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=-6.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 F301DC433E1 for ; Thu, 27 Aug 2020 15:20:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BF1D12080C for ; Thu, 27 Aug 2020 15:20:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="iJGHl6OP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728185AbgH0PUu (ORCPT ); Thu, 27 Aug 2020 11:20:50 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:44549 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728649AbgH0LdI (ORCPT ); Thu, 27 Aug 2020 07:33:08 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1598527981; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=tK2E5OHaYdIMnHynVyzOX85+jSQpnlWbWxI1ka3rMpQ=; b=iJGHl6OPlX/bSFOwWs6Tl5Z5Fd+juMSODETyFwMqsD6H0OtAMMBztX6PTiI/tM+0FSGL6H cWodOzu+cBJhPRhANWsb0Nu/pBdtpgR/+P7oby2wJvrWPv5ylQFyGW3dv66DvRLQ+V7mM+ 4ossNlXy9iHK2P5ycyQ5Ixu0T4eTOvE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-88-GHCIpvapPlWFtEXqEva68w-1; Thu, 27 Aug 2020 07:24:30 -0400 X-MC-Unique: GHCIpvapPlWFtEXqEva68w-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 455E080EFBE; Thu, 27 Aug 2020 11:24:29 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.194.8]) by smtp.corp.redhat.com (Postfix) with SMTP id CC68F5D9E8; Thu, 27 Aug 2020 11:24:27 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 27 Aug 2020 13:24:28 +0200 (CEST) Date: Thu, 27 Aug 2020 13:24:26 +0200 From: Oleg Nesterov To: syzbot Cc: axboe@kernel.dk, linux-kernel@vger.kernel.org, peterz@infradead.org, syzkaller-bugs@googlegroups.com Subject: Re: WARNING: ODEBUG bug in get_signal Message-ID: <20200827112426.GE28468@redhat.com> References: <00000000000068340d05add74c29@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <00000000000068340d05add74c29@google.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/27, syzbot wrote: > > __debug_check_no_obj_freed lib/debugobjects.c:967 [inline] > debug_check_no_obj_freed+0x301/0x41c lib/debugobjects.c:998 > kmem_cache_free.part.0+0x16d/0x1f0 mm/slab.c:3692 > task_work_run+0xdd/0x190 kernel/task_work.c:141 I don't understand this trace, work->func(work) can call kmem_cache_free() but task_work_run() doesn't do this. In theory the patch below makes sense anyway, but I have no idea if it can explain the problem. Oleg. --- x/kernel/task_work.c +++ x/kernel/task_work.c @@ -137,7 +137,7 @@ void task_work_run(void) raw_spin_unlock_irq(&task->pi_lock); do { - next = work->next; + next = READ_ONCE(work->next); work->func(work); work = next; cond_resched();