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=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,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 7A6FEC433E0 for ; Tue, 5 Jan 2021 15:10:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4AA9022B45 for ; Tue, 5 Jan 2021 15:10:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726721AbhAEPJq (ORCPT ); Tue, 5 Jan 2021 10:09:46 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:41519 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725817AbhAEPJp (ORCPT ); Tue, 5 Jan 2021 10:09:45 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1609859299; 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=Il8hr7wLf2mLphtD87oDHygkD/T/28vf7dmL69XSemI=; b=XN+CCBt5dWScQbG+sV1Ht4mAcaPpkzMrYK0KKLlNpN7r5lBkAA2N8aM15ek1VriEDvWvGV Z1uvH+Vnce3sQUaBZlJPzMYbUli/ybxhWr/2nwGKRwdwSfPOSso1fPz4cOOx1y8WalavOG wxhYC0pmJsU+hC3GGDPZqfg6O7aBkq4= Received: from mail-qk1-f199.google.com (mail-qk1-f199.google.com [209.85.222.199]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-344-ck8EXQYrNLWkcXNNrwUZ4A-1; Tue, 05 Jan 2021 10:08:17 -0500 X-MC-Unique: ck8EXQYrNLWkcXNNrwUZ4A-1 Received: by mail-qk1-f199.google.com with SMTP id l138so49691qke.4 for ; Tue, 05 Jan 2021 07:08:17 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=Il8hr7wLf2mLphtD87oDHygkD/T/28vf7dmL69XSemI=; b=Gj7UggZwrdBVzZa02YHiF/cqT2H5j2BexxIgPC5w9WROz0XdD63TCROdD74isShnYp w8+5XGmFKztQtQkLlp2dDRDpqAsiPc1ruOKMco9HUTySF+fCzRjiWY7JLIKyRzNs2bMJ U4OKaK0NS6eLqeH4c6ijfWhHoHVDr+trICELsFvtUJ4WV2efhDMo1cMZcht+mbos1RxY YCm0sXJpTlZ2nh+Iv7SQ5yXWOTyJy4V5/c99xCllEfQgYabIGipcucTPB/Xo7fAAjOeB mLTSjl1lJgZu/p1V11LLHtdNimAEszbLTQWYjovE6uCvhYsLfHy7Ev+cGExo6OT+YTNt xFAQ== X-Gm-Message-State: AOAM530mSpygx3ShtCncRYzu9SaeZ+Y7SeIBjRdN14DZU/caCNuJcPfs DdJ4AzxJedkRx7JYmE2ThpH9Kk46UVdn/KsTGX32MSW/1kth5AEUCu2Hx7XEDVO5T2lucbxTcsT js8jCTC9980FmQuMDNMhqmewO X-Received: by 2002:ac8:7601:: with SMTP id t1mr76309076qtq.323.1609859296852; Tue, 05 Jan 2021 07:08:16 -0800 (PST) X-Google-Smtp-Source: ABdhPJyzp+lVmcL8qYOjocLDZQq1MhjmhAcKocjxHH9hVgaT+EXCdRx0D2tTRuz1UkwXAYCBXzPnZA== X-Received: by 2002:ac8:7601:: with SMTP id t1mr76309049qtq.323.1609859296649; Tue, 05 Jan 2021 07:08:16 -0800 (PST) Received: from xz-x1 ([142.126.83.202]) by smtp.gmail.com with ESMTPSA id c20sm7537qtj.29.2021.01.05.07.08.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Jan 2021 07:08:15 -0800 (PST) Date: Tue, 5 Jan 2021 10:08:13 -0500 From: Peter Xu To: Nadav Amit Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Nadav Amit , Andrea Arcangeli , Yu Zhao , Andy Lutomirski , Pavel Emelyanov , Mike Kravetz , Mike Rapoport , Minchan Kim , Will Deacon , Peter Zijlstra Subject: Re: [RFC PATCH v2 1/2] mm/userfaultfd: fix memory corruption due to writeprotect Message-ID: <20210105150813.GB149908@xz-x1> References: <20201225092529.3228466-1-namit@vmware.com> <20201225092529.3228466-2-namit@vmware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20201225092529.3228466-2-namit@vmware.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 25, 2020 at 01:25:28AM -0800, Nadav Amit wrote: > diff --git a/mm/mprotect.c b/mm/mprotect.c > index ab709023e9aa..c08c4055b051 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -75,7 +75,8 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, > oldpte = *pte; > if (pte_present(oldpte)) { > pte_t ptent; > - bool preserve_write = prot_numa && pte_write(oldpte); > + bool preserve_write = (prot_numa || uffd_wp_resolve) && > + pte_write(oldpte); Irrelevant of the other tlb issue, this is a standalone one and I commented in v1 about simply ignore the change if necessary; unluckily that seems to be ignored.. so I'll try again - would below be slightly better? if (uffd_wp_resolve && !pte_uffd_wp(oldpte)) continue; Firstly, current patch is confusing at least to me, because "uffd_wp_resolve" means "unprotect the pte", whose write bit should mostly be cleared already when uffd_wp_resolve is applicable. Then "preserve_write" for that pte looks odd already. Meanwhile, if that really happens (when pte write bit set, but during a uffd_wp_resolve request) imho there is really nothing we can do, so we should simply avoid touching that at all, and also avoid ptep_modify_prot_start, pte_modify, ptep_modify_prot_commit, calls etc., which takes extra cost. Thanks, -- Peter Xu