From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D7878C5B578 for ; Wed, 3 Jul 2019 04:19:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AB31F21721 for ; Wed, 3 Jul 2019 04:19:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1562127581; bh=c5IcqDtjzCk/RqZsxVYMwUsTPpfSVIdXZc35qImX9lE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=ZU8u4zDMBw5uUj9Jwg1EuXRkj0SjcJSuFHWDR1vdCL9OgtiFzQkx3ENnk5QM3ntct D2fQ0yoyrz6fF8Pcr7SepWGtE46M4CS8ac6UzqNFsorD4IPL3SEnuXpYIN3JWjMMQ0 nXtnbdGhPYAqsAepxnG0/m93LpnwDJl+yRviVyAw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725944AbfGCETV (ORCPT ); Wed, 3 Jul 2019 00:19:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:56058 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725785AbfGCETV (ORCPT ); Wed, 3 Jul 2019 00:19:21 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D83A320989; Wed, 3 Jul 2019 04:19:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1562127560; bh=c5IcqDtjzCk/RqZsxVYMwUsTPpfSVIdXZc35qImX9lE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=iu5XLbaJalqL60SF18HDTpBTL91+ai/Of7NBf1IlSjWTofopMLciGI4xQL1A5gBON jkSR2qMdhFxAwByjOYPiWcVmo/TlusoNPTDpQjzhUKY00QZ7weDAJTbUsJdlaLPEIr g93FbkWMKvGndqEsLzWwu2OYoP+jRoHfpAdixchY= Date: Tue, 2 Jul 2019 21:19:18 -0700 From: Eric Biggers To: Ravi Bangoria Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Song Liu , Kan Liang , Alexander Shishkin , Jiri Olsa , Namhyung Kim , syzkaller-bugs@googlegroups.com, Oleg Nesterov Subject: Re: Reminder: 22 open syzbot bugs in perf subsystem Message-ID: <20190703041918.GB633@sol.localdomain> References: <20190702054342.GB27702@sol.localdomain> <5a99f556-7449-55da-d901-0249352a5e15@linux.ibm.com> <20190703035550.GA633@sol.localdomain> <4d6ce02e-9325-4247-3d9b-51cdfcfaee07@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4d6ce02e-9325-4247-3d9b-51cdfcfaee07@linux.ibm.com> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 03, 2019 at 09:29:39AM +0530, Ravi Bangoria wrote: > Hi Eric, > > On 7/3/19 9:25 AM, Eric Biggers wrote: > > On Wed, Jul 03, 2019 at 09:09:55AM +0530, Ravi Bangoria wrote: > >> > >> > >> On 7/2/19 11:13 AM, Eric Biggers wrote: > >>> -------------------------------------------------------------------------------- > >>> Title: possible deadlock in uprobe_clear_state > >>> Last occurred: 164 days ago > >>> Reported: 201 days ago > >>> Branches: Mainline > >>> Dashboard link: https://syzkaller.appspot.com/bug?id=a1ce9b3da349209c5085bb8c4fee753d68c3697f > >>> Original thread: https://lkml.kernel.org/lkml/00000000000010a9fb057cd14174@google.com/T/#u > >>> > >>> Unfortunately, this bug does not have a reproducer. > >>> > >>> No one replied to the original thread for this bug. > >>> > >>> If you fix this bug, please add the following tag to the commit: > >>> Reported-by: syzbot+1068f09c44d151250c33@syzkaller.appspotmail.com > >>> > >>> If you send any email or patch for this bug, please consider replying to the > >>> original thread. For the git send-email command to use, or tips on how to reply > >>> if the thread isn't in your mailbox, see the "Reply instructions" at > >>> https://lkml.kernel.org/r/00000000000010a9fb057cd14174@google.com > >>> > >> > >> This is false positive: > >> https://marc.info/?l=linux-kernel&m=154925313012615&w=2 > >> > > > > What do you mean "false positive"? Your patch says there can be a deadlock. > > Also, your patch hasn't been merged yet. So doesn't it still need to be fixed? > > Please see Oleg's reply to the patch: > https://marc.info/?l=linux-kernel&m=154946017315554&w=2 > > """ > But this is false positive, right? if CPU1 calls update_ref_ctr() then > either ->mm_users is already zero so binder_alloc_free_page()->mmget_not_zero() > will fail, or the caller of update_ref_ctr() has a reference and thus > binder_alloc_free_page()->mmput() can't trigger __mmput() ? > """ > Even if it's a lockdep false positive you can't ignore it. People rely on lockdep to find bugs, and they will keep sending you bug reports. So someone has to fix something. Did you see Oleg's suggestion to change mmput() to mmput_async() in binder_alloc_free_page()? https://marc.info/?l=linux-kernel&m=155119805728815&w=2 If you believe that is the right fix, I can reassign this report to binder subsystem and nag the binder maintainers instead... - Eric