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=-24.9 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, URIBL_BLOCKED,USER_AGENT_SANE_1,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 3F88DC11F65 for ; Wed, 30 Jun 2021 19:13:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2829961462 for ; Wed, 30 Jun 2021 19:13:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233608AbhF3TQK (ORCPT ); Wed, 30 Jun 2021 15:16:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34042 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233152AbhF3TQH (ORCPT ); Wed, 30 Jun 2021 15:16:07 -0400 Received: from mail-wr1-x42a.google.com (mail-wr1-x42a.google.com [IPv6:2a00:1450:4864:20::42a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 337BBC061756 for ; Wed, 30 Jun 2021 12:13:37 -0700 (PDT) Received: by mail-wr1-x42a.google.com with SMTP id u8so4937536wrq.8 for ; Wed, 30 Jun 2021 12:13:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=LwMx6mpf58K+dt89atcRzUa+xJG7iS/9NXSnO3QAijk=; b=r7y6xbzz3Ru117IKa1A1HqYQLPsQ9JWTt80K0/sfpiwfqVG1bSJD0SFSYl/jMHoCJ2 ob3TpfUWHwHuwt70WI4j1pKseqgibuQ5m4T4+kBD+5X/Bv38bChnS+jbYWPjkjI6EjUo G/39As31rcJBFn/TdNWaDFYEVqq/MFEqS9de5nZt01bJR5tya6r0t+hff3JJ1iQaFL6q dB7TWBXgRhxSKJ7KbJGzlDhCLUgE6zw1ZuoAEHVgShC17Fx8OFPzpryUET3AzY1C1mhQ /Xv8NisXpCuGG5Ni7I7u/OU/OthuU1kcuTvSAoWLDujFEbHTJ+JOsHYi3+V0+37L6dy3 6FeQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=LwMx6mpf58K+dt89atcRzUa+xJG7iS/9NXSnO3QAijk=; b=CgPpmnEBe3zQ/DNv6u09hr8Lk2hVFU10QSyKh+DdehQ9AE7VVDvVuEvbQwemS2dOkd cI1bBk23jLZ6mOL8JSiEIOP+MrEaocIHiRi9ehqx/o0digl/0qW5Nvsbye4L73sZf5PB +1CWPfSQfU+//XzmMrqIS3ClUhIctKFy7QnFxNJWklbQNjIysthmLFcO0ugI10zfNHOI sNpNf/YPasTg4IiZFtH2yjE6c5PMR5cptkLRz87s2GuY9EMB2ySAK4VLE/OC0Y5THyG1 9qqSKQWzU7Iz74/UeS+bTHiH83irNUhnRLiuBkkcLxH42n7wpwC6Toj3NvT6U66x8K0H LHFg== X-Gm-Message-State: AOAM53220ofsd8Dq6OZ0p0qgYetcjNn95j1tPGRUlh3adTWaJiPYtoKg GN7V0oSw+SrtVIGpULLa80GWpw== X-Google-Smtp-Source: ABdhPJwGJqNIQjt34+ofqYDqSFhTn0KnMtEPFfjP2mQPalcDH63xTtPzA6qVHWDm/uGp300DxtbuOA== X-Received: by 2002:adf:c18a:: with SMTP id x10mr41309800wre.193.1625080415431; Wed, 30 Jun 2021 12:13:35 -0700 (PDT) Received: from elver.google.com ([2a00:79e0:15:13:8b0e:c57f:ff29:7e4]) by smtp.gmail.com with ESMTPSA id o20sm6991115wms.3.2021.06.30.12.13.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Jun 2021 12:13:34 -0700 (PDT) Date: Wed, 30 Jun 2021 21:13:27 +0200 From: Marco Elver To: yee.lee@mediatek.com Cc: andreyknvl@gmail.com, wsd_upstream@mediatek.com, Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Andrew Morton , Matthias Brugger , "open list:KASAN" , "open list:MEMORY MANAGEMENT" , open list , "moderated list:ARM/Mediatek SoC support" , "moderated list:ARM/Mediatek SoC support" Subject: Re: [PATCH v3 1/1] kasan: Add memzero init for unaligned size under SLUB debug Message-ID: References: <20210630134943.20781-1-yee.lee@mediatek.com> <20210630134943.20781-2-yee.lee@mediatek.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210630134943.20781-2-yee.lee@mediatek.com> User-Agent: Mutt/2.0.5 (2021-01-21) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 30, 2021 at 09:49PM +0800, yee.lee@mediatek.com wrote: > From: Yee Lee > > Issue: when SLUB debug is on, hwtag kasan_unpoison() would overwrite > the redzone of object with unaligned size. > > An additional memzero_explicit() path is added to replacing init by > hwtag instruction for those unaligned size at SLUB debug mode. > > The penalty is acceptable since they are only enabled in debug mode, > not production builds. A block of comment is added for explanation. > > Signed-off-by: Yee Lee > Suggested-by: Marco Elver > Suggested-by: Andrey Konovalov > Cc: Andrey Ryabinin > Cc: Alexander Potapenko > Cc: Dmitry Vyukov > Cc: Andrew Morton In future, please add changes to each version after an additional '---'. Example: --- v2: * Use IS_ENABLED(CONFIG_SLUB_DEBUG) in if-statement. > --- > mm/kasan/kasan.h | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > index 8f450bc28045..6f698f13dbe6 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -387,6 +387,16 @@ static inline void kasan_unpoison(const void *addr, size_t size, bool init) > > if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK)) > return; > + /* > + * Explicitly initialize the memory with the precise object size > + * to avoid overwriting the SLAB redzone. This disables initialization > + * in the arch code and may thus lead to performance penalty. > + * The penalty is accepted since SLAB redzones aren't enabled in production builds. > + */ Can we please format the comment properly: diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index 6f698f13dbe6..1972ec5736cb 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -388,10 +388,10 @@ static inline void kasan_unpoison(const void *addr, size_t size, bool init) if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK)) return; /* - * Explicitly initialize the memory with the precise object size - * to avoid overwriting the SLAB redzone. This disables initialization - * in the arch code and may thus lead to performance penalty. - * The penalty is accepted since SLAB redzones aren't enabled in production builds. + * Explicitly initialize the memory with the precise object size to + * avoid overwriting the SLAB redzone. This disables initialization in + * the arch code and may thus lead to performance penalty. The penalty + * is accepted since SLAB redzones aren't enabled in production builds. */ if (IS_ENABLED(CONFIG_SLUB_DEBUG) && init && ((unsigned long)size & KASAN_GRANULE_MASK)) { init = false; > + if (IS_ENABLED(CONFIG_SLUB_DEBUG) && init && ((unsigned long)size & KASAN_GRANULE_MASK)) { > + init = false; > + memzero_explicit((void *)addr, size); > + } > size = round_up(size, KASAN_GRANULE_SIZE); > > hw_set_mem_tag_range((void *)addr, size, tag, init); I think this solution might be fine for now, as I don't see an easy way to do this without some major refactor to use kmem_cache_debug_flags(). However, I think there's an intermediate solution where we only check the static-key 'slub_debug_enabled' though. Because I've checked, and various major distros _do_ enabled CONFIG_SLUB_DEBUG. But the static branch just makes sure there's no performance overhead. Checking the static branch requires including mm/slab.h into mm/kasan/kasan.h, which we currently don't do and perhaps wanted to avoid. Although I don't see a reason there, because there's no circular dependency even if we did. Andrey, any opinion? In case you guys think checking static key is the better solution, I think the below would work together with the pre-requisite patch at the end: diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index 1972ec5736cb..9130d025612c 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -6,6 +6,8 @@ #include #include +#include "../slab.h" + #ifdef CONFIG_KASAN_HW_TAGS #include @@ -393,7 +395,8 @@ static inline void kasan_unpoison(const void *addr, size_t size, bool init) * the arch code and may thus lead to performance penalty. The penalty * is accepted since SLAB redzones aren't enabled in production builds. */ - if (IS_ENABLED(CONFIG_SLUB_DEBUG) && init && ((unsigned long)size & KASAN_GRANULE_MASK)) { + if (slub_debug_enabled_unlikely() && + init && ((unsigned long)size & KASAN_GRANULE_MASK)) { init = false; memzero_explicit((void *)addr, size); } [ Note: You can pick the below patch up by extracting it from the email and running 'git am -s '. You could then use it as part of a patch series together with your original patch. ] From: Marco Elver Date: Wed, 30 Jun 2021 20:56:57 +0200 Subject: [PATCH] mm: introduce helper to check slub_debug_enabled Introduce a helper to check slub_debug_enabled, so that we can confine the use of #ifdef to the definition of the slub_debug_enabled_unlikely() helper. Signed-off-by: Marco Elver --- mm/slab.h | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/mm/slab.h b/mm/slab.h index 18c1927cd196..9439da434712 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -215,10 +215,18 @@ DECLARE_STATIC_KEY_TRUE(slub_debug_enabled); DECLARE_STATIC_KEY_FALSE(slub_debug_enabled); #endif extern void print_tracking(struct kmem_cache *s, void *object); +static inline bool slub_debug_enabled_unlikely(void) +{ + return static_branch_unlikely(&slub_debug_enabled); +} #else static inline void print_tracking(struct kmem_cache *s, void *object) { } +static inline bool slub_debug_enabled_unlikely(void) +{ + return false; +} #endif /* @@ -228,11 +236,10 @@ static inline void print_tracking(struct kmem_cache *s, void *object) */ static inline bool kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t flags) { -#ifdef CONFIG_SLUB_DEBUG - VM_WARN_ON_ONCE(!(flags & SLAB_DEBUG_FLAGS)); - if (static_branch_unlikely(&slub_debug_enabled)) + if (IS_ENABLED(CONFIG_SLUB_DEBUG)) + VM_WARN_ON_ONCE(!(flags & SLAB_DEBUG_FLAGS)); + if (slub_debug_enabled_unlikely()) return s->flags & flags; -#endif return false; } -- 2.32.0.93.g670b81a890-goog