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=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL 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 B4DB7C433DB for ; Fri, 5 Mar 2021 15:46:45 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2B2C665092 for ; Fri, 5 Mar 2021 15:46:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2B2C665092 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id AFBC06B0073; Fri, 5 Mar 2021 10:46:44 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A84AD6B0074; Fri, 5 Mar 2021 10:46:44 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8D7636B0075; Fri, 5 Mar 2021 10:46:44 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0186.hostedemail.com [216.40.44.186]) by kanga.kvack.org (Postfix) with ESMTP id 6BB876B0073 for ; Fri, 5 Mar 2021 10:46:44 -0500 (EST) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 2F6AF18026112 for ; Fri, 5 Mar 2021 15:46:44 +0000 (UTC) X-FDA: 77886248328.20.B82DECA Received: from mail-pg1-f182.google.com (mail-pg1-f182.google.com [209.85.215.182]) by imf06.hostedemail.com (Postfix) with ESMTP id 7E1B5C001C49 for ; Fri, 5 Mar 2021 15:46:27 +0000 (UTC) Received: by mail-pg1-f182.google.com with SMTP id a4so1642681pgc.11 for ; Fri, 05 Mar 2021 07:46:27 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=P/UOJ2ouh3jCawvJJDBF9MwK+LARNE7PChR+Eq9d4AQ=; b=S5LjfiLSKYQc9wli5WdLPG7UnO4uz8ho5JaGL0zEOrrBBkr/6p95xugqZkpfkhKuem jqnwm4JkB28oVYhXnDY6GQsBItbTDGOTEeqtzua5N4FrMc3ZMxGnNZlkQ10JQfaNMlaS 4fYA81RQP9+uqpFVfwGPC6TqQjWRTAA3Mhf5Fh9kKxd/6vu0dOFTjuV9jiW/hFs8kru9 QykbmTgx7Awo9enlnhQnT8EAJhlik04Oq8+JYAj9N3/drT05icPaByhZx10IDltb4Ydp c1WY30SghrZlHPlWXRhQSKv5SRVyeDHmOgR6jQx0MxHGTjkIgfxL9JGdsMSUzY2W14vw u0eQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=P/UOJ2ouh3jCawvJJDBF9MwK+LARNE7PChR+Eq9d4AQ=; b=tS0o26Tfbj/kKgnNgnIB3PkC2/hME1kpPS8/W3/zTewqR3nPVig/Yd/dLIJ/L6wBL0 ZgZw2SUfDSMDWXtZKDKjeG+z5NZ9ecRn59mBXbNbCtNqhFKN0q2bclvaKjQKdiXuq4tS KvWPXcNxIujOmGhB7yr9noaomPE0KX5FC+9tYpOVxLOSuHkU5riUffUBAsJ5umzF7lfG 1ndAP65F778g7d16cR34l4NfigkOM1iilNsX/MVffbLngdhJm2A/0h0pjsMzadIUB+u9 calxkXcBRB1JQcUIPQc5ETuIjVZcsl5pJFtRWquGYGT7aMPw+4ZLtc8Nwn1/A9ATQ0St d58Q== X-Gm-Message-State: AOAM532/g1feBguuVWJvcd7IprH1AwObnBPdNAeLZ8Lc81Prxm5YbbQ4 obE96Fs6oTkaoI30w8adFFVIHvXuXslk9cfYL6V3QA== X-Google-Smtp-Source: ABdhPJzD0IwSq/hfOwQNOKZVQtfXWou6YobAr/snMkCbwdnO2pajqgzJFqn1NKRMbXz24kvC5QKlTxfaMxooPJ0CJR8= X-Received: by 2002:a63:455d:: with SMTP id u29mr8980133pgk.286.1614959186302; Fri, 05 Mar 2021 07:46:26 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Andrey Konovalov Date: Fri, 5 Mar 2021 16:46:15 +0100 Message-ID: Subject: Re: [PATCH v2 1/2] kasan: initialize shadow to TAG_INVALID for SW_TAGS To: Andrew Morton Cc: Catalin Marinas , Will Deacon , Vincenzo Frascino , Dmitry Vyukov , Andrey Ryabinin , Alexander Potapenko , Marco Elver , Peter Collingbourne , Evgenii Stepanov , Branislav Rankov , Kevin Brodsky , Christoph Hellwig , kasan-dev , Linux ARM , Linux Memory Management List , LKML Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 7E1B5C001C49 X-Stat-Signature: dfu35p9bf5c185kfgbwdzax457jpmo8x Received-SPF: none (google.com>: No applicable sender policy available) receiver=imf06; identity=mailfrom; envelope-from=""; helo=mail-pg1-f182.google.com; client-ip=209.85.215.182 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614959187-150242 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Feb 19, 2021 at 1:22 AM Andrey Konovalov wrote: > > Currently, KASAN_SW_TAGS uses 0xFF as the default tag value for > unallocated memory. The underlying idea is that since that memory > hasn't been allocated yet, it's only supposed to be dereferenced > through a pointer with the native 0xFF tag. > > While this is a good idea in terms on consistency, practically it > doesn't bring any benefit. Since the 0xFF pointer tag is a match-all > tag, it doesn't matter what tag the accessed memory has. No accesses > through 0xFF-tagged pointers are considered buggy by KASAN. > > This patch changes the default tag value for unallocated memory to 0xFE, > which is the tag KASAN uses for inaccessible memory. This doesn't affect > accesses through 0xFF-tagged pointer to this memory, but this allows > KASAN to detect wild and large out-of-bounds invalid memory accesses > through otherwise-tagged pointers. > > This is a prepatory patch for the next one, which changes the tag-based > KASAN modes to not poison the boot memory. > > Signed-off-by: Andrey Konovalov > --- > include/linux/kasan.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/include/linux/kasan.h b/include/linux/kasan.h > index 14f72ec96492..44c147dae7e3 100644 > --- a/include/linux/kasan.h > +++ b/include/linux/kasan.h > @@ -30,7 +30,8 @@ struct kunit_kasan_expectation { > /* Software KASAN implementations use shadow memory. */ > > #ifdef CONFIG_KASAN_SW_TAGS > -#define KASAN_SHADOW_INIT 0xFF > +/* This matches KASAN_TAG_INVALID. */ > +#define KASAN_SHADOW_INIT 0xFE > #else > #define KASAN_SHADOW_INIT 0 > #endif > -- > 2.30.0.617.g56c4b15f3c-goog > Hi Andrew, Could you pick up this series into mm? The discussion on v1 of this series was hijacked discussing an unrelated issue. Thanks!