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=-9.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 295F2C33C9E for ; Fri, 17 Jan 2020 23:45:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F0E7521D56 for ; Fri, 17 Jan 2020 23:45:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="gYMCiMCk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730302AbgAQXpN (ORCPT ); Fri, 17 Jan 2020 18:45:13 -0500 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:16830 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730184AbgAQXpN (ORCPT ); Fri, 17 Jan 2020 18:45:13 -0500 Received: from pps.filterd (m0148461.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 00HNSNUf017480 for ; Fri, 17 Jan 2020 15:45:11 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : mime-version : content-type; s=facebook; bh=Sok7U8dg0bqgNO0xZwUMVKyUbAR6McyeiedSKBbUSf0=; b=gYMCiMCkEkailKk2vKOemzTki7hd38dnEXrDKcefj1t2pyrP8g8uZAqIjytsh8TF944M VpcQhn2lBR/J92Flw1rW9xONlweP9PpMwmm43YLuKUaNIq/pMjovy7ZJbzcpeH+gMU6B E4SeSiv86MLXG8bT4priMAbYbtLhr75hD7o= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 2xk0rpn9av-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Fri, 17 Jan 2020 15:45:11 -0800 Received: from intmgw001.06.prn3.facebook.com (2620:10d:c085:208::11) by mail.thefacebook.com (2620:10d:c085:11d::5) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1779.2; Fri, 17 Jan 2020 15:45:11 -0800 Received: by devbig006.ftw2.facebook.com (Postfix, from userid 4523) id 1F6F662E3453; Fri, 17 Jan 2020 15:45:06 -0800 (PST) Smtp-Origin-Hostprefix: devbig From: Song Liu Smtp-Origin-Hostname: devbig006.ftw2.facebook.com To: CC: , Song Liu , Alexander Shishkin , Arnaldo Carvalho de Melo , Jiri Olsa , Peter Zijlstra Smtp-Origin-Cluster: ftw2c04 Subject: [PATCH] perf/core: fix mlock accounting in perf_mmap() Date: Fri, 17 Jan 2020 15:45:03 -0800 Message-ID: <20200117234503.1324050-1-songliubraving@fb.com> X-Mailer: git-send-email 2.17.1 X-FB-Internal: Safe MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-01-17_05:2020-01-16,2020-01-17 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 phishscore=0 lowpriorityscore=0 bulkscore=0 spamscore=0 priorityscore=1501 clxscore=1015 impostorscore=0 malwarescore=0 adultscore=0 mlxlogscore=937 mlxscore=0 suspectscore=1 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-2001170178 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org sysctl_perf_event_mlock and user->locked_vm can change value independently, so we can't guarantee: user->locked_vm <= user_lock_limit When user->locked_vm is larger than user_lock_limit, we cannot simply update extra and user_extra as: extra = user_locked - user_lock_limit; user_extra -= extra; Otherwise, user_extra will be negative. In extreme cases, this may lead to negative user->locked_vm (until this perf-mmap is closed), which break locked_vm badly. Fix this with two separate conditions, which make sure user_extra is always positive. Fixes: c4b75479741c ("perf/core: Make the mlock accounting simple again") Signed-off-by: Song Liu Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Peter Zijlstra --- kernel/events/core.c | 28 ++++++++++++++++++++++++---- 1 file changed, 24 insertions(+), 4 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index a1f8bde19b56..89acdd1574ef 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5920,11 +5920,31 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma) if (user_locked > user_lock_limit) { /* - * charge locked_vm until it hits user_lock_limit; - * charge the rest from pinned_vm + * sysctl_perf_event_mlock and user->locked_vm can change + * value independently, so we can't guarantee: + * + * user->locked_vm <= user_lock_limit + * + * We need be careful to make sure user_extra >=0. + * + * Using "user_locked - user_extra" to avoid calling + * atomic_long_read() again. */ - extra = user_locked - user_lock_limit; - user_extra -= extra; + if (user_locked - user_extra >= user_lock_limit) { + /* + * already used all user_locked_limit, charge all + * to pinned_vm + */ + extra = user_extra; + user_extra = 0; + } else { + /* + * charge locked_vm until it hits user_lock_limit; + * charge the rest from pinned_vm + */ + extra = user_locked - user_lock_limit; + user_extra -= extra; + } } lock_limit = rlimit(RLIMIT_MEMLOCK); -- 2.17.1