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=-8.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 ECB52C433E0 for ; Mon, 28 Dec 2020 22:59:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BEECE222BB for ; Mon, 28 Dec 2020 22:59:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731985AbgL1W4Z (ORCPT ); Mon, 28 Dec 2020 17:56:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49506 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729615AbgL1WNT (ORCPT ); Mon, 28 Dec 2020 17:13:19 -0500 Received: from mail-lf1-x12b.google.com (mail-lf1-x12b.google.com [IPv6:2a00:1450:4864:20::12b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3B510C0613D6 for ; Mon, 28 Dec 2020 14:12:39 -0800 (PST) Received: by mail-lf1-x12b.google.com with SMTP id x20so26883306lfe.12 for ; Mon, 28 Dec 2020 14:12:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=tveTiSW3kXI18qkd/ZaB+nQ0L/9zQTBwJzflX/XFRO4=; b=zArwFJCb5RJFbnwqQOcGRmO9THjhSHIcad6u0iuLaWRPbpzDkqfwNGoJrsxucPcimm jwI/yVKRYRBMnwUpQ2zQyOfYjlraEt7alLh8N1hmGiQB+MkzgL7kCkzi6KM8tYMnXTaR AC1tLDiH8chACCfWto4A/LsOZvqlWRSEZlLSaOjzYCWXt0r3+QtuEWvUJ2sP4jsPkRXI TiZJS0EavQZPgg80200E0VCRSE0tFLTRNrgBobsi0TgfdXhrhOlPOjnfw8h3RUS/96F3 qEYGSwlzUpvdIKwvYtvigqclnGrTxAUroQ9X1rnqoDVaa6CL4MBqc5ef+1i+D7ilblZl AAOA== 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=tveTiSW3kXI18qkd/ZaB+nQ0L/9zQTBwJzflX/XFRO4=; b=On6QvKtUNc3L/lvXXkv41s5NUOgTWuPy97PrPFt3RzVeRnEILVOpgPKRF61D9FA8HU arSJR5X9VmjC+IpWjhUAb9QGz7RQHRnoX/dcriXuWEqV37CBM8ixcEf/mGVvzRiJxKML e35dp9IkwWpTU11bhzUW1greXG+FuFZhmYdjNsrYn4RC2pV/KlrZ1GrVSgAllmI44SDn ruuMLE8fMZ9t6WBu18ikm6h1xsNG1/KMySK6YPgqh5nmHmo+UYssKrpDumhbZsTUr8UE eR5B9i/lKlebeeMi22onabtRvnrzkLRGP7NOBN7onFk64wfQp22tvNIwqk900Z4Be//g hNHg== X-Gm-Message-State: AOAM5302SE175Tblzx/aCgq/C2JBIplSQWBKCtVSrcHrh4u3n54io3Q8 elMJsplcgLMv2Y4qd+D/pDmFsA== X-Google-Smtp-Source: ABdhPJySQycOonv7NhIpwPNHFfA/dnUsLfdgmjGLC7V51EjW7hZO8cBlM/z70OqkOOFQUJSip5xYLg== X-Received: by 2002:a19:6c7:: with SMTP id 190mr21005693lfg.614.1609193557628; Mon, 28 Dec 2020 14:12:37 -0800 (PST) Received: from box.localdomain ([86.57.175.117]) by smtp.gmail.com with ESMTPSA id a15sm6433563lji.105.2020.12.28.14.12.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Dec 2020 14:12:36 -0800 (PST) Received: by box.localdomain (Postfix, from userid 1000) id 15841100F3B; Tue, 29 Dec 2020 01:12:37 +0300 (+03) Date: Tue, 29 Dec 2020 01:12:37 +0300 From: "Kirill A. Shutemov" To: Linus Torvalds Cc: Hugh Dickins , Matthew Wilcox , "Kirill A. Shutemov" , Will Deacon , Linux Kernel Mailing List , Linux-MM , Linux ARM , Catalin Marinas , Jan Kara , Minchan Kim , Andrew Morton , Vinayak Menon , Android Kernel Team Subject: Re: [PATCH 1/2] mm: Allow architectures to request 'old' entries when prefaulting Message-ID: <20201228221237.6nu75kgxq7ikxn2a@box> References: <20201226224016.dxjmordcfj75xgte@box> <20201227234853.5mjyxcybucts3kbq@box> <20201228125352.phnj2x2ci3kwfld5@box> <20201228220548.57hl32mmrvvefj6q@box> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201228220548.57hl32mmrvvefj6q@box> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 29, 2020 at 01:05:48AM +0300, Kirill A. Shutemov wrote: > On Mon, Dec 28, 2020 at 10:47:36AM -0800, Linus Torvalds wrote: > > On Mon, Dec 28, 2020 at 4:53 AM Kirill A. Shutemov wrote: > > > > > > So far I only found one more pin leak and always-true check. I don't see > > > how can it lead to crash or corruption. Keep looking. > > > > Well, I noticed that the nommu.c version of filemap_map_pages() needs > > fixing, but that's obviously not the case Hugh sees. > > > > No,m I think the problem is the > > > > pte_unmap_unlock(vmf->pte, vmf->ptl); > > > > at the end of filemap_map_pages(). > > > > Why? > > > > Because we've been updating vmf->pte as we go along: > > > > vmf->pte += xas.xa_index - last_pgoff; > > > > and I think that by the time we get to that "pte_unmap_unlock()", > > vmf->pte potentially points to past the edge of the page directory. > > Well, if it's true we have bigger problem: we set up an pte entry without > relevant PTL. > > But I *think* we should be fine here: do_fault_around() limits start_pgoff > and end_pgoff to stay within the page table. > > It made mw looking at the code around pte_unmap_unlock() and I think that > the bug is that we have to reset vmf->address and NULLify vmf->pte once we > are done with faultaround: > > diff --git a/mm/memory.c b/mm/memory.c Ugh.. Wrong place. Need to sleep. I'll look into your idea tomorrow. diff --git a/mm/filemap.c b/mm/filemap.c index 87671284de62..e4daab80ed81 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2987,6 +2987,8 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf, unsigned long address, } while ((head = next_map_page(vmf, &xas, end_pgoff)) != NULL); pte_unmap_unlock(vmf->pte, vmf->ptl); rcu_read_unlock(); + vmf->address = address; + vmf->pte = NULL; WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss); return ret; -- Kirill A. Shutemov 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=-8.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,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 EF48BC433DB for ; Mon, 28 Dec 2020 22:14:03 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A43B222262 for ; Mon, 28 Dec 2020 22:14:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A43B222262 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=shutemov.name Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=YaJvsTQV+jcsF7lG3kuzVST01gwb8KbKnEyErlgqDLY=; b=FspWa63k43iaet/lBouU3C/wB kNVYZQTwDiJYL+9GjBNrJLqqxG3uk8fGto1wnjyPYgdeBDMNhMCsnL8/WgFY9xjS7qddTO2VA9fZ7 OrUwhonoFkSLo1i0EBvh3XufVWKllu3GbDbzbnxxwkc2F4DzDHpgaumkq0JMoGuxMlolL+KRQBJb1 TgL+ZNYUp6L+YcyQEytyAicwGa14UILugHL5W9YtPG8qsxQj9UhLgRN0HWbriUCKO3JVHmimSShxH AWrRmExeE9coMB7dA7/zxOVtx+ztervP9XXFi3yFfSew+Es0qpqztcXyKPo2BbTaMPc8sD11O9iwH /ygR26bEg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1ku0kt-0007OC-B5; Mon, 28 Dec 2020 22:12:43 +0000 Received: from mail-lf1-x131.google.com ([2a00:1450:4864:20::131]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1ku0kq-0007N0-R4 for linux-arm-kernel@lists.infradead.org; Mon, 28 Dec 2020 22:12:41 +0000 Received: by mail-lf1-x131.google.com with SMTP id a12so26958030lfl.6 for ; Mon, 28 Dec 2020 14:12:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=tveTiSW3kXI18qkd/ZaB+nQ0L/9zQTBwJzflX/XFRO4=; b=zArwFJCb5RJFbnwqQOcGRmO9THjhSHIcad6u0iuLaWRPbpzDkqfwNGoJrsxucPcimm jwI/yVKRYRBMnwUpQ2zQyOfYjlraEt7alLh8N1hmGiQB+MkzgL7kCkzi6KM8tYMnXTaR AC1tLDiH8chACCfWto4A/LsOZvqlWRSEZlLSaOjzYCWXt0r3+QtuEWvUJ2sP4jsPkRXI TiZJS0EavQZPgg80200E0VCRSE0tFLTRNrgBobsi0TgfdXhrhOlPOjnfw8h3RUS/96F3 qEYGSwlzUpvdIKwvYtvigqclnGrTxAUroQ9X1rnqoDVaa6CL4MBqc5ef+1i+D7ilblZl AAOA== 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=tveTiSW3kXI18qkd/ZaB+nQ0L/9zQTBwJzflX/XFRO4=; b=lGl+4cT+4pg/xD9p3BczMEzWodZx94W2yLmcOJDCXt/XK/JLfu5LEJz9pY4nZPCxMo qPGNWips1wORLgCH0ioEQHez5TDquWbnPfzym6HqkeO0KHHIAbQfn9yuqxg1v+U13ash MiL5Lvtq60ICpBqzCoyIALRkxH2qnWwuUTvpkp0IaZXVyOokyzW8sPYIW5yPHc/YM7rR 1xa3d3Zjz8zW6n5zh0BuHcp4fcIvngwUMmokoCQw7FN1OrUSnDFDOLLKzTJWeg42rogD Ux8b9kbkxBXB7Kx+qFviEicRkOXCJLpB1DVj+XTHpKrwuVXcQ8qmDTF+zJ52aUEigb0s KJ9g== X-Gm-Message-State: AOAM5320im79Ew6RCKF2seCWZmV1Hrdwfx8KYreQDsLz2QzrxYcegOIY QkPF+zLos6GMr4n3S+xsssG5lA== X-Google-Smtp-Source: ABdhPJySQycOonv7NhIpwPNHFfA/dnUsLfdgmjGLC7V51EjW7hZO8cBlM/z70OqkOOFQUJSip5xYLg== X-Received: by 2002:a19:6c7:: with SMTP id 190mr21005693lfg.614.1609193557628; Mon, 28 Dec 2020 14:12:37 -0800 (PST) Received: from box.localdomain ([86.57.175.117]) by smtp.gmail.com with ESMTPSA id a15sm6433563lji.105.2020.12.28.14.12.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Dec 2020 14:12:36 -0800 (PST) Received: by box.localdomain (Postfix, from userid 1000) id 15841100F3B; Tue, 29 Dec 2020 01:12:37 +0300 (+03) Date: Tue, 29 Dec 2020 01:12:37 +0300 From: "Kirill A. Shutemov" To: Linus Torvalds Subject: Re: [PATCH 1/2] mm: Allow architectures to request 'old' entries when prefaulting Message-ID: <20201228221237.6nu75kgxq7ikxn2a@box> References: <20201226224016.dxjmordcfj75xgte@box> <20201227234853.5mjyxcybucts3kbq@box> <20201228125352.phnj2x2ci3kwfld5@box> <20201228220548.57hl32mmrvvefj6q@box> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201228220548.57hl32mmrvvefj6q@box> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201228_171240_920328_490EA0F9 X-CRM114-Status: GOOD ( 26.27 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Android Kernel Team , Jan Kara , Minchan Kim , Catalin Marinas , Hugh Dickins , Linux Kernel Mailing List , Matthew Wilcox , Linux-MM , Vinayak Menon , Linux ARM , Andrew Morton , Will Deacon , "Kirill A. Shutemov" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Dec 29, 2020 at 01:05:48AM +0300, Kirill A. Shutemov wrote: > On Mon, Dec 28, 2020 at 10:47:36AM -0800, Linus Torvalds wrote: > > On Mon, Dec 28, 2020 at 4:53 AM Kirill A. Shutemov wrote: > > > > > > So far I only found one more pin leak and always-true check. I don't see > > > how can it lead to crash or corruption. Keep looking. > > > > Well, I noticed that the nommu.c version of filemap_map_pages() needs > > fixing, but that's obviously not the case Hugh sees. > > > > No,m I think the problem is the > > > > pte_unmap_unlock(vmf->pte, vmf->ptl); > > > > at the end of filemap_map_pages(). > > > > Why? > > > > Because we've been updating vmf->pte as we go along: > > > > vmf->pte += xas.xa_index - last_pgoff; > > > > and I think that by the time we get to that "pte_unmap_unlock()", > > vmf->pte potentially points to past the edge of the page directory. > > Well, if it's true we have bigger problem: we set up an pte entry without > relevant PTL. > > But I *think* we should be fine here: do_fault_around() limits start_pgoff > and end_pgoff to stay within the page table. > > It made mw looking at the code around pte_unmap_unlock() and I think that > the bug is that we have to reset vmf->address and NULLify vmf->pte once we > are done with faultaround: > > diff --git a/mm/memory.c b/mm/memory.c Ugh.. Wrong place. Need to sleep. I'll look into your idea tomorrow. diff --git a/mm/filemap.c b/mm/filemap.c index 87671284de62..e4daab80ed81 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2987,6 +2987,8 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf, unsigned long address, } while ((head = next_map_page(vmf, &xas, end_pgoff)) != NULL); pte_unmap_unlock(vmf->pte, vmf->ptl); rcu_read_unlock(); + vmf->address = address; + vmf->pte = NULL; WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss); return ret; -- Kirill A. Shutemov _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel