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[23.128.96.18]) by mx.google.com with ESMTP id b15si14082705ejl.351.2021.06.15.03.10.25; Tue, 15 Jun 2021 03:10:48 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b="W/lfR0zL"; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231496AbhFOKLS (ORCPT + 99 others); Tue, 15 Jun 2021 06:11:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34864 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231396AbhFOKLR (ORCPT ); Tue, 15 Jun 2021 06:11:17 -0400 Received: from mail-ot1-x331.google.com (mail-ot1-x331.google.com [IPv6:2607:f8b0:4864:20::331]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3935CC061574 for ; Tue, 15 Jun 2021 03:09:12 -0700 (PDT) Received: by mail-ot1-x331.google.com with SMTP id i12-20020a05683033ecb02903346fa0f74dso13727069otu.10 for ; Tue, 15 Jun 2021 03:09:12 -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=D/L9M46eaaH0QBqlJTDr9j5/a1oRGHp298rEoHobuSk=; b=W/lfR0zLReQdc7PHjJRVB6Z9hn6GJnOFkroA8pyiE5Y0liNQOgHCt87KS4/bkAX7eE ruHOuoF3srORlhSJjFmg2JbJjF5kGBzDUdqoQ0xbY3+7U7KDtUEKQoFIW1wmxShxQmod 7IyMraVpNr1qagN5T38H67gQWcRWPStkYlkY11tL5rOY+XXsGhRyP8nZUCYVpimFgaQE TDDfZ1AGYIcueALqYy5l63YjogRbXNbuef49nv3KDRdF0RjbjFT7pI243T186J46J90u GYwjsGeX4c5nDZ3pG35tX5Es3IqFrw8pDn67QjzsbdqHfe/JYmQpn0mp/7J6DK3wRnbU rLsQ== 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=D/L9M46eaaH0QBqlJTDr9j5/a1oRGHp298rEoHobuSk=; b=hLcuH17v7hXrjPwC7mcy7OeyNu5IBz4O9BYl+Kb1fuwtWg0Dyh1Kvf5RfR2+rZ5wzV rg/C7nBOHAC8/i0f/DCRLYxNgpxxpEHp2j91RWkElZRmbXQNDjDHvlv3/877tdhQAE9q ezjDndWZvkqcW/2se1dERZ8p3IQeiaRheh2JDBKUrWW1l7DsRuGQbCOuAxaJd1Kx9gQK Sd/VjZJJnSrGEVu+koqSuFkTDRaSpKv1bUGcjmOLM8gM2hyta19iTAJTUOJNnPIj6nrt +nvncQzbihjIeqGYT+jDyVZeUwfnEjKvPsadA5GS3gYuikyy9a6l6qkTcVwP4lw+kzwl GIwA== X-Gm-Message-State: AOAM530K/+B6HzGWJsPEYDt2YSErgeya7tVmUpfGybDAR29Yzkf3CC6f EvYMDvqoVauE4uBGQkeU30PFzWvyDW1wpeuJoe5SmA== X-Received: by 2002:a05:6830:1c7b:: with SMTP id s27mr17651144otg.233.1623751751394; Tue, 15 Jun 2021 03:09:11 -0700 (PDT) MIME-Version: 1.0 References: <20210615014705.2234866-1-dja@axtens.net> <20210615014705.2234866-3-dja@axtens.net> In-Reply-To: <20210615014705.2234866-3-dja@axtens.net> From: Marco Elver Date: Tue, 15 Jun 2021 12:08:59 +0200 Message-ID: Subject: Re: [PATCH v12 2/6] kasan: allow architectures to provide an outline readiness check To: Daniel Axtens Cc: LKML , Linux Memory Management List , linuxppc-dev@lists.ozlabs.org, kasan-dev , 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 Tue, 15 Jun 2021 at 03:47, 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 > > -- > > I discuss the justfication for this later in the series. Also, > 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 > --- > mm/kasan/common.c | 4 ++++ > mm/kasan/generic.c | 3 +++ > mm/kasan/kasan.h | 4 ++++ > mm/kasan/shadow.c | 4 ++++ > 4 files changed, 15 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..19323a3d5975 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -449,6 +449,10 @@ 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; } > +#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..74134b657d7d 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; > + What about kasan_poison_last_granule()? kasan_unpoison() currently seems to potentially trip on that.