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=-12.3 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,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 0EB40C433DB for ; Thu, 18 Feb 2021 10:19:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B3A7464E85 for ; Thu, 18 Feb 2021 10:19:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232462AbhBRKIm (ORCPT ); Thu, 18 Feb 2021 05:08:42 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:47578 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230403AbhBRI4w (ORCPT ); Thu, 18 Feb 2021 03:56:52 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613638518; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=XKvhMYbPeIfjBqzilW6MTKDEALceHhOMd9Ttih7NUzc=; b=MLxzsSEVj2slcN2G0gOS9NGNTTTtDX/I3+UxLbpfWQaaQDqlilvG9xdWB6eGg0HIc/1e73 uKPpIGc+Tcvnpq3GZSlsaTvIRO1FrAYlIIYwH79smBxvMIitbyLnCIuXFVT2p7UNTX72O2 EqkQ9GvduS5wen0IKDUAjbhDI1mF2pQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-558-Q0uAD2YWMX25mfx7NX_YEw-1; Thu, 18 Feb 2021 03:55:15 -0500 X-MC-Unique: Q0uAD2YWMX25mfx7NX_YEw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0A5146EE20; Thu, 18 Feb 2021 08:55:13 +0000 (UTC) Received: from [10.36.114.59] (ovpn-114-59.ams2.redhat.com [10.36.114.59]) by smtp.corp.redhat.com (Postfix) with ESMTP id ADBD96E407; Thu, 18 Feb 2021 08:55:08 +0000 (UTC) Subject: Re: [PATCH] mm, kasan: don't poison boot memory To: Andrey Konovalov , Andrew Morton , Catalin Marinas , Vincenzo Frascino , Dmitry Vyukov , George Kennedy , Konrad Rzeszutek Wilk Cc: Will Deacon , Dmitry Vyukov , Andrey Ryabinin , Alexander Potapenko , Marco Elver , Peter Collingbourne , Evgenii Stepanov , Branislav Rankov , Kevin Brodsky , Christoph Hellwig , kasan-dev@googlegroups.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <487751e1ccec8fcd32e25a06ce000617e96d7ae1.1613595269.git.andreyknvl@google.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: Date: Thu, 18 Feb 2021 09:55:07 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <487751e1ccec8fcd32e25a06ce000617e96d7ae1.1613595269.git.andreyknvl@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17.02.21 21:56, Andrey Konovalov wrote: > During boot, all non-reserved memblock memory is exposed to the buddy > allocator. Poisoning all that memory with KASAN lengthens boot time, > especially on systems with large amount of RAM. This patch makes > page_alloc to not call kasan_free_pages() on all new memory. > > __free_pages_core() is used when exposing fresh memory during system > boot and when onlining memory during hotplug. This patch adds a new > FPI_SKIP_KASAN_POISON flag and passes it to __free_pages_ok() through > free_pages_prepare() from __free_pages_core(). > > This has little impact on KASAN memory tracking. > > Assuming that there are no references to newly exposed pages before they > are ever allocated, there won't be any intended (but buggy) accesses to > that memory that KASAN would normally detect. > > However, with this patch, KASAN stops detecting wild and large > out-of-bounds accesses that happen to land on a fresh memory page that > was never allocated. This is taken as an acceptable trade-off. > > All memory allocated normally when the boot is over keeps getting > poisoned as usual. > > Signed-off-by: Andrey Konovalov > Change-Id: Iae6b1e4bb8216955ffc14af255a7eaaa6f35324d Not sure this is the right thing to do, see https://lkml.kernel.org/r/bcf8925d-0949-3fe1-baa8-cc536c529860@oracle.com Reversing the order in which memory gets allocated + used during boot (in a patch by me) might have revealed an invalid memory access during boot. I suspect that that issue would no longer get detected with your patch, as the invalid memory access would simply not get detected. Now, I cannot prove that :) -- Thanks, David / dhildenb