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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 68415C3A59D for ; Wed, 21 Aug 2019 00:53:28 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3BEAE2087E for ; Wed, 21 Aug 2019 00:53:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3BEAE2087E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 035396B026E; Tue, 20 Aug 2019 20:53:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id F28026B026F; Tue, 20 Aug 2019 20:53:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E3E806B0270; Tue, 20 Aug 2019 20:53:26 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0214.hostedemail.com [216.40.44.214]) by kanga.kvack.org (Postfix) with ESMTP id C439F6B026E for ; Tue, 20 Aug 2019 20:53:26 -0400 (EDT) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id 6487152C3 for ; Wed, 21 Aug 2019 00:53:26 +0000 (UTC) X-FDA: 75844611612.16.sofa89_752b0ca940144 X-HE-Tag: sofa89_752b0ca940144 X-Filterd-Recvd-Size: 2272 Received: from huawei.com (szxga07-in.huawei.com [45.249.212.35]) by imf03.hostedemail.com (Postfix) with ESMTP for ; Wed, 21 Aug 2019 00:53:25 +0000 (UTC) Received: from DGGEMS401-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 90AFC6EB68EC1F723933; Wed, 21 Aug 2019 08:53:20 +0800 (CST) Received: from [127.0.0.1] (10.133.217.137) by DGGEMS401-HUB.china.huawei.com (10.3.19.201) with Microsoft SMTP Server id 14.3.439.0; Wed, 21 Aug 2019 08:53:18 +0800 Subject: Re: [PATCH] userfaultfd_release: always remove uffd flags and clear vm_userfaultfd_ctx To: Oleg Nesterov CC: linux-mm , Andrea Arcangeli , Peter Xu , Mike Rapoport , Jann Horn , Jason Gunthorpe , Michal Hocko , Andrew Morton , Tetsuo Handa , References: <20190820160237.GB4983@redhat.com> From: Kefeng Wang Message-ID: Date: Wed, 21 Aug 2019 08:53:17 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190820160237.GB4983@redhat.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [10.133.217.137] X-CFilter-Loop: Reflected X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2019/8/21 0:02, Oleg Nesterov wrote: > userfaultfd_release() should clear vm_flags/vm_userfaultfd_ctx even > if mm->core_state != NULL. > > Otherwise a page fault can see userfaultfd_missing() == T and use an > already freed userfaultfd_ctx. > > Reported-by: Kefeng Wang > Fixes: 04f5866e41fb ("coredump: fix race condition between mmget_not_zero()/get_task_mm() and core dumping") > Cc: stable@vger.kernel.org > Signed-off-by: Oleg Nesterov > --- > fs/userfaultfd.c | 25 +++++++++++++------------ > 1 file changed, 13 insertions(+), 12 deletions(-) Tested on lts4.4 and 5.3-rc4, Thanks.