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=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 C5419C48BDF for ; Sun, 20 Jun 2021 11:16:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A9845610EA for ; Sun, 20 Jun 2021 11:16:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229615AbhFTLSy (ORCPT ); Sun, 20 Jun 2021 07:18:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38408 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229541AbhFTLSu (ORCPT ); Sun, 20 Jun 2021 07:18:50 -0400 Received: from mail-ed1-x529.google.com (mail-ed1-x529.google.com [IPv6:2a00:1450:4864:20::529]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C2210C061574 for ; Sun, 20 Jun 2021 04:16:37 -0700 (PDT) Received: by mail-ed1-x529.google.com with SMTP id i24so4247557edx.4 for ; Sun, 20 Jun 2021 04:16:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=N/chto6jVnmlN7DfH7wDHpFEeSqaG7VTzK76gQyfhdE=; b=D6mAsQ+aCAXO3wRcDlfa3JmPrKUwhheHJIVfPvMzhvnOnAYK/uP0OBKIc9QIiQCrJ6 AFb57u1TufCkRDQAVTj4KAhAJUg8+iVUxYEayPLDkiFc0vUITKcD64lJu7rfxY7fAaU1 QyLkoIcV5Cydq+N/8tMpN0/g9wjK7zMIaXSYaRR3u5lkJ/jS4PIs+mZoqzs8hNHIKOpm hW9eh5cmX09P6x0txhMBBboVUb9OcszdeKdDIfUabtGfbjT6mAIfzjQtXt6uvKC6cOzN w7r9k3jSPtvkWs8cJPCh62P+hR6T55Zh4GOfD7Pd2PJ71WxOA0/OURYbwlVoXvrDvBaF 9I/w== 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=N/chto6jVnmlN7DfH7wDHpFEeSqaG7VTzK76gQyfhdE=; b=O8p/Xpc9cl2Rbg9WuFLM2th7dSHuMxHc16GfDzm5BO5YvC0RZX4XLOhUOLP61SWlfy fCCHCKvZtlDgapQy1wsoKnmkXzrALXfjeMwcrqVyU9dTHjQUBsYaqViVyROhWUSm6Zwb iIZ5lUg1lvuyhQCCVSWXajVaN9sMeX/Jt6owTREltKeB1W9nY2fHwcOR2ynMhq2PuRCZ JLiZGYNgUWfKfP8/06mhOzwz7wVuqwVDATqJ6uoefTR4EGYi/8V19WdfyE77+2X2vXkn rKoRaLFvBvQPiSVGkzAMtmTMoG8WlDmCaukfTp7tg+adxjgYtaM1CicxvjKtdzpW7fzJ EaQg== X-Gm-Message-State: AOAM533sGZ+yUV8mHhQKlf0s+mn0Ud2GyMNuGJS6Nxomo5ldBv3Yldgt 4RMxlZjs9p8FQhOBNK5xBRnfHBwj0zfb66wYYu4= X-Google-Smtp-Source: ABdhPJxYK3lUOrWNlEP54WBPv+Re8m3kZDwbqiAXmFxidAhd1z49biOTmktDCYU4Ol8bTnqZWRygtohw0sg9Yj17ftc= X-Received: by 2002:aa7:cd05:: with SMTP id b5mr2787046edw.190.1624187796446; Sun, 20 Jun 2021 04:16:36 -0700 (PDT) MIME-Version: 1.0 References: <20210617093032.103097-1-dja@axtens.net> <20210617093032.103097-3-dja@axtens.net> In-Reply-To: <20210617093032.103097-3-dja@axtens.net> From: Andrey Konovalov Date: Sun, 20 Jun 2021 14:16:16 +0300 Message-ID: Subject: Re: [PATCH v15 2/4] kasan: allow architectures to provide an outline readiness check To: Daniel Axtens Cc: LKML , Linux Memory Management List , kasan-dev , Marco Elver , Andrew Morton , linuxppc-dev@lists.ozlabs.org, christophe.leroy@csgroup.eu, aneesh.kumar@linux.ibm.com, bsingharora@gmail.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 17, 2021 at 12:30 PM 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 > Reviewed-by: Marco Elver > Signed-off-by: Daniel Axtens > > -- > > 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 > > Build tested on arm64 with SW_TAGS and x86 with INLINE: the error fires > if I add a kasan_arch_is_ready define. > --- > mm/kasan/common.c | 4 ++++ > mm/kasan/generic.c | 3 +++ > mm/kasan/kasan.h | 6 ++++++ > mm/kasan/shadow.c | 8 ++++++++ > 4 files changed, 21 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 */ This comment brings no value. The fact that we bail is clear from the following line. The comment should explain why we bail. > + if (!kasan_arch_is_ready()) > + return false; Have you considered including these checks into the high-level wrappers in include/linux/kasan.h? Would that work? > + > 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..4dbc8def64f4 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -449,6 +449,12 @@ 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; } > +#elif !defined(CONFIG_KASAN_GENERIC) || !defined(CONFIG_KASAN_OUTLINE) > +#error kasan_arch_is_ready only works in KASAN generic outline mode! > +#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 > 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=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 8D18AC48BDF for ; Sun, 20 Jun 2021 11:16:39 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 12195610EA for ; Sun, 20 Jun 2021 11:16:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 12195610EA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 90F0B6B0070; Sun, 20 Jun 2021 07:16:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 897D68D0001; Sun, 20 Jun 2021 07:16:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6EBF56B0073; Sun, 20 Jun 2021 07:16:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0009.hostedemail.com [216.40.44.9]) by kanga.kvack.org (Postfix) with ESMTP id 3B0476B0070 for ; Sun, 20 Jun 2021 07:16:38 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id C5C8A181AEF00 for ; Sun, 20 Jun 2021 11:16:37 +0000 (UTC) X-FDA: 78273849234.14.DC74396 Received: from mail-ed1-f54.google.com (mail-ed1-f54.google.com [209.85.208.54]) by imf19.hostedemail.com (Postfix) with ESMTP id 8B6DD9001E7C for ; Sun, 20 Jun 2021 11:16:37 +0000 (UTC) Received: by mail-ed1-f54.google.com with SMTP id i13so14905293edb.9 for ; Sun, 20 Jun 2021 04:16:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=N/chto6jVnmlN7DfH7wDHpFEeSqaG7VTzK76gQyfhdE=; b=D6mAsQ+aCAXO3wRcDlfa3JmPrKUwhheHJIVfPvMzhvnOnAYK/uP0OBKIc9QIiQCrJ6 AFb57u1TufCkRDQAVTj4KAhAJUg8+iVUxYEayPLDkiFc0vUITKcD64lJu7rfxY7fAaU1 QyLkoIcV5Cydq+N/8tMpN0/g9wjK7zMIaXSYaRR3u5lkJ/jS4PIs+mZoqzs8hNHIKOpm hW9eh5cmX09P6x0txhMBBboVUb9OcszdeKdDIfUabtGfbjT6mAIfzjQtXt6uvKC6cOzN w7r9k3jSPtvkWs8cJPCh62P+hR6T55Zh4GOfD7Pd2PJ71WxOA0/OURYbwlVoXvrDvBaF 9I/w== 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=N/chto6jVnmlN7DfH7wDHpFEeSqaG7VTzK76gQyfhdE=; b=V471S9wQWLggkEXF56RyItYooN3E5GKnQ80Z4dZM+yTrixy2czhZRRnPMDz5QXPThh O+5o5GdbU+ZPQVoWWmXxfudKdHclzwTLD5jhkkUVkMdpTFLAKsH5YuL5H529xs99rCht QPjIpaSiERj0LQrIK9FizVzw2JYc8tiLoyxpFrgMjeybruY/FoXq9V9wuk3LHAkhW1In RT5nsL1n42wQC16z6X1R6JAXCPtxdanYek0ZZwShi7tAiY6YV9Yuqdv0r+abspG7mJ7o RmJ09j03nilzj4MoOGt9v1a/t/XKVjlFnutgnHKgdwwtDHDRtsbNOW8wfhPKFRUGFz0p Fdjw== X-Gm-Message-State: AOAM530HqveLrc/qpSSjvKG/VFEhpPE0lCh5KZVBEP6Ayj9gQn6tN4q2 gaHuZjz1pJ8v2jSNkGFly+RuU7TlPcoW2RE8i50= X-Google-Smtp-Source: ABdhPJxYK3lUOrWNlEP54WBPv+Re8m3kZDwbqiAXmFxidAhd1z49biOTmktDCYU4Ol8bTnqZWRygtohw0sg9Yj17ftc= X-Received: by 2002:aa7:cd05:: with SMTP id b5mr2787046edw.190.1624187796446; Sun, 20 Jun 2021 04:16:36 -0700 (PDT) MIME-Version: 1.0 References: <20210617093032.103097-1-dja@axtens.net> <20210617093032.103097-3-dja@axtens.net> In-Reply-To: <20210617093032.103097-3-dja@axtens.net> From: Andrey Konovalov Date: Sun, 20 Jun 2021 14:16:16 +0300 Message-ID: Subject: Re: [PATCH v15 2/4] kasan: allow architectures to provide an outline readiness check To: Daniel Axtens Cc: LKML , Linux Memory Management List , kasan-dev , Marco Elver , Andrew Morton , linuxppc-dev@lists.ozlabs.org, christophe.leroy@csgroup.eu, aneesh.kumar@linux.ibm.com, bsingharora@gmail.com Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=gmail.com header.s=20161025 header.b=D6mAsQ+a; spf=pass (imf19.hostedemail.com: domain of andreyknvl@gmail.com designates 209.85.208.54 as permitted sender) smtp.mailfrom=andreyknvl@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Stat-Signature: m8bg9kjdz1g6bhxqk3jggms77xh4ky1g X-Rspamd-Queue-Id: 8B6DD9001E7C X-Rspamd-Server: rspam06 X-HE-Tag: 1624187797-257824 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 Thu, Jun 17, 2021 at 12:30 PM 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 > Reviewed-by: Marco Elver > Signed-off-by: Daniel Axtens > > -- > > 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 > > Build tested on arm64 with SW_TAGS and x86 with INLINE: the error fires > if I add a kasan_arch_is_ready define. > --- > mm/kasan/common.c | 4 ++++ > mm/kasan/generic.c | 3 +++ > mm/kasan/kasan.h | 6 ++++++ > mm/kasan/shadow.c | 8 ++++++++ > 4 files changed, 21 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 */ This comment brings no value. The fact that we bail is clear from the following line. The comment should explain why we bail. > + if (!kasan_arch_is_ready()) > + return false; Have you considered including these checks into the high-level wrappers in include/linux/kasan.h? Would that work? > + > 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..4dbc8def64f4 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -449,6 +449,12 @@ 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; } > +#elif !defined(CONFIG_KASAN_GENERIC) || !defined(CONFIG_KASAN_OUTLINE) > +#error kasan_arch_is_ready only works in KASAN generic outline mode! > +#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 > 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=-10.5 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 ABD62C48BDF for ; Sun, 20 Jun 2021 11:46:53 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 F421C60D07 for ; Sun, 20 Jun 2021 11:46:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F421C60D07 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4G79qc3VDcz3c69 for ; Sun, 20 Jun 2021 21:46:52 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20161025 header.b=D6mAsQ+a; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=gmail.com (client-ip=2a00:1450:4864:20::52c; helo=mail-ed1-x52c.google.com; envelope-from=andreyknvl@gmail.com; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20161025 header.b=D6mAsQ+a; dkim-atps=neutral Received: from mail-ed1-x52c.google.com (mail-ed1-x52c.google.com [IPv6:2a00:1450:4864:20::52c]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4G798m42ccz2ymQ for ; Sun, 20 Jun 2021 21:16:40 +1000 (AEST) Received: by mail-ed1-x52c.google.com with SMTP id c7so13980566edn.6 for ; Sun, 20 Jun 2021 04:16:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=N/chto6jVnmlN7DfH7wDHpFEeSqaG7VTzK76gQyfhdE=; b=D6mAsQ+aCAXO3wRcDlfa3JmPrKUwhheHJIVfPvMzhvnOnAYK/uP0OBKIc9QIiQCrJ6 AFb57u1TufCkRDQAVTj4KAhAJUg8+iVUxYEayPLDkiFc0vUITKcD64lJu7rfxY7fAaU1 QyLkoIcV5Cydq+N/8tMpN0/g9wjK7zMIaXSYaRR3u5lkJ/jS4PIs+mZoqzs8hNHIKOpm hW9eh5cmX09P6x0txhMBBboVUb9OcszdeKdDIfUabtGfbjT6mAIfzjQtXt6uvKC6cOzN w7r9k3jSPtvkWs8cJPCh62P+hR6T55Zh4GOfD7Pd2PJ71WxOA0/OURYbwlVoXvrDvBaF 9I/w== 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=N/chto6jVnmlN7DfH7wDHpFEeSqaG7VTzK76gQyfhdE=; b=O/4skk8BnctuS7q0eETDamFIlTM+1tFhi7me59C+t+XibZV2xyTR7ulSuay5ovs0BW 2+yPYUx288WnlimU2fvoLDwRJprRBYhkliJ8w5m1yRUCsvEz+4eBovU9q3u/FcmSRFy4 MnvIASlbuHpbVfCRzaHM38pAcPw9zHFwCcPB6qD3vIEjAtCDF2rS5zoZCg37nubK9pev c0FMTTkFqB08aAyixs+jgn2xql0Qz9BC68CNi+v264iHYCdC42lqS2cgZzHCXnMjKktS t+qamDnhFyzu3ph7hdYeaWiwThBVIMzLFPLuhk66fk9tSdIBFOoW0LZqUDgtoibXbaK+ XP1w== X-Gm-Message-State: AOAM530X+xZP15w61M2Q/Z79UitsQ3FjGCNeG5nxSsI5VWeokxrqfzDC rsrsUx3QuBA0L5K6fI1wSbW8Yy7sg++7POo/G0A= X-Google-Smtp-Source: ABdhPJxYK3lUOrWNlEP54WBPv+Re8m3kZDwbqiAXmFxidAhd1z49biOTmktDCYU4Ol8bTnqZWRygtohw0sg9Yj17ftc= X-Received: by 2002:aa7:cd05:: with SMTP id b5mr2787046edw.190.1624187796446; Sun, 20 Jun 2021 04:16:36 -0700 (PDT) MIME-Version: 1.0 References: <20210617093032.103097-1-dja@axtens.net> <20210617093032.103097-3-dja@axtens.net> In-Reply-To: <20210617093032.103097-3-dja@axtens.net> From: Andrey Konovalov Date: Sun, 20 Jun 2021 14:16:16 +0300 Message-ID: Subject: Re: [PATCH v15 2/4] kasan: allow architectures to provide an outline readiness check To: Daniel Axtens Content-Type: text/plain; charset="UTF-8" X-Mailman-Approved-At: Sun, 20 Jun 2021 21:46:05 +1000 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Marco Elver , aneesh.kumar@linux.ibm.com, LKML , kasan-dev , Linux Memory Management List , Andrew Morton , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Thu, Jun 17, 2021 at 12:30 PM 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 > Reviewed-by: Marco Elver > Signed-off-by: Daniel Axtens > > -- > > 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 > > Build tested on arm64 with SW_TAGS and x86 with INLINE: the error fires > if I add a kasan_arch_is_ready define. > --- > mm/kasan/common.c | 4 ++++ > mm/kasan/generic.c | 3 +++ > mm/kasan/kasan.h | 6 ++++++ > mm/kasan/shadow.c | 8 ++++++++ > 4 files changed, 21 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 */ This comment brings no value. The fact that we bail is clear from the following line. The comment should explain why we bail. > + if (!kasan_arch_is_ready()) > + return false; Have you considered including these checks into the high-level wrappers in include/linux/kasan.h? Would that work? > + > 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..4dbc8def64f4 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -449,6 +449,12 @@ 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; } > +#elif !defined(CONFIG_KASAN_GENERIC) || !defined(CONFIG_KASAN_OUTLINE) > +#error kasan_arch_is_ready only works in KASAN generic outline mode! > +#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 >