From patchwork Thu Oct 29 07:19:23 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Song Liu X-Patchwork-Id: 316058 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=-6.9 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_GIT 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 03230C55178 for ; Thu, 29 Oct 2020 07:47:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A8108214DB for ; Thu, 29 Oct 2020 07:47:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="VixOnPxN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732737AbgJ2HqA (ORCPT ); Thu, 29 Oct 2020 03:46:00 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:30702 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730754AbgJ2Hpv (ORCPT ); Thu, 29 Oct 2020 03:45:51 -0400 Received: from pps.filterd (m0109331.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 09T7Iw9f013466 for ; Thu, 29 Oct 2020 00:20:00 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : mime-version : content-transfer-encoding : content-type; s=facebook; bh=JLzH51fIRRW8lUnrE08RZYYgZ99JFA8voFiaOqr+L40=; b=VixOnPxNVqbzZ+bkoBfyYrRYj3kp6whmAW7iQSDmjd4PHPKGyVGeVYWhhelKSL68jRca cScaiLap22uCVm7wE7HKzLy1YpAdREyXajJ8BY7q+g3b+eqHKz3ysFmQmJQzFdOpnhwx Dfd5196OgwsE2UNZDdq8RH9tWWe3vhVST2s= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 34egnfcnh1-2 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Thu, 29 Oct 2020 00:20:00 -0700 Received: from intmgw001.08.frc2.facebook.com (2620:10d:c085:208::11) by mail.thefacebook.com (2620:10d:c085:11d::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1979.3; Thu, 29 Oct 2020 00:19:58 -0700 Received: by devbig006.ftw2.facebook.com (Postfix, from userid 4523) id 4E1A362E580C; Thu, 29 Oct 2020 00:19:46 -0700 (PDT) From: Song Liu To: , CC: , , , , , Song Liu Subject: [PATCH bpf-next 0/2] bpf: safeguard hashtab locking in NMI context Date: Thu, 29 Oct 2020 00:19:23 -0700 Message-ID: <20201029071925.3103400-1-songliubraving@fb.com> X-Mailer: git-send-email 2.24.1 MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312, 18.0.737 definitions=2020-10-29_03:2020-10-29,2020-10-29 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxlogscore=454 mlxscore=0 suspectscore=0 phishscore=0 impostorscore=0 malwarescore=0 bulkscore=0 lowpriorityscore=0 adultscore=0 clxscore=1015 priorityscore=1501 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2010290051 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org LOCKDEP NMI warning highlighted potential deadlock of hashtab in NMI context: [ 74.828971] ================================ [ 74.828972] WARNING: inconsistent lock state [ 74.828973] 5.9.0-rc8+ #275 Not tainted [ 74.828974] -------------------------------- [ 74.828975] inconsistent {INITIAL USE} -> {IN-NMI} usage. [ 74.828976] taskset/1174 [HC2[2]:SC0[0]:HE0:SE1] takes: [...] [ 74.828999] Possible unsafe locking scenario: [ 74.828999] [ 74.829000] CPU0 [ 74.829001] ---- [ 74.829001] lock(&htab->buckets[i].raw_lock); [ 74.829003] [ 74.829004] lock(&htab->buckets[i].raw_lock); Please refer to patch 1/2 for full trace. This warning is a false alert, as "INITIAL USE" and "IN-NMI" in the tests are from different hashtab. On the other hand, in theory, it is possible to deadlock when a hashtab is access from both non-NMI and NMI context. Patch 1/2 fixes this false alert by assigning separate lockdep class to each hashtab. Patch 2/2 introduces map_locked counters, which is similar to bpf_prog_active counter, to avoid hashtab deadlock in NMI context. Song Liu (2): bpf: use separate lockdep class for each hashtab bpf: Avoid hashtab deadlock with map_locked kernel/bpf/hashtab.c | 126 +++++++++++++++++++++++++++++++------------ 1 file changed, 92 insertions(+), 34 deletions(-) --- 2.24.1