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=-12.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 98109C433FE for ; Wed, 22 Sep 2021 14:31:00 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2475E61214 for ; Wed, 22 Sep 2021 14:31:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 2475E61214 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 889306B006C; Wed, 22 Sep 2021 10:30:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 838BE900003; Wed, 22 Sep 2021 10:30:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7004D900002; Wed, 22 Sep 2021 10:30:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0184.hostedemail.com [216.40.44.184]) by kanga.kvack.org (Postfix) with ESMTP id 627186B006C for ; Wed, 22 Sep 2021 10:30:59 -0400 (EDT) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 06D342C6B6 for ; Wed, 22 Sep 2021 14:30:59 +0000 (UTC) X-FDA: 78615446238.05.061063F Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf13.hostedemail.com (Postfix) with ESMTP id 8C0E11282349 for ; Wed, 22 Sep 2021 14:30:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1632321058; 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=H9MFwjIYK3NzURsIL5ZeXXjauXt11emCz529o4qozFY=; b=RDXhkccJok5H6fMPJGPvKH+D6VD23YKtFt/ITvNl23chYDBPmro6xOAki/ASCUvIiJpedt p4sYdNyUVSCZtoVc6qc5Qtx9BYL26hjJiVPyIzxeF581VD0HbTZcYXqM7mYPoXSAvUNoZV 6+TE/dPBTNIl92KYWgr9eh+ZDHsAOzc= Received: from mail-qv1-f71.google.com (mail-qv1-f71.google.com [209.85.219.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-228-dqAvuc4QOXOkY4HZ7KFLVg-1; Wed, 22 Sep 2021 10:30:56 -0400 X-MC-Unique: dqAvuc4QOXOkY4HZ7KFLVg-1 Received: by mail-qv1-f71.google.com with SMTP id h18-20020a0cffd2000000b0037e78fb2552so12211879qvv.12 for ; Wed, 22 Sep 2021 07:30:56 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=H9MFwjIYK3NzURsIL5ZeXXjauXt11emCz529o4qozFY=; b=lrnayibE8wkYSyFhA3at4XR/emtEz860ylTcKAjQKKbToy/zWxcDpCPMGdMzsTC8pw aUfSF8WlzXy6w2jE1WqzD16oJz4Eo0snehmgAN8xZmCu3lKX6ryIRFwP+M19o3cUiSBZ CH6WTm/vMQmXSIH7FnEgOJhUUWI3x00eGL5qu0RMyUf5JXi95qK3iZ9fbTVwA1X92fZJ h4unV9p4U1MinEddlsF2JYQ3jlGg1XzR/7nxU8aVwL5l6XGmd0oZIl3KHu2AB42zi3xA Qcwmgr6ffQldNrdmv4rvba7L1YM0W9uQJ3cuUwHgJc3s1ALQYGdDzWRpKeDwUjtNdWB7 X9vg== X-Gm-Message-State: AOAM532F8LKm7ffOO0FVIYM4LhPLADdlqjM5SocrO9dS3XaWYEm6xu4i nDd/xOMm0r15pzp+a/tu5wsE2vhPittbwzOmLUHDaJtSnY5AqxYM/4rssH89FSrwlicdPxxGsRD 0WAmnxRYSFuw= X-Received: by 2002:ac8:1c6:: with SMTP id b6mr32958212qtg.221.1632321056091; Wed, 22 Sep 2021 07:30:56 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyQAVBr6hBwwFSYKO7U1/khHUr5y9tSTMCIoPdoZ894eUZ+OrVYZ3xfOPFjOhJbFSSfttPIFg== X-Received: by 2002:ac8:1c6:: with SMTP id b6mr32958174qtg.221.1632321055765; Wed, 22 Sep 2021 07:30:55 -0700 (PDT) Received: from t490s ([2607:fea8:56a2:9100::d3ec]) by smtp.gmail.com with ESMTPSA id f83sm1917615qke.79.2021.09.22.07.30.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Sep 2021 07:30:55 -0700 (PDT) Date: Wed, 22 Sep 2021 10:30:53 -0400 From: Peter Xu To: Nadav Amit Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Nadav Amit , Andrea Arcangeli , stable@vger.kernel.org Subject: Re: [PATCH] userfaultfd: fix a race between writeprotect and exit_mmap() Message-ID: References: <20210921200247.25749-1-namit@vmware.com> MIME-Version: 1.0 In-Reply-To: <20210921200247.25749-1-namit@vmware.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 8C0E11282349 Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=RDXhkccJ; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf13.hostedemail.com: domain of peterx@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=peterx@redhat.com X-Stat-Signature: dnejjizjjxqu4zkajamuwckobdbzc9z9 X-HE-Tag: 1632321058-294960 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Sep 21, 2021 at 01:02:47PM -0700, Nadav Amit wrote: > From: Nadav Amit > > A race is possible when a process exits, its VMAs are removed > by exit_mmap() and at the same time userfaultfd_writeprotect() is > called. > > The race was detected by KASAN on a development kernel, but it appears > to be possible on vanilla kernels as well. > > Use mmget_not_zero() to prevent the race as done in other userfaultfd > operations. > > Cc: Peter Xu > Cc: Andrea Arcangeli > Cc: stable@vger.kernel.org > Fixes: 63b2d4174c4ad ("userfaultfd: wp: add the writeprotect API to userfaultfd ioctl") > Signed-off-by: Nadav Amit Reviewed-by: Peter Xu Thanks! -- Peter Xu