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Mon, 05 Jul 2021 03:45:22 -0700 (PDT) MIME-Version: 1.0 References: <20210705103229.8505-1-yee.lee@mediatek.com> <20210705103229.8505-3-yee.lee@mediatek.com> In-Reply-To: <20210705103229.8505-3-yee.lee@mediatek.com> From: Marco Elver Date: Mon, 5 Jul 2021 12:45:11 +0200 Message-ID: Subject: Re: [PATCH v6 2/2] kasan: Add memzero int for unaligned size at DEBUG To: yee.lee@mediatek.com Cc: linux-kernel@vger.kernel.org, nicholas.tang@mediatek.com, Kuan-Ying.Lee@mediatek.com, chinwen.chang@mediatek.com, Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Andrew Morton , Andrey Konovalov , Matthias Brugger , "open list:KASAN" , "open list:MEMORY MANAGEMENT" , "moderated list:ARM/Mediatek SoC support" , "moderated list:ARM/Mediatek SoC support" Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=google.com header.s=20161025 header.b=rzSYkZK4; spf=pass (imf16.hostedemail.com: domain of elver@google.com designates 209.85.210.52 as permitted sender) smtp.mailfrom=elver@google.com; dmarc=pass (policy=reject) header.from=google.com X-Stat-Signature: peurpnu3ccns5fmwjmu3syipx7r6hkjr X-Rspamd-Queue-Id: 97DD1F000091 X-Rspamd-Server: rspam06 X-HE-Tag: 1625481923-750958 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 Mon, 5 Jul 2021 at 12:33, 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. > > Cc: Andrey Ryabinin > Cc: Alexander Potapenko > Cc: Dmitry Vyukov > Cc: Andrew Morton > Suggested-by: Marco Elver > Suggested-by: Andrey Konovalov > Signed-off-by: Yee Lee Reviewed-by: Marco Elver Thank you! > --- > mm/kasan/kasan.h | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > index 98e3059bfea4..d739cdd1621a 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -9,6 +9,7 @@ > #ifdef CONFIG_KASAN_HW_TAGS > > #include > +#include "../slab.h" > > DECLARE_STATIC_KEY_FALSE(kasan_flag_stacktrace); > extern bool kasan_flag_async __ro_after_init; > @@ -387,6 +388,17 @@ 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. > + */ > + if (__slub_debug_enabled() && > + 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); > -- > 2.18.0