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=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 AFEC6C2B9F4 for ; Thu, 17 Jun 2021 07:06:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8AB7E6135C for ; Thu, 17 Jun 2021 07:06:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229827AbhFQHI1 (ORCPT ); Thu, 17 Jun 2021 03:08:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48980 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229666AbhFQHIX (ORCPT ); Thu, 17 Jun 2021 03:08:23 -0400 Received: from mail-ot1-x329.google.com (mail-ot1-x329.google.com [IPv6:2607:f8b0:4864:20::329]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 81F82C061574 for ; Thu, 17 Jun 2021 00:06:16 -0700 (PDT) Received: by mail-ot1-x329.google.com with SMTP id 66-20020a9d02c80000b02903615edf7c1aso5111157otl.13 for ; Thu, 17 Jun 2021 00:06:16 -0700 (PDT) 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=nhqmE1vBTbQZlPad3fKuDW4Qef6o+8lKl4ONa0J/G/8=; b=eGrVtvwA+i6aNAMo3ETYrgy4DVEWUiimdDfxOE2LFye56wFHpr1W4MnbrblQ8rRQcC xJ75y+uRuCGoD3u+AwSOr3k3oP8buzdYF7JppwE5mTFUR0Oe2ouOwNKfRRuPgh7Rr/zk RyQf66jXNR/8yk3XRkGerNoLo+WDXQA6ePmSKgvat2HJxflCZPul4uR6rRSq1QM9w53J 2TE6qCvLxMRjTV1m+KDKmwdi6doQ3jZ+Roh6f2GRMQZ7Uk/4Z11RLlP8MRyTk+7ApLA2 rL5GXw+oTZeFmgnFcHUqZTo1Ehtao2FNASwGb3WRDOZm6rnFo/I35o+YxhzFb9V+4O/Y 35jA== 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=nhqmE1vBTbQZlPad3fKuDW4Qef6o+8lKl4ONa0J/G/8=; b=lmTc+o72LX3McvyeBXRvVeDC5wYIAKKFX0PH58XQjzIDr+CWeZSNMAkG1K9KCLqp6Z +TYCo53/2BgzyvuswwrMwLRJRS/QAsZvN52HXh9J2l59orQWYQM1uS0II1vCixI5Fq1W IhM1kw7wTEHwYUv9cXQGn7A5CgALWstgZAUjwARUKZ+tGJj/7nlTRlRq2EHDfQpG0ZWa OAvjNLbjJUpes6UPOOPGKdqyly3GXTRvWbMXb4X4KZeXS9+WZwr/HWezIJQZ7JHnaeoe kvxmGzCAgNdYCm7zyscreLOcVA3WHS832cmlxGTkqiY5QhyBPBZzuuaGEVKnPtEOnkzb /dNQ== X-Gm-Message-State: AOAM533vCLKZsEgnjsqj9IlzN+rhhbE/kO5QlTI5yxpGiU/+tGjq3t// dLlKWil9GFdaHziCzsXFmZZiOUa2p0kSVi8Lf6qlDQ== X-Google-Smtp-Source: ABdhPJzb3pydS4fL1OGc3+kLyBtkxKVQSv+5ySB2k1JVkAvfcK53EAa09UHM2AiBfuP55Icc+GyGNfs+i3l/fcRAo0o= X-Received: by 2002:a9d:4e7:: with SMTP id 94mr3260598otm.233.1623913575674; Thu, 17 Jun 2021 00:06:15 -0700 (PDT) MIME-Version: 1.0 References: <20210617063956.94061-1-dja@axtens.net> <20210617063956.94061-3-dja@axtens.net> In-Reply-To: <20210617063956.94061-3-dja@axtens.net> From: Marco Elver Date: Thu, 17 Jun 2021 09:06:02 +0200 Message-ID: Subject: Re: [PATCH v14 2/4] kasan: allow architectures to provide an outline readiness check To: Daniel Axtens Cc: LKML , Linux Memory Management List , kasan-dev , Andrew Morton , Andrey Konovalov , linuxppc-dev@lists.ozlabs.org, Christophe Leroy , aneesh.kumar@linux.ibm.com, Balbir Singh , "Aneesh Kumar K . V" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 17 Jun 2021 at 08:40, Daniel Axtens wrote: > > Allow architectures to define a kasan_arch_is_ready() hook that bails > out of any function that's about to touch the shadow unless the arch > says that it is ready for the memory to be accessed. This is fairly > uninvasive and should have a negligible performance penalty. > > This will only work in outline mode, so an arch must specify > ARCH_DISABLE_KASAN_INLINE if it requires this. > > Cc: Balbir Singh > Cc: Aneesh Kumar K.V > Suggested-by: Christophe Leroy > Signed-off-by: Daniel Axtens With Christophe's suggestion: Reviewed-by: Marco Elver > -- > > Both previous RFCs for ppc64 - by 2 different people - have > needed this trick! See: > - https://lore.kernel.org/patchwork/patch/592820/ # ppc64 hash series > - https://patchwork.ozlabs.org/patch/795211/ # ppc radix series > > I haven't been able to exercise the arch hook error for !GENERIC as I > don't have a particularly modern aarch64 toolchain or a lot of experience > cross-compiling with clang. But it does fire for GENERIC + INLINE on x86. > --- > mm/kasan/common.c | 4 ++++ > mm/kasan/generic.c | 3 +++ > mm/kasan/kasan.h | 8 ++++++++ > mm/kasan/shadow.c | 8 ++++++++ > 4 files changed, 23 insertions(+) > > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > index 10177cc26d06..0ad615f3801d 100644 > --- a/mm/kasan/common.c > +++ b/mm/kasan/common.c > @@ -331,6 +331,10 @@ static inline bool ____kasan_slab_free(struct kmem_cache *cache, void *object, > u8 tag; > void *tagged_object; > > + /* Bail if the arch isn't ready */ > + if (!kasan_arch_is_ready()) > + return false; > + > tag = get_tag(object); > tagged_object = object; > object = kasan_reset_tag(object); > diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c > index 53cbf28859b5..c3f5ba7a294a 100644 > --- a/mm/kasan/generic.c > +++ b/mm/kasan/generic.c > @@ -163,6 +163,9 @@ static __always_inline bool check_region_inline(unsigned long addr, > size_t size, bool write, > unsigned long ret_ip) > { > + if (!kasan_arch_is_ready()) > + return true; > + > if (unlikely(size == 0)) > return true; > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > index 8f450bc28045..b18abaf8c78e 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -449,6 +449,14 @@ static inline void kasan_poison_last_granule(const void *address, size_t size) { > > #endif /* CONFIG_KASAN_GENERIC */ > > +#ifndef kasan_arch_is_ready > +static inline bool kasan_arch_is_ready(void) { return true; } > +#else > +#if !defined(CONFIG_KASAN_GENERIC) || !defined(CONFIG_KASAN_OUTLINE) > +#error kasan_arch_is_ready only works in KASAN generic outline mode! > +#endif > +#endif > + > /* > * Exported functions for interfaces called from assembly or from generated > * code. Declarations here to avoid warning about missing declarations. > diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c > index 082ee5b6d9a1..3c7f7efe6f68 100644 > --- a/mm/kasan/shadow.c > +++ b/mm/kasan/shadow.c > @@ -73,6 +73,10 @@ void kasan_poison(const void *addr, size_t size, u8 value, bool init) > { > void *shadow_start, *shadow_end; > > + /* Don't touch the shadow memory if arch isn't ready */ > + if (!kasan_arch_is_ready()) > + return; > + > /* > * Perform shadow offset calculation based on untagged address, as > * some of the callers (e.g. kasan_poison_object_data) pass tagged > @@ -99,6 +103,10 @@ EXPORT_SYMBOL(kasan_poison); > #ifdef CONFIG_KASAN_GENERIC > void kasan_poison_last_granule(const void *addr, size_t size) > { > + /* Don't touch the shadow memory if arch isn't ready */ > + if (!kasan_arch_is_ready()) > + return; > + > if (size & KASAN_GRANULE_MASK) { > u8 *shadow = (u8 *)kasan_mem_to_shadow(addr + size); > *shadow = size & KASAN_GRANULE_MASK; > -- > 2.30.2 >