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=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 934F8C433F5 for ; Wed, 22 Sep 2021 14:31:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 76A686115A for ; Wed, 22 Sep 2021 14:31:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235379AbhIVOcb (ORCPT ); Wed, 22 Sep 2021 10:32:31 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:44621 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232401AbhIVOca (ORCPT ); Wed, 22 Sep 2021 10:32:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1632321060; 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=EuG47Y/ikTAr49j+3zjGmNyrj3KUAI8/JWlB335KkQp9hRfVqGbYhPK6OmXF8PWA9+rh/A ig3qCKKCY3JEYQPsCEMI/YMZTo1gJtMOPTD0uaJQB2rBWcmZ2d1s50vikn/mIe1wZiWK9s QMtosJdAZYTW1EJoqN2QrWveLNiz1Yk= 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-238-dcRGBCA9Mlm5RHyhWH8zVQ-1; Wed, 22 Sep 2021 10:30:56 -0400 X-MC-Unique: dcRGBCA9Mlm5RHyhWH8zVQ-1 Received: by mail-qv1-f71.google.com with SMTP id a15-20020a0ce34f000000b0037a944f655dso12732563qvm.5 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=2wzfIUPlDk5O1rvqlXfL2HHvWYuL9QcAXWRW0lVGRYQj6qy4YARYNmr90xQoHMqVLb rHSJ0mog0RHPTQKQFyhca/nvN4pBdYQ0Ay4e25Zi/3zpRf5ITKixYeypB/pOQbEiGPNR JZvhIcMJE673E9v/tpPMpvKj+8nc7sF/bUNJvrpmzFVxo56NOgcAicmG4fGdFA2UPQJA UZxJWOqgd+R+vgCpI7JWAq+i3VLs3UJ3dPK9fP+89u9u5U1CJmgSXtHQbNFKjQfPQZeR ptgTvsjBCGCWaiZGPOaWoYF63alp8IIt8qg8g4kMFAxQYtWJiMJihe0lxkePv2CM6NI+ uUPg== X-Gm-Message-State: AOAM533PXh5W9oOesMUTwXg2AMzWi8Zpx6oAPtgrtH7G/at6x3hc+d2+ WzDZuZPh8TS/XQV8tedkXnr9imd29lUObeu5bjltCmWCbhL+/G7oF+6H7CJe6aqth5XDGkQvFPc KJH+2R32pFELI35Z7 X-Received: by 2002:ac8:1c6:: with SMTP id b6mr32958206qtg.221.1632321056079; 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 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210921200247.25749-1-namit@vmware.com> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 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