triggers this warning, which is being discussed in another > > thread, so CC Josh. The full dmesg attached, too. > > > > Please press Enter to activate this console. > > [ 138.605622] WARNING: kernel stack regs at be299c9a in procd:= 340 has bad 'bp' value 000001be > > [ 138.605627] unwind stack type:0 next_sp: (null) mask:0x2 gr= aph_idx:0 > > [ 138.605631] be299c9a: 299ceb00 (0x299ceb00) > > [ 138.605633] be299c9e: 2281f1be (0x2281f1be) > > [ 138.605634] be299ca2: 299cebb6 (0x299cebb6) > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git mast= er > > > > commit b09be676e0ff25bd6d2e7637e26d349f9109ad75 > > locking/lockdep: Implement the 'crossrelease' feature Hello, I'm sorry for late. It was the biggest traditional holiday in Korea until yesterday. > Can we consider just reverting the crossrelease thing? > = > The apparent stack corruption really worries me, and what worries me > most is that commit wasn't even supposed to change anything as far as > I can tell - it only adds infrastructure, no actual users that *set* > the cross-lock thing. All users of wait_for_completion() and lock_page() are implicitly actual users with CONFIG_LOCKDEP_CROSSRELEASE enabled, which sets the crosslock thing internally on its initialization. --===============8230784282573207855==-- From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752259AbdJJFIt (ORCPT ); Tue, 10 Oct 2017 01:08:49 -0400 Received: from LGEAMRELO11.lge.com ([156.147.23.51]:54390 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751809AbdJJFIr (ORCPT ); Tue, 10 Oct 2017 01:08:47 -0400 X-Original-SENDERIP: 156.147.1.151 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 10.177.222.33 X-Original-MAILFROM: byungchul.park@lge.com Date: Tue, 10 Oct 2017 14:08:42 +0900 From: Byungchul Park To: Linus Torvalds Cc: Fengguang Wu , Ingo Molnar , "Peter Zijlstra (Intel)" , Linux Kernel Mailing List , LKP , Josh Poimboeuf , kernel-team@lge.com Subject: Re: [lockdep] b09be676e0 BUG: unable to handle kernel NULL pointer dereference at 000001f2 Message-ID: <20171010050842.GB3323@X58A-UD3R> References: <20171003140634.r2jzujgl62ox4uzh@wfg-t540p.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 03, 2017 at 09:54:31AM -0700, Linus Torvalds wrote: > On Tue, Oct 3, 2017 at 7:06 AM, Fengguang Wu wrote: > > > > This patch triggers a NULL-dereference bug at update_stack_state(). > > Although its parent commit also has a NULL-dereference bug, however > > the call stack looks rather different. Both dmesg files are attached. > > > > It also triggers this warning, which is being discussed in another > > thread, so CC Josh. The full dmesg attached, too. > > > > Please press Enter to activate this console. > > [ 138.605622] WARNING: kernel stack regs at be299c9a in procd:340 has bad 'bp' value 000001be > > [ 138.605627] unwind stack type:0 next_sp: (null) mask:0x2 graph_idx:0 > > [ 138.605631] be299c9a: 299ceb00 (0x299ceb00) > > [ 138.605633] be299c9e: 2281f1be (0x2281f1be) > > [ 138.605634] be299ca2: 299cebb6 (0x299cebb6) > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master > > > > commit b09be676e0ff25bd6d2e7637e26d349f9109ad75 > > locking/lockdep: Implement the 'crossrelease' feature Hello, I'm sorry for late. It was the biggest traditional holiday in Korea until yesterday. > Can we consider just reverting the crossrelease thing? > > The apparent stack corruption really worries me, and what worries me > most is that commit wasn't even supposed to change anything as far as > I can tell - it only adds infrastructure, no actual users that *set* > the cross-lock thing. All users of wait_for_completion() and lock_page() are implicitly actual users with CONFIG_LOCKDEP_CROSSRELEASE enabled, which sets the crosslock thing internally on its initialization.