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Authentication-Results: mx.google.com; spf=pass (google.com: domain of walter-zh.wu@mediatek.com designates 210.61.82.184 as permitted sender) smtp.mailfrom=walter-zh.wu@mediatek.com X-UUID: 1f96f75078614a5b9e1f0250f0a67e06-20190611 X-UUID: 1f96f75078614a5b9e1f0250f0a67e06-20190611 Received: from mtkcas07.mediatek.inc [(172.21.101.84)] by mailgw02.mediatek.com (envelope-from ) (mhqrelay.mediatek.com ESMTP with TLS) with ESMTP id 1348057515; Tue, 11 Jun 2019 20:01:15 +0800 Received: from mtkcas08.mediatek.inc (172.21.101.126) by mtkmbs07n1.mediatek.inc (172.21.101.16) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Tue, 11 Jun 2019 20:01:14 +0800 Received: from [172.21.84.99] (172.21.84.99) by mtkcas08.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1395.4 via Frontend Transport; Tue, 11 Jun 2019 20:01:14 +0800 Message-ID: <1560254473.29153.16.camel@mtksdccf07> Subject: Re: [PATCH v2] kasan: add memory corruption identification for software tag-based mode From: Walter Wu To: Dmitry Vyukov CC: Andrey Ryabinin , Alexander Potapenko , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Matthias Brugger , "Martin Schwidefsky" , Arnd Bergmann , "Vasily Gorbik" , Andrey Konovalov , "Jason A. Donenfeld" , Miles Chen =?UTF-8?Q?=28=E9=99=B3=E6=B0=91=E6=A8=BA=29?= , kasan-dev , LKML , Linux-MM , Linux ARM , "linux-mediatek@lists.infradead.org" , wsd_upstream Date: Tue, 11 Jun 2019 20:01:13 +0800 In-Reply-To: References: <1559651172-28989-1-git-send-email-walter-zh.wu@mediatek.com> <1560151690.20384.3.camel@mtksdccf07> <1560236742.4832.34.camel@mtksdccf07> <1560249891.29153.4.camel@mtksdccf07> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit MIME-Version: 1.0 X-MTK: N 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 Tue, 2019-06-11 at 13:39 +0200, Dmitry Vyukov wrote: > I should have been asked this earlier, but: what is your use-case? We need KASAN to help us to detect memory corruption at mobile phone. It is powerful tool. > Could you use CONFIG_KASAN_GENERIC instead? Why not? > CONFIG_KASAN_GENERIC already has quarantine. > We hope to use tag-based KASAN, because it consumes more less memory(1/16) than generic KASAN(1/8), but we also hope the tag-based KASAN report is easy read and able to identify the use-after-free or out-of-bound. > On Tue, Jun 11, 2019 at 1:32 PM Dmitry Vyukov wrote: > > > > On Tue, Jun 11, 2019 at 12:44 PM Walter Wu wrote: > > > > > > On Tue, 2019-06-11 at 10:47 +0200, Dmitry Vyukov wrote: > > > > On Tue, Jun 11, 2019 at 9:05 AM Walter Wu wrote: > > > > > > > > > > On Mon, 2019-06-10 at 13:46 +0200, Dmitry Vyukov wrote: > > > > > > On Mon, Jun 10, 2019 at 9:28 AM Walter Wu wrote: > > > > > > > > > > > > > > On Fri, 2019-06-07 at 21:18 +0800, Dmitry Vyukov wrote: > > > > > > > > > diff --git a/include/linux/kasan.h b/include/linux/kasan.h > > > > > > > > > index b40ea104dd36..be0667225b58 100644 > > > > > > > > > --- a/include/linux/kasan.h > > > > > > > > > +++ b/include/linux/kasan.h > > > > > > > > > @@ -164,7 +164,11 @@ void kasan_cache_shutdown(struct kmem_cache *cache); > > > > > > > > > > > > > > > > > > #else /* CONFIG_KASAN_GENERIC */ > > > > > > > > > > > > > > > > > > +#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY > > > > > > > > > +void kasan_cache_shrink(struct kmem_cache *cache); > > > > > > > > > +#else > > > > > > > > > > > > > > > > Please restructure the code so that we don't duplicate this function > > > > > > > > name 3 times in this header. > > > > > > > > > > > > > > > We have fixed it, Thank you for your reminder. > > > > > > > > > > > > > > > > > > > > > > > static inline void kasan_cache_shrink(struct kmem_cache *cache) {} > > > > > > > > > +#endif > > > > > > > > > static inline void kasan_cache_shutdown(struct kmem_cache *cache) {} > > > > > > > > > > > > > > > > > > #endif /* CONFIG_KASAN_GENERIC */ > > > > > > > > > diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan > > > > > > > > > index 9950b660e62d..17a4952c5eee 100644 > > > > > > > > > --- a/lib/Kconfig.kasan > > > > > > > > > +++ b/lib/Kconfig.kasan > > > > > > > > > @@ -134,6 +134,15 @@ config KASAN_S390_4_LEVEL_PAGING > > > > > > > > > to 3TB of RAM with KASan enabled). This options allows to force > > > > > > > > > 4-level paging instead. > > > > > > > > > > > > > > > > > > +config KASAN_SW_TAGS_IDENTIFY > > > > > > > > > + bool "Enable memory corruption idenitfication" > > > > > > > > > > > > > > > > s/idenitfication/identification/ > > > > > > > > > > > > > > > I should replace my glasses. > > > > > > > > > > > > > > > > > > > > > > > + depends on KASAN_SW_TAGS > > > > > > > > > + help > > > > > > > > > + Now tag-based KASAN bug report always shows invalid-access error, This > > > > > > > > > + options can identify it whether it is use-after-free or out-of-bound. > > > > > > > > > + This will make it easier for programmers to see the memory corruption > > > > > > > > > + problem. > > > > > > > > > > > > > > > > This description looks like a change description, i.e. it describes > > > > > > > > the current behavior and how it changes. I think code comments should > > > > > > > > not have such, they should describe the current state of the things. > > > > > > > > It should also mention the trade-off, otherwise it raises reasonable > > > > > > > > questions like "why it's not enabled by default?" and "why do I ever > > > > > > > > want to not enable it?". > > > > > > > > I would do something like: > > > > > > > > > > > > > > > > This option enables best-effort identification of bug type > > > > > > > > (use-after-free or out-of-bounds) > > > > > > > > at the cost of increased memory consumption for object quarantine. > > > > > > > > > > > > > > > I totally agree with your comments. Would you think we should try to add the cost? > > > > > > > It may be that it consumes about 1/128th of available memory at full quarantine usage rate. > > > > > > > > > > > > Hi, > > > > > > > > > > > > I don't understand the question. We should not add costs if not > > > > > > necessary. Or you mean why we should add _docs_ regarding the cost? Or > > > > > > what? > > > > > > > > > > > I mean the description of option. Should it add the description for > > > > > memory costs. I see KASAN_SW_TAGS and KASAN_GENERIC options to show the > > > > > memory costs. So We originally think it is possible to add the > > > > > description, if users want to enable it, maybe they want to know its > > > > > memory costs. > > > > > > > > > > If you think it is not necessary, we will not add it. > > > > > > > > Full description of memory costs for normal KASAN mode and > > > > KASAN_SW_TAGS should probably go into > > > > Documentation/dev-tools/kasan.rst rather then into config description > > > > because it may be too lengthy. > > > > > > > Thanks your reminder. > > > > > > > I mentioned memory costs for this config because otherwise it's > > > > unclear why would one ever want to _not_ enable this option. If it > > > > would only have positive effects, then it should be enabled all the > > > > time and should not be a config option at all. > > > > > > Sorry, I don't get your full meaning. > > > You think not to add the memory costs into the description of config ? > > > or need to add it? or make it not be a config option(default enabled)? > > > > Yes, I think we need to include mention of additional cost into _this_ > > new config.